GB2211790A

GB2211790A - A device for impressing characters

Info

Publication number: GB2211790A
Application number: GB8822405A
Authority: GB
Inventors: Thomas Schaf; Armin Weise; Hans Gropp
Original assignee: TA Triumph Adler AG
Current assignee: TA Triumph Adler AG
Priority date: 1987-10-31
Filing date: 1988-08-23
Publication date: 1989-07-12
Also published as: FR2622509A1; JPH01154778A; SE8802426L; SE8802426D0; IT1217957B; IT8821149A0; GB8822405D0

Abstract

The invention relates to a device for impresssing characters 4 disposed on a multiple-type carrier, by means of a hammer 10. Mounted on the shaft 8 of a motor 7 is a cam 9 which drives the pivotable hammer 10 against the action of a spring 12. The hammer 10 acts in free flight after separating from the cam 9. By selectively controlling the current applied to the motor according to overall areas of the particular character to be printed, it is possible to achieve a uniform presentation regardless of whether it is a character with a small or a large area. <IMAGE>

Description

A DEVICE FOR IMPRESSING CHARACTERS This invention relates to devices for impressing characters disposed on a multiple-type carrier, such as a daisy-wheel, in an imprinting machine, such as a typewriter.

It is known, in such machines, to effect impressions by means of an intermediate member, driven by an electric motor, which acts against the spokes carrying the individual characters. For example, in DE-OS 27 17 975 the said member is constituted by a ram operated by an eccentric driven by the motor. The eccentric operates continuously, and a complicated and expensive mechanism is required to effect synchronization between movements of the ram and positioning of the daisy-wheel.

Other arrangements are known, for example, from DE-AS 18 07 387 and DE-OS 21 01 995, which require additional control members.

In one case, the additional member takes the form of a rocker which co-operates with selection levers, and in the other case, it is an electromagnet which drives a wedge between the eccentric and the selected character. These additional control mechanisms are also expensive and complicated. To this must be added the fact that in the known devices there is no possibility of allowing the impression strength to act differently according to the area of the character to be impressed. Thus it must be doubted whether a satisfactory presentation pattern can be achieved with these known devices. Unequal impressions are rather to be expected since all the characters are impressed with the same energy regardless of whether they are small or large in area.

The present invention provides a device which aims at removing or reducing these disadvantages.

In accordance with the invention there is provided a device for impressing characters disposed on a multiple-type carrier, comprising a hammer driven by an electric rotary motor, wherein the-motor is operated intermittently and acts on the hammer through a cam mounted on the motor shaft, the hammer being yieldingly biassed to bear against the cam but being adapted to separate from the cam under its own kinetic energy in the final stage of movement of the hammer in each impressing operation.

As a result of the fact that the motor acts in start-stop operation on the printing hammer, no additional intermediate members need to be introduced. From this it follows that the motor can be arranged to turn the cam through 3600 per impression, so that the hammer can cause the impression of the set character in "free flight", i.e. losing contact with the cam in the final stage of its operating movement. In order to present a uniform presentation pattern, it is preferable to apply current differently to the motor depending on which character is being impressed. The individual current-application patterns can be read automatically out of a store and supplied to the motor.Thus a different run-up may be selected, for example to achieve a weaker impression such as is needed for the full-stop or the comma, from that which is needed for the impression of a large-area letter such as the "W" and the "M" for example. A stepping motor is particularly suitable as a motor for the impression drive.

The construction of the device according to the features of Claim 4 has the advantage that a pressure is not exerted continuously on the bearings of the motor shaft and the rebound of the hammer does not affect the motor shaft. This contributes very considerably to the life of the device and to the stabilization of the quiet running.

The drawing illustrates one form of device in accordance with the invention, illustrated diagrammatically. it shows a side view of the device, parts which have no direct connection with the actual invention being omitted in the interests of clarity.

A type wheel 3 with type characters 4 is mounted on a rotary adjustment shaft 2 in front of the platen 1 in known manner. The motor for the rotary adjustment of the type wheel 3 has not been shown. A rotary stepping motor 7 is secured to a pedestal 6 on a support 5 which may be a carriage movable along the platen 1. Mounted on the shaft 8 of the motor is a cam 9 which can cooperate with a hammer 10. The hammer 10 is pivotable about a pin 11 and is pulled towards a stop 13 by means of a spring 12.

For each impression, current is applied to the motor 7 so that it turns the cam 9 through 3600.

In the course of this movement, the cam 9 accelerates the hammer 10 about its pin 11 in the impression direction so that the set character 4 of the type wheel 3 is impressed. In the final stage of impression movement, the hammer 10 separates from the cam 9 under its own kinetic energy, against the action of spring 12, and in particular is out of contact with the cam when it presses the character 4 against the platen 1.

It will be seen that this device for the impression of characters is considerably simpler in construction than the known devices mentioned above.

This is primarily attributable to the fact that the motor 7 causes the impression in intermittent operation. It will also be easily understood, that by applying current differently to the motor 7, different impression strengths of the characters can be achieved. If the motor 7 is a stepping motor, this can be easily achieved by fixing specific acceleration and braking curves. If the motor 7 were a direct-current motor, it would have to be provided with an angle setter or another suitable device so that different courses, or amplitudes of movement cause different impression strengths.

As a result of the fact that the hammer 10 acts in "free flight" on the spokes of the type wheel 3, hammer 10 and cam 9 can move independently of one another. This applies in particular to the return movement of the hammer 10 until it comes to bear against the stop 13, thus relieving the cam 9, shaft 8 and motor 7 of shock loading.

Claims

CLAIMS:

1. A device for impressing characters disposed on a multiple-type carrier, comprising a hammer driven by an electric rotary motor, wherein the motor is operated intermittently and acts on the hammer through a cam mounted on the motor shaft, the hammer being yieldingly biassed to bear against the cam but being adapted to separate from the cam under its own kinetic energy in the final stage of movement of the hammer in each impressing operation.

2. A device according to claim 1, wherein the motor is connected to control means which permit the motor to operate differently in order to produce different impression strengths for different characters.

3. A device according to claim 1 or 2, wherein the motor is a stepping motor.

4. A device according to claim 1, 2 or 3 wherein the hammer, in its position of rest between operations bears against a stop.

5. A device for impressing characters, substantially as herein described with reference to the accompanying drawing.