GB2023774A - Pressure regulator - Google Patents

Abstract

The regulator comprises a casing 1 having a bore in which a piston 3 is slidable, the priston being biased by an adjustable spring 6 towards one end of the bore and coupled by a pivotal lever 4 to an electric switch 5. A control port 14 communicates with the end 2 of the bore and a chamber 13 defined by a reduced diameter portion 10 of the piston between an inlet port 9 for pressure fluid and a drain port 8. In operation the piston is moved under the forces of the spring 6 and the pressure in the end 2 of the bore to control the supply and discharge of fluid to and from the chamber 13 to maintain the pressure communicated through port 14 constant. <IMAGE>

Description

SPECIFICATION Pressure relay The invention relates to the mechanical engineering, and more specifically to pressure reiays.

The invention may be used in machine tools and other machines where hydraulic devices are employed and where a controlled pressure lower than that in the hydraulic system is to be maintained simultaneously with the control thereof.

The invention resides in that in a pressure relay comprising a casing having a bore accommodating a spring-biased cylindrical piston having a spring adjustment member and operatively connected to an electric switch, and wherein there is provided a controlled pressure hydraulic line communicating with an end space of the casing at the end of the bore, and drain hydraulic line connected to the casing bore at the peripheral surface of the piston, according to the invention, the casing is provided with a main pressure hydraulic line extending between the drain hydraulic line and the end space, the main pressure hydraulic line communicating with the casing bore, and the piston having a portion of a reduced diameter limited by end surfaces having working areas in such a manner that a working chamber is defined in the casing bore between the drain hydraulic line and the main pressure hydraulic line, the working chamber being limited by the reduced diameter portion of the piston and the casing bore wall, the controlled pressure hydraulic line being connected to the working chamber. The invention will now be described with reference to a specific embodiment thereof illustrated in the accompanying drawings, in which: Figure 1 is a sectional view of the pressure relay according to the invention; Figure 2 is a hydraulic circuit diagram of the hydraulic system for quill positioning and clamping by means of the pressure relay according to the invention.

The pressure relay comprises a casing (Fig.

1) having a bore and an end space at the end of the bore. The bore of the casing 1 accommodates a cyiindrical piston 3 which is operatively connected by means of an arm 4 to a pin of an electric switch 5. The piston 3 is loaded by a spring 6 whose force is adjustable by means of an adjustment member 7. The casing 1 has a drain hydraulic line 8 connected to the bore of the casing 1 at the peripheral surface of the piston 3. The casing 1 also has a main pressure hydraulic line 9 which is located between the drain hydraulic line 8 and the end space 2 and communicates with the bore of the casing 1.The piston 3 has a reduced diameter portion 10 of its surface which is limited by end surfaces having working areas 11, 1 2. A working chamber 1 3 is defined in the bore of the casing 1 between the drain hydraulic line 8 and the main pressure hydraulic line 9, which is limited by the reduced diameter portion 10 of the piston 3 and the wall of the bore of the casing 1. Furthermore, the casing 1 has a controlled pressure hydraulic line 14 which communicates with the end space 2 and with the working chamber 1 3. The main pressure hydraulic line 9 communicates with the controlled pressure hydraulic line 14 via the working chamber 1 3.

The pressure relay (Fig. 2) which is only diagrammatically shown is connected to a hydraulic cylinder 1 5 of a quill 16. The pressure relay ensures the positioning and clamping of the quill 1 6 against a workpiece (not shown).

The pressure relay functions in the following manner.

In case there is no working fluid pressure, or at a low pressure of working fluid in the chamber of the hydraulic cylinder 1 5 of the quill 1 6 (Fig. 2), which occurs when the quill 1 6 moves towards the workpiece, the piston 3 is retracted by the spring 6, and the arm 4 actuates the electric switch 5 which feeds an electrical signal indicative of the absence of a required pressure in the hydraulic line 14 of controlled pressure hence in the chamber of the hydraulic cylinder 1 5 and absence of clamping of the quill 1 6 against the workpiece.

Upon clamping of the quill 1 6 against the workpiece the pressure in the chamber of the hydraulic cylinder 1 5 increases, and the pressure force applied by the working fluid to the end face of the piston 3 grows, the piston 3 is caused to displace to overcome the force of the spring 6.

The flow of working fluid from the main pressure hydraulic line 9 is throttled through the working area 1 2 of the piston 3 and is fed through the working chamber 1 3 and the controlled pressure hydraulic line 14 to the chamber of the hydraulic cylinder 1 5. When displacing in the direction of compression of the spring 6 the piston 3 turns off the electric switch 5 by means of the arm 4.At the same time, the piston 3 throttles with its working area 11 the flow of working fluid admitted to the working chamber 1 3 from the main pressure hydraulic line, and the flow of working fluid moving from the working chamber 1 3 to the drain hydraulic line 8, thereby maintaining the pressure of working fluid in the working chamber 13, hence in the chamber of the hydraulic cylinder 1 5 of the quill 1 6 at a constant level and below the pressure in the main pressure hydaulic line 9. The electric switch 5 feeds an electrical signal indicative of the presence of a required pressure.

The value of working fluid pressure in the chamber of the hydraulic cylinder 1 5 of the quill 1 6 is determined by the setting of the adjustment member 7. Accidental changes in the pressure in the working chamber 1 3 result in an axial displacement of the piston 3 in the direction towards diminishing of the error.

Upon a pressure drop in the working fluid in the chamber 1 5 of the quill 1 6 during the clamping of the quill against the workpiece, hence in the working chamber 13, below the adjustment pressure level of the pressure relay, the spring 6 retracts the piston 3, and the arm 4 turns on the electric switch 5 to fed an electrical signal indicative of the absence of a required pressure in the chamber of the hydraulic cylinder 1 5.

Re-adjustment of the controlled pressure is effected by means of the adjustment member 7 to vary the force of the spring 6. During the re-adjustment of the controlled pressure in the hydraulic system (Fig. 2) no additional adjustment of the pressure relay is needed since the piston 3 is set in one and the same position relative to the casing 1, hence the arm 4 is set in one and the same position relative to the electric switch 5 once the pre-set pressure is obtained.

The pressure relay according to the invention combines the functions of two devices: pressure relay and pressure regulator so that pressure control in a system may be simplified, the time for re-adjustment of the controlled pressure may be reduced and the reliability of operation of the hydraulic system improved.

Claims (2)

1. A pressure relay comprising a casing having a bore, a piston slidable in the bore and biased by spring means towards one end of the bore, an electric switch coupled to the piston to be actuated thereby, the casing having a drain port communicating with the bore at a position spaced from said one end, and an inlet port for connection to a source of pressurised fluid communicating with the bore between the drain port and said one end of the bore, the piston having a reduced diameter portion intermediate the ends thereof defining with the casing a chamber between the drain port and the inlet port, and control port means in the casing communicating with the bore at said one end and the chamber, whereby, in use, the valve serves to regulate and is responsive to the fluid pressure communicated to the control port means.

2. A relay according to claim 1 wherein the spring means is adjustable.

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