DE3125482A1 - Control valve - Google Patents

Abstract

In the case of a control valve, having a valve piston which can be locked into the individual switching positions and can be automatically returned to the neutral position, provision is to be made to ensure that the permissible pressures are not exceeded and that the control valve is nonetheless reliably returned to the neutral position under a very wide range of operating conditions. This is achieved according to the invention in that a transmitter (7) is arranged in the pump feed pipe (6) leading to the working cylinder (2) and determines whether or not the hydraulic medium is flowing in this feed pipe (6) and triggers the return of the valve piston (1a) to the neutral position if no flow is detected. <IMAGE>

Description

Control spool

The invention relates to a control slide, the slide piston can be locked in the individual switch positions and an automatic ratchet position is subject to the neutral position.

With known control spools of this type there is the problem of preventing that in the respective end position of the working cylinder a permanent or longer Unacceptably high pressure is maintained over time, leading to energy losses in Form of heat and, due to the increased wear and tear, also to damage the pump, which in many cases, especially with small hydraulic oil quantities, is destroyed after a very short time.

For this reason, it is known to reset the pressure-dependent Control slide in the neutral position, in which the Pump into Free can encourage to make. These known arrangements have the disadvantage However, on the one hand, such a control slide cannot be used universally is because the reset depends on the respective operating pressure of the individual devices must be made and that, on the other hand, the full pump output in order to respond for the purpose of restitution, is not exploitable. But if the full pump output is to be used, the permissible pressure head is exceeded, so that the above-described disadvantages of increased wear and / or also stop the destruction of the pump.

The invention is accordingly based on the object of a control slide of the type mentioned so that while avoiding the disadvantages of known arrangements a safe return of the control slide in the neutral position is guaranteed under a wide variety of operating conditions.

This object is achieved according to the invention in that in the pump feed line a sender is arranged for the working cylinder (in front of or behind the control slide), which determines whether the hydraulic medium is flowing in this supply line or not and the return of the slide piston to the neutral position when there is no flow triggers.

With this arrangement it is achieved that in any case if the working cylinder has reached its end position and therefore the flow in the Pump feed comes to a standstill, a return of the spool into the Neutral position is brought about so that the pump can deliver again into the open and the disadvantageous heating and damage cannot occur under any circumstances.

This process continues despite the activation of a pressure relief valve because this - as is usual with such arrangements - before the inlet to the control slide is arranged.

It is particularly advantageous if the encoder is in the working cylinder belonging pump supply line is arranged in front of the control slide, since it is then his Effect also when connecting any number of consumers behind the control slide unfolded.

The triggering of the resetting of the spool can be done electrically, be done hydraulically or mechanically.

For this purpose, a latching device is expediently provided which keeps the spool locked in the individual switching positions and the through the transmitter can be disengaged, so that the return of the slide piston into its neutral position he follows.

The transmitter can be used as a turbine wheel or a propeller - as in flow measuring systems known per se - be designed, with the triggering of the locking device either can be done electrically by induction of a rotating magnet or mechanically.

An arrangement can also be used as a transmitter that is used in flowmeters is known per se, in which a floating body is in a flow direction opening conical tube is arranged, which is under the force of a counter to the flow direction acting spring stands and through the flow pressure in the direction of larger openings of the conical tube is moved.

This float inductively acts on one outside of the conical tube arranged ring that is floating in an outer glass cylinder. the Movement of the float in the direction of flow therefore forms a measure of the flow rate.

The electrical release can consist, for example, in that in the manner of a tachometer, one driven by the turbine wheel or the propeller rotating magnet or a soft iron part rotating in a magnetic field an element of a switching contact, which is open in the working state, and the latching device can be switched on by the force of a spring. When the encoder is at a standstill the contact is closed and the disengagement against the via an electromagnet Force of the spring causes.

Conversely, the switching contact can also be closed in the working position be, and the spring can cause the disengagement.

The mechanical release can consist in the fact that a Turbine wheel driven slip clutch via a lever or the like against the force of a spring keeps the locking device switched on. Also here causes at a standstill the spring disengages.

It is particularly advantageous and cost-effective here if the control slide is acted upon in a manner known per se by a return spring, which him brings into the neutral position after disengaging the locking device. This return spring can also be replaced by a hydraulic system attached to the pump circuit or is connected to a separate control pressure circuit.

The locking device can be circulated in a manner known per se end locking grooves of a portion of the control slide piston engaging balls exist, which are arranged on both sides of a detent spring. Here it is advantageous when the side of the detent spring facing away from the detent section of the control slide piston is acted upon by a control cam, which in turn can be actuated by the encoder.

It is particularly advantageous if this control curve with an in the pump supply line arranged actuating piston is connected by a Return spring is acted upon against the direction of flow, with none being present Flow the control cam causes the disengagement. This ensures that the actuating piston is displaced against the force of its return spring when a flow occurs, at the same time the locking is made in this actuation state. When the working cylinder has come to a standstill, there is before and after the Actuating piston in the pump feed line the same pressure, so that now the force the return spring and the actuating piston and thus the control cam moves in the opposite direction, with the control curve now making it possible that the detent spring is relaxed and the disengagement takes place.

For this purpose, the control cam is expediently designed as a rotating part, which is provided with a section of reduced diameter in the area of the detent spring is in which the ball on the one facing the latching portion of the control slide piston Can enter the end of the detent spring.

It is particularly advantageous if the actuating piston is operated at the same time as the moving part of a check valve is trained, which is closed against the direction of flow by its return spring. Such check valves are usually used in hand-operated hydraulic systems required, since negative overlaps can occur there, which can lead to a backflow of the hydraulic oil can lead in the pump direction. In this way, the inventive arrangement of this check valve with corresponding cost savings are used simultaneously for the circuit according to the invention.

A particular advantage of the arrangement according to the invention is that that when the pump is switched off, i.e. when there is no flow, independent depending on the encoder used, the control slide is in the disengaged position is located, i.e.

So from the return spring or the hydraulic return in its neutral position is maintained. This means that when the pump is at a standstill the control spool cannot be switched to one of the two working positions, but is always automatically returned to its neutral position.

The hazards occurring with the known arrangements that are contained therein exist that a working position can be switched on even when the pump is at a standstill and when the drive motor is subsequently switched on, the hydraulics immediately begins to work, are therefore not present in the arrangement according to the invention.

In addition, the arrangement according to the invention always ensures that the operator can always assume that when switched off Motor or pump switched off, the control lever is always in the neutral position, so that the usability is foolproof.

Another advantage of the arrangement according to the invention is that that good fine control is possible before the actual latching process, because in the initial overlaps of the control slide initially relatively little liquid flows past the moving part of the check valve, so that initially the locking device is kept disengaged. There is no pressure in this area the catch or the ball on the locking groove edges, so that an automatic locking not yet done at first.

The invention is illustrated below with reference to exemplary embodiments in the drawing explained in more detail.

Fig. 1 is a schematic circuit diagram of a control slide in erfindungsge according training.

Fig. 2 shows a schematic representation of an embodiment for electrical transmission of the signal from a rotating encoder.

Fig. 3 shows a schematic representation of another embodiment for electrical transmission.

Fig. 4 shows a schematic representation of an embodiment for mechanical transmission.

Fig. 5 shows an embodiment for mechanical / hydraulic transmission.

Fig. 6 shows the structural design of the arrangement according to Fig. 5.

According to FIG. 1, a control slide designed in a manner known per se is shown 1 upstream of one or more working cylinders 2, which is controlled by a manual lever 3 can be actuated. The control slide 1 is shown in Fig. 1 in its neutral position, in which a pump 4 delivers from the oil tank 5 back into the latter. at a shift of the control slide 1 to the left in Fig. 1, the piston of the Working cylinder 2 acts on the piston rod side and therefore moves in the illustrated embodiment downwards, while he is at a shift of the control slide 1 to the right in Fig. 1 on the piston bottom side applied and accordingly moves upwards.

In the pump feed line 6 to the working cylinder 2 in front of the control slide 1, a transmitter 7 is arranged, which determines whether the hydraulic medium in this Feed line 6 flows or not and the return of the slide piston when there is no flow of the control slide 1 in the neutral position shown in Fig. 1 triggers.

For this purpose, the encoder 7 is via a transmission device 8 mm% of a locking device 9 connected, which consists of locking grooves 10 and 11 in a locking section 12 of the control slide piston may exist, in which a detent 13 engages. the two locking grooves 10 and 11 correspond to the two to the right and to the left in Fig. 1 shifted switching positions in which the working cylinder 2 in the described Way is acted upon. In these switching positions, the catch 13 engages in the grooves and holds the spool valve there against the force of a return device, for example, a return spring 14 fixed in the respective switching position.

By means of the transmitter 7, however, the latching device 9 is over the transmission device 8 triggered in such a way that the detent is switched off, 8o that under the force of the Reset device 14 the control spool piston into the position shown in Fig. i reproduced neutral position is performed.

In Fig. 1 there is also a pressure relief valve 15 in a secondary line 16 to the pump feed line 6 reproduced, in a manner known per se at too high Pressing responds and the promotion in the oil reservoir 5 allowed.

The mode of operation of the arrangement described is as follows an activation of the control slide 1 to the right or to the left in Fig. 1 and the resulting loading of the working cylinder 2 moves it, there is initially a flow of the hydraulic medium through the transmitter 7. this causes the locking device 9 to engage in the respective switching position remain. When the piston of the working cylinder 2 has one or the other end position reached, the flow through the encoder 7 comes to a standstill, whereby ore in accordance with the locking device 9 is disengaged, so that now under the force of the restoring device 14 the piston of the control slide 1 in its neutral position shown in FIG. 1 is automatically returned. In this position, the pump 4 can now be in again convey the storage container without heating or damage occurring can. This automatic return to the neutral position happens before the Pressure relief valve 15 responds.

Fig. 2 shows a schematic representation of an embodiment of the Transmission device 8 and the encoder 7. In this embodiment, the encoder 7 designed as a turbine wheel 17 arranged in the pump feed line 6, which A tachometer-like device 19 with a rotating magnet or via a shaft 18 Soft iron part drives, which moves an element 20 of a switching contact 21 and in the working state, so when the turbine wheel 17 is in the direction of the arrow 22 rotates - as shown - holds open.

If the flow comes to a standstill, contact 21 is closed, 8o that the coil 23 of an electromagnet 24, which is supplied by a current source 23a is acted upon and the catch 13 against the force of a compression spring acting on it 25 triggers, i.e. from the grooves 10 and 11 assigned to it (cf.

Fig. I) pulls out.

This arrangement can of course also work in reverse by in the working state, the switching contact 21 is closed and the magnet 24 engages causes, while when the contact is opened at a standstill the now in the opposite direction acting Spring 25 causes the disengagement. The latter Arrangement has the advantage that for the disengagement and thus for the return no current is required in the neutral position, so that the neutral position also applies to Shutdown of all aggregates is achieved.

This embodiment (energized magnet in the working state) is reproduced in connection with the arrangement according to FIG.

There the transmitter consists of a sensor known per se in flowmeters Arrangement in which a floating body 26 is in a flow direction opening conical tube 27 is arranged, which is under the force of a counter to the flow direction acting spring 28 is. Due to the flow pressure, it becomes larger in the direction Openings of the conical tube 27, that is, in the direction of arrow 29, moved. This Floating body inductively acts on a one arranged outside the conical tube Ring 30, which is floatingly mounted in an outer glass cylinder 31 Movement of the floating body 26 in the direction of the arrow 29 against the force of the spring 28, the coil 23 of the magnet 24 becomes through the power source 23a due to the change the inductance in the ring 30 applied so that the magnet 24 responds and the Notch 13 moves against the force of its spring 25 in the direction of arrow 32. Turns when the flow of the floating bodies 26 is at a standstill in his in Fig. 3 due to the force of the spring 28 back, so the The coil 23 of the magnet 24 is de-energized and the catch 13 is out of the respective catch groove 10 or 11 removed.

In contrast to the arrangement according to FIG. 2, the spring moves here 25 the catch 13 does not go into the catch grooves 10 or 11, but out of these, so that when all units are switched off, the control slide returns to its starting position can return.

In the case of the embodiment according to FIG. 4, the transmission is from the encoder formed mechanically on the latching device, which here is in the direction the arrow 22 rotating turbine wheel 17 via a chain gear 33 or the like, which is provided with a slip clutch 34, a lever 35 in the direction of the Arrow 36 moves, which moves the catch 13 against the force of the compression spring assigned to it 25 holds in engagement with one of the locking grooves 10 or 11.

If the turbine wheel 17 comes to a standstill, the spring 25 pulls the Latch 13 out of the latching groove so that the control slide is in its starting position returns.

In the arrangement according to FIG. 5, the transmitter consists of one in the pump feed line arranged actuating piston 37, which by the flow in the direction of the arrow 38 can be displaced against the force of a spring 39. The actuating piston 37 is with a control cam 40 connected, which via an intermediate Spring 41 acts on the catch 13. The mode of operation of this arrangement is as follows When the piston of the working cylinder 2 is in the respective switched-on position Has reached the end position and thus the flow in the pump feed line 6 to a standstill comes, the pressure on both sides of the actuating piston 37 is the same, so that the spring 39 moves this to the left in FIG. 5 into the position shown there. In this Position the spring 41 is relaxed, so that the catch 13 from the locking grooves assigned to it 10 and 11 step out or pushed out by the force of the return spring 14 can be.

In the working or flow state, however, the actuating piston is 37 to the right in Fig. 5, that is, in the direction of arrow 42, shifted so that the Control cam 40 acts on the spring 41 and thus the detent 13 in one of the detent grooves 10 or 11 pushes in.

Instead of the return spring 14, as indicated by dashed lines at 43 - A hydraulic return can also be provided.

Fig. 6 shows a structural embodiment for the arrangement according to Fig. 5. Thereafter, a piston 1a is in a housing 44 Control slide arranged, which is acted upon by the return spring 14 and by the handle 3 can be actuated.

At one end it has the latching portion 12, which with the Locking grooves 10 and 11 is provided. A ball 45 is assigned to the locking grooves 10 and 11, which is located at one end of a detent spring 46, at the other end of a further ball 47 is arranged. The ball 47 fits into a reduced diameter Section 48 of a rotating part 49 which forms the cam control according to FIG. 5. The rotating part 49 is connected to the actuating piston 37 via a connecting rod 50 (see. Fig. 5) in connection, wherein the connecting rod 50 is in the pump supply line 6 is located. The actuating piston 37 is acted upon by its return spring 39.

In this embodiment, the actuating piston 37 forms at the same time a check valve in the pump feed line 6.

The latching member 46 is in the neutral position shown in FIG. 6 relaxed, so that due to the force of the return spring 14, the ball 45 from the Locking grooves 10 or 11 can be pressed out into the neutral position. The check valve is through the sealing edges 51 of the valve body on the one hand and formed by the truncated cone 52 on the actuating piston 37 on the other hand

Claims (16)

n proverbs rw ~ control spool, its spool in the individual Switching positions can be locked and an automatic return to the neutral position subject, characterized in that in the pump feed line (6) to the working cylinder (2) a transmitter (7) is arranged, which determines whether the hydraulic medium is in this supply line (6) flows or not and the resetting of the non-flow The spool (ia) triggers in the neutral position. 2. Control slide according to claim 12, characterized in that the Sensor (7) is arranged in the pump feed line (6) in front of the control slide (i). 3. Control slide according to claim t or 2, characterized in that that the triggering of the return of the slide piston (ia) electrically, hydraulically or done mechanically. 4. Control slide according to one of the preceding claims with a Locking device that engages the slide piston in the individual switching positions holds, characterized in that the locking device (9) can be disengaged by the encoder (7) is. 5. Control slide according to one of the preceding claims, characterized characterized in that the encoder (7) is designed as a turbine wheel (17) or propeller is, the triggering of the locking device (9) either electrically by induction a rotating magnet or mechanically. 6. Control slide according to one of claims t to 4, characterized in that that the encoder (7) from one in the flow direction opening Cone tube (27) consists in which one under the force of one against the direction of flow acting spring (28) standing floating body (26) is arranged, the inductive one outside the conical tube (27) arranged ring (30) acted upon and at a Ver displacement of the float (26) in the direction of flow an electromagnet (24) keeps switched on, which acts on the latching device (9) in the closing direction. 7. Control slide according to claim 5, characterized in that a rotating magnet driven by the turbine wheel (17) or the propeller or a soft iron part rotating in a magnetic field an element (20) of a switching contact (21) moves, which is open in the working state and the locking device (9) can be switched on by the force of a spring (25), while the switching contact (21) is closed in the flow standstill and switches on an electromagnet (24), which causes the disengagement against the force of the spring (25). 8. Control slide according to claim 5, characterized in that a by the turbine wheel (17) or the propeller driven rotating Magnet or a soft iron part rotating in a magnetic field an element (20) a switching contact (21) is moved, which is closed in the working state and the locking device (9) against the force of a spring (25) via an electromagnet (24) keeps switched on, while the contact (21) is open when the flow has stopped and the spring (25) causes the disengagement. 9. Control slide according to claim 5, characterized in that a provided by the turbine wheel (17) or the propeller driven slip clutch (34) is, which via a lever (35) or the like against the force of a spring (25) in the working state, the locking device (9) keeps switched on, while in the flow standstill the spring (25) causes the disengagement. 10. Control slide according to one of the preceding claims, characterized characterized in that the slide piston (ia) is acted upon by a return spring (14) which leads it into the neutral position after disengaging the locking device (9). llo control slide according to one of claims 1 to 9, characterized in that that a hydraulic arrangement (43) is provided which is connected to the pump circuit (6) or is connected to a separate control pressure circuit and the reset of the control spool piston (la) in the neutral position after disengaging the locking device (9) causes. 12e control slide according to one of the preceding claims, characterized characterized in that the locking device (9) in circumferential locking grooves (10, 11) of a section (12) of the control slide piston (ia) engaging balls (45, 47) consists, which are arranged on both sides of a detent spring (46). 13e control slide according to claim 12, characterized in that the the side of the detent spring facing away from the detent section (12) of the control spool piston (ia) (46) is acted upon by a control cam (40), which in turn can be actuated by the encoder (7) is. 14. Control slide according to claim 13, characterized in that the Control cam (40) with an actuating piston arranged in the pump feed line (6) (37) is connected by a return spring (39) against the direction of flow is beauischlagt, the control cam (40) disengaging when the flow has stopped the locking device (9) causes. 15. Control slide according to claim 14, characterized in that the Control cam (40) is designed as a rotary part (49) which is located in the area of the detent spring (46) is provided with a portion of reduced diameter (48) into which the ball (47) on the one facing the latching section (12) of the control slide piston (ia) Can enter the end of the detent spring (46). 16. Control slide according to claim 14 or 15, characterized in that that the actuating piston (37) at the same time as the movable part of a check valve is formed in the pump feed line (6), which counter to the direction of flow is closed by its return spring (39).