GB2473899A

GB2473899A - Barrier clamp with inclined jaw

Info

Publication number: GB2473899A
Application number: GB201006293A
Authority: GB
Inventors: John Dawson; Adrian Lawrence Midgley
Original assignee: Melba Products Ltd
Current assignee: Melba Products Ltd
Priority date: 2009-09-29
Filing date: 2010-04-15
Publication date: 2011-03-30
Also published as: GB2473889A; GB2473892A; GB0917025D0; GB201006293D0; GB201000350D0; GB2473876A; GB201004618D0

Abstract

A clamp for clamping to a temporary barrier, comprises a first clamp member, 412a a second clamp member 412b which move towards each other to tighten the clamp. Preferable there is a channel 500 at both ends of the clamp. The gap between the jaws of one channel should be parallel to the channel; while the gap between the jaws of the other channel should be inclined relative to the channel, or helically extending around it. The clamp can be tightened by a bolt whose thread pitch is greater than the jaw overlap, so a single rotation is required to release the clamp. Alternatively the clamp can be tightened by a care which pushed against a bias in which when closed the cam must move towards the bias for release. The cam could be actuated by a separate or integral tool 428.

Description

Barrier Clamp [0001] This invention relates to a clamp, and in particular to a clamp for clamping to a control barrier.

BACKGROUND

[0002] Control barriers are well known in the art and are typically used for directing the flow of traffic or pedestrians. Examples of their uses include directing traffic and/or pedestrians around road works, or to simply fence off and prevent access to hazardous working areas. A typical barrier is described in US-A-2002014619 (Off the Wall Products, LLC) that comprises a barrier wall that is supported by one or two support assemblies.

[0003] Some barriers have arms designed to receive a clamping bracket so that two or more barriers can be clamped together to form a continuous wall of barriers. Typical clamps for this purpose comprise two components that define a pair of channel shaped jaws for clamping onto the arm of a barrier. Generally, the two components are restrained to one another by a nut and bolt assembly whereby the two components are moved towards one another, clamping around the arms of the barrier as they do so, by tightening the nut on the bolt.

[0004] UK Patent GB-B-2391560 describes one example of such a clamp that is designed for clamping fence panels together. Other similar clamps are described in DE-U-202005013392, GB-A-2338770, GB-A-2248860, and GB966351.

[0005] It is an object of the present invention to provide an improved clamp for clamping to a control barrier. In particular, the present invention seeks to provide a clamp that securely clamps onto a control barrier and allows quick and easy engagement and release. Moreover it is another object to provide a clamp whose clamping force is factory-set so that the clamp reliably has a balance between being too loose so that the barrier does not reliably remain integral and too tight so that it feasibly does not separate when, for example, it is struck and picked up by a passing vehicle. The latter is an extra hazard at roadworks where a vehicle could conceivably catch a barrier and since they do not tend to be fixed a chain of barrier elements may be dragged along by the vehicle presenting a significant risk. Another object is to provide a clamp that provides a measure of security against unauthorized tampering. Even at roadworks where barriers are merely to separate passing traffic from a working area, barriers are sometimes moved by mischievous people who should be deterred. This has to be set against the convenience and ease with which workforce personnel can dismantle and reposition barriers as they need to do from time to time.

BRIEF SUMMARY OF THE DISCLOSURE

[0006] In accordance with a first aspect of the present invention there is provided a clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; restraining means connecting the first clamp member and the second clamp member together; bias means, to urge said clamp members apart, and a clamping mechanism to urge the clamp members towards one another to clamp an object therebetween, wherein the clamping mechanism is mounted on the first clamp member and is movable relative thereto between three positions: a first position in which the clamp members are at a maximal separation to release an object between the clamp members, a second intermediate position in which the clamp members are at a minimal separation to clamp an object between the clamp members, said bias means being strained to a maximal extent, and a third position in which the clamp members are in a clamping position to clamp an object between the clamp members, said bias means being strained to an intermediate extent, and, the clamping mechanism cannot move from the first position to the third position without moving through said second position.

[0007] According to one embodiment of the clamp according to the first aspect of the present invention, preferably: * said clamping mechanism comprises a movable cam element and an opposing cam feature of said first clamp member, one of said cam element and feature having first and second cam surfaces separated by an intermediate face and the other of said cam element and feature having a cam follower, and wherein, when the clamping mechanism is in said first position, the cam follower engages the first cam surface, when the clamping mechanism is in said third position, the cam follower engages the second cam surface, when the clamping mechanism is in said second, intermediate position, the cam follower engages the intermediate face, and in the clamping position, the clamp members are at a separation intermediate the maximal and minimal separations.

* said restraining means comprises a bolt passing through said clamp members so as to limit separation of the clamp members to said first position.

* said bias means comprises a spring washer between the bolt and one of the clamp members.

* said spring washer comprises a progressive force device.

* said progressive force device comprises an annular elastomeric washer having a base of a first annulus width and a top of a second annulus width that is less than the base annulus width.

* said washer is stepped between a cylindrical section at said first annulus width and a cylindrical section at said second annulus width.

* said step is both on an internal surface of said washer and on an external surface thereof.

* said cam element is rotatably disposed on said bolt between the bolt and first clamp member and said cam surfaces and cam follower are at a fixed radius with respect to said bolt.

* said cam is engageable with a tool for rotating the cam between the first and third positions.

* said cam and tool are coded so that only said coded tool can engage and rotate the cam.

* said code comprises the cam having holes for engaging with pegs of the tool for rotating the cam between the first and third positions.

* said code comprises a polygonal section flange on one of the tool and cam and a corresponding recess on the other of said tool and cam, said section being other than hexagonal.

* said polygonal flange is protected by a circular flange on one of the tool and cam and a corresponding circular recess on the other of said tool and cam, whichever of the recess and flange being on the cam is concentric with said cam, whereby said circular flange and recess are axially engaged before said polygonal flange and recess are engaged, so that rotation of the tool with respect to the cam facilitates angular alignment of the polygonal sections for subsequent complete axial engagement of the tool and cam.

* said cam comprises a handle element for rotating the cam by hand between the first and third positions.

* the handle is integrally formed with the cam.

* said handle comprises wings.

* said handle is engageable by a tool to facilitate turning thereof, the tool including a slot to receive said wings.

* said first and second cam surfaces are disposed substantially perpendicularly with respect to one another about said bolt.

[0008] According to an alternative embodiment of the clamp according to the first aspect of the present invention, preferably: * said clamping mechanism comprises a toggle lever disposed between the first and second clamp members.

* said toggle lever is connected to one of the first and second clamp members by an adjustable element that alters the positions of the first and second clamp members with respect to one another in said first, second and third positions.

* said adjustable element is a threaded bolt received in the one clamp member.

* said restraining means comprises the connection of said toggle lever to both of said first and second clamp members.

* said toggle lever comprises a pair of opposed levers.

* said pair of opposed levers are slidably mounted to the other of said first and second clamp members.

* the adjustable element is rotationally mounted to said pair of opposed levers.

* said toggle lever is moved from the first position to the third position by rotation of the threaded bolt about 90 degrees.

* in the clamping position, the clamp members are at minimal separation.

[0009] According to either embodiment of the clamp according to the first aspect of the present invention, preferably: * the first clamp member comprises at least one first jaw and the second clamp member comprises at least one second jaw, wherein the at least one first jaw and the at least one second jaw form at least one channel section for gripping an object therein when the clamping mechanism is in the third position.

* the at least one first jaw is integrally formed in the first clamp member and the at least one second jaw is integrally formed in the second clamp member.

* the first clamp member comprises two first jaws being disposed at opposite ends of the first clamp member and the second clamp member comprises two second jaws being disposed at opposite ends of the second clamp member; and the first and second jaws form two channel sections.

* the at least one channel section is substantially cylindrical.

* one of the first and second clamp members comprises a protrusion element and the other of the first and second clamp members comprises a socket for receiving the protrusion element, wherein engagement of the protrusion element and the socket inhibits rotation of the first clamp member about the second clamp member when the clamping mechanism is in the third position.

[0010] In accordance with a second aspect of the present invention there is provided a clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; restraining means connecting the first clamp member and the second clamp member; and a threaded bolt screwable in a threaded bore of one of the first and second clamp members; wherein screwing of the bolt in the bore varies the amount that the first clamp member may move relative to the second clamp member in a direction parallel to a longitudinal axis of the bolt; each of the first and second clamp members comprises at least one open channel defined by a jaw at an end of the clamp member; where each jaw has an overlap length equal to the distance from the end of the jaw to the base of the corresponding channel in a direction parallel to the longitudinal axis of the bolt; and each at least one jaw of the first clamp member forms a pair of jaws with one of the at least one jaw of the second clamp member; the sum total of the overlap lengths of the jaws of the or each pair of jaws equates to a release distance; and the pitch of the thread of the bolt is greater than or equal to the release distance.

[0011] In one embodiment of the clamp according to the second aspect of the present invention, the bolt comprises the restraining means, and the bolt has a flanged end wherein the thread of the bolt retains one of the first and second clamp members, and the flanged end restrains the other of the first and second clamp members.

[0012] In an alternative embodiment of the clamp according to the second aspect of the present invention, the restraining means comprises a rod having flanged ends for restraining the first and second clamp members each flanged end. Preferably, the bolt is rotatably mounted on the rod and is screwable in the bore so as to abut one of the flanged ends of the rod.

[0013] In either embodiment according to the second aspect of the present invention, the pitch of the thread is equal to four times the release distance.

[0014] In accordance with a third aspect of the present invention there is provided a clamp for clamping a pair of control barriers, comprising: a first clamp member; and a second clamp member; where the first and second clamp members form a first pair of jaws defining a first channel for receiving a first object to be clamped, and a second pair of jaws defining a second channel for receiving a second object to be clamped, wherein each of said first and second channels has a longitudinal axis that is parallel to the longitudinal axis of the other of said first and second channels; and ends of the jaws of each pair are separated along a first direction that is transverse said longitudinal axes to define a first gap associated with the first pair of jaws and a second gap associated with the second pair of jaws; wherein the first clamp member is moveable relative to the second clamp member along the first direction between a first position and a second position, wherein in the first position the first gap is greater along a direction parallel to the first direction than it is in the second position and the second gap is greater along a direction parallel to the first direction than it is in the second position; and wherein the first gap extends at an inclined angle with respect to said longitudinal axes whereas the second gap extends substantially parallel to said longitudinal axes.

[0015] The clamp may therefore be semi-permanently attached to one barrier, since rotation of the clamp relative to an object clamped in the first channel is required to release it. This is unlikely to occur without conscious user intervention. This clamp may therefore be attached to a barrier in transit and/or may be sold attached to a barrier.

[0016] Preferably, in said first position, said second gap is greater than said first gap along a direction parallel to the first axis. This facilitates quick and easy attachment/release through the second gap.

[0017] Preferably, each of the first and second channels has a substantially circular cross section when the first clamp member is in the first position relative to the second clamp member. Further preferably, the first gap extends helically about the longitudinal axis of said first channel.

[0018] In one particularly preferable embodiment, the clamp according to the third aspect of the present invention additionally has the features of the clamp according to the first aspect of the present invention.

[0019] In accordance with a fourth aspect of the present invention there is provided a clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; and a clamping mechanism to urge the clamp members towards one another to clamp an object therebetween, wherein the clamping mechanism is mounted on the first clamp member and is movable relative thereto between two positions: a first, release position, in which the clamp members are at a maximal separation permitted by the clamping mechanism to release an object between the clamp members, and a second, lock position, in which the clamp members clamp an object between them; wherein the clamping mechanism comprises a bolt-element passing between the clamp members through apertures therethrough, a cam being disposed between a head of the bolt element and one of the clamp members, which cam is operable by a tool such that the cam moves the clamping members between said first and second position, which tool is separable from the cam.

[0020] According to an embodiment of the clamp according to the fourth aspect of the present invention, optionally: * said cam is coded so that only an appropriately design tool can engage the cam.

* said coding comprises a shaped aperture into which a correspondingly shaped tool is

insertable.

* said cam is pivoted to said bolt about a cam axis, the cam having a cylindrical surface engaging said one clamp member, the cam axis being eccentric the axis of said cylindrical surface.

[0021] Thus, embodiments of the present invention permit one or more of the following advantages: * the clamping mechanism can be quickly and conveniently set; * the clamping mechanism, when set, can be arranged to have a specific clamping force that can be between two extremes, in most weather conditions, such that it is neither too tight that sudden forces do not cause separation of barriers joined by the clamp nor so loose that casual separation with minimum effort is possible; * a special tool can be provided that both facilitates operation of the clamping mechanism yet in its absence offers some degree of security against unauthorised operation of the clamp.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Embodiments of the invention are further described hereinafter with reference to the accompanying drawings, in which: Figures 1A and lB show a clamp according to a first embodiment of the present invention where the clamp is in an open position in Figure 1A and in a closed position in Figure 1B; Figures 2A and 2B are cross sectional views corresponding to the clamps of Figures 1A and 1 B respectively; Figure 3 shows an exploded view of one of the clamp members and the cam element of Figures 1 and 2; Figure 4 shows a detailed view of the cam element of Figure 3; Figure 5 shows the cam element of Figures 3 and 4 and a cam tool for engaging with and rotating the cam element; Figure 6 shows an alternative embodiment of the cam element; Figures 7A and 7B show a clamp according to a second embodiment of the present invention where the clamp is in an open position in Figure 7A and in a closed position in Figure 7B; Figure 8 shows a detailed view of the toggle mechanism of Figure 7; Figure 9 shows a clamp according to a second aspect of the present invention; Figures 1OA and lOB show an alternative embodiment of a clamp according to the second aspect of the present invention; Figure 11 shows a perspective view of a clamp according to a further alternative embodiment of the invention; Figure 12 shows a side view of the clamp of Figure 11; Figures 1 3A and 1 3B each show an end view of the clamp of Figures 11 and 12; Figure 14 is a tool suitable for operating the handle of cam element of Figure 6; Figures iSA and 15B are a perspective view and section through a progressive resistance washer, for optional use in the embodiments of the present invention illustrated in Figures 1 to6 and 11 to 13; Figures 16A, 16B andl6C are respectively a side section, plan view and detailed section 160 from Figure 1 6A of an embodiment of the fourth aspect of the present invention; Figure 17 is a view of a suitable tool for the clamp of Figures 1 6A, 1 6B and 160; and Figures 18A and 18B are perspective views of alternative tool and cam element for optional employment in the embodiment the present invention illustrated in Figures 1 to 6.

DETAILED DESCRIPTION

[0023] Figures 1A and lB show a clamp 10 according to a first embodiment of the present invention. The clamp comprises a first clamp member 12a and a second clamp member 12b that are moveable in relation to one another between an open position (as shown in Figure 1A) and a closed position (as shown in Figure 1B). In the embodiment shown in the Figures, the first clamp member 12a comprises a first jaw 14a at each end, and the second clamp member 12b comprises a second jaw 14b at each end. In the closed position, the first clamp member 12a and the second clamp member 12b are closer to one another than they are in the open position. Consequently, in the closed position, the first jaws 14a of the first clamp member and the second jaws 14b of the second clamp member form channel sections that are capable of gripping and clamping an object therein. In the preferable embodiment shown in the Figures, the jaws 14a,b are formed as part of the first and second clamp members 12a,b respectively, however in alternative the jaws may be separately formed components that are specially adapted for gripping a particular object that may be attached to the first and second clamp members 12a,b.

[0024] As shown in the cross-sectional views of Figures 2A and 2B, the first and second clamp members 12a,b are connected to one another and restrained by a nut 16 and bolt 18 assembly. In particular, the first and second clamp members 12a,b are restrained between the head 18a of the bolt 18 and the nut 16 that is screwed to the bolt 18. Two resilient spring washers 20 are disposed between the nut 16 and the second clamp member 12b which act to urge the second clamp member 12b away from the nut 16 when compressed. In alternative embodiments any number of spring washers 20 may be used, or indeed any other suitable resilient biasing means. In the depicted embodiment, the spring washers 20 may have the same or different physical properties. For example, the two spring washers 20 may have the same or different elasticities.

[0025] In detail X in Figure 2B, spring washer 20' is of the type illustrated in Figures 1 5A and 1 SB. A steel washer 20a is disposed between the spring washer 20' and the nut 16. The purpose and effect of washer 20' is described further below.

[0026] A cam element 22 is disposed between the first clamp member 12a and the head 18a of the bolt 18. The cam element 22 is mounted on the bolt 18 in a recess 13 of the first clamp member 12a, so as to be able to rotate about the bolt 18. As seen more clearly in Figure 4, the cam element 22 has a pair of first cam surfaces 22a, a pair of second cam surfaces 22b and an set of intermediate faces 22c disposed between each adjacent first and second cam surface 22a,b. The cam element 22 has a circular profile around a first axis 23 and the first cam surfaces 22a are arranged at an inclined angle with respect to the second cam surfaces 22b about the first axis 23. In the preferable embodiment shown in the Figures, the first cam surfaces 22a are arranged perpendicularly with respect to the second cam surfaces 22b about the first axis 23. Furthermore, the first cam surfaces 22a are offset with respect to the second cam surfaces 22b and the intermediate faces 22c in a direction parallel to the first axis 23. In particular, along the direction that is parallel to the first axis 23, the second cam surfaces 22b lie between the first cam surfaces 22a and the intermediate faces 22c.

[0027] As described above, the cam element 22 is rotatably mounted on the bolt 18 within the recess 13 of the first clamp member 12a such that the cam element 22 can rotate with respect to the first clamp member 12a.

[0028] The first clamp member 12a comprises a primary cam follower 24 that is adapted to engage with the first cam surfaces 22a and the second cam surfaces 22c (as shown in Figure 3). In the embodiment shown in Figure 3, the first clamp member 12a further comprises a secondary cam follower 25 that is arranged to engage with one of the first and second cam surfaces 22a,b when the primary cam follower 24 is engaged with the other of the first and second cam surfaces 22a,b such that the surfaces 22a,b,c of the cam element 22 can sit flush with the first clamp member 12a in the recess 13.

[0029] In the open position (Figures 1A and 2A), the first cam surfaces 22a are engaged with the primary cam follower 24. In this position, the clamp members 12a,b are at a maximal separation such that an object can be inserted between the jaws 14a,b or removed therefrom.

Rotation of the cam element 22 about the bolt 18 disengages the first cam surfaces 22a from the primary cam follower 24 and the intermediate surfaces 22c move into engagement with the primary cam follower 24. Movement from a first position where the first cam surfaces 22a are engaged with the primary cam follower 24 to a second, intermediate position in which the intermediate surfaces 22c are engaged with the primary cam follower 24, causes the first clamp member 12a to move closer to the second clamp member due to interference between the cam element 22 and the primary cam follower 24.

[0030] In the second position, the clamp members 12a,b are at a minimal separation and are capable of gripping and clamping an object between jaws 14a,b if previously placed therebetween. In addition, the spring washers 20 are under maximal strain due to compression between the nut 16 and the second clamp member 12b and consequently apply an elastic force against the second clamp member 12b away from the nut 16.

[0031] Further rotation of the cam element 22 causes the cam follower 24 to disengage with the intermediate surfaces 22c and engage with the second cam surfaces 22b. In this third position, the clamp members 12a,b are at an intermediate separation in relation to the first and second positions since the first clamp member 12a moves away from the second clamp member 12b by a small amount as the spring washers 20 elastically expand slightly. It is in this third position that the clamp 10 is in its operational clamping position since the cam follower 24 is fully engaged with the second cam surfaces 22b and must ride out over the intermediate faces 22c to fully disengage. Since the elastic force of the compressed spring washers 20 are acting against the second clamp member 12b and the first clamp member 12a, the cam follower 24 is urged along a direction parallel to the first axis 23 against the second cam surfaces 22b. Therefore the risk of accidental disengagement is significantly minimised and the clamp 10 will remain in the third position until the cam element 22 is intentionally rotated to disengage the cam follower 24 from the second cam surfaces 22b. The cam element 22 may be rotated to the first position to release any clamped object from the jaws 14a,b.

[0032] The cam element 22 may be rotated by engagement with a cam tool 26 as shown in Figure 5. The cam tool has a plurality of projecting pegs 26a that are sized to engage in holes 27 of the cam element 22. The cam tool 26 comprises a polygonal socket 26b that may engage with an appropriate turning tool such as a torque wrench. Of course, any tool that is capable of engaging with the cam element 22 or the cam tool 26 and applying a torque may be used to rotate the cam element 22 about the bolt 18.

[0033] In the alternative embodiment shown in Figure 6, a modified cam element 22' comprises an integrated handle 28 that may be used to rotate the cam element 22' by hand.

[0034] The clamp 10 further comprises a mechanism whereby relative rotation between the first clamp member 12a and the second clamp member 12b is inhibited when the clamp is in a closed position. In particular, the second clamp member 12b comprises a longitudinal rib 30 that projects towards a longitudinal slot 32 in the first clamp member 12a. As the first clamp member 12a moves towards the second clamp member 12b, the rib 30 engages with the slot 32 to prevent the first clamp member 12a rotating about the bolt 18.

[0035] The tightness of the clamp 10 may be adjusted according to the position of the nut 16 on the bolt 18. In particular, this will affect the degree of compression experienced by the spring washer 20 and therefore will determine the biasing force produced thereby.

[0036] The purpose of the clamp is to connect two barriers end to end. Such barriers have an application in various situations. One situation is in roadworks. It is desirable in such situations that the clamp is not so tight that passing road traffic that accidentally or otherwise collides with the barrier does not pick up a long chain of barriers and increase the hazard already presented by the initial collision. It is to be borne in mind that such barriers are temporary structures that are not fixed to the ground and need to be easily repositioned from time to time as work demands. Thus, such a hazard can present itself if the barrier elements are strongly interconnected. It is desirable therefore that when some impact force is applied, the jaws 14a,b should spring apart around the barrier element limbs, releasing the barrier so that a long chain is not picked up and swept along by a vehicle. At the same time, the clamp should not be so slack that barrier elements can be easily separated without undoing the clamp 10. Moreover, in many situations, some minor level of security is desirable against unauthorized opening of the clamp and separation of the barrier. This is to be avoided so that barriers are not dislocated or even stolen. The present invention in this embodiment permits the tightness of the clamping to be "factory-fitted", assuming the barrier limbs are known with which the clamps will operate. That is to say, the nut 16 is locked in position by some known means (eg locking adhesive) at a specific position along the bolt 18. Thus, the clamp can be arranged to be reasonably tight (ie within a range that satisfies the two conflicting requirements mentioned above within various climatic conditions -such conditions obviously having an impact on the rigidity of plastics material out of which the barriers themselves might be constructed, as well as the clamp 10). Indeed, the clamps may be arranged so tight in use that a casual user cannot undo the cam 22 without the requisite tool 26. They might not easily be able to open the cam 22', despite its handle 28. In this event, a simple tool as shown in Figure 14 might be provided. This tool 500 comprises a handle 502 and a slot 504 shaped to fit on the handle 28, facilitating its turning.

[0037] Given that the clamp 10 may be arranged so tight that a tool is needed to actuate and de-actuate it, it is desirable that initial loading of the spring washer 20 should be slight, so that the start of rotation of the cam 22 is not unduly inhibited. The washer 20' permits a gradual increase in spring bias as it is axially compressed. Turning to Figures iSA and 15B, washer 20' comprises two concentric annuli 512,514. The washer is made of an elastomeric material having a Shore hardness of about 60. The width w of the annulus 512 is about half that v of the annulus 514. Consequently, when the washer 20a begins to compress the washer 20', the annulus 512 provides the initial reaction which is relatively small given its small radial dimension. However, once it is largely compressed, the wider annulus 514 offers considerably more resistance to compression. It is not essential that the washer 20 be steeped. A coned washer would be equally effective in providing a progressive increase in stress per unit deflection.

[0038] An alternative form of cam element 22" is shown in Figure 1 8B, and the cam tool 26" for operating it is shown in Figure 1 8A. Any form of coding between the tool and cam is desirable to offer a level of security so that a "normal" tool, such as a 13 mm (half-inch) square drive or a hexagonal socket or plug cannot drive the cam element. In Figure 18B, the cam 22" has a pentagonal flange 27" and the tool a corresponding recess 26"a. Of course, they could be reversed. Here, however, the flange 27" has a protecting upstanding circular flange 25" and the recess 26"a has a further circular recess 23" in its base. This circular flange serves two purposes. First it increases the level of security and coding, because the tool that is capable of engaging the cam element 22" must also have the recess 23" to receive the flange 25". Secondly, the height of the flange 25" is arranged to be slightly greater than the depth of the polygonal section 26"a of the tool 26". This means that it is the circular flange/recess 25"/23" that engage first when the tool is offered up to the cam element. This facilitates engagement. Once they are engaged, the tool can be rotated about the axis of the circular flange/recess until the pentagonal flange/recess 27"/26"a are angularly aligned and can also be axially engaged. Preferably, the axis of the circular flange/recess is concentric with the rotation axis 23 of the cam element 22", although this is not essential. Likewise, the central axis of the pentagonal flange/recess is also concentric with the axis of the circular flange recess, but again this is not essential and, indeed, a certain degree of further security can be provided if they are not. Finally, although pentagonal is described, any non-circular (probably polygonal) section of the flange/recess 27"/26"a, including star-shaped, is possible.

[0039] It is to be noted that the tool 26" has a square section drive aperture 26b, as per the tool 26 in Figure 5. Also, a notch 21" is provided indicating the position of an apex of the pentagonal recess 26"a, again facilitating engagement with the cam flange 27".

[0040] A second embodiment of a clamp 10' according to the present invention is shown in Figures 7A and 7B. The clamp 10' comprises a first clamp member 12a' and a second clamp member 12b' that are moveable in relation to one another between an open position (as shown in Figure 7A) and a closed position (as shown in Figure 7B). As with the first embodiment, the first clamp member 12a' comprises a first jaw 14a' at each end, and the second clamp member 12b' comprises a second jaw 14b' at each end.

[0041] The clamps of the first and second embodiments 10,10' share the same principles of operation in that a clamping mechanism moves between three positions to alter the separation of the first and second clamp members. In the second embodiment, the clamping mechanism comprises a toggle lever 102 that is shown in detail in Figure 8.

[0042] The toggle lever 102 comprises a first set of levers 104a pivotally mounted about pivots 105 to a second set of levers 1 04b in an opposed arrangement. The levers of each of the first and second sets of levers 104a,b are rigidly connected to one another by a rigid rod 106. The rods 106 pass through slots 110 in the second clamp member to mount the toggle lever 102 thereto. The toggle lever 102 further comprises a drive plate 108 that is pivotally coupled to the pivots 105 and comprises a threaded bolt 100. The threaded bolt 100 is rotatably mounted to the drive plate 108 such that it is free to rotate about its longitudinal axis.

[0043] The threaded bolt 100 is received in a correspondingly threaded aperture 101 of the first clamp member 12a'. Since the toggle lever 102 is connected to both of the first and second clamp members 12a',b', rotational adjustment (arrow A) of the threaded bolt 100 in the aperture 101 varies the separation of the first and second members 12a',b'.

[0044] In the open position shown in Figure 7A, the toggle lever 102 is in a first position wherein the rods 106 are disposed at inner end llOa of the slots 110. In this position, the first and second clamp members 12a',12b' are at maximal separation. It is in this position that objects can be inserted between or removed from the jaws 14a',b'. Rotating the threaded bolt 100 so that it screws into the first clamp member 12a' causes the first and second clamp members 12a',b' to move towards one another (arrows B and C). As the bolt 100 is screwed into the first clamp member 12a', by virtue of the connection between the bolt 100 and the drive plate 108, the drive plate 108 and hence pivots 105 are moved towards an in line position with respect to the rods 106. This causes the rods 106 to move from the inner ends llOa of the slots 110 towards the outer ends 11 Ob of the slots 110. Continued rotation of the bolt 100 moves the toggle lever 102 to a second position in which the pivots 105 and rods 106 are all aligned and the rods 106 are at maximum separation at the outer ends 11 Ob of the slots 110.

The distance between the rods 106 in the second position is actually greater than the distance between the outer ends 1 lOb of the slots 110 when the second clamp member is in a relaxed position (e.g. the open position shown in Figure 7A). Therefore, for the toggle lever 102 to reach the second position, there must be some deformation of the slots 110 and/or second clamp member 12b'. Alternatively, the slots 110 could comprise resilient elements such as springs that are compressed when the toggle lever 102 moves into the second position.

[0045] Continued rotation of the bolt 100 causes the drive plate 108 and pivots 105 to move out of alignment with the rods 106 to a third position (Figure 7B). In the third position, the slots and/or second clamp member 12b' are somewhat less deformed than they are in the second position (where they are under maximal strain). In this third position, the first and second clamp members 12a'b' have moved together so that an object previously placed therebetween is clamped. The slots 110 and/or second clamp member 12b' are still deformed by an amount and the rods 106 are still disposed at the outer ends 11 Ob of the slots. In certain possible positions beyond the third position, the slots 110 and/or second clamp member 12b' may have relaxed entirely and the rods 106 may have moved by an amount from the outer ends IlOb towards the inner ends llOa.

[0046] Effectively, at positions between the second and first positions, when the rods 106 are still disposed at the outer ends 11 Ob of the slots, the toggle lever 102 is biased towards the first position by the deformed slots 106 and/or second clamp member 106. Similarly, at positions between the second and third positions, when the rods 106 are still disposed at the outer ends 11 Ob of the slots, the toggle lever 102 is biased towards the third position by the deformed slots 106 and/or second clamp member 106. Therefore, in both moving from the first position to the third position and the third position to the first position, the bias of the deformed slots 110 and/or second clamp member 12b' (which are at maximum deformation in the second position) must be overcome. It is therefore practically impossible that the clamp 10' will be moved between the first and second positions unintentionally. The biasing therefore provides an effective obstacle that must be overcome to move the clamp 10' between the open and closed positions. In normal operating conditions, this will require intentional rotation of the bolt 100 in the aperture 101 of the first clamp member 12a'.

[0047] In alternative embodiments, the clamping mechanism comprises a bolt screwing directly into one of the first and second clamp members. In the embodiment shown in Figure 9, a clamp 10" comprises a first clamp member 12a" and a second clamp member 12b". The first clamp member 12a" has an open channel 206a at each end (only one shown) which defines a first jaw 14a". Similarly, the second clamp member has an open channel 206b at each end (only one shown) which defines a second jaw 14b". The first and second jaws 14a"b" form a pair of jaws that are capable of clamping an object when the clamp 10" is in a closed clamping position. A bolt 200 having a screw thread 202 is threaded into a threaded bore 201 in the second clamp member 12b". The bolt 200 has a flange 204 at an opposite end to the thread 202.

[0048] Figure 9 shows the clamp 10" in a closed clamping position wherein the bolt 200 has been screwed into the threaded bore 201 moving the flange 204 towards the second clamp member 12b" and restraining the first clamp member 12a" between the flange 204 and the second clamp member 12b". Figure 9 shows the clamp 10" clamping around an object 208 having a circular cross section of diameter C. Typically, the object 208 will be a tubular arm of a control barrier. In the closed clamping position shown in Figure 9, the first and second jaws 14a",b" surround part of the circumference of the object 208. Each jaw 12a",b" has an overlap length equal to the distance from the base of its adjacent channel 206a,b to an end 210a,b (respectively) of thejaw 14a",b". In Figure 9, the overlap length of thefirst jaw 14a" is denoted x, while the overlap length of the second jaw is denoted y. The first clamp member 12a" must move away from the second clamp member 12b" by a distance that is greater than or equal to D (the "release distance"), where D = x + y, for the object 208 to be released from the pair of jaws 12a",b". The release distance D is preferably a suitable proportion of the diameter C of the clamped object 208 such that it is securely clamped between the jaws 14a",b". In one particularly preferable embodiment, the release distance D is equal to approximately C/b where, in a further preferable embodiment, x = C/5 and y = C/5. In alternative embodiments, a different release distance D may be more appropriate and the jaws 14a",b" may overlap the object 208 to different degrees such that x!= y.

[0049] The thread 202 of the bolt 200 has a pitch P where P »= D such that one revolution, or less, of the bolt 200 in the bore 201 moves the flange 204 away from the second clamp member 12b" by a distance D, which in turn allows the first clamp member 12a" to move by a distance D away from the second clamp member 12b" and release the clamped object 208 from the jaws 14a",b". In a particularly preferable embodiment, a quarter turn of the bolt 200 in the bore 201 (i.e. P/4 = D) is required to move the flange 204 away from the second clamp member 12b" by a distance D, such that the first clamp member 12a" may move a distance D away from the second clamp member 12b" and release a clamped object from the jaws 12a",b".

[0050] In alternative embodiments, the object 208 and jaws 14a"b" need not necessarily have a circular profile. For example, the object 208 may be any polygonal tube and the jaws 14a",b" may be shaped appropriately.

[0051] A further embodiment of the invention is shown in Figures 1OA and lOB. Figure 1OA shows a partial view of a clamp 10" comprising a first clamp member 12a" and a second clamp member 12b" (the jaws of the clamp 10" are not visible in Figures 1 OA and 1 OB). The first and second clamp members 12a" and 12b" are connected to one another and restrained by a rod 304 have a flange 304a,b at each end. Any alternative suitable restraining means having flanged ends (such as a nut and bolt assembly) may be used in place of the rod 204.

[0052] The first clamp member 12a" has a threaded bore 301 circumferentially surrounding the rod 304. A bolt 300 having a screw thread 302 of pitch P is received in the bore 301, where the bolt 300 also has a bore 300a such that the bolt circumferentially surround the rod 304 and is rotatably mounted thereon.

[0053] Figure 1OA shows the clamp 10" in an open position where the first clamp member 12a" and bolt 300 that is screwed in the bore 301 are able to move in a direction parallel to the rod 304 by a distance F between the flange 304a of the rod 204 and the second clamp member 12b". Therefore, in this state, the first and second clamp members 12a",b" may be moved to insert an object therebetween, or preferably, between jaws (not shown).

[0054] The clamp 10" may be moved to a closed clamping position, as shown in Figure lOB, by screwing the bolt 300 out of the bore 301 until the bolt 300 abuts the flange 304a.

Continued screwing of the bolt 300 in this direction causes the first clamp member 12a" to be urged against the second clamp member 12b" thereby establishing a secure clamping hold on any objects that may be disposed between them of jaws at their ends.

[0055] In the case where the clamp 10" comprises jaws like those shown in Figure 9, where the jaws have an overlap length and the two overlap lengths equate to a release distance D, the first clamp member 12a" must move away from the second clamp member such that it is separated therefrom by a distance greater than or equal to the release distance D for a clamped object to be released. As with the embodiment shown in Figure 9, the pitch P of the bolt 300 is dimensioned such that P »= D. Therefore the bolt 300 must be rotated in the bore 301 by one revolution or less, from the clamping position shown in Figure lOB, for the first and second clamp members 12a",b" to separate by an amount sufficient to release a clamped object. In a particularly preferable embodiment, a quarter turn of the bolt 300 in the bore 301 is sufficient to allow the first clamp member 12a" to move away from the second clamp member 12b" by an amount equal to the release distance D and release a clamped object (i.e. P/4=D).

[0056] A further embodiment of the invention is shown in Figures 11 to 13 which show a clamp 410 having a first clamp member 412a and a second clamp member 412b. The first and second clamp members 412a,b are moveable relative to one another along a central axis 413 of the clamp 410 between an open position and a closed position (all of Figures 11 to 13 show the clamp 410 in a closed position). The clamp 410 has a cam mechanism 422 with an integrated handle 428, like the one shown in Figure 6, for moving the first clamp member 412a between the open position and closed position relative to the second clamp member 412b.

[0057] The first clamp member 412a has a first modified jaw 414a at one end and a first unmodified jaw 414a' at the other end. The second clamp member has a second modified jaw 414b at one end and a second unmodified jaw 414b' at the other end. The first modified jaw 414a and the second modified jaw 414b form a first pair of jaws that define a first channel 417 for receiving an object to be clamped, such as a barrier arm. Similarly, the first unmodified jaw 414a' and the second unmodified jaw 414b' form a second pair of jaws that define a second channel 417' for receiving a second object to be clamped, such as another barrier arm. The clamp 410 (like all of the clamps described in the present application) is particularly suited for clamping two control barriers to one another. In the embodiment shown in Figures 11 to 13, the first channel 417 has a substantially circular cross section centered on a longitudinal axis 500 while the second channel 417' also has a substantially circular cross section that is centered on a longitudinal axis 500'.

[0058] Each of the first modified jaw 414a and the first unmodified jaw 414a' has an end 415a and 415a' respectively that is separated from ends 415b and 415b' of the second modified jaw 414b and the second unmodified jaw 414b' respectively along a first direction that is substantially parallel to the central axis 413 of the clamp 410. In particular, ends 41 5a and 415b of the first modified jaw 414a and the second modified jaw 414b are separated along the first direction by a first gap G, and ends 415a' and 415b' of the first unmodified jaw 414a' and the second unmodified jaw 414b' are separated along the first direction by a second gap G'.

[0059] The clamp 410 is moved between the open and closed positions by moving the first clamp member 412a along the central axis 413 of the clamp 410 relative to the second clamp member 412b. In the open position, each of the first and second gaps G and G' is greater than it is when the clamp 410 is in a closed position. In the embodiment shown in Figures 11 tol 3, the first gap G is smaller than the second gap G' in all positions although in alternative embodiments, this need not necessarily be the case.

[0060] The ends 415a and 415b of the first modified jaw 414a and the second modified jaw 414b are skewed at an inclined angle 0 with respect to the longitudinal axis 500 of the first channel. Consequently, the first gap G extends at an inclined angle 0 with respect to the longitudinal axis 500.

[0061] Conversely, the ends 415a' and 415b' of jaws 414a' and 414b' are orientated parallel to the longitudinal axis 500' of the second channel such that the second gap G' extends parallel relative to the longitudinal axis 500'.

[0062] Since the first channel 417 is substantially circular in cross section, the gap G extends helically, to a certain extent, about the longitudinal axis 500. In alternative embodiments however, the gap G may be entirely straight or conform to the shape of a channel with an alternative cross-section. In each variation, however, it is important that the gap G extends at an inclined angle with respect to the longitudinal axis.

[0063] In operation, the clamp 410 is moved to its closed position around two tubular objects by rotating the cam 422 in the manner described above. In the closed position, the first and second gaps G and G' are reduced to a size that prevents the objects from laterally moving out of the first and second channels 417, 417'. To release the clamped objects, the clamp 410 is moved to its open position. In the open position, the second gap G' is larger than the diameter of the clamped object so that the clamped object can pass through the second gap G' to be released. However, in the open position, the size and orientation of the first gap G is such that a tubular object cannot pass through by lateral movement (i.e. movement transverse to the longitudinal axis of the tubular object). To pass through the gap G, when the first clamp member 412a is in the open position relative to the second clamp member 412b, the object must be rotated by an angle 0 to align it with the inclined gap G. [0064] Clearly, the size of the gap G in the open position is crucial to the operation of this embodiment of the invention and its actual size will be related to the dimensions of the channel 417 and the object that is intended to be clamped.

[0065] The skewed jaw arrangement described above allows the clamp 410 to be semi-permanently attached to one barrier, with a barrier arm in the first channel 417, whilst permitting quick and easy releasable fastening to another barrier (through the larger second gap G'). The reason for this is that rotation of the clamp 410 relative to the clamped object is required to release a clamped object from the first channel 417 when the clamp 410 is in the open position. In contrast, no rotation is required to release an object from the second channel 417' when the clamp 410 is in the open position. Since the rotation of the clamp 410 is unlikely to occur accidentally, the clamp 410 will remain clamped (albeit loosely) to one barrier, with the clamped object (i.e. the barrier arm) in the first channel, when the clamp 410 is in the open position, unless the user consciously rotates the clamp 410 to effect the release. A clamp of this type can be transported attached to a barrier and/or may be sold together with a barrier attached.

[0066] Whilst the clamp 410 utilises the cam mechanism described above in relation to Figures 1 to 6, alternative types of clamp may operate with the skewed jaw arrangement described above in relation to Figures 11 to 13. In particular, any clamp having two channels that is movable between an open and closed position may benefit from the skewed jaw arrangement.

[0067] In a fourth aspect of the present invention, the clamp 600 of Figure 1 6A comprises clamp members 612a,b provided with jaws 614. A bolt 618 joins the two, one end of the bolt having a head 618a having two integral pins or arms 618b, and the other end being threaded to receive a nut 616 with steel washer 620 underneath. The arms 618b are received in eccentric bores 621 of a cam 623. The cam 623 comprises two cam elements connected by a bridge 625. The cam elements each have a bore 627 in a circumferential surface, the profile of which may be keyed in some way, such as by having an unusual cross-section. The cam 623 is received in a part cylindrical trough 637 in the surface of clamp member 612a. The trough 637 has a centre of curvature 635 which is coincident with the centre of rotation of the cam 623.

[0068] In the position shown in Figure 1 6A, the jaws are in an open position whereby the barrier limbs 629 can be fitted. There is a gap 631 between the clamp members, although they are still restrained together. In this position, the cam 623 is in such rotational position (around its own axis 635) that the eccentric bores 621 are near the base of the trough 637, permitting the nut 616 to depart to a maximal extent from the clamp member 612a, thereby creating the gap 631 between the clamp members.

[0069] A tool 650 is shown in Figure 17, comprising a handle 652, stem 654 and bits 656.

The bits 656 have the cross-section (not shown in Figures 1 6A or 1 6B) of the bores 627 of the cam, and these are shown in Figure 17 as being four-pointed star shapes in cross-section.

Any profile is possible. When the bits are inserted in the bores 627, the cam 623 can be rotated about its axis 635 pulling the bolt 618 and its nut 616 and washer 620 into contact with the clamp member 612a, drawing that towards the clamp member 612b, closing the gap 631 and squeezing the jaws 614 around the barrier limbs 629. Since the rotation of cam 623 also causes lateral dislocation of the arms 618b, the bore 643 through the clamp member 612 is slightly elongate in the plane perpendicular to the axis 635 to accommodate that dislocation.

[0070] Once the clamp has been tightened to the desired extent (or the tool 650 has been rotated to the maximal extent (as approached in Figure 160, the tool can be removed leaving the clamp relatively tamper-proof.

[0071] Any features of the above embodiments that are not mutually exclusive may be incorporated into any embodiment.

[0072] Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of them mean "including but not limited to", and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0073] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0074] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

Claims

CLAIMS1. A clamp for clamping a pair of control barriers, comprising: a first clamp member; and a second clamp member; where the first and second clamp members form a first pair of jaws defining a first channel for receiving a first object to be clamped, and a second pair of jaws defining a second channel for receiving a second object to be clamped, wherein each of said first and second channels has a longitudinal axis that is parallel to the longitudinal axis of the other of said first and second channels; and ends of the jaws of each pair are separated along a first direction that is transverse said longitudinal axes to define a first gap associated with the first pair of jaws and a second gap associated with the second pair of jaws; wherein the first clamp member is moveable relative to the second clamp member along the first direction between a first position and a second position, wherein in the first position the first gap is greater along a direction parallel to the first direction than it is in the second position and the second gap is greater along a direction parallel to the first direction than it is in the second position; and wherein the first gap extends at an inclined angle with respect to said longitudinal axes whereas the second gap extends substantially parallel to said longitudinal axes.
2. A clamp according to claim 1, wherein in said first position, said second gap is greater than said first gap along a direction parallel to the first axis.
3. A clamp according to claim 1 or 2, wherein each of the first and second channels has a circular cross section when the first clamp member is in the first position relative to the second clamp member.
4. A clamp according to claim 3, wherein the first gap extends helically about the longitudinal axis of said first channel.
5. A clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; restraining means connecting the first clamp member and the second clamp member together; bias means, to urge said clamp members apart, and a clamping mechanism to urge the clamp members towards one another to clamp an object therebetween, wherein the clamping mechanism is mounted on the first clamp member and is movable relative thereto between three positions: a first position in which the clamp members are at a maximal separation to release an object between the clamp members, a second intermediate position in which the clamp members are at a minimal separation to clamp an object between the clamp members, said bias means being strained to a maximal extent, and a third position in which the clamp members are in a clamping position to clamp an object between the clamp members, said bias means being strained to an intermediate extent, and, the clamping mechanism cannot move from the first position to the third position without moving through said second position.
6. A clamp according to claim 5, wherein said clamping mechanism comprises a movable cam element and an opposing cam feature of said first clamp member, one of said cam element and feature having first and second cam surfaces separated by an intermediate face and the other of said cam element and feature having a cam follower, and wherein, when the clamping mechanism is in said first position, the cam follower engages the first cam surface, when the clamping mechanism is in said third position, the cam follower engages the second cam surface, when the clamping mechanism is in said second, intermediate position, the cam follower engages the intermediate face, and in the clamping position, the clamp members are at a separation intermediate the maximal and minimal separations.
7. A clamp according to claim 5 or 6, wherein said restraining means comprises a bolt passing through said clamp members so as to limit separation of the clamp members to said first position.
8. A clamp according to claim 7, wherein said bias means comprises a spring washer between the bolt and one of the clamp members.
9. A clamp according to claim 8, wherein said spring washer comprises a progressive force device.
10. A clamp according to claim 9, wherein said progressive force device comprises an annular elastomeric washer having a base of a first annulus width and a top of a second annulus width that is less than the base annulus width.
11. A clamp according to claim 10, wherein said washer is stepped between a cylindrical section at said first annulus width and a cylindrical section at said second annulus width.
12. A clamp according to claim 11, wherein said step is both on an internal surface of said washer anbd on an external surface thereof.
13. A clamp according to claim 7 or 8 when dependent on claim 6, wherein said cam element is rotatably disposed on said bolt between the bolt and first clamp member and said cam surfaces and cam follower are at a fixed radius with respect to said bolt.
14. A clamp according to claim 13, wherein said cam is engageable with a tool for rotating the cam between the first and third positions.
15. A clamp according to claim 14, wherein said cam and tool are coded so that only said coded tool can engage and rotate the cam.
16. A clamp according to claim 15, wherein said code comprises the cam having holes for engaging with pegs of the tool for rotating the cam between the first and third positions.
17. A clamp according to claim 15, wherein said code comprises a polygonal section flange on one of the tool and cam and a corresponding recess on the other of said tool and cam, said section being other than hexagonal.
18. A clamp according to claim 17, wherein said polygonal flange is protected by a circular flange on one of the tool and cam and a corresponding circular recess on the other of said tool and cam, whichever of the recess and flange being on the cam is concentric with said cam, whereby said circular flange and recess are axially engaged before said polygonal flange and recess are engaged, so that rotation of the tool with respect to the cam facilitates angular alignment of the polygonal sections for subsequent complete axial engagement of the tool and cam.
19. A clamp according to claim 13, wherein said cam comprises a handle element for rotating the cam by hand between the first and third positions.
20. A clamp according to claim 19, wherein the handle is integrally formed with the cam.
21. A clamp according to claim 19 or 20, wherein said handle comprises wings.
22. A clamp according to claim 21, wherein said handle is engageable by a tool to facilitate turning thereof, the tool including a slot to receive said wings.
23. A clamp according to claim 6, or any of claims 7 to 22 when dependent on claim 6, wherein said first and second cam surfaces are disposed substantially perpendicularly with respect to one another about said bolt.
24. A clamp according to claim 5, wherein said clamping mechanism comprises a toggle lever disposed between the first and second clamp members.
25. A clamp according to claim 24, wherein said toggle lever is connected to one of the first and second clamp members by an adjustable element that alters the positions of the first and second clamp members with respect to one another in said first, second and third positions.
26. A clamp according to claim 25, wherein said adjustable element is a threaded bolt received in the one clamp member.
27. A clamp according to claim 25 or 26, wherein said restraining means comprises the connection of said toggle lever to both of said first and second clamp members.
28. A clamp according to any of claims 24 to 27, wherein said toggle lever comprises a pair of opposed levers.
29. A clamp according to claim 28 when dependent on claim 25, wherein said pair of opposed levers are slidably mounted to the other of said first and second clamp members.
30. A clamp according to claim 29, wherein the other of said first and second clamp members is resilient and said bias means comprises said other of said first and second clamp members.
31. A clamp according to claim 29 or 30, or claim 28 when dependent on claim 25, wherein the adjustable element is rotationally mounted to said pair of opposed levers.
32. A clamp according to claim 26, or any of claims 27 to 31 when dependent on claim 26, wherein said toggle lever is moved from the first position to the third position by rotation of the threaded bolt about 90 degrees.
33. A clamp according to any of claims 24 to 32, wherein in the clamping position, the clamp members are at minimal separation.
34. A clamp according to any of claims 5 to 33, wherein the first clamp member comprises at least one first jaw and the second clamp member comprises at least one second jaw, wherein the at least one first jaw and the at least one second jaw form at least one channel section for gripping an object therein when the clamping mechanism is in the third position.
35. A clamp according to claim 34, wherein the at least one first jaw is integrally formed in the first clamp member and the at least one second jaw is integrally formed in the second clamp member.
36. A clamp according to claim 34 or 35, wherein the first clamp member comprises two first jaws being disposed at opposite ends of the first clamp member and the second clamp member comprises two second jaws being disposed at opposite ends of the second clamp member; and the first and second jaws form two channel sections.
37. A clamp according to any of claims 34 to 36, wherein the at least one channel section is substantially cylindrical.
38. A clamp according to any of claims 5 to 37, wherein one of the first and second clamp members comprises a protrusion element and the other of the first and second clamp members comprises a socket for receiving the protrusion element, wherein engagement of the protrusion element and the socket inhibits rotation of the first clamp member about the second clamp member when the clamping mechanism is in the third position.
39. A clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; restraining means connecting the first clamp member and the second clamp member; and a threaded bolt screwable in a threaded bore of one of the first and second clamp members; wherein screwing of the bolt in the bore varies the amount that the first clamp member may move relative to the second clamp member in a direction parallel to a longitudinal axis of the bolt; each of the first and second clamp members comprises at least one open channel defined by a jaw at an end of the clamp member; where each jaw has an overlap length equal to the distance from the end of the jaw to the base of the corresponding channel in a direction parallel to the longitudinal axis of the bolt; and each at least one jaw of the first clamp member forms a pair of jaws with one of the at least one jaw of the second clamp member; the sum total of the overlap lengths of the jaws of the or each pair of jaws equates to a release distance; and the pitch of the thread of the bolt is greater than or equal to the release distance.
40. A clamp according to claim 39, wherein the bolt comprises the restraining means, and the bolt has a flanged end wherein the thread of the bolt retains one of the first and second clamp members, and the flanged end restrains the other of the first and second clamp members.
41. A clamp according to claim 39, wherein the restraining means comprises a rod having flanged ends for restraining the first and second clamp members each flanged end.
42. A clamp according to claim 39, wherein the bolt is rotatably mounted on the rod and is screwable in the bore so as to abut one of the flanged ends of the rod.
43. A clamp according to any of claims 39 to 42, wherein the pitch of the thread is equal to four times the release distance.
44. A clamp according to any of claims 5 to 33, wherein the first and second clamp members form a first pair of jaws defining a first channel for receiving a first object to be clamped, and a second pair of jaws defining a second channel for receiving a second object to be clamped, wherein each of said first and second channels has a longitudinal axis that is parallel to the longitudinal axis of the other of said first and second channels; and ends of the jaws of each pair are separated along a first direction that is transverse said longitudinal axes to define a first gap associated with the first pair of jaws and a second gap associated with the second pair of jaws; wherein the first clamp member is moveable relative to the second clamp member along the first direction between a first position and a second position, wherein in the first position the first gap is greater along a direction parallel to the first direction than it is in the second position and the second gap is greater along a direction parallel to the first direction than it is in the second position; and wherein the first gap extends at an inclined angle with respect to said longitudinal axes whereas the second gap extends substantially parallel to said longitudinal axes.
45. A clamp according to claim 44, wherein in said first position, said second gap is greater than said first gap along a direction parallel to the first axis.
46. A clamp according to claim 44 or 45, wherein each of the first and second channels has a substantially circular cross section when the first clamp member is in the first position relative to the second clamp member.
47. A clamp according to claim 46, wherein the first gap extends helically about the longitudinal axis of said first channel.
48. A clamp for clamping to a control barrier, comprising: a first clamp member; a second clamp member; restraining means connecting the first clamp member and the second clamp member; and a clamping mechanism to urge the clamp members towards one another to clamp an object therebetween, wherein the clamping mechanism is mounted on the first clamp member and is movable relative thereto between two positions: a first, release position, in which the clamp members are at a maximal separation permitted by the clamping mechanism to release an object between the clamp members, and a second, lock position, in which the clamp members clamp an object between them; wherein the clamping mechanism comprises a bolt-element passing between the clamp members through apertures therethrough, a cam being disposed between a head of the bolt element and one of the clamp members, which cam is operable by a tool such that the cam moves the clamping members between said first and second position, which tool is separable from the cam.
49. A clamp as claimed in claim 48, in which said cam is coded so that only an appropriately design tool can engage the cam.
50. A clamp as claimed in claim 49, in which said coding comprises a shaped aperture into which a correspondingly shaped tool is insertable.
51. A clamp as claimed in claim 48, 49 or 5, in which said cam is pivoted to said bolt about a cam axis, the cam having a cylindrical surface engaging said one clamp member, the cam axis being eccentric the axis of said cylindrical surface.
52. A clamp substantially as hereinbefore described with reference to any of the accompanying drawings.