Locking mechanism

Abstract

A locking mechanism including a plunger, a plurality of locking elements, a cage including apertures in which the locking elements are housed, and a sleeve, with the sleeve moveable with respect to the cage between an unlocked position and a locked position, and when the sleeve is in the locked position, the sleeve maintains the locking elements in engagement with a recess on the plunger to restrict movement of the plunger.

Claims

1. An electric strike, comprising: a housing; a keeper pivotally mounted in the housing and moveable between a closed position and an open position; a plunger operably engaged with the keeper; a cage defining a plurality of apertures; a plurality of locking elements positioned within the apertures in the cage; and a sleeve movable with respect to the cage between an unlocked position and a locked position, wherein the sleeve maintains the plurality of locking elements in engagement with the plunger and restricts movement of the plunger when in the locked position to prevent movement of the keeper from the closed position to the open position.

2. The electric strike of claim 1, wherein the sleeve is displaced between the unlocked position and locked position by rotation of the sleeve.

3. The electric strike of claim 1, wherein the sleeve releases the engagement of the locking elements with the plunger when the sleeve is in the unlocked position.

4. The electric strike of claim 1, wherein the unlocked position of the sleeve permits movement of the plunger to allow the keeper to move from the closed position to the open position.

5. The electric strike of claim 1, wherein movement of the keeper from the closed position to the open position causes corresponding movement of the plunger through cooperation of the plunger with a formation on the keeper.

6. The electric strike of claim 1, wherein the sleeve includes a threaded portion, and wherein rotation of the sleeve causes linear movement of the sleeve.

7. The electric strike of claim 1, wherein the plunger is biased towards an extended position in which the plunger engages with a formation on the keeper.

8. The electric strike of claim 1, further comprising a motor that drives rotation of the sleeve to move the sleeve between the unlocked position and the locked position.

9. The electric strike of claim 8, wherein a gearbox is engaged between the sleeve and the motor.

10. The electric strike of claim 8, wherein the motor is powered by an external power source, and wherein the electric strike further comprises an onboard power source arranged to provide power to the motor to selectively rotate the sleeve and to move the sleeve to the unlocked position when power from the external power source is removed.

11. The electric strike of claim 8, wherein the motor is structured to rotate the sleeve to the unlocked position in response to an unlocking signal, and to rotate the sleeve to the locked position in response to a locking signal.

12. The electric strike of claim 11, further comprising a controller in communication with the motor, wherein the controller includes an onboard power source and is structured for connection to an external power source, wherein the controller is configured to use power from the onboard power source in response to failure of the external power source.

13. The electric strike of claim 12, wherein the controller is selectively operable in each of a fail secure mode and a fail safe mode.

14. The electric strike of claim 13, further comprising a dip switch in communication with the controller, wherein the controller is configured to operate in the fail secure mode in response to a first position of the dip switch and to operate in the fail safe mode in response to a second position of the dip switch.

15. The electric strike of claim 12, wherein the onboard power source comprises a capacitor.

16. The electric strike of claim 12, wherein the motor is structured to rotate the sleeve in a first direction in response to the unlocking signal and to rotate the sleeve in a second direction opposite to the first direction in response to the locking signal.

17. The electric strike of claim 1, wherein the cage includes a flange engaged with the housing, and wherein engagement between the flange and the housing restricts movement of the cage with respect to the housing.

18. The electric strike of claim 1, wherein the sleeve further comprises a dog; wherein a protrusion extends from the cage and into the dog; and wherein engagement between the dog and the protrusion limits rotation of the sleeve to move between the unlocked and locked positions with respect to the cage.

19. The electric strike of claim 1, wherein the locking elements are generally spherical.

20. The electric strike of claim 1, wherein the locking elements comprise balls.

21. An electric strike, comprising: a housing; a keeper pivotally mounted in the housing and moveable between a closed position and an open position; a plunger operably engaged with the keeper; a cage defining a plurality of apertures; a plurality of locking elements positioned within the apertures in the cage; and a sleeve movable with respect to the cage between an unlocked position and a locked position; wherein the sleeve maintains the plurality of locking elements in engagement with the plunger and restricts movement of the plunger when in the locked position, to prevent movement of the keeper from the closed position to the open position; and wherein the sleeve releases the engagement of the locking elements with the plunger, when the sleeve is in the unlocked position, and wherein the unlocked position of the sleeve permits movement of the plunger to allow the keeper to move from the closed position to the open position.

22. The electric strike of claim 21, further comprising a motor, and wherein the sleeve is displaced between the unlocked position and locked position by rotational actuation of the sleeve by the motor.

23. An electric strike, comprising: a housing; a keeper pivotally mounted in the housing and moveable between a closed position and an open position; a plunger operably engaged with the keeper; a cage defining a plurality of apertures; a plurality of locking elements positioned within the apertures in the cage; a sleeve movable with respect to the cage between an unlocked position and a locked position, wherein the sleeve maintains the plurality of locking elements in engagement with the plunger and restricts movement of the plunger when in the locked position to prevent movement of the keeper from the closed position to the open position; and an actuator that displaces the sleeve between the unlocked position and the locked position, wherein the actuator is powered by an external power source, and wherein the electric strike further comprises an onboard power source arranged to provide power to the motor to selectively move the sleeve to the unlocked position when power from the external power source is removed.

24. The electric strike of claim 23, wherein the actuator comprises a motor that drives rotation of the sleeve between the unlocked position and the locked position.

25. The electric strike of claim 23, further comprising a controller in communication with the motor, wherein the controller includes the onboard power source and is structured for connection to the external power source, wherein the controller is configured to use power from the onboard power source in response to failure of the external power source.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 is an exploded perspective view of a locking mechanism according to an embodiment of the invention;

(3) FIG. 2 is a rear perspective view of an electric strike incorporating the locking mechanism of FIG. 1;

(4) FIG. 3 is an exploded perspective view of the electric strike of FIG. 2;

(5) FIGS. 4 to 6 are cross sectional views of the strike of FIG. 2 illustrating switching from the locked condition to the unlocked condition whilst under pre-load;

(6) FIG. 7 is an exploded perspective view of another embodiment of a locking mechanism;

(7) FIG. 8 illustrates additional views of the locking mechanism of FIG. 7;

(8) FIGS. 9 and 10 illustrate the locking mechanism of FIG. 7 incorporated into an electric strike; and

(9) FIGS. 11 to 13 depict a sequence of operation of the electric strike of FIG. 9.

DETAILED DESCRIPTION

(10) Referring to FIG. 1, a locking mechanism 16 is shown in exploded detail and includes a plunger 20, four locking elements in the form of spherical balls 22, a sleeve 24, and a cage 26 which retains balls 22 in apertures 28. Cage 26 includes a mounting flange 27 and bears an external screw thread 30 which engages with an internal screw thread 31 provided inside sleeve 24. Sleeve 24 includes a dog 38 which is used to rotate the sleeve, as will be later described. Plunger 20 includes a tail which is inserted through both cage 30 and sleeve 24 and is secured by way of circlip 34 which engages with groove 36 on tail 32. Plunger 20 can move against the biasing force of compression spring 39 if the sleeve is in a position wherein balls 22 are free to move out of engagement of recess 40 of plunger, as will be later described. Rubber O rings 41, 43 keep dust or other debris from entering the mechanism.

(11) Referring to FIG. 2, an electric strike 10 is shown including the locking mechanism 16 of FIG. 1. Strike 10 includes a keeper 12 and a housing 14. Keeper 12 is pivotally mounted to housing and is moveable between a closed position as seen in FIG. 1 to an open position, as is well known in the art. In the closed position the keeper retains a latch of a mechanical door lock (not shown). Locking mechanism 16 controls whether the strike is in a locked or unlocked condition depending upon whether plunger 20 is free to move inwardly of cage 26, as will now be described.

(12) Referring to FIG. 3, locking mechanism 16 is mounted in housing 14 by way of inserting cage 26 into aperture 42 from the right hand side, as shown in the figure. Mounting flange 27 limits the depth of insertion of cage 26 and prevents movement of cage 26 to the left, as shown in the drawings.

(13) A motor 46 and gearbox 48 arrangement is used to rotate sleeve 24. The output shaft of gearbox 48 carries a second dog 50 which engages with dog 38 of sleeve 24. The dogs 50, 38 are arranged in a sliding fit with one another. As will be seen, dog 50 remains in a laterally fixed position within the housing 14 on the end of the output shaft of gearbox 48, whereas sleeve 24 moves linearly to the left and to the right as sleeve 24 rotates by interaction of screw threads 30 and 31. The dogs 50, 38 accommodate the linear movement of the sleeve to maintain rotational control of sleeve 24 by the motor 46 and gearbox 48 combination.

(14) Referring to FIG. 4, the strike is shown in cross sectional view in the locked and closed position. It can be seen that plunger 20 includes a tapered end, which is lying in a correspondingly tapered recess 13 in keeper 12. If a force is applied to keeper 12 to move the keeper to the open position, then this force is translated to urge the plunger to move linearly to the left in the drawings by interaction of the tapered plunger 20 and tapered recess 13.

(15) As can be seen from FIG. 4, the balls 22 are engaged with recess 40 of plunger 20 to prevent movement of plunger 20. The balls are retained in engagement with recess 40 by being surrounded by sleeve 24. The engagement of the balls 22 with recess 40 prevents movement of plunger 20, and therefore the strike is in a locked condition. Load applied to the keeper is transmitted to the plunger and is resisted by the balls 22 being restrained from moving outwardly by sleeve 24, and being restrained from moving to the left by apertures 28 of cage 26. It is to be noted that cage 26 cannot move to the left (as seen in the drawings) by way of engagement of flange 27 with aperture 42. Therefore, load applied to the keeper when in a locked state is borne by cage 26 in a lateral direction and radially by sleeve 24.

(16) Operation of the strike to move from the locked condition to the unlocked condition is illustrated by the sequence shown in FIGS. 4 to 6. Referring to FIG. 5, with load applied to the keeper 12, lock has received a signal to move to the unlocked condition. Motor 46 has been activated to rotate sleeve 24 to cause it to move to the left in the drawings by way of rotating on screw thread 30. There is a frictional force between balls 22 and the inside surface of sleeve 24 due to the plunger 20 urging the balls 22 radially outwardly. However, motor 46 and gearbox combination 46, 48 provides sufficient rotational force to overcome this. Furthermore, the sleeve 24 and balls 22 are formed from stainless steel with a smooth surface finish to minimize these frictional forces. In FIG. 5, the balls 22 are almost at the point where they are free to move radially outwardly and out of engagement with recess 40.

(17) Referring to FIG. 6, the sleeve 24 has continued to rotate and has moved further to the left, and the strike is now in the unlocked condition. Balls 22 are no longer retained by sleeve 24. The balls 22 have moved outwardly to come out of engagement with recess 40, and plunger 20 has moved to the left, coming out of engagement with recess 13 as keeper 12 has rotated to the open position, thereby releasing a door latch.

(18) Strike includes an on-board controller board or onboard power source 45 which provides power to the motor 46 to control the motor. The polarity of the power applied to the motor dictates whether the motor moves in a clockwise or anti-clockwise direction. The controller board senses when the sleeve is in the locked position by way of microswitch 17 which is actuated by the sleeve acting on pushrod 15. In other embodiments, the controller board may detect that the motor has reached the end of its stroke by the fact that, when unable to move further, the motor draws more current. This increase in current can be used to assume that the sleeve has reached a desired position. In other embodiments optical sensors or Hall effect sensors are used to sense the position of the sleeve.

(19) Lock 10 can operate in two modes, Fail Safe and Fail Secure. In the Fail Secure mode, in the event of a power cut to the lock, the lock remains in the locked position. In the Fail Safe mode, if power to the lock is cut, then the lock moves to the unlocked position (FIG. 6). The Fail Safe mode requires an on board power supply such as a battery, capacitor or super capacitor. In the event of a power cut, the on board power supply is used to power the motor. The lock is switched between modes by way of a jumper or dip-switch provided on the controller PCB of the electric strike (not shown). The change of direction Fail Safe/Fail Secure can be made by either a manual function or electronically by means of reversing polarity on any form of electrical storage device, such as batteries or super capacitors.

(20) An alternative embodiment of a locking mechanism 116 and electric strike 110 will be described with reference to FIGS. 7 to 13. Parts corresponding to those seen in locking mechanism 16 will be indicated by like reference numerals prefixed by the number 1. Identical parts to those used in locking device 16 will be indicated by the same reference numbers. The major difference in locking device 116 is that the sleeve rotates through only 45 degrees to move between the locked and unlocked conditions.

(21) Referring to FIG. 7, a locking mechanism is shown including a sleeve 124, a cage 126 and a plunger 120. Cage 126 includes four apertures 128 in which are located locking elements in the form of balls 22. Sleeve 124 includes a series of four recesses 125 provided about its inside surface. When assembled, retaining pin 160 maintains sleeve 124 engaged to cage 126, and also serves to limit to the rotation of sleeve 124 with respect to cage 126 by engaging with arms of dog 138.

(22) Referring to FIG. 8, as best seen at section B-B, when the sleeve 124 is in the unlocked position, recesses 125 align with the positions of balls 22. In this position, plunger 120 may be pushed inwardly as balls 22 are free to move outwardly to enter recesses 125.

(23) To move to the locked position, sleeve 124 is rotated by 45 degrees. As best seen in section D-D, balls 22 are now prevented from moving outwardly, but are retained by sleeve 124 in engagement with recess 140 of plunger 120. In this position, plunger 120 cannot be pushed inwards.

(24) Referring to FIGS. 9 and 10, locking mechanism 116 fits to housing 114 by being inserted into aperture 142 from the left side as seen in the figures, and is secured by set screw 158 engaging with aperture 156 (see FIG. 8).

(25) Sleeve 124 is arranged to be rotated by way of a motor 146 and gearbox 148 combination which engages with sleeve 124 by way of dog 150.

(26) A ramp 154 provided on the end of sleeve 124 actuates pushrod 15 to depress microswitch 17, thus enabling remote monitoring of whether the strike 110 is in a locked condition.

(27) The sequence of operation of the strike 110 moving from the locked to the unlocked and open conditions is shown in FIGS. 11 to 13. In FIG. 11, sleeve 124 is in the locked position. Plunger 120 is prevented from being pushed into cage 126 by way of balls 22 engaging with recess 140 of plunger 120, and therefore keeper 12 is maintained in the closed position.

(28) In FIG. 12, sleeve 124 has been rotated through 45 degrees so that the recesses 125 align with balls 22.

(29) In FIG. 13, keeper 12 has rotated to the open position, pushing plunger 120 inwardly of cage 126.

(30) It has been found that locking mechanisms according to embodiments of the invention have excellent operating characteristics under pre-load conditions. That is, the sleeve of the locking mechanism can be moved with respect to the cage even whilst a considerable force is simultaneously being applied to the plunger of the mechanism.

(31) Whilst the above described embodiment utilizes a motor and gearbox to drive the lock mechanism, in other embodiments, a motor could be used without a gearbox. As a further alternative, the mechanism can be driven by a solenoid.

(32) Whilst the locking mechanism has been described with reference to use in a locking device in the form of an electric strike, it can similarly be used in locks of other types including gate locks, drop bolts and electric mortise locks.

(33) It can be seen that embodiments of the invention have at least one of the following advantages.

(34) The locking mechanism has excellent pre-load characteristics.

(35) In the event of loss of power, the lock can be moved to its unlocked condition using on board power supply.

(36) Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.

(37) Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention.