GB2079982A

GB2079982A - An Adjustable Throttle Valve

Info

Publication number: GB2079982A
Application number: GB8119753A
Authority: GB
Original assignee: Barmag Barmer Maschinenfabrik AG
Current assignee: Oerlikon Barmag AG
Priority date: 1980-06-28
Filing date: 1981-06-26
Publication date: 1982-01-27

Abstract

The present invention relates to an adjustable throttle valve comprising a choke piston (6) which is connected on its control surface (35) to the oil supply by an inlet channel (7) having a throttle point (36) and which has an axial outlet channel (8). A follow-up piston (10) is guided in alignment with the outlet channel (8) and forms an edge control therewith. An adjusting piston (13) is connected mechanically with the follow-up piston (10) and is charged with a control pressure (Ps) against the action of a spring (19). The follow-up piston (10) penetrates the adjusting piston (13) and is held in the closing direction by a spring (17) independently of the adjusting piston (13). A stop (15) of the adjusting piston (13) interacts with a stop (16) of the follow-up piston (10) when a dead path (34) has been overcome. The valve may be positioned either by providing a variable control pressure or by actuating a solenoid valve 23. <IMAGE>

Description

SPECIFICATION An Adjustable Throttle Valve The present invention relates to an adjustable throttle valve. A known throttle valve which has a hydraulic sequential control and is made by Towler has, as the main stage, a choke piston which, on its control end, i.e. on the end remote from the outlet end, is connected on the one hand to the oil supply by an inlet channel having a throttle point and is connected on the other hand to the oil discharge end of the piston by an axial outlet channel. A follow-up piston is guided in alignment with the axial outlet channel and it forms an edge control with the opening of the axial outlet channel. The follow-up piston is positioned hydraulically by an adjusting piston, depending on a pre-control pressure which is predetermined by a pre-control stage.For this purpose, the known throttle valve has a mechanical connection between the adjusting piston and the follow-up piston, as well as a spring which causes a mechacical return of the position of the adjusting piston.

An object of an embodiment of the present invention is to further develop a throttle valve of this type such that the complex pre-control with a power return may be omitted and the construction size may be reduced without impairing the operational efficiency.

According to the invention there is provided an adjustable throttle valve comprising a two-way seat valve, the hydraulically operated piston of which has a surface ratio which is not equal to 1:1 is connected on its hydraulically charged control surface to the oil supply by an inlet channel having a throttle point, is connected to the oil discharge by an outlet channel, and on the throttle surface which is remote from the control surface is charged with the pressure of the oil flow which is running out; a follow-up piston which is guided in alignment with the outlet channel of the piston and forms an edge control therewith; and an adjusting piston which is connected mechanically to the follow-up piston and is charged with a control pressure in the opening direction of the follow-up piston against a spring; wherein the follow-up piston penetrates the adjusting piston and has a mechanical stop at its end for the mechanical connection with the adjusting piston; and the follow-up piston is spring-loaded in the closing direction, independently of the adjusting piston.

The follow-up piston can move in the opening direction independently of the adjusting piston and the adjusting piston can move in the closing direction independently of the follow-up piston.

The adjusting piston and the follow-up piston are prestressed by springs which are independent of each other, in the closing direction of the two-way valve. Thus, the spring supporting the adjusting piston may be adapted to the pre-control pressure without impairing the prestress force of the follow-up piston.

A dead path is preferably provided for the upwards movement of the adjusting piston, before it reaches the stop of the follow-up piston.

As a result of this measure, the follow-up piston tightly closes the axial outlet channel of the choke piston with all of its spring force, when no control pressure is applied.

Where there is a reversed throughflow direction, the throttle valve acts as a check valve.

The choke piston and the follow-up piston are then adjusted against the spring force.

The area of use of the throttle valve according to the invention may furthermore be expanded if the control pressure is produced by a pressure relief valve, preferably by a pressure relief valve which is controlled proportionately and electromagnetically.

An embodiment of the invention will be described in the following with reference to the accompanying drawing which shows a section through an embodiment of a throttle valve according to the invention.

The two-way seat valve illustrated in the drawing acts as a throttle valve in the throughflow direction shown by the arrows 4 and 5 and it acts as a check valve in the reverse throughflow direction. The valve has a choke piston 6 in a housing 1. When the choke piston 6 closes in a sealing manner on the seat 32, it is pressed by the pressure P1 on the oil supply side, on the differential annular piston surface 33 which is substantially formed by the difference between the seat area of the housing and the seat area of the piston. The choke piston 6 has an oil inlet channel 7 with a throttle point 36, which connects the oil inlet channel 2 to the cylinder chamber 9. Furthermore, the choke piston 6 has an axial oil outlet channel 8 which opens out into the oil discharge 3 on the throttle end 37 of the piston.However, the outlet channel 8 is closed in the idle position of the follow-up piston 10 in the seat 11. The follow-up piston 10 is guided in a straight line in the guide 12 and it penetrates the concentrically positioned adjusting piston 13 such that they are both movable relative to each other.

The adjusting piston 1 3 is guided in a sealing manner in the adjusting cylinder 14 and it may be charged with a pressure via the control pressure lines 21 and 24. Its idle position is predetermined by the collar 1 5. The adjusting piston 1 3 and the follow-up piston 10 interact at the stop 1 6 of the follow-up piston 10, and the adjusting piston 1 3 has to travel a certain dead path 34 for this purpose. The follow-up piston 10 is pressed against the seat 11 of the control piston 6 by a spring 17 which is supported at one end against the spring plate 1 8 and against the stop 1 6 of the follow-up piston 10 at the other end, the follow-up piston 10 being pressed as long as the adjusting piston 13 has not overcome the dead path 34.The adjusting piston 13 is positioned on the housing with the collar 1 5 by a spring 19 which is supported at one end against the spring plate 20 and at the other end against the collar 1 5 of the adjusting piston 13, the adjusting piston 13 being so positioned as long as the compressive force produced by the control pressure PS is smaller than the prestressing force of the spring 19. The springs 17 and 19 are mounted in the spring chamber 31 to which is connected return channel 22.

The combined throttle and check valve described above functions in the following manner with the throughflow direction of the arrows 4 and 5. The pressure P1 is applied on the annular surface 33 of the choke piston 6.

However, since the oil outlet channel 8 is closed by the follow-up piston 10 in the seat 11, the pressure P1 is also applied on the annular control surface 35 via the channel 7. Since the annular control surface 35 is larger than the annular surface 33, the closing force predominates and the choke piston 6 closes the oil supply into the oil discharge channel 3 serving the point of use.

When a specific pre-control pressure is now provided in the adjusting cylinder 14 via the precontrol channels 21 and 24, the adjusting piston 1 3 moves upwards against the force of the spring 19. After the dead path 34 is traversed, the follow-up piston 10 with the stop 16 is affected by this movement and it moves upwards against the force of the spring 17. An equilibrium position of the adjusting piston 13 is then obtained which is predetermined by the pre-control pressure on the one hand and by the path-dependent resilience of the springs 17 and 1 9 on the other hand.Due to the fact that the follow-up piston 10 lifts up from the seat 11 , oil flows out through the outlet channel 8 so that the closing pressure P0 in the cylinder chamber 9 acting on the annular control surface 35 falls as a result of the effect of the throttle point 36, until the pressure Pl on the annular surface 33 causes the choke piston 6 to lift off from the seat 32. During this operation, the choke piston 6 with the seat 11 follows the control edge of the follow-up piston 10 such that the compressive forces acting on the piston are in a state of equilibrium and the piston occupies the equilibrium position predetermined by the followup piston 10. The oil flow may be choked in a definite manner as a result of this, depending on the control pressure Ps.

It is also possible to produce the control pressure by adding a pressure relief valve or a pressure reducing valve which may be continuously adjusted in particular by a proportional magnet. The pressure relief valve 23 which is illustrated comprises a housing with a control channel 24 and a return channel 30, a seat 25 and a baffle plate 26. The baffle plate is impacted with a definite force by the rammer 27 and the proportional pre-control magnet 28 and as a result of this, the pressure Ps in the cylinder chamber of the pressure relief valve is restricted to a pre-determined value. Since the pressure relief valve 23 is connected in parallel with the adjusting cylinder 13, the definitely adjusted precontrol pressure Ps also prevails in the adjusting cylinder 14. The electromagnet 28 is designed as a commerically conventional proportional magnet. This means that the adjusting power of the rammer 27 is proportional to the input electrical current. As a result of this, it is possible to achieve a definite adjustment of the piston 6 which is substantially proportional to the electrical current, by adjusting a specific electrical current.

Claims

1. An adjustable throttle valve comprising a two-way seat valve, the hydraulically operated piston of which has a surface ratio which is not equal to 1:1, is connected on its hydraulically charged control surface to the oil supply by an inlet channel having a throttle point, is connected to the oil discharge by an outlet channel, and on the throttle surface which is remote from the control surface is charged with the pressure of the oil flow which is running out: a follow-up piston which is guided in alignment with the outlet channel of the piston and forms an edge control therewith; and an adjusting piston which is connected mechanically to the follow-up piston and is charged with a control pressure in the opening direction of the follow-up piston against a spring; wherein the follow-up piston penetrates the adjusting piston and has a mechanical stop at its end for the mechanical connection with the adjusting piston; and the follow-up piston is spring-loaded in the closing direction, independently of the adjusting piston.

2. A throttle valve according to claim 1, wherein there is a definite spacing between a stop surface of the adjusting piston and the stop of the follow-up piston.

3. A throttle valve according to claim 1 or 2, which further comprises a pressure relief valve which is connected in parallel with the adjusting * piston and the adjusting cylinder.

4. A throttle valve according to claim 3, wherein the pressure relief valve is controlled proportionately and electromagnetically to produce a definite control pressure.

5. A throttle valve substantially as herein described with reference to the accompanying drawing.