US2330506A

US2330506A - Snap switch construction

Info

Publication number: US2330506A
Application number: US414716A
Authority: US
Inventors: Lynn H Matthias
Original assignee: Allen Bradley Co LLC
Current assignee: Allen Bradley Co LLC
Priority date: 1941-10-13
Filing date: 1941-10-13
Publication date: 1943-09-28
Anticipated expiration: 1960-09-28

Description

Sept. 28, 1943- H. MATTHIAS SNAP SWITCH CONSTRUCTION Filed Oct. 15, 1941 2 Sheets-Shegt 1 FIG. 2.

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DID

INVENTOR LYNN H. MATTHIAS ATTORNEZ p 1943- L. H. MATTHIAS 2,330,506

SNAP SWITCH CONSTRUCTION Filed Oct. 15, 1941 2 Sheets-Sheet 2 FIG. 58. FIG. 5C

LI.) 0 n: o LL H I iF L; j E

\ I DEFLECTION v E v v J UNRESTRAINED MOTION TO OPEN POSlTION. I UNRESTRAINED Mqno N T0 CLOSED POSITION.

' INVENTOR LYNN H; MATTHIAS.

WLmJG ATTORNEY Patented Sept. 28, 1943 srr OFFICE SNAP SWITCH CONSTRUCTION Application October 13, 1941, Serial No. 414,716

3 Claims. (01. 200-67) This invention relates to an improvement in switch operating mechanisms and is more particularly adaptable to switch operating mechanisms of the snap action type.

The object of this invention is to secure a snap action mechanism that has means to increase the force available for maintaining adequate switch contact pressure.

A further object of this invention is to secure a snap switch in which substantial contact pressure is maintained until after initiation of the snap action mechanism to move the switch to open position. The contact pressure is thus reduced to zero during the period of free or dynamic motion of the snap action mechanism.

A further object of this invention is to secure a snap switch construction in which the force of a snap action mechanism efiective to establish contact pressure in the closed position is supplemented with an additional force obtained from a biasing means independent of the snap action mechanism.

A furtherobject of this invention is to secure a snap switch construction in which the movable contact member has a biasing means positioned in line with the switch contacts to initiate and assist the movement of the movable contact member to the closed position, to improve the character of operation of the switch contacts to the closed position and to supplement the force of the snap action mechanism effective to establish contact pressure in the closed posinon.

A further object is to improve the construction of the snap switch disclosed in the pending application of Gustav O. Wilms, Serial No. 235,760, filed Qctober 19, 1938, now Patent No. 2,260,964 dated Oct. 28, 1941, whereby the horsepower rating of the switch is substantially increased.

The snap switch construction includes a movable contact making member that is operated by a snap action mechanism alternately from closed position to open position with the snap action mechanism suitably coupled to the movable contact making member so as to exert a force on the movable contact member in a direction to maintain either open or closed" position. The biasing means for the movable contact member in the "open position of the switch is less than and oppositely directed to the force exerted by the switch operating mechanism on the movable contact member to maintain the open position. In the closed position of the switch thdbiasing means of the movable contact member is assisted by the force exerted by the switch operating mechanism on the movable contact member in a direction to maintain the movable contact member in closed position. The force exerted by the switch operating mechanism during the actuation of the movable contact member from closed to open position becomes greater than the bias of the movable contact member after the snap action mechanism passes the neutral or over-center position. There is thus a force effective to hold the contacts closed up to the time that the snap action mechanism is in a state of unrestrained motion to complete the movement of the contact member from "closed to open position.

The switch construction of this invention is especially adaptable to switch operating mechanism of the so-called snap action type. Even though the snap action mechanism has a definite dead-center position, the switch contacts can still be maintained in the closed position by a definite contact pressure that is independent of the snap action device. After the deadcenter position has been passed and dynamic motion of the snap action device continues, a point is reached where the contact pressure is reduced to zero and the contacts open during the period of unrestrained motion of the snap action mechanism.

The preferred form of this invention is shown on the attached drawings in which Fig. 1 is a plan view of a complete snap switch utilizing the biased movable contact member.

Fig. 2 isa sectional side view of the switch mechanism shown in Fig. 1.

Fig. 3 is a simplified side view showing the essential elements of this invention in the open position.

Fig. 4 is a simplified side view showing the essential elements of this invention in the closed position.

Fig. 5A, B, C, D, E and F showin diagrammatic form the sequence of operations in moving the switch from open to closed position and from closed to open position. These diagrams show the forces effective to secure the improved operation of the snap switch of this invention.

Fig. 6 shows the relationship of the deflection of the snap switch mechanism to the forces actuating the movable contact member.

The snap switch construction, that is the subject of this invention, is shown in connection with a snap action switch of the type disclosed in the Wilms application referred to above.

Figures 1, 2, 3 and 4 show in detail the construction of the preferred form of this invention. The

complete switch comprises a base member I, movable contact member 6, stationary contact 2| and a snap action mechanism that includes movable contact member 6, a center-leaf spring I I and an over-center spring IT.

The base member I is made of molded insulating material having a raised portion 2 that serves as a means for mounting the movable contact member 6, center-leaf spring II and the formed member I3. There is an opening 3 in base member I for receiving actuator 22. A raised portion 5 on the molded base I provides support for the member 26, pin 29 and biasing spring I 9. The molded base I also provides a raised portion 2 that serves as a lower stop for the center-leaf spring II.

The movable contact member 6 and the centerleaf spring I I are made from a single piece of fiat spring material. These two members are formed by a cutout portion 9 that permits the centerleaf spring II to be flexed to alternate positions on either side of the movable contact member 6. The fixed end Ill, of the movable contact member 6 and center-deaf spring II, is mounted on the raised portion 2 supporting both members in cantilever fashion. The member I3, that serves as the movable contact terminal, is used to hold in place the fixed end I by means of rivets that pass through the raised portion 2. The member I3 has attached thereto a pin I that provides support for a bias spring I6 that is used to return the center-leaf spring II to the position shown in Figures 2 and 3. The free end of the member I3 provides an upper stop for the centerleaf spring II when in the position shown in Fig. 4.

The free end of the movable contact member 6 is provided with a contact I and at the end of the cutout portion 9 adjacent to contact I a pivot 8 for engaging an over-center spring II. The free end of the center-leaf spring II also has a pivot I2 for engaging the over-center spring II. Thus the compression spring IT, with a cup member I8 at each end thereof, is spaced between the pivots 8 and I2 forming an over-center spring mechanism in which the center-leaf spring I I can be actuated to alternate positions on either side of the plane of the movable contact member 6.

A stationary contact 2| is mounted to molded base I and positioned opposite the movable contact I so that in the normal position of the snap action mechanism the movable contact I will be disengaged from stationary contact 2|. Upon movement of the over-center spring mechanism to the alternate position, contact I is moved into I engagement with stationary contact 2 I A projecting pin mounted to member 26 provides support for the compression spring I9 and serves as a stop for the movable contact member 6 when in the position shown in Figures 2 and 3. The biasing spring I9 supplements the force exerted by the over-center spring mechanism on the movable contact member 6 when in the closed position and is of such character as to not prevent snap motion of the movable contact member 6.

Actuator 22 is inserted in the opening 3 and prevented from extreme motion in one direction by the shoulder 24 and in the other directionby the lock ring 25. This actuator is adapted to apply pressure to the center-leaf spring II at a point 23 that is intermediate pivot I2 and the rigidly mounted end II] of the center-leaf spring The over-center spring mechanism and' the actuator 22 operate in the manner set forth in the application of Wilms referred to above. In the normal position of the mechanism shown in Figures 2 and 3 upon application of pressure by means of actuator 22, flexure of the center-leaf spring II continues until sufficient energy is stored therein to initiate and carry through the motion of the over-center spring mechanism to the position shown in Fig. 4. Upon release of actuator 22, spring I5 flexes the center-leaf spring II in the reverse direction until sufficient energy is stored therein to initiate and carry through the motion of the over-center spring mechanism to the normal position.

In the design of this switch the construction is such that snap motion in either direction occurs before the pivot I2 reaches the overcenter position. The characteristics of the springs are such that upon motion of actuator 22 in either direction, to the point of instability on either side of the movable contact member 6, sufficient energy is stored within the center-leaf spring II to carry to completion the snap motion of the over-center spring from one position of equilibrium to another.

In order to explain the mode of operation of the improved snap switch construction a series of diagrams are shown giving the forces effective to move the contact member to alternate positions. The relation of the forces effective to move the contact member throughout the range of deflection of the snap action mechanism and the resulting contact pressure are shown in Fig. 6. In this diagram, force is plotted against deflection of the pivot point l2 of the center-leaf spring II. Throughout the range of motion of the pivot I2, biasing spring I9 is effective to pro- 'vide a force represented by the curve A. Likewise throughout the range of deflection of the pivot I2, the over-center spring I! is effective to provide a force on the movable contact member 6 that is designated by curve B. The resultant of the two forces A and B effective to provide contact pressure is shown by curve C.

With the contacts of the switch in the normally opened position, application of pressure to the actuator 22 to the point where unrestrained motion of the center-leaf spring II to the open po sition begins creates a condition of stress that is shown in Fig. 5A. This condition of stress corresponds to the point E in Fig. 6. At this point the center-leaf spring II is flexed and sufiicient energy is stored therein to carry pivot I2 to point D with snap motion independent of further movement of actuator 22. At the point E the vector B, shown in Fig. 5A, is opposed by the sum of vectors S and A. The vector A being the force exerted by the spring I9 and vector S being the force exerted by the pin 20.

The unrestrained motion from point E to D is of an indeterminant character but it is known that it follows a curve of the general type shown by the broken line between those two points. During the period of motion to the closed" position, vector B first diminishes to zero and then changes in direction and increases to the value shown in Fig. 50. There is an intermediate position such as that shown in Fig. 53, where vector B is equal and opposite to vector A. It is at this point that motion from the open to the closed position begins. The movement of the movable contact member 6 from the open" to the closed position is initiated by a force designated by vector A. Simultaneously with the reversal of the over-center spring I], the force exerted on the movable contact member 6 to the closed" position is supplemented by a force designated by vector B. In the final closed position of the contacts the contact pressure designated by vector C is equal to the sum of vectors A and B as shown in Fig. C.

With the contacts in the closed position, release of actuator 22 to point D initiates unrestrained motion to the "open position. Unrestrained motion and decrease in the value of vector B continue, without movement of the movable contact member 6, until the point corresponding to G in Fig. 6 is reached. This point corresponds to the condition shown in Fig. 5E. At this point the over-center spring mechanism has already moved to the opposite side of the movable contact member 6 and the vector.B is equal and opposed to vector A and the contact pressure is zero. Upon further movement of the over-center spring and further increase in the value of the vector B the contacts separate and move to the open position shown in Fig. 5F. In Fig. 5F the vector B is opposed by the vector S which is the force exerted by the stop 20 and the vector A which is the force effected by the bias spring 19.

The characteristics of the movable contact biasing means must be properly related to the snap action mechanism to insure true snap action to both open and closed position. During movement to the open position the biasing spring l9, in moving from point G to H on Fig. 6, must not increase at too rapid a rate or ultimately attain a value greater than the value for curve B as it approaches point E. If this condition is not maintained, the snap acting mechanism will complete its motion and come to rest before sufilcient force has been developed to actuate the movable contact member to the open" position.

Upon operation of the switch to the closed position the change in the value of the vector B from point E to D must continue at such a rate related to the force exerted by the biasing means that true snap action to the closed" position takes place. It is, therefore, necessary that the value of the vector B be greater than the value of vector A until after point E has been passed and the snap action mechanism is operatingdefinitely within the zone of unrestrained motion. The point where vector B is equal and opposite to vector A must be within the zone of unrestrained motion and the value of the vector B must be greater than the value of the vector A as it approaches the end of the period of unrestrained motion to the closed position.

When the snap switch construction is used in connection with a snap action mechanism where upon movement to the closed position the value of vector B is less than the value of vector A at point E, the movement 'of the movable contact member 6 will occur before point E. is reached and closure will occur without snap action. If, however, upon movement of the movable contact member 6 the pivot 8 moves sufiiciently, before the closed position is reached, to initiate unrestrained motion of the snap action mechanism the switch will operate in asatisfactory manner.

Snap action mechanisms of the type that have a dead-center position or a very limited zone of unrestrained motion can be operated in accordance with the teachings of this invention if the movement of the movable contact member by the force of the biasing means is sufficient to carry the pivot point of the over-center mechanism across the dead-center position or into the zone of unrestrained motion before the contacts close. This mode of operation results in a snap switch construction that difiers only slightly from the mode of operation of the preferred form herein disclosed and is deemed to come within the scope of the invention.

It is to be noted in the snap switch construction herein disclosed that the biasing means for the movable contact member comprises a coil spring l9 that is in line with and directly behind the movable contact I. The biasing spring l9 positioned directly behind the movable contact 1 is effective in improving the operation of the switch contacts from the open to the closed position. There are numerous alternative ways in which the movable contact member 6 could be biased so as to operate in the manner of this invention. It has been found, however, that the location of the bias directly in line and behind the movable contact is particularly advantageous. It is thought that the improved operation resulting from positioning the biasing spring I9 directly behind the contact I is that in movement to the closed position there is less rebound of the contacts and therefore less chance for the contacts to weld on closure of the switch.

The snap switch construction of this invention provides a switch that is more efficient than the conventional over--center snap acting switch. The improved switch operation and increased contact pressure are obtained without requiring any increase in the amount of energy required to actuate the switch. In the disclosed-form of this invention it is possible to remove the biasing spring l9 and the remaining switch structure will operate in the manner set forth in the Wilms application referred to above. The force and deflection required to actuate the center-leaf spring I I from one point of unrestrained motion to another (points E and D of Fig. 6) will not be altered by the removal of the biasing spring. Therefore, by the addition of the biasing spring I9 in the manner set forth in the disclosure above, it is possible to increase the horsepower rating of the snap switch without requiring an expenditure of an additional amount of energy to actuate the switch from one position to another.

I claim as my invention:

1. The combination with aswitch comprising a movable contact engageable with a stationary contact, a contact carrier movable in a fixed path carrying said movable contact and shiftable to opposite positions to engage and disengage said contacts, a contact spring engaging said carrier and arranged to shift said contact carrier to either position by tilting of said spring, a movable actuating spring arranged between a support and said contact spring at its end opposite the contact carrier to maintain said contact spring under compression in either position and operable to tilt said contact spring from either position to its corresponding other position, of means in constant engagement with said contact carrier and biasing the same to its engaged position and the force exerted by said contact spring during movement of the contact carrier to disengaged position.

2. The combination with a switch comprising a movable contact engageable with a stationary contact, a contact carrier movable in a fixed path carrying said movable contact and shiftable to opposite positions to engage and disengage said contacts, a contact spring engaging said carrier and arranged to shift said contact carrier to either position by tilting of said spring, a mov- 1 able actuating spring arranged between a support and said contact spring at its end opposite the contact carrier to maintain said contact spring under compression in either position and operable to tilt said contact spring from either 1 position to its corresponding other position, of a biasing spring in constant engagement with said contact carrier and arranged to bias said movable contact to its engaged position and said biasing spring-to be deflected in the line of movement of said movable contact and the force exerted by said contact spring as derived from the actuating spring to actuate said movable contact carrier from engaged to disengaged position being greater than the bias of the'contact carrier 2 in its engaged position and during movement of the contact carrier to disengaged position.

3. The combination with a switch comprising a movable contact engageable with a stationary contact, a contact carrier movable in a fixed path carrying said movable contact and shiitable to opposite positions to engage and disengage said contacts, a contact spring engaging said carrier and arranged to shift said contact carrier to either positionby tilting of said spring, a movable actuating spring arranged between a support and said contact spring at its end opposite the contact carrier to maintain said contact spring under compression in either position and operable to tilt said contact spring from either position to its corresponding other position, of a coiled biasing spring in constant engagement with said contact carrier and arranged at the back of said movable contact with the axis of said biasing spring to be at the center substantially of the movable contact and said biasing spring to be deflected in the line of movement of, and biasing, said movable contact to its engaged position and the force exerted by said I contact spring as derived from the actuating