GB2361959A - Lock mechanism with rollers - Google Patents

Abstract

Rollers 108, 110 serve to enable dead bolt 104 to move easily out of engagement with bolt member 54 when the dead bolt is released by release mechanism 14. Both rollers rotate about axes 113, 116 which are perpendicular both to the direction of movement of the dead bolt and of the bolt member. A roller 90 may also be provided on the bolt member so that the rolling surface of roller 90 contacts the surface of roller 110 when the dead bolt is in the engaged position and hence facilitates the movement of the dead bolt.

Description

2361959 LOCK MECHANISM The present invention relates to a lock mechanism

and in particular, but not exclusively, to a lock mechanism which may be easily and reliably released a pre-determined time interval after being actuated.

In many countries it is a requirement that public buildings be provided with emergency exits for use in the case of fire or some other emergency which necessitates the urgent evacuation of the building concerned. Typically these emergency exits comprise a door which is hinged within a doorframe and moveable between a closed position and an open position in which use may be made of the exit. Usually the door is is held in the closed position by a latch or some other mechanism which is not accessible from the outside of the door in order to prevent the emergency exit being used for ordinary ingress and egress from the building. By contrast, on the inside of the door the door is provided with a handle, panic bar or some other suitable actuator which enables the latch holding the door in the closed position to be released and the door hinged to the open position.

The fact that to date public buildings have been provided with such an easy to use and readily accessible means of escape does cause particular problems for certain classes of public buildings. For example, supermarkets have found that shoplifters can make a quick and easy escape from the supermarket without paying for the goods they have taken by making use of the emergency exits that are provided. Similarly, prisoners awaiting trial in a court room may be tempted to make their escape through one of the emergency exits with which by law the court must be provided and which cannot be locked in case of tire.

2 Accordingly, there has been a need for a lock mechanism for use with emergency exits which, whilst ensuring a reliable, failsafe means of evacuating a building, none the less presents a deterrent to the casual or criminal user who attempts to pass through the emergency exit only as a means of avoiding a more correct means of exit located elsewhere.

According to the present invention there is provided a lock mechanism comprising at least one bolt member moveable between an engaged position and a disengaged position; means for retaining said at least one bolt member in said engaged position; and means for releasing said retaining means, at least one of said retaining means and said at least one bolt member including a rolling support means, said retaining means retaining said at least one bolt member in said engaged position by the engagement of the other of said retaining means and said at least one bolt member with a surface of said rolling support means so that, when released by said releasing means, said retaining means moves easily out of engagement with said at least one bolt member.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1 is an elevational view of a lock mechanism embodying the present invention from which one of the cover plates has been removed and in which some of the parts are shown broken away for the sake of clarity; Figure 1A is an enlarged view of part of the lock mechanism of Figure 1; Figure 2 is a cross-sectional view taken along line II-II of Figure 1 and from which certain parts have been omitted, again for the sake of clarity; Figure 3 is an elevational view of part of the lock mechanism of Figure 1 and from which a further cover plate has been removed; Figure 4 is an elevational side view of that part of the lock mechanism shown in Figure 3; Figure 5 is a cross-sectional view taken along line V-V of Figure 3; and Figure 6 is a cross-sectional view taken along line VI-VI of Figure 3.

Referring to Figure 1 there is shown a lock mechanism comprising a bolt mechanism 10, a retaining mechanism 12, a release mechanism 14 and a timer 15.

The bolt mechanism 10 is shown in more detail in Figure 3 to comprise a housing 16 formed by a base plate 18 and a cover plate 20 and defined by side walls 22,24,26 and 28. The cover plate 20 is secured to the base plate 18 by means of screws 30 which pass through suitable apertures 32 provided in the base plate. The screws 30 are in turn received within a suitably threaded blind bore 34 of a boss 36 attached to the cover plate. The housing itself 16 may be attached to either a door or some other member moveable within a frame by means of further screws or other suitable fastening means which pass through aligned apertures 38 and 40 provided in both the base plate 18 and cover plate 20. Alternatively the housing 16 may be attached to the frame itself in a similar manner.

Within the housing 16 the bolt mechanism 10 is provided with a pair of mutually spaced, toothed drive wheels 42 and 44 which are mounted for rotational movement with respect to the base plate 18 about respective axes 46 and 48. The drive wheels 42 and 44, which are of substantially the same diameter, are so arranged that a line joining their respective axes 4 of rotation 46 and 48 extends substantially parallel to the side walls 24 and 28 of the housing 16. At the same time the drive wheels are so spaced as to accommodate a first bolt member 50 which is interposed therebetween and which extends from the housing through an aperture 52 provided in side wall 28. Two further bolt members 54 and 56 extend perpendicularly to the first bolt member 50 and project from the housing 16 through respective apertures 58 and 60 provided in side walls 22 and 26. Both of the second and third bolt members 54 and 56 extend generally parallel to the side walls 24 and 28, albeit in opposite directions, and each is located between a respective one of the drive wheels 42,44 and the side wall 28. Both are provided at an end remote from that which projects from the housing 16, and on a surface facing their respective drive wheel 42, 44, with a rack engageable by the teeth of the drive wheels such that a rotation of the respective drive wheel results in a translational movement of the second and third bolt members 54,56. At the same time, the first bolt member 50 is provided at an end remote from that which projects from the housing 16, and on opposed surfaces, with a pair of racks 66, 68 which are also respectively engaged by the teeth of the drive wheels 42 and 44. In this way a rotation of, say, the second drive wheel 44 results not only in a translational movement of the third bolt member 56 but also of the first bolt member 50, albeit in an orthogonal direction. At the same time the translational movement of the first bolt member 50 also causes the first drive wheel 42 to rotate, albeit in the opposite sense from that of the second drive wheel 44, and this rotational movement of the first drive wheel in turn causes translational movement of the second bol member 54. Similarly, a rotational movement of the first drive wheel 42 will, as well as causing the translational movement of the first and second bolt members 50,54, also cause the second drive wheel 44 to rotate, resulting in the translational movement of the third bolt member 56. Accordingly, by providing a handle or some other suitable actuator to generate an initial rotation of one or other of the drive wheels 42,44 it is possible to simultaneously move all three of the bolt members 50,54 and 56 between their retracted and extended positions. By suitably gearing the drive wheels 42,44 and the racks 62,64,66 and 68 it is possible to ensure that a 450 handle movement is sufficient to fully retract the bolt members the length of their respective travels.

If the housing 16 is attached to a door or some other moveable member, the projecting ends of all three bolt members 50,54,56 are arranged, when extended, to be received within suitable keepers (not shown) located at appropriate points around the frame in which the door or moveable member is mounted. If by contrast the housing 16 is attached to the frame then the keepers are located at suitable points around the perimeter of the door. In either case when the bolt members 50,54,56 are extended they serve to retain the door or other moveable member in a closed position within the frame.

In order that the bolt members 50,54 and 56 may be biased towards their extended positions, each of the drive wheels 42 and 44 is provided with a respective spring or other suitable biasing means 70 which, in the embodiment shown, extends in an S formation between an attachment point 72 provided on the drive wheel and another attachment point 74 attached to the base plate 18. In this way, in. order 6 to retract the bolt members 50,54 and S6 the handle or other actuator needs to be moved against the action of the biasing means and, if the handle or actuator should subsequently be released, the bolt members will automatically return to their extended positions.

Returning again to a consideration of Figure 1, it will be seen that the retaining mechanism 12, release mechanism 14 and timer 15 are all contained within a second housing 76 adjacent the first housing 16. Indeed, in some arrangements the two housings 16 and 76 may comprise a unitary structure.

As can be seen, one of the bolt members, in this case the second bolt member 54, extends from the first housing 16 through the second housing 76 and into engagement with its respective keeper (not shown). In order to provide support to the bolt member 54 as it passes through the second housing 76, the bolt member is received within a generally U-shaped channel provided in a guide 80 which is itself secured to the second housing 76. Although not shown in any of Figures 3 to 6, the portion of the bolt member 54 which projects from the first housing 16, and which is received within the second housing 76, is shaped in a number of respects. Firstly, the bolt member 54 is provided on an inwardly directed surface 81 with a notch 82 which serves to define first and second shoulder surfaces 84 and 86. The upper of these two shoulder surfaces 84 merges with the inwardly directed surface 81 by means of an arcuate surface 88 but is additionally cut away on a surface of the bolt member 54 perpendicular to the inwardly directed surface 81 so as to provide a location for mounting a roller 90 within the overall dimensions of the bolt member. The roller 90 is mounted for rotation with respect to the bolt member about an axis 92 which extends 7 substantially perpendicularly to that in which the bolt member extends. At the same time the roller 90 is so sized, and the axis 92 so positioned, that a circumferential surface of the roller projects beyond the arcuate surface 88 and into the void left by the notch 82.

The bolt member 54 is also shaped in that a threaded throughbore 94 is provided through the bolt member in the region of the notch 82. The throughbore communicates with the notch on one side and an outwardly directed surface 96 of the bolt member on the other and serves to receive a correspondingly treaded grub screw 95. In addition, above the guide 80, the bolt member 54 is provided on the inwardly directed surface 81 with a second, smaller notch 98 which is engaged by a sensor arm 100 of a microswitch 102.

In contrast to the bolt member 54, the retaining mechanism 12 comprises a dead bolt 104 moveable in a direction transverse and substantially perpendicular to the direction of movement of the bolt member between a first position in which the dead bolt engages the notch 82 and a second, retracted position in which it does not. The dead bolt 104 is supported in this movement as a result of being received within a second channel 106 within the guide 80 and which extends in a direction substantially perpendicular to the first U-shaped channel 78. The movement of the dead bolt 104 is further facilitated by two rollers 108 and 110, the first of which is located adjacent a lower surface of the dead bolt 112. The roller 108 is mounted for rotation with respect to the dead bolt 104 about an axis 113 which extends substantially perpendicularly to the direction of movement of the dead bolt. At the same time the roller 108 is;o 8 sized as to present a circumferential surface which is substantially flush with the lower surface of the dead bolt 112 and which therefore defines a rolling surface with which to engage a confronting wall 114 of the channel 106.

The second roller 110 is also mounted for rotation about an axis 116 substantially perpendicular to the direction of movement of the dead bolt 104 but is located adjacent an upper edge of the dead bolt close to where an upper surface 118 merges with a projecting end surface 120 by means of an arcuate surface 122. As with the roller 90 provided on the bolt member 54, the roller 110 is so sized, and the axis 116 so positioned, that a circumferential surface of the roller projects beyond the arcuate surface 122 and, if the dead bolt 104 is in the extended position, into the void left by the notch 82.

The dead bolt 104 is moved between its projecting and retracted position by means of the release mechanism 14. The release mechanism 14 is mounted on a sub-plate 124 secured to the housing 76 and comprises a solenoid 126 and a rotating disc 128. The rotating disc 128 is mounted for rotation with respect to the sub-plate 124 about a shaft 130 which defines an axis 132 and which extends substantially perpendicular to the plane of the sub-plate. The rotating disc 128 is partially cut away in the plane of the disc so as to present a shoulder 134 which extends as a chord passing to one side of the axis 132. On the other side of the axis 132, the rotating disc 128 is provided with an outwardly projecting stud 136 while at another location 138 the rotating disc 128 is pivotally connected to one end of a connecting rod 140, the other end of which 142 is pivotally connected to the dead bolt 104. When the dead bolt 9 104 is in its engaged position, the pivot points 138 and 142 are so arranged that a line joining the two would extend in a direction substantially parallel to the direction of movement of the dead bolt 104 and, if continued, would pass through the axis 132.

Between the solenoid 126 and the rotating disc 128 a trigger plate 144 is mounted on one end of a threaded actuator rod 146 which projects from the solenoid and which is moveable in a direction substantially parallel to the direction of movement of the dead bolt 104 and substantially perpendicular to the direction of movement of the bolt member 54. The trigger plate 144 is of substantially inverted L-shape and is provided at an end remote from the actuator rod is 146 with a recess 148, partially defined by opposed surfaces 150 and 152, and which serves to receive the outwardly projecting stud 136. In addition to the recess 148 the trigger plate 144 is also provided with an extension piece 154 which extends perpendicularly to the actuator rod 146 and which is attached to the retaining mechanism 12 at opposite ends by a pair of coil springs 156 and 158. The coil springs 156 and 158 serve to urge the extension piece 154, and hence the trigger plate 144 to which it is attached, in the direction of the retaining mechanism 12. This in turn tends to cause a first of the opposed surfaces 150 of the recess 148 to engage the outwardly projecting stud 136 and rotate the disc 128 in a clockwise direction about axis 132. In order to counteract this the solenoid 126 is so arranged that, when actuated, the actuator rod 146 is urged in a direction away from the retaining mechanism 12, causing the trigger plate 144 and the extension piece 154 to pull against the action of the coil springs 156 and 158 and bringing the second opposed surface 152 of the recess 148 into engagement with the outwardly projecting stud 136.

This engagement tends to cause the disc 128 to rotate about axis 132 in an anticlockwise direction however, this rotational movement is constrained by the engagement of an adjustment screw 160 with the shoulder 134. This adjustment screw 160, which is mounted with respect to the sub-plate 124 and extends in a direction generally perpendicular to the direction of movement of the dead bolt 104, can be rotated with respect to the sub-plate to ensure that, when the solenoid 126 is actuated, the pivot points 138 and 142 of the connecting rod 140 remain co-linear with the axis 132.

Also located within the housing 76 is the timer is 15 which is connected to both the microswitch 102 and the solenoid 126 via relays (not shown). In this way the timer 15 serves to interrupt the power supply and deactuate the solenoid 126 a predetermined time after a signal is received from the mircoswitch 102.

In use and in the locked position the bolt members 50,54 and 56 extend out of the housing 16 so that their projecting ends are received within a respective keeper (not shown) provided on the other of the door or frame depending upon which member the lock mechanism is mounted. At the same time, the dead bolt 104 projects from the guide 80 and is received within the notch 82 provided in the second bolt member 54 to prevent the bolt member from being retracted. The extent to which the dead bolt 104 projects is in part defined by the grub screw 95 which can be rotated within the threaded throughbore 94 so as to engage the projecting end surface 120 of the dead bolt. In this way it is possible to prevent the dead bolt 104 from projecting too far into the notch 82 and ensure that when the dead bolt is in the projecting position the axis 116 of roller 110 is in vertical alignment with the axis 92 of roller 90. At the same time the connecting rod 140 connecting the dead bolt 104 to the rotating disc 128 is maintained in tension by actuating the solenoid 126 and retracting the actuator rod 146 which serves to adjust the distance between the solenoid and the trigger plate 144 while, as previously stated, rotation of the adjustment screw ensures that the pivot points 138 and 142 remain co-linear with the axis 132.

In order to open the door a handle, panic bar or other suitable device attached to one or both of the drive wheels 42 or 44 is actuated so as to rotate the drive wheels and retract the bolt members 50,54 and is 56. However, because of the receipt of the dead bolt 104 within the notch 82, it is not possible to retract the second bolt member 54 and, because all three bolt members 50,54 and 56 are interlinked by the two drive wheels 42 and 44, this means that it will also not be possible to retract the other two bolt members 50 and 56. Instead, the upper shoulder surface 84 of the notch 82 is brought into engagement with the upper surface 118 of the dead bolt 104. More particularly, a circumferential surface of the roller 90 is brought into engagement with a circumferential surface of the roller 110 and, despite these two surfaces being rolling surfaces, if the axes 92 and 116 are in vertical alignment, however much downward force is applied to the bolt member 54 there will be no component of that force in a direction tending to retract the dead bolt 104. Accordingly, irrespective of the number of times the handle, panic bar or other suitable device is actuated and irrespective of the amount of force applied to it, the door will not open.

However, the initial downward movement of the 12 bolt member 54 which is stopped by the mutual engagement of the two rollers 90 and 110 is sufficient to deflect the sensor arm 100 of the microswitch 102 engaged by the smaller notch 98. The microswitch 102 interprets this deflection as an attempt to open the door and sends a signal to the timer 15 to start an appropriate clock. At the same time the microswitch 102 may also send an appropriate signal to an alarm unit (not shown) which might initiate an audible and/or visual alarm signal to indicate that an attempt is being made to use the emergency exit. If that use is in any way criminal, such as the use that might be made of an emergency exit by a shoplifter or an escapee from a court room, then the alarm signal combined with the refusal of the door to open, will provide security staff with the necessary time and opportunity to apprehend the person concerned.

When the handle, panic bar or other suitable device is first operated the microswitch 102, as well as operating the timer 15, sets a hold in contact on an external relay (not shown). The relay serves to provide continuity of electrical power to the timer 15 in the event that a user, on hearing the alarm, releases or shakes the handle, panic bar or other suitable device, possibly operating the microswitch 102 several times. In this way the timer 15 is not continuously reset so that it never reaches the predetermined value. In a true emergency situation represented by a complete loss of electrical power to the system the timer 15 is over-ridden and the door may be opened immediately.

Under normal circumstances however, after a predetermined time interval has elapsed which might, for example, be of the order of 15 seconds, the timer 15 interrupts the power supply to the solenoid i26 and 13 deactuates it. As a result, the solenoid 126 is no longer able to hold the trigger plate 144, and the extension piece 154 to which it is connected, against the action of the coil springs 156 and 158. The springs 156,158 urge the trigger plate 144 in the direction of the retaining mechanism 12 and bring the first of the opposed surfaces 150 of the recess 148 into engagement with the outwardly projecting stud 136. The opposed surfaces 150 and 152 are so spaced (in other words, the recess 148 is sufficiently wide) that by the time the first of the opposed surfaces 150 engages the outwardly projecting stud 136 it has been accelerated by the action of the coil springs 156 and 158 to a speed sufficient to knock the outwardly projecting stud with some force, thereby causing the rotating disc 128 to partially rotate about axis 132 in a clockwise direction. This in turn causes pivot point 138 to also rotate and, as it does so, it pulls the connecting rod 140 and the dead bolt 104 to which it is connected out of engagement with the notch 82.

Although the retaining mechanism 12 and release mechanism 14 can be adapted so that the action of the coil springs 156 and 158 is able to substantially withdraw the dead bolt 104 to its retracted position, this is not actually necessary since all that is required is to move the axis 116 of the roller 110 out of vertical alignment with the axis 92 of the roller 90. once this has been achieved any downward force applied to the bolt member 54 will impart a component to the dead bolt 104 in the direction of retraction.

Furthermore, since rollers 90 and 110 present confronting rolling surfaces even the smallest downward force on the bolt member 54 which also has a component in the direction of retraction of the dead bolt 104 will cause the two rollers to roll past each 14 other, pushing the dead bolt out of engagement with the notch 82. Likewise, the rolling surface provided by the roller 108 greatly facilitates the movement of the dead bolt 104 so that it is able to move in response to even the smallest component of force in the direction of retraction. In addition, as the dead bolt 104 starts to move, so the component of force in the direction of retraction grows steadily larger until such time as the rollers 90 and 108 slip past each other, enabling the bolt member 54 to be retracted.

The same is also true even if a large downward force is applied to the bolt member 54. One of the problems with many of the prior art lock mechanisms is is that a large downward force on the bolt member 54 results in a large contact force between the upper surface 118 of the dead bolt 104 and the upper shoulder 84 of the notch 82. In the past under such circumstances it has proved impossible to withdraw the dead bolt 104 from the notch 82 against the high frictional forces that are generated. The same however, is not the case in the present arrangement.

Since the retraction of the second bolt member 54 enables, if not causes, the retraction of the other two bolt members 50 and 56, it will be apparent that the described arrangement provides a lock mechanism which will not open when first actuated but will not fail to open once a predetermined time interval has elapsed. In this way an honest user of the emergency exit may have no fear about the failure of the door to open when initially actuated while those with criminal intent will be deterred from using the emergency exit to make good their escape.

As the bolt members 50, 54 and 56 are retracted, a restraint mechanism (not shown) engages a suiable notch (also not shown) located close to the projecting end of the second bolt member 54. The engagement of the restraint mechanism serves to hold the bolt members 50, 54 and 56 in their retracted positions once the handle, panic bar or other suitable device has been released and the door opened. The act of re closing the door brings the restraint into engagement with either the frame or a suitable catch located on the frame and the restraint is released. The bolt members 50, 54 and 56 are then free to return to their extended positions under the action of the biasing means 70.

An external reset switch is provided to break the line to the relay and reset the system.

is In order to provide added security a further switch may be located within the housing 76 to establish that the dead bolt 104 is in its projecting position to lock the system.

Claims (19)

CLAIMS:

1. A lock mechanism comprising at least one bolt member moveable between an engaged position and a disengaged position; means for retaining said at least one bolt member in said engaged position; and means for releasing said retaining means, at least one of said retaining means and said at least one bolt member including a rolling support means, said retaining means retaining said at least one bolt member in said engaged position by the engagement of the other of said retaining means and said at least one bolt member with a surface of said rolling support means so that, when released by said releasing means, said retaining means moves easily out of engagement with said at least one bolt member.

2. A lock mechanism comprising at least one bolt member moveable between an engaged position and a disengaged position; means for retaining said at least one bolt member in said engaged position; and means for releasing said retaining means to allow said at least one bolt member to move to said disengaged position, said release means being actuated to release said retaining means a predetermined time interval after an attempt is made to move said at least one bolt member from said engaged position to said disengaged position.

3. A lock mechanism in accordance with claim 2 and including a sensor to detect when an attempt is made to move said at least one bolt member from said engaged position to said disengaged position and a 17 timer, the sensor being adapted to send a signal to the timer when an attempt is made to move said at least one bolt member and the timer being adapted to actuate said release means a predetermined time interval after the signal is received.

4. A lock mechanism in accordance with claim 2 or claim 3, wherein at least one of said retaining means and said at least one bolt member includes a rolling support means, said retaining means retaining said at least one bolt member in said engaged position by the engagement of the other of said retaining means and said at least one bolt member with a surface of said rolling support means so that, when released by said is releasing means, said retaining means moves easily out of engagement with said at least one bolt member.

5. A lock mechanism in accordance with claim 1 or claim 4, wherein said rolling support means is adapted to rotate about an axis which extends perpendicularly both to the direction in which said at least one bolt member moves from said engaged position to said disengaged position and to the direction in which said retaining means moves out of engagement with said at least one bolt member.

6. A lock mechanism in accordance with any of claims 1, 4 or 5 wherein both said retaining means and said at least one bolt member are provided with rolling support means, said retaining means retaining said at least one bolt member in said engaged position by the mutual engagement of said rolling support means.

7. A lock mechanism in accordance with claim 6, wherein both said rolling support means are adapted to 18 rotate about axes which extend perpendicularly both to the direction in which said at least one bolt member moves from said engaged position to said disengaged position and to the direction in which said retaining means moves out of engagement with said at least one bolt member.

8. A lock mechanism in accordance with claim 6 or claim 7, wherein ' when said retaining means retains said at least one bolt member in said engaged position, the axes of the rolling support means are spaced in the direction in which said at least one bolt member moves from said engaged position to said disengaged position.

9. A lock mechanism in accordance with claim 1 or any of claims 4 to 8, wherein the or each rolling support means is so located with respect to said retaining means or said at least one bolt member that the or each rolling support means presents rolling surfaces on orthogonal faces of said means or member concerned.

10. A lock mechanism in accordance with claim 1, wherein said release means is actuated to release said retaining means a predetermined time interval after an attempt is made to move said at least one bolt member from said engaged position to said disengaged position.

11. A lock mechanism in accordance with any preceding claim, wherein said retaining means is guided in moving into and out of engagement with said at least one bolt member by guide means, at least one of said retaining means and said guide means being provided 19 with rolling support means which is adapted so as to present a rolling surface to a confronting surface of the other of said retaining means or guide means thereby further facilitating the movement of said retaining means.

12. A lock mechanism in accordance with any preceding claim, wherein said retaining means engages said at least one bolt member as a result of being received within a slot provided in said at least one bolt member.

13. A lock mechanism in accordance with claim 12, wherein the extent to which the retaining means is received in said slot is adjustable by means of an adjustment means which extends from the slot and engages a surface of said retaining means.

14. A lock mechanism in accordance with any preceding claim, wherein said release means comprises a solenoid which, when actuated, holds said retaining means in engagement with said at least one bolt member against the action of biasing means, said release means being actuated by deactuating the solenoid.

15. A lock mechanism in accordance with claim 14, wherein said release means includes a member pivotally mounted about an axis, the solenoid and biasing means being coupled to said pivotal member on one side of said axis and said retaining means being coupled to said pivotal member on the other side of said axis.

16. A lock mechanism in accordance with claim 15, wherein the solenoid, when actuated, and said biasing means tend to rotate said pivotal member in opposite directions about said axis.

17. A lock mechanism in accordance with claim 16, wherein said solenoid and biasing means are attached to a trigger means and are coupled to said pivotal member by the engagement of respective confronting surfaces of a recess provided in said trigger means with a projection provided on said pivotal member.

18. A lock mechanism in accordance with claim 17, wherein said confronting surfaces are so spaced that when the solenoid is first deactuated the biasing means urges the confronting surface not then in contact with the projection into engagement with the projection with an impulse sufficient to cause said pivotal member to rotate about said axis.

19. A lock mechanism in accordance with any of claims 15 to 18, wherein said retaining means is coupled to said pivotal member by means of a connecting rod having opposite ends, one of said ends being pivotally connected to said retaining means and the other of said ends being pivotally connected to said pivotal member.