Rotary switch

Information

  • Patent Grant
  • 6596950
  • Patent Number
    6,596,950
  • Date Filed
    Friday, September 6, 2002
    21 years ago
  • Date Issued
    Tuesday, July 22, 2003
    20 years ago
Abstract
A rotary switch suitable for use as a transmission gear selection switch. The switch includes a housing and a rotor rotationally connected to the housing, the rotor being rotational about a first axis. A cam follower connected to the rotor has a cam surface substantially centered about a radial axis, the radial axis being normal to the first axis. An electrical contact carried by the rotor has a contact surface spaced from the cam surface along the radial axis.
Description




FIELD OF THE INVENTION




The present invention relates to an electrical switch, and, more particularly, to a cam follower mechanism for a rotary switch as found in a transmission selection rotary switch of a vehicle.




BACKGROUND OF THE INVENTION




Electrical switches are well known. One common type of electrical switch is a rotary switch having a rotating shaft connected to a terminal capable of making or breaking an electrical connection with one or more other terminals. Rotary switches may convert positions into binary numbers; such switches are known as coded switches. For example, a three terminal coded switch can output a binary code equivalent to eight positions. The three terminals electrically reflecting the binary equivalent of the eight switch positions.




Rotary switches contain contacts which may be non-shorting contacts, otherwise known as break-before-make contacts, which operate by breaking a preceding circuit before closing the next circuit. Converse to that, rotary switches may also have shorting contacts, which operate as make-before-break contacts. The make-before-break feature indicates that an electrical contact is made with the next position before breaking the electrical contact with the current position.




Rotary switches are also known which have three ball bearings therein to provide a rotational and a detent feature within the rotary switch. Rotary switches are known to have moveable electrical contacts therein, which slide from one electrical contact on a printed circuit board or substrate to another electrical contact on the printed circuit board or substrate. The wiping action of a movable contact relative to a stationary contact within the rotary switch allows the rotary switch to connect electrical circuits subject to the rotational position of the shaft.




A problem with rotary switches is that the wiping of the movable contact from one stationary contact to another stationary contact causes a migration of conductive material across a nonconductive separating material, thereby causing intermittent or shorted conditions among the stationary contacts.




What is needed in the art is a break-before-make rotary switch, which doesn't short between contacts.




SUMMARY OF THE INVENTION




The present invention provides an apparatus for breaking electrical contact on both a common and signal surface before making electrical contact with a second signal surface.




The invention comprises, in one form thereof, a rotary switch including a housing and a rotor rotationally connected to the housing. The rotor is rotatable about a first axis. A cam follower is connected to the rotor, and has a cam surface substantially centered about a radial axis. The radial axis is normal to the first axis. An electrical contact has a contact surface spaced from the cam surface along the radial axis.




The invention comprises, in another form thereof, a method of passing a signal to a common terminal. The method includes steps of providing a rotary switch having a plurality of conductors and an electrical contact connected to a cam follower, the cam follower being connected to a rotor rotatable about a first axis, and biased toward at least one of the conductors with a biasing device in a direction substantially parallel to the first axis, the electrical contact being electrically connectable with at least one of the plurality of conductors; placing an electrical signal on at least one of the plurality of conductors; and connecting the electrical signal through the electrical contact to the common terminal.




The invention comprises, in yet another form thereof, a transmission gear selection switch including a housing and a rotor at least partially disposed in the housing. The rotor is rotatable about a first axis. A cam follower is connected to the rotor and is movable along a second axis, the second axis being parallel to the first axis. The cam follower is disposed to follow a path in the housing. At least one ridge is positioned along the path, oriented along a corresponding radial axis, the radial axis being normal to the first axis.




An advantage of the present invention is that the rotary switch breaks both a common and a signal contact by movement of a single cam follower.




Another advantage of the present invention is that a three contact conductor connects a common terminal to a signal terminal, the three contact connections providing mechanical stability to the conductor in the rotary switch.




Yet another advantage is that the contact is held in electrical contact with contact sectors with a spring, thereby compensating for contact wear.




Yet still another advantage is that the conductive material from one sector does not migrate to another sector since the contact is lifted from one sector and placed onto an adjacent sector.




Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.











BRIEF DESCRIPTION OF THE DRAWINGS




The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent, and the invention will be better understood by reference to the following description of an embodiment of the invention, taken in conjunction with the accompanying drawings, wherein:





FIG. 1

is a partially sectioned top view of an embodiment of a rotary switch of the present invention;





FIG. 2

is a partially sectioned side view along section line


2





2


of the rotary switch of

FIG. 1

; and





FIG. 3

is an enlarged partially sectioned view along section line


3





3


illustrating a cam follower encountering a ridge of the rotary switch of FIGS.


1


and


2


.











Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof.




DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT




Referring now to the drawings, and more particularly to

FIGS. 1 and 2

, there is shown a rotary switch


10


in accordance with the present invention. The exemplary embodiment of switch


10


is a transmission gear selection switch


10


including a housing


12


, a cover


14


, a connector


16


, a rotor


18


, O-rings


20


, conductors


22


, cam interface ridges


24


, a biasing device such as coil spring


26


, a cam follower


28


and a contact


30


.




Housing


12


includes separators


32


and O-ring retaining surface


34


. Housing


12


is integral with connector


16


both being formed from a non-conductive plastic by way of an injection molding process. Housing


12


interfaces with cover


14


to provide an environmental seal for the inner workings of rotary switch


10


. O-rings


20


provide a water and dust seal by way of the compression of cover


14


with rotor


18


and housing


12


. Conductors


22


are molded into the inner body of housing


12


, with one side of conductors


22


being exposed for electrical connection with contact


30


.




Separators


32


are located between adjacent conductors


22


, and prevent electrical contact between adjacent conductors


22


. Separators


32


are also positioned along a radial axis such as radial axis R


1


or R


2


. Separators


32


are made of nonconductive material and are integral with housing


12


.




O-ring retaining surface


34


is in contact with an O-ring


20


that is compressed by the presence of rotor


18


as it is positioned into housing


12


during assembly of switch


10


.




Cover


14


includes O-ring retaining surface


36


and housing interface


38


. Cover


14


is made from a material that is compatible with housing


12


and is positioned to environmentally seal housing


12


. O-ring retaining surface


36


interfaces with an O-ring


20


that is compressed between O-ring retaining surface


36


and rotor


18


. Housing interface


38


interconnects with an edge of housing


12


. The contacting surfaces of housing


12


and cover


14


may be sealed using an adhesive or thermal bonding method. Cover


14


has a central opening


15


thereby allowing external access to rotor


18


.




Connector


16


includes a retaining protrusion


40


and signal terminals


58


-


68


located therein. Connector


16


is formed in an integral manner with housing


12


. Connector


16


allows for a polarized connection with a corresponding plug (not shown). Retaining protrusion


40


is positioned to prevent the mating of connector


16


with an incorrectly shaped plug. Retaining protrusion


40


also serves to retain a plug (not shown) connected with connector


16


.




Rotor


18


includes a D-shaped opening


42


, a shoulder


44


, a rotor arm


46


, a coil spring cavity


48


and cam retainer openings


50


. Rotor


18


is rotatable about an axis X within rotary switch


10


. A cylindrical portion of rotor


18


interfaces with O-rings


20


to seal contamination out of rotary switch


10


. D-shaped opening


42


extends through rotor


18


along axis X, and is shaped to accommodate a D-shaped shaft (not shown). The D-shaped shaft (not shown) is rotated to a desired angular position, thereby causing a rotation of rotor


18


. Shoulder


44


may be a series of fluted edges that wipe along the top of O-ring


20


to provide mechanical compression thereagainst, yet allow for tolerances in the manufacture of rotor


18


and assembly tolerances of housing


12


and cover


14


.




Rotor arm


46


includes a coil spring cavity


48


and cam retainer openings


50


. Rotor arm


46


extends outward from the body of rotor


18


in a manner normal to axis X. On rotor arm


46


there are four cam retainer openings


50


to position and retain cam follower


28


. Coil spring cavity


48


is molded into a portion of rotor arm


46


to position and stabilize coil spring


26


. Coil spring cavity


48


is positioned to be in alignment with a spring recess


74


of cam follower


28


. Cam follower


28


is retained by rotor arm


46


and is moveable along axis Y, which is parallel to axis X. Cam follower


28


is positioned along a side of rotor arm


46


at a fixed radius from axis X. Cam follower


28


follows a path that is based on the location of cam follower


28


on rotor arm


46


and the rotation of rotor


18


. The path being normal to, and at a fixed radius from, axis X.




Conductors


22


include contact sectors


52


, a common sector


53


, interconnection portions


54


, positioning holes


56


, signal terminals


58


,


60


,


64


,


66


and


68


, and a common terminal


62


. Signal terminals


58


,


60


,


64


,


66


and


68


include a high terminal


58


, a low terminal


60


, a neutral terminal


64


, a reverse terminal


66


and a park terminal


68


. Terminals


58


,


60


,


64


,


66


and


68


are each electrically connected to a corresponding contact sector


52


. Contact sectors


52


lie in a plane normal to axis X at a radial distance from axis X. Contact sectors


52


are concentrically located about axis X with each contact sector


52


being a portion of an arc. The ends of adjacent contact sectors


52


are electrically isolated from each other by separators


32


. Terminal


62


is connected to common sector


53


, which is positioned close to rotor


18


in the same plane as contact sectors


52


. Terminals


58


,


60


,


64


,


66


and


68


are electrically connected to corresponding contact sectors


52


by way of interconnection portions


54


. Positioning holes


56


are located to assist in the injection molding process for the positioning of conductors


22


in a mold prior to injection molding taking place.




Each contact sector


52


is electrically connected to a corresponding terminal


58


,


60


,


64


,


66


or


68


, and sectors


52


are separated, in a radial direction from axis X, by separators


32


. Contact sectors


52


are located a radial distance from axis X that is different than the radial distance of cam follower


28


from axis X, which are each different than the radial distance of common sector


53


from axis X. Separators


32


are part of housing


12


and are approximately level with or slightly below the surface of sectors


52


.




Terminals


58


-


68


are used to transmit electrical signals that are representative of the angular position of a manually operated D-shaped shaft (not shown) inserted into rotor


18


. The position of rotor arm


46


variously electrically connects at least two of terminals


58


-


68


to each other. The signal that results from the positioning of rotor arm


46


may then be used to select the gear of an automatic transmission. The position of rotor arm


46


, is positioned by a vehicle operator, using a lever (not shown) connected to the D-shaped shaft (not shown), thereby selecting a transmission gear of high, low, neutral, reverse or park. The signal of the selected gear is electrically transmitted to common terminal


62


. High terminal


58


, low terminal


60


, neutral terminal


64


, reverse terminal


66


and park terminal


68


are so labeled and used relative to the terms for transmission gears in an automatic transmission of a vehicle. The selection of electrical signals and the passing of those signals to a common terminal by way of rotary switch


10


can encompass any electrical signal, not just those associated with an automatic transmission. Rotary switch


10


conveys a signal or conduction path from terminals


58


,


60


,


64


,


66


or


68


to common terminal


62


based upon the position of contact


30


, which is determined by the rotational position of rotor


18


. The positioning of rotor


18


causes an electrical connection between a sector


52


and common terminal


62


by way of the positioning of contact


30


.




Now, additionally referring to

FIG. 3

, there is shown cam follower


28


retained by rotor


18


. Cam follower


28


includes a cam surface


70


, contact retaining protrusions


72


, a spring recess


74


, arms


75


and retaining fingers


76


. Cam surface


70


is positioned in rotary switch


10


to encounter ridges


24


as rotor


18


is rotated. Ridges


24


extend in a radial direction from axis X along radial axis R


1


or R


2


as shown in

FIG. 1

or along any other radial axis originating at axis X and normal thereto. Ridges


24


do not extend radially into the area where sectors


52


or common sector


53


are located, and thereby do not cause any interference with the movement of contact


30


. Ridges


24


have a ramped surface to co-act with cam surface


70


to lift cam follower


28


and thereby respectively break electrical connection of contacts


78


and


80


with sectors


52


and


53


. Cam surface


70


is centered about a radial axis R


3


, which is normal to axis X and axis Y.




Contact


30


includes common sector contacts


78


and signal contact


80


. Common sector contacts


78


each have a contact surface


82


that is directed toward common sector


53


. Contact surfaces


82


come into sliding electrical contact with common sector


53


when cam surface


70


is not in contact with a ridge


24


. Signal contact


80


has a contact surface


84


that is directed to a contact sector


52


. Contact surface


84


comes into sliding electrical contact with a contact sector


52


when cam surface


70


is not in contact with a ridge


24


. Contact surface


84


is centered about contact plane P.




Contact retaining protrusions


72


extend from the body of cam follower


28


to hold contact


30


such that contact


30


will move with cam follower


28


. Cam follower


28


is biased by spring


26


to hold contacts


78


and


80


in electrical connection with corresponding sectors


53


,


52


, that is except for when cam surface


70


encounters ridge


24


. While coil spring


26


is shown as a biasing device, it should be understood that other structures including springs or other biasing devices can be used for biasing contacts


78


and


80


toward corresponding sectors


53


,


52


.




Arms


75


extend from the body of cam follower


28


through cam retainer openings


50


and are free to slide, thereby allowing cam follower


28


to move along the Y-axis. Retaining fingers


76


are located at an end of each respective arm


75


, thereby retaining cam follower


28


to rotor


18


and preventing spring


26


from fully extending. Spring recess


74


co-acts with coil spring cavity


48


to hold coil spring


26


in position to properly bias cam follower


28


.




Signal contact


80


is centered around contact plane P as shown in FIG.


3


. Axis X, axis Y, and radial axis R


3


are coplanar with contact plane P. Cam surface


70


is also centered along contact plane P such that as cam follower


28


transitions across ridge


24


, cam follower


28


is displaced along axis Y, causing contact


80


to lift from contact sector


52


proximate to the location of separator


32


, thereby breaking the electrical connection between signal contact


80


and contact sector


52


. Also as a result of cam follower


28


being displaced along axis Y, the electrical connection between common sector contacts


78


and common sector


53


is broken. The co-acting of two common sector contacts


78


along with signal contact


80


and coil spring


26


bring stability to contact


30


particularly as it slides along sectors


52


and


53


. The stability is the result of there being three physical points of contact with sectors


52


and


53


.




Rotary switch


10


is mounted to an assembly and is electrically connected to a transmission control system. A D-shaped shaft (not shown) is placed into D-shaped opening


42


of rotor


18


and connected with a user operable lever. As the user operable lever is moved, rotor


18


correspondingly moves, to/from high, low, neutral, reverse and park designations. The positioning of the lever (not shown) corresponds with the electrical connections of contact sectors


52


, which establish an electrical connection to common terminal


62


, thereby providing a signal on common terminal


62


that corresponds to the physical positioning of the lever (not shown). The positioning of rotor


18


can correspond to other physical phenomenon associated with a rotational position. More or fewer contact sectors may be utilized to provide signals or grounding type control systems by way of terminals located in rotary switch


10


. In addition rotary switch


10


may be ganged in multiple layers to provide additional positional information to an automotive or other system.




Variations and modifications of the foregoing are within the scope of the present invention. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention. The embodiments described herein explain the best modes known for practicing the invention and will enable others skilled in the art to utilize the invention. The claims are to be construed to include alternative embodiments to the extent permitted by the prior art.




Various features of the invention are set forth in the following claims.



Claims
  • 1. A rotary switch, comprising:a housing; a rotor rotationally connected to said housing, said rotor rotatable about a first axis; a cam follower connected to said rotor, said cam follower having a cam surface substantially centered about a radial axis, said radial axis normal to said first axis; and an electrical contact carried by said cam follower, said electrical contact having a contact surface spaced from said cam surface along said radial axis.
  • 2. The switch of claim 1, wherein said rotor includes a rotor arm, said cam follower being attached to said rotor arm, said cam follower being biased in a direction normal to said rotor arm.
  • 3. The switch of claim 2, further comprising a plurality of contact sectors, at least one of said contact sectors being in breakable electrical connection with said contact surface of said electrical contact.
  • 4. The switch of claim 3, wherein said contact sectors are substantially disposed in a plane.
  • 5. The switch of claim 3, wherein said plurality of contact sectors include a first contact sector and a second contact sector, both said first contact sector and said second contact sector having a first end, said first end of said first contact sector and said first end of said second contact sector disposed proximate each other along an other radial axis.
  • 6. The switch of claim 5, further comprising at least one ridge including a first ridge disposed along said other radial axis, said ridge positioned apart from said first end of said first contact sector and said first end of said second contact sector.
  • 7. The switch of claim 6, wherein said cam follower is configured to encounter said first ridge thereby breaking an electrical connection between said electrical contact and at least one of said plurality of contact sectors.
  • 8. The switch of claim 7, further comprising a biasing device operatively disposed between said cam follower and said rotor arm.
  • 9. The switch of claim 8, further comprising a plurality of electrical terminals each being electrically connected to a corresponding one of said plurality of contact sectors.
  • 10. The switch of claim 1, further comprising:a ridge connected to said housing; and at least one contact sector electrically connectable to said electrical contact, said cam surface co-acting with said ridge to reposition said cam follower thereby electrically disconnecting said electrical contact from at least one said contact sector.
  • 11. A method of passing a signal to a common terminal, comprising the steps of:providing a rotary switch having a plurality of conductors and an electrical contact connected to a cam follower, said cam follower being connected to a rotor rotatable about a first axis, said cam follower biased toward at least one of said plurality of conductors with a biasing device in a direction substantially parallel to said first axis, said electrical contact electrically connectable with at least one of said plurality of conductors; placing an electrical signal on at least one of said plurality of conductors of said rotary switch; and connecting said electrical signal through said electrical contact to the common terminal.
  • 12. The method of claim 11, further comprising steps of providing a ridge in said switch, rotating said rotor such that said cam follower encounters said ridge, and terminating an electrical connection of said electrical signal with the common terminal when said cam follower encounters said ridge.
  • 13. The method of claim 12, wherein said terminating step further comprises the sub-step of moving said cam follower against said biasing device and away from said plurality of conductors when said cam follower encounters said ridge.
  • 14. A transmission gear selection switch, comprising:a housing; a rotor at least partially disposed in said housing, said rotor rotatable about a first axis; a cam follower connected to said rotor, said cam follower movable along a second axis, said second axis being parallel to said first axis, said cam follower disposed to follow a path in said housing as said rotor is rotated; and at least one ridge positioned along said path, said at least one ridge oriented along a corresponding radial axis, said radial axis normal to said first axis.
  • 15. The switch of claim 14, further comprising an electrical contact carried by said rotor, said electrical contact having a contacting surface substantially centered about a plane, said plane including said first axis and said second axis.
  • 16. The switch of claim 15, wherein said contact is movable in a direction substantially parallel with said second axis.
  • 17. The switch of claim 15, further comprising a plurality of contact sectors connected to said housing, said plurality of contact sectors being concentrically located along a portion of an arc around said first axis at a first radius.
  • 18. The switch of claim 17, further comprising a common contact sector being concentrically located with said plurality of contact sectors at a second radius from said first axis, said electrical contact having an other contacting surface in electrical connection with said common contact sector.
  • 19. The switch of claim 18, wherein said path is substantially circular and normal to said first axis and said second axis.
  • 20. The switch of claim 19, wherein said at least one ridge includes a first ridge located at a distance from said first axis greater than said second radius and less than said first radius.
CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 60/318,535, filed Sep. 10, 2001.

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Provisional Applications (1)
Number Date Country
60/318535 Sep 2001 US