FIELD OF INVENTION

This invention relates to prop assemblies, suitable for providing support in a variety of applications, including mining, construction and building. In some embodiments, the prop assembly of the invention may be useful for use a temporary support in these applications, as well as during rescue operations

BACKGROUND ART

Props have been used for permanent or temporary support in mining for quite some time, to help prevent roof collapse and to control rock pressure. Original props ('pit props') were made of timber and were cut to a chosen length. They suffered from the drawback that they were not adjustable and therefore it was difficult to re-use them.

More recently, support in mines has become more sophisticated. Many countries require compliance with Standards or rules, based on safety concerns. A permanent support system may be installed, usually including a mine roof mesh. Temporary props are used to support the roof mesh until it can be fixed more permanently. Prior art temporary props may be sacrificial or reusable.

One form of prior art prop is hydraulic assisted and requires access to a source of water or compressed air for pumping into the prop in order for the prop to be adjusted to the desired height. A pump is also required. These requirements can be a drawback. Another type of prop is height adjustable using a lifting tool engaging a cam nut. An inner cylinder is lifted relative to an outer cylinder until the desired height is achieved. Once lifting is completed, the lifting tool is disengaged and a locking peg or pin is fitted into an aperture drilled in the outer cylinder. The outer cylinder has a plurality of apertures for this purpose, but to maintain strength of the prop the apertures must be adequately spaced apart vertically. This means that, at the desired height of the prop, the closest available aperture may be slightly below the optimum required, so the prop is not in full contact with the roof mesh or other surface it is to support. In addition, when the prop is l to be removed, it can be quite difficult to remove the locking peg. In particular, the load on the prop needs to be removed before the locking peg can be extracted.

A further drawback with known adjustable height props is the time taken to extend the prop to the desired height. The lifting mechanism is one-paced and laborious and it can be time-consuming to install the prop correctly. Such props are also slow to disengage if it is desired to remove them. The lifting mechanism, which may use a sleeve rotating with a nut which bears against the locking peg, must be used to wind down the prop and once again its use is time-consuming and laborious. Further, the nut is rotated by a handle designed to be lifted and moved horizontally. This requires sufficient space to effect the rotation and can prevent the prior art prop from being used in a confined space or up against a wall.

A temporary prop for mining has been developed, referred to as a 'pogo stick' prop. This type of prop is intended for use where the load is relatively light, such as support for dividers in a ventilations system. A pogo stick prop is usually lightweight and easy to transport. It can be height adjustable, having an internal cylinder mounted within an external cylinder. The internal cylinder is spring-biased towards extension. However, the variation in height achieved by using the spring-based extension is limited. As a result, the prior art pogo stick prop has limited versatility and a range of different length pogo stick props may be required for use on a site with varying height requirements. Props, including pogo stick props, have also been used in the construction and building industries, both as vertical props and as angled or horizontal props, for example to hold a wall or ceiling panel in place until it is permanently secured. The same problems as for mining props can be encountered in known props intended for building or construction. Further, known props used in construction are able to push against a building component but are not designed to be able to pull the building component if it is desired to move the building component to a different position, for example. There is a need for a prop assembly, which is height adjustable and which alleviates or avoids some or all of the drawbacks referred to above or which at least provides a useful alternative.

STATEMENT OF INVENTION Accordingly, this invention provides a prop assembly including: a pole subassembly having a first prop part and a second prop part, the first prop part being axially movable with respect to the second prop part; a first extending means adapted to enable the first prop part to be moved in a first adjustment with respect to the second prop part; and either: - a second extending means adapted to enable the first prop part to be moved in a second adjustment with respect to the second prop part; or a third extending means, adapted to adjust a length of the prop assembly.

Optionally, the prop assembly of the invention has a first end and a second end and may include a foot at the first end only or a foot at the second end only or a foot at each of the first and second ends. In the embodiment where there is a foot at each end, the foot at the first end may be the same as or different from the foot at the second end. Each foot may be fixed or pivotable, as desired, noting that a pivotable foot may be useful for construction or rescue applications.

If no foot is included in the prop assembly of the invention, it is preferred that a spike or similar is included, especially if the prop assembly is intended for mining use. A spike can be useful to engage a floor or roof in a mine. Preferably, such a spike is replaceable in case of damage or wear.

Embodiments of the assembly of the invention are preferably constructed for use in mining specifically, or in building or construction specifically. The embodiments intended for mining use may be capable of bearing a higher load than embodiments intended for use in construction or building. In addition, a prop intended for mining use is preferably configured to be used in a substantially vertical position, while a prop for building or construction may be configured to be used at an angle as well as substantially vertically.

If desired, the prop assembly of the invention may be essentially the same for construction and mining use. If desired, that the assembly intended for mining use may be longer than that intended for construction use.

It will be appreciated that the prop assembly of the invention may also be used in other applications, such as for rescue operations, for example, to provide support or stability where a rescue must be performed in an unstable environment.

It is preferred that the assembly of the invention is of rugged, durable construction so that it may be reused many times and can cope with typically rough handling.

The pole subassembly may be made of any suitable material, having regard to its intended use. There may be restrictions on material: for example, in some jurisdictions a prop assembly intended for use in some types of mining must not be made from aluminium. On the other hand, for transport and handling it is desirable that the assembly of the invention is as light as possible. It is preferred that the first prop part and the second prop part of the pole subassembly are made from steel tubing, one of which is slidably movable within the other.

The first and second extending means may take different forms. In one embodiment, the first extending means has a quick release mechanism and the second extending means uses a winding mechanism. In another embodiment, the first and second extending means are combined in a winding mechanism, which is capable of two speeds. In yet another embodiment, which can be particularly useful for pogo stick prop assemblies, the first extending means has a quick release mechanism and the second extending means is a spring-loaded extension. Any winding mechanism may need to provide 1 kN force and be self-locking to be able to support up to 5 tonnes, should this be necessary for mine or construction use. If the winding mechanism has a crank handle, preferably the handle can be folded down out of the way or disabled when not in use, so that accidental collision with the crank handle is not able to change the extension setting. It is also desirable that the crank handle is lockable, for example by a padlock fitted to the handle, to prevent unauthorised operation. If desired, a safety lockout hasp may be engaged with the handle, to accommodate multiple locking devices, such as padlocks, all of which must be unlocked in order to release the handle.

Optionally, the assembly of the invention may include all of the first extending means, the second extending means and the third extending means. An example of the third extending means is a spring-loaded foot, located at the top or bottom of the assembly.

The assembly of the invention is preferably extendible from 2.6 to 3.6 metres. It is to be understood that other ranges are possible and the invention is not limited to the range of 2.6 to 3.6 metres. An example is use of a relatively short prop assembly of about 60 cm in length, which can be used to hold kitchen cupboards in place while being installed above a kitchen bench.

For use, the assembly of the invention may require a foot at the top and bottom of the pole subassembly. The foot may be of a different configuration for mining compared to that for building or construction. Examples are shown in the drawings, described below. For mining use, it is preferred that each foot is made of steel. For building or construction, the flat plate of the foot at the top of the pole assembly is preferably also made of metal, preferably steel. If desired, the flat plate may have a layer of rubber or other suitable material, designed to avoid damage to the surface it contacts. It is also preferred that a foot for building or construction can swivel with respect to the pole subassembly, to facilitate use of the prop at an angle of less than 90 degrees to the vertical. Such a foot may also be temporarily attachable to a building component (such as a panel intended for installation as a ceiling or wall), so that the building component may be pushed into place while being fixed and/or pulled away for relocation or repositioning if required.

If desired, the assembly of the invention may be designed to accept a range of specialised modular feet, to increase versatility and to enable the same assembly to be used for different purposes, by attaching the appropriate feet. Accordingly, in a second aspect, this invention provides a modular foot assembly for a hollow end of a prop assembly, the foot assembly including a subassembly adapted to be removably secured within the hollow end and including a spike or a plate which protrudes from the hollow end in use and means for retaining the spike or plate in the sub-assembly.

Preferably, when the foot assembly includes a spike, the spike is stabilised by a body surrounding a base of the spike.

If the foot assembly includes a plate, the plate may have a relatively flat annular region formed with or joined to a concave body, so as to be suitable for use in construction. The plate may be pivotable around a pivot point as described above.

In another embodiment, the plate may be relatively flat except for peripheral load bearing spiked parts, suitable for use in mines. The plate in this embodiment may also be pivotable around a pivot point as described above.

In one embodiment, the plate may be retained in the sub-assembly by connection to a bracket, via a cap having a flange at each end, for example.

The sub-assembly of the foot assembly may be removably secured within the hollow end of the prop assembly by any suitable means - most conveniently by a pair of screws, but the invention is not limited to this.

The modular foot assembly of the invention is intended to be easily removed from the hollow end of the prop assembly and replaced with a similar or different modular foot assembly, as required or as desired. Thus, a damaged foot assembly can be replaced or a foot assembly intended for mining use can be replaced by a foot assembly intended for construction use.

The modular foot assembly of the invention is preferably combined with the prop assembly of the invention, but may be used with other props.

It will be appreciated that use of the modular foot assembly of the invention can reduce inventory and enable different versions of the prop assembly of the invention to be assembled swiftly and conveniently.

Prior art pogo stick assemblies typically do not have any foot.

When the assembly of the invention is intended for use as a support for mine roof mesh, that mesh is typically a wire mesh being 100mm x 100mm square x 5mm thick, in sheets 6 m x 1.2 m and weighing 13 -15 Kg. Consequently, it is preferred that this embodiment of the assembly of the invention is rated to 1KN, with the ability to be able to withstand a maximum of 3 KN with a 3:1 safety rating. In this embodiment, it is preferred that the maximum weight of the assembly is 15 Kg, including feet.

For mining use, it is preferred that the assembly of the invention is white or light- coloured, with reflective tape, to increase visibility in the typically dark mine environment.

The invention in the form of a pogo stick may be able to carry a load of up to about 200 kg. This embodiment may be useful for mining use, to hold electric cables above the ground and to prevent them being damaged by vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

Figure 1 is a front elevation of a first embodiment of the assembly of the invention, intended for mining use; Figure 2 is a side elevation of the assembly of Figure 1;

Figure 3 is a front cross-section of an embodiment of an upper sprung foot in the embodiment in Figures 1 to 2;

Figure 4 is a side cross-section of the embodiment of the upper sprung foot in Figures 1 to 3; Figure 5 is a front elevation of a second embodiment of the assembly of the invention, intended for mining use; Figure 6 is a side elevation of the assembly of Figure 5;

Figure 7 is a top view and Figure 8 is a front elevation of an embodiment of an upper foot suitable for the embodiments in Figures 1 to 6;

Figure 9 is a front elevation of an embodiment of bottom foot and Figure 10 is an underside plan view of that foot, suitable for the embodiments in Figures 1 to 6;

Figure 11 is a front cross-section and Figure 12 is a side cross-section of the bottom foot of Figures 9 and 10;

Figure 13 is a front elevation of a third embodiment of the assembly of the invention, intended for mining use as a pogo stick; Figure 14 is a side elevation of the assembly of Figure 13;

Figure 15 is a cross section of the embodiment of Figure 13;

Figure 16 shows a detail of the collet mechanism marked A in Figure 15;

Figure 17 shows a partial cross section of the collet mechanism of Figure 16 in a locked state, while Figure 18 shows the unlocked state; Figure 19 and Figure 20 are views corresponding and very similar to Figures 1 and

2, but showing a fourth embodiment, intended for building use and also suitable for use during rescue operations, for example;

Figure 21 is a cross section of the embodiment of Figure 19;

Figure 22 is a detail of the winder and collet mechanism marked A in Figure 21; Figure 23 is a front cross-section of an embodiment of an upper sprung foot in the embodiment in Figures 19 to 22;

Figure 24 is a side cross-section of the embodiment of the upper sprung foot in Figures 19 to 22;

Figures 25 and 26 are views corresponding and very similar to Figures 5 and 6, but showing a fifth embodiment, intended for building use;

Figure 27 is a cross section of the embodiment of Figure 25;

Figure 28 is a detail of the winder mechanism marked A in Figure 27;

Figure 29 is an exploded view of the winder mechanism shown in Figure 28 (without the first or second prop parts);

Figure 29A shows a first embodiment of a locking arrangement for a winder mechanism;

Figure 29B shows a second embodiment of a locking arrangement for a winder mechanism; Figures 30 and 31 are views corresponding and very similar to Figures 13 and 14, but showing a sixth embodiment, being a pogo stick intended for building use;

Figure 32 is a top view and Figure 33 is a front elevation of an embodiment of an upper foot suitable for the embodiments in Figures 19 to 31;

Figure 34 is a front elevation of an embodiment of a bottom foot and Figure 35 is an underside plan view of that foot, suitable for the embodiments in Figures 19 to

31;

Figure 36 is a front cross-section and Figure 37 is a side cross-section of the bottom foot of Figures 34 and 35;

Figure 38 is a top view and Figure 39 is a front elevation of a further embodiment of an upper swivel foot suitable for the embodiments in Figures 19 to 31;

Figure 40 is a front elevation of a further embodiment of a bottom swivel foot and Figure 41 is an underside plan view of that foot, suitable for the embodiments in Figures 19 to 31;

Figure 42 is a front cross-section and Figure 43 is a side cross-section of the bottom foot of Figures 40 and 41; Figure 44 is a top view and Figure 45 is a front elevation of a further embodiment of a swivel upper foot suitable for the embodiments in Figures 1 to 6;

Figure 46 is a front elevation of a further embodiment of a swivel bottom foot and Figure 47 is an underside plan view of that foot, suitable for the embodiments in Figures 1 to 6;

Figure 48 is a front cross-section and Figure 49 is a side cross-section of the bottom foot of Figures 46 and 47;

Figure 50 is a top view and Figure 51 is a front elevation of an embodiment of a fixed upper foot suitable for the embodiments in Figures 1 to 6; Figure 52 is a front elevation of an embodiment of a fixed bottom foot and Figure

53 is an underside plan view of that foot, suitable for the embodiments in Figures 1 to 6;

Figure 54 is a front cross-section and Figure 55 is a side cross-section of the bottom foot of Figures 52 and 53; Figure 56 is a top view and Figure 57 is a front elevation of an embodiment having an upper engaging spike, suitable for the embodiments in Figures 1 to 6;

Figure 58 is a front elevation and Figure 59 is an underside plan view of an embodiment having a lower engaging spike, suitable for the embodiments in Figures 1 to 6; and Figure 60 is a front cross-section and Figure 61 is a side cross-section of the lower engaging spike of Figures 58 and 59.

DETAILED DESCRIPTION OF THE DRAWINGS

Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. Reference is first made to Figures 1 and 2, which are a front elevation and a side elevation, respectively, of a first embodiment of the assembly of the invention, intended for mining use. In this embodiment, prop assembly 10 has a pole subassembly including first prop part 14 and second prop part 16. First prop part 14 is axially movable with respect to the second prop part 16, to elongate prop assembly 10.

Prop assembly 10 has a first extending means 18, adapted to enable first prop part 14 to be moved in a first adjustment with respect to second prop part 16. First extending means 18 has a quick release collet mechanism, described in more detail in connection with Figures 16 to 18. Prop assembly 10 also has second extending means 22, adapted to enable first prop part 14 to be moved in a second adjustment with respect to second prop part 16. Second extending means 22 is in the form of a winding mechanism and is described in more detail in connection with Figures 21 and 22.

Rings 38 are useful for hanging or attaching items. For example, in mining it is useful to retain electrical cables above the ground; rings 38 may be used for this purpose.

Prop assembly 10 has a third extending means 24, being a spring-loaded top section detailed in Figures 3 and 4. Figure 3 is a front cross-section of third extending means 24, while Figure 4 is side cross-section. Third extending means 24 is shown in its extended position, which is its 'at rest' position. Third extending means 24 can be compressed by pressing upper foot 42 against a mine roof or other surface. Coil spring 36 is compressed and cylinder 30 travels downwards, to be received within first prop part 14.

Guide pin 26, attached to floor 28 of cylinder 30, travels downwards in channel 32, being confined within channel 32 by lower channel end 33. At that point, cylinder 30 is prevented from any further travel downwardly. Once pressure on upper foot 42 is removed, spring 36 causes cylinder 30 together with guide pin 26 to travel upwardly, until guide pin 26 reaches upper channel end 34.

Cuff 40 is located at the upper end of first prop part 14, to provide a neat appearance and to cover any sharp edge.

A second embodiment of the assembly of the invention, suitable for mining, construction or rescue use, is illustrated in Figures 5 and 6. In contrast to prop assembly 10 in Figures 1 and 2, in the embodiment in Figures 5 and 6, prop assembly 110 has a dual winding mechanism 118.

Dual winding mechanism 118 is capable of two speeds and combines the first and second extending means. Using the first speed, dual winding mechanism 118 is adapted to enable first prop part 114 to be moved in a first (faster) adjustment with respect to second prop part 116. Using the second speed, dual winding mechanism 118 is adapted to enable first prop part 114 to be moved in a second (slower) adjustment with respect to second prop part 116. Dual winding mechanism 118 is described in detail below in connection with Figures 28 and 29.

Prop assembly 10 in Figures 1 to 4 and prop assembly 110 in Figures 5 and 6 have upper and lower feet appropriate to prop assembles used for these applications. Details are shown in Figures 7 to 12.

Upper foot 42 is shown in Figures 7 and 8. Upper foot 42 is designed to be fitted into the upper end of cylinder 30 (first embodiment in Figures 1 to 4) or the upper end of first prop part 114 (second embodiment in Figures 5 and 6). Upper foot 42 has load-bearing parts 44 and a recess 46. This configuration may avoid moisture and debris being trapped between upper foot 42 and the surface it contacts.

Upper foot 42 has two first barbs 48 which work in the same way as barbs 58 in lower foot 52 (Figures 11 and 12). Each first barb 48 snap fits into aperture 50, one of which is shown in Figure 8. Upper foot 42 also has second barbs 49 which work the same way as second barbs 59 in lower foot 52. If it is desired to replace upper foot 42, upper foot 42 may be removed from the upper end of cylinder 30 or first prop part 114 by squeezing barbs 48 so they disengage apertures 50.

Lower foot 52 is shown in Figures 9 and 10, and in cross-section in Figures 11 and 12. Lower foot 52 is of larger dimensions than upper foot 42 in this embodiment. Lower foot 52 is designed to be fitted into the lower end of cylinder 51 which is fitted to the lower end of second prop part 16 (first embodiment in Figures 1 to 4), or into the lower end of second prop part 116 (second embodiment in Figures 5 and 6). Lower foot 52 has load-bearing parts 54 and a recess 56. This configuration may avoid moisture being trapped between lower foot 52 and the surface it contacts. If desired, lower foot 52 may be rubber-backed to prevent slippage.

Lower foot 52 has two first barbs 58, each of which snap fits into aperture 60, one of which is shown in Figure 9. Figure 12 illustrates first barbs 58 engaged with apertures 60. Lower foot 52 also has second barbs 59 which are shown in cross-section in Figure 11.

If it is desired to replace lower foot 52, barbs 58 may be squeezed so that they disengage apertures 50.

Turning now to Figures 13 to 15, this third embodiment of the assembly of the invention may be used in mining, construction or rescue as a pogo stick. This embodiment may also be used in construction, for example to hold up a protective cloth, for example. Rings located on the prop on side of prop may be used in both mining and constructions to hang electrical cables or cords.

Prop assembly 210 has first prop part 214 and second prop part 216. First prop part 214 is axially movable with respect to second prop part 216 by collet mechanism 18, described in more detail in Figures 16 to 18. Second prop part 216 includes along most of its length a number of spaced grooves 217, for engagement by collet mechanism 18. For convenience, only a few of grooves 217 are labelled in Figures 13 to 16.

Prop assembly 210 incorporates a spring-loaded upper portion 24, which works essentially as described in Figure 3 and 4, except that prop assembly 210 does not have an equivalent to upper foot 42. It will be noted that prop assembly 210 does not have an equivalent to lower foot 52, either. However, in this embodiment the upper and lower extremities of prop assembly 210 are designed to accept an upper foot and/or a lower foot of the same or similar design to upper foot 42 and lower foot 52 in the previous embodiments. Apertures 50 and 60 are provided for this purpose. If any foot is attached, it can be designed to swivel in relation to the longitudinal axis of the prop, for example up to about 30 degrees.

Figure 17 shows a partial cross section of collet mechanism 18 in a locked state, while Figure 18 shows the unlocked state. In the locked state in Figure 17, collet mechanism 18 is at rest. Annular tooth 63 is engaged in groove 217 and locked in that position because tooth 63 abuts inner wall 64 of collet mechanism 18. Figures 17 and 18 are shown rotated through 180 degrees compared to Figure 15, for convenience.

To unlock collet mechanism 18, collet 18 is pushed downwards in the direction of arrow 66, while holding second prop part 216. Tooth 63 no longer abuts inner wall 64 but has sufficient space to move radially into cavity 68, as shown in Figure 18. Once downward pressure is released, tooth 63 engages and is locked into the next available groove 217. In this way, prop assembly 210 can be quickly released and extended (or contracted), as can prop assembly 10, which uses the same collet mechanism 18. Further adjustment in the length of prop assembly 210 is effected using spring-loaded upper portion 24.

This embodiment may be used in different lengths for mining and construction, if desired.

The fourth embodiment, intended for building, construction or rescue use, is shown in Figures 19 to 24. Prop assembly 310 in Figures 19 and 20 is almost identical to prop assembly 10 in Figures 1 and 2, the main differences being in the design of the upper and lower feet and the shorter minimum length of prop assembly 310 compared to that of prop assembly 10. Accordingly, labels in Figures 19 to 21 for essentially similar parts have the same labels as in Figures 1 and 2, or the same labels with the addition of the prefix '3', and will not be described in detail. Upper foot 62 and lower foot 72 are described below in relation to Figures 32 to 35.

Figure 22 shows a detail of the winder and collet mechanism marked A in Figure 21. Winder 22 and collet mechanism 18 are the same as in Figures 1 and 2. Collet mechanism 18 has already been described in more detail in Figures 17 and 18. Winder 22 works in known manner. Handle 74 engages pinion 76 when rotated. Pinion 76 in turn engages crown wheel 78 in order to wind worm thread 80 up or down, depending on the direction in which handle 74 is wound.

Spring loaded top section 324 in Figures 23 and 24 is substantially the same as spring loaded top section 24 in Figures 3 and 4. The same labels are used, except for upper foot 62.

Prop assembly 410, the fifth embodiment shown in Figures 25 and 26, is intended for building use but otherwise is very similar to the embodiment in Figures 5 and 6, having the same dual winding mechanism 118. As described for Figures 5 and 6, dual winding mechanism 118 is capable of two speeds and combines the first and second extending means. Using the first speed, dual winding mechanism 118 is adapted to enable first prop part 414 to be moved in a first (fast) adjustment with respect to second prop part 416. Using the second speed, dual winding mechanism 118 is adapted to enable first prop part 414 to be moved in a second (fine) adjustment with respect to second prop part 416. Prop assembly 410 includes upper foot 62 and lower foot 72, which are described below in relation to Figures 32 to 35.

Dual winding mechanism 118 is now described in detail in connection with Figures 28 and 29, Figure 28 being a detail of the winder mechanism 118 marked A in Figure 27.

Handle 174 has three positions: a first position in which handle 174 is pulled outwardly (to the right in Figure 28). Handle 174 moves worm thread 180 at a higher speed, so that first prop part 414 can be extended or contracted rapidly with respect to second prop part 416.

In the second position, handle 174 is pushed inwardly (to the left in Figure 28), to a neutral position, where handle 174 is disengaged. In this second position, accidental contact with handle 174 will not affect movement of first prop part 414 with respect to second prop part 416.

In the third position, handle 174 is pushed further inwardly. Handle 174 moves worm thread 180 at a lower speed, so that first prop part 414 can be extended or contracted more slowly with respect to second prop part 416.

With reference to Figure 29, handle 174 has a pinion 82, adapted to engage aperture 84 in carrier 86, which has three planetary gears 88 (only two of which are visible). In the first position, planetary gears 88 engage and drive ring gear 90; pinion 92 engages crown wheel 94 and worm thread 180 is wound at the higher speed.

In the third position, ring gear 90 is held stationary and worm thread 180 is wound at the lower speed.

It will be noted from Figure 27 that, in prop assembly 410, worm thread 180 is quite long. In this situation, worm thread 180 may need support to prevent it bending. For this purpose, ball plunger 96 is inserted in worm thread 180. Ball plunger 96 has a partially exposed ball, biased outwardly by a spring within ball plunger 96, in known fashion. When the ball encounters a vertical surface, it is pushed into the ball plunger a small distance. If that distance enables the ball to clear the vertical surface, ball plunger 96 (Figure 28) does not impede movement of worm screw 180. The vertical surfaces in dual winding mechanism 118 are all designed so that the ball clears them, except for brace 98. Once ball plunger 96 encounters the lower surface 100 of brace 98, brace 98 is moved upwardly with worm thread 180, to provide support to worm thread 180.

When dual winding mechanism 118 is reversed to draw in first prop part 414 with respect to second prop part 416, brace 98 travels downwards with ball plunger 96 until brace 98 is once again seated within dual winding mechanism 118, as shown in Figure 28.

Figures 29A and 29B show embodiments of a locking arrangement for a winder handle. In these embodiments, the winder is winder 174 of dual winding mechanism 118. However, a similar winder locking arrangement can be used with other winders, such as winder 74 in Figure 22. In both Figures 29A and 29B, apertures 93 are provided for accepting a locking means. In Figure 29A, the locking means is padlock 95, having a shackle 97 for passing through apertures 93 before being locked in known manner. Padlock 95 may be adapted to be unlocked using a key. In a variation, padlock 95 may have a combination lock, unlocked by inputting a code.

In Figure 29B, the locking means is in the form of a lockout hasp 99, having apertures 101 (only three are labelled) designed to accept one or more padlocks (not shown). In locking hasp 99 as illustrated, up to six padlocks may be locked into lockout hasp 99. All padlocks must be unlocked before winder 174 can be released.

Turning now to Figures 30 and 31, the sixth embodiment, being a pogo stick prop intended for building use, is very similar to the mining prop in Figures 13 and 14.

Prop assembly 510 has first prop part 514 and second prop part 516. First prop part 514 is axially movable with respect to second prop part 516 by collet mechanism 18, described in more detail in Figures 16 to 18. Second prop part 516 includes along most of its length a number of spaced grooves 517, for engagement by collet mechanism 18. For convenience, only a few of grooves 517 are labelled in Figures 30 and 31.

Prop assembly 510 incorporates a spring-loaded upper portion 24, which works essentially as described in Figure 23 and 24. In contrast to the prop in Figures 13 and 14, prop assembly 510 includes an upper foot 62 and a lower foot 72, described in detail in relation to Figures 32 to 37.

Upper foot 62 is shown is top view in Figure 32 and in front elevation in Figure 33. Upper foot 62 is designed to be fitted into the upper end of cylinder 30, as shown in Figures 23 and 24 or the upper end of first prop part 414 (Figures 25 and 26). Upper foot 62 has a flat, load-bearing surface 102, for contact with and support to a panel or the like. As shown in Figure 32, load bearing surface 102 has four apertures 104 (only two are labelled), in which screws or other attachment means may be inserted, if it is desired to temporarily attach prop assembly 510 to a panel or other building component. This can facilitate manoeuvring of a panel or similar into position during construction and holding it in place until permanent fixing has occurred. Or the panel or other building component can be moved from one location to another, as desired. Once the panel or other building component is permanently fixed in position, the screws or other attachments means may be removed from apertures 104 and prop assembly 510 is available for use elsewhere.

Upper foot 62 is designed so that it can pivot around pivot point 106. This enables the construction prop assembly to support a panel or similar which is vertical or at an angle between vertical and horizontal, without load bearing surface 102 being perpendicular to the rest of prop assembly 510. For example, prop assembly 510 may be used to support a vertical panel, load bearing surface 102 being in a vertical position, attached to the vertical panel or merely supporting it, while the rest of prop assembly 510 is at an angle of between about 30 and 60 degrees to the vertical panel. Prop assembly 510 may be used in a horizontal configuration, of course, to support a vertical building component. Two of barbs 108 (only two are labelled) in recess 110 may snap into apertures 112 (one only is shown in the Figures), in a similar manner to upper foot 42 of the mining embodiments. If it is desired to replace upper foot 62, upper foot 62 may be removed from upper end of cylinder 30 or first prop part 414 by squeezing barbs 108 so they disengage apertures 112. Lower foot 72 is shown in Figure 34 (front elevation) and Figure 35 (underside plan view). In this embodiment, lower foot 72 is identical to upper foot 62, although the invention is not limited in this respect. If upper foot 62 is identical to lower foot 72, there is greater versatility in being able to replace an upper foot 62 or a lower foot 72 from a reduced inventory of spare parts. The same labels as for upper foot 62 are used for lower foot 72. It will be appreciated that apertures 104 in lower foot 72 may be used to attach lower foot 72 to a floor or other surface for added stability.

Lower foot 72 is shown in cross-section in Figures 36 (front) and Figure 37 (side).

Lower foot 72 is designed to be fitted into the lower end of cylinder 351 which is fitted to the lower end of second prop part 316 (Figures 19 to 21), or into the lower end of second prop part 416 (Figures 25 and 26) or 516 (Figures 30 to 31).

The detail in Figures 36 and 37 is the same for upper foot 62. Barbs 108 snap fit into aperture 112. Turning now to the embodiment of upper and lower swivel feet in Figures 38 to 43, upper foot 162 is shown is top view in Figure 38 and in front elevation in Figure 39. Upper foot 162 is designed to be fitted into the upper end of cylinder 30, as shown in Figures 23 and 24 or the upper end of first prop part 414 (Figures 25 and 26). Upper foot 162 has a flat, load-bearing surface 202 on a body 205, for contact with and support to a panel or the like. As shown in Figure 38, load bearing surface 202 has four apertures 204 (only one is labelled), in which screws or other attachment means may be inserted, if it is desired to temporarily attach prop assembly 510 to a panel or other building component. This can facilitate manoeuvring of a panel or similar into position during construction and holding it in place until permanent fixing has occurred. Or the panel or other building component can be moved from one location to another, as desired. Once the panel or other building component is permanently fixed in position, the screws or other attachments means may be removed from apertures 204 and prop assembly 510 is available for use elsewhere. Upper foot 162 is designed so that it can pivot around pivot point 206. This enables the construction prop assembly to support a panel or similar which is vertical or at an angle between vertical and horizontal, without load bearing surface 202 being perpendicular to the rest of prop assembly 510. For example, prop assembly 510 may be used to support a vertical panel, load bearing surface 202 being in a vertical position, attached to the vertical panel or merely supporting it, while the rest of prop assembly 510 is at an angle of up to about 60 degrees to the vertical panel. Prop assembly 510 may be used in a horizontal configuration, of course, to support a vertical building component.

Cap 208 is designed with a flange at each end to snap into bracket 209 and body 205 to secure them together. Figures 42 and 43 show details of cap 208 in cross-section. Retaining screw 207 (see especially Figure 43) may be removed to allow the sub-assembly which includes bracket 209, body 205 and pivot point 206 to be removed and replaced in case of wear or damage.

Lower foot 172 is shown in Figure 40 (front elevation) and Figure 41 (underside plan view). In this embodiment, lower foot 172 is identical to upper foot 162, although the invention is not limited in this respect. If upper foot 162 is identical to lower foot 172, there is greater versatility in being able to replace an upper foot 162 or a lower foot 172 from a reduced inventory of spare parts. The same labels as for upper foot 162 are used for lower foot 172. It will be appreciated that apertures 204 in lower foot 172 may be used to attach lower foot 172 to a floor or other surface for added stability.

Lower foot 172 is shown in cross-section in Figures 42 (front) and Figure 43 (side).

Lower foot 172 is designed to be fitted into the lower end of cylinder 351 which is fitted to the lower end of second prop part 316 (Figures 19 to 21), or into the lower end of second prop part 416 (Figures 25 and 26) or 516 (Figures 30 to 31).

The detail in Figures 42 and 43 is generally the same for upper foot 162, except for added detail as already noted above.

Upper foot 142 is shown in Figures 44 and 45. Upper foot 142 is designed to be fitted into the upper end of cylinder 30 (first embodiment in Figures 1 to 4) or the upper end of first prop part 114 (second embodiment in Figures 5 and 6). Upper foot 142 has load-bearing spiked parts 144, for engaging the roof of a mine, for example, and a flat plate 146.

Like the previous embodiment in Figures 38 to 43, upper foot 142 is held to bracket 209 by cap 208 and can swivel or pivot around pivot point 206, up to about 60 degrees.

If it is desired to replace upper foot 142, upper foot 142 may be removed from the upper end of cylinder 30 or first prop part 114 by removing screws 207, as for lower foot 152 (see Figure 49).

Lower foot 152 is shown in Figures 46 and 47, and in cross-section in Figures 48 and 49. Lower foot 152 is the same as upper foot 142 in this embodiment. Lower foot 152 is designed to be fitted into the lower end of cylinder 51 which is fitted to the lower end of second prop part 16 (first embodiment in Figures 1 to 4), or into the lower end of second prop part 116 (second embodiment in Figures 5 and 6).

Lower foot 152 has load-bearing spiked parts 144 and a flat plate 146. If desired, lower foot 152 may be rubber-backed to prevent slippage.

The embodiment in Figures 50 to 55 shows a fixed upper foot 342 and a fixed lower foot 352, suitable for the embodiments in Figures 1 to 6. In this embodiment, upper foot 342 and lower foot 352 are similar to upper foot 42 and lower foot 52 of the embodiment in Figures 7 to 12, in that they have load-bearing spiked parts 344 and a recess 346. This configuration may avoid moisture and debris being trapped between each of upper foot 342 and lower foot 352 and the surfaces they contact.

However, in contrast to the embodiment in Figures 7 to 12, each of upper foot 342 and lower foot 352 is secured in sub-assembly 360, similarly to that in the embodiments in Figures 38 to 49. Sub-assembly 360, best seen in Figures 54 ad 55, is held within the relevant prop part by a pair of screws 207. Once those screws are removed, sub-assembly 360 together with body 305 may be replaced if damaged or worn. The replacing unit may be identical to that removed, or it may be the swivel foot shown in Figures 48 and 49.

Figures 56 to 61 show an embodiment having an upper engaging spike 442 and a lower engaging spike 452, suitable for the embodiments in Figures 1 to 6, for example.

Like the previous embodiment, each of upper engaging spike 442 and lower engaging spike 452 is retained in the relevant prop part by a pair of screws 207, engaging sub- assembly 360, which in the current embodiment includes threaded screw spike 370. Once those screws 207 are removed, sub-assembly 360 together with screw spike 370 may be replaced if damaged or worn. The replacing unit may be identical to that removed, or it may be the swivel foot shown in Figures 48 and 49 or the fixed foot shown in Figures 50 to 55.

INDUSTRIAL APPLICABILITY

It will be appreciated that the invention in its various embodiments represents a significant advance in the art, providing greater versatility while reducing time and labour in installing and removing props, for various applications, such as mining, construction and/or rescue.