GB2543291A

GB2543291A - Clamping device

Info

Publication number: GB2543291A
Application number: GB1518098.7A
Authority: GB
Inventors: Walker Russell
Original assignee: Atwell Int Ltd
Current assignee: Atwell Int Ltd
Priority date: 2015-10-13
Filing date: 2015-10-13
Publication date: 2017-04-19
Also published as: GB201518098D0

Abstract

A clamping device 100, comprising a frame 1, and two clamps 6a, 6b, secured to the frame; each clamp 6a, 6b, having a clamping surface 20a, 20b, adapted to grip an element (31, fig. 6), which may be a guide rail, wherein at least one of the clamps 6a, 6b, is movable towards another of the clamps 6a, 6b to grip the element (31, fig. 6) between the clamping surfaces 20a, 20b, wherein the clamping surface 20a, 20b, comprises a friction element 17a, 17b, retained within a recess 21 in the clamping surface 20a, 20b, the recess 21 having a wall or walls configured such that, in use, the friction element 17a, 17b cannot slide out of the recess 21 in any direction in or parallel to the plane of the clamping surface 20a, 20b. The friction element 17a, 17b may be fixed in place by means of an adhesive. The clamping device may be used in a lift or elevator braking system. There may be an actuating rod 11, which can actuate the clamps 6a, 6b, toward the element (31, fig. 6) which may be a guide rail.

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 transportation system such as a lift.

In many countries there is a legal obligation to provide a safety device in lifts (also known as elevators) to brake downward movement of the lift carriage in the event of rapid downward acceleration. Many countries have similar legislation to brake upward movement of the lift carriage in the event of rapid upward acceleration.

Safety devices for this purpose include a clamping device fixedly secured to the lift carriage; the clamping device is provided with a clamp for gripping a lift cable or guide rail external to the carriage. A governor is also provided, which is responsive to the downward and/or upward 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 the guide rail. This causes 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 the guide rail disposed between the clamps. In the former arrangement, the governor moves the movable clamp towards the fixed clamp to grip the guide rail between the clamps. In the latter arrangement, the governor causes both clamps to move towards one another to grip the guide rail between the clamps. In both arrangements, it is desirable for the clamping device to be self-actuating once the governor has provided the initial impetus to bring the clamps in contact with the guide rail.

In order to be self-actuating, the gripping force must be provided by the frictional engagement of the clamps with the guide rail. Thus, the dynamic coefficient of friction between the clamp and the guide rail is of critical importance. The value of the dynamic coefficient of friction depends on a number of factors including the contact pressure, the surface roughness, the presence of any lubrication and the material properties of the clamp and the rail. In order to be self-actuating, the frictional force generated between the clamp and the rail must be greater than the force resisting engagement.

As well as being self-actuating, it is generally desirable to provide a clamping deice that does not significantly damage the guide rail when it engages the guide rail. GB2314070A discloses an example of a self-actuating clamping device, intended for a lift, which causes little or no damage to an element, e.g. a guide rail, to be clamped. The clamping device of GB2314070A comprises at least two clamps each having a clamping surface for gripping an element to be clamped, wherein at least one of the clamps can be swung into engagement with the element, along an arcuate path, without any substantial change in the orientation of the clamping surface. A problem with known clamping devices for lifts is that they may meet applicable legal standards when installed, but may not operate as intended when required in an emergency situation. This can be because testing to meet the applicable legal standards is generally carried out on a relatively new, steel guide rail. However, when an emergency situation occurs, the guide rail may not have the same friction characteristics of the new, steel guide rail on which testing took place. As a consequence, the clamping device may not operate correctly and/or may fail to bring the lift carriage to a safe halt.

In practice, the guide rail may become worn as a lift carriage moves up and down the guide rail over a period of time. The repeated movement of the lift carriage up and down the guide rail over the period of time for which the lift has been installed may polish and smooth the surface of the guide rail. Thus, when the clamp engages the guide rail in an emergency the dynamic coefficient of friction between the clamp and the guide rail may not be as high as it was in testing. As noted above, there are other factors which can affect the coefficient of friction between the clamp and the guide rail including, for example, the presence of any fluids such as lubricants on the guide rail, debris and/or corrosion.

Another factor which can affect the dynamic coefficient of friction between the clamp and the guide rail is the material from which the guide rail is made. There is a trend towards making guide rails out of aluminium rather than steel, in order to save weight, particularly when installing lifts in very tall buildings. Aluminium is relatively soft compared with steel. Aluminium also has different surface and material characteristics from steel. Accordingly, a clamping device which operates effectively with a steel guide rail may not necessarily operate effectively with an aluminium guide rail.

Another problem, which can adversely affect the operation of clamping devices for halting lifts in an emergency is that, in use, the guide rail and the clamp may not always be perfectly aligned. Thus, when the clamps are brought into engagement with the guide rail, in order to bring the lift carriage safely to a halt, the clamps and the guide rail may experience significant shear forces. In a worst case scenario, the shear forces may be such that the clamp fails. A first aspect of the invention provides a clamping device, comprising a frame, and two clamps secured to the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is movable towards another of the clamps to grip the element between the clamping surfaces, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the recess having a wall or walls configured such that, in use, the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface.

Advantageously, since the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface, the clamping device may be better able to withstand shear forces.

In an embodiment, the wall or walls of the recess may extend around the entire perimeter of the friction element.

In an embodiment, the clamping surface may comprise at least one retaining lip arranged to overlie an edge portion of the friction element.

In an embodiment, the friction element may be held within the recess by an adhesive.

In an embodiment, the friction element may be formed as a single piece. In an embodiment, the friction element may have no apertures passing through it.

In an embodiment, the friction element may comprise, or consist essentially of, a metal, a carbide or a ceramic. In an embodiment, the friction element may comprise, or consist essentially of, tungsten carbide.

In an embodiment, the friction element may have rounded edges and/or may have few or no sharp comers.

In an embodiment, the friction element may comprise a plurality of ridges or protrusions configured to stand proud of the clamping surface.

In an embodiment, the friction element may comprise a plurality of ridges extending in a lengthwise direction parallel to the element to be gripped.

In an embodiment, either or each of the clamps may comprise one or more surfaces extending from the clamping surface at an angle away from the element to be gripped. Either or each of the clamps may comprise two surfaces extending from the clamping surface at an angle away from the element to be gripped. The two surfaces may extend from the clamping surface at the same angle or at different angles from the element to be gripped.

The provision of one or more surfaces extending from the clamping surface at an angle away from the element to be gripped gives the clamp a profiled shape, which can be beneficial in reducing swarf build-up and/or promoting heat dissipation when the element is being gripped, in use, between the clamps.

The one or more surfaces extending from the clamping surface at an angle away from the element to be gripped may be substantially flat or at least partially curved and/or multi-faceted.

In an embodiment, the frame may be formed as a single piece.

In an embodiment, the or each movable clamp may be pivotally mounted to the frame with at least two separate pivotable linkages, whereby the or each movable clamp can be swung into engagement without any substantial change in the orientation of its clamping surface.

In an embodiment, the or each movable clamp may be movable between a first position, in which it cannot engage the element to be gripped, and a second position, in which it can engage the element to be gripped. It may be desirable that the or each movable clamp is biased towards the first position, when not in engagement with the element to be gripped. The biasing force may be provided by gravity.

An actuating element may be provided in order to initiate movement of the or each movable clamp, e.g. from the first position to the second position. The clamp may be self-actuating.

The actuating element may be connected to a control system operable to control actuation of the actuating element. For instance, when the clamping device is to be used in a lift, a governor can be provided to actuate the actuating element in an emergency in order to stop the lift. A second aspect of the invention provides a clamping device, comprising a frame, and two clamps secured to the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is movable towards another of the clamps to grip the element between the clamping surfaces, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the friction element being formed as a single piece with no apertures therethrough.

By forming the friction element as a single piece with no apertures therethrough, the friction element may be more robust and less likely to fail, in use.

In an embodiment, the friction element may have rounded edges and/or may have few or no sharp corners.

In an embodiment, the recess may have a wall or walls configured such that, in use, the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface.

In an embodiment, the frame may be formed as a single piece.

The actuating element may be connected to a control system operable to control actuation of the actuating element. For instance, when the clamping device is to be used in a lift, a governor can be provided to actuate the actuating element in an emergency in order to stop the lift. A third aspect of the invention provides a clamping device, comprising a frame, and two clamps secured to the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is movable towards another of the clamps to grip the element between the clamping surfaces, wherein at least one of the clamps comprises one or more surfaces extending from the clamping surface at an angle away from the element to be gripped.

Either or each of the clamps may comprise two surfaces extending from the clamping surface at an angle away from the element to be gripped. The two surfaces may extend from the clamping surface at the same angle or at different angles from the element to be gripped.

In an embodiment, the clamping surface may comprise a friction element retained within a recess in the clamping surface.

In an embodiment, the friction element may be formed of a single piece and/or may have no apertures therethrough.

In an embodiment, the frame may be formed as a single piece.

The actuating element may be connected to a control system operable to control actuation of the actuating element. For instance, when the clamping device is to be used in a lift, a governor can be provided to actuate the actuating element in an emergency in order to stop the lift. A fourth aspect of the invention provides a clamping device, comprising a frame, and two clamps secured to the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is movable towards another of the clamps to grip the element between the clamping surfaces, wherein the frame is formed as a single piece.

By providing the frame as a single piece, the use of joining techniques such as welding, gluing, bolting or riveting can be avoided. Thus, manufacture and assembly of the frame, and therefore the clamping device, may be less time consuming.

To be effective, joining techniques such as welding and bolting need to be applied correctly, i.e. considerable care and skill are required. If the joining technique is not applied correctly, then the resulting join could present an area of weakness that may be susceptible to failure. In addition, the nature of the join(s), even if applied correctly, could present an area of weakness. Therefore, by providing the frame as a single piece, the frame may be relatively strong and robust and less likely to fail in use. Accordingly, since failure of the frame would lead to failure of the clamping device, the reliability of the clamping device may be improved by providing the frame as a single piece.

In an embodiment, the or each clamping surface may comprise a friction element retained within a recess in the clamping surface.

The actuating element may be connected to a control system operable to control actuation of the actuating element. For instance, when the clamping device is to be used in a lift, a governor can be provided to actuate the actuating element in an emergency in order to stop the lift. A further aspect of the invention provides a transportation system comprising one or more carriages for transporting goods and/or passengers which move relative to an elongate element, wherein at least one clamping device according to the first, second, third or fourth aspect of the invention is provided on one or more of the carriages, preferably on each carriage, and the clamping device is arranged such that at least one of the clamps is movable towards another of the clamps to grip the elongate element between the clamping surfaces.

The elongate element may comprise a rail (e g. a guide rail or part thereof) or a cable.

The transportation system may comprise a lift or a funicular railway or a theme park or amusement park ride such as a roller coaster. A further aspect of the invention provides a carriage for transporting goods and/or passengers in a transportation system in which the carriage moves relative to an elongate element, the carriage being provided with at least one clamping device according to the first, second, third of fourth aspect of the invention. A further aspect of the invention provides a clamp for use in a clamping device, the clamp having a clamping surface adapted to grip an element, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the recess having a wall or walls configured such that, in use, the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface. A further aspect of the invention provides a clamp for use in a clamping device, the clamp having a clamping surface adapted to grip an element, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the friction element being formed as a single piece with no apertures therethrough. A further aspect of the invention provides a method of braking a transportation system comprising one or more carriages for transporting goods and/or passengers by applying a braking force to an elongate element associated with said transportation system, the arrangement being such that the application of the braking force to said element causes the carriage(s) to reduce speed or stop, wherein said braking force is applied by bringing a clamping surface of a clamp of a clamping device according to the first, second, third or fourth aspect of the invention into frictional engagement with the elongate element.

In an embodiment, bringing the clamping surface into frictional engagement with the elongate element may comprise moving the clamping surface towards the elongate element along an arcuate path such that the orientation of the clamping surface, relative to the elongate element, is substantially constant.

In an embodiment, the elongate element may comprise a rail (e.g. a guide rail or part thereof) or a cable.

In an embodiment, the transportation system may comprise a lift or a funicular railway or a theme park or amusement park ride such as a roller coaster.

In order that the invention may be well understood, it will now be described by way of example only with reference to the accompanying drawings, in which:

Figure 1 is a front view of an embodiment of a clamping device according to the invention;

Figure 2 is a front perspective view of the clamping device shown in Figure 1;

Figure 3 is a rear perspective view of the clamping device shown in Figure 1 and Figure 2;

Figure 4 shows an embodiment of a friction element and a clamp according to the invention;

Figure 5 shows an embodiment of a clamp according to the invention; and

Figure 6 shows an embodiment of a clamping device according to the invention arranged on a guide rail.t

Referring to Figures 1 to 3, there is shown a clamping device 100 according to the invention. The clamping device 100 comprises a frame 1 having a top wall 32, a bottom wall 33, and two opposing side walls 34, 35. The top wall 32 is provided with a slot 9a for receiving, in use, a guide rail. A similar slot 9b is provided in the bottom wall 33. The slot 9a in the top wall 32 is located directly above the slot 9b in the bottom wall 33.

The clamping device 100 comprises two movable clamps 6a, 6b, which are pivotally mounted within the frame 1. The clamps 6a, 6b are adapted to clamp an element to be clamped, such as a guide rail for a lift. The clamp 6a has a clamping surface 20a, while the clamp 6b has a clamping surface 20b. The clamping surfaces 20a, 20b face each other.

The clamp 6a is connected to a stabilising member 2a. The stabilising member 2a extends from the top wall 32 to the bottom wall 33 of the frame 1. A shaft is connected to the stabilising member 2a. The shaft passes through the side wall 34 and is secured in place with a nut 12a, which engages with a threaded end portion of the shaft. Arranged around the shaft between the side wall 34 and the stabilising member 2a is a spacer 23a located adjacent the side wall 34 and a biasing means 22a comprising a plurality of disc springs. The stabilising member 2a is operatively connected to the biasing means 22a.

The clamp 6a is pivotally connected to the stabilising member 2a by linkages 4a, 4b. The linkages 4a, 4b are disposed parallel to each other; the clamp 6a is disposed parallel to the stabilising member 2a. Thus, the linkages 4a, 4b, the stabilising member 2a and the clamp 6a form a parallelogram.

The linkage 4a is pivotally connected to an upper end of the clamp 6a at a clamp pivot point 5a. At its other end, the linkage 4a is pivotally connected to the stabilising member 2a at a stabilising member pivot point 3a.

The linkage 4b is pivotally connected to a lower end of the clamp 6a at a clamp pivot point 5b. At its other end, the linkage 4b is pivotally connected to the stabilising member 2a at a stabilising member pivot point 3b.

The clamp 6b is connected to a stabilising member 2b. The stabilising member 2b extends from the top wall 32 to the bottom wall 33 of the frame 1. A shaft is connected to the stabilising member 2b. The shaft passes through the side wall 35 and is secured in place with a nut 12b, which engages with a threaded end portion of the shaft. Arranged around the shaft between the side wall 35 and the stabilising member 2b is a spacer 23b located adjacent the side wall 35 and a biasing means 22b comprising a plurality of disc springs. The stabilising member 2b is operatively connected to the biasing means 22b.

The clamp 6b is pivotally connected to the stabilising member 2b by linkages 4c, 4d. The linkages 4c, 4d are disposed parallel to each other; the clamp 6b is disposed parallel to the stabilising member 2b. Thus, the linkages 4c, 4d, the stabilising member 2b and the clamp 6b form a parallelogram.

The linkage 4c is pivotally connected to an upper end of the clamp 6b at a clamp pivot point 5c. At its other end, the linkage 4b is pivotally connected to the stabilising member 2b at a stabilising member pivot point 3c.

The linkage 4d is pivotally connected to a lower end of the clamp 6b at a clamp pivot point 5d. At its other end, the linkage 4d is pivotally connected to the stabilising member 2b at a stabilising member pivot point 3d.

Final, accurate adjustment of the clamping device 100 can be effected during assembly of the clamping device 100 by adjusting the nuts 12a, 12b.

The clamping surfaces 20a, 20b each comprise a friction member 17a, 17b retained within a recess. The clamp 6a comprises at either end of the clamping surface 20a an upper sloping surface 8a' and a lower sloping surface 8a". The sloping surfaces 8a', 8a" are arranged such that, in use, they each extend from the clamping surface 20a at an angle away from an element such as a guide rail located between the clamps 6a, 6b.

Simlarly, the clamp 6b comprises at either end of the clamping surface 20b an upper sloping surface 8b' and a lower sloping surface 8b". The sloping surfaces 8b', 8b" are arranged such that, in use, they each extend from the clamping surface 20b at an angle away from an element such as a guide rail located between the clamps 6a, 6b.

The clamps 6a, 6b are provided with pins 7a, 7b respectively. The pins 7a, 7b are provided between the clamp pivot points 5a, 5b; 5c, 5d and extend rearwards through horizontal slits 15a, 15b respectively in a u-shaped member 10. The u-shaped member 10 forms part of a clamp actuating mechanism, which also includes an actuating rod 11. The u-shaped member 10 is connected at its ends to the actuating rod 11. The actuating rod 11 extends through a pair of side plates 16a, 16b connected to, and extending rearwards from, the side walls 34, 35 respectively. End portions 13a, 13b of the actuating rod 11 are adapted to be connected to an actuating lever (not shown). In use, the actuating lever is removably secured to one of the end portions 13a, 13b of the actuating rod 11, so that the actuating lever can be disconnected therefrom, and, if desired, resecured to the opposite end portion 13a, 13b of the actuating rod 11.

As can be seen in Figures 2 and 3, the top wall 32 is provided with a pair of elongate slits 14a, 14b either side of the slot 9a. The elongate slit 14a is arranged to receive locating studs on the top of the stabilising member 2a. The elongate slit 14b is arranged to receive locating studs on top of the stabilising member 2b. A similar arrangement of elongate slits (not shown) in provided in the bottom wall 33. In use, locating studs move along the length of the elongate slits in the top wall 32 and the bottom wall 33, thereby guiding movement of the stabilising members 2a, 2b towards an element to be clamped.

An upper surface of the bottom wall 33 serves as a lower stop surface for the clamps 6a, 6b, as illustrated in Figures 1 and 2. In Figures 1 and 2, the clamping device 100 is shown in a first position, in which the clamps 6a, 6b are held apart from one another. When actuated in an emergency, the clamps 6a, 6b swing into a second position (not shown), in which the clamps 6a, 6b are brought closer together and clamp on to.to engage with an element such as a guide rail located therebetween. A lower surface of the top wall 32 provides an upper stop surface for the clamps 6a, 6b. The upper stop surface places a limit on the upward movement of the clamps 6a, 6b.

Stop members may be provided on the lower surface of the top wall to provide the upper stop surface(s). Such stop members may, for example, each comprise a bolt screwed into a plate that is fixed to the lower surface of the top wall 32. The provision of such stop members is, however, not essential, since the lower surface of the top wall 32 may perform the function of limiting the upward movement of the clamps 6a, 6b.

Similarly, stop members may be provided on the upper surface of the bottom wall.

With reference to Figures 1 and 2, it will be appreciated that the clamps 6a, 6b are mounted within the frame such that at the limit of their upward movement (i.e. into the second position) following actuation, the linkages 4a, 4b, 4c, 4d will be disposed substantially horizontally. Thus, the clamps 6a, 6b cannot swing upwards, in use, beyond the position where the clamps 6a, 6b are closest to each other.

Advantageously, the frame 1 may be made as a single piece. For instance, the frame 1 may be cast or moulded as a single piece. Alternatively, the frame 1 could be made as a single piece using an additive manufacturing process. By providing the frame 1 as a single piece, the use of joining techniques such as welding, gluing, bolting or riveting can be avoided. Thus, manufacture and assembly of the frame, and therefore the clamping device, may be less time consuming.

Advantageously, the clamping device 100 is relatively compact and has relatively few moving parts. By providing a relatively compact clamping device, size and weight may be reduced or minimised. A relatively small, light clamping device may be technically and/or aesthetically more appealing than a larger, heavier clamping device capable of handling similar loads.

The strength of the biasing members 22a, 22b can be adjusted by changing the number and arrangement of disc springs.

Instead of disc springs, the biasing members could comprise one or more leaf springs, compression springs or other resilient members.

Advantageously, the stabilising member 2a provides a common rigid base for the linkages 4a, 4b connecting the stabilising member 2a to the clamp 6a. The stabilising member 2b likewise provides a common rigid base for the linkages 4c, 4d connecting the stabilising member 2b to the clamp 6b. Thus, the stabilising members 2a, 2b may help to keep the clamps 6a, 6b respectively at the same orientation while they swing into engagement with an element to be gripped, e.g. a guide rail or part thereof. The presence of the stabilising members may provide even closer control of the orientation of the clamps. A further advantage is that only one biasing means may be required per parallelogram linkage, the one biasing means being operatively connected to the linkages via the stabilising member. Thus, for example, when assembling the clamping device, it is not necessary to match the strength of parallel biasing means.

However, while their presence may be preferred in some embodiments, the stabilising members 2a, 2b are not essential to the clamping device of the present invention. Alternatively, the linkages could be operatively connected directly to the biasing means. For instance, each linkage could be operatively connected independently to a separate biasing means.

Figure 4 shows the clamp 6b and the friction member 17b. The clamp 6a and friction member 17a are substantially identical to the clamp 6b and the friction member 17b. Like reference numerals are used in Figure 4 to denote like features that are described in reference to Figures 1 to 3, Figure 5 and Figure 6.

The clamping surface 20b comprises a recess 21 for receiving the friction member 17b. The recess 21 is located centrally on the clamping surface 20b. The recess 21 comprises a continuous perimeter wall.

The clamp 6b comprises three through apertures arranged one above the other. An uppermost through aperture 24a receives, in use, a means for securing the linkage 4c at the clamp pivot point 5c. A lowermost through aperture 24b receives, in use, a means for securing the linkage 4d at the clamp pivot point 5d. A central through aperture 25 receives, and has secured therein, in use, the pin 7b.

The upper and lower sloping surfaces 8b', 8b" can be seen clearly in Figure 4. The upper and lower sloping surfaces 8b', 8b" extend from the clamping surface 20b at an angle a. In a preferred embodiment, the angle a may be 26.57° (tana = 0.5).

The friction member 17b comprises a lozenge made of a single piece of tungsten carbide. The friction member 17b comprises a central parallel-sided central region 18 and two semi-circular regions 19a, 19b. The parallel-sided central region 18 has a plurality of ridges extending, parallel to one another, in a lengthwise direction along the friction member 17b.

The friction member 17b can be secured within the recess 20 using an adhesive. In addition, the edges of the continuous perimeter wall may be deformed (e.g. by peening) to provide one or more securing lips to overlie one or more edge portions of the friction member 17b, thereby to further secure the friction member 17b within the recess 20. In an embodiment, a single securing lip may be provided which extends around, and overlies, substantially the whole perimeter of the friction member 17b

Furthermore, the continuous perimeter wall of the recess serves to prevent the friction member 17b moving relative to the clamp 6b under the influence of any shear stresses that occur when the clamp 6b engages an element such as a guide rail or part thereof.

Figure 5 shows the clamp 6b connected to the stabilising member 2b. A shaft 26 is connected to the opposite side of stabilising member 2b from the clamp 6b. In a fully-assembled clamping device, a biasing means would be arranged around the shaft 26 and the shaft would extend to a side wall of the frame.

The stabilising member 2b has a pair of locating studs 29a, 29b on its top surface. The locating studs 29a, 29b are received, in use, in the elongate slit 14b in the top surface 32 of the frame 1. Similarly, a pair of locating studs (only one of which, labelled 36a, can be seen in Figure 5) is disposed on the bottom surface of the stabilising member 2b. The locating studs disposed on the bottom surface of the stabilising member 2b are received, in use, in an elongate slit (not shown) in the bottom surface 33 of the frame 1. The top and/or bottom surfaces of the stabilising member 2b could have any number of (i.e. one or more) locating studs disposed thereon.

In Figure 5, the friction member 17b is shown securely retained in the recess in the clamping surface 20b. The ridges disposed on the central parallel-sided region of the friction member 17b stand proud of the clamping surface 20b. It is these ridges which are brought into contact with an element such as a guide rail when the clamping device 100 is actuated.

As can be seen in Figure 5, the front side of the clamp 6b is connected to the front side of the stabilising member 2b by linkages 4c, 4d, while the rear side of the clamp 6b is connected to the rear side of the stabilising member 2b by linkages 4c', 4d'. Linkage 4c' is equivalent to linkage 4c, but on the opposite side of the clamp 6b, while linkage 4d' is equivalent to linkage 4d, but on the opposite side of the clamp 6b. Equivalent pivot points on the front and rear surfaces of clamp 6b and the stabilising member 2b may be joined by securing means passing through apertures through the clamp 6b and the stabilising member 2b respectively. In Figure 5, rear clamp pivot points 5c' and 5d' are labelled, which are equivalent to clamp pivot points 5c, 5d, but on the opposite side of the clamp 6b.

By providing linkages on the front and rear sides of the clamp 6b, the clamp 6b may be held more securely in place, in use, thereby better to resist shear forces.

When the clamping device 100 is actuated and the clamps 6a, 6b are brought into engagement with an element such as a guide rail or part thereof, the friction element 17a, 17b is brought into contact with the element.

The friction element 17a, 17b may have any number of ridges or other protrusions arranged thereon. It may be preferred that the ridges extend in a direction parallel to the longitudinal axis of the element to be clamped.

The friction element may be made from a friction material of combination of materials. The friction element may comprise one or more of: a metal such as bronze; a carbide such as silicon carbide or a metal carbide such as tungsten carbide, titanium carbide of cementite; or a ceramic. A friction element comprising a carbide such as tungsten carbide may be preferred, due to the hard-wearing nature of such materials.

The friction element may be made as a single piece, e.g. in a mould. The friction element may have any suitable shape, although shapes having rounded edges and/or no or few sharp comers may be preferred, since sharp edges and corners can act as stress raisers and such shapes may be easier to mould or cast.

By providing the friction element as a single piece, the chances of the friction element failing may be reduced. In addition, the friction element may be produced relatively quickly and cost-effectively.

By retaining the friction element within a recess, which is configured such that the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface, the clamping device may be more reliable, since the friction element will be less likely to fail under shear stress. The side wall or walls of the recess need not extend continuously around the perimeter of the friction element to achieve this function. There could, for example, be gaps between side wall sections defining the recess.

Similarly, by providing a lip at least partially around the perimeter of the friction element, the friction element may be even more securely retained within the recess.

Furthermore, by using an adhesive to secure the friction element within the recess, the use of mechanical fastening means such as a retaining screw or the like can be avoided. This may be advantageous, since no apertures for receiving fastening means need be provided in the friction element, thereby maximising the surface area available for engaging with an element to be clamped. Furthermore, such apertures may act as stress raisers within the friction element. In addition, fastening means such as retaining screws may fail, in use, in particular when the friction element is subjected to shear stresses.

By way of contrast, the friction elements in the clamping device of GB2314070A are held in an open-sided recess in the clamp by means of a retaining screw. The retaining screw may be an M3 threaded screw or the like. Such a retaining screw is not capable of withstanding significant shear forces. Thus, if there is unwanted sideways motion between the clamp and the element being clamped, the resulting shear forces could be such as to cause the screw to fail and the friction element could consequently slide out of the open-sided recess.

It will be appreciated that the clamping device 100 has been designed such that it is less susceptible to failing due to shear forces.

The sloping surfaces 8a', 8a", 8b', 8b" have been found to be effective in reducing, minimising, or preferably substantially eliminating, the build-up of swarf when the clamping device 100 is actuated in an emergency to clamp a guide rail and bring a lift to a stop. The sloping surfaces 8a', 8a", 8b', 8b" also beneficially promote heat dissipation during braking. Consequently, the chances of the guide rail and/or swarf and/or the clamp becoming welded together by heat and friction may be reduced.

The applicant has found that clamps comprising sloping surfaces, which extend from the clamping surface at an angle of around 26.57° perform consistently well on a variety of braking surfaces, e g. new, worn and/or lubricated steel and aluminium guide rails. In an embodiment, the or each sloping surface may be disposed at an angle of at least 20°, preferably 25° or more, from the clamping surface. The or each sloping surface may be disposed at an angle of up to 60°, preferably up to 45°, from the clamping surface.

Each clamp may comprise only one sloping surface. The or each sloping surface may be substantially flat. Alternatively, the or each sloping surface may be at least partially curved and/or multi-faceted. The sloping surface or sloping surfaces give the clamp a profiled shape.

The clamping device of the present invention has been found in testing to provide consistent braking on a variety of guide rails, including new, lubricated and/or worn guide rails made of steel or aluminium. Without wishing to be bound by any theory, this consistent braking performance across a range of different braking surfaces is thought to be a consequence of improvements in: the material selection and/or selected geometry of the friction element; the securing and retaining of the friction elements within the clamps; and/or the provision of clamps with a profiled shape to reduce the build-up of swarf and improve heat dissipation.

Figure 6 shows the clamping device 100 arranged on a guide rail 27. Like reference numerals are used in Figure 6 to denote like features that are described in reference to Figures 1 to 5.

The guide rail 27 has a generally T-shaped cross-section. The guide rail 27 comprises a base 30 and a rail element 31 protruding perpendicularly from the base 30. The guide rail may be made from a metal or alloy, typically a steel, aluminium or aluminium alloy.

The rail element 31 is received in the slots 9a, 9b such that the clamps 6a, 6b are located either side of the rail element 31. Connected to a lower surface of the lower wall 33 of the frame 1 is a guide shoe 28. The guide shoe 28, which is not an essential component of the clamping device 100, serves to keep the clamping device 100 in position relative to the guide rail 27.

The clamping device 100 may be secured to a part of a lift carriage (not shown) which travels, in use, up and down a lift shaft in which the guide rail is located.

The operation of the clamping device 100 will now be described. It will be assumed that the clamping device is being used as a safety device for a lift, and is secured to part of the lift carriage (not shown) such that the rail element 31 of the guide rail 27 can run freely between the clamps 6a, 6b.

In an emergency, a control system operates to activate the actuating mechanism. This causes the actuating lever (not shown) to pivot about the axis of the actuating rod 11; the actuating rod 11 rotates with the actuating lever, thereby pivoting the u-shaped member 10 about the axis of the actuating rod 11. As the u-shaped member 10 pivots, the pins 7a, 7b are lifted by the u-shaped member 10, and slide in the slots 15a, 15b provided in the u-shaped member 10. The upward movement of the pins 7a, 7b causes a corresponding upward movement of the clamps 6a, 6b. The clamp 6a pivots relative to the linkages 4a, 4b, while the clamp 6b pivots relative to the linkages 4c, 4d. This causes the clamps 6a, 6b to move upwardly along a curved pathway (i.e. to swing upwardly) towards the rail element 31. Importantly, the orientation of the clamping surfaces 20a, 20b does not change during the upward movement, so that the clamping surfaces 20a, 20b maintain a constant angle with respect to the rail element 31 at all times.

After a certain amount of upward movement, the clamps 6a, 6b contact the rail element 31 of the guide rail 27. At this point, the clamping device 100 becomes self-actuating: upward movement of the rail element 31 relative to the clamps 6a, 6b causes the clamps 6a, 6b to grip the rail element 31 more tightly so that any relative movement between the rail element 31 (and guide rail 27) and the clamping device 100 is quickly prevented. At this point the lift carriage will have been brought to a complete stop by the clamping device 100. During full engagement of the clamps 6a, 6b with the rail element 31, the biasing means 22a, 22b ensure that the correct pressure is maintained on the rail element 31 by the clamps 6a, 6b.

Advantageously, the clamping device of the present invention can be used on all guide rails, even relatively smooth and/or soft guide rails, to safely halt a lift in an emergency and without damaging the guide rail.

The clamping device of the present invention is capable of meeting all of the requirements of European lift regulations (EN81 standards). In particular, the European lift regulations require all lifts to have precautions against free fall, excessive speed, unintended movement and creeping of the lift carriage. This can be in either direction (up or down), due to the counterbalancing system typically used in lifts.

While example embodiments of the clamping device have been described in relation to lifts, it will be appreciated that the clamping device of the invention may be used in or on other transportation systems, in which one or more carriages move relative to a guide element, e.g. a guide rail or a guide cable.

Generally, the term lift or elevator may refer to a transportation system which conveys goods and/or people (passengers) in a vertical direction or in a direction no more than 15° from the vertical. A transportation system which conveys goods and/or people (passengers) upwards and downwards at an angle of more than 15° from the vertical may be known as an inclined lift. A funicular railway may be an example of an inclined lift.

For example, the present invention may find utility with: lifts/elevators; inclined lifts; funicular railways; and theme park and amusement park rides such as roller coasters.

The clamping device may be used in any application requiring self-actuated clamping.

The clamping device may be fixed to a carriage, e.g. a lift carriage, during manufacture and assembly of the carriage.

Alternatively, the clamping device may be retro-fitted to a carriage that is already in situ.

The clamping device may be delivered to an intended site at least partially assembled or fully assembled. Alternatively, the clamping device may be delivered to an intended site of use as a kit of parts to be assembled at the intended site of use.

Claims

1. A clamping device, comprising a frame, and two clamps secured to the frame, each clamp having a clamping surface adapted to grip an element, wherein at least one of the clamps is movable towards another of the clamps to grip the element between the clamping surfaces, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the recess having a wall or walls configured such that, in use, the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface.

2. A clamping device according to claim 1, wherein the wall or walls of the recess extend around the entire perimeter of the friction element.

3. A clamping device according to claim 1 or claim 2, wherein the clamping surface comprises at least one retaining lip arranged to overlie an edge portion of the friction element.

4. A clamping device according to claim 1, claim 2 or claim 3, wherein the friction element is held within the recess by an adhesive.

5. A clamping device according to any one of the preceding claims, wherein the friction element is formed as a single piece.

6. A clamping device according to any one of the preceding claims, wherein the friction element has no apertures passing through it.

7. A clamping device according to any one of the preceding claims, wherein the friction element comprises, or consists essentially of, a metal, a carbide or a ceramic.

8. A clamping device according to any one of the preceding claims, wherein the friction element has rounded edges and/or may have few or no sharp corners.

9. A clamping device according to any one of the preceding claims, wherein the friction element comprises a plurality of ridges or protrusions configured to stand proud of the clamping surface.

10. A clamping device according to any one of the preceding claims, wherein the friction element comprises a plurality of ridges extending in a lengthwise direction parallel to the element to be gripped.

11. A clamping device according to any one of the preceding claims, wherein either or each of the clamps comprises one or more surfaces extending from the clamping surface at an angle away from the element to be gripped.

12. A clamping device according to claim 11, wherein either or each of the clamps comprises two surfaces extending from the clamping surface at an angle away from the element to be gripped.

13. A clamping device according to claim 11 or claim 12, wherein the one or more surfaces extending from the clamping surface at an angle away from the element to be gripped is/are substantially flat or at least partially curved and/or multi-faceted.

14. A clamping device according to any one of the preceding claims, wherein the frame is formed as a single piece.

15. A clamping device according to any one of the preceding claims, wherein the or each movable clamp is/are pivotally mounted to the frame with at least two separate pivotable linkages, whereby the or each movable clamp can be swung into engagement without any substantial change in the orientation of its clamping surface.

16. A clamping device according to any one of the preceding claims, wherein an actuating element is provided in order to initiate movement of the or each movable clamp.

17. A clamping device according to claim 16, wherein the actuating element is connected to a control system operable to control actuation of the actuating element.

18. A transportation system comprising one or more carriages for transporting goods and/or passengers which move relative to an elongate element, wherein at least one clamping device according to any one of claims 1 to 17 is provided on one or more of the carriages, and the clamping device is arranged such that at least one of the clamps is movable towards another of the clamps to grip the elongate member between the clamping surfaces.

19. A carriage for transporting goods and/or passengers in a transportation system in which the carriage moves relative to an elongate element, the carriage being provided with at least one clamping device according to any one of claims 1 to 17.

20. A clamp for use in a clamping device according to any one of claims 1 to 17, the clamp having a clamping surface adapted to grip an element, wherein the clamping surface comprises a friction element retained within a recess in the clamping surface, the recess having a wall or walls configured such that, in use, the friction element cannot slide out of the recess in any direction in or parallel to the plane of the clamping surface.

21. A method of braking a transportation system comprising one or more carriages for transporting goods and/or passengers by applying a braking force to an elongate element associated with said transportation system, the arrangement being such that the application of the braking force to said element causes the carriage(s) to reduce speed or stop, wherein said braking force is applied by bringing a clamping surface of a clamp of a clamping device according to any one of claims 1 to 17 into frictional engagement with the elongate element.

22. A clamping device or a clamp for use in a clamping device substantially as described herein with reference to the accompanying drawings.

23. Use of a clamping device to apply a braking force to an elongate element associated with a transportation system to reduce the speed of or stop a carriage of the transportation system substantially as described herein with reference to the accompanying drawings.