EP0477043B1 - Self-primping hydraulic pump with valves - Google Patents

Description

The present invention relates to the problem of self-priming of piston pumps with delivery valves counter-held by return springs.

It is known to close and open the delivery orifices of a piston pump by scrolling past said orifices a plate whose surface is polished and which is provided in certain places with orifices: when the orifices in the plate are opposite the orifices of the pump, there is a backflow, and this backflow is prohibited in the other positions of said plate; the pumps thus equipped are called "ice" pumps. These pumps operate very satisfactorily, especially with regard to the problem of self-priming, but they are much more expensive to manufacture than piston pumps with discharge valves.

In said discharge valve pumps the problem of self-priming of the pump, when it is at a level higher than the level of the hydraulic fluid reservoir, is very difficult to solve. The difficulty in overcoming comes from the fact that the spring which counter-holds each valve must have sufficient rigidity to provide rapid and frank closing of the valve, but then this rigidity is such that when the pump delivers air during the priming phase, the air thus compressed does not reach a sufficient pressure to be able to lift the valve; so that the priming is not carried out. The practical result is that the ice pump, although more expensive than the valve pump, supplants it in many applications.

The applicant company, which specializes in the manufacture of bias plate pumps and discharge valves, has repeatedly attempted to find a satisfactory solution to this problem.

Firstly, in its patent 79.03708, of February 14, 1979, it proposed to make each discharge valve in two superposed stages by arranging a main valve, closing the discharge opening and counter-held by a spring with a high load. , said main valve being itself traversed by a central bore and this central bore in turn being closed by a second valve held against by a spring with lower setting. It has been found in use that, in particular in barrel pumps where the pump body carrying the cylinders and the pistons (and called barrel) rotates, the bias plate being fixed in rotation, the secondary valve moves laterally and no longer wears properly in its seat, while the springs interfere with each other. The Applicant has abandoned this manufacture and the corresponding patent.

Then, in its patent 82.00573, of January 15, 1982, the plaintiff proposed to provide each valve with a rod actuated by the bias plate. This arrangement is perfectly satisfactory in theory, but it has been found in use that the stems break. This solution and the corresponding patent have in turn been abandoned.

Thirdly, the applicant imagined having a small air purge valve in the bias plate itself. This solution is relatively effective and is used; it was the subject of a patent No. 82.03819 of March 13, 1982 and its addition No. 83.04025, but the manufacture of such pumps is expensive and their operation is not absolutely reliable.

The Applicant then imagined having a light in each piston, which, when the piston reaches its top dead center, communicates with a drain pipe which is opened and closed manually. This arrangement, described in patent No. 83.09672, of June 10, 1983, works, but has the serious drawback of not being automatic and of requiring manual intervention by the user.

It is therefore after 11 years of research and five fruitless attempts that the applicant has arrived at the solution which is the subject of the present invention, which, for its part, is entirely satisfactory.

The present invention relates to a discharge valve for hydraulic piston pump of the type comprising a main valve, closing the pump discharge conduit and counter-held by a spring with high load, and an auxiliary valve, intended to allow evacuation air during the priming phase, characterized in that said auxiliary valve is constituted by a washer, centered on a boss formed on the body of the main valve, said washer being placed on a plurality of small holes provided in crown through the body of the main valve.

The present invention may also include the following provisions: the stroke of the auxiliary valve is very short and limited to approximately one millimeter; this limitation can be obtained by abutment against the spring of the main valve.

• Figure 1 : une vue en coupe longitudinale d'un piston muni d'un clapet selon l'invention ;
• Figure 2 : une vue de détail, à échelle agrandie, du clapet de la figure 1 ;
• Figure 3 : une variante de réalisation du clapet de la figure 2.

By way of nonlimiting example and to facilitate understanding of the invention, the accompanying drawings show:

• Figure 1: a longitudinal sectional view of a piston provided with a valve according to the invention;
• Figure 2: a detail view, on an enlarged scale, of the valve of Figure 1;
• Figure 3: an alternative embodiment of the valve of Figure 2.

Referring to these figures, it can be seen that the piston 1 slides in a bore 2 made in a pump body 3. The reciprocating movement is printed on the piston 1 by a bias plate 4, against which the piston 1 is supported by the '' through a stud 5, which slides on the surface of the bias plate 4. By sliding on the surface of the bias plate 4, the stud 5 passes astride a light 6, through which the hydraulic fluid arrives. The piston 1 is hollow so that the liquid passes through it and is discharged through the pipe 7. The pipe 7 is closed by a valve 8, which is counter-held by a spring 9, the calibration of which is strong enough to obtain a rapid and frank closing of the valve 8. The spring 9 is held by a plug 10, which has a skirt 11, which serves as a guide for the valve 8. At its other end, the spring 9 is fitted on a cylindrical boss 8a of the valve 8 The valve 8 has another boss 8b with a diameter slightly larger than that of the boss 8a on which a washer 12 is centered. This washer 12 rests on a series of holes 13, drilled through the valve 8.

Thus, during the priming phase, when the pistons such as the piston 1 discharge air, the washer which is free, in the sense that it is not counter-held by a spring, lifts and lets the air discharged into the holes 13; then, when the air has been completely evacuated, the hydraulic fluid arrives through the pipe 7 and lifts the valve 8, the holes 13 no longer playing any role.

Figure 3 illustrates an alternative embodiment in which the same elements have the same references. The only difference with the valve of Figure 1 is that the valve is no longer guided by the skirt 11 of the plug 10, but is more simply centered on the orifice of the pipe 7 by a peripheral bevel.

In both cases, it is important that the stroke of the washer 12 is small; that is to say either practically equal to or slightly greater than the diameter of the holes 13. In the examples shown, this stroke is of the order of a millimeter. For this purpose, the spring 9 of the main valve is used to serve as a stop against which the washer comes to bear. It suffices to give the boss 8a a height equal to the thickness of the washer plus the desired stroke and to give it a diameter slightly greater than that of the boss 8a, but less than the outside diameter of the spring 9, so that the latter protrudes slightly beyond the boss 8b, while resting on it.

Claims (4)

1. A flow valve for an hydraulic piston pump of the type including a main valve, blocking the flow conduit of the pump and retained by an opposing high load spring, and an auxiliary valve intended to permit evacuation of air during the priming phase, characterised by the fact that said auxiliary valve is constituted by a washer (12) centred on the main valve (8) by a boss (8a) formed on the latter, said washer (8) being disposed over a plurality of small holes (13) formed in a circle through the body of the main valve (8).
2. A valve according to Claim 1 in which the travel of the washer is free, that is to say that whilst guided by the boss (8a) on which it is centred, it is not subjected to a return force.
3. A valve according to Claim 1 or 2 in which the travel of the washer is small, that is to say substantially equal to or slightly greater than the diameter of the holes (13).
4. A valve according to any one of the preceding claims in which the travel of the washer is limited by the spring (9) of the main valve, which serves as an abutment.

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