US2356177A - Fluid actuated switch - Google Patents

Description

Aug. 22, 1944. L Q PERSON 2,356,177

FLUID ACTUATED SWITCH Filed June 29, 1942 Leslie C. Pierson,

b5 WM 2M OPHQS.

Patented Aug. 22, 1944` FLUID Ac'rUA'rEn SWITCH Leslie C. Pierson, Schenectady, N. Y., assigner to General Electric Corporation, a corporation of New York Application June 29, 1942, Serial No. 448,919

7 Claims.

My invention relates to fluid operated electric switches and more particularly to fluid operated switches of the quick action type.

One object of my invention is to provide quick, or snap, action of the switch both in the switch closing and in the switch opening actuations, and for a consideration of what I believe to be novel and my invention attention is directed to the following specification and to the claims appended thereto.

In the accompanying drawing Fig. 1 is a sectional elevation of a fluid pressure switch embodying my invention; Fig. 2 is a sectional view, taken ln the direction of arrows 2-2 in Fig. l; Fig. 3 is a perspective view of one element of the switch of Fig. l; and Fig. 4 is a perspective view of another element of the switch illustrated in Figs. l and 2.

Referring to the drawing in detail, the switch comprises a generally cylindrical metal housing III having a flange II at its lower end through which bolts II project to attach the housing to a suitable fixture (not shown) for supplying actuating fluid to the housing. The housing is further provided with a central bore which is divided into two compartments by a horizontal wall I2 having therein a vent opening I3. A pair of switch contact blocks I4 and I5 provided respectively with contact surfaces I4' and I5 are mounted in the bore above the wall I2. These blocks are insulated from the wall by a. layer of suitable insulation I6 and from the bore surface by a layer of insulation I1. The contact blocks are held in place by studs I8 and I9 projecting through the wall of the housing and insulated therefrom by insulating sleeves 20. The studs terminate in prongs I8 and I9. Flanges 2| and 22, provided at the base of the prongs, engage the surface of an insulating block 23 placed against the outside surface of the housing. When the studs I8 and I9 are respectively screwed into the blocks I3 and I4 the blocks are pulled tightly against the wall of the housing. A gasket 23' is placed between the block 23 and the housing wall to seal the holes against fluid leakage. A protecting sleeve 24 projecting from the wall of the housing surrounds the prongs I3 and I9 to protect them against injury and to guide a connecting plug to the prongs.

A circuit between the contact blocks I4 and I5 is controlled by a dished disk 25. This disk is normally urged into engagement with the contact surfaces I4 and I5 by an actuating disk 26, made of a suitable insulating material, and urged downwardly by a spring 21 mountedwithn an annular recess in a plug 23. The plug 23 is screwed into the upper end oi the bore in the housing I0 against gasket 23' and thereby clos the upper compartment, or chamber, between the wall I2 and itself. This plug 2B is locked into its nal position by a wire loop 29 threaded through the plug and through a suitable lug 3l projecting from the sleeve 24. This Contact chamber is vented :by a port 3| connected to an annular groove 32 in the end surface of the housing III by a duct 33 in the wall of the housing.

The switch disk 25 is actuated by a pin 35 made of a suitable insulating material mounted in the end of a metal piston rod 36 and actuated by a piston 31 (see also Fig. 4). The piston 31 is mounted in a cylinder 38 which is in the form of a sleeve extension to a plug 39 (se` also Fig. 3) screwed into the lower end of the housing, thereby closing the lower compartment. This cylinder is provided with a relatively short groove 40 upon its inner surface extending from the end of the cylinder to a contiguous bypass slot 4I. I'his Igroove is of small cross section and'constitutes a restricted bypass for fluid from the under side to the upper side of the piston. The slot 4I is relatively wide and extends through the wall of the cylinder. It provides an unrestricted )bypass for fluid past the piston when the piston moves below the end of the groove 40,. The piston rod 36 projects freely through an opening in the wall I2 above the piston 31 and projects below the piston 31 into a bore 43 in the plug 39 in the form of a sleeve 44 which is in sliding contact with the surface of the bore 43. Within this sleeve extension is mounted an auxiliary piston 46 which is normally urged into its lowermost position in the sleeve 44 by a spring 41 against a retaining ring 48 sprung into an annular groove in the wall of the sleeve 44. A port 49 is provided in the sleeve 44. It is positioned just below the end of the cylinder 38 within the bore 43 when the piston 31 is in its lowermost position being closed by the bore surface. Another port 50 is provided in the piston rod 36 connected by a duct 5I to the bore within the piston rod which bore is an extension of therJ inner surface of the sleeve 44 and forms, with; the sleeve 44, the cylinder for the auxiliary piston 46. Port 50 and duct 5I are provided to give free egress to fluid which may leak past the auxiliary piston 46 into this bore. The piston 31 is urged into its lowermost position by a spring 52 mounted in an annular recess in the piston 31 and vplaced under compression between the bottom of this recess and .the lower surface of the wall l2. In this position the piston 31 rests upon the surface of the plug 39. The actual surface of the piston in Contact with the plug surface is that of pads or bosses 53 and 54 (see Fig. 4). These pads are separated from the ibase of the sleeve 44 by an annular groove 55 and create a space for the accumulation of fluid leaking past the sleeve 40. This available space is further increased by tapering the end of the piston as at 56. The space so created for the accumulation of leakage fluid prevents a slow increase in pressure of this fluid which may effect a creeping action of the piston before the proper fluid pressure is built up in the bore 43.

In operation, actuating fluid is directed to the bore 43 and upon a predetermined pressure raises the auxiliary piston 46 to its uppermost position against the force of spring 41 in which it uncovers port 49. An additional rise in the pressure of the actuating fluid to another predetermined value raises the piston 31, against the force of spring 52, sufficiently to permit fluid to pass through the port 49 into the cylinder 38 and thereby expose the complete area of the piston surface to the actuating fluid. The additional rise in pressure of the actuating fluid must overcome the pressure of the spring 52 having available, initially, as an actuating area the end surface of the sleeve 44 and of the auxiliary piston 42. When the port 49 opens into cylinder 38, the area upon which this actuating fluid operates suddenly increases to the full end-surface of the piston 31 and thereby correspondingly increases its operating force to effect a snap action of the piston 3l. In the lowermost position of the piston 31 the actuating pin 35 is slightly spaced from the switch disk 25. The pin engages this disk after the port 49 is opened into cylinder 38 and the entire area oi the piston is exposed to the actuating fluid. The breaking of the circuit between the contact blocks takes place, therefore, during the high speed movement of the piston and reduces arcing to a minimum.

A slight reduction of the actuating fluid pressure does not permit the spring 52 to move the piston 3i downwardly from its uppermost position because of the much larger piston area now effective. However, when the iiuid pressure does drop to a predetermined value, the auxiliary piston 46 is forced down by spring 41 independently of piston 31 until port 49 is closed, thereby trapping the fluid under the piston and simultaneously cutting down the effective piston area to that of the sleeve 44 and auxiliary piston 46. Bypass groove 4U then permits a slow bypass of the trapped uid to the upper side of the piston and allows spring 52 to move the piston slowly downward for the length of the groove. When the piston drops past the end of this groove it opens up the bypass slot 4l to increase the flow of the fluid past the piston and allows the piston to be moved downwardly by the spring 52 against an effective pressure area equal to the end of the sleeve 44 and auxiliary piston 46. Thus, the piston 31 moves downwardly at full speed in response to the pressure of spring 52. The actuation of the switch is thereby a quick, or snap, actuation in the direction of opening as Well as in the dlrection of closing.

Looking at my invention from another viewpoint, the pressure responsive switch has a casing i with a plug 39 screwed into an opening of the casing and forming a differential cylinder for accommodating a differential piston. The differential piston has a large diameter portion 31 and a small diameter portion 44, which latter has a central bore with a port 49 .through its wall. An auxiliary piston 46 is slidably disposed in the bore of the piston portion 44 and biased into an end position by a spring 41 against the fluid pressure exerted thereon. The auxiliary piston normally covers one side of the port 49 while the other side of this port is covered by the small diameter part of the differential cylinder. The large diameter portion of the differential piston has a differential surface with a projection or projections 54 which in the lower end position of the differential piston engage the bottom of the differential cylinder. As explained above, with this arrangement a space is formed between the differential surfaces of the piston and the cylinder which in the lower end position of the piston is filled with leakage fluid so that a sudden increase of the fluid pressure may be effected when communication is established through the port 49 with the bore 43, an increase in fluid pressure in the bore 43 causes upward movement of the differential piston and the auxiliary piston 46 until the latter uncovers the port 49 and communication is established between the large diameter bore of the cylinder and the bore 43. The moment this happens the fluid pressure in said annular space is suddenly increased because the annular space formed between the differential piston and the differential cylinder in the lower end position of the piston is already filled with liquid and only little additional liquid need be supplied to effect rapid upward or opening movement of the differential piston. tion of the switch in the closing direction, as explained above, is accomplished by the provision of a variable bypass for operating iluid around the large diameter portion of the differential piston. The bypass formed by recesses 40, 4| in the inner surface of the large diameter part of the differential cylinder offers a considerable restriction to flow of fluid while the piston is in its upper end position. This resistance to flow is considerably reduced the moment the upper edge of the large diameter piston portion moves below the juncture of' the recesses 40, 4I so that fluid may be quickly bypassed from the lower to the upper side of the large diameter piston portion and quick closing action may be effected by action of the spring 52. The upper edge of the large diameter piston portion alines with the juncture of the recesses 40, 4l when the upper edge of the port 49 is in alinement with the differential surface oi' the cylinder. Thus, with this arrangement the bypassing of operating fluid with regard to the large diameter piston portion is considerably reduced the moment the port 49 establishes communication between the bore 43 and the large diameter cylinder and, vice-versa, said communication through the port 49 is interrupted during downward movement of the piston the moment the restriction of the bypass through recesses 40, 4ll is considerably reduced.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A quick-acting fluid operated switch including the combination of a cylinder, a fluid supply conduit. a piston in said cylinder provided with a sleeve in sliding relationship with said conduit and provided with a port connecting the bore of said sleeve to said cylinder, an auxiliary piston mounted in the bore of said sleeve and operable in response to a predetermined fluid pressure in said conduit to control said port. whereby upon a predetermined increase in fluid pressure said The quick acport is uncovered to expose said actuating piston to fluid pressure and said port is closed to cut off the actuating fluid supply to said actuating piston upon a predetermined reduction in fluid pressure.

2. In a quick acting fluid pressure switch the combination of a cylinder, an actuating piston therein, means for exposing a fractional area of said piston to a fluid pressure until a predetermined fluid pressure is reached and thereafter exposing the complete piston area to said fluid, means providing a slow bypass of iiuid from the high pressure side of said piston to the low pressure side thereof after the actuation of said piston, and means providing for a large bypass of fluid at a predetermined lower fluid pressure whereby a quick action of said piston is obtained both in the switch closing direction and in the switch opening direction.

3. In a quick acting fluid pressure switch, the combination of a cylinder provided with a restricted bypass duct at one end thereof and an unrestricted bypass duct contiguous thereto, a piston in said cylinder, an auxiliary piston mounted within said first mentioned piston, means for moving said pistons to their respective initial positions, means for initially exposing said auxiliary piston to actuating fiuid, means effected by operation of said auxiliary piston in response to a predetermined fluid pressure for increasing the effective operating area of said first mentioned piston to actuating fluid, and means effected by operation of said auxiliary piston in response to a lower fluid pressure for reducing the effective operating area of said first mentioned portion and simultaneously bypassing the actuating fluid past said piston, whereby upon an increase in fluid pressure an initial slow movement of said first mentioned piston is suddenly increased to a quick action and upon a predetermined reduction of uid pressure an initially slow return movement is suddenly increased to a quick action.

4. In a quick acting fluid pressure switch, the

combination of a cylinder, a conduit connecting said cylinder to a source of fluid pressure, a piston in said cylinder provided with a sleeve extending into and in sliding relationship with said conduit, an auxiliary piston mounted in said sleeve and operable to open and close a port in said sleeve connecting the space within said sleeve to the space within said cylinder, a spring arranged to move said piston to an initial position in which said port is closed by said conduit, and a second spring arranged to move said auxiliary piston to an initial position in which it closes said port, said second spring being overcome by a predetermined fluid pressure in said conduit to move said auxiliary piston into a port opening position and said first spring is overcome by a predetermined greater pressure to move said first piston to open said port to said cylinder whereby the operating fluid fiows into said cylinder to increase the effective operating area of said piston, said second spring overcoming said fluid pressure upon a predetermined lower fluid pressure to move said auxiliary piston to a port closing position thereby reducing the effective operating area of said piston and effecting a quick return of said piston by said first spring.

5. In a quick acting fluid pressure switch, the combination of a cylinder, a conduit connecting said cylinder to a source of fluid pressure, a. piston in said cylinder provided with a sleeve extending into and in sliding relationship with said conduit, an auxiliary piston mounted in said sleeve and operable to open andclose a port in said sleeve connecting the space within said sleeve to the space within said cylinder, a spring arranged to move said piston to an initial position in which said port is closed by said conduit, a second spring arranged to move said auxiliary piston to an initial position in which it closes said port, said second spring being overcome by a predetermined fluid pressure in said conduit to move said auxiliary piston into a port opening position at the end of its cylinder and a further increase of fiuid pressure overcomes said first spring to move said piston to open said port whereby the operating fluid flows into said cylinder to increase the effective operating area of said piston, said second 'spring overcoming said fluid pressure upon a predetermined lower fluid pressure to move said auxiliary piston to a port closing position thereby reducing the effective operating area of said piston, and bypass ducts in said cylinder permitting a bypass of the trapped fluid in said cylinder subsequent to the closing of said port to effect a return movement of said piston by action of said first mentioned spring.

6. A quick-acting fluid pressure switch comprising means including a casing forming a differential cylinder, a differential piston slidable in the cylinder and having a projection on its differential surface to form an annular space when engaging the differential surface of the cylinder, means including a port in the small diameter portion of the piston for conducting nuid under pressure to said space, means for controlling fluid fiow through said port, a bypass for operating fluid between the lower and upper sides oi' the large diameter piston portion, and means for automatically increasing the restriction to fluid now through the bypass upon fluid flow through said port.

7. The combination of a differential cylinder, a differential piston movable in the cylinder, the piston having a large diameter portion with a projection facing the differential surface of the cylinder to form an annular space between the piston and the cylinder, the small diameter portion of the piston having a central bore and a port from the bore through the piston wall, means including an auxiliary piston within the bore for controlling the port, the outer end of the port being controlled by relative movement between the differential `piston and the cylinder, and a I bypass between the lower and upper surfaces of the large diameter portion of the differential piston formed in the cylinder wall and controlled by movement of the piston, the bypass having a restricted part to reduce the flow of fluid therethrough upon the differential cylinder uncovering said port to admit fluid under pressure to said annular space.

LESLIE C. PIERSON.

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