GB2539663A - Builders' trestles - Google Patents

Abstract

A builders' trestle 10 comprises a pair of upright supports 12, 14 connected by a crossbar 20 for supporting planks or boards to make a platform. At least one of the upright supports has an upward extension 26 above the crossbar to which rails can be attached to form a safety barrier. At least part 26a of the upward extension is hingedly attached to the remainder of the trestle so that it is movable between an upright, rail-supporting position and a downwardly folded position. The trestle may include a latch mechanism 30, such as a bolt and keeper or a stabiliser sleeve, to hold the upward extension in the upright position. The upward extension may be attached to the trestle by a recessed hinge comprising curved ends having interengaging gear teeth or knurling.

Description

BUILDERS' TRESTLES This invention relates to trestles ("bandstands") for supporting working platforms used on building sites and the like. Two or more such trestles are usually used together with scaffolding boards supported between them to make up the platform. The scaffolding boards rest on crossbars forming the top of each trestle. The invention relates more particularly to safety rail supports for such trestles and platforms.

0B2364733 concerns a safety rail for such trestles, formed by one or more horizontal bars each of which is connected between a pair of vertically extending legs. Each safety rail leg can be secured to the upright support of a conventional builder's trestle. The trestles are designed to be used in groupings of four, with the safety rails being of appropriate length for the grouping to support standard scaffolding boards of 3.9 metres long.

Preferably however, the trestles themselves are modified so as to have one upright support which extends above the board supporting crossbar, for attachment of the safety rails. Such a trestle is disclosed in C3B2378978. The integral upright support provides a dependable, sturdy support which is always available for attachment of the safety rails. This makes the trestles quick to set up and encourages practices which comply with the appropriate working at height safety regulations. However, because the upright support increases the overall height of the trestles, it makes them more difficult to transport. Larger sizes of trestles will not fit upright into the back of a medium-sized van, without removing an upper part of the trestle comprising the upright support and the crossbar, from a lower base part, in which the upper part is normally telescopically received for height adjustment of the trestle. The overall height of the assembled trestle can exceed 2.3 m even with the crossbar adjusted to its lowest position, which also means that the trestle will not pass upright through a standard sized doorway. Its height makes it generally awkward to handle e.g. when trying to load/unload from lorries and vans or when being transported to, from or around a building site. The present invention aims to address these problems.

Accordingly the present invention provides a builders' trestle comprising a pair of upright supports connected by a crossbar upon which planks or boards can be supported in use to make a platform, at least one of the upright supports having an upward extension above the crossbar to which rails can be attached to form a safety banier; at least part of the upward extension being hingedly attached to the remainder of the trestle so that it is movable between an upright, rail-supporting position and a downwardly folded position. With the upward extension folded downwardly, the overall height of the trestle is decreased so that it is easier to transport and store. The hinged attachment is preferably permanent, so that the upward extension is always available to be brought into use.

The hinged attachment may be arranged so that when folded downwardly, the movable part of the upward extension touches the crossbar. The movable part therefore prevents scaffolding boards from being placed on the crossbar, helping to ensure that the movable part of the upward extension is hinged into its upright position before the trestle is put into use. This therefore encourages proper assembly of the safety rail before the trestle is used. This configuration of the hinge mechanism also allows trestles to be nested closely adjacent to each other during transport.

Alternatively, the hinged attachment may be arranged so that the movable part of the upward extension is hinged laterally of the crossbar when moving towards its downwardly folded position. This allows scaffolding boards or other equipment to be stacked on top of the trestles during transport and storage.

Preferably the trestle comprises a latch mechanism arranged to hold the movable part of the upward extension releasably in the upright position. This provides a stable support for safety rails attached to the upward extension.

The hinged attachment may comprise a hinge provided on one side of the upward extension. The latch mechanism may comprise a bolt slidably attached to another, preferably opposite, side of the upward extension and having an end releasably engageablc in a keeper.

Preferably the slidable attachment of the bolt is with the movable part of the upward extension, so that the bolt is held in the keeper under gravity when the movable part of the upward extension is in the upright position.

The bolt may comprise an end which engages the keeper as the movable part of the upward extension is hinged towards the upright position, the end forming a cam surface which is shaped to raise the bolt until it is free to enter the keeper. This ensures that the bolt will automatically lock into the keeper and hold the movable part upright, simply by hinging the movable part of the upward extension into the upright position. The bolt can be manually released from the keeper when it is desired to fold the movable part of the upward extension downwardly.

Yet alternatively, the movable part of the upward extension can be attached to the remainder of the trestle by a recessed hinge. The movable part of the upward extension may then be rcleasably locked in the upright position by a stabiliser slidablc over the hinge. The stabiliser is preferably telescopically slidable on the upward extension and may comprise a tubular shape.

To provide a greater range of angular movement, the recessed hinge may comprise a pair of hinge pins connected by an intermediate link. The intermediate link may extend across opposed, curved ends of the movable part and of an adjacent part of the upward extension.

The opposing curved ends may be provided with interengaged gear teeth, knurling or other roughening. The stabiliser may be provided with internal clearances which allow it to slide over any projecting part of the gear teeth etc., when the movable part of the upward extension is hinged to the upright position.

The invention and some of its preferred features and advantages are further descrthed below with reference to illustrative embodiments shown in the drawings, in which: Figure 1 shows a first trestle embodying the invention, with the movable part of the upward extension in the upright position; Figure 2 corresponds to Figure 1, but shows the movable part in the downwardly folded position; Figure 3 shows a second trestle embodying the invention, with the movable part in the downwardly folded positon; Figure 4 is a more detailed view of the hinge and latch mechanism of Figures 1 and 2, shown in the latched condition and seen from the hinge side; Figure 5 corresponds to Figure 4, but shows the latch mechanism bolt and keeper; Figure 6 corresponds to Figure 5, but shows the upward extension's movable part hinged part-way towards the upright position, so that the bolt is beginning to engage in the keeper; Figure 7 shows a partly assembled alternative hinge and latch mechanism, comprising a recessed hinge and a sliding stabiliser sleeve; and Figure 8 shows a partly assembled alternative hinge and latch mechanism, comprising a recessed hinge formed by a pair of hinge pins, an intermediate link and a sliding stabiliser sleeve.

The builders' trestle 10 shown in Figure 1 has a frame formed from heavy gauge, square sectioned steel tubing. A base part of the frame comprises tubular uprights 12 and 14, each provided with a respective foot assembly 16, 18, to stably support the trestle on a level surface. An upper part of the frame comprises tubes which are telescopically slidable inside the respective base uprights 12, 14 to provide height adjustment of the trestle. Each tube and the upright in which it slides, thus forms an upright support of the trestle. Because Figure 1 shows the trestle adjusted to the lowest height (convenient for transport and storage), the telescopically slidable tubes are not clearly visible, being mostly hidden within the uprights 12, 14. Their upper ends are connected to a scaffolding board supporting crossbar 20. The telescopically slidable tubes are each provided with a series of through going, transverse holes which may be brought selectively into registration with a corresponding through hole in the respective uprights 12, 14. The holes in the uprights are each aligned with a respective locking pin 22 which is captively slidable on an upper crossbar 24 of the trestle base part. In this way, the crossbar 20 may be supported at any one of a series of heights, as dictated by the positions of the holes in the telescopically slidable tubes.

The tube which is telescopically slidable in the base upright 14 extends upwardly beyond the crossbar 20, so as to form the upward extension 26 Rails (not shown) may be fitted to attachment ears 28 carried by the upward extension 26, so as to form a safety barrier. An upper part 26a of the upward extension 26 is attached to the remainder of the trestle 10 by a hinge and latch assembly 30.

Referring now to Figure 2, it can be seen that the hinge and latch assembly 30 allows the upper part 26a of the upward extension 26 to be hinged about an axis which extends parallel to the crossbar 20. Therefore when the latch of die hinge and latch assembly 30 is released, the upper part 26a of the upward extension 26 may be swung downwardly to lie adjacent to the upright 14, to one side of the plane of the trestle uprights 12, 14. Details of various possible hinge and latch assemblies that may be used for these purposes are further described below with reference to Figures 4-8. In the orientation of Figures 1 and 2, elements of the hinge and latch assembly 30 do not protrude towards a toeboard bracket 32 which is welded or otherwise suitably fixed to the crossbar 20. A toeboard may therefore be placed and held between the bracket 32 and the upward extension 26 in the conventional way, without interference from the hinge and latch assembly 30.

Figure 3 shows an alternative trestle with a slightly different frame construction, but whose major components are substantially the same as those described above with reference to Figures 1 and 2. Another difference with respect to Figures 1 and 2 is that the hinge axis of the hinge and latch assembly 30 shown in Figure 3 extends at right angles to the crossbar 20, so that the free end of the upward extension's movable part 26a touches the crossbar 20, when moved to the downwardly folded position. The non-movable part 26b of the upward extension is made tall enough so that the hinge and latch assembly 30 does not interfere with placement of toeboards between the part 26b and the toeboard bracket 32. When folded to the downward position as shown in Figure 3, the upward extension's movable part 26a prevents scaffolding boards from being placed on the crossbar 20 to form a working platform. Alternatively, the hinge and latch assembly 30 may be orientated so that the upward extension's movable part 26a hinges laterally of the plane of the trestle uprights 12, 14, as in Figure 2. Yet alternatively the upward extension's movable part 26a may be hinged in the plane of the uprights 12, 14 so as to lie against the side of the upright 14 opposite to the crossbar 20 in the down position. By the same token, the hinge and latch assembly 30 in Figure 2 may be oriented such that the upward extension's movable part 26a hinges in the plane of the uprights 12, 14, to touch the crossbar 20 when folded downwardly, i.e. similar to the arrangement shown in Figure 3; or to lie next to the opposite side of the upright 14. Again a suitable clearance is preferably provided between the hinge and latch assembly 30 for unhindered insertion of a toeboard between the bracket 32 and the fixed part 26b of the upright extension 26.

Figure 4 is an enlarged view of part of the trestle of Figure 1, showing the hinge and latch assembly 30, viewed from the hinge side. The hinge is formed by a mounting plate 34, a bearing sleeve 36 and a yoke 38. The yoke 38 has a channel-shaped head portion 40 which enfolds and is welded to the lower end of the upward extension's movable part 26a. The opposing sides of the channel shaped head portion are extended to form parallel clevis arms 42 which project axially from the upward extension's movable part 26a. The mounting plate 34 is welded flat against one side of the upward extension's fixed part 26h, at the top of that side. The bearing sleeve 36 is fixed to the top end of the mounting plate 34, e.g. by welding, so as to stand proud of the mounting plate 34 and the underlying surface of the upward extension. A hinge pin (not shown) is joumalled in the bearing sleeve 36 and spans between the cicvis arms 42. The hinge pin axis lies at right angles to that of the upward extension 26. Each end of the hinge pin is attached to a respective one of the arms 42, e.g. by being welded or swaged into a hole in that arm. The position of one end of the hinge pin is indicated by dotted lines in Figure 5. The upward extension's fixed and movable parts 26b, 26a are thereby hingedly interconnected. The hinge pin is fixed to the clevis arms 42 in a position such that, with the upward extension's movable part 26a in the upright, rail supporting position, the fixed and movable parts 26a, 26b of the upward extension are brought into coaxial alignment. Because the hinge pin lies outwardly to one side of the upward extension in this configuration, the movable part 26a of the upward extension is able to swing freely about the hinge pin through substantially 180 degrees, as can be seen by comparing Figures 1 and 2. The same components may be used for hinged attachment of the upward extensions' upper portion 26a to the remainder of the trestle as shown in Figure 3; only in that case the yoke 38 and mounting plate 34 are orientated so that the hinge pin lies outward of that side of the upright, upward extension which faces towards the toeboard bracket 32.

Figure 5 shows the components of the latch mechanism in the hinge and latch assembly 30 of Figures 1-4. These are a guide sleeve 46, a bolt 48, a bolt retainer stop 50 and a keeper 52. The guide sleeve 46 is tubular and is welded to the lower end of the upward extension's movable part 26a, on the side opposite to the hinge pin 44. The axis of the guide sleeve runs parallel to that of the movable part 26a. The bolt 48 is L-shaped, with a longer limb slidably received in the guide sleeve 46. A shorter limb of the bolt 48 forms a projecting handle by which the bolt can be manually raised, as further described below. The keeper 52 is of similar tubular form to the guide sleeve 46 and is welded to the upper end of the upward extension's fixed part 26b. The keeper is positioned so that when the upward extension's movable part 26a is in the upright position as shown in Figure 5, the guide sleeve 46 and the keeper 52 are coaxially aligned, next to one another. With the bolt 48 in a lowered position as shown in Figure 5, a lower end of the bolt projects from the guide sleeve 46 and into the keeper 52. In this position, the bolt 48 therefore spans the hinged connection between the upright extension's parts 26a and 26b and locks the movable part 26a in the upright position. The projecting handle may be manually raised by so as to withdraw the lower end of the bolt 48 from the keeper 52. This unlocks the hinge for hinging movement. When slid to its raised position in the guide sleeve 46, the bolt 48 is held captive by the retainer stop 50. The bolt 48, guide sleeve 46 and keeper 52 are of matched cross-sections to provide a close sliding fit, whereby the movable part of the upward extension 26a is held firmly in the upright position when the bolt 48 is engaged in the keeper 52. These cross-sections may be square or other non-round, as shown, to prevent rotation of the bolt 48; however this is not essential.

Figure 6 shows the upward extension's movable part 26a in the process of being raised towards the upright position. At the angle shown, the bolt 48 has fallen under its own weight, into its lowered position in the sleeve 46. The lower end face of the bolt is angled to form a cam surface 54 which butts up against an upper edge of the keeper 52. Continued rotation of the upward extension's movable part. 26a towards the upright position causes the cam surface 54 to press against the keeper 52's upper edge, and to cam the bolt upwardly in the guide sleeve 46. When the upward extension is fully upright, the bolt 48 is brought into coaxial alignment with the keeper 52 and is free to fall into the keeper under its own weight.

The movable part of the upward extension 26a is therefore automatically locked in the upright position merely by moving it to that position.

Figures 7 and 8 are further non-limiting examples of hinge and latch assemblies 30 that may be used in any of the previously described trestles in any of the previously described orientations, where compatible. In Figure 7, an insert is welded in place inside the upward extension's movable part 26a. An end 56 of the insert protrudes from the bottom end of the movable part 26a. The protruding insert end has a part cylindrical surface 58 centred on a transverse through hole 60. One half 62 of the lower edge of each side of the movable part 26a orthogonal to the axis of the hole 60, has a concave curvature which is a continuation of the curvature of the part cylindrical end surface 58. The opposite half 64 of this edge has a straight profile tangential to this curve, sloping slightly upwardly away from the point at which it meets the concave curve, relative to the transverse plane of the movable part. The upper end of the upward projection's fixed part 26b is cut to form a clevis. More specifically, two opposing sides of this upper end are formed with a semi-circular profile 66, centred on an opposed pair of holes 68 (only one of which is visible in Figure 7). A tubular stabilising sleeve 70 is received over the end of the upward projection's movable part 26a, as a close sliding fit. The sleeve 70 has a nudge lip 72.

The hinge and latch assembly of Figure 7 is assembled as follows. The projecting part of the insert 56 is inserted into the clevis end of the upward projection's fixed part 26b, so as to bring the holes 60, 68 into coaxial alignment.. A hinge pin 44 is then inserted through the aligned holes 60, 68 and its ends are swaged, welded or otherwise suitably fixed in the holes 68. The upward projection's movable part 26a is thus captively joumalled on the hinge pin 44 to form a recessed hinge. With the movable part 26a fully upright (i.e. in axial alignment with the upward projection's fixed part 26b), the stabilising sleeve 70 may be slid downwardly or fall under its own weight, to a position in which it spans and surrounds the recessed hinge. The sleeve 70 is held in this position by a stop 74 welded or otherwise suitably fixed to the upward extension's fixed part 26b. In this position, the stabilising sleeve 70 locks and stabilises the recessed hinge so as to prevent relative movement between the parts of the upward extension 26a, 26b. To release the recessed hinge for movement when it is desired to lower the movable part 26a, the stabilising sleeve 70 is manually moved upwardly, if necessary by tapping against the nudge lip 72.

The hinge and latch assembly 30 of Figure 8 has some similarities with that of Figure 7, but in the case of Figure 8 the connected ends of the upward extension's fixed and movable parts 26a, 26b are each formed as a clevis (76a and 76b, respectively). The insert is replaced by an intermediate link 78 which is journallal on a pair of hinge pins 44a, 44b, via a pair of holes 60 (only one of which is visible in Figure 8). The hinge pins 44a, 44b are swaged, welded or otherwise fixed in holes 68a, 68b in the respective devises 76a, 76h. The devises have mutually similar, semi-circular edges 66a, 66b, centred on the holes 68a, 68b respectively. The centre to centre spacing of the two holes 60 in the intermediate link 78 is preferably only slightly greater than the diameter of the semicircles, so that the opposed edges 66a, 66b nearly touch each other when assembled. The resulting recessed hinge has planar freedom of movement of substantially 360 degrees. It is locked and unlocked by sliding movement of a stabilising sleeve 70 towards and away from a stop 74, in the same way as the sleeve and stop described above with reference to Figure 7. The meeting semi-circular edges 66a, 66b of the devises may be provided with meshing gear teeth, knurling or similar roughening. This prevents sliding movement between the semicircular edges, so that each edge rolls on the other, and hinging movement of the joint is more controlled. The semi-circular edges 66a, 66b shown in Figure 8 then represent the pitch circles of the gear teeth etc. Portions of the gear teeth etc. therefore project slightly beyond the width of the upward extension 26a, 26b. The stabilising sleeve 70 may therefore be provided with internal, longitudinally extending slots 80, enabling the sleeve 70 to slide over these projections. Alternatively, the diameter of the semi-circular edges can be reduced (and likewise the spacing between the holes 60), so that the teeth etc. do not project beyond the width of the upward extension 26a, 26b. However, this may slightly restrict the range of movement of the hinged connection. Rather than being semi-circular, the edges 66a, 66b (or gear tooth etc. pitch lines) may comprise opposed quadrant shapes; the remainder of each edge 66a, 66b being straight and normal to the axis of the respective upward extension part 26a, 26h. This restricts the relative hinging movement of the two parts 26a, 26b to substantially 180 degrees.

As shown in Figures 1-3, the end portion of the crossbar 20 opposite to the upward extension 26 overhangs the base upright 12 and the tube of the height adjustable upper part of the frame received therein. The end of this overhanging crossbar portion carries a socket 82. A removable upright post (not shown) may be inserted in the socket 82. Further rails (not shown) may be attached to the removable post, to form a further safety barrier on this side of the working platform. In all of the trestle configurations described above, the socket 82 may be replaced by a hinged upward extension for the attachment of safety rails, otherwise similar to the upward extensions 26 and hinge and latch assemblies 30 previously described. Yet alternatively, the very end of the crossbar 20 may be fixed (e.g. welded) to the tube which is slidahle in the upright 12, so as to eliminate the overhang. In such an arrangement, the slidable tube extends above the crossbar 20 and is provided with a hinge and latch assembly, so as to mirror the hinge and latch assembly 30 and the fixed 26b and movable 26a parts of the upward extension 26 at the opposite end of the crossbar 20. Thus in either case, the trestle is provided with a pair of hinged upward extensions. In either case, the hinging directions of the upward extensions relative to the trestle may be the same as or different to each other.

Claims (20)

1. CLAIMS1. A builders' trestle comprising a pair of upright supports connected by a crossbar upon which planks or boards can be supported in use to make a platform, at least one of the upright supports having an upward extension above the crossbar to which rails can be attached to form a safety barrier; at least part of the upward extension being hingedly attached to the remainder of the trestle so that it is movable between an upright, rail-supporting position and a downwardly folded position.
2. 2. A builders' trestle as defined in claim 1, in which the movable part of the upward extension when folded downwardly touches the crossbar.
3. 3. A builders' trestle as defined in claim 1 in which the movable part of the upward extension is hinged laterally of the crossbar when moving towards its downwardly folded position.
4. 4. A builders' trestle as defined in any preceding claim and which comprises a latch mechanism arranged to hold the movable part of the upward extension releasably in the upright position.
5. 5. A builders' trestle as defined in any preceding claim in which the hinged attachment comprises a hinge provided on one side of the upward extension.
6. 6. A builders' trestle as defined in claim 5 in which the latch mechanism comprises a bolt slidably attached to another side of the upward extension and having an end releasably engageable in a keeper.
7. 7. A builders' trestle as defined in claim 6 in which the bolt is attached to the side of the upward extension opposite to the side on which the hinge is provided.
8. 8. A builders' trestle as defined in claim 6 or 7 in which the slidable attachment of the bolt is with the movable part of the upward extension.
9. 9. A builders' trestle as defined in any of claims 6-8 in which the bolt comprises an end which engages the keeper as the movable part of the upward extension is hinged towards the upright position, the end forming a cam surface which is shaped to raise the bolt until it is free to enter the keeper.
10. 10. A builders' trestle as defined in claim 9 in which the bolt can be manually released from the keeper.
11. 11. A builders' trestle as defined in any of claims 1-5 in which the movable part of the upward extension is attached to the remainder of the trestle by a recessed hinge.
12. 12. A builders' trestle as defined in claim 11 in which the movable part of the upward extension is releasably lockable in the upright position by a stabiliser slidable over the recessed hinge.
13. 13. A builders' trestle as defined in claim 12 in which the stabiliser is telescopically slidable on the upward extension.
14. 14. A builders' trestle as defined in claim 13 in which the stabiliser comprises a tubular shape.
15. 15. A builders' trestle as defined in any of claims 11-14 in which the recessed hinge comprises a pair of hinge pins connected by an intermediate link.
16. 16. A builders' trestle as defined in claim 15 in which the intermediate link extends across opposed, curved ends of the movable part and of an adjacent part of the upward extension.
17. 17. A builders' trestle as defined in claim 16 in which the opposing curved ends are provided with interengaged gear teeth, knurling or other roughening.
18. 18. A builders' trestle as defined in any of claims 12-14 and 17 in which the stabiliser is provided with internal clearances which allow it. to slide over any projecting part of the gear teeth, knurling or other roughening, when the movable part of the upward extension is hinged to the upright position.
19. 19. A builders' trestle as defined in any preceding claim, comprising a pair of the upward extensions, each having a said hingedly attached part.
20. 20. A builders' trestle substantially as shown in or described with reference to Figures 1, 2 and 4-8, or Figures 3 and 4-8, of the drawings.