GB2124156A - Keyboards - Google Patents

Abstract

A keyboard sub-assembly for a typewriter has a baseboard (1) formed with a plurality of upstanding projections (3) which receive keys (4) with a snap action. Each key (4) is a push-fit onto the correponding projection (3), and each key (4) is retained on the baseboard (1) by means of a lug (15) having a lip (17) which snap-engages within a recess (12) on the underside of the baseboard (1). A coil compression spring (18) is interposed between each key (4) and the corresponding projection tion (3). The sub-assembly of the baseboard (1) and the keys (4) can be assembled into a deck with a push-fit, as a result of the baseboard having projecting lugs (27) which snap-engage within slots formed in the deck. The keys (4) shroud the projections (3) so as to prevent foreign matter reaching the underside of the baseboard (1). <IMAGE>

Description

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GB 2 124156 A

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SPECIFICATION Keyboards

5 This invention relates to keyboards for typewriters, word processors, computers or similar pieces of apparatus.

Conventional keyboards have keys mounted on the ends of individial levers. The movement of each 10 of the levers is sensed or detected in order to move a respective type bar, a typing head or a typing wheel. Such keyboards are, therefore, essentially mechanical in operation, and so are expensive by virtue of the mechanical linkages used in transmitting motion 15 from each key to the location where lever movement is sensed. Moreover, the keys are normally positioned in a large aperture in a deck, so that there is nothing to prevent foreign matter falling down between the keys and between the keys and the deck 20 aperture. In consequence, foreign matter can easily enter the inside of the keyboard with virtually no facility for cleaning. Such considerations are very important if the keyboard is to be used by children.

The aim of the invention is to provide a keyboard 25 which is simple and cheap to assemble, and which is particularly suitable for home or leisure use, where it is desirable to protect the underside of the keyboard from contamination as a result, for example, of liquid being spilt on the keyboard.

30 The present invention provides a keyboard subassembly comprising a base member and a plurality of keys, the base member being constituted by a panel whose upper surface is provided with a plurality of spaced upstanding projections, each of 35 the keys being associated with a respective upstanding projection, wherein the keys and the panel have cooperating retaining means which retain the keys on the projections, but which allow the keys to be moved between raised and depressed positions with 40 respect to the base member, and wherein each of the keys shrouds the associated projection.

Because the projections are shrouded by the keys, and because the base member blanks off the spaces between the projections, it is hardly possible for 45 foreign matter spilt on or around the keys to reach the underside ofthe base member. This is particularly important where electrical circuitry for detecting movement ofthe keys is located beneath the base member.

k 50 Preferably, the panel is provided with a peripheral upstanding lip. Thus, if the liquid is spilt on or around the keys, it will be prevented from reaching the underside ofthe base member, and will collect within the tray-like base member. The spaces be-55 tween the projections define a labyrinth-like collecting area for spilt liquid.

In a preferred embodiment, each ofthe keys is provided with a downwardly-projecting lug which passes through an aperture formed in the associated 60 projection, and the underneath surface ofthe panel is formed with a respective recess adjacent to each ofthe apertures, each ofthe lugs being provided with a retaining lip which snaps into the associated recess on assembly ofthe respective key onto the 65 base member, the lugs and recesses constituting the retaining means. The keys can, therefore, be located on the base member simply by pushing the keys until they snap into position and are retained by the retaining means.

Advantageously, each key has a downwardly-projecting spigot adjacent to its lug, each ofthe spigots passing through a hole formed in the associated projection. Preferably, the lugs, spigots, apertures and holes are such that the keys are prevented from rotating with respect to the projections. Each ofthe spigots may be longer than the lugs ofthe associated key, whereby the free end of each spigot constitutes an actuator for engagement with a respective sensor for sensing movement of that key. Conveniently, each ofthe spigots is generally cylindrical, and is an easy sliding fit within the associated hole, and each ofthe lugs is generally rectangular in cross-section.

Each ofthe projections may be constituted by a boss-like base and a central formation extending upwardly from the base, the central formation having a smaller cross-section than the base. Advantageously, the apertures and holes are formed in the central formations ofthe projections. Preferably, each ofthe keys is provided with a downwardly-depending skirt which shrouds the associated projection, the skirt of each key being of such a length that it extends down to the base ofthe associated projection when the key is in its raised and depressed positions.

Preferably, resilient means are incorporated between each key and the base member to urge each key towards its raised position, and to provide a spring return after each key has been depressed and then released. Advantageously, each ofthe resilient means is constituted by a coil compression spring which rests on the upper surface ofthe base ofthe associated projection and surrounds the central formation of that projection. Conveniently, the base member is a moulded member made of ABS plastics material.

The invention also provides a keyboard comprising a keyboard sub-assembly as defined above, and a deckforsupporting and surrounding the keyboard sub-assembly. Advantageously, the keyboard subassembly is push-fitted in position on the deck. This means that the base member, keys and springs may be assembled together to form the keyboard subassembly, which can then readily be incorporated in any sort of apparatus or appliance. In a preferred embodiment the base member is provided with retaining lugs, each of which is a snap-fit within a respective aperture formed in the deck. Alternatively, the base member can be detachably fixed to the deck in any other suitable way.

The keys and the deck are preferably made from a synthetic plastics material such as high-impact polystyrene.

As mentioned above, the lower ends of the key spigots are preferably used to detect key movement. A preferred arrangement is for depression of a key to be detected electrically immediately underneath that key, thereby avoiding the mechanical linkages ofthe prior art. A preferred way of doing this is for key depression to cause the key spigot to press together

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two plastics sheets carrying printed circuits. Thus, the keyboard may further comprise plastics sheet means carrying two printed electrical circuits, each ofthe circuits having a respective node in alignment 5 with each ofthe keys, and wherein the arrangement is such that the two nodes aligned with each ofthe keys are normally spaced apart, and such that said two nodes can be brought into electrical contact by the downward movement ofthe spigot ofthe 10 associated key as that key moves from its raised position to its depressed position. Preferably, the two electrical circuits are printed on a pair of overlapping synthetic plastics sheets, and a perforated insulating spacer sheet is positioned between 15 the pair of synthetic plastics sheets, the perforations in the spacer sheet being located at the overlapping nodes and underneath the spigots ofthe keys. The plastics sheets may be mylar sheets.

Assembly of the keyboard is then extremely 20 straightforward. The plastics sheets and insulating spacer are laid in position in a shaped recess in the deck, after which the keyboard sub-assembly is simply snapped into position in the deck, each spigot being automatically positioned over a correspond-25 ing pair of aligned nodes, so that depression of a selected key causes the printed circuit on the two overlapping mylar sheets to make contact at the appropriate nodes. This signal is then fed to drive means, such as a solenoid, which is used to move a 30 printing head, preferably a daisy wheel printing head.

Atypewriter keyboard constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying draw-35 ings, in which:-

Figure 1 is a plan view of the base member of the keyboard;

Figure 2 is an end view of the base member, looking inthe direction ofthe arrow Ashown in 40 Figure 1;

Figures 3,4 and 5 are respectively side, plan and end views of one ofthe keys ofthe keyboard;

Figure 6 is an enlarged cross-section taken on the line VI-VI of Figure 1, but shows a key in position on 45 the base member;

Figures 7 and 8 are side and underneath views of a bar space key;

Figure 9 is a cross-section taken on the line IX-IX of Figure 8;

50 Figure 10 is a plan view of a deck into which the base member fits;

Figure 11 is a cross-section taken on the line Xl-X! of Figure 10;

Figure 12 is a plan view of a plastics sheet (shown 55 unfolded) which bears a printed circuit; and

Figure 13 is a plan view of a perforated plastics sheet which forms an insulating spacer between the two halves ofthe plastics sheet shown in Figure 12 when these are folded together.

60 Referring to the drawings. Figures 1 and 2 show a keyboard base member in the form of a baseboard 1 made from ABS plastics material. At each of a plurality of locations, the baseboard 1 has a corresponding upstanding projection 3 (seven of which are 65 indicated in Figure 1). Further similar projections 3

are centred at the points B in Figure 1, there being five rows of projections. There are eleven projections 3 in each of the three uppermost rows, ten projections 3 in the fourth row and two widely-70 spaced projections 3 in the fifth row, which is positioned along the lowermost edge of the baseboard 1.

The forty-three projections 3 in the four uppermost rows define the position for keys 4 (one of which is 75 shown in Figures 3 to 6). The two widely-spaced projections 3 adjacent to the lowermost edge of the baseborad 1 are provided to receive a space bar key 5 (see Figures 7 to 9).

Referring to Figures 1 to 6, it can be seen that each 80 projection 3 has a boss-like base 6, from which projects a central formation 7. The central formation 7 of each projection 3 is provided with a cylindrical hole 8, and a substantially rectangular-section hole 9 adjacent to the cylindrical hole. The rectangular hole 85 9 tapers downwardly along one edge 19, from its mouth towards the base 6. The central formation 7 of each projection 3 is strengthened by three ribs 10. The base ofthe hole 9 of each projection 3 has an angled recess 12.

90 As shown in Figures 3 to 6, each key 4 has a slightly recessed top surface 13, from the underside of which projects a cylindrical spigot 14 and a lug 15 of generally rectangular cross-section. The spigot 14 and the lug 15 of each key 4 are surrounded by a 95 peripheral wall 16ofthatkey. The extremity of each lug 15 is formed with a lip 17 (see Figure 6).

Each key 4 is pushed into position on its corresponding projection 3, with the interposition of a coil compression spring 18 (see Figure 6) which acts to 100 urge that key towards its raised position, and to provide a spring return action forthat key. To assemble a given key 4 on the baseboard 1, its spring 18 is placed in position so that it rests on the base 6 ofthe respective projection 3, and surrounds 105 the central projection 7 of that projection. The key 4 is then simply pushed into position so that its spigot 14 passes down the hole 8, and its lug 15 passes down the hole 9. As the lug moves into the hole 9, its lip 17 rides down the tapered edge 19 of that hole 110 until its lip 17 springs with a snap action within the recess 12. The key 4 is then located in position on its corresponding projection 3 in the manner illustrated in Figure 6. All forty-three keys 4 are pushed into position on the forty-three projections 3 in a similar 115 manner.

The space bar key 5 (see Figures 7 to 9) is symmetrical about the centre line C-C. Towards each end, the bar 5 has a respective spigot 22 and a respective lug 23, the pair of spigots 22 and lugs 23 120 locating in two pairs of holes 24 and 25 in the two projections 3 adjacent to the lower edge ofthe baseboard 1. A coil compression spring (not shown, but similarto the spring 18) is positioned between each of these two projections 3 and the space bar 125 key 5, in a similar manner to that described and illustrated with respect to Figure 6 for the keys 4.

The keys 4 and 5, which are made of high-impact polystyrene, can simply be pushed into position at their desired locations on the baseboard 1. This 130 results in a compact, easily-handled sub-assembly in

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which the keys 4 and 5 are firmly held with respect to the baseboard 1, but which may be detached therefrom by springing back the lugs 15 and 23, if required.

5 The baseboard 1 also has slots 11 for the passage of other keys such as tabulation keys and shift keys.

The two projections 3 which locate the space bar key 5 are similar to the projections 3 which locate the keys 4, but have holes 24 and 25 which are a little 10 largerthan the holes 8 and 9.

The baseboard 1 has a peripheral, upstanding lip 26 which gives the baseboard a tray-like appearance. Around its periphery, the baseboard 1 has eleven, integrally-moulded, downwardly-projecting lugs 27. 15 Each lug 27 has an end ledge or lip 28 (see Figure 2). The lugs 27 are provided to enable the sub-assembly ofthe baseboard 1,the keys 4 and 5 and the springs 18 to be snapped into position in a typewriter deck 29 (see Figures 10 and 11). The deck 29, which is 20 moulded from high-impact polystryene, has a shallow recess 30 (see Figure 10) shaped to receive the baseboard 1. The deck 29 also has eleven rectangular notches 32, which receive the respective lugs 27.

The deck 29 also has a channel 33 for a typewriter 25 ribbon cassette (not shown), and a portion (cut-away from Figures 10 and 11) for covering a solenoid which drives a daisy wheel print head (not shown). The underside ofthe deck 29 has slotted projections

34 for the passage of keys such as tabulation keys 30 and shift keys (or their operating levers).

Figure 12 shows a plastics sheet 35 carrying two printed circuits having nodes (such as 31 and 31a) at the locations ofthe short transverse lines printed on the circuitry. In use, the sheet 35 is folded about the 35 line D-D, so that the two printed circuits overlap, and a perforated insulating sheet (see Figure 13) is interposed between the two printed circuits. With the sheet 35 folded around the sheet 36 in this manner, the folded deck locates accurately in the 40 recess 30 in the deck 29, the portion 37 ofthe sheet

35 being passed through a slot 38 (see Figure 11) in the deck 29 to enable the printed circuits to be electrically connected to circuitry for detecting which keys ofthe keyboard are depressed.

45 Hence, the keyboard is assembled by folding the sheet 35 around the perforated sheet 36, and by laying the sheets in the recess 30. This automatically positions each ofthe perforations in the insulating sheet 36 between a respective pair of overlapping 50 nodes such as 31 and 31a. The sub-assembly ofthe baseboard 1, the keys 4 and 5 and the springs 18 are then snapped into position, the lips 28 engaging with a snap action behind the notches 32. This automatically aligns the lower end of each key spigot 14 with a 55 corresponding pair of nodes such as 31 and 31a,

with the result that depression ofthe corresponding key 4 causes the nodes 31 and31atomake contact through the corresponding perforation in the insulating sheet 36. The electrical connection ofthe nodes 60 31 and 31a is sensed, and the solenoid moves the daisy wheel print head to the appropriate location. It will be appreciated that the insulating sheet 36 holds apart all pairs of overlapping nodes otherthanthe pair of nodes pressed together by the depression of 65 a given key 4.

It will be apparent that the keyboard sub-assembly described above has a number of important advantages, particularly when used as part of a toy typewriter. Thus, the baseboard and the keys are 70 easy and cheap to make, as they can be moulded from cheap plastics materials. Moreover, the keyboard sub-assembly can be assembled easily and quickly by snapping the keys into position on the baseboard, the sub-assembly can easily be snapped 75 into position on the deck of a toy typewriter. Once assembled, the keys shround the projections provided on the baseboard, and thus prevent foreign matter reaching the underside ofthe baseboard, where the electrical circuitry is positioned. The 80 keyboard sub-assembly is particularly efficient at preventing liquids spilled on or around the keys from reaching the underside ofthe baseboard. This is because ofthe labyrinth-like interconnected spaces between the projections, and the tray-like formation 85 ofthe baseboard. Thus, any spilled liquid is directed by the skirts ofthe keys onto the upper surface ofthe baseboard, the entire area of which is available for collecting the liquid.

Another advantage ofthe arrangement described 90 above, is the particular formation of lugs and spigots beneath the keys. The cylindrical formation ofthe spigots permit the keys to be freely mounted for movement between their raised and depressed positions within the corresponding holes in the 95 upstanding projections. This permits the keys to be raised and depressed without substantial risk of jamming. Moreover, the generally rectangular formation ofthe lugs (and the associated lips) constitutes a very simple arrangement for snapping the 100 keys into position on the baseboard. Furthermore, the particular formation ofthe lugs and spigot enables the keys to be formed in a single, simple moulding operation. This is to be contrasted with the keys of known assemblies, which require compli-105 cated and multiple moulding operations.

Claims (22)

1. A keyboard sub-assembly comprising a base 110 member and a plurality of keys, the base member being constituted by a panel whose upper surface is provided with a plurality of spaced upstanding projections, each ofthe keys being associated with a respective upstanding projection, wherein the keys 115 and the panel have cooperating retaining means which retain the keys on the projections, but which allow the keys to be moved between raised and depressed positions with respect to the base member, and wherein each ofthe keys shrouds the 120 associated projection.

2. A keyboard sub-assembly as claimed in claim 1, wherein the panel is provided with a peripheral upstanding lip.

3. A keyboard sub-assembly as claimed in claim 125 1 or claim 2, wherein each of the keys is provided with a downwardly-projecting lug which passes through an aperture formed in the associated projection, and wherein the underneath surface ofthe panel is formed with a respective recess adjacent to 130 each ofthe apertures, each ofthe lugs being

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provided with a retaining lip which snaps into the associated recess on assembly ofthe respective key onto the base member, the lugs and recesses constituting the retaining means.

5 4. A keyboard sub-assembly as claimed in claim 3, wherein each key has a downwardly-projecting spigot adjacent to its lug, each ofthe spigots passing through a hole formed in the associated projection.

5. A keyboard sub-assembly as claimed in claim

10 4, wherein the lugs, spigots, apertures and holes are such that the keys are prevented from rotating with respect to the projections.

6. A keyboard sub-assembly as claimed in claim 4 or claim 5, wherein each ofthe spigots is longer

15 than the lug ofthe associated key, whereby the free end of each spigot constitutes an actuator for engagement with a respective sensor for sensing movement of that key.

7. A keyboard sub-assembly as claimed in any

20 one of claims 4 to 6, wherein each ofthe spigots is generally cylindrical, and is an easy sliding fit within the associated hole.

8. A keyboard sub-assembly as claimed in any one of claims 3 to 7, wherein each ofthe lugs is

25 generally rectangular in cross-section.

9. A keyboard sub-assembly as claimed in any one of claims 1 to 8, wherein each of the projections is constituted by a boss-like base and a central formation extending upwardly from the base, the

30 central formation having a smaller cross-section " than the base.

10. A keyboard sub-assembly as claimed in claim 9 when appendant to claim 4, wherein the apertures and holes are formed in the central formations ofthe

35 projections.

11. A keyboard sub-assembly as claimed in claim 9 or claim 10, wherein each ofthe keys is provided with a downwardly-depending skirt which shrouds the associated projection, the skirt of each key being

40 of such a length that it extends down to the base of the associated projection when the key is in its raised and depressed positions.

12. A keyboard sub-assembly as claimed in claim 3, or in any one of claims 4 to 11 when appendant to

45 claim 3, wherein resilient means are incorporated between each key and the base member to urge the key towards its raised position.

13. A keyboard sub-assembly as claimed in claim 12 when appendantto claim 9, wherein each ofthe

50 resilient means is constituted by a coil compensating spring which rests on the upper surface ofthe base ofthe associated projection and surrounds the central formation of that projection.

14. A keyboard sub-assembly as claimed in any

55 one of claims 1 to 13, wherein the base member is a moulded member made of ABS plastics material.

15. A keyboard sub-assembly substantially as hereinbefore described with reference to, and as illustrated by, the accompanying drawings.

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16. A keyboard comprising a keyboard subassembly as claimed in any one of claims 1 to 15, and a deck for supporting and surrounding the keyboard sub-assembly.

17. A keyboard sub-assembly as claimed in claim

65 16, wherein the keyboard sub-assembly is pushed fitted in position on the deck.

18. A keyboard as claimed in claim 17, wherein the base member is provided with retaining lugs, each of which is a snap fit within a respective

70 aperture formed in the deck.

19. A keyboard as claimed in anyone of claims

16 to 18, wherein the keys and the deck are made of high-impact polystyrene.

20. A keyboard as claimed in any one of claims 75 16 to 19 when appendantto claim 4, further comprising plastics sheet means carrying two printed electrical circuits, each ofthe circuits having a respective node in alignment with each ofthe keys, and wherein the arrangement is such that the two nodes

80 aligned with each ofthe keys are normally spaced apart, and such that said two nodes can be brought into electrical contact by the downward movement ofthe spigot ofthe associated key as that key moves from its raised position to its depressed position. 85

21. A keyboard as claimed in claim 20, wherein the two electrical circuits are printed on a pair of overlapping synthetic plastics sheets, and wherein a perforated insulating spacer sheet is positioned between the pair of synthetic plastics sheets, the 90 perforations in the spacer sheet being located at the overlapping nodes and underneath the spigots of the keys.

22. A keyboard substantially as hereinbefore described with reference to, and as illustrated by, the 95 accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1984.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.