Prop

Abstract

The present disclosure relates to a prop (10) comprising a first tube (14) and a second tube (16). The first tube (14) is telescopically connected to the second tube (16) for axially displacing the second tube (16) between a retracted position and an extended position. The first and second tubes (14, 16) each comprise a loading end for receiving an axial load from opposing load surfaces (62, 64) in the extended position. The first tube (14) and the second tube (16) are made from a plastics material.

Claims

1. A prop comprising a first tube and a second tube, the first tube being telescopically connected to the second tube for axially displacing the second tube between a retracted position and an extended position, the first and second tubes each comprising a loading end for receiving an axial load from opposing load surfaces in the extended position, wherein the first tube and the second tube are made from a plastics material, the prop further comprising a linear actuator to connect telescopically the first and second tubes, wherein the linear actuator is spaced from the loading ends of the first and second tubes when the prop is in the extended position, the first and second tubes electrically insulating the linear actuator from the respective loading ends, wherein the linear actuator comprises a threaded section associated with the first tube, a ring threadingly engaged with the threaded section, and a pin coupled to the second tube for transferring the axial load between the second tube and the ring, wherein the linear actuator comprises a sleeve attached to the first tube, the sleeve comprising the threaded section.

2. The prop of claim 1, further comprising a first foot connected to the loading end of the first tube for engaging a load surface and a second foot connected to the second tube for engaging an opposing load surface, wherein the first and second feet are made from a plastics material.

3. The prop of claim 2, wherein the first foot and/or the second foot comprises a base plate and a spigot extending therefrom, the spigot and the respective first tube or second tube comprising complimentary threads.

4. The prop of claim 3, wherein the first tube and/or the second tube comprises an attachment sleeve fixed to an interior surface thereof, the attachment sleeve including the threads.

5. The prop of claim 1, wherein the plastics material of one or more of the first tube, the second tube, the first foot, and the second foot comprises fiber reinforcements.

6. The prop of claim 5, wherein the fiber reinforcements comprise carbon.

7. The prop of claim 1, wherein the ring comprises a handle integrally formed therewith.

8. The prop of claim 1, wherein the sleeve comprises an annular wall to abut an end of the first tube opposite to the loading end.

9. The prop of claim 1, wherein one or more of the sleeve, the ring, and the pin are made from a plastics material.

10. The prop of claim 1, wherein one or more of the plastics materials is a thermoplastic.

11. The prop of claim 10, wherein the thermoplastic is nylon.

12. The prop of claim 1, wherein the axial load is transferred through the plastics material.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The subject-matter of the present disclosure is described below with reference to the accompanying figures, in which:

(2) FIG. 1 shows an exploded view of a prop according to certain embodiments;

(3) FIG. 2 shows a perspective view of the prop from FIG. 1;

(4) FIG. 3 shows a cross section view of an embodiment of the prop from FIG. 1;

(5) FIG. 4 shows a perspective view of the prop from FIG. 1 installed in a trench to support opposing sidewalls; and

(6) FIG. 5 shows a cross section view of a further embodiment of the prop from FIG. 1.

DETAILED DESCRIPTION

(7) With reference to FIG. 1, a prop 10 comprises a first foot 12, a first tube 14, a second tube 16, a second foot 18, and a linear actuator 20.

(8) The first and second feet 12, 18 each include a substantially flat plate 22, 22 and a spigot 24, 24 perpendicularly connected to the flat plate 22, 22. The outer diameter of each spigot 24, 24 corresponds to the inner diameter of the respective first and second tubes 14, 16. In particular, the outer diameters of the spigots 24, 24 may be an interference fit with the inner diameters of the first and second tubes 14, 16. The first and second feet 12, 18 may be made from a plastics material. The plastics material may be reinforced with fibers to provide additional load bearing strength. The plastics material may be a carbon fiber reinforced plastics material. In this way, if either foot 12, 18 contacts an electrical component, such as a cable, when installed, the foot 12, 18 will electrically insulate the prop 10.

(9) The first tube 14 comprises a loading end 26 and an actuation end 28. The loading end 26 connects to the spigot 24 of the first foot 12. In this way, an axial load is received by the loading end 26 and transferred axially through the first tube 14. The first tube 14 includes a longitudinal slot 30 extending axially and provided on opposing sides of the first tube 14 (only one slot is shown in FIG. 1). The longitudinal slot 30 is provided in the vicinity of the actuation end 28.

(10) The second tube 16 comprises an actuation end 32 and a loading end 34. The outer diameter of the second tube 16 is smaller than the interior diameter of the first tube 14. In this way, the second tube 16 has a sliding fit with the first tube 14. The second tube 16 includes a plurality of pin sockets 36 formed by holes passing through opposing sides of the first tube 14. The pin sockets 36 are axially spaced.

(11) The first and second tubes 14, 16 are made from a plastics material. In this way, if either tube 14, 16 contacts a stray electrical component, such as a cable, the prop 10 will be electrically insulated. This is particularly important for the tubes 14, 16 as opposed to other parts of the prop since an operator would touch the tubes to install or remove the prop 10 and any stray electrical components would likely be in the vicinity of load surfaces (e.g. trench walls). The plastics material may comprise fiber reinforcements to provide additional load bearing strength, particularly in an axial direction. The plastics material may be carbon fiber reinforced plastic.

(12) The linear actuator 20 telescopically connects the first tube 14 to the second tube 16 for axially displacing the second tube between a retracted position and an extended position. The linear actuator 20 comprises a sleeve 40, a ring 42 and a pin 44.

(13) The sleeve 40 has a threaded section, which is externally threaded along the entire length of the sleeve 40. The sleeve 40 is elongate and has a longitudinal slot 46 substantially the same shape and configuration as the longitudinal slot 30 of the first tube 14. The sleeve 40 has an interior diameter corresponding to the outer diameter of the first tube 14. The sleeve 40 connects to the actuation end 28 of the first tube 14. In this way, the prop 10 has a threaded section associated with the first tube 14. An annular wall 41 (FIG. 3) is provided to abut the actuation end 28 of the first tube 14 to transfer an axial load from the sleeve 40 to the first tube 14. The annular wall 41 also provides a fail-safe in case the bonding attaching the sleeve 40 to the first tube 14 fails.

(14) Various methods of attaching the sleeve 40 to the first tube 14 may be used, for instance by welding, bonding, or using an adhesive. These attachment methods are not limiting. When attached, the longitudinal slot 30 of the first tube 14 overlays the longitudinal slot 46 of the sleeve 40 to provide a longitudinal channel through both the sleeve 40 and the first tube 14.

(15) The ring 42 comprises a ring body 48 and a handle 50. The ring body 48 is internally threaded for threading engagement with exterior threads of the sleeve 40. The handle 50 is provided as a stub rigidly formed and integral with the ring body 48.

(16) The pin 44 has an outer diameter corresponding to the diameter of the pin sockets 36 of the second tube 16. In particular, the pin 44 is arranged to be in sliding fit with the pin sockets 36 when assembled.

(17) One or more of the sleeve 40, the ring 42, and the pin 44 are made from a plastics material. The plastics material may be a thermoplastics material, for instance nylon. Nylon allows threads to be cut into the surface without unacceptably compromising the strength of the linear actuator 20. In addition, nylon may be self-lubricating, which is desirable for threaded components.

(18) The linear actuator 20 is likely to be the last part of the prop 10 to be contacted by an operator during installation and the first part of the prop 10 to be contact by an operator during removal. However, as will be appreciated from the description below, the linear actuator 20 is spaced from the loading ends 26, 34 of the first and second tubes 14, 16 when the prop 10 is in an extended configuration (see below) and thus suspended away from load surfaces (e.g. trench walls). Accordingly, the linear actuator 20 is electrically insulated by the plastic tubes 14, 16, and/or the plastic feet 12, 18 from any stray electrical components protruding from the load surfaces and which may contact the prop 10. Since the linear actuator 20 is electrically insulated from high risk electrical exposure areas, it is possible to make the linear actuator 20 from a metallic material, such as steel, to accommodate the transfer of a load between the first and second tubes 14, 16.

(19) Operation of the linear actuator 20 is described now with reference to FIGS. 2 and 3.

(20) The pin 44 is removed and the second tube 16 is axially displaced from a stowed position to a retracted position where the feet 12, 18 are in the vicinity of load surfaces (e.g. trench walls). The pin 44 is then passed through the longitudinal slots 30, 46 and through a nearest pin socket 36. The handle 50 is turned to progress the ring 42 toward the loading end 34 of the second tube 16. The ring 42 abuts the pin 44 to displace the second tube 16 axially between the retracted position and an extended position.

(21) With reference to FIG. 4, in-use, the prop 10 is installed in a trench 60. The trench 60 has opposing sidewalls 62, 64, and a floor 66. The prop 10 is lowered into the trench 60 by an operator (not shown). The first foot 12 is positioned to engage one of the sidewalls 62. The linear actuator 20 is operated manually by the operator in the foregoing way to displace the second tube 16 from the retracted position to the extended position where the second foot 18 engages the opposing wall 64. The linear actuator 20 may be used to further extend the prop 10 to apply a support force against the opposing sidewalls 62, 64 to prevent them from collapsing whilst the operator performs tasks within the trench 60. The sidewalls 62, 64 thus become load surfaces and the reactive axial load is transferred through the prop 10. In particular, the axial load is received at respective loading ends 26, 34 of the first and second tubes 14, 16. The axial load is transferred through the threaded section associated with the first tube 12, provided by virtue of the sleeve 40 (FIG. 1). In turn, the load is then transferred through the ring 42 and the pin to the second tube 16.

(22) To remove the prop 10, the reverse process is carried out. Namely, the ring 42 is turned toward the loading end 26 of the first tube 14. The load from the sidewalls 62, 64 serves to retract the second tube 16. Once loose, the pin 44 (FIG. 1) may be removed and the second tube 16 retracted fully into the first tube 14. The pin 44 may be reinstalled to a subsequent socket 36 (FIG. 1) to stow the prop 10.

(23) Whilst the operator performs tasks in the trench 60, subterranean objects such as electrical components (E) may be disturbed and become exposed. The electrical components (E) may include stray cables, which may suffer damage when excavating the trench or during tasks performed within the trench. A stray cable is most likely to contact the feet 12, 18 or either tube 14, 16 since those components are in closest proximity to the sidewalls 62, 64. Any contact between the electrical component (E) and the feet 12, 18 or tubes 14, 16 will not result in an electrical injury to an operator touching the tubes 14, 16 or feet 12, 18 when removing the prop 10 by virtue of them being made from a plastics material.

(24) The linear actuator 20 is spaced from the loading ends 26, 34 and is thus suspended away from the sidewalls 62, 64 and also the floor 66 and so is unlikely to come into contact with electrical components (E). Accordingly, the linear actuator 20 is electrically insulated from the loading ends 26, 34 reducing the risk of an injury to an operator. However, a plastics material, such as nylon, may be preferable to reduce the electrical injury risk further, especially since the linear actuator 20 is likely to be the first part of the prop 10 to be touched by an operator when removing the prop 10. In addition, plastics materials may be desirable to reduce the risk of corrosion.

(25) With reference to FIG. 5, an embodiment of the prop 110 may include alternative first and second feet 112, 118. The remaining components are substantially the same as described above and so duplicated description has been omitted. Reference signs used in this embodiment correspond to those used in the foregoing embodiment, but preceded with a 1.

(26) The first foot 112 includes a plate 122 and a spigot 124. The first tube 114 includes an interior surface. The first tube 114 also includes an attachment sleeve 170. The outer diameter of the attachment sleeve 170 corresponds to an inner diameter of the first tube 114. The attachment sleeve 170 is fixed to the first tube 114 by bonding. A resin or glue may be used for fixing the attachment sleeve 170 to the first tube 114. The interior surface of the attachment sleeve 170 is threaded and an exterior surface of the spigot 124 is threaded. In this way, the spigot 124 and the attachment sleeve 170 include complimentary threads. The complimentary threads enable the first foot 112 to be removably mounted to the first tube 114.

(27) The second foot 118 includes a plate 122 and a spigot 124. The second tube 116 includes an interior surface. The second tube 116 also includes an attachment sleeve 170. The outer diameter of the attachment sleeve 170 corresponds to an inner diameter of the first tube 114. The attachment sleeve 170 is fixed to the second tube 116 by bonding. A resin or glue may be used for fixing the attachment sleeve 170 to the second tube 116. The interior surface of the attachment sleeve 170 is threaded and an exterior surface of the spigot 124 is threaded. In this way, the spigot 124 and the attachment sleeve 170 include complimentary threads. The complimentary threads enable the second foot 118 to be removably mounted to the second tube 116.

(28) The first and/or second feet 112, 118, and the attachment sleeve(s) 170, 170 may comprise a plastics material. A suitable plastics material is a thermoplastic, and may include nylon in order to accommodate cutting the threads. The first and/or second feet 112, 118 and/or the attachment sleeve(s) 170, 170 may be manufactured by compression or injection molding. Alternatively, the first and/or second feet 112, 118, and/or the attachment sleeve(s) 170, 170 may comprise a metallic material. A suitable metallic material includes mild steel.