Technical Field

This invention relates to a personnel hoist which can be used by one or more persons who, for example, need to gain access to parts of buildings or equipment disposed above ground level or who may alternatively require a raised platform for other purposes such as for observation or signalling.

Personnel hoists of this kind are known in which the platform is connected to a telescopic mast and the platform is lifted by a wire rope or chain and pulley mechanism which may itself be actuated manually or electrically or by hydraulically actuated piston and cylinder units. Such an arrangement, especially where a wire rope is employed, is prone to wear and accordingly has to be subjected to a careful inspection and maintanence program if a high level of safety is to be maintained in operation. Also, considerable frictional forces arise in the operation of pulley mechanisms. Known personnel hoists are usually constructed so that they can raise the platform only to a maximum predetermined height and they cannot easily be altered to raise the platform to a greater height at a later stage.

Disclosure of Invention.

It is an object of this invention to provide an improved personnel hoist in which the above mentioned disadvantages are overcome or substantially reduced.

According to this invention there is provided a personnel hoist comprising a ground engaging base,

a mast extending upwardly from the base and a platform which is connected to the mast, characterised in that the mast comprises at least two pieces, a rack section being provided on one side of each mast piece and the upper end of a mast piece being adapted to be connected to the lower end of another mast piece in a longitudinally aligned relationship in which the rack sections of the aligned mast pieces form a continuous rack, and the hoist further comprises a support member connected to the platform, a pinion mounted on the support member for engaging the rack sections, means for rotating the pinion, and means for preventing unintentional descent of the platform relative to the mast.

Thus, the platform is lifted by a rack and pinion mechanism and such a mechanism is not prone to wear to the same degree as a wire rope or chain and pulley mechanism. By forming the mast from at least two pieces, the height to which the platform can be raised may be increased by adding further mast pieces.

Preferably, the means for rotating the pinion comprises at least one handle connected to the pinion and manually rotatable by a user standing on the platform of the hoist. By providing at least one handle, the hoist can be operated readily by the user and this removes the necessity to provide electrical or hydraulic apparatus to operate the hoist.

Preferably, each mast piece is formed as a tube of generally square or rectangular configuration, and said mast includes at least one connecting member for connecting each pair of adjoining mast pieces together. By forming each mast piece as a tube, a safe and rigid structure is obtained.

Brief Description of the Drawings.

This invention will now be described in more detail, by way of example, with reference to the drawings in which: Figure 1 is a perspective view of the lower part of a personnel hoist embodying this invention;

Figure 2 is a perspective view of the lower part of the hoist with the legs in a folded position;

Figure 3 is perspective view of the middle part of the hoist;

Figure 4 is horizontal sectional view of the hoist through a pinion forming part of the hoist mechanism;

Figure 5 is a fragmentary side view of the hoist, partly in section on the line 5-5 of Figure 4; and

Figure 6 is a fragmentary sectional view on the line 6-6 of Figure 5.

Best Mode of Carrying out the Invention

Referring now to Figure 1, there is shown the lower part of a personnel hoist. The hoist includes a base generally indicated by the reference number 10 from which a mast 11 extends upwardly. The base is provided with four legs 12, 13, 14 and 15, which are provided with ground engaging wheels 16. Each of the legs 12 to 15 is provided with an extension 17. Each extension 17 carries a foot 18 which can be adjusted by a screwing action in order that its lower end can engage the ground. The extension pieces 17 can be held in their extended positions by pins 20. With each of the extensions 17 in their extended positions and with all the feet 18 engaging the ground, the base 10 provides a very stable mounting for the mast 11.

The leg 12 is rigidly secured to the mast 11 whilst the legs 15 and 17 are connected to mast 11 by hinges 22. The legs 15 and 17 are also connected to stays 23, the upper ends of which are connected to mast 11 by hinges 24. The legs 15 and 17 are also connected to the leg 12 by a pair of stays 25, 26, which are hinged in the middle. The stays 25, 26 can be held in their open position by a tube 28. The tube 28 for the stay 26 is omitted in order to show the hinge at its middle. The leg 12 is connected to the mast 11 by a stay 29. The leg 14 is connected to the mast 11 by a hinge, not shown, which permits this leg either to be held rigidly in the open position or folded under the mast 11. As shown in Figure 2, the legs 12 to 15 can be arranged in a folded manner for storage or transport of the hoist.

Referring now to Figure 3, there is shown the middle part of the hoist together with a platform or cage, generally indicated by the reference numeral 30, in which the user of the hoist can stand. On one side, the platform 30 is connected to a box section 31. At its upper end, the box section 31 is connected to the operating mechanism for the hoist and which is generally indicated by reference numeral 32. The operating mechanism 32 will be described in more detail below.

Referring especially to Figures 1, 3, 4 and 5, the mast is formed from a number of mast pieces. In a particularly convenient arrangement the mast is formed from five mast pieces but, in the present example, the mast is formed from three mast pieces and these are denoted by reference numerals lla_, IIJD and lie. Each mast piece is conveniently 1.1 metres long. Each mast piece is formed as an aluminum extrusion and is formed as a tube of generally

rectangular configuration in cross-section. This configuration together with an appropriate choice of dimensions and wall thickness provides the mast pieces with a high moment of inertia. Consequently, the mast 11 has a high resistance to torsional and bending forces with the result that the platform 30 is held in a very stable manner even when it is at the top of the mast 11.

Each pair of mast pieces is connected together by a pair of connecting members. Thus, in Figure 1, the mast pieces lla_ and lib are connected together by a pair of connecting members 40 and 41 and, in Figure 3, the mast pieces llb_ and ll£ are held together by a pair of connecting members 42 and 43. The connecting members are received inside the mast pieces and, prior to assembling the mast, each connecting member is secured to one mast piece by a screw. Thus, in Figure 3, the connecting member 43 is secured to the mast piece lie by a screw 44 having a U-shaped handle 45 and the connecting member 42 is connected to the mast piece llb_ by a screw 46 having a U-shaped handle 47. In order to aid assembly of the mast pieces, one connecting member of each pair is slightly longer than the other. After the mast pieces have been assembled the connecting members are secured in position as will now be described with reference to mast pieces llb_ and lie.

Referring to Figure 4, two opposite sides of mast piece llb_ are provided with trough-shaped recesses 47 and 48 having inwardly convergent sides. Each of the connecting members 47 and 48 also has a trough-shaped recess with inwardly convergent sides and the configuration is such that the convergent sides of a connecting member can engage the convergent sides of a respective trough-shaped recess

in mast piece llb_. Connecting member 42 has an internal nut 49 which receives the screw 46 and connecting member 43 has an internal nut 50 which receives a hardened steel -insert 51. Prior to assembly of the mast pieces llb_ and ll£, the screw 46 is positioned so that connecting member 43 can enter mast piece lib. After the mast pieces are in position, screw 46 is rotated so that its end engages the insert 51 and causes the connecting members 42 and 43 to be urged outwardly into engagement with the walls of mast piece 11]D. When the screw 46 has been tightened sufficiently, the handle 47 will be in a vertical orientation, and consequently received in recess 48, and so will not interfere with passage of the platform 30.

One side of mast piece llb_ is provided with a recess 55 having a pair of retaining lips 56. A rack section 57 is secured in recess 55 by a pair of screws 59 at each end of the mast section. The rack piece 57 is formed from a moulded synthetic resin material such as nylon. When the mast pieces are assembled together, the rack sections form a continuous rack. The rack sections are carefully shaped so that .there will be no interruption to the regularity of the teeth in the part of the rack section which bridges the joint between two mast pieces.

The operating mechanism 32 will now be described.

Referring to Figures 4 and 5, a pair of side plates 61 and 62, and a pair of spacer members 63, 64 are connected to the box section 31 by nut and bolt fasteners 65. The other ends of plates 61 and 62 are connected together by a U-shaped end member 66 held

in position by nut and bolt fastenings 67.

A shaft 70 is rotatably mounted in plates 61 and 62 by bearings 71 held in support members 72 and shaft 70 is located axially by a pair of spacer members 73. The shaft 70 carries a pinion 74 which engages rack section 57. The diameter of shaft 70 on each side of pinion 74 is identical to the pitch circle diameter of pinion 74 and these parts of shaft 70 engage the face of mast piece llb_ on each side of recess 55 thereby acting as rollers.

A handle 80 is connected to one end of shaft 70 by a connecting plate 81 and bolt 82. A handle 83 together with a pulley 84 is connected to the other end in a manner to be described below.

The end of shaft 70 adjacent handle 83 is provided with a screw thread which is engaged by a stepped braking member 85 and a further braking member 86. A toothed wheel 87 and a pair of annular brake pads 88 are rotatably mounted on the smaller diameter portion of braking member 85. The braking member 86 is secured to the handle 83 of pulley 84 by bolts 89.

As shown in Figures 5 and 6, there is also provided a pawl 90 pivotally mounted on side plate 62. The pawl 90 has a tooth 91 which is biased into engagement with the toothed wheel 87 by a torsion spring 92. Under the action of spring 92, pawl 90 permits the toothed wheel 87 to rotate in one direction only. The pawl 90 is provided with a second tooth 93 which rides over the teeth of wheel 87. If spring 92 fails, the tooth 93 ensures that tooth 91 engages the teeth of wheel 87.

Braking members 85 and 86, wheel 87, pads 88 and pawl 90 together from a braking mechanism and this mechanism is enclosed by a cover 94. A pair of rollers 100 and 101 are rotatably mounted at vertically spaced positions on box section 31. As shown in Figure 4, the roller 100 is mounted on a hollow shaft 102 held in position by a pair of bolts 103 and roller 101 is mounted in a similar manner. Apertures are cut in box section 31 through which rollers 100 and 101 protrude. These rollers engage a rectangular recess in a side of mast 11, the recess in mast piece llb_ being indicated by reference numeral 105. The roller 101 keeps the pinion 74 in engagement with the rack and the roller 101 is kept in contact with the mast 11 by the weight of the user standing on platform 30.

In operation, when the user desires to ascend, he rotates the handles 80 and 83 in the direction indicated by arrow A in Figure 6. This causes the braking members 85 and 86, wheel 87 and pads 88 to be pressed firmly together and so shaft 70 rotates with handles 80 and 83 and so the platform 30 ascends. During ascent, the pawl 90 permits rotation of wheel 87. When the user releases handles 80 and 83, pawl 90 prevents rotation of wheel 87 and the action of the screw thread on shaft 70 ensures that braking members 85 and 86, wheel 87 and pads 88 are held firmly together. Consequently, unintentional descent of platform 30 is prevented. When the user wishes to descend, he rotates the handles 80 and 83 in the direction indicated by arrow B in Figure 5, The action of the screw thread on shaft 70 releases the force with which the members 85, 86, wheel 87 and pads 88 are held together thereby permitting descent of platform 30.

If the user is incapacitated, the platform may be operated from the ground by passing a rope over pulley wheel 84.

When assembling the hoist, the legs of the base 10 are opened out and the platform 30 is positioned on mast piece lla_. The user then positions as many mast pieces as may be required on platform 30 and operates handles 80 and 83 until the hoisting mechanism 83 approaches the top of mast piece 11a. At this stage, the user connects the next mast piece to the top of mast piece 11a and operates the handles until he reaches the top of this next mast piece. Assembly is continued in this fashion until all desired mast pieces have been connected together. Whilst assembling the hoist, the mast pieces can, if desired, be stored in some suitable 'container or brackets connected to platform 30.

As above described the personnel hoist is relatively inexpensive to construct and it provides a safe and strong structure for lifting a platform or cage to any desired height. Although in the embodiment described above, the pinion 74 is operated by the handles 80 and 83, but, if desired, a power operated mechanism may be supplied for rotating this pinion.