ARRANGEMENT FOR A HYDRAULIC LIFTING TABLE

Abstract: Arrangement for a hydraulic lifting table of the scissor type. This has two pairs of mutually attached scissor arms (1a, 1b; 2a, 2b), which at their ends are connected by means of pivots and rollers to a lower frame section (3) and an upper table section (4). The scissor arms (1a, 1b; 2a, 2b) are mutually and operatively connected to the pivotable connection (5) to the frame section (3). The lifting table comprises a power transmission arrangement (7, 8, 9, 11) for raising and lowering the table section (4). The invention is characterized in that the power transmission arrangement (7, 8, 9, 11) contains for each pair of scissor arms (1a, 1b; 2a, 2b) a hydraulic cylinder (7a; 7b) pivotally mounted at said connection (5). The piston rod (8a, 8b) of the cylinder is so arranged as to interact via rollers (9a, 9b, 9c) with guide curves (11a, 11b, 11c) arranged in conjunction with the common bearing shaft (1c, 2c) for the scissor arms (1a, 1b; 2a, 2b) and operatively connected to the respective scissor arm (1a, 1b; 2a, 2b).

Description: Arrangement for a hydraulic lifting table The present invention relates to an arrangement for a hydraulic lifting table of the scissor type with two pairs of mutually 5J attached scissor arms, which at their ends are connected by means of pivots and rollers to a lower frame section and an upper table section, and are mutually and operatively connected to the pivotable connection, comprising a power transmission arrangement for raising and lowering the table section. 10 In the case of those lifting tables which are intended to be used, for example in conjunction with a hand-operated truck or in vehicle workshops, for raising a vehicle to a comfortable working height for repair work to be carried out, it is of value 15 for the lifting table to exhibit the minimum height possible. This is determined partly by the dimensions of the power transmission arrangement, since this must be enclosed by the table in its collapsed position, and partly by the mechanical construction of the table with regard to its intended carrying 20 capacity and stability. On the other hand the lifting capacity of the table is determined by the maximum pressure available from the power transmission arrangement. In a previously disclosed lifting table of the aforementioned 25 kind, the power transmission arrangement is pivotally secured to the frame section and is so arranged, on the lifting table being raised, as to exert a separating effect on guide curves which, at the pivotal connection to the frame section, are operatively connected to it and to one of the scissor arms of each pair of 30." scissor arms. Since a turning moment is generated at one end of the respective " - scissor arm in this design, the scissor arm concerned must be designed to withstand the resulting stress along its whole 35. ' length. This means that the lifting table, as a consequence of the dimensions of the scissor arm, is given a minimum height which is unacceptably large for many applications. One object of the present invention is to make available a hydraulic lifting table in which the above—mentioned disadvantages have been eliminated, which is made possible by the combination of the following distinguishing features: the power transmission arrangement contains for each pair of scissor arms a hydraulic cylinder pivotally mounted at said connection; the pi-ston rod of the hydraulic cylinder is so arranged as to interact ,duπ ' ng the whole of the raising and lowering movement of the lifting table via rollers with at least two guide curves arranged in conjunction with the common bearing shaft for the scissor arms and operatively connected to the respective scissor arm; and the mutually and operatively connected scissor arms, which are pivotally connected to the frame section, consist of a beam of 'U'—section open towards the top, in which the appropriate power transmission arrangement is arranged. The invention is described in more detail below with reference to the accompanying drawing, in which Fig. 1 is a perspective view illustrating an embodiment of a lifting table in accordance with the present invention. Fig. 2 illustrates a plan view from the side showing details of the interaction of the power transmission arrangement with the guide curves. The designations 1a, 1b and 2a, 2b are used in Fig. 1 in respect of scissor arms connected together by means of shafts 1c, 2c for a hydraulic lifting table of the scissor type, which consists of a lower frame section 3 and an upper table section 4. The scissor arms 1a, 2a are mutually connected at their lower ends to a shaft 5 and are pivotally mounted about same relative to the frame section 3. The upper ends of the scissor arms 1b, 2b are pivotally mounted in the table section 4. The lower ends of the scissor arms 1b, 2b and the upper ends of the scissor arms 1a, 2a are executed with rollers 6, of which those at the upper end of the scissor arm 2a and at the lower end of the scissor arm 2b are not shown in the drawing. The purpose of the rollers 6 is to facilitate the movement of the aforementioned ends of the scissor arms along the frame sections and table sections, 3 and 4. Each of the scissor arms 1a and 2a consists of a beam of 'U 1 —section open towards the top, in which there is arranged, pivotally mounted on the shaft 5, a hydraulic cylinder 7a and 7b for raising and lowering of the table section 4. Each of the scissor arms 1b and 2b is manufactured from two flat steel profiles connected together at their respective ends by means of cross— ieces. Since the power transmission from the cylinders 7a and 7b to the pairs of scissor arms 1a, 1b and 2a, 2b are executed in an identical fashion, only the power transmission belonging to the cylinder 7a is described below with reference to Fig. 2. Three rollers 9a, 9b and 9c are arranged on a common shaft 10 at the outer end of the piston rod 8a of the hydraulic cylinder 7a. The roller 9b interacts with a guide curve 11b, which is operatively connected to the scissor arm 1b. The rollers 9a and 9c, which are arranged to either side of the roller 9b in order to achieve a symmetrical load distribution, interact with two guide curves 11a and 11c, which are operatively connected to the scissor arm 1a. The guide curves 11a and 11c constitute a linear gradient, and their primary function is to provide a moment arm, designated by 12 in Fig. 2, between the point of engagement of the roller 9b with the guide curve 11b and the common angle of pivoting 1c of the pair 1a, 1b of scissor arms. The fact that the force necessary for lifting is divided between two hydraulic cylinders 7a, 7b enables these dimensions to be kept within limits such that the lifting table has a very small minimum height. A. contribution to this is also made by the characterizing feature of the invention, that is to say that the guide curves 11a, 11b and 11c against which the Lifting force acts are arranged at the common support for the respective pair of scissor arms.

Claims: P a t e n t C l a i m 1. Arrangement for a hydraulic lifting table of the scissor type with two pairs of mutually attached scissor arms (1a, 1b; 2a, 2b), which at their ends are connected by means of pivots and rollers to a lower frame section (3) and an upper table section (4), and are mutually and operatively connected to the pivotable connection (5) to the frame section (3), .comprising a power transmission arrangement (7, 8, 9, 11) for raising and lowering the table section ( 4), c h a ra c t e r i zed by the combination of the following distinguishing features: the power transmission arrangement (7, 8, 9, 11) contains for each pair of scissor arms (1a, 1b; 2a, 2b) a hydraulic cylinder (7a; 7b) pivotally mounted at said connection (5); the piston rod (8a, 8b) of the hydraulic cylinder is so arranged as to interact during the whole of the raising and lowering movement of the lifting table via rollers (9a, 9b, 9c) with at least two guide curves (11a, 11b, 11c) arranged in conjunction with the common bearing shaft (1c, 2c) for the scissor arms (1a, 1b; 2a, 2b) and operatively connected to the respective scissor arm (1a, 1b; 2a, 2b); the mutually and operatively connected scissor arms (1a, 2a), which are pivotally connected to the frame section (3), consist of a beam of 'U 1 —section open towards the top, in which the appropriate power transmission arrangement (7, 8, 9, 11) is arranged.

Inventors: JOHANSSON LARS, JOHANSSON, LARS
Applicants: HYMO AB
Application year: 1988
Main classification: B66F7
IPC codes: B66F7