GB2399596A

GB2399596A - Shoot bolt drive mechanism

Info

Publication number: GB2399596A
Application number: GB0405438A
Authority: GB
Inventors: Terence James Dolman
Original assignee: Trojan Hardware and Design Ltd
Current assignee: Trojan Hardware and Design Ltd
Priority date: 2003-03-15
Filing date: 2004-03-11
Publication date: 2004-09-22
Anticipated expiration: 2024-03-11
Also published as: GB0305949D0; GB0405438D0; GB2399596B

Abstract

A shoot bolt drive mechanism comprises a primary drive gear and two reversing pinions 16, 17 arranged, upon rotation of the gear, to drive two toothed racks 18, 20 in opposite directions between an open position and a closed position. A first rack 18 is engaged with said primary drive gear, and the two pinions 16, 17 are spaced circumferentially about the primary gear wherein at least in the closed position the two reversing pinions 16, 17 are engaged with both the primary drive gear and the second rack 20. The two reversing pinions 16, 17 may remain in contact with the primary drive gear in all positions.

Description

SHOOT BOLT DRIVE MECHANISM

This invention is concerned with improvements in or relating to bidirectional shoot bolt mechanisms such as those used for securing opening windows and doors in closed positions.

Such mechanisms comprise a housing for a drive mechanism which is adapted to be accommodated in a recess in an edge member of a window or door. Two ordinarily strip-like bolt arms extend in opposite directions from a front face of the drive mechanism, to be moved longitudinally by the mechanism. The bolt arms are usually adapted to be accommodated in shallow channels formed in the edge member, end portions of the arms being protectable beyond guide members, secured to corners of the window or door, for engagement with keeps on an adjacent window or door frame. In an open condition of the mechanism, the bolt ends are drawn back from the keeps to the guide members to permit the window or door to be opened. In a closed condition of the mechanism the bolt ends are engaged with the keeps, typically in the window or door frame, thereby preventing the window or door from being opened.

For securement in edge members of standardised extruded section, it is necessary that the dimensions of the drive mechanism housing come within certain predetermined limits. In particular, the depth of the mechanism from front to rear is so limited. For operation by means of a handle, the mechanism ordinarily comprises a primary drive gear (commonly a quadrant gear) which is slotted axially to receive a drive spindle on which the handle is fixed. It is necessary that the spindle axis be well removed from the front face of the edge member and, therefore, that the primary drive gear be positioned as rearwardly as possible within the housing. Intermediate drive mechanism, acting between the primary drive gear and transmission links of the bolt arms, needs to be accommodated between the primary drive gear and the front face of the mechanism.

This arrangement means that there tends to be a front to rear thrust on the primary drive gear in operation. The thrust has to be borne by the housing, and as a consequence of this, some of the available depth for the mechanism needs to be occupied by a rear most portion of the housing supporting the primary gear. This in turn has limiting implications for the design of the primary drive gear and intermediate mechanism especially when security and provision of a durable mechanism is of importance.

It is known for the intermediate mechanism to comprise first and second toothed racks and a reversing pinion. The primary drive gear engages the first rack directly while the second rack engages with the reversing pinion which engages with the primary drive gear. In our earlier Patent, GB 2 312 236, we proposed the use of two reversing pinions which successively engage the primary drive gear. This has the advantage of increasing the "throw" of the mechanism, however it is an object of the present invention to provide improvements relating to the design of a shoot bolt drive mechanism which enables effective use to be made of the limited space available.

According to a first aspect of the present invention we provide a shoot bolt drive mechanism comprising a primary drive gear and two reversing pinions arranged, upon rotation of the gear, to drive two toothed racks in opposite directions between an open position and a closed position, one rack being engaged with said primary drive gear and the two pinions being spaced circumferentially about the primary gear wherein at least in the closed position the two reversing pinions are engaged with both the primary drive gear and the other rack.

Having two reversing pinions engaged with the primary gear and one of the racks at least when the mechanism is in the second position results in a substantial engagement between the reversing pinions and the rack.

The closed position may correspond to the racks being fully extended and the open position may correspond to the racks being fully retracted.

Preferably, the two reversing pinions are engaged with one of the racks in the open as well as the closed position, and most preferably at all positions during the operation of the mechanism. It is also preferable that both reversing pinions are engaged with the primary gear at all positions during the operation of the mechanism. Most preferably, both reversing pinions are engaged with both the rack and the primary gear at all positions. This improves the durability of the mechanism.

Such an arrangement also provides the advantage of being very compact, and can also enable the reversing gears to be well constrained.

The primary drive gear may be a quadrant gear which presents teeth around an arc of, typically, between 135 and 180 . The open and closed positions may correspond to positions of the quadrant at the extreme opposite ends of its range of travel, usually limited by the housing design.

The primary drive gear may be formed by casting, the gear presents two sets of teeth which are circumferentially off-set from one another, one set being arranged to be engaged by said one of the racks and the other being arranged to be engaged by the reversing pinion. The two sets may be off-set by half a pitch.

The shoot bolt drive mechanism may be incorporated in a shoot bolt assembly and this forms a second aspect of the invention.

According to a second aspect of the present invention we provide a shoot bolt mechanism comprising a primary drive gear arranged upon rotation to drive two bolt arms between an open position and a closed position, each bolt arm being driven by means of a toothed rack one rack being engaged with said primary drive gear and the other rack being engaged by two reversing pinions at least when the mechanism is in the closed position, the two pinions being spaced circumferentially about the primary gear and both engaged with said primary drive gear at least when the mechanism is in the closed position, whereby said two bolt arms become driven in opposite directions upon rotation of said primary drive gear.

There now follows a detailed description, to be read with reference to the accompanying drawings, of a shoot bolt mechanism which illustrates the present invention by way of example.

In the accompanying drawings: Figure 1 is a side view of an embodiment of a shoot bolt drive mechanism (with a housing half removed) in an initial condition; Figure 2 is a view similar to Figure 1 but with the mechanism in an engaging condition; Figure 3 is a side view of an embodiment of the drive mechanism (with a housing half removed) incorporated in a shoot bolt mechanism; Figure 4 is a side view of a quadrant gear having a staggered tooth form; and Figure 5 is a view in section on line XI-XI of Figure 4.

Figures 1 and 2 show an embodiment of a drive mechanism according to the first aspect of the invention. Figure 3 shows a complete shoot bolt mechanism, for securing a window or door, incorporating an embodiment of the drive mechanism similar to that shown in figures 1 and 2.

The drive mechanism of figures 1 and 2 comprises two halves 10, 12 of a housing that provide support between them for a primary-drive quadrant gear 14, two reversing pinions 16, 17 and first and second racks 18 and 20. The drive mechanism shown in figures 1 and 2 has the first rack 18 removed.

Figure 3 includes two transmission links comprising bars 22, 24 of oppositely directed bolts that are attached to respective racks.

The quadrant gear 14 is formed with an axially aligned slot 26 of square cross-section to receive a drive spindle which is secured to an operating handle (spindle and handle not shown, but can be of conventional form). As seen in Figures 1 to 3, the slot 26 extends through a cylindrical hubforming portion 28 of the quadrant gear which is of equal axial length to the width of the housing. A tooth-providing crest 30 of the gear extends about part only of the circumference of the hub-forming portion 28, being of shorter length than the hub-forming portion and being positioned centrally (in the axial direction). At each end of the gear, a groove 32 is cut into the root of the crest, adjacent to the cylindrical surface of the hub-forming portion 28, the groove extending about the hub-forming portions for the full extent of the crest 30.

The grooves 32 provide part-circular, open-ended, recesses to receive flanges (not shown) of corresponding dimensions, projecting inwardly from the housing halves 10, 12; the grooves 32 and flanges are concentric with the axis of the quadrant gear 14, and the flanges bound circular openings (not shown) in which opposite end portions of the hub- forming portion 28 of the gear are received.

The flanges (not shown) of the housing halves provide radial support for the quadrant gear in the direction away from the racks 18, 20 and reversing pinions 16, 17. This support reduces the demands on the housing halves at the openings which form further bearings for the hub forming portion 28 of the quadrant gear. As a consequence, it is not necessary for the housing to surround the quadrant gear completely and, as best seen in Figures 1 and 2, the rearmost surface 44 of the hub- forming portion of the gear is exposed through an opening in the housing and is generally flush with a rear face 46 of the housing. Rotation of the quadrant gear is so guided by the combination of the flanges and the part- cylindrical bearing surfaces formed by the housing halves around the openings.

The pinion 16, 17 and first rack 18 are positioned side by side (i.e. axially spaced) on the quadrant gear and the two racks 18, 20 are likewise spaced axially of the gear, the teeth of the second rack 20 being at a greater radial distance from the axis of the gear for accommodation of the reversing pinion therebetween. The transmission bars 22, 24 are of flat strip form and are retained in place by means of a cover plate 48 (shown in figure 3) applied to the front face of the housing.

The first drive rack 18 (not shown) engages the drive quadrant 14 directly. The second drive rack 20 is arranged to be driven by the two reversing pinions 16, 17 simultaneously. Figure 1 shows the drive mechanism in an initial condition, in which the second rack 20 abuts the right hand side of the housing 10 and the quadrant gear teeth are held in engagement with the reversing pinions 16,17. The pinions are further held in engagement with the teeth of the second rack 20. Although not shown in figures 1 and 2, in the initial condition, the first rack 18 abuts the left hand side of the housing 10 and the teeth of the quadrant gear are held in direct engagement with the teeth of the first rack 18.

Upon rotation of the quadrant gear clockwise from the open position (shown in Figure 1) to a closed position (shown in Figure 2) the first rack 18 (not shown) is driven from left to right and the second rack 20 is driven, in the opposite direction from the first rack (i.e. from right to left).

The mechanism shown in Figures 1 to 3 is arranged such that both reversing pinions 16, 17 are in engagement with the drive quadrant 14 and rack 20 at all positions during the operating movement from an open position to a closed position, due to the rotation of the drive quadrant 14.

However, the arrangement could be such that both reversing pinions 16, 17 are in engagement with the drive quadrant 14 and rack 20 at least when the mechanism is in the engaging condition.

The shoot bolt assembly shown in figure 3 may be used as a locking mechanism in a door or window. When the drive mechanism is incorporated in a shoot bolt assembly it can be used to control the movement of the transmission links 22, 24. The door or window could be locked by bolt arms, attached to the transmission links 22, 24, that engage with keeps mounted in the door or window frame (not shown).

The initial condition of the drive mechanism may correspond to an open condition of the shoot bolt mechanism in which the door or window can be opened. In the closed condition the movement of the racks 18, 20 cause transmission bars 22, 24 to drive respective bolts into a securing position which prevents the window or door from being opened.

It will be appreciated that the mechanism as shown in Figures 1 to 3, as so constructed and arranged provides a durable, and therefore secure mechanism as, on average, there are twice as many reversing pinion teeth engaged with the second rack 20 and drive quadrant 14 when compared to the prior art mechanisms, such as that known from GB 2 312 236.

A preferred design of a cast quadrant gear, usable in any of the three versions of drive mechanism described, is shown in Figures 4 and 5. The gear presents, around its circumference, first and second sets 62, 64 of teeth for engagement with the first drive rack 18 and the reversing pinions 16, 17 respectively. The tooth sets are off-set from one another by one half of one pitch, the two sets meeting on a split plane P of the casting. In this manner a compact yet very strong gear is produced.

Claims

1. A shoot bolt drive mechanism comprising a primary drive gear and two reversing pinions arranged, upon rotation of the gear, to drive two toothed racks in opposite directions between an open position and a closed position, one rack being engaged with said primary drive gear and the two pinions being spaced circumferentially about the primary gear wherein at least in the closed position the two reversing pinions are engaged with both the primary drive gear and the other rack.

2. A shoot bolt drive mechanism according to claim 1 in which the closed position corresponds to the racks being fully extended.

3. A shoot bolt drive mechanism according to claim 1 in which the open position corresponds to the racks being fully retracted.

4. A shoot bolt drive mechanism according to any preceding claim in which the two reversing pinions are engaged with one of the racks in the open as well as the closed position.

5. A shoot bolt drive mechanism according to any preceding claim in which the two reversing pinions are engaged with one of the racks at all positions during the operation of the mechanism.

6. A shoot bolt drive mechanism according to any preceding claim in which the two reversing pinions are engaged with the primary gear at all positions during the operation of the mechanism.

7. A shoot bolt drive mechanism according to any preceding claim in which the primary drive gear is a quadrant gear which presents teeth around an arc of between 135 and 180 .

8. A shoot bolt drive mechanism according to claim 7 in which the open and closed positions correspond to positions of the quadrant at the extreme opposite ends of its range of travel.

9. A shoot bolt drive mechanism according to any preceding claim in which the primary drive gear is formed by casting.

10. A shoot bolt drive mechanism according to any preceding claim in which the primary drive gear presents two sets of teeth which are circumferentially off-set from one another, one set being arranged to be engaged by said one of the racks and the other being arranged to be engaged by the reversing pinion.

11. A shoot bolt drive mechanism according to claim 10 in which the two sets are off-set by half a pitch.

12. A shoot bolt mechanism comprising a primary drive gear arranged upon rotation to drive two bolt arms between an open position and a closed position, each bolt arm being driven by means of a toothed rack, one rack being engaged with said primary drive gear and the other rack being engaged by two reversing pinions at least when the mechanism is in the closed position, the two pinions being spaced circumferentially about the primary gear and both engaged with said primary drive gear at least when the mechanism is in the closed position, whereby said two bolt arms become driven in opposite directions upon rotation of said primary drive gear.

13. A shoot bolt drive mechanism substantially as hereinbefore described with reference to and as illustrated in Figures 1 to 5 of the accompanying drawings.

14. A shoot bolt mechanism substantially as hereinbefore described with reference to and as illustrated in Figure 3 of the accompanying drawings.