GB2050950A

GB2050950A - Printing selection and control mechanism for a typewriter

Info

Publication number: GB2050950A
Application number: GB8017604A
Authority: GB
Original assignee: Hermes Precisa International SA
Current assignee: Hermes Precisa International SA
Priority date: 1979-06-19
Filing date: 1980-05-29
Publication date: 1981-01-14
Also published as: DE3023193A1; FR2459136A1; JPS565768A; IT8067951A0

Abstract

A typewriter has a type member (1) and a locking device (11) to prevent movement of the member (1). The device is released by arm (12) during each type selecting operation. To prevent unnecessary release of the locking device during a no-print cycle of operation a control device is actuated to prevent the arm (12) being moved by cam follower (13). <IMAGE>

Description

SPECIFICATION Printing selection and control mechanism for a typewriter The present invention relates to a printing selection and control mechanism for a typewriter.

In a known mechanism there is provided a car riage for a printing device which is displaceable along a motor shaft parallel to the platen of the typewriter. The printing device is provided, on its periphery, with an assembly of characters arranged in two groups. The mechanism is actuated by the motor shaft and comprises a decoding device con trolling a movement device permitting the selection of one of the two groups of characters, a selection device for causing a selected one of the characters of that group to be brought into the printing position locking means for locking the printing device in the position of printing of the character and a printing control device for causing either printing or non printing when a desired character is in the printing position.

A mechanism of this type is described in Swiss Patent No. 554243. In such mechanism, non-printing occurs when the user is effecting the selection of a group of characters. The two groups are, generally, the upper and the lower case letters, and such selection is effected by actuating a shift key. When such key is actuated, the control shaft usually effects a rotation through a pre-determined angle, generally one complete revolution. This provides the neces sary energy to the carriage for the decoding device.

The rotation of the control shaft entrains locking means so that no printing is effected. The result is an unnecessary and unequal wear of the locking means particularly since the position of the printing device during the shift does not necessarily correspond to the printing position of a character.

The present invention sekks to provide a mechan ism which obviates, or at least reduces this wear of the locking means.

According to the present invention there is pro vided a printing selection and control mechanism for a typewriter having a carriage for a printing member, the carriage being displaceable along a motor shaft in a direction parallel to the platen of the typewriter, the printing member having a periphery on which an assembly of characters are arranged in two groups, the mechanism comprising a decoding device con trolling a shift device permitting selection of a desired one of the groups of characters, a selection device capable of causing a desired one of the characters of the selected group to be moved into a printing position, means for locking the printing member in the printing position of the selected character during printing, and a control device for controlling and causing printing or non-printing of the selected character in the printing position, the control device comprising retaining means for the locking means which retaining means are sensitive to a non-printing command so as to be actuated by the operation of the shift device.

The invention will be further described, by way of example, with reference to the accompanying drawings, in which Figure l is a side elevation, partially in section, of a part of a typewriter and showing a mechanism in accordance with the present invention; and Figure 2 is a perspective view of retaining means forming part of the mechanism of the present invention.

The typewriter shown in Figure 1 has a single printing head, often known as a golf-ball head, which is well known in the art. Accordingly, only those features thereof which are indispensible for the comprehension of the present invention will be further described.

The printing member or head 1 shown in Figure 1 is in the form of a portion of a sphere limited by two planes extending perpendicularly to a polar axis XX'.

All the signs and characters adapted to be typed by the machine, for example 96, are formed in relief on the surface 2 of the sphere. The signs and characters are arranged in four rows which extend parallel to the two planes, so that there are 24 signs or characters per row. The signs and characters are disposed on twenty-four meridians, so that there are 24 columns on the periphery of the printing member.

A selection device for selecting the appropriate row and column is known per se and will therefore not be described further.

The printing head 1 is mounted on a carriage 3 capable of translational movement parallel to the axis of a platen 4. During such translational movement, the carriage 3 slides along a motor shaft 5 pivotally mounted at each of its ends on a frame, not shown, of the machine, and along a bar 6 fixed to the frame.

The printing member 1 is supported by a collar 7 fixed to an oscillating support 8. The support 8 is mounted between the two lateral faces 9 of the carriage 3, only one of which faces is shown in the drawing, in such a manner as to be oscillatable around an axis parallel to the axis of the platen 4.

During the striking of a character key, the support 8 rapidly oscillates through the angle necessary to bring the character occupying the position P into contact with the platen 4 at position P'. This action is effected by the printing control mechanism. Known locking means permit the printing member 1 to be fixed in position during the striking of a character.

These locking means are, as shown, in the form of a toothed crown 10 integral with the printing head 1 which co-operates with a pivotal finger 11 and by a second tooth arrangement, not shown, which cooperates with a second finger for retaining the selected row of characters in position. The toothed crown 10 has twenty-fo u r teeth corresponding to the twenty-four columns of characters.

The pivotal finger 11, and the other finger, are operated by means of an arm 12 pivotally mounted at one of its ends on the oscillating support 8, the other end of the fingers bearing against a lever 13.

This lever 13 is pivotally mounted on a support member 14 fixed to the lateral face, not shown, of the carriage 3. At its lower end the lever carries a finger 15 co-operating with an axial cam 16 integral with the control shaft 5.

The support member 14 has a bend 17 on which a pawl 18 is pivotally mounted. This pawl 18 is acted upon buy a spring 19 acting so as to bias the pawl into abutment with a lever 15. The lever 25 bears against a second lever 26 which, in turn, abuts against a lug 28 under the effect of a spring 27. The lug 28 forms part of a coupling member 23 which is actuated when a non-printing command is given.

If a non-printing command is given, the pawl 18 is caused to contact an adjustable abutment member.

This abutment member comprises a screw 20 mounted in the support member 14 and locked by a locknut 21. In such circumstances, the free end of the pawl 18 moves into engagement with the underside of the arm 12 and so acts as a retaining member for the arm 12.

The control shaft 5 effects a rotation of one turn each time a printing or shift order is transmitted to the carriage 3 by a de-coding device. This latter comprises coupling members 23 operated by universal bars 24, only one of which is shown in the drawing.

During printing, the non-printing coupling member 23 is not lowered, the levers 25 and 26 therefore remain in their rest position and the retaining member 22 of the pawl 18 remains disengaged from the arm 12, thus freeing it from the locking of the head. The arm 12 is controlled by the profile of the axial cam 16 so as to work normally during typing.

During a shift control associated with a nonprinting order, the non-printing coupling member 23 is lowered by the universal bar 25 causing the lever 26 to pivot. By means of the lever 25, the lever 26 allows the pawl 18 to bear against the abutment screw 20 under the action of the spring 19, the retaining member 22 of the pawl 18 thus being located in the path of the arm 12 and prevents it from transmitting the movement of the lever 13 to the locking means. The screw 20 permits the adjustment of the position of the pawl 18 to the level of the arm 12 when the oscillating support 8 is in its rest position and that the non-printing is ordered.

Claims

1. A printing selection and control mechanism for a typewriter having a carriage for a printing member, the carriage being displaceable along a motor shaft in a direction parallel to the platen of the typewriter, the printing member having a periphery on which an assembly of characters are arranged in two groups, the mechanism comprising a decoding device controlling a shift device permitting selection of a desired one of the groups of characters, a selection device capable of causing a desired one of the characters of the selected group to be moved into a printing position, means for locking the printing member in the printing position of the selected character during printing, and a control device for controlling and causing printing or nonprinting of the selected character in the printing position, the control device comprising retaining means for the locking means, which retaining means are sensitive to a non-printing command so as to be actuated by the operation of the shift device.

2. A mechanism as claimed in claim 1, in which the printing member is a spherical printing head mounted on an oscillating support, the locking means being controlled by means of an arm pivotally mounted on the oscillating support, the arm bearing against the end of a lever co-operating with an axial cam integral with the motor shaft, the retaining means comprising a pawl presenting a retaining portion capable of co-operating with an end of the arm when the control means causes non-printing.

3. A mechanism as claimed in claim 2further comprising a spring acting on the pawl so as to bias the pawl against a lever which is retained by a non-printing control member.

4. A printing selection and control mechanism for a typewriter constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.