This disclosure relates generally to locks and in particular to locks that are resistant to forceful attacks.
One of the most common type of lock used today is a cylinder lock. It is often used to secure an interior space of a device in a public area. For example, such a lock may be used to secure a coin vault door or access panel of a parking meter or vending machine. Such a lock may also be used in securing cabinets or other housings, such as electrical or telecommunication cabinets.
Due to their popularity and vulnerability, traditional cylinder locks have been a target of vandals and thieves wishing to gain access to the space being secured by the lock. Cylinder locks may be vulnerable to unauthorized opening through lock picking techniques, or more forceful techniques that break the lock.
As seen in
The inner cylinder 106 is prevented from rotating within the housing 102 by a plurality of spring loaded pins 112 that project between the housing 102 and the inner cylinder 106. Each pin is composed of at least two portions 112a and 112b, with a shear line 114 created between the two portions. In order to allow the inner cylinder 106 to rotate within the housing 102, all of the pins 112 need to be aligned within the inner cylinder 106 and housing 102 so that the shear line 114 of each pin 112 is aligned with a shear line 116 of the lock where the inner cylinder 106 meets the housing 102.
A key 108 having a specific cut or pattern will cause the plurality of spring loaded pins 112 to be pushed or pulled in or out (the direction depending on the cylinder lock design) of the housing 102 and inner cylinder 106, and to align the shear line 114 of each pin with the shear line 116 of the lock. Once the pins 112 are properly aligned the inner cylinder 106 can freely rotate. Other components may be mechanically coupled to the inner cylinder 106 of the lock to also rotate or disengage allowing a door to be opened or a locked cavity to be accessed when the inner cylinder 106 is rotated.
Most cylinder locks rely solely on the lock pins to prevent the rotation of the inner cylinder in a lock. Although other techniques of unlocking a lock without a key exist, a common method of lock attack, depicted in
A similar method of lock attack, depicted in
In accordance with the disclosure there is provided a tamper resistant lock comprising a primary locking mechanism and a secondary locking mechanism. The primary locking mechanism has a longitudinal cylinder within a housing, the longitudinal cylinder rotatable within the housing, the longitudinal cylinder coupled to an actuator that is rotatable between a locked position and an unlocked position when an appropriate key is received within the longitudinal cylinder. The secondary locking mechanism prevents rotation of the actuator when a tampering force parallel to a longitudinal axis of the longitudinal cylinder is applied to the primary locking mechanism. The secondary locking mechanism, when engaged, couples the actuator to the housing of the primary locking mechanism.
In accordance with the disclosure there is also provided a securable device comprising a body having an interior space to be secured, an access panel in the body and a tamper resistant lock in accordance with the disclosure.
Tamper resistant locks are described with reference to the drawings. Like numbers are used to denote similar elements throughout the drawings in which:
A tamper resistant lock system is described that has a secondary locking mechanism. Attempts to forcefully unlock the tamper resistant lock system by shearing the pins of the lock will engage the secondary locking mechanism and prevent unlocking. Although forceful attacks may damage or destroy components of the cylindrical lock, the secondary locking mechanism, when engaged, prevents the lock from rotating and thus safeguards the contents of the locked space.
The tamper resistant lock system described herein may be used to secure a vault door to a cash box of an unattended parking meter. The tamper resistant lock described herein may also be used in various devices other than a parking meter.
When a vandal attacks the parking meter in the field, they may slide an anti drill cover shielding the lock to the side and then forcefully drive a tip a flat blade screwdriver into the keyway slot of the inner cylinder of the lock. This can be done by using a hammer or sledge to strike the back handle of the screwdriver. The screwdriver must be driven into the keyway slot with sufficient force that it will not come loose when subsequently forcing the inner cylinder to rotate. Alternatively the inner cylinder may be struck with sufficient force to drive the inner cylinder partially through the housing. Both attacks require a substantial amount of force be applied to the inner cylinder.
In order to secure the door, even when the cylindrical lock is forcefully attacked, a secondary locking mechanism is included. The secondary locking mechanism is engaged when a force is applied to the cylindrical lock that is above a threshold. As described further herein, this tampering force causes an interacting component coupled to the inner cylinder to be displaced towards a corresponding interacting component coupled to the housing. The two interacting components, when displaced relative to each other can engage with each other and prevent the cam plate of the tamper resistant lock from rotating and so prevents the tamper resistant lock from unlocking.
The tamper resistant lock 500 comprises a backing plate 502. The backing plate 502 may be part of a frame of a door that is being secured, or part of a housing of a device incorporating the tamper resistant lock 500, or other suitable component. A mounting plate 316 is secured to the backing plate 502 by one or more members 506. As depicted, the members 506 may surround a pin, bolt or similar means 508 fastened to the backing plate 502. A fastener 510, such as a nut or cap, may be used to secure the mounting plate 316 to the member 506. The member 506 displaces the mounting plate 316 from the backing plate 502.
A cylindrical lock 314 may be used as the primary locking mechanism of the tamper resistant lock 500. The cylindrical lock 314 comprises a housing 514 that is securely mounted to the mounting plate 316. The housing 514 may include an exterior lip 516 that is secured against the mounting plate by a nut 518 on the housing 514 tightened on the opposite side of the mounting plate 316. The cylindrical lock 314 further comprises a longitudinal cylinder 520 within the housing 514. The longitudinal cylinder 520 is free to rotate within the housing 514. As will be appreciated, the rotation of the inner longitudinal cylinder 520 is prevented by a plurality of pins that can be aligned to allow rotation of the inner longitudinal cylinder 520 with an appropriate key. A cam plate 318 is secured to the longitudinal cylinder 520. The cam plate 318 may be coupled to the longitudinal cylinder 520 using, for example, a pair of nuts 524, 526 on the longitudinal cylinder 520, or more securely by welding. The cam plate 318 allows the rotation of the longitudinal cylinder 520 to actuate one or more locking bars 320 each rotatably connected to the cam plate 318 through respective connecting pins 530. It will be appreciated that the cam plate 318 is one example of an actuator. Various other actuators may be used in order to actuate the locking bars 320 or other means used to secure the locked space. An actuator may be coupled to the longitudinal cylinder 520, or form a part of the longitudinal cylinder 520 as described further herein.
Rotation of the longitudinal cylinder 520 within the housing 514 may cause the cam plate 318 to also rotate between a locked and an unlocked position. The rotation of the cam plate 318 actuates the locking bars 320 so that they are extended in the locked position, and retracted in the unlocked position.
As described further below, the tamper resistant lock 500 further comprises a secondary locking mechanism for securing the cam plate 318 from rotating when the secondary locking mechanism is engaged. The secondary locking mechanism includes a locking pin 532 that is securely mounted, for example by welding, to the backing plate 502, and is aligned with a corresponding locking hole 534 in the cam plate 318 when the cam plate 318 is in the locked position. The locking pin 532 and corresponding locking hole 534 are longitudinally displaced from each other when the secondary locking mechanism is not engaged, allowing the cam plate 318 to rotate freely with the longitudinal cylinder 520.
The thickness of the mounting plate may be selected so that it will deform when a force greater than a threshold force is applied. The particular threshold of the force required to deform the mounting plate, and so engage the secondary locking mechanism, may be determined based on the requirements of the tamper resistant lock 500.
In order to reduce the possibility of shearing off the locking pin 532, and so disengage the secondary locking mechanism, by forceful rotation of the longitudinal cylinder 520, the coupling of the cam plate 318 to the longitudinal cylinder 520 may be made so as to allow the cam plate 318 and longitudinal cylinder 520 to slip relative to each other. This slippage may be accomplished by sufficiently tightening the nuts 524, 526 securing the cam plate 318 to the longitudinal cylinder 520 so that the longitudinal cylinder 520 and cam plate 318 will be secured and work under normal operation and torque applied to the longitudinal cylinder 520, but will slip when a greater torque is applied. This allows the longitudinal cylinder 520 to rotate, while the cam plate 318 that actuates the locking bars 320 remains secured in position by the secondary locking mechanism.
The tamper resistant lock 600 further includes a secondary locking mechanism that, similar to the tamper resistant lock 500, is engaged by the application of a force above a threshold parallel to the longitudinal axis of the longitudinal cylinder 520. The secondary locking mechanism comprises a locking pin 532 that interacts with a locking hole 534 on the cam plate 318 when the secondary locking mechanism is engaged. The secondary locking mechanism also includes an engaging component that allows longitudinal movement of the cam plate when a large force is applied to the longitudinal cylinder 520. However, unlike the tamper resistant lock 500 that used a deformable mounting plate 316, the mounting plate 604 does not deform significantly under the tampering force. In the case of tamper resistant lock 600, the engaging component is provided by the primary locking mechanism. That is, pins of the cylindrical lock act as an engaging component. As described above with reference to
The tamper resistant lock 700 has an engaging component of the secondary locking mechanism that differs from the engaging components of the tamper resistant locks 500 and 600. As depicted in
The tamper resistant lock 800 has an engaging component of the secondary locking mechanism that differs from the engaging components of the tamper resistant locks 500, 600 and 700. As depicted in
The tamper resistant locks 500, 600, 700 and 800 described above have included a secondary locking mechanism that included a locking pin 532 on the backing plate 502 and a corresponding locking hole 534 on a cam plate 318. It will be apparent that the secondary locking mechanism may comprise a plurality of locking pins and corresponding locking holes. Furthermore, the pins and holes may be located on different parts than those described. Further still, it will be appreciated that the secondary locking mechanism does not require the use of a locking pin and locking hole, and may comprise an interacting component having a first interacting component coupled to the longitudinal cylinder and a second corresponding interacting component coupled to the housing.
The force that may be applied to pull the cam plate away from the backing plate may not be large as there are limited locations for applying the force. As such, the tertiary lock as described in either of
Although not depicted in
A tamper resistant lock has been described by way of several variations. It will be appreciated that components of one variation may be incorporated into other variations. Furthermore, variations and modifications not described herein will be apparent to one of ordinary skill in the art having regard to the description herein.
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