US1678686A - Light-dimming switch - Google Patents

Light-dimming switch Download PDF

Info

Publication number
US1678686A
US1678686A US192519A US19251927A US1678686A US 1678686 A US1678686 A US 1678686A US 192519 A US192519 A US 192519A US 19251927 A US19251927 A US 19251927A US 1678686 A US1678686 A US 1678686A
Authority
US
United States
Prior art keywords
switch
contactor
terminal
contacts
ratchet
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 - Lifetime
Application number
US192519A
Inventor
Robert K Winning
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Clum Manufacturing Co Inc
Original Assignee
Clum Manufacturing Co Inc
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Clum Manufacturing Co Inc filed Critical Clum Manufacturing Co Inc
Priority to US192519A priority Critical patent/US1678686A/en
Application granted granted Critical
Publication of US1678686A publication Critical patent/US1678686A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01HELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H13/00Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
    • H01H13/02Details
    • H01H13/12Movable parts; Contacts mounted thereon
    • H01H13/14Operating parts, e.g. push-button
    • H01H13/16Operating parts, e.g. push-button adapted for operation by a part of the human body other than the hand, e.g. by foot

Definitions

  • ROBERT K WINNING, OF WAUWATOSA, WISCONSIN, ASSIGNOR TO CLUE MANUIAO TUBING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISGONSIN.
  • Figure l is a side elevation of my improved switch.
  • Figure 2 is a front elevation.
  • Figure 3 is a detail view taken 1n sect1 on in the plane indicated by line 33 in Figure 1. v
  • Figure 4 is a side elevation of the casing for the switch mechanism shown in Figures 1, 2, and 3.
  • Figurefl is a detail of the actuating rack.
  • Figure 6 is a detail ofthe mountlng of the moving switch contactor on its driving sleeve.
  • the frame 10 upon which the switch mechanism is assembled comprisesmerely a strip of sheet metal bent along transverse lines at 11 and 12 to provide a top wall 13, a front wall-14 and a rear wall 15. Integral cars 16 and 17 project horizontally from the ends of the top wall 13 and are apertured to receive mounting 'bolts or screws.
  • a terminal head 19 is shouldered at 20 to seat in a correspondingly formed openin in the front wall 14 of the switch frame. be two flat sides of the terminal head and the correspondingly formed margins of the opening permit no possible tendency of the terminal head to rotate in its mounting.
  • An axis pin or shaft 21 is riveted at its ends to engage the rear wall 15 of the switch to the terminal head and thus serves to hold the terminal head in the position defined.
  • the moving switch contactor comprises a thin disc of sheet metal mounted on a carrier disc 26 towhich it is engaged by means of tongues 27.
  • Contacts 28 are embossed to project forwardly from the face of disc 25 to a position where engaged with the fixed terminal contacts 29, 30, 31 and 32.
  • Terminal contacts 29 and 30 are connected by the strip conductor 33 so that the contacts 28 of the moving contacting" device will engage them successively and will simultaneously make connection with a fixed terminal diametrically opposite. During successive switch operations, terminal 29 will be con nected electrically to terminal 31 and then terminal 30 will be connected to terminal 32,
  • the means for operating the moving contactor and maintainingit in operative relascribed The means for operating the moving contactor and maintainingit in operative relascribed.
  • control member consists of a reciprocable plunger or foot button which includes a rod 35 and cap 36.
  • the rod is guided for vertical reciprocation by the guide sleeve 37 mounted in the Y tion to the terminal head will now be detured to fit upon rod' 35 while head 42 fits upon the reduced end of the rod which is riveted thereover at 43.
  • the material of this stamping is cut away to leave narrow strips of metal at 44 which serve as rack teeth which, in the limited reciprocative movement of the plunger, interact with the teeth 45 of the ratchet member 46.
  • the driving ratchet member 46 comprises a disc with three teeth 45 from which the ratchet pawls or tongues 47 are stamped to project integrally.
  • the driving ratchet is mounted for rotation on shaft 21 and is spaced from the rear wall of the switch frame by means of a collar 48.
  • the ratchet pawls 47 interact with similarly formed pawls 49 which are opposed thereto on the face of the driving ratchet member 50.
  • the driven ratchet member 50 is carried by and imparts motion to'squared sleeve 52 which is in splined relation to the contact carrier fibre disc 26.
  • a compression spring 55 interposed between the driven ratchet member 50 and the contact carrier disc 26 permits the dual function of maintaining the ratchet and the switch parts in their proper respective relations.
  • the terminals 32 are tubular and provide recesses vat their extremities into which the moving contact protuberances 28 enter in reaching positions of contact.
  • Spring 55 furnishes the pressure necessary to effect proper engagement of the parts in such ositions and it yieldably permits the protuberances to leave the terminals upo each operation of the switches.
  • the impositive definition of the switch positions arises from the above described organization of the-switch contacts in which the switch terminal recess is sufficient to hold the switch against movement while the dogs or pawls 47 of the driving ratchet member -46 force their way past the complementary pawls 49 of the driven ratchet member 50.
  • the relative yielding of the two ratchet members in an axial direction to .permit the-pawls to pass each other in this manner is made possible by the provision of spring 55 and the splined connection be"- ratchet action takes place on the downward movement of'the control button or plunger. There is no adjustment of the switch effected the control plunger is moving -upwardly under the compression of spring 38.
  • the ratchet pawls or teeth 47 and 49 are so spaced that when the plunger makes a full stroke the motion transmitted through the ratchet to the switch contactor will be exactly sufficient to advance the contactor to a new operative position at the next succeeding station. If the downward movement of the plunger is less than the fullstroke required to effect switch adjustment from one station to another the inclined surfaces of I complete in itself, it is preferred to encase the operating mechanism in a cover which co-operates with the frame 10 to keep dust and dirt from the moving parts. ing comprises a narrow strip of metal shown in elevation in Figure 4 stamped to fit about the side margins of the front and rear frame walls 14 and 15.
  • the width of the casing strip 56 is just suflicientto enable it to rest upon such margins, and its intermediate portion is embossed inwardly at 57 to fit be- The castween-such margins and thereby to fix the position of the casing to the frame.
  • the ends of the casing strip are turned upwardly at 58 and apertured to receive rivets'59, whereby it is permanently attached to the ears 16 and 17 of the switch frame.
  • the rivets employed for this purpose are tubular so that securing bolts or screws may be passed therethrough to mount the device as above described.
  • the several terminal contacts are equidistant from the axis of shaft 21 and are angularly spaced at 60 in the set and 120 between sets.
  • the rotatable contactor has its contacts at the same rotatstrip with reference able distance from the center of shaft 21 v and 30. The same result might be achieved with two moving contact buttons, but a190 rotation would be required.
  • the organization above described accomplishes the result with a 60 rotation and a correspondingly simplified actuating mechanism.
  • I claim 1 Acombination with a switch mechanism and a clutch mechanism including co-' clutch part and contactor, and by its reaction adapted to press together the spring of said clutch and said switch.
  • the combination with a switch mechanism and a clutch mechanism including rotatably connected and axially movable parts in axial alignment in the respective mechanisms, of a co-axial compression spring seated at its ends against said parts and yieldably pressing said parts in opposite directions to their proper respective positions in said mechanisms.
  • a switch mechanism and a clutch mechanism including co-axially rotatable-parts in the respective mechanisms, a shaft for the support of said parts, a splined connection between said parts adapt ed topermit them to move toward each other upon said shaft elements relatively fixed against axial movement and complementary to said parts in the respective mechanisms, and a compression spring interposed between said parts and adapted in its reaction to press each such part toward its respective complementary element.
  • a combination with a switch mechanism and a clutch mechanism each of which includes an element relatively fixed against axial movement, of a shaft extending between said elements, a sleeve upon said shaft, axially movable parts respectively in said clutch mechanism and said switch mechanism and mounted on said sleeve in splined connection with each other and complementary to the axially fixed elements of their respective mechanisms, and a spring wound about said sleeve and seated against said parts whereby yieldably to maintain said parts in opera; tive relation to said elements.
  • a device of the character described including a terminal head provided with terminal contacts, a rotatable contactor asso ciated with said .head, an actuating means including a pinion connected to impart motion to said contactor, 'a' reciprocable head, and a rack connected with said head and meshed with teeth of said pinion, said rack comprising a stamping having upturned ears engaging said rod and an intermediate upturned flange notched to provide teeth in mesh with said pinion.
  • a device of the character described including a frame having front and rear face members connected by a top member, a terminal head seated in one of said face members and provided with terminalcontacts, a transverse shaft between said face members fixing said terminal head to its seat, and a movable switch contactor between said face members upon said shaft.
  • a device of the character described including a frame having front and rear face members connectedby atop member, a terminal head seated in one of said face members and provided with terminal contacts. a transverse shaft between said face members fixing said terminal head to its seat,
  • a movable switch contactor between said face members upon said shaft, together with actuating means for said contactor, includmg a plunger reciprocably mounted in said top member and motion transmitting connections including a rack and pinion between said plunger and said contactor.
  • a device of the character described including a pair of spaced plates, insulated terminal contacts supported in one of saidv plates, a moving contactor between said plates in a position'to engage said contacts in step by step rotation, a one-way clutch adapted to produce said rotation and including a pair of complementary ratchet members aligned with each other and said contactor, one of said ratchet members being fixedagainst axial movement and the other being in splined connection with said contactor, means for oscillating said first mentioned ratchet member, and compression spring means interposed. between said second ratchet. member and said contactor.
  • a switch mechanism including a terminal head provided with terminals arranged in pairs at like radial distances from Hill a common center, the terminals of each pair being spaced at like distances and the space between the pairs being double the distance; of a switch contactor co-axial with said center and provided atv a radius for registration upon said terminals with three contact ele ments in mutually conductive relation and spaced at equal angular distances whereby in each successive movement of said eontactor two of said elements are adapted to bridge between terminals of opposite sets.
  • a switch mechanism including a terminal head provided with terminals arranged in pairs at like radial distances from a common center, the terminals of each pair being spaced at like distances and the space between the pairs beingdouble the distance; of a switch contactor co-axial with said cen- 'ter and provided at a radius for registration upon said terminals with three contact elements in mutually conductive relation and spaced at. equal angular distances whereby in each successive movement of said contaetor two of said elements are adapted to bridge between terminals of opposite sets, and alternate terminals of one of said sets.
  • a device of the character described including a terminal head provided with contacts, a rotatable switch element asso ciated with said head and adapted to interact with said contacts, actuating means said rack.

Landscapes

  • Push-Button Switches (AREA)

Description

' July31, 1928.
1,678,686 R. K. WINNING I LIGH'I DIIIING SWITCH Filed Kay 19. 192'! IN VEN TOR.
Patented July 31, 1928.
1,678,686 PATENT OFFICE.
ROBERT K. WINNING, OF WAUWATOSA, WISCONSIN, ASSIGNOR TO CLUE MANUIAO TUBING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISGONSIN.
LIGHT-DIMMING SWITCH.
Application filed May 19,
connect either of two live terminals alternative] y and successively with a current supply terminal during successive operations of the switch, the switch being so designed that it is not possible to operate the switch m such a manner as to leave both circuits open.
While the switch made in accordance with this invention has other fields of utility, it
is particularly servceable in the above indicated field for the reason that the operator cannot properly control a foot switch so designed as to require any delicate adjustment. It is highly objectionable to have a foot switch so constructed that anything less than a full operating movement of the control member will leave both circuits open.
It is one oft-he important purposes of the present invention to provide a novel construction insuring that if the switch operates at all, it will make its full movement to 1ts new position. Thus the operator will never be left without one light or the other, when theswitch is used to control the bright and dim headlights of a motor vehicle.
Further objects of the invention relate '00 compactness of organization, the elimination of parts, economy of manufacture and simplicity of design. It will be understood that from these standpoints the invention is not confined to the particular function of controlling the change from bright to dim of automobile headlight circuits or even to the more general field of automotive lighting control.
In the drawings: Figure l is a side elevation of my improved switch.
Figure 2 is a front elevation.
Figure 3 is a detail view taken 1n sect1 on in the plane indicated by line 33 in Figure 1. v
Figure 4 is a side elevation of the casing for the switch mechanism shown in Figures 1, 2, and 3. Figurefl is a detail of the actuating rack. Figure 6 is a detail ofthe mountlng of the moving switch contactor on its driving sleeve.
Like parts are identified by the same reference characters throughout the several views.
1927. Serial No. 182,519.
The frame 10 upon which the switch mechanism is assembled comprisesmerely a strip of sheet metal bent along transverse lines at 11 and 12 to provide a top wall 13, a front wall-14 and a rear wall 15. Integral cars 16 and 17 project horizontally from the ends of the top wall 13 and are apertured to receive mounting 'bolts or screws.
A terminal head 19 is shouldered at 20 to seat in a correspondingly formed openin in the front wall 14 of the switch frame. be two flat sides of the terminal head and the correspondingly formed margins of the opening permit no possible tendency of the terminal head to rotate in its mounting. An axis pin or shaft 21 is riveted at its ends to engage the rear wall 15 of the switch to the terminal head and thus serves to hold the terminal head in the position defined.
The moving switch contactor comprises a thin disc of sheet metal mounted on a carrier disc 26 towhich it is engaged by means of tongues 27. Contacts 28 are embossed to project forwardly from the face of disc 25 to a position where engaged with the fixed terminal contacts 29, 30, 31 and 32.
Terminal contacts 29 and 30 are connected by the strip conductor 33 so that the contacts 28 of the moving contacting" device will engage them successively and will simultaneously make connection with a fixed terminal diametrically opposite. During successive switch operations, terminal 29 will be con nected electrically to terminal 31 and then terminal 30 will be connected to terminal 32,
these connections being established alternately in each repetition of the cycle of operations.
The means for operating the moving contactor and maintainingit in operative relascribed.
For this particular invention the control memberconsists of a reciprocable plunger or foot button which includes a rod 35 and cap 36. The rod is guided for vertical reciprocation by the guide sleeve 37 mounted in the Y tion to the terminal head will now be detured to fit upon rod' 35 while head 42 fits upon the reduced end of the rod which is riveted thereover at 43. The material of this stamping is cut away to leave narrow strips of metal at 44 which serve as rack teeth which, in the limited reciprocative movement of the plunger, interact with the teeth 45 of the ratchet member 46.
The driving ratchet member 46 comprises a disc with three teeth 45 from which the ratchet pawls or tongues 47 are stamped to project integrally. The driving ratchet is mounted for rotation on shaft 21 and is spaced from the rear wall of the switch frame by means of a collar 48.
The ratchet pawls 47 interact with similarly formed pawls 49 which are opposed thereto on the face of the driving ratchet member 50. The driven ratchet member 50 is carried by and imparts motion to'squared sleeve 52 which is in splined relation to the contact carrier fibre disc 26. A compression spring 55 interposed between the driven ratchet member 50 and the contact carrier disc 26 permits the dual function of maintaining the ratchet and the switch parts in their proper respective relations. It will be noted that the terminals 32 are tubular and provide recesses vat their extremities into which the moving contact protuberances 28 enter in reaching positions of contact. Spring 55 furnishes the pressure necessary to effect proper engagement of the parts in such ositions and it yieldably permits the protuberances to leave the terminals upo each operation of the switches.
The impositive definition of the switch positions arises from the above described organization of the-switch contacts in which the switch terminal recess is sufficient to hold the switch against movement while the dogs or pawls 47 of the driving ratchet member -46 force their way past the complementary pawls 49 of the driven ratchet member 50. The relative yielding of the two ratchet members in an axial direction to .permit the-pawls to pass each other in this manner is made possible by the provision of spring 55 and the splined connection be"- ratchet action takes place on the downward movement of'the control button or plunger. There is no adjustment of the switch effected the control plunger is moving -upwardly under the compression of spring 38. The ratchet pawls or teeth 47 and 49 are so spaced that when the plunger makes a full stroke the motion transmitted through the ratchet to the switch contactor will be exactly sufficient to advance the contactor to a new operative position at the next succeeding station. If the downward movement of the plunger is less than the fullstroke required to effect switch adjustment from one station to another the inclined surfaces of I complete in itself, it is preferred to encase the operating mechanism in a cover which co-operates with the frame 10 to keep dust and dirt from the moving parts. ing comprises a narrow strip of metal shown in elevation in Figure 4 stamped to fit about the side margins of the front and rear frame walls 14 and 15. The width of the casing strip 56 is just suflicientto enable it to rest upon such margins, and its intermediate portion is embossed inwardly at 57 to fit be- The castween-such margins and thereby to fix the position of the casing to the frame.
The ends of the casing strip are turned upwardly at 58 and apertured to receive rivets'59, whereby it is permanently attached to the ears 16 and 17 of the switch frame. The rivets employed for this purpose are tubular so that securing bolts or screws may be passed therethrough to mount the device as above described. I
It will be noted that the several terminal contacts .are equidistant from the axis of shaft 21 and are angularly spaced at 60 in the set and 120 between sets. The rotatable contactor has its contacts at the same rotatstrip with reference able distance from the center of shaft 21 v and 30. The same result might be achieved with two moving contact buttons, but a190 rotation would be required. The organization above described accomplishes the result with a 60 rotation and a correspondingly simplified actuating mechanism.
I claim 1. Acombination with a switch mechanism and a clutch mechanism including co-' clutch part and contactor, and by its reaction adapted to press together the spring of said clutch and said switch.
3. In a device of the character described, the combination with a switch mechanism and a clutch mechanism including rotatably connected and axially movable parts in axial alignment in the respective mechanisms, of a co-axial compression spring seated at its ends against said parts and yieldably pressing said parts in opposite directions to their proper respective positions in said mechanisms.
' 4. In a device of the character described, the combination of a switch mechanism and a clutch mechanism, including co-axially rotatable-parts in the respective mechanisms, a shaft for the support of said parts, a splined connection between said parts adapt ed topermit them to move toward each other upon said shaft elements relatively fixed against axial movement and complementary to said parts in the respective mechanisms, and a compression spring interposed between said parts and adapted in its reaction to press each such part toward its respective complementary element.
5. in a device of the character described, a combination with a switch mechanism and a clutch mechanism each of which includes an element relatively fixed against axial movement, of a shaft extending between said elements, a sleeve upon said shaft, axially movable parts respectively in said clutch mechanism and said switch mechanism and mounted on said sleeve in splined connection with each other and complementary to the axially fixed elements of their respective mechanisms, and a spring wound about said sleeve and seated against said parts whereby yieldably to maintain said parts in opera; tive relation to said elements.
6. A device of the character described, including a terminal head provided with terminal contacts, a rotatable contactor asso ciated with said .head, an actuating means including a pinion connected to impart motion to said contactor, 'a' reciprocable head, and a rack connected with said head and meshed with teeth of said pinion, said rack comprising a stamping having upturned ears engaging said rod and an intermediate upturned flange notched to provide teeth in mesh with said pinion.
7. A device of the character described, including a frame having front and rear face members connected by a top member, a terminal head seated in one of said face members and provided with terminalcontacts, a transverse shaft between said face members fixing said terminal head to its seat, and a movable switch contactor between said face members upon said shaft.
8. A device of the character described, including a frame having front and rear face members connectedby atop member, a terminal head seated in one of said face members and provided with terminal contacts. a transverse shaft between said face members fixing said terminal head to its seat,
and a movable switch contactor between said face members upon said shaft, together with actuating means for said contactor, includmg a plunger reciprocably mounted in said top member and motion transmitting connections including a rack and pinion between said plunger and said contactor.
9. A device of the character described, including a pair of spaced plates, insulated terminal contacts supported in one of saidv plates, a moving contactor between said plates in a position'to engage said contacts in step by step rotation, a one-way clutch adapted to produce said rotation and including a pair of complementary ratchet members aligned with each other and said contactor, one of said ratchet members being fixedagainst axial movement and the other being in splined connection with said contactor, means for oscillating said first mentioned ratchet member, and compression spring means interposed. between said second ratchet. member and said contactor.
10. A switch mechanism including a terminal head provided with terminals arranged in pairs at like radial distances from Hill a common center, the terminals of each pair being spaced at like distances and the space between the pairs being double the distance; of a switch contactor co-axial with said center and provided atv a radius for registration upon said terminals with three contact ele ments in mutually conductive relation and spaced at equal angular distances whereby in each successive movement of said eontactor two of said elements are adapted to bridge between terminals of opposite sets.
11. A switch mechanism including a terminal head provided with terminals arranged in pairs at like radial distances from a common center, the terminals of each pair being spaced at like distances and the space between the pairs beingdouble the distance; of a switch contactor co-axial with said cen- 'ter and provided at a radius for registration upon said terminals with three contact elements in mutually conductive relation and spaced at. equal angular distances whereby in each successive movement of said contaetor two of said elements are adapted to bridge between terminals of opposite sets, and alternate terminals of one of said sets.
12. In a device of the character described, the combination with a contactor movable between successive stations in a step by step movement and provided with spaced projecting contacts mutually in electrical connection, of two sets of terminal contacts adapted to be engaged by the contacts of said contactor, one set of terminal contacts being mutually connected electrically and the contacts of the other set being mutually insulated and so positioned that one or the in circuit with other thereof is alternatively d first mentione the terminal contacts of sai set at each stationary position of said con-' tactor.
13. A device of the character described, including a terminal head provided with contacts, a rotatable switch element asso ciated with said head and adapted to interact with said contacts, actuating means said rack.
ROBERT K. WINNING.
US192519A 1927-05-19 1927-05-19 Light-dimming switch Expired - Lifetime US1678686A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US192519A US1678686A (en) 1927-05-19 1927-05-19 Light-dimming switch

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US192519A US1678686A (en) 1927-05-19 1927-05-19 Light-dimming switch

Publications (1)

Publication Number Publication Date
US1678686A true US1678686A (en) 1928-07-31

Family

ID=22710001

Family Applications (1)

Application Number Title Priority Date Filing Date
US192519A Expired - Lifetime US1678686A (en) 1927-05-19 1927-05-19 Light-dimming switch

Country Status (1)

Country Link
US (1) US1678686A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2451105A (en) * 1946-12-20 1948-10-12 Harold C Macnamara Push-button stepping switch
US3041429A (en) * 1959-09-14 1962-06-26 Gen Motors Corp Circuit controller

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2451105A (en) * 1946-12-20 1948-10-12 Harold C Macnamara Push-button stepping switch
US3041429A (en) * 1959-09-14 1962-06-26 Gen Motors Corp Circuit controller

Similar Documents

Publication Publication Date Title
US5079530A (en) Circuit breaker with a self-illuminating power switch
US4002874A (en) Double-throw rocker switch with selective lockout means
US3775576A (en) Butt-contact speed control trigger switch
JP4354921B2 (en) Trigger switch circuit, electric tool and trigger switch
US3104300A (en) Two circuit door switch
US4398075A (en) Mechanical switch
US1678686A (en) Light-dimming switch
US2779827A (en) Control device
US5796057A (en) Rocker-type electrical switch
US3604863A (en) Multiposition electrical switch
US4378541A (en) Time delay switch
US2283630A (en) Dimmer switch
US2429770A (en) Electric snap-action switch
US2298781A (en) Switch mechanism
US2807680A (en) Control device
US2341837A (en) Switch
US3165612A (en) Lighted push button switch with latching mechanism
US2929891A (en) Snap acting switch
US1981064A (en) Electric switch
US4496810A (en) Column mounted switching device for automobiles
JPH046051B2 (en)
US1950716A (en) Electric switch
US2529970A (en) Electric switch
US2298782A (en) Dimmer switch
US1935467A (en) Interrupter switch