Semi-automatic rear view mirror assembly

Background of the Invention

The present invention relates to rear view mirror assemblies such as those used in automobiles, and, in particular, to rear view mirror assemblies which provide high reflectivity position and low re­flectivity position for night time conditions.

Many conventional rear view mirror as­semblies employ prismatic mirrors which can be posi­tioned by the vehicle operator in a high reflectivity or low reflectivity disposition. Such prismatic mir­rors can be movably driven by a mechanical actuator mounted, for example, on the housing of the mirror assembly, or by an electronic circuit having a motor or solenoid driven actuator to manipulate the mirror or mirror/housing combination between the low and high reflectivity dispositions.

For example, U.S. Patent No. 4,443,057, which issued to Bauer et al, discloses an automobile rear view mirror whose housing is moved by an ec­centric cam driven by a uni-directional DC motor. As is disclosed in the above-identified Bauer et al pat­ent, the energization of the DC motor is controlled by limit switches, which switches sense when the mir­ror is in the low and high reflectivity dis­positions. The limit switches cut off current to the DC motor. The use of limit switches is typical of many conventional automotive rear view mirror assem­blies.

There are numerous inherent disadvantages associated with the use of limit switches. First, the housing of the rear view mirror provides limited space for carrying the electronic circuitry and mechanical structure associated with moving the mir­ror between the low and high reflectivity dis­positions. A pair of limit switches usually require associated gearing, camming or other structure to actuate the switches, and such structure takes up an inordinate amount of space. Second, the mechanisms used for actuating and mounting the switches are re­latively complex, making assembly and repair of the rear view mirror assembly difficult and time con­suming.

Another disclosed mechanism in U.S. Patent No. 3,680,951 to Jordan et al is a photo-­electronically controlled rear view mirror which in­cludes a first photocell to switch the mirror between "normal" and "adjusted" positions in response to in­cident light on the mirror, and a second photocell to monitor ambient light thereby preventing switching of the mirror to the "adjusted" position during daylight hours and at night where high ambient light con­ditions exist. Jordan et al utilize a pair of per­manent magnets in combination with an electromagnet therebetween in which polarity can be alternated to drive a cam back and forth, which, in turn, moves a projection bearing thereagainst in order to adjust a mirror between positions of high and low reflect­ ivity. The solenoid of Jordan et al must be con­tinually energized to maintain the mirror in the de­sired orientation and the cam/cam follower combina­tion does not provide a smooth transition between the different reflectivity positions.

Other disclosures for mechanically changing the reflectivity orientation of rear view mirrors variously include electromagnetic means and pivotal base mounted mirrors, etc. However, it has become continuously clear that a smooth-operating two-position rear view mirror is required for auto­mobiles in order to provide smooth and dependable switching for conditions of high and low ambient light.

Thus, it is an object of the present in­vention to provide a rear view mirror assembly which can be efficiently manufactured to provide smooth and dependable switching between positions of high and low reflectivity.

Another object of this invention is to pro­vide a mechanical drive for smooth continuous move­ment of the mirror by use of a dependable bi-directional DC motor.

It is also an object of the present in­vention to provide an electronic control circuit for a motor driven rear view mirror assembly.

It is another object of the present in­vention to provide a motor control circuit for a rear view mirror assembly which eliminates the need for limit switches.

It is a further object of the present in­vention to provide a control circuit for an auto­mobile rear view mirror assembly, which control cir­cuit is relatively simple and reliable and takes up relatively little space in the housing of the rear view mirror assembly.

It is yet another object of the present in­vention to provide a mirror control circuit for an automobile rear view mirror assembly which overcomes the inherent disadvantages of conventional rear view mirror assemblies.

Summary of the Invention

In accordance with the present invention a variable reflectivity mirror assembly is provided which is operable to provide high and low re­flectivity orientations. The assembly includes a support member for securing the assembly to a struc­ture which is immovable relative to the assembly, a housing mounted on the support member, a reflective panel connected to the support member for rotation between the high and low reflectivity orientations, such panel having a first side which provides the high reflectivity and a second side which provides low reflectivity. The assembly also includes motor means mounted in the housing which includes a drive element movable in opposite directions in response to oppositely directed currents applied to the motor, and actuation means secured to the housing for driv­ing engagement with the drive element to rotate the reflective panel between the high and low re­flectivity orientations.

Finally, the present assembly also includes a timed-drive circuit means for directing current through the motor in one of the opposite directions in response to orientation selection means for a pre­determined period of time sufficient to drive the actuation means to a selected orientation.

The motor is preferably a bi-directional rotary motor which has a drive shaft that is used with a worm gear to interconnect with a threaded gear means. In this embodiment an actuation means can in­clude a gear means to engage the drive shaft and a transfer cam rod assembly coupled with the gear for linear movement responsive to the drive gear. The cam rod assembly can have at one end a cam surface against which a depending projection can bear against for providing oscillatory motion to a mirror while the cam moves linearly back and forth. The opposite end of the cam assembly rod can include a nut as a gear means which is fixed against rotation in a pas­sageway provided in the cam rod. Preferably the nut is positioned in the passageway between two compres­sion means such as compression springs so that when the worm gear is threaded through the nut, linear travel is damped by action of the compression springs against the nut.

The present invention also includes a motor control circuit for an automobile rear view mirror assembly which provides current to a reversible DC motor of the assembly for a predetermined duration. The DC motor drives the reflective panel, e.g., a prismatic mirror, between a high reflectivity and low reflectivity orientation.

The motor control circuit basically com­prises a momentary contact switch which is actuatable by the vehicle operator to alternately position the mirror in the high reflectivity or low reflectivity orientation. The switch is coupled to a toggle cir­cuit, which circuit provides first and second logic output signals which are in alternate states and which change states in response to actuation of the switch.

First and second timing circuits are coupled to the toggle circuit. Each of the first and second timing circuits provides a pulsed output signal in response to the first and second outputs of the toggle circuit, respectively. The pulsed output signals of the timing circuits are of a predetermined duration, and effect the energization of the motor for substantially the predetermined duration of the pulsed output signals.

The motor control circuit also includes first and second motor drive circuits. The first and second motor drive circuits are coupled to the first and second timing circuits, respectively, and are responsive to the pulsed output signals of the timing circuits. The first and second drive circuits are coupled to the motor and selectively provide energizing current bi-directionally to the motor to effect motor movement alternately in a forward and a reverse direction for substantially the predetermined duration of the pulsed output signals of the first and second timing circuits.

As a result of the present invention, a semi-­automatic rear view mirror assembly can be provided which has high and low reflectivity orientations, and which can be manufactured in a very efficient manner and which provides highly dependable and smooth operation to switch between the high and low reflectivity orientations. As a consequence of the unique motor control circuits, the bi-directional DC motor can be operated to smoothly move the reflective panel or mirror between the high and low reflectivity positions for a time period sufficient to drive the motor to allow attaining the high reflectivity and low reflectivity positions but limiting the time operation so that the motor is not activated a sufficient time beyond the attaining of such positions. As a result of this circuitry and mechanism, there is no need to provide limit switches which unnecessarily complicate the structure of the assembly.

For a better understanding of the present invention, together with other and further objects, reference is made to the following description, taken in conjunction with the accompanying drawings, and its scope will be pointed out in the appended claims.

Brief Description of the Drawings

• Fig. 1 is a side elevational schematic of the assembly of a rear view mirror assembly con­structed in accordance with the present invention;
• Fig. 2a and 2b are side elevational and front elevational views, respectively, of a part of the support which holds the housing for pivotal move­ment;
• Fig. 3 is a plan view in partial section of the actuation means between the motor drive element and the base portion shown in Fig. 2a and 2b;
• Fig. 3a is an end view of the left-hand side of the actuator means shown in Fig. 3 in whole;
• Fig. 4 is a plan view in partial section similar to that shown in Fig. 3, but includes the actuator completely assembled with a drive gear in­serted therein;
• Fig. 5 is a block diagram of the motor con­trol circuit of the present invention;
• Fig. 6 is a schematic diagram of the motor control circuit illustrated by Fig. 5;
• Fig. 7 is an isometric view of a push-button switch, which is actuated by the vehicle operator to change the reflectivity of the mirror, formed in accordance with the present invention;
• Fig. 8 is a side view of the push-button switch with its housing partially broken away;
• Fig. 9 is an exploded view of the push-button switch shown in Figures 7 and 8;
• Fig. 10 is a plan view of a contact as­sembly, partially assembled, used in the push-button switch of the rear view mirror assembly;
• Fig. 11 is an enlarged, detailed side view of the contact assembly used in the push-button switch; and
• Fig. 12 is a partial exploded perspective view of the assembly in accordance with the present invention.

Detailed Description of the Invention

The Assembly

Referring to Figures 1 and 12, an assembly 10 as shown constructed in accordance with the in­vention can be seen therein. The assembly includes in general a housing 12 on which have been rigidly mounted by means of bracket 14′, a bi-directional DC motor 14 having a drive element shown therein as a worm gear 16. The worm gear 16 extends from the motor 14 to an actuator such as cam rod assembly 18 which is also rigidly fixed to the housing 12. The cam rod assembly 18, in turn, has a drive end 18a seen on the left-hand side of the assembly and a cam­ming end 18b shown on the right-hand side of the as­sembly. When the cam rod assembly 18 is driven by the motor 14 through worm gear 16, the cam rod as­sembly is driven back and forth from right to left. The phantom lines shown extending from the right end of the cam rod assembly in Figure 1 depict the farthest point of travel of the assembly.

The housing also has trunnions 20 spaced apart in the center of the housing for receipt of a support member 40 therein. In order to assemble the frame 12 onto the support, it is necessary to insert, such as by snap fitting, arms 41 of the support mem­ber 40 into trunnions 20. The support member 40 also has a projection 42 extending from beneath the main body of the member 40 for receipt by the cam rod 18.

The assembly 10 also includes a circuit board 44 as well as an actuating switch S1 having a housing 46 and a switch head portion 48 resembling an oversized button which can be easily operated to con­trol the position of the rear view mirror by a pas­senger.

In the embodiment shown herein, a mirror 11 having a trapezoidal cross section and consequently modes of high and low reflectivity is fixed to the frame 12 for simultaneous movement therewith. Fur­thermore, the cam rod assembly 18 is fixed to the back of housing 12 so that upon movement of the cam rod assembly, the housing is likewise moved therewith.

Referring now to Figs. 2a and 2b, the in­terconnecting support member 40 is shown in greater detail. In Fig. 2a the support member 40 is shown having a stem 50 which extends to a ball 52 which is connected with, for example, a windshield support by means of a ball socket for mating relationship with the ball 52. Stem 50 and ball 52 extend from the back of the frame 12 so that the rear view mirror can be adjusted for individual passenger viewing. The housing is attached to the support member by means of side arms 41 which can be fitted into trunnions 20 which are fixed to the housing of the rear view mir­ror. Furthermore, projection 42 extends from beneath the body of the member 40 for insertion into a diag­onal slot 17 in the cam rod assembly 18, which shall be explained in greater detail hereinbelow. In oper­ation, the member 40 remains in place with the wind­shield support while the rear view mirror is caused to actuate by pivoting around the side arms 41. To this end, it has been found suitable to mount the side arms 41 in the trunnions 20 by virtue of a snap fit whereby relative rotation between the surface of the arms 41 and the trunnions 20 can be easily ef­fected.

Referring now to Fig. 3, the cam rod as­sembly can be seen in greater detail, with the right-hand portion of the assembly 18 having a diag­onal slot 17 formed therein with end limits 17′ and 17˝. On either side of the diagonal slot 17, there are surfaces 17a and 17b which bear against the pro­jection 42 during operation of moving the mirror be­tween high and low positions of reflectivity.

Referring to the left-hand side of the as­sembly 18, a passage 15 can be seen formed therein in the partial section view. The passage 15 along with reduced passage area 15a has been provided to accom­modate driving elements for the cam rod assembly and the motor 14. One convenient means of driving the cam rod assembly 18 is by use of a combination worm gear and drive nut which can be inserted in the pas­sageway 15. Thus, the passageway 15 can have a gen­erally square cross section as shown in the end view of Fig. 3a while the reduced portion of the passage­way 15a can have a generally circular cross section for receipt of the worm gear after it passes through a drive nut.

The entire assembly as described above is shown in Fig. 4, wherein a drive nut 13 has been pro­vided in passageway 15 along with compression springs 4 fixed on either side thereof to provide damped travel of the cam rod assembly back and forth. This damping effect provides smooth and easy travel of the mirror when being driven by the worm gear 16.

In operation, the worm gear 16 can be driven by the DC motor in a clockwise direction to threadedly engage the drive nut 13, thereby pulling the drive nut to the left in Fig. 4. The drive nut 13 bears against compression spring 4 and thence against the end cap 18′ of the cam rod assembly 18. The cam rod 18 is driven to the left so that projection 42 is cammed alongside the slot sides 17a and 17b until it rests against slot end 17′. This pivots the frame 12 and the trapezoidal mirror 11 to the position of reflectivity associated therewith. The springs 11 help prevent the nut 13 from fitting too tightly against end cap 18′ and against the other end of the passage 15, when the nut 13 is driven toward them after the desired orientation is reached.

When the worm gear 16 is rotated by bi-direc­tional DC motor 14 in the counterclockwise direction, the nut 13 is threadedly engaged to be moved to the right-hand side in Fig. 4 thereby bearing against compressions spring 4 and thence to the shoulders of the passageway 15 of the cam rod assembly. In this mode of operation the assembly is thereby pushed to the right so that the projection 42 is cammed against sides 17a and 17b to drive the cam rod assembly and housing fixed thereto simultaneously to the position provided by the end 17˝in slot 17.

It is important that in the present assembly, the motor control circuit provide current to actuate the worm gear 16 a sufficient time to move the rod assembly between the two limiting positions 17′ and 17˝ of slot 17. The time controlled nature of the drive reduces the time period that the motor is acti­vated to be just beyond the necessary to attain the desired orientation without excessive use of electric­ity. Furthermore, the present invention provides smooth and relatively uninterrupted travel between the two positions by virtue of the damping provided by compression springs 11 so that uneven travel resulting from surfaces sticking to one another can be prevented from being translated into jerky transition between positions of high and low reflectivity.

Motor Control Circuit

Referring to Fig. 5 of the drawings, it will be seen that the motor control circuit of the rear view mirror assembly constructed in accordance with the present invention includes, in its most basic form, a motor driving circuit 60, a timing cir­cuit 62 and an operator actuatable switching circuit 64.

The motor driving circuit 60 is coupled to the reversible DC motor 14, which motor is operative­ly linked to the prismatic mirror 11 of the mirror assembly to drive the mirror between a low re­flectivity disposition and a high reflectivity dis­position. The motor driving circuit selectively sup­plies a current bi-directionally to the motor 14 to drive the motor.

The timing circuit 62 is used for con­trolling the time during which current is supplied to the motor 14. The timing circuit 62 provides an out­put signal, and the motor driving circuit 60 is re­sponsive to the output signal of the timing circuit, and thus supplies current to the motor only for a predetermined duration determined by the timing cir­cuit 62.

The switching circuit 64 of the motor con­trol circuit is controllable by the vehicle operat­or. The switching circuit 64 is used for controlling the direction current is supplied to the motor 14. The switching circuit 64 provides an output signal, and the timing circuit 62 generates its output signal in response to the output signal of the switching circuit 64.

In a more preferred form of the motor con­trol circuit of the present invention, the motor driving circuit 60 includes a first drive circuit 70 and a second drive circuit 72. Each of the first and second drive circuits 70, 72 are coupled to the motor 14. The first and second drive circuits 70, 72 are operable in a first state, where current is supplied to the motor 14 in a first direction so that the motor shaft rotates in a forward direction; in a second state, where current is supplied to the motor 14 in a second direction which is opposite to the first direction, so that the motor 14 rotates in a reverse direction; and in a third state, where no current is supplied to the motor 14 so that the motor does not turn and the mirror 11 remains in a particular disposition.

Similarly, in its preferred form, the tim­ing circuit 62 of the motor control circuit includes a first timing circuit 74 and a second timing circuit 76. The first and second timing circuits 74, 76 are coupled to the first and second drive circuits 70, 72, respectively, and to the operator actuatable switching circuit 64. Each of the first and second timing circuits 74, 76 selectively provide a pulsed output signal of a predetermined duration in response to the output signal of the operator actuatable switching circuit 64. The first and second drive circuits 70, 72 are responsive to the pulsed output signals of the first and second timing circuits 74, 76, respectively, to supply or not supply current to the motor 14.

The operator actuatable switching circuit 64 preferably includes a switch S1, disposed on the outside of the mirror assembly housing 12 for the vehicle operator to actuate, and a toggle circuit 80 coupled to the switch S1. The switch S1 is a momentary contact switch, and the toggle circuit 80 provides a logic output which changes logic states in response to actuation of the momentary contact switch.

Referring now to Fig. 6 of the drawings which schematically illustrates a preferred form of the motor control circuit, it will be seen that the momentary contact switch S1 is basically a push-button switch, and the toggle circuit 80 in­cludes first and second NAND gates 82, 84, each of which has its inputs connected together so that each gate acts as an inverter. Ihe output of the first gate 82 is coupled to the input of the second gate 84, and the output of the second gate 84 is coupled back to the input of the first gate 82 through a feedback resistor R1. Furthermore, the output of the first gate 82 is connected to a storage device, such as a capacitor C1, through a resistor R2, and the capacitor C1 is selectively coupled to the input of the first gate 82 through the push-button switch S1.

As its name implies, the toggle circuit 80 provides alternate logic states at the outputs of the first and second gates 82, 84, which outputs change state every time the push-button switch S1 is actuated.

If, for example, the outputs of the first and second gates 82, 84 are respectively at a high and low logic level, the capacitor C1 will charge through the resistor R2 to a voltage comparable to a high logic level. When the push-button switch S1 is actuated, the charge on the capacitor C1 is transfer­red through the switch to the input of the first gate 82, causing the first gate to change states (in the example, the output of the first gate 82 goes to a low logic level). Because the two gates are coupled together, the first gate 82 causes the output of the second gate 84 to change states (that is, to a high logic level). The high logic level of the second gate's output is fed back to the input of the first gate 82 through the resistor R1, which logic level is the same as the logic level initially impressed on the first gate 82 by the capacitor C1.

The capacitor C1 will now discharge to a low logic level, which logic level will be impressed on the input of the first gate 82, causing the output of the first and second gates 82, 84 to change states, when the push-button switch S1 is actuated a second time.

Thus, the switching circuit 64 acts as a low speed debouncing circuit which provides logic output signals that are in alternate states and that change states every time the push-button switch S1 is actuated.

As mentioned previously, the first and second timing circuits 74, 76 are connected to the toggle circuit 80 and, more specifically, to the out­puts of the first and second logic gates 82, 84, re­spectively. Each of the first and second timing cir­cuits 74, 76 preferably includes a timing capacitor C2, C3 and a timing resistor R3, R4, which are con­nected together, and a logic NAND gate whose inputs are connected together so that each NAND gate acts as an inverter. The inputs of the NAND gates 86, 88 are connected to their respective timing resistors R3, R4 and capacitor C2, C3. The timing capacitors C2, C3 are connected to the outputs of the first and second gates 82, 84 of the toggle circuit 80.

The capacitors C2, C3 of the timing cir­cuits 74, 76 will charge through their respective timing resistors R3, R4 to either a high logic level or a low logic level, depending upon the state of the first and second gates 82, 84 of the toggle circuit. If, for example, the outputs of the first and second gates 82, 84 are respectively high and low, the tim­ing capacitors C2, C3 of the first and second timing circuits 74, 76 will charge to a low and high logic level, respectively. However, under steady state conditions, the inputs of the NAND gates 86, 88 of the first and second timing circuits will be pulled up to a high logic level through their respective timing resistors R3, R4 so that the outputs of the NAND gates 86, 88 will be at a low logic level.

When the toggle circuit 80 changes states, the inputs of the NAND gates 86, 88 of the timing circuits 74, 76 will see the pre-existing charge on the timing capacitors C2, C3 coupled with the new logic level of the first and second gates 82, 84. Thus, in the example given above, the input of the first timing circuit's gate 86 will see the low logic level charge of the timing capacitor C2 in combina­tion with the low output state of the first gate 82 of the toggle circuit 80 and, accordingly, the output of the gate 86 will change from a low logic level to a high logic level.

In an analogous fashion, the gate 88 of the second timing circuit 76 will see the high logic level charge on the capacitor C3 coupled with the new high logic level on the output of the second gate 84. Because the input of the NAND gate 88 was al­ready at a high logic level (under steady state con­ditions), its output will remain at a low logic level.

The timing capacitors C2, C3 will now charge to new logic levels. The timing capacitor C2 of the first timing circuit 74 will charge to a high logic level, and the timing capacitor C3 of the second timing circuit 76 will discharge to a low logic level. When the timing capacitor C2 of the first timing circuit 74 has charged sufficiently, the input of the NAND gate 86 will be pulled up to a high logic level, causing its output to go low. The out­put of the NAND gate 88 of the second timing circuit 76 will remain low, as its input remains at a high logic level.

Thus, in the example given above, a pulsed output signal is provided on the output of the NAND gate 86 of the first timing circuit 74. The NAND gate's output provides a high going pulse having a pulse width which is proportional to the product of the resistance of the timing resistor R3 and the capacitance of the timing capacitor C2.

When the push-button switch S1 is actuated a second time, causing the outputs of the toggle cir­cuit 80 to alternate in state, the output of the NAND gate 88 of the second timing circuit 76 will now pro­vide a high going pulsed signal whose pulse width is determined by the resistance and capacitance of the corresponding timing resistor R4 and capacitor C3, while the output of the NAND gate 86 of the first timing circuit 74 will remain low. As will be seen, the DC motor 14 of the motor control circuit will only be driven substantially for the duration of the high going pulse on the output signals of the NAND gates of the first and second timing circuits 74, 76.

As mentioned previously, the motor driving circuit includes first and second drive circuits 70, 72 which are coupled to the motor 14. As will be seen, the first and second drive circuits 70, 72 re­spectively operate as a source of and a sink for cur­rent supplied to the motor 14 when the circuits are in one state, and respectively operate as a sink for and a source of current when the circuits are in a second state.

Each of the drive circuits 72, 74 includes a transistor T1, T2, which acts as a switch, coupled to the motor 14; a load resistor R5, R6 which is coupled to the transistor T1, T2 and to the motor 14; and a base resistor R7, R8 which is coupled to the base of the transistor T1, T2. The base resistors R7, R8 of the first and second drive circuits 70, 72 are connected to the outputs of the NAND gates 86, 88 of the first and second timing circuits, respectively.

The transistors T1, T2 of the first and second drive circuits 70, 72 are driven on and off in response to the pulsed output signals of their re­spective timing circuits 74, 76 to which they are connected so that they either conduct current through the motor 14 or do not conduct current.

Under steady conditions, when the outputs of the NAND gates 86, 88 of the first and second tim­ing circuits 74, 76 are at a low logic level, the transistors T1, T2 of the first and second drive cir­cuits 70, 72 will be cut off so that they do not con­duct current. In this state, neither transistor T1, T2 acts as a sink for motor current, and as a result, the motor 14 does not rotate.

If, for example, actuation of the push-button switch S1 causes a high going pulse at the output of the first timing circuit's NAND gate 86, the high going pulse is provided to the base of the transistor T1 of the first drive circuit through the base resistor R7. The transistor T1 will be turned on and will conduct current through the motor supplied by the load resistor R5. The logic output of the second timing circuit 76 remains low during the presence of the high going pulse on the first timing circuit's output; as a result, the transistor T2 of the second drive circuit 72 remains cut off so that it does not conduct current through the motor 14. Consequently, current flows through the motor in one direction so that the motor 14 will rotate in the forward direction.

The transistor T1 of the first drive cir­cuit 70 will remain on only for the duration of the high going pulse on the first timing circuit's out­put. When the output of the first timing circuit 74 returns to a low, steady state level, the transistor T1 will be cut off and stop conducting current through the motor 14. The motor will, of course, stop rotating in the forward direction when no cur­rent flows through it.

If the push-button switch S1 is actuated a second time, a high going pulse is now provided by the second timing circuit 76 through the base re­sistor R8 to the transistor T2 of the second drive circuit 72. The transistor T2 will conduct current through the motor 14 supplied by load resistor R6, while during this time the transistor T1 of the first drive circuit 70 will remain non-conductive. Ac­cordingly, current is now supplied through the motor 14 in an opposite direction, causing the motor to rotate in a reverse direction.

The transistor T2 of the second drive cir­cuit 72 will conduct for the duration of the high going pulse of the second timing circuit 76. Both transistors T1, T2 of the first and second drive cir­cuits are cut off and will not conduct current through the motor 14 when the outputs of the first and second timing circuits 74, 76 return to their low, stead state logic level.

Thus, it can be seen that every time the push-button switch S1 is actuated by the vehicle operator, the motor 14 controlling the disposition of the mirror 11 will be driven in either the forward direction or the reverse direction for a time deter­mined by the values of the resistors R3, R4 and capacitors C2, C3 of the first and second timing cir­cuits 74, 76. The values of these components are selected to ensure that the motor 14 is driven suf­ficiently in each direction so that the mirror 11 is placed in either a low reflectivity disposition or a high reflectivity disposition. Thus, the motor con­trol circuit of the present invention eliminates the need for limit switches employed in conventional rear view mirror assemblies to control the current through the mirror positioning motor.

The motor control circuit may further in­clude an indicator 90 which is mounted on the mirror housing 12 and which is visible to the vehicle op­erator to indicate when the mirror is in the low re­flectivity mode. Preferably, the indicator 90 is a light emitting diode which is coupled through a cur­rent limiting resistor R9 to the output of the first gate 82 of the toggle circuit 80. Thus, whenever the output of the first gate 82 goes to a high logic level, the light emitting diode 90 will conduct to indicate that the mirror 11 is in the low re­flectivity disposition.

It is also desirable for the mirror control circuit to automatically switch the mirror 11 to a high reflectivity disposition whenever the automobile is backing up. For this purpose, the input of the first gate 82 of the toggle circuit 80 is connected to the vehicle's hot lead 92 of the back lights through a resistor R10 and a diode D2, connected in series with resistor R10. When the vehicle operator puts the automobile transmission into reverse, the hot lead 92 to the backup lights will be energized, impressing a high logic level on the input of the first gate 82. If the mirror 11 is not already in the high reflectivity disposition, the mirror control circuit will energize the motor 14 to drive the mir­ror to that particular disposition.

One of the further advantages of the particular configuration of the motor drive circuit is that it helps brake the rotation of the motor shaft after the motor has been energized for the time determined by the timing circuit. This prevents the motor 14 from "coasting" after it has already placed the mirror 11 into either reflectivity disposition. The "braking" effect is caused by the connection of the load resistors R5, R6 to the motor 14. After the transistors T1, T2 of the first and second drive circuits 70, 72 become non-conductive, the motor 14 continues to turn slightly. The motor thus becomes a generator and provides a reverse voltage across the load resistors R5, R6. This reverse voltage causes reverse current to flow through the motor 14, stop­ping it in a relatively short period of time.

The motor control circuit further includes a power control circuit comprising a zener diode D1 coupled to a resistor R11. The zener diode D1 helps protect the circuit from surges in the line voltage, or from connecting the motor control circuit in­advertently to a voltage source of incorrect polarity.

The motor control circuit of the present invention provides a bi-directional current to the DC motor 14 which drives the mirror 11 between low re­flectivity and high reflectivity dispositions. The motor is driven in the forward or reverse directions for substantially the time determined by the values of the resistors R3, R4 and capacitors C2, C3 of the first and second timing circuits.

The motor control circuit of the present invention eliminates the need for limit switches found in conventional rear view mirror assemblies. The circuit has relatively few components, which in­creases its reliability and enhances its ability to be easily fitted into the housing of the rear view mirror assembly.

The Switch

Referring initially to Figures 7-9 of the drawings, it will be seen that the push-button switch S1 constructed in accordance with the present in­vention basically includes a housing 46, an actuator 102, and a contact assembly 104.

The housing 46 is preferably formed by in­jection molding although other techniques may be used. Advantageously, the housing is formed from two substantially identical half housing members 106 which are joined together by press fitting or the like. Thus, only one mold is needed in the injection molding process of forming the half housing members 106.

Each half housing member 106 has a mating surface 108 which engages the mating surface of the other when the two are joined together. A pin 110 extends outwardly of the mating surface 108 of each half housing member, and a hole 112 is also formed in each mating surface 108. The pin 110 of each half housing member is received by the hole 112 formed in the other half housing member so that the two can be press fitted together to define the housing 100 of the push-button switch S1. The pin and hole arrange­ment allows the half housing members 106 to be joined together without gluing or other fasteners, although such may be used if desired.

An opening 114 and a slot 116 are formed in the housing to receive the actuator 102 and the con­tact assembly 104, respectively. The opening 114 is formed in the bottom side 118 of the housing, and the slot 116 is formed near the top side 120 of the hous­ing and extends through the housing's opposite lat­eral sides 122. The slot 116 overlies the opening 114 so that the contact assembly 104 will be in axial alignment with the actuator 102 when the two are as­sembled in the housing.

Preferably, as shown in Figure 9, each half housing member 106 is formed with half the slot 116 and half the opening 114 so that when the housing members are joined together, they define the full slot and full opening of the housing. As will be seen, forming each housing member 106 with slot and opening portions will facilitate assembly of the push-button switch S1.

The actuator 102 is the component of the push-button switch which the vehicle operator presses to effect an electrical path through the switch. The actuator 102 includes a cylindrical stem portion 124 which is received by the housing opening 114 and which includes two opposite ends. On one end of the stem portion 124 is mounted a tip portion 126 which is disposed in the interior of the housing 100 when the switch is assembled. The tip portion 126 is a rather bulbous formation which is adapted to engage the contact assembly 104.

A head portion 48 is mounted on the other end of the stem portion 124. The head portion 48 resembles an oversized circular button, and is dis­posed exteriorly of the housing 100. The user press­es the head portion 48 to actuate the switch S1.

The diameter of the housing opening 144 is less than those of the tip portion 126 and the head portion 48 of the actuator so that the actuator 102 will be retained in the housing opening when the push-button switch is assembled.

The housing 100 and actuator 102 may each be formed of a plastic material, which lends itself to fabrication by molding, although other materials may suitably be used.

As shown in Figures 10 and 11 of the draw­ings, the contact assembly 104 of the push-button switch basically includes first and second elec­trically conductive contact members 130, 132, and first and second insulating members 134, 136. The first and second insulating members 134, 136 may be formed from a single sheet of insulating material 138 that is folded in half from one side of the sheet to the other opposite side. Thus, the fold line 140 (shown as a dashed line in Fig. 10) defines the junc­ture between the first and second insulating members 134, 136. Of course, the first and second insulating members may be separate from each other and formed from their own sheet of insulating material.

A pair of parallel, spaced-apart slots 142-145 are formed through the thickness of each of the first and second insulating members 134, 136. Preferably two slots are provided in each member, although it is envisioned to be within the scope of this invention to have one or more slots formed in each member.

The first and second contact members 130, 132 are inserted through the slots of the first and second insulating members 134, 136, respectively, so that each contact member is disposed in an alter­nating underlying and overlying relationship with its respective member.

As shown in Figure 10, the first contact member 130 is inserted through the right-hand slot 142 of the first insulating member 134 from the rear side 146 of the insulating member, passes across the front side 148 of the insulating member and is in­serted through the left-hand slot 143 from the front side 148 of the insulating member 134. Similarly, the second contact member 132 is inserted through the left-hand slot 144 of the second insulating member 136 from the rear side 146 of the insulating member, passes across the front side 148 of the insulating member 136, and is inserted through the right-hand slot 145 of the insulating member from the front side of the member 136.

The slots 142-145 of each insulating member 134, 136 thus define a central portion 150 between them over which the contact members 130, 132 are ex­posed on the front side 148 of the insulating member and define with a respective proximate lateral edge 152 of the member a pair of side portions 154 over which the contact members are not exposed on the front side 148 but are exposed on the rear side 146.

Once assembled with the contact members 130, 132 inserted properly in the slots, the sheet of insulating material 138 is folded at the fold line 140 so that the first contact member 130 and first insulating member 134 are disposed in overlying re­lationship with the second contact member 132 and the second insulating member 136. When disposed in this manner, a portion of the first contact member 130 situated at the central portion 150 of the first in­sulating member 134 faces a portion of the second contact member 132 situated at the central portion 150 of the second insulating member 136, and a por­tion of the first insulating member 134 (i.e., the side portions 154 on the first insulating member's front side 148) faces a portion of the second in­sulating member 136 (i.e., the side portions 154 on the second insulating member's front side 148).

As can be seen from Figure 11, when the contact assembly 104 is assembled as described above, with the facing portions of the first and second in­sulating members 134, 136 in contact with one another, the facing portions of the first and second contact members 130, 132 are maintained in a spaced-apart relationship a distance equal to the combined thicknesses of the first and second insulat­ing members.

The contact assembly 104 is mounted in the housing 100 with the central portions 150 of the in­sulating members in axial alignment with the actuator 102. When a force is exerted on the head portion 48 of the actuator, the tip portion 126 will engage the second insulating member 136 at its central portion 150 and force the facing portion of the second con­tact member 132 to engage the facing portion of the first contact member 130, thus completing an elec­trical path through the switch. When pressure on the actuator 102 is released, the second contact member 132 will return to its normal disposition out of en­gagement with the first contact member 130.

In a preferred form of the invention, the first contact member 130 is made relatively thicker than the second contact member 132 and is sub­stantially rigid. The second contact member 132 is made from a much thinner material than the first con­tact member 130 so as to provide the second contact member with some resiliency. For example, the second contact member 132 may be formed from a spring tem­pered brass having a thickness of about .008 inches, and the first contact member 130 may be formed from quarter tempered brass having a thickness of about .031 inches. Brass is preferred because of its springiness; however, other electrically conductive materials may be used to form the first and second contact members.

The first and second insulating members 134, 136 are preferably formed from the same sheet of insulating material, such as Mylar (TM). The thick­ness of each insulating member is preferably .005 inches. Thus, when the contact assembly is formed as shown in Figure 11, with the facing portions of the first and second insulating members 134, 136 in con­tact with each other, the gap between the first and second contact members 130, 132 is twice the thick­ness of the insulating members, or .010 inches.

Mylar (TM) is chosen in the construction of the insulating members because of its dimensional stability and its heat resistance, and because it does not absorb water and is rather inexpensive. Of course, other materials having electrical insulating properties may be chosen to form the first and second insulating members 134, 136.

The push-button switch of the present in­vention is assembled by positioning the stem portion 124 of the actuator in a portion of the housing open­ing 114 formed in one of the half housing members 106, positioning the contact assembly 104 in the por­tion of the housing slot 116 also formed in one of the half housing members 106, and press fitting the two half housing members 106 together so that the contact assembly 104 and actuator 102 are captured respectively in the housing slot 116 and housing opening 114. Alternatively, the half housing members 106 and actuator 102 may be assembled together, fol­lowed by the insertion of the contact assembly 104 into the housing slot 116 from one lateral side of the housing 100. A portion of each contact member 130, 132 preferably extends beyond an edge of its respective insulating member 134, 136 and outwardly from opposite lateral sides 122 of the housing. This facilitates connection of the push-button switch S1 to the rest of the mirror control circuit.

Because the slot 116 extends between the opposite lateral sides 122 of the housing, the por­tion of each contact member which extends beyond the housing may be bent to define a slight shoulder 160 which engages the housing sides. This prevents the contact assembly 104 from moving laterally within the housing slot 116.

In the preferred form of the push-button switch S1, the actuator 102 is seated in its normal disposition with its tip portion 126 in contact with the second insulating member 136. Therefore, only slight movement of the actuator will displace the second contact member 132 sufficiently to bridge the gap between the contact members so that the two will contact to provide an electrical path to the switch. Thus, in the example given above, actuator movement of only .010 inches will actuate the switch. When pressure is released from the head portion 48 of the actuator, the resilience of the second contact member 132 will cause it to disengage from the first contact member 130 and return to its normal disposition, breaking the electrical path through the switch.

The push-button switch may be operated in its normally downward disposition, as shown in Figure 1, or in the opposite disposition with the actuator 102 on top. This is because the actuator 102 is of minimal weight and will still return to its normal position due to the resiliency of the second contact member 132.

Although the illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be effective therein by one skilled in the art without departing from the scope or spirit of the invention.