GB2065216A

GB2065216A - Bolt mechanism

Info

Publication number: GB2065216A
Application number: GB8037088A
Authority: GB
Original assignee: SPONMECH Ltd
Current assignee: SPONMECH Ltd
Priority date: 1979-12-13
Filing date: 1980-11-19
Publication date: 1981-06-24
Also published as: GB2065216B

Abstract

A bolt mechanism, particularly intended as a machine guard shot bolt, comprises an axially slidable bolt head 11 and an actuator element 14 axially slidable with respect to the bolt head 11. Adjacent faces 15, 16 of the head 11 and element 12 can abut, and the head 11 and element 12 are interengaged by a linkage 19 which extends when the faces 15, 16 are in contact, so as to be unable to pass through an aperture 22 in a relatively stationary housing 10. Movement of the element 12 to withdraw the bolt head 11 collapses the linkage 19, but the head 11 cannot be pushed to a withdraw position unless the element 12 is first moved. <IMAGE>

Description

SPECIFICATION Bolt mechanism This invention relates to bolt mechanisms and in particular to such mechanisms when intended for shot bolts for machine guards.

Shot bolts for machine guards are commonly spring-biased towards an engaged position, and are operated away from the engaged position by a suitable actuating device when associated interlocking safety devices on the machine indicate that it is safe for the guard to be opened or removed. It is frequently possible for such shot bolts to be manually moved against their-biasing springs, enabling the machine guard to be opened or removed in an unauthorised manner, for example to clear a stoppage on the machine, even though the aforesaid interlocking safety devices do not indicate a safe condition. Such a practice is clearly dangerous, since clearing a stoppage, or other fault, can cause the machine to resume operation without warning.

It is an object of the invention to provide a bolt mechanism which can be withdrawn by an actuating force applied to an end of the mechanism remote from the bolt head, but which cannot be withdrawn by a force applied directly to the bolt head.

A bolt mechanism according to the invention comprises a housing, a bolt head, an actuator element, said head and said element being axially slidable with respect to each other and to said housing, said head and said element having respective opposed inter-engageable abutment faces, a linkage pivotally engaging said head and said element, said linkage having a first limiting operating position when said abutment faces are in contact, and a second limiting operating position when said faces have moved apart by a predetermined amount, a spring biasing said head against movement by said actuating element as said abutment faces move apart, and an aperture in said housing, through which aperture said linkage can pass only when adjacent its second limiting position.

In a preferred embodiment said linkage comprises a first arm pivotally mounted on said head and a second arm pivotally mounted on said actuator element, said first and second arms being pivotally interengaged at locations thereon remote from their pivotal engagement with said head and said actuator element respectively.

A particular embodiment includes a plurality of said first arms and of said second arms.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1, is a section through a bolt mechanism, in a first limiting position, Figure 2 shows a part of the mechanism of Figure 1 in a second limiting position, and Figure 3 is a view on arrow 3 in Figure 1 and with parts cut away for clarity.

The bolt mechanism includes a housing 10 in which a bolt head 11 is axially slidable. The head 11 includes a collar 12 which is engaged by a spring 13 which also engages a part of the housing and biases the head 11 towards a position in which it can engage a suitable boltreceiving means. An actuator element in the form of a stem 14 is also slidable within the housing 10 and is axially aligned with the bolt head 11.The head 11 and stem 14 have respective, opposed, axially-directed abutment faces 1 5, 16. The bolt head 11 and stem 14 are provided with respective devises 1 7, 1 8, adjacent the respective abutment faces 1 5, 1 6. A four-bar linkage 1 9 comprises a pair of arms 20 pivotally secured to the head 11 within the clevises and a pair of arms 21 pivotally secured to the stem 14 within the devises 1 8. The arms 20 are pivotally connected to respective ones of the arms 21 at locations spaced from the pivotal connections with the head 11 and stem 14.

The stem 14 passes through an aperture 22 in the housing 10, and the dimensions of the linkage 19 are such that when the abutment faces 1 5, 1 6 are in contact the linkage 1 9 will not pass through the aperture 22. The arms 20 have faces 23 which, in the operating position shown in Figure 1, extend normal to the sliding axis of the head 11 and stem 14, and can abut the housing 10 on opposite sides of the aperture 22. A force applied directly to the head 11 to move the latter against the spring 13 will bring the linkage 1 9 into engagement with the housing. Typically the stem 14 is movable by suitable pneumatic device, but may alternatively be operated by an electromagnet or other suitable means.The stem 14 may be moved leftward from the position shown in Figure 1 to that shown in Figure 2, causing the linkage 19 to collapse inwardly to a limiting position in which the arms 20, 21 abut, in which position the linkage 1 9 can pass through the aperture 22. Subsequent leftward movement of the stem 14 draws the head 11 leftward against the spring 13. When the stem 14 is in the position shown in Figure 2 it may be biased with a suitable light spring towards engagement with the adjacent face 15 of head 11.

As indicated above the bolt arrangement described is particularly intended as a shot bolt for a machine guard, the stem 14 being operated in unison with machine operation to prevent removal of the guard in which condition the bolt head 11 cannot be operated manually to release the guard.

1. A bolt mechanism comprising a housing, a bolt head, an actuator element, said head and said element being axially slidable with respect to each other and to said housing, said head and said element having respective opposed interengageable abutment faces, a linkage pivotally engaging said head and said element, said linkage having a first limiting operating position when said abutment faces are in contact, and a second limiting operating position when said faces have moved apart by a predetermined amount, a spring

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Bolt mechanism This invention relates to bolt mechanisms and in particular to such mechanisms when intended for shot bolts for machine guards. Shot bolts for machine guards are commonly spring-biased towards an engaged position, and are operated away from the engaged position by a suitable actuating device when associated interlocking safety devices on the machine indicate that it is safe for the guard to be opened or removed. It is frequently possible for such shot bolts to be manually moved against their-biasing springs, enabling the machine guard to be opened or removed in an unauthorised manner, for example to clear a stoppage on the machine, even though the aforesaid interlocking safety devices do not indicate a safe condition. Such a practice is clearly dangerous, since clearing a stoppage, or other fault, can cause the machine to resume operation without warning. It is an object of the invention to provide a bolt mechanism which can be withdrawn by an actuating force applied to an end of the mechanism remote from the bolt head, but which cannot be withdrawn by a force applied directly to the bolt head. A bolt mechanism according to the invention comprises a housing, a bolt head, an actuator element, said head and said element being axially slidable with respect to each other and to said housing, said head and said element having respective opposed inter-engageable abutment faces, a linkage pivotally engaging said head and said element, said linkage having a first limiting operating position when said abutment faces are in contact, and a second limiting operating position when said faces have moved apart by a predetermined amount, a spring biasing said head against movement by said actuating element as said abutment faces move apart, and an aperture in said housing, through which aperture said linkage can pass only when adjacent its second limiting position. In a preferred embodiment said linkage comprises a first arm pivotally mounted on said head and a second arm pivotally mounted on said actuator element, said first and second arms being pivotally interengaged at locations thereon remote from their pivotal engagement with said head and said actuator element respectively. A particular embodiment includes a plurality of said first arms and of said second arms. An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1, is a section through a bolt mechanism, in a first limiting position, Figure 2 shows a part of the mechanism of Figure 1 in a second limiting position, and Figure 3 is a view on arrow 3 in Figure 1 and with parts cut away for clarity. The bolt mechanism includes a housing 10 in which a bolt head 11 is axially slidable. The head 11 includes a collar 12 which is engaged by a spring 13 which also engages a part of the housing and biases the head 11 towards a position in which it can engage a suitable boltreceiving means. An actuator element in the form of a stem 14 is also slidable within the housing 10 and is axially aligned with the bolt head 11.The head 11 and stem 14 have respective, opposed, axially-directed abutment faces 1 5, 16. The bolt head 11 and stem 14 are provided with respective devises 1 7, 1 8, adjacent the respective abutment faces 1 5, 1 6. A four-bar linkage 1 9 comprises a pair of arms 20 pivotally secured to the head 11 within the clevises and a pair of arms 21 pivotally secured to the stem 14 within the devises 1 8. The arms 20 are pivotally connected to respective ones of the arms 21 at locations spaced from the pivotal connections with the head 11 and stem 14. The stem 14 passes through an aperture 22 in the housing 10, and the dimensions of the linkage 19 are such that when the abutment faces 1 5, 1 6 are in contact the linkage 1 9 will not pass through the aperture 22. The arms 20 have faces 23 which, in the operating position shown in Figure 1, extend normal to the sliding axis of the head 11 and stem 14, and can abut the housing 10 on opposite sides of the aperture 22. A force applied directly to the head 11 to move the latter against the spring 13 will bring the linkage 1 9 into engagement with the housing. Typically the stem 14 is movable by suitable pneumatic device, but may alternatively be operated by an electromagnet or other suitable means.The stem 14 may be moved leftward from the position shown in Figure 1 to that shown in Figure 2, causing the linkage 19 to collapse inwardly to a limiting position in which the arms 20, 21 abut, in which position the linkage 1 9 can pass through the aperture 22. Subsequent leftward movement of the stem 14 draws the head 11 leftward against the spring 13. When the stem 14 is in the position shown in Figure 2 it may be biased with a suitable light spring towards engagement with the adjacent face 15 of head 11. As indicated above the bolt arrangement described is particularly intended as a shot bolt for a machine guard, the stem 14 being operated in unison with machine operation to prevent removal of the guard in which condition the bolt head 11 cannot be operated manually to release the guard. CLAIMS

1. A bolt mechanism comprising a housing, a bolt head, an actuator element, said head and said element being axially slidable with respect to each other and to said housing, said head and said element having respective opposed interengageable abutment faces, a linkage pivotally engaging said head and said element, said linkage having a first limiting operating position when said abutment faces are in contact, and a second limiting operating position when said faces have moved apart by a predetermined amount, a spring biasing said head against movement by said actuating element as said abutment faces move apart, and an aperture in said housing, through which aperture said linkage can pass only when adjacent its second limiting position.

2. A mechanism as claimed in claim 1 in which linkage comprises a first arm pivotally mounted on said head and a second arm pivotally mounted on said actuator element, said first and second arms being pivotally interengaged at locations thereon remote from their pivotal engagement with said head and said actuator element respectively.

3. A mechanism as claimed in claim 2 in which said linkage includes a plurality of said first arms and of said second arms.

4. A mechanism as claimed in any preceding claim in which said linkage is mounted within devises at adjacent ends of said bolt head and said actuator element.

5. A bolt mechanism substantially as hereinbefore described with reference to the accompanying drawings.