GB2543295A

GB2543295A - Clamping device

Info

Publication number: GB2543295A
Application number: GB1518123.3A
Authority: GB
Inventors: Stuart Cameron David
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-13
Filing date: 2015-10-13
Publication date: 2017-04-19
Anticipated expiration: 2035-10-13
Also published as: GB201518123D0; GB2543295B

Abstract

A clamping device comprises a frame 2 and two clamps 4 secured within the frame 2, each clamp having a clamping surface 6 adapted to grip an element 8 such as a rail, at least one of the clamps 4 is movable towards another of the clamps 4 to grip the element 8 between the clamping surfaces 6, and each movable clamp 4 is coupled to a linkage support member 10 by two pivotable linkages 12, 14 so that each movable clamp 4 can be swung into engagement with the element 8 without any substantial change in the orientation of its clamping surface 6. The frame comprising a first and second guides 16, 18 extending substantially parallel to a guide axis 20, the linkage support member 10 including guide portions 24 engaged with the first and second guides 16, 18 such that movement of the linkage support member 10 within the frame 2 is substantially prevented in directions other than substantially parallel with the guide axis. The guides 16, 18 may be defined by slots in top and/or bottom plates 26, 28 and by the gap between the top and bottom plates 26, 28. The clamping device may be used for safety purposes in a lift.

Description

Clamping Device

This invention relates to a clamping device. More particularly, the invention relates to a clamping device that can be used for safety purposes in a lift, for example to limit or prevent unwantedly rapid movement or acceleration in the downwards, or upwards, direction.

In many countries there is a legal obligation to provide a safety device in lifts to brake downward movement of the lift carriage in the event of rapid downward movement or acceleration. Many countries have proposed similar legislation to brake upward movement of the lift carriage in the event of rapid upward movement or acceleration.

Known clamping devices for this purpose are typically secured to the lift carriage. The clamping device is provided with a clamp for gripping a lift cable or a guide rail external to the carriage and relative to which the carriage is expected to move. A governor is also provided, which may be responsive to the downward acceleration or speed of the lift carriage. If the acceleration or speed exceeds a predetermined value the governor actuates the clamping device to cause the clamp to grip, for example, the guide rail. This can cause the lift carriage to decelerate, and come to a halt.

Known clamping devices for lifts generally have either one movable clamp and one fixed clamp, or two movable clamps, with a guide rail disposed between the clamps. In the former arrangement, the governor causes the movable clamp to move towards the fixed clamp to grip the rail between the clamps. In the latter arrangement, the governor causes both clamps to move towards one another to grip the rail between the clamps.

It is known, for example from GB 2314070, to provide a clamping device which is self-actuating once the clamps have made contact with a rail.

According to the invention there is provided a clamping device comprising a frame, and two clamps, the two clamps being secured within the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is a movable clamp which is movable towards another of the clamps to grip the element between the clamping surfaces, and wherein the, or each, movable clamp is coupled to a linkage support member by two pivotable linkages whereby the or each movable clamp can be swung into engagement with the element without any substantial change in the orientation of its clamping surface, the frame comprising a first guide and a second guide, the first and second guides extending substantially parallel to a guide axis, the linkage support member including guide portions engaged with the first and second guides such that movement of the linkage support member within the frame is substantially prevented in directions other than substantially parallel with the guide axis.

Limiting movement of the linkage support member in this way allows the position of the clamps to be controlled more precisely as the position of a part to which the pivotable linkages are connected is more closely controlled than was previously possible. Providing control in this way allows for the possibility that the clamping device can be made smaller and consequently lighter and also enables a higher clamping force to be achieved.

It has been found that by constraining the movement of the linkage support member to be substantially parallel with a guide axis using guides and guide portions it is possible to overcome a significant problem with the prior art, that of undesired movement of the clamps. Prior construction relied on the tolerance fit between a shaft and the frame to restrict unwanted movement of the clamps and other solutions have been proposed which guide the clamp and or which include additional stop elements to restrict movement in one direction. However, the present invention uses guides in the frame to cooperate with guide portions on the linkage support member to restrict movement of the linkage support member in all directions except substantially parallel to a predetermined axis. The linkage support member must be moveable to allow for resilient biasing of the clamping force to be applied, but restricting the movement in this way substantially reduces possible unwanted movement of the clamps. A clamp may be any suitable member that includes a clamping surface. For example a block of metal, or other material, may be suitable for use as a clamp. However, as friction plays an important role in clamping the clamp may be fabricated from a substance which has a rough surface and/or high hardness, or otherwise provides a high coefficient of friction when in use. For example a clamp may comprise an insert holder and an insert. The insert holder may be fabricated from, for example a metal such as steel, while the insert, which may provide some, or all, of the clamping surface of the clamp may be comprise carbide, for example a sintered carbide. The carbide, sintered or otherwise, may comprise tungsten carbide.

The movable clamps are movable between a rest position, in which the clamps are arranged when the clamping device is not in use and an engaged position in which the clamping surfaces of the clamps are engaged with the element to be gripped. The rest position may be a passive position in which the clamps remain under gravity, or the clamps may be retained in that position by, for example a breakable connection, or a resilient coupling.

The frame may be of any suitable construction for supporting and securing the clamps, linkage support members and pivotable linkages when in use. As previously noted, the element to be gripped may be, for example, an elongate cable or rail relative to which the clamping device will move when in use and which will provide the required retardation force when the clamps engage therewith.

The linkage support member is a member to which the two pivotable linkages are coupled and may be fabricated from a single part, for example from a single block of metal. The two linkages are coupled to the clamp and to the linkage support member such that when the clamp is moved into engagement with the element to be gripped, the orientation of the clamping surface of the clamp does not substantially change. This allows the orientation of the clamp to be pre-set for engagement with the element and variations in the element will not result in contact at an unexpected orientation angle.

The pivotable linkages couple the respective clamps to associated linkage support members and may comprise any form of linkage, simple or complex that provides the required functionality. However, a linkage may be provided by an arm which extends from a pivot in the linkage support to a pivot in the clamp. Two such linkages arranged substantially in parallel provide the required functionality in a simple way.

The use of a linkage support member to which both pivotable linkages are coupled has been found to simplify construction. It has also been found that controlling the positon of the linkage support member, which provides control over one end of the pivotable linkages, can be readily achieved using suitable guides and guide portions.

The guide axis may be any suitable axis. The guide axis preferably extends substantially perpendicular to the clamping surfaces of the clamps and/or the surface to be clamped as this simplifies the required linkage construction.

Guides can take any suitable form, for example rails, grooves or recesses. The guide portions of the linkage support member engage with that guide such that the movement of the linkage support member is restricted by the engagement. Some guide portions may extend at least partially over or around a guide such as a rail. Some guide portions may comprise a projection from the linkage support member which engages within a groove, recess or slot which forms the guide. The first and second guides cooperate with the guide projections from the linkage support member to restrict the freedom of movement of the linkage support member so that when the guide portions are engaged with the first and second guides movement of the linkage support member is substantially prevented except in a direction parallel with the guide axis along which the guides extend. The first and second guides may extend parallel with the guide axis as this simplifies construction.

The frame may comprise at least one plate and the first guide may be defined by a slot in or on said plate. The slot may extend parallel with the guide axis and may comprise a hole through said plate, although recesses or tracks are also contemplated by the present invention. The engagement of a guide portion with the slot can restrict the movement of the linkage support member so that it can move along or through the slot and this substantially limits movement of the linkage support member along one axis.

The frame may comprise a top plate and a bottom plate and the second guide may be defined by a gap defined between the top plate and the bottom plate. The space between the top and bottom plate essentially defines a slot and the engagement of the guide portions with said slot can restrict movement of the linkage support member from movement in a direction perpendicular to the plates (it limits movement in one axis). The, or each, plate forming part of the frame may be substantially planar. It should be understood that the second guide may be provided in or on another feature of the frame, but by using the space between the plates the requirement for additional parts is reduced.

The first guide may be defined by a slot in the top plate or a slot in the bottom plate. The clamping device may include a third guide which extends substantially parallel with the guide axis. The third guide may be defined in the other of the top and bottom plate. The third guide may be defined by a slot. The slots of the first and third guides may substantially overlie one another in the frame.

The first guide may be defined in a first plane and the second guide defined in a second plane, the second plane being substantially perpendicular to the first.

At least some of the guide portions of the linkage support member may be provided as projecting portions. The projecting portions may extend into, and possibly through, a slot guide with which it is engaged.

The guide portions may be elongate in a direction substantially parallel with the guide axis. Such elongate guide portions can help to restrict or prevent rotation of the linkage support member within the frame.

The linkage support member may be secured to the frame by a single shaft. The single shaft may comprise, for example a threaded bar, or a bolt. A threaded bar need not be threaded along its entire length. The single shaft may extend substantially parallel with the guide axis.

The shaft may include threaded portions, either external or internal. One of the end portions may include an internally threaded opening which allows the linkage support member to be bolted to the shaft. An opposite end of the shaft may be externally threaded and may be received within a position nut. The shaft may pass through an opening in the frame arranged between the position nut and the linkage support member. The clamping device may further include a biasing means, for example a spring or stack of spring washers. A brake nut may be arranged between the frame and the linkage support member. The brake nut may be arranged to adjust the compression, or the biasing force, of the biasing means when the clamping member is at rest.

The, or each, movable clamp may be coupled, or able to be coupled, to an actuating mechanism capable of moving the clamp from a rest position into an engagement position. All the clamps in the clamping device may be movable clamps. The actuating device may comprise an actuating member which, when actuated moves the clamps from their rest position into an engagement position in which they engage the element to be clamped. Once the clamps have made sufficient contact with the element to be clamped they are essentially self-actuating as is known.

The clamping device may be assembled using a plurality of fixing members, for examples bolts or similar threaded fixings. The clamping device could be assembled and held together by welding, chemical bonding or other substantially permanent methods. A combination of such methods with threaded fixings is also possible. To prevent threaded fixings from working loose a releasable or permanent locking compound, such as a thread-lock, may be applied to the threads, or a mechanical lock may be applied to the fixing to prevent unexpected loosening.

It should also be understood that two or more clamping devices may be employed for some applications to provide additional clamping capacity or a backup device. The two or more clamping devices may be stacked.

The invention extends to a lift comprising one or more clamping devices substantially as described or shown herein. The lift, also known as an elevator, may be a passenger, goods, or other lift as are known in the art.

It should be understood that this clamping device has been described above in terms of a clamping device which is intended to prevent a rapid downward motion, either powered or under gravity, when coupled to a lift. The relative terms top, bottom, upper, lower and other similar terms apply to the device when configured for this use, but suitable adjustment may be necessary in the event that the device is invented or intended to be used to halt or retard rapid upward movement.

The invention will now be described by way of example only with reference to the following figures in which:

Figure 1 shows a view from below of a clamping device;

Figure 2 shows a view from the front of the clamps of the clamping device of Figure 1 in a rest position;

Figure 3 shows the view of Figure with the clamps in an engaged position;

Figure 4 shows a cross section through the clamping device showing the actuating mechanism;

Figure 5 shows the view of Figure 3, but with a modified clamp assembly;

Figure 6 shows a side view of a linkage support member;

Figure 7 shows a front view of the linkage support member of Figure 6.

Figures 1 and 4 show a clamping device 1 comprising a frame 2 and two clamps 4 (clamps shown only in Figure 4 for clarity). The two clamps 4 are secured within the frame 2 and each clamp 4 has a clamping surface 6 adapted to grip an element 8. In this case the element 8 is a rail. Both of the clamps 4 are movable clamps and can be moved towards one another grip the element 8 between the clamping surfaces 6 as shown in Figure 4. Each clamp 4 is coupled to a linkage support member 10 by two pivotable linkages 12,14 (only pivotable linkage 12 is shown in Figure 4, but the linkages can be seen better in Figures 2 and 3). Each movable clamp 4 can be swung into engagement with the element 8 without any substantial change in the orientation of its clamping surface 6 by movement of the pivotable linkages 12,14. The frame 2 comprises a first guide 16 and a second guide 18 and the first and second guides extend substantially parallel to a guide axis 20. The linkage support member 10 includes guide portions 22, 24 (best seen in other figures) engaged with the first and second guides 16,18 such that movement of the linkage support member 10 within the frame 2 is substantially prevented in directions other than substantially parallel with the guide axis 20.

The frame 2 comprises a top plate 26 and a bottom plate 28 which are spaced apart by spacers 30 and the frame is secured together using a plurality of bolts 32. In the case of the front spacers 31, they also include a projection 33 that fits within a mounting hole 35 on the plates 26,28. A front edge of the top and bottom plates 28,30 include cut out portions 34 into which the element 8 to be clamped fits and through which it passes thereby allowing the clamps 4 within the frame to be arranged on opposite sides of the element 8.

At a rear portion 36 of the frame 2 there is arranged an actuation shaft 38 which is coupled to a ‘U’ shaped actuation member 40. An actuation lever 42 is attached to one end of the actuation shaft 38. In use the actuation shaft 38 can be rotated to bring the actuation member 40 into contact with actuation pins 44 carried by the clamps 4 and to move the clamps 4 from a rest position to an engaged position.

As can be seen from Figure 4, each pivotable linkage 12 comprises a pair of arms 46 pivotably connected on opposing sides of the clamp 4 and the linkage support member 10.

The linkage support member 10 is coupled to the front spacer 31 by a shaft 48. The shaft 48 is connected to the linkage support member 10 by a bolt (shown in Figure 3), passes through an opening 50 in the front spacer 31 and is secured by a position nut 52 coupled to a threaded end portion 54 of the shaft 48. Between the linkage support member 10 and the front spacer 31 there is a spring stack 56, which may include spacers, retained against the front spacer 31 by a brake nut 58 engaged with a further threaded section 60 of the shaft 48. The position nut 52 is used to adjust the initial engagement angle of the clamp by moving the linkage support member 10 towards or away from the element 8. The brake nut 58 is used to adjust the initial biasing force of the spring stack 56.

Figure 2 shows a view from the front of the clamps 4 of the clamping device 1 of Figure 1 in a rest position. The clamps 6 comprise insert holders 62 which carry a carbide insert 64 which provides the clamping surface 6.

The linkage support member 10 comprises guide portions 22 (best seen in Figures 6 and 7) which extend from the body and into the first guide 16 which, in this case is a slot 64 formed in the top plate 26. A third guide 66 is also provided in the form of a slot 68 in the bottom plate 28. The guide portions 22 extend into the slots and thereby constrain the movement of the linkage support member 10 to be only along or through the slots 64,68. The slots extend substantially parallel with the guide axis 20 so the movement of the linkage support member 10 is restricted along at least one axis by the engagement of the guide portions 22 in the slots 64,68.

The linkage support member 10 further comprises guide portions 24. The gap between the plates 26,28 provides the second guide and the guide portions 24 extend into the gap between the top and bottom plates 26,28 to restrict the movement of the linkage support member 10 in a direction perpendicular to the plane of the plates 26,28.

In this way the first and second guides 16,18, together with the guide portions 22,24 restrict the movement of the linkage support member to be substantially parallel with the guide axis 20 only.

Figure 3 shows the same view as Figure 2, but with the clamps 4 in an uppermost engagement position. The top plate 26 acts as a ‘top stop’ to prevent further upward movement of the clamps 4. The element 8 to be clamped is not shown in this Figure, but it should be understood that engagement of the clamps 4 with the element may occur before the uppermost engagement position (as shown) is reached.

Figure 3 shows the detail of the bolts 70 that couples the linkage support members 10 to the shaft 48.

Figure 5 shows a similar view to Figure 3, but shows a different embodiment of the clamping device. In this case the braking nut 58 is removed and replaced by a shoulder 72 on the shaft 48. This means that the position of the linkage support members 10 and the biasing force provided by the spring stack 56 cannot be independently adjusted, but the entire assembly can be made more compact. The cut-out 34 in the bottom plate 128 has been increased in size to allow the clamps to pass though the bottom plate 128 so that they can adopt a lower rest positon.

Figure 6 and 7 show front and side views of the linkage support member 10. The guide portions 22 and 24 can be clearly identified and it is clear that the guide portions 22, 24 cooperate to provide shoulders 74 and 76 respectively whose faces are arranged in planes that extend perpendicular to one another.

It should be understood that the invention has been described by way of example only and that modifications in detail can be made without departing from the scope of the invention as defined in the claims.

Claims

1. A clamping device comprising a frame, and two clamps, the two clamps being secured within the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is a movable clamp which is movable towards another of the clamps to grip the element between the clamping surfaces, and wherein the, or each, movable clamp is coupled to a linkage support member by two pivotable linkages whereby the or each movable clamp can be swung into engagement with the element without any substantial change in the orientation of its clamping surface, the frame comprising a first guide and a second guide, the first and second guides extending substantially parallel to a guide axis, the linkage support member including guide portions engaged with the first and second guides such that movement of the linkage support member within the frame is substantially prevented in directions other than substantially parallel with the guide axis.

2. A clamping device as claimed in claim 1, in which the frame comprises at least one plate and the first guide is defined by a first slot in said plate.

3. A clamping device as claimed in claim 2, in which the slot is a hole through the plate.

4. A clamping device as claimed in any preceding claim, in which the frame comprises a top plate and a bottom plate and the second guide is defined by a gap defined between the top plate and the bottom plate.

5. A clamping device as claimed in claim 4, in which the first guide is defined by a slot in the top plate or a slot in the bottom plate.

6. A clamping device as claimed in claim 5, in which a third guide is defined in the other of the top and bottom plate.

7. A clamping device as claimed in claim 6, in which the third guide is defined by a slot in said plate.

8. A clamping device as claimed in any preceding claim, in which the first guide is defined in a first plane and the second guide is defined in a second plane, the second plane being substantially perpendicular to the first.

9. A clamping device as claimed in any preceding claim, in which at least some of the guide portions of the linkage support member are provided as projecting portions.

10. A clamping device as claimed in any preceding claim, in which the clamping surface comprises a friction insert held by an insert holder.

11. A clamping device as claimed in claim 10, in which the insert comprises carbide.

12. A clamping device as claimed in any preceding claim, in which linkage support member is secured to the frame by a single shaft.

13. A clamping device as claimed in claim 12, in which the single shaft extends substantially parallel with the guide axis.

14. A clamping device as claimed in claim 12 or claim 13, in which the shaft includes threaded end portions, one end of which includes an internally threaded portion allowing the linkage support member to be bolted to the shaft an opposite end of which includes an external thread and is received within a position nut, the shaft passing through an opening in the frame between the position nut and the linkage support member.

15. A clamping device as claimed in claim 14, in which the clamping device further includes a biasing means and a brake nut arranged between the frame and the linkage support member, the brake nut arranged to adjust the compression of the biasing force of the biasing means when the clamping member is at rest.

16. A clamping device as claimed in any preceding claim, in which the, or each, movable clamp is coupled to an actuating mechanism capable of moving the clamp from a rest position into an engagement position.

17. A clamping device as claimed in any preceding claim, in which the clamping device is assembled using a plurality of fixing members.

18. A clamping device as claimed in any preceding claim, in which all the clamps are movable clamps.

19. A clamping device substantially as herein described with reference to, or as shown in, the Figures.

20. A lift comprising a clamping device, the clamping device being as claimed in any preceding claim.