Directional Control Valves For The Power Cylinders Of Operating Elements Of Machines

Abstract

A directional control valve for the power cylinders of operating elements of machines, particularly, road-building machines and tractors, wherein the bi-directional floating position of the power cylinder is obtained by the introduction into the hydraulic system of differential valves communicating with non-return valves.

Description

The present invention relates to directional control valves for the power cylinders of operating elements of machines, mainly road-building machines and remote-controlled tractors.

It is known that in the road-building machines, in addition to the "LIFT", "LOWER" and "NEUTRAL" /or locked/ positions of the operating element it is necessary to provide the so-called floating position of the power cylinder in which its piston can be moved by an external force applied to, and transmitted by the operating element.

To ensure such a floating position, the hydraulic systems of these machines incorporate four-position directional control valves in which the circular recesses of the main slide valve communicate through channels with the spaces of the power cylinder as well as with the pump and return line. Such valves can be controlled either manually or at a distance.

In the manually controlled directional control valves the floating position of the power cylinder is ensured by the main slide valve which has additional circular recesses communicating through channel with the above-mentioned elements of the system.

A disadvantage of these valves lies in that they hamper the arrangement of the hydraulic system on the machine because the directional control valve should be installed within reach of the operator. Besides, the hydraulic system with this type of valve is very heavy and bulky.

The widely employed directional control valves with remote electromagnetic control and a flow rate of the service fluid ranging from 300 to 500 l/min have two main slide valves one of which ensures the "floating" position of the power cylinder. Such a slide valve can be controlled directly by a powerful electromagnet or via an auxiliary low-power slide valve utilizing the pressure supplied from a hydraulic accumulator or the hydraulic system.

The disadvantages of such control valves include heavy weight of the valve proper; besides, the entire hydraulic system is very heavy, bulk and insufficiently reliable owing to a high pressure when the hydraulic accumulator is used or at the moment when the hydraulic system is shifted over to the floating position of the power cylinder.

An object of the invention is to eliminate the aforesaid disadvantages of the known directional control valves.

The main object of the invention resides in providing such a device for ensuring the "floating" position of the power cylinder which would simplify the design of the directional control valve and reduce its dimensions.

This object is carried into effect by providing a directional control valve for the power cylinders of the operating elements of machines, particularly road building machines and tractors, wherein the circular recesses in the body of the main slide valve communicate through channels with the spaces of the hydraulic pump and the auxiliary slide valve of the power cylinder and there is a device for ensuring the "floating" position of the power cylinder according to the invention, differential valves with throttles installed in the channels which communicate the recesses of the main slide valve with the spaces of the power cylinders, and the non-return valves communicating with the differential valves and with each other, which also communicate with an additional auxiliary slide valve, are used as a device, ensuring the "floating position" of the power cylinder.

To diminish hydraulic losses, it is practicable that the differential control valves be in communication with the circular recesses of the main slide valve through channels connected with the control spaces of the same slide valve.

This allows the differential valves to be used for draining the service fluid from the spaces of the power cylinder.

This also reduces the dimensions of the directional control valve.

Now the invention will be described in detail by way of an example of a road building machine with reference to the accompanying drawings in which:

FIG. 1 is an elementary diagram of the hydraulic drive of an operating element of a road building machine with a directional control valve according to the invention;

FIG. 2 is a section through the directional control valve of the hydraulic system, shown in FIG. 1;

FIG. 3 is another version of the same hydraulic system in which the differential valves communicate via additional channels with the recesses of the main slide valve, said recesses being connected with the control spaces of this slide valve;

FIG. 4 is a section of the directional control valve in the hydraulic system realized according to the second version of the invention.

The hydraulic system of the operating element of a road-building machine is illustrated by two elementary diagrams of the directional control valve communications realized, according to the invention, in two versions.

The hydraulic system of a road building machine comprises a hydraulic pump 1 /FIG. 1 and 3/, an oil tank 2, an unloading valve 3 with a solenoid 4 of the control electromagnet, a power cylinder 5 with cavities 6 and 7, and a directional control valve.

The directional control valve consists of a main spool 8 /8a/ /FIG.1-4/, an auxiliary spool 9 and a valve 10 ensuring the "floating" position of the power cylinder 5.

The main spool 8 /8a/ /FIG.2,4/ of the directional control valve has a cylindrical shape and is accommodated in a sleeve II /IIa/ installed in a body I2 /I2a/.

The main spool 8 FIG.2 in the first version has circular recesses I3,I4,I5,I6,I7 on the external surface. The recesses I3 and I7 of the spool 8 are interconnected by passageways I8.I9,20. The inner surface of the sleeve II is provided with circular recesses 2I, 22,23,24 communicating via passageways 25,26,27,28 with the recesses 29,30,3I,32 on the external surface of the barrel. The recesses 29,30,3I,32 correspond to the recesses 33,34,35,36 on the internal surface of the body I2. The recesses 30,3I,32,33 merge into passageways 37,38,39,40.

The recesses 33, 34, 35 and 36 merge into corresponding passageways 40, 37, 38 and 39.

The main spool 8a in the second version FIG.4 has circular recesses I4,I5,I6,4I,42 on the external surface.

The circular recesses 2I,22,23,43,44 on the internal surface of the sleeve IIa communicate via the passageways 25,26,27,45,46, respectively, with the recesses 29,30,31, 47,48 made on the external surface of the sleeve IIa.

The recesses 29,30,3I,47,48 correspond to the recesses 33,34,35,49,50 on the internal surface of the body I2a. The recesses 33,35,49,50 merge into the passageways 37,38,5I,52.

The control cavities 53 and 54 /FIGS. 2 and 4/ of the main spool 8 /8a/ are formed by its end faces and the inner surface of the sleeve II /IIa/.

The cavity 53 is limited by a cover 55 which is fastened by bolts 56 to the sleeve II /IIa/. The cavity 53 accommodates a spring 57 designed to set the spool 8 /8a/ to the neutral position.

The cavity 54 is limited by a flange 58.

The body 59 of the spool 9 is fastened by bolts 60 on the body I2 and I2a of the main spool 8/8a/. The spool 9 is connected by rod 6I with an armature 62 of an a solenoid 63 and with a washer 64, against which bears a spring 65, ensuring the neutral position of the armature 62.

The sleeve 66 of the spool 9 has circular recesses 67,68,69,70 and 7I.

The device I0 /FIGS.1,3/ according to the invention, comprises differential valves 72 and 73, non-return valves 74 and 75 and an additional auxiliary spool 76. The differential valves 72 and 73 incorporate flow restrictors 77. The additional auxiliary spool 76 FIG. 2 is accommodated in a sleeve 78 and connected with a solenoid 79.

In both versions of the directional control valve, the control cavities 53 and 54 communicate with the auxiliary spool 9 through passageways 80 /FIG.2,4/ and 8I made in the sleeve II /IIa/ of the body 59 of the auxiliary spool 9. In the directional control valve according to the first version, the differential valves 72 and 73, non-return valves 74 and 75 and the auxiliary additional spool 76 with the sleeve 78 of the valve I0 are assembled in the body 82 which is connected with the body I2 of the main spool.

The differential valves 72 and 73 are installed in the body 82 (12a) and are in communication with cavities 83 and 84 below the valves, intermediate cavities 39, and cavities above the valves 38 and 40.

In the directional control valve according to the second version FIG.4 the control cavities 53 and 54 are connected by the internal passageways 89 and 90 in the main spool 8a with the circular recesses 4I and 43 of the same spool 8a. The differential valves 72 and 73, non-return valves 74 and 75 of the valve I0 are mounted in the spool. body I2a of the main spool. The differential valves 72 and 73 are installed in the cavities 83 and 84 of the body I2a.

The directional control valve according to the first version (FIG.1,2) functions as follows.

In the "neutral-locked" position the solenoids 4, 63 and 79 / FIGS. 1 and 2/ are deenergized. The spring 57 keeps the main slide valve in the middle neutral position.

The differential valves 72 and 73 are tightly closed by the springs 91 and by the fluid pressure, urged from the cavity of the cylinder 5 which is under load through the restrictions 77 into the cavity 83 (84). The power cylinder 5 is locked. The service fluid is discharged through the unloading valve 3 into the tank 2.

To lift the operating element, the windings of the solenoids 4 of the unloading valve 3 and one of the windings of the solenoid 63 are energized. The service fluid ceases to be discharged through the unloading valve 3 and is directed into the directional control valve. Now the unloading valve functions as a safety valve.

Concurrently, the armature 62 of the solenoid 63 moves the auxiliary spool 9 via the connecting rod 6I, say, to the right. In this case the service fluid flows from the passageway 26 and through the passageways /not shown/ in the sleeve II and body 59 to the recess 69 on the sleeve 66 of the auxiliary spool 9 and thence, through the recess 92 on the spool 9 to the recess 68 and through the passageway 80 into the control cavity 53 of the main spool 8.

The spool 8 is moved by the fluid pressure to the extreme right position, compressing the spring 57.

From the control cavity 54 the service fluid is forced through the passageway 8I, recess 70, recess 93 of the spool 9, recess 7I and the passageways not shown/ in the body 59 and sleeve II into the return passageway of the directional control valve.

From the passageway 37 the service fluid flows through the circular recesses 30 and 34, passageways 26, circular recesses 22,I5,23 and the passageways 27 into the circular recesses 3I,35 communicating with the cavity 7 of the power cylinder 5. From the return cavity 6 of the power cylinder 5 the fluid is forced into the circular recesses 33 and 29 through the passageways 25, recesses 2I,I3, passageways I8,I9,20, recesses I7,24, passageways 28 and recesses 36,32 into the return passageway 39.

The rod of the power cylinder 5 is lifted. To stop the lifting motion, the solenoids 4,62 must be deenergized. The auxiliary spool 9 and main spool 8 are returned by the springs 65 and 57 into the NEUTRAL position. The power cylinder 5 is locked and the unloading valve returns the fluid back into the tank 2.

When the valve is shifted to the "LOWER" position the rod of the power cylinder 5 is forced down. The control valve functions in the same way as in the "LIFT" position with the sole difference that the auxiliary and main spools move in the direction contrary to their position during lifting.

The service fluid enters the cavity 6 of the power cylinder 5 from which it has been discharged in the "LIFT" position; and is discharged from the space 7 which has previously been under pressure.

To ensure the floating position of the power cylinder 5, the electromagnet 79 is energized while the electromagnet 63 of the auxiliary slide valve 9 and the electromagnet 4 of the pressure relief unit remain deenergized. The auxiliary 9 and main 8 slide valves are in the neutral position. The service fluid flows from the pump 1 through the pressure relief unit 3 into the tank 2.

The electromagnet 79 moves the additional auxiliary slide valve 76. In this case the spaces 85 and 86 of the non-return valves 74 and 75 are put in communication through the channels 94 and slide valve 76 with the return channel 39 of the hydraulic selector.

Let us assume that the action of an external force has produced a certain service pressure fluid in the space 6 of the cylinder 5 communicated by the channels 95 with the circular recess 38 of the control valve body.

Inasmuch as the cavity 83 communicates through the non-return valve 74, passageways 94 and the opened auxiliary spool 76 with the return passageway 39 of the control valve, the pressure of the service fluid flowing through the flow restrictor 77 in the cavity 83 above the differential valve 72 will be lower than its pressure in the cavity 40 under the valve. Owing to the difference of pressures under and above the differential valve 72, the latter will open, overcoming the resistance of the spring 9I, and the service fluid will be discharged from the cavity of the power cylinder 5 into the return passageway 39 of the directional control valve.

Meanwhile, vacuum is built up in the cavity 7 of the power cylinder 5; through the throttles 77 this vacuum is transmitted into the cavity 84 of the differential valve 73. Under the action of the difference of fluid pressures under and above the valve 73 and of the fluid pressure in the return passageway 39 of the control valve, the differential valve 73 opens and the service fluid flows from the return passageway 39 of the control valve into the cavity 7 of the power cylinder, said space being under vacuum at the moment.

If the load is applied to the rod of the power cylinder 5 from the opposite direction, the differential valves will operate in the same manner.

Functioning of the hydraulic selector according to the second version / FIGS. 3,4/ differs from that according to the first version only in the "LIFT" and "LOWER" positions and in that the service fluid is discharged from the hydraulic cylinder through the differential valves.

During the "LIFT" operation, the service fluid flows into the cavity 7 of the power cylinder 5 in the same manner as in the first version.

The service fluid will be discharged from the cavity 6 through the differential valve 72 in the following way.

While the main spool 8a moves to the extreme right position, the recess 4I of the spool 8a will get in line with the recess 43 on the internal surface of the sleeve IIa. The cavity 83 of the differential valve will be put in communication through the passageway 5I, recesses 49,47, passageways 45, recesses 43,4I and passageway 90 with the control cavity 54 of the spool 8a connected with the return passageway 39 of the control valve in the manner described in the first version.

The fluid pressure above the differential valve 72 will be higher than in the cavity 83 communicating with the return line.

Under the action of the difference of fluid pressures, the differential valve 72 will open and the service fluid will be discharged from the power cylinder 5 into the passageway 39 of the directional control valve.

The differential valve 73 at this moment remains closed since the cavity 84 communicates through the passageway 52,recesses 48,50, passageway 46 and recess 44 with the recess I6 of the spool 8 where the fluid is under pressure.

The differential valve 73 is closed tightly under the effect of the difference of fluid pressures under and in the cavity 40 of said valve.

The operation of the control valve in the "LOWER" position does not differ from its operation in the "LIFT" position with the sole difference that the auxiliary spool 9 and main spool 8a move in the direction opposite to that in which they moved during the "LIFT" operation. In this case the service fluid enters the cavity 6 of the power cylinder 5 and is discharged from its cavity 7 through the differential valve 73.

In the second version, the losses in the control valve are reduced which allows the valve dimensions to be reduced too while preserving the same rate of fluid flow.

The advantages of the directional control valve according to the invention are as follows.

The use of the differential and non-return valves with an additional slide valve or spool in the power cylinder as a device, ensuring the "FLOATING" position makes it possible to provide four positions in the power cylinder, that is, "NEUTRAL-LOCKED", "LIFT", "LOWER", and "FLOATING".

The control valve according to the invention is of a simple and compact design, has small dimensions and weight in spite of a considerable passing capacity /300-350 l/min/. This control valve accordingly is convenient in control and operation.

Claims

What is claimed is:

1. A directional control valve providing bidirectional floating for controlling the operating elements of machines, such as road-building machines and tractors or the like, said elements including a hydraulic pump, a tank supplying said pump, and a power cylinder having chambers, said control valve comprising: a valve body having circular recesses; a main valve spool being mounted in said valve body; passages communicating said circular recesses with said hydraulic pump, with said tank and with the chambers of said power cylinder; a control cavity being provided in said main valve spool; an auxiliary valve spool being mounted in said valve body; passages communicating said auxiliary valve spool with the control cavity in said main valve spool and with the circular recesses in said valve body; differential valves having throttles being installed in the passages communicating said valve body with the chambers in said power cylinder; three cavities being formed by each of said differential valves, said last-mentioned cavities including a first cavity forming a connection between an upper end of said differential valve and the passages communicating the chambers of said power cylinder with said main valve spool, a second cavity forming a connection between the intermediate portion of said differential valve and with the supply tank; a second auxiliary valve spool being mounted in said valve body and connected to said second cavity; and spring biased non-return valves each communicating with each other, with a third cavity connected to a lower end of said differential valve and with said second auxiliary valve spool for providing a floating position.

2. A directional control valve according to claim 1, wherein said differential valves communicate through said passages with said circular recesses of said main valve body, said recesses being in communication with said control cavity of said main valve spool.