GB2290340A - Security bolt operated by splined key - Google Patents

Abstract

The invention relates to a security bolt comprising a bolt member (16) received in a housing (10), the bolt member (16) including a bolt (18) and a rack (24) engageable with co-operating splines of a splined key (not shown), which is rotatable, when engaged, in one sense to extend the bolt (18) from the housing (10) and in an opposite sense to retract the bolt (18) into the housing (10). In one embodiment the bolt member (16) also includes a region (30) for contacting the key to limit the rotation of the key in said one sense and so to limit the extension of the bolt (18) from the housing (10). <IMAGE>

Description

SECURITY BOLT The invention relates to security bolts.

A common type of security bolt comprises a bolt member received in a housing, the bolt member including a bolt and a rack engageable with co-operating splines of a splined key rotatable, when engaged, in one sense to extend the bolt from the housing and in an opposite sense to retract the bolt into the housing. Extension and retraction of the bolt are limited by means of a projection extending from the housing and moving within a groove provided in the bolt member. Thus extension of the bolt is limited when the projection contacts an end wall of the groove and retraction is limited when the projection contacts another end wall of the groove.

Alternatively, extension and retraction of the bolt can be limited by providing a projection extending from the bolt member and moving similarly within a groove or slit in the housing.

However, the provision of a projection and a corresponding groove or slit for limiting movement of the bolt involves machining steps and thus increases the cost and time for manufacturing such security bolts.

According to a first aspect of the invention there is provided a security bolt comprising a bolt member received in a housing, the bolt member including a bolt and a rack engageable with co-operating splines of a splined key rotatable, when engaged, in one sense to extend the bolt from the housing and in an opposite sense to retract the bolt into the housing, the bolt member also including a region for contacting the key to limit the rotation of the key in said one sense and so to limit the extension of the bolt from the housing.

Preferably the security bolt has no other means whereby to limit the extension of the bolt when the key is engaged with the rack.

According to a second aspect of the invention there is provided a security bolt having a bolt member received in a housing member, the bolt member including a bolt and a rack engageable with co-operating splines of a splined key rotatable, when engaged, in one sense to extend the bolt from the housing and in an opposite sense to retract the bolt into the housing wherein, when the key is engaged with the rack, extension of the bolt is limited by means other than a projection on one of the members moveable within a slot or groove in the other one of the members such that contact between the projection and an end of the slot or groove defines the limit of extension.

A security bolt embodying the invention is described below by means of example, reference being made to the accompanying drawings in which: Figure 1 is a diagrammatic representation of the security bolt wherein parts within the barrel and not in line with the holes therein are shown with a broken line; Figure 2 is a similar type of representation to Figure 1 showing the security bolt with the bolt extended; Figure 3 is an enlarged diagrammatic representation of part of the security bolt in which parts within the barrel but not in line with the holes therein are shown with a broken line; and Figure 4 is a cross-sectional, diagrammatic representation of the rack of the security bolt.

Making reference to Figures 1 and 4 the security bolt comprises a cylindrical barrel 10 having first and second open ends 12,14 and an elongate member 16 which is housed within the barrel 10.

One end of the member 16 forms a cylindrical bolt 18 which has a diameter slightly less than the bore of the barrel 10 and the remainder of the member 16 forms an operating portion 20 which is longer than the bolt 18. The portion 20 is formed as a continuation of the bolt 18 generally in the shape of a minor segment of the cross-section of the bolt 18 with a flat 22 which is provided intermediate its ends with a rack 24 having parallel teeth 26.

The free end 19 of the bolt 18 lies at the first end 12 of the barrel 10 and the free end 21 of the operating portion 20 lies at the second end 14 of the barrel 10.

The barrel 10 has a pair of diametrically opposed, equally sized, circular holes 28 provided approximately equidistantly from the first and second ends 12,14. The member 16 is orientated within the barrel 10 such that the rack 24 lies generally parallel to an axis passing through both holes 28 - rotation of the member 16 within the barrel 10 being resisted by a means described below.

The rack 24 is configured and the holes 28 are sized such that a splined key (not shown) of known type having radially projecting and angularly spaced splines of a similar pitch to the teeth 26 of the rack 24 can be inserted through either hole 28 to interlock with the teeth 26 of the rack 24 and then emerge through the other hole 28.

First and second regions 30,32 of the flat 22 are located at respective ends of the rack 24 and extend in a direction parallel to the axis of the barrel 10 for a greater distance than the pitch of the teeth 26. The first region 30 is thus located further from the bolt 18 and the second region 32 is thus located closer to the bolt 18.

A rectangular section groove 36 is provided in the flat 22 between the first region 30 and the end 21 of the operating portion 20.

The barrel 10 also houses a detent 40 which is located in the space between the rack 24 and the barrel 10 and between the holes 28 and the second end 14 of the barrel 10. The features of the detent 40 are most clearly seen in Figure 3.

The detent 40 is mounted on an axle 41 which extends across the barrel 10 in a direction parallel to the axis of the holes 28 and to the plane of the rack 24. The portion of the detent 40 to the side of axle 41 closer to the holes 28 is provided with a projection 42 which, in the position of the detent 40 shown in Figure 3, projects into an imaginary cylinder extending between the holes 28. This portion is also provided with a tooth 43 projecting in a direction normal to the plane of the rack 24 and located for engagement with the member 16 in a manner described below. The detent 40 is urged towards the rack 24 by a spring 44 acting between the detent 40 and the barrel 10.

The barrel 10 is connected to a face plate 46 which extends around the first open end 12 perpendicularly to the axis of the barrel 10 and which is provided with two screw holes 48.

The operation of the security bolt is described below with reference to Figures 1 to 4.

In the position described above and shown in Figure 1 where the bolt 18 is fully retracted into the barrel 10, movement of the member 16 towards either end 12,14 of the barrel 10 is resisted by the engagement of the tooth 43 between two adjacent teeth 26 of the rack 24 (urged into this position by the spring 44).

The bolt 18 can be partially extended from the first end 12 of the barrel 10 to the position shown in Figure 2 by insertion of a key (not shown) of the kind described above through either of the two holes 28 and into engagement with the rack 24. Insertion of the key deflects the projection 42 towards the wall of the barrel 10 against the force of the spring 44 causing rotation of the detent 40 about the axle 41 such that the tooth 43 disengages from the teeth 26 of the rack 24. Subsequent rotation of the key in the appropriate direction causes the bolt 18 to extend from the first end 12 of the barrel 10 the splines of the key co-operating with the teeth 26 of the rack 24.

Rotation of the key and the accompanying extension of the bolt 18 can be continued until a spline of the key contacts the first region 30. As the first region 30 is too large to be accommodated between adjacent splines of the key continued rotation of the key in the same direction is no longer possible. The bolt is now fully extended as shown in Figure 2.

As the key remains engaged with the rack 24 attempts to further extend the bolt 18 by applying a force directly to the bolt 18 while the key remains in place are also resisted.

Withdrawal of the key when the bolt 18 is in this extended position allows the detent 40 to rotate under the action of the spring 44 and the tooth 43 to enter the rectangular section groove 36 in the flat 22 (as shown in Figure 3).

This engagement of the detent 40 with the rack 24 resists movement of the member 16 in a direction parallel with the axis of the barrel 10 and rotation of the member 16 within the barrel 10.

To retract the bolt 18 into the barrel 10 the key is inserted through either of the two holes 28 so that the splines of the key interlock with the teeth 26 of the rack 24. Insertion of the key causes the tooth 43 to disengage from the rack 24 as described above. Rotation of the key in the direction opposite to the direction in which the key is turned to extend the bolt causes the bolt 18 to retract into the barrel 10 - the splines of the key co-operating with the teeth 26 of the rack 24.

Rotation of the key and the accompanying retraction of the bolt 18 can be continued until a spline of the key contacts the second region 32 of the flat 22. As the second region 32 is too large to be accommodated between adjacent teeth of the key continued movement of the key in the same direction is no longer possible. The bolt is now fully retracted as shown in Figure 1.

As the key remains engaged with the rack 24 attempts to push the member 16 towards the second end 14 of the barrel 10 by applying a force directly to the bolt 18 are resisted.

Withdrawal of the key causes the detent 40 to rotate about the axle 41 to the position described above with reference to Figure 1 where the tooth 43 engages with the rack 24.

If the key is used to extend partially the bolt 18, subsequent withdrawal of the key causes the tooth 43 to interlock between two adjacent teeth 26 of the rack 24 thereby resisting movement of the member 16 in a direction parallel to the axis of the barrel 10.

In use the security bolt is fitted to a leaf, such as a door or a window sash, openable and closable out of and into a co-operating frame. The bolt is inserted into an edge surface of the leaf which lies in a plane normal to the plane of the leaf and which is adjacent a corresponding frame surface when the leaf is closed into the frame. The face plate 46 is secured to the leaf, flush with the edge, by means of two screws which pass through respective ones of the screw holes 48. A hole is provided in the leaf, extending between the sides of the leaf and aligned with the holes 28, to allow the splined end of the key to be inserted into one or other of the holes 28.

Another hole is provided in the frame edge surface and is aligned to receive the bolt when the leaf is closed and the bolt is extended. The bolt can thus be extended as described above with reference to the drawings to engage the frame and thus lock the leaf to the frame. Retraction of the bolt as described above with reference to the drawings releases the leaf for opening and closing movement.

The arrangement of the embodiment of the invention described above whereby extension and retraction of the bolt 18 is limited by contact between the key and the first and second regions 30,32 respectively makes the provision of other means for limiting the extension and retraction of the bolt unnecessary and thus simplifies the manufacturing process.

It will be appreciated that the security bolt described above can be configured in other ways. For example, the regions 30,32 against which the splines of the key contact to limit respectively extension and retraction of the bolt 18 do not have to be provided on the flat 22 but could be provided on respective ones of projections extending from the flat at respective ends of the rack 24.

As seen in Figure 4, the two portions of the flat 22 immediately adjacent the groove 36 are co-planar.

However, this need not be so. The portion of the flat 22 closer to the end 21 may lie in a plane spaced from the plane of the other portion of the flat 22 in a direction towards the axis of the barrel 10.

Claims (8)

1. A security bolt comprising a bolt member received in a housing, the bolt member including a bolt and a rack engageable with co-operating splines of a splined key rotatable, when engaged, in one sense to extend the bolt from the housing and in an opposite sense to retract the bolt into the housing, the bolt member also including a region for contacting the key to limit the rotation of the key in said one sense and so to limit the extension of the bolt from the housing.

2. A security bolt according to claim 1 wherein the bolt member has a further region for contacting the key to limit the rotation of the key in the said opposite sense and so to limit the retraction of the bolt.

3. A security bolt according to claim 1 or claim 2, wherein the rack is provided on an operating portion which extends from an end of the bolt which lies within the housing when the bolt is fully extended, and the first-mentioned region is provided on the portion between the rack and an end of the portion spaced from the bolt.

4. A security bolt according to claim 3, when dependent on claim 2, wherein the further region is provided on the portion between the rack and the bolt.

5. A security bolt according to claim 4, wherein the first-mentioned region and the further region are co-planar and lie in the same plane as ends of the teeth of the rack.

6. A security bolt according to any preceding claim having no other means whereby to limit the extension of the bolt when the key is engaged with the rack.

7. A security bolt having a bolt member received in a housing member, the bolt member including a bolt and a rack engageable with co-operating splines of a splined key rotatable, when engaged, in one sense to extend the bolt from the housing and in an opposite sense to retract the bolt into the housing wherein, when the key is engaged with the rack, extension of the bolt is limited by means other than a projection on one of the members moveable within a slot or groove in the other one of the members such that contact between the projection and an end of the slot or groove defines the limit of extension.

8. A security bolt substantially as hereinbefore described with reference to the accompanying drawings.