US3664435A - Hydraulic hammer with automatic stopping action - Google Patents

Abstract

An improved hydraulic hammer assembly including an automatically operable system for connecting the inlet to the outlet and bypassing the control system of the hammer when the hammer moves past a predetermined point as when the work performing element of the assembly is not in contact with the work. In the exemplary embodiment, a bypass conduit extends from the inlet to the outlet and is normally closed by a valve. When the hammer does not move past the position where it would normally encounter the tool, the application of fluid under pressure to first and third surfaces of the valve maintains the valve closed notwithstanding the application of pressure to a second surface thereon in opposed hydraulic relation to the first and third surfaces. However, when the hammer moves past the position mentioned above, the third surface on the valve is vented to the outlet and the application of fluid under pressure to the second surface causes the valve to open to establish a bypass flow path for the hydraulic fluid which avoids entirely the control system used to control reciprocation of the hammer.

Description

United States Patent [151 3,664,435

Klessig May 23, 1972 [54] HYDRAULIC 1 il' =-l R WITH: Primary Examiner-Ernest R. Purser AUTOMATIC SOPPING ACTION Attorneyl-lofgren, Wegner, Allen, Stellman & McCord [72] Inventor: Ernest F. Klessig, Racine, Wis [57] ABSTRACT Assign: Worthington corpofation "8f An improved hydraulic hammer assembly including an auto- Qompmr and Engme lmemm'onal matically operable system for connecting the inlet to the outsmn) Holyoke, Mass let and bypassing the control system of the hammer when the [22] Filed: N0 9, 1970 hammer moves past a predetermined point as when the work performing element of the assembly is not in contact with the pp 87,965 work. In the exemplary embodiment, a bypass conduit extends from the inlet to the outlet and is normally closed by a valve. 52] us. Cl ..173/17, 91 /220, 173/134 when the hammer Past the Q P" 51 lm. Cl ..B25d 9/18 wuld many amount" the ml, the aPPhcmm fluld [58] Field of Search 173/16 17; 91/220, 235 u der pressure to first third surfaces of the valve mamtains the valve closed notwithstanding the application of pressure to a second surface thereon in opposedhydraulic relation 56 References Cited to the first and third surfaces. However, when thehammer 1 moves past the position mentioned above, the third surface on UNITED STATES PATENTS the valve is vented to the outlet and the application of fluid under pressure to the second surface causes the valve to open 2,837,317 6/1958 l-lulshlzer ..l73/17 to establish a bypass fl path f the hydraulic fl id which 3,207,043 1965 y 173/17 X avoids entirely the control system used to control reciproca- 3,399,602 9/1968 Klessig et a1 ..9l/235 tion fth hammer 8 Claims, 2 Drawing Figures 68'l I III 54 56 62 2 76 J 4 72 inI81 70 44 l6 7 52 l t I 4l2 92 45l42 A3293 I 50 I 4; 96 9 84 66HO I02 r l 86 I08 ll lO6 7 05 p4 7 aSHEET 2 OF 2 FIGZ BACKGROUND OF THE INVENTION Hydraulic hammers are now available to do work as efficiently and more economically than air hammers and without the high noise level. Manually controlled hydraulic hammers include a control valve for controlling operation. Frequently, a hydraulic hammer. will be mounted on a boom or other support and moved relative to the work such as concrete or the like. Operation of the boom requires attention of the operator and rather than also require attention of the operator to operate a control valve for the hammer, it is preferable to have the hammer operate automatically dependent on its engagement with the work. This ensures that the hammer will only operate when engaging the work and avoids unnecessary vibrations.

It has been suggested that the problem be overcome by the use of valve channels on the hammer which will permit fluid under pressure from the inlet in passing through the control valve to flow about the hammer to an outlet when the hammer descends beyond a predetermined point in the bore as, for example, when the tool is suspended from its mounting means at the end of the bore due to the fact the tool is not in contact with the work. 1

One difficulty with the foregoing approach is that the machining of the valve channels on the hammer is a relatively costly operation. A second difiiculty is that such an approach does not employ a positive bypass of the hammer control system and the system may be rendered ineffective if the valve channels, for any reason, become clogged.

SUMMARY OF THE INVENTION It is the principal object of the invention to provide a new and improved hydraulic hammer including means for automatically terminating operation of the hammer when the hammer descends beyond a predetermined point within a casing bore, as when the tool associated therewith is no longer in engagement with the work.

The exemplary embodiment accomplished the foregoing object by means of a bypass conduit within the hammer casing extending from the inlet directly to the outlet. A bypass valve normally closes the bypass conduit and includes three pressure sensitive surfaces. The first two are associated with the inlet and are hydraulically opposed while the third is hydraulically parallel to the first and will be in fluid communication with the inlet whenever the hammer has not moved beyond the position mentioned previously. The three surfaces are arranged so that when inlet pressure is applied against the first and third surfaces, the bypass valve will be closed while when inlet pressure is applied only against the first and second surfaces, the bypass valve will be opened.

Fluid communication between the third surface and the inlet is normallv established through the bore in which the hammer reciprocates by means of a hammer shank having a lesser diameter than the inside diameter of the bore. Fluid communication between the third surface and the inlet may be precluded when an end portion of the hammer, which also serves as a piston, and which has a diameter equal to that of the bore, descends below a predetermined point in the bore as when not restricted in movement by the tool and blocks the fluid path mentioned previously. At the same time, a reduced diameter portion on the hammer used for other valve purposes in conjunction with a control valve which controls the reciprocation of the hammer vents the third surface to the outlet thereby permitting the bypass valve to open.

Other objects and advantages of the invention will become apparent from the following specification taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation, with parts shown in section, of a hydraulic hammer made according to the invention with the elements shown in one position wherein the bypass valve is closed; and

FIG. 2 is a side elevation, with parts shown in section with the elements in the position wherein the bypass valve is opened.

I "DESCRIPT ION OF THE PREFERRED EMBODIMENT An exemplary embodiment of a hydraulic hammer made according to the invention is illustrated in FIGS. I and 2 and is seen to include a casing, generally designated 10, having acentral bore 12 therein. Disposed within thebore 12 for reciprocation therein is a hammer element, generally designated 14, having an upper valve end including an annular reduceddiameter portion 16 and a pressureresponsive piston 18. Thehammer element 14 also includes a lower, enlargedhammer 20 which is disposed within an enlargeddiameter portion 22 of thebore 12.

Secured to the lower end of thecasing 10 is atool mount 24 having acentral bore 26 receiving amovable tool 28 which is disposed to be struck by thehammer 20 and which has a lower, work performing end (not shown). Alternatively, that portion of thetool 28 illustrated could be an anvil having its lower end operatively associated with a selected tool to be used in conjunction with the hammer. For example, the lower end of such an anvil may ride on the upper end of the tool. Thetool 28 includes akey way 30 and akey 32 which extends through thetool mount 24 and thekey way 30 to restrict the movement of thetool 28 within thetool mount 24 to the length of thekey way 30.

Thecasing 10 includes aninlet 34 which may be connected to any suitable source of hydraulic fluid under pressure to serve as a source of energy for reciprocating thehammer 20 within thecasing 10 to impart energy to thetool 28. In fluid communication with the inlet is aconventional accumulator 36. Thecasing 10 further includes anoutlet 38 and asecond accumulator 40 in fluid communication with theoutlet 38.

Aport 42 transverse to thebore 12 in thecasing 10 and in fluid communication with theinlet 34 is arranged to permit the application of fluid under pressure to alowermost surface 44 of thepiston 18 of thehammer element 14. As will be seen, this application of fluid under pressure serves to move thehammer element 14 upwardly in thebore 12 for its return stroke. A series ofsmall grooves 45 extend upwardly partially to theport 46 from theport 42 for purposes to be seen.

Aport 46 normally in fluid communcation with theport 42 through thebore 12 and reduceddiameter portion 16 provides fluid under pressure to a hydraulically operated control valve spool, generally designated 50, which is operative to control the reciprocation of thehammer element 14 within thebore 12. Thespool 50 includes a reduceddiameter portion 52. Thespool 50 is shiftable within abore 54 to a first position (illustrated in FIG. 1) wherein fluid under pressure from theinlet 34 passing through theport 42 and theport 46 is fed along the reduceddiameter portion 52 to the upper end of thebore 12 via aconduit 56 in communication with both thebore 54 and thebore 12 and applied to anupper surface 58 on thepiston 18 of thehammer element 14. Thesurface 58 is larger than thesurface 44 so that when fluid under pressure is applied to the former, notwithstanding the fact that fluid under pressure is also applied to the latter, thehammer element 14 will be driven downwardly to strike thetool 28.

A second position of thespool 50 within thebore 54, shown in FIG. 2, is one wherein thespool 50 is shifted upwardly from the position shown in FIG. 1 and wherein an enlargedlower end 60 blocks off the path of fluid under pressure from theinlet 34 to the upper end of thebore 12 while an enlargedupper end 62, in conjunction with the reduceddiameter portion 52 permits fluid in the upper end of the bore above thesurface 58 to exit to theoutlet 38 via aconduit 64. Interposed between theconduit 64 and theoutlet 38 and hydraulically prior to the point of connection of theaccumulator 40 to theoutlet 38 is a restriction ororifice 65 for purposes to be seen.

When thespool 50 is in the just-mentioned position, the fact that thesurface 58 is subjected to outlet pressure while thesurface 44 is subjected to inlet pressure will cause the hammer to move upwardlv for its return stroke.

Positioning of thespool 50 is controlled by a differential pindevice including pins 66 in the lowermost end of thespool 50 andpins 68 at the opposite end thereof. Thepins 66 have a lesser effective area than thepins 68 and are continuously subjected to inlet pressure. Thepins 68 are intermittently subjected to inlet pressure dependent upon the position of thehammer 14 within thebore 12 and when such is the case, thespool 50 will be driven by thepins 68 to the position shown. When such is not the case, thepins 68 will drive thespool 50 upwardly to the second-mentioned position above. For a more detailed statement of the operation and specific construction of the differential pin device, reference may be had to U.S. Pat. No. 3,399,602 to Klessig et al., the details of which are herein incorporated by reference.

As mentioned previously, one of the difficulties encountered in the operation of hvdraulic hammers is variations in the frequency of operation principally due to varying back pressure. Specifically, the rate of return of the hammer element during the return stroke will be generally dependent upon the ratio of the area of thesmaller surface 44 and the pressure supplied thereto to the area of thelarger surface 58 and the pressure applied thereto. Since, during return, the latter surface is subjected only to outlet pressure, an increased back pressure will cause a slower rate of return than would be the case with little or no back pressure present. Accordingly, the exemplary embodiment of the invention includes means by which the back pressure against thesurface 58 during the return stroke of thehammer element 14 is maintained constant so that cycling frequency will be constant.

Specifically, a restriction of constant size is located in the flow path from the upper end of thebore 12 to theoutlet 38 and which is established when thevalve 50 is in the second position mentioned above. More particularly, the restriction is in the form of a venturi, generallv designated 70 and carried on the upper end of the reduceddiameter portion 52 of thespool 50. Theventuri 70 is generally defined by aland 72 having a diameter less than the diameter of thebore 54 and greater than that of the reduceddiameter portion 52; an upstream taperedshort side 74; and a downstream taperedlong side 76. That is, the longitudinal extent of theupstream side 74 of theland 72 is less than the longitudinal extent of thedownstream side 76.

When thespool 50 is moved upwardly to the second-mentioned position, the same in conjunction with aportion 78 of thebore 54 interposed between theconduit 64 define an annular venturi. The annular venturi effectively isolates the pressure in theconduit 56 from pressure variations normally encountered in thereturn conduit 64.

It should be specificallv noted that while the exemplary embodiment employs a venturi on thespool 50, the same could be located at any one of a variety of downstream points in fluid communication with theoutlet 38. However, because the casing is generally formed as a casting and the various conduits contained therein are frequently defined by bores, the forming of a restriction in one of the conduits would require a rather complex machining or casting operation. In contrast, the formation of theventuri 70 on thespool 50 may be accomplished relatively easily during the formation of the reduceddiameter portion 52 thereon.

The exemplary embodiment further includes abypass conduit 80 which extends between theinlet 34 and theoutlet 38 and which is normally closed by a bypass valve, generally designated 82. Thebypass valve 82 is mounted for reciprocation within abore 84 in thecasing 10. One end of thebore 84 is closed by aplug 86 which serves to position aspring 88 in arecess 90 formed in the body of thevalve member 82 to bias thevalve member 82 against aseat 92 surrounding thebypass conduit 80 as shown in FIG. 1.

Thebypass valve 82, intermediate its ends, includes a reduceddiameter portion 93 which normally permits fluid under pressure to flow from theinlet 34 to theport 42 for use in driving the hammer in the manner mentioned previously.

Thebypass valve 82 further includes a pair of pressureresponsive surfaces 94 and 96 with thesurface 94 being larger than thesurface 96. The recess terminates in a third pressuresensitive surface 98 on thevalve 82. The arrangement is such that the combined areas of thesurfaces 96 and 98 is greater than the area of thesurface 94 but thesurface 94 is greater in size than thesurface 96 alone. More particularly, thesurfaces 94, 96, 98 and thespring 88 act such that when inlet pressure is applied against thesurface 96 and the surface 94 (as will always be the case) and is applied to the surface 98 (as will usually be the case) thevalve 82 will be in the position shown in FIG. 1. However, when inlet pressure is not applied to thesurface 98, the valve will shift downwardly to the position shown in FIG. 2 to open thebypass 80 whereupon fluid under pressure from theinlet 34 will flow directly to theoutlet 38 bypassing entirely thecontrol valve 50. As a result, reciprocation of the hammer element will cease.

Returning to FIG. 2, fluid under pressure from theinlet 34 is normally applied to thesurface 98 via theport 42 and asection 100 of thebore 12 interconnecting theport 42 and aport 102. Thebore section 100 is of slightly greater diameter than the shank of thehammer element 14 but, for purposes to be seen, is of the same diameter as the diameter of thepiston 18.

Referring now to FIG. 2, the relief of fluid pressure against thesurface 98 so as to permit thevalve 82 to open for bypass purposes is accomplished by means of aport 104 in the bottom of astationary sleeve 106 embracing the shank of thehammer element 14. Also included are a series of small grooves extending upwardly a short distance from theport 104 to permit the establishment of fluid communication to theport 104 through thebore section 100 slightly before the reduced diameter portion moves to the u per boundary of theport 104. Achannel 108 is in fluid communication with theport 104 and abore 110 which empties into thehollow center 112 of thespool 50. From thehollow center 112, fluid may flow through aradial bore 114 in the uppermost end of thespool 50 to theconduit 64 to theoutlet 38. The arrangement is such that when thehammer element 14 has been driven downwardly past a position wherein it would normally encounter thetool 28 and not yet has encountered the tool as shown in FIG. 2, the side of thepiston 18 will enter thebore portion 100 thereby blocking fluid communication between theinlet 34 via theport 42 to thesurface 98. Simultaneously, the reduceddiameter portion 16 on thehammer element 14 will establish fluid communication between theport 102 and theport 104 through thegrooves 105 thereby permitting the fluid under pressure bearing against thesurface 98 to flow to theoutlet 38 via the path mentioned previously.

This relieving of the pressure against thesurface 98 will cause the inlet pressure to shift thevalve 82 downwardly thereby permitting fluid from theinlet 34 to flow directly to theoutlet 38 via thecontrol valve 50. Furthermore, the presence of theorifice 65 in the return line will, when theaccumulator 40 dumps, cause a largeback pressure area 58 of thepiston 18 through theport 64, theventuri 70 and theport 56 to tend to keep the hammer in its down position. Also, thegrooves 45 permit flow of fluid from thepressure port 42 into the upper portion of thebore 12 to tend to fill the cavity caused by cavitation as thepiston 18 cuts off flow through theport 46 during downward movement.

As a result of the foregoing, reciprocation of thehammer 14 will cease. It will therefore be apparent that whenever the tool is at a predetermined position within itsbore 26 and lower than the desired position, as for example, when it is not bearing against work, the hammer will automatically cease to operate.

From the foregoing, it will be appreciated that a hydraulic hammer made according to the invention possesses a number of significant advantages over those heretofore known. For example, a positive bypass is provided as opposed to one wherein the hydraulic fluid will flow through a control system for the hammer. Secondly, the exemplary construction does not require any special machining operations on the hammer element. Specifically, the reduceddiameter portion 16 on the hammer element, which is operative to relieve pressure against thethird surface 98 of thecontrol valve 92 when hammer reciprocation is to cease would normally be employed in the hammer in any event for controlling the application of hvdraulic fluid to thelarge piston surface 58. It is therefore believed apparent that the invention provides an improved hammer of economical construction and which is positive in its operation for ceasing, automatically, the reciprocation of the hammer when the same has moved beyond a predetermined point in the bore.

I claim:

1. A hydraulic hammer comprising:

a casing having a bore;

a hammer received within said bore for reciprocating movement therein;

a tool adjacent one end of the bore and normally positioned to be struck by said hammer, said tool being movably mounted and movable to a position wherein it cannot be struck by said hammer;

a hydraulic fluid inlet in said casing;

a hydraulic fluid outlet in said casing;

means, including a hydraulically operated control valve for intermittently directing hydraulic fluid from said inlet to the hammer to drive the same in one direction within said bore;

means for driving the hammer within said bore in a direction opposite said one direction; and

means associated with said inlet and said outlet and responsive to movement of the tool to said position thereof for directing hydraulic fluid from said inlet to said outlet in a flow path that bypasses said control valve.

2. A hydraulic hammer according toclaim 1 wherein said directing means includes a bypass conduit within said casing extending from said inlet to said outlet and a valve normally closing said bypass conduit.

3. A hydraulic hammer according toclaim 1 wherein said directing means comprises a bypass conduit within said casing extending from said inlet to said outlet, a valve member positioned to close said bypass conduit, said valve having a pair of opposed pressure sensing surfaces with one of said surfaces having a larger area than the other of said surfaces, said valve further including a third pressure sensitive surface hydraulically parallel to said other surface, said pair of surfaces being arranged with respect to each other and to said inlet and said bypass conduit so that said valve will be moved to open said bypass conduit whenever pressure is not applied to said third surface, and means for applying fluid under pressure to said third surface whenever said anvil is not in said position wherein it cannot be struck by said hammer.

4. A hydraulic hammer according to claim 3 wherein said means for applying pressure to said third surface includes conduit means on said hammer normallv establishing fluid communication between said inlet and said third surface and cooperating means within said casing for blocking said conduit means when said hammer moves within said bore past a portion wherein it would normally strike said tool.

5. A hydraulic hammer comprising:

a casing having a bore;

a tool movably mounted adjacent one end of a bore and normally positioned to be struck by a hammer;

a hammer received within said bore for reciprocating movement to a position wherein it would normally strike said tool;

a hydraulic fluid inlet in said casing;

a hydraulic fluid outlet in said casing;

means, including a hydraulically operated control valve for intermittently directing hydrualic fluid from said inlet to said hammer to drive the same towards said tool; and means associated with said inlet and said outlet and responsive to movement of said hammer past said position wherein it would normally strike said tool for directing hydraulic fluid from said inlet to said outlet in a flow path that bypasses said control valve.

6. A hydraulic hammer according to claim 5 wherein said directing means comprises a bypass conduit extending between said inlet and said outlet, a hydraulic operated bypass valve normally closing said bypass conduit and means for normally directing fluid under pressure from said inlet to said bypass valve to bias the same to a closed position, and means on said hammer for blocking the application of fluid under pressure from said inlet to said b pass valve when said hammer moves beyond the position at which it would normally strike said tool.

7. A hydraulic hammer according to claim 6 further including means on said hammer for directing fluid from said bypass valve to said outlet when said hammer moves beyond said position at which it would normally strike said too]; said bypass valve further including pressure responsive surface means in fluid communication with said inlet and responsive to the fluid under pressure to cause movement of said bypass valve to an open position when said hammer has moved beyond said position wherein it would normally strike said tool.

8. A hydraulic impact device having a casing having a bore, a hammer element reciprocable in said bore in a cycle between normal limit positions by controlled application of pressure fluid to opposed areas of the hammer, said casing having a pressure fluid inlet and a fluid outlet, a control valve for controlling the intermittent application of fluid to one of said areas of the hammer, a bypass passage in said casing connecting said inlet and outlet and bypassing said control valve, a bypass valve closing said bypass passage, and means, including a valve section on said hammer, responsive to movement of the hammer beyond a normal limit position to open said bypass valve and stop cycling of the hammer element.

Claims (8)

1. A hydraulic hammer comprising: a casing having a bore; a hammer received within said bore for reciprocating movement therein; a tool adjacent one end of the bore and normally positioned to be struck by said hammer, said tool being movably mounted and movable to a position wherein it cannot be struck by said hammer; a hydraulic fluid inlet in said casing; a hydraulic fluid outlet in said casing; means, including a hydraulically operated control valve for intermittently directing hydraulic fluid from said inlet to the hammer to drive the same in one direction within said bore; means for driving the hammer within said bore in a direction opposite said one direction; and means associated with said inlet and said outlet and responsive to movement of the tool to said position thereof for directing hydraulic fluid from said inlet to said outlet in a flow path that bypasses said control valve.

2. A hydraulic hammer according to claim 1 wherein said directing means includeS a bypass conduit within said casing extending from said inlet to said outlet and a valve normally closing said bypass conduit.

3. A hydraulic hammer according to claim 1 wherein said directing means comprises a bypass conduit within said casing extending from said inlet to said outlet, a valve member positioned to close said bypass conduit, said valve having a pair of opposed pressure sensing surfaces with one of said surfaces having a larger area than the other of said surfaces, said valve further including a third pressure sensitive surface hydraulically parallel to said other surface, said pair of surfaces being arranged with respect to each other and to said inlet and said bypass conduit so that said valve will be moved to open said bypass conduit whenever pressure is not applied to said third surface, and means for applying fluid under pressure to said third surface whenever said anvil is not in said position wherein it cannot be struck by said hammer.

4. A hydraulic hammer according to claim 3 wherein said means for applying pressure to said third surface includes conduit means on said hammer normally establishing fluid communication between said inlet and said third surface and cooperating means within said casing for blocking said conduit means when said hammer moves within said bore past a portion wherein it would normally strike said tool.

5. A hydraulic hammer comprising: a casing having a bore; a tool movably mounted adjacent one end of a bore and normally positioned to be struck by a hammer; a hammer received within said bore for reciprocating movement to a position wherein it would normally strike said tool; a hydraulic fluid inlet in said casing; a hydraulic fluid outlet in said casing; means, including a hydraulically operated control valve for intermittently directing hydrualic fluid from said inlet to said hammer to drive the same towards said tool; and means associated with said inlet and said outlet and responsive to movement of said hammer past said position wherein it would normally strike said tool for directing hydraulic fluid from said inlet to said outlet in a flow path that bypasses said control valve.

6. A hydraulic hammer according to claim 5 wherein said directing means comprises a bypass conduit extending between said inlet and said outlet, a hydraulic operated bypass valve normally closing said bypass conduit and means for normally directing fluid under pressure from said inlet to said bypass valve to bias the same to a closed position, and means on said hammer for blocking the application of fluid under pressure from said inlet to said bypass valve when said hammer moves beyond the position at which it would normally strike said tool.

7. A hydraulic hammer according to claim 6 further including means on said hammer for directing fluid from said bypass valve to said outlet when said hammer moves beyond said position at which it would normally strike said tool; said bypass valve further including pressure responsive surface means in fluid communication with said inlet and responsive to the fluid under pressure to cause movement of said bypass valve to an open position when said hammer has moved beyond said position wherein it would normally strike said tool.

8. A hydraulic impact device having a casing having a bore, a hammer element reciprocable in said bore in a cycle between normal limit positions by controlled application of pressure fluid to opposed areas of the hammer, said casing having a pressure fluid inlet and a fluid outlet, a control valve for controlling the intermittent application of fluid to one of said areas of the hammer, a bypass passage in said casing connecting said inlet and outlet and bypassing said control valve, a bypass valve closing said bypass passage, and means, including a valve section on said hammer, responsive to movement of the hammer beyond a normal limit position to open said bypass valve and stop cycling of the hammer element.

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