GB2070864A

GB2070864A - Keyboard assembly

Info

Publication number: GB2070864A
Application number: GB8112573A
Authority: GB
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1979-09-10
Filing date: 1980-07-22
Publication date: 1981-09-09
Also published as: DE3033808A1; GB2058458A; GB2058458B; GB2070864B

Abstract

A keyboard assembly, e.g. for data entry, is made in a multi-layer manner, with the basic frame 100 arranged in generally rectangular cells 104 in each of which is a keyswitch. Each cell has ribs 106 to locate the actuating key 153 of a snap action keyswitch. The key 153 bears on the free end 149 of an actuating spring 136 overlying a snap action contact spring 132, which is movable into engagement with a printed circuit contact 175 when the key 153 is depressed. The contact springs 132 of a row of switches are integrally connected together. The actuating springs 136 are also integrally connected. <IMAGE>

Description

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SPECIFICATION

Keyboard assembly

5 The present invention relates to keyboard assemblies using key switches of the snap-action type.

Key switches are much used to enable manual entry of alphanumeric information or other instructions in data-processing equipment, typewriters and 70 teleprinters, calculators, and similar equipment. A number of individual key switches, typically of a single-pole single-throw type, are usually assembled together in a common frame to form a keyboard for data entry. Each switch has a key cap which displays 15 a symbol representing the switch function, and which is depressed by an operatorto actuate the switch.

An object of the invention is to provide a simplified keyboard assembly using such key switches. 20 According to the present invention there is provided a keyboard assembly, including a housing; and a plurality of key switches supported on the housing; wherein each key switch has a conductive snap-action spring carrying a movable contact nor-25 mally spaced apart from a fixed contact on the housing, an actuator spring having a free end movable to deflect a portion of the actuator spring against the snap-action spring, and a keystem movably mounted on the housing and having a portion bear-30 ing on the free end of the actuator spring to apply an actuating force through the actuator spring to the snap-action spring to close the contacts, the direction of actuating force being generally parallel to the direction of keystem motion.

35 An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 is a pictorial bottom view of a portion of a keyboard housing cover for key switch used as one 40 element of an array of switches forming a keyboard embodying the invention;

Fig. 2 is a top plan view of the keyboard housing cover;

Fig. 3 is a bottom view, partly broken away, of a 45 keyboard assembly embodying the invention;

Fig. 4 is a top plan view of a portion of a strip defining multiple snap-action springs;

Fig. 5 is a viewon line 15-15 of Fig. 4;

Fig. 6 is a viewon line 16-16 of Fig. 4;

50 Fig. 7 is a viewon line 17-17 of Fig. 4;

Fig. 8 is a viewon line 18-18 of Fig. 4;

Fig. 9 is a top plan view of a portion of a strip defining multiple actuator springs;

Fig. 10 is a viewon line 20-20 of Fig. 9;

55 Fig. 11 is a sectional elevation of an individual key switch used in the keyboard embodying the invention;

Fig. 12 is a sectional view on line 22-22 of Fig. 11; and

60 Fig. 13 is a pictorial view of a keystem.

The drawings show an integrated array of individual key switches forming a keyboard, the individual switches being mounted in a housing with a cover100, see Figs. 1-2. The cover is an integrally-65 moulded plastics part which accommodates enough individual key switches to form, for example, a keyboard for a typewriter, teleprinter, computer-entry device, or the like.

Cover 100 has atop panel 101 with downwardly 70 extending longitudinally walls 102 and lateral walls

103 which intersect to define individual cells or compartments 104 to accommodate the individual key switches. Extending from the inner surface of each of the four walls defining a compartment 104 are a

75 pair of tabs 106 which are spaced apart to define a channel 107 (Figs. 1 and 3) in which a keystem is received as described below. A hollow and centrally positioned turret 108 extends from the upper surface of panel 101 above each compartment 104, see Figs. 80 2 and 11, and the top surface of each turret defines a keyed cruciform slot 109 (Fig. 2).

One of the longitudinal walls of each compartment

104 has a downwardly extending locating pin 111, and one of the lateral walls of each compartment has

85 a downwardly extending locking pin 112. Enlarged bosses 113 are positioned at intervals along the housing cover in the lateral walls, and each boss has a central threaded recess 114 to receive a screw (not shown) when the keyboard is assembled. Longitudi-90 nal walls 102 are extended beyond the matrix of compartments 104 to provide mounting arms 116 with openings 117 therethrough enabling the keyboard assembly to be secured to another device.

Each row of compartments has a spring-metal 95 strip 120 which defines a plurality of snap-action springs 121 (Figs. 4-8). The strip has a longitudinally extended base 122 having evenly spaced lateral extensions 123. The end of each lateral extension is bifurcated and curved (Fig. 5) to form a pair of con-100 tact fingers 124. The body of each lateral extension also has a generally rectangular opening 125 with a short tab 126 extending into it. Circular openings 127 are formed through base 122 between each pair of lateral extensions 123, and these openings are 105 positioned to receive locating pins 111 on the housing cover.

Each snap-action spring 121 is supported at the end of a tab 129 which extends longitudinally from one side of its lateral extension 123. After being 110 stamped from a larger sheet of spring metal, the snap-action spring is a generally rectangular flat panel. A pair of longitudinally extending grooves 130 are then formed at opposite ends of the panel to deform it into a stressed and arcuately bowed snap-115 action spring.

When viewed from the side. Fig. 8, the spring is similar in shape to a steel measuring tape, and pressure applied atthe central part of the top surface of the spring deforms the spring into a second bi-stable 120 position, providing the desired snap-action. Elongated contacts 132 are partially severed from the main body of the spring, and are bent to extend

The date of filing shown above is that provisionally accorded to the application in accordance with the provisions of Section 15(4) of the Patents Act 1977 and is subject to ratification or amendment at a later stage of the application proceedings.

Claims

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slightly below the undersurface of the spring. Fig. 7.

Referring to Figs. 9 and 10, a second spring-metal strip 135 defines actuator springs 136. The strip has a longitudinally elongated base 137 having spaced cir-5 cular openings 138 (similar to openings 127 in base 122 of the strip of snap-action springs) to receive locating pins 111. Strip 135 is shown as a flat blank in Fig. 9 as stamped from a larger sheet of spring metal. Longitudinally spaced lateral extensions 140 10 extend from the base, each having a circular opening 141 to receive a locking pin 112 on the housing cover. Each spring 136 extends longitudinally from its extension 140, and each spring has a generally rectangular end portion 143 integrally joined at a 15 fold line 144 with a tapered intermediate portion 145 which is integrally joined to the end of the extension 140.

The originally flat actuator spring is then bent into its final form. Fig. 10, by further steps. First, adown-20 wardly extending dimple or depression 147 is formed adjacent fold line 144 in the positron indicated by phantom line 148 in Fig. 9. A free terminal end 149 of the spring is then bent into a curved configuration (Fig. 10) along phantom line 150 in Fig. 9. 25 Finally, the actuator spring is bent upwardly along fold line 144, and also where the intermediate portion joins lateral extension 140 as shown in Fig. 10.

Each key switch of the array is fitted with a keystem 153 (Figs. 3 and 11-13) which is preferably 30 integrally moulded from a plastics material. The keystem has a base 154, and a pair of stops 155 extend from opposite sides of the base to terminate in downwardly extending tips 156. A guide tab 157 extends from a third side of the base, and a second 35 guide tab 158 of enlarged width extends from the base opposite tab 157.

A post 159 extends upwardly from the top of base 154, and a pair of guide blocks 160 are formed on opposite sides of the post to give the upper end of 40 the post a generally cruciform cross-section which makes a slip fit within cruciform slot 109 in the housing cover. An angled cruciform head 161 extends from the top of post 159 to receive a key cap 162 (Fig. 11). Angulation of the head may be eliminated if no 45 slope of the top of the key cap is desired.

Fig. 3 is a multiple broken-away bottom view of housing cover 100 showing the addition of the various components which are assembled to form a complete keyboard assembly 164. Portion A of Fig. 3 50 is a bottom view of a portion of the housing cover alone. Portion B shows the appearance of the assembly after a plurality of keystems 153 have been fitted into the housing cover with stops 155 and guide tabs 157 received in channels 107, and keys-55 tem posts 159 in turrets 108 so the upper ends of the posts project beyond the top of the turrets with heads 161 accessible for the fitting of key caps.

The next step in the assembly is to position strips 135 over locating pins 111 and against the undersur-60 face of the housing coverto position an actuator spring 136 over each compartment 104, see Portion C of Fig. 3. Strips 135 are further positioned by locking pins 112 which fit within circular openings 141 (Fig. 9) in each strip of actuator springs. 65 In Portion D of Fig. 3, strips 120 of snap-action springs are superimposed over the strips 135, with circular openings 127 (Fig. 4) receiving locating pins 111 to ensure proper alignment of the strips. Rectangular openings 125 in strip 120 make an interference fit over locking pins 112, and tabs 126 in each opening 125 grip the locking pins to hold the strips of snap-action springs in place.

Portion E of Fig. 3 shows a sheet 165 of an insulating plastics material fitted over the superimposed strips of actuator and snap-action springs. The sheet has openings 166 to receive pfns 111 and 112 on the housingcoverfor proper alignment of the sheet with respect to the compartments 104.

Relatively large circular openings 167 are formed through the dielectric sheet, each being centrally positioned over an associated compartment 104 to expose contacts 132 on the snap-action springs. At least one circular opening 168 is also formed through the sheet for each row of large openings 167, and opening 168 is aligned with one set of contact fingers 124 on each strip of snap-action springs.

The final step of the assembly is to fit a printed-circuit board 170 over the sheet 165, the board having small openings 171 to recieve locating pins 111 and locking pins 112 to ensure proper alignment of the board with the other components of the keyboard. The board is secured in place by screws 173 threaded into recesses 114 (Fig. 1) in the housing cover. The printed-circuit board thus forms a base forthe keyboard, and completes the housing for each individual key switch.

The upper surface of the printed-circuit board bears plated conductive terminal strips 175 (shown in phantom line in Fig. 3), each strip being centered overan opening 167 in the insulating sheetto underlie contacts 132. Common contact terminal strips 176 are also positioned on the board in alignment with openings 168 and in electrical contact with contact fingers 124. The common contact strips thus place the strips of snap-action springs in connection with the circuit board, and individual switch closures are completed when a snap-action spring is driven "through centre" by depression of the associated key cap and keystem to snap movable switch contacts 132 against the underlying individual conductive strip 175 which serves as a fixed switch contact.

Upward movement of the keystem is limited by the top surface of keystem base 154 which abuts the undersurface of housing-covertop panel 101 (Fig. 21) until the keystem is depressed. Downward movement of the keystem is limited by stop tips 156 which straddle the snap-action spring to abut the top surface ofthe printed-circuit board. The actuator and snap-action springs are configured to close the switch before the keystem bottoms, providing the desired characteristics of overtravel, tactile sensing of switch closure, and hysteresis to prevent "teasing" ofthe switch contact at the closure point. CLAIMS

1. A keyboard assembly,, including a housing; and a plurality of key switches supported on the housing; wherein each key switch has a conductive snap-action spring carrying a movable contact normally spaced apart from a fixed contact on the housing, an actuator spring having a free end movable to

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deflect a portion ofthe actuator spring against the snap-action spring, and a keystem movably mounted on the housing and having a portion bearing on the free end ofthe actuator spring to apply an 5 actuatingforcethroughthe actuator spring to the snap-action spring to close the contacts, the direction of actuating force being generally parallel to the direction of keystem motion.

2. An assembly as claimed in claim 1, wherein at 10 least some ofthe key switches are arranged in rows, the key switches in a given row having snap-action springs which are integrally connected together, and actuatorsprings which are integrally connected together.

15 3. An assembly as claimed in claim 2, wherein each ofthe integrally connected actuator springs has an anchored end secured to the housing, the portion ofthe actuator spring which contacts the snap-action spring to close the contacts being between the 20 anchored end and the free end.
4. A keyboard assembly, including a housing on which a plurality of key switches is supported, wherein each said key switch has a conductive snap-action spring carrying a movable contact nor-

25 mally spaced apart from a fixed contact on the housing, an actuator spring having a free end which is movable to deflect a portion ofthe actuator spring against the snap-action spring, and a keystem movably mounted on the housing, wherein the keystem 30 has a portion bearing on the free end ofthe actuator spring to apply an actuating force through the actuator spring to the snap-action spring to close the contacts, the direction of motion ofthe actuating force being parallel to the direction ofthe keystem 35 motion, and wherein at least some ofthe key switches are arranged in rows, the key switches in a given row having snap-action springs which are integrally connected together by a conductive strip and the actuatorsprings for a said row are integrally 40 connected together by a second conductive strip.
5. A keyboard assembly including:

(a) a printed circuit board having at least one row of conductive layers thereon;

(b) a housing mounted on said board and

45 embodying at least one row of key switch cavities open to said board, each said cavity being positioned over a corresponding one of said conductive layers;

(c) a snap-action spring in each said cavity 50 embodying a movable contact normally spaced above said corresponding layer;

(d) a first conductive strip between said housing and said board interconnecting at least some of said snap-action springs;

55 (e) an actuator spring in each said cavity having a free end movable to urge a portion ofthe actuator spring against the snap-action spring;

(f) a second conductive strip between said housing and said board interconnecting at least some of

60 said actuatorsprings; and

(g) a plurality of keystems mounted on said housing each for one of said cavities, each said keystem having a portion bearing on the free end ofthe actuator spring in its respective cavity to apply an

65 actuating force through the actuator spring to the snap-action spring to cause said movable contact to engage said corresponding conductive layer, the direction of actuating force being generally parallel to the direction of keystem motion. 70
6. An assembly as claimed in claim 5, wherein said second conductive strip overlies said first conductive strip.
7. An assembly claimed in claim 6, wherein said housing embodies intersecting longitudinal and lat-75 eral walls defining said cavities; wherein one of said longitudinal walls embodies downwardly extending locating pins; and wherein said first and second conductive strips underlie said one longitudinal wall and embody aligned openings receiving said pins. 80
8. An assembly as claimed in claim 5,6 or 7

wherein said printed circuit board has a second conductive layer thereon underlying one of said cavities; and wherein said first conductive strip has a spring finger attached thereto engaging said second 85 conductive layer.
9. An assembly as claimed in claim 5 or 6,7 or 8, wherein said spring finger is formed on a lateral extension of said first conductive strip; wherein said snap-action spring is a generally rectangular sheet of

90 spring metal bowed between a pair of generally parallel sides providing an upraised intermediate section engageable by said portion of said actuator spring; wherein said parallel sides of said snap-action spring are generally perpendicularto said first 95 conductive strip; and wherein a tab connects one of said sides of said snap-action spring to said lateral extension.
10. A keyboard assembly substantially as described with reference to the accompanying draw-

100 ings.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1981.

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