Electricity: circuit makers and breakers – Multiple circuit control – Combined pivoted and reciprocating contact
Reexamination Certificate
2000-03-03
2001-08-28
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Multiple circuit control
Combined pivoted and reciprocating contact
C200S0050EA, C200S565000, C200S336000
Reexamination Certificate
active
06281453
ABSTRACT:
TECHNICAL FIELD
The present invention relates to selector switches for vehicle accessories such as headlights and the like.
BACKGROUND ART
Automotive vehicles include a wide variety of accessories and systems such as headlights, windshield wipers and the like that are controlled by selector switches mounted on the dash or steering column. It is important that selector switches are easy to operate and that they provide the proper “feel”. Selector switches must also be durable and robust to provide users with the feeling of quality.
Vehicle manufacturers have set stringent design standards for selector switches. Vehicle manufacturers have also imposed design requirements to assure that customer expectations as to the operation of manual controls are fulfilled.
For example, vehicle light controls must be easy to operate but sufficient turning torque must be required for operation to provide a quality feel. For selector switches that are adjusted by rotating a knob, design requirements are set by vehicle manufacturers to assure that the knob cannot be turned past predetermined arcuate limits. End stops that limit knob movement must be positive and sufficiently durable to resist breakage.
Selector switches for automotive applications have evolved into relatively large complicated structures to meet vehicle manufacturer standards. Different types of selector switches have been developed including switches having rotary switch contacts and switches having sliding switch contacts. One example of a rotary switch is disclosed in U.S. Pat. No. 4,885,434 that discloses a composite push-pull headlight and rotary switch. Typically, a dash-mounted headlight control switch includes multiple functions and may be 3-4 inches in depth. These types of control switches are provided with thick copper contacts that must have the capacity to carry operational circuit current loads. This type of switch is relatively expensive to manufacture and lacks design flexibility.
In an attempt to reduce vehicle cost and weight, vehicle manufacturers have recently begun to utilize multiplexed digital controls for vehicle accessories. In multiplex controls, only digital control level current carrying wiring harnesses are required to connect switches to control circuits. Control circuits are interfaced with operational circuits by relays, SCR or MOSFET interfaces. This can reduce the cost of wiring harnesses by reducing the number and size of wires in wiring harnesses. Control switches can be reduced in size and switch contacts can be designed with lower current-carrying capacity when only control circuit level currents must be carried by the selector switches. Since less current is being controlled by the selector switches, the switches may be designed with reduced heat resistance properties.
Encoders have been developed as standardized electronic components that are used to provide a digital indication of the rotational position of a shaft. Usually, encoders are designed for full rotation and do not include end stops that would prevent rotation in a full circle. Encoders normally are designed to provide only low levels of rotational torque resistance. Encoders also generally provide a large number of digital outputs. For example, a four-bit encoder would generally have sixteen potential outputs, or stops. Few if any automotive systems require as many as sixteen outputs to be controlled by a single switch. The additional potential outputs are unacceptable for automotive accessory controls because the provision of additional no-function stops for a selector switch would be confusing to a automobile operator.
These and other problems in the prior art are addressed by the present invention as summarized below.
DISCLOSURE OF INVENTION
According to the present invention, a selector switch assembly for control of multiple functions of a vehicle accessory, or accessories, is provided. The selector switch includes a rotary switch having a body portion and a shaft having a rotary axis. The shaft extends from the body portion and terminates at a distal end thereof. A knob has an internal receptacle for receiving the distal end of the shaft. The knob has at least one rib that forms part of a positive stop. A carrier is provided that has an opening through which the shaft is received. The carrier is assembled to the shaft between the body of the rotary switch and the knob. The carrier has at least one spring and at least one ball contained in a cavity formed in the carrier. The spring biases the ball radially outwardly. A face plate is provided for enclosing the rotary switch. The face plate has at least two end stops formed at circumferentially spaced locations on the face plate. The two end stops are positioned to be engaged by the rib as the knob is rotated to provide positive stops for limiting rotation of the knob in both the clockwise and counterclockwise directions. The face plate has a set of circumferentially arranged detents that are engaged by the ball retained in the carrier to provide intermediate position stops for the knob.
According to one aspect of the present invention, the rotary switch may be a digital encoder that produces a digital signal representative of the position of the shaft as signified by the generation of one of a plurality of digital codes. The digital encoder is connected to a circuit that is used to control at least one vehicle accessory based upon the digital code provided as the digital signal produced by the digital encoder. The rotary switch or digital encoder is preferably secured to a circuit board and has electrical contacts that are electrically connected to the circuit board.
In accordance with the invention, a shaft having a D-shaped cross-section is provided. The knob is assembled to the D-shaped shaft by a spring clip that is affixed to the knob and has a portion that encircles and engages the shaft. The opening in the carrier is preferably D-shaped and the shaft has a corresponding D-shaped cross-section that aligns the knob, carrier and shaft.
In one form of the invention, the cavity formed in the carrier has a longitudinal axis that extends radially outwardly. The spring is aligned with the longitudinal axis of the cavity to bias the ball into engagement with the detents formed on the face plate. In a preferred form of the invention, two springs and two balls are provided in the carrier at diametrically opposite locations to provide a knob with balanced and smooth operation. Two sets of detents are provided at diametrically spaced locations. The balls in the carrier are biased into contact with the detents formed on the face plate.
According to another aspect of the invention, the face plate defines a cavity in which a circuit board may be secured. The circuit board is preferably contained in the cavity by a backing board that allows the selector switch assembly to be modular in design.
In one form of the invention, the selector switch is used to control a set of headlights, a set of parking lights, and a dome light of a vehicle. The headlights may be turned on at a first position without delay, turned on with a first delay in a second position, and turned on with a second delay in a third position. The parking lights may be turned on separately in a fourth position and are also turned on in each of the first, second and third positions with the headlights. A dome light may be independently controlled by providing a momentary push switch as part of the rotary switch.
According to the present invention, a multi-function automotive accessory switch can be provided utilizing a simple and inexpensive digital encoder. The knob and carrier including spring-biased detents can provide a selector switch with the appropriate level of rotational torque resistance even though the encoder itself provides only minimal torque resistance. The selector switch also provides robust and durable end stops that limit the arcuate movement of the knob to the desired range of movement. In this way, a compact, inexpensive and reliable selector switch can be provided in modular form that meets vehicle
Brooks & Kushman P.C
Friedhofer Michael
Lear Corporation
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