US2302534A - Pressure controlled electric switch - Google Patents

Description

Nov. 17, 1942. s. R. DU BRIE PRESSURE CONTROLLED ELECTRIC SWITCH 3 Sheets-Sheet 1 4 mp 7 H L w 6 n 0 2 a W 8 J v E m b. a. II

Nov. 17, 1942. s. R. DU BRIE 2,302,534

PRESSURE CONTROLLED ELECTRIC SWITCH Filed Oct. 16, 1940 s Sheets-Sheet 2 I 26- Jfwr/sw Z DUE/v:

INVENT OR.

Nov. 17, 1942. s. R. DU BRIE PRESSURE CONTROLLED ELECTRIC, SWITCH File d Oct. 16, 1940 3 Sheets-Sheet 3 Patented Nov. 17, 1942 PRESSURE CONTROLLED ELECTRIC SWITCH .Stanley R. Du Brie, Detroit, Mich., assignor to Pickering Products Corp, Detroit, Mich., a corporation of Michigan Application October 16, 1940, Serial No. 361,360

' Claims.

This invention relates to pressure controlled electric switches for use in conjunction with electrically driven air compressors or the like.

The usual compressors of this character have a pump and storage tank wherein the pressure is required to be maintained between certain high and low. limits.

The object of my invention is to provide a new form ofswitchoperating to close the electric circuit to the motor at certain low tank pressure and to break the circuit and cease operation of the pump at certain high tank pressure and includes a new and unique make and break mechanism for the electric circuit. It also, preferably, includes a means for relieving the compressor from pressure when the electric circuit is broken thereby enabling the compressor to be started practically free from load.

The invention 'further seeks to provide certain new structural features including a unique form of make and break switch actuated by variation in tank pressure, all of which is hereinafter more fully described and claimed.

The preferred form of construction of a pressure controlled switch apparatus is shown in the accompanying drawings in which Fig. 1 is a plan view of the switch mechanism, the casing being broken away to show parts thereof.

Fig. 2 is avertical section taken on line 22 of Fig. 1.

Fig. 3 is a vertical section taken on line 3-3 of Fig. 1.

Fig. .4 is a vertical section taken'on line 4-4 of Fig. 1.

Fig. 5 is a perspective view ofan adjustable block for varying the pressure at which the apparatus will function to break the circuit.

Fig. 6 is a plan view showing the pivotal support for the breaker arm taken on the bracketed line 6 in Fig. 2.

Fig. 7 is a section showing the said pivoted support on line l-'! of Fig. 2 and of Fig. 6.

Fig. 8 is an elevation showing a typical installation of my improved switch as associated with an air compressor and storage tank.

My improved apparatus as hereinafter described is for use in the maintenance of an under pressure in storage tanks providing a source of supply for conduits leading to air controlled or operated apparatus, as for instance hammers. and in which system it is desired to maintain the pressure between a minimum and maximum pressure.

The apparatus under control of the switch mechanism may be typically as shown in Fig. 8 in which there is a storage tank I, a compressor 2 driven by a belt from the pulley of the electric motor 3. The compressor intake 4 is screened and the outlet 5 to the tank I has an enlarged chambered portion 6 from which a conduit I extends to a housing 8 which also has a conduit 9 discharging to atmosphere and the function of which is hereinafter described. The motor is here shown as having a three wire circuit indicated generally at l0 which leads into the casing ll of the switch indicated at H in Fig. 1 and leads therefrom by the wires l2 to the'motor, the casing having fittings I3 and I4 through which the wires pass into and from the casing.

Within the casing is the switch block l5 of insulating material having parallel grooves in the upper face in which are secured the terminals l6 and I! in the respective grooves for each of the three'wires. This arrangement will be clearly m'iderstood from Figs. 2 and 3 in which is a cover [B'for these grooves. The terminals l6 and I! have horizontal portions shown in dotted lines in'Fig. 2 ,spaced'apart and engageable by the contact l9 each carried by the upper end of the respective switch stem-20 which are vertically movable in the relationship of the parts shown to break the circuit when in the position shown in dotted lines in Fig. 4-or closethe circuit by the respective springs 20a in the position shown in full lines in said figure.

In'order to make or break the'three wire circuit here shown the three switch stems-must be simultaneously engaged to compress the springs 20a and break the circuit and to likewise simultaneously release the stem to close the circuit and as heretofore stated it is desirable to' break the circuit onattainment of predetermined pressure in thestorage tank andautomatically close the circuit when the pressure has decreased to a predetermined extent. It is also desirable that thesmake or break of each circuit be rapid: in order to reduceor prevent'arcing at the terminals. Furthermore it is desirable that the switch apparatusbe adjustable to make or break thecircuitiata lower or a higher'pressure as may be'required depending upon the service demanded byithe air line 2| leading from the tank to the pressure operated apparatus.

For this purpose I provide a switch actuator shown in longitudinal section in Fig. 4 which comprises a-plate 22 having an aperture to receive a pin 23 supported by a plate 24 which inturn is secured to a'fiexible' diaphragm'25 within the chamber 26 connected by aconduit 21 with the interior of the tank. The position of the diaphragm is determined by the pressure in the tank and this determines the position of the plate 22 which may occupy the position shown in section in Fig. 2 or may occupy the dotted line position shown in Fig. 2. This plate 22, as shown in plan view in Fig. 1, has a recess 23 opening centrally through one edge thereof and on opposite sides of the opening the plate is pressed downwardly by coiled springs 29 mounted on the bolts 30 and having a retaining cap 3 l The bolts are each threaded at the upper end to receive a nut 32 by which the tension of the spring 36 may be varied. The plate 22 at the end thereof opposite the spring restrained end is pivoted on a shaft 33 by the ears 34 on opposite sides of the casing as shown clearly in Fig. 3. The switch block I is supported in position in the upper part of the casing by the sheet metal standards 35 on opposite sides thereof as will be understood from Figs. 2, 3 and 4. Each of these standards has an inturned portion 36 of V-form and the stem actuator 3? has legs 33 on each of its opposite sides which are notched to fit into the V-form portion 36 which functions as a pivot for the stem actuator 31.

This actuator shown in Fig. 3 is of sheet metal form and lies with the crowned portion thereof beneath the switch stems and has a substantially vertical portion 39 at the end opposite the pivots to the lower end of which is attached one end of the coiled spring 40, the opposite end of which is secured to the lugs 4| of the adjusting block 42. The block 42 has grooves 43 in its opposite side edges which engage the 0pposite edges of the recess 28 in the plate 22 as clearly shown in Fig. 1. The block further has a central threaded aperture 44 to receive the screw 45 which has a head 45 provided with flat sides which may engage the spring 41 on the sliding block 42 which prevents accidental rotation of the screw. By rotation of the screw the block is caused to be moved in one direction or the other in the recess to increase or decrease the tension of the spring 40. In the position of the parts shown in Fig. 4, the end of the spring attached to the block is above a horizontal lin extending through the point of attachment of the spring with the down-turned flange 39 of the switch actuator and normally tends to hold the actuator in the position shown in section in Fig. 4. Under the said relationship of parts the contact l9 carried by each of the stems 20 are maintained in contact with the respective terminals [6 and H by the respective springs 20a.

In this position of the contact elements, the circuit to the motor is closed thereby causing the compressor to be operated and to discharge air under pressure to the tank I and as the conduit 21 is open to the tank, pressure will be produced in the chamber which exerts pressure on the plate 22 tending to raise the same under restraint of the springs to the position shown in dotted lines in Fig. 4. This raises the end of the spring attached to the sliding block and at a certain point above the horizontal line passing through the point 40, the tension of the spring will cause the actuator to snap upwardly under tension of the spring to tain degree the spring 30 tends to move the plate 22 downwardly from the dotted position to the full line position shown, permitting the circuit to again be closed by influence of the springs 20a causing engagement of the contact I9 with the terminals l6 and H.

Upon cessation of operation of the motor and consequently of the compressor, the air pressure at the head of the pistons is approximately equal to the pressure in the tank and under such condition the motor would be required to start the compressor under full load. To obviate such undesirable condition, I provide a means for relieving the pressure in the cylinder head and conduits 5, B and 7 between the check valve and the compressor which check valve '50 is closed by pressure in the tank I.

The conduit 1 opens to a housing 8 which has a spring seated valve 5! provided with a stem 52 projecting from the lower side of the housing and a spring 53 tending to seat the valve. The housing also has a conduit 9 open to the chamber therein and discharging to atmosphere. A pivoted lever 54 is provided having an end extending into the casing and has a down-turned end portion 55 extending over th upper surface of the actuator 31. When the actuator is in the position shown in full lines in Figs. 3 and 4, the valve is seated and when the actuator is moved to the dotted line position shown in Fig. 4 the lever 54 is raised to the dotted line position shown in Fig. 3 raising the valve 5| to the dotted line position thereby permitting escape of air from the compressor cylinder and pressure conduits 5, 5 and 7 thus relieving the cylinder from pressure and permitting the compressor to be started free from excess load.

It is to be understood that the invention is not limited to use in a three wire electric circuit as the device may be readily designed for use with circuits involving one or more wires. A basic feature of the invention is involved in the structure of the switch actuating mechanism which includes the switch actuator 31, the spring 40 and a means for varying the tension of the spring and the arrangement of parts wherein variation in pressure in the service line or storage tank varies the position of the plate 22 and consequently the positioning of the spring in such angular relation to the switch actuator as to move the same in one direction or the other in response to a high or a low pressure condition in the tank or service line.

It is believed evident from the foregoing description that the various features and objects of the invention are attained by the described relationship of parts and that various changes may be made in the structure and form of parts within the spirit and scope of the appended claims.

Having thus fully described my invention, its utility and mode of operation, what I claim and desire to secure by Letters Patent of the United States is:

l. A pressur actuated switch comprising a frame, a pair of contacts of an electric circuit supported in insulated relation by the frame, a movable contact element associated with said pair of contacts to make or break the circuit, a spring tending to move said movable contact to make the circuit, means for moving said movable contact to break the circuit comprising a plate pivoted at one end to the frame, a spring at the opposite movable end of the plate for resisting turning of the plate in one direction on its pivot, pressure actuated means for turning the plate on its pivot against the tension of said spring means, a switch actuator comprising an L-shaped member pivotally supported at one end to the frame in a plane vertically above the plane of the pivotal point of said plate and with the opposite end normally in contact with the plate, an adjustable member at the end of the plate opposite the pivoted end, a spring having one end attached to the said adjustable member and the other end attached to the free end of the L-shaped member said point of attachment of the spring to the adjustable member being in a plane between the pivot point of the L shaped member and the pivot point of the plate, said adjustable member providing for variation in the tension of the spring attached thereto, the arrangement providing that, on turning the plate on its pivot by said pressure actuated means against the tension of said spring at the movable end thereof, the actuator spring is caused to turn the actuator on its pivot and move said movable contact element to break the circuit.

2. A pressure actuated switch comprising a frame, a pair of contacts of an electric circuit supported in insulated relation by the frame, a movable contact element associated with said pair of contacts to make or break the circuit, a spring tending to move said movable contact to make the circuit, means for moving said movable contact to break the circuit comprising a plate pivoted at one end to the frame, a spring at the opposite movable end of the plate for resisting turning of the plate in one direction on its pivot, pressure actuated means for turning the plate on its pivot against the tension of said spring means, a switch actuator comprising a member pivotally supported at one end to the frame and with the opposite end normally in contact with the plate, an adjustable member slidable in slots provided at the end of the plate opposite the pivoted end, means for varying the position of the adjustable member in the slot a spring having one end attached to the said adjustable member and the other end attached to the pivoted switch actuator, movement of said adjustable member in the slot varying the tension of the spring attached thereto, the arrangement providing that, on turning the plate on its pivot by said pressure actuated means against the tension of said spring at the movable end of the plate, the actuator spiing is caused to turn the actuator on its pivot and move said movable contact element to break the circuit, and means for varying the tension of the plate spring to thereby determine the pressure at which the switch will function to break the circuit.

3. A pressure controlled switch for making or breaking an electric circuit comprising a frame having contacts for the circuit, a movable switch element for making or breaking the circuit, a spring for moving the switch element to make the circuit, a switch actuator comprising an L-shaped plate pivoted at its long end to the frame for moving the switch element to break the circuit, a coiled spring having one end connected to the short free end of the L-shaped plate and the opposite end supported at a point substantially equi-distantly between the horizontal planes respectively occupied by the free end of the actuator in the switch actuating and non-actuating positions, means for varying the tension of the coiled spring, and a pivoted spring-restrained plate engaged by the short free end of the L-shaped plate responsive to predetermined pressure to turn the L-shaped plate on its pivot to position to permit the coiled spring to thereafter move the Lshaped plate to engage the switch element and break the circuit.

4. A pressure controlled electric switch comprising a frame, a pair of contacts of an electric circuit supported in insulated relation by the frame, a movable contact element for making and breaking the circuit, a spring tending to move the said movable contact element to make the circuit, means for moving said movable contact to break the circuit comprising a plate pivoted at one end to the frame, spring means at the opposite movable end of the pivoted plate for resisting turning of the plate in one direction on its pivot, pressure actuated means for turning the plate on its pivot against the tension of said spring means, a switch actuator comprising an L-shaped plate pivotally supported at one end by the frame at a point spaced from the movable end of the first named pivoted plate, and with the opposite end engaging the first named pivoted plate adjacent its pivot point, a spring attached at one end to the L-shaped plate adjacent the end thereof in contact with the first named pivoted plate, and means on the plate supporting the other end of the spring in a plane between the point of attachment of the first named end thereof to the actuator and the pivot point of the actuator, the arrangement providing that, as the first named pivoted plate is moved on its pivot, the end of the spring supported by said movable end of the first named plate is moved to one side of the pivot point of the actuator, the said actuator is turned on its plane occupied by the pivot by the spring to move the said movable contact against the tension of its pring to break the circuit.

5. A pressure controlled electric switch comprising a frame, a pair of contacts of an electric circuit supported in insulated relation by the frame, a movable contact element for making and breaking the circuit, a spring tending to move the said movable contact element tomake the circuit, means for moving said movable contact to break the circuit comprising a plate pivoted at one end to the frame, spring means at the opposite movable end of the plate for resisting turning of the plate in one direction on its pivot, pressure actuated means for turning the plate on its pivot against the tension of said spring means, a switch actuator comprising an L-shaped member pivotally supported at one end by the frame at a point spaced from the movable end of the plate, and with the opposite free end engaging the plate adjacent its pivot point, a spring attached at one end. to the L-shaped member adjacent the end thereof in contact with the plate, and means at the movable end of the plate supporting the other end of the spring in a plane between the point of attachment of the first named end thereof to the L-shaped member and the pivot point of the plate, the arrangement providing that, as the plate is moved on its pivot, the end of the spring for the L-shaped member supported at said movable end of the plate is moved to one side of the plane occupied by the pivot point of the plate, the said L-shaped member is turned on its pivot by its spring to move the said movable contact against the tension of its spring to break the circuit. and means carried by the plate for varying the tension of the actuator spring.

STANLEY R. DU BRIE.

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