GB2305964A

GB2305964A - Releasably fastening machine guards to machines

Info

Publication number: GB2305964A
Application number: GB9520667A
Authority: GB
Inventors: Timothy Christopher Stubbs; Simon Bailey
Original assignee: Fortress Interlocks Ltd; Halma Safety Ltd
Current assignee: Fortress Interlocks Ltd; Halma Safety Ltd
Priority date: 1995-10-10
Filing date: 1995-10-10
Publication date: 1997-04-23
Anticipated expiration: 2015-10-10
Also published as: GB9520667D0; GB2305964B

Abstract

A key mounted on a machine guard is inserted into a lock 2 and has a tongue 8 with a lateral projection 9 that interacts successively with a wheel 13 and a pinion 19 which cannot turn until a cut-out 29 in the wheel 13 faces the pinion 19 and a pin 24 has been pushed aside by the tongue 8. A latching mechanism comprising a plunger 31 and a latching lever 34 prevents reverse rotation of the pinion 19, so that the key 4 is locked in. Sensors 38,39 detect the locked state and permit operation of the machine. The latching mechanism 31,34 is released by a solenoid 41 when the machine is inoperative.

Description

Safety Device This invention relates to a safety device comprising first and second mutually connectable components, the first component comprising a key and the second component comprising a lock which can prevent removal of the key until it is safe to do so.

Such devices are used in conjunction with machine guards, one component (usually that with the key) being mounted on the (movable) guard, the other being mounted on the machine, with the following purposes: a) To safeguard personnel, in that opening of the guard will halt/prevent restarting of the machine. This must be achieved with a very high degree of certainty, and to this end, a set of switches is usually connected in series, and then duplicated, to provide dual safety circuits.

b) To prevent access to the machine/hazardous area, until the hazard has been halted. This is usually achieved via a machine control system, where the operator will select "stop at end of cycle", which will bring the machine to a controlled stop.

The machine may then utilise an electronic time delay, to provide an allowance for any time required to bring the machine completely to rest. A signal is then provided to a solenoid, which will be energised, thus allowing access through the guard.

In one aspect the invention provides a safety device with key-responsive mechanisms which interact when the key is inserted into the lock and which are difficult to defeat by inserting another object into the lock.

In another aspect, the invention provides a safety device with a latching mechanism which interacts with a key-responsive mechanism in order to prevent removal of the key.

Preferred and optional features of the safety device are set forth in the claims.

The invention will be described further, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cut-away diagrammatic side elevation of a safety device, in an open position; Figure 2 is an isometric view of two wheels of a first key-responsive mechanism of the safety device; Figure 3 is an isometric view of one pinion of a second key-responsive mechanism of the safety device; Figure 4 is a side-elevation of the other pinion of the second key-responsive mechanism; Figure 5 is a plan view of the pinion shown in Figure 4; Figure 6 is a section on line VI-VI in Figure 5; and Figure 7 is similar to Figure 1, but shows the safety device in the locked position.

The safety device illustrated in the drawings comprises a first component 1, which is mounted on a machine guard (not shown) and a second component consisting of a lock 2, which is mounted on a machine (not shown). The first component 1 comprises a bar 3 on which a key 4 is slidably mounted. The bar 3 has a series of depressions, in which a spring loaded element 7 on the key 4 can selectively engage in order to locate.the key at a selected position along the bar 3. Thus the key 4 can be kept in alignment with the lock 2, even if the guard becomes deformed as a result of age or abuse. The key 4 has a pair of elongate tongues 8 (only one of which is visible in Figures 1 and 7), each having an inwardly directed lateral projection 9 of circular cross-section, for interacting with two key-responsive mechanisms 11,12 in the lock 2.

The first key-responsive mechanism 11 comprises a pair of wheels 13 (Figure 2) which are independently rotatably mounted in the lock 2 and which have a common axis of rotation. Each wheel 13 has a groove 14 for accommodating the respective tongue 8 of the key 4. Each wheel 13 also has a peripheral recess 16 into which the respective lateral projection 9 fits as the key is inserted into the lock, causing the wheels 13 to rotate through about 900 in the clockwise direction against the action of a return spring 17 acting on an integral peg 18 on the outside face of each wheel 13.

The e second key-responsive mechanism 12 comprises a pair of independently rotatable pinions 19 (one of which is visible in Figure 1 and is shown in Figure 3, and the other of which is shown in Figures 4 to 6). Each pinion 19 has a groove 21 which accommodates the corresponding tongue 8 and which is terminated by a wall 22 that blocks complete insertion of the key 4 until the pinion 19 is free to rotate. Each pinion 19 also has a peripheral recess 23 into which the corresponding lateral projection 9 fits as the key 4 is inserted, causing the pinion 19 to turn through approximately 900 in a clockwise direction when the pin ions are free to rotate (about a common axis parallel to the common axis of the wheels 13).

The first key-responsive mechanism also includes a pair of spring-loaded sliding elements 24 which are received in slots 26 in the outer sides of the pinions 19. Figure 7 shows the head of one pin 24 in chain-dotted line. In the open position of the device (Figure 1) the enlarged head of the pin occupies an enlarged recess 27 at the end of the slot 26 and prevents the pinion 19 from rotating until the tongue 8 has pushed the pin 24 outwards (the pin normally projecting through the slot 26 into the tongue-receiving groove 21).

Each pinion 19 has a cut-out 28 in which the periphery of the corresponding wheel 13 is received, thereby preventing rotation of the pinion 19 in the open position shown in Figure 1.

Each wheel 13 has a cut-out 29 in which the periphery of the corresponding pinion 19 is received when the wheel has been rotated by insertion of the key, thereby permitting rotation of the pinion 19.

The second key-responsive mechanism 12 interacts with a latching mechanism comprising a plunger 31 urged upwards into contact with each pinion 19 by a spring (not shown). The plunger 31 is provided with a flexible seal arrangement 32. Each pinion 19 has a peripheral recess 33 into which the plunger 31 rises as the pinion is rotated to the position shown in Figure 7, thereby resisting subsequent rotation of the pinion. As the plunger 31 moves into this position, a latching lever 34 (including a counterweight 36) falls under the effect of a spring (not shown) from the position shown in Figure 1 to a latching position shown in Figure 7 in which it engages under a step 37 on the plunger 31 to prevent the plunger from moving out of the peripheral recess 33. In this way, the key 4 is prevented from being removed from the lock.

Microswitches 38,39, respectively, cooperate with the lever 34 and the bottom end of the plunger 31 to detect whether the lock 2 is in a locked state. The operation of the machine is controlled in response to the output of the detectors 38,39.

Control means responsive to the operational state of the machine include a solenoid 41 which moves the lever 34 to the unlatching position (Figure 1) only when the machine has ceased to operate. The key 4 can then be removed from the lock 2, during which procedure the parts of the lock return to the positions shown in Figure 1, in which the plunger 31 and lever 34 are prevented from activating the sensors 38,39. The step 37 prevents the lever 34 from moving from the position shown in Figure 1 if the solenoid 41 happens to be energised or de-energised while the key 4 is out of the lock.

The counterweight 36 on the latching lever 34 protects against accidental unlatching of the plunger 31 due to shock and vibration during the operation of the machine.

A rotary member 42 can be turned by a key to move a cam 43 from an inactive position (shown in full line in Figs. 1 and 7) to an active position (shown in chain-dotted line in Fig. 7) in which it pushes the solenoid core down to unlatch the plunger 31 in an emergency or if the solenoid 41 has failed.

The above-described device offers high security against defeat of the key-lock interface mechanisms due to the duplicated (mirrored) key-responsive wheels and pinions.

Claims

Claims:

1. A safety device comprising first and second mutually connectable components, the first component comprising a key and the second component comprising a lock, wherein the lock comprises: a first key-responsive mechanism which interacts with the key, the said first mechanism changing from a first state to a second state when the key is inserted into the lock and changing from the second state to the first state when the key is removed from the lock;; a second key-responsive mechanism which interacts with the key and with the said first mechanism, the said second mechanism changing from a first state to a second state when the key is inserted into the lock and changing from the second state to the first state when the key is removed from the lock, the said first mechanism in its first state preventing the said second mechanism from changing states and in its second state permitting the said second mechanism to change states; a latching mechanism which interacts with the said second mechanism, the latching mechanism having an unlatched state in which it permits the said second mechanism to change states and a latched state in which it prevents the said second mechanism from changing from its second state to its first state and thereby prevents removal of the key; control means for selecting the state of the latching mechanism; and detecting means for detecting whether the lock is in a locked state in which the said first and second mechanisms are in their respective second states and the latching mechanism is in its latched state.

2. A safety device as claimed in claim 1, in which the said second key-responsive mechanism comprises a pinion which is rotated by the key during insertion and removal.

3. A safety device as claimed in claim 2, in which the said first key-responsive mechanism comprises a wheel which is rotated by the key during insertion and removal.

4. A safety device as claimed in claim 3, in which the pinion has a cut-out in which the periphery of the wheel is received when the said second mechanism is in its first state, thereby preventing rotation of the pinion, and the wheel has a cut-out in which the periphery of the pinion is received when the said first mechanism is in its second state, thereby permitting rotation of the pinion.

5. A safety device as claimed in any of claims 2 to 4, in which the said first key-responsive mechanism comprises a sliding element which abuts against an abutment surface in the pinion in the absence of the key, thereby preventing rotation of the pinion, and which is slid by the inserted key to a position in which it no longer abuts against the abutment surface, thereby permitting rotation of the pinion.

6. A safety device as claimed in any of claims 2 to 5, in which the latching mechanism comprises a plunger which is received in a recess in the periphery of the pinion, thereby preventing rotation of the pinion, when the said second mechanism is in its second state and the latching mechanism is in its latched state.

7. A safety device as claimed in claim 6, in which the latching mechanism includes a latch which, when the plunger is received in the said recess, is movable to and from a latching position in which it prevents the plunger from moving out of the recess.

8. A safety device as claimed in claim 7, in which the latch comprises a lever.

9. A safety device as claimed in claim 8, in which the lever has a counterweight which acts so as to resist accidental unlatching.

10. A safety device as claimed in any preceding claim, in which the first and second key-responsive mechanisms are each duplicated.

11. A safety device as claimed in any preceding claim, in which the detecting means comprises at least one sensor responsive to the latched state of the latching means.

12. A safety device as claimed in any preceding claim, in which the key comprises at least one elongate tongue and at least one lateral projection for interacting with the said key-responsive mechanisms.

13. A safety device as claimed in any preceding claim, in which the said first component comprises a bar on which the key is slidably mounted, and locating means for locating the key at a selected position along the bar.

14. A safety device as claimed in any preceding claim, in which one of the said first and second components is mounted on a machine and the other is mounted on a machine guard, the operation of the machine being controlled in response to the said detecting means, and the said control means being responsive to the operational state of the machine so as to select the unlatched state of the latching mechanism only when the machine is inoperative.

15. A safety device substantially as described with reference to the accompanying drawings.