EP0091284B1

EP0091284B1 - Contact keyboard and method of its manufacture

Info

Publication number: EP0091284B1
Application number: EP83301831A
Authority: EP
Inventors: Mario Maquignaz; Eugenio Bassetti; Orlando Spinoni
Original assignee: Ing C Olivetti and C SpA
Current assignee: TIM SpA
Priority date: 1982-04-02
Filing date: 1983-03-31
Publication date: 1987-12-23
Also published as: EP0091284A2; IT1155482B; IT8267433A0; DE3375001D1; EP0091284A3

Description

The present invention relates to a contact keyboard for a typewriter or other office machine and to a method of manufacturing the keyboard. The keyboard according to the invention is of the type set forth in the introductory part of claim 1.
Such a keyboard is known from DE-A 2309041. This keyboard has a good feel and has some advantages associated with the modularity of the keys. However it suffers from the drawback of being rather costly as it requires the assembly of the keys one-by-one.
A keyboard is also known from US 4315114 in which the actuators are connected together by resilient hinge arms cantilevered from a common cross member and which assist the domes in returning the key after it is released. Such a keyboard does not provide the good feel required for a typewriter keyboard.
The object of the present invention is to provide a contact keyboard which has a limited number of parts to be assembled and which is reliable and inexpensive and moreover gives the good feel required for a typewriter keyboard.
In accordance with this object, the keyboard according to the invention is characterised in the manner set forth in claim 1. The invention further provides a method of manufacturing as set forth in claim 4.
The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a sectional side view of a key of the keyboard according to the invention;
Fig. 2 is a perspective view of some details of the keyboard according to the invention;
Fig. 3 is a median section of another detail of the keyboard according to the invention in a first embodiment;
Fig. 4 is a median section of the detail of Fig. 3 in a second embodiment;
Fig. 5 is a plan view of a further detail of the keyboard according to the invention;
Fig. 6 is a side view of the detail of Fig. 5;
Fig. 7 is a perspective view of some parts of the keyboard according to the invention and of some apparatus necessary for the manufacture thereof;
Fig. 8 is a perspective view of the parts of the keyboard of Fig. 7 after their assembly;
Fig. 9 is a perspective view of other parts of the keyboard according to the invention and of other apparatus necessary for the manufacture thereof;
Fig. 10 is a perspective view of the parts of the keyboard of Figs. 7 and 9 after their assembly; and
Fig. 11 is a perspective view of further parts of the keyboard according to the invention and of a further apparatus necessary for the manufacture thereof.

Referring to Fig. 1, the keyboard according to the invention comprises a plurality of keys 10 each of which has a cap 13 mounted on an actuator 11 which is slidable axially within a cylindrical recess 12 formed in a block 15 of thermoplastic material.
According to a characteristic of the invention, all the recesses 12 of the keyboard are formed in the block 15 (Fig. 2) by moulding.
The block 15 is mounted on a support plate 16 (Fig. 1) with the interposition of a mat 17 of sound-absorbing material, for example rubber. To facilitate the mounting of the block 15 on the plate 16, the block itself may be constituted by several elements 20 (Fig. 2), in each of which there is formed a plurality of recesses 12 and interconnected by flexible tongues 21 produced in one piece with the elements 20.
The actuators 11 are also of thermoplastic material, are formed in a cluster during a single moulding stage and are interconnected by sprues 30. The arrangement of the actuators 11 in the cluster corresponds to that of the recesses 12 in the block 15. The sprues 30 are suitable for being removed after the cluster of actuators 11 has been inserted in the corresponding recesses 12 in the block 15, as will be described later on.
An elastic element 22 (Fig. 1) constituted by a dome of silicone rubber in the form of an inverted cup is adapted to cooperate with the bottom part of each actuator 11. According to a first embodiment, the median section of each elastic element 22 is that illustrated in Fig. 3, while in a second embodiment each elastic element22 may have the median section of the type illustrated in Fig. 4. Each actuator 11 (Fig. 1) is urged by the corresponding elastic element 22 towards the sound-absorbing mat 17, against which it is arrested by two stop elements 18 of the actuator.
A cylindrical pad 23 (Figs. 1, 3, 4) of conductive silicone rubber is fixed to the inside of each dome 22 and is adapted to short-circuit two elements 24 and 25 of a printed circuit 26 when the key 10 is depressed, to generate in this way in known manner a corresponding electric signal. The shape of the elastic elements 22 ensures snap contact of the pad 23 on the elements 24 and 25.
The elastic elements 22 of the keyboard may be produced individually or formed in one or more rubber mats 28 (Figs. 5 and 6), in an arrangement corresponding to that of the recesses 12, by technologies known per se.
The method of manufacture of the keyboard hereinbefore described, which is one of the characteristics of the invention, is as follows.
The plate 16 is arranged on a work bench 40 (Fig. 7) and the mat 17 of sound-absorbing material is fixed to this plate. The block 15 with the recesses 12 is formed by moulding in a press 41 of known type and is thereafter mounted on the mat 17. In this way, the group A illustrated in Figure 8 is produced.
The group A so formed is placed in an apparatus 42 (Fig. 9) on which is also arranged the cluster of sliders 11 which has been formed by moulding in a press 43 of known type. The apparatus 42 inserts the sliders 11 automatically into the corresponding seats 12 in the block 15 and removes the sprues 30 therefrom. In this way, the group B illustrated in Fig. 10 is produced.
The group B so formed is placed in a machine 44 also prearranged for testing the keyboard itself. The elastic elements 22 are then arranged to correspond with the actuators 11. This is done with the aid of a tray 45 when each elastic element 22 is independent of the others, or by directly arranging the rubber mats 28 on the block 15.
Finally, the printed circuit 26 is mounted. Before fixing the printed circuit 26 to the block 15 and the plate 16 with screws, each single key 10 is tested by the machine 44 in any known manner.
After this last stage, the keyboard according to the invention is finished and ready to be packed.

Claims

1. A contact keyboard for a typewriter or other office machine comprising a base plate (26) supporting a set of contacts (24, 25), a plurality of keys (10) each having a collapsible elastomer dome portion (22) inside which is fixed a pad (23), and an actuator (11) movable axially in opposition to the action of the dome portion to cause the pad to short-circuit two of the contacts (24, 25), and in which each actuator comprises a first portion slidable in a corresponding guide recess (12), and a second portion cooperating with the dome portion, characterised by a single support block (15) of plastics material moulded to produce a plurality of the guide recesses (12); in that the actuators (11) are of plastics material and are produced as a single moulding with their second portions interconnected by sprues (30) defining a planar cluster faced to the single support block and such that the first portion of each actuator is aligned with one corresponding recess; in that the sprues are removable after the insertion of the said first portions into the recesses, and in that the support block (15) is interconnected with the base plate (26) and the dome portions (22).

2. A contact keyboard according to claim 1, characterised by a sound absorbing mat (17) disposed over the single block (15) and in that each actuator (11) has a stop portion (18) which is arrested by the mat when the key is released and rises under the action of its dome portion (22).

3. A contact keyboard according to claim 1 or 2, characterised in that each pad (23) is conductive and short-circuits the corresponding two fixed contacts (24, 25) through the pad.

4. A method of manufacturing a contact keyboard of the type comprising a base plate (26) supporting an electric circuit provided with a set of fixed contacts (24, 25), a corresponding set of actuating sliders (11) movable axially in opposition to the action of collapsible resilient dome portions (22) for closing electric circuit associated with the movable sliders, and a corresponding set of guide elements (12) for the sliders positioned according to the desired distribution of the keyboard, and wherein each of the actuating sliders (11) has a first portion for cooperating with its guide element (12) and a second portion for cooperating with the corresponding dome portion, characterised by the following steps:

a) producing the set of guide elements (12) in a single support block (15) of plastics material;

b) disposing this block on a base, such that the guide elements are inverted with respect to the normal working arrangement;

c) producing the movable sliders (11) such that their second portions are interconnected through sprues (30) to lie on a common cluster;

d) arranging the cluster of sliders on a support, the sliders being inverted with respect to the normal arrangement and in the same arrangement as the guide elements;

e) producing the set of collapsible dome portions (22) and arranging them on a support, these being inverted and in the same arrangement as the guide elements;

f) inserting the first portions of the sliders into the corresponding guide elements (12);

g) removing the sprues (30) from the common cluster to separate the sliders;

h) superposing the dome portions (22) on the second portions of the sliders;

i) superposing the base plate (26) with the fixed contacts (24, 25) on the dome portions; and

j) fixing the base plate to the single support block (15).