GB2195102A - Method of making a key switching device - Google Patents
Method of making a key switching device Download PDFInfo
- Publication number
- GB2195102A GB2195102A GB08718504A GB8718504A GB2195102A GB 2195102 A GB2195102 A GB 2195102A GB 08718504 A GB08718504 A GB 08718504A GB 8718504 A GB8718504 A GB 8718504A GB 2195102 A GB2195102 A GB 2195102A
- Authority
- GB
- United Kingdom
- Prior art keywords
- key
- mat
- switching device
- bodies
- 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.)
- Withdrawn
Links
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 239000002775 capsule Substances 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims abstract description 16
- 229920002725 thermoplastic elastomer Polymers 0.000 claims abstract description 13
- 239000004033 plastic Substances 0.000 claims abstract description 9
- 229920003023 plastic Polymers 0.000 claims abstract description 9
- 238000002347 injection Methods 0.000 claims abstract description 7
- 239000007924 injection Substances 0.000 claims abstract description 7
- 239000000654 additive Substances 0.000 claims abstract description 4
- 239000000206 moulding compound Substances 0.000 claims description 13
- -1 polybutylene terephthalate Polymers 0.000 claims description 10
- 239000005020 polyethylene terephthalate Substances 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 7
- 229920000139 polyethylene terephthalate Polymers 0.000 claims description 7
- 239000004721 Polyphenylene oxide Substances 0.000 claims description 6
- 229920000570 polyether Polymers 0.000 claims description 6
- 229920001707 polybutylene terephthalate Polymers 0.000 claims description 5
- 150000002148 esters Chemical class 0.000 claims description 4
- 238000000465 moulding Methods 0.000 claims description 4
- WXZMFSXDPGVJKK-UHFFFAOYSA-N pentaerythritol Chemical compound OCC(CO)(CO)CO WXZMFSXDPGVJKK-UHFFFAOYSA-N 0.000 claims description 3
- 229920001283 Polyalkylene terephthalate Polymers 0.000 claims description 2
- 238000001746 injection moulding Methods 0.000 claims description 2
- 229920001169 thermoplastic Polymers 0.000 abstract description 3
- 239000004416 thermosoftening plastic Substances 0.000 abstract description 3
- 102100040428 Chitobiosyldiphosphodolichol beta-mannosyltransferase Human genes 0.000 description 8
- 229920001971 elastomer Polymers 0.000 description 4
- 229920002379 silicone rubber Polymers 0.000 description 4
- 239000006229 carbon black Substances 0.000 description 3
- 239000004020 conductor Substances 0.000 description 3
- 239000000806 elastomer Substances 0.000 description 3
- 239000004945 silicone rubber Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
- 235000019589 hardness Nutrition 0.000 description 2
- 229920000909 polytetrahydrofuran Polymers 0.000 description 2
- 238000004073 vulcanization Methods 0.000 description 2
- 229920002614 Polyether block amide Polymers 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- WERYXYBDKMZEQL-UHFFFAOYSA-N butane-1,4-diol Chemical compound OCCCCO WERYXYBDKMZEQL-UHFFFAOYSA-N 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000002093 peripheral effect Effects 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920001748 polybutylene Polymers 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000004926 polymethyl methacrylate Substances 0.000 description 1
- 229920002223 polystyrene Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 230000008092 positive effect Effects 0.000 description 1
- 229920006346 thermoplastic polyester elastomer Polymers 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
- B29C45/16—Making multilayered or multicoloured articles
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
- B29L2031/00—Other particular articles
- B29L2031/46—Knobs or handles, push-buttons, grips
- B29L2031/466—Keypads, keytops
-
- 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
- H01H2209/00—Layers
- H01H2209/002—Materials
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2215/00—Tactile feedback
- H01H2215/004—Collapsible dome or bubble
- H01H2215/008—Part of substrate or membrane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2221/00—Actuators
- H01H2221/002—Actuators integral with membrane
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H2229/00—Manufacturing
- H01H2229/044—Injection moulding
- H01H2229/046—Multi-colour or double shot injection moulding
Abstract
A key switching device is produced in that hard key bodies (5) on the one hand and electrically conducting contact capsules (3) on the other hand are formed on a flexible key mat (1). To simplify the manufacture, the key mat with key body and the contact capsules of thermoplastics materials are injection moulded in a multi-stage manufacturing process inside a plastics injection mould and firmly bonded together. The key body is made of plastics material; the key mat of a thermoplastic elastomer and the contact capsule of a thermoplastic elastomer containing electrical conducting additives. <IMAGE>
Description
SPECIFICATION
Method of making a key switching device
This invention relates to a method of making a key switching device.
Such a device is known wherein a flexible elastic key mat carries, on the one hand, hard key bodies which are made from plastics material, especially PBTP (polybutylene terephthalate) moulding compounds or PETP-(polye- thylene terephthalate)-modified moulding compounds, and, on the other hand, contact capsules which can be contacted with contact surfaces and are made from a material similar to that of the key mat but electrically conducting.
In the literature source Markt & Technik ("Market & Engineering"), number 4 of 28.01.1983, page 20, key mats of silicone rubber are described. These are connected by hot vulcanisation with contact capsules, which are of a rubber which has been made electrically conducting by admixing of amorphous carbons. It is possible so to mould the key mats that the key bodies are themselves formed from the silicon rubber. Such key bodies are, however, scarcely suitable for keyboards of typewriters or data input devices. In these cases, separately manufactured key bodies of PBTP-(polybutylene terephthala te)-moulding compounds or PETP (polyethylene terephthalate)-modified moulding compounds are placed upon the key mat.Such key bodies of PBTP-(polybutylene terephtha late)-moulding compounds of PETP-(polye- thylene terephthalate) modified moulding compounds have the advantage that they are sufficiently hard, wear-resistant, dimensionally stable to manufacture and can be easily printed or made multi-coloured.
In DE-OS 30 45 962, a keyboard is described, wherein the key mat is of polymethyl methacrylate, polystyrene, polyvinyl chloride or rubber-elastic elastomers, preferably silicone rubber. Conventional key bodies of PBTP-(polybutylene terephthalate)-moulding compounds or PETP-(polyethylene terephtha late)-modified moulding compounds are not disclosed in that patent specification.
If a key switching device is manufactured from a key mat and separate key bodies, then special measures must be taken for connecting and aligning the key bodies with the key mat. This makes construction expensive and assembly complicated.
According to one aspect of the present invention there is provided a method of making a key switching device, wherein a flexible elastic key mat carried hard key bodies which are made of plastics material and contact capsules, which can be contacted with contact surfaces and are made from a material similar to that of the key mat but electrically conducting, wherein the key mat is made from a thermoplastic elastomer, the contact capsules also are made from a thermoplastic elastomer, which has been made electrically conducting by additives, and the mouldings constituting the key bodies, the key mat and the contact capsules are firmly bonded to one another in a multi-stage manufacturing process inside a plastics injection mould.
According to another aspect of the present invention, there is provided a key switching device that has been made essentially by the method defined in the preceding paragraph.
Thermoplastic polyester-elastomers (polyether esters) are commercially known, for example, by the name Hytrel. The basis of such a thermoplastic elastomer is polytetramethylene ether glycol (PTMEG) and 1.4 butane diol and terephthalic acid. By adjusting the relative proportions of these substances, differing hardnesses and elasticities can be obtained. Since, in spite of the variations in the relative components, the substances belong to one polymer group, they readily form a permanent bond with one another.
A further thermoplastic elastomer is known commercially by the name PEBAX. Here, by chemical procedures, by the deliberate choice of flexible polyether segments and stiff polyether segments, the positive properties and easy workability of the thermoplastics are combined with the flexibility of the elastomers.
Different hardnesses or flexibilities can be obtained.
The polybutylene terephthalate moulding compounds or the modified polyethylene terephthalate moulding compounds, from which the key bodies are to be moulded, are so adjusted in composition that the key bodies become hard in the usual manner. The thermoplastic elastomer, from which the key mat is to be made, is so adjusted and processed that the key mat becomes flexibly elastic. The thermoplastic elastomer, from which the contact capsules are to be made, is made conducting by electrically conducting additives, for example carbon black, or carbon black substitutes. It is of especial advantage that the mouldings consisting of the chemically like elastomers and constituting the key bodies, the key mat and the contact capsules, combine to form a one-piece whole.
For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, in which:
Figure 1 is a sectional view of part of a switching device, and
Figure 2 is a plan view of the switching device shown in Figure 1.
A plurality of key domes 2 is formed on a flexible key mat 1. The key mat is electrically non-conducting. Inside on each key dome 2, a contact capsule 3 is provided, which, in a fully assembled keyboard, is above two conductors of a base plate, not shown. The two conductors can be electrically connected with each other by the electrically conducting contact capsule 3, when the key dome 2 is pressed down.
A cylindrical neck 4 is integrally formed at the top of the key dome 2. This continues into a key body 5 of substantially rectangular form in plan (see Figure 2). The key body 5 possesses a peripheral rim 6, which engages over the neck 4 and has a shape well-known in typewriter keys. By pressure upon the key body 5, the flexible, elastic key dome 2 responds, causing its contact capsule 3 to connect together the aforementioned conductors.
After the key body 5 has been released, the key dome 2 resets the key body 5.
The key body 5 is hard compared with the key mat 1, not only because the wall thicknesses in the region of the key body 5 are larger than that of the key mat 1, but also because the material in the-region of the key body 5 is harder than that of the key mat 1.
The key body 5 is printed with appropriate symbols or made in two-colour injection moulding.
The making of the described key switching device is carried out generally as follows.
A multi-part injection mould has, in one mould part, depressions corresponding to the form of the contact capsules 3 and key dome 2 and, in another mould part, depressions corresponding to the key bodies 5. Surfaces of the mould parts facing each other are formed corresponding to the shape of the key mat 1 and its key domes 2 respectively.
A thermoplastic elastomer, e.g. polyether ester, which has been rendered electrically conducting by carbon black, is injected in the depressions of the one mould part. A nonconducting thermoplastic elastomer, e.g. polyether ester is injected into the corresponding depressions for the key domes. A polyalkylene terephthalate moulding compound, especially modified by PBTP or PETP, is injected into the depressions of the other mould part, if desired in two-colour injection, this compound being so adjusted that the key bodies 5 become hard. This is accompanied by high wear resistance and good dimensional stability of the key bodies 5. The boundary lines between the material of the key bodies 5 and that of the key mat 1 on the one hand and the material of the contact capsules 3 and that of the key mat 1 on the other hand are shown in dot-and-dash line in Figure 1.
In this multi-stage manufacturing process, the materials of the key mat 1 and the contact capsules 3, on the one hand, and of the key bodies 5, on the other hand, bond intimately together, since they are based upon the same material group. The melting points of the materials are close together.
In total, a single-piece key switching device is thereby created, which is adapted in the mechanical and electrical properties of its individual zones to the requirements demanded.
A further advantage of the described method consists in the fact that the hardening of the thermoplastics material takes place more rapidly than a vulcanisation in the case of the known silicone rubber key mats.
Claims (11)
1. A method of making a key switching device, wherein a flexible elastic key mat carries hard key bodies which are made of plastics material and contact capsules, which can be contacted with contact surfaces and are made from a material similar to that of the key mat but electrically conducting, wherein the key mat is made from a thermoplastic elastomer, the contact capsules also are made from a thermoplastic elastomer, which has been made electrically conducting by additives, and the mouldings constituting the key bodies, the key mat and the contact capsules are firmly bonded to one another in a multi-stage manufacturing process inside a plastics injection mould.
2. A method according to claim 1, wherein the key bodies are made from polyalkylene terephthalate especially PBTP (polybutylene terephthalate)-moulding compounds and/or
PETP (polyethylene terephthalate) modified moulding compounds.
3. A method according to claim 1 or 2, wherein the key bodies, multicoloured if required, the key mat and the contact capsules are made in a multi-stage injection moulding process as a single plastics moulding.
4. A method according to claim 1, 2 or 3, wherein firstly, the key bodies are injection moulded in one half-mould and the contact capsules in another half-mould, and, before the hardening of the key bodies and the contact capsules, the key mat is injected between them and thereafter the key bodies, the key mat and the contact capsules are hardened together.
5. A method according to any one of the preceding claims, wherein said thermoplastic elastomer is a polyether ester.
6. A method of making a key switching device according to claim 1, substantially as hereinbefore described.
7. A key switching device, made according to any one of the preceding claims, wherein the key bodies are of a harder plastics material than the key mat and are integrally moulded as one piece on key domes of the key mat.
8. A key switching device according to claim 7, wherein each key body is seated on a neck of the key dome.
9. A key switching device according to claim 8, wherein the neck is of cylindrical form and the key body is rectangular in crosssection.
10. A key switching device according to claim 8 or 9, wherein the key body possesses a rim engaging over the neck.
11. A key switching device, substantially as hereinbefore described with reference to the accompanying drawing.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19863627554 DE3627554A1 (en) | 1986-08-14 | 1986-08-14 | METHOD FOR PRODUCING A KEY SWITCHING DEVICE AND KEY SWITCHING DEVICE |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8718504D0 GB8718504D0 (en) | 1987-09-09 |
| GB2195102A true GB2195102A (en) | 1988-03-30 |
Family
ID=6307367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08718504A Withdrawn GB2195102A (en) | 1986-08-14 | 1987-08-05 | Method of making a key switching device |
Country Status (4)
| Country | Link |
|---|---|
| DE (1) | DE3627554A1 (en) |
| FR (1) | FR2602909A1 (en) |
| GB (1) | GB2195102A (en) |
| IT (1) | IT1222452B (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2301794A (en) * | 1995-06-06 | 1996-12-18 | Nec Corp | Composite moulded product and method of manufacturing the same |
| EP0999515A2 (en) * | 1998-11-02 | 2000-05-10 | PSC Scanning, Inc. | Multi-stage trigger for a data reading device |
| CN100431080C (en) * | 2005-04-29 | 2008-11-05 | 乐金电子（昆山）电脑有限公司 | Press button module and its producing method |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0611507B2 (en) * | 1986-10-08 | 1994-02-16 | 末広産業株式会社 | Molding method for resin molded product having a plurality of movable protrusions |
| JPH02146725U (en) * | 1989-05-16 | 1990-12-13 | ||
| DE19844614C1 (en) * | 1998-09-29 | 2000-11-02 | Veeser Plastik Werk Gmbh & Co | Circuit board for foil keyboard has circuit foil incorporating key contacts applied to profiled carrier substrate and overlaid with spacer element having complementary surface profile |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2476900A1 (en) * | 1980-02-27 | 1981-08-28 | Telephonie Ind Commerciale | PUSH BUTTON FOR CONTROL KEYBOARD AND METHOD OF MAKING SAME |
| US4425263A (en) * | 1981-06-03 | 1984-01-10 | E. I. Du Pont De Nemours & Co. | Flexible screen-printable conductive composition |
| DE3144084C2 (en) * | 1981-11-06 | 1988-08-18 | Preh, Elektrofeinmechanische Werke Jakob Preh Nachf. Gmbh & Co, 8740 Bad Neustadt | Process for the manufacture of a contact mat suitable for a push button panel |
| DE3307659C2 (en) * | 1983-03-04 | 1986-10-30 | Standard Elektrik Lorenz Ag, 7000 Stuttgart | Push button switch |
| JPS60110938U (en) * | 1983-12-28 | 1985-07-27 | 日通工株式会社 | Contact structure in key switch |
-
1986
- 1986-08-14 DE DE19863627554 patent/DE3627554A1/en not_active Ceased
-
1987
- 1987-08-05 GB GB08718504A patent/GB2195102A/en not_active Withdrawn
- 1987-08-06 IT IT21599/87A patent/IT1222452B/en active
- 1987-08-13 FR FR8711630A patent/FR2602909A1/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2301794A (en) * | 1995-06-06 | 1996-12-18 | Nec Corp | Composite moulded product and method of manufacturing the same |
| GB2301794B (en) * | 1995-06-06 | 1998-04-08 | Nec Corp | Composite molded product and method of manufacturing the same |
| US5779230A (en) * | 1995-06-06 | 1998-07-14 | Nec Corporation | Method of making a composite button of an electrical device |
| US6238771B1 (en) | 1995-06-06 | 2001-05-29 | Nec Corporation | Composite molded product for use as a button for electric devices and method of manufacturing the same |
| EP0999515A2 (en) * | 1998-11-02 | 2000-05-10 | PSC Scanning, Inc. | Multi-stage trigger for a data reading device |
| EP0999515A3 (en) * | 1998-11-02 | 2001-08-29 | PSC Scanning, Inc. | Multi-stage trigger for a data reading device |
| CN100431080C (en) * | 2005-04-29 | 2008-11-05 | 乐金电子（昆山）电脑有限公司 | Press button module and its producing method |
Also Published As
| Publication number | Publication date |
|---|---|
| IT8721599A0 (en) | 1987-08-06 |
| GB8718504D0 (en) | 1987-09-09 |
| IT1222452B (en) | 1990-09-05 |
| DE3627554A1 (en) | 1988-02-25 |
| FR2602909A1 (en) | 1988-02-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |