Push button microswitch with wiping contact effect

A switch is disclosed having a movable piece with a movable contact and a movable plate coil, a fixed terminal provided with a fixed contact facing the movable contact, a movable coil spring with an end being fixed at a standing piece of a common terminal, wherein the other end of the coil spring is coupled to the end of a movable piece, and wherein the movable plate coil is biased by the movable coil spring with one end of the movable plate coil swingably held by a holding piece of the common terminal, and a push-button for pressing the upper portion of the movable coil. The switch has an actuator having a supporting member which rotatably engages with the case, wherein the supporting member is formed in a plane generally perpendicular to a rotary shaft of the actuator.

BACKGROUND AND SUMMARY OF INVENTION 
There are several types of microswitches. The prior art microswitch shown 
in FIG. 5 has a movable contact 51 which is provided at an end of movable 
piece 54. The other end of the movable piece 54 is fixed at an end of 
holding piece 53. The movable piece 54 can swing around the holding piece 
53 which is a portion of a common terminal 52. Fixed contacts 55 and 56 
are connected to fixed terminals 57 and 58, respectively. A coil spring 60 
is provided between standing member 59 and a middle portion of movable 
piece 54. A push-button 61 is disposed to push the coil spring 60 in the 
free position of the switch, wherein the movable contact 51 is on the 
upper fixed contact 55. If the push-button 61 is pressed down the coil 
spring 60 is distorted downwardly so that the movable piece 54 is clicked 
down around the other end to make the movable contact 51 with the fixed 
contact 56, thus, performing a switching operation. 
FIG. 6 shows another type of conventional microswitch. A movable piece 64 
has a movable contact 62 and a movable plate spring 63, one end of which 
rests on a holding piece 69 which is made in one piece with a common 
terminal 70. Fixed contacts 65 and 60 are connected to fixed terminal 67 
and 68, respectively. Push-button 72 is provided to push receiving member 
71, both ends of which are connected to common terminal 70 and the end 
portion of movable piece 64. In the free position of this switch a movable 
contact 62 rests on fixed contact 65. When push-button 72 is pushed down, 
the end of movable piece 64 is moved downwardly through the receiving 
member 71. When movable piece 64 passes over a certain point, movable 
plate spring 63 turns around to make its movable contact 62 with fixed 
contact 60. 
The switch shown in FIG. 5 is simple in construction, but in its switching 
operation, movable piece 54 swings around a holding piece, so that a 
wiping effect by movable contact 51 cannot be expected. The wiping effect 
of movable contact 51 is necessary for avoiding the welding of contacts 
often observed in this type of high-capacity switch. More specifically, an 
arc flows between contacts when a switch makes and breaks to weld the 
contacts. Wiping is required to remove melted substance from the surface 
of contacts and to improve the reliability of switch operation. On the 
other hand, in the switch shown in FIG. 6, the swinging point of receiving 
member 71 is located under the conjunction point of receiving member 71 
and movable piece 64, so that when pushbutton 72 is pressed down, the 
movable piece 64 moves a little bit backward. Therefore, when the movable 
contact 62 comes away from fixed contact 65, it can have a wiping effect 
on the fixed contact 65. However, this type of switch needs receiving 
member 71, which makes the structure more complicated. 
The actuator 18 which is positioned to cover the push-button 12 can be 
modified as shown in FIGS. 7-9. Initially, however, an actuator in the 
prior art has been illustrated in FIGS. 10-11. Shown in FIG. 10 is a 
switch having a switching mechanism contained in case 101 which has a 
push-button 102 and an actuator 103 for pressing on the button 102. The 
actuator 103 is a metal plate, a portion of which is folded downwardly to 
form a regulating member 104. A pair of actuator portions 105 are formed 
as supporting members for the actuator 103, while the other end of the 
actuator 103 is folded to form a pair of roller supporting members 109. 
Both sides 101B of the case 101 have cuts 101D at the corners of case 101. 
A pin 106 is formed with one piece with the case 101 to permit the 
supporting members 105 to be rotatably engaged. A roller 108 has a rotary 
shaft 107 which is coupled to roller supporting member 109. The actuator 
103 which is rotatably supported by the pin 106 is positioned over the 
push-button 102. Normally, the actuator 103 is held up by the restoring 
force of the push-button 102. When an object hits the roller 108, the 
actuator 103 moves around pin 106 and pushes the push-button 102 against 
its restoring force, thus, operating the contact switching mechanism 
housed within the case 101. After the depressing force is removed from the 
actuator 103, the actuator 103 is instantly raised by the restoring force 
of push-button 102. When the actuator 103 rotates, the regulating member 
104 contacts side 101C of the case 101 in order to stop the rotation of 
the actuator 103. However, the regulating member 104, as shown in FIG. 10, 
has problems adjusting the rotation of the actuator 103 due to an unstable 
folding angle. Moreover, when the actuator 103 is held up in a forceful 
manner, the regulating member 104 is pressed against side 101C of the case 
101, thereby, distorting the regulating member 104. Therefore, the switch 
illustrated in FIGS. 10 and 11 is highly unreliable. 
To solve the above-discussed problems, especially concerning the lever 
portion of the switch, this invention further provides a switch having a 
regulating member for rotating an actuator which can be manufactured with 
significant accuracy. Moreover, the switch of the instant invention is 
highly capable of maintaining it reliability during operation. 
One feature of this invention is a switch with a simple structure and which 
has an improved life span because of the wiping of the surfaces of 
contact. Moreover, the switch of the instant invention comprises a switch 
having an outwardly protruding push-button for operating a contact 
switching mechanism housed within the case. Further, there is in this 
invention an actuator having at one end a pair of supporting members 
folded downwardly and rotatably engaged with the case, whereby the other 
end of the actuator is a free end. The supporting members of the actuator 
are formed in one piece with the regulating member which contacts one side 
of the case in order to stop the rotation of the actuator.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1-4, the switch of this invention is divided into two 
parts as shown in FIG. 3, i.e., switch 1 and cover 2, which are designed 
to be separately assembled before the switch 1 is inserted into the cover 
2. Cover 2 has slide walls 3, front wall 4, rear wall 5, and upper wall 6. 
The bottom of cover 2 has an opening into which the switch 1 is inserted. 
A pair of side walls 3 has two attachment passing holes 7 therethrough and 
two engagement holes 8. Inside the pair of side walls 3, there are 
provided grooves 9 which extend from the bottom of cover 2 and include the 
attachment through holes 7 and engagement holes 8. The internal surfaces 
of front wall 4 and rear wall 5 have steps 10 for positioning the upper 
limit of switch 1 inserted from the bottom of cover 2 and projections 11 
for positioning the lower limit of switch 1. The upper wall 6 has a hole 
13 through which a push-button 12 is attached to cover 2 through a 
water-resistant rubber cap 14. The cap 14 is tightly engaged in the groove 
15 formed around the push-button 12. The lower portion of cap 14 is 
engaged in groove 16 which surrounds the hole 13. Another holding piece 17 
presses the end of cap 14 over the groove 16. In this way, the push-button 
12 is biased upwardly by elasticity of cap 16. 
An end of actuator 18 is rotatably attached to the upper portion of cover 
2. Actuator 18 is positioned to cover the push-button 12. The other end of 
the actuator 18 has a roller 19, the shaft 20 of which is rotatably 
mounted thereto. 
Switch 1 is made up of base 21 made of resin, usually epoxy resin, a 
normally closed fixed terminal 22, a normally open fixed terminal 23, a 
common terminal 24, a movable coil spring 25, and a movable piece 26. The 
base 21 has passing through holes 29 which pass through between side 
surfaces 27 and 28 and confront face-to-face with attachment holes 7 of 
cover 2. The side surfaces 27 and 28 have engagement hooks 30 which engage 
with engagement holes 8. Side surfaces 27 and 28 of switch 1 have elevated 
areas 31 which meet with the groove 9 formed on an internal surface of 
side walls 3 of cover 2. Around the elevated areas 31, a lead-groove for 
seal 32 is provided which goes from the bottom of base 21, turns around 
passing through hole 29 and returns to the bottom of base 21. 
The base 21 has three vertical passing-through holes 34, 35, and 36 into 
which the common terminal 24, normally open fixed terminal 23 and normally 
closed fixed terminal 22 are pressed, respectively. Normally closed 
terminal 22 and normally open terminal 23 have fixed contacts 22a and 23a, 
respectively, facing each other at one end of each terminal. The other 
ends of the terminals extend downwardly. The common terminal 24 has a 
standing piece 43 and folding piece 37 at one end, while the other end of 
common terminal 24 extends downwardly. 
A movable coil spring 25 made of piano wire is mounted in a tensioned 
condition with one end hooked in hole 38 in standing piece 43 and the 
other end hooked in hole 39 defined in movable piece 26. The movable piece 
26 has a movable plate spring 44 which stands out of movable piece 26 and 
is fitted into a notch 40 formed in a holding piece 37. A movable contact 
26a is attached to an end of movable piece 26 which is biased by the 
movable plate spring 44 so as to make the movable contact 26a contact with 
the fixed contact 22a. Each terminal 22, 23 and 24 extending downwardly is 
soldered to a lead 41. In this way, separatelY assembled switch body 1 and 
cover 2 are coupled by inserting switch body 1 into cover 2. 
The external contour of switch body 1 is designed to fit within the 
internal surface of cover 2 to have each side surface thereof contacted 
with the counterpart of cover 2. The insertion of switch body 1 continues 
until the upper surface of switch body 1 lands into step 10 on switch 
cover 2. At the same time, the projection 11 projects under switch body 1 
thereby positioning the body 1 in the cover 2. In this condition, the 
bottom portion of push-button 12 rests on the upper portion of movable 
coil spring 25 and the attachment holes 7 of cover 2 confront face-to-face 
with the passing through holes 29 of switch 1. In addition, the engagement 
hook 30 of switch body 1 is fitted in the engagement hole 8 of cover 2 to 
strengthen the condition of their coupling. Further, the internal groove 9 
of cover 2 is filled with elevated areas 31 of switch body 1. 
After inserting switch body 1 into cover 2, the sealing resin, for example 
epoxy resin, is injected into space 42 defined in the lower portion of 
cover 2 with the cover 2 being upside down. Thus, the switch body 1 is 
fixed in the cover 2 with its terminals 22, 23 and 34 soldered to lead 41. 
When the resin is injected into cover 2, it passes through the lead-groove 
for seal 32 and secures the seal around the passing through holes 7 and 29 
respectively defined in cover 2 and switch body 1, as well as the 
contacting portion between the engagement hole 8 and engagement hook 30, 
thereby preventing water coming therefrom. 
A switch assembled in this way is mounted to an appliance for use by 
driving screws into holes 7 and 29. When an object strikes against roller 
19 and actuator 18 is pressed down to depress push-button 12, the lower 
portion of push-button 12 presses the movable coil spring 25. If the 
push-button 12 passes over a certain point, then the movable plate spring 
44 turns around to make the movable contact 26a come into contact with 
fixed contact 23a. When the pressing force to actuator 18 is removed, the 
push-button 12 is pushed up by the restoring force of movable coil spring 
25 and the movable plate spring 44 turns around to bring the movable 
contact 26a again into contact with the fixed contact 22a. 
It should be noted that when the movable contact 26a moves off the contact 
22a, the spring force of movable coil spring 25 is added to the spring 
force of movable plate spring 44, so that the wiping effect takes place on 
the surfaces of contact 26a. On the contrary, when the movable contact 26a 
comes into contact with the other contact 23a, the spring force of movable 
plate spring 44 is added by the pressing force of movable coil spring 25 
pressed by the push-button 12, so that the movable contact 26a is strongly 
pressed against the other contact 23a. As a result, greater wiping effect 
is achieved and larger contact pressure can be applied to the contact, 
thereby providing a switch of high-capacity type. In addition, the 
pressing force of push-button 12 is absorbed by the distortion of movable 
coil spring 25, which reduces excessive force applied to movable plate 
spring 44, thus expanding its life span. 
Referring now to FIGS. 7 and 8, a case 110 is shown preferably made out of 
resin for housing a contact switching mechanism. A top wall 110A of case 
110 has a push-button 111 outwardly protruding therefrom. An actuator 112 
is rotatably supported at one end so as to be capable of pressing the 
pushbutton 111. The actuator 112 has at one end a pair of metal portions 
which are downwardly folded to form a pair of supporting members 113. A 
pair of metal portions at the other end of the actuator 112 are upwardly 
folded to form roller supporting members 120. At the corners of side wall 
110B of case 110, cuts 110D are provided for receiving supporting members 
113. In the cuts 110D, a pair of pins 116 protrude to engage with holes 
117 defined in the supporting members 113. As shown in FIG. 9, upper sides 
116A of pins 116 are preferably sloped. In assembling the switch, a pair 
of supporting members 113 of actuator 112 are slidably pushed along the 
sloped portion of upper side 116A of pin 116 until hole 117 engages with 
the pins 116. The actuator 112 is rotatably held at one end by pressing a 
pair of protruding pins 116. A roller 119 has a rotary shaft 118 for 
engaging with a pair of holes defined in the roller supporting members 
120. 
Each supporting member 113 has a regulating member 114 which is formed in 
substantially the same plane of the supporting member 113. The regulating 
member 114 stops the rotation of the actuator 112 by contacting the rear 
wall 110C of the case 110. Normally, the actuator 112 is held by the 
returning force of push-button 111 and the pair of regulating members 114 
which contact the rear wall portion 110C. When an object contacts the 
actuator 112, the actuator 112 is pushed in a downward direction and 
presses the push-button 111 against the button's returning force, thus, 
operating the switch contact mechanism housed within the case 110. When 
the pressing force on the push-button 111 is removed, the actuator 112 is 
instantly pushed upwards by the returning force of the push-button 111. 
The actuator 112 stops its rotation when the regulating members 114 
contact the rear wall portion 110C. The regulating members 114 are formed 
in substantially the same plane as the supporting members 113. In other 
words, the regulating members 114 are formed substantially perpendicular 
to the rotary pin 116 so that the regulating members 114 do not deform 
even when a substantial external force is applied to the actuator 112. 
Preferably, the regulating members are molded together with the metal 
plate of the actuator 112 thereby minimizing the manufacturing tolerance 
or dimensional discrepancies. 
While the invention has been particularly shown and described in reference 
to preferred embodiments thereof, it will be understood by those skilled 
in the art that changes in form and details may be made therein without 
departing from the spirit and scope of the invention.