DE767740C - United control and relief valve for pumps with constant delivery rate for driving machine tools, especially broaching machines - Google Patents

Description

United control and relief valve for pumps with constant Delivery rate for the drive of machine tools, in particular broaching machines. The invention refers to a control and relief valve for pumps with a constant flow rate for driving machine tools, in particular broaching machines, in the case of one with a controllable outlet opening (throttle valve) provided at the control housing a line leads to the working part of the machine (piston) and with an overflow valve, on the one hand under: the pressure in the pressure line and on the other Side under the variable pressure at the point of use by the throttle valve stands. It has already become known a control device for pumps in which instead of the usual overflow valve, by means of which the smaller Quantities as the largest ever occurring amount of too much fluid delivered in a differential spill valve is used will. This differential overflow valve is on one side under the pressure in the pressure line and on the other hand under the variable by throttle organs Pressure at the place of consumption so that it corresponds to the ratio of these two Pressure is misaligned and excess amounts of liquid when it is opened the pressure line allows it to flow back into the suction container.

In this known device there is no high pressure limitation provided, which is solely due to the performance of the pump. Would but attach a pressure relief valve and this in the pressure line of the pump are before the throttle control, the pressure relief valve would have to take the entire excess amount to process. but what is disadvantageous.

In contrast, according to the invention, the device is made so that in the connecting line between the pressure line to the consumer and the A throttle point is provided above the regulator piston and the chamber is present an auxiliary valve is also arranged in connection with this chamber. This will the advantage achieved that by connecting the replacing such a pressure relief valve Auxiliary valve to the chamber located above the regulator piston, which is under the pressure is in the pressure line to the consumer, the valve mentioned is no longer for discharge serves the total excess amount, but rather acts as a distinct auxiliary valve, that the excess amount over the overflow valve, which is already working during normal operation flows off. The auxiliary valve can thus be very small and structurally simple and can be combined with the control valve to save space. The throttle point in the connection between the pressure line to the consumer and the one above the regulator piston located chamber has a retarding and thus dampening, which causes a flutter of the Control valve and a rattling of the power-moved 1laschinenteils are suppressed.

In the drawings, an embodiment of the invention is shown by way of example, namely: FIG. 1 is a schematic view of the combined control and relief valve according to the invention; Fig. 2 is an enlarged detail view he dr, a , and illustrates the essential working parts of the combined control and relief valve.

The combined control and relief valve can be used as a unit in the most diverse types of hydraulic circuits in machine tools to be built in. As can be seen from Fig. I, the working medium (preferably Oil) from a container i by means of a line 2 by the static effect of a Pump 3 removed, which always delivers the same amount. The one under pressure Liquid is through a line 4 in a chamber 5 of the combined control and Relief valve out (Fig. 2). Regulation of the flow of the liquid from the chamber 5 to the part to be driven takes place through a throttle valve 6.

In order to maintain the constant flow through the throttle valve 6, so that the flow rate from the chamber 5 to the line 7 regardless of the The amount of resistance due to the driven part is constant, is a piston 8 is provided, the lower part of which forms the upper wall of the chamber 5 (Fig. I) and the upper part of which forms the lower wall of a chamber 9. In the housing is above of the piston 8 a guide chamber io provided, while at the lower end of the Piston an exhaust valve is provided which has a valve seat i i and a conical Has regulator valve body 12. The inside of the piston 8 is preferably hollow, as shown in FIG Fig. 2 shows. The area of the regulator valve body 12 below the piston 8 is essentially balanced by a guide 13 which protrudes into the chamber io. The effective size of the opening of the throttle valve 6 and consequently that through the latter The volume of liquid flowing through is controlled by an adjustable lever 14. Forwarding of the hydraulic fluid from the combined control and relief valve to the place of consumption takes place via a standard four-way valve or a piston valve, which has a piston rod 15 and two pistons 16 and 17 connected to lines 18 and i9 work together to supply the pressurized fluid to one or the other other end of a cylinder 20 and into the chambers 21 and 22 to insert the To control movement of the piston 23. The liquid emerging from the cylinder 2o is through one of the lines 18 or 19 by means of the piston valve and the lines 25 returned to the storage container. One with a constriction or restriction The line 24 provided connects the line 7 to the chamber 9 above the piston B. A pressure relief or auxiliary valve 28, which by a predetermined spring tension 29 is kept closed, which can be changed by an adjusting means, regulates the flow of liquid through channel 32, which in comparison to the throttle point 2.1 is a relatively wide channel. An auxiliary exhaust line 27 connects the chamber surrounding the spring 29 to the main return line 26. To the Piston 23 can have a constant speed over the entire path of its stroke according to a given setting of the throttle valve 6. on the other hand can adjust the speed of this piston by moving the handle 14, which is from Can be made manually or automatically, can be changed. A fast Return of the pressure fluid can be achieved through a bypass valve 33 will. Mode of operation It should first be assumed that the handle 1 ¢ adjustable throttle valve 6 from the one located below the regulator piston 8 Room 5 to line 7 is completely closed. In this case, the entire, Amount of liquid delivered by the pump through the valve 12 into the reservoir return. Under this condition, the auxiliary control valve 28 remains closed, since the pressure in the chamber 9 located above the piston 8 corresponds to that in the line 7 corresponds and this is smaller than the spring pressure on the valve 28. As a result this pressure equality in the line 7 and in the chamber 9 is no flow through the throttle point 24 is present therethrough.

The spring 31 and the pressure prevailing in the chamber 9 always have the effort to close the valve 12. Caused at constant flow rate each reduction of the valve opening an increase in pressure in space 5, so that as soon as a pressure prevails in space 5 which is higher by one pressure equal to that of the spring force 31 is than the .Druck in the chamber 9, the tendency of the spring 31, the valve l2 still to close further, is zero.

When the throttle 6 is gradually opened, a gradually flows increasing part of the total flow rate from space 5 via the throttle6 into the Line 7. To the same extent as the part flowing through the throttle 6 Increased delivery rate, since the total delivery of the pump must be constant remains, reduce the exiting through the valve 12 part of the delivery rate. Of the Flow of part of the constant delivery rate through the throttle 6 into the line 7 and thus the corresponding reduction in the amount flowing through the valve 12 causes a drop in the pressure prevailing in room 5. Everyone, no matter how small Pressure drop in space 5 leads to a reduction in the pressure difference between the space 5 and the chamber 9 and thus to a predominate the spring force 31 and thus reducing the valve opening. So the valve opening adapts itself automatically of the gradually decreasing flow rate through valve 12 at.

In the opposite case, that is, when the opening of the throttle 6 is gradual is reduced and thus also a reduction in the amount flowing from 5 to 7 occurs, the amount flowing through the valve 12 must increase accordingly. Any increase in this flow rate through the valve 1: 2 as a result of the decrease the flow rate through the throttle 6, however, causes the prevailing in space 5 to rise Pressure. But as soon as the pressure difference between the space 5 and the chamber 9 the Tries to exceed spring force 31 by an amount even after such a small amount, the valve opening increases and adapts to the gradually increasing Flow rate.

The pressure difference between the space 5 and the chamber 9 has in the steady state thus always the same value, namely it corresponds to the pressure of the spring 31.

Since in the assumed case in the chamber 9 and in the line 7 of the same pressure prevails, the throttle 6 is under a constant pressure gradient.

The amount required at the place of consumption can therefore be adjusted through the throttle 6 set and is independent of the fluctuations in the working pressure of the valve 12 held at the set value.

In the event of very sudden fluctuations in the working pressure in the line 7 are through the throttle point 2q. prevents the control valve from moving too quickly, thereby preventing the valve from rattling.

Wtenn the pressures in line 7 above the setting of the auxiliary control valve 28, the result is the following.

This should initially be based on consumption pressure which is below the setting of the valve 28. It should continue to be accepted be that the total delivery of the pump is 8o 1 per minute and the throttle 6 is set for a quantity of 72 liters per minute required at the place of consumption.

According to the above, the control valve 12 then arises automatically so that it lets out an amount of 81 per minute.

Now an increase in the working resistance and therefore a Increase in pressure in line 7 occur. The associated increase in pressure but stops in the chamber 9 as soon as the setting pressure of the valve 28 is reached is because this valve opens as soon as the working pressure in the line 7 the setting pressure of the Valve 28 exceeds. The valve 28 thus keeps the pressure in the chamber 9 constant. But with that there is between the Line 7 and the chamber 9 a pressure difference, which causes a permanent part the amount of liquid from the line 7 through the throttle point 24 into the chamber 9 flows and exits from this through the valve 28.

The pressure in space 5 is now always kept by the control valve 12 by the same amount above the pressure in chamber 9, and this pressure in space 5 therefore remains from the point in time when the working pressure in line 7 exceeds the setting pressure of the valve -28, constant, so that every increase in the pressure in the line 7 also means a reduction in the pressure drop in the throttle 6 at the same time. With a constant throttle opening, however, every decrease in the pressure gradient between the space 5 and the line j means a decrease in the flow rate through the throttle valve 6, and with constant delivery of the pump the flow rate through the valve 12 must increase to the same extent as the length flowing through the throttle valve 6 is reduced. however, any increase in the length flowing through valve i2 causes the pressure prevailing in chamber 5 to rise. As soon as the pressure difference between the space 5 and the chamber 9 tries to exceed the force of the spring 31 by an amount, no matter how small, the valve opening becomes larger and thus an adaptation to the gradually increasing flow rate through this valve 12 through.

Due to the increasing pressure in the pipe; caused reduction the pressure drop in the throttle 6 has exactly the same effect as the above explained gradual closing of the throttle, as it is for the action of the control valve It is irrelevant whether the reduction in the amount flowing through the throttle 6 is concerned by closing this throttle 6 or by reducing the pressure drop takes place in this throttle.

Now it should be assumed that the pressure in the line 7 is higher than the setting pressure of the valve 28 by a pressure equal to the spring tension 31 Throttle 6 through it, but the control valve 12 allows the entire delivery rate of the pump, ie 8o 1 in the minute, to flow out.

Since, under this condition, there is a greater pressure in the line 7 if there is more than in the chamber 9, there is a flow through the throttle point 2.1. from 7 to 9, and thus piston b moves downwards. Will now be at the place of consumption if the line 7 is closed, there is again a flow through the throttle 6, since there is again a pressure gradient between the line 7 and the space 5. These Flow is caused by the pressure difference between space 5 and chamber 9. Their strength depends on your total resistance of the two throttling points 6 and 21 from, and the pressure drop is distributed proportionally between these two throttling points their resistances, so that the pressure established in the line 7 by one small amount under the pressure in space 5.

The opening of the throttle point 24 is now, however, in comparison with the full opening of the throttle 6 is very small, and also the maximum pressure gradient in this throttle point:.,. I still slightly smaller than the pressure difference between the room 5 and the chamber 9. As a result, the maximum flowing through The amount is very small, so that the valve 28 can be very small. The largest by far Part of the amount to be returned to the collecting tank when the set pressure is exceeded Amount therefore flows out through valve 12. The valve 12, which at normal working pressures serves to keep the pressure drop for the throttle 6 constant, so it causes in connection with the auxiliary valve 28 and the constriction or throttle point 24 avoidance of exceeding the set maximum pressure.

Claims (2)

PATENT CLAIMS: i. Combined control and relief valve for pumps with constant flow rate for driving machine tools, in particular broaching machines, in which a line leads from a chamber of the control housing provided with a controllable outlet opening (throttle valve) to the working part of the machine (piston), and with an overflow valve, which is on the one hand under the pressure in the pressure line and on the other hand under the pressure at the point of consumption, which can be changed by the throttle valve, characterized in that in the connecting line between the pressure line (;) to the consumer and the one above the regulator piston (8 ) a throttle point (24) is provided for the overflow valve (i2) existing chamber (9) and an auxiliary valve (28, 29) is also arranged in connection with this chamber (g). 2. Valve according to claim i, characterized in that that the auxiliary valve (28, 29) and the regulating valve controlling the overflow opening (ii) (i2) and the throttle valve (6) are combined into one unit. For demarcation the subject of the invention from the prior art is the following in the grant procedure Document considered: German Patent No. 392 443e