GB2091644A

GB2091644A - Improvements in typewriters

Info

Publication number: GB2091644A
Application number: GB8102263A
Authority: GB
Original assignee: Dobson Park Industries Ltd
Current assignee: Joy Global Industries Ltd
Priority date: 1981-01-26
Filing date: 1981-01-26
Publication date: 1982-08-04
Also published as: GB2091644B

Abstract

A type bar typewriter has a printing ribbon 24 contained in a cassette 20 which has spool housings 32 and 34 on the ends of arms 38 joined by a elongate member 42, the arms 38 and member 42 defining an opening through which the type bars can move without interference. Movement of the ribbon is effected by a one-way drive mechanism, consisting of a belt 100 and a one- way clutch, which rotates a spindle 60 at a take-up spool position. To reverse the direction of movement of the ribbon, the cassette 20 is lifted and turned over, so that the positions of the two spools 50 and 70 are interchanged. This obviates the need for a reversing mechanism in the ribbon drive. <IMAGE>

Description

SPECIFICATION Improvements in typewriters This invention relates to typewriters.

More particularly, but not exclusively, the invention relates to toy typewriters.

The invention is concerned with typewriters of the kind having a platen mounted in a carriage movable stepwise on the body of the typewriter, an array of keys each adapted to cause a selected printing member to strike the platen at a printing position, means for guiding a printing ribbon from a supply spool to a take-up spool past the printing position and a ribbon drive mechanism for advancing the ribbon on each stepwise movement of the carriage.

In such typewriters the ribbon drive mechanism usually comprises a drive train to each of the spools, with a mechanism for reversing the drive io the spools when the supply spool is exhausted, so that the supply spool then becomes the take-up spool. The need to provide a reversing mechanism makes such a drive mechanism complicated and expensive, which is undesirable, particularly in a toy typewriter.

This invention consists of a typewriter of the kind set forth, in which the supply and take-up spools consist of two spools mounted in a single cassette adapted to be positioned in either of two orientations on the body of the typewriter, the ribbon extending in each orientation from one spool to the other through the printing position and one spool being at a take-up spool position on the body of the typewriter, the arrangement being such that on moving the cassette from one orientation to the other the positions of the two spools are interchanged, so that the direction of travel of the ribbon between the spools is reversed, and the ribbon drive mechanism comprises a one-way drive to the spool occupying the take-up spool position adapted to rotate the spool at that position on each stepwise movement of the carriage in a direction to cause ribbon to be drawn onto the spool.

Since the orientation of the cassette can be changed when the ribbon has been fully withdrawn from one spool, so that the empty spool then occupies the take-up spool position, the need for reversal of the drive to the spools is obviated, and the ribbon drive mechanism can be made very simple.

Preferably, the ribbon drive mechanism comprises a drive pulley coupled to the carriage so as to rotate on each stepwise movement of the carriage, a driven pulley connected to a spindle rotatably mounted in the body of the typewriter so as to drivingly engage a spool located at the spool take-up position, and a driving belt connecting the drive and driven pulleys. Suitably, a one way clutch mechanism acting on the driven pulley allows it to be rotated in only one direction, the drive belt slipping on the pulleys when the drive pulley attempts to rotate the driven pulley in the opposite direction.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a typewriter in accordance with the invention, Figure 2 is a perspective view of the typewriter with the ribbon cover removed, Figure 3 is a perspective view of the typewriter with the ribbon cassette removed, Figure 4 is a fragmentary vertical section through the typewriter, with the carriage omitted, showing the ribbon drive mechanism, Figure 5 is a fragmentary plan view of the ribbon cassette, Figure 6 is an exploded view of the driven pulley and one way clutch of the ribbon drive mechanism, and Figure 7 is a plan view of the driven pulley of the ribbon drive mechanism.

Referring to the drawings, a typewriter has a body 10, which supports a movable carriage 12, a keyboard 14 and a typebar assembly 16. A disposable cassette 20, which rests on a flat surface 18 of the body 10, contains an ink ribbon or carbon film ribbon 22, an exposed length 24 of which is guided through guides 26 at a printing position. The type bar assembly is arranged so that when a key of the keyboard 14 is depressed a type-head on the corresponding type bar strikes the platen 28 of carriage 12 through the ribbon 24. The keyboard and type bar assembly may be of any known form, for example as described in United States patent specification 4 195 935.

The cassette 20 consists of a casing 30 formed in one piece from plastics material and including two spool housings 32 and 34. The spool housings are connected to one another by a connecting piece 36 shaped so that the cassette can rest on the surface 1 8 of the typewriter body whilst not interfering with the movement of the type bars. The connecting piece 36 thus has two arms 38 generally parallel to one another extending from the two spool housings 32 and 34 and joined by an elongate portion 42.

A spool 50 is rotatably mounted in the spool housing 32, reduced diameter portions 52 at the axial ends of the spool fitting into circular apertures 44 in the walls of the housing. One end of the ribbon 22 is permanently attached to the spool 50 by means of a retaining pin 54 which is snap-fitted into a correspondingly shaped recess in the spool to trap the ribbon in the recess. The ribbon 22 is wound onto the spool and emerges from the housing 32 through an opening 48 in the side wall of the housing. The spool 50 has a central bore 54 to receive a drive spindle 60, and on each face of the spool a number of ribs 56 define recesses to receive a drive pin 62 on a drive collar 64 fixed to the drive spindle 60.

Each face of the spool housing 32 is formed with an upstanding flange 46 which surrounds the aperture 44 and which fits into one of two locating recesses 66 and 68 in the typewriter body 10 to locate the cassette 20 in position on the typewriter.

The other spool housing 34 of the cassette 20 is identical to the housing 32 and contains an identical spool 70, to which the other end of the ribbon 22 is permanently attached. When the cassette 20 is positioned on the typewriter as shown in Figure 2, the ribbon 22 emerges from the spool housing 34, passes around a guide post 72, through the ribbon guide 26 (which may be a ribbon vibrator as described for example in United States patent specification 4 204 780), around a second guide post 74 and to the spool housing 32. The spool 50 in housing 32 is driven by the drive spindle 60, as described below, to draw the ribbon 22 from the other spool 70 onto spool 32.

When the ribbon has been completely unwound from the spool 70, the cassette 20 can be lifted from its position, turned over and replaced with the positions of the spool housings 32 and 34 reversed, so that the spool 70 in housing 32 is engaged by the drive spindle 60.

A removable cover 76 fits over the cassette 20 and is held in, position by the engagement of lugs (not shown) on the cover in locating slots 82 in surface 18 and of beads 80 on the rear wall of the cover in apertures 84 in the typewriter body. The cover 76 both conceals the cassette and retains it in position on the typewriter.

The drive train from the carriage 12 to the drive spindle 60 will now be described. The carriage is mounted on a slide 86 movable on a support 88.

A rack 90 on the slide 86 engages a pinion 82 fixed to a spindle 94. The spindle is biased to rotate in one direction by means of a spring 96 acting between the spindle 94 and the body of the typewriter. The spring is wound up when the carriage 12 is moved manually from left to right, as seen in Figure 1, and unwinds to move the carriage from right to left through a preset distance each time the carriage escapement (not shown) is operated by actuation of one of the typewriter keys. The spring 96 and the carriage escapement can take any known form, for example as described in the above-mentioned United States patent specification 4 204 708.

Fixed to the lower end of spindle 94 is a drive pulley 98. A resilient belt 100, of synthetic rubber or other suitable material, connects the drive pulley 98 to a driven pulley 102 fixed to the lower end of the ribbon drive spindle 60. Above the driven pulley 102 is a pawl member 108 which is axially slidable on a boss 104 of the pulley 102.

The pawl member 108 is held against rotation by engagement of an upwardly extending portion 110 of the pawl member with a web 11 6 on the typewriter body, and is biased downwards into engagement with the drive pulley 102 by a compression spring 114 acting between the pawl member and the typewriter body. On the lower face of the pawl member are two wedge-shaped cam projections 112, which engage between the ribs 107 of the driven pulley 102. The cam projections are so shaped that when the driven pulley 102 is rotated in the direction of the arrow in Figure 6, the projections ride over the ribs 107, the pawl member 108 moving upwards. If, however, the driven pulley 102 begins to rotate in the opposite direction, the vertical faces 113 of cam projections 112 engage ribs 107 on the driven pulley to prevent its rotation.The driven pulley 102, and the ribbon drive spindle 60, can thus only rotate in one direction, which corresponds to the direction of rotation of the spool 50 which draws the ribbon 22 into the spool housing 32. The pulley 102 is driven in this driven direction by rotation of the drive pulley 98 corresponding to the movement of the carriage 12 by spring 96 from right to left as seen in Figure 1.

When the carriage 1 2 is moved in the opposite direction, the drive pulley 98 rotates but driven pulley 102 is held against rotation, the drive belt 100 slipping on the pulleys.

In operation, on actuation of a key 14 the carriage 12 moves through one step under the influence of spring 96, and the drive spindle 60 is rotated as described above to advance the ribbon 22 through one step. When the ribbon 22 has been completely unwound from spool 70, the cassette can be turned over, so that spool 70 is then driven by spindle 60 to wind the ribbon in the opposite direction. The ribbon 22 remains permanently attached to the two spools 50 and 70. When a new ribbon is needed, the cassette 20 is discarded and a fresh cassette inserted.

Claims

CLAIMS 1. A typewriter having a platen mounted in a carriage movable stepwise on the body of the typewriter, an array of keys each adapted to cause a selected printing member to strike the platen at a printing position, means for guiding a printing ribbon from a supply spool to a take-up spool past the printing position and a ribbon drive mechanism for advancing the ribbon on each stepwise movement of the carriage, in which the supply and take-up spools consist of two spools mounted in a single cassette adapted to be positioned in either of two orientations on the body of the typewriter, the ribbon extending in each orientation from one spool to the other through the printing position and one spool being at a take-up spool position on the body of the typewriter, the arrangement being such that on moving the cassette from one orientation to the other the positions of the two spools are interchanged, so that the direction of travel of the ribbon between the spools is reversed, and the ribbon drive mechanism comprises a one-way drive to the spool occupying the take-up spool position adapted to rotate the spool at that position on each stepwise movement of the carriage in a direction to cause ribbon to be drawn onto the spool. 2. A typewriter as claimed in claim 1, in which the ribbon drive mechanism comprises a drive pulley coupled to the carriage so as to rotate on each stepwise movement of the carriage, a driven pulley connected to a spindle rotatably mounted in the body of the typewriter so as to drivingly engage a spool located at the spool take-up position, and a driving belt connecting the drive and driven pulleys, New claims or amendments to claims filed on 11 March 1982. Superseded claims 1 and 2. New or amended claims: CLAIMS

1. A typewriter having a platen mounted in a carriage movable stepwise on the body of the typewriter, an array of type bars, each pivoted on the body of the typewriter so that on depression of a corresponding key of the typewriter keyboard the type bar swings upwards to strike the platen at a printing position, means for guiding a printing ribbon from a supply spool to a take-up spool past the printing position and a ribbon drive mechanism for advancing the ribbon on each stepwise movement of the carriage, in which the supply and take-up spools are mounted in a single cassette comprising two spool housings fixed to the ends of respective arms which are joined to one another by an elongate connecting piece so that the arms and elongate connecting piece define an opening through which the typebars can move without interference, the cassette being adapted to be positioned in either of two orientations on the body of the typewriter in each of which one of the spools is at a unique take-up spool position on the body of the typewriter, the arrangement being such that on moving the cassette from one orientation to the other the positions of the two spools are interchanged, and the ribbon drive mechanism comprises a one-way drive to the spool occupying the take-up spool position adpated to rotate the spool at that position in a direction to cause ribbon to be drawn onto the spool.

2. A typewriter as claimed in claim 1, in which the ribbon drive mechanism comprises a drive pulley coupled to the carriage so as to rotate on each stepwise movement of the carriage, a driven pulley connected to a spindle rotatably mounted in the body of the typewriter so as to drivingly engage a spool located at the spool take-up position, and a driving belt connecting the drive and driven pulleys.

3. A typewriter as claimed in claim 2, characterised in that a one-way clutch mechanism acting on the driven pulley allows it to be rotated in only one direction, the drive belt slipping on the pulleys when the drive pulley attempts to rotate the driven pulley in the opposite direction.

4. A typewriter constructed, arranged and adapted to operate substantially as described with reference to, and as shown in, the accompanying drawings.