US2879877A

US2879877A - Automatic cut off device

Info

Publication number: US2879877A
Application number: US478716A
Authority: US
Inventors: Stig B Tibbling
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1954-12-30
Filing date: 1954-12-30
Publication date: 1959-03-31
Anticipated expiration: 1976-03-31
Also published as: CH335700A; FR1143287A; DE1085175B; NL92126C; BE544050A; GB816830A

Description

March 31, 1959 s.B`.1-|BBL1NG AUTOMATIC CUT oFF DEVICE Filed Dec. so, 1954 United States Patent O national Business Machines Corporation, New York, N.Y., a corporation of New York Application December 30, 1954, Serial No. 478,716 '7 clama. (cl. 191-17) This invention relates to typewriters and more particularly to an automaticpower cut off device for an electricallyoperatcd typewriter.

In a conventional embodiment, the typewriter has an electric motor operable under switch control to drive a power driving mechanism for the individual type bars in the typewriter. Modern machines are built so that the motor runs so quietly as not to be detected, and accordingly, it sometimes happens that the motor is unintentionally* left on for prolonged periods.

Accordingly, it is a. first object of this invention to provide an improved automatic cut olf device for the electric motor of apower operated typewriter.

It is a further object of this invention to provide an improved automatic cut off device for power operated typewriters which is automatically resettable to its inoperative position.'

It is a further object of this invention to provide an improved automatic cut oi device for a power operated typewriter which is simple in construction and efficient 1n use.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the accompanyingdrawings, which disclose,by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 isa perspective view of some of the component parts of a power driven typewriter;

Fig. 2 is a section view taken along the plane 2-2 of Fig. 1 in the direction of the arrows;

Fig. 3 is an exploded view of the cut off device shown in Fig. 2. v

Briefly, this invention relates to an. automatic cut oil device mounted in a bracket that isV pivotally supported on the typewriter for engagement with a continuously driven power roll. A drivingwheel, an operating cam, and a climbing wheel are coaxially mounted in the bracket for engagement with the continuously operated power roll. If the machine is left unattended for a predetermined period, the climbing wheel will frictionally engage the operating cam which will act to cut olf the power to the electric motor. The climbing wheel is resettable to its rest position upon operation of selected ones of the functioning device of the typewriter.

Referring to the drawings, a power roll 2 is represented as being continuously rotated in the direction of the arrow under the control of an electric motor which is not shown. The electric motor is represented as being operable under the control of an electricswitch 4 having oli and on position and shown in the o position in Fig. l. The switch 4 is conventionally operated by a link system 6 which is actuated under the control of a switch arm 8 pivotally mounted on a pin 10 supported by the typewriter frame 12. If the switch arm 8 is rotated clockwise as viewed in Fig. 1, the arm 14 of the switch v 21,879,877 Patented Mar. 31, `1959 4 will be moved to the dotted line position, thereby en-v ergizing the electric motor.

The improved cut oit device is shown as comprising ra bracket 16, a driving wheel 18, a power cam 20, a climbing wheel 22, and associated mechanisms for holding the parts in assembled relation.

The cut off device is shown pivotally .mounted byy a.

pin or shaft-28 passing through apertures 30 in bracket 16, and mounted in the typewriter frame in such a manner that the driving wheel 18 and the climbing wheel 22 are swingable into and out of peripheral engagement with the continuously rotating power roll 2. A spring 32 biases the bracket normally counterclockwise about pivot 28 to maintain contact of both the driving wheel 18and the climbing wheel 22 with the continuously rotated power roll 2.

The driving wheel 18 has integrally therewith a shaft 34, loosely mounted about a supporting pin 36. A threaded bushing 24 is frictionally or force fitted on the shaft 34 for rotation therewith. The threaded bushing serves the dual function of positioning the cam 20 adjacent the driving wheel, and acting as a screw for loosely accommodating an internally threaded bore 37 of the climbing wheel 22. A More specically, as the climbing wheel 22 is rotated counterclockwise, in Fig. 3, relative to the threaded bushing 24, the climbing wheel will move to the right towards the driving wheel 18.

The cam element 20 is loosely mounted about the drive shaft 34 and is supported by

bushings

38, 40 so that the drive shaft 34 may rotate within its central bore 42, while the cam 20 is held in a rest position (Fig. l). The peripheral surface of cam 20 comprises a serrated surface 44 and a reduced surface 46. The latter surface is normally positioned so as to be slightly spaced peripherally from the continuously rotating power roll 2. However, if the `power cam 2t) is rotated slightly counterclockwise from its position shown in Fig. 1 and Fig. 3, the smallest radius of the serrated surface 44 will engage the power roll, thereby establishing a driving relation between the power roll and cam sending the latter through a liip cycle wherein the serrated surfaceof cam 20 will run in peripheral contact with the power roll 2 until after the point of maximum radius of serrated surface 44 has left the power roll, whereupon the power cam 20 will continue on its own momentum until it has reached-its rest position.

The latter position is determined by a spring wire 49 which is positioned for tangential engagement with a corresponding iiat surface 51 on the hub of the power cam 20. The spring wire 49 holds cam 20 from rotating while t shaft 34 rotates through its center.

It has been mentioned that the climbing wheel 22 is loosely mounted on the threaded bushing 24, which construction provides-for the gradual moving of the climbing wheel 22 to the right as viewed in Fig. 3, as the climbing wheel rotates counterclockwise relative to the threaded bushing 24, while the loose construction (i.e. the bore 37 being greater than the diameter of bushing 24) permits an axial movement of the climbing wheel 22 relative to the threaded bushing 24 when the climbing wheel 22 has been disengaged from the power roll. More specifically, the climbing relationship between climbing wheel 22 and threaded bushing 24 exists only when a radial pressure is applied between the climbing wheel and the threaded bushing, for example, when the -climbing wheel is in engagement with the power roll. The relative axial movement can take place when this radial pressure is relieved as by disengaging the driving wheel from the power roll. In order to elect this axial displacement, a spring 26 is axially interpositioned between the climbing wheel 22 and the power cam 20. With this arrangement of parts, every time the climbing wheel 22 is removed from the power roll, the spring 26 will act to move the climbing wheel to the left as viewed in Fig. 3, to its rest position. In a specific embodiment the threaded bushing 24 is a spirally wound spring which provides rounded threads having za maximum outside diameter smaller than the minimum inside diameter of the threaded wheel 22. Accordingly, when the wheel 22 is in engagement with the power roll, the threads of the wheel and the bushing spring, respectively, are in tangential engagement, with the :axis of the wheel 22 lbeing eccentric with respect to the bushing spring. Upon release from the power roll the wheel 22 will become concentric so that the spring 26 will slide the wheel 22 towards the left relative to the bushing vspring as viewed in Fig. 3.

In operation, the drivingwheel 18 and the climbing wheel 22 are in continuous peripheral engagement with the power roll 2, and, therefore, both rotate in the same direction (counterclockwise as viewed in Fig. 1). The climbing wheel 22, however, has a slightly smaller dam eter than that of the driving wheel 18; therefore, the climbing wheel will rotate at a slightly faster rate than the driving wheel 18 and accordingly, it will rotate relative to the threaded shaft 24 thereby permitting the climbing wheel 22 to move to the right along the thread carried by the shaft 24. After some predetermined period, depending upon the length of the threaded shaft 24, and the rate of relative rotation between the shaft and climbing wheel, the right side of the latter (as viewed in Figs. l and 3), will come into frictional engagement with the hub of the power cam 20, which frictional engagement will tend to rotate the power cam 20 in spite of the restraining force of spring 49 so that the smallest point of serrated surface 44 will engage the power roll and thus initiate a tlip cycle.

As the power cam 20 goes through the llip cycle, the gradually increasing radius with respect to the central supporting shaft 36 will rock the bracket 16 clockwise about the supporting stud 28 as viewed in Fig. l, a distance determined by the maximum radius of the serrated surface 44. This clockwise pivoting of the bracket 16 acts through a connecting link 50 on a yoke 52 carried by the link 6, and accordingly, the link 50 will act to pull the toggle arm 14 of the switch 4 from the dotted line position to the solid line position, thus shutting olf the power to the electric motor (not shown).

In order to disable the cut olf mechanism, so that it will not shut off the switch while the typewriter is being operated, provision is made for resetting the climbing wheel to its rest position every time certain ones of the typewriter function key are operated. To illustrate this resettingprinciple without being limited to a reset through only the illustrated function, the bracket 16 of the automatic cut off device is connected via the arm 54 to the shift mechanism.

Reference is made to U.S. Patent '2,15 17,989 to Dodge, which describes in complete detail the case shifting mechanism for an IBM typewriter, but briefly, the depression of the shift lever S6 conditions a power mechanism (not shown) to rock a shift plate 58 about its supporting stud 60. In the reference patent, connections are made from the plate 58 to the type basket supporting means for vertically displacing the basket to position either the upper or lower case of the type bars for printing. In the drawings, Fig. 1 shows the plate S in its rest position or lower case position and when the plate 5S is rotated counterclockwise about stud 60, to move the basket to an upper case position, the pin 62 will rotate counterclockwise about the supporting stud 60 thereby pushing on arm 54 which will lift the bracket 16 away from the power roll 2. As soon as the bracket is rocked, slightly--just far enough to relieve the. driving engagement between the power roll and the climbing wheel 22,- the spring 26 will act to displace the climbing t 1i wheel 22 axially back to its start position. It will be noted that arm 54 has a deep yoke 63 acted on by pin 62. The purpose of this structure is that the extent of throw of arm 54 is controlled; i.e. depending on the depth of the yoke, the pin 62 will move through a considerable distance before the arm 54 moves, and consequently, the bracket 16 will be only displaced slightly from the position of Fig. l, and not far enough to shut off the switch 4.

Operation With this mechanism, the normal operation of the automatic cut off device is such that the climbing wheel 22 and the driving wheel 18 will be in engagement with the power roll 2 to permit the smaller diameter of the climbing wheel to produce relative movement with respect to threaded bushing 24. Accordingly, the climbing wheel will move gradually axially towards the power cam 20. When the climbing wheel has reached a frictional engagement with the hub of power cam '20, the latter will be rotated into engagement with the power roll thereby elfecting a flip cycle, which in turn, will cut off the switch of the typewriter. If, at any stage'during the climbing of the wheel 22 towards the cam 20, the bracket 16 is rocked clockwise about its supporting shaft 28, then the spring 26 will automatically displace the climbing wheel 22 axially to its left hand position to reset it to start the cut off period running over again.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understoodl that various omissions and su-bstitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the-art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated lby the scope of the following claims.

What is claimed is:

l. In a power driven typewriter-having a power roll, driving means therefor, and an electrical switch for coutrolling said driving means, 'an automatic cut olf device comprising a driving wheel, a power cam, a climbing wheel, and bracket means mounting said parts in co-axial alignment, means pivotally mounting said bracket means for movement from a rest position wherein said wheels are in peripheral engagement with said power roll to an operative position, said climbing wheel-having a slightly smaller diameter than that of said driving wheel to provide for a relative rotational movement therebetween, means operable in response to said differential movement for advancing said climbing wheel laterally toward said driving wheel from a normal or rest position to an actuating position wherein said climbing wheel is in frictional driving engagement with said power cam to urge the latter into peripheral engagement with said power roll to initiate a cam flip cycle, means mounting said power cam on said bracket means to move the latter to its operative position in response to said power cam going through a flip cycle, and means interconnecting 'said bracket means and said switch to shut off said switch when said bracket means is rocked to its operative position.

2. In a power driven typewriter having a power roll, driving means therefor, and an electrical switch for controlling said driving means, an automatic cut ot device comprising a driving wheel, a power cam, a climbing wheel, and bracket means mounting said parts in co-axial alignment, means pivotally mounting said bracket for movement from a rest position wherein said wheels are in peripheral engagement with said power roll to' an operative position, said climbing wheel having a slightly smaller diameter than that of said driving wheel to provide for a relative rotational movement therebetween, means operable in response to said differenti-al movement for advancing said climbing wheel laterally' toward said driving wheel from a normal or rest position to an actuating position wherein said climbing" wheel is in frictional4 driving engagement with said power cam to urge the latter into peripheral engagement with said power roll to initiate a cam flip cycle, means mounting said power cam on said bracket means to move the latter to its operative position in response to said power cam going through a ip cycle, means interconnecting said bracket means and said switch to shut off said switch when said bracket means is rocked to its operative position and spring means carried by said bracket means for restoring said climbing wheel to its rest position when said climbing wheel is relieved from peripheral contact with said power roll.

3. In a power driven typewriter having a power roll, driving means therefor, and an electrical switch for controlling said driving means, an automatic cut off device comprising a driving wheel, a power cam, a climbing wheel having a diameter slightly smaller than that of said driving wheel and bracket means mounting the same in sequential co-axial alignment, means pivotally mounting said bracket for movement from a normal position wherein said wheels are in peripheral engagement with said power roll to an operative position, spring means biasing said bracket to its normal position, said power cam having a relieved portion normally positioned proximate said power roll and spaced therefrom, screw thread means mounted for rotation with said driving wheel, said climbing wheel having a threaded bore centrally thereof loosely fitting over said screw thread means whereby when said climbing wheel and said driving wheel are in peripheral engagement with said power roll the relative rotation between said screw thread means and said climbing wheel causes the latter to advance laterally towards said power cam, means responsive to the movement of said climbing wheel toward said power cam for urging the latter into peripheral contact with said power roll thereby initiating a flip cycle of said power cam, said power cam being dimensioned to rotate said bracket means from its rest position to its operative position as said power cam goes through a ilip cycle, and means interconnecting said bracket means and said typewriter switch to shut off the latter when said bracket means is moved to its operative position.

4. In a power driven typewriter having a power roll, driving means therefor, and an electrical switch for controlling said driving means, an automatic cut off device comprising a driving wheel, a power cam, a climbing wheel having a diameter slightly smaller than that of said driving wheel and bracket means mounting the same in sequential co-axial alignment, means pivotally mounting said bracket means for movement from a normal position wherein said wheels are in peripheral engagement with said power roll to an operative position, spring means biasing said bracket means to its normal position, said power cam having a relieved portion normally positioned proximate said power roll and spaced therefrom, screw thread means mounted for rotation with said driving wheel, said climbing wheel having a threaded bore centrally thereof loosely tting over said screw thread means whereby when said climbing wheel and said driving wheel are in peripheral engagement with said power roll the relative rotation between said screw thread means and said climbing wheel causes the latter to advance laterally towards said power cam, means responsive to the movement of said climbing wheel tow-ard said power cam for urging the latter into peripheral contact with said power roll thereby initiating a flip cycle of said power cam, said power cam -being dimensioned to rotate said bracket means from its rest posi tion to its operative position as said power cam goes through a llip cycle, means interconnecting said bracket means and said typewriter switch to shut olf the latter when said bracket means is moved to its operative position and spring means carried by said bracket means for restoring said climbing wheel to its rest position when said climbing wheel is relieved from peripheral contact with said power roll.

5. In a power driven typewriter having rotatable power imparting means, driving means therefor, and an electrical switch for controlling said driving means, an automatic cut off device comprising a bracket pivotally mounted in said typewriter for movement from a rest position to an operative position, linkage means interconnecting said bracket and said switch to shut off the latter when said bracket has been moved to its operative position, and actuating means carried by said bracket for rocking the latter from its rest position to its operative position after a predetermined uninterrupted period, said actuating means comprising a pair of wheels of different diameters coaxially mounted in said bracket for rotation in response to the operation of said rotatable power imparting means when said bracket is in its rest position, means for displacing one of said wheels laterally in response to a predetermined diferential rotation of said wheels, and cam means operated in response to the lateral displacement of said one wheel for rocking said bracket from its rest position to its operative position.

6. In a power driven typewriter having -a power roll, a driving motor and a switch for control thereof, an automatic cut off device comprising a pair of wheels mounted for rotation about a common axis and driven -by the power roll at different speeds, a differential screw connection between said wheels, whereby there will be relative movement of one of the wheels along said axis with respect to the other, and means elective when said relative movement exceeds a predetermined amount for causing operation of said switch to stop said motor.

7. In a power driven typewriter having a driving motor and a switch for control thereof, a pair of wheels mounted for rotation about a common axis, means actuated by said motor for driving said wheels at different speeds, and means responsive to a predetermined differential move ment between said wheels for causing operation of said switch to stop said motor.

References Cited in the le of this patent UNITED STATES PATENTS 1,557,457 Hawley Oct. 13, 1925 2,602,529 Smathers July 8, 1952