Daisy-wheel typewriter

Abstract

 A typewriter of the kind having a rotatable type carrier (30) comprising flexible radial fingers (34) each having a printing element (38) at its duter end, drive means for positioning the type carrier (30) on depression of a character key so that the corresponding printing element is at a printing position, and a hammer (55) operable to strike the printing element at the printing position. The drive means for the type carrier (30) comprises a mechanical coupling between the type carrier (30) and each character key (54) of the typewriter operable on depression of the key to rotate the type carrier (30) from an initial ppsition, an array of stops (60), each corresponding to one of the printing elements (38) and each coupled to the corresponding key (54) so that on depression of the key the stop (60) is moved from a retracted position, in which the stop (60) is clear of the type carrier (30) during its rotation, to a projected position in which the stop (60) is in the path of an abutment (41 or 43) on the type carrier (30), engagement of the abutment with the stop causing the type carrier (30) to be arrested with the printing element (38) corresponding to the key (54) at the printing position, the coupling between each key (54) and the type carrier (30) being resilient to enable the key to continue its travel after engagement of the abutment (41 or 43) with the stop (60). The use of mechanical couplings to rotate the type carrier and stop it at the correct position avoids the need for an electric drive motor and complex control arrangements. The hammer may also be coupled to the keys, so that the typewriter can be made purely mechanical.

Description

[0001] This invention relates to typewriters.

[0002] More particularly, the invention relates to typewriters of the kind having a rotatable type carrier comprising flexible radial fingers each having a printing element at its outer end, drive means for rotating the type carrier and operable on depression of a selected key of the typewriter to move the type carrier to a position in which the printing element associated with the selected key is at a printing position, and a hammer operable to strike the printing element at the printing position to move it into engagement with a platen.

[0003] Known typewriters of this kind usually employ an electric motor, such as a stepping motor, to drive the type carrier, the motor rotating through the appropriate angle, under the control of an electronic circuit, so as to move the type carrier to the position corresponding to the particular key depressed. Such drive means are relatively expensive, and the typewriters also have the disadvantage that they require an electric power source, in the form of a mains supply or batteries. Examples of such typewriters are shown in British patent specifications 1 188 637, 1 514 272, 1 602 670 and 1 604 578, and United States patent specifications 3 677 386 and 3 677 387.

[0004] British patent specification 1 584 136 (corresponding to United States patent 4 198 169) describes a daisy-wheel typewriter in which the type carrier is rotated by an electric motor through a slipping clutch, and on depression of a key is stopped in the position corresponding to that key by engagement of a pin on the type carrier mounting plate with a retractable stop corresponding to that key. The stops, one for each character, are mounted on a plate and are moved by levers pivoted on a segment and each connected to the corresponding key by a wire. The stops are not directly connected to the levers so that a separate mechanism is required to re-set the stops after each key depression. This typewriter also suffers from the disadvantage that a power supply is required for the electric motor.

[0005] It is an object of this invention to provide a typewriter of the kind referred to above which does not require complex electronic control circuits.

[0006] This invention consists in a typewriter of the kind referred to, in which the drive means for the type carrier comprises a mechanical coupling between the type carrier and each character key of the typewriter operable on depression of the key to rotate the type carrier from an initial position, an array of stops, each corresponding to one of the printing elements and each coupled to the corresponding key so that on depression of the key the stop is moved from a retracted position, in which the stop is clear of the type carrier during its rotation, to a projected position in which the stop is in the path of an abutment on the type carrier, engagement of the abutment with the stop causing the type carrier to be arrested with the printing element corresponding to the key at the printing position, the coupling between each key and the type carrier being resilient to enable the key to continue its travel after engagement of the abutment with the stop.

[0007] Suitably, the fingers on the type carrier are arranged in two groups, and depression of a key corresponding to a printing element on a finger in one group causes the type carrier to rotate in one direction from the initial position to bring the printing element to the printing position whilst depression of a key corresponding to a printing element on a finger in the other group causes the type carrier to rotate in the opposite direction from the initial position to bring the corresponding printing element to the printing position.

[0008] In a preferred form of the invention, the coupling between the type carrier and each character key comprises at least one flexible tension element connected to the type carrier and to a coupling mechanism arranged so that depression of a character key actuates the coupling mechanism to apply tension in one direction or the other to the flexible element thereby to rotate the type carrier. The flexible tension element may be an element, such as a wire, passing round a pulley connected to the type carrier and extending from the pulley to the coupling mechanism.

[0009] In one form of the invention, the coupling mechanism includes two coupling memebers, each connected to the keys of a respective one of the said two groups, so that depression of a key effects movement of the associated coupling member to rotate the type carrier in the corresponding direction. Preferably, the mechanism further comprises a third member to which the two ends of the flexible element are connected, the third member being resiliently biased into engagement with both coupling members and arranged so that movement of a coupling member in response to depression of a key effects rotation of the third member in a corresponding direction thereby to effect rotation of the type carrier, the resilient biasing of the third member allowing continued movement of the coupling member and third - member after rotation of the type carrier has been arrested. The third member may be pivotally mounted on a pivot which is movable in the general direction of movement of the two coupling members, and the third member is resiliently biased by at least one spring acting between the third member and the body of the typewriter.

[0010] Preferably, each stop is coupled to the corresponding key by an elongate flexible element, depression of the key applying tension to the element to move the stop to its projected position, and spring means are provided to return the stop to its retracted position on release of the key. The stops may be slidable in an array of slots formed in a segment on which the type carrier is mounted.

[0011] Each finger of the type carrier may have more than one printing element, spaced radially from one another, for example two elements corresponding to upper-case and lower-case characters for each key. The segment on which the type carrier is mounted may then be movable vertically between positions corresponding to each of the printing elements, on actuation of one or more shift keys of the typewriter.

[0012] The hammer may be operated by a mechanism mechanically coupled to the keys, so that all the operations required to print a character are effected mechanically by depression of a key, without the need for any power source. Suitable mechanisms of well-known form may be provided for indexing the carrier after, each printing stroke.

[0013] The invention also includes a typewriter of the kind referred to in which the drive means for the type carrier comprises means for rotating the type carrier, an array of stops, each corresponding to one of the printing elements and each movable from a retracted position, in which the stop is clear of the type carrier during its rotation, to a projected position in which the stop is in the path of an abutment on the type carrier, engagement of the abutment with the stop causing the type carrier to be arrested with the printing element corresponding to the key at the printing position, each stop being connected to one end of an elongate element the other end of which is connected to a corresponding key so that on depression of the key the stop is moved to the projected position, and restoring spring means acting on each elongate element to move the stop back to the retracted position on release of the key.

[0014] The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:-

Figure 1 is a cross-section through a typewriter in accordance with the invention,

Figure 2 is a view similar to that of Figure 1, but showing the position of certain components on depression of a key, ,

Figure 3 is a section on line III-III of Figure 1, and

Figure 4 is a plan view of the printing mechanism of the typewriter, with some components omitted,

Figures 5 and 6 are plan views similar to Figure 4, but showing the position of components when keys are depressed to rotate the type carrier,

Figure 7 is a perspective view of the hammer of the typewriter, and

Figure 8 shows the hammer in the actuated position.

[0015] Referring to the drawings, a typewriter comprises a body 10 on which is mounted a keyboard 12, a carriage 14 and a printing mechanism including a rotatable type carrier 30. The carriage 14 has a rotatable cylindrical platen 16, and a printing ribbon 18 passes between the platen 16 and the type carrier 30 at a printing position. Suitable mechanisms, which may be of well-known form, are provided for effecting movement of the carriage 14 and feeding the ribbon 18.

[0016] The type carrier 30 consists of a hub 32 from which extend a number of resiliently flexible radial fingers 34. Each finger 34 has at its free end a head 36 formed with two radially spaced printing elements 38. Also extending from the hub are two rigid arms 40 and 42, positioned almost diametrically opposite one another. The fingers 34 are arranged between the arms 40 and 42, in two groups 44 and 46, each containing twenty fingers. The type carrier is mounted in a segment 50 for rotation about an axis 52 so that the head 36 of each finger 34 can be moved to the printing position between the platen and a printing hammer 53. As described below, the segment 50 is itself movable between upper and lower positions, in each of which a respective one of the two printing elements 38 on the head 36 of a finger 34 is positioned so that actuation of the hammer causes that printing element to be moved into engagement with the platen 16.

[0017] Each finger 34 of the type carrier 30 is associated with a respective one of the character keys 54 of the typewriter keyboard 12. On depression of a key 54 the type carrier is rotated to bring the associated finger 34 to the printing position, by a mechanism which will now be described.

[0018] The lower part of the segment 50 is formed with a number of rectangular apertures 58 arranged along an arc of a circle centred on the axis of rotation of the type carrier 30. Each aperture 58 accommodates a retractable stop 60 which is coupled by a flexible element 62 to a respective one of the keys 54, as described below, so as to be movable between a retracted position (Figure 1) and a projected position (Figure 2). each stop 60 corresponds to one of the fingers 34 of the type carrier, and accordingly the apertures 58 are arranged in two groups 64 and 66 corresponding to the two groups 44 and 46 of fingers. The apertures in the group 64, on the right-hand side of the segment as seen in Figure 3, are positioned so that, when the type-carrier is rotated in the clockwise direction from its central position as shown in Figure 3, the right-hand arm 42 of the type carrier moves over the apertures until an abutment face 43 on the arm 42 meets a stop 60 in the projected position. The angular relationship between the apertures 58, face 43 and fingers 34 is such that when the face 43 is in engagement with one of the stops 60, the corresponding finger 34 in the group 44 (on the left-hand.side as seen in Figure 3) is at the printing position. The apertures 58 in the group 66 on the left-hand side as seen- in Figure 3 are similarly arranged so that when the type carrier 30 is rotated anticlockwise as seen in Figure 3, the left hand arm 40 of the type carrier moves over the apertures until an abutment face 41 on the arm engages a projected stop 60, at which point the corresponding finger 34 of the group 46 of fingers (on the right as seen in Figure 3) is at the printing position.

[0019] Each stop 60 is of rectangular cross-section so as to slide in the corresponding aperture 58, and is joined to the flexible element 62 by a portion 61 which extends from the lower part of the stop so that the arm 40 or 42 does not engage the portion 66 when the stop 60 is in the retracted position.

[0020] Each flexible element 62 extends from one of the stops 60 to the corresponding key 54. Each key 54 has a shank 68 which protrudes through a rectangular hole 70 formed in the body 10 of the typewriter and is carried on a lever 69 pivoted at 103 to the body 10, and the flexible element 62 is trained over an edge of the hole 70 and is secured at its end to the shank 68 so that on depression of the key 54 the flexible element is drawn back, to move the stop 60 to the projected position, as shown in Figure 2. To return the stop 60 and the key 54 after release of the key, a separate return spring 72 is provided for each flexible element 62. Each spring 72 comprises a strip of resiliently flexible plastics fixed at one end to the body of the typewriter and formed at its free end with a hole or slot through which the flexible element 62 passes. The portion 74 of the element 72 extending from the stop 60 to the spring 62 is sufficiently rigid to ensure that the stop 60 is moved to its retracted position when the spring 72 moves the element 62. The remaining portion 76 of the flexible element 62 which extends from the spring 72 to the key 54 is thinner and more flexible, and the junction between the two portions forms a shoulder which engages the spring 72. The flexible element 62 may be formed from plastics and may be connected to the key 54 in the manner described in British patent specification No. 1 591 986.

[0021] The mechanism for effecting rotation of the type carrier 30 on depression of a key 54 will now be described. Fixed to the type carrier 30 is a pulley 80 rotatable about the same axis as the type carrier. A wire 82 passes round the pulley 80 and extends horizontally in opposite directions from the pulley. The part of the wire 82 extending to the left as seen in Figure 3 is trained around an idler pulley 84, from which it extends forwards to an idler pulley 85 and then laterally to a quadrant plate 110. The wire is secured at 112 to the plate 110 and then extends further to an idler pulley 91, from where it extends rearwards to a tension spring 92, to which the wire is fixed. The part of the wire 82 extending to the right in Figure 3 is trained around an idler pulley 90 and is fixed to the other end of spring 92.

[0022] The quadrant plate 110, which is generally triangular in shape, is pivotally mounted, for rotation about a vertical axis, on one end 122 of a rod 120. The rod 120 extends laterally and is pivotally mounted at its other end 124 on the body of the typewriter for rotation about a vertical axis, the end 122, and the quadrant plate 110, is free to move forwards and backwards to a limited extent. The plate 110 is biased rearwards, i.e. towards the platen 16, by a tension spring 126 connected at one end to the plate, near the pivot 122, and at its other end to the body of the typewriter. The quadrant plate 110 is formed, at the base of the triangle, with projections 114 and 116, spaced one on each side of and somewhat to the rear of the pivot 122. The projections 114 and 116 engage respective coupling members 88 and 94, and are normally held in contact with the coupling members by the spring 126.

[0023] The coupling member 88 comprises a rigid plate positioned between the keyboard 12 and the springs 72 acting on the flexible elements 62 connected to the left-hand group 66 of stops 60. The coupling member 88 has a series of holes 96 through which the flexible elements 62 pass. The coupling member is pivoted on the body 10 of the typewriter for rotation about a horizontal axis 98, and is normally held by the tension of the springs 126, acting through quadrant plate 110, in engagement with the springs 72, as shown in Figure 1. On depression of any of the keys 54 corresponding to the left hand group 44 of type fingers 34, for example key 54', the movement of the corresponding flexible element 62 and spring 72 causes the coupling member 88 to pivot to the position shown in Figures 2 and 5. This causes the quadrant plate 110 to rotate about the pivot 122 to the position shown in Figure 5, the other coupling member 94 remaining substantially stationary during this movement. Since the point 112 of attachment of the wire 82 to the plate 110 is spaced forwardly from the pivot 122, this point moves to the right, as seen in Figure 5, on rotation of the plate. The tension thus applied to the wire 82 causes the pulley 80 and type carrier 30 to rotate in the anticlockwise direction as seen in Figure 5. Rotation of the type carrier 30 continues until the abutment 41 of the type carrier engages the stop 60' corresponding to the depressed key 54'. The point 112 of the plate 110 is then prevented by the wire 82 from further lateral movement. Continued depression of the key 54' to its fully depressed position is accommodated by movement of the quadrant plate 110 away from the other coupling member 94 against the tension of the spring 126, the pivot 122 moving forwards as the rod 120 rotates about its own pivot 124. The forward movement of the point 112 of attachment of the wire 82 to the quadrant plate 110 is accommodated by extension of the spring 92, which also acts to maintain the tension in the wire 82.

[0024] The second coupling member 94 is similarly pivoted about an axis 100 collinear with the axis 98, and has holes or slots 102 through which pass the flexible elements 62 connected to the right-hand group 64 of stops 60. The coupling member 94 normally rests against the corresponding springs 72, but is pivoted on depression of a corresponding key 54" to cause the plate 110 to rotate in the direction shown in Figure 6. The point of attachment 112 is moved to the left, causing the wire 82 to rotate the type carrier 30 in the clockwise direction until the abutment 43 engages the corresponding stop 60", further movement of the key 54" and the coupling member 94 being accommodated by forward movement of the plate 110 and by extension of the helical springs 126 and 92.

[0025] The hammer 55 is carried on a shank 130 which is pivoted on a horizontal shaft 132. The shank 130 is connected to the quadrant . plate 110 by a wire 134 connected at one end to a point on the shank below the shaft 132 and at its other end to the plate 110. Forward movement of the plate 110 on depression of a key 54 carries the shank to pivot from the position shown in Figure 7 to that shown in Figure 8, so that the hammer strikes a finger at 34 at the printing position.

[0026] A suitable mechanism is also provided to index the carriage after each stroke. This mechanism may also be connected to the quadrant plate 110 so as to be actuated by movement of the coupling member 88 or 94. Various carriage indexing mechanisms will be well known to those skilled in the art.

[0027] The segment 50 on which the type carrier 30 is mounted is movable up and down in a mounting 140 fixed to the body of the typewriter. The segment 50 is movable between two positions, in each of which a corresponding one of the printing elements 38 on a finger 34 is aligned with the hammer 54. Movement of the segment is effected by means of one or more shift keys (not shown) connected by a suitable mechanism to the segment. The mechanism may take any of several forms well known to those skilled in the art.

[0028] In operation of the typewriter, depression of a key 54 causes the type carrier 30 to rotate in one or another direction, as described, until the abutment 41 or 43 engages the corresponding stop 60. Depression of the key causes the hammer 55 to be actuated, to print a character on paper on the platen,16. On release of the key, the corresponding spring 72 returns the key to its upper position and the stop 60 to its retracted position. The helical spring 126 returns the quadrant plate 110 and the coupling member 88 or 94 to their initial positions, and so returns the type carrier 30 to its initial position.

[0029] The springs 126 and 92 act not only to accommodate movement of the keys 54, irrespective of the angle through which the type carrier 30 must rotate, but also apply a continuing force on the type carrier to hold it positively against the stop 60 until the key 54 is released, thus ensuring that the corresponding finger of the type carrier 30 is held in the printing position during the printing stroke of the hammer.

[0030] The described embodiment of the invention thus provides a typewriter which is simple in construction yet enables a full range of characters to be typed. The typewriter can therefore be manufactured relatively inexpensively, and can for example be provided as a toy typewriter for children.

[0031] It will be appreciated that many modifications could be made in the described embodiments. For example, other hammer mechanisms could be used. The mechanical connection between the keys and the type carrier could take other forms.

Claims

1. A typewriter having a rotatable type carrier comprising flexible radial fingers each having a printing element at its outer end, drive means for rotating the type carrier and operable on depression of a selected key of the typewriter to move the type carrier to a position in which the printing element associated with the selected key is at a printing position, and a hammer operable to strike the printing element at the printing position to move it into engagement with a platen, characterised in that the drive means for the type carrier comprises a mechanical coupling between the type carrier and each character key of the typewriter operable on depression of the key to rotate the type carrier from an initial position, an array of stops, each corresponding to one of the printing elements and each coupled to the corresponding key so that on depression of the key the stop is moved from a retracted position, in which the stop is clear of the type carrier during its rotation, to a projected position in which the stop is in the path of an abutment on the type carrier, engagement of the abutment with the stop causing the type carrier to be arrested with the printing element corresponding to the key at the printing position, the coupling between each key and the type carrier being resilient to enable the key to continue its travel after engagement of the abutment with the stop.

2. A typewriter as claimed in claim 1, characterised in that the fingers on the type carrier are arranged in two groups, and depression of a key corresponding to a printing element on a finger in one group causes the type carrier to rotate in one direction from the initial position to bring the printing element to the printing position whilst depression of a key corresponding to a printing element on a finger in the other group causes the type carrier to rotate in the opposite direction from the initial position to bring the corresponding printing element to the printing position.

₃. A typewriter as claimed in claim 2, characterised in that the coupling between the keys and the type carrier includes two coupling members, each connected to the keys of a respective one of the said two groups, so that depression of a key effects movement of the associated coupling member to rotate the type carrier in the corresponding direction.

4. A typewriter as claimed in claim 3, characterised in that the coupling further comprises a third member connected to the type carrier, the third member being resiliently biased into engagement with both coupling members and arranged so that movement of a coupling member in response to depression of a key effects rotation of the third member in a corresponding direction thereby to effect rotation of the type carrier, the resilient biasing of the third member allowing continued movement of the coupling member and third member after rotation of the type carrier has been arrested.

5. A typewriter as claimed in claim 4, characterised in that the third member is pivotally mounted on a pivot which is movable in the general direction of movement of the two coupling members, and the third member is resiliently biased by at least one spring acting between the third member and the body of the typewriter.

6. A typewriter as claimed in any one of claims 3 to 5, characterised in that each stop is coupled to the corresponding key by an elongate flexible element, depression of the key applying tension to the element to move the stop to its projected position, and each flexible element has an abutment which engages the corresponding one of the said coupling members thereby to move the coupling member and rotate the type carrier on depression of the key.

7. A typewriter as claimed in any preceding claim, characterised in that the coupling between the type carrier and each character key includes at least one flexible tension element connected to the type carrier so that depression of a character key actuates the coupling mechanism to apply tension in one direction or the other to the flexible element thereby to rotate the type carrier.

8. A typewriter as claimed in any preceding claim, characterised in that the hammer is operable by means of a mechanism mechanically coupled to the character keys so as to be actuated on depression of any one of the keys.

9. A typewriter as claimed in any preceding claim, characterised in that each finger of the type carrier has more than one printing element, radially spaced from one another, and the type carrier and stop assembly, or the platen and hammer, are movable vertically between shift positions corresponding to the printing elements on each finger.

10. A typewriter having a rotatable type carrier comprising flexible radial fingers each having a printing element at its outer end, drive means for rotating the type carrier and operable on depression of a selected key of the typewriter to move the type carrier to a position in which the printing element associated with the selected key is at a printing position, and a hammer operable to strike the printing element at the printing position to move it into engagement with a platen, in which the drive means for the type carrier disc comprises means for rotating the type carrier, an array of stops, each corresponding to one of the printing elements and each movable from a retracted position, in which the stop is clear of the type carrier during its rotation, to a projected position in which the stop is in the path of an abutment on the type carrier, engagement of the abutment with the stop causing the type carrier to be arrested with the printing element corresponding to the key at the printing position, each stop being connected to one end of an elongate element the other end of which is connected to a corresponding key so that on depression of the key the stop is moved to the projected position, and restoring spring means acting on each elongate element to move the stop back to the retracted position on release of the key.

11. A typewriter as claimed in claim 10, characterised in that the stops are slidable in an array of slots formed in a segment on which the type carrier is mounted.

Drawing