US2790870A - Fluid pressure actuated switch - Google Patents

Description

April so., 1957 G. H, HANSEN 4.2,790,870

FLUID PRESSURE ACTUATED SWITCH Filed Dec. 8. 1954 2 Sheets-Sheet 1 INVENToR.

Aprxl 30, 1957 G. H. HANSEN 2,790,870

FLUID PRESSURE ACTUATED SWITCH Filed Dec. 8. 1954 2 Sheets-Sheet 2 MMM IN V EN TOR.

United States Patent O Firice FLUID PRESSURE ACTUATED SWITCH Gilbert H. Hansen, Batavia, Ill., assignor to Furnas Electric Company, Batavia, Ill., a corporation of Illinois Application December 8, 1954, Serial No. 473,823

1 Claim. (Cl. 200-83) The present invention relates in general to improvements in electrical switches, and relates more specifically to improvements in the construction and operation of fluid pressure actuated switch units.

The primary object of this invention is to provide an improved fluid pressure actuated electric switch which is simple and durable in construction and which functions with utmost precision and dependability.

It has heretofore been proposed as shown and described in my prior Patent No. 2,598,536 granted May 27, 1952, to provide a fluid pressure actuated switch unit wherein two sets of contacts are closed by a fluid pressure actuated stirrup and are opened by an adjustable helical main spring both coacting with a rigid lever cooperating with a toggle to produce snap action of the movable contacts during closing and opening thereof. While this prior switch has proven highly satisfactory and successful in commercial use, it is somewhat complicated by the fact that it included means for positively holding the contacts open by preventing movement of the movable contact actuating bar member which is recprocable by one of the toggle elements. The construction requires the provision of differential adjusting or modifying means for the main pressure predetermining spring, associated with the fulcrum of the rigid lever through a special bracket, and the differential adjustment for the main spring of the patented assemblage is also difficult to manipulate in order to obtain the desired precision. Then, too, the previous unit made no provision for holding certain parts of the switch together when removed from its housing, and the device is therefore rather difficult to assemble and to adjust.

It is therefore an important object of my present invention to provide various improvements in fluid pressure operated switches of the general type revealed in my prior patent above referred to, whereby the entire assembly is simplified and made more compact, While the functioning of such switches is also radically improved.

Another important object of this invention is to provide a toggle actuated electric switch in which the predetermined pressure at which the mechanism is intended to operate can be readily regulated by simplified means and with utmost precision.

A further important object of the invention is to provide a fluid pressure actuated electric switch unit in which the operating stirrup is maintained in position when the assemblage is removed from the fluid pressure supply source, but may be readily removed from the unit if so desired.

Still another important object of the present invention is to provide various refinements in the structure of fluid pressure actuated electric switches whereby the construction and assembling of such devices is facilitated while the useful life thereof is prolonged.

These and other more specific objects and advantages of the invention will be apparent from the following description from which it should be noted that the gist 2,790,8'7il Patented Apr. 30, 1957 of the improvement is the provision of improved instru-l mentalities for effecting precise functioning of fluid pres# sure actuated switches in accordance with required conditions, and for facilitating construction, assembly and installation of such switch units.

A clear conception of the features constituting my present improvement, and of the construction and opera-v tion of a typical commercial fluid pressure actuated switch unit embodying the invention, may be had by referring to the drawings accompanying and forming a part of this specification in which like reference characters designate the same or similar parts in the various views.

Fig. l is a top view of one of the improved fluid pressure actuated switch units located within its protective housing, but with the cover removed;

Fig. 2 is a side elevation of the switchunit of Fig. l,

confined within its normal housing and cover through which a central vertical section has been taken, a fragment of the fluid pressure supply parts also being shown in section and the main actuating lever and toggle being shown in contact closed position; j Fig. 3 is a central vertical section through the same switch unit taken along the line 3 3 of Fig. l, but illustrating the main actuating lever and toggle in contact open position;

Fig. 4 is a fragmentary off-center vertical section taken through the switch unit along the line 4-4 of Fig. 1, but showing one set of fixed and movable contacts and the actuating bar member for the movable contact in elevation;

Fig. 5 is an elevation of the pressure differential regulating spring alone;

Fig. 6 is a perspective view of the improved fiuid pressure transferring stirrup and its frictional retainer;

Fig. 7 is a plan view of the rigid toggle plate element for displacing the movable switch contacts; and

Fig. 8 is a plan view of the reciprocable movable contact actuating bar member of the improved switch.

While the improved switch has been illustrated somewhat enlarged and especially adapted for application to switch units embodying two sets of fixed and movable contacts for controlling the operation of electric motors or the like, it is not intended to restrict the improved features by virtue of this limited embodiment; and it is also contemplated that specific descriptive terms be given the broadest possible interpretation consistent with the disclosure.

Referring to the drawings, the improved fluid pressure actuated electric switch shown therein, comprises in general, a main frame 9 having a base 1t) provided with integral T-shaped opposite side walls 11 and with an integral end wall 12; a rigid main lever 13 having one end provided with opposite projections 14 fulcrumed in notches in the frame walls 11 while its opposite swinging end has recesses 15 therein and an integral abutment 16 thereon; two laterally separated sets of fixed and movable contacts 17, 18 respectively, carried by a terminal board 19 secured to the upper ends of the frame side walls 11, and which is provided with a central socket 20 and with an off-center bore 21; a toggle having a pair of leaf spring elements 22 the corresponding ends of which are fulcrumed in the frame end wall 12, and also having a rigid plate element 23 the opposite end of which is fulcrumed in the lever recesses 15, while the adjacent ends of the toggle elements 22, 23 are pivotally interconnected; a stirrup disk 24 having upstanding opposite side pro jections 25 provided with knife edges coacting with detents 26 formed in the medial portion of the lever 13; a main spring 27 coacting with the medial portion of the lever 13 between the detents 26 and reacting at its upper end with adjustable means at the top of the socket 20 in the terminal board 19; an upright bar member 28 guided for vertical reciprocation in the frame base and in the terminal board 19 and having therein a central slot 29 coacting with an integral central projeetion 30 on the toggle plate element 23, the upright bar member 28 also being provided with opposite side recesses 31 coacting with resilient carrier arms 32 for the movable contacts 18; and a differential adjustment spring 33 confined within the bore 21 of the terminal board 19 and having a lower cylindrical end 34 with which the lever abutment 16 is cooperable.

The main frame 9 together with its base 10, side walls 11 and end wall 12, may be formed of a single blank of heavy sheet metal with the aid of punches and dies,

and the upper extremities of the side walls 11 are provided with screw threaded ofi-sets 36 with which attaching screws 37 coact to firmly but detachably clamp the terminal board 19 to the frame, see Figs. 1 and 2. The end wall 12 ofL the frame is also provided with an integral tongue 38 which coacts with a similar tongue 39 formed on the terminal board 19 to firmly clamp a sheet 40 of insulation between the frame 9 and the board 19 when the attaching screws 37 are applied; and the frame base 10 is adapted to be fastened to the bottom of a cup-shaped sheet-metal casing or housing 41 having a lower opening 42 through which the stirrup disk 24 is freely movable and also having a side opening 43 through which the electrical conductors for the switch may be extended.

The rigid main lever 13 with its fulcrum projections 14 and abutment 16 may also be formed of durable shcet-metal with the aid of punches and dies, and the elongated curved toggle elements 22 which are fulcrnmed at their corresponding ends in notches formed in the frame end wall 12 are formed of leaf springs, while the other toggle element 23 is formed of thin but rigid sheetmetal of approximately the shape shown in Fig. 7. The lever and toggle assembly is such that when the lever 13 is swung upwardly about its fulcrum projections 14, the interconnected toggle elements 22, 23 upon passing across dead center will snap the toggle plate 23 into the position illustrated in Fig. 3, whereas downward swinging movement of this lever across dead center of the toggle will cause the toggle plate 23 to snap into the position depicted in Fig, 2. The sockets 26 are formed in the top plate of the lever 13, which is also provided with a central elevated portion 45 between these sockets for retaining the lower end of the spring 27 in proper position, as shown in Fig. 3.

The terminal board 19 is formed of insulation and the stationary or fixed contacts 17 are secured within metal bushings 46 embedded within the insulation board;

while the `resilient metal supporting arms` 33 which carry the movable contacts 13 at their free ends, have their opposite ends secured to other metal bushings 47 also embedded in the board 19, by means of screws 48, see Fig. 4. i attaching screws 49 and the bushings 47 are provided with similar terminal attaching screws 50 spaced remote from the screws 49, and the electrical conductors which enter the housing 41 through the opening 43 and may be attached to the screws 49, 50 in a well known manner. The upper portion of the terminal board 19 is also provided with a cover attaching stud 51 to which a nut 52 is applicable as shown in Fig. 2, in order to firmly attach a sheet-metal cover 53 to the housing 41, thereby completing the enclosure of the switch unit while permitting convenient access thereto. i

The stirrup disk 24 and its projections 25 may also be formed of a single blank of sheet-metal with the aid ot' punches and dies, and the lower face of this disk 24 engages a flexible diaphragm 55 clamped to the bottom of the casing 4l by a fluid pressure supply fitting 56 as shown in Fig, 2. This fitting 56 may be placed in communication with the source of iluid under pressure which is to be utilized to actuate the switch unit, and may have a restricted orifice plate 57 mounted therein The bushings 46 are provided with terminal for preventing sudden surges in the fluid pressure from reaching the diaphragm 55. In order to retain the stirrup in proper operating position regardless of the disposition of the switch and to also incidentally prevent the stirrup from dropping out of place when the switch unit is removed from the casing 41, ya U-shaped leaf spring 58 is applied to the disk 24 as illustrated in Figs. 2, 3 and 6. This leaf spring 58 has upwardly extending outwardly biased wings which project snugly through slots 59 in the disk 24 and are adapted to frictionally engage the opposite sides of a central rectangular opening 60 formed in the frame base 10, but which still allow full resilience and freedom of motion of the stirrup. By pressing the resilient Wings of the spring 58 toward each other they may be readily inserted through the opening 60, and when released, the wings will spread apart so as to frictionally suspend the saddle from the frame 9, but the saddle disk 24 can also be conveniently withdrawn when desired.

The main helical compression spring 27 the lower end of which coacts with the mid-portion of the lever 13 around the elevation 45, and the upper part of which is contined within the terminal board socket 20, is adjustable by means of a cap screw 62 coacting with a reaction plate 63 with which the upper end of the spring 27 directly coacts. The screw 62 is embraced directly beneath its head by a washer 64 which engages the top of the socket 20, and the opposite ends of the reaction plate 63 are provided with recesses 65 either of which is slidably engageable with a guide lug 66 formed on the terminal board 19 within the socket 20. The tension of the spring 27 may be varied to approximately predetermine the pressures at which the switch will open and close, by merely rotating the vadjusting screw 62 to cause the reaction plate 63 to move up or down, and the recess coacting with the lug 66 positively prevents the plate 63 from rotating, see Fig. 3.

The upright vertically reciprocable bar member 28 is also formed of insulation and has its lower end 67 guided for movement in 'a slot 68 formed in the frame 9, while its upper end portions 69 are likewise guided in recesses 70 formed in the terminal board 19. The pressure differential adjusting spring 33 and its lower cylindrical end 34 are formed of a single continuous spring wire, and the junctionlbetween the upper and lower spring portions forms a shoulder 71 adapted to coact with the bot- Vtom of the bore 21. The upper open end of the bore 21 is provided with internal screw threads 72"whi'ch are engageable with the periphery of a thin adjusting disk 73 having `slots for receiving a screw driver, and by rotating thisdisk 73 it may be moved up or d-own so that the tension of the spring 33 may be varied in order tomodify the action of the main spring 27. The simple diterentialadjustment made possible with the aid Iof thesetw'o relatively inexpensive parts, namely, the helical spring 33 and disk 73, is very important in order to obtain precision functioning of the main helical spring 27 in opening `and closing the contacts 17, 18 at the proper moments.' The spring 33 embodies a resilient compression portion and the'rigid extension 34 formed integral with each other out of a single continuous wire; while the disk 73 acts asan adjustment member for the spring tension and also has'an inherent tension retaining ability. Although this disk 73 is normally flat, when it is applied to the screw threads 72 it 'assumes the shape of a one turn helix and thereby provides suiiicient tension to keep it in the desired position of adjustment.

When the various parts of the improved fluid pressure actuated switch unit have been properly constructed, they may be readily assembled with the aid of an ordinary screw driverfand applied to a casing 41 so as to cause the stirrup disk 24 to engage the flexible diaphragm 55. The fitting 56 may then be connected to the source of Huid pressure and after the conductors of the motor or other machine which is to be controlled by the switch are properly connected to the terminal screws 49, 50, the system may be operated and the main adjusting screw 63 should be manipulated to approximately establish the pressure range at which the switch mechanism is to function. After this preliminary setting has been effected, operation of the system may be continued while the tension of the differential spring 33 is being varied by adjustment of the disk 73 so as to modify the action of the main spring 27 and to obtain precise functioning of the switch as the tluid pressure varies.

The switch unit will then continue to operate as follows: When the main lever 13 is in lowerrnost position as shown in Fig. 2, and the diaphragm 55 is subjected to increasing fluid pressure, the stirrup plate 24 will rise and swing the lever 13 upwardly about its fulcrum projections 14 until the toggle elements 22, 23 cross dead center position, whereupon the toggle spring elements 22 will quickly swing the lever 13 into its uppermost position as shown in Fig. 3 with a decided snap action. The main spring 27 which coacts directly with the lever 13 will be compressed constantly while this lever is being swung upwardly, but the differential spring 33 will be compressed only when the lever abutment 16 strikes the depending cylindrical spring end 34, and when this ccurs the switch contacts 17, 18 will be closed with a snap action by the bar member 28 as depicted in Fig. 4. If the spring 33 were to be entirely removed from the switch, the mechanism would have an inherent differential and it only would be affected by the main adjustvment spring 27. In other words, lever 13 has definite tripping points. These tripping points in terms of pressure applied to the switch are shifted up and down through the adjustment of the main spring 27. In order to extend the top pressure tripping point, without affecting the lower, the additional small compression spring 33 then cornes into action. This serves to add an additional pressure that lever 13 must encounter just before the actual upward tripping point is reached. The amount of preloading on spring 33 determines how far the upward tripping point shall extend. When the lever 13 is in its uppermost position as shown in Fig. 3, and the diaphragm is subjected to decreasing lluid pressure, the stirrup plate 24 will drop and permit the springs 27, 33 to swing the lever 13 downwardly about its fulcrum projections but the switch contacts 17, 18 will remain closed until this lever has swung down sutliciently to cause the toggle elements to again cross dead center position. The toggle spring elements and the spring 27 will then cause the lever 13 to swing into its lower most position as in Fig. 2, thereby also causing the bar member to open the switch contacts 17, 18 with a snap action. While this action is taking place the differential spring 33 will expand to the fullest extent permitted by the adjusting disk 73, and the alternate closing and opening of the switch will continue as long as the fluid pressure continues to vary sufficiently to cause the toggle to move across dead center.

From the foregoing detailed description of the improved tluid pressure actuated toggle switch unit, it should be apparent that the present invention provides a mechanism composed of relatively few simple but durable parts which may be easily assembled to produce a compact unit, and which may also be conveniently adjusted to effect dependable precision performance. The improved differential adjustment for modifying the functioning of the main spring 27 besides being simple and readily adjustable, functions with utmost precision to regulate the pressure ranges at which the switch is operable, and the retainer spring 58 associated with the pressure actuated stirrup enables this stirrup disk 24 to be maintained as part of the switch unit while the latter is being applied to or removed from its housing 41. Most of the parts of the improved switch assemblage can be produced with the aid of punches and dies, and the invention has gone into satisfactory and highly successful commercial use.

lt should be understood that it is not desired to limit this invention to the exact details of construction and operation of the typical switch unit, herein shown and described, for various modifications within the scope of the appended claim may occur to persons skilled in the art.

l claim:

In a fluid pressure actuated electric switch, a rigid frame having therein an opening bounded by spaced opposite edges, a lever fulcrumed at one end upon said frame and having its medial portion swingable relative to said opening, fixed and movable switch contacts mounted upon said frame, toggle elements operable by said lever to close and open said contacts with a snap action, a spring coacting with one face of said medial lever portion to displace said toggle elements in one direction, a U-shaped fluid pressure actuated stirrup coacting with the opposite face of said medial lever portion to displace said toggle elements in the opposite direction, said stirrup having a rigid medially slitted disk adapted to be subjected to fluid pressure and also having integral upstanding projections pivotally cooperable with said medial lever portion on the opposite sides of said opening but spaced from the adjacent portion of said frame, and a U-shaped retainer having upstanding resilient outwardly biased arms insertible through the slits in said stirrup disk to prevent separation of the retainer from said stirrup and said arms having their free upper ends insertible through said frame opening and frictionally cooperable with said opening edges to maintain the stirrup suspended from the frame.

References Cited in the file of this patent UNITED STATES PATENTS 2,039,957 Hall May 5, 1936 2,259,265 Pearce Oct. 14, 1941 2,307,265 Hansen Jan. 5, 1943 2,307,731 Rickmeyer Ian. 5, 1943 2,393,455 Beeman Ian. 22, 1946 2,529,785 Persons Nov. 14, 1950 2,541,385 Rothwell Feb. 13, 1951 2,598,536 Hansen May 27, 1952

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