AU765783B2 - Mechanical latch mechanism - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name of Applicant: BRIAN Actual Inventor: BRIAN Address for Service: FRANCIS PREDDEY FRANCIS PREDDEY Chrysiliou Moore Martin CMC Centre 143 Sydney Road Fairlight Sydney NSW 2094 Invention Title: Mechanical Latch Mechanism The following statement is a full description of this invention, including the best method of performing it known to me/us: \\server\e\docs\ltr\99 I2c028.docvb o:\patents\comp\8986a.doc Mechanical Latch Mechanism Technical Field This invention relates to a mechanical latch mechanism. In particular, this invention relates to a mechanical latch suitable for use in connection with cam locks, although the invention is not necessarily limited to this application.

Background Art It is known to use latching mechanisms for doors and drawers. In many cases, the latching mechanisms are small in size. This limits the amount of "throw" or "travel" relating to the catch of the latch mechanism. Generally, the greater amount of "throw" or "travel" the catch has, the more secure the latch mechanism.

Consequently, small latching mechanisms are generally of low security.

Another problem with prior art latching mechanisms is that it is difficult to achieve automatic dead-latching in small mechanisms. In particular, it is desirable to automatically dead-latch cash drawers and cash boxes of poker machines. It is desirable to automatically dead-latch such apparatus, so that when the latch is slammed shut it will spring out behind the strike plate into a deadlock position, so that the latch can be opened only with the correct key.

Traditionally, latching mechanisms have been produced as a complete unit containing both the latch and the locking mechanism. Such latching mechanisms usually cannot be separated, so that it is not possible to use the latch with a lock of a different manufacture, or vice versa.

At least in some embodiments, it is an object of the present invention to provide a mechanical latch mechanism which will overcome or at least obviate some of the disadvantages of the prior art.

25 Disclosure of the Invention Accordingly, this invention provides a latch mechanism which includes a sliding latch bolt adapted to be retained behind a striker plate when in a locked position, means for retracting the latch bolt when the means are pressed against the front i:\docs\patents\comp\8986amend.doc of the striker plate and biasing means to urge the latch bolt into the locked position, wherein the latch bolt is adapted to swivel to an unlocked position.

Preferably, the latch mechanism of the invention also includes a dead-lock mechanism, a preferred embodiment of which is described below.

As indicated above, the latch mechanism of the invention is particularly suitable for use in conjunction with cam locks, specifically keyed cam locks. For convenience, the description below will focus on the use of the latch mechanism of the invention in conjunction with a cam lock used to lock the door of a poker machine. However, it is to be understood that the invention is not limited to this environment.

The sliding latch bolt of the mechanism of the invention is preferably made of steel and is generally U-shaped in cross-section, with a flat base. In one embodiment, the retracting means includes a taper on the latch bolt. In another embodiment, the retracting means includes an arm pivotally connected to the latch bolt by an axle. The axle can have an important function in relation to deadlocking of the mechanism, as will be described later.

While the retracting arm is pivotally connected to the latch bolt at one end via the axle, the other end is preferably pivotally connected to a support bracket which i includes a latch return spring, which can comprise the biasing means for urging 20 the latch bolt into the closed position.

The construction of the latch mechanism of the present invention permits a door on which the mechanism is mounted to be slammed closed. When the door is slammed, the retracting means will press against the striker plate and cause the latch bolt to be retracted. The mechanism will then move past the striker plate.

25 Because of release of pressure on the retracting means, the latch bolt will be released into the locked position, behind the striker plate.

0 •The dead-locking mechanism preferably includes a pair of angled slots, one each in an upstanding arm of the U-shaped latch bolt. The axle for the retracting arm is .i o:\patents\comp\8986a.doc mounted in the angled slots. The angled slots are preferably identical and may, for example, be shaped like a V, U, L or J. When the axle travels from a first part of the angled slots, past the angle into the second part of the angled slots, the latching mechanism of the invention is dead-locked. To release the dead-lock, it is necessary to apply pressure to the retracting arm and this is not accessible after the door is closed until the latching mechanism is opened via the keyed cam lock.

On the other hand, when the door on which the latch mechanism is mounted is slammed closed, pressure will be applied to the retracting arm, so that the axle will move out of the dead-locked position to enable the latch bolt to be retracted around the striker plate.

It will be appreciated from the above and after a consideration of the detailed description of the drawings, below, that, at least in some embodiments, the latch mechanism of the present invention can incorporate a high degree of "throw" or "travel", thus producing a latch mechanism of relatively high security, compared to its size.

Moreover, in preferred embodiments, the latch bolt may be swivelled to an unlocked position in an action separate from unlocking of the mechanism by a key.

It will also be appreciated that the latch mechanism of the present invention can o 20 be attached to various forms of cam locks. This has decided advantages, since the latch mechanism of the present invention can be retro-fitted to existing cam locks, thus enabling a significant increase in security without high cost or the need to replace the entire lock.

It will further be appreciated that, because the latch mechanism of the present 25 invention enables a door on which it is mounted to be slammed closed, this overcomes a drawback with many currently-used cam locks, such as those on cash drawers, where the cam is easily bent out of shape if the drawer is slammed closed when the cam is in the exposed position.

o:\patents\comp\8986a.doc Brief Description of the Drawings: The invention will now be described in connection with the attached drawings, in which: Figure 1 is an exploded perspective view of a first embodiment of the invention, showing the components disengaged from a cam lock; Figure 2 shows in perspective view the first embodiment attached to the cam lock; Figure 3 shows the first embodiment in a final assembled position, ready for use; Figure 4 illustrates the first embodiment bearing against a striker plate; Figure 5 shows the first embodiment in the locked position behind the striker plate; Figure 6 shows the first embodiment after it has been rotated through 900; Figure 7 is a plan view (from below) of the first embodiment in the 15 configuration in Figure 6; Figure 8 is an enlarged view of the angled slot shown in Figure 7; Figure 9 is a side elevation of the first embodiment, viewed in the direction of arrow X in Figure 7; 00:0 Figure 10 is a front elevation of the first embodiment, viewed in the direction of arrow Y in Figure 7; Figure 11 is a plan view of a prior art latch and illustrates an example of the amount of "throw" or "travel" in the prior art latch; Figure 12a shows a plan view of the first embodiment in the locked position, while Figure 12b shows the same view in the unlocked position, Figures 12a and 12b together showing the increase in locking engagement achieved in the case of the first embodiment; 4 o:\patents\comp\8986a.doc Figure 13 shows the forces applicable to the first embodiment when deadlocked; Figure 14 is a plan view of the first embodiment and shows the effect of applying pressure to the retracting arm in the first embodiment; Figure 15 shows in front elevation the external appearance of a poker machine door carrying the first embodiment of the invention; Figure 16 shows in perceptive view a second embodiment of the latch mechanism of the invention, before final assembly; Figure 17 shows the second embodiment in the assembled position; Figure 18 is a perspective exploded view of a third embodiment of the latch mechanism of the invention; Figure 19 is a perspective view of the third embodiment, assembled; Figure 20 is a plan view of the third embodiment in the latching position in relation to a striker plate; and 15 Figure 21 is a plan view of the third embodiment in the locked position.

Turning first to Figure 1 relating to the first embodiment, latch mechanism 10 has a sliding latch bolt 12 which is generally U-shaped in cross-section, the having a flat base. In Figures 1 to 5 one side of bolt 12 is partially broken away to show the flat base. The base of bolt 12 includes an elongated slot 13. Angled slots 32 ••loel 20 are formed in bolt 12. Each slot 32 is generally L-shaped and has a first part 34 which is approximately at right angles to the second part 36. It is to be appreciated that angled slot 32 may have a shape other than the one illustrated :00i and that first part 34 and second part 36 of angle slot 32 may be inclined to each other at an angle other than 900.

S.0 25 Latch bolt retracting arm 14 is pivotally connected to bolt 12 by means of axle 16 which bridges slots 32 and is received within those slots. Axle 16 can move from first part 34 to second part 36 of slot 32, and vice versa.

o:\patents\comp\8986a.doc Pivotally connected to arm 14 is support bracket 18, in which is formed slot 19.

Latch return spring 20 is connected at the base of slot 19 at one end and to an aperture in arm 14 at the other.

Bracket 22 is sized to fit within latch bolt 12 and secure cam lock 28 via spacer ring 26 and securing nut 24 adapted to mate with screw thread 27 on cam lock 28. Bracket 22 does not impede the sliding action of bolt 12. Elongated slot 13 permits bolt 12 to slide until cam lock 28 meets one end or the other of slot 13.

Securing screw 30 is for securing support bracket 18 to bracket 22, securing screw 30 passing through holes 31 and 33.

In Figure 2, nut 24 and spacer ring 26 are shown assembled with bracket 22 and cam lock 28. It will be noted that easy access to nut 24 is afforded by the fact that arm 14 and bracket 18 are rotated out of the way.

In Figure 3, latch mechanism 10 is shown in assembled position, ready for use, with securing screw 30 for bracket 18 in place. Axle 16 has moved down first part 34 of slot 32 and has deadlocked into second part 36 of slot 32.

In Figure 4, latch mechanism 10 is shown with arm 14 in the depressed position it assumes when encountering the front of striker plate 38. In contrast to the configuration of Figure 3, in Figure 4 pressure by striker plate 38 against arm 14 has caused axle 16 to be pushed out of second part 36 of slot 32 and to travel to 20 the other end of first part 34 of slot 32. This causes retraction of bolt 12, thus permitting latch mechanism 10 to pass striker plate 38.

In Figure 5, latch mechanism 10 is shown in locked position behind striker plate 38. Once striker plate 38 no longer applies pressure to retracting arm 14, bolt 12 is no longer retracted and springs out to the locked position shown behind striker So 25 plate 38. At the same time, axle 16 moves down slot 32 to second end 36, to assume the deadlocked position. Once this position is achieved, latch mechanism is caught behind striker plate 38 and cannot be released until rotated after insertion of the correct key in cam lock 28.

o:\patents\comp\8986a.doc This is illustrated in Figure 6, which shows how, after the correct key has been inserted in cam lock 28, latch mechanism 10 is rotated through 900 so that it clears striker plate 38 and the door to which latch mechanism 10 is attached can be opened.

Turning now to Figures 7, 8 and 9, it can be seen that axle 16 is trapped in second part 36 of slot 32 and this prevents retraction of bolt 12. Pressure on arm 14 (for example, when it presses against striker plate 38) will push axle 16 further down slot 32 into first part 34 and thus permit retraction of bolt 12 Figure 10 clearly illustrates slot 13 which defines the amount of "throw" or "travel" which can be achieved by bolt 12. Cam 28 is opened by an appropriate key inserted in key profile Figure 11 shows a prior art latch mechanism 42, showing how bolt 44 has a relatively small amount of "throw" or "travel", the amount being indicated by arrow 46, in relation to striker plate 38.

This is contrasted with latch mechanism 10, since as can be seen from Figures 12a and 12b, the amount of "throw" or "travel" afforded by reason of the construction of bolt 12, arm 14 and bracket 18 to a triangular configuration is i. ,.much more substantial, as indicated by arrow 48. Thus it will be appreciated that latch mechanism 10 is likely to be far more secure than latch mechanism 42.

20 AS will be seen from Figure 13, when bolt 12 is in the locked position, axle 16 is in second part 36 of slot 32 and thus bolt 12 is deadlocked. Pivot point A and slot 36 are in fixed positions with regard to each other at this stage. Any attempt to retract bolt 12 will jam it; any attempt to retract bolt 12 without pressing on arm 14 would require point A and slot 36 to move closer to each other, which cannot be .i 25 done for practical purposes.

With reference now to Figure 14, it will be seen that pressure applied to arm 14 in gille""the direction of arrow 50 moves axle 16 out of second part 36 of slot 32. Axle 16, once clear of the angle in slot 32, is free to move down into first part 34 and latch 12 can be retracted.

o:\patents\comp\8986a.doc It will be appreciated (and this is illustrated in Figure 15) that when latch mechanism 10 is mounted behind a door 54, when latch mechanism 10 is in the closed position, only bolt 12 is accessible through gap 52 between door 54 and jamb 56. Consequently, if an unauthorised person attempted to "spring" latch mechanism 10, by means of a knife or screwdriver, for example, pressure applied on latch 12 would not release latch 12, for the reason described above in connection with Figure 13.

The second embodiment in Figures 16 and 17 (latch mechanism 110) is very similar to the embodiment described above, the main difference being that bolt 112 is of somewhat slimmer and smaller configuration compared to bolt 12 in the previous Figures. Bracket 118 includes slot 119 to which latch return spring 120 is connected. Cam lock 128 is similar to cam lock 28 in Figures 1 to 5. Figure 17 clearly shows pivot point 60 for arm 114 in its attachment to bracket 118. Arrow 62 is intended to show the rotational path of arm 114.

Referring now to the third embodiment in Figures 18 to 21, latch mechanism 210 is similar to latch mechanism 10 in Figures 1 to 5 in that it has sliding latch bolt 212 having a flat base in which there is an elongated slot 213.

However, latch mechanism 210 lacks a latch bolt retracting arm like arm 14 in Figures 1 to 5. In the third embodiment, the means for retracting latch bolt 212 20 include tapered portion 214.

Securing bracket 222 is sized to fit within latch bolt 212 and secure cam lock 228 via spacer ring 226 and securing nut 224 adapted to mate with screw thread 227 SSl *on cam lock 228. (Bracket 222 does not impede the sliding action of bolt 212).

Elongated slot 213 permits bolt 212 to slide until cam lock 228 meets one end or •25 the other of slot 213.

Sl Spring 220 provides the means for biasing latch bolt 212 into the locked position.

It will be noted from Figure 19 that there is easy access to nut 224.

As shown in Figure 20, when latch mechanism 210 is being closed, taper 214 presses against striker plate 238, causing latch bolt 212 to retract against the bias o:\patents\comp\8986a.doc of spring 220. As soon as latch mechanism 210 clears striker plate 238, latch bolt 212, under the bias of spring 220, slides to the locked position shown in Figure 21.

To unlock latch mechanism 210, the correct key is inserted in cam lock 228 and latch mechanism 210 is rotated through 90° in the same manner as in the case of the first embodiment.

It will be readily appreciated that the latch mechanism of the present invention can be fitted to numerous cam locks manufactured by various manufacturers.

Consequently, the latch mechanism of the present invention can be installed on existing sites, especially poker machine doors or drawers. It is also appreciated that the latch mechanism of the present invention is capable of providing a secure degree of locking. In some embodiments, the square channel configuration of bolt 12, 112 or 212 can add to the strength of the lock.

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Claims (8)

1. A latch mechanism which includes a sliding latch bolt adapted to be retained behind a striker plate when in a locked position, means for retracting the latch bolt when the means are pressed against the front of the striker plate and biasing means to urge the latch bolt into the locked position, wherein the latch bolt is adapted to swivel to an unlocked position.

2. The mechanism of claim, wherein the means for retracting the latch bolt include a taper on the latch bolt.

3. The mechanism of claim 1, wherein the means for retracting the latch bolt include an arm pivotally connected to the latch bolt by an axle.

4. The mechanism of claim 3 which includes a dead-lock mechanism.

The mechanism of claim 4 where in the dead-lock mechanism includes a pair of angled slots in which the axle for the retracting arm is mounted.

6. The mechanism of claim 2 or 3, wherein the biasing means includes a latch return spring.

7. The mechanism of any one of claims 1 to 6, when used in conjunction with a keyed cam lock.

8. A latch mechanism substantially as herein described with referent to Figures 1 to 10 and 12a to 15, or Figures 16 and 17 or Figures 18 to 21 of the accompanying drawings. Dated this 9 th day of July 2003 BRIAN FRANCIS PREDDEY By his Patent Attorneys SL..aw Chrysiliou Law