CA1078442A - Snap action switches - Google Patents
Snap action switchesInfo
- Publication number
- CA1078442A CA1078442A CA283,226A CA283226A CA1078442A CA 1078442 A CA1078442 A CA 1078442A CA 283226 A CA283226 A CA 283226A CA 1078442 A CA1078442 A CA 1078442A
- Authority
- CA
- Canada
- Prior art keywords
- blade
- switch
- arms
- base portion
- operating element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H5/00—Snap-action arrangements, i.e. in which during a single opening operation or a single closing operation energy is first stored and then released to produce or assist the contact movement
- H01H5/04—Energy stored by deformation of elastic members
- H01H5/18—Energy stored by deformation of elastic members by flexing of blade springs
- H01H5/22—Energy stored by deformation of elastic members by flexing of blade springs blade spring with at least one snap-acting leg and at least one separate contact-carrying or contact-actuating leg
Landscapes
- Thermally Actuated Switches (AREA)
- Push-Button Switches (AREA)
- Rotary Switch, Piano Key Switch, And Lever Switch (AREA)
Abstract
ABSTRACT
A snap action switch blade has a pair of resiliently flexible arms projecting cantilever fashion from a support and drawn together to prestress the blade for snap action, the blade being anchored to the support by two lugs projecting in the opposite direction to the arms and an electrical contact being mounted off-axis near one of the arms of the blade.
A snap action switch blade has a pair of resiliently flexible arms projecting cantilever fashion from a support and drawn together to prestress the blade for snap action, the blade being anchored to the support by two lugs projecting in the opposite direction to the arms and an electrical contact being mounted off-axis near one of the arms of the blade.
Description
:1~78442 This invention relates to snap action switches.
An object of the invention is to provide a snap action switch having a contact-carrying blade which effects snap movement between a closed and open condition of the switch in response to a narrow range of movement of a switch operating element, and which, having made such movement, can accommodate overtravel of the switch operating element by resilient deformation of the switch blade, without such overtravel resulting in a change of state of the switch.
According to the invention there is provided a snap action switch blade of resilient sheet metal formed with a base portion having two longitudinally extending arms, means interconnecting the arms at their ends remote from the base portion so as to induce a dish stressing of the base portion, two lugs projecting outwardly from the base portion adjacent the arms and affording mounting points for the blade, and an electrical contact carried by one of the arms of forming at least part of the means interconnecting the arms.
A central tongue preferably projects from the base portion between the two arms and is acted upon in use of the blade by a switch operating element.
It can be arranged that snap formation of the switch blade can be effected by means of a narrow range of movement of the s~itch operating element, so as to cause snap transition of the blade from its initial dished configuration to~ards the opposite disched configuration, causing snap
An object of the invention is to provide a snap action switch having a contact-carrying blade which effects snap movement between a closed and open condition of the switch in response to a narrow range of movement of a switch operating element, and which, having made such movement, can accommodate overtravel of the switch operating element by resilient deformation of the switch blade, without such overtravel resulting in a change of state of the switch.
According to the invention there is provided a snap action switch blade of resilient sheet metal formed with a base portion having two longitudinally extending arms, means interconnecting the arms at their ends remote from the base portion so as to induce a dish stressing of the base portion, two lugs projecting outwardly from the base portion adjacent the arms and affording mounting points for the blade, and an electrical contact carried by one of the arms of forming at least part of the means interconnecting the arms.
A central tongue preferably projects from the base portion between the two arms and is acted upon in use of the blade by a switch operating element.
It can be arranged that snap formation of the switch blade can be effected by means of a narrow range of movement of the s~itch operating element, so as to cause snap transition of the blade from its initial dished configuration to~ards the opposite disched configuration, causing snap
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movement of the electrical contact carried by the blade.
The base portion, the arms and the lugs are preferably all formed from a single piece of sheet metal, for example, a beryllium-copper alloy. The means interconnec-tir.g the arms may comprise a bridge portion, integral with the remainder of the blade or welded to it. The requisite dish stressing of the blade may be effected by shortening of the bridge portion, for example by crimping or by severing the bridge portion and then lap-welding the adjacent severed ends of the bridge portion. Alternatively, the bridge portion and the electrical contact carried or formed thereby may be attached to the cantilevered ends of -the ' arms, for example, by welding, maintaining the arms at a relative spacing which results in the dish stressing of the base portion.
The invention also provides a snap action switch having a switch blade as defined above, a support or housing to ~hich the two lugs of the blade are anchored and from which the blade projects cantilever-fashion, a fixed contact carried by the support or housing and cooperating with the contact carried by the switch blade, and an operating ` element arranged to act on a cantilevered part of the blade in a sense to cause snap transition thereof towards an opposite dish deformation to effect snap movement of the contact carried by the blade relative to the fixed contact.
The two lugs are attached to the support, leaving the - 10~78442 ' remainder of the blade including the base portion free to undergo transition from its original state of` dish deformation towards the opposite state upon movemen-t of the operating element. Once the switch blade has undergone such snap movement further movemen-t of the switch operating element in the same direction will simply result in further deformation of the switch blade, without snap transition, so that the switch blade can accommodate a wide range of overtravel movement of the operating elemen-t. This is a particularly useful feature ~here the switch is of the temperature - or pressure-responsive type in which the operating element is actua-ted by a temperature- or pressure-responsive element such as a bellows or diaphragm. In practice the switch operating element may be connected directly to a temperature- or pressure-responsive element such as a bellows, diaphragm or bimetal device, without :
any interposed operating linkage, since any overtravel of the operating element as a result of excessive temperature or-pressure is accommodated by deformation of` the switch ~ ~
blade as previously mentioned. ~ -The contact carried by the s~itch blade may be disposed in a different longitudinal plane from the point of the blade ~-at which the operating element acts, the said point being spaced from the support or housing in both the open and closed condition of the contacts, so that after movement of the operating element in a direction so as to cause snap opening or closing of the s~itch contacts further movement _ 4 _ 10'7~3~42 - of the operating element in the same direction results in twisting of the blade about a longitudinal axis without change of state of the switch. The contact carried by the blade is preferably located at or adjacent the cantilevered end of one of the two arms of the blade, the operating element acting at a point disposed symmetrically between the said two arms.
The differential of the switch when acting as a temperature or pressure-responsive switch, that is, the difference in temperature or pressure necessary to induce operation of the switch in opposite senses, can be pre-set by means of an adjustable stop carried by the switch ; support or housing and engaging a part of the switch blade.
Preferably this adjustable stop, which may be in the form of a screw, acts upon the opposite face of the switch -~ blade to that carrying the contact, at a point spaced from . .
the ?atter in a transverse direction. By adjusting the setting of this stop the gap between the fixed contact and the contact carried by the blade in the open condition of the switch can be adjusted. The adjustable stop may be disposed on the opposite side of the longitudinal axis of symmetry of the blade from the contact carried by the blade.
By suitable positioning of the fixed contact and the , 25 adjustable stop it is possible to arrange that the switch `~ is either monostable or bistable in operation. Where the ;'. ,. : ' : .
' 10'784~Z
switch blade undergoes snap transition into an opposi-te stable state of dish deformation in response to movement of the switch operating element and is therefore bistable in operation, a biassing spring may be provided to act upon S the switch blade in opposition to the operating element to return the blade to its original dish deformation when the operating element is released. The biassing spring may comprise a helical spring reacting against the switch support or housing and acting upon the opposite ~ace of the switch blade from that which is engaged by the switch operating element. The biassing spring may alternatively comprise a leaf spring.
The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a blank from which a snap action switch blade according to one embodiment of the present invention is made;
` Figure 2 is a diagrammatic perspective view of a switch blade according to one embodiment of the present invention incorporated in a temperature-responsive switch, parts only of the switch being shown diagrammatically;
Figure 3 is an end view of the switch blade in the direction of arrow III in Figure 2;
Figure 4 is a diagrammatic perspective view similar to Figure 2 but showing the switch blade after operation of the switch, ancl .- . . . ..
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Figure ~ is an end vie~ o~ the s~itch blade~ corresponding to ~igure 3, taking in the'direction of arrow V in ~iO~ure 4.
The switch blade according to the present invention is made ~rom a sinOle piece o~ be~yllium-copper alloy. A
blank havin~ the shape sho~,in ~igure 1 is ~irst stamped or cut ~rom a sheet o~ beryllium~copper alloy~ the sheet .. . .
.. . .
typically having a thicXness o~ 0.3 mm. ~he blank has a base portion 1 formed ~ith two arms 2, 3 adjoining opposite ends o~ the base portion, a central ~ongue 4 projecting from the base portion 1 and disposed symmetrically betw2en the ~wo arms, and two outwardly projecting lugs 5, 6 extenaing ~rom opposite ends o~ the base portion 1 adjoining the two arms 2, 3. ~le two lugs 5, ~ are ~ormed ~ith holes at their ends ~or the reception of fixing scre~s or rivets by me~ns o~ which the ~lade is anchor2d to a support or switch housing to projec~ cantilever-~ashion, as described with re~erence to Figures 2 to S. The c2ntilevered ends ~î the two ar,ms 2, 3 opposite ~he base portion 1 are interconnected ~y an in~egral brid~e portion 7. A hole is lormed in one ena of the bridge portion 7 adjacent one o~ the'arms 2 ~or the a~tachment of a switch contact, on one side of the longitudinal axis of symmetry X-X o~ the blaae blank.
~ne two arms 2, 3 in ~he ~lat condi~ion o~ the, blank diverg2 relatively to each other aw~y ~rom the b~se portion 1.
~ter stamping o~ the blank in a flat condition the biade i3 pre-strec;sed with a dish deformation by shortening the - . .
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bridge portion 7, either by crimping the bridge portion or, in this example, by making a cut in the bridge portion 7 and then forming a lap-joint between the cut ends of the bridge portion 7, as illustrated in Figures 2 and ~, so S that the length of the bridge portion is ef~ectively -~ reduced. The result of this shortening o~ the bridge portion 7 is to draw the two arms 2, 3 together so that they are substantially parallel with each other, at the same time inducing a dish deformation in the base portion 1 of the blade, as shown in Figure 2.
A contact 9 is attached to the blade at the position of the hole 8 by rive-tting or swaging. Alternatively, a . contact may be formed integrally with the bridge portion 7 '~ or may in fact constitute the bridge portion 7 itself, in which case it may be attached to the arms 2, 3 by welding in such a way as -to hold the arms at the requisite spacing to cause the dish stressing of the blade.
A typical mounting for the switch blade is illustrated in Figures 2 and 3. The blade is attached to a housing 10, part of which is shown diagrammatically, by rivets, screws or other attachments passing through the lugs 5, 6 so that the blade projects cantilever-fashion within the housing. `
The contact 9 carried by the blade cooperates with a fixed contact 11 carried by the housing 10. In the illustrated embodiment the s~vitch is normally closed with the contact 9 pressed into engagement with the fixed contact 11 by the dish stressing o~ the blade which in the illus-trated example .
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~ L~7 r results in the blade being convex upwardly as viewed in Fi~ure 2.
A differential setting screw 12 is mounted in the housing 10 and acts upon the opposite face of the blade ~rom the contact-car~yin~
~ace, at the end of the bridge portion 7 opposite the contact 9, that is, on the opposite side of the longitudinal axis of symmetry OI the blade ~rom the contact 9.
A switch operating element 13, which may, for example, be movable by a deformable temperature responsive bellows or diaphra~m or by a bimetal aevice, acts upon the central tongue 4 of the switch blade adjacent the base portion 1~ on the opposite face of the switch blade ~rom that which carries the contact 9. Displacement o~ the operatin~
element 13 in the direction o~ arrow 0 opposes the dish de~or~ation of the switch blade, and when this displacement reaches a certain point the switch blade will undergo snap transition towards its opposite dished conliguration, sho~m in ~i~ure 4, in ~hich the blade is shown concave upwardly. ~his snap transition will result in rapid movement o~ the contact 9 carried by the swi-tch blade away from the ~ixed contact 11, causing snap opening of the switch (Figure 5).
lhe switch blade could be set up ~or monostable or bistable op2ration by suitable selection OI the position of the fixed contact 11 and the blade anchorage points. .In the illustrated embodiment the switch blade is bistable, so that once the switch has-been opened by movement o~ the switch operating element 13 as described above, subsequent release o~ the switch operating element 13 would not result in return of the switch to its original closed condition, the dished co~iguration adopted by the -` 10~44z svitch blade in the open condition (Figures 4 and 5) being a stable condition. In order to make the switch effectively monos~ble in operation a helical biassing spring 14 is provided, one end of the spring 14 reacting against the switch housing 10 and the other end bearing against the tongue 4 on the "` opposite face -thereof from the switch operating element 13.
The spring 14 exerts a sufficiently stron return force on the tongue 4 to cause the latter to return to its initial position when the switch operating element 13 is released, so that the switch blade reverts to i-ts original dished configuration (Figures 2 and 3) with the contacts 9, 11 closed.
~ y adjusting the setting of the differential screw 12 the dish deformation of the switch blade can be ad~usted within fine limits so as to approach the point of snap transition to the opposite dished configuration. This in ;turn adjusts the sensitivity or "differnetial" of the switch, since it predetermines the separation of the contacts 9 and 11 when the switch is open (Figure 5). The differential of the switch is, therefore, finely adjustable by means of the screw 12.
Once the switch blade has been caused to snap into its open condition by movement of the operating element 13 as shown in Figures 4 and 5 any further movement of the switch operating element 13 in the direction of arrow 0, for example due to excessive temperatures sensed by the bellows, diaphragm or other device controlling the operating !
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element 13, will result in resilient deformation of the tongue 4 and the adjacent base portion 1 of the blade, at the same time twisting the blade about a longitudinal axis by virtue o~ the engagement of the asym~etrically positioned setting screw 12 with the blade, such deformation having no éflect on the condition of the switch - that-is, the switch contacts 9, 11 will remain open. The switch blade can accommodate a wide range o~ overtravel movement of the switch operating element in this way without suf~ering damage or affecting its subsequent operation.
Although the illustrated switch is of the normally closed type, a nor.~ally open switch can easily be maae by positioning the fixed contact 11 adjacent the opposite face OI the switch blade from ~he position sho~n in Figures 2 to 5~ so that closure of the switch occurs upon movement o~ the switch operating element 13 in the direetion o~ arrow 0.
A further possible variant o~ the invention is a changeover switch having a further pair of contacts including a second ~ixed contact cooperating ~Jith a second contact positioned, ~or example, at the end of the arm 2 on the opposite face of the blade from-the contact 9 of the illus~rated embodiment. ~ne second fixed contact would occupy the position of the dif~erential setting screw 12 of the illustrated embodiment, and the further pair o~ contacts would be open when the first pair of contacts 9, 11 are closed and closed when the lirst pair of contacts 9, 11 are open.
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movement of the electrical contact carried by the blade.
The base portion, the arms and the lugs are preferably all formed from a single piece of sheet metal, for example, a beryllium-copper alloy. The means interconnec-tir.g the arms may comprise a bridge portion, integral with the remainder of the blade or welded to it. The requisite dish stressing of the blade may be effected by shortening of the bridge portion, for example by crimping or by severing the bridge portion and then lap-welding the adjacent severed ends of the bridge portion. Alternatively, the bridge portion and the electrical contact carried or formed thereby may be attached to the cantilevered ends of -the ' arms, for example, by welding, maintaining the arms at a relative spacing which results in the dish stressing of the base portion.
The invention also provides a snap action switch having a switch blade as defined above, a support or housing to ~hich the two lugs of the blade are anchored and from which the blade projects cantilever-fashion, a fixed contact carried by the support or housing and cooperating with the contact carried by the switch blade, and an operating ` element arranged to act on a cantilevered part of the blade in a sense to cause snap transition thereof towards an opposite dish deformation to effect snap movement of the contact carried by the blade relative to the fixed contact.
The two lugs are attached to the support, leaving the - 10~78442 ' remainder of the blade including the base portion free to undergo transition from its original state of` dish deformation towards the opposite state upon movemen-t of the operating element. Once the switch blade has undergone such snap movement further movemen-t of the switch operating element in the same direction will simply result in further deformation of the switch blade, without snap transition, so that the switch blade can accommodate a wide range of overtravel movement of the operating elemen-t. This is a particularly useful feature ~here the switch is of the temperature - or pressure-responsive type in which the operating element is actua-ted by a temperature- or pressure-responsive element such as a bellows or diaphragm. In practice the switch operating element may be connected directly to a temperature- or pressure-responsive element such as a bellows, diaphragm or bimetal device, without :
any interposed operating linkage, since any overtravel of the operating element as a result of excessive temperature or-pressure is accommodated by deformation of` the switch ~ ~
blade as previously mentioned. ~ -The contact carried by the s~itch blade may be disposed in a different longitudinal plane from the point of the blade ~-at which the operating element acts, the said point being spaced from the support or housing in both the open and closed condition of the contacts, so that after movement of the operating element in a direction so as to cause snap opening or closing of the s~itch contacts further movement _ 4 _ 10'7~3~42 - of the operating element in the same direction results in twisting of the blade about a longitudinal axis without change of state of the switch. The contact carried by the blade is preferably located at or adjacent the cantilevered end of one of the two arms of the blade, the operating element acting at a point disposed symmetrically between the said two arms.
The differential of the switch when acting as a temperature or pressure-responsive switch, that is, the difference in temperature or pressure necessary to induce operation of the switch in opposite senses, can be pre-set by means of an adjustable stop carried by the switch ; support or housing and engaging a part of the switch blade.
Preferably this adjustable stop, which may be in the form of a screw, acts upon the opposite face of the switch -~ blade to that carrying the contact, at a point spaced from . .
the ?atter in a transverse direction. By adjusting the setting of this stop the gap between the fixed contact and the contact carried by the blade in the open condition of the switch can be adjusted. The adjustable stop may be disposed on the opposite side of the longitudinal axis of symmetry of the blade from the contact carried by the blade.
By suitable positioning of the fixed contact and the , 25 adjustable stop it is possible to arrange that the switch `~ is either monostable or bistable in operation. Where the ;'. ,. : ' : .
' 10'784~Z
switch blade undergoes snap transition into an opposi-te stable state of dish deformation in response to movement of the switch operating element and is therefore bistable in operation, a biassing spring may be provided to act upon S the switch blade in opposition to the operating element to return the blade to its original dish deformation when the operating element is released. The biassing spring may comprise a helical spring reacting against the switch support or housing and acting upon the opposite ~ace of the switch blade from that which is engaged by the switch operating element. The biassing spring may alternatively comprise a leaf spring.
The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a plan view of a blank from which a snap action switch blade according to one embodiment of the present invention is made;
` Figure 2 is a diagrammatic perspective view of a switch blade according to one embodiment of the present invention incorporated in a temperature-responsive switch, parts only of the switch being shown diagrammatically;
Figure 3 is an end view of the switch blade in the direction of arrow III in Figure 2;
Figure 4 is a diagrammatic perspective view similar to Figure 2 but showing the switch blade after operation of the switch, ancl .- . . . ..
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~L~713~4 .,. ; .
Figure ~ is an end vie~ o~ the s~itch blade~ corresponding to ~igure 3, taking in the'direction of arrow V in ~iO~ure 4.
The switch blade according to the present invention is made ~rom a sinOle piece o~ be~yllium-copper alloy. A
blank havin~ the shape sho~,in ~igure 1 is ~irst stamped or cut ~rom a sheet o~ beryllium~copper alloy~ the sheet .. . .
.. . .
typically having a thicXness o~ 0.3 mm. ~he blank has a base portion 1 formed ~ith two arms 2, 3 adjoining opposite ends o~ the base portion, a central ~ongue 4 projecting from the base portion 1 and disposed symmetrically betw2en the ~wo arms, and two outwardly projecting lugs 5, 6 extenaing ~rom opposite ends o~ the base portion 1 adjoining the two arms 2, 3. ~le two lugs 5, ~ are ~ormed ~ith holes at their ends ~or the reception of fixing scre~s or rivets by me~ns o~ which the ~lade is anchor2d to a support or switch housing to projec~ cantilever-~ashion, as described with re~erence to Figures 2 to S. The c2ntilevered ends ~î the two ar,ms 2, 3 opposite ~he base portion 1 are interconnected ~y an in~egral brid~e portion 7. A hole is lormed in one ena of the bridge portion 7 adjacent one o~ the'arms 2 ~or the a~tachment of a switch contact, on one side of the longitudinal axis of symmetry X-X o~ the blaae blank.
~ne two arms 2, 3 in ~he ~lat condi~ion o~ the, blank diverg2 relatively to each other aw~y ~rom the b~se portion 1.
~ter stamping o~ the blank in a flat condition the biade i3 pre-strec;sed with a dish deformation by shortening the - . .
.. :
.- ' - ~ ' :
1~7~1~4Z
bridge portion 7, either by crimping the bridge portion or, in this example, by making a cut in the bridge portion 7 and then forming a lap-joint between the cut ends of the bridge portion 7, as illustrated in Figures 2 and ~, so S that the length of the bridge portion is ef~ectively -~ reduced. The result of this shortening o~ the bridge portion 7 is to draw the two arms 2, 3 together so that they are substantially parallel with each other, at the same time inducing a dish deformation in the base portion 1 of the blade, as shown in Figure 2.
A contact 9 is attached to the blade at the position of the hole 8 by rive-tting or swaging. Alternatively, a . contact may be formed integrally with the bridge portion 7 '~ or may in fact constitute the bridge portion 7 itself, in which case it may be attached to the arms 2, 3 by welding in such a way as -to hold the arms at the requisite spacing to cause the dish stressing of the blade.
A typical mounting for the switch blade is illustrated in Figures 2 and 3. The blade is attached to a housing 10, part of which is shown diagrammatically, by rivets, screws or other attachments passing through the lugs 5, 6 so that the blade projects cantilever-fashion within the housing. `
The contact 9 carried by the blade cooperates with a fixed contact 11 carried by the housing 10. In the illustrated embodiment the s~vitch is normally closed with the contact 9 pressed into engagement with the fixed contact 11 by the dish stressing o~ the blade which in the illus-trated example .
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~ L~7 r results in the blade being convex upwardly as viewed in Fi~ure 2.
A differential setting screw 12 is mounted in the housing 10 and acts upon the opposite face of the blade ~rom the contact-car~yin~
~ace, at the end of the bridge portion 7 opposite the contact 9, that is, on the opposite side of the longitudinal axis of symmetry OI the blade ~rom the contact 9.
A switch operating element 13, which may, for example, be movable by a deformable temperature responsive bellows or diaphra~m or by a bimetal aevice, acts upon the central tongue 4 of the switch blade adjacent the base portion 1~ on the opposite face of the switch blade ~rom that which carries the contact 9. Displacement o~ the operatin~
element 13 in the direction o~ arrow 0 opposes the dish de~or~ation of the switch blade, and when this displacement reaches a certain point the switch blade will undergo snap transition towards its opposite dished conliguration, sho~m in ~i~ure 4, in ~hich the blade is shown concave upwardly. ~his snap transition will result in rapid movement o~ the contact 9 carried by the swi-tch blade away from the ~ixed contact 11, causing snap opening of the switch (Figure 5).
lhe switch blade could be set up ~or monostable or bistable op2ration by suitable selection OI the position of the fixed contact 11 and the blade anchorage points. .In the illustrated embodiment the switch blade is bistable, so that once the switch has-been opened by movement o~ the switch operating element 13 as described above, subsequent release o~ the switch operating element 13 would not result in return of the switch to its original closed condition, the dished co~iguration adopted by the -` 10~44z svitch blade in the open condition (Figures 4 and 5) being a stable condition. In order to make the switch effectively monos~ble in operation a helical biassing spring 14 is provided, one end of the spring 14 reacting against the switch housing 10 and the other end bearing against the tongue 4 on the "` opposite face -thereof from the switch operating element 13.
The spring 14 exerts a sufficiently stron return force on the tongue 4 to cause the latter to return to its initial position when the switch operating element 13 is released, so that the switch blade reverts to i-ts original dished configuration (Figures 2 and 3) with the contacts 9, 11 closed.
~ y adjusting the setting of the differential screw 12 the dish deformation of the switch blade can be ad~usted within fine limits so as to approach the point of snap transition to the opposite dished configuration. This in ;turn adjusts the sensitivity or "differnetial" of the switch, since it predetermines the separation of the contacts 9 and 11 when the switch is open (Figure 5). The differential of the switch is, therefore, finely adjustable by means of the screw 12.
Once the switch blade has been caused to snap into its open condition by movement of the operating element 13 as shown in Figures 4 and 5 any further movement of the switch operating element 13 in the direction of arrow 0, for example due to excessive temperatures sensed by the bellows, diaphragm or other device controlling the operating !
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element 13, will result in resilient deformation of the tongue 4 and the adjacent base portion 1 of the blade, at the same time twisting the blade about a longitudinal axis by virtue o~ the engagement of the asym~etrically positioned setting screw 12 with the blade, such deformation having no éflect on the condition of the switch - that-is, the switch contacts 9, 11 will remain open. The switch blade can accommodate a wide range o~ overtravel movement of the switch operating element in this way without suf~ering damage or affecting its subsequent operation.
Although the illustrated switch is of the normally closed type, a nor.~ally open switch can easily be maae by positioning the fixed contact 11 adjacent the opposite face OI the switch blade from ~he position sho~n in Figures 2 to 5~ so that closure of the switch occurs upon movement o~ the switch operating element 13 in the direetion o~ arrow 0.
A further possible variant o~ the invention is a changeover switch having a further pair of contacts including a second ~ixed contact cooperating ~Jith a second contact positioned, ~or example, at the end of the arm 2 on the opposite face of the blade from-the contact 9 of the illus~rated embodiment. ~ne second fixed contact would occupy the position of the dif~erential setting screw 12 of the illustrated embodiment, and the further pair o~ contacts would be open when the first pair of contacts 9, 11 are closed and closed when the lirst pair of contacts 9, 11 are open.
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Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A snap action switch blade of resilient sheet metal formed with a base portion, two longitudinally extending arms projecting from one side of the base portion, means interconnecting the arms at their ends remote from the base portion to induce a dish stressing of the base portion, two lugs projecting outwardly from parts of the base portion adjacent the respective arms, the lugs affording mounting points for the blade and being disposed on the opposite side of the base portion from the arms, and an electrical contact forming at least part of said means interconnecting the arms.
2. The switch blade defined in Claim 1, including a central tongue projecting from the base portion between the two arms, the tongue being acted upon in use of the blade by a switch operating element.
3. The switch blade defined in Claim 1, wherein the blade has a longitudinal axis of symmetry, the electrical contact being located on one side of said axis of symmetry.
4. The switch blade defined in Claim 1, wherein the base portion, the arms, and the lugs are formed from a single piece of resilient sheet metal.
5. The switch blade defined in Claim 1, wherein the means interconnecting the arms comprise a bridge portion secured to the two arms and drawing said two arms together to effect the dish stressing of the base portion.
6. The switch blade defined in Claim 1, wherein the means interconnecting the arms comprise a bridge portion integral with the remainder of the blade.
7. The switch blade defined in Claim 6,wherein the dish stressing of the blade is effected by shortening of the bridge portion to draw together the ends of the arms remote from the base portion.
8. The switch blade defined in Claim 7, wherein the two arms have end portions projecting laterally inwardly towards each other at the ends of the arms remote from the base portion, said end portions being welded together to form the bridge portion.
9. The switch blade defined in Claim 1, wherein the two outwardly projecting lugs diverge relative to each other from the base portion.
10. A snap action switch comprising:
_a switch blade of resilient sheet metal formed with a base portion, two longitudinally extending arms projecting from one side of the base portion, means interconnecting the arms at their ends remote from the base portion to induce a dish stressing of the base portion, two lugs projecting outwardly from parts of the base portion adjacent the respective arms, the lugs affording mounting points for the blade and being disposed on the opposite side of the base portion from the arms, and an electrical contact forming at least part of said means interconnecting the arms;
-a support to which the two lugs of the blade are anchored and from which the blade projects cantilever-fashion;
-a fixed contact carried by the support and cooperating with said electrical contact carried by the switch blade, and _an operating element acting upon a part of the blade in a sense to cause snap transition thereof towards an opposite dish deformation to effect snap movement of the contact carried by the blade relative to the fixed contact.
_a switch blade of resilient sheet metal formed with a base portion, two longitudinally extending arms projecting from one side of the base portion, means interconnecting the arms at their ends remote from the base portion to induce a dish stressing of the base portion, two lugs projecting outwardly from parts of the base portion adjacent the respective arms, the lugs affording mounting points for the blade and being disposed on the opposite side of the base portion from the arms, and an electrical contact forming at least part of said means interconnecting the arms;
-a support to which the two lugs of the blade are anchored and from which the blade projects cantilever-fashion;
-a fixed contact carried by the support and cooperating with said electrical contact carried by the switch blade, and _an operating element acting upon a part of the blade in a sense to cause snap transition thereof towards an opposite dish deformation to effect snap movement of the contact carried by the blade relative to the fixed contact.
11. The switch as defined in Claim 10, including a biassing spring acting upon the switch blade in opposition to the operating element to return the blade to its original dish deformation when the operating element is released.
12. The switch defined in Claim 10, wherein the contact carried by the switch blade is disposed in a different longitudinal plane from the part of the blade upon which the operating element acts, the said part being spaced from the support in both the open and closed condition of the contacts, so that after movement of the operating element in a direction so as to cause snap operation of the switch further movement of the operating element in the same direction results in twisting of the blade about a longitudinal axis without change of state of the switch.
13. The switch defined in Claim 12, wherein the contact carried by the blade is closer to one of the arms of the blade than the other, the operating element acting upon a part of the blade disposed symmetrically between the said two arms.
14. The switch defined in Claim 11 wherein the blade has a central tongue projecting from the base portion between the two arms, the operating element and the spring acting on opposite faces of said tongue.
15. The switch defined in Claim 13, including an adjustable stop carried by the support and acting upon the opposite face of the switch blade to that carrying the contact, at a point closer to the other of the two arms of the blade.
16. The switch defined in Claim 13, including a second fixed contact and a second contact carried on the opposite face of the blade from the first mentioned contact carried by the blade, closer to the other of the two blade arms, the said second contacts being closed when the first contacts are open and open when the first contacts are closed.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3073076A GB1576329A (en) | 1976-07-23 | 1976-07-23 | Snap action electric switches |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1078442A true CA1078442A (en) | 1980-05-27 |
Family
ID=10312254
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA283,226A Expired CA1078442A (en) | 1976-07-23 | 1977-07-21 | Snap action switches |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1078442A (en) |
| DE (1) | DE2732867A1 (en) |
| FR (1) | FR2359495A1 (en) |
| GB (1) | GB1576329A (en) |
| IT (1) | IT1083590B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4796355A (en) * | 1987-09-15 | 1989-01-10 | B/K Patent Development, Inc. | Snap action devices and methods and apparatus for making same |
-
1976
- 1976-07-23 GB GB3073076A patent/GB1576329A/en not_active Expired
-
1977
- 1977-07-20 FR FR7722262A patent/FR2359495A1/en active Granted
- 1977-07-21 CA CA283,226A patent/CA1078442A/en not_active Expired
- 1977-07-21 DE DE19772732867 patent/DE2732867A1/en not_active Ceased
- 1977-07-22 IT IT6871777A patent/IT1083590B/en active
Also Published As
| Publication number | Publication date |
|---|---|
| FR2359495B3 (en) | 1980-04-11 |
| FR2359495A1 (en) | 1978-02-17 |
| DE2732867A1 (en) | 1978-01-26 |
| GB1576329A (en) | 1980-10-08 |
| IT1083590B (en) | 1985-05-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |