GB2202491A

GB2202491A - Line spacing mechanism

Info

Publication number: GB2202491A
Application number: GB08715594A
Authority: GB
Inventors: Gerhard Kours; Egon Zurawski; Heinz Meier
Original assignee: TA Triumph Adler AG
Current assignee: TA Triumph Adler AG
Priority date: 1987-03-20
Filing date: 1987-07-02
Publication date: 1988-09-28
Also published as: GB8715594D0; JPS63237973A

Abstract

A line spacing mechanism for the platen of a typewriter or the like comprises a d.c. motor (13) coupled through gearing (14, 15) to an eccentric (17), one revolution of which oscillates an indexing lever (188) whose drive pin (21) engages a platen ratchet wheel (4) so as to advance it through one tooth space. Free rotation of the platen is restrained by a spring loaded detent lever (8) engaging a separate detent wheel (6). <IMAGE>

Description

Line spacing mechanisms This invention relates to line spacing mechanisms for the platens of typewriters or like machines.

German Patent Specification 3034836 discloses the use for this purpose of a power driven pawl mechanism, but it is of somewhat complicated construction and tends to require frequent re-adjustment in service.

Stepping motors are also used, one such arrangement being described in German DOS 2943493. Usually, a driven pinion meshes with a gear wheel on the platen and driving engagement is effected by means of the magnetic field in the motor. Such a motor is relatively large and expensive, and requires complex control electronics.

In accordance with the present invention, there is provided a line spacing mechanism for the platen of a typewriter (or like machine), comprising a line space ratchet wheel and a detent wheel both drivingly coupled to the platen, a spring-loaded detent co-operating with the detent wheel and a d.c. motor drivingly coupled to an eccentric which acts on an indexing lever so as to bring it alternately into and out of engagement with the ratchet wheel and to advance it while so engaged by one tooth pitch for each complete revolution of the eccentric.

Such a mechanism may operate reliably with a relatively small number of components and using a small, inexpensive d.c. motor, since it is a simple matter to design the mechanism, particularly the indexing lever, to secure favourable transmission ratios. Furthermore, no expensive electronic control circuitry is needed.

By arranging that one tooth pitch of the ratchet wheel corresponds to half a line space, it is a simple matter to provide for one, two, three or more revolutions to be effected for half, one, one and a half or more line spaces.

By providing an electric switch to be operated in each revolution of the eccentric, electric signals can be initiated by way of acknowledgement. For example, an index pulse signal can be passed on to the machine logic circuitry.

In the embodiment described below, it would be possible to produce most components as injection mouldings.

In machines in which a line spacing clutch is provided1 this can simply be arranged between the platen and either the ratchet wheel or the detent wheel.

One form of mechanism in accordance with the invention will now be described, by way of example, with reference to the accompanying drawing in which: Figure 1 is a side view of the line spacing mechanism, and Figure 2 shows the sequence of movements of a part of the mechanism.

All that is indicated of the machine frame, in dot-dash lines, is a side wall 1. Mounted in the side wall is the spindle 2 of the platen 3. The spindle also carries a line space ratchet wheel 4 which has a toothing 5, and a detent wheel 6 which has a detent toothing 7.

If no line spacing clutch is provided, the platen 3 and the wheels 4 and 6 are all fast for rotation with the spindle 2. The detent toothing 7 of the detent wheel 6 is engaged by a detent lever 8 which is mounted by means of an open ended notch or cut-out 9 on a fixed pin 10, under the action of a spring 11. This provides a simple "plug-in" assembly for the detent lever 8.

Arranged securely against rotation on the drive shaft 12 of a d.c. motor 13 is a pinion 14, meshing with a gearwheel 15, which is mounted on a spindle 16. The gearwheel 15 is provided with an integral eccentric 17, on the outer circumference of which is rotatably mounted an indexing lever 18. The lever 18 is additionally mounted by means of a slot 19 on a fixed pin 20. The lever 18 carries at its free end a drive pin 21 which is engageable in the toothing 5 of the line space ratchet 4.

The other end of the adjusting lever 18 is designed as a lug 22, which acts on an electric switch 24 through a leaf spring 23.

If the command "line space" is given, the machine logic causes the motor 13 to execute, for example, two revolutions. As a result, the pin 21 of the indexing lever 18 moves anti-clockwise in a loop from the position identified by I in Figure 2 and back again. The path of movement of the pin 21 is indicated in Figure 2. Here the position I of the pin 21 corresponds to the lowest deadcentre position of the lever 18. Since, as explained above, one revolution of the eccentric corresponds to half a line space, the operation is repeated. During one operating cycle, the pin 21 enters the toothing 5 of the line space ratchet 4, advances the ratchet by one pitch and then retracts again from the toothing 5. During the rotation of the line space ratchet 4, the detent wheel 6 also advances by one tooth pitch.The detent lever 8 is thereby lifted over the next tooth against the action of the spring 11.

When the motor 13 has come to a standstill, the pin 21 resumes the position designated by I. In each revolution of the eccentric 17, the lug 22 operates the switch 24 once by means of the leaf spring 23. The pulse emitted hy the switch can be evaluated in the machine logic as an acknowledgement.

The operation described above corressonds to a normal line spacing, such as takes place in every typewriter when the end of a line is reached. With suitably equipped typewriters, the mechanism can also be used for paperfeed. If the wiring of the d c. motor 13 permits, and the tynewriter is appropriately modified, line spacing can also be performed in the opposite direction by reversing the poles of the motor 13. This is useful, for example, if certain characters have to be written above or below the normal line of type, for example when writing technical-scientific text.

Since, after a complete revolution of the eccentric 17, the pin 21 is out of engagement with the line space ratchet 4, the detent lever 8, along with the toothing 7 of the detent wheel 4, restrains the platen against free rotation.

Claims

CLAIMS:

1. A line spacing mechanism for the platen of a typewriter (or like machine), comprising a line space ratchet wheel and a detent wheel both drivingly coupled to the platen, a spring-loaded detent co-operating with the detent wheel and a d.c. motor drivingly coupled to an eccentric which acts on an indexing lever so as to bring it alternately into and out of engagement with the ratchet wheel and to advance it while so engaged by one tooth pitch for each complete revolution of the eccentric.

2. A mechanism according to claim 1 in which one tooth pitch of the ratchet wheel corresnonds to half a line space.

3. A mechanism according to claim 1 or 2, including an electric switch arranged to be operated during each revolution of the eccentric.

4. A mechanism according to claim 3, wherein the said switch is actuated by a portion of the indexing lever.

5. A mechanism according to any preceding claim, wherein the detent lever has an open ended notch engaged over a fixed pivot pin to facilitate mounting of the lever.

6. A line spacing mechanism substantially as herein described with reference to the accompanving drawing.