Push button support structure for push switch

A push button support structure for a push switch is provided with a housing, a push switch secured to the housing which has an actuator thereon, and a push button reciprocally moveable between on and off positions so as to responsively engage the actuator and thereby perform on and off switching actions, respectively. A pair of first elongate engagement posts is provided on one of the push button or housing which defines a circular cross-sectional geometry. Each elongate engagement post is positioned on a respective side of the push switch so that the push switch is disposed between the pair of first elongate engagement posts. A pair of second elongate engagement posts, in alignment with the pair of first elongate engagement posts, is also provided on the other of the push button or housing and defines a square cross-sectional geometry. Respective ones of the first and second pairs of elongate engagement posts are coaxially mated with one another for relative slidable movement therebetween, and are sized and configured so as to establish orthogonally oriented pairs of diametrically opposed linear contact regions therebetween. As a result, frictional resistance is minimized during reciprocal movement of the push button.

BACKGROUND OF THE INVENTION 
The present invention relates to a support structure for supporting the 
push button mounted to the actuator of the push switch for turning on and 
off the indoor room lithts such as a light attached to the center of the 
roof of the automotive room, the map lamp forwardly of the driver's seat 
or the like to prevent the push button from listing at the time when said 
switch is pressed down for turning on and are again pressed down for 
turning off the lights. 
One example of the map lamps for automotive indoor illumination used in the 
prior art will be explained with reference to FIGS. 7 through 9. 
A housing 1 to which a lamp (not shown) is attached has a transparent or 
translucent lens 2 secured thereto at a front thereof. Said housing 1 has 
a push switch 3 (hereinafter referred to as merely a switch) for turning 
on and off said lamp and said switch is secured to a platform 11 formed 
integrally to one side of said housing 1. Said switch 3 has an actuator 31 
which are to be engaged with a push button 4 and is adapted to be operated 
from the front of the housing. On the underside of the push button 4, a 
cylindrical rod 41 is integrally formed thereto to be inserted into a 
cylindrical bearing 12 integrally formed to the platform 11. 
The terminal (not shown) of the thus constructed switch 3 is electrically 
connected to the power source (or the automotive battery) and is adapted 
to turn on the switch 3 to put on the light by being pressed down and to 
turn off the same to put out the light by again being pressed down again. 
Since the rod 41 is guided along said bearing 12 therewithin, the button is 
prevented from listing sideways at the time of the push button 4 being 
pressed down to ensure that said push button 4 is vertically pressed down 
to in turn press down the actuator 31 positively to assure a proper 
switching on and off actions. 
In this connection, said push button having rods 41 being inserted into the 
bearing 12 which is tubular provides a large contact area between the rods 
41 and the bearing 12. This structure gives a rise to a considerable 
frictional resistance when pressing down the push button 4, thus 
preventing a smooth pressing down of the same. 
Further, the prior art as described in the foregoing employs cylindrical 
rods 41 and tubular bearings 12, which can prevent smooth pressing down of 
the push button if the outer diameter of the rods 41 and the inner 
diameter of the bearings 12 are substantially equal because it provides 
too tight engagement while if the difference between said outer diameter 
and said inner diameter are too large, an unnecessary play can cause a 
resultant deflection of the push button at the time of the pressing down 
action. 
SUMMARY OF THE INVENTION 
The present invention is intended to solve the problems referred to in the 
foregoing and its object is to provide a push button support structure for 
the push switch by constructing either of the rod and the bearing in a 
cylindrical structure and the other in a polygonal structure such that 
corners of one member are brought into the other to minimize the contact 
area. As a result, the frictional resistance is reduced as well as 
preventing any unnecessary play between the rod and the bearing. 
The push button support structure for the push switch of the present 
invention is to solve the problems referred to in the foregoing and 
essentially the invention provides a push button support structure for a 
push switch comprising a housing; a push switch secured to said housing 
and having an actuator thereon; a push button to be brought into 
engagement with said actuator to perform switching on and off actions; 
first engagement means provided on the underside of said push button; and 
second engagement means provided on the housing to mate with said first 
engagement means, said second engagement means being sized to provide a 
bearing/rod engagement in cooperation with said first engagement means, 
said bearing/rod engagement including a polygon/cylinder fit to produce a 
linear contact therebetween.

DESCRIPTION OF THE EMBODIMENTS 
Hereinafter, one mode of embodiment according to the present invention 
relating to the push button support structure for a push button for the 
push switch will be explained with reference to FIG. 1 and FIG. 2. 
In this connection, since similar numerals and similar characters to those 
used in the aforementioned prior art denote similar members, the 
explanation of such numerals and characters will be omitted. 
In this mode of embodiment, while square pillar rods 42 are provided on the 
push button 4, cylindrical bearings 12 are provided on the platform 11. 
Further, said cylindrical bearings 12 have inner walls which are sized to 
be brought into linear contact with corners of said square pillar rods 42. 
FIG. 3 and FIG. 4 show the second mode of embodiment, in which cylindrical 
rods 41 are provided on the push button 4 while square bearings 13 are 
provided on the platform 11 such that the cylindrical peripheral surface 
of the cylindrical rods 41 is sized to be brought into linear contact with 
the inner walls of the square bearings 13 at four positions. 
In the thus constructed support structure of the present invention, the 
cylindrical rods 41 on the push button 4 are maintained in linear and snug 
contact with the square bearings 12 and 13 on the housing 1 with the 
result that the push button 4 is pressed down with fewer frictional 
resistance and without unnecessary play therebetween, thus assuring 
turning on and off actions by smooth pressing down of the switch 3. 
The afore-mentioned two modes of embodiment show the use of the rods on the 
push button 4 and the bearings on the housing 1 but bearings may be 
provided on the push button 4 and cylindrical rods, on the platform 11 as 
shown in FIG. 5 and FIG. 6-1. Also in this modification, positive on and 
off actions of the switch 3 is assured by smooth and play-free pressing 
down. 
In this connection, it is also acceptable to modify the embodiment of FIG. 
5 and FIG. 6-1 that such bearings 43 on the button 4 are provided in the 
form of a cylinder while the rods 14 on the housing 11 are square pillars. 
Further, the tubes for the bearings or the pillars for the rods are not 
limited to square ones but it is needless to say that triangular or 
polygonal ones are also acceptable. 
Further, the rods or bearings provided in pairs in any of the embodiments 
described in the foregoing are provided all in the same forms on the push 
button or on the housing but said pair of rods may include a polygonal 
member and a cylindrical member while said pair of bearings into which 
said rods are inserted may include a cylindrical member and a polygonal 
member as shown in FIG. 6-2. In such cases, errors in mounting the button 
4 to the platform 11 are forestalled in the event that the orientation of 
the members are fixed. 
Since the present invention is characterized in that one of the rods is 
provided in a cylindrical form and a corresponding one of the bearings is 
polygonal, corners of the polygonal members are brought into a linear 
contact with the mating cylindrical members to assure the reduction in the 
contact area for minimizing a frictional resistance therebetween. As a 
result, an unnecessary play between the rods and the bearings are 
prevented even in a snug fit to ensure that the switch on and off actions 
are smoothly performed. 
Further, the modification by arranging such that one of the rods in the 
pair is polygonal or cylindrical while the corresponding one of bearings 
in the pair is cylindrical or polygonal assures the prevention of error in 
amounting the push button onto the housing in accordance with the 
orientation fixed in advance.