US3436501A

US3436501A - Snap action switch using overtravel

Info

Publication number: US3436501A
Application number: US567633A
Authority: US
Inventors: Lyndon Walkup Burch
Original assignee: Individual
Current assignee: Individual
Priority date: 1966-07-25
Filing date: 1966-07-25
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01
Also published as: DE1615773A1; GB1200160A; GB1199957A

Description

April 1, 1969 L. w. BURCH CTION SWITCH USING OVERTRAVEL SNAP A Filed July 25, 1966 Sheet FIG I V/.//V//V.//// Vv/Vr 3 G n H/ April 1, 1969 L. w. BURCH 3,436,501

SNAP ACTION SWITCH USING OVERTRAVBL Filed July 25, 1966 Sheet 2 of 2 [C48 I04 F|G4 108 I04 F|G5 FIG 8 United States Patent US. Cl. 200-68 12 Claims ABSTRACT OF THE DISCLOSURE Snap action switches are shown of the type having a snap member whose contact is snapped to break position by direct wiping and camming 0f the snap contact and whose actuator for the make position and the snap member are arranged for relative actuating and overtravel movement in a path at a substantial angle to the direction of the snap movement. An auxiliary surface disposed in the path of relative overtravel and a cooperating surface associated with the snap member are shown mutually constructed to engage and resist further relative overtravel movement and simultaneously increase the engagement for electric current flow between the terminals of the switch. Shown also are such a switch in which the snap member makes with a third contact after it breaks with a second, a portion of the third contact comprising the actuator for making with the second; and a spring biased carrier member for the snap element. A cooperating surface is also shown connected to one terminal and an auxiliary surface connected to the other terminal so that a second electrical path is formed between the terminals. Other features are shown.

This invention relates to snap action electrical switches.

A general problem with snap switches is the inability to control the current if the snap member or contacts should fail. This is a particular problem in the case of snap action elements made of thin metal sheet, usually a beryllium copper alloy, seldom over ten thousandths of an inch thick. Such material will quickly anneal if overheated by an overload current or may even be evaporized if the overload current is great enough.

Another shortcoming of snap action switches generally is their susceptibility to forces of vibration and sudden acceleration that interfere with the electrical paths made through the snap action element. When the vibrations are at the resonant frequency of the snap action element this deleterious effect is greatly magnified.

Accordingly it is an object of this invention to provide a snap action switch which significantly reduces the possibility of damage to the snap action element from overload currents and which can function even if the snap action element should be destroyed or should have its conducting or snapping properties impaired.

A further object of this invention is to provide a snap action switch which can maintain proper contact engagement under vibration and acceleration forces.

A further object of this invention is to provide such a switch which has increased current carrying capacity without increasing size.

Another object is to provide improvement in snap action switches along the lines indicated above without the necessity of more parts than used in conventional snap action switches and with little or no additional cost of manufacture.

The invention features a snap member having a first contact on it and a secondary structure having a second contact on it, the first and second contacts being engageable with each other. The snap member and at least part of the secondary structure are mounted to provide for tive movement of the snap member and the secondary structure.

At least some overtravel movement beyond the point where snapping occur is permitted between the snap member and the secondary structure.

The invention features an auxiliary member mounted at the overtravel path, arranged to engage a cooperating surface associated with the snap member, and these cooperating parts are constructed and arranged to modify the electrical path through the switch during at least slight overtravel after snap action has occurred.

A feature of the invention is that the cooperating parts form a shunt path through the auxiliary member, to shunt the current flowing through the main contacts after snapping. In cases where the current flows through the body of a snap element, a feature is that this shunt path is provided so that full current flows through the body of the snap element only at the time of switching. Another feature is that the carrier member for the snap element can provide the cooperating surface which engages the auxiliary member upon overtravel to form a shunt path. A feature is that the auxiliary member at the same time serves as a stop to prevent further overtravel, and biasing of the carrier against the stop ensures that the shunt path is preserved.

It is a feature that the mounting of the snap member be electrically conductive, e.g. connected to the common terminal, either the mounting or the contact not on the snap member being movable to actuate the switch, and an extension of either the mounting or said contact being provided to engage the other, providing both a stop and the shunt path.

The invention also features the electrical path modified with overtravel by an auxiliary member arranged to increase the pressure between the contacts, thus, by elastic deformation, increasing the area of metal-to-metal engagement of the contacts, and accordingly increasing the current carrying ability of the contacts. For this feature, the auxiliary member can take the form of a deflector or wedge member which engages the snap contact during overtravel, and forces it against the other contact. In those instances where the switch is double pole, and an actuator member is moved between the contacts to separate the movable contact from one stationary contact, and cause it to snap against the opposite one, the auxiliary wedge can be joined bodily with the actuator member, so that overtravel movement causes the wedge to engage the movable contact, and force it harder against the second stationary contact. A similar feature is the use of an insulated, wedge-shaped extension of the first stationary contact for this purpose.

The shunt and wedge features can be combined, such that, as the movable contact is wedged or forced against its pole by the auxiliary member, the same auxiliary member, or a second one, creates a shunt path.

Another feature of the invention lies in the ability to use, as an actuating member, to force the contacts apart, an insulative member which accomplishes a slow-break of the contacts, as is desirable with certain alternating currents.

Another feature is the rotary mounting of the movable member, e.g. the carrier for the blade itself, providing amplification and the desired movement, the stops to limit rotary motion defining the shunt path.

Other objects, features, and advantages will appear from the following description of a preferred embodiment of the invention, taken together with the attached drawings thereof, in which:

FIG. 1 is a perspective view of the switch of this invention with the cover partially broken away;

FIG. 2 is an elevation of the switch in FIG. 1;

FIG. 3 is a sectional view taken along line 33 in FIG. 2;

FIG. 4 is a sectional view of a switch in accordance with a second embodiment of this invention with its contacts in a first position;

FIG. 5 is the same as FIG. 4 but with the contacts in a second position;

FIG. 6 is a perspective view of the actuator used in the second embodiment shown in FIGS. 4 and 5;

FIG. 7 is a sectional view of a switch in accord nce with a third embodiment of this invention with its contacts in a first position;

FIG. 8 is the same as FIG. 7 but with the contacts in a second position; and

FIG. 9 is a perspective view of an actuator for use in the third embodiment shown in FIGS. 7 and 8.

For purposes of illustration, a snap member of the integral thin sheet type is shown, specifically on M blade in accordance with US. Patent 3,213,228, to which reference is made for mounting details, etc.

There is shown in FIG. 1 a double throw switch having a housing 12 of insulating material.

A support bracket 16 of conducting material, such as copper or aluminum, is fastened to the housing. A shaft 26, pivoted to bracket 16, rotatably supports a carrier member 30, here being shown with an extension protruding through slot 36 to serve as an actuator.

Spring 38, connected to the extension and to bracket 16, establishes an over-center force on carrier 30, tending to keep the carrier to one side or the other of vertical line L.

A metal button 44 is fastened to the lower end of carrier 30, and has a recess securing adjacent edges of the internal arms 50 of the snap action element 52. Although an M shaped element is used here, no particular shape of a snap action element is essential to the invention here disclosed.

The conductive path extends from common terminal 11 through bracket 16, shaft 26, carrier member 30, button 44 to the internal arms 50, to contact 60 on the front surface of element 52 and to contact 64 on the rear surface of element 52.

The housing defines a ridge 76 lying in a vertical plane through shaft 26, and on either side at ridge 76 is a

contact

72 and 74 disposed to be engaged by contact 60, and connected respectively to terminals 9 and with pivotal movement of carrier 30, contact 60 slides on

contact

72, and 74, in the direction parallel to the plane of the flat snap element 52 to break incipient weld, in accordance with principles disclosed in my Patent 2,899,512. As the carrier member approaches ridge 76, e.g. along arrow A, the ridge acts as a camming surface to move snap element 52 through its over-center position.

In this embodiment a plate 20 made of a conducting material, is attached to bracket 16 and has a center portion 21 connecting two resilient

slanted arms

23 and 25 located opposite

contacts

72 and 74 respectively. After contact snaps away from contact 74, under the camming action of slanted edge 74 of the contact backed by ridge 76, and with further movement in direction A, slanted arm 25 earns the contact and the element snaps back engaging contact 72.

As can be seen from FIGURE 3, the make and break action of the contacts occur in contact region C, while a path is open for the contacts 60 to overtravel to regions T, maintaining pressure between the contacts without increasing the stress of the blade.

According to one aspect of the invention the range of movement T is limited by

stop members

77 and 78 arranged to engage the carrier member (in this case button 44). These stop members being connected electrically to the

contacts

72 and 74 respectively. Advant geously, as shown, the stop members are integral with the members 72a and 74b which form the contacts. Thus, when the carrier member is moved until it engages the stop, e.g. under the influence of spring 38, an electrical path is formed from carrier member 30 through button 44, stop 77 and terminal 9, thus shunting out the snap element 52. This not only protects the element from overload during normal closed condition, but also serves as a safety switch: if snap element 52 does not operate properly, in an emergency the carrier member can be forced into engagement with the stop 77 to control the circuit.

Referring still to FIG. 3, with movement in direction A, as contact 64 moves beyond L and is cammed to overcenter position by arm 25, contact 64 jumps away from arm 25, to make snap contact with contact 72.

However, in region T, arm 25 converges further toward contact 72. With overtravel of contact 64 beyond C, contact 64 re-engages arm 25 thus wedging the

contacts

60 and 72 more tightly together and creating an alternate path for the current from bracket 16 to which arm 25 is connected to arm 25, thence through

contact

64 and 60 to contact 72.

This entrapment makes the switch immune from many vibrational effects and reduces the electrical load on contact 60. (Note that this embodiment is symmetrical with line L and what is said for arm 25 holds also for arm 23 when the member moves in the opposite direction.)

Resilient yieldability of arm 25 allows full overtravel to occur to complete a shunt path with. stop 77, by which electric current can be transmitted even if the entire snap member and its contacts should be destroyed.

A push-pull embodiment is shown in FIGS. 4-6. Actuator is made of an insulating material, as is housing 92, and is slidable in a recess of the housing 92. Snap action element 96 is similar to element 52 and is fastened to a bracket 98 by a button -100, which is similar to button 44. Element 96 has a pair of integrally formed

contacts

102, 104 on its active end, FIGS. 4 and 5. Contact 102 engages contact 106, which is bonded to housing 92 and contact 104 engages contact 108 also bonded to housing 92, as shown in FIGS. 4 and 5, respectively. External connection to

contacts

106, 108, and 102 and 104 is made through appropriate lugs.

Element 96 is driven by

cross-arms

116 and 118 of actuator 90 as it is slid in and out of recess 94. Arm 116, FIG. 6 contains an opening 120 and has a conductive internal camming insert '122 at its forward end. Arm 118, slightly shorter than arm 116, contains an external carnming surface 124 at its forward end.

In operation, FIG. 4, as actuator 90 is moved in the direction of the arrow, with

contacts

102 and 106 engaging, cam surface 122 bears against contact 102 separating it from contact 106, for the moment electrical continuity between

contacts

102 and 106 being maintained through insert 122. In the course of this travel element 96 is driven through its over-center position and it snaps away from insert 122 to the position shown in FIG. 5. Overtravel of actuator 90 causes insulative surface on the under side of arm 116 to bear on contact 102 wedging contact 104 against contact 108. Arm 118 is sized to allow contact 104 to engage contact 108 clear of cam surface 124. When actuator 90 is moved in the opposite direction, cam surface 124 bears on contact 104 separating it from contact 108. Element 96 is thus driven through its over-center position and snaps to the position shown in FIG. 4, where contact 102 engages contact 106 through opening 120. Overtravel of actuator 90 causes surface 117 on the upper side of arm 118 to bear on contact 104 wedging contact 102 against contact 106.

The separation of

contacts

102, 104, from

contacts

106, 108, respectively, caused by

cam surfaces

122, 124, respectively, is slow compared to the separation of

contacts

102, 104 from cam surfaces 122, 124, respectively, caused by the snapping of element 96. Advantageously,

for alternating current, the conductive camming surfaces 122 and 124 are omitted and replaced with insulative material, as shown in FIG. 5. A slow separation or break of contacts is desirable in switching alternating current, for if the current passes through zero, as it does twice each cycle, while the contacts are separating, arcs between the contacts will be extinguished. This embodiment thus achieves slow break and snap action make of the contacts.

As indicated above, for DC. current, a fast separation is accomplished by

cam surfaces

122, 124 formed by metallic strips 122.

A third embodiment, FIGS. 7-9, uses an actuator consisting of resilient

metallic arms

132, 134 bonded to an insulating block 136 each of the arms having in it an opening 138. Insulated cam-shaped

lifting ears

144, 152, connected to the housing are arranged along the path. As the actuator is moved in the direction of the arrow in FIG. 7, bridge 142 of arm 132 wedges between

contacts

102 and 106 and forces the contact over-center causing contact 104 to engage contact 108. Overtravel movement causes bridge 142 to be driven downward by cars 152, until bridge 142 disengages from contact 106, and, with further movement and camrning action, re-engages contact 102 wedging it downwands to trap the

contacts

104 and 108 together. Reverse movement accomplishes the reverse effect with bridge 150 and lifting ear 152.

Other embodiments will occur to those skilled in the art and are within the following claims.

What is claimed is:

1. In a snap action switch of the type comprising a snap member having an unstable position and carrying a first electrical contact connected to a first terminal, secondary structure including at least one second electrical contact connected to a second terminal, said snap member movable with snap action from and to said second contact to break and make an electric circuit, first actuating mean-s including said second contact to apply a wiping actuating force directly upon said first contact to cause said first contact to snap from said second contact to break said circuit, second actuator means engageable with said snap member to make said circuit, said snap member and said second actuator means mounted for relative actuating and overtravel movement in a path disposed at a substantial angle to the direction of the snap movement of said snap member; the irnprovement comprising an auxiliary surface disposed in said path of relative overtravel of said snap member and a cooperating surface movable relatively with said snap member, said auxiliary surface positioned to engage said cooiperating surface during said overtravel, said auxiliary and cooperating surfaces mutually constructed to resist further relative overtravel movement and simultaneously increase the engagement for electric current flow between said first terminal and said second terminal.

2. The switch of claim 1 wherein said cooperating surface and said auxiliary surface are conductive, said surfaces engageable to complete a second electrical path between said first terminal and said second terminal.

3. The switch of claim 2 wherein said auxiliary surface is an integral extension of the contact engaged by the snap member.

4. The snap action switch of claim 2 wherein said snap member is mounted on a conductive carrier member, said snap member and said carrier member are connected to said first tenminai, said cooperating surface is provided by said carrier member and is in electrical circuit with said carrier member, and said auxiliary surface is electrically connected to said second terminal, whereby when said auxiliary surface and cooperating surface engage a shunt path is formed lay-passing said sna'p member.

5. The switch of claim 2 wherein said auxiliary surface comprises a stop member engaging said cooperating surface to prevent further relative overtravel between said snap member and said second actuator, and said second electrical path shunts the entire said snap member and its contact.

6. The switch of claim 1 having a third contact, said snap member arranged to make with said third contact after it breaks with the second contact and vice versa, a portion of the third contact comprising the actuator for directly camming said first contact to a position where said snap member snaps into engagement with said second contact.

7. The switch of claim 1 wherein said second actuator means includes a spring, separate from said snap member, interconnected between said snap member and said auxiliary surface, said spring constructed and arranged to urge said cooperating surface and said auxiliary surface into engagement with one another.

8. The switch of claim 7 in the form of a toggle switch and having two stationary contacts said snap member being mounted for actuating and overtravel movement from engagement with one stationary contact to engagement with the other stationary contact, and vice versa, said spring forming an over-center device adapted to resiliently hold said carrier and snap member in whichever of the positions to which it has been actuated.

9. The switch of claim 8 wherein the direction of snap movement of said snap member is perpendicular to the direction of said relative movement of said snap member.

10. The switch [of claim 1 wherein said snap member is substantially rigid in said direction of relative movement, said second actuating means is a surface stationary relative to said second contact, said actuating surface extending at an angle to both the direction of said snap movement and the direction of said relative movement, to cam said first contact until it snaps against said second contact.

11. The switch of claim 10 wherein an integral conductive extension of said second contact is disposed at anangle to both the direction of movement of said snap movement and the direction of said relative movement, said extension comprising said first actuating means positioned to cam said first contact until it snaps out of engagement therewith npon reverse relative movement of said snap member.

12. The switch of claim 1 wherein said snap member is mounted to move relative to and in slideable engagement with said second contact during said overtravel.

References Cited UNITED STATES PATENTS 2,191,926 2/1940 Lemire 20016 2,753,413 7/1956 Anderson 200-151 X 3,239,629 3/ 1966 Lesser. 3,324,261 6/ 1967 Burn-s 200-68 X ROBERT K. SCHAEFER, Primary Examiner. DAVID SMITH, 1a., Assistant Examiner.

US. Cl. X.R.