GB1586969A - Printing apparatus - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO PRINTING APPARATUS (71) We, HENRY GROSS and SAMUEL GROSS, both British Subjects and of "Braewood", 45 Winnington Road, London, N.2. and "Springcroft", 43 Winnington Road, London, N.2. do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to printing wheels of the kind having print characters and ratchet teeth on its periphery. The main object of the invention is to provide a wheel which will enable the overall number of parts of a printing device to be reduced.The kind of printing device for which the wheel of the present invention is intended is suitable for electrical connection to the output of a calculator (e.g. cash register or data terminal) which gives out the results of its calculations in the form of electrical pulses.

According to the invention we provide a printing wheel having a plurality of sets of printing characters each from 0 to 9, the sets being on different parts of its exterior periphery and at least one set of stop teeth on another part of its exterior periphery suitable for engagement by an electronically controlled stop member. For example two sets of printing characters 0 to 9 may be provided on the periphery of the wheel whereby an audit roll and a ticket for the customer can be printed simultaneously.

The sets of printing characters may each occupy about one third of the periphery of the wheel, the other third being occupied by a corresponding set of ratchet teeth. Suitable printing platens will be arranged spaced apart around the periphery of the wheels. A number of wheels will be arranged on a common driving shaft and preferably each wheel will have an inner periphery with a small recess for engagement by a spring pressed ball or other friction driving member. The wheel may be very thin and may be solid between its inner and outer peripheries, i.e. it has no recess for a spring and no opening for a bail or like driving member.

A constructional form of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings, wherein: Figure 1 is a plan view of a shaft with wheels made in accordance with the invention and Figure 2 is a sectional view on the plan 2-2 on Figure 1.

A shaft 10 has integral end spindles 11, 12 whereby it can be mounted and driven. The shaft 10 is provided with a number of bores 13 which extend radially part way through the shaft and accommodate springs 14 and steel balls 15.

Printing wheels 20 have central bores whereby they are mounted on the shaft 10 in a freely rotatable manner. The inner periphery of each wheel has a small recess 24 engageable by the ball 15 whereby the shaft can drive the wheel through the ball 15.

The wheels at the ends of the shaft may be used for carrying printing words such as "paid out" while the inner wheels may for example carry only numbers 0 to 9.

The wheel has two sets of printing characters 0 to 9 at 27, 28 respectively. A hyphen or negative sign may be provided at 29, 29A.

The wheels have stop teeth 30 for engagement by pawls operated by electromagnets (not shown). The wheel has a stop shoulder 36 engageable with a pawl (not shown) and gaps 37, 37A for use where no printing is required. The wheel is solid and of constant thickness between boss 25 and the printing characters i.e. free from cavities to contain springs or openings to contain wheel moving means - except for any lightening holes or cavities although these are unnecessary and preferably not provided.

The pawl normally seats on a peripheral ledge 40 of the wheel. The diameter of the wheel to the tips of the stop teeth is less (e.g. by twenty thousands of an inch) than the radius of the ledge 40 to ensure that the teeth will clear the pawl when the wheel is returning to its zero position and also in the forward direction.

Each series of characters occupies nearly one third of the periphery and the ratchet teeth occupy nearly the remaining third.

The ledge 40 is spaced from the first ratchet tooth by a land 41 which is longer than the ratchet teeth to ensure adequate time for the electric motor which drives the shaft to achieve a suitable speed able when required for the pawl to engage the first tooth.

The shaft is driven and controlled by mechanism such as described in our copending British Patent Application 31995/77 (Serial No. 1586970).

The wheels are driven forwards and each wheel is stopped at its required position whereupon the associated ball comes out of its positive driving engagement with the depression and then engages the wheel with light frictional engagement and the ball then overruns the wheel to the end of its forward movement. The shaft is then driven in reverse and the balls re-engage the depressions and bring all the wheels back to starting positions in alignment with each other.

The wheels are made in pairs, the wheels of each pair 20A, 20B being different from each other, i.e. one wheel 20A has its recess 24 opened out to the outer side surface of the wheel in one axial direction while the wheel 20B has its recess 24 similarly opened out but to the opposite direction. By this means the wheels 20A, 20B can have very slight movement towards each other but they are prevented by the balls from moving into contact with the wheels on either side of this pair of wheels. This arrangement avoids the use of circlips in grooves in the shaft for separating the wheels from each other. If the wheels were allowed to contact each other throughout the set of wheels, the friction involved would be greater than in this construction.

WHAT WE CLAIM IS: 1. A printing wheel having a plurality of sets of printing characters each from 0 to 9, the sets being on different parts of its exterior periphery and at least one set of stop teeth on another part of its exterior periphery suitable for engagement by an electronically controlled stop member.

2. A printing wheel as claimed in claim 1 having a depression in its inner periphery for engagement by a spring pressed detent.

3. A set of printing wheels each as claimed in claim 2, mounted on a common shaft the wheels being made as pairs, each pair having the depressions opened out away from each other to the adjacent surfaces of the wheels of the pair, each pair being floatable axially towards each other but restrained from axial movement towards an adjacent pair by the detents.

4. A printing apparatus substantially as described and substantially as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (4)

**WARNING** start of CLMS field may overlap end of DESC **. preferably not provided. The pawl normally seats on a peripheral ledge 40 of the wheel. The diameter of the wheel to the tips of the stop teeth is less (e.g. by twenty thousands of an inch) than the radius of the ledge 40 to ensure that the teeth will clear the pawl when the wheel is returning to its zero position and also in the forward direction. Each series of characters occupies nearly one third of the periphery and the ratchet teeth occupy nearly the remaining third. The ledge 40 is spaced from the first ratchet tooth by a land 41 which is longer than the ratchet teeth to ensure adequate time for the electric motor which drives the shaft to achieve a suitable speed able when required for the pawl to engage the first tooth. The shaft is driven and controlled by mechanism such as described in our copending British Patent Application 31995/77 (Serial No. 1586970). The wheels are driven forwards and each wheel is stopped at its required position whereupon the associated ball comes out of its positive driving engagement with the depression and then engages the wheel with light frictional engagement and the ball then overruns the wheel to the end of its forward movement. The shaft is then driven in reverse and the balls re-engage the depressions and bring all the wheels back to starting positions in alignment with each other. The wheels are made in pairs, the wheels of each pair 20A, 20B being different from each other, i.e. one wheel 20A has its recess 24 opened out to the outer side surface of the wheel in one axial direction while the wheel 20B has its recess 24 similarly opened out but to the opposite direction. By this means the wheels 20A, 20B can have very slight movement towards each other but they are prevented by the balls from moving into contact with the wheels on either side of this pair of wheels. This arrangement avoids the use of circlips in grooves in the shaft for separating the wheels from each other. If the wheels were allowed to contact each other throughout the set of wheels, the friction involved would be greater than in this construction. WHAT WE CLAIM IS:

1. A printing wheel having a plurality of sets of printing characters each from 0 to 9, the sets being on different parts of its exterior periphery and at least one set of stop teeth on another part of its exterior periphery suitable for engagement by an electronically controlled stop member.

2. A printing wheel as claimed in claim 1 having a depression in its inner periphery for engagement by a spring pressed detent.

3. A set of printing wheels each as claimed in claim 2, mounted on a common shaft the wheels being made as pairs, each pair having the depressions opened out away from each other to the adjacent surfaces of the wheels of the pair, each pair being floatable axially towards each other but restrained from axial movement towards an adjacent pair by the detents.

4. A printing apparatus substantially as described and substantially as shown in the accompanying drawings.