GB2073111A - Stair climbing trucks - Google Patents

Abstract

A stair climbing truck has a clutch means on the spider axis for resisting rotation of the axis when moving downstairs. The resistance can be varied to allow for different truck weights. In a preferred embodiment, a one way clutch device is incorporated in the clutch means so as to resist the axis rotation when moving downstairs but not when moving upstairs. Also means are provided for locking the spiders relative to the track frame for travelling on level ground. <IMAGE>

Description

SPECIFICATION Stairclimbing trucks FIELD OF INVENTION: The invention relates to stairclimbing trucks which are trucks having grips at the top for an operator and wheels at the bottom to enable the truck to be pushed along by an operator.

BACKGROUND OF INVENTION: Stairclimbing trucks incorporate sets of individually rotatable wheels mounted on a spider or star-like mounting which can rotate the.

wheels bodily to enable the truck to be negotiated up or down stairs by a tumbiing action of the wheels. The British Patent Specification 1,032,136 discloses a means for locking the spider against rotation so that the truck can be supported on one pair of wheels on a level surface for ease of turning.

The trucks can be difficult to control on stairs when carrying a heavy load.

It is the object of the invention to make stair climber trucks safer in use.

SUMMARY OF INVENTION: According to the invention there is provided a stair climbing truck having a frame, a pair of spiders, each mounting a set of rotatable wheels and being themselves rotatable about an axis fixed with respect to the frame, clutch means for resisting rotation of the spiders about the axis and means for varying the resistance provided by the clutch.

The means for varying the resistance is most conveniently and simply a manually adjustable arrangement but an automatic arrangement, responsible to the load carried by the truck is also conceivable.

The clutch means thus restrains the tumbling action of the wheels and enables the operator to descend the stairs more safely. By varying the resistance, the clutch can function in this manner for a wide variety of truck weights.

Although the clutch means could be in any form which imparts resistance and be a hydraulic friction clutch, the preferred clutch is a friction clutch which can be constructed simply and can be adjusted to provide a wide range of resistances to rotation. With a friction clutch, the resistance can be controlled conveniently by a manually operable device. To reduce trial and error in the friction clutch adjustment conveniently the manually operable device is associated with means to give an indication of the friction applied by the friction clutch. The indication means may be a scale indicating the friction clutch adjustment position.

Most advantageously the clutch means include a one-way clutch mechanism for imparting the resistance to the rotation of the spiders when moving the truck downstairs but not when moving the truck upstairs. In this way, stairs can be ascended whilst the friction clutch is ineffective.

At the same time should the operator wish to turn back downstairs, the resistance will be re-applied to the spiders immediately without requiring any intermediate clutch adjustment. Suitably the one way clutch mechanism includes pawl means for engaging to impart resistance after less than 60O of rotation of the spider axis to make the resistance effective after a small downstairs movement of the truck.

The clutch means can be conveniently and compactly constructed so as not to foul the steps of the stairs by constructing it to include a first annular body rotatable conjointly with the spider axis, a second annular body surrounding the first for locking with a first body in one direction of rotation only, a brake lining surrounding the second annular body and a brake band surrounding the lining and adjustable to clamp the lining against the second body to varying extents.

The brake band may be adjustable to lock the second body in position and enable the truck to be supported on a level surface. However an operator would then have to adjust the clutch means repeatedly whenever descending a staircase.

Preferably therefore a means is provided for locking the spiders with respect to the frame which means engages the spider mountings and the clutch means is mounted directly on the spider axis. The locking means can be independantly operated. The spiders may be locked by fixing the spider axis but a stronger construction, still leaving space for the clutch means, results by locking the spider mountings directly on each side of the truck.

Whilst the invention is mainly concerned with improved safety by the use of clutch means, the locking means acting on the spider mountings, may be used in the absence of any clutch means and forms a separate inventive aspect in that case.

DRAWINGS: Figure 1 shows a perspective view of a stairclimber truck of the invention; Figure 2 shows a partsection of a clutch mechanism of the truck Figure 1; Figure 3 shows a part view of means for locking the wheel mounting; and Figure 4 shows a schematic view of part of the truck on a staircase.

DESCRIPTION OF SPECIFIC EMBODIMENT: With reference to Figure 1, a truck 2 for climbing stairs has a frame 4 with a wheel assembly indicated at 6 below and grips 8 at the top. The frame 4 pivotably supports a load platform 10. The wheel assembly 6 includes a spider axis 12 retained in blocks 1 4 (See Figure 3) on the frame 4; spiders 1 6 rotatable conjointly with the axis 1 2 and individually rotatable wheels 1 8 turnable about three equidistant axes formed by the spiders 1 6.

The truck 2 further includes clutch means generally indicated at 20 controllable by a rod 22 and a knob 24, the rod 22 being supported by a bracket 26 on the frame 4. The bracket 26 may carry a scale co-operating with a pointer on the rod 22 to indicate the extent to which the rod 22 has been turned.

The truck further includes locking means generally indicated at 60 with brackets 62 on the frame 4, posts 64 slidably retained in the brackets 62, a transverse rod interconnecting the posts 64 and lock elements 68, U-shaped in section, on the lower ends of the posts 64 to engage the spider ends as will be explained.

With reference to Figure 2 the clutch means 20 includes a first annular body 30 joined by a grub screvy 32 to the spider axis 12 and located inside a second annular body 34 or sleeve. The body 30 has recesses 36 for two pawls 38 pivoted on pins 40 and biased onwards by springs 42. The sleeve 34 has three recesses 44 which can be engaged by one of the pawls 38. Thus the body 30 can lock to the sleeve 34 in any one of six positions spaced mutually at 60 .

The sleeve 34 is surrounded by a brake band 48 having a lining 46 lying against the outside of the sleeve 34. Lugs 50 are fastened to the end of the band, one upper lug sliding with respect to the control rod 22, the other lower lug threadingly engaging the rod 22. The upper lug 50 has a pin 52 engaging in a reaction bracket 54 (See Figure 3) fast to the frame 4. Thus when the control rod 22 is turned, the lower lug 50 is screwed up or down whilst the upper lug 50 remains in place so increasing or decreasing the friction between the lining 46 and the sleeve 34.

The sleeve 34 has holes 56. Cover plates 58 can thus be located by screws 59 on either side of the sleeve for shielding the working parts of the clutch means 20. With reference to Figure 4, when the truck 2 is being moved downward in the direction of arrow A, the spider wheels 1 8 tumble clockwise causing one of the pawls 38 to engage in a recess 44 after a movement of no more than 60 . The sleeve 34 from then on rotates bodily with the spider axis 1 2 and is frictioned to the required degree by the brake band 48 and lining 46. If the truck is reversed and ascends in the direction of Arrow B, the pawls 38 will move past the recesses 44 and the axis 12 will turn without being frictioned appreciably by the lining 46, as the sleeve 34 does not now rotate.

With reference to Figure 3, whatever the friction between the lining 46 and the sleeve 34, the spider 1 6 can be locked with respect to the frame 4 by lowering the elements 68 until they slide over the ends of one of the spider legs as shown. The truck 2 can thus be rolled over a level surface on one pair of wheels instead of two pairs as would be the case if the spider axis were free to rotate.

Catch or equivalent devices can be used to hold the elements either in a high or low position.

It can be seen how an operator can easily move the truck on a level surface as it is only supported on one pair of wheels, whilst at the same time a safety friction clutch mechanism is brought into operation when the locking elements are lifted.

The clutch mechanism does not provide any additional restriction on moving upwards on a staircase. The truck can be controlled easily and is relatively simple and compact construction.

Claims (12)

1. Stair climbing truck having a frame, a pair of spiders, each mounting a set of rotatable wheels, and being themselves rotatable about an axis fixed with respect to the frame, clutch means for resisting rotation of the spiders about the axis and means for varying the resistance provided by the clutch.

2. Truck according to claim 1, in which the clutch means include a friction clutch and the means for varying the resistance include a manually operable device for varying the friction.

3. Truck according to claim 2, in which the manually operable device is associated with means to give an indication of the friction applied by the friction clutch.

4. Truck according to any of the preceding claims in which the clutch means include a oneway clutch mechanism for imparting the resistance to the rotation of the spiders when moving the truck downstairs but not when moving the truck upstairs.

5. Truck according to claim 4 in which the one way clutch mechanism includes pawl means for engaging to impart resistance after less than 60 of rotation of the spider axis.

6. Truck according to claim 4 or claim 5, in which the clutch means include a first annular body rotatable conjointly with the spider axis, a second annular body surrounding the first for locking with the first body in one direction of rotation only, a brake lining surrounding the second annular body and a brake band surrounding the lining and adjustable to clamp the lining against the second body to varying extents.

7. Truck according to claim 6, in which the brake band is adjustable to lock the second body in position.

8. Truck according to any of the preceding claims in which a means is provided for locking the spiders with respect to the frame which means engages the spider mountings and the clutch means is mounted directly on the spider axis.

9. Stair climbing truck having a frame, a pair of spiders mounting each a set of wheels and rotatable bodily about an axis fixed with rnspectto the frame and locking means for engaging the spider mountings eccentrically to lock the spiders into position.

10. Truck according to claim 9 in which the spider axis carries a clutch means for resisting rotation of the spiders spearately of the locking of the spiders by the locking means and means are provided for varying the extent of resistance to rotation.

11. Truck according to claim 10 in which the clutch means include a one-way clutch mechanism for imparting the resistance to the rotation of the spiders when moving the truck downstairs but not when moving the truck upstairs

12. Stair climbing truck substantially as shown in and described with reference to the Figures.