GB2115114A

GB2115114A - Hydraulic control valve

Info

Publication number: GB2115114A
Application number: GB08304025A
Authority: GB
Inventors: Laszlo Ladanyi; Bertalan Boncser; Bela Nemet; Gyulane Kallai
Original assignee: DEBRECENI MEZOEGAZDASAGI
Current assignee: DEBRECENI MEZOEGAZDASAGI
Priority date: 1982-02-17
Filing date: 1983-02-14
Publication date: 1983-09-01
Also published as: ATA260882A; FR2521683B1; DE3227116A1; GB8304025D0; AT385136B; DD210333A1; IT8223586A0; DE3227116C2; GB2115114B; PL238521A1; HU185200B; SU1269751A3; FR2521683A1; IT1152873B

Abstract

A compact control valve for regulating the pressure in a duct is provided. The flow of liquid from the duct into a by-pass passage 7 is controlled by a valve member 9 which is urged away from a valve seat 8 when the pressure in the duct is above a pre-set limit. The movement of the valve member 9 is controlled by a pressure- sensitive diaphragm 11 which is connected to the valve member 9 by a housing 12 containing a spring 13, whose tension is adjustable and which urges the valve member 9 against the valve seat. The pressure in a closed chamber above the diaphragm 11 is controllable. Thus, the pressure prevailing in the duct before the valve member will open is governed by (i) the relative areas of the diaphragm and the value seat, (ii) the pressure differential across the diaphragm and (iii) the tension in the spring, the latter two influences being adjustable to give the desired upper pressure limit in the duct. <IMAGE>

Description

SPECIFICATION Hydraulic control valve The invention relates to hydraulic control valve, mainly to valve controlled by hydraulic pressure.

The invention is characterized by a differential control apparatus with recessed spring casing, where the membrane actuadted by the pressure variation and the locking member of the by pass duct are interconnected with a spring case. The connection ensures their co-action while moving on the centrally arranged spring shank. The combined movement brought about by the pressure variation can be influenced with adjustably pretensioned spring. The upper limit of the hydraulic pressure depends on the extent of the spring force. The control range can be altered: - mechanically by manual turn of the spring shank, or by remote control with electric motor, - pneumatically by variation of the pressure in the space above the membrane.

The low power level of the control allows the use of low-power electric motors in case of the automa tically control led alternatives.

Use of the valve for electric and pneumatic operations without the need of any modification offers special advantage.

The range of application possibilities is extensive where the requirement is: control in considerably varying pressure range even in case of liquids polluted with coarse grain size; or process control with remote controlled cock operated at low power level.

The spray solution system of plant protective machines may be mentioned as an example, the strictly specified parameters of which require safely operated and extremely sensitive pressure control device.

The control unit according to the invention ensures the fundamental condition of the uniform distribution of the spray solution, i.e. the constant pressure, or its control according to the travelling speed.

The directly operated control valves used for the mentioned purpose vary the choking of the by-pass duct according to the pressure fluctuation and thereby the pressure determining the quantity of the discharged spray solution is controlled. Movement of the locking member of the by-pass duct takes place against the pretensioned spring. It is desrirable to keep the spring force at constant value during the movement, since softness of the characteristic curve of the spring ensures uniform control. By increasing the length of the spring the required accuracy is attained, however this results in structurally unfavourable dimensions. In case of control valves used in wide pressure range, series connected springs or replacement of the springs becomes necessary.

According to the GFR patent specification No. 1 550 164 a selector switch-operated pressure control valve is used, where the operating range is covered by two springs actuated as selected.

The invention is aimed at the realization of a highly sensitive, continuously adjustable and suitably small valve, which has reliable characteristic curve even if the pressure range is significantly altered.

Essence of the invention is that choking of the by-pass duct is varied with a differential membrane device at reduced power level, and the mobile frictional parts of the control valve are not in contact with the controlled medium, consequently accurate response is attained to the variations of the pressure acting on the membrane.

The invention is in the construction mode of the control valve described in detail with the aid of drawing, in which: Figure 1: Side view of the valve according to the invention, consisting of intermediate housing 6, cover 3, by-pass duct 7, interconnected with bolts 5.

Position of the spring shank 1 protruding from cover 3 is secured by lock nut 2.

Figure 2: Top view of said valve shown with the connecting hole 4 of the pneumatic duct.

Figure 3: Sectional view of the control valve according to the invention shown in a larger scale.

Two ducts intersecting each other are formed in the intermediate housing 6, one of which ensures free through-flow, while the other one is the socalled by-pass duct closed at one side by locking member 9 on the spring case 12 and by membrane 11 on the other side. The outer flange of membrane 11 is pressed to the intermediate housing 6 by cover 3, while the inner flange is clamped by threaded cover 10 of the spring case 12.

The threaded cover 10 of the spring case is provided with a centrally arranged fitting hole, which ensures the guiding an spring shank 14. The threaded end of spring shank 14 extends through the cover and it is flattened. A contacting shoulder part is formed on the spring shank 14 limiting the movement ofthreaded cover 10, while its base supports the spring case and its jacket surface against the lateral forces.

The control spring 13 is between the threaded cover 10 and base of the spring case 14 in pretensioned condition. Shaped valve seat 6 between the intermediate housing 6 and by-pass duct 7 ensures sealed condition.

Operation of the valve according to the invertion is based on the condition, that the hydraulic pressure acting on the locking member 9 and producing the rise from the valve seat 8 is in equilibrium with the sum of forces of the actuating membrane 11 and control spring 13.

The state of equilibrium sets in at varying pressures according to the pretensioning of spring 13.

As a result of the surface proportions of membrane 11 and locking member 9 a low opening force effect arises from the hydraulic pressure compensated by pretensioning of the control spring 13. In case of increasing pressure the threaded cover 10 of spring case 12 moving together with membrane 11 and locking member 9 compresses the contril spring 13. At rise of the locking member 9 choking of the by-pass duct is reduced, while the quantity of liquid flow increases, as a result of which the set pressure value returns to the set value in the direction of free flow.

The operating pressure can be set by turn of the spring shank 14, which results in altered pretensioning of the control spring 13, or it is set indirectly by bringing about gas pressure acting against the membrane force, or by combined use of both possibilities. The pneumatic control method reduces the maximim pressure value fixed by the spring force to the required low level. This way the said alternative of the valve has dual safety degree. The equilibrium of the control valve is fairly independent from the position of the locking member 9, since increase of the spring force within the range of movement is negligible, consequently the equilibrium represents highly stable pressure value.

Claims

1. Hydraulic control valve with membrane moving according to the pressure variations, with locking member controlling the flow through the by-pass duct, connecting element ensuring co-action of the membrane and locking member, as well as a control spring acting against the combined movement, characterized in that its connecting element is formed as spring case guided by centrally arranged spring shank.

2. Control valve as claimed in claim 1., characterized in that the centrally arranged spring shank is threaded to cover, upon the turn of which the pretensioning of control spring is altered.

3. Control valve as claimed in claim 1 or 2., characterized in that a closed space is formed between membrane and cover, the connection of which with the pressurized space allows reduction of the membrane force acting against the control spring i.e. pneumatic control of the pressure is realizable.

4. A hydraulic valve for controlling the pressure prevailing in a duct, the valve comprising a by-pass passage closable by a valve member, a diaphragm movable by pressure variation within the duct, a member connecting the diaphragm and the valve member, and resilient means acting on the movement of the member and/or the diaphragm, wherein the connecting member is a hollow member housing the resilient means.

5. A hydraulic valve substantially as hereinbefore described in connection with and as illustrated in Figure 1 of the accompanying drawings.