Hydrostatically Balanced Plate Valve With Low Flow Resistance

Abstract

The invention relates to a valve having low flow resistance. The valve is hydrostatically balanced with a pressure field located eccentrically opposite a kidney-shaped control slot in a valve disc.

Description

The invention relates to a hydrostatically balanced valve with valve disc of low flow resistance, intended particularly for hydraulic machines.

The invention provides a valve with the lowest possible flow resistance. It is a further aim of the invention to ensure that valves, even after long periods of operation and at varying temperatures, operate with the greatest possible fluid tightness, in order to keep leakage as low as possible. On the other hand, the abrasion factor should be minimal in order to ensure high starting efficiency and to restrict the development of heat.

It is well known that concentrically operating valve discs or eccentric valves are inserted in hydraulic machines; these, however, do not leave the cross-section of flow sufficiently free but apply a relatively high flow resistance.

It is well known that by narrowing the manufacturing tolerances, or inserting washers, the sealing gaps may be kept to a minimum. Owing to abrasion and variations in temperature, however, the original values are reduced and the position worsened. This disadvantage can be noted in many types of valves with valve discs, valve spools, or valve pistons. There are also rotary valve spools with piston rings. These valve spools form an impervious seal with the piston rings but allow considerable oil leakage as well between the reversing as between the kidney-shaped balancing slots and produce a relatively high steady braking torque, owing to the sealing conditions of the piston rings. At that, there is a disadvantageous large number of seals with the valve spools producing further oil leakage. Furthermore, these seals are endangered by seizure of the valve spool and/or valve liner, especially since the forces working upon the piston rings cannot be balanced. It is also well known that an axially operating, concentrically running valve disc can be sealed by a concentric contact pressure system. In this case, however, the side of the valve disc away from the pressure, as a result of operation, is subjected to greater pressure, resulting again, in a relatively high steady braking torque.

Other axially operating, concentrically running valves have balanced forces; the unbalanced hydraulic couples, however, will cause wear seizure of the sliding surfaces and lift off of the valve plate. Known valves with hydraulically balanced forces and couples are complicated in construction, difficult to manufacture, have large lengths of seals, and do not make the best use of the space they are built in. Eccentric valves exist which can be separated in order to achieve automatic adjustment of gap sealing. Such eccentric valves, however, have the disadvantage of high flow resistance and, owing to their construction, they are, to a certain extent, unreliable in operation.

The basic aim of this invention is to reduce the flow resistance arising from the valves. It also provides a valve which applies only the contact pressure to the valve disc which is required for sealing and with which the gap sealing will be kept at the desired minimum, independently of manufacturing tolerances, operating pressures, abrasion and temperature differences.

According to this invention, an eccentric valve kidney is connected through a linking channel with an eccentrically arranged pressure area which is also connected with a concentric admission or discharge port. Also according to this invention, it is possible to arrange two or more areas whose joint center of force is arranged eccentrically. As a result of this, large cross-sections with low flow resistance remain free at and in the valve.

According to a further embodiment of the invention, the part, ensuring adjustment of the gaps, of a pressure disc is situated eccentrically on the valve disc. Through this, the pressure medium flows axially into the opening in the pressure disc, oil is deflected and led through a connecting channel into the control slots associated with the opening in the pressure disc, and from there into the cylinder channel. As a result of this, the valve disc is pressed against the control surface in such a way that the force acting on the pressure disc side of the valve disc is somewhat greater than the force emanating from the pressure control slot of the valve disc, and the two lines of force coincide substantially.

According to one embodiment of the present invention, a thrust collar is situated between the valve disc and the pressure disc, which ensures additional contact of the valve disc and the pressure disc on the working surfaces, when there is reciprocal admission of pressure of the valve disc and pressure disc on the working surface. In a further modification of the invention, the thrust collar can be replaced by a rubber washer. If the additional contact is eliminated, according to the invention it is also possible to seal the valve disc and the pressure disc directly together.

In order to make the seals between the valve disc and the pressure disc static, in one embodiment of the invention it is provided that the pressure disc should be prevented from turning on the valve disc, although it is allowed to move axially. This can be achieved, for example, by the use of a pin or by centering it on a flange, the center line of which deviates from the center line of the opening in the pressure disc. It is also possible to hold the pressure disc firm by means of a tenon projecting from the valve disc.

The advantages which can be achieved from the invention consist particularly of low flow resistances, low leakage losses, high starting efficiency, and low development of heat.

The invention will be described with reference to the accompanying drawings, in which

FIG. 1 shows, in section, a portion of a hydromotor incorporating the valve, which is represented diagrammatically;

FIG. 2a is a view from the right of the longitudinal section shown in FIG. 2b;

FIG. 2b is a longitudinal section;

FIG. 2c is a view from the left of the longitudinal section shown in FIG. 2b;

FIG. 3a is a sectional view of a modified valve, taken on line 3a--3a of FIG. 3c;

FIG. 3b is a sectional view of the valve taken on line 3b--3b of FIG. 3c;

FIG. 3c is an end view of the modified valve in accordance with the invention;

FIG. 4a shows a valve compensating for sealing gaps, this embodiment being without a thrust collar but with a securing pin, and

FIG. 4b shows a valve compensating for sealing gaps, this embodiment being with axial flow of oil through both the inlet and the outlet of the valve.

FIG. 1 shows the portion of a hydromotor incorporating the valve parts, of conventional design, e.g., a construction with radial pistons, with the valve 17.

The pressure medium, for instance, is admitted through inlet 1 in the hydromotor and passes through the guide channel 2 and the connecting channel 18, reaching the valve 17 and the kidney-shaped control slot 19, where it is directed to the cylinder channel 3. After the pressure medium has passed its energy through pistons or similar devices to the crankshaft 16, it flows through the cylinder channel 3a back to the valve 17, i.e., into the kidney-shaped control slot 19a, through a groove 4 or bore in the circular channel 20, and to the outlet 5 of the hydromotor. The flow can, of course, also take place in the opposite direction.

A bushing 10 with recessed square is inserted in the valve disc 7 and prevented from turning, and this is held by the crankshaft. The crankshaft and the valve disc 7 therefor turn at the same speed of rotation. A thrust collar 9 is situated on the cam 21 of the valve disc 7; this is sealed against the valve disc 7 by the packing 13 and it can be moved axially. On the thrust collar 9 the pressure disc 8 is centered which, in relation to the valve disc 7, can be moved axially. The pressure disc 8 and the thrust collar 9 are sealed from each other by the packing 12. The valve disc 7 and the pressure disc 8 are operated upon by compression springs 11. The pressure disc 8 is prevented from turning by being centered on the flange 15 of the valve disc.

The mode of operation of the valve is as follows:

At no-pressure from the operating medium the valve disc 7 and the pressure disc 8 are pressed apart from each other imperviously by the springs 11. In this way, there is practically no connection between the inlet 1, the outlet 5 and the crank area 22 (FIG. 1), as the working surface 14 of the valve disc rests on the control surface 23 of the hydromotor, and the working surface 14a rests on the cover plate 24. If pressure oil is admitted at inlet 1, the valve disc 7 and pressure disc 8 will be forced apart additionally by hydrostatic pressure, intensifying the impermeability, which is further increased by means of the thrust collar 9.

If pressure oil is applied to the outlet 5, the same action takes place. During the admission of pressure at the inlet 1, the pressure disc 8 can be compared with a slide shoe, and upon application of pressure at the outlet 5, it can be compared with an inverse slide shoe, i.e., one operated upon from outside.

The valve can be so constructed that the forces acting upon the valve disc 7 from the side of the pressure disc for the purpose of more certain impermeability are slightly greater than the forces originating from the control slots 19 or 19a; the same applies in respect of pressure disc 8. In this way mainly two oil pressure columns reinforce each other and merely the residual forces required for impermeability produce abrasion.

FIGS. 3a, 3b, and 3c show a modification of the valve according to the invention as shown in FIGS. 2a, 2b, and 2c, the flange 15 for holding the pressure disc 8 being replaced by a pin 15a (FIG. 3b) or two pressure pins 15b (FIG. 3c); the bushing 10 with recessed square, inserted in the valve disc 7 and prevented from turning, is replaced by a groove for an adjusting spring (FIG. 3c); the recess 4 in the valve disc 7 is replaced by radial bores 4a and the connecting channel 18 shown in FIG. 1 in the form of bores is replaced by a kidney-shaped recess 18a (FIG. 3c) in which the flow velocity of the pressure medium is substantially constant over the entire cross-section; the thrust collar 9, together with the packings 12 and 13, is replaced by a packing 9a which functions both as a thrust collar and as a packing. The pin 15a (FIG. 3b) may be replaced by two pressure pins 15b (FIG. 3c), which give somewhat more hydrostatic balance in the areas between the control slots while controlling the bores 3, 3a (FIG. 1). The pressure pins can be pressed against the cover plate 24 by springs and can be balanced hydrostatically at the working surface.

FIG. 4a illustrates a further modification of the invention, compared to the valve shown in FIGS. 2a, 2b, and 2c, in which the valve and, in particular the pressure disc 8 are balanced almost to the limit of equilibrium. This is made possible by means of one or more packings 13a fitted in the valve disc 7 or in the pressure disc 8.

FIG. 4b depicts another modification to the invention as shown in FIG. 4a, in which the pressure medium is admitted and exhausted axially. In this case, the pressure disc 8 is fitted with a second packing surface 14b.

The valve naturally lends itself to the possibility of further modifications of an inventive nature, with particular reference to the desired degree of balance, optimum flow formation, reduced cost of manufacture and choice of pressure medium and temperature range. For example, instead of simple O-rings, thrust rings or metal packings can be fitted.

The limitation of the cam located on the valve disc or on the pressure disc can be in any desired form; it can, for example, be trochoidal, with a view of achieving even lower flow resistance and to obviating the necessity for a special device to prevent turning.

The valve disc can be of any desired shape. For example, its control slots 19 (FIG. 2b) on the cam side may be so shaped that its contour is identical with or similar to the recess 18a (FIG. 3c). In addition the groove 4 can be extended over the entire width of the valve disc and further towards the center than is shown in FIG. 2b, enabling it to assume the functions of the control slot 19a.

The pressure disc can be of any desired shape; it can for example be secured against turning by means of a flange, an eccentrically mounted pin or a lug projecting centrally from the valve disc.

The flow path of the pressure medium is optional. It can, for example, pass once through the valve and once externally around the valve. It also can pass both times through the valve (FIG. 4b) in which case, in addition, one of the flow paths can be opened radially outwards.

It is understood that, for purposes of control, a rotary channel can be led axially up to the valve or through the valve which can, for example, be sealed by means of a slide ring pacing or by O-rings.

The eccentrically fitted pressure surface situated opposite a control slot can be of any shape. It also can be divided into several smaller pressure surfaces, connected internally and with their overall center of gravity eccentrically located. Naturally, the valve can be fitted with bearings independent of those of the crankshaft.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and the invention includes all such modifications.

Claims

I claim:

1. A hydrostatically relieved control for use in pressure operated machines, comprising a housing, a valve means and a valve disc means, wherein said valve means and valve disc means are rotatable relative to said housing and wherein a pressure field is arranged eccentrically in relation to the axis of rotation of said valve means and opposite to a control slot in said valve disc means.

2. A control in accordance with claim 1, wherein a section of a pressure disc serving to adjust the slot is located eccentrically opposite the valve disc means.

3. A control in accordance with claim 2, wherein an axially adjustable thrust collar is fitted between the valve disc means and the pressure disc.

4. A control in accordance with claim 2, wherein a packing producing an axial force is fitted between the valve disc means and the pressure disc.

5. A control in accordance with claim 2, wherein the pressure disc is axially adjustable and is fitted in such a way that it cannot turn.

6. A control in accordance with claim 1, including a plurality of control slots at least one of which differs in width in a radial direction from the axis of rotation.

7. A control in accordance with claim 1, including a plurality of control slots at least one of which is opened radially.

8. A control in accordance with claim 1, wherein the valve has its own bearings.

9. A control in accordance with claim 1, including a pressure pin between a plurality of the control slots.