US3764172A - Latch assembly - Google Patents

Abstract

A latch assembly for a door swingable towards and away from a doorjamb comprising a pair of mechanically engageable latch means mounted on the doorjamb and movable relatively between an engaged, mechanically latched position and an unlatched position. Permanent magnet means is provided for holding mechanically latched engagement between said latch means, and electromagnet means is provided having a polarity while energized opposing said permanent magnet for overcoming the holding force thereof to cause unlatching. One of said pair of latch means includes a pair of relatively movable members with one member being fixed to the jamb and the other member movable relative thereto. Said permanent magnet means is positioned in fixed magnetic relation to the fixed member and normally attracts said movable member to a latch holding position in contact therewith. Said electromagnet means is positioned to act through a lever and repel the movable latch member away from said latched position to said unlatched position when said electromagnet means is momentarily energized.

Description

[451 Oct. 9, 1973 1 LATCH ASSEMBLY [75] Inventor: Helmut Standke, Woodland Hills, Calif.

[73] Assignee: Consolidated Controls Corporation,-

Bethel, Conn. g

22 Filed: Oct. 29, 1971 211 Appl. No.: 193,782

521- vs. Cl. 292/15, 292/252 [51] Int. Cl. E056 5/00 [58] Field of Search 292/251.5, 252, 261,

[56] References Cited UNITED STATES PATENTS 3,658,370 4/1972 Wang.....' 292/201 3,635,511 l/l972 Waller 292/251.5 1,467,782 9/1923 Englu nd 292/15 2,348,967 5/1944 I Duby' 335/290 2,584,480 2/1952 Manting 292/25115 R23,636 3/1953 Mark et al. 292/251.5 X 2,888,290 5/1959 Pierce 292/251.5 3,312,492 4/1967 .Remhof 292/201 2,593,662 4/1952 Dickinson... 292/252 3,125,790 3/1964 Gaylord 292/15 X 3,475,715 10/1969 Venaleck 339/91 B X Primary Examiner-Richard E. Moore Attorney-Richard D. Mason et al.

57 ABSTRACT A latch assembly for a door swingable towards and away from a doorjamb comprising a pair of mechanically engageable latch means mounted on the doorjamb and movable relatively between an engaged, mechanically latched position and an unlatched position. Permanent magnet means is provided for holding mechanically latched engagement between said latch -means, and electromagnet means is provided having a polarity while energized opposing said permanent magnet for overcoming the'holding force thereof to cause unlatching. One of said pair of latch means includes a pair of relatively movable members with one member being fixed to the jamb and the other member movable relative thereto. Said permanent-magnet means is positioned in fixed magnetic relation to the fixed member and normally attracts said movable member to a latch holding position in contact therewith. Said electromagnet means is positioned to act through a lever and repel the movable latch member away from said latched position to said unlatched position when said electromagnet means is momentarily energized.

13 Claims, 7 Drawing Figures LATCH ASSEMBLY The present invention relates to a new and improved latch assembly wherein a permanent magnet force is used to hold or lock a pair of mechanically engageable latch members together in latched engagement. The magnetic latching assembly of the present invention is especially well suited for application in modern passenger aircraft for use in latching doors or closure panels on compartments carrying life support equipment, or the like. Because the doors or closure panels are only opened or unlatched under emergency conditions or during testing out of the aircraft systems, it is desirable that the latching assembly be extremely trustworthy and reliable in operation.

The latch assembly of the present invention comprises an improvement over the latch assembly shown and described in copending United States patent application Ser. No. 3,132, filed Jan. 15, 1970, now US. Pat. No. 3,658,370, and assigned to the same assignee as the present application. The latch assembly of the present invention is especially designed and adapted to withstand relatively high forces acting to open the door without unlatching, yet is readily unlatchable when desired by either electrical means or by manual means with very little force being required. The latch assembly employs a pair of mechanically engaged latching surfaces for maintaining the door latched in the closed position and employs a permanent magnet force for holding the latching surfaces of the latch members in latched engagement to hold the door closed. Opening of the latch assembly is normally accomplished by momentarily energizing an electromagnet to oppose the holding force of the permanent magnet, or, in the alternative, unlatching can be accomplished by manual means. In addition, the novel latch assembly of the present invention permits setting of the latch before closing of the door, with subsequent holding of the door in the closed, latched condition without requiring resetting of the latch assembly after the door is closed.

It is an object of the present invention to provide a new and improved latch assembly of the character described which employs a pair of mechanically engaged latching surfaces for holding a door in a closed, latched position with a permanent magnet force holding the pair of latching surfaces in latched engagement.

Another object of the present invention is to provide a new and improved latch assembly of the character described wherein unlocking of the engaged latch members may be accomplished either by electromagnetic means or by manual means.

Still another object of the present invention is to provide a new and improved latch assembly of the charac-' ter described which can be preset in a latched condition with the door open and, subsequently, the door may be closed and latched automatically without resetting of the latch or disengagement of the latched condition.

Another object of the present invention is to provide a new and improved latch assembly of the character describedwhich is low in cost, simple in construction, and extremely reliable and foolproof in operation.

Another object of the present invention is to provide a new and improved latch assembly of the character described which can be readily mass produced in volume quantities, yet which can meet present safety' requirements of reliability of operation in an environment wherein excessive forces may be applied tending to unlatch the mechanism.

Another object of the present invention is'to provide a new and improved latch assembly of the character described wherein permanent magnet means is provided for maintaining latched engagement between a pair of latching members and said permanent magnet means is mounted in a fixed position relative to one of the movable latching members.

The foregoing and other objects and advantages of the present invention are accomplished in an illustrated embodiment thereof which comprises a latch assembly especially adapted for use with a door swingable toward and away from a doorjam in an environment such as a compartment in an aircraft for containing lift support equipment. The latch assembly comprises a pair of mechanically engageable latch members which are mounted on the compartment door and jamb, respectively, and which are movable relatively between an engaged, mechanically latched position and an unlatched position. Permanent magnet means is provided for maintaining the mechanically latched engagement between the pair of latch means, and electromagnet means, having a polarity while energized opposing magnetic force of the permanent magnet means, is provided for unlatching the assembly so that the'compartmentdoor may be opened. One of the latch means includes a pair of relatively movable latch members, one being fixed relative to the doorjamb and the other movable relative thereto. Said permanent magnet means is in a fixed magnetic relation to the fixed member and normally attracts the other, movable member into a latch holding position in contact therewith. Electromagnet means is positioned for repelling the other movable member out of latching engagement away from contact with the fixed means, thereby releasing the latching engagement between the latch members and permitting opening of the door.

For a better understanding of the present invention, reference should be had to the following detailed description, in which:

FIG. 1 is aside elevational view of a typical aircraft seat including a compartment mounted in the back portion of the seat for containing life support equipment for the passengers on board the aircraft;

.FIG. 2 is an enlarged, fragmentary, sectional view taken on a plane through the life support compartment substantially along line 2-2 of FIG. 1 showing a latch assembly constructed in accordance with the features of the present invention in a latched condition;

FIG. 3 is a fragmentary, end, elevational view of the latching assembly looking in the direction of the arrows 3-3 of FIG. 2;

FIG. 4 is a fragmentary, sectional view of the latch assembly shown in a positionwherein a latch member on the door is being moved toward latching engagement with a latch member mounted on the compartment wall;

FIG. 5 is a fragmentary view similar to FIG. 2 illustrating the latch assembly in an unlatched condition wherein the compartment door may be opened;

FIG. 6 is a transverse, fragmentary, sectional view taken substantially along line 6-6 of FIG. 2; and

FIG. 7 isa transverse, fragmentary, sectional view similar to FIG. 6 but showing the unlatched position as taken along line 7-7 of FIG. 5.

Referring now, more particularly, to the drawings, in FIG. 1 therein is illustrated a typical aircraft seat indicated generally by the numeral and having a base orseat cushion 12 supported on the floor I4 of an aircraft or other vehicle. The seat includes an upstanding, slopedback portion 16 having an upper headrest 16a and the back portion is pivotally mounted on the seat orbase 12 for angular adjustment therewith in order to provide for comfort of the passengers in the aircraft. In order to provide for life support equipment such as an oxygen source and an oxygen mask for the passengers in case of an emergency, an enclosure or compartment, generally indicated as 18, is mounted in the back portion of the seat.

Thecompartment 18 includes afront wall 20, abottom wall 22, a pair ofsidewalls 24, and atop wall 26, and onesidewall 24 serves a doorjamb structure for aswingable compartment door 28 which is hingedly attached along its lower edge to thebottom wall 22, as shown in FIG. I. In normal conditions, thedoor 28 is positively latched in a closed position and forms a portion of the surface of theback portion 16 of the aircraft seat. However, in an emergency situation wherein oxygen is required, thedoor 28 is unlatched and pivots to the open position as shown by the arrow A (FIG. I), so that the interior of thecompartment 18 is readily accessible. Oxygen masks may be mounted on or secured to the inside surface of the door in a typical installation.

In accordance with the present invention, a new and improved latch assembly 30'is provided for positively latching and holding thedoor 28 in the closed position. The latch assembly normally is electrically activated to the unlatched condition for permitting thedoor 28 to open. If electrical actuation is not available, the door may be unlatched manually and opened. Manual opening is usually accomplished for servicing and inspection of the compartments one at a time on a seat-by-seat basis in an aircraft. Manual unlatching is accomplished by inserting a finger in between adjacent seats on the side of the seat backportions 16 in the direction indicated by the arrow B, as shown in FIG. 1, and pushing a manualunlatching tab 32 or by inserting a small tool into the interior of the compartment through an opening 22a in thewall 22 to operate anunlatching push rod 25. The actuatingtab 32 is formed on the outer end of alever 34 for releasing the latch mechanism to open the door.

In accordance with the present invention, thelatch assembly 30 includes alatching stem 36 supported in cantilever fashion on the inside of thecompartment door 28 adjacent the upper edge portion thereof. Thestem 36 extends inwardly into thecompartment 18 at the right angles to the door and includes an enlarged,washerlike base 37 which is backed up by a filler ofresilient material 39. Thefiller 39 is carried in adishlike annulus 40 having a circular aperture in the center thereof larger in diameter than the stem to permit limited lateral movement thereof. Thebaseplate 40 includes a pair ofmounting lugs 41 having openings therein to accommodate washer andnut assemblies 42 or other fasteners for securing the baseplate in place on the inside surface of the door.

The stem includes an enlarged ball-type,head portion 36a at is outer end, anintermediate stem portion 36b of reduced diameter, and a frustoconically taperedportion 36c which transitions between theportion 36b to the nominal diameter of the base portion of the stem,

as at 36d. Because thestem base 37 is backed up by theresilient filler 39, the stem is movable to a limited extent and the angle between the stem and the inside surface of thedoor 28 m'ay vary slightly. The enlarged diameter aperture in the mountingbase 40 permits limited flexure or movement of the stem as latching engagement is made or broken. The stem moves generally in an arcuate path, as indicated by the dotted line C in FIG. 1, as thecompartment door 28 is opened or closed and is adapted to cooperate with a relatively fixed, latching subassembly generally indicated as 44 (FIG. 2) which is secured to the compartmenttop wall 26 with mountingscrews 45, or other suitable fasteners, as best shown in FIG. 3.

In accordance with the present invention, the latchingsubassembly 44 includes abody 46 having a hollow,cylindrical sleeve 48 which is open at the end away from the door and which is partially closed at the opposite end by anannular end flange 50 having a frustoconically tapered, concave, central aperture for guiding thestem 36 axially into the bore of the sleeve. The minimum diameter of the'aperture defined by theannular flange 50 is larger than thehead portion 36a of the stem in order to permit free passage of the stem into and out of axial alignment inthesleeve 48.

Thelatch body 46 includes a mountingbase 52 having flange portions at the outer end which are apertured to receive thebolts 45 for fixedly mounting the body on thecompartment wall 26. The latch body is preferably integrally formed of strong, lightweight, molded plastic material, such as polycarbonate resin and is shaped to include an upstanding,bifurcated support bracket 56 having apivot pin 58 extended transversely through the outer end portion for pivotally supporting thelatch lever 34 intermediate its ends. The latch body is formed with a recess 60 (FIG. 3) in which is mounted apole piece 62 formed of readily magnetizable material, such as soft iron or the like. A bar-typepermanent magnet 64 is mounted in therecess 60 of the body with one side in contact with thepole piece 62, and the other sideof the permanent magnet contacts one leg of an L-shaped,coil supporting bracket 66 formed of soft iron or other readily magnetizable material. The L-shaped bracket includes a dependingleg 66 for supporting a cylindrical, soft iron armature orcoil core 68 on which is mounted an annular, electromagnetic coil indicated by the numeral 70. The electromagnetic coil is energized through a pair of color coded leads 72 in order to provide the proper magnetic polarity when the coil is energized. The coil may be provided with a diode or rectifier in series therewith for use with common aircraft power, such a I 15V, 400 Hz AC current, and the coil winding direction is chosen appropriately to achieve the desired magnetic polarity.

Thelatch lever 34 is preferably formed of lightweight, high strength material, such as aliminum, or the like, and is normally maintained in the latching position (as shown in FIG. 2) by magnetic force supplied by thepermanent magnet 64 which attracts alever armature 74 formed of magnetizable material, such as soft iron, mounted adjacent the lower end of the latch lever. When the latch lever is in the latched position, thelever armature 74 is in contact at its upper end with one end face of thepole piece 62, and the lower end of the armature is in contact with the exposed outer end of thecoil core 68. A complete magnetic circuit is provided from thepermanent magnet 64 through thepole piece 62,lever armature 74,coil core 68, and the L-shapedsupport bracket 66. Thecoil 70 is wound with a polarity so that when current is momentarily supplied through theleads 72, the magneto motive force developed is in direct opposition to the magnetic holding force developed by thepermanent magnet 64. The electromagnetic force from thecoil 70 is sufficiently strong relative to the permanent magnetic force supplied by themagnet 64 to cause thelever armature 74 to be repelled, and, with the help of aspring 91, moves outwardly away from thepole piece 62 andcoil core 68. When this occurs, the latch lever is pivoted about thepivot pin 58 to the unlatched position, as shown in FIG. 5. Pivoting of thelever 34 from the latched position of FIG. 2 to the unlatched position of FIG. 5 may also be accomplished manually, as previously de-' scribed, by actuation of thetab 32. Once thelatch lever 34 is in the unlatched position and thecoil 70 is subsequently de-energized, thepermanent magnet 64 does not provide sufficient magnetic pull on thelever armature 74 to relatch the lever, and normally it is desirable to manually reset the lever into the latched position.

From the foregoing, it will be seen'that thelatch lever 34 is normally maintained or held in the latched position by magneto motive force supplied by thepermanent magnet 64. When thecoil 70 is energized momentarily, a strong magneto motive force in opposition to the permanent magnet force is developed and this causes the lever to pivot to the unlatched position driven by the force of acoil spring 91 and transmitted via aplunger 84 andadjustment screw 86 to thelever 34. With the coil de-energized, when-it is desired to relatch thelever 34, thetab 32 is moved until thelever armature 74 is sufficiently close to thepole piece 62 to be attracted by the magneto motive force of thepermanent magnet 64. Preferably, thepole piece 62,permanent magnet 64, andcoil support bracket 66 are secured in position in thegroove o'r recess 60 in the lower portion of thebody 46 by means of suitable epoxy adhesive material. g r

Thelever armature 74 is secured onto aprojection 34a on the lower end of thelatch lever 34 by adish ed washer 76 in order to provide limited pivoting movement of the armature on the lever for good contact seating of the armature simultaneously against the facing ends of thepole piece 62 and thecoil core 68. The lever armature is allowed to swivel within limits in order to provide self-aligned seating contact against the pole piece and coil core end faces, as shown in FIG. 2.

In accordance with the present invention, direct mechanical latching engagement between thestem 36 and the latchingsubassembly 44 is provided by a plurality ofspherical latch balls 80 which are mounted at the forward end of thesleeve 48 inside theend flange 50. Theballs 80 are drilled with apertures therein and are mounted on a C-ring 82 (FIGS. 6 and 7) formed of spring steel wire which normally tends to expand the balls radially outwardly to engage the walls of the sleeve. When the C-ring 82 expands and theballs 80 move radially outwardly in the sleeve to the unlatch position shown in FIGS. 5 and 7, the internal clearance in the center of the ring of latch balls is sufficiently large to permit theenlarged head portion 360 of the stem to move freely into and out of thesleeve 48 through the aperture in theend flange 50. When the balls are moved radially inwardly around theintermediate portion 36b of the stem to the latching position, as shown in FIGS. 2 and 6, latching engagement between the balls and with theenlarged head portion 36a of thestem 36 will prevent withdrawal of the stem outwardly of thesleeve 48. In this manner, latching of thedoor 28 in the closed position is accomplished by mechanical means and the latching action thus provided is strong enough to resist acceleration and deceleration as much as 250 times that of gravity in a direction generally axially of the stem, tending to withdraw the stem from thesleeve 48, and as high as 300 times gravity in any other direction.

. In accordance with the present invention, a generally cylindrical, hollow,cam plunger 84 is mounted for axial sliding movement in thesleeve 48. The hollow cam plunger includes an outwardly extending stem 'portion 84a having avertical slot 85 formed therein. The

lever 34 extends through theslot 85 and normally intersects the longitudinal axis of the cam plunger at right angles in the latched position (FIG. 2). The rearward end of the hollow cam plunger is provided with an end wall having a threaded axial bore for receiving anadjustment setscrew 86 which limits the amount of angular displacement between thelatch lever 34 and the plunger, as best shown in FIG. 5. A cuplike biasing member87 having a hollow, cylindrical sidewall and an annular flange facing the flange50 is mounted in the bore of thecam plunger 84. The flange of the biasing member 87'is adapted to urge thelatch balls 80 towards theflange 50 of thesleeve 48. Theopen end of thecam plunger 84 is shaped with an inwardly convex frustoconically taperedfirst cam surface 88 which is adapted to cam' thelatch balls 80 radially inwardly toward the latching position (FIG. 2) as the cam plunger is moved longitudinally in thesleeve 48 from the unlatched position of FIG. 5 to the latched position of FIG. 2.

When the cam plunger is in the latched position, the balls are maintained radially inwardly in the latched position around the intermediate portion of thestem 36b by an internal bore surface 93 (FIGS. 2 and 6) of thecam plunger 84. The bore surface is slightly tapered (approximately 7) and is frustoconical in shape in order to compensate for friction and to aid in the release oftheplunger 84 whenthe mechanism is unlatched under load. In this latched position, the flanged end of the biasingmember 87 urges the balls toward theend flange 50 of the body and this force is supplied by acoil spring 91 mounted inside the bores of thecam plunger 84 andmember 87. Inthis position, thelatch lever 34 held by the holding force ofpermanent magnet 64 prevents further expansion of thebias spring 91.

When, however, the magnetic holding force is overcome by energization of thecoil 70, thespring 91 is effective to bias thecam plunger 84 from the latched position of FIG. 2 to the unlatched position shown in FIG. 5, and when this occurs, thefrustoconical cam surface 88 on the open end of thecam plunger 84 shifts longitudinally in the sleeve, permitting thelatch balls 80 to radially inwardly to the latched position of FIGS. 2 and 6. Resetting of thecam plunger 84 to the latched position may be accomplished while thedoor 28 is open or closed, and in the latter condition the latch balls are urged radially inwardly around the intermediate portion of the stern 36b, as shown in FIG. 2. If the compartment door is open when thecam plunger 84 is reset, the permanent magnetic holding force supplied by thepermanent magnet 64 through thepole piece 62,bracket 66, and thecoil core 68 holds thelever armature 74 in the latched position against the force of thebias spring 91. In this position, thelatch balls 80 are maintained in the latched position of FIG. 2. Subsequently, when the compartment door is closed, theenlarged head portion 360 of the stem is forced inwardly into thesleeve 48 in the direction of the arrow D (FIG. 4). As this occurs, thestem head 36a moves theballs 80 axially within the bore of the cam plunger against force of thespring 91 exerted on the biasingmember 87. During the axial movement of the balls, as the dooris closed, the balls are also permitted to move radially outwardly in the bore into an internal, annular recess 89 (FIG. 4), and in this position the head portion of thestem 36a passes by the balls until theintermediate portion 36b of reduced diameter is adjacent the balls in therecess 89.

After theenlarged head portion 360 of the stem passes by the ring of latch balls which are forced radially outwardly thereby, thespring 91 is effective to bias themember 87 toward theplunger 50 and urge theballs 80 axially toward the flange and inwardly around the intermediate portion of thestem 36b to the latched position. A second, frustoconically tapered, cam surface designated as 90 is spaced axially inwardly of theconvex cam surface 88 and has a slope in the opposite direction for effecting the aforedescribed action. Engagement of theballs 80 against thecam surface 90 drives the'balls radially inwardly into the latched position of FIG. 2, wherein the slightly tapered bore surface 93 (FlG. 6) maintains the latching engagement. From the foregoing, it will be seen that latchingassembly 30 may be reset when the door is either open or closed and, once reset, with the door open, the door can be subsequently closed and latching occurs automatically without necessitating further release and reset of the mechanism. Thespring 91 is of sufficient strength to move thecam plunger 84 to the unlatched position whenever thelever armature 74 is moved a slight distance away from the holding end face of the pole piece,

motive holding force and allowing thelever armature 74 to move away from the coil core and pole piece, because thespring 91 is then rendered effective to unlatch the lever permitting axial movement of thecam plunger 84 in thesleeve 48 and movement of thelatch balls 80 to the unlatched position.

The latchingassembly 30 of the present invention is extremely reliable and foolproof in operation and can be unlatched either manually or electrically. In addition, the latch can be reset with the door either open or closed and if reset while the door is open, subsequent closing of the door automatically effects latching and does not require further unlatching and resetting of the latch. The mechanical latching engagement be tween theenlarged head of thestem 36a and the locking balls is sufficiently strong to withstand extremely high forces in a direction tending tov open thedoor 28. The magnetic holding force of thepermanent magnet 64 is used for normally maintaining thelatch lever 34 in the latched position. The permanent magnet provides a magnetic holding force for securing the door in a closed position against opening forces applied to thestem 36 which are as high as 25 times the amount of the holding force at thelever armature 74.

While there has been illustrated and described a single embodiment of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes'and modifications while fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A latch assembly for a door swingable toward and away from a doorjamb, said latch assembly comprising a pair of mechanically e ngageable latch means mounted on said door and jamb, respectively, and movable relatively between an engaged mechanically latched position and an unlatched position, permanent magnet means for retaining said mechanically latched engagement between said latch means while in said latched position, electromagnet means having a polarity while energized opposing said permanent magnet means for overcoming the retaining force thereof for .unlatching movementof said latch means to said unlatched position pennitting said door to be opened, one of said latch means including a pair of relatively movable members, one member fixed relative to said jamb and the other movable relative thereto, said permanent able member including a lever mounted for pivotal movement relative to said fixed member toward and away from said permanent magnet, said permanent .magnetic force normally biasing said lever toward said latch holding position, said movable member including a latch subassembly connected to said lever and movable to engage and release said other latch means, said lever including a magnetic armature means engageable with said 'permanent magnet means and a pole face of said electromagnet means in said latch holding position. 2. The latch assembly of claim 1 wherein said subassembly includes spring means for biasing said lever away from said latch holding position against the magnetic holding force of said permanent magnet means. 3. The latch assembly of claim 1 wherein the other of said latch means includes an elongated stem supported at one end in cantilever fashion and an enlargement mounted adjacent the outer free end of said stem for latching engagement with said one latch means when in saidmechanically engaged latched position.

largement comprise-s a spherical ball mounted on said stem, said stem being laterally flexible adjacent said outer free end and movable toward and away from said one latch means upon opening and closing of said door into and out of latching engagement therewith.

5. The latch assembly ofclaim 3 wherein said fixed member comprises'socket forming means including a plurality of circumferentially spaced latching balls movable radially of the axis of said stem'into and out of latching engagement with said enlargement on said stern and means for moving said balls into and out of latching engagement with said enlargement.

6. The latching assembly of claim 5 wherein said socket forming means includes a hollow sleeve for containing said balls and a cam plunger mounted for axial sliding movement relative to said sleeve permitting radial movement of said balls in response to the axial position thereof, said permanent magnet means normally urging said plunger into an axial position wherein said balls are urged into latched engagement around said stem.

7. The latching assembly ofclaim 6 wherein the force exerted by said electromagnet means while energized is active to move said plunger into a second axial position permitting said balls to move radially outward out of latched engagement with said enlargement.

8. The latch assembly ofclaim 6 including a lever pivotally mounted with respect to said sleeve and connected to move said plunger therein, said permanent magnet means positioned to exert bias on said lever normally maintaining said plunger in said sleeve in a latching position urging said balls into latching engagement around said stem. v

9. The latch assembly of claim 8 wherein said lever carries a magnetic armature thereon and said electro magnet means includes a pole piece in magnetic circuit with said permanent magnet means, said lever armature adapted to magnetically interconnect one end of said pole piece and said permanent magnet means for holding said plunger in a latching position, said electromagnet means operable to repel said lever armature away from said pole piece upon energization to move .larged head on a free outer end and movable axially into and out of said sleeve through said opening for latching engagement therein; a plurality of retaining balls in said sleeve adjacent said flange for controlled latching engagement with saidenlarged head of said stem; a cam plunger slidable in said sleeve including a first surface for camming said balls inwardlytoward a latching position around said stem; a second oppositely sloping cam 'surface spaced axially of said first for urging said balls inwardly into said latching position, means for biasing said balls axially of said plunger toward said flange, and holding means including a permanent magnet for normally maintaining said plunger in a first axial positionrin said sleeve wherein said balls are urged inwardly intoa latching position around said stem whereby withdrawal of said stem from the socket is prevented by engagement between said balls and said enlarged head.

II. The latching assembly ofclaim 10 wherein said second cam surface defines a wall portion of an annular recess internally of said plunger for receiving said balls in an unlatched position permitting passage of said head thereby upon axial movement of said stem into said socket.

12. The latching assembly ofclaim 10 including electromagnet means having a polarity when energized opposing said permanent magnet for activating s'aid holding means to move said plunger axially in said socket to a ball releasing position wherein said balls are movable outwardly away from said stem.

13. The latching assembly ofclaim 10 wherein said plunger includes a third internal cam surface of gently tapered frustoconical shape for supporting said balls in latched position around said stem, said third cam surface compensating for friction between said stem head,

load is applied to unlatch said stem.

Claims (13)

1. A latch assembly for a door swingable toward and away from a doorjamb, said latch assembly comprising a pair of mechanically engageable latch means mounted on said door and jamb, respectively, and movable relatively between an engaged mechanically latched position and an unlatched position, permanent magnet means for retaining said mechanically latChed engagement between said latch means while in said latched position, electromagnet means having a polarity while energized opposing said permanent magnet means for overcoming the retaining force thereof for unlatching movement of said latch means to said unlatched position permitting said door to be opened, one of said latch means including a pair of relatively movable members, one member fixed relative to said jamb and the other movable relative thereto, said permanent magnet means in fixed magnetic relation to said fixed member and normally attracting said movable member to a latch holding position in contact therewith, said electromagnet means positioned to repel said movable member away from contact with said permanent magnet means to a latch releasing position when said electromagnet means is momentarily energized, said movable member including a lever mounted for pivotal movement relative to said fixed member toward and away from said permanent magnet, said permanent magnetic force normally biasing said lever toward said latch holding position, said movable member including a latch subassembly connected to said lever and movable to engage and release said other latch means, said lever including a magnetic armature means engageable with said permanent magnet means and a pole face of said electromagnet means in said latch holding position.

2. The latch assembly of claim 1 wherein said subassembly includes spring means for biasing said lever away from said latch holding position against the magnetic holding force of said permanent magnet means.

3. The latch assembly of claim 1 wherein the other of said latch means includes an elongated stem supported at one end in cantilever fashion and an enlargement mounted adjacent the outer free end of said stem for latching engagement with said one latch means when in said mechanically engaged latched position.

4. The latch assembly of claim 3 wherein said enlargement comprises a spherical ball mounted on said stem, said stem being laterally flexible adjacent said outer free end and movable toward and away from said one latch means upon opening and closing of said door into and out of latching engagement therewith.

5. The latch assembly of claim 3 wherein said fixed member comprises socket forming means including a plurality of circumferentially spaced latching balls movable radially of the axis of said stem into and out of latching engagement with said enlargement on said stem and means for moving said balls into and out of latching engagement with said enlargement.

6. The latching assembly of claim 5 wherein said socket forming means includes a hollow sleeve for containing said balls and a cam plunger mounted for axial sliding movement relative to said sleeve permitting radial movement of said balls in response to the axial position thereof, said permanent magnet means normally urging said plunger into an axial position wherein said balls are urged into latched engagement around said stem.

7. The latching assembly of claim 6 wherein the force exerted by said electromagnet means while energized is active to move said plunger into a second axial position permitting said balls to move radially outward out of latched engagement with said enlargement.

8. The latch assembly of claim 6 including a lever pivotally mounted with respect to said sleeve and connected to move said plunger therein, said permanent magnet means positioned to exert bias on said lever normally maintaining said plunger in said sleeve in a latching position urging said balls into latching engagement around said stem.

9. The latch assembly of claim 8 wherein said lever carries a magnetic armature thereon and said electromagnet means includes a pole piece in magnetic circuit with said permanent magnet means, said lever armature adapted to magnetically interconnect one end of said pole piece and said permanent magnet means for holding said plunger in a latching position, said electromagnet means operable to repel said lever armature away from Said pole piece upon energization to move said plunger to an unlatch position.

10. A latching assembly including a hollow sleeve having an inwardly directed annular flange at one end defining an axial opening; a latch stem having an enlarged head on a free outer end and movable axially into and out of said sleeve through said opening for latching engagement therein; a plurality of retaining balls in said sleeve adjacent said flange for controlled latching engagement with said enlarged head of said stem; a cam plunger slidable in said sleeve including a first surface for camming said balls inwardly toward a latching position around said stem; a second oppositely sloping cam surface spaced axially of said first for urging said balls inwardly into said latching position, means for biasing said balls axially of said plunger toward said flange, and holding means including a permanent magnet for normally maintaining said plunger in a first axial position in said sleeve wherein said balls are urged inwardly into a latching position around said stem whereby withdrawal of said stem from the socket is prevented by engagement between said balls and said enlarged head.

11. The latching assembly of claim 10 wherein said second cam surface defines a wall portion of an annular recess internally of said plunger for receiving said balls in an unlatched position permitting passage of said head thereby upon axial movement of said stem into said socket.

12. The latching assembly of claim 10 including electromagnet means having a polarity when energized opposing said permanent magnet for activating said holding means to move said plunger axially in said socket to a ball releasing position wherein said balls are movable outwardly away from said stem.

13. The latching assembly of claim 10 wherein said plunger includes a third internal cam surface of gently tapered frustoconical shape for supporting said balls in latched position around said stem, said third cam surface compensating for friction between said stem head, said balls and said plunger allowing said plunger to move toward a stem head releasing position when axial load is applied to unlatch said stem.

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