Hydraulic Drive for Operating an Elevator

This invention relates generally to elevators, and more specifically to a hydraulic drive for operating an elevator and disposed inside the elevator shaft on one side of the load-lifting member of the elevator.

Conventional hydraulic drive means in an elevator shaft for a load-lifting member that is to be lifted to a considerable height comprise a plurality of hydraulic ram cylinders so disposed that the rams become operative in succession. The lengths of the piston rods of the ram cylinders must be so designed that there is no danger of the piston rods bucking under the load. This danger is present in forms of construction in which the ram cylinders are designed jointly to lift the load-lifting member to its maximum height. Frequently this will not be sufficient to meet particular needs. Arrangements in which the hydraulic rams operate in succession are naturally expensive because of the need for the provision of a plurality of such rams, which are costly. Moreover, such drives are of complicated construction. Furthermore, in the event of their being disposed on the side of the load-lifting member, e.g. of an elevator cage, they call for the provision of complicated coupling means for automatically coupling and uncoupling the rams to and from the cage. A hydraulic drive for operating an elevator has already been proposed which comprises a hydraulic cylinder containing two ram pistons connected by an interposed hollow cylindrical member having an external diameter corresponding with the internal diameter of the hydraulic cylinder. This cylindrical member is fitted with a carrier resembling a bracket arm which projects to the outside through an axial slot in the wall of the hydraulic cylinder for carrying the elevator cage. The slot is sealed by a sealing strand which partly embraces the hydraulic pistons and extends through the cylindrical member to permit the carrier arm on the cylindrical member to project through the slot in the hydraulic cylinder. However, in the event of the cage being required to ascend to a major height a pressure-tight seal of the slot in the wall of the hydraulic cylinder is impossible to achieve because of the magnitude of the pressure range, particularly bearing in mind that continuous operation leads to premature wear of the seal.

It is therefore the object of the invention to provide a hydraulic drive for operating an elevator, which permits an elevator cage to be lifted to nearly any height with the aid of only one hydraulic ram.

To attain this object the present invention provides a hydraulic drive for operating an elevator and disposed inside the elevator shaft on one side of the load-lifting member of the elevator, which comprises a hydraulic ram cylinder having two straight cylinder portions connected by a portion forming an arcuate bend, one straight cylinder portion extending up the path of ascent of a load-lifting member and the other straight cylinder portion slidably containing a hydraulic ram piston attached to one end of a universally flexible thrust-transmitting strand of which the other end is attached to a cylindrical body arranged to slide up and down said one straight cylinder portion, said cylindrical body being provided with a carrier arm projecting to the outside through an axial slot in said one straight cylinder portion of supporting the load-lifting member of the elevator.

The invention will now be described by way of example and with reference to the accompanying drawings, in which:

FIG. 1 is a longitudinal section of one embodiment of the proposed drive;

FIG. 2 is a longitudinal section of another embodiment of the invention;

FIG. 3 is a longitudinal section of a third embodiment;

FIG. 4 is a perspective view of one member of the flexible strand;

FIg. 5 is an enlarged cross section taken on the line V -- V of FIG. 3;

FIG. 6 is a longitudinal section of yet another embodiment of the invention, and

FIG. 7 is an enlarged cross section taken on the line VII -- VII of FIG. 6.

With reference to FIG. 1 there is provided a hydraulic drive comprising a U-shaped hydraulic ram cylinder 1 having two straight portions 2 and 3 connected by an arcuate bend 4. The straight portion 2 slidably contains a hydraulic ram piston 5 provided with sealing rings 6. The underside of the hydraulic piston 5 is formed with an extension 7 shaped like a truncated cone. The upper end of the straight portion 2 of the ram cylinder 1 is closed by a cap 8. The latter contains an opening 9 for the passage therethrough of a hydraulic fluid which can be pumped by a pump (not shown) into the working chamber 10 of the hydraulic ram cylinder 1. The thrust of the hydraulic piston 5 is transmitted by a flexible thrust-transmitting strand consisting of a plurality of ball-shaped members 11 which are slidably contained in the interior of the hydraulic ram cylinder 1. The ball-shaped members 11 have a diameter which corresponds to the internal diameter of the hydraulic ram cylinder 1 and are separated by spacers 12 which have an overall diameter that is less than the internal diameter of the hydraulic ram cylinder 1. That is, the strand has a cross-sectional linear dimension effective to be contained between opposing sides of the housing so that axial movement of the piston 5 within the housing 2 effects a corresponding axial movement of a carrier body 14. For the purpose of forming a joint between each two neighboring ball-shaped members 11 each spacer 12 is formed with two spherical sockets 13 each for the reception of part of one of the two neighboring ball-shaped members. The other straight portion 3 of the hydraulic ram cylinder 1 contains the cylindrical carrier body 14 which has an external diameter designed to fit the inside diameter of the straight portion 3 of the hydraulic ram cylinder. On its underside the cylindrical body 14 likewise has an extension 15 shaped like a truncated cone. The free end of each of the two extensions 7 and 15 contains a spherical socket 16 and 17 forming a bearing for the adjoining ball-shaped members 11. All the ball-shaped members 11 are thus associated with the interposed spacers 12 to form a universally flexible thrust-transmitting strand. Attached to the body 14 is a carrier arm 18 which projects from the hydraulic ram cylinder 1 to the outside through an axial slot 19 in the side of the straight portion 3. This carrier arm 18 supports a load-lifting member, e.g. an elevator cage 20, of which only a small portion is actually shown in the drawings. The axial slot 19 extends up the entire height the elevator cage 20 is intended to ascend. The arcuate bend 4 of the hydraulic ram cylinder 1 is contained in a reservoir 21 filled with a lubricant. The walls of the bend 4 of the hydraulic ram cylinder 1 are provided with openings 22 through which the lubricant can enter. Consequently the ball-shaped members 11 and the spacers 12 inside the bend 4 where most of the friction arises are completely immersed in the lubricant.

The described arrangement functions as follows:

Operation of a switch starts up the pump which at once pumps fluid through the opening 9 in the cap 8 of the straight portion 2 of the hydraulic ram cylinder 1 into the working chamber 10. The hydraulic ram piston 5 is forced downwards and through the intermediate chain of ball-shaped members 11 and spacers 12 simultaneously lifts the cylindrical body 14 and thus the elevator cage 20. The lubricant which is entrained escapes through the axial slot 19 in the wall of the straight portion 3 of the hydraulic ram cylinder 1 and is returned into the reservoir 21. The elevator cage 20 descends when fluid is exhausted from the working chamber 10 to allow the piston 5 to be pushed back into its former position by the weight of the cage 20 forcing the cylindrical body 14 downwards and displacing the ball-shaped members 11 and spacers 12 of the flexible strand.

In the embodiment illustrated in FIG. 2 of the drawings the flexible strand has the form of a helical coil spring 23 which is likewise immersed in lubricant in a reservoir 21 which contains the U-bend 4 of the hydraulic ram cylinder 1. One end of the coil spring 23 bears against the hydraulic ram piston 5, whereas the other end bears against the cylindrical carrier body 14.

In the arrangement illustrated in FIGS. 3 to 5 the flexible strand is composed of a train of mutually contacting cylindrical members 24. These are placed with their axes in the horizontal and their lateral ends slidably bearing against the inside of the hydraulic ram cylinder 1, the ends being of convex shape to correspond with the internal cylinder radius. These members 24 each contain a slot 25 and the slots align to enable them slidably to receive two steel ribbons 26 and 27 which abut face to face and fix the relative positions of all the members 24. One end of the two steel ribbons 26 and 27 is fitted into an extension 28 having a part cylindrical rounded face on the underside of a hydraulic ram piston 5, whereas the other ends are fitted into an extension 29 on the underside of a cylindrical carrier body 14. This extension 29 is formed on its underside with a part cylindrical concavity 30. Each member 24 is also formed with a like part cylindrical concavity 31. Each of these concavities forms the bearing surface for the next member 24 and adjacent the ram piston 5 for the spherically rounded extension 28. Moreover, the member 24 which adjoins the extension 29 of the body 14 engages the part cylindrical concavity 30 in the extension 29. In the described manner the members 24 all positively and hingeably interfit from the extension 28 of the hydraulic ram piston 5 to the extension 29 on the cylindrical body 14 and they form a solid flexible strand or ram. Each member 24 also contains a recess 32 normal to the plane of the steel ribbons 26 and 27, this recess being open towards the steel ribbons 26 and 27 as well as towards the external circumference of the member 24. In the arcuate bend 4 of the hydraulic ram cylinder 1 a rail 33 is provided and curved to correspond with the radius of the bend 4. The two ends of the rail are both secured to the inside wall of the hydraulic ram cylinder 1 and inside the reservoir 21 the rail is supported by stays 34. The stays 34 pass through a slot 35 in the wall of the bend 4 of the hydraulic ram cylinder 1. The rail 33 engages the recesses 32 of those members 24 which are in course of being guided through the bend 4, and it thus serves as a slideway for the adjacent steel ribbon 27 as it negotiates the bend. The components of the flexible strand are again lubricated by a lubricant inside a reservoir 21, the lubricant entering the interior of the bend 4 through the slot 35 in its wall.

In the embodiment illustrated in FIGS. 6 and 7 of the drawings cylindrical elements 36 which interfit horizontally are mounted between the steel ribbons 26 and 27 on which the members 24 are strung. Each element 36 contains a part cylindrical concavity 37 which extends along the length of the element, the adjacent cylindrical element 36 engaging this concavity. The elements 36 are thus interfitted in a manner forming a flexible strand or train. The longitudinal edges of the slot 36 in the wall of the bend 4 of the hydraulic ram cylinder 1 are formed with flanges 38 and 39. 40 is a box-shaped tank enclosing the bend 4 and 41 are rollers on axles 42. These axles are mounted in the flanges 38 and 39. The rollers 41 project into the recesses 32 of the nearest cylindrical member 24 and their peripheries bear against the nearest steel ribbon 27. Whe the arrangement is in operation the steel ribbon 27 of the strand passing through the bend 4 makes rolling contact with the rollers 41 and this minimizes the friction experienced in the bend 4 of the hydraulic ram cylinder 1 which is otherwise here greater than elsewhere in the cylinder.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The embodiments are therefore to be considered in all respects as illustrative and not restrictive.