GB2296896A - A typewriter having a resilient mechanism so as to return a bail to an initial position on release of a key - Google Patents

Abstract

A typewriter having a platen (6), an array of type bars (12), an array of keys (18) each connected to one of the type bars (12) by a respective tension element (16) so that depression of the key (18) exerts a tensile force on the tension element (16) to pivot the associated type bar (12) from a lowered position to a raised position (see Fig.3), so as to cause a type head (36) on the type bar (12) to strike the platen (6) of the typewriter, and a movable bail (40) one face of which is engaged by a cam face (38) on each of the type bars (12) so that pivotal movement of any of the type bars (12) from a lowered position to a raised position (see Fig.3) causes movement of the bail (40) from a first position to a second portion, thereby to actuate a mechanism for stepwise movement of the platen (6), characterised in that a resilient mechanism (e.g. a spring (60)) acts directly between the body (2) of the typewriter and the bail (40) so as to exert a force on the bail (40) to return the bail (40) to its first position on release of the key (18).

Description

Typewriter This invention relates to typewriters.

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

The invention is concerned particularly with typewriters of the kind having a platen, an array of type bars, each pivoted for movement between a lowered position and a raised position, an array of keys each connected to one of the type bars by a respective tension element so that depression of the key exerts a tensile force on the tension element to pivot the associated type bar from its lowered position to its raised position, to cause a type head on the type bar to strike the platen of the typewriter, and a movable bail one face of which is engaged by a cam face on each of the type bars so that pivotal movement of any of the type bars from its lowered to its raised position causes movement of the bail from a first to a second position, thereby to actuate a mechanism for stepwise movement of the platen.

A typewriter of this kind is described in United Kingdom patents 1591986 and 1591987.

A problem with such typewriters is that after a key is struck the associated type bar may not return to its lowered position, particularly if the weight of the type bar is relied upon to return the type bar and key to their initial positions. In the typewriter of United Kingdom patent 1 591 986, this problem is solved by means of a return spring mechanism having a separate spring arm acting on each tension element to provide a return force on the associated type bar and key. A disadvantage of this mechanism is that it is difficult to fit the tension elements to the spring arms during assembly of the typewriter.

It is an object of this invention to provide a typewriter with an improved return spring mechanism.

This invention consists in a typewriter of the kind referred to, in which a resilient mechanism acts directly between the body of the typewriter and the bail so as to exert a force on the bail to return it to its first position on release of the key.

Preferably, the resilient mechanism comprises a spring acting between the bail and the body of the typewriter.

Suitably, the spring is a leaf spring fixed at one end to the body of the typewriter and bearing at its free end on the face of the bail opposite the face engaged by the type bars.

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 toy typewriter incorporating the invention, Figure 2 is a fragmentary view, partly in section, showing a key, type bar and associated mechanisms of the typewriter, with the type bar in its rest position, Figure 3 is a view similar to that of Figure 2, but showing the type bar in its raised position as the type head strikes the platen, Figure 4 is a perspective view from the rear of the segment, the bail and part of the type bar array of the typewriter, and Figure 5 is an exploded view of the segment, the bail and a type bar of the typewriter.

Referring to the drawings, the typewriter comprises a body 2, a carriage 4 movable on the body and including a platen 6, a type bar assembly 8 and a keyboard 10.

The type bar assembly 8 comprises a series of type bars 12 each pivotally mounted on a segment 14 and connected by a flexible actuating string 16 to an associated key 18 of the keyboard 10. Each type bar 12 is formed near its inner end with a V-shaped recess 20 which receives a bead 22 on the segment 14, the bead 22 acting as a fulcrum on which the type bar 12 pivots.

The type bar pivots between a lowered, rest position, shown in Figure 2, in which the inner end 24 of the type bar 12 engages a stop 26 formed on the segment 14, and a raised position, shown in Figure 3. At its inner end the type bar 12 is shaped to form a hook portion 28 to which is attached one end of the actuating string 16. The actuating string 16 passes through a guide slot 30 in the typewriter body 2, into a bore 32 in which the shank 34 of the associated key 18 moves, and is attached at its other end to the shank 34. The actuating string and its attachment to the key may be as described in the abovementioned United Kingdom patent 1 591 986. A type head 36 is moulded onto the outer end of each type bar 12. The edge of type bar 12 opposite the recess 20 forms a cam face 38 which engages a bail 40, as described below.

The segment 14 is a plastics moulding formed on one side with ribs 42 defining guide channels for the type bars 12. Slots 44 in the lower part of the segment allow the cam portions 38 of the type bars 12 to project through the segment to engage the front face of the bail 40. A type bar guide 46 is fixed to the upper part of the segment to guide the final movement of each type bar 12 as it strikes the platen 6. On its rear side the segment 14 is formed with an arcuate recess 48 to receive the bail 40. The bail 40, which is in the form of a flat steel plate, fits relatively loosely in the recess 48, the lower edge 50 of the bail resting on spaced ribs 52 on the lower wall of the recess. Two locating pins 54 projecting from the rear face of the segment 14 engage loosely in holes 56 in the bail 40.An escapement release lever 66 engages the rear face of the bail 40 through part of a leaf spring 60, as described below. Operation of any of the type bars 12 causes the bail to pivot about its lower edge 50, thereby to push rearwards the escapement release lever 66. Movement of the escapement release lever effects operation of the carriage escapement and associated mechanisms. The mechanisms may, for example, be as described in United Kingdom patent 1591987, in which the escapement release lever directly engages the bail. The escapement release lever is itself springbiassed to return to its initial position when the type bar moves back to its rest position, but the force exerted by the escapement release lever on the bail in the typewriter described in patent 1591987 is insufficient to move the bail and the type bar if the type bar gets stuck in its raised position.

To deal with this problem, in the typewriter of this invention, a return spring 60 acts on the rear face of the bail 40. The spring 60 is a leaf spring, fixed at its lower end to the segment 14, by means of a self-tapping screw 62 extending through a hole 64 in the spring. The upper end of the spring engages a tongue 58 pressed out of the bail 40. The spring 60 is shaped so that it bears against the bail 40, exerting a resilient force on the bail.

In operation, when a key 18 is struck, the end of the associated actuating string 16 is pulled downwards into the bore 32, exerting a tension on the string which causes the associated type bar 12 to pivot about the fulcrum 22 and the type head 36 to strike the platen 6. Engagement of the cam face 38 of the type bar 12 with the bail 40 causes the bail to pivot as described above and to move the escapement release lever 66. On release of the key 18, the force of the return spring 60 acting on the rear face of the bail 40 causes the bail to pivot, exerting a force on the type bar 12 through engagement of the bail with the cam face 38. This ensures that the type bar pivots away from the platen 6 and the type bar guide 46, whereupon the type bar returns to its rest position under its own weight and the force of the return spring 60. The tension exerted on the actuating string 16 by the type bar acts to lift the key 18 to its initial position.

Claims (3)

Claims:

1. A typewriter having a platen, an array of type bars, each pivoted for movement between a lowered position and a raised position, an array of keys each connected to one of the type bars by a respective tension element so that depression of the key exerts a tensile force on the tension element to pivot the associated type bar from its lowered position to its raised position, to cause a type head on the type bar to strike the platen of the typewriter, and a movable bail one face of which is engaged by a cam face on each of the type bars so that pivotal movement of any of the type bars from its lowered to its raised position causes movement of the bail from a first to a second position, thereby to actuate a mechanism for stepwise movement of the platen, characterised in that a resilient mechanism acts directly between the body of the typewriter and the bail so as to exert a force on the bail to return it to its first position on release of the key.

2. A typewriter as claimed in claim 1, in which the resilient mechanism comprises a spring acting between the bail and the body of the typewriter.

3. A typewriter as claimed in claim 2, in which the spring is a leaf spring fixed at one end to the body of the typewriter and bearing at its free end on the face of the bail opposite the face engaged by the type bars.