US1976854A - Switch - Google Patents

Description

Oct. 16, 1934.

F. MAYER SWITCH Filed Oct. 21, 1930 His A'ttorneg.

Patented a. 16, 1934 1 PATENT OFFICE SWITCH Frank Mayer, Chicago, Ill., assignor to Edison General Electric Appliance Company, Chicago, 111., a corporation of New York Application October 21, 1930, Serial No. 490,243

15 Claims. (Cl. 200-139) My invention relates to switches, more particularly to electric switches of the quick make and break type, and has for its object the provision of an improved switch of this character.

Although it is not limited thereto, my invention is especially applicable to electric switches intended to be used in connection with temperature control devices in which temperature responsive members, such as bimetallic strips, are provided to actuate the switch.

More or less difiiculty has been experienced with the quick make and break switches heretofore generally used, especially when operating the switch to interrupt the controlled circuit, because of the tendency for the pressure between the switch contacts to become lighter and lighter just preceding the snap movement of the switch to its open contact position. This tendency was particularly pronounced when the switch was 20 used in those temperature control devices wherein the switch is actuated by means of a bimetallic strip, or like member, by reason of the fact that the movements made by the bimetallic strip in response to normal temperature changes are slow and small. It has been found at times that the switch contacts would actually creep apart before the snap action took place. This resulted in considerable arcing at the switch contacts; this arcing rapidly destroyed the contacts necessitating frequent repairs and replacements.

In one of its aspects, my invention contemplates the provision of an electric switch of the quick make and break type which is exceptionally positive and sensitive in its action.

In carrying my invention into effect in one form thereof, I provide a flexible switch operating arm which normally is flexed so as to maintain the switch contacts in engagement. Cooperating with 'the flexible switch arm is a resilient member arranged so that its elastic force tends to maintain the contacts closed. This resilient member operates in the opening movement of the switch arm to apply an elastic force so as to maintain the contacts in engagement with a substantial pressure until the flexure in the switch arm has been absorbed, after which it applied an elastic force to quickly move the switch arm to its open contact position. The resilient member is arranged to apply an elastic force not only to maintain the contacts closed until the flexure in the switch arm has been absorbed during the opening period, and thereafter to quickly open the contacts, but also operates to apply an elastic force to the flexible switch arm in the closing cycle so as to move it quickly to its closed contact position.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a fragmentary perspective view illustrating a temperature control device having an electric switch embodying my invention; Fig. 2 is an elevation of the electric switch embodying my invention, parts being removed so as to illustrate certain structural details, the switch being shown in its closed position; and Fig. 3 is a view similar to Fig. 2 but illustrating the switch in its open position.

Referring to the drawing, I have shown my invention in one form as applied to an electric switch of the quick make and break type intended to be used in connection with a temperature control device. Referring more particularly to Figs. 2 and 3, my electric switch 10 comprises a support or casing 11 having a peripheral wall 12 defining a chamber 13. The chamber 13 is provided at one end with a passageway or opening 14 leading from the chamber to the exterior of the casing. The support or casing 11 is molded or otherwise formed from a suitable electrically insulating material, such as a phenol condensation product.

As shown, a limited portion of each side wall adjacent the closed end of the chamber, and also the end wall portions are considerably thicker than the remaining portions of the side walls, the thickened side wall portions preferably being so shaped that their inner surfaces converge toward each other from the thickened closed end portion toward the open end of the chamber. These thickened wall portions serve to mount or support various elements of the switch. Mounted within one of these thickened side wall portions, for example the upper portion, as viewed in Figs. 2 and 3, is a fixedswitch contact '15, ar-- ranged so that its end projects for a short distance into the chamber 13. This contact may be and as shown is screwed into a suitable threaded hole 16 provided for it in the thickened wall portion. A suitable lock nut 17 is provided for the threaded contact. It will be observed that the foregoing arrangement lends itself readily to adjustments of the fixed contact in the wall portion.

Also mounted within the chamber 13 is a suitable flexible switch arm 18 formed from some suitable strip material having considerable flexibility, such as phosphor bronze. This arm as shown is provided with a portion 18a projecting at an angle from the body of the arm at one end thereof and rigidly secured to the lower right hand wall portion below the opening 14 by means 01' a bolt 19 passed through a suitable hole 20 provided for it in the wall. Preferably the arm 18 will be secured to the wall so that the juncture 21 between the body of the arm and its projecting portion 180. will be located considerably above the fixed lower end of the portion 18a. This arrangement gives the switch arm a very flexible mounting within its support 11. The opposite or movable end or the flexible switch arm 18 is provided with a contact 22 to cooperate with the fixed contact 15. A suitable operating lever 23 is rigidly secured, as by means of a rivet, to the flexible switch arm 18. As shown, this lever projects from the casing through the aperture 1450 that it may be engaged by, any suitable operating means on the exterior of the casing.

The switch arm 18 may or may not serve as a conductor in the electrical circuit to be controlled. In the form of my invention shown in the drawing I have included the switch arm 18 in this circuit. As shown, I have provided a-pair of binding terminal screw socket members 25 and 26 arranged in the thickened side wall portions of the casing on opposite sides of the chamber 13. The screw socket 25 is in electrical contact with the fixed contact 15, while the screw socket 26 is connected electrically with the switch arm 18 by means of a suitable lead member 2'7. As shown, one end 27a of this member is projected at an angle from the body of the member and is rigidly secured in good electrical contact with the projecting portion 18a of the Switch arm by means of the bolt 19. The other end of the lead member 2'7 is secured in good electrical contact with the binding screw socket 26 by means of a suitable stud 28 screwed through the side wall so as to be in contact with the binding socket. Suitable binding screws 29 and 30 are threaded into the sockets 25 and 26 respectively. It will be understood that these screws will serve to connect the .switch in the current to be controlled, or in a controlling circuit for the circuit to be controlled.

It will be observed by reference to the drawing that the body portion of the flexible switch arm 18 and its projecting portion 18a are so proportioned and are arranged at such an angle to each other that when the switch arm is in position in the casing 10 it will be flexed to ,a sufllcient degree to normally maintain the movable contact 22 in engagement with the fixed contact 15. It will be understood that in order to provide for this flexure of the arm 18, the projected portion 18a will have been arranged at such an angle ,with the body portion of thearm that if the body portion were permitted to straighten itself, the

movable contact 22 would overlap the fixed contact. 15 to a limited degree. For example, the projecting portion 18a may have been formed .atan angle of approximately 106 with the body portion of the bar, and is proportioned so that when the switch arm is assembled in its casing this angle will be reduced to approximately 103" )by virtue of the position of the fixed contact 15 of the flexible switch arm 18 is provided a similar knife-edge ,bearing 32. The knife-edge bearing 32 in the flexible switch arm 18 may be provided by cutting away a portion of the material forming the switch arm so as to leave therein an aperature, havingits edge remote from the contact 22 positioned substantially at right angles to the longitudinal axis of the arm. This edge forms the bearing 32. It is desirable that the knife-edge bearing 32 be located a distance from the contacts 15 and 22 which is substantially equal to the distance the conical bearing 31 is from these contacts.

Interposed between the bearings 31 and 32 is a substantially U-shaped resilient spring memberf33, one arm of this member resting on the bearing 31 and its other arm resting on the bearing 32. As shown the arms of the spring memher are provided with suitable seats fitting in the bearings so as to hold the spring member in place.

The bearing -31 lies in the plane of movement of the flexible switch arm 18 in such position that at a certain position of the flexible arm 18, known as the neutral position, the knife-sedge bearing 32 on the flexible arm will lie on a line passing through the bearing 31 and the effective point of support of the bar. The effective point of support of the bar, i. e., the point about which the body 18 of the bar moves, is located approximately at the juncture 21 between the portions 18 and 18a. In the specific arrangement shown the knife-edge bearing 32 when in the neutral position will lie in an imaginary line making an angle of approximately 103. with the projected portion 18a of the switch arm and in cluding the bearing 31.

The spring member 33 has two important functions; it serves as a spring member to apply an elastic force to the flexible switch arm 18 to move the arm quickly from its closed contact to its open contact position, and vice versa, and it serves to maintain the contacts in engagement during the switch opening operation until the switch arm has been unflexed and moved to its neutral position.

It will be observed that the arms of the U- shaped spring member 33 tend to separate by reason of the inherent resiliency of the spring member, the arms being compressed and interposed between the bearings 31 and 32, whereby the member 33 exerts a force on the movable end portion of the flexible switch arm on one side or the other of the neutral position. In the neutral position, however, the entire force exerted by the spring member 33 is lengthwise of the switch arm in the direction of the point of support, i. e., along the 103 line in the specific arrangement shown.

In the operation of the switch, the contact 22- is held in engagement with the fixed contact 15 by a force made up of two components, viz., the force exerted by the flexible switch arm 18 by reason of its flexure, and the component at right angle-to the switch arm of the force applied to the'arm by the spring member 33. Upon the application of a force to the operating lever 23 in a counterclockwise direction, as viewed in Figs. 2 and 3, the switch arm will tend to unflex, the intermediate portion of the arm being moved toward the neutral position. As the operating lever 23 is thus moved andas the switch arm is being unflexed, it will be observed that the bearing 32 will be moved downwardly toward the neutral position, the bearing being moved about the point of engagement of the contact 22 as a center. Thus it will be observed that the bearing 32 is moved toward the neutral position independently of the contact 22 which is still held in engagement with the contact 15. When the "magnitude of the actuating force acting on the lever 23 becomes such that its moment about the center of action, which is approximately the juncture point 2lbetween the arm 18 and its projection 18a, is equal to the moment of the total contact force,

acting about this center of action, an unstable condition is reached and the contact 22 suddenly snaps to the open position. This condition will have been reached when the switch arm has been substantially unflexed and has substantially alined itself in the neutral position.

It will be observed that as the switch arm is being unflexed or straightened in its opening contact movement, the opposing force exerted by the spring member 33 gradually decreases in view of the fact that the spring exerts its force more nearly in the direction of the line of support of the switch arm. It is to be understood, however, that in spite of th's gradual decrease in the effective force applied by the spring member 33 during the opening operation, the contact pressure by virtue of the location of the contacts relative to the arms of the spring member 33 decreases but little during the opening movement of the switch arm from its fully ilexed to the neutral position with the result that the contacts are positively held closed until snap action takes place. In other words, the rate of decrease in the contact pressure during theopening cycle is so small that a considerable pressure remains up to the instant of opening, this pressure being suflicient to prevent creeping apart of the contacts. I have found that I have eliminated practically all chattering of the contacts during the opening operation.

A suitable stop p'n 34 projecting upwardly from the bottom of the casing is provided to limit the open contact position of the switch arm 18. The operating lever 23 also is provided with a suitable stop, which is designated in the drawing by the numeral 35. As shown, this stop comprises a suitable strip-like member having one end rigidly secured to the upper right-hand wall portion above the opening 14 by means of a suitable bolt 35a. The strip is bent or otherwise formed at right angles to the secured portion and is directed to project through the opening 14. The projecting portion of the stop is suitably positioned in thepath of movement of the operating lever 23 so that when the switch has been opened and the switch arm has straightened itself with the contact 22 in engagement with the stop 34, the lever 23 will be stopped so as to prevent undue distortion of the switch arm 18 in the opening direction. Preferably, the stop 35 will be located so that the switch arm will be substantS-ally straight when in its open position (Fig. 3), the arm being slightly flexed in the opening direction byreason of the elastic force applied to it by the spring member 33.

In closing; when the force applied to the actuating lever 23 has decreased to such a value that the switch arm has substantially alined itself in the neutral position the arm portion bearing the movable contact 22 will be quickly moved to carry the contacts into engagement under the influence of the elastic force applied by the spring member 33. As the force applied to the actuating lever 23 is relieved, the switch arm will gradually assume its completely flexed position shown in Fig. 2. v

The chamber 13 is provided with a cover member 36, formed froma suitable electrically insulating material, such as laminated fibre, and is secured to the wall 12 by means of suitable screws 37.

It will be understood that my switch is applicable generally to the control of electric circuits; the'switch may be used either in a circuit to be controlled or in a controlling circuit for the circuitto be controlled. My switch is especially useful, however, in connection with thermostatic control apparatus for electrically heated devices, such as described in the United States Patent No. 1,494,045, issued to W. A. Rankin, dated May 20, 1924. In the apparatus there described a switch of the quick make and break type is mounted upon an adjustable pivoted arm so that the switch may be moved as a whole to any desired position within a limited arc of movement. Cooperating with the switch is an operating arm movable about a pivot on an axis with the pivot of the switch arm. This second arm is operated by means of a bimetallic thermostatic member mounted within the oven whose temperature is to be controlled. In operation: it will be understood that the switch arm will be moved to the desired temperature position at which the cooking operation is to take place. It will also be understood that it is necessary for the thermostat to move the switch actuating arm a distance commensurate' with the setting of the switch arm before the switch will be operated to its open contact position. The switch actuating arm, of course,'is provided with suitable means for engaging a certain portion or actuating member of the snap switch so that when the operating arm has been moved to the position of the setting of the switch arm, the snap switch will be engaged to move to its open position. Therefore, when the temperature of the oven reaches a value substantially equal to the temperature setting of the switch arm, the actuating arm will have been advanced to a point where the switch will be actuated to its open circuit position.

Referring to Fig. 1, I have shown a similar thermostatic control device using an electric switch embodying my invention. The switch 10 is mounted within a suitable casing (not shown) to rotate about a substantially fixed axis through a limited arc of movement. The switch 10 is arranged to move with a suitable operating knob 40, which is mounted to rotate in a suitable bearing provided for it in the casing (not'shown). The knob 40 is mechanically connected to rotate the switch 10 by means of a projecting portion 41 having some non-circular cross-section, as for instance, a hexagonal cross-section, this member being received in a similarly shaped socket 42 provided for it in the switch 10. Preferably the knob 40 will be mounted against a suitable friction spring member (not shown) which operates to hold the knob and consequently its associated switch member 10 in any position to which it may have been moved.

Also mounted within the casing (not shown) and on the same axis of rotation as the switch 10 is a switch actuating arm 43. As shown, this arm is provided with a pin or stud 44 projected inwardly toward the switch and positioned radially of the arm 43 a distance from its axis of rotation suilicient to engage the switch actuating lever 23 (Figs. 1 and 3).

The switch arm 43 is secured to rotate with a shaft 45 suitably mounted to rotate on the same axis as the switch 10. This shaft is operated by means of a suitable bimetallic thermostat element 46. This element is made of two strips'of metal having dissimilar temperature coefllcients of expansion, such as invar steel and monel, these .strips being securely welded together lengthwise,

the integral structure thus formed being helically wound as shown in Fig. 1. One end of this bimetallic element is secured to a fixed support 47, while its other end is secured to the shaft 45 so that when the thermostat is distorted in ii. sponse to temperature changes the shaft will be rotated. A suitable protective cage or like arrangement 48 is arranged about the coiled thermostat 46.

A suitable quadrant 50 provided with graduated scale 51 to act as an index for the switch 10 and the arm 43 is mounted within the casing (not shown). The switch 10 is provided with a pointer 52 to cooperate with the scale 51, and the switch actuating arm 43 is provided with a similar pointer 53.

Preferably, a spring connection (not shown) will be provided between the thermostat 46 and the switch actuating arm 43. This spring connection gives the thermostat a chance to move in response to increases in temperature independently of the setting of the switch 10. It will be noted that if the temperature increases somewhat above the temperature for which the pointer 52 is set, and this will probably occur to some extent in the operation of the control device, the engagement of the pin 44 with the switch actuating lever 23 when the latter has been moved to engage its stop 35 tends to prevent movement of the thermostat and, in order to move further, the thermostat must carry the entire switch mechanism 10 along with it. This imposes an increased load on the thermostat which might be sufficient to cause permanent set, and thus impair its accuracy. With the spring connection, however, the spring yields to allow continued movement of the thermostat so that the thermostat oppose .only the spring.

In the operation of the temperature control device, the electric switch 10 will be located in a controlling circuit (not shown) for the oven heating units (not shown), and the thermostat ele-v ment 46 will be located so as to respond to the oven temperature. The attendant will set the pointer 52 by means of the knob 40 to the temperature at which the cooking operation is to take place, say, for instance, 400 F. Assuming the oven to be cold, it will be understood that the switch operating arm 43 and its pointer 53 will be in the off or zero position. When the temperature of the oven reaches substantially 400 F., the arm 43 will have advanced to a point where the pin 44 associated therewith will engage the switch operating lever 23 so as to effect an opening of the heating circuit. The temperature of the oven will now start to decrease, and the arm 23 as a result will move back and thereby allow the switch contacts to again close the heating .circuit. The temperature of the oven again will begin to'rise, and the switch actuating arm 43 again will move to a point where it will open the switch 10, after which the temperature will begin to decrease and the arm 43 will again move away to allow the closing of the circuit. In this way the temperature within the oven will be held at a substantially constant value.

While I have shown a particular embodiment of my invention, it will be understood, of course,

that I do not wish to be limited thereto since many modifications may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

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

l. A switch comprising cooperating contacts, a flexible switch operating arm for said contacts movable between a pair of positions, means for applying a force to said arm to move the arm to operate said contacts between said positions and a separate elastic member bearing on said switch arm at a point between said contacts and said force applying means arranged to move said arm to one or the other of said positions depending on the position of said switch arm with reference to a neutral position and to maintain said contacts in fixed relation with respect to each other while said switch arm is being moved by said force applying means from one position to the other position until said arm has been moved substantially to said neutral position, whereupon said elastic member moves said switch arm to said other position. I

2. A switch comprising cooperating contacts, a flexible switch operating arm for said contacts, means engaging said arm to normally flex the arm so as to force said contacts into inter-engagement, means for actuating said-switch arm, and resilient means operably associated with said switch arm arranged to apply a force to said arm at a point between said contacts and the point of engagement of said means flexing said arm so as to increase the flexure of said switch arm and thereby the pressure between said contacts whereby when said arm is being actuated to its open contact position said contacts are maintained in engagement with a pressure which retains a substantial value until the flexure in said am has been absorbed, whereupon said contact arm is moved quickly to its open contact position.

3. A switch comprising a fixed contact, a flexible switch arm secured at one end and carrying on its other end a contact to cooperate with said fixed contact, said switch arm being normally flexed so as to force said contacts into interengagement and resilient means arranged to apply an elastic force to said switch arm intermediate its length between the contact carried thereby and its secured end tending to maintain said contacts in interengagement until said arm has been moved substantially to a neutral position after which said resilient means moves said arm quickly to another position.

4. A switch comprising a fixed contact, a movable contact, a flexible switch arm for operating said movable contact, said arm being normally flexed so as to urge said contacts into interengagement, means for applying actuating forces to said switch arm to unflex said arm and thereby operate said movable contact to disengage said fixed contact, and resilient means operably associated with said switch arm to apply a force to said arm at a distance from said contacts so as to increase the flexure of said arm and thereby the pressure between said contacts, said resilient means constantly resisting the unflexing of said arm by said force applying means so as to maintain the contact pressure until said arm has been moved substantially to a neutral position, after which said resilient means moves said arm quickly to another position.

5. An electric switch comprising a support, a stationary contact on said support, a flexible switch arm carrying a contact for movement with respect to said stationary conta t, means mounting said switch arm on said support whereby said switch arm is flexed so that said movable contact is urged into engagement with said stationary contact, means for operating said switch arm so that said movable contact can be moved out of engagement with said stationary contact, and an elastic member acting on said switch arm at a point between said contacts and said mounting means tending to move said arm to its contact closing or to its contact opening position depending on the position of said switch arm with respect to a neutral position, but operating to maintain said contacts in engagement with a substantial pressure during movement of said arm to its open contact position until said arm has been moved substantially to said neutral -'position at which said elastic member tends to move said switch arm to its open contact position.

6. An electric switch comprising a support, a contact fixedly mounted on said support, a flexible switch arm having one end secured to said support and its other end movable laterally, a contact on said other end for cooperation with said flxed contact, said switch arm being flexed to hold its contact in engagement with said fixed contact, and a spring member bearing on said movable end at a point between said contact and said secured end so as to resist movement of said movable end to a position to open said contacts but operating to move said switch arm quickly to its open contact position after said arm has been moved toward its open contact position a distance sufficient to substantially absorb the flexure therein. 7. A switch comprising a flexible arm having, one end fixed and its other end free, a stop limiting the movement of said free end, and a separate resilient member arranged to apply a force to said arm at a point between said stop and the fixed end of said arm.

8. A switch comprising a contact, a flexible switch arm carrying on one end a contact to cooperate with said first contact, means supporting said flexible switch arm at its other end, a bearing seat on said switch arm positioned between the contact carried thereby and said supporting means and a resilient member engaging said bearing seat and arranged to apply an elastic force to said arm.

9. A switch comprising a contact, a flexible switch arm carrying on one end a contact to cooperate with said first contact, means for supporting said flexible switch arm at its other end portion so as to bias said contact into engage 'ment, and a spring member having one arm .bearing on a fixed pivot and another arm hearing on said flexible switch arm at a point between the contact carried thereon and the supported end portion or said arm so as to resist movement -01 said arm from its contact closing position to a neutral position and then to move said arm arm resting on said pivot and its other arm resting on said switch arm at a point between the contact carried thereon and the secured end of said arm.

11. A switch comprising a support, a fixed contact secured to said support, a flexible switch arm secured at one end to said support and having its other end movable laterally, a contact carried by said movable end to cooperate with said fixed contact, said switch arm being flexed so as to bias said contacts into engagement, a fixed pivot bearing adjacent the movable end of said arm in substantial alignment with said arm and a U-shaped spring member having one arm resting on said pivot and its other arm resting on said switch arm at a point between the contact carried thereon and the secured end of said arm such that said contact is substantially midway between said bearings.

12. An electric switch comprising a support, a stationary contact secured to said support, a flexible switch arm carrying a contact for cooperating with said stationary contact, means mounting said switch arm on said support so that said switch arm normally is flexed to force said movable contact into engagement with said stationary contact, a U-shaped spring member having a fixed pivot in approximate alinement with said flexible switch arm and a bearing connection with said switch arm so that said movable contact is positioned between the arms of said U-shaped spring member, and means for operating said resilient switch arm.

13. An electric switch comprising a support, a fixed contact member on said support, a flexible switch arm carrying on one end a contact to cooperate with said fixed contact and having at its other end a portion projecting at an angle there'- from and secured to said support, said arm and said projecting portion being proportioned so that said arm normally is flexed to hold said contacts in engagement, :3. fixed pivot in approximate alinement with said flexible arm when the latter is substantially unflexed and said contacts are in engagement, a bearing on said switch arm positioned a distance from its contact substantially equal to the distance from said contact to said fixed pivot, and a U-shaped spring member having one arm resting on said fixed pivot and its-other arm resting on said bearing provided in said switch arm.

14. A switch comprising a contact, a flexible switch arm carrying on one end a contact to cooperate with said first contact, said switch arm being initially flexed so as to force said contacts into engagement, and a spring member bearing on said flexible switch arm between the contact carried thereby and the other end of said arm so as to apply a force to said arm to increase the flexure thereof and thereby increase the contact pressure, and to maintain said pressure until said arm has been moved to a predetermined neutral position, whereupon said spring means moves said switch arm quickly to separate said contacts.

15. A switch comprising a contact, a flexible switch arm carrying a contact to cooperate with said first contact, means supporting said flexible switch arm and a spring arranged to apply an elastic force to said switch arm having one end resting on a fixed bearing and its other end resting on a bearing positioned between the contact carried by said switch arm and said supporting means and movable with said switch arm in its plane of movement.

FRANK MAYER.

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