HYDRAULIC LIFTING SYSTEM

Abstract: Hydraulic lifting system especially for the tipping of truck bodies and being of the character in which hydraulic oil is supplied to a tipping cylinder through a stop valve, the valve body (8) of which is connected by e.g. a chain (10) to the movable piston of the cylinder in such a manner that the valve body against the force of a spring (6) is conveyed to rest against a valve seat (7) so that the valve will close immediately before the highest point of the tipping piston is reached. The chain (10) is connected to one end of a reciprocating manoeuvre rod (5) which by the said spring (6) is squeezed to a position from which it will prevent the valve body (8) to reach the valve seat (7), but by a pull of the chain will be led away from the valve seat. The valve body (8) and the manoeuvre rod (5) can be designed in such a manner that their mutual contact surface is smaller than the end surface of the manoeuvre rod turning towards the valve body, so that the oil can be pressed against the end surface.

Description: HYDRAULIC LIFTING SYSTEM The invention relates to a hydraulic lifting system especially for the tipping of truck " bodies and being of the character in which hydraulic oil is supplied to a tipping cylinder through a stop valve, the valve body of which is connected by e.g c a chain to the movable piston of the cylinder in such a manner that the valve body against the force of a spring is conveyed to rest against a valve seat so that the valve will close immediately before the highestpoint of the tipping piston is reached. The stop valve body can e.g. be connected to one end of a chain, the other end of which is fastened to the lower side of the dump body, in that the chain is exactly so long that the valve is closed and will pre¬ vent admission of oil to the cylinder when the dump body is in its outer position. By elder known systems it is necessary to open the stop valve manually in order to empty the tipping cylinder. For this purpose can e.g. to the stop valve - body be fastened a wire pull. This involves, however, a risk that the stop valve can be opened unintentional¬ ly, whereby its function - to stop the tipping movement - is prevented. In case the supply of oil to the tipping cylinder is not closed, the cylinder unit could be destroyed. Consequently a use of a two-way-flow stop valve rendering the system self-releasing has been suggested, so that direct manual control of the stop valve is un¬ necessary and impossible. Such a valve is for instance known from specification to Danish patent No. 121841 and is comparatively complicated. A hydraulic system of the described character usually incorporates also an overpressure valve, in¬ tended to ensure that the pressure in the cylinder shall not exceed a set value. The object of the present invention is to devise a hydraulic lifting system of the described character being self-releasing, but in which the stop valve is of a simpler and accordingly more inexpensive construction than hitherto known. This is according to the invention achieved in that the chain is connected to one end of a reciprocating manoeuvre rod which by the said spring is squeezed to a position from which it will prevent the valve body to reach the valve seat, but by a pull of the chain will be led away from the valve seat. By the said construction is achieved that the valve will open when the oil supply pressure is lowered, be¬ cause the valve body is not as is the case of known stop valves unreleasably connected to the movable piston in the tipping cylinder. In designing the valve as specified in Claim 2 is further achieved that the stop valve fur¬ thermore acts as overpressure valve, as the spring force on the manoeuvre rod is adjusted in such a manner that an overpressure will force the rod away from the valve body, so that the latter is free to close the valve. The invention will be described in detail below in relation to the drawing showing a section through the valve applied in the lifting system according to the invention. The valve shown in ;the drawing is Jin the hydraulic lifting system according to the invention inserted bet¬ ween a manoeuvre valve and a tipping cylinder not shown in the drawing. The valve consists of a valve casing 1, in which there is cylinder-shaped bore 2 with an inlet opening 3, OMPI that is connected to the not shown manoeuvre valve. The other end of the bore 2 is closed by way of e.g. screwed- in end bottom 4. Through this end bottom 4 is for sealing purposes inserted a reciprocating manoeuvre rod 5. By means of a spring 6 tightened in between the end bottom 4 and a sleeve on the rod 5 the manoeuvre rod is pressed against the inlet opening 3 of the bore. The rod 5 is thus stretching through a ring-shaped valve seat 7 in the bore and preventing that the valve body 8 will reach the valve seat and thereby close the valve. On the side of the valve seat turning from the in¬ let opening 3 an outlet channel 9 will open into the bore 2, which said channel is connected to the not shown tipping cylinder. To the end of the manoeuvre rod 5 protruding out of the casing is fastened e.g. a chain 10, the other end of which is fastened to the lower side of a truck dump body, which is to be lifted. When the dump body reaches its outer posistion the chain 10 will against the effect of the spring 6 pull the manoeuvre rod 5 away from the valve body 8, so that the latter by the oil pressure is acti¬ vated for interaction with the valve seat 7, whereby the valve will close. When the oil pressure is lowered by means of the manoeuvre valve the pressure in the outlet channel 9, possibly against the force of a relatively weak spring inserted between the inlet opening 3 and the valve body 8, press the valve body 8 away from the seat and effect that the valve will open and the tipping cylinder auto¬ matically relieved. Hereby the dump load is lowered, and the pull from chain 10 will cease, so that the spring 6 will lead the manoeuvre rod 5 back to the initial posi¬ tion shown in the drawing. In the embodiment shown in the drawing the valve body 8 is spherical. In this manner or other suitable manner is ensured that the surface of contact between the valve body and the manoeuvre rod 5 is smaller than OMPI the bottom surface of the rod. The part of the manoeuvre rod 5 remaining outside the surface of contact is con¬ sequently exposed direct to the oil pressure in the bore. By a suitable choice of the force of the spring 6 and the exposed part of the end surface may be effected that an overpressure will force the manoeuvre rod 5 against the force of the spring away from the valve body 8 and the latter will close ' the valve. The shown shop valve will accordingly act also as overpressure valve, which means that a separate overpressure valve in the system can be left out. OMPI

Claims: P A T E N T C L A I M S 1. Hydraulic lifting system especially for the tip¬ ping of truck bodies and being of the character in which hydraulic oil is supplied to a tipping cylinder through a stop valve, the valve body (8) of which is connected by e.g. a chain (10) to a movable piston of the cylinder in such a manner that the valve body against the force of a spring (6) is conveyed to rest against a valve seat (7) so that the valve " will close immediately before the highest point of the tipping piston is reached, c h a ¬ r a c t e r i z e d i n t h a t the chain (10) is connected to one end of a reciprocatin manoeuvre rod (5) which by the said spring (6) is squeezed to a position from which it will prevent the valve body (8) to reach the valve seat (7), but by a pull of the chain will be led away from the valve seat. 2. Hydraulic lifting system according to claim 1, c h a r a c t e r i z e d i n t h a t the valve body (8) and the manoeuvre rod (5) are designed in such a manner that their mutual contact surface is smaller than the end surface of the manoeuvre rod turning to¬ wards the valve body.

Inventors: KRISTENSEN V
Applicants: KRISTENSEN V
Application year: 1980
Main classification: F15B15
IPC codes: B60P1