US3106623A

US3106623A - Snap action differential actuator

Info

Publication number: US3106623A
Authority: US
Inventors: Robert J Lynn
Original assignee: Vapor Corp
Current assignee: Vapor Corp
Priority date: 1961-12-15
Filing date: 1961-12-15
Publication date: 1963-10-08
Anticipated expiration: 1980-10-08
Also published as: GB1004763A; FR1340414A; DE1296241B

Description

Oct. 8, 1963 R. J. LYNN SNAP ACTION DIFFERENTIAL ACTUATOR 2 Sheets-Sheet 1 Filed Dec. 15, 1961 INVENTOR.

ROBERT J. LYNN m- ATTORNEY Oct. 8, 1963 LYNN 3,106,623

SNAP ACTION DIFFERENTIAL ACTUATOR Filed Dec. 15, 1961 2 Sheets-Sheet 2 g 5 m I W m 1 51% V w 5 m I co \2 2 m g ;%V v m m 9 8 g a LL 00 m V \A Z A 7 3 Ln 0' 1 i E ,6

O A m N Q\ kgr O 00 6 A 8 i INVENTOR.

ROBERT J. LYNN man-0,11

AT TORNEY United States Patent 3,1tl6,623 SNAP ACTlfiN DIFFERENTIAL ATUATR Robert 3!. Lynn, Morton Grove, ill, assignor to Vapor (Importation, Chicago, ill., a corporation at liclaware Filed Dec. is, 961, 9i'- No. 159,715 8 Clai-nis. (Cl. Edd-3) This invention relates in general to a pressure actuator, and more particularly to a snap action differential pres sure actuator for use in operating electrical switches or wherever there is needed a quick acting thrust force, although other uses and purposes will be apparent to one skilled in the art.

A particular use of the present invention is in providing pressure actuated electrical switches such as for use in operating an air compressor or the like. Heretofore, slow acting diaphragm type actuators have been employed for use in operating compressors or the like which have not been fully satisfactory because of the condition of possible zero contact pressure.

It is therefore an object new and improved pressure snap action.

Another object of this invention is in the provision of a snap action differential pressure actuator for use in actuating electrical switches or other devices, wherein positive snap action is provided with no modulation.

A further object of this invention is in the provision of a snap action differential pressure actuator especially useful for operating snap action electrical switches, wherein the undesirable condition of possible zero contact pressure in switches with slow acting actuators is eliminated.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is an axial sectional view taken through a snap action differential actuator according to the invention, and illustrating some parts in elevation for purposes of clarity, and further illustrating the position of the parts during the time when insuliicient pressure exists to operate the actuator;

FIG. 2 is a fragmentary axial sectional view of the device of FIG. 1 and illustrating the position of the parts when the actuator has been energi ed or operated by a predetermined pressure;

FIG. 3 is a transverse sectional view taken substantially along line 3-3 of FIG. 1;

FIG. 4 is a perspective view of a diaphragm or bellofram used in the actuator of the present invention; and

FIG. 5 is an axial sectional view taken through a modified actuator of the present invention.

Referring now to the drawings and particularly to the embodiment disclosed in FIGS. l3, the snap action differential actuator of the present invention includes a sectional housing or casing having a center section or partition lit), a head section ll secured to one side of the center section, and a hollow end section 12; secured to the other side of the center section. The three sections are substantially cylindrical in shape, although it may be appreciated that they may be of some other shape.

A pair of diaphragms which may be more accurately described as belloirams, generally designated by the numerals l3 and 14, are secured between the engaging housing sections. Each bellofrarn, as shown particularly in FIG. 4, is bell or hat shaped in its normal shape wherein it includes a cup-shaped center 15 having a conical wall 116 and an end wall 17, and an annular rim or flange 13 extending from the open end of the cup-shaped portion. The belloframs are constructed of a suitable flexible msof this invention to provide a actuator capable of providing Z2. terial, such as reinforced rubber or the like, and may be further provided with a plurality of circumferentially spaced holes through which fasteners may extend in se curing the housing sections together. The center section ll) is provided on each end with annular recesses 19 and ill which respectively serve to receive the annular rims of the belloframs l3 and id. Mating portions Eli and 22 of the head section 11 and the hollow end section 12, respectively, are respectively telescopically received in the recesses 1& and 26 to firmly grip the rim portions of the belloframs l3 and 14, respectively. A plurality of fasteners 23, such as screws, are provided for securing the head section ill to the center section id while the plurality of screws 24 are provided to secure the hollow end section l2 to the center section ltl. Thus, the rim portions of the bellofrarns are sandwiched and gripped between the adjacent surfaces of the housing sections.

The bellofram i4 is secured at its center to a piston 25 by means of a pin 2s. The piston 25 is provided with a bore 2'7 which receives in press-fit relationship the shank 28 of the pin 2s. The pin also includes a head having an annular flange 2% which overlaps the center of the bellofram and holds it against the end of the piston 25. A circular recess 3% is provided in the center housing ection to receive the head of the pin 26 and to define with the head of the pin and the bellofram a pressure chamber dl. A source of controlling pressure is delivered to the pressure chamber 31 through a conduit fitting 32 that is threadedly received in a tapped bore 33 in the center housing section in, which bore intercomrnunicates with an inlet passage 34 that leads to the pressure chamber 31.

The piston 25 is slidably guided in a plastic guide 35 which may be constructed of nylon, Teflon or the like, and which is provided with a bore an extending therethrough which receives the piston. The bore 36 merges with an enlarged bore 37 which is in alignment with a bore of the same diameter in the hollow end section 1.2 and designated by the numeral 38. It may also be noted that the bore 33 is of the same diameter and in alignment with the recess 3i in the center section it. The plastic guide is secured to the hollow end section 12 by means of the screws 24 which also serve to secure the hollow end section 22 to the center section it The pin 26 in the piston 25 is also provided with a dome-shaped head 39 adjacent the flange 29 which coacts with an annular seat ill defined by one end of a plastic sleeve 41 press-fitted within a recess 42 or" the center housing section ill. The plastic sleeve ll. may be constructed of nylon, Teflon, or any other suitable material, and includes a central bore 43 of the same size as a central bore 44 in the center section to define a passageway 45 extending through the center housing section ill The passageway 45 intercominunicates the pressure chamber 31 with a second pressure chamber as defined by the bellofram l3 and a recess l7 formed about the corresponding end of passageway 45.

Normally the bellofram 13 is held in a position as shown in FIG. 1 by means of a switch actuating plunger 48 having a bell-shaped head 49 that mates with a bell or cup-shaped portion of the bellofram. Extending from the need is the main body cylindrical in shape and designated by the numeral Sil which engages a switch plunger 51 of a switch mounted on the end of the head section 111 by means of screws 53. Although the present invention is shown in connection with the operation of an electrical switch, it should be appreciated that other uses and purposes will be apparent to one skilled in the art. The head 49 of the plunger 43 and the bellshaped portion of the bellofrarn are positioned in a passageway defined by a cylindrical recess 54 in the center aroaoas 3 housing section ill which is of a larger diameter than the recess 47, and a cylindrical recess 55 in the head section ill which is of the same diameter as the cylindrical recess 54. A diametrically reduced cylindrical recess 5s extends from the recess 55 and is in axial alignment therewith, and defines with a still further reduced bore 5"! a shoulder 5%. The bore 57 also serves as a guide for the main body 5%? of the switch actuating plunger l8. An annular slot is formed in the underside of the head it? of the switch actuating plunger and identified by the numeral 5i, and serves to receive one end of a coil spring 6i), the other end of which is bottomed on the shoulder -53. The coil spring (Al normally maintains the switch actuating plunger and bellofram in the position as shown in H6. 1, but will be compressed upon a certain amount of pressure being applied against the belloiram from the chamber :6 so that the switch 52. may be actuated.

When the pressure is below a predetermined amount, the valve between the pressure chambers 3i and 4-6 is closed as shown in HG. l and maintained in closed position until the pressure within the chamber 3-1 reaches a predetermined amount. The valve or piston '25 is held in the position as shown in FIG. 1 by means of a strong coil spring 61 arranged within the hollow end section 12 and hearing at one end against a sleeve spacer as which is maintained in position within the hollow end section 12 by means of a cap 63 threaded into the open end of the end section 12. The other end of the spring fill bears against a flange 64- formed on a cup-shaped spring stabilizer 65. An axially extending aperture as is provided in the stabilizer 65 to receive a diametrically reduced portion 67 of the piston 25. The reduced portion 67 defines with the main body of the piston a shoulder 63 which receives the stabilizer 55. The opening or aperture as in the stabilizer 65 is lot a lesser diametrical dimension than the diameter of the main body of the piston 25. Thus, the spring 61 normally maintains a piston 25 in the position as shown in FIG. 1 to close the valve between the chambers 31 and as.

The piston 25 is provided with an axially extending passageway 69 therethrough defined by a bore '70 that extends clear through the pin 26 and a bore '71 extending from the bore 27 to the other end of the piston, which serves to dump the air pressure when the pressure within the chambers is reduced to a predetermined amount. The pressure is dumped into the hollow end section 12 and out through vents '72 provided in the side wall of the end section. Any number of vents 72, may be provided in the end section 12. To close the passageway 69 during the time when mined amount to actuate the switch, a ball check valve '73 is provided to seat on the end of the bore 71 and to be held in position thereon by an axially extending and adjustable stop 74 which is threadedly received in the cap 63 and locked in position by means of a locking nut 75. The ball check valve 73 is held from moving laterally out of position on the end of the bore '71 by means of a recess 76 in the end of the piston 25 within which the ball check valve is received. The general operation of the actuator, wherein the snap action is accomplished results from the pressure reaching a predetermined limit and causing the valve between the pressure chambers 31 and 46 to open by forcing the piston 25 toward the right against the spring 61. This action of the piston closes the end of the passageway 69 by forcing the ball check valve '73 against the end of the bore 71 and substantially at the same time forces the switch actuating plunger 43 toward the left to actuate the switch 52. The switch actuating plunger 48 remains in its extended position until the air in the chamber 4-6 is suddenly released to atmosphere, and at that time the switch actuating plunger 48 snaps back to its original position thereby giving a snap action in both directions.

More specifically, the snap action differential pressure actuator of the present invention will operate on any the pressure reaches a predeter- 7 l differential pressure and as an example on a differential of 10 pounds per square inch. To further exemplify the operation of the actuator, assuming that it is constructed for operation within certain limits such as to operate the switch when a pressure of 160 psi. is obtained and to deactuate the switch when pressure of p.s.i. is reached. it should be appreciated that these pressure figures may be changed for whatever difi erential and pressure values desired, these values being governed by the seat area of the valve between the pressure chambers 31 and as, the effective area across the bellofram 14, when the piston is in open position, and the constant of spring oil. When the pressure within the chamber 31 reaches p.s.i., this pressure acting on the exposed area of the bellofram id will force the piston 25 to the right by overcoming the biasing effect of the spring dd. As the piston 25 moves to the right, the rather small but significant area of the seat 39 (the area now exposed by the unseating of the piston) will also be exposed to the 160 p.s.i. pressure and the added force will assist in driving the piston 25 to its extreme position thereby seating the ball check valve 73 against the end of the bore 71 to prevent air from leaking through the passageway 69'. Actually, the end of the piston adiacent the ball check valve 7 3 bottoms against the ball to close the passageway 6-9 by means of the ball hitting the stop '74. Thus, the ball check valve is controlled by movement of the piston '25. At the time that the passageway 45 is opened by movement of the piston 25, the pressure will then operate against the exposed area of the hello-tram 13 in the chamber 46 to overcome the biasing of t is spring 69 and drive the switch actuating plunger d? to the left against the switch plunger 51 to operate the switch 52. As the bellofram l3 and switch actuating plunger 43 move to the left, a larger area of the bellofram, as limited new only by the recess 54, will be exposed to the working pressure. Thus, as the operating pressure diminishes through the range of the differential, 10 p.s.i., the switch actuating plunger 48 will be held in the position as shown in FIG. 2 and the other parts will also assume the positions as shown in FIG. 2.

As the differential pressure is traversed, and the operating pressure approaches the lower limit of 150 p.s.i., the piston 25 will start to move back to the left as urged by the spring at. Movement of the piston 25 in this direction allows the ball check valve '73 to unseat from the end of the bore "7i. and open the passageway 69 from the pressure chambers 31 and 46 to the atmosphere. The pressure is then dumped to the atmosphere permitting the piston 25 to reseat and thereby permit the bellofram l3 and switch actuating plunger 48 to snap back under the influence of the spring 64 and deactuate the switch 52. The actuator is then prepared to repeat this cycle.

Once the piston 25 is seated, it does not unseat again until the pressure increases by the differential of 10 p.s.i. or in the example given to 160 p.s.i. after which the above sequence is repeated again. And of course, the piston therefore, would not move again toward the left to the seated position until the pressure drops to 150 p.s.i. or the differential of 10 psi The operating range of the actuator may be varied by adjustment of the stop '74 in the cap 63, within certain predetermined limits.

A modification of the invention is shown in FIG. 5 which only differs from the embodiment of FIGS. 1-3 in structural details. Actually, the operation of this embodiment is substantially identical to that of the embodiment above escribed. Like numerals will be applied to like parts, and only the differences in structure will be pointed out.

The housing sections iii, ill and 12 are substantially identical to the housing sections in PEG. 1 with the exception that they do not have telescoping mating portions and in other small details. It may be noted that the switch actuating plunger 43 protrudes from the end of the head section 11 in this embodiment, while it is wholly received within the head section 11 in FIG. 1. Because the plunger does protrude from the head section 11, spacers 80 are provided between the switch 52 and the head section around the fasteners 53 to properly space the switch and its plunger 51 relative to the switch actuating plunger 48.

One other major difference is in the construction of the piston 25 which in this embodiment includes an elongated cylindrically stepped member having large and small diametrical sections 81 and 82 defining a shoulder 83. The smaller section 82 extends through the aperture 66 of the spring stabilizer 65, and the shoulder 83 bears against the inner side of the stabilizer. The closure cap in this embodiment differs and may therefore be designated by the numeral 84 and is provided at its interior side with a guide bushing 85 having a guide bore 36 for receiving in guiding relationship the smaller diametrical section 820i the piston 25. A recess 87 is provided in the cap 84 against which the ball check valve 73 bottoms during closing of the passageway 69 extending to the piston 25. Ports 88 extend through the bushing 85 for purposes of permitting the air to be dumped through the passageway 69 and out through the vents 72 during the deactuating of the actuator. The bushing 85 may be secured to the cap 84 in any desired manner such as being in press-fitted relationship therewith.

Gne other difference lies in the pin 26 at the valve end of the piston 25. This pin is provided with a threaded body 59 which is threadedly received in the end of the piston 25, and a head 9%) for securing the bellofram M on the end of the piston, and for also providing a conically shaped valve seat 91 for seating against the corresponding end of the bore 44 that defines the passageway 45 between the pressure chambers 31 and 46. Like the pin 26 in the first embodiment, this pin also is provided with a bore extending therethrough and identified by the numeral )2 for connecting to the air pressure dumping passageway 69. As explained above, the operation of this actuator is identical to the operation of the actuator disclosed in FIGS. 1-3 and as already explained.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is hereby claimed as follows:

1. A snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means for supplying a pressure to said first pressure chamber, means for intercommunicating said chambers, first and second belloframs respectively responsive to the pressures in said first and second pressure chambers, valve means operable by said first bellofram to selectively open and close said intercommunicating means in response to a predetermined pressure in said first chamber, an actuator'operable by said second bellofram in response to a predetermined pressure in said second chamber, and means for normally maintaining said predetermined pressure when said valve means is in open position and for dumping the pressure in said second chamber to atmosphere when said valve means is in closed position.

2. A snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means for supplying a pressure to said first pressure chamber, means for intercommunicating said chambers, first and second belloframs respectively responsive to the pressures in said first and second pressure chambers, valve means operable by said first bellofram to selectively open and close said intercommunicating means in response to a predetermined pressure in said first chamber, spring means acting against said valve means to continually urge it into closed position, an actuator engaging said second bellofram and driven in one direction thereby in response to a predetermined pressure in said second chamber, spring means for driving said actuator in the opposite direction in the absence of said pressure in said second chamber, and means for normally maintaining said predetermined pressure when said valve means is in open position and for dumping the pressure in said second chamber to atmosphere when said valve means is in closed position.

3. A snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means for supplying a pressure to said first pressure chamber, means for inter-communicating said chambers, first and second belloframs respectively responsive to the pressures in said first and second pressure chambers, valve means operable by said first bellofram to selectively open and close said intercommunicating means in response to a predetermined pressure in said first chamber, means operable by said valve means for intercornrnunicating said second pressure chamber with the atmosphere when said valve means is in closed position to dump the pressure from said second pressure chamber and for closing communication between said second pressure chamber and atmosphere when said valve means is in open position, and an actuator operable by said second bellofram in response to a predetermined pressure in said second chamber.

4. A snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means for supplying a pressure to said first pressure chamber, means for intercommunicat-ing said chambers, first and second belloiframs respectively responsive to the pressures in said first and second pressure chambers, valve means operable by said first bellofra-m to selectively open and close said in-tercommunicating means in response to a predetermined pressure in said first chamber, means operable by said valve means for intercommunicating said second pressure chamber with the atmosphere when said valve means is in closed position to dump the pressure from said second pressure chamber and for closing communication between said second pressure chamber and atmosphere when said valve means is in open position, spring means acting against said valve means to continually urge it into closed position, an actuator engaging said second bellofram and driven in one direction thereby in response to a predetermined pressure in said second chamber, and spring means for driving said actuator in the opposite direction in the absence of said pressure in said second chamber.

5. A snap action differential pressure actuator com prising a casing, first and second spaced pressure chambers in said casing, means :for supplying a pressure to said first pressure chamber, means for interconrmunicating said chambers, first and second belloframs respectively responsive to the pressures in said first and second pressure chambers, valve means operable by said first bellofram to selectively open and close said inter-communicating means in response to a predetermined pressure in said firs-t chamber, ball check valve means operable by said valve means into closed position when said valve means is in open position and for intercommunicatin-g said second pressure chamber with the atmosphere when said valve means is in closed position to dump the pressure from said second pressure chamber, an actuator engaging said second bellofram and driven in one direction thereby in response to a predetermined pressure in said second chamber, and spring means for driving said actuator in the opposite direotion in the absence of said pressure in said second chamber.

6. In combination with an electric switch, a snap action difierential pressure actuator for operating said switch, said snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means connecting said first chamber with a source of variable pressure, passage means inter-communicating said chambers, first and second bellofra ms respectively responsive to predetermined pressures in said first and second pressure chambers, valve means operable by said first bellotram to selectively open and close said passage means in response to a predetermined pressure in said first chamber, means operable by said valve means for intercommunicating said second pressure chamber with the atmosphere when said valve means is in closed position to dump the pressure from said second pressure chambers and for closing communication between said second pressure chamber and atmosphere when said valve means is in open position, spring means acting against said valve means to continually urge it into closed position, an actuator engaging said second bellofram and driven in one direction thereby in response to a predetermined pressure in said second chamber, said actuator couple to said electric switch for controlling same, and spring means for driving said actuator in the opposite direction in the absence of said pressure in said second chamber.

7. in combination with an electric switch, a snap action differential pressure actuator for operating said switch, aid snap action differential pressure actuator comprising a casing, first and second spaced pressure chambers in said casing, means connecting said first chamber with a source of variable pressure, passage means intercommunicating said chambers, first and second beiloframs respectively re sponsive to predetermined pressures in said first and secand pressure chambers, first valve means operable by said first bellofram to selectively open and close said passage means in response to a predetermined pressure in said first chamber, second valve means operable by said first valve means for intercommunicating said second pressure chamber with the atmosphere when said first valve means is in closed position for dumping the pressure from said second pressure chamber and for closing communication between said second pressure chamber and atmosphere when said first valve means is in open position, an actuator engaging said second bellofram and driven in one direction thereby in response to a predetermined pressure in said second chamber, said actuator coupled to said electric switch for controlling same, and spring means for driving said actuator in the opposite direction in the absence of said pressure in said second chamber.

8. A snap action difierential pressure actuator comprising a pair of spaced diaphragms, a partition extending between said diaphragrns thereby defining a pair of pressure chambers, an aperture in said partition intercommunieating said chambers, one of said diaphragms acting against a spring biased plunger and the other of said diaphragms being secured to a piston, spring means normally biasing piston against one end of said aperture thereby sealing the chambers from each other, means for supplying pressure to said chamber having the diaphragm secured to the piston whereby a predetermined pressure acts against said diaphragm to unseat the piston and operates to drive said diaphragm against said spring biased plunger to displace same, and means for normally maintaining said predetermined pressure and for dumping the pressure when it decreases a predetermined amount to permit the piston to reseat and the plunger to return to its normal position.

References (lited in the file of this patent UNITED STATES PATENTS 2,326,763 Trautman June 1, 1943 2,487,418 Birkemcier et a1 Nov. 8, 1949 2,659,381 Seljos Nov. 17, 1953 2,786,109 Esken Mar. 19, 1957 2,959,352 Cunningham Nov. 8, 1960

Claims

1. A SNAP ACTION DIFFERENTIAL PRESSURE ACTUATOR COMPRISING A CASING, FIRST AND SECOND SPACED PRESSURE CHAMBERS IN SAID CASING, MEANS FOR SUPPLYING A PRESSURE TO SAID FIRST PRESSURE CHAMBER, MEANS FOR INTERCOMMUNICATING SAID CHAMBERS, FIRST AND SECOND BELLOFRAMS RESPECTIVELY RESPONSIVE TO THE PRESSURES IN SAID FIRST AND SECOND PRESSURE CHAMBERS, VALVE MEANS OPERABLE BY SAID FIRST BELLOFRAM TO SELECTIVELY OPEN AND CLOSE SAID INTERCOMMUNICATING MEANS IN RESPONSE TO A PREDETERMINED PRESSURE IN SAID FIRST CHAMBER, AN ACTUATOR OPERABLE BY SAID SECOND BELLOFRAM IN RESPONSE TO A PREDETERMINED PRESSURE IN SAID SECOND CHAMBER, AND MEANS FOR NORMALLY MAINTAINING SAID PREDETERMINED PRESSURE WHEN SAID VALVE MEANS IS IN OPEN POSITION AND FOR DUMPING THE PRESSURE IN SAID SECOND CHAMBER TO ATMOSPHERE WHEN SAID VALVE MEANS IS IN CLOSED POSITION.