AU631324B2 - Improvements in fixing means - Google Patents

Description

TC I--L I 1 P/00/011 Regulation 3.2 AUSTRALIA 3 4 PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

ORIGINAL

i t TO BE COMPLETED BY APPLICANT Name of Applicant: ART CRAFT ENGINEERING PTY. LTD.

Actual Inventor(s): Paul Anthony Nuendorf and John Andrew Petrie SAcdress for Service: CALLINAN LAWRIE, 278 High Street, Kew, 3101, Victoria, Australia fiention Title: "IMPROVEMENTS IN FIXING MEANS" The following statement is a full description of this invention, including the best method of performing it known to me:- I _I The present invention relates, in general terms, to damping devices for attaching a sign or other display means to a post or other upright support. More specifically, but not exclusively, the present invention relates to damping devices which have two converging members which co-operate to surround a support post or the like member and damp a sign or other display means thereto by fixation of the sign or other display means to at least one of the members of the damping device.

A variety of devices and methods have been developed over the past years for attaching a sign or other display means to an upright post, sign support or the like. Where the sign support is a free-standing structure, such as a post, tube, channel or other upright support structure which supports circumferential attachment of a damp therearound, several types of device have been developed.

For example, a circular damp which attaches at its periphery to the sign and is 0a bolted directly to the sign post or support structure is well known. Typically, such ,°215 mounting configurations involve dri 1 1 "ng a hole through the support post or otherwise securing a screw, bolt or the like means within the post structure.

0 Although such a technique is suitable in some instancea concrete posts or other support structures which are somewhat difficult to penetrate pose a difficult challenge. Furthermore, where signs are changed periodically, new holes must be "24y~ 0 drilled, thereby weakening the sign support or defacing its appearance.

Other circumscribing attachment devices have been developed which 000. include a pair of circular damps open at one side and including projecting flange members which enable joining at the flanges by any suitable means, such as for example a bolt and nut. Typically, the inner diameter of the overall damp is less than the outer diameter of the post. In such instances, the forces retaining the attachment device at the sign post are tangential forces along the post exterior which are applied by tightening the respective flanges into dose contact, thereby squeezing the sign post within the shortened diameter. This necessitates -2appropriate sizing of the clamp to properly grasp the sign post at internal faces of the clamp structure.

Such a configuration involves the application of direct forces applied by pulling the two clamp halves into close relationship. Naturally, the application of such direct forces requires the use of bolts or the like fixing means, which restrain the clamp halves bidirectionally, both towards the joining faces of the clamps, as well as at opposing orientations directed away from the clamp faces. Such clamping structures are typically more cumbersome to install and detach and are frequently subject to deformation around the post by virtue of the forces applied at each side of the clamp. Furthermore, the use of bolts on opposite sides of the clamp requires some balancing of force between the opposing bolts. This balancing must be accomplished by placing the approximate same number of t-urns with respect to each bolt, thereby maintaining an approximate common distance of separation between the opposing clamp members.

These complications characterise the typical problems associated with o 0 known clamping structures for signs. These problems generally involve difficulty o0 of attachment, labor intensive procedures for attachment to the post and fabrication procedures which tend to be costly where several components are to make up a single clamp structure. What is needed is a general clamp Os j configuration which reduces fabrication costs and labor and provides for simple 000$ o. 0 installation techniques, which is versatile with respect to any sign post requiring o circumferential attachment of the sign and the attached clamp structure.

Accordingly, the present invention seeks to provide a circumscribing clamp which is adapted to be quickly and easily coupled to a sign or the like display means and attached to a support post in a configuration which is readily detachable and yet adjustable both vertically along the height of the support post and also as regards the angular presentation to the observer.

The present invention also seeks to provide a clamp structure which is -3adapted to be applied to any support post which is of lesser diameter than the interior diameter of the clamp itself, yet which does not require conformance of the interior clamp surface with the exterior surface of the support post.

The present invention also seeks to provide a sign clamp which is easily manufactured and requires minimal storage space in its unassembled configuration.

Furthermore, shipment costs may be varied from a cost/volume basis to a cost/weight base, as in the use of aluminium.

In accordance with a first aspect of the present invention, therefore, there is provided a circumscribing clamp for attaching a sign or other structure to a post or other support structure permitting circumferential positioning of the clamp there around, said clamp including: a first clamp member having a central base section positioned in a first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; a second damp member having a central base section positioned in a third plane of reference which is parallel with the first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane and third planes, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; said first distal ends including first interlock means and said second distal ends including second interlock means, said first and second interlock means being configured for unidirectional interlocking engagement along a single engagement orientation parallel with the second plane, which interlocking engagement is stabilized by imposition of opposing counter forces along the single engagement -4orientation and between the respective interlock means; and counter force imposing means coupled to at least one of the respective bases of the first and second clamp members being operable to generate the opposing counter forces along the engagement orientation for stabilizing the interlocking engagement of the first and second clamp members.

In accordance with yet another aspect of the present invention there is provided a method for manufacturing a circumscribing clamp useful for attaching a sign or other structure to a post or other support structure permitting circumferential positioning of the clamp there around, said method including: preparing a first clamp member having a central base section positioned in a first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; preparing a second clamp member having a central base section positioned in a third plane of reference which is parallel with the first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along the second plane of reference which is orthogonal with respect to the first and third planes, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; configuring said first distal ends to include first interlock means and said second distal means to include second interlock means adapted for interlocking engagement along a unidirectional orientation parallel with the second plane; and providing means for imposing a counter force to the respective bases of the first and second clamps to generate the opposing counter forces along the directional orientation for stabilizing the interlocking engagement of the first and second clamp members.

Imur~amarPma~---rr~--- In order that the invention may be more dearly understood and put into practical effect there shall now be described in detail a preferred embodiment of a circumscribing clamp in accordance with the invention. The ensuing description is given by way of non-limitative example only and is with reference to the accompanying drawings, wherein: Fig. 1 is an exploded perspective view utilising a pair of attachment dclamps which are to be secured to a support post; Fig. 2 illustrates a single length of extruded material which is adapted to be used to form both clamp members making up a single clamp structure in accordance with the present invention; and Fig. 3 illustrates the attached configuration of a preferred embodiment of the present invention, with a sign and circumscribed sign post.

Referring now to the drawings, a separated view of sign dclamps constructed in accordance with the present invention are generally illustrated as items 10, 11, 12 and 13. These dclamps include a circumscribing structure for attaching a sign 14 or other similar structure (display means) to a post 15 or other type of support structure. These dclamps include gkpairsof clamp members 10 and 11, 12 and 13 which respectively interlock in a circumferential position around post as is described in greater detail hereinafter.

In the preferred embodiment illustrated, each clamp member 10, 11, 12 and 13 is of exactly the same configuration, yet is able to interconnect in the described circumferential position to conveniently and securely attach the desired sign 14 at the support structure 15. Although the drawings illustrate clamp members having a substantially identical configuration, it will be apparent to those skilled in the art that the broader aspect of the present invention can be practiced with different types of clamp members which co-operate in a manner which is set forth in the following paragraphs. Accordingly, the initial description sets forth a construction wherein the clamp members are not identical in configuration but -6x are described instead as first and second clamp members.

In Fig. 1, a first clamp member 10 is identified and includes a central base section 16 which is positioned in a first plane of reference X-Y; typically, this plane will be parallel with the face 17 of sign 14. This central base section 16 operates as a mounting support wherein the backside 18 of the sign 14 abuts against a contacting face 19 of the central base section 16. For this reason, the contacting face 19 is of flat configuration to thereby stabilise sign 14 to be somewhat rigid within the plane X-Y or parallel therewith.

The central base section 16 further includes a threaded opening which extends all the way through the base section to allow passage of a screw or the like fixing means 21. This configuration is more clearly illustrated in Fig. 3, which shows the sign 14 with the screw 21 which extends through a sign opening 22 and into the threaded opening 20 of the central base section 16. In this 0 manner, screw 21 is journalled in threaded opening 20 and operates to stabilise the sign by imposing abutting contact between faces 18 and 19. It will be apparent 0o Q S, that other configurations may be adapted for the central base section to implement O, 0 its primary purpose of providing a mounting location for the sign 14 to the first clamp member Projecting forwardly from the central base section 16 are first and second wing sections 25 and 26 respectively, which are respectively attached at opposing 0000 sides of the base section 16. These wing sections 25 and 26 project forwardly, with ,o a directional component extending along a second plane X-Z which is orthogonal with respect to the first-mentioned plane X-Y. Although the illustrated 0, o embodiment is shown with the respective wing sections 25 and 26 being contained or parallel with the second plane X-Z, it will be apparent to those skilled in the art that these respective wing sections 25 and 26 could be inclined with respect to this plane, so long as the inclination includes a directional component which extends along or parallel with this X-Z plane. These first and second wing sections 25 and -7- I 26 include respective first and second distal ends 27 and 28. Extending between these distal ends 27 and 28 is an intermediate, internal face 30 which faces towards the exterior surface of sign post 15 being circumscribed by the clamps.

The second clamp member 11 has a similar construction, including a central base section 31 which is positioned in a third plane of reference which is orthogonal with respect to the first and third planes of reference. These wing sections 32 and 33 also include first and second distal ends 34 and 35 and an intermediate, internal face 36 therebetween. The components of the second clamp member 11 operate in a manner similar to the components indicated with respect to t- first clamp member 10. Also included is a central opening 37 which is threaded and receives a screw or the like member 38. This second screw 38 operates to impose counter forces between the first and second clamp members and 11, which co-operate to securely attached the coupled sign 14 to the upright post 15. This mechanism is discussed hereinafter.

15' The described engagement of the first and second clamp members and 11 with respect to the post 15 is accomplished by interlock means configured at each of the distal ends 27, 28, 34 and 35 of the respective clamp members and 11. The first distal ends 27 and 35 each include a respective first interlock means, 40 and 41, which is configured to interlock and engage with second o 2Q "0 interlock means 42 and 43 in a manner similar to that illustrated in Figure 3. This "o interlocking engagement occurs along a directional orientation which is parallel 0 with a second plane of reference The specific interlock means structure illustrated in the drawings includes a tongue-in-groove type mechanism which is stabilised by counter-forces applied between a tongue element 44 of the second distal end 28 with a groove element 45 of the first distal end 27. This groove 45 includes a channel formed at an internal face of the first distal end 27, which channel is approximately parallel in orientation with respect to the first plane of reference X-Y. This channel includes a first engagement face 46 which is orientated towards the attached central base section 47 and which is configured at its most distal end in the internal face to include a V-shaped groove 48 wherein the first engagement face 44 includes one side of the V-shaped groove 48, said V-shaped groove 48 having its open end oriented towards the central base section 47 attached to its wing section 32.

The tongue section 44 of the second distal end is configured with an external face which fits within the groove 34 of the first distal end. This external face 49 includes a V-shaped wedge 50 formed at its more proximate side with respect to the attached wing and base sections and configured to seat within the V-shaped groove 48 of the first distal end. This V-shaped wedge 50 includes a second engagement face 51 which is oriented towards its attached base section In this manner, the first and second interlock means are configured for a unique counter-directional engagement wherein the interlocking engagement occurs only along a single direction of contact between the V-shaped wedge and V-shaped groove as previously described. This directed contact corresponds to the direction of applied counter-forces which are generated by use of screw 38.

Generally speaking, these counter-forces may be imposed by any means coupled to the respective central base sections 16 and 47 .a the first and second clamp members 10 and 11, provided the coupled means develops a set of opposing counter-forces F 1 and F 2 which are translated into abutting forces against the respective first and second engagement faces 46 and 51 of the respective interlock means. These forces operate to stabilise the required interlocking engagement and maintain the clamp members in their desired positions. These respective counterforces F 1 and F 2 are orientated along the referenced direction of contact 52, meaning the direction of contact between the first and second engagement faces 46 and 51. It will be apparent that the degree of force applied will depend upon the extent to which screw 38 (in combination with screw 21) is introduced within -9the enclosed area 53 and into contact 54 and 55 with the post A disclosed preferred embodiment includes several additional features which are of interest. The geometric cross-section as shown in Figure 3 defines a circular opening 53 which is formed by reason of the respective first and second arcuate clamp members 10 and 11. It should be apparent that optional configurations could be developed, depending upon the configuration of the sign post 15 to which the pair of clamps was to be secured. For example, if post was rectangular or square-shaped, a rectangular clamp member could be used instead of the arcuate shape identified in the present disclosure.

Figure 1 shows the expected application of the present invention in combination with a second pair of clamp members 12 and 13. The configuration and the utility of clamp member 12 corresponds to the same description supplied previously with respect to claim member 10. Similarly, clamp member 13 S corresponds to clamp member 11 in both configuration and operation. The o Q a 15 additional clamp members 12 and 13 are secured to post 15 at a second elevation oo0 by means of a displacement screw 56 which corresponds to screw 21. This screw 4, 56 is directed through a sign opening 57 and into a threaded opening 58 within 0 1 the clamp member 12. As with the previous disclosure, a second screw 59 is applied from the opposite direction to establish the referenced direction of contact 4,,20 or directional orientation 60 which corresponds to the application of counter-forces

F

1 and F 2 as described with respect tc clamp members 10 and 11.

oo GThe engaged pairs of clamp members 10 and 11, 12 and 13 securely orient the attached sign 14 in place with respect to the post 15. Secure engagement is accomplished as illustrated in Figure 3. Release is realised by merely rotating displacement screws 38 and 59 to relax tension between contact faces 46 and 51. As soon as the counter-forces are released (which requires very little rotation of the respective displacement screws 38 and 59), the second clamp members are released and fall free from the sign post 15. A spacer element 61 may be added at either screw on opposing sides of the direction of force 52 to facilitate sign emplacement as well as post diameter.

A typical method of installation of the sign 14 to a post 15 utilising the present invention would be in accordance with the following steps. A first clamp member 10 would be attached to the sign 14 utilising a screw or the like means 21.

If the screw 21 extends too far into the interior 53 of the pair of clamp members, a spacer 61 may be applied to reduce the degree of penetration of the screw within this enclosed area 53. The second clamp member 12 is similarly attached to the sign 14. The sign 14 with attached dclamp members 10 and 12 is then nested on the post, with approximately one-half of the post seated within the arcuate area between first and second wing sections 25 and 26.

The second dclamp member 11 is then similarly oriented slightly above or below the distal ends 27 and 28 of the first clamp member, with the respective interlocking means 40 and 42 in approximate vertical alignment. In this configuration, the tongue element 44 easily slides into the groove element where slight rotation of the displacement screw 38 engages the post 15 at contact point 54. The sign is then secured. The second clamp member 13 is similarly attached to the first clamp member 12, completing installation.

In addition to the improved convenience and simplicity of the disclosed sign dclamp, the present invention enables clamp construction from a single extruded piece of dclamp material. Such an extruded piece is illustrated in Figure 2 generally as item 70. This extruded piece of material 70 can be of continuous length, greatly reducing the cost of manufacture by fabricating in accordance with well known techniques of extrusion, including conventional pultrusion methods which enable the use of plastics material having fibre reinforcement for additional st-ength. Similarly, extrusion of aluminium enables the fabrication of the sign cross-section in a sturdy, metallic construction.

Fabrication of damp members or components is accomplished by merely 11 j_ cutting sections of the continuous extruded material as indicated at broken line 71.

It will be apparent that such a technique can be developed as part of an assemblyline operation where the extruded material is rapidly cut in segments after it passes through a forming guide which provides the desired configuration in crosssection.

The illustrated configuration of the extruded material in Figure 2 is the same as the clamp construction previously described and shown in Figures 1 and 3. This configuration includes the central section 72 and projecting wing sections 73 and 74. Distal ends 75 and 76 include the tongue 77 and groove 78 combination previously discussed. Additional interior grooves 79 and 80 are formed within the cross-section to facilitate stacking of multiple extruded members along a common vertical axis. These grooves 79 and 80 receive the distal edges 83 and 84 of the central base section 72. This configuration not only facilitates stacking and storage in a reduced space, but also enables the formation of the threaded opening 85 by drilling and tapping a multiple set of extruded members with a single pass.

The present invention provides a significant advance in the state of the art of sign attachment structure by reason of the enhanced convenience of attachment and the improved efficiency of manufacture. These combined benefits are realised by a single extruded section, such as is illustrated in Figure 2, supplying both sides of the clamping device (clamp members 10 and 11) with a single cross-section which is interchangeable.

The bracket in accordance with the present invention is designed to act as either a single-sided sign support. When used as a single-sided sign support, it is not necessary to employ a second bolt (or the like fixing means) on the opposing side for purposes of clamping, since the length of the sign bolt itself will be sufficient to keep pushing against the post until such time as the reverse side of the bracket is in contact with the post, when clearance has been generated between the inner annular face of the bracket and the post, and to ensure that the -12sign bolt head and the bracket sign face come together to actually clamp the sign.

The posts used can consist of standard 2" I.D. water pipe or 2 3/8" O.D. light gauge tube. When using the tube, because indentation of the hardened bolt point can occur, everything works when tightening the bolt up to maximum clamp pressure on the sign. However, when using heavy water or steam pipe, indentations may or may not occur, and it then becomes a problem when undue stress is thrown onto the bracket wings, generally marked 32 on Figure 3, since something has to stretch. There will be cases of double-sided sign mounting, or over-sized diameter standard pipe, which will not allow the bolt to be tightened sufficiently to clamp the sign. Therefore point 11 on the embodiment of Figure 1, which is also a retainer for piggyback machining together with dimple, point X is built into the design to act as give points to provide an extra dimension or stretch of the wings, to either the over-sized pipe, double sign mounting, etc. In essence, they have the tendency to straighten out a little without the aluminium reaching 15 yield point and provide the extra dimension required for the post size difficulties.

o' I I The bolt is preferably pointed or coned at the end and also case- S hardened to assist in the penetration of the pipe or tube without mushrooming, which then makes the bolt non-removable which then requires the bracket to be thrown away. The bolt can simply be replaced if it becomes rusty, mushrooming o becomes evident and overall extends the life of the bracket pieces, by re-use and o o cannibalising.

Finally, it is to be understood that the aforegoing description refers merely to preferred embodiments of the invention, and that variations and modifications will be possible thereto without departing from the spirit and scope of the invention, the ambit of which is to be determined from the following claims.

-13-

Claims (14)

1. A circumscribing clamp for attaching a sign or other structure to a post or other support structure permitting circumferential positioning of the clamp there around, said clamp including: a first clamp member having a central base section positioned in a first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; a second clamp member having a central base section positioned in a third plane of reference which is parallel with the first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane and third planes, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; said first distal ends including first interlock means and said second distal ends including second interlock means, said first and second interlock means being configured for unidirectional interlocking engagement along a single engagement orientation parallel with the second plane, which interlocking engagement is stabilized by imposition of opposing counter forces along the single engagement orientation and between the respective interlock means; and counter force imposing means coupled to at least one of the respective bases of the first and second clamp members being operable to generate the opposing counter forces along the engagement orientation for stabilizing the interlocking engagement of the first and second clamp members.

2. The device as defined in claim 1, wherein the first and second clamps have identical configurations. 14

3. The device as defined in claim 1 or claim 2, wherein the respective first and second clamp members are formed by cutting each clamp from a common piece of extruded material having a uniform cross-section corresponding to the desired clamp cross-section.

4. The device as defined in any one of the preceding claims, wherein the interlock means of the first and second distal ends include a tongue-in-groove interlock mechanism which is stabilized by counter forces applied by a tongue element of the interlock mechanism against a groove element thereof.

The device as defined in claim 4, wherein the interlock means of the first distal end includes a groove formed at an internal face of the first distal end which is parallel in groove orientation with respect to the first plane and which includes a first engagement face oriented toward its attached base section, said interlock means of the second distal end comprising a tongue element configured at an external face of the second distal end to fit within the groove within the internal face of the first distal end and including second engagement face oriented toward its attached base section.

6. The device as defined in claim 5, wherein a most distal end of the groove in the internal face includes a V-shaped groove wherein the first engagement face includes one side of the V-shaped groove, said V-shaped groove having its open end oriented toward the base section attached to its wing section, said second distal end including a V-shaped wedge formed at its more proximate side with respect to the attached wing and base sections and being configured to seat within the V-shaped groove of the first distal end.

7. The device as defined in any one of the preceding claims, wherein the first and second wings of the respective first and second clamps project forward in an arcuate configuration such that the respective internal faces between the interlocking distal ends form a circular configuration for the clamp.

8. The device as defined in any one of the preceding claims, wherein the 15 counter force imposing means includes a displacement screw journalled within a threaded opening disposed within the base section of the second clamp means in an orientation parallel with the second plane of reference such that rotation of the screw inward displaces a forward end of the screw into contact with the post or other support structure, thereby imposing a countei force upon further inward rotation of the screw.

9. The device as defined in claim 8, wherein the counter force imposing means includes a second displacement screw journalled within a threaded opening disposed within the base section of the first clamp means in an orientation parallel with the second plane of reference such that rotation of the second screw inward displaces a forward end of the screw into contact with the post or other support structure opposite from contact arising from the first screw, thereby imposing a counter force upon further inward rotation of the second screw.

A method for manufacturing a circumscribing clamp useful for attaching a sign or other structure to a post or other support structure permitting circumferential positioning of the clamp there around, said method including: preparing a first clamp member having a central base section positioned in a first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along a second plane of reference which is orthogonal with respect to the first plane, said wing sections having corresponding first and second distal ends and an intermediate, internal face therebetween; preparing a second clamp member having a central base section positioned in a third plane of reference which is parallel with the first plane of reference and first and second wing sections respectively attached at opposing sides of the base section and extending forward from the base section with a directional component along the second plane of reference which is orthogonal with respect to the first and third planes, said wing sections having corresponding first and second distal 16 ends and an intermediate, internal face therebetween; configuring said first distal ends to include first interlock means and said second distal means to include second interlock means adapted for interlocking engagement along a unidirectional orientation parallel with the second plane; and providing means for imposing a counter force to the respective bases of the first and second clamps to generate the opposing counter forces along the directional orientation for stabilizing the interlocking engagement of the first and second clamp members.

11. The method as defined in claim 10, including the more specific step of fabricating the first and second clamps from a single length of extruded material such that both the first and second clamp members have identical configurations in cross-section along the second plane of reference.

12. The method as defined in claim 11, wherein the fabricating step includes forming the extruded clamp members from a length of extruded material which is passed through a single die configuration, each clamp member being cut along a plane which is orthogonal to the longitudinal axis of the extruded material from the single length of material as a clamp segment.

13. A circumscribing clamp as claimed in claim 1, substantially as described herein with reference to the accompanying drawings.

14. A method for manufacturing a circumscribing clamp as claimed in claim substantially as described herein with reference to the accompanying drawings. DATED this 21st day of September 1992. ART CRAFT ENGINEERING PTY. LTD. By their Patent Attorneys: CALLINAN LAWRIE -17- ABSTRACT A circumscribing clamp for attaching a sign (14) to a post or other support structure (15) and permitting circumferential positioning of the clamp therearound. The clamp includes a first clamp member (10) having a central base section (16) positioned in a first plane of reference and first and second wing sections, (25) and extending therefrom. A second clamp member (11) of similar construction is provided having a central base section (31) and first and second wing sections (32) and with first and second distal ends, (34) and The first distal ends, (27) and of each respective clamp member, (10) and (11), include ar interlock structure which engages with an interlock structure of the second distal ends, (28) and along a directional orientation which is approximately perpendicular to the plane of reference identified for the first a clamp member The respective clamp members (10) and (11) are stabilised in interlocking engagement by application of counter-forces imposed by at least one displacement screw (38) which operates to urge one clamp member away from the other by pushing with respect to the contained post thereby securing the clamp members, and the clamp in general, with respect to the post -18