WO2020097663A1

WO2020097663A1 - Assembly for clamping formwork

Info

Publication number: WO2020097663A1
Application number: PCT/AU2019/000144
Authority: WO
Inventors: John REITANO; Siegfried Mehl
Original assignee: Form Jig Pty Ltd
Priority date: 2018-11-16
Filing date: 2019-11-18
Publication date: 2020-05-22
Also published as: US20210404128A1

Abstract

An assembly (10) for clamping formwork boards (120) for forming an elongate slab having a lower base (192) and an upper shaped gutter (194), the assembly comprising: first and second posts (12a, 12b) to be disposed on opposite sides of the slab to be formed, formwork board clamping means for mounting to the posts, the clamping means comprising jaws (16) for retaining the formwork boards, the jaws comprising: a first jaw (16a) for mounting to the first post and for retaining a first formwork board (120a), the first formwork board for forming a first side of the slab, a second jaw (16b) for mounting to the second post and for retaining a second formwork board (120b), the second formwork board for forming a second side of the slab and a second side of the gutter, the second jaw having a post mount (80) for a third board holder (90), and a third board holder (90) for extending from the second jaw and for retaining a third formwork board (120c) to be held over the slab to be formed, the third formwork board for forming a first side of the gutter.

Description

ASSEMBLY FOR CLAMPING FORMWORK

Field of the Invention

[1] The present invention relates to an assembly for clamping formwork for making concrete slabs and in particular, shaped concrete slabs. The invention is however not limited to this application.

Background of the Invention

[2] The present invention is a development of the invention described in the applicant’s PCT Patent Application PCT/AU2015/050554, which entered national phases as Australian Patent Application No. 2015318828 and USA Patent Application 15/760392. The disclosure of these applications are fully incorporated herein by reference.

[3] Formwork is temporary or permanent moulds into which concrete or similar materials are poured, for forming concrete structures such as slabs, pavement, walls and the like. Formwork is another term for shuttering, and are typically made from timber beams mounted in place ready for concrete pour. The formwork is then removed after the concrete is set.

[4] The present invention seeks to overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[5] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Invention

[6] According to a first aspect, the present invention provides an assembly for clamping formwork boards for forming an elongate slab having a lower base and an upper shaped gutter, the assembly comprising:

first and second posts to be disposed on opposite sides of the slab to be formed, formwork board clamping means for mounting to the posts, the clamping means comprising jaws for retaining the formwork boards, the jaws comprising:

a first jaw for mounting to the first post and for retaining a first formwork board, the first formwork board for forming a first side of the slab,

a second jaw for mounting to the second post and for retaining a second formwork board, the second formwork board for forming a second side of the slab and a second side of the gutter, the second jaw having a post mount for a third board holder, and a third board holder for extending from the second jaw and for retaining a third formwork board to be held over the slab to be formed, the third formwork board for forming a first side of the gutter.

[7] In a preferred embodiment, the first and second posts each have a spiked end for driving into the ground.

[8] In another preferred embodiment, the spiked end additionally includes radially extending fins for further stability in the ground and resistance to rotation.

[9] In another preferred embodiment, the first jaw comprises an angled bracket to engage a corner edge of the first formwork board.

[10] In another preferred embodiment, the second jaw comprises an angled bracket having a first web and an outwardly projecting second web extending from a top edge of the first web, wherein the post mount extends upwardly from the first web or the second web.

[11] In another preferred embodiment, the posts are spaced from and connected to each other via a spacer which has a variable length.

[12] In another preferred embodiment, ends of the spacer are adapted to be lockable to their respective post.

[13] In another preferred embodiment, the first and second jaws comprises a releasable clamp formation having a body in the form of a tube defining a bar receiving passage configured for receiving the post, the releasable clamp body having a passage in a sidewall thereof for holding a locking element to engage the post.

[14] In another preferred embodiment, the locking element is a threaded screw operable via a rotatable handle.

[15] In another preferred embodiment, the locking element is operable via a pivotable handle.

[16] In another preferred embodiment, the first jaw is to engage an upper corner edge of the first board with a lower edge of the first board engaging the ground.

[17] In another preferred embodiment, the first post comprises two first jaws to respectively engage the upper and lower edges of the first board and clamp the first board therebetween.

[18] In another preferred embodiment, the second post comprises a first jaw to engage the lower edge of the second board.

[19] In another preferred embodiment, a releasable clamp formation is mounted to the first web, the clamp formation comprising clamp body having a ba r receiving passage configured for receiving the second post, the clamp body having a passage in a sidewall thereof for holding a locking element to engage the post.

[20] In another preferred embodiment, the second web includes a second threaded passage for holding a second screw operable to penetrate the passage to engage the second board to provide additional clamping force to the second board.

[21] In another preferred embodiment, the post mount is a tube extending upwardly from the second jaw and includes a third threaded passage for holding a third screw operable to engage and lock an end of the third board holder.

[22] In another preferred embodiment, the assembly further comprises guide plates for extending between the third board and the second board.

[23] In another preferred embodiment, the third board holder is a generally upside down U- shaped rod having a first leg, a second leg and a bent upper portion therebetween, wherein the first leg is for insertion into the post mount of the second jaw and the second leg is angled outwardly.

[24] In another preferred embodiment, the holder further includes a movable clamping bar extending between the first leg and the second leg, wherein when the clamping bar is disposed adjacent the upper portion, the first and second legs are allowed to move away from each other, and when the clamping bar is moved downwardly, the first and second legs are forced towards each other.

[25] In another preferred embodiment, the assembly further comprises bracing for the second post, the bracing comprising one or more distal spikes driven into ground spaced from the second post and connectors extending between and connecting the spike and the second post.

[26] In another preferred embodiment, the connector comprises a variable length rod formed by having telescoping sections.

[27] In another preferred embodiment, the first and second jaws comprise U-shaped channels for engaging the upper or lower edge, the U-shaped channels engaging both the front and rear surfaces of the board to holds the board 120 in position relative to the posts.

[28] In another preferred embodiment, the assembly further includes guide plates disposed in a spaced manner along the second board, with the third board 120c positioned on the opposite side of the guide plates.

[29] In another preferred embodiment, the third board is urged towards the second board via the third board holder. [30] In another preferred embodiment, the third board holder comprises a first leg, a second leg and a connector upper portion therebetween, wherein the second leg has a pin at a lower inner edge thereof to engage a lower edge of the third board.

[31] In another preferred embodiment, the first leg has a movable clamping plate which engages the second board, the clamping plate being movable towards the second board which provides an urging force to the third board towards the second board with the guide plates therebetween, to retain the third board in place.

[32] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[33] Notwithstanding any other forms which may fall within the scope of the present invention, preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings in which:

[34] Figure 1 shows (a) side view, (b) top view and (c) end view an assembly for clamping formwork according to a preferred embodiment.

[35] Figure 2 shows two examples of posts for the assembly.

[36] Figure 3 shows (a) side and (b) top views of a spacer for the assembly.

[37] Figure 4 shows (a) perspective, (b) end, (c) top, and (d) side views of a first jaw for the assembly.

[38] Figure 5 shows (a) side, (b) top, and (c) end views of an alternative first jaw for the assembly.

[39] Figure 6 shows (a) side, (b) top, and (c) end views of a second first jaw for the assembly.

[40] Figure 7 shows (a) perspective, (b) side, (c) end, and (d) top views of an alternative second jaw for the assembly.

[41] Figure 8 shows two examples of guide plates for the assembly.

[42] Figure 9 shows (a) side, (b) front and (c) top views of a third board holder for the assembly.

[43] Figure 10 shows the assembly of Figure 1 with bracing.

[44] Figure 11 (a) to (d) shows connector fittings for the bracing.

[45] Figures 12 and 13 show side elevation views of two examples of bracing arrangements. [46] Figure 14 (a) shows connectors for the bracing and (b) shows an example configuration of the connector with fittings.

[47] Figure 15 shows (a) end and (b) side views of an alternative jaw for the assembly, and (c) shows the removable plate for the alternative jaw

[48] Figure 16 shows a front view of a modified third board holder for the assembly.

[49] Figure 17 shows modified versions of the jaws for the assembly, where (a) is an angle and depth adapter fitting for the third board, (b) is an upper jaw with rotatable clamp, and (c) is an upper jaw with a quick flip clamp

[50] Figure 18 shows a perspective view an assembly for clamping formwork according to another preferred embodiment.

[51] Figure 19 shows details of the wood peg clamping device for the assembly of Figure 18

[52] Figure 20 shows a wood peg board clamping assembly; and

[53] Figure 21 shows a steel peg board clamping assembly.

Description of Embodiments

[54] It should be noted in the following description that like or the same reference numerals in different embodiments denote the same or similar features.

[55] Figure 1 show various views of a plurality of assemblies 10 for clamping formwork. In the example shown, the assemblies 10 are used for holding formwork for forming an elongate slab 190 having a lower base 192 and an upper shaped gutter 194. A series of assemblies 10 is used to hold elongated formwork boards 120.

[56] The formwork boards 120 comprise:

a. a first board 120a - for forming/defining a first side of the base 192 for the slab 190

b. a second board 120b - taller height than the first board 120a, facing, spaced, and parallel to the first board 120a - for a second side of the slab 190. The first board 120a and a lower portion of the second board 120b define a first internal space for forming the base 192 therebetween. The second board 120b forms/defines the second side of the gutter 194.

c. a third board 120c - to be held above the base 192 to be formed, spaced from the second board 120b in an angled orientation, to form/define a first side of the gutter 194. The third board 120c and an upper portion of the second board 120b define a second internal space to form the upper gutter 194. [57] The boards 120 are engaged to be held at their upper and lower edges and outer surfaces to keep their inner surfaces free and clear for the concrete to be poured.

[58] Each assembly 10 comprises two spaced posts 12 in the form of an elongated rod, which as shown in Figure 2, has a circular or rectangular cross section. The post 12 has a spiked end 14 for driving into the ground. The spiked end 14 can additionally include radially extending fins 15 for further stability in the ground and resistance to rotation. The posts 12 are disposed on opposite sides of the slab 190 to be formed and each is for mounting formwork board clamping means thereto.

[59] The posts 12 are spaced from each other via a spacer 20 as shown in Figure 3. The spacer 20 comprises a rod 22 which has a variable length via being formed with telescopic sections. The sections are lockable in position to each other which fixes the length of the rod 22 via a threaded passage 23 into which a bolt can be inserted. A first end of the rod includes a post receiving passage 26 configured for receiving one post 12 and the second end of the bar includes an angled bracket 27 for engaging the other post 12. The posts 12 in use extend vertically and the rod 22 extends horizontally between the posts 12. The passage 26 and the bracket 27 thus extend perpendicularly to the rod 22. The passage 26 and the bracket 27 can be adapted to be lockable to their respective posts 12.

[60] The formwork board clamping means comprises jaws 16 for engaging the formwork boards 120. The jaws 16 comprise a first jaw 16a as further shown in Figure 4. The jaw 16a comprises an angled bracket 32 having a first web 33 and an outwardly projecting second web

34 which defines a corner 35. A corner edge of a formwork board 120 is received in the corner

35 in use.

[61] A releasable clamp formation 40 is mounted to the first web 33. The clamp formation has a body 44 in the form of a tube defining a bar receiving passage 46 configured for receiving the post 12, The releasable clamp body 44 has a threaded passage 45 formed in the tube sidewall for holding a screw 46 operable to penetrate the passage 46 to engage the post 12. The tube body 44 is movable along the post 12. When the tube body 44 is in position along the post 12, the screw 46 is tightened to lock the first jaw 16a in position. The screw 46 in this embodiment comprises a pivotable handle 49 for quick rotation. The passage 46 extends in a vertical direction in use with the second web 34 extending horizontally in use, either for engaging a lower edge or an upper edge of a formwork board.

[62] In the example shown in Figure 1, the first jaw 16a is disposed along the first post 12a to engage an upper corner edge of the first board 120a with a lower edge of the first board 120a engaging the ground. The first jaw 16a is thus used to clamp down on the first board 120a. It is however possible to use a pair of the first jaws 16a to respectively engage the upper and lower edges of the first board 120a and clamp the first board 120a therebetween.

[63] Figure 5 shows a modified embodiment of the first jaw 16a configured primarily for rectangular cross-section posts 12. The drawings show round or rectangular passages and it is to be understood that these are interchangeable and are matched with the cross-section shape of the posts 12.

[64] At the other side of the slab 190, another first jaw 16a is disposed on the second post 12b to engage the lower edge of the second board 120b. A second jaw 16b is used to engage the upper edge of the second board 120b.

[65] The second jaw 16b is further shown in Figure 6. The second jaw 16b comprises a larger angled bracket 52 having a first web 53 and an outwardly projecting second web 54 which defines a corner 55. The second web 54 extends from a top edge of the first web 53. A top corner edge of the second board 120b is received in the corner 55 in use.

[66] A releasable clamp formation 60 is mounted to the first web 33. The clamp formation 60 similarly has a tube body having a bar receiving passage 66 configured for receiving the second post 12b. The body also has a threaded passage 65 for holding a screw 68 operable to penetrate the passage 66 to engage the post 12b. The passage 66 extends in the vertical direction in use.

[67] The second web 54 includes a second threaded passage 75 for holding a second screw 78 operable to penetrate the passage 75 to engage the second board 120b. This provides additional clamping force to the second board 120b.

[68] The second web 54 further includes a post mount 80 for a third board holder 90. The post mount 80 is a tube extending upwardly from the second web 55 and includes a third threaded passage 85 for holding a third screw 88 operable to engage and lock an end of the holder 90 as further described below. The post mount 80 and the second threaded passage 75 are disposed on opposite sides of the tube body 64.

[69] Figure 7 shows an alternative embodiment of the second jaw 16b which does not include the second screw 78 and where the post mount 80 is mounted to extend upwardly from the first web 53. The tube body 64 can also include an open side 67 for easier mounting.

[70] The above assembly allows for concrete pouring and forming of the base 192 of the slab 190. To form the gutter 194, the third board holder 90, the third board 120c and guide plates 100 are used.

[71] Figure 8 shows two examples of the guide plates 100. The guide plates 100 comprise small flat plates having a vertical first edge 101, a horizontal upper edge 102, a horizontal lower edge 103, and a downwardly angled second edge 104. A first tab 106 is formed at the corner between the first edge 101 and the upper edge 102. A second tab 107 is formed at the corner between the second edge 104 and the lower edge 103.

[72] The guide plate 100 is used to correctly position, in terms of space and angular orientation, the third board 120c relative to the second board 120b. A guide plate 100 is disposed for each assembly 90.

[73] The third board holder 90 is further shown in Figure 9. The holder 90 is a generally upside down U-shaped rod having a first leg 91, a second leg 92 and a bent upper portion 93 therebetween. The first leg 91 extends vertically and is dimensioned for insertion into the post mount 80 of the second jaw 16b. The second leg 92 is angled outwardly by an angle corresponding to the second edge 104 of the guide plate 100. The holder 90 further includes a movable clamping bar 95 extending between the first leg 91 and the second leg 92. When the clamping bar 95 is disposed adjacent the upper portion 93, the first and second legs 91 and 92 allowed to move away from each other. When the clamping bar 95 is moved downwardly, the first and second legs 91 and 92 are forced towards each other.

[74] One method of use involves pouring of concrete to form the base 192 of the slab 190 first and letting this set. Once set, the guide plates 100 are then placed over the formed base 192 with the first tab 106 engaging an inner upper edge of the second board 120b, The first edge 101 extends along the second board 120b, and the lower edge 103 extends along the formed base 192. The second edge 104 and the second tab 107 then define seats and receive the third board 120c thereon. The holders 90 are then mounted to the second jaws 16b and the clamping bars 95 are moved downwardly such that the second legs 92 engage an external surface of the third board 120c. Concrete can then be poured between the third board 120c and the second board 120b to form the gutter 194.

[75] In a second method of use, the guide plates 100 can be mounted to the second board 120b. The third board 120c is then placed in position with the holder 90. This allows concrete to be poured to form the base 192 and the gutter 194 simultaneously.

[76] In a third method, the third board 120c is mounted to the second leg 92 via suitable means, such as fasteners or the first jaws 16a . The guide plates 100 are then used as positioning and spacing guides, and concrete can be poured to form the base 192 and the gutter 194 simultaneously.

[77] Figure 10 shows a sub-assembly 11 with bracing 200. The bracing 200 essentially comprises one or more distal spikes 210 driven into ground spaced from the second post 12b, and connectors 216 extending between and connecting the spike 210 and the second post 12b. [78] The spike 210 is essentially a pointed post or other suitable anchor. The connector 216 comprises a variable length rod formed by having telescoping sections.

[79] Figure 11 shows fittings 220 for the connector 216. The fittings 220 each include what will be referred to as a“lock sleeve 230”, being a tube body with a threaded passage for a screw. Each lock sleeve 230 is adapted to receive a tube or post therethrough and being lockable thereon by tightening the screw.

[80] The first fitting 220a includes a lock sleeve 230a for the second post 12b and another lock sleeve 230b extending perpendicularly therefrom for the connector 216. The lock sleeve 230b additionally includes a pivot mount 235 for the connector 216 being spaced webs with a bolt. This allows the first end of the connector 216 to be pivotably connected to the second post 12b.

[81] A second fitting 220b includes a lock sleeve 230c for inline receiving the distal end of the connector 216. The second fitting 220b further includes an open lock bracket 231 for mounting to the spike 210.

[82] A third fitting 220c includes a lock sleeve 230d for inline receiving the connector 216 and for positioning along the connector 216. The third fitting 220c includes a sleeve 232 extending perpendicularly to the lock sleeve 230d. The sleeve 232 is for receiving additional spikes or posts along the connector 216 as shown in Figure 14.

[83] A fourth fitting 220d is similar to the third fitting 220c, but where the sleeve 232 is also a lock sleeve.

[84] Figure 10 shows an example with two bracing assemblies 200, the first with a vertically extending spike and horizontal connector and the second with an outwardly angled spike and a downwardly extending connector. Figure 12 and 13 further show these examples with multiple spikes at increasing distances from the second post 120b and increasing length connectors 216.

[85] Figure 14 shows examples of the connectors 216 and configuration of the connectors 216 with the fittings 220

[86] Figure 15 shows a different embodiment of an upper jaw 16c, being a shaped guide. The guide 16c is a thin plate which is attached to a lock sleeve 220, with the thin plate defining a downwardly extending seat 240 for engaging a formwork board. The seat 240 defines an upper edge 242 and an inner edge 244 for engaging the formwork board. The guide 16c is thin and removable from the lock sleeve 220 and can be retained in the formed slab.

[87] After the wet concrete has set and the concrete slab formed, the plurality of sub- assemblies 11 are unclamped from the formwork boards and removed from the ground. [88] Figures 16 and 17 show a modified third board holder 90a and modified jaws 16 for the assembly. This third board holder 90a includes an angle and depth adapter fitting 16d for the third board, an upper jaw 16a with rotatable clamp 49, and is a jaw 16c with a quick flip clamp 49. The fitting 16d has offset holes 46b which provides adjustment of the angle and depth of the board 120c.

[89] Figure 18 a plurality of assemblies 10b according to another embodiment for clamping formwork for forming an elongate slab 190 having similar features to the assembly 10 above. Similar features have corresponding numbers.

[90] The boards 120 are engaged to be held at their upper and/or lower edges via U-shaped channels to positively engage the boards and prevent movement thereof relative to the posts 12

[91] The first board 120a is held by spaced posts 12a each with a jaw 16. The jaws 16 comprise U-shaped channels 37 shaped for engaging the upper or lower edge of the board 120. The U-shaped channels 37 engage both the front and rear surfaces of the board 120 and holds the board 120 in position relative to the posts 12.

[92] Similarly, the second board 120b is held by spaced posts 12b each with a jaw 16. The U-shaped channels 37 engage the upper edge of the board 12b. Each post 12b can be supported by bracing 200 which includes a distal spike 210 and a connector 216, connected via fittings 230d. These secure the board 120b in place.

[93] Guide plates 100 are then disposed in a spaced manner along the second board 120b, with the third board 120c positioned on the opposite side of the guide plates 100. The third board 120c is then urged towards the second board 120 via a third board holder 90b.

[94] As best shown in Figure 19, the third board holder 90b is also generally upside down U-shaped having a first leg 91, a second leg 92 and a connector upper portion 93 therebetween. The second leg 92 has a pin 195 at a lower inner edge thereof to engage a lower edge of the third board 120c.

[95] The first leg 91 has a movable clamping plate 310 which engages the second board 120b, the clamping plate having an upper flange 311 which can rest on the upper edge of the second board 120b. The clamping plate 310 is movable via a threaded rod 312 threadingly received in the first leg 91 towards the second board 120b, which provides an urging force to the third board 120c towards the second board 120b, with the guide plates 100 therebetween. This retains the third board 120c and the clamping plates 100 in place. [96] Figure 20 shows a wood peg board clamping assembly using square cross section posts 12 and jaws 16 with the U-shaped channels 37. The jaws 26 are arranged to alternatingly engage the upper and lower edges of the board 12.

[97] Figure 21 shows a similar steel peg board clamping assembly using round cross- section posts 12.

Claims

Claims The claims defining the invention are as follows:

1. An assembly for clamping formwork boards for forming an elongate slab having a lower base and an upper shaped gutter, the assembly comprising:

2. The assembly of claim 1 wherein the first and second posts each have a spiked end for driving into the ground.

3. The assembly of claim 1 wherein the spiked end additionally includes radially extending fins for further stability in the ground and resistance to rotation.

4. The assembly of claim 1 wherein the first jaw comprises an angled bracket to engage a corner edge of the first formwork board.

5. The assembly of claim 1 wherein the second jaw comprises an angled bracket having a first web and an outwardly projecting second web extending from a top edge of the first web, wherein the post mount extends upwardly from the first web or the second web.

6. The assembly of claim 1 wherein the posts are spaced from and connected to each other via a spacer which has a variable length.

7. The assembly of claim 6 wherein ends of the spacer are adapted to be lockable to their respective post.

8. The assembly of claim 1 wherein the first and second jaws comprises a releasable clamp formation having a body in the form of a tube defining a bar receiving passage configured for receiving the post, the releasable clamp body having a passage in a sidewall thereof for holding a locking element to engage the post.

9. The assembly of claim 8 wherein the locking element is a threaded screw operable via a rotatable handle.

10. The assembly of claim 8 wherein the locking element is operable via a pivotable handle.

1 1. The assembly of claim 1 wherein the first jaw is to engage an upper corner edge of the first board with a lower edge of the first board engaging the ground.

12. The assembly of claim 1 wherein the first post comprises two first jaws to respectively engage the upper and lower edges of the first board and clamp the first board therebetween.

13 The assembly of claim 1 wherein the second post comprises a first jaw to engage the lower edge of the second board.

14. The assembly of claim 5 wherein a releasable clamp formation is mounted to the first web, the clamp formation comprising clamp body having a bar receiving passage configured for receiving the second post, the clamp body having a passage in a sidewall thereof for holding a locking element to engage the post

15. The assembly of claim 5 wherein the second web includes a second threaded passage for holding a second screw operable to penetrate the passage to engage the second board to provide additional clamping force to the second board.

16. The assembly of claim 1 wherein the post mount is a tube extending upwardly from the second jaw and includes a third threaded passage for holding a third screw operable to engage and lock an end of the third board holder.

17. The assembly of claim 1 further comprising guide plates for extending between the third board and the second board.

18. The assembly of claim 1 wherein the third board holder is a generally upside down U- shaped rod having a first leg, a second leg and a bent upper portion therebetween, wherein the first leg is for insertion into the post mount of the second jaw and the second leg is angled outwardly.

19. The assembly of claim 18 wherein the holder further includes a movable clamping bar extending between the first leg and the second leg, wherein when the clamping bar is disposed adjacent the upper portion, the first and second legs are allowed to move away from each other, and when the clamping bar is moved downwardly, the first and second legs are forced towards each other.

20. The assembly of claim 1 further comprising bracing for the second post, the bracing comprising one or more distal spikes driven into ground spaced from the second post and connectors extending between and connecting the spike and the second post.

21. The assembly of claim 20 wherein the connector comprises a variable length rod formed by having telescoping sections.

22. The assembly of claim 1 wherein the first and second jaws comprise U-shaped channels for engaging the upper or lower edge, the U-shaped channels engaging both the front and rear surfaces of the board to holds the board 120 in position relative to the posts.

23. The assembly of claim 22 further including guide plates disposed in a spaced manner along the second board, with the third board 120c positioned on the opposite side of the guide plates.

24. The assembly of claim 23 wherein the third board is urged towards the second board via the third board holder.

25 The assembly of claim 24 wherein the third board holder comprises a first leg, a second leg and a connector upper portion therebetween, wherein the second leg has a pin at a lower inner edge thereof to engage a lower edge of the third board.

26. The assembly of claim 25 wherein the first leg has a movable clamping plate which engages the second board, the clamping plate being movable towards the second board which provides an urging force to the third board towards the second board with the guide plates therebetween, to retain the third board in place.