US3715538A

US3715538A - Hydraulic pressure differential switch with snap over leaf contact

Info

Publication number: US3715538A
Application number: US00141141A
Authority: US
Inventors: S Ito
Original assignee: Tokai Rika Co Ltd
Current assignee: Tokai Rika Co Ltd
Priority date: 1971-05-07
Filing date: 1971-05-07
Publication date: 1973-02-06
Anticipated expiration: 1990-02-06

Abstract

A switch assembly for detecting a difference in hydraulic pressure and capable of detecting and issuing an alarm if leakage occurs in either one of two hydraulic pressure systems independent of each other, such as the pressure systems for the front and rear brakes in a motor-car, by means of an equilibrating piston acted on by the two independent pressures on its opposite ends and adapted to shift toward one end when leakage occurs in the corresponding system. In response to shifting of the piston, a leaf spring is pushed upward to come into contact with a switch terminal connected to a warning circuit thereby issuing an alarm for the leakage. The present switch assembly has the advantage that the alarm remains actuated without interruption until the spring is pushed back by an external force after repair, thereby completely avoiding an accident due to failure in repairing the leakage.

Description

United States Patent 1 Ito [ 1 Feb. 6, 1973 [75] Inventor:

[73] Assignee: Kabushiki Kaisha Tokai Rika Denki Seisakusho, Nishikasugai-gun, Japan May 7, 1971 Shinya Ito, Tsushima, Japan [22] Filed:

, [21] Appl. No.: 141,141

[52] U.-S. Cl. ..200/82 D, 200/67 DA, 200/153 LA it! i t FOREIGN PATENTS OR APPLICATIONS 74,421 11/1953 Netherlands ..200/67 DE Primary Examiner-Herman .l. Hohauser Assistant ExaminerRobert A. Vanderhye Att0rneyW0odhams, Blanchard & Flynn [57] ABSTRACT A switch assembly for detecting a difference in hydraulic pressure and capable of detecting and issuing an alarm if leakage occurs in either one of two hydraulic pressure systems independent of each other, such as the pressure systems for the front and rear brakes in a motor-car, by means of an equilibrating piston acted on by the two independent pressures on its opposite ends and adapted to shift toward one end when leakage occurs in the corresponding system. In response to shifting of the piston, a leaf spring is pushed upward to come into contact with a switch terminal connected to a warning circuit thereby issuing an alarm for the leakage. The present switch assembly has the advantage that the alarm remains actuated without interruption until the spring is pushed back by an external force after repair, thereby completely avoiding an accident due to failure in repairing the leakage.

7 Claims, 2 Drawing Figures PATENTEDFEB 6 '91s 3,715,538

INVENTOR. Sly/WW4 7 0 HYDRAULIC PRESSURE DIFFERENTIAL SWITCH WITH SNAP OVER LEAF CONTACT This invention relates to a switchassembly for detecting a difference in hydraulic pressure, and more particularly to a switch assembly capable of detecting leakage in one of two hydraulic pressure systems which are independent of each other, such as the pressure systems for the front and rear wheel brakes in a motorcar, by exerting respective hydraulic pressures on both ends of an equilibrating piston provided in said switch assembly. Said equilibrating piston is ordinarily maintained in a neutral position and is adapted to shift toward one or the other end thereof when leakage occurs in either of said two systems. Coincidently, a leaf spring provided in the switch assembly is pushed upward to come into contact with a switch terminal connected to a warning lamp thereby to keep the lamp lit until the leaf spring is pushed back by an external force after the cause of the leakage has been repaired.

In such hydraulic pressure systems as those used for cylinder; an equilibrating, piston contained in said operating the brakes in a motor-car as described hereinabove, wherein the respective main cylinders of the two oil pressure systems are effective only in case of need, a leakage in one of the systems cannot be detected unless both the cylinders simultaneously work. In view of the above, there was provided a leakage warning device comprising an equilibrating piston which bears the respective pressures of the two systems on its respective ends and the piston is adapted to shift toward one of the two systems in which leakage has occurred instantaneously in response to a difference in the pressures applied from said two systems on the opposite ends of the piston, thereby closing a circuit for a warning lamp to keep it lit during the shift of said piston.

Such conventional device, however, has the defect that the circuit opens to turn off the lamp when the main cylinder stops working and fails to give a continuous warning, which is apt to result in a serious accident due to failure to immediately attend to the leakage.

The present invention was made for the purpose of overcoming the above defect in such conventiona leakage warning device.

It is, therefore, an object of the present invention to pressure systems which are independent of each other,

thereby to give an alarm if leakage occurs in either of the two systems. I

It is another object of the present invention to provide a switch assembly for detecting a difference in hydraulic pressure which can maintain the alarm by keeping lit a warning lamp until the warning circuit is opened by an external force, thereby enabling the leakage to be repaired without fail.

According to this invention, there is provided a switch assembly for detecting a difference in hydraulic pressure, which assembly comprises a body having a cylinder formed therein with a plurality of openings connected to two hydraulic pressure systems which are independent of-each other; a switch chamber formed in said body and communicating with said cylinder in the middle thereofin its longitudinal direction; a neck portion formed between said switch chamber and said said neck portion when said piston is in a neutral posi-.

tion, said piston being adapted to shift in response to a difference in hydraulic pressures acting on its opposite ends; a leaf spring having a plurality of radially extending legs fitted in an annular groove formed in the circumference of the switch chamber near the neck portion, the central portion of said leaf spring being curved toward the neck portion in the neutral position of the equilibrating piston and adapted to be deflected or bent upward by the shift of the piston and to be returned to its original position by an external force; a ball slidably fitted in said neck portion in abutment on said reduced portion of the equilibrating piston and adapted to be lifted up by the shifting of the piston to push upward said leaf spring; a switch terminal provided in said switch chamber and adapted to come into contact with said leaf spring when the spring is pushed upward; and a warning circuit connecting the switch terminal to an electric source, thereby detecting a difference in the hydraulic pressures between two independent hydraulic pressure systems and enabling an alarm to be maintained on until said spring is curved back by an external force.

, Various further and more specific objects, features and advantages of the invention will be made apparent from the detailed descriptions of the preferred embodiment of this invention taken in connection with the accompanying drawings in which:

FIG. 1 is a vertical sectional view of a switch assembly for detecting a difference in hydraulic pressures according to this invention, taken along the center line I thereof and partly shown in relief; and

FIG. 2 is a plan view of the leaf spring employed in the present embodiment.

Referring now to the drawings, numeral 1 designates a body of the switch assembly. Numeral 2 designates a cylinder formed in said body 1 and having end portions 3 and 4 which are enlarged in diameter. In the middle of said cylinder 2 in its longitudinal direction, there is formed an opening to a switch chamber 5 which communicates with the cylinder 2 by means of a neck portion 6. Numeral 7 designates an equilibrating piston contained in said cylinder 2. Said equilibrating piston 7 has, inthe middle thereof in its longitudinal direction, a reduced'portion or groove 8 with sloping end walls 9 on both sides. The portion 8 is adapted to confront said neck portion 6 when the equilibrating piston 7 is in the neutral position as shown in FIG. 1.

From the end portions 3 and 4, branch openings 3a and 40 extend transversely. Numerals 10 and 11 are equilibrating springs loosely contained in said end portions 3 and 4 with their inner ends fitted to both ends of the equilibrating piston 7 through washers 12 and 13 I and with their outer ends engaged with respective inner switch chamber 5 near the neck portion 6. The central portion of said leaf spring 17 is curved toward the neck portion 6 as shown by solid lines in FIG. 1. Numeral l9 designates a ball slidably fitted in said neck portion 6 to abut on said reduced portion 8 of the piston 7. Numeral designates a switch body threaded and fixed in said switch chamber 5. Numeral 21 designates a switch terminal slidably inserted in said switch body 20 through an insulating sleeve 22 for insulating said switch terminal 21 from the switch body 20. The switch terminal 21 is so adapted that a contact face thereof in its lower end having a flange 23 exactly confronts the leaf spring 17. Between said flange 23 of the switch terminal 21 and a lower end of the switch body 20, there is pro-' vided an annular oil-proof rubber packing 24, and between an upper flange of said insulating sleeve 22 and the switch body 20, there is provided a push spring 25.

Numeral 26 is a warning circuit connecting said terminal 21 to an electric source B through a warning lamp 27. Numeral 28 is a ground circuit taken out of the body 1.

The operation is described as follows.

Two hydraulic pressure systems independent of each other are respectively connected to the switch assembly of this invention through the openings in the end portions 3 and 4 or the branch openings 3a and 4a to exert hydraulic pressures on both ends of the equilibrating piston 7 so that the piston is kept in the neutral position, as depicted in FIG. 1, by means of the equilibrating springs 10 and 11 and equilibrium between the two hydraulic pressures.

When leakage occurs in one of said two hydraulic pressure systems, the equilibrium between the hydraulic pressures on both ends of the piston 7 is lost and the piston shifts toward the end portion 3 or 4 on which the reduced pressure is applied. Accordingly, the ball 19 is lift-ed up as shown by the dotted line of FIG. 1 to push the center of the leaf spring 17 upward with its legs fitted in the annular groove 16 so that the center of the leaf spring comes into contact with the switch terminal 21, as shown by the dotted line in FIG. 1. Thereupon the warning circuit 26 is completed and the warning lamp 27 is lighted up to give an alarm for the leakage. The upwardly curved configuration of the leaf spring remains as it is to keep on the warning lamp 27 even after repair until the spring ispushed back by an external force as shown in a solid line.

In the present embodiment, the switch terminal 21 is so constructed as to be pressed downward by hand or by some other means against the push spring 25 to restore the original configuration of the leaf spring 17. Alternatively, the switch terminal 21 may be fixed in the switch body 20 and every time an accident happens, which is a rare occasion, the switch body 20 may be removed to push back the leaf spring 17 by fingers or other means after repair.

Since the switch assembly'for detecting a difference in hydraulic pressure according to the present invention has such construction and operation as described hereinabove, the equilibrating piston 7 shifts in response to a difference in the hydraulic pressures acting on the opposite ends thereof and consequently the leaf spring is pushed upward in the center by the ball to bring the spring into contact with the switch terminal thereby to close the warning circuit. The alarm issued from the warning lamp continues until the leaf spring is returned to its original state by an external force, whereby the difference in hydraulic pressure between the two hydraulic pressure systems which are independent of each other and effective only in case of need, such as oil brake circuits in a motor-car, can be detected without interruption thereby to enhance the warning efficiency of the switch assembly.

What is claimed is:

l. A control device for detecting and signalling a difference in two fluid pressures, which comprises:

a body having a longitudinal bore therein and having a switch chamber extending transversely from said bore at a location between the ends of said bore, said body also having a neck portion extending between said switch chamber and said bore and providing communication therebetween;

first and second inlets connected to opposite ends of said bore for supplying pressurized fluid from two independent fluid pressure systems to said opposite ends of said bore;

an equilibrating piston slidably disposed in said bore and having a reduced portion which is positioned in confronting relation to said neck portion in the neutral position of said piston when the fluid pressure forces acting on opposite ends of said piston are substantially equal, said piston being slidable longitudinally in one or the other direction out of said neutral position in response to a difference in the fluid pressures acting on opposite ends of said piston;

a bowed leaf spring mounted in said switch chamber adjacent said neck portion, said leaf spring having a plurality of radially extending legs received in an annular groove in the wall of said switch chamber, the central portion of said leaf spring being movable between a first position in which it is curved toward the neck portion in the neutral position of said equilibrating piston and a second position in which it is curved away from said neck portion;

a ball slidably disposed in said neck portion and projecting into said reduced portion of said piston in the neutral position thereof, said ball being disposed to contact the central portion of the leaf spring so that longitudinal movement to said piston out of said neutral position will move said ball outwardly of said bore and said ball will move said leaf spring from said first position to said second position; switch terminal disposed in said switch chamber and disposed to contact said leaf spring in said second position thereof;

a warning circuit having a signalling device connected in circuit with an electric power source and said switch terminal, whereby a difference in the fluid pressure acting on opposite ends of said equilibrating piston will cause said signalling device to be actuated and the same will remain actuated until the spring is returned to said first position.

2. A device according to claim 1, in which said switch terminal comprises an elongated slidable rod projecting through said switch chamber and outwardly of said body, the outer end of said rod being manually engageable to move said rod inwardly to return said leaf spring to said first position.

3. A device according to claim 2, including an electrical insulating sleeve surrounding said rod.

4. A device according to claim 3, in which said rod and said sleeve are disposed in a switch casing which is threaded into said body.

5. A device according to claim 1, in which said switch terminal is disposed in a switch casing which is threaded into said body, said switch terminal being insulated from said casing.

6. A device according to claim 1, including spring LII

Claims

1. A control device for detecting and signalling a difference in two fluid pressures, which comprises: a body having a longitudinal bore therein and having a switch chamber extending transversely from said bore at a location between the ends of said bore, said body also having a neck portion extending between said switch chamber and said bore and providing communication therebetween; first and second inlets connected to opposite ends of said bore for supplying pressurized fluid from two independent fluid pressure systems to said opposite ends of said bore; an equilibrating piston slidably disposed in said bore and having a reduced portion which is positioned in confronting relation to said neck portion in the neutral position of said piston when the fluid pressure forces acting on opposite ends of said piston are substantially equal, said piston being slidable longitudinally in one or the other direction out of said neutral position in response to a difference in the fluid pressures acting on opposite ends of said piston; a bowed leaf spring mounted in said switch chamber adjacent said neck portion, said leaf spring having a plurality of radially extending legs received in an annular groove in the wall of said switch chamber, the central portion of said leaf spring being movable between a first position in which it is curved toward the neck portion in the neutral position of said equilibrating piston and a second position in which it is curved away from said neck portion; a ball slidably disposed in said neck portion and projecting into said reduced portion of said piston in the neutral position thereof, said ball being disposed to contact the central portion of the leaf spring so that longitudinal movement to said piston out of said neutral position will move said ball outwardly of said bore and said ball will move said leaf spring from said first position to said second position; a switch terminal disposed in said switch chamber and disposed to contact said leaf spring in said second position thereof; a warning circuit having a signalling device connected in circuit with an electric power source and said switch terminal, whereby a difference in the fluid pressure acting on opposite ends of said equilibrating piston will cause said signalling device to be actuated and the same will remain actuated until the spring is returned to said first position.

4. A device according to claim 3, in which said rod and said sleeve are disposed in a switch casing which is threaded into said body. 5. A device according to claim 1, in which said switch terminal is disposed in a switch casing which is threaded into said body, said switch terminal being insulated from said casing.

6. A device according to claim 1, including spring means acting on opposite ends of said equilibrating piston for normally maintaining said equilibrating piston in said neutral position in the absence of unbalanced fluid pressures acting on the opposite ends of said equilibrating piston.