GB2215192A - A trestle - Google Patents

Abstract

A trestle comprises two identical generally U-shaped members (2) of circular cross-section linked together, and means for limiting the opening angle between the linked members to a desired maximum value, the free ends (2b) of the side limbs (2a) of each member being bent towards each other through a right angle and housed side by side in the two ends of a tubular component (3) having substantially the same length as the middle portions (2c, 2'c) of the members (2) and an internal cross-sectional contour which embraces the external cross-sections of the linked pair of bent ends (2b) on the side branches (2a) of the two members (2), the ends of the tubular component (3) thus acting as linking bearings. <IMAGE>

Description

A TRESTLE The present invention relates to a trestle.

Two major types of trestles are known, viz., wooden and metallic trestles respectively.

A wooden trestle usually consists of two rigid frames linked together along one edge by hinges which allow them to move between two extreme positions viz., a stacking position in which the frames lie flat together and a working position in which they are swung apart through an opening angle of at the most 200 to 300, calipers or other means being provided to limit the opening angle to the above maximum value.

Because of the operations involved in making the frames and fitting the hinges and the calipers limiting their opening angle to the maximum value, wooden trestles are relatively costly.

A metallic trestle usually consists of two identical generally U-shaped tubular members linked together by two pins, each of which passes through an adjacent pair of side limbs of the members, near the middle portion on the one and near the free ends on the other, so that after assembly the two members are joined to stand together in relatively inverted positions, the means provided for limiting the opening angle to the desired maximum value consisting of calipers, small chains or hooks.

In addition to the operations of bending the tubular members, the manufacture of this type of trestle involves piercing and riveting operations and the fitting of means for limiting the opening angle, which considerably augment the costs.

The object of the present invention is to remedy these disadvantages and devise a very inexpensive trestle.

According to the present invention, a trestle comprises two identical generally U-shaped members of circular cross-section linked together, and means for limiting the opening angle between the linked members to the desired maximum value, the free ends of the side limbs of each member being bent towards each other through a right angle and housed side by side in the two ends of a straight tubular component having substantially the same length as the middle portions of the members and an internal cross sectional contour which embraces the external cross-sections of the juxtaposed pair of bent ends of the side limbs of the two members, the ends of the tubular component thus acting as linking bearings.

The fabrication of such a trestle is very straightforward, since after bending its two members to the desired profile a simple elastic deformation suffices to insert the bent free ends. of the two side limbs of each member into the corresponding ends of the tubular component, which act as linking bearings.

The resilience of the U-shaped members normally suffices to retain the housed bent ends of the side limbs in the tubular component and prevent any inadvertent collapse of the trestle. Nevertheless, two radial indentations are preferably provided at each end of the tubular component, each of which indentations coincides with a radial indentation on the bent free ends of each side limb of each member. The indentations are preferably formed after assembling the trestle, by simultaneously punching the tubular component and the bent free ends of the side limbs of the members housed therein.The mutual engagement of the indentations not only ensures that the bent free ends of the side limbs of the members are securely held in the corresponding ends of the tubular component, but also constitutes the means of limiting the opening angle to the desired maximum value, by restricting their angular displacement in the tubular component.

It is naturally possible to provide additional or alternative opening limiting means, such as calipers, hooks or small chains.

An embodiment of the invention will now be described, purely by way of non-limiting example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a trestle in accordance with the invention in the open or working position; Figure 2 is a cross-section taken from the line II-II of Figure 1; and Figure 3 is a cross-section taken on the line III-III in Figure 1; on a larger scale.

The trestle shown in the drawings consists of two identical U-shaped members 2, the free ends 2b of the side limbs 2a of which are bent inwards through a right angle, i.e., towards each other, for housing in a straight tubular component 3 of metal or the like, the internal crosssectional contour of which embraces the external crosssections of the juxtaposed free bent ends 2b to link the pair of side limbs 2a of the two members 2.

As indicated by the cross-hatching in Figure 3 the members 2 are metal tubes of circular cross-section and the tubular component 3 has an internal cross-section with its length equalling the sum of the external diameters of the tubular members 2 i.e., twice their diameter, while its internal height is equal to the said diameter. The tubular component 3 thus acts as a bearing for the bent free ends 2b of the members 2, which can therefore pivot freely one against the other between a stacking position in which they lie flat together, as shown by the broken lines in Figure 2, and the open or working position shown in Figures 1 and 2 to which -they are brought by being swung apart through a prescribed opening angle.

The length of the tubular component exceeds the distance between the opposing free ends 2b of the side limbs 2a on each member 2, but is less than the distance separating the said side limbs 2a, i.e., substantially the same length as the middle portions 2c, 2'c of the members 2, and the free ends cn be inserted into the tubular component 3 by a simple elastic deformation of the members 2, their resilience thereafter contributing to the maintenance of the assembled state.

As will be appreciated from this description, the cost of producing such trestles is very low, since there are no specific operations of piercing or the like, only the bending of the members 2 prior to assembly, to provide for hinging of the members together.

The means provided to limit the opening angle between the members 2 to the desired maximum value can obviously include the traditional means, such as a hook 4 permanently linked at one end 4a to the middle portion 2c of one of the members 2 and temporarily engaging, at the other end 4b, the middle portion 2'c of the other member 2. In the embodiment illustrated in the drawings, the permanent linkage between the hook 4 and the middle portion 2c of the one member 2 is obtained by inserting a bent tip on the end 4a into a di am etral hole 5 through the middle portion 2c, and bending over the protruing tip 4c so that the end 4a of the hook 4 cannot be disengaged from the hole 5.The temporary linkage between the other end 4b of the hook 4 and the middle portion 2'c of the other member 2 can be obtained quite simply by inserting a bent tip 4d on this end into a radial hole 6 provided for this purpose in the middle portion 2'c. The length of the hook 4 obviously determines the distance separating the middle portions 2c and 2'c of the members 2 when the trestle is in the working position, and hence determines the maximum opening angle between members 2.

If it is required to prevent axial movement between the tubular component 3 and the bent free ends 2b of the members 2, one can simultaneously form radial indentation 9 in the component 3 and each bent end 2b, as illustrated in Figure 3. These indentations 9 can obviously be formed very simply by punching, so that in the assembled trestle the tubular component 3 has four such indentations two adjacent each end, which indentations are preferably disposed, for aesthetic reasons, on the underside as indicated by the arrows 7 and 8 in Figure 1. By opposing any inadvertent escape of the bent ends 2b of the side limbs 2a of the members 2 from the tubular component 3, these indentations 9 prevent any undesired or accidental collapse of the trestle.

-The mutual engagement between the indentations 9 in the tubular component 3 and each bent free end 2b of the side limbs 2a of the members 2 cannot prevent the angular movement of the members 2 required to set the trestle up in the working position, since the maximum opening angle between the members 2 is only of the order of 150 to 3 0 and the angular movement of each tubular member 2 in relation to the tubular component 3 is thus less than 150.

The indentations 9 can obviously be used as the means of limiting the opening angle between the members 2 to the desired maximum value, though it is also possible to combine them with other conventional means such as the hook 4 already described or analogous means such as calipers, small chains or the like.

In the embodiment illustrated in the drawings, the members 2 are metal tubes, but they could equally well be solid rods in any suitably ductile material.

Claims (6)

1. A trestle comprising two identical generaly Ushaped members of circular cross-section linked together, and means for limiting the opening angle between the linked members to the desired maximum value, the free ends of the side limbs of each member being bent towards each other through a right angle and housed side by side in the two ends of a straight tubular component having substantially the same length as the middle portions of the members and an internal cross-sectional contour which embraces the external crosssections of the juxtaposed pair of bent ends on the side limbs of the two members, the ends of the tubular component thus acting as linking bearings.

2. A trestle as in Claim 1, wherein two radial indentations are provided at each end of the tubular component, each of which indentations coincide with a radial indentation on the bent free ends of each side limb of each member.

3. A trestle as in Claim 1 or Claim 2, wherein the members are tubular.

4. A trestle as in any one of Claims 1 to 3, wherein the members are metallic.

5. A trestle as in any one of Claims 1 to 4, wherein the tubular component is metallic.

6. A trestle substantially as hereinbefore described with reference to the accompanying drawings.