US3415166A - Automatically operative position holding arrangement for directional control valve device - Google Patents

Description

1963 H. HINRICHS ETAL 3,415,166

AUTOMATICALLY OPERATIVE POSITION HOLDINQ ARRANGEMENT FOR DIRECTIONAL CONTROL VALVE DEVICE Filed May 26. 1966 lg, l 152 8 INVENTOR HORST HINRICHS BY FRIEDRICH GROSS ATTORNEY I United States Patent Office 3,415,166 AUTOMATICALLY OPERATIVE POSITION HOLD- ING ARRANGEMENT FOR DIRECTIONAL CON- TROL VALVE DEVICE Horst Hinrichs, Hannover, and Friedrich Gross, Harenberg, Bergfeld, Germany, assignors to Westinghouse Bremsenund Apparatebau, G.m.b.H., Hannover, Germany Filed May 26, 1966, Ser. No. 553,141 Claims priority, application Germany, June 4, 1965, W 39,287 1 Claim. (Cl. 91-426) ABSTRACT OF THE DISCLOSURE Automatically operative valve position hold and release arrangement for a directional control valve device in which a pressure chamber acting on the end of a spool valve is series connected between the exhaust end of a cylinder and the return passage in a fluid pressure system by movement of the spool valve from a neutral position against spring-return to a cylinder operating position, which chamber is pressurized to hold the spool valve in the operating position by a pressure limiting valve in the return line, and is pressure relieved to provide automatic return of the valve to the neutral position via a choke connecting the pressure chamber in the return line in bypass of the pressure limiting valve when the fluid flow ceases in the pressure system.

Heretofore, fluid directional control devices of this type have included a slide or spool valve that is moved into its end location by hand where it is held secure by means of the mechanical spring-loaded catch and that this catch is released by means of a fluid medium. The fluid mediums that are required for this purpose comprise a fluid pressure operated cylinder, and a special primary directional control valve that is fluid pressure activated to alternately reverse operation of the cylinder. The directional valve is connected into the pressure piping of the pump and its pressure is regulated by means of a pressure limiting valve having an application valve of approximately 175 atmospheres (2,485 p.s.i.). It is conventionally known that pressure limiting valves that are loaded so high have considerable switch tolerances by which value with this arrangement the operating pressure of the installation loosens at utilization points. An additional disadvantage of the aforementioned hold and release arrangement is its multiple port construction whereby it is expensive and subject to malfunction.

The present invention establishes as its purpose the provision of a valve holding and releasing arrangement for directional control valves of the above mentioned design which is simpler and cheaper, that is activated purely by fluid pressure to the elimination of a mechanical catch and which is integrally connected with the slide or spool valves of the directional control valve devices.

In order to achieve this purpose in the present invention, one of the control slide valve surfaces on the end of the slide valve is activated by the system return flow pressure overcoming the force of the return spring, whereby pressure is provided by a flow restricting arrangement installed in the return flow piping after installation of the directional control valves. In addition, the control slide valve is provided on both end surfaces with a throat which is connected with a piston slide valve in a coaxial manner, and that the piston slide valve is movable in a cylindrical addition to the slide valve bore out of which it shifts shortly before the slide valve is shifted to its opposite end position in such a manner that the return flow ring canal in the 3,415,166 Patented Dec. 10, 1968 directional valve body bore is connected with the cylindrical addition while the piston slide valve at the opposite end of the control valve shifts into its corresponding cylinder continuation. An additional characteristic is that the restricting arrangement consists of a pressure limiting valve that is installed in the collective piping of the return flow, and restricting chokes that are arranged between each cylinder addition and the pressureless return flow in such a manner that the return flow of the operating cylinder is branched into two return flow circuits by means of the control slide valve wherever it attains either of its end positions. The proposition that the restricting arrangement consists of pressure limiting valves in combination with parallel disposed restricting chokes which are arranged between the cylinder additions and the pressureless return passage, are operated by a single pump, is a feature of a system including plural directional valves each opearting a cylinder.

These and other objects will become more readily apparent in the following description when taken with the accompanying drawing, in which:

FIG. 1 is a schematic illustration of a fluid pressure system showing our invention;

FIG. 2 is a sectional view of one end of the one directional control valve showing the valve member in one position;

FIG. 3 is a sectional view of the directional control valve end of FIG. 2, showing the valve member in another position; and

FIG. 4 is a sectional view of the directional control valve of FIG. 2, showing the valve member in yet another position.

In accordance with FIG. 1, a fluid pump 1 operates to apply a pressure medium against one or the other piston surface of each of two operating cylinders 2 and 2a while the hand operated directional control valves 3 and 3a effect switching of direction of the fluid pressure. In the illustrated middle position of the directional control valve devices, the cylinder piping 4 and 5 and 4a and 5a are closed off and the supply from the pump 1 is guided through the pump piping 6 into the pressureless return flow piping 7. The last mentioned piping 6 and 7 are also connected by means of the pressure limiting valve 8 which is adjusted to a higher operating pressure than that normally present in the system. For the return flow from the operating cylinders there is provided additional piping 9 and 10 that is installed after installation of the directional control valves and which are interconnected by the means of piping -11 which connects them through a second return flow check 12 that is adjusted to approximately 3 atmospheres (42.6 p.s.i.), to the pressure return flow piping 7.

The directional control slide valves 3 and 3a are basically of conventional design with respect to their three control functions. However, the ends of each slide or spool valve member is connected with a throat 13 (FIGS. 1 and 2) and this in turn is connected with a piston slide valve member 14 in a coaxial manner, which member 14 is movable in the cylindrical addition 15 in a conventionally sealed manner. The piston chambers 16 above the piston slide valve 14 are connected by means of piping 17, which include the restricting chokes 18 to the pressureless return piping 7.

The directional control slide valve cylindrical bore, in contrast to conventional design, is equipped additionally with a ring canal 19 (FIGS. 2-4) to which the return flow pipings 20 and 10 as well as the chambers 16 (FIGS. 2-4) are joined to the return flow 20. In this schematic drawing the conventional return springs are not shown in detail.

In the operation of the above described automatically operative valve position holding arrangement, the pump 1 delivers pressure to the pressureless circuit 6, 7 when the control slide valves 3 and 3a are in the central one of their three positions (FIG. 1). The piping 4 and 5 and 4a and 5a, respectively, of the operating cylinders 2 and 2a are cut off. Correspondingly, in FIG. 2 the operating cylinder piping 4 is separated from the return circuit 20. If the path control slide valve in directional control valve 3 in the drawing (FIG. 1) is moved downward, then it closes off, initially, the pump piping 6 from the subsequently connected directional control valve 3a with respect to the return flow piping 7. Upon further downward movement, the pressure limiting valve 8 responds to provide an upper limit to pressure in piping 6. After additional movement downward, the control slide valve connects the pressure fiow piping 22 with the cylinder piping 5 and at the same time connects the cylinder piping 4 with the return flow circuit 21, 11 which is held, for example, to approximately 3 atmospheres (42.3 pounds per square inch) by means of the return holding or pressure limiting valve 12. Referring now to FIG. 3, it is seen that in this downward direction, before reaching the end position of the slide valve, the control edge 23 on the piston 14 opposite to the control edge 24 on the valve bod has now opened a passage between piping 4 and ring 19, While the control edges 25 on the piston end 26 on the body are still lapped otf; the ring canal 19 also has no connection to the cylinder addition 16. The cylinder piping 4 is connected with the return circuit piping 20, 11, 10. Up to now, the control slide valve is pressure equalized and therefore remains sensitive to operation. If now the control slide valve is guided to its lower contact position, not shown, then shortly before the occurrence thereof the control edges 25, 26 separate. The cylindrical addition 16, and therewith the end surfaces of the control slide valve, are pressurized by the return flow pressure which holds the control slide valve in the end position so long as pressure is present in the cylinder addition 16. It is seen that now there is a second return circuit through the piping 17 open to the pressureless piping 7, however, piping 17 is choked by means of the holding choke 18 in such a manner that the return flow pressure that is approximately 3 atmospheres (42.3 pounds per square inch) remains in effect in the cylindrical addition 16. Under these conditions, if the piston of the operating cylinder 2 remains in any one of its end positions whereby the return flow is stopped then the return flow pressure in the cylindrical addition 16 lowers by exhaustion through the choke 18, after a minute pressure medium flow off. Consequentially, the pressure in cylindrical addition 16 quickly becomes less than the force of the biasing spring which immediately returns the slide valve to its middle position. The foregoing sequence also occurs with a failure of the hydraulic pipe 1, because the operating piston will stop in any position in which its movement direction reverses under the influence of the load exerted on it. This reversal movement serves for the return movement of the control slide valve to its middle position as descirbed above, in which event the piping 4 and 5 as well as 4a and 5a, respectively, are closed off so that the disposition of the piston established at the time of pump failure prevents the return dropping of the loaded operating piston. Accordingly, it is seen that by the foregoing structure, the need for the corresponding supplementary apparatus, such as a return pressure valve, is eliminated.

If the control slide valve is moved in an upward direction, in accordance with FIG. 4 of the drawing, to reverse operation of the piston, then the holding choke 18 serves the purpose of draining the cylindrical addition 16.

As described above, the arrangement in accordance with the present invention holds the control slide valve securely in its corresponding end position with the help of the pressure that is developed by means of the return 5 backing valve 12, and releases the slide valve with the lowering of this pressure. Utilizing the present structure the shift tolerance of the directional control valve is relativcly small since a relatively weak slide valve return spring may be thereby utilized. Therewith, the utilization range of the operating pressure is only slightly reduced.

As a further advantage, the automatic position holding and releasing arrangement is activated solel by fluid pressure and is therefore a simpler, less expensive means. Having now described the invention, what We claim a as new and desire to secure by Letters Patents is:

1. A directional control valve device, comprising:

(a) a body having a bore therein;

(b) a spool valve member selectively axially movable in said bore to either one of a first and second position;

(c) means operable in response to movement of said spool valve to said second position to communicate the opposite ends of a cylinder with pressure passage and a return passage and operable in said first position to sever communication of said cylinder with said pressure passage and said return passage;

(d) a pair of axially spaced ring canals in said bore, one of said canals being disposed nearer the end of said bore;

(e) first passage means in said body for communicating the other of said canals to the exhaust end of said cylinder;

(f) second passage means in said body for communicating said one ring canal to a fluid return passage;

(g) said end of said bore comprising a piston chamber;

(h) the end of said spool valve member adjacent said end of said bore comprising a piston disposable in said end of said bore to sever communication between said end of said bore and said one ring canal when said spool valve is disposed in said first position, and withdrawable from said end of said bore to communicate said one ring canal with said end of said bore when said spool valve is disposed in said second position;

(i) land means and necked portion means on said spool valve member operable to sever communication between said pair of ring canals when said spool valve member is disposed in said first axial position and operable to intercommunicate said pair of ring canal members when said spool valve member is disposed in said second position; and

(j) additional passage means through said body for communicating said one end of said bore directly to choke means disposed externally of said body.

References Cited UNITED STATES PATENTS 2,864,402 12/1958 Presnell 9l426 US. Cl. X.R. 91-42l; 137-62166.

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