CN111188885A - Double nut ball screw pair - Google Patents

Abstract

The invention provides a double-nut ball screw pair, which comprises a screw, a main nut and an auxiliary nut, wherein the main nut and the auxiliary nut are sleeved on the screw in series; a key groove is formed in the outer peripheral surface of one side, facing the auxiliary nut, of the main nut along the axial direction of the main nut, and a bearing key is embedded in the key groove; a sleeve integrally formed with the auxiliary nut is arranged on one side, facing the main nut, of the auxiliary nut, the sleeve is provided with a round hole coaxial with the auxiliary nut, and an arc-shaped hole is formed in the sleeve; the sleeve is sleeved on the end part of the main nut facing the auxiliary nut, the part of the bearing key, which is protruded from the key groove and is far away from the lead screw, is embedded into the arc-shaped hole, and the bearing key is suitable for moving in the arc-shaped hole along the circumferential direction of the sleeve; a pre-tightening piece is also embedded in the arc-shaped hole; an annular pre-tightening hoop is arranged around the sleeve in a surrounding mode, and the pre-tightening hoop is pressed against the pre-tightening sheet. The invention can eliminate the axial clearance newly generated by the abrasion of the screw rod, the main nut and the auxiliary nut of the double-nut ball screw pair, and the pre-tightening force of the opposite vertex of the main nut and the auxiliary nut is convenient to adjust.

Description

Double-nut ball screw pair

Technical Field

The invention relates to the technical field of ball screw nut pair transmission, in particular to a double-nut ball screw pair.

Background

At present, in the precise ball screw nut pair transmission, besides a certain unidirectional feeding precision, the axial clearance between a nut and a screw is strictly controlled, otherwise, when the screw reversely rotates, a backlash error is generated. In order to eliminate backlash error caused by an axial clearance between a nut and a screw, a ball screw nut pair generally adopts double nuts for pre-tightening and backlash elimination. The invention patent with the patent number ZL201610943955.X discloses a double-nut pre-tightening ball screw pair, and the pre-tightening structure is as follows: the device comprises a screw rod, a main nut, an auxiliary nut, a pre-tightening block and a pressing strip; the screw rod is sleeved with a main nut and an auxiliary nut, a main groove is formed in the end part, facing the auxiliary nut, of the main nut, an auxiliary groove is formed in the end part, facing the main nut, of the auxiliary nut, and the main grooves in the end part of the main nut and the auxiliary grooves in the end part of the auxiliary nut are aligned one by one; the bottom surface of the main groove is inclined or the bottom surface of the auxiliary groove is inclined, or the bottom surfaces of the main groove and the auxiliary groove are both inclined; the pre-tightening block is provided with an inclined surface, the pre-tightening block is embedded in a main groove of the main nut and an auxiliary groove of the auxiliary nut and can move in the main groove and the auxiliary groove, two side surfaces of the main groove and the auxiliary groove are in contact with corresponding surfaces on the pre-tightening block, and the inclined surface of the pre-tightening block is in contact with the bottom surface of the main groove or the bottom surface of the auxiliary groove; the pressing strip is arranged around the joint of the main nut and the auxiliary nut and pressed on or indirectly pressed on the pre-tightening block. The principle of pre-tightening is as follows: the relative rotation of the main nut and the auxiliary nut is limited by the aid of the pre-tightening blocks embedded in the main groove and the auxiliary groove, and the main nut and the auxiliary nut are separated from each other towards two sides in the axial direction by means of centripetal movement of the pre-tightening blocks in the main groove and the auxiliary groove, so that pre-tightening clearance elimination of the double-nut ball screw pair is achieved. The double nut pre-loaded ball screw assembly disclosed in the zl201610943955.x patent has the following disadvantages: because errors exist in manufacturing and installation, pretightening forces generated by each pretightening block and used for separating the main nut and the auxiliary nut from each other along the axial direction to two sides are unequal, so that a moment for enabling the axis of the auxiliary nut to generate angular displacement relative to the axis of the main nut is formed, and adverse effects are generated on transmission of the ball screw nut pair.

Disclosure of Invention

The invention aims to provide a double-nut ball screw pair, which aims to solve the technical problem of pre-tightening and eliminating axial gaps existing after a screw, a main nut and an auxiliary nut of the double-nut ball screw pair are worn.

In order to realize the purpose of the invention, the technical scheme adopted by the invention is as follows:

a double nut ball screw assembly comprising: the screw rod, the main nut and the auxiliary nut are sleeved on the screw rod in series; wherein

The end part of the main nut, facing the auxiliary nut, is provided with a cylindrical surface which is coaxial with the axis of the main nut; a key groove is formed in the outer peripheral surface of one side, facing the auxiliary nut, of the main nut along the axial direction of the main nut; a bearing key is embedded in the key groove;

a sleeve integrally formed with the auxiliary nut is arranged on one side of the auxiliary nut facing the main nut; the sleeve is provided with a round hole which is coaxial with the axis of the auxiliary nut; an arc-shaped hole is formed in the sleeve, and two hole walls of the arc-shaped hole along the circumferential direction of the sleeve are parallel to the axis of the sleeve;

the sleeve is suitable for being sleeved on a cylindrical surface of the end part of the main nut, facing the auxiliary nut, and forms a running fit, and after the sleeve is sleeved with the main nut, the part of the bearing key, which protrudes out of the key groove along the radial direction of the lead screw, is suitable for being embedded into the arc-shaped hole, and the bearing key is suitable for moving in the arc-shaped hole along the circumferential direction of the sleeve;

a pre-tightening piece is also embedded in the arc-shaped hole, and the pre-tightening piece is of an arc-shaped structure; the arch back of the pre-tightening sheet faces the arc-shaped hole back; one end part of the pre-tightening piece along the circumferential direction of the sleeve is suitable for abutting against one hole wall of the arc-shaped hole, and the other end part of the pre-tightening piece along the circumferential direction of the sleeve is suitable for abutting against the outer side wall of the force bearing key; the hole walls of the arc-shaped holes which are suitable for being propped against the two end parts of the pre-tightening pieces along the circumferential direction of the sleeve and the outer side walls of the bearing keys are in a relative distribution relationship; and

the periphery of the sleeve is also provided with a pre-tightening hoop in a surrounding way, the pre-tightening hoop is of an annular structure with an opening, and the pre-tightening hoop is suitable for being pressed against the pre-tightening sheet; and a threaded connecting piece consisting of a bolt and an adjusting nut is arranged at the opening of the pre-tightening hoop.

In a preferred embodiment of the invention, a slight gap exists between two ends of the pre-tightening piece along the axial direction of the sleeve and two hole walls of the arc-shaped hole along the axial direction of the sleeve.

In a preferred embodiment of the present invention, a pair of the key slots is disposed on the main nut, and a pair of the arc holes is correspondingly disposed on the sleeve; and

the double-nut ball screw pair comprises a pair of bearing keys and a pair of pre-tightening pieces.

In a preferred embodiment of the present invention, a pair of flanges adapted to abut against two end portions of the pre-tightening piece in the axial direction of the sleeve are provided at a portion of the pre-tightening band contacting the pre-tightening piece, so that a cross section of the portion of the pre-tightening band contacting the pre-tightening piece is formed in a shape of a cross section

Is formed in a groove shape.

In a preferred embodiment of the present invention, the pre-tightening strap comprises a left strap half and a right strap half hinged together by a hinge and both in a semi-circular structure.

In a preferred embodiment of the invention, the pre-tensioning sheet comprises a main portion and a sub portion which are rotationally engaged to form an arch.

In a preferred embodiment of the invention, a V-shaped groove is arranged at the end part of the main part suitable for being matched and connected with the branch part, and the groove bottom of the V-shaped groove is an inward concave arc surface;

the end part of the branch part, which is suitable for being matched with the main part, is provided with a cylindrical surface which is suitable for being rotationally matched with the groove bottom of the V-shaped groove.

In a preferred embodiment of the invention, the main portion is adapted to abut a side wall of the section mating end against a pre-tightening strap; and

the side wall of the main part, which is suitable for being abutted against the pre-tightening hoop, is a circular arc surface.

In a preferred embodiment of the invention, an embedded edge integrally formed with the force bearing key is arranged at the end part of the force bearing key in the length direction, and the height of the embedded edge is slightly smaller than the depth of a key groove of the main nut;

the key groove formed in the axial direction of the main nut extends to the end face, facing the auxiliary nut, of the main nut, and the length of the key groove in the axial direction of the main nut is greater than the total length of the force bearing key and the embedded edge; the total length of the force bearing key and the embedded edge is greater than the axial width of the arc-shaped hole along the auxiliary nut, and the length of the force bearing key is slightly smaller than the axial width of the arc-shaped hole along the auxiliary nut;

the embedded edge is suitable for being completely accommodated in the key groove and is covered by the sleeve barrel wall around the arc-shaped hole, and the part of the bearing key protruding out of the embedded edge is suitable for being embedded into the arc-shaped hole.

In a preferred embodiment of the invention, both ends of the force bearing key in the length direction are provided with embedded edges.

Compared with the prior art, the double-nut ball screw pair has the advantages that ① can eliminate new axial clearance between the screw and the main nut and the auxiliary nut due to abrasion, ② does not generate moment for enabling the axis of the auxiliary nut to generate angular displacement relative to the axis of the main nut, ③ is convenient to adjust the opposite pre-tightening force of the main nut and the auxiliary nut, and only the threaded connecting piece needs to be screwed or unscrewed.

Drawings

The contents of the description, as well as the references in the drawings, are briefly described as follows:

FIG. 1 is a schematic diagram of the basic structure of a double nut ball screw assembly according to the present invention;

FIG. 2 is a cross-sectional view taken along line A-A of FIG. 1, showing one top edge of the preload tab abutting the wall of the arcuate hole of the secondary nut and the other top edge of the preload tab abutting the side of the load bearing key embedded in the key slot, with the back of the preload tab facing away from the arcuate hole; also shown is the pretensioning band placed around the sleeve of the secondary nut and pressing against the arch back of the pretensioning sheet; also shown is a threaded connection consisting of a bolt and an adjusting nut provided at the opening of the pre-tightened band;

FIG. 3 is a schematic structural view of the primary nut and the secondary nut, showing the configuration of the keyway on the primary nut; the structure that a sleeve is arranged on the auxiliary nut and an arc-shaped hole is formed in the sleeve is also shown; the part of the bearing key exposed out of the key groove is positioned in the arc-shaped hole;

FIG. 4 shows the configuration of the primary nut and the secondary nut from another perspective, showing the configuration of the keyway on the primary nut; the structure that a sleeve is arranged on the auxiliary nut and an arc-shaped hole is formed in the sleeve is also shown; when the bearing key with the embedded edge is installed, the part of the bearing key protruding out of the embedded edge needs to be inserted into the arc-shaped hole from the inside of the round hole of the sleeve to the outside;

fig. 5 shows that the cylindrical surface of the main nut is inserted into the circular hole of the sleeve, a bearing key is embedded in the key slot of the main nut, and the part of the bearing key exposed out of the key slot is positioned in the arc-shaped hole;

FIGS. 6-1 and 6-2 illustrate the construction of the pretensioning sheet (wherein FIG. 6-2 illustrates α);

FIG. 7 shows that a rib is arranged at the contact part of the pre-tightening hoop and the pre-tightening piece; the pre-tightening hoop is also shown to be formed by hinging and connecting two semi-annular left semi-hoops and right semi-annular semi-hoops through a hinge;

FIG. 8 shows the improved prefastening tab being comprised of a main portion and a sub portion;

fig. 9 shows that one top edge of the pretensioning sheet composed of the main part and the branch part is against the wall of the arc-shaped hole of the secondary nut, the other top edge is against the side surface of the bearing key embedded in the key groove, the branch part and the main part of the pretensioning sheet form an eight-shaped opening facing the cylindrical surface of the primary nut, and the V-shaped groove of the main part of the pretensioning sheet and the end part of the branch part inserted into the V-shaped groove are both positioned in the V-shaped groove of the pretensioning band

A shaped groove;

FIG. 10 is a schematic view of the structure of the force-bearing key, showing that the force-bearing key is provided with embedded edges at both ends in the length direction thereof, so that the force-bearing key with embedded edges at both ends is in a shape of a Chinese character' tu

The labels in the figures are: the device comprises ascrew rod 1, amain nut 2, a key groove 2-1, anauxiliary nut 3, apre-tightening piece 4, an arch back 4-1, a top edge 4-2, a main portion 4-3, a V-shaped groove 4-4, a sub portion 4-5, apre-tightening hoop 5, a left half hoop 5-1, a right half hoop 5-2, a hinge 5-3, a flange 5-4, an adjustingnut 6, asleeve 11, an arc hole 11-4, a hole wall 11-5, aforce bearing key 12 and an embedded edge 12-1.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings of the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

Example 1:

fig. 1 and 2 show the basic structure of the invention, and a double-nut ball screw pair comprises ascrew 1, amain nut 2, anauxiliary nut 3, aforce bearing key 12, apre-tightening piece 4 and apre-tightening hoop 5. Thelead screw 1 is provided with amain nut 2 and anauxiliary nut 3 in a serial connection mode, the end face of themain nut 2 facing one side of theauxiliary nut 3 is in close contact with the end face of theauxiliary nut 3 facing one side of themain nut 2, and themain nut 2 and theauxiliary nut 3 can rotate relatively.

Referring to fig. 3 and 4, the outer circumferential surface of themain nut 2 facing thesub nut 3 is a cylindrical surface coaxial with the axis of the main nut 2 (the axis of themain nut 2 is the axis of the hole of themain nut 2 through which thelead screw 1 passes, the same applies below), and a key groove 2-1 is formed on the outer circumferential surface of themain nut 2 along the axis of themain nut 2. Asleeve 11 integrated with theauxiliary nut 3 is arranged on one side of theauxiliary nut 3 facing themain nut 2, thesleeve 11 is provided with a round hole coaxial with the axis of the auxiliary nut 3 (the axis of theauxiliary nut 3 refers to the axis of a hole on theauxiliary nut 3 penetrated by thelead screw 1. the same applies below), an arc-shaped hole 11-4 is arranged on thesleeve 11, and two hole walls 11-5 of the arc-shaped hole 11-4 along the circumferential direction of thesleeve 11 are both parallel to the axis of thesleeve 11; the arc-shaped holes 11-4 penetrate through the wall of the sleeve 11 (i.e. the arc-shaped holes 11-4 extend from the circular hole surface of thesleeve 11 to the peripheral surface of the sleeve 11). Thesleeve 11 is suitable for being sleeved on the end part, facing theauxiliary nut 3, of themain nut 2, the cylindrical surface of the specificmain nut 2 is located in the circular hole of thesleeve 11 and matched with the circular hole of thesleeve 11, and themain nut 2 and theauxiliary nut 3 can rotate relatively.

Referring to fig. 2, 3 and 5, aforce bearing key 12 is embedded in a key groove 2-1 of themain nut 2, theforce bearing key 12 can be a national standard common flat key, the length of theforce bearing key 12 is slightly smaller than the axial width of the arc-shaped hole 11-4 along theauxiliary nut 3, the part of theforce bearing key 12 protruding out of the key groove 2-1 along the radial direction of thescrew rod 1 is located in the arc-shaped hole 11-4, and theforce bearing key 12 can move along the circumferential direction of thesleeve 11 in the arc-shaped hole 11-4.

Referring to fig. 2, 6-1 and 6-2, for this embodiment, thepretensioning sheet 4 is made of elastic material (e.g. spring steel), thepretensioning sheet 4 is bent into an arch shape with an arch back 4-1 at the middle part along the circumferential direction of thesleeve 11, and two end parts of thepretensioning sheet 4 away from the arch back 4-1 (i.e. two end parts of thepretensioning sheet 4 along the circumferential direction of the sleeve 11) are top edges 4-2. Referring to fig. 1 and 2, thepre-tightening piece 4 is disposed in the arc-shaped hole 11-4, and the arch back 4-1 of thepre-tightening piece 4 faces away from the arc-shaped hole 11-4 (in other words, the arch opening of thepre-tightening piece 4 faces the arc-shaped hole 11-4. or the arch opening of thepre-tightening piece 4 faces the screw rod 1). One top edge 4-2 of thepre-tightening piece 4 abuts against the hole wall 11-5 of theauxiliary nut 3, and the other top edge 4-2 of thepre-tightening piece 4 abuts against the side face of thebearing key 12 embedded in the key slot 2-1 (in other words, the two top edges 4-2 of thepre-tightening piece 4 respectively abut against the side face of thebearing key 12 embedded in the key slot 2-1 and the side face of thebearing key 12 abutted against the hole wall 11-5 on theauxiliary nut 3 by the top edges 4-2 and the hole wall 11-5 are distributed face to face).

Referring to fig. 1 and 2, thepre-tightening ring 5 is made of elastic material (such as spring steel), thepre-tightening ring 5 is in an open ring shape, thepre-tightening ring 5 is arranged around thesleeve 11 of thesecondary nut 3 and pressed on the arch back 4-1 of thepre-tightening piece 4, and the opening of thepre-tightening ring 5 is provided with a bolt and an adjustingnut 6 which are suitable for forming a threaded connection.

Preferably, referring to fig. 3 and 4, the outer circumferential surface of themain nut 2 is provided with two key grooves 2-1 which are symmetrical relative to the axis of themain nut 2, and thesleeve 11 of theauxiliary nut 3 is provided with two arc-shaped holes 11-4 which are symmetrical relative to the axis of theauxiliary nut 3. Obviously, the number of the key grooves 2-1 formed on themain nut 2 can be three or more, and the number of the arc-shaped holes 11-4 formed on theauxiliary nut 3 can be three or more; in addition, the number of theforce bearing keys 12 is equal to that of the key slots 2-1, and the number of the key slots 2-1 is equal to that of the arc-shaped holes 11-4 and equal to that of thepre-tightening pieces 4.

The specific working principle of the double-nut ball screw pair of the embodiment is as follows:

referring to fig. 1 and 2, when the threaded connector at the opening of thepre-tightening ring 5 is screwed, the opening of thepre-tightening ring 5 is reduced, the inner diameter of the annularpre-tightening ring 5 is reduced, the centripetal pressure of thepre-tightening ring 5 pressing against the arch back 4-1 of thepre-tightening piece 4 is increased, so that the archpre-tightening piece 4 elastically deforms and tends to be straight, the distance between the top edges 4-2 at the two ends of thepre-tightening piece 4 is increased, the top edges 4-2 at the two ends of thepre-tightening piece 4 push themain nut 2 and theauxiliary nut 3 to rotate around thescrew rod 1 in opposite directions respectively, and themain nut 2 and theauxiliary nut 3 are axially abutted and pre-tightened, so that the axial gap between the main nut and the auxiliary nut and the screw rod is.

Specifically, if the right-handed screw 1 is adopted, thepre-tightening piece 4 needs to push themain nut 2 to rotate clockwise and push theauxiliary nut 3 to rotate counterclockwise (the clockwise and counterclockwise directions are determined by using fig. 2); if the left-handed screw 1 is used, thepre-tightening piece 4 should push themain nut 2 to rotate counterclockwise and theauxiliary nut 3 to rotate clockwise (clockwise and counterclockwise are determined by fig. 2), and the right-handed screw 1 is taken as an example in this embodiment. Referring to fig. 1 and 2, by adjusting the tightness of the threaded connection piece at the opening of thepre-tightening ring 5, the centripetal pressure of thepre-tightening ring 5 pressing on the arch back 4-1 of thepre-tightening piece 4 can be adjusted, and the pushing forces of the top edges 4-2 at the two ends of thepre-tightening piece 4 pushing themain nut 2 and theauxiliary nut 3 to rotate around thescrew rod 1 in opposite directions are adjusted, so that the butting force of themain nut 2 and theauxiliary nut 3 is adjusted, that is, the pre-tightening force between themain nut 2, theauxiliary nut 3 and thescrew rod 1 is adjusted. The threaded connecting piece at the opening of thepre-tightening hoop 5 is screwed, so that centripetal pressure of thepre-tightening hoop 5 pressed on the arch back 4-1 of thepre-tightening piece 4 is increased, thepre-tightening hoop 5 is elastically deformed, when thescrew rod 1, themain nut 2 and theauxiliary nut 3 are abraded, thepre-tightening piece 4 is further pushed by elastic force reserved by elastic deformation of thepre-tightening hoop 5 to be elastically deformed, so that thepre-tightening piece 4 tends to be more straight, the distance between the top edges 4-2 at two ends of thepre-tightening piece 4 is further enlarged, the top edges 4-2 at two ends of thepre-tightening piece 4 push themain nut 2 and theauxiliary nut 3 to further rotate around thescrew rod 1 in opposite directions respectively, and new axial gaps generated by abrasion among themain nut 2, theauxiliary nut 3 and thescrew rod 1 are automatically eliminated.

The double-nut ball screw assembly of the embodiment can eliminate axial gaps between the main nut and the auxiliary nut and the screw; the pre-tightening force of the opposite tops of themain nut 2 and theauxiliary nut 3 can be adjusted, the pre-tightening force is convenient to adjust, and only the threaded connecting piece needs to be screwed or unscrewed; after thescrew rod 1, themain nut 2 and theauxiliary nut 3 are worn, axial gaps between the screw rod and the main nut and between the screw rod and the auxiliary nut, which are caused by wear, can be automatically eliminated. Compared with the double-nut pre-tightening ball screw pair disclosed by the ZL201610943955.X patent, the ZL201610943955.X patent adopts the main nut and the auxiliary nut to be separated along the axial direction to two sides to eliminate the axial clearance between the main nut and the screw, and the ZL201610943955.X patent adopts themain nut 2 and theauxiliary nut 3 to be pre-tightened along the axial direction to the opposite top to eliminate the axial clearance between the main nut and the screw, so the moment for causing the axial line of theauxiliary nut 3 to generate angular displacement relative to the axial line of themain nut 2 can not be generated.

The cylindrical surface of themain nut 2 is positioned in the round hole of thesleeve 11 and forms a fit with the round hole of thesleeve 11, and the advantages are that: referring to fig. 1, the cylindrical surface of themain nut 2 is matched with the circular hole of thesleeve 11 of theauxiliary nut 3, so that themain nut 2 positions theauxiliary nut 3 in the radial direction, and themain nut 2 and theauxiliary nut 3 are ensured to have good coaxiality under the action of a jacking pretension force.

In the present embodiment, thesleeve 11 is provided on thesub-nut 3 as an example. Obviously, the following modifications can be made to the present embodiment to achieve the above-described advantageous effects. The specific modification content is as follows: the peripheral surface of the auxiliary nut 3 positioned at one side of the main nut 2 is a cylindrical surface which is coaxial with the axis of the auxiliary nut 3, and a key groove 2-1 is formed in the peripheral surface of the auxiliary nut 3 along the axis direction of the auxiliary nut 3; a sleeve 11 integrated with the main nut 2 is arranged on one side, located on the auxiliary nut 3, of the main nut 2, a round hole of the sleeve 11 is coaxial with the axis of the main nut 2, an arc-shaped hole 11-4 is formed in the sleeve 11, the arc-shaped hole 11-4 penetrates through the wall of the sleeve 11, and the arc-shaped hole 11-4 is provided with a hole wall 11-5 parallel to the axis of the main nut 2; the cylindrical surface of the auxiliary nut 3 is positioned in the round hole of the sleeve 11 and is matched with the round hole of the sleeve 11, and the main nut 2 and the auxiliary nut 3 can rotate relatively; the key groove 2-1 of the auxiliary nut 3 is embedded with a bearing key 12, the part of the bearing key 12 exposed out of the key groove 2-1 is positioned in the arc-shaped hole 11-4, and the bearing key 12 can move along the circumferential direction of the sleeve 11 in the arc-shaped hole 11-4.

It should be added to this embodiment that, referring to fig. 1, for thepretensioning sheet 4 of this embodiment, a small gap exists between two end portions of thepretensioning sheet 4 along the axial direction of thesleeve 11 and two hole walls of the arc-shaped hole 11-4 along the axial direction of thesleeve 11, where the small gap may be 0.1-1 mm. The significance of the design is that when thepre-tightening hoop 5 applies pressure to thepre-tightening piece 4 to stretch and deform thepre-tightening piece 4, the existence of the small gap can reduce the friction force between thepre-tightening piece 4 and two hole walls of the arc-shaped hole 11-4 along the axial direction of thesleeve 11 when thepre-tightening piece 4 deforms, namely reduce the resistance of thepre-tightening piece 4 to deform; on the other hand, the gap is relatively small, so that the pressure applied by thepre-tightening band 5 to thepre-tightening piece 4 can maximally deform thepre-tightening piece 4 along the circumferential direction of thescrew rod 1, and the deformation of thepre-tightening piece 4 along the axial direction of thescrew rod 1 is reduced, because for the present embodiment, the purpose of eliminating the gap between themain nut 2 and thesub-nut 3 can be achieved through the deformation of thepre-tightening piece 4 along the circumferential direction of thescrew rod 1.

In addition, supplementary explanation is needed for the length of the arc-shaped hole 11-4 along the circumferential direction of thesleeve 11 in the present embodiment. Referring to fig. 1, the force-bearingkey 12 divides the arc-shaped hole 11-4 into two regions along the circumferential direction of thesleeve 11, wherein one region is embedded with thepre-tightening piece 4 and the other region is reserved for the movement of the force-bearingkey 12. The length of the region where thepretensioning sheet 4 is embedded along the circumferential direction of thesleeve 11 is required to accommodate the lowerarched pretensioning sheet 4 and also to enable thepretensioning sheet 4 to stretch and deform in the region; the size of the area reserved for the movement of the force bearing key 12 along the circumferential direction of thesleeve 11 is larger than the maximum distance of the force bearing key 12 along the circumferential direction of thesleeve 11. Therefore, the length of the arc-shaped holes 11-4 along the circumferential direction of thesleeve 11 should be greater than the maximum extension length of thepre-tightening piece 4 along the circumferential direction of thesleeve 11 plus the width of the bearingkey 12 along the circumferential direction of thesleeve 11 plus the maximum distance of the bearing key 12 moving along the circumferential direction of thesleeve 11.

Referring to fig. 6-2, it should be further explained that thepretensioning sheet 4 of the present embodiment may adopt an arc structure with a regular structure in consideration of convenience of processing, taking thepretensioning sheet 4 of the present embodiment adopting an arc structure with a regular structure as an example, in order to improve the efficiency of converting the pressure applied by thepretensioning hoop 5 to thepretensioning sheet 4 into the deformation of thepretensioning sheet 4, for thepretensioning sheet 4 of the arc structure, if an included angle formed between a circle center corresponding to thepretensioning sheet 4 of the arc structure and top edges 4-2 at two ends of thepretensioning sheet 4 is defined as α, then α is 120-140 °, and the efficiency of eliminating the axial gap between thelead screw 1 and themain nut 2 and thesub nut 3 by thepretensioning sheet 4 being deformed by thepretensioning hoop 5 through thepretensioning sheet 4 of thepretensioning hoop 5 in this angle range of thepretensioning sheet 4 can be improved.

Example 2:

the double-nut ball screw pair according to the present embodiment is substantially the same as the double-nut ball screw pair according toembodiment 1 in structure, except that the double-nut ball screw pair according to the present embodiment is provided with a rib 5-4 (see fig. 7) at a portion where thepreload band 5 contacts thepreload piece 4, and the cross section of thepreload band 5 at this portion is formed to be the same as the cross section of thepreload band 5

Is formed in a groove shape. The beneficial effect of the improvement is that: the bow 4-1 of thepre-tightening sheet 4 is embedded into thepre-tightening hoop 5

In the groove, thepre-tightening sheet 4 is used for positioning thepre-tightening hoop 5 in the axial direction of thescrew rod 1 so as to prevent thepre-tightening hoop 5 from being axially displaced along thescrew rod 1 and being out of contact with thepre-tightening sheet 4. While the axial positioning of thepretensioning plate 4 with respect to thescrew 1 is given by the arc-shaped holes 11-4.

Thepre-tightening strap 5 of this embodiment can also be modified. Referring to fig. 7, thepre-tightening band 5 is formed by two half-ring-shaped left half-band 5-1 and right half-band 5-2 hinged together by a hinge 5-3. The beneficial effect of the improvement is that: the left half hoop 5-1 and the right half hoop 5-2 of thepre-tightening hoop 5 can rotate relatively by using the hinge 5-3, so that the opening of thepre-tightening hoop 5 can be opened to be larger during installation, and thepre-tightening hoop 5 is convenient to surround thesleeve 11 of theauxiliary nut 3.

Example 3:

for the double-nut ball screw pair ofembodiment 1 orembodiment 2, the bow-shapedintegral pretensioning sheet 4 has a simple structure, but has the following disadvantages: thepre-tightening band 5 is pressed on thepre-tightening piece 4 by centripetal pressure, wherein a part of the centripetal pressure is used for overcoming the elastic force of thepre-tightening piece 4 to enable the pre-tightening band to be straight, the rest centripetal pressure is used for pushing themain nut 2 and theauxiliary nut 3 to rotate around thescrew rod 1 in opposite directions respectively, namely only a part of the centripetal pressure of thepre-tightening band 5 on thepre-tightening piece 4 is used for pushing themain nut 2 and theauxiliary nut 3 to rotate around thescrew rod 1 in opposite directions respectively.

Referring to fig. 8 and 9, in order to improve the utilization rate of the centripetal pressure of thepre-tightening band 5 on thepre-tightening piece 4, thepre-tightening piece 4 of the double-nut ball screw pair provided by the embodiment is composed of a main part 4-3 and a branch part 4-5 which are rotatably connected. It should be noted here that in the case where thepretensioned sheet 4 of the present embodiment is composed of the main portion 4-3 and the branch portions 4-5 which are rotatably coupled, thepretensioned sheet 4 is deformed by the action of thepretensioned collar 5 through the rotation coupling between the main portion 4-3 and the branch portions 4-5, so that the main portion 4-3 and the branch portions 4-5 of the present embodiment are made of a material (e.g., tool steel) which is not necessarily made of an elastic material, but may be made of a material having high hardness and strength.

With respect to the detailed rotational engagement between the main portion 4-3 and the sub-portion 4-5, an alternative case is shown, see fig. 8, in which the main portion 4-3 is sheet-like, the main portion 4-3 has two opposite and parallel ends (in other words, the main portion 4-3 has two opposite and parallel edges, which are referred to herein as edges, the same applies hereinafter), one end is the top edge 4-2 of the main portion 4-3 and the other end is provided with a V-shaped groove 4-4 in the vicinity thereof, the V-shaped groove 4-4 is parallel to the top edge 4-2 of the main portion 4-3 and the groove bottom surface is a concave circular arc surface; the section 4-5 is in the form of a sheet, the section 4-5 having two opposite and parallel ends (in other words, the section 4-5 has two opposite and parallel edges, where said ends are referred to as edges, the same applies hereinafter), one end being the top edge 4-2 of the section 4-5 and the other end being provided with a cylindrical surface; the end part of the subsection 4-5 provided with the cylindrical surface is inserted into the V-shaped groove 4-4 of the main part 4-3, so that the subsection 4-5 and the main part 4-3 form an 'eight' shape, the subsection 4-5 and the main part 4-3 can rotate relatively, namely the size of the included angle between the sheet-shaped subsection 4-5 and the sheet-shaped main part 4-3 can be changed. In the working state, the included angle between the sheet-shaped subsection 4-5 and the sheet-shaped main part 4-3 can be selected to be 90-110 degrees, and thepre-tightening piece 4 in the angle range can improve the efficiency of eliminating the axial clearance between thescrew rod 1 and themain nut 2 and theauxiliary nut 3 by pressing thepre-tightening piece 4 through thepre-tightening hoop 5 to deform thepre-tightening piece 4. Referring to fig. 9, the top edge 4-2 of the main portion 4-3 and the top edge 4-2 of the branch portion 4-5, wherein one top edge 4-2 abuts against the hole wall 11-5 of the arc hole 11-4 and the other top edge 4-2 abuts against the side surface of the force bearing key 12 embedded in the key groove 2-1, the opening of the splay formed by the branch portion 4-5 and the main portion 4-3 of thepretension sheet 4 faces the cylindrical surface of themain nut 2. The side wall of the end of the main portion 4-3 adapted to mate with the section 4-5 (side wall here refers in particular to the surface of the end of the main portion 4-3 adapted to mate with the section 4-5 facing thepre-tightening band 5, the same applies hereinafter) abuts against thepre-tightening band 5; and the side wall of the main portion 4-3 adapted to abut thepre-tightening band 5 is a circular arc surface.

Referring to fig. 8, the main portion 4-3 and the branch portions 4-5 may be both of an arc-shaped structure or a flat-plate-shaped structure, and this embodiment is not limited thereto.

Referring to fig. 9, the V-shaped groove 4-4 of the main portion 4-3 of theprefastening plate 4 and the end of the branch portion 4-5 inserted into the V-shaped groove 4-4 are both located in the form of theprefastening band 5

The V-shaped groove is such that the end of the subsection 4-5 that is inserted into the V-shaped groove 4-4 cannot move out of the V-shaped groove 4-4 of the main part 4-3 in the axial direction of the cylindrical surface of the subsection 4-5.

Referring to fig. 8 and 9, theimproved pretensioning sheet 4 has the following beneficial effects: theimproved pretension sheet 4 is in a shape of a Chinese character 'ba' formed by the branch part 4-5 and the main part 4-3, and the distance between the top edge 4-2 of the branch part 4-5 and the top edge 4-2 of the main part 4-3 is enlarged by the relative rotation of the branch part 4-5 and the main part 4-3 instead of elastic deformation, so that the centripetal pressure of thepretension hoop 5 on thepretension sheet 4 can be completely used for pushing themain nut 2 and theauxiliary nut 3 to rotate around thescrew rod 1 in opposite directions without overcoming the elastic force of thepretension sheet 4.

Example 4:

referring to fig. 10, on the basis of the double-nut ball screw pair ofembodiment 1,embodiment 2, orembodiment 3, the force-bearingkey 12 of the double-nut ball screw pair provided in this embodiment may be improved on the basis of a common flat key, an embedded edge 12-1 integrally formed with the force-bearingkey 12 is disposed at an end of the force-bearingkey 12 in the length direction, and the height of the embedded edge 12-1 is slightly smaller than the depth of the key slot 2-1, so that an L-shaped step is formed between the embedded edge 12-1 and the force-bearingkey 12. When the bearingkey 12 is embedded into the key groove 2-1 of themain nut 2, the embedded edge 12-1 arranged on the bearingkey 12 is completely embedded into the key groove 2-1 (i.e. the embedded edge 12-1 of the bearingkey 12 is not exposed out of the key groove 2-1, and the embedded edge 12-1 is not exposed out of the key groove 2-1). Preferably, the two ends of the bearing key 12 in the length direction are both provided with embedded edges 12-1, and the bearing key 12 with the embedded edges 12-1 at the two ends is in a convex shape. The total length of the force bearing key 12 and the embedded edge 12-1 is greater than the axial width of the arc-shaped hole 11-4 along theauxiliary nut 3, and the length of the force bearing key 12 is slightly less than the axial width of the arc-shaped hole 11-4 along theauxiliary nut 3, so that the part of the force bearing key 12 protruding out of the embedded edge 12-1 can be placed in the arc-shaped hole 11-4 and can move along the circumferential direction of thesleeve 11 in the arc-shaped hole 11-4 (see fig. 1 and 5). Referring to fig. 3, the key groove 2-1 formed on the outer peripheral surface of themain nut 2 along the axial direction of themain nut 2 extends to the end surface of themain nut 2 on one side of theauxiliary nut 3, and the length of the key groove 2-1 along the axial direction of themain nut 2 is greater than the total length of the force bearing key 12 plus the embedded edge 12-1, so that the key groove 2-1 can accommodate the force bearing key 12 with the embedded edge 12-1. The beneficial effect of the improvement is that: referring to fig. 3, 4 and 5, the embedded edge 12-1 embedded in the key groove 2-1 is covered by the wall of thesleeve 11 around the arc-shaped hole 11-4, so that the force-bearingkey 12 cannot move out of the key groove 2-1 along the radial direction of the main nut 2 (in other words, the force-bearingkey 12 is radially positioned in the key groove 2-1).

Referring to fig. 3, 4 and 5, when the bearing key 12 with the embedded edge 12-1 is installed, the part of the bearing key 12 protruding out of the embedded edge 12-1 is inserted into the arc hole 11-4 from the circular hole of thesleeve 11, then the cylindrical surface of themain nut 2 is inserted into the circular hole of thesleeve 11, when the cylindrical surface of themain nut 2 is inserted into the circular hole of thesleeve 11, the position of the part of the bearing key 12 protruding out of the embedded edge 12-1 in the arc hole 11-4 needs to be adjusted, the bearingkey 12 is aligned with the key slot 2-1, and when the cylindrical surface of themain nut 2 is inserted into the circular hole of thesleeve 11, the bearing key 12 with the embedded edge 12-1 is also inserted into the key slot 2-1.

In light of the foregoing description of the preferred embodiment of the present invention, many modifications and variations will be apparent to those skilled in the art without departing from the spirit and scope of the invention. The technical scope of the present invention is not limited to the content of the specification, and must be determined according to the scope of the claims.

In the description of the present invention, it is to be understood that the terms indicating an orientation or positional relationship are based on the orientation or positional relationship shown in the drawings only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or the orientations or positional relationships that the products of the present invention are conventionally placed in use, and are only used for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," "third," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance.

Furthermore, the terms "horizontal", "vertical", "overhang" and the like do not imply that the components are required to be absolutely horizontal or overhang, but may be slightly inclined. For example, "horizontal" merely means that the direction is more horizontal than "vertical" and does not mean that the structure must be perfectly horizontal, but may be slightly inclined.

In the present invention, unless otherwise expressly stated or limited, the first feature may be present on or under the second feature in direct contact with the first and second feature, or may be present in the first and second feature not in direct contact but in contact with another feature between them. Also, the first feature being above, on or above the second feature includes the first feature being directly above and obliquely above the second feature, or merely means that the first feature is at a higher level than the second feature. A first feature that underlies, and underlies a second feature includes a first feature that is directly under and obliquely under a second feature, or simply means that the first feature is at a lesser level than the second feature.

Claims (10)

1. A double-nut ball screw pair is characterized by comprising: the screw rod (1), a main nut (2) and an auxiliary nut (3) are sleeved on the screw rod (1) in series; wherein

The end part of the main nut (2) facing the auxiliary nut (3) is provided with a cylindrical surface which is coaxial with the axis of the main nut (2); a key groove (2-1) is formed in the outer peripheral surface of one side, facing the auxiliary nut (3), of the main nut (2) and along the axial direction of the main nut (2); a bearing key (12) is embedded in the key groove (2-1);

a sleeve (11) which is integrally formed with the auxiliary nut (3) is arranged on one side of the auxiliary nut (3) facing the main nut (2); the sleeve (11) is provided with a round hole which is coaxial with the axis of the auxiliary nut (3); an arc-shaped hole (11-4) is formed in the sleeve (11), and two hole walls (11-5) of the arc-shaped hole (11-4) along the circumferential direction of the sleeve (11) are parallel to the axis of the sleeve (11);

the sleeve (11) is suitable for being sleeved on a cylindrical surface of the end part, facing the auxiliary nut (3), of the main nut (2) and forming a running fit, and after the sleeve (11) is sleeved with the main nut (2), the part, protruding out of the key groove (2-1), of the bearing key (12) along the radial direction of the lead screw (1) is suitable for being embedded into the arc-shaped hole (11-4), and the bearing key (12) is suitable for moving in the arc-shaped hole (11-4) along the circumferential direction of the sleeve (11);

a pre-tightening piece (4) is also embedded in the arc-shaped hole (11-4), and the pre-tightening piece (4) is of an arch structure; the arch back (4-1) of the pre-tightening sheet (4) is back to the arc-shaped hole (11-4); one end part of the pre-tightening piece (4) along the circumferential direction of the sleeve (11) is suitable for abutting against one hole wall (11-5) of the arc-shaped hole (11-4), and the other end part of the pre-tightening piece (4) along the circumferential direction of the sleeve (11) is suitable for abutting against the outer side wall of the force bearing key (12); the hole walls (11-5) of the arc-shaped holes (11-4) which are suitable for being propped against the two end parts of the pre-tightening sheet (4) along the circumferential direction of the sleeve (11) and the outer side walls of the bearing keys (12) are in a relative distribution relation; and

the periphery of the sleeve (11) is also provided with a pre-tightening hoop (5) in a surrounding manner, the pre-tightening hoop (5) is of an annular structure with an opening, and the pre-tightening hoop (5) is suitable for being pressed against the pre-tightening sheet (4); and a threaded connecting piece consisting of a bolt and an adjusting nut (6) is arranged at an opening of the pre-tightening hoop (5).

2. The double nut ball screw pair according to claim 1, wherein a slight clearance exists between both ends of the preload disc (4) in the axial direction of the sleeve (11) and both hole walls of the arc-shaped hole (11-4) in the axial direction of the sleeve (11).

3. The double nut ball screw pair according to claim 1, wherein a pair of said keyways (2-1) are provided on said main nut (2), and correspondingly, a pair of said arcuate holes (11-4) are provided on said sleeve (11); and

the double-nut ball screw pair comprises a pair of bearing keys (12) and a pair of pre-tightening pieces (4).

4. The double nut ball screw pair according to claim 1, wherein a pair of flanges (5-4) adapted to abut against both end portions of the preload sheet (4) in the axial direction of the sleeve (11) are provided at a portion where the preload ring (5) contacts the preload sheet (4), respectively, so that the cross section of the portion where the preload ring (5) contacts the preload sheet (4) is formed in a channel shape of "╔ ╗".

5. The double nut ball screw pair according to any one of claims 1 or 4, wherein said pre-clamping band (5) comprises a left half band (5-1) and a right half band (5-2) which are hinged together by a hinge (5-3) and are each in a semi-annular configuration.

6. The double nut ball screw pair according to any one of claims 1 or 4, characterized in that said pretensioning sheet (4) comprises a main portion (4-3) and a branch portion (4-5) which are rotationally fitted to form an arch.

7. The double nut ball screw pair according to claim 6, characterized in that a V-shaped groove (4-4) is provided at the end of the main portion (4-3) adapted to mate with the sub portion (4-5), and the bottom of the V-shaped groove (4-4) is a concave arc surface;

the end part of the subsection (4-5) which is suitable for being matched with the main part (4-3) is provided with a cylindrical surface which is suitable for being matched with the groove bottom of the V-shaped groove (4-4) in a rotating way.

8. The double nut ball screw pair according to claim 7, characterized in that the side wall of the end of the main portion (4-3) adapted to mate with the subsection (4-5) abuts against the pre-tightening ferrule (5); and

the side wall of the main part (4-3) which is suitable for being abutted to the pre-tightening hoop (5) is a circular arc surface.

9. The double-nut ball screw pair according to claim 1, characterized in that the end part of the force bearing key (12) in the length direction is provided with an embedded edge (12-1) which is integrally formed with the force bearing key (12), and the height of the embedded edge (12-1) is slightly smaller than the depth of the key groove (2-1) of the main nut (2);

the key groove (2-1) formed along the axial direction of the main nut (2) extends to the end face, facing the auxiliary nut (3), of the main nut (2), and the length of the key groove (2-1) along the axial direction of the main nut (2) is greater than the total length of the force bearing key (12) plus the embedded edge (12-1); the total length of the force bearing key (12) and the embedded edge (12-1) is greater than the axial width of the arc-shaped hole (11-4) along the auxiliary nut (3), and the length of the force bearing key (12) is slightly less than the axial width of the arc-shaped hole (11-4) along the auxiliary nut (3);

the embedded edge (12-1) is suitable for being completely accommodated in the key groove (2-1) and is covered by the wall of the sleeve (11) around the arc-shaped hole (11-4), and the part of the force bearing key (12) protruding out of the embedded edge (12-1) is suitable for being embedded into the arc-shaped hole (11-4).

10. The double-nut ball screw pair according to claim 9, wherein both ends in the length direction of the bearing key (12) are provided with embedded edges (12-1).

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