Lifting tools of this kind include a hydraulic lifting piston-and-cylinder unit, said unit being coupled to a pumping lever which the operator actuates in order to raise, by pumping, for instance an articulated table or a load resting on a pair of fork members of the lift- ing device. In order to produce sufficient lifting power to raise also heavy loads, the device usually is con- structed with a long pumping lever which is used to per- form large pivotal movements while at the same time the lifting movements as such are comparatively small. In many situations this mode of operation therefore may be felt as tedious, for instance when the load is not par- ticularly heavy or when an articulated table is to be elevated to a substantially higher level, in which case a reduced number of pumping movements is desired and the work involved therefore is felt as time-consuming.

The invention provides a device which makes it pos- sible to adjust the number of pumping movements to the task involved, whereby the pumping work may be optimally adjusted to the weight of the load or to the elevation distance over which a support on which the load rests is intended to be lifted. The characteristic features of the invention appear from the appended claims.

The invention will be described in more detail in the following with reference to the accompanying drawings, wherein Fig. 1 is an exploded perspective view of the device, Fig. 2 is a lateral view of the device in one position of adjustment thereof, and

Fig. 3 is an identical lateral view of the device but showing the latter in a different position of adjustment.

In a stand 1 is mounted a hydraulically operated lifting piston-and-cylinder unit 2 which may be coupled to a lifting device of some kind, not shown, such as a stacker, a pallet truck, an articulated table or the like. A piston rod 3 projects from the piston-and- cylinder unit 2, a transverse bolt 4 connecting said rod with a mounting bracket 5 designed to attach a pumping lever 6. The transverse bolt 4 is rotationally mounted in the lever mounting bracket 5. In accordance with the embodiment shown in the drawings, a drawing bar 7 extends inside the pumping lever 6 and is arranged to be dis- placed to and fro in the longitudinal extension of the pumping lever 6. A guide means 8 mounted on the drawing bar 7 ensures that the latter is maintained in a centred position inside the pumping lever 6. The drawing bar 7 is formed with an angularly bent portion 9 which is located internally of the bracket 5.

A transverse rail 10 attached to the angularly bent portion 9 of the drawing bar 7, projects through and to the exterior of the bracket 5 and extends through an aperture 11 formed in a mobile adjustment disc 12, the latter being disposed on the external face of the bracket 5. The transverse rail 10 is displaceable in the trans- verse direction in a slit 13 formed in the mounting bracket 5, the rail thus being instrumental in bringing along the adjustment disc 12 in its movements. The adjustment disc 12 is formed with a pivot pin 14 arranged to move in a slit 15 which extends in parallel with the slit 13 formed in the mounting bracket 5 and which is formed in a sheet-metal attachment plate 16 disposed externally of the adjustment disc 12.

A spring means in the form of a compression spring 17 is disposed inside the pumping lever 6, said spring biasing the drawing rod 7 against movement in the

direction of extraction thereof, i.e. opposing movement of the pivot pin 14 in a direction towards the transverse bolt 4.

A stop means also is provided, and in accordance with the embodiment shown in the drawing the stop means consists of a locking washer 18 (visible only in Fig 2), which is placed around the drawing bar 7 and which by means of a spring 19 is pressed against an abutment 20 formed inside the pumping lever 6, and against the inner end of a catch 21, the latter projecting into the pumping lever interior through an opening 22 formed in the lever and being pivotally mounted on said lever. The locking washer 18 is arranged, by assuming an oblique position relative to the drawing bar 7, to stop the drawing bar 7 as the latter is moving inwards, into the pumping lever 6, and to prevent continued displacement of said lever in that direction. The drawing bar 7 is released from its blocked position in response to pivotal movement of the catch 21 and to raising of the locking washer 18 at the washer side opposite the abutment As should be apparent from Fig. 1, the device con- struction is identical on both sides of the mounting bracket 5 and it functions in the following manner. The position illustrated in Fig. 2 may be regarded as the device starting position. When the pumping lever 6 is pivoted in the direction indicated by arrow 23, the pivotal movements will be centred in the pivot pin 14, which is positioned in parallel with the transverse bolt 4. The forces deployed will urge the drawing bar 7 to initially move successively upwards in the direction indicated by arrow 24, see Fig. 3, with consequential displacement of the angularly bent portion 9 obliquely upwards to the right, whereby said portion, via the transverse rail 10 and the adjustment disc 12, will move the pivot pin 14 in the direction towards the transverse bolt 4. The extent of displacement of the various parts depends on the interaction of the inertia-induced

resistance of the piston rod 3 against being depressed and the bias of the spring means 17. Upon continued pivotal movement of the pumping lever 6 the piston rod 3 will be pressed into the cylinders 2 at a speed which depends on the distance existing between the centres of the transverse bolt 4 and the pivot pin 14, respectively.

Return pivotal movement of the pumping lever 6 causes the locking washer 18 to assume its oblique position as described above, retaining the drawing bar 7 and the pivot pin 14 in this intermediate position with the spring means 17 in the biased condition. Consequently, the drawing bar 7, the angularly bent portion 9, and the pivot pin 14 need not be displaced again during the subsequent pumping movement, but the retraction of the piston rod 3 into the cylinder may be started directly.

The bias of the compression spring 17, opposing extraction of the drawing bar 7, may be adjusted in consideration of the existing moment of pivotal movement, the latter in turn depending on the spacing between the transverse bolt 4 and the pivot pin 14 as well as on the weight of the load to be lifted.

The arrangement of the compression spring 17 as indicated offers several advantages. It opposes only to a predetermined extent the movement of the pivot pin 14 towards the transverse bolt 4. When this limit is ex- ceeded, i.e. upon increase of the forces required to actuate the pumping lever 6, the pivot pin 14 con- sequently will move in the direction towards the trans- verse bolt 4, thus making it easier to perform the pumping movement.

The arrangement including the compression spring 17 also has a safety aspect. Should the weight of a load require that a force is applied on the pumping lever 6 that considerably exceeds the opposing force of the com- pression spring 17, the pivot pin 14 will move to a position straight in front of the transverse bolt 4. This eliminates the moment of pivotal movement entirely, with

the result that the hydraulic pressures that may arise in the system need never reach a level involving risks of valve damages or leakage.

As appears from the description above, the device in accordance with the invention makes it possible to easily alter the position of adjustment, at a given pumping speed, from a comparatively rapid regulation of the level of the support carrying a load to a slower regulation of that level with deployment of a comparatively larger force. Owing to the possibility of simple and quick automatic adjustment of the device, the adjustment change may very well be effected during one and the same pumping sequence. To be able to do this is often needed, for instance when a pair of loading forks, assuming their lowermost level, are inserted underneath a loading pallet to be pumped into contact with the load, whereupon additional force is required to lift the load.

The invention is not limited to the embodiment shown and described herein but could be modified in a variety of ways within the scope of the appended claims. For example, the transverse rail 10 may be soldered or welded to the adjustment disc 12 instead of, in the manner illustrated, projecting through the aperture 11. In addition, it is conceivable to locate the drawing bar 7 along one side of the pumping lever 6 instead of, as illustrated, inside the lever so as to extend through the latter, and as a consequence of this alternative arrange- ment, the stop means 18-21 may be differently configured and the spring means 17 be positioned elsewhere, for example intermediate the guide 8 and an abutment means positioned underneath said guide.