US3889794A

US3889794A - Typewriter platen releasing mechanism having an elastically deformable gear disc

Info

Publication number: US3889794A
Application number: US419723A
Authority: US
Inventors: Toshikatu Terashima
Original assignee: Nakajima All Co Ltd
Current assignee: NER KK; Nakajima All Co Ltd
Priority date: 1973-04-02
Filing date: 1973-11-28
Publication date: 1975-06-17
Anticipated expiration: 1992-06-17
Also published as: JPS49138905U

Abstract

A platen releasing mechanism in a typewriter, having a single spring disc incorporated in a clutching mechanism between a platen and a platen gear. The disc has gear serrations therearound and is adapted for engagement with associated gear serrations of the platen gear. The spring disc may be caused to be elastically deformed into a dished form, away from the platen gear, for disconnecting the platen from the platen gear by means of a push button disposed in a recess of a platen knob through an interlocking member. This releases the engagement of the platen with the platen gear for free manual rotation of the former, irrespective of the engagement between the platen gear and a line changing mechanism of the typewriter. This allows relocating at a printing position a previously typewritten line of characters, which may require the correction or letter or a addition of a letter or a character.

Description

United States Patent 1 1 Terashima 1 June 17, 1975 [22] Filed: Nov. 28, 1973 [21] Appl. No; 419,723

[30] Foreign Application Priority Data Apr. 2, 1973 Japan 48-38727[U] [52] US. Cl. 197/123 [51] Int. Cl B4lj 19/80 [58] Field of Search 197/114 R, 114 A, 114 B,

[56] References Cited 7 UNITED STATES PATENTS 11/1900 Wallace 197/123 7/1910 Uhlig.... 197/123 1,749,835 3/1930 Myers r 197/123 FOREIGN PATENTS OR APPLICATIONS I.l3l,706 6/1962 Germany l97/l23 Primary Examiner-Ernest T. Wright, Jr. Attorney. Agenl, ur FirmHaseltine, Lake & Waters [57) ABSTRACT A platen releasing mechanism in a typewriter, having a single spring disc incorporated in a clutching mechanism between a platen and a platen gear. The disc has gear serrations therearound and is adapted for engagement with associated gear serrations of the platen gear. The spring disc may be caused to be elastically deformed into a dished form, away from the platen gear, for disconnecting the platen from the platen gear by means of a push button disposed in a recess of a platen knob through an interlocking member. This releases the engagement of the platen with the platen gear for free manual rotation of the former, irrespective of the engagement between the platen gear and a line changing mechanism of the typewriter. This allows relocating at a printing position a previously typewritten line of characters, which may require the correction or letter or a addition of a letter or a character.

6 Claims, 4 Drawing Figures TYPEWRITER PLATEN RELEASING MECHANISM HAVING AN ELASTICALLY DEFORMABLE GEAR DISC BACKGROUND OF THE INVENTION The present invention relates in general to a typewriter, and particularly to a platen releasing mechanism of the typewriter. More particularly, this invention is concerned with a mechanism incorporated within the platen construction for releasing the engagement of the platen with a line changing mechanism, which is designed to release the engagement of the platen to enable the latter to be manually turned free from a preset rotating advancing motion of the platen, for the correction or addition of a previously typewritten letter or a character.

In a known typewriter design, there is provided a device designed for releasing the platen from engagement with the line changing mechanism for manual angular rotation of the platen, free from a preset line changing or angular advancing motion by the line changing mechanism, thereby to enable the platen to be rotated by a desired angular advancing motion so as to accurately relocate the position of a line to be corrected or added with a letter or a charcter therein which was previously erroneously typewritten.

More specifically, a platen or a platen shaft is provided with a connecting member which is designed to be axially slidable with respect to the platen or platen shaft by means of a slot or key construction incorporated therein, and which connecting member is further provided with gear serrations on the inner circumference thereof so that the connecting member may be engaged with gear serrations of the same tooth pitch, formed on the outer circumference of a piaten gear, which is intermittently driven by the line changing mechanism, for a stepwise rotating motion in accordance with a preset degree of rotation or, in other words, the desired line interval.

Normally the platen is engaged with the line changing mechanism of the typewriter, and is intermittently rotated by the line changing mechanism through the abovementioned connecting member. When a button or the like, provided in a platen knob, is pushed or pulled so as to cause the connecting member to slide axially with respect to the platen, there occurs a disengagement between the platen gear and the connecting member incorporated within the platen, whereby the platen is allowed to be rotated manually free from the line changing mechanism.

In the case of the typewriter construction wherein the platen gear is directly installed on the platen, the platen releasing mechanism is of such construction that the connecting member, that engages the gear serrations provided on the platen gear as described above, is provided in an axially slidable manner with respect to the platen and the like by means ofa key and the like. Consequently, there might inevitably occur a relative play between the mutually engaging platen and the connecting member due to wear in the keyway or the like, thus resulting in a longitudinal deviation or staggering of a typewritten line of characters which should be properly aligned with a straight line. For preventing such an occurrence it is essential to finish the key or the keyway by high-precision machining, which results in high production costs.

This invention is particularly directed to cope with such drawbacks accompanying the conventional platen releasing mechanisms as described above.

SUMMARY OF THE INVENTION It is therefore a primary object of this invention to provide a novel and useful platen releasing mechanism having advantageous features over the conventional mechanisms such as being much simpler yet more reliable, and having a durable construction with the resultant relatively low manufacturing costs.

It is another object of this invention to provide a unique and useful platen releasing mechanism which does not require any keyway or the like in the construction thereof, that would necessitate high precision machining, and which is entirely free from play between the platen and the platen gear due to wear thereof dur ing use, thus effectively preventing deviation or staggering in the line of typewritten characters.

The foregoing and other objects, characteristics and advantages of the invention will be more fully understood from the following detailed description of a preferred embodiment thereof, when read with reference to the accompanying drawing, in which like parts are designated by like reference numerals.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a front view, partly in longitudinal section, showing a preferred, exemplary embodiment of the platen releasing mechanism according to this invention;

FIG. 2 is a perspective view, partly cut away, showing a platen arbor used in the mechanism of this invention;

FIG. 3 is a front veiw showing an example of a resilient disc, having a gear serration therearound', and

FIG. 4 is a front view of a modified example of the resilient disc, having a ring member fixed therearound.

DETAILED DESCRIPTION Referring now to FIG. 1, there is shown a conventional platen l of a typewriter, in fragmentary longitudinal section, and in the interior of one end of the platen l a boss 2 having a cylindrical sleeve 2a is press fitted.

In the interior of the sleeve 20 is inserted a sleeve-like extension 30 of a platen gear 3 to be driven by a conventional line changing mechanism of the typewriter in such a manner that it may rotate in and along the inner circumference of the sleeve 2a. A projection 2b will be described somewhat later.

On the outer circumference of the outer end of the platen gear 3, there is provided a ratchet wheel 3a for driven engagement with a driving pawl (not shown) of the line changing mechanism, while there is formed an opening (preferably, a frustoconical opening) in the free or inner end of the sleevelike extension 3c, as shown in FIG. 1. Inner gear serrations 3b are formed on the inner frusto-conical surface of the opening.

On the other hand, in the central portion of the boss 2, a platen arbor 5 is threadedly fitted at the right end thereof as viewed in FIG. 1, the platen arbor 5 having a knob 4 at the opposite or left end thereof. Projections 4a will be described further down. More specifically, the platen arbor 5 comprises an extension 6 ofa smaller diameter having screw-threads 6a thereon for threaded engagement with the boss 2, and a barrel portion 7 of a larger diameter extending outwardly from the platen 1 when installed, and there is formed a shoulder 7a between the extension 6 and the barrel portion 7.

The barrel portion 7 is provided therein with a bore 7b extending in the axial direction thereof and opening outwardly therefrom, and is further provided with a plurality of, for instance, two radial slots 7c originating from the shoulder 70 and extending in the axial direction to join with the abovementioned bore 719. The screw threads 60 are left-hand threads so that they are prevented from being loosened due to the rotation of the platen 1 during typographical operations.

On the extension 6 of the platen arbor 5, there is disposed a resilient disc 8, as shown in FIG. 3, which is made of elastic metal, for example, and has outer gear serrations 8a on the outer circumference thereof for meshing engagement with the inner gear serrations 3b on the frustoconical surface of the platen gear 3, the resilient disc 8 being rigidly clamped between the shoulder 7a and the earlienmentioned annular projection 2b, formed on the central portion of the boss 2, so that the resilient disc 8 may not be loosened relative to the boss 2 and hence the platen 1 during the operation.

There is disposed a cylindrical sleeve member 9 on the outer circumference of the barrel portion 7 of the platen arbor 5, the inner end portion thereof facing the platen l and having an enlarged diameter which is in contact with the outer marginal portion of the resilient disc 8. At the outer end (opposite to the platen side) of the abovementioned cylindrical sleeve member 9, there are provided, for instance, two arms 9a projecting radially inwardly through the respective slots 70 into the axial bore 7b in the barrel portion 7, so that the member 9 can slide relative to the arbor only in the axial direction thereof.

In the axial bore 7b of the platen arbor 5, there is inserted a core member 11 under the bias of a resilient member such as a compression coil spring 10. The inner end of the member 11 abuts the abovementioned arms 90, while the outer end of the member 11 is provided with a push button 12. The latter is set in position in a recess of the platen knob 4 in such a manner that a flanged portion 12a formed on the outer circumference of the push button 12 abuttingly engages the earlier mentioned, radially inwardly extending projections 4a on the platen knob 4, whereby the core member 11 is prevented from axially outwardly moving beyond the position shown in FIG. 1 under the bias of the spring 10. Parts 18, 18a, 18b will be described later in connec tion with FIG. 4.

The operation of the platen releasing mechanism will now be described. In the condition shown wherein the core member [1 is being urged in the outward direction or to the left as viewed in FIG. 1 under the bias of the spring 10, and wherein the flanged portion 120 of the push button 12 is kept in abutting engagement with the projections 4a of the platen knob 4, the resilient disc 8 is kept free from the pushing force of the cylindrical sleeve member 9. Therefore, meshing engagement is established between the inner gear serrations 3b on the frusto-conical surface of the platen gear 3 and the outer gear serrations 8a on the resilient disc 8.

Consequently, the platen l and the platen gear 3 may now be caused to work as an integral unit through the resilient disc 8 and the boss 2, the platen 1 being thus driven in rotation by the line changing mechanism (not shown) of the typewriter in accordance with a preset extent of rotation or anguglar advancing motion in terms of a given pitch of the ratchet wheel 3a on the platen gear 3.

In contrast, when the push button 12 is manually pushed against the bias of the spring 10 so as to move the core member 11 inwardly, the cylindrical sleeve member 9 is caused to travel axially inwardly along the platen arbor 5, toward the right as viewed in FIG. I, with the inner end (the rightmost part in FIG. 1) of the member 11 abutting the arms 9a of the member 9. By this travel of the member 9, the peripheral portion of the resilient disc 8 is caused to be deformed or warped elastically away from the serrations 3b in the inward direction of the platen 1, thereby disengaging the serrations 8a from the serrations 3b and thus permitting the platen l and the platen gear 3 to be disconnected from each other for free manual rotation.

As a consequence, when the platen knob 4 is manually turned in this state, although the platen gear 3 is still in engagement with the line changing mechanism, of the platen 1 can be rotated manually, entirely free from the line changing mechanism, and can be realigned to meet any angular position of a line of characters on the paper, which requires correction or addition of a letter or a character previously typewritten.

When the push button 12 is released, the core member 11 returns to the original position thereof as shown in FIG. 1, thus the resilient disc 8 assumes its original flat form again by its own resilience so that the engagement between the outer gear serrations 8a of the resilient disc 8 and the inner gear serrations 3b of the platen gear 3 may be restored. Consequently, the platen gear 3 is connected to the platen 1 and the latter is brought under the control of the line changing mechanism.

As an alternative example, the resilient disc 8 may be of a construction comprising a single resilient disc 18 and a ring member 18b secured to the disc 18 and having outer gear serrations 18a as illustrated in FIG. 4.

As described hereinbefore, according to the present invention, there is provided a unique and useful platen releasing mechanism which features the following advantages over conventional mechanisms. By virtue of the use of the spring disc having resilience in the axial direction of the platen, while having rigidity in the rotating direction of the platen over the entire circumference thereof, used for the engagement between the platen and the platen gear, there is no need for the provision of any key construction in the power transmitting portion between the two members as in conventional mechanisms, which would inevitably result in high production costs.

In addition, the platen releasing mechanism according to this invention features a simple yet reliable and durable construction, which in turn enables the production as well as the maintenance costs to be cut substantially.

What I claim is:

l. A releasing mechanism for a cylindrical platen of a typewriter, the typewriter further including a line changing mechanism, the releasing mechanism comprising, in combination: a boss secured in the interior of said platen at one end thereof; a platen gear rotatably and coaxially inserted in said boss and having means forming an opening with inner, first gear serrations at the axially inner end thereof, and a ratchet wheel on the outer circumference and at the axially 0pposite end thereof, for driven engagement with said line changing mechanism; a platen arbor having the axially inner end rigidly secured to a central portion of said boss. and the other end extended outwardly from said platen in the axial direction of said platen; a platen knob secured to the outer end of said arbor; a resilient. disc-shaped member rigidly mounted on said arbor and having second gear serrations on the outer circumferencc thereof for meshing engagement with said first gear serrations; a sleeve member mounted on said arbor. slidable in the axial direction of said arbor nonrotatable relative to said arbort and abutting a radially outer portion of said resilient member; and operating means axially slidably mounted in said arbor. having one end thereof in contact with said sleeve member. and the other end thereof manually pushable from out side; the manual pushing operation on said operating means causing said sleeve member to deform said resilient member in a manner that said second gear serrations move out of meshing engagement with said first gear serrations, whereby driving connection between said gear and said platen is broken.

2. The platen releasing mechanism as defined in claim 1, wherein said arbor includes a smaller diameter extension and a larger-diameter barrel portion with a shoulder formed therebetween, and wherein said extension is threadly secured to said boss, and said resilient member is rigidly clamped between said boss and said shoulder.

3. The platen releasing mechanism as defined in claim 1, wherein said opening having said first gear serrations is in the form ofa frusto-conical opening diverging toward an axially central part of said platen.

4. The platen releasing mechanism as defined in claim I, wherein said arbor has an axial bore therein and said operating means includes a core member re ceived in said bore. and further comprising a push button disposed in said knob. rigidly secured to the axially outer end of said core member.

5. The platen releasing mechanism as defined in claim 4. further comprising a spring disposed in said arbor and resiliently urging said core member in an axially outward direction, and further comprising means for limiting the axial outward movement of said core member.

6. The platen releasing mechanism as defined in claim 4, wherein said arbor has at least one axially extending radial slot joining said bore in the arbor. said sleeve member has at least one arm passed radially through said slot into said bore. and wherein said arm is in contact with the axially inner end of said core

Claims

1. A releasing mechanism for a cylindrical platen of a typewriter, the typewriter further including a line changing mechanism, the releasing mechanism comprising, in combination: a boss secured in the interior of said platen at one end thereof; a platen gear rotatably and coaxially inserted in said boss and having means forming an opening with inner, first gear serrations at the axially inner end thereof, and a ratchet wheel on the outer circumference and at the axially opposite end thereof, for driven engagement with said line changing mechanism; a platen arbor having the axially inner end rigidly secured to a central portion of said boss, and the other end extended outwardly from said platen in the axial direction of said platen; a platen knob secured to the outer end of said arbor; a resilient, disc-shaped member rigidly mounted on said arbor and having second gear serrations on the outer circumference thereof for meshing engagement with said first gear serrations; a sleeve member mounted on said arbor, slidable in the axial direction of said arbor, non-rotatable relative to said arbor, and abutting a radially outer portion of said resilient member; and operating means axially slidably mounted in said arbor, having one end thereof in contact with said sleeve member, and the other end thereof manually pushable from outside; the manual pushing operation on said operating means causing said sleeve member to deform said resilient Member in a manner that said second gear serrations move out of meshing engagement with said first gear serrations, whereby driving connection between said gear and said platen is broken.

2. The platen releasing mechanism as defined in claim 1, wherein said arbor includes a smaller-diameter extension and a larger-diameter barrel portion with a shoulder formed therebetween, and wherein said extension is threadly secured to said boss, and said resilient member is rigidly clamped between said boss and said shoulder.

3. The platen releasing mechanism as defined in claim 1, wherein said opening having said first gear serrations is in the form of a frusto-conical opening diverging toward an axially central part of said platen.

4. The platen releasing mechanism as defined in claim 1, wherein said arbor has an axial bore therein and said operating means includes a core member received in said bore, and further comprising a push button disposed in said knob, rigidly secured to the axially outer end of said core member.

5. The platen releasing mechanism as defined in claim 4, further comprising a spring disposed in said arbor and resiliently urging said core member in an axially outward direction, and further comprising means for limiting the axial outward movement of said core member.

6. The platen releasing mechanism as defined in claim 4, wherein said arbor has at least one axially extending radial slot joining said bore in the arbor, said sleeve member has at least one arm passed radially through said slot into said bore, and wherein said arm is in contact with the axially inner end of said core member.