GB2146728A - Lightweight scaffolding - Google Patents

Abstract

A lightweight scaffolding clamp eg made from aluminium, having a longitudinal axis (52) comprises a first (54) and second (56) circumferentially extending arms pivotally secured to each other, the free end of the first arm carrying a radially outwardly directed flange (64) at the end thereof, the free end of the second arm carrying a pair of spaced flanges (66) (68) at the end thereof, the inner face of flange (66) being generally convex in shape and presenting a pair of oppositely directed ramps, and an endless tapered keeper (74) which has a first side edge for abutting the radially outwardly directed flange (64) at the end of the first arm and a second side edge angled with respect to the first side edge for abutting the surface of one of the ramps on the flange (66) when the keeper is pushed into the channel between the flanges. Two such clamps are rivetted back-to- back to be either fixed or relatively pivotable. <IMAGE>

Description

SPECIFICATION Lightweight scaffolding FIELD OF INVENTION This invention relates to lightweight scaffolding that is rugged, easily assembled and dismantled, and easily manufactured, and components therefor.

BACKGROUND OF THE INVENTION Scaffolding is in common use in the construction industry enabling workmen to stand and work at various levels during the erection and repair of building structures. Examples of prior art proposals in scaffolding are shown in United States Letters Patent 3,131,784; 3,438,460; 3,613,832 and 3,791,486. The difficulty with these and other prior art proposals is that the scaffolding is assembled, disassembled and used by workers who tend to be impatient, rough and careless with the scaffolding and components.For example, where platforms are provided to span sections of the scaffolding at given work levels (See United States Patent 3,374,861; 3,434,567 and 3,628,628) the platforms are usuaily carelessly handled and often dropped, most often landing on their ends with the result that the fasteners at their ends are rendered unusable, in many instances snapping from the platform by the force of striking the ground. Because in most instances, the fastener forms an integral part of the rail extending the length of the platform, use of the platform is lost. In the case of fasteners removably connected to the side rails (See United States Letters Patent 3,628,628), the fasteners snap when the platform lands on end.

Compounding the inherent deficiencies of the scaffolding is the fact that in most instances, the structures are employed by unskilled workers who tend to abuse the scaffolding. To ensure the survival and structural integrity of scaffolding in the hands of these workers, any scaffolding provided must be strong, able to take punishment, yet be assembled and dismantled easily.

To this end, invention proposes scaffolding and component parts therefor which are easily assembled, and capable of absorbing considerable abuse before breaking or becoming unusable. Where the scaffolding or components do break, the broken parts are easily and quickly repaired or replaced.

Further and other objects of the invention will be realised by those skilied in the art from the following summary of the invention and detailed description of embodiments thereof.

SUMMARY OF THE INVENTION According to one aspect of the invention scaffolding is provided comprising uprights, horizontal rails connecting the uprights, and cross-bracing, the improvement comprising clamps connected to other clamps for connecting the uprights and horizontal rails connecting the uprights to each other or other tubular members, each clamp having a longitudinal axis extending longitudinally through the centre of the clamp, and comprising first and second circumferentially extending, preferably extruded aluminum arms, pivotally secured to each other at one end of each of the arms, the free end of the first arm carrying a radially outwardly directed flange at the end thereof (preferably the free end of the first arm comprising a circumferentially extending slot in the free end providing a pair of spaced fingers spaced by the slot, each finger carrying a radially outwardly directed flange at the end thereof), the free end of the second arm carrying a pair of spaced flanges at the end thereof, each flange extending in a direction parallel to the longitudinal axis of the clamp to define a longitudinally extending channel therebetween, a thin shaft extending between the flanges, the flange closer the free end of the arm having an outer face and an inner face facing the other flange, the said face being generally convex in shape and presenting a pair of ramps, one ramp extending from each longitudinal end of the flange towards the centre of the inner surface of the flange at the same angle to the outer face as the other ramp, the ramps meeting proximate the centre of the surface at the apex disposed closer to the other flange than the longitudinal ends of the flange, the inner face of the other flange preferably being a flat longitudinally extending face, an endless keeper, preferably of extruded aluminum, comprising a long thin member tapering from a wider end to a narrower end, the narrower end being narrower than the channel, the keeper having a transverse slot therethrough, extending for a major part of its length to accommodate the shaft therethrough so as to carry the keeper thereon, the keeper also having a first side edge for abutting the radially outwardly directed flange at the end of the first arm (in the preferred embodiment the spaced fingers) and a second side edge angled with respect to the first side edge for abutting the surface of one of the ramps when the keeper is pushed into the channel between the flanges when the clamp is secured to an upright horizontal rail or other tubular member.

The clamps are preferably connected to one another by connecting the first arms of individual clamps. They be connected so that they swivel relative to one another or are locked with respect to one another. For locking purposes, a central portion of the outer surface of each first arm may be modified to carry an open ended square channel having a pair of upstanding channel side walls, the clamp arms turned 90 to one another, the channel bottoms abutted and the clamps secured to gether as for example with a rivet.

By spacing the arms sufficiently as by the use of washers between the channel bottoms, the clamps may be secured together to pivot with respect to one another.

According to another aspect of the invention, scaffolding is provided comprising uprights, horizontal rails connecting the uprights, and cross-bracing, the improvement comprising a platform suitable for spanning spaced horizontal rails, and for supporting a deck of for example, plywood, each platform comprising a pair of side rails, and cross-rails, (both the side rails and cross-rails being preferably of extruded aluminum), each side rail being of a modified configuration in cross-section, presenting a central vertical web and outwardly directed bottom and top flanges, each flange joined at a central part thereof to the ends of the web, the portions of the bottom and top flanges extending from one side of the web carrying projections or lips on the ends of each of the flanges directed towards the other flange to define a channel on one side of the web, the other side of the web carrying two spaced ledges extending laterally from the side, intermediate the bottom and top flanges, the upper ledge spaced from the top flange, being wedged shaped in crosssection of least width at the ledge's and remote the web and presenting an inwardlydownwardly directed ramp extending to the web on the underside of the ledge, the distance between the top flange and upper surface of the upper ledge providing a channel therebetween to secure the deck, as for example, a sheet of plywood, each cross-rail being of the same height as the distance between the top surfaces of the two ledges and being bevelled at its ends proximate the top surface at a complementary slope to the ramp on the underside of the upper ledge for permitting the seating of the cross-rail on the lower edge and under the upper ledge so that the top surface of the cross-rail lies in the same plane as the top surface of the upper ledge, fastening means for removably securing the cross-rails to the side rails and a plurality of hooks for securing in the channels extending along one side of each web of the side rails.

Each hook may comprise a frontal hook portion, a rear mounting plate offset the frontal hook portion, a connector between the frontal hook portion and rear mounting plate, and laterally extending lips extending from the connector, the lips extending for a total distance from the connector by a distance greater than the depth of the channel into which the hook is to be secured, and fastening means for fastening the mounting plate to the side rails. In use with the platform as described above, the lips extend from the connector by a distance greater than the depth of the channel between the lips extending from the top and bottom flanges and the web of the side rail and the fastening means for fastening the mounting plate to the side rail, secures the mounting plate to the side rail preferably through the web of the side rail.Preferably, the frontal hook portion includes a nose or protrusion secured in advance or forwardly of the frontal hook portion (preferably in advance of the upper part of the hook).

According to another aspect of the invention, there is provided scaffolding comprising uprights, horizontal rails connecting the uprights and cross-bracing, the improvement comprising an additional vertical upright extending between the upper and lower horizontal rails at, at least one end of the scaffolding.

to form with another of the uprights. a pair of stiles for a ladder, and a plurality of removably securable rungs to the stiles. Preferably the additional vertical upright provides a vertically oriented channel facing the other upright, and a plurality of spaced apertures through one of the side walls defining the channel, the other upright presents a plurality of slots, at least one slot in the upright at the same level as each aperture, preferably directed towards the channel, and each of the removable rungs extends between and is secured to, the uprights, each rung presenting at least one projection for insertion in the at least one slot, and a spring latch protruding from one side of the rung to snap through the aperture in the channel wall when the rung is to be locked in the channel.Preferably, the at least one slot comprises two slots set side by side and the number of projections on one end of the rung to be inserted into the slots, numbers two.

According to another aspect of the invention, the individual components described above are provided as suitable for use with scaffolding or for any other structure for which their use would be suitable.

The invention will now be illustrated with reference to the following drawings illustrating embodiments of the invention and the detailed description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front view of scaffolding constructed according to an embodiment of the invention; Figure 2 is an end view of the scaffolding shown in Fig. 1; Figure 3 is a perspective view of the scaffolding constructed according to another embodiment of the invention; Figure 4 is a close-up partly exploded view of part of the structure shown in Fig. 3; Figure 5 is a top plan view of part of the scaffolding structure according to the embodiment of the invention shown in Fig. 4; Figures 6 and 6A together form a close-up view of part of the structure shown in Fig. 5; Figure 7 is a perspective view of part of the structure shown in Fig. 2; Figure 8 is a top plan view of the structure shown in Fig. 7 assembled;; Figure 9 is a perspective view of a pair of clamps suitable for use in the erection of scaffolding according to another embodiment of the invention; Figures 10, 11, 12 and 13 are various views of clamps similar in construction to the components in Fig. 9; Figures 14, 15 and 16 are perspective views of extrusions used to construct the clamps in Figs. 9 to 1 3 inclusive.

DETAILED DESCRIPTION OF THE EMBODI MENTS With reference to Figs. 1 and 2 there is shown scaffolding 30 comprising vertical sections 30A surmounted one on the other and joined one to the other by pins 40 (See Fig.

3) to form scaffolding 30. Each of sections 30A comprises uprights 32, horizontal rails 34 connecting uprights 32 and cross-bracing 36 secured to uprights 32 by locks 38 (See Fig. 4) constructed in accordance with the teachings of United States Letters Patent 3.091.485.

Exterior platforms 42 are secured on triangular outriggers 44 (one at each end-see Fig. 3) secured to uprights 32 by clamps 46-See Fig. 4. Each outrigger 44 is triangular in shape made up of tubular members 48 of rectangular cross-section. Outriggers 44 are used in two ways-See Fig. 3-to support the platform 44, with hypoteneuse 48A angularly positioned for reinforcement and to stabilise scaffolding 30 at the foot thereof with cross-bracing 50 secured to each outrigger 44.

While clamps 46 are used to secure outriggers 44 to uprights 32 of scaffolding 30, they may be joined to other clamps 46 as shown in Fig. 9 to 1 3 for use to join vertically and horizontally extending members.

Each of clamps 46 has longitudinally extending axis 52 through the centre and comprises a pair of extruded aluminum circumferentially extending arms 54 and 56 pivotally secured to each other at 58, the free end of arm 54 carrying slot 60 spacing fingers 61.

Each finger 6 1 carries a radially outwardly directed flange 64 at the end thereof. The free end of arm 56 carries a pair of spaced flanges 66 and 68 extending in a direction parallel to the longitudinal axis 52 of clamp 46 to define longitudinally extending channel 70 therebetween. Shaft 72 (See Fig. 12) bridges channel 70 between flanges 66 and 68 and carries keeper 74 thereon. Flange 66 has flat planar longitudinally extending outer surface or face 66A and inner face 66B facing flange 68, generally convex in appearance, presenting a pair of equilength ramps 66C (See Fig.

13), one ramp 66C extending from each longitudinal end of flange 66 towards the centre of inner surface 66B of the flange at the same angle to the outer faces as the other ramp, the ramps meeting at the centre of the inner surface 66B at apex 66D disposed closer to flange 68 than the longitudinal ends of the flange. The inner face of flange 68 is a flat longitudinally extending surface. Extruded aluminum keeper 74 is endless and comprises a long thin member tapering from wider end 74A to narrower end 74B. End 74B is narrower than channel 70.

Keeper 74 has transverse slot 76 through a major part of the keeper's length to receive shaft 72 therethrough to secure keeper 74 in channel 70 between flanges 66 and 68 to rotate on shaft 72 when arm 56 is free of arm 54. Keeper 74 carries longitudinally extending first side edge 78 (extending parallel to longitudinal axis 54) to extend proximate the inner surface of flange 68 and a second side edge 80 angled with respect to edge 78 at a complementary angle as the angle of ramp 66C to engage and abut the surface of one of the ramps 66C when keeper 74 is pushed into channel 70 between flanges 66 and 68 when the clamp is secured to a tubular member, to provide a bearing surface between keeper 74 and the inner surface 66B of flange 66.

With reference to Figs. 14, 1 5 and 16, each of arms 54 and 56 and keeper 74 are severed from extrusions 86, 88 and 90 shown in Figs. 15, 14 and 16 respectively.

Particularly profile 90 for keeper 74 is severed at an angle from the profile to provide wider and narrower ends 74A and 74B respectively and side edge 80 at the complementary angle to ramp 66C. The next keeper served from the profile is severed at an angle normal to the longitudinal axis of the profile so that the wider and narrower ends 74A and 74B of the adjacent severed keeper are on opposite sides of the profile. Thereafter, the keepers are severed at an angle from the profile, then normal to the longitudinal axis of the profile, and so on.

Profile extrusion 86 has flat back 94 forming the bottom 94A of channel 96, and side walls 98 on either side of channel bottom 94A. Arms 54 severed from extrusion profile 86 are of a length "n" equal to the channel width between side walls 98.

The severed portions are then appropriately modified to provide the necessary slots and connected to form clamp 46 which is used as in Figs. 3 and 4 to secure the outriggers 44 or be connected to other clamps 46. In this regard, each flat back 94 of arm 54 severed from profile extrusion 86 forms a square n X "n". Arms 54 of clamp 46 to be joined are rotated at 90 to one another with channel bottoms 94A of the two clamps 46 abutting and side walls 98 of both clamps 46 engaging the open ends of channel 96 to close the space. Apertures (not shown) through flat backs 94 permit the use of a rivet to connect the clamps together with either the ability or inability to pivot. In this regard, reference should be had to Figs. 9 and 10.

With reference to Figs. 9 to 1 3 inclusive, clamp 46 is to be secured to a pipe P-See Figure 1 2-. Arms 54 and 56 extruded to the appropriate shape are brought to grasp and close round pipe P to cause flange 66 to pass through the slot between flanges 64.

Keeper 74 has been rotated on shaft 72 to present leading narrower end 74B to channel 70. With the positioning of the flanges as above, keeper 74 is pushed into channel 70 with side edge 78 engaging surfaces 64A, (and flange 68 if the inner surface of flange 68 is co-planar with the inner faces 64A of flanges 64 of fingers 62) and with angled side edge 80 sliding on ramp 66C (See Fig.

14) until keeper 74 is wedged in position.

With reference to Figs. 3 to 6 inclusive, platform 42 is shown mounted on spaced outriggers 44 for illustration purposes. With particular reference to Figs. 3 and 4, platform 42 comprises a pair of extruded aluminum cross-rails 102 connecting side rails 100.

Each side rail is of a modified configuration in cross-section, presenting central vertical web 104 spacing horizontally disposed outwardly directed bottom and top flanges 106 and 108, each joined at a central part thereof to web 104. On one end of flanges 106 and 108 are lips 110 (seen best in Fig. 6) directed towards the other flange, to define channel 11 2 on one side of web 104. The other side of web 104 carries two vertically spaced ledges 114 and 11 6 extending laterally or horizontally from web 104 intermediate the bottom 108, and top 106, flanges.Upper ledge 114 is spaced from top flange 106 and is wedge-shaped in cross-section of least width at the ledge's outer end 11 8 remote web 104 presenting inwardly-downwardly directed ramp 1 20 extending to web at an angle of 45" to the upper ledge. The distance between top flange 106 and upper ledge 114 provides channel 1 22 for securing the edge of plywood sheet 1 24 therein.

Each cross-rail 102 is of the same height as the distance between the upper surface of ledge 11 6 and the upper surface of ledge 114 and is of modified configuration in cross-section (See Fig. 4) having lips on the ends of the upper and lower horizontal flanges for reinforcement and circular channel 1 25 intermediate the upper and lower flanges for receiving the end of a screw fastener for assisting to secure each cross-rail 102 to side rails 102.

The ends of each cross-rail 102, for example end 1 26, are bevelled at the same angle as ramp 1 20 so that cross-rail 102 slides under ledge 114 and engages ramp 1 20. Therefore, the upper surface of cross-rail 102 lies in the same plane as ledge 11 4 to support sheet 1 24.

Fastening hooks 1 30 have been provided for securing platform 42 to the upper rails of triangular outriggers 44 (See Figs. 4 and 6).

Each fastening hook 1 30 is of extruded aluminum (see Fig. 6) and includes frontal hook portion 132, rear mounting plate 1 34 offset from frontal hook portion 132, connector 1 36 between frontal hook portion 1 32 and mounting plate 134, and laterally extending lips 1 38 extending laterally from connector 1 36, for a distance greater than the depth of channel 112 from lips 110 to web 104.

Frontal hook portion 1 32 includes nose or protrusion 1 32A secured in advance of the upper part of frontal hook portion 1 32.

Mounting plate 1 34 carries two apertures 1 40 for receiving fasteners (not shown) therethrough. Hooks 1 30 are secured to side rails 42 by fasteners (not shown) passing through apertures 140 through web 104 after mounting plate 1 34 is positioned in channel 11 2 against web 104 with one of lips 1 38 abutting the end face 142 of web 104.

In use, if side rails 100 fall on end, nose 1 32 of hook 1 30 protects the hook portion 1 32. In addition, the force of the blow is transferred from nose 1 32A through hook portion 1 32 through connector 1 36 to lips 1 38 (one of which engages end face 1 42), through end face 1 42 to web 104 and thus to side rail 100 to dissipate the force. In that way, the connection between hooks 1 30 and side rails 100 in most cases is maintained, and does not receive the brunt of the blow.

Because hooks 1 30 comprise offset sections-hook portion 1 32 and mounting plate 134--adjacent platforms may be connected to the same horizontal rail and be aligned to the next adjacent platform-See Fig. 5.

Hooks 1 30 are severed from the aluminum extrusion shown in Fig. 6, and appropriately modified as for example, by the removal of material to form mouth 1 30A and nose 132A.

With reference to Figs. 2,3,7 and 8, scaffolding 30 provides a removable ladder 1 50 on each section 30A employing one of the vertical uprights 32 and a second upright 32' spaced from it and connected at the top of each section 30A to horizontal rails 34. Removable rungs 1 52 are removably secured to uprights 32 and 32' for use as required as part of a ladder or, removed when not needed or will interfere with the work being performed.

With particular reference to Figs. 7 and 8, uprights 32 and 32' form a pair of stiles for the ladder 150, upright 32' being U-shaped and presenting vertically oriented channel 154 opening towards upright 32 and carrying a plurality of spaced apertures (one of which is shown at 156) through one of side walls 1 58 defining the lateral extent of channel 154, the other upright 32 carrying two parallel slots 1 6 at the same horiziontal levels as aperture 1 56. Removable rungs 1 52 extend between stiles 32 and 321, each rung 1 52 being secured at one end in channel 1 54 of stile 321 and at the other to stile 32.To this end, rung 1 52 presents U-shaped spring 1 62 with projection 1 62A secured between side walls 1 64 and 1 66 with projection 1 62A projecting through aperture 1 68 in side wall 164. Projections 1 70 are carried on the other end of rung 1 52 for insertion into slots 1 60 (See Fig. 8).

Rung 1 52 is mounted between uprights 32 and 32' by inserting projections 1 70 into slots 1 60 with rung 1 52 angled 45" to upright 32. Rung 1 52 is then swung downwardly to position the end of rung 1 52 carrying aperture 1 68 in channel 1 54 compressing projection 1 62A towards wall 1 66 within rung 1 52 until projection 1 62A is depressed inwardly into the body of the rung releasing the rung from wall 1 64.

As many changes could be made to the embodiments of the invention without departing from the scope of the invention, it is intended that all matter contained herein with respect to the description of the embodiments be interpreted as illustrative of the invention and not in a limiting sense.

Claims (16)

1. Scaffolding comprising uprights, horizontal rails connecting the uprights, and crossbracing, the improvement comprising clamps connected to other clamps for connecting the uprights and horizontal rails connecting the uprights to each other or other tubular members, each clamp having a longitudinal axis extending longitudinally through the centre of the clamp, and comprising first and second circumferentially extending arms pivotally secured to each other at one end of each of the arms, the free end of the first arm carrying a radially outwardly directed flange at the end thereof, the free end of the second arm carrying a pair of spaced flanges at the end thereof, each flange extending in a direction parallel to the longitudinal axis of the clamp to define a longitudinally extending channel therebetween, a thin shaft extending between the flanges, the flange closer the free end of the arm having an outer face and an inner face facing the other flange, the said inner face being generally convex in shape and presenting a pair of ramps, one ramp extending from each longitudinal end of the flange towards the centre of the inner face of the flange at the same angle to the outer face as the other ramp, the ramps meeting proximate the centre of the inner face at an apex disposed closer to the flange than the longitudinal ends of the flange, an endless keeper, comprising a long thin member tapering from a wider end to a narrower end, the narrower end being narrower than the channel, the keeper having a transverse slot therethrough extending for a major part of its length to accommodate the shaft therethrough so as to carry the keeper thereon, the keeper also having a first side edge for abutting the radially outwardly directed flange at the end of the first arm and a second side edge angled with respect to the first side edge for abutting the surface of one of the ramps when the keeper is pushed into the channel between the flanges when the clamp is secured to an upright, horizontal rail or other tubular member.

2. The clamps of Claim 1, wherein each of the arms and keeper are of extruded aluminum.

3. The clamps of Claim 1, wherein the free end of the first arm carrying a radially outwardly directed flange at the end thereof provides a circumferentially extending slot in the free end of the arm, providing a pair of spaced fingers spaced by the slot, each finger carrying a radially outwardly directed flange at the end thereof, whereby when the clamp is secured to an upright, horizontal rail or other tubular member, the first side edge of the keeper abuts the radially outwardly directed flange at the end of each finger.

4. The clamps of Claim 2, wherein the free end of the first arm carrying a radially outwardly directed flange at the end thereof provides a circumferentially extending slot in the free end of the arm, providing a pair of spaced fingers spaced by the slot, each finger carrying a radially outwardly directed flange at the end thereof, whereby when the clamp is secured to an upright, horizontal rail or other tubular member, the first side edge of the keeper abuts the radially outwardly directed flange at the end of each finger.

5. The clamps of Claim 1, wherein each clamp presents an open ended square channel having a pair of upstanding channel side walls along two sides of the channel on the outer surface of each arm.

6. The clamps of Claim 5, wherein two of the said clamps are connected to one another by rotating the first arms of the individual clamps 90 to one another abutting the channel bottoms and securing the clamps together.

7. The clamps of Claim 2, wherein each clamp presents an open ended square channel having a pair of upstanding channel side walls along two sides of the channel on the outer surface of each arm.

8. The clamps of Claim 7, wherein two of the said clamps are connected to one another by rotating the first arms of the individual clamps 90 to one another abutting the channel bottoms and securing the clamps together.

9. The clamps of Claim 5, wherein two of the said clamps are connected to one another by rotating the first arms of the individual clamps 90 to one another, spacing the channel bottoms from one another and securing the clamps together to permit the clamps to pivot with respect to one another.

10. The clamps of Claim 7, wherein two of the said clamps are connected to one another by rotating the first arms of the individual clamps 90 to one another, spacing the channel bottoms from one another and securing the clamps together to permit the clamps to pivot with respect to one another.

11. A clamp suitable for connecting to other clamps for connecting uprights, horizontal rails and other tubular members of scaffolding, the clamp having a longitudinal axis extending longitudinally through the centre of the clamp, and comprising first and second circumferentially extending arms pivotally secured to each other at one end of each of the arms, the free end of the first arm carrying a radially outwardly directed flange at the end thereof, the free end of the second arm carrying a pair of spaced flanges at the end thereof, each flange extending in a direction parallel to the longitudinal axis of the clamp to define a longitudinally extending channel therebetween, a thin shaft extending between the flanges, the flange closer the free end of the arm having an outer face and an inner face facing the other flange, the said inner face being generally convex in shape and presenting a pair of ramps, one ramp extending from each longitudinal end of the flange towards the centre of the inner face of the flange at the same angle to the outer face as the other ramp, the ramps meeting proximate the centre of the inner face at an apex disposed closer to the flange than the longitudinal ends of the flange, an endless keeper, comprising a long thin member tapering from a wider end to a narrower end, the narrower end being narrower than the channel, the keeper having a transverse slot therethrough extending for a major part of its length to accommodate the shaft therethrough so as to carry the keeper thereon, the keeper also having a first side edge for abutting the radially outwardly directed flange at the end of the first arm and a second side edge angled with respect to the first side edge for abutting the surface of one of the ramps when the keeper is pushed into the channel between the flanges.

1 2. The clamp of Claim 11, wherein each of the arms and keeper are of extruded aluminum.

1 3. The clamp of Claim 11, wherein the free end of the first arm carrying a radially outwardly directed flange at the end thereof provides a circumferentially extending slot in the fee end of the arm, providing a pair of spaced fingers spaced by the slot, each finger carrying a radially outwardly directed flange at the end thereof.

14. The clamps of Claim 12, wherein the free end of the first arm carrying a radially outwardly directed flange at the end thereof provides a circumferentially extending slot in the free end of the arm, providing a pair of spaced fingers spaced by the slot, each finger carrying a radially outwardly directed flange at the end thereof.

1 5. The clamp of Claim 11, wherein the clamp presents an open ended square channel having a pair of upstanding channel side walls along two sides of the channel on the outer surface of the arm.

16. The clamp of Claim 12, wherein the clamp presents an open ended square channel having a pair of upstanding channel side walls along two sides of the channel on the outer surface of the arm.

1 7. Clamps substantially as hereinbefore described with reference to each of the embodiments thereof illustrated in the accompanying drawings.