US3851922A

US3851922A - Hook latch

Info

Publication number: US3851922A
Authority: US
Inventors: R Mccoy
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1974-01-07
Filing date: 1974-01-07
Publication date: 1974-12-03
Anticipated expiration: 1991-12-03

Abstract

A latch for equipment cabinet doors adaptable for joining wall panels and like structures includes a cam having a hook mounted thereon for engaging a sill pin to latch the doors or structures. The latch further includes a trigger and a stop pin which engage shoulders on the cam to provide positive engagement and disengagement features to prevent malfunctioning of the latch hook during closing and opening, respectively. These features are set for proper operation before the latch can be disengaged during opening.

Description

United States Patent In] 3,851,922 McCoy Dec. 3, 1974 [54] HOOK LATCH FOREIGN PATENTS OR APPLlCATlONS 1 1 lnvfimofl Robert Gordon MCCOY, whiPPflny, 100,095 10/1940 Sweden 292/111 [73] Assignee: Bell Telephone Laboratories Primary EXamin@rRihard E- Moore Incorporated, Murray Hill, Attorney, Agent, or FIrm-A. D. Hooper [22] Filed: Jan. 7, 1974 Appl. No.: 431,032

[57] ABSTRACT A latch for equipment cabinet doors adaptable for joining wall panels and like structures includes a cam having a hook mounted thereon for engaging a sill pin to latch the doors or structures. The latch further includes a trigger and a stop pin which engage shoulders on the cam to provide positive engagement and disengagement features to prevent malfunctioning of the latch hook during closing and opening, respectively. These features are set for proper operation before the latch can be disengaged during opening.

5 Claims, 9 Drawing Figures PATENTEL BEE 31974 SHEEI 1 OF 2 PATENTEL

BEE W4 sum

2 or 2 HooK LATCH BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to latches and more particularly to a hook latch for doors of equipment cabinets and adaptable for joining wall panels and the like.

2. Description of the Prior Art Numerous latches of locks have been designed for latching the doors of equipment cabinets and the like. Many of these latches utilize an eccentric to operate a hook which engages a sill pin to thereby latch the doors. However, these existing latches have various limitations which reduce their-usefulness on equipment cabinets which are installed in publicly accessible locations and which require good security to prevent unauthorized entry into the cabinet. For example, many of the known latches include no positive engagement or disengagement features which insure proper operation of the latch. Even where a positive engagement feature is provided, such feature is readily nullified if the latch is not rotated to the fully open position during the opening cyclebecause this feature is set up only at the very end of the opening cycle and often requires substantial torque in existing latches. Latches not having a positive disengagement feature may fail to open properly if excessive resistance is encountered during the opening cycle. Furthermore, latches not having positive engagement features or in which the positive'engagement-feature is not activated because of insufficient opening rotation or torque may appear to close properly though, in fact not being engaged.

A further limitation of hook-eccentric type latches is their tendency to release with only partial rotation of the eccentric coupled with the users tendency to stop turning the eccentric when release occurs. Upon subsequent closing, the hook frequently fails to engage the sill pin but gives no indication-of lack of engagement.

Another limitation of some existing latches includes mounting on the exterior of the cabinet doors which makes the latch readily accessible and vulnerable to tampering.

Still another limitation is that many existing latches do not provide a sufficient pulling force when used with L-shaped doors which are hinged out of the front plane of the doors where the latch is located, and many do not accommodate reasonable misalignment of the doors.

Accordingly, it is an object of this invention to provide a cabinet latch having positive engagement and disengagement features of much greater reliability. Another object is to improve latches for cabinet doors so that such latches provide greater security for the cabinets.

SUMMARY OF THE INVENTION The foregoing objects and others are achieved in accordance with the invention ,by a latch for a cabinet which includes a sill pin and a hook for engaging the sill pin to lock the cabinet. The hook is frictionally mounted on a cam which rotates to move the hook into and out 'of engagement with the sill pin. The hook includes a first pin which engages a tab on the latch cover to cause rotation of the cam with respect to the hook so that the hook can be extended away from the sill pin during the. initial unlocking movement. A spring biased mating therewith to operate the latch.

trigger mounted on the hook includes a lip which engages a shoulder on the cam immediately prior to complete extension of the hook from the sill pin during this initial unlocking movement. This provides a positive engagement force during a subsequent locking movement. An arm of the trigger engages the sill pin to pivot the lip away from the shoulder and allows completion ofthe locking movement when the hook and sill pin are properly engaged. The shoulder on the cam contacts a second pin on the hook during unlocking to provide a positive disengagement force if the hook encounters excessive resistance during the disengagement movement. The hook and sill pin have cam or tapered surfaces thereon which return the hook to the disengage position if an attempt is made to close the cabinet doors when the hook is in an engage position.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more fully comprehended from the following detailed description and accompanying drawing in which: i

FIG. 1 is an exploded perspective view partly broken away of one embodiment of the latch of this invention mounted on cabinet doors as viewed from the inside of the cabinet;

FIG. 2 is an elevation view of the latch area of the cabinet doors as viewed from the outside of the cabinet with the doors latched; and

FIGS. 3 through 9 are schematic illustrations of the latch mechanism at various positions during the opening and closing thereof as viewed from the inside of the cabinet.

DETAILED DESCRIPTION FIG. 1 shows the latch 101 of this invention comprising a sill pin 103 and a latch assembly 102, respectively, mounted on the inside of

cabinet doors

104 and 106. The only portion of latch 101 which is visible and accessible from the outside of the cabinets when doors 104 and .106 are latched or closed as indicated in FIG. 2 are the head 13 of a stepped shaft 12 and the ends of hardware 108 such as rivets or screws used for mounting latch 101 to

doors

104 and 106. The latch is operated, i.e., opened and closed, thereby unlatching and latching

doors

104 and 106, by placing an appropriate tool over shaft head 13 and rotating head 13 until pointer 52 thereon is aligned with an

appropriate index

54 or 56 indicating closed and open positions, respectively. Head 13 is substantially flush with the outside front face of door 106 and is accessible through hole 111 in door 106. Accordingly, latch 101 offers good security against tampering in that head 13 which is the only accessible part, can be given any desired type of configuration which requires a special tool for Although latch 101 can be utilized with any type of cabinet doors, it isvery advantageous when used with L-shaped doors which have hinges lying out of the plane of

front faces

109 and 110 of

doors

104 and 106. Latch 101 provides a strong pulling force in the plane of

front faces

109 and 110 to tightly join the overlapping edges of

doors

104 and 106 in this plane; This feature would also make a latch in accordance with this invention useful in joining wall panels and the like as previously mentioned.

Sill pin 103 includes a substantially L-shaped bracket 3 which is mounted to the inside of door 104 by appropriate hardware 108 such as rivets or screws. A stud 4 extends inward substantially perpendicular to bracket 3 and door 104. Stud 4 includes a tapered face 5 and a necked down portion 6 which joins it to bracket 3.

Latch assembly 102 includes a base plate or bracket 60 by which it is mounted to the inside of door 106 by hardware 108. Plate 60 includes four legs or flanges 62 extending therefrom to which a cover 64 is mounted by hardware 66 to define a chamber or space therebetween. Shaft 12 is journaled in cover 64 and plate 60 for rotation therein by appropriate bushings or bearings 68 known in the art.

Secured to shaft 12 between plate 60 and cover 64 for rotation with shaft 12 is a cam or eccentric l0. Cam 10 is mounted off center with respect to shaft 12 so that its periphery follows an eccentric path with respect to shaft 12. Cam 10 includes a circular hub portion 14 and a contoured portion 16 on which cam surfaces or

shoulders

18 and 19 are formed for purposes to be discussed subsequently.

A hook member 2 having an end 72 adapted to embrace the necked down portion 6 of sill pin stud 4 when latch 101 is closed is mounted on hub portion 14 of cam 10. End 72 of hook 2 includes a tapered edge 74 having a slope or taper matching the taper of face 5 on stub 4 for purposes to be disclosed hereafter. A lip 76 is placed on the tip of end 72 to further insure that hook 2 remains in position about stud 4 when latch 101 is closed.

An axial compressive or squeezing force along shaft 12 is supplied between hook 2 and cam 10 by forming the portion of cover 64 in which shaft 12 is mounted in the form of a cantilever spring 65 as shown. A spacer washer 70 is rotatably mounted on shaft 12 and contacts hook 2 about the periphery of hub 14 to squeeze hook 2 between washer 70 and the shouldered portion 16 of cam 10 by utilizing the compressive force of spring 65. This establishes a frictional force or drive between cam 10 and hook 2 which causes book 2 to rotate with cam 10 unless book 2 encounters a resistance exceeding the frictional drive.

A trigger 24 is rotatably mounted on hook 2 by a stud 26 and is biased bya spring 28 to tend to rotate with respect to hook 2 so that a lip 40 on an arm 38 thereof engages shoulder 19 on contoured portion 16 of cam 10. Trigger 24 includes a second arm '36 adapted to contact stud 4 to pivot lip 40 on arm 38 away from contact with shoulder 19 as will be explained subsequently.

Hook 2 includes two studs or pins and 22 extending outward therefrom toward cover 64. Cover 64 includes a tab or lip extending inwardly toward hook 2 and adapted to contact pin 20 during aportion of the opening cycle of latch 101. Cover 64 also includes a cutout or slot 78 along an edge thereof adapted for re ceiving stud 4 therein. The entrance 79 to slot 78 advantageously can be tapered to guide stud 4 into slot 78 when

doors

104 and 106 are being closed.

The operation of latch 101 will now be discussed in detail with reference to FIGS. 3-9 which schematically represent the latch in various positions, as viewed from the interior of the cabinet. during a complete opening and closing cycle. In FIG. 3 the latch is shown fully closed with the end 72 of hook 2 fully engaging stud 4. In this

position doors

104 and 106 cannot be moved any appreciable amount with respect to each other but are held in a tightly closed or locked overlapping relationship. In this configuration shaft 12 is rotated fully counterclockwise (as viewed from the interior of the cabinet) until pointer 52 on shaft head 13 is aligned with index 54. Further rotation of shaft 12 in the locking direction is prevented by the engagement of pin 22 on hook 2 with shoulder 18 on cam 10.

To open latch 101, shaft 12 is rotated clockwise (as viewed from the interior of the cabinet) thereby rotating cam 10 mounted thereon clockwise. As shown in FIG. 4, upon the initial rotation of shaft 12 and cam l0. hook 2 also rotates clockwise a very small amount as indicated by arrow 32 because of the frictional drive between book 2 and cam 10. This initial rotation of hook 2 continues until pin 20 thereon contacts tab or flange 30 which acts as a stop to prevent further rotation of book 2 until pin 20 can get by or escape from tab 30. At this point hook 2 is still engaged with sill pin stud 4 and thus

doors

104 and 106 cannot be opened though their tightly closed relationship has been somewhat relaxed. This initial rotation of hook 2 also allows a corresponding counterclockwise rotation of trigger 24 with respect to book 2 because of the force of spring 28 to rotate arm 38 of trigger 24 into closer proximity to cam 10.

After pin 20 contacts tab 30, the frictional drive between hook 2 and cam 10 is overcome. Thus upon continued clockwise rotation of shaft 12 and cam 10, hook 2 does not rotate therewith but instead is forced or extended outward away from stud 4 by the eccentric motion of cam 10 as indicated by arrow 34 in FIG. 4. This extension of hook 2 outward from stud 4 also causes pin 20 to move outward along tab 30 as indicated. Hook 2 remains in sufficient engagement with stud 4 during this outward extension to maintain

doors

104 and 106 in a locked configuration even though the doors can move with respect to each other an amount equal to the extension of hook 2.

When hook 2 has been substantially fully extended, pin 20 reaches the edge of tab 30 and begins the escape therefrom as shown in FIG. 5. This restores the frictional drive between hook 2 and cam 10 so that any subsequent rotation of shaft 12 and cam 10 will produce rotation of book 2. Just before pin 20 completes the escape from tab 30, cam 10 has rotated clockwise allowing trigger 24 to rotate counterclockwise under the influence of spring 28 sufficiently for lip 40 on trigger arm 38 to drop past the rear or trailing edge 42 of shoulder 19 to establish the positive engagement feature previously mentioned and to be discussed in more detail subsequently. It should be clear that this positive engagement feature is set up or established before hook 2 completely escapes sill pin stud 4 and Consequently before

doors

104 and 106 can be completely opened. Accordingly, this insures that during any subsequent closure of latch 101, all parts must be properly positioned with respect to each other or the latch cannot be closed.

Continued rotation of shaft 12 and cam 10 from the position of FIG. 5 produces a corresponding rotation of hook 2 in the direction of arrow 44 completing the escape of pin 20 from tab 30 as indicated in FIG. 6 because of the restored frictional drive between hook 2 and cam 10. This rotation continues until hook 2 completely disengages sill pin 4 so that

doors

104 and 106 can be opened. After this complete disengagement hook 2 can be further rotated until it contacts one of the frame legs 62 or some other fixed stop such as the 5 and 7 hook 2 encounters sufficient resistance to overcome the frictional drive between it and cam 10, hook 2 will stop and cam 10 will continue to rotate until the front edge 46 of shoulder 19 thereon encounters pin 22. Thereafter cam 10 imparts a positive drive force to rotate hook 2 to the position shown in FIG. 7. This is the positive disengagement feature previously mentioned. This positive disengagement feature is especially important in situations such as when

doors

104 and 106 do not mate satisfactorily and thus tend to cause hook 2 to bind. The positive drive'disengagement force insures that such binding can be overcome so that latch 101 can be fully opened.

When it is desired to close latch 101, shaft 12 and cam 10 are rotated counterclockwise. Hook 2 also rotates counterclockwise as indicated by arrow 48 in FIG. 8 because of the frictional drive between hook 2 and cam 10. Hook 2 is fully extended outward during this initial closing rotation. If at any time during this rotation hook 2 encounters sufficient resistance to overcome the frictional drive between it and cam 10, hook 2 will stop and cam 10 will continue to rotate until the rear edge 42 of shoulder 19 engages lip 40 on trigger. arm 38. Subsequently cam 10 will apply a positive engagement torque or force to hook 2 through trigger 24 to force hook 2 to rotate therewith.

If excessive resistance to the rotation of hook 2 occurs before pin clears tab as indicated in FIG. 8, hook 2 may withdraw slightly causing pin 20 to be blocked or stopped by tab 30. Trigger arm 36 will then fail to contact stud 4 andfurther closure is prevented.

Tab 30 can be designed with sufficient thickness 31 to minimize the angle of rotation during which such blockage could occur.

The counterclockwise rotation of cam 10, trigger 24 and hook 2 continues until trigger arm 36 contacts sill pin st'ud 4 as shown in FIG. 8. Upon further counterclockwise rotation of cam 10, trigger 24 is rotated clockwise as shown by arrow 51 because of the force exerted on trigger arm 36 by stud 4. This pivots lip 40 away from contact with rear edge 42 of shoulder 19 and allows rotation of cam 10 and hook 2 until hook 2 encounters stud 4 to stop the rotation thereof. Completion of the disengagement oflip 40 from edge 42 occurs just before hook 2 contacts stud 4. At this point hook 2 is still substantially fully extended but is in engagement with stud 4 as indicated in FIG. 9.

Doors

104 and 106 can be moved with respect to each other an amount approximately equal to the extension of hook 2 but cannot be completely opened. Upon subsequent additional counterclockwise rotation of cam 10, book 2 does not rotate but withdraws as indicated by arrow until it returns to its initial position illustrated in FIG. 3.

If all parts of latch 101 are not properly positioned with respect to each other the positive engagement feature prevents complete rotation of shaft 12 and cam 10. For example, if an attempt is made to rotate cam 10 and hook 2 to the closed position while

doors

104 and 106 are open so that stud 4 is not within engageable reach of hook 2, lip 40 on trigger arm 38 locks up cam 10 somewhat after the position shown in FIG. 8 is reached because trigger 24 is not pivoted in a direction to remove lip 40 out of the path of edge 42 of shoulder 19 as occurs in normal operation. Hence cam 10 and shaft 12 can be rotated slightly past the position of FIG. 9 but cannot be rotated to the initial position of FIG. 3. This will be made obvious by the latch operatorobserving that pointer 52 is not aligned with index 54. The amount of rotation required by cam 10 and shaft 12 in moving from the fully opened position of FIG. 7 to the engaged but fully extended position of FIG. 9 is only a small .fraction of the total rotation required, i.e., most of the rotation of cam 10 and shaft 12 occurs during withdrawal of hook 2 as depicted by arrow 50. A typical example is that shaft 12 rotates approximately 27 in going from the fully opened position of FIG. 7 to the engaged but fully extended position of FIG. 9. On the other hand shaft 12 rotates about 191 degrees during the withdrawal of hook 2 in going from the position of FIG. 9 to initial the fully closed position of FIG. 3. Thus it is clear that pointer 52 will not remotely approach index 54 indicating a locked position unless the parts of latch 101 have been properly positioned and the latch has operated normally. I

The edge 107 of door 106 fits inside the edge 108 of door 104 in normal operation; If hook 2 is inadvertently rotated without

doors

104 and 106 being prop- .erly closed with respect to each other, pin 20 on hook 2 engages tab 99 on cover 64 to prevent rotation of hook 2 significantly past the position shown in FIG. 9. The subsequent closing of door 104 will return hook 2 to the completely open and disengage position approximated in FIG. 6. This is accomplished when door 104 is swung into position over door 106 by tapered surface 5 on stud 4 contacting matching tapered edge 74 on book 2 and applying a lifting force thereto to return hook 2 to the disengage position.

It should be clear from the foregoing that an operator can be assured that latch 101 has operated properly unless shaft 10 refuses to turn. The operator need only rotate head 13 of shaft 12 until pointer 52 thereon is aligned with the

appropriate index

54 or 56 in order to definitely know that the latch is fully and properly closed or opened, respectivelyjlf the operator cannot rotate shaft 12, he knows that the parts of latch 101 are not properly positioned. The positive engagement feature insuring proper closing of latch 101 during any subsequent closing operation is automatically set up before latch 101 can be completely opened. Thus this feature cannot be nullified or circumvented as it can be in existing latches.'The positive disengagement feature insures that latch 101 can be opened regardless of any resistance or binding which may be encountered. The tapered surfaces on hook 2 and stud 4 insure that latch 101 is positioned for proper operation even if an attempt is made to operate latch assembly 102 while the cabinet doors on which latch 101 is mounted are open.

While the invention has been described with reference to a specific embodiment thereof, it is to be understood that various modifications thereto might be made by those skilled in the art without departing from its spirit and scope.

What is claimed is:

1. A latch comprising a sill pin; a rotary eccentric cam having a first shoulder on the periphery thereof; a

hook member mounted on said cam and adapted to move into and out of engagement with said sill pin in response to a rotation of said cam to close and open said latch, respectively, a trigger rotatably mounted with respect to said hook member and having a lip thereon adapted to engage said first shoulder on said cam to preventrotation of said cam to close said latch until said cam, said hook member and said sill pin are properly positioned with respect to each other, characterized in that said latch includes:

first means for maintaining said hook member in engagement with said sill pin until said lip has engaged said first shoulder and until said hook member has been substantially fully extended when said latch is being opened; and

second means for removing said lip from engagement 7 with said first shoulder after said hook member has moved into engagement with said sill pin when said latch is being closed.

2. Apparatus in accordance with claim 1 wherein said latch includes:

a spring for biasing said trigger in a direction to cause said lip to engage said first shoulder;

a cover having a tab thereon extending outward therefrom toward said hook member;

said first means includes a first pin on said hook extending outward therefrom and adapted to contact said tab to prevent rotation of said hook member with said cam during a substantial portion of said rotation of said cam when said latch is being opened, whereby said cam rotates with respect to said hook member until said lip engages said first shoulder; and

said second means includes an arm on said trigger adapted to contact said sill pin to pivot said lip away from contact with said first shoulder.

3. Apparatus in accordance with claim 2 wherein said hook member includes a second pin extending outward therefrom and said cam includes a second shoulder, said first shoulder being adapted to contact said second pin to provide a positive rotation force to said hook member when said hook member encounters resistance before said latch is fully open and to prevent further rotation of said cam in an opening direction when said latch is fully open. and said second pin being adapted to contact said second shoulder to prevent further rotation of said cam in a closing direction when said latch is fully closed.

4. Apparatus in accordance with claim 3 wherein said latch is adapted for mounting on doors of a cabinet. said sili pin includes a tapered face and said hook mcmber has an end tapered to match said face of said sill pin and adapted to contact said face to return said hook member to a position out of engagement with said sill pin when said hook member is rotated into a position for engaging said sill pin while said doors are open.

5. A latch comprising, in combination:

a latch cover having an outstanding tab thereon;

a rotary eccentric cam having a shoulder on the periphery thereof;

a sill pin;

a hook member mounted on said cam and responsive to the rotation of said cam to move into and out of engagement with said sill pin to close and open said latch;

a trigger including a first arm having a lip thereon adapted for engaging said shoulder to prevent rotation of said cam to close said latch unless said sill pin, said hook member and said trigger are properly positioned with respect to each other, and a second arm adapted for engaging said sill pin to remove said lip from engagement with said cam and permit said rotation when said sill pin, said hook member and said trigger are properly positioned with respect to each other; and

an outstanding pin on said hook member adapted for engaging said tab on said cover for maintaining said hook in engagement with said sill pin until said lip engages said shoulder when said latch is being opened.

Claims

1. A latch comprising a sill pin; a rotary eccentric cam having a first shoulder on the periphery thereof; a hook member mounted on said cam and adapted to move into and out of engagement with said sill pin in response to a rotation of said cam to close and open said latch, respectively, a trigger rotatably mounted with respect to said hook member and having a lip thereon adapted to engage said first shoulder on said cam to prevent rotation of said cam to close said latch until said cam, said hook member and said sill pin are properly positioned with respect to each other, characterized in that said latch includes: first means for maintaining said hook member in engagement with said sill pin until said lip has engaged said first shoulder and until said hook member has been substantially fully extended when said latch is being opened; and second means for removing said lip from engagement with said first shoulder after said hook member has moved into engagement with said sill pin when said latch is being closed.

2. Apparatus in accordance with claim 1 wherein said latch includes: a spring for biasing said trigger in a direction to cause said lip to engage said first shoulder; a cover having a tab thereon extending outward therefrom toward said hook member; said first means includes a first pin on said hook extending outward therefrom and adapted to contact said tab to prevent rotation of said hook member with said cam during a substantial portion of said rotation of said cam when said latch is being opened, whereby said cam rotates with respect to said hook member until said lip engages said first shoulder; and said second means includes an arm on said trigger adapted to contact said sill pin to pivot said lip away from contact with said first shoulder.

3. Apparatus in accordance with claim 2 wherein said hook member includes a second pin extending outward therefrom and said cam includes a second shoulder, said first shoulder being adapted to contact said second pin to provide a positive rotation force to said hook member when said hook member encounters resistance before said latch is fully open and to prevent further rotation of said cam in an opening direction when said latch is fully open, and said second pin being adapted to contact said second shoulder to prevent further rotation of said cam in a closing direction when said latch is fully closed.

4. Apparatus in accordance with claim 3 wherein said latch is adapted for mounting on doors of a cabinet, said sill pin includes a tapered face and said hook member has an end tapered to match said face of said sill pin and adapted to contact said face to return said hook member to a position out of engagement with said sill pin when said hook member is rotated into a position for engaGing said sill pin while said doors are open.

5. A latch comprising, in combination: a latch cover having an outstanding tab thereon; a rotary eccentric cam having a shoulder on the periphery thereof; a sill pin; a hook member mounted on said cam and responsive to the rotation of said cam to move into and out of engagement with said sill pin to close and open said latch; a trigger including a first arm having a lip thereon adapted for engaging said shoulder to prevent rotation of said cam to close said latch unless said sill pin, said hook member and said trigger are properly positioned with respect to each other, and a second arm adapted for engaging said sill pin to remove said lip from engagement with said cam and permit said rotation when said sill pin, said hook member and said trigger are properly positioned with respect to each other; and an outstanding pin on said hook member adapted for engaging said tab on said cover for maintaining said hook in engagement with said sill pin until said lip engages said shoulder when said latch is being opened.