US2767270A

US2767270A - Quick breaking electrical switch

Info

Publication number: US2767270A
Application number: US366123A
Authority: US
Inventors: Laurence M Perkins
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1953-07-06
Filing date: 1953-07-06
Publication date: 1956-10-16
Anticipated expiration: 1973-10-16

Description

Oct. 16, 1956 M. PERKINS QUICK BREAKING ELECTRICAL SWITCH 2 Shets-Sheet 1 Filed July 6, 1953 bx/U 2 f 7 5 a g 1 //L,], H 2 Q g IIIH. HIIIIFILIIIIIIIIIIUMHIHHU 2 W 4 Z 0 O 5 w Q 2 a 2 Z Z Oct. 16, 1956 L. M. PERKINS I 2,

QUICK BREAKING ELECTRICAL SWITCH Filed July 6, 1953 2 Sheets-Shee 2 IN VEN TOR.

United States Patent QUICK BREAKING ELECTRICAL SWITCH Laurence M. Perkins, Whitefish Bay, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application July 6, 1953, Serial No. 366,123

7 Claims. (Cl. 200-67) This invention relates to toggle actuated snap action switches suitable for opening and closing electrical contacts in response to slowly advancing actuation while maintaining substantial contact pressure until the moment of contact throw, and it more specifically resides in a snap action switch having a contact carrying arm displaceable between two positions of rest by the reversible transverse force exerted by a floating toggle mechanism comprising a base anchored actuating blade and a rockable resiliently expandable transverse force reversing member pivotally mounted on the contact carrying arm and pivotally engaging the unanchored end of the actuating blade.

Toggle actuated snap action switches that retain sufficient contact pressures in all stable positions of the switch are well suited for applications where the actuating member of the toggle is advanced slowly as in thermostatic controls and the like. In such instances a switch may hover for considerable periods in the close vicinity of the snap over point and if contact damage is to be avoided contact pressure must remain substantial during such intervals and up to the moment when throw-over occurs.

Toggle switches have heretofore been provided which maintain substantial contact pressure up to the point of throwing, by providing for a storage of energy as the toggle mechanism is brought toward the snap over point. Such energy then initiates snap over before the toggle elements are aligned with the center line or the line of maximum compression of the toggle. In switches of this type, heretofore employed, the transverse components determining contact pressure have been limited by the smaller toggle angles which their structures required or by resilient forces acting within the toggle itself in such fashion as to subtract from the efiective transverse component.

It is an object of this invention to provide a snap switc in which vanishing contact pressure at and near the throwing positions is avoided and in which enhanced transverse force for a given toggle tension is made available.

It is another object of this invention to provide a snap action switch in which a hammerlike blow is delivered to the contact carrier during the throw of the toggle after kinetic energy is built up within the toggle and to provide in such a switch an improved degree of uniformity of response to actuating forces.

It is still another object of this invention to provide, in a switch of the class described, pivoted engagement between distinct toggle elements to more accurately locate the toggle centers and to avoid subtractive transverse forces.

These and other objects and advantages of this invention will appear in the description to follow. In the description reference is made to the accompanying drawings which form a part hereof and in which there is shown by way of illustration and not of limitation one specific form in which this invention may be embodied.

Inthe drawings:

Fig. 1 is a front view in elevation of a pressure responsive actuator upon which a snap action switch constructed in accordance with this invention is mounted,

Fig. 2 is a side view in elevation of the apparatus shown in Fig. l with the snap action switch portion thereof shown in section as viewed through the plane 22 in Fig. 1,

Fig. 3 is a top plan view of the apparatus shown in Figs. 1 and 2,

Fig. 4 is a side view of the contacts and contact actuating portions of the switch shown in Figs. 1, 2, and 3,

Fig. 5 is a side view of the contacts and contact actuating elements shown in Fig. 4 in an alternate position of rest,

Fig. 6 is a view in perspective of the movable contact support and toggle actuating blade which are a part of the switch shown in the previous figures,

Fig. 7 is a view in perspective of the compression spring retainer that forms a part of the switch, shown in the previous figures, and

Fig. 8 is a view in perspective of the compression spring and the end cup that form a portion of the switch shown in the previous figures.

The apparatus shown in Figs. 1, 2 and 3 is in form suitable for use as a refrigeration control, the same being adapted to respond to fluid pressure changes induced, for example, by temperature changes in a refrigerator. The apparatus, as shown, includes pressure responsive parts which are related to but form no part of this invention such as inlet fitting 1 leading to and entering an expandable bellows, not shown, within a bell-shaped spring cage 2 that moves in unison with the expansion and contraction of the bellows. Extending from the spring cage 2 to the left as viewed in Fig. 2, is an actuating rod 3 that likewise moves in unison with the bellows. The rod 3 terminates in a conical toggle actuator 4 that extends within a switch 5 in accordance with this invention and mounted as shown. The fitting 1 is mounted on the formed end of a bent metal frame 6 that forms the two sides and the back of the control. A top panel 7 is turned downwardly at the front thereof for attachment to the frame 6 and to provide a support for the switch 5.

A slotted adjustment head 8 rotatably mounted on the top face of the panel 7 engages a stamped pinion 9 directly beneath the panel 7. The pinion 9 meshes with a compression regulating gear 10 to turn a threaded shaft 11 encircling the control rod 3 which moves a spring retainer 12, held from rotation by a pair of indicator cars 13 in slidable engagement with oppositely disposed edges of the top panel 7. The axial displacement of the spring retainer 12 is measured by a scale 14 marked on the margin of the face of the panel 7 adjacent one of the indicators 13. Held in compression between the spring retainer 12 and the lower flanged edge of the bell shaped spring cage 2 is a main spring 15. The spring 15 acts to urge the spring cage 2 rearwardly in opposition to changing pressure within the bellows, varying in response to a temperature change. Thus, an increase in temperature causes a forward travel of the actuator 4 and the extent of this travel is depend ent upon the loading of the spring 15 which may be adjusted by the setting of the spring retainer 12.

The switch 5 is assembled on a base 16 formed of a suitable insulating material secured by means of mounting screws 17 shown in Fig. 1. Held in place near the top of the switch 5 by means of rivets is a pair of

stationary contact arms

18 and 19 that carry

contacts

20 and 21 respectively. The

contacts

20 and 21 are spaced from one another in facing relationship to permit a movable contact to be positioned therebetween.

3 The

contact arms

18 and 19 are extended ,as shown to provide appropriate

terminal connections

22 and 23 respectively. For adjustment of the position of the contact a hexagonal nut 24 is seated within the base .16' and a set screw 25 extends through the nut 24 with the tip thereof-pressing upon the back of the contact arm 18. By adjustment of the screw 25 the contact arm 18 and contact 20 may be sprung toward or away from the contact 21. A third terminal'26 for connection to a movable contact is provided atthe bottom of the switch 5. Formed integrally with the terminal 26 is a vertical finger 27 that extends outwardly from the base 16 to act as a stop for an actuating blade of toggle mechanism to be hereinafter described. A second stop 49 spaced rearwardly from the finger 27 is formed by a raised portion of the base 16 Anchored between the terminal 26 and the base 16 is a combined contact carrier and actuator 23 formed 'as a single stamping'from thin resilient sheet material positioned for movement between the stationary con- 7

tacts

20 and 21. To increase the stiflness of the upper portions or" the arms 38, ribs 33 are formed therein by embossing. The arms carry inwardly extending offsets to provide pivot shoulders 34 and abutments 35 at the upper deflectable ends for purposes to be noted.

Member 28 includes a toggle actuating blade 36 disposed between the pair of contact arms 36 and merged integrally with the base 29. The resilience of the material forming the member 28 is such as to permit elastic distortion or bending of the blade 36. The blade 36 is stiffened, however, along a major portion of its length by embossed ribs 37, to confine a greater part of the flexure to the lower portion of the blade 36 adjacent the base 29. Upon mounting the member 28 beneath the terminal 26 electrical connection between the latter and contacts 32 is provided.

Arms 30 and the actuating blade 36 are free to be deflected entirely independently of one another, and for this reason the blade 36 may be formed separately from the contact arms 34) if desired. Beryllium-copper alloy is preferred for making up the member 28, since it may be easily formed in annealed state and then heat treated to develop the desired resilience. The blade 36 may be formed so that under zero stress it will occupy'a position divergent from the arms 36. The blade 36 as shown in the drawings is so formed to render the switch in greater detail in Fig. 7. The head of the retainer 38 includes a spring seat 39 formed as a centrally located boss 46 which retains a spring 46 seated thereon in its intended position. The upper margins of the spring seat 39 are cut away to present limiting

shoulders

41 and 42. Extending downwardly from the head of the floating toggle member, to a position in alignment with the seat 39, is a pair of hooked fingers 43 each shaped to provide pivot notches 44 adapted to seat upon and pivot about the pivot shoulders 34 of the contact carrying arms 30. With the notches 44 bearing against the shoulders 34 and with the spring seat 39 between the abutments 35 the floating toggle member 38 may be rocked between the positions shown in Figs. 4 and 5 which pivotal movement is limited by engagement of the

limiting shoulders

41 and 42 with the abutments 35.

Disposed between the free end 45 of the actuating blade 36 and the spring seat 39 is a compression spring 46, previously noted, one end being seated against the seat 39 and the opposite end housed within an end cup y 47. The base of thecup 47 is indented and perforated as shown in Fig. 8 to provide spaced knife edge seats on opposite sides of an opening 43 which receives the pointed end 45 of the blade 36, so that the cup 47 and the blade end 45 are confined to a rocking motion with respect to one another.

The anchored member of the toggle of'the switch consists of the defiectableactuating .blade 36 the upper end of which communicates through spring .46 with the floating toggle member 38 which is carried in turn upon the movable contact carrier 30. With the actuating rod 4 retracted so as not to apply a pressure upon the blade 36 theelements ofthe switch will assume the position shown in Fig. 4. The unstresseddivergence of the blade 36 from member 30 acts to maintain blade 36 rearwardly, or to the right as viewed in Fig. 4, so as to bear lightly against the stop 49 that forms a part of the base 16. The compression spring 46 urges the spring retainer 38 to pivot counterclockwise, as viewed in Fig; 4, about the shoulders 34 sothat the shoulders 41 rest against the abutment surfaces 35 of the contact carrying arms 30. The spring 46 is thus angularly disposed to provide a component of force inthe line of action of the contacts 32 to provide contact pressure. The reaction of spring 46 at the same time reenforces the normal tendency of the blade 36 tobear against stop 49.

As the actuator 4 is moved forwardly in response to pressure increase in the bellows housed by the cage 2 an actuating-force is applied to the-blade 36. The blade 36 is consequently deflected forwardly and acts as a multiplying lever to enlarge small increments of movement of the actuator 4 into corresponding substantial movement at the -end45. Deflection of the blade'and movement of its end 45 carries the spring 46 toward alignment with the contact arms 30. The location of the shoulders 41 at 'one side of the efiective line of thrust of thespring 46 permits a substantial obliquity of the spring 46 with respect to the contact arms 30. This obliquity ensures substantial contact pressures until reversal of the line of :action of the floating toggle 38. Movement=of the blade '36 consequently may .be continued to a position nearly in alignment with the contact arms 30' without disappearance of contact pressure. Before such'alignment is achieved the toggle mechanism becomes involved in a discharge of'stored energy which ensures a reversal.

Resilience of the blade 36 admits of distortion which results in storageof 'a'slight but'perc eptible amount of springenergy therein because of the thrust of spring 46. As movement of the-blade 36 toward discharge position is continued'the incidence of the trust of spring 46 decreases, thus reducing the component of the force exerted by spring 46 acting normal to the path of the end 45 of blade 36. A position is thereforlultimately reached in which the counter-stress in blade 36 exceeds the resisting component of spring 46 whereupon, the stored energy in blade 36 is discharged. At the time of such discharge, the amount of energy stored is sufiicient to invert the floating toggle-38. Substantial contact pressure is thus maintained'up to the time of the inversion.

Snap over is accompanied by a clockwise rotation of spring retainer 38. Shoulders 41 are disengaged from abutments 35 of the contact arms 39 and within the space of lost motion of the retainer 38 in which the shoulders- 42.are advancing toward engagement with the arms '30 a rapid build up of kinetic energy may occur. The impact of shoulders 42 upon the contact arms 30 thus delivers a hammerlike blow to aid a rapid excursion of the contact .32 from the position of rest of Fig. 4 to the positionof'rest of Fig. 5. The Now delivered not onlyieflects rapid travel for the contact 32 but may be of suflicient force to break loose small welds that otherwise would immobilize the contact 32 and disrupt switch action; 7

Upon retraction of the actuator 4 the action of the toggle will be reversed and the position of Fig. 4 will be resumed. The permanent set of the blade 36 provides for suflicient force to actuate the toggle in the returning direction.

By placing the end 45 of blade 36 close to the pivots 34 and below the same the blade 36 may be moved nearly into alignment with the contact arms 30 without causing inversion of the floating toggle 38 and thus the so-called diflerential or space between actuating points may be made quite small. The stable positions of the toggle elements are thus maintained without snap over or extinction of contact pressure until the blade 36 approaches close alignment with the arms 30. If desired, the upper end of blade 36 may be made to extend slightly above the pivots 34 and when such is done a switch reresults which will throw from one position of finite contact pressure to another, with no intermediate position of equilibrium in which contact pressure vanishes, without dependence upon storage of energy due to resilience in parts such as the blade 36 or carrier 30. While some advantages may be obtained in this way, the actuating difierential is increased so that this construction is less desirable than the one previously described where the end 45 of the blade is below the pivots 34 and advantage is taken of stored energy in the blade 36 to maintain contact force until the moment of snap over while at the same time reducing the differential movement between snap in opposite directions.

I claim:

1. In a snap action switch a deflectable contact carrier blade anchored at its inner end and having a deflectable outer end furnishing a movable mounting for an electrical contact, a movable contact mounted on the outer end of said carrier blade, spaced contact arresting means limiting the excursion of said movable contact, a floating toggle member separate from said carrier blade pivotally connected thereto for limited rocking movement about a pair of spaced aligned pivots on said carrier near the outer end thereof, an inwardly facing spring seat on said floating toggle disposed outwardly from said spaced pivot points, a carrier deflecting expansion spring seated on said spring seat extending inwardly therefrom towards said spaced pivots and between the same inclinable with said floating toggle when rocked to impose transverse deflecting forces upon said carrier, an

actuating blade having an anchored inner end and a deflectable outer end extending toward and engaging the inner end of said expansion spring to maintain a compressive force therein, and means cooperatively engaging said actuating blade for moving the defiectable end thereof transversely of the carrier blade to and from opposite sides of said spaced pivots to reverse the inclination of said expansion spring and floating toggle with a snap action to cause said movable contact to be moved with a snap action.

2. In a snap action switch in accordance with claim 1 an apparatus in which the means for moving the actuating blade consists of transversely movable means engaging said blade to apply a transverse force thereto at 'a point near the inner end thereof.

3. A snap action switch in accordance with claim 1 wherein the spaced contact arresting means comprise at least one stationary electrical contact.

4. A snap action switch in accordance with claim 1 wherein said floating toggle includes spaced stop means engageable with said carrier blade to limit the rocking angle of inclination thereof and to engage said carrier blade with an impact force when snap action occurs.

5. A snap action switch in accordance with claim 1 wherein the carrier blade comprises spaced side legs joining the inner end thereof with the movable contact mounting and the actuating blade is disposed between said legs and movable across the space between said legs.

6. A snap action switch in accordance with claim 1 wherein spaced stationary stop means are disposed in the path of movement of the deflectable end of said actuating blade to limit the excursion of movement thereof land to contribute to the reaction forces resisting the expansive force of said expansion spring.

7. A snap switch in accordance with claim 1 wherein the floating toggle member comprises a pair of hooked pivot fingers engaging aligned inwardly extending shoulders on the carrier blade.

References Cited in the file of this patent UNITED STATES PATENTS