Multiple circuit switch with rockable activator and linearly movable contact holder

A switch apparatus comprises an arm which is rotated by a rotational force added to an operation knob and thus linearly drives a contact holder through an engagement portion so as to change over contacts points. The engagement portion is received in a groove formed in the contact holder and has surfaces which hold the center line in the radial direction of the arm, each surface having a circular arc form with a center substantially in the same place at a position equi-distance on either side of the center line so that the change in movement of the contact holder with the change in rotational angle of the arm is substantially constant.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a knob switch apparatus which causes a 
contact holder to linearly move by means of an arm using the rotational 
operation of an operation knob. Description of the Related Art 
An example of conventional switch apparatuses for wipers in automobiles 
comprises a spherical pressure portion provided at the end of an arm which 
is swung by the rotationaloperation of an operational knob provided at the 
end of a lever, the pressure portion being inserted into a groove of a 
contact holder. The contact holder is linearly moved by being pressed by 
the pressure portion of the arm when the operational knob is rotated. The 
switch is consequently switched corresponding to the movement of the 
contact holder. 
In the above-described conventional arrangement, as shown in FIG. 7, a 
contact holder is moved along a distance a when an arm 1 is rotated 
through angle .alpha. in the direction shown by the arrow A from the 
standard state wherein a pressure portion 2 of the arm 1 points in a 
vertical direction. When the arm 1 is further rotated through angle 
.alpha. in the direction shown by the arrow A, the contact holder is also 
moved along a distance b. Movement distance b is smaller than movement 
distance a (b&lt;a). That is, there is a disadvantage in that the distance of 
movement of the contact holder is reduced as the rotation angle of the arm 
1 increases even if the operational angle of the operation knob is 
constant. 
Accordingly, it is an object of the present invention to provide a knob 
switch apparatus which is capable of preventing the difference in movement 
of a contact holder from being increased due to the difference in the 
rotational angle of an arm. 
SUMMARY OF THE INVENTION 
In a knob switch apparatus of the present invention in which an arm is 
rotated by the rotational operation of an operation knob, a contact holder 
is linearly moved by being pressed by a pressure portion provided at the 
end of the arm with the rotation of the arm so that the state of the 
switch is changed. It is characterized in that the pressure portion has a 
surface which comprises two circular arc portions each having a center at 
a given distance from the center line in the direction of extension of the 
arm, as well as holding the center line therebetween. 
The above-described means causes the distance from the rotational center of 
the arm to the contact point of the pressure portion which contacts the 
contact holder to be increased as the rotational angle of the arm 
increases, as compared with conventional apparatus. The distance in which 
the contact holder is moved is therefore not significantly decreased as 
the rotational angle of the arm increases, whereby the distance of 
movement of the contact holder can be made constant.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
In FIGS. 2 and 3, a lever 11 comprises a cylindrical body 13, which is 
engaged with the periphery of the end of a support body 12 which is 
rotatably mounted on the steering column (not shown) of an automobile. 
When the lever 11 is moved in the direction shown by the arrow B in FIG. 2 
or in the reverse direction, a turn signal switch (not shown) provided in 
the steering column is operated. A receiving body 14 is engaged with the 
internal periphery of the cylindrical body 13, and an operation knob 15 is 
provided on the periphery thereof. The operation knob 15 is provided at 
the end of the cylindrical body 13 so as to be rotatable relative to the 
lever 11 around the axis thereof and movable relative to the lever 11 in 
the axial direction thereof. A rod 16 is provided in the lever 11 so as to 
pass through the receiving body 14 and has an end which is fixedly 
connected to a cylindrical portion 15a of the operation knob 15 by means 
of a pin 17 so as to be rotated and axially moved integrally with the 
operation knob 15. 
A return spring 18 comprising a compression coil spring is interposed 
between the operational knob 15 and a stop ring 19.which is provided in 
the periphery of the end of the receiving body 14. The operational knob 15 
is urged by the force of the spring 18 in the direction (shown by the 
arrow C in FIG. 3) in which the operation knob 15 is pushed out from the 
lever 11. In this case, if the operation knob 15 is pushed against the 
urging force of the return spring 18 in the direction reverse to the 
direction shown by the arrow C, the rod 16 is moved in the same direction 
so as to allow an end 16A of the rod 16 which is shown in the lower right 
portion in FIG. 3 to operate a washer switch (not shown). 
A detent case 20 is provided on the periphery of the receiving body 14 in 
such a manner that it is rotated integrally with the operation knob 15 
when the operational knob 15 is rotated, but so that it does not move when 
the operational knob 15 is moved in the direction shown by the arrow C or 
in the reverse direction. In the detent case 20, are disposed a detent 
spring 21 comprising a compression coil spring and a detent piece 22 urged 
by the detent spring 21. The detent piece 22 is brought into press contact 
with a groove (not shown) provided in the internal surface of the 
receiving body 14 to form a detent mechanism which causes the operational 
knob 15 to be imparted with the detent function when the operational knob 
15 is rotated. 
On the other hand, a cylindrical portion 25 of an arm 23 is rotatably 
inserted into the base end of the lever support body 12 so as to support 
the vicinity of the end 16A of the rod 16. The cylindrical portion 25, is 
also engaged with a pin (not shown) which is provided in the rod 16 so 
that, when the operational knob 15 is rotated in the direction shown by 
the arrow D in FIG. 2 or in the reverse direction, with the rod 16 being 
rotated in the same direction, the arm 23 is subjected to a rotational 
force and thus swung in the direction shown by the arrow E in FIG. 1 or in 
the reverse direction with a center at the rod 16. 
The arm 23 projects in the lengthwise direction which deviates from the 
plane vertical to the axis of the lever 11 and has an end provided with a 
pressure portion 24 which is inserted into a groove 27 formed in a contact 
holder 26. When the arm 23 is rotated, the contact holder 26 is pressed by 
the pressure portion 24 and guided so as to move in the direction shown by 
the arrow F in FIG. 1 and in the reverse direction. The states of a wiper 
switch 30 are changed following the movement of the contact holder 26. 
The wiper switch 30 can be switched in that a movable contact point 32 
which is moved together with the contact holder 26 is connected with, any 
one of fixed contact points 34A, 34B, 34C and 34D. 
The pressure portion 24 is substantially cordiform, and, particularly, as 
shown in FIG. 4, has outer surfaces which are symmetric with respect to 
the center line c in the direction of extension of the arm 23 and which 
are each formed into a substantially circular arc having a center 0 at a 
position at a given distance from the center line c which is held 
therebetween. In this case, the radius r of the circular arc is determined 
to be the same as the width d of the groove 27 (refer to FIG. 1) in the 
contact holder 26 so as to be tightly receivable in the groove 27. As 
shown in FIG. 5, the pressure portion 24 also has outer surfaces each 
having a circular arc-shaped cross section so that each of the two sides 
on either side of a widthwise center 24a has a width smaller than that at 
the center 24a. Both widthwise sides of the pressure portion 24 are 
therefore apart from the internal sides 27a of the groove 27, as compared 
with the widthwise center 24a thereof. Thus the periphery of the pressure 
portion 24 is always brought into contact with the internal sides 27a of 
the groove 27 even if the lever 11 is rotated in the direction shown by 
the arrow D or in the reverse direction. 
The aforementioned configuration therefore causes the arm 23 to be rotated 
in the direction shown by the arrow E in FIG. 1 with the center at the rod 
16, as the rod 16 is rotated integrally with the operation knob 15 in the 
same direction as that of rotation of the operational knob 15 in the 
direction shown by the arrow D in FIG. 2. With the rotation of the arm 23, 
the contact holder 26 is linearly moved in the direction shown by the 
arrow F in FIG. 1 by being pressed by the pressure portion 24, while the 
contact point of the pressure portion with the internal sides 27a of the 
groove 27 in the contact holder 26 is successively changed. The movement 
of the contact holder 26, causes the states of the wiper switch 30 to be 
switched from an OFF state produced by the fixed common contact point 33 
and the fixed contact point 34A to an ON state produced by the fixed 
common contact point 33 and the fixed contact point 34B and then to an ON 
state produced by the fixed common contact point 33 and the fixed contact 
point 34C, whereby a wiper is operated with the speed increasing in steps. 
And, with rotation of the arm 23 between the INT SLOW and the INT FAST 
positions shown in FIG. 1, the condition with the movable contact 32 
connecting the fixed common contact point 33 and the fixed contact point 
34B does not change. However the rotation of the rod 16 is detected by a 
detector (not shown) and depending on the angular rotation, the 
intermittent operation interval of the wiper is changed. In the condition 
with the fixed common contact point 33 connected to the fixed the contact 
34B, 34C or 34D by the movable contact 32, rotation of the operation knob 
15 so that the arm 23 returns to the OFF position (FIG. 1), results in the 
movable contact 32 moving to the position to connect the fixed common 
contact point 33 and the fixed contact point 34A. In order to return the 
wiper to its origin position the switch circuit is then changed. 
In the above-described embodiment, as shown in FIG. 6, the distance e in 
which the contact holder 26 is moved by rotation of the arm 23 through an 
angle .alpha. in the direction shown by the arrow E from a standard state 
wherein the center line of the pressure portion 24 of the arm 23 points in 
the vertical direction, is substantially the same distance f in which the 
contact holder 26 is.moved by further rotation of the arm 23 through an 
angle .alpha. in the direction shown by the arrow E. 
If the embodiment is compared with the conventional apparatus shown in FIG. 
7, the distance L between the center of rotation (the rod 16) of the arm 
23 and the pressure point of the pressure portion 24 serving to press the 
contact holder 26 is increased to a value greater than the distance 1 in 
the conventional arm (L&gt;l) as the rotational angle of the arm 23 
increases. Unlike the conventional configuration in which the distance of 
movement of the contact holder is decreased as the rotational angle of the 
arm increases, this embodiment enables the distance of movement of the 
contact holder 26 to be made substantially constant even if the rotational 
angle of the arm 23 increases. It also enables the effective operational 
angle of the operation knob 15 to be set at a large value. 
The embodiment of the present invention concerns a form in which the arm 23 
projects toward the rod 16 in a cantilever manner. But an arm 23A may be 
projected from the rod 16 on the extension of the arm 23, as shown by the 
phantom lines in FIG. 1, so that the arm 23A is imparted with a rotational 
force.