GB2062965A - Push button switches - Google Patents
Push button switches Download PDFInfo
- Publication number
- GB2062965A GB2062965A GB8035853A GB8035853A GB2062965A GB 2062965 A GB2062965 A GB 2062965A GB 8035853 A GB8035853 A GB 8035853A GB 8035853 A GB8035853 A GB 8035853A GB 2062965 A GB2062965 A GB 2062965A
- Authority
- GB
- United Kingdom
- Prior art keywords
- base plate
- dome
- switch
- push button
- movable contact
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229920001971 elastomer Polymers 0.000 claims abstract description 11
- 239000000806 elastomer Substances 0.000 claims abstract description 6
- 239000012777 electrically insulating material Substances 0.000 claims description 3
- 239000011796 hollow space material Substances 0.000 claims description 2
- 230000008602 contraction Effects 0.000 description 2
- 230000000994 depressogenic effect Effects 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 101100005631 Mus musculus Ccni gene Proteins 0.000 description 1
- 240000008042 Zea mays Species 0.000 description 1
- 235000005824 Zea mays ssp. parviglumis Nutrition 0.000 description 1
- 235000002017 Zea mays subsp mays Nutrition 0.000 description 1
- 235000005822 corn Nutrition 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000005802 health problem Effects 0.000 description 1
- 230000010365 information processing Effects 0.000 description 1
- 229940110676 inzo Drugs 0.000 description 1
- 239000000463 material Substances 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
- H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
- H01H13/78—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites
- H01H13/785—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard characterised by the contacts or the contact sites characterised by the material of the contacts, e.g. conductive polymers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H13/00—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch
- H01H13/70—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard
- H01H13/702—Switches having rectilinearly-movable operating part or parts adapted for pushing or pulling in one direction only, e.g. push-button switch having a plurality of operating members associated with different sets of contacts, e.g. keyboard with contacts carried by or formed from layers in a multilayer structure, e.g. membrane switches
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2201/00—Contacts
- H01H2201/022—Material
- H01H2201/032—Conductive polymer; Rubber
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2215/00—Tactile feedback
- H01H2215/004—Collapsible dome or bubble
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2217/00—Facilitation of operation; Human engineering
- H01H2217/02—After travel
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2227/00—Dimensions; Characteristics
- H01H2227/022—Collapsable dome
Landscapes
- Push-Button Switches (AREA)
Abstract
A push button switch has a base plate (1) provided with at least one pair of fixed contacts (2) thereon and a switch cover member (3) made of a rubbery elastomeric sheet and having at least one dome-like raised portion on the inner surface of which is mounted a movable contact (4) of conductive rubber elastomer, extending over the fixed contacts (2), and having an annular rib (7) surrounding the movable contact member (4) for engagement by the push button. The ratio of the radial distance "b" between the outer periphery of the rib (7) and the foot (10) of the riser portion (6) to the radial distance "a" between the outer periphery of the movable contact member (4) and the inner periphery of the rib (7) is between 0.8 and 1.8 the arrangement being such that over-travel of the push-button takes place by distortion of the thin wall 8 after the contacts (2,4) have engaged. <IMAGE>
Description
SPECIFICATION
Push button switches
The present invention relates to push button switches and, more particularly, to push button switches suitable for use in a key board switch panel in which long-life durability of the push button switch is of utmost importance.
It is well known to use push button switches on a key board switch panel. Such a push button switch is usually formed by mounting a switch cover member made of an electrically insulating rubber sheet, having at least one dome-like raised portion, on a base plate having at least one pair of fixed contact points thereon.Pushing down the centre top flat of the doine-like raised portion brings a movable contact member bonded to the inner surface of the centre of oaths dome-like raised portion inzo contact with the fixed contact points on he base plate so as to close the electric circuit between them, and release of the pushing force enables the movable contact member to move apart from the fixed contact points by virtue of the elastic resilience of the switch cover member.
Conventional push button switches of the above described type are not always satisfactory in respect of the degree of touch required in pushing or feeling in operation since, when the movable contact member once has come into contact with the fixed contact points, further thrusting of the top of the switch cover member is no longer possible even by an increased pushing force of the finger tip, thus causing hard touch to the finger tip.
In recent years, it has been desired to improve the pushing touch along with the peiformance and reliability in the switching action per se. That is, push button switches under trial are directed to give a buffer action to the pushing finger tip when the movable contact member has come to contact with the fixed contact points by enabling further thrusting of the centre top of the switch cover member.
Most of the push button switches with improved pushing touch as above mentioned comprise a switch cover member made of an electrically insulating rubber sheet and provided with at least one dome-like raised portion facing the fixed contact points on the base plate with an annular outwardly or inwardly protruded rib around the centre top flat of the dome-like raised portion, surrounding the movable contact member which is bonded to the inward surface of the centre top flat of the dome-like raised portion. Push button switches of this type are widely used on key board switch panels in which the pitch of the respective push button switches is in the range, say, from 14mm to 25mm, such as in cash registers, electric typewriters, computers, copying machines and other information processing instruments.
One of the problems in such a push button switch, with which an additional thrusting or so-called over-stroke of the centre top of the switch cover member is obtained after contacting of the movable contact member with the fixed contact points, is in the durability of the switch cover member, which may fail due to rupture in the dome-like raised portion either in the thin walled portion of the centre top flat between the movable contact member and the annular rib or in the thin walled riser portion of the dome between the annular rib and the basal flat at which the switch cover member is mounted on the base plate.
This limitation in the durability of these portions is caused by the elastic fatigue of the rubber sheet of the portion being subjected to repeated stretching and contraction by the pushing down of the centre top with an overstroke and releasing. For example, serviceable life of conventional push button switches of this type in pushing operation does not usually exceed 1,000,000, operations of switching on and off and no intensive investigations have been undertaken to obtain a push button switch of this type having a desired life in excess of 5,000,000 to 10,000,000 operations.
Thus, the push button switch of the present invention comprises a base plate made of an electrically insulating material; at least one pair of fixed contact points on the base plate; a switch cover member, comprising an electrically insulating rubbery elastomer, mounted on the base plate and having at least one dome-like raised portion over the fixed contact points on the base plate, to form a hollow space therebetween, the top of the dome-like raised portion having an outwardly or inwardly extending annular rib, the switch cover member being placed on or bonded to the base plate at a lower flat portion circumscribing the riser portion of the dome-like raised portion; and a movable contact member formed of an electrically conductive rubbery elastomer and bonded to the inner surface of the top of the dome-like raised portion of the switch cover member to project inwardly therefrom over the fixed contact points on the base plate, the ratio of the radial distance from the outer periphery of the annular rib to the foot of the riser portion of the dome-like raised portion to the radial distance from the outer periphery of the movable contact member to the inner periphery of the annular rib being in the range from 0.8 to 1.8.
Examples of switches constructed in accordance with the invention will now be described with reference to the accompanying drawings in which:
Figure 1 is a cross-sectional view of a typical model of the push button switch of the invention in the undepressed state;
Figure2 is a cross-sectional view of the same push button switch as in Figure 1 with a key top depressed to the state of overstroke;
Figure 3 and 4 are each a cross-sectional view of a different embodiment of the push button switch of the invention; and
Figure 5 is a cross-sectional view of another typical model of the push button switch of the invention in which the annular rib protrudes inwardly of the surface of the centre top flat instead of outwardly.
Figure 1 illustrates a typical embodiment of the push button switch according to the invention in cross-section, the switch being composed of a base plate 1 made of an electrically insulating material which preferably rigid, a pair of fixed contact points 2 2 provided on the surface of the base plate 1, a switch cover member 3 made of an electrically insulatir,,--- member sheet and a movable contact member 4 formed, preferably, ofan electrically conductitSe rubber bonded to the inner surface of the centre top flat 5 of the dome-like raised portion of the switch cover member 3.The movable contact member 4 is in the form of a downwardly extending stud as is shown in Figure 1 The switch cover member 3 is provided with an outwardly protruding annular rib 7 around the centre tcrj flat 5, surrounding the movable contact membe; 4 bonded to the reverse side of the cent be ,9p flat 5 and leaving an annular thin walled portion 8 between the movable contact member t and the rib 7 having a radial width "a" as is indicated in Figure @.In other words, tha radial distance from the cuter periphery of the movable contac- n-c-.mber 4 to he inner pe-iph--e;'; y, Or the rib 7 is give:--. by 'c3". The annular rib 7 is circumscribed by a riser portion 6 which in turn leads to a ci.-cumferen- tial basal fiat portion 11 at the foot 10. he switch cover member 3 is bonded to the base plate 1 at the basal flat portion 11.
When this switch cover member 3 is pushed down at the annular rib 7 through key top 9 as is shown in
Figure 2, the switch cover member 3 is deformed first at the side surface or riser 6 of the dome-like raised portion until the lower surface of the movable contact member 4 comes to contact with the fixed contact points 2,2 on the base plate 1. During this stroke, the centre top flat 5 is kept flat without deformation.
When the key top 9 is .lu.-ther pushed down beyond this critical ccni - cu the movable contact member 4 is no longer downwardly movable so that the rib 7 is depressed down relative to the movable contact member 4 until the lower surface of the rib 7 cornes into contact with the surface of the base plate 1 as is shown in Figure 2. As is readily understood from this figure, the thin walled portion 8 between the movable contact member 4 and the rib 7 is in a stretched state in this ultimate state of overstroke.
Release of the pushing force on the key top 9 naturally restores the switch cover member 3 to its original undepressed state shown in Figure 1 in which the thin walled portion 8 is consequently in an unstretched state. Thus, the thin walled portion 8 is subjected to the repetition of stretching and contraction in each pushing operation of the push button switch so that the elastic fatigue in this portion 8 is the limiting factor for the durability of the push button switch.
In a key board switch panel used in cash registers, electric typewriters, computers and the iike, the distance of and/or the load for the cverstroke must be adjusted in certain ranges from time standpoint of working efficiency as well as the health problem of operators. For example, key board switch panels are usually designed so as that the working load on the key top before the critical contact is in the range from 40 to 150 g, the load of overstroke at the moment when the lower surface of the ring-wise rib is near to contact with the base plate is in the range from 70 to 200 g and the distance of the overstroke is in the range from 1.0 to 2.5 mm.
The above described desired conditions are large lydetermined by the form and material of the switch cover member 3. For example, the hardness of the rubbery elastomer for the switch cover member 3 is preferably in the range from 30 to 70 by the JIS scale having an ultimate elongation at break of 150 to 500 %, though this is not limitative. Further, the thickness of the thin walled portion 8 should be in the range from 0.15 to 0.50 mm in order that the load for the overstroke is in the above specified preferable range.
In carrying out extensive investigations for improving the touch of pushing as well as the durability of the push button switches of the above described type, it was found that a significant determinant parameter for the above purpose is the ratio of the radial distance "b" from the outer periphery of the rib 7 to the footline 10 of the riser 6 to the radial distance "a" from the outer periphery of the movable contact member 4 to the inner periphery of the rib 7.
The stretching force which the annular thin walled portion 8 receives is increased with the decrease of the radial distance "a" from the movable contact member 4 to the rib 7 and the buckling load of the riser 6 of the dome-like raised portion is increased with the decrease of the radial distance "b" from the ring-wise rib 7 to the footline 10. The above mentioned requirements for the increase of both of the radial distances "a" and "b" are not compatible with each other. That is, increase of the radial distance "a" with the object of decreasing the stretching force in the annular thin walled portion 8 to increase the durability of the push button switch necessarily leads to a decrease of the radial distance "b" since the diameter of the dome-like raised portion of the switch cover member 3 is naturally limited according to the desired arrangement of the key switches in the key board.On the other hand, the increase of the radial distance "b" with the object of avoiding possibie rupture in the riser portion 6 necessarily leads to a decrase of the radial distance "a" so that the danger of rupture increases in the annular thin-walled portion 8. Simultaneous increase of the radial distances "a" and "b" is of course impracticable without enlargement of the dome-like raised portion as a whole.
The inventors have carried out numbers of trials to find the optimum condition with respect to the radial distance "a" and "b" for key board switches having the diameter of the movable contact member 4 of 2.5 to 6mm, stroke gap between the movable contact member 4 and the fixed contact points 2,2 of 1 to 2,5 mm, overstroke distance of 1 to 2.5 mm, overall stroke of the dome-like raised portion of 2 to 4.5mm -and height of the movable contact point 4 of 1 to 3.5mm. The conclusion of the above study is that the mi of the radial distance "b" to the radial distance "a" i.e. b/a, should be in the range from 0.8 to 1.8 or, preferably, from 0.9 to 1.5 or, more preferably, from 1.0 to 1.2. With a design to satisfy this ratio between the radial distances "b" and "a", good balance is obtained between the stretching force in the annular thin walled portion 8 and the buckling load in the riser portion 6 so that the durability of the key board switch is remarkably improved to by used in more than 10,000,000 times of operation of the switch.
When the above defined ratio b/a is smaller than the
above range, the danger of rupture in the riser
portion 6 increases while a larger ratio of b/a than
the above range leads to the increased danger of
rupture in the thin walled portion 8.
Figures 3 and 4 each illustrate a cross-sectional
view of a part of a different model of the inventive
key board switches, in which the annular thin walled
portion 8 is not flat as in the model illustrated in
Figure 1 but is curved or inclined. The essential
relationship between the radial distance "b" and "a"
is also the same in these models as in the model of
Figure 1 and sufficient durability of the key board
switch is obtained with the ratio b/a in the range
from 0.8 to 1.8 inclusive.
Figure 5 illustrates a cross-sectional view of
another embodiment of the inventive key board
switch, in which the ring-wise rib 7 around the centre
top flat 5 is protruded inwardly on the same surface
as the movable contact member 4 instead of the
outwardly protruded ring-wise rib 7 in Figure 1.
Despite the seeming difference in the outer appear
ance, the principle of the present invention is
applicable also to this model in just the same
manner as in the model of Figure 1 expect for the
difference in the form of the key top 9 which is
provided with a ring-wise protruded rib 9a for
pushing down the ring-wise rib 7 of the switch cover
member 3. The figure illustrates, though not essen
tial, air-escape passages 12 and 13 on the lower
surfaces of the basal flat portion 11 of the switch
cover member 3 and the ring-wise protruded rib 9a
of the key top 9, respectively, to facilitate entry and
exit of air.
Claims (4)
1. A push button switch comprising a base plate
made of an electrically insulating material; at least
one pair of fixed contact points on the base plate; a
switch cover member, comprising an electrically
insulating rubbery elastomer, mounted on the base
plate and having at least one dome-like raised
portion over the fixed contact points on the base
plate, to form a hollow space therebetween, the top
of the dome-like raised portion having an outwardly
or inwardly extending annular rib, the switch cover
member being placed on or bonded to the base plate at a lower flat portion circumscribing the riser
portion of the dome-like raised portion; and a
movable contact member formed of an electrically conductive rubbery elastomer and bonded to the
inner surface of the top of the dome-like raised
portion of the switch cover member to project
inwardly therefrom over the fixed contact points on the base plate, the ratio of the radial distance from the outer periphery of the annular rib to the foot of the riser portion of the dome-like raised portion to the radial distance from the outer periphery of the
movable contact member to the inner periphery of
the annular rib being in the range of from 0.8 to 1.8.
2. A switch according to claim 1, wherein the
ratio b/a is between 0.9 and 1.5.
3. A switch according to claim 2, wherein the ratio b/a is between 1.0 and 1.2.
4. A switch according to claim 1, substantially as described with reference to any of the examples shown in the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15532879U JPS5672424U (en) | 1979-11-09 | 1979-11-09 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB2062965A true GB2062965A (en) | 1981-05-28 |
| GB2062965B GB2062965B (en) | 1983-10-19 |
Family
ID=15603481
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8035853A Expired GB2062965B (en) | 1979-11-09 | 1980-11-07 | Push button switches |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS5672424U (en) |
| GB (1) | GB2062965B (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4540865A (en) * | 1983-03-01 | 1985-09-10 | Plessey Overseas Limited | Push buttons |
| US4766271A (en) * | 1984-12-12 | 1988-08-23 | Shin-Etsu Polymer Co., Ltd. | Elastomer-made push button switch covering member |
| US4851626A (en) * | 1987-06-30 | 1989-07-25 | Topre Corporation | Key switch device |
| US4891013A (en) * | 1988-03-07 | 1990-01-02 | Sharp Kabushiki Kaisha | Connector for a thin electronic appliance |
| GB2260444A (en) * | 1991-10-08 | 1993-04-14 | Silitek Corp | Switch |
| GB2260443A (en) * | 1991-10-08 | 1993-04-14 | Silitek Corp | Switch. |
| US5298705A (en) * | 1991-04-19 | 1994-03-29 | Marquardt Gmbh | Snap disk type switch |
-
1979
- 1979-11-09 JP JP15532879U patent/JPS5672424U/ja active Pending
-
1980
- 1980-11-07 GB GB8035853A patent/GB2062965B/en not_active Expired
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4540865A (en) * | 1983-03-01 | 1985-09-10 | Plessey Overseas Limited | Push buttons |
| EP0117732A3 (en) * | 1983-03-01 | 1986-09-24 | Plessey Overseas Limited | Push buttons |
| US4766271A (en) * | 1984-12-12 | 1988-08-23 | Shin-Etsu Polymer Co., Ltd. | Elastomer-made push button switch covering member |
| US4851626A (en) * | 1987-06-30 | 1989-07-25 | Topre Corporation | Key switch device |
| US4891013A (en) * | 1988-03-07 | 1990-01-02 | Sharp Kabushiki Kaisha | Connector for a thin electronic appliance |
| US5298705A (en) * | 1991-04-19 | 1994-03-29 | Marquardt Gmbh | Snap disk type switch |
| GB2260444A (en) * | 1991-10-08 | 1993-04-14 | Silitek Corp | Switch |
| GB2260443A (en) * | 1991-10-08 | 1993-04-14 | Silitek Corp | Switch. |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2062965B (en) | 1983-10-19 |
| JPS5672424U (en) | 1981-06-15 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |