FIELD OF INVENTION The present invention relates to an elevator arrangement for a stairway, said arrangement comprising a load supporting platform and a guide arrangement which enables the platform to be moved up and downs the stairway, wherein the guide arrangement includes at least one guide rail and a wheeled guide element which can be connected to the platform by means of a carrier element and which is adapted for movement along the guide rail, wherein the guide rail is adapted to be disposed along at least a part of said stairway and to essentially follow the slope thereof, and wherein the platform is associated with a drive arrangement that includes an hydraulic or pneumatic piston-cylinder device associated with a pressure source for moving the platform along the guide rail.

An elevator arrangement of this kind is known from CA-A-1 266 448. The elevator arrangement described in this prior publication is adapted for wheelchairs and includes a horizontally orientated platform which can be moved up and down the stairway along rails provided on respective sides of said stairway. The platform includes arms that carry circular-cylindrical wheels which run in guide rails of rectangular cross-sectional shape. It is necessary for the frame to be given a thick construction in order to be able to manage the load to which it is subjected. For this reason, a cavity that can accommodate the frame is provided in the floor at the foot of the stairway.

Another wheelchair elevator arrangement is known from US-A-4 438 830.

Other elevator arrangements installed in straight stairway comprise a load supporting platform which is adapted to be driven up and down the stairway along a conveyor rail fixedly mounted by the side of the stairway. The construction is

expensive in manufacture and is normally electrically operated and therewith space consuming, particularly when it shall be used for heavy transports, such as wheelchair-bound persons. The construction also constitutes a troublesome obstacle for other transports up and down the stairway, despite the fact that the platform can be folded up against one wall.

Consequently, it is still a usual practice for goods in the form of beer crates, waste, garbage and like materials to be transported manually from the basement floor to the ground floor in restaurants and commercial premises, for instance, often resulting in serious back injuries to the people concerned, particularly in the case of deliveries to and from restaurants and stores, which are often carried out under great pressure with respect to time. Trolleys, wheeled rubbish bins and like devices can only be transported in such stairways with great difficulty, as stairways of this kind are normally both narrow and confined.

Should the elevator arrangement according to CA-A-1 266 448 be used to transport heavy goods, problems will occur if the goods are not positioned centrally on the platform, as this would result in a different torque load on the wheels in the guide rail and therewith possibly cause the wheels running in the rail to become jammed or stuck therein.

The object of the present invention is to eliminate this drawback.

SUMMARY OF THE INVENTION This object has been achieved with an elevator arrangement of the kind defined in the introduction, by providing said arrangement with a guide arrangement that includes means for preventing the platform from fastening in an undesired position.

This enables heavy goods to be transported on the platform, even when the goods are not positioned centrally thereon.

Said means will suitably include at least one longitudinally extending angled guide section along the guide rail and at least one ring-shaped bevel on the rolling surface of said wheels, said guide section and said bevel being adapted to coact with one another. This prevents the wheels from becoming jammed in the guide rail.

The wheels are preferably mounted in pairs to form a bogey that includes a common axle about which the wheels can rotate, wherein said ring-shaped bevels are provided on the rolling surfaces of respective wheels, and wherein said guide rail includes two longitudinally extending and angled guide sections for coaction with the ring-shaped bevels on respective wheels. This results in greater stability, which, in turn, lowers the risk of the wheels jamming in the guide rail to an even greater extent.

The longitudinally extending guide sections will preferably extend on respective sides of the boggy wheel pairs, transversely to said axle. This reduces the risk of wheel jamming in several directions.

The load carrying platform has beneficially two generally parallel sides, of which one is positioned adjacent the guide rail, wherein the platform includes at least one carrier arm which is angled relative to the platform and adapted to extend parallel with the guide rail. The carrier arm includes at least two mutually similar and mutually spaced carrier elements, wherewith two bogeys are connected to respective carrier elements. This results in distribution of loads and torque, therewith further reducing the risk of the wheels jamming in the guide rail.

The piston-cylinder device will preferably include a piston rod that is connected to said guide element via a force transmission element that runs over guide rollers.

The guide rail will suitably comprise a part of a housing that delimits a guide element accommodating space and a space for accommodating said hydraulic or

pneumatic cylinder. All power transmission from the cylinder will thereby take place in a single plane, therewith avoiding torque that originates from such force transmission and therewith further avoiding wheel jamming.

The guide arrangement will preferably include two such guide rails disposed parallel with one another on their respective sides of the platform. This results in force symmetry therewith reducing torque in the guide arrangement and consequently avoiding wheel jamming to a still greater extent.

In addition, or alternatively, the guide arrangement includes a first further guide rail disposed essentially above the first-mentioned guide rail, and a second further guide rail disposed essentially below said first-mentioned guide rail, said first and said second further guide rails being disposed parallel with the first-mentioned guide rail, and the guide arrangement includes at least one upper wheel for movement along said first further guide rail, and a second wheel for movement along said second further guide rail, wherewith the rotational axes of said upper and lower wheels respectively are perpendicular to the rotational axis of the guide element wheel.

The platform is preferably a one-piece structure and has a thickness of 10-20 mm.

This obviates the need of providing the floor with a platform accommodating cavity at the foot of the stairway.

The platform is suitably a one-piece structure having a thickness of 12 mm. This thickness is an optimal thickness for a load of 600 kg.

Respective carrying elements will preferably include means for adjusting the height and angle of the platform. This reduces the accuracy required when installing the guide rails, therewith enabling installation to be effected relatively quickly.

DRAWING SUMMARY The present invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 is a perspective view of an elevator arrangement according to a first embodiment that includes a carrier arm; Figure 2 is a sectional view taken on the line II-II in Figure 1; Figure 3 is a sectional view taken on the line III-III in Figure 2 and showing a carrier element, among other things; Figure 4a is a view of the carrier element shown in Figure 1 from above; Figure 4b illustrates a carrier element connecting device; Figure 5a illustrates an alternative carrier arm; Figure 5b is a sectional view taken on the line VB-VB in Figure 5a; Figure 6 is a perspective view of a second embodiment of an inventive elevator arrangement; Figure 7 is a perspective view of a third embodiment of an inventive elevator arrangement; and Figure 8 is a sectional view taken on the line VIII-VIII in Figure 7 and seen obliquely from above.

DETAILED DESCRIPTION Figure 1 illustrates a first embodiment of an elevator arrangement 2 according to the invention. A housing 4 accommodates a guide arrangement 6 that includes a guide rail 8 mounted on one side of a stairway 10. The housing 4 may either be secured to a wall (not shown) or to vertical posts or braces (not shown).

The elevator arrangement also includes a load carrying platform 12 which includes a carrier arm 14 that extends parallel with the housing 4, i. e. parallel with the guide rail 8. Also housed in the housing 4 is a drive arrangement in the form of an hydraulic piston-cylinder device 16 connected to a hydraulic pump 18 via conduits 20a, 20b, for movement of the platform 12 up and down the stairway 10.

Figure 2 is a cross-sectional view of the housing 4 and shows an elevator arrangement 2 according to a second embodiment of the invention. The piston- cylinder device 16 is accommodated in an upper space 22, with respective ends of the cylinder connected to the conduits 20a, 20b. A piston rod 24 extends upwardly along the housing 4, from the upper end of the cylinder. One end 28 of a chain 26 is connected to the upper end of the housing. The chain 26 runs around a guide roller 30 in the form of a toothed wheel carried on the upper end of the piston rod 24. The chain 26 also runs around a further guide roller 32 in the form of a toothed wheel carried at the upper end of said housing.

The bottom space 34 in the housing 4 accommodates bottom and top carrier elements 36a, 36b, which are fixedly disposed in said carrier arm 14. Each carrier element 36a, 36b includes a guide element 38 that coacts with the bottom space 34 of the housing 4, said bottom space functioning to form the guide rail 8. The upper end of the upper carrier element 36b is connected to the other end 40 of the chain 26.

As the piston rod 24 of the cylinder 16 pulls on the chain 26, the chain is cause to run over the toothed wheels 30, 32 and the pulling force is transmitted to the carrier arm 14, causing the platform 12 to move from a bottom limit position to a top limit position, i. e. from the foot of the stairway to its top.

When wishing to move the platform 12 from the upper limit position to the lower limit position, the cylinder piston rod 24 is caused to move upwards in the longitudinal direction of the cylinder.

Figure 3 is a cross-sectional view of the housing 4, which is an aluminium profile in the illustrated case. The guide element 8 forms the bottom space 34 in which the guide element 38 is accommodated, by means of a floor 42, a lower and an upper projection 44,46 that together define a longitudinally extending slot 47, an inner wall 48 and a roof 50. The guide element 38 includes a pair of wheels 52,54 that form a bogey 55 with a common axle A-A. The wheels 52,54 are adapted to roll on either the floor 42 or on the roof 50 depending on the torque exerted on the carrier arm 14 by the load carried on the platform 12. The lower and the upper projection 44,46 prevent the wheel 54 from sliding off the floor 42 through the slot 47.

In order to prevent the wheels 52,54 becoming jammed against the wall 48 and the projections 44,46, said projections are provided with an angled section or surface 56 at their junction with the roof 50 and the floor 42 respectively. The wheels 52,54 are provided with a bevel 58 corresponding to the angled sections 56, to the same end.

The piston-cylinder device 16 is accommodated in the upper space 22. The cylinder is covered by a removable cover 60 along the full length of the housing 4.

Figure 4a shows the upper carrier element 36b from above. It will be seen that the carrier element 36b includes two inner wheels 52, which are adapted to be disposed proximal to the wall 48, and two outer wheels 54, which are adapted to be disposed

proximal to the projections 44,46. The carrier element also includes a spherical bearing 62 and a fastener device 63 for said other end 40 of the chain 26.

Figure 4b illustrates a connector 64 which includes an eccentrically disposed pin 66 adapted for insertion into the spherical bearing 62. The connector 64 also includes a threaded hole 68 for receiving a screw for connection of the carrier element 36a, 36b to the carrier arm 14.

The carrier arm 14 is connected to two carrier elements 36a, 36b by means of a respective connector 64. Rotation of the connector 64 causes the eccentric pin to raise or lower the carrier arm 14 to a corresponding degree. This enables the height and the angle of the platform to be adjusted relative to the floor, at either end of the stairway 10.

Figure 5a illustrates an alternative carrier arm 14"connected to the platform 12, two carrier elements 36a, 36b, and to an upper support element 70 and a lower support element 72.

Figure 5b is a cross-sectional view of the housing 4 and a cross-sectional view of a hollow upper guide rail 74 and a hollow lower guide rail 76. A wheel or a wheel pair forming a bogey of the upper support element 70 runs in the upper guide rail 74, while a wheel or a wheel pair forming a bogey of the lower support element 72 runs in the lower guide rail 76.

The wheels of respective support elements 70 and 72 have an axle B-B which extends perpendicular to the axle A-A of the wheels 52,54. This enables torque resulting from loads placed on the platform 12 to be taken-up.

Figure 6 illustrates a second embodiment of the inventive elevator arrangement 2.

This second embodiment coincides with the first embodiment described above in all details with the exception that a housing 4 is provided on both sides of the stairway,

as seen in their longitudinal direction. The platform 12 is provided with two carrier arms 14, each of which is connected to two carrier elements 36a, 36b that are moveable in the bottom space 34 of the carrier arm 14, said space being formed by respective guide elements 8.

Only one of the housings 4 is provided with a hydraulic piston-cylinder device.

In the case of this embodiment, the alternative carrier arm 14'may be arranged on the carrier platform, in which case the guide rails 74,76 will be disposed above and beneath respective housings 4.

Figure 7 illustrates a third embodiment of an elevator arrangement 2 according to the invention. This third embodiment differs from the second embodiment by virtue of an hydraulic piston-cylinder device mounted in respective housings 4.

The alternative carrier arm 14'may, of course, also be disposed on the platform 12 in accordance with this embodiment, in which case the guide rails 74,76 will be arranged as in the second embodiment.

Figure 8 is a perspective, cross-sectional view of the left housing 4 shown in Figure 7.

The elevator arrangement is constructed so that when the platform is located in its lowermost position, it will rest flat on the lowermost plane and, owing to the thinness of the platform, will not obstruct the stairway. The platform 12 has a thickness of between 10 and 20 mm Tests have shown that a steel plate produced as a one-piece structure and given a thickness of 12 mm is able to manage loads of about 600 kg.

It will naturally understood that the piston-cylinder device may alternativelye'a pneumatic device.

The aforedescribed chain may be replaced with a rope or a belt, in which case the toothed wheels will be replaced with rollers.