US3703948A

US3703948A - Reciprocally engageable clutch mechanism

Info

Publication number: US3703948A
Application number: US119170A
Authority: US
Inventors: Ronald H Mack; Robert H Wilczewski; Nicholas Kondur Jr
Original assignee: Burroughs Corp
Current assignee: Unisys Corp
Priority date: 1971-02-26
Filing date: 1971-02-26
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28

Abstract

A clutch mechanism for reciprocatingly engaging a driven member with a driving member wherein the driven member is biased in one rotational direction and alternately driven over a predetermined arc in the opposite direction. The respective angular positions of engagement and disengagement of the driven member with the driving member are determined by angularly displaced restraining means that actuate an engagement control member carried with the driving and driven members.

Description

United States Patent Mack et al.

[ RECIPROCALLY EN GAGEABLE CLUTCH NIECHANISM [72] Inventors: Ronald Mack, Plymouth; Robert H. Wilczewski, Northville, both of Mich.; Nicholas Kondur, Jr., Rolling Meadows, Ill.

[73] Assignee: Burroughs Corporation, Detroit,

Mich.

[22] Filed: Feb. 26, 1971 [21] Appl. No.1 119,170

[52] US. Cl..., .;.192/33 R, 74/1255, 192/14 [51] Int. Cl ..Fl6d 43/00 [58] Field of Search 192/33, 14; 74/1255, 118,

[56] References Cited UNITED STATES PATENTS 1,76 5, 5 27 6/1930 Gollnick et a1 ..192/33 R [451 Nov. 28, 1972 3,048,246 8/ 1 962 Paige ..l92/33 R Primary ExaminerBenjamin W. Wyche Assistant Examiner-Ra.nda.ll l-leald Attorney-Kenneth L. Miller and Edwin W. Uren ABSTRACT A clutch mechanism for reciprocatingly engaging a driven member with a driving member wherein the driven member is biased in one rotational direction and alternately driven over a predetermined arc in the opposite direction. The respective angular positions of engagement and disengagement of the driven member with the driving member are determined by angularly displaced restraining means that actuate an engagement control member carried with the driving and driven members.

; r 15am, 7 D W SV l EQ T RECIPROCALLY ENGAGEABLE CLUTCH MECHANISM BACKGROUND OF THE INVENTION This invention relates generally to clutch mechanisms and, more specifically, to mechanisms for alternatingly engaging and disengaging a driven member with a driving member.

A particular need is seen in the printing art for a clutch mechanism of the variety herein disclosed.

Many printing mechanisms, and especially those associated with business machines or computers print serially across the narrow dimension of a paper strip such as in a common adding machine or cash register. The strip paper is driven by feeding means, such as opposing rollers, past the printing position in the mechanism. The feeding means must be controlled to drive the paper from print line to print line according to a particular printing format. Usually the paper is spaced to the next line as soon as a printed line is completed across the width of the paper strip.

In some applications it is desirable to print several lines of information identical to that printed on the paper strip on another medium such as a document. Such may be the case with an account deposit slip in a banking operation where a record of a bank tellers transactions are normally maintained on the paper strip or roll. When a customer presents a deposit slip to the teller appropriate information must be printed both on the paper strip and deposit slip. To save space and cost it is desirable that the document feeding mechanism be commonly driven by the same means that drives the strip paper. Provision should also be made for beginning the printing operation at varying vertical positions on the document so as to coincide with the document format and the particular information to be printed thereupon.

SUMMARY OF THE INVENTION It is, accordingly, an important object of the present invention to provide a document feeder option for a strip paper printing machine that utilizes the same driving means as drives the strip paper feeder.

It is another important object of the present invention to couple a driven member with a unidirectionally rotatable strip feed driving member in such a manner that the driven member is periodically engaged with and disengaged from the driving member to lift a document in successive print lines upon engagement and to return the driven member to a starting position upon disengagement, thus reciprocating the driven member in an arc between two predetermined positions.

It is a related object of the invention to provide a mechanism in which variation of the arc of reciprocation of the driven member may be easily accomplished.

It is also an object of the invention to effect disengagement of the driven member by merely restraining its rotational motion.

It is an allied object of the invention to permit adjustment of the magnitude of the restraint necessaryto effect disengagement.

It is a further object of the present invention to provide a compactly constructed clutch mechanism for effecting reciprocation.

It is an associated object of the invention to provide a clutch mechanism in which the driven member may be latched in a home position at a predetermined location within its arc of reciprocation.

In accordance with the invention, a driven member is biased in a second rotational direction. A portion of an engaging member is displaceable into engagement with a driving member to drivably couple the driven member therewith in a first rotational direction. The engaging member is yieldably biased for resilient angular displacement in the first rotational direction with respect to the driven member. An engagement control member, that is also yieldably biased with respect to the driven member, serves to hold the engaging portion of the engaging member out of engagement with the driving member until such time as the engagement control member is displaced in the first rotational direction with respect to the engaging member. The engagement control member being so displaced, permits the engaging portion of the engaging member to move into engagement with the driving member to initiate rotation of the driven member in the first rotational direction. When the driven member is restrained while moving in the first rotational direction, the engaging portion of the engaging member cams out of engagement with the driving member; thus disengaging the driven member therefrom.

BRIEF DESCRIPTION OF THE DRAWINGS To facilitate a'more complete understanding of the invention, a preferred embodiment thereof will hereinafter be described in connection with the drawings in which: FIG. 1 is a side elevation view showing the preferred clutch mechanism embodied in a printing machine;

FIG. 2 is an exploded view of the preferred clutch mechanism;

FIG. 3 is a detailed orthographic view taken from FIG. 2;

FIG. 4 is a side elevation viewing the clutch clutch mechanism initially disengaged.

' DETAILED DESCRIPTION Turning now to the drawings wherein like reference characters designate identical elements in each of the Figures and, particularly to FIG. 1, there is shown a preferred clutch mechanism embodied in a printing machine. As illustrated, a strip of paper 10 or other such medium is normally moved in the printing machine to successive print lines by the driving action of a paper driving wheel 12 and pinch roller 14. The paper strip 10 is guided through a printing position 16 in the machine by guide rollers 18 disposed radially apart from the periphery of the paper driving wheel 12 and in the direction of paper feed from the pinch roller 14. The paper driving wheel 12 is one of three disc-like sectors, all being mutually rotatable about a common axis 20. One of the other sectors 22 has a geared periphery that meshes with a like geared periphery of a driving pinion 24. The driving pinion 24, in turn, is controllably rotated to move the paper driving wheel 12 at a predetermined speed and for a predetermined interval in order to properly position the paper with respect to the printing position 16 of the machine. During a normal printing operation the driving pinion 24 incrementally rotates the geared sector 22 and paper driving wheel 12 so that after the completion of each printed line the paper strip 10 is fed for a predetermined distance to the next print line.

A third sector that is mutually rotatable with the paper driving wheel and geared sector is a driving member or ratchet wheel 26. In order that the printing machine may optionally print one or more lines of information upon a document 27 as well as upon a paper strip, the invention provides a driven member or arm 28 that lifts the document 27 from print line to print line in conjunction with-the ratchet wheel 26. A document engaging recess 30 on the driven arm 28 servesto position the bottom edge of a document thereupon. In utilizing the document printing option of the machine an operator depresses a keyed latch 32 that releases a bail 34 holding the driven arm 28 in a home position, as shown. The arm 28 is rotated in a second direction or clockwise, as illustrated in FIG. 1, by a return biasing means or spring 36. This clockwise rotation causes an engaging portion such as a pivotal pawl 38 of an engaging member 40 to pivot into engagement with the ratchet wheel 26. With the pivotal pawl 38 thus positioned, the engaging member 40 is driven a predetermined number of increments in a first rotational direction, or counterclockwise, as shown, with the rotating ratchet wheel 26. The engaging member 40 is coupled to the driven arm 28 by means of an arm biasing follower or spring 42 so that the rotational force of the ratchet wheel 26 is transmitted to the driven arm to raise the document in the same manner as the paper strip 10 is raised by the paper driving wheel 12. When the rotation of the driven arm 28 is opposed by a second restraining means or stop 44 the pivotal pawl 38 or the engaging member 40 is cammed out of engagement with the driving member or ratchet wheel 26 in a manner that will hereinafter be described. With the pivotal pawl 38 disengaged the driven arm 28 is rotated clockwise by the return biasing spring 36 until the bail 34 engages the keyed latch 32 at the home position of the driven arm.

A reset arm 46 is provided to actuate the displacement of the driven arm 28 to the home position whenever the document 27 has been lifted in the first rotational direction beyond that position. This feature permits an operator to reset the driven arm 28 when the desired printing operation on the document is completed before the document has been lifted to its maximum height rather than having to wait for the driven arm to pivot all the way to its rotational limit before it is restored. v

The mechanism that couples the driven member or arm 28 to the driving member or ratchet wheel 26 may generally be described as a fractional engagement clutch wherein the driven member 28 is drivably engaged for a fractional portion of full rotation with the driving member 26. Disengagement of the driven member 28 is effected by restraining the rotational motion of the driven member 28 to initiate the displacement of the engaging member or pawl 38 from the driving member 26. Biasing means such as a spring 36 returns the driven member 28 to a predetermined angular position whereupon the engaging member 40 is displaced back into engagement with the driving member 26 to continue an unbroken reciprocal chain.

Reciprocation may be interrupted by intercepting and restraining the driven member 28 as it returns in the second rotational direction, as earlier described in connection with the keyed latch 32 and bail 34 (FIG. 1

Describing the clutch mechanism now in greater detail, with reference to FIG. 2, an extension 41 of the driven member 28 on which is formed the document engaging recess 30 projects from an annular sleeve 48. The inner diameter of the sleeve is of such a dimension that it freely rotates about a shaft 50 of the driving member 26 upon which it is mounted. The bail 34' (shown in FIG. 1 that holds the driven member 28 in the home position engages the driven member by means of bail engaging stud 52. A fastener finger 54 and a fastener opening 56 of the-driven member 28 serve to respectively attach the arm biasingspring 42 and a control member biasing spring 58 thereto. One end of the return baising spring 36 is attached to a connector opening 60 in the extension 41 of the driven member 28. g

The engaging member 40 has an annular sleeve 62 that fits loosely about the outer periphery of the sleeve 48 of the driven member 28. The driven member 28 and the engaging member 40 assume a torsionally tensioned relationship due to the force of the arm biasing follower or spring 42 that interconnects the two members. A slot 64 in the sleeve of the driven member 28 is engaged by a stop (not shown) in the inner periphery of the sleeve 62 of the engaging member, thus holding the two members angularly apart in a predetermined axial relationship. An arm 66 of the engaging member 40 carries a pivot shaft 68 for pivotally mounting the engaging portion or' pivotal pawl 38, the pawl being biased in an engaged or counterclockwise position by a torsion spring, as shown in FIGS. 2 and 3'. A limit to counterclockwise rotation of the pivotal pawl 38 is established by abutment of an edge section 70 of an engagement control member 72 with a lip 74 of I the pivotal pawl 38. Two opposing

walls

76 and 78 of the pawl 38 form a slot 79 through which a camming sector 80 of the engagement control member 72 projects to assist in maintaining the camming section 80 in proper spatial relationship with the pawl. The slot 79 is terminated at respective ends by a driven cam or camming shaft 82 and a cam engaging means such as a roller 84.

The engaging portion or pawl 38 of the engaging member 40, being biased into engagement with the driving member or ratchet wheel 26, is maintained in a disengaged pivotal position by the action of the engagement control member 72. The engagement control member 72 is positioned between the engaging member 40 and the driven member 28 and is loosely mounted to rotate on the sleeve 48 of the latter member. A control member biasing means such as a spring 58 biases the camming sector 80 of the engagement control member 72 at a limited or disengaged position such that a cam engaging edge 86 of the camming sector cams the roller 84 of the pivotal pawl 38 downwardly, as shown. A projection 88 on the sleeve 62 of the engaging member 40 serves to limit the rotation of the engagement control member 72 in the first rotational direction by blocking a step 90 on the inner periphery thereof.

The operation of the invention may be more readily understood with reference to FIGS. 4-7, where there is shown the driven member 28 biased pivotally in a second rotational direction (or counterclockwise, as shown) by the force of the return biasing spring 36. With the pawl 38 pivoted out of engagement with the ratchet wheel 26, the return biasing spring 36 is effective to pivot the driven member 28 counterclockwise, as shown in FIG. 4. Such action may be initiated by the depression of the keyed latch 32 (FIG. 1) that normally holds the driven member or arm 28 in the home position, as hereinbefore described. As the return biasing spring 36 rotates the driven arm 28 counterclockwise a stop engaging extension 91 of the engagement control member 72 meets a first restraining means or stop 92, thus limiting the pivoting motion of the control member in the second rotational direction, as shown in FIG. 5. With the rotation of the control member 72 restrained, the biasing force of the return biasing spring 36 continues to pivot the driven member 28 in opposition to the biasing tension imposed between it and the engagement control member 72 by the control member biasing spring 58. As the engaging member 40 and pawl 38 are rotatably coupled by the arm biasing follower spring 42, the pawl 38 is carried counter clockwise with respect to the now stationary engagement control member 72 until a limit arm 94 of the driven member 28 contacts the first stop 92. At this point the camming sector 80 of the engagement control member 72 is positioned completely free of either end of the pawl slot 79 through which it extends, thus enabling the torsion spring to pivot the pawl 38 counterclockwise, as shown in FIG. 5, into engagement with the ratchet wheel 26. With the pivotal pawl 38 in such a position, the driven member 28 is then drivingly coupled with the driving member or ratchet wheel 26 through the arm biasing spring 42 that couples the engaging member 40 with the driven member 28.

The engaging portion or pawl of the engaging member 40 is held in engagement with the ratchet wheel 26 not only by the pivoting force of the torsion spring, as heretofore described, but also by a counterclockwise moment of force applied to the pawl 38 by the driving force of the ratchet wheel. This advantageous result is obtained by positioning the pivot point or shaft 68 of the pawl in an offset relationship with the resultantdirection of the force applied by the ratchet 26 to the pawl 38. Still another factor that assists the pivotal pawl 38 in remaining engaged with the ratchet wheel 26 concerns the particular shape of the camming sector 80 of the engagement control member 72. In the engaged state, the cam engaging roller 84 of the pivotal pawl 38 rests upon a step edge 96 of the camming sector 80. The step edge 96 is so disposed that a clockwise or disengaging pivot the pawl 38 must act in opposition to the tensional force imposed on the engagement control member 72 by the control member biasing spring 58.

With the pawl 38 firmly engaged the driven member 28 is rotated with the driving member 26 in a clockwise or first rotational direction, as shown in FIG. 6, until the driven member is subjected to a restraining load,

such as by the second restraining means or stop 44 positioned in its path of rotation. When the rotation of the driven member 28 is restrained, as in FIG. 7, the engaging member 40 continues to rotate with the ratchet wheel 26 in opposition to the biasing force of the arm biasing spring 42 that couples the two members. The coupling or tensioning force of the arm biasing spring 42 can be adjusted so that disengagement occurs under any predetermined restraining load imposed on the driven member 28. When the engaging member 40 continues to rotate clockwise with respect to the driven member 28, the driven member camming shaft 82 of the engaging member moves into abutment with a camming surface 98 (FIG. 2) of the driven member 28. As the engaging member 40 continues to rotate clockwise with respect to the restrained driven member 28, the camming surface 98 of the driven member begins to cam the pivotal pawl 38 clockwise. The relative motion between the engaging member 40 and the driven member 28 causes the cam engaging roller 84 of the pawl 38 to roll over the step edge 96 of the camming sector and onto the cam engaging edge 86 thereof where the tensioning force applied to the engagementcontrol member 72 of the control member biasing spring 58 cams the pawl 38 clockwise into complete disengagement with the ratchet wheel 26, as illustrated in FIG. 7..With the pawl 38 disengaged the return biasing spring 36 then reinitiates the cycle by rotating the driven member 28 counterclockwise until the stop engaging extension 91 of the engagement control member 72 is restrained in its pivotal displacement by the first restraining means or stop 92, whereupon engagement again occurs. Such reciprocation would continue indefinitely until a cycle is interrupted, such as by the operation of the keyed latch 32 and bail 34, as heretofore described.

In the specific application earlier described, where the clutch mechanism is utilized in a printing machine to provide a document spacing option, the driven member 28 is held by the keyed latch 32 and bail 34 in a home position with the engaging portions 38 of the engaging member 40 being disengaged from the ratchet wheel 26. Release of the driven member 28 from the home position allows the return biasing spring 36 to pivot the driven member and its associated members counterclockwise to initiate engagement of the engaging sector or pawl 38. The keyed latch 32 and bail 34 hold the driven member in the home position after the engaging pawl has been disengaged from the ratchet wheel 26. A further feature of the clutch mechanism, as applied in a document spacer option, is a provision for controlled disengagement of the pawl 38 from the ratchet wheel 26 whenever the driven member 28 is rotated beyond its home position in the first rotational direction. This feature is accomplished by a reset arm 46 having a bifurcated end comprised of an upper finger and a lower finger 102, as shown in FIG. 1. Whenever the driven member 28 is driven beyond its home position a restraining lug 104 thereon moves free of the lower surface 106 of the upper finger 100 thus permitting the reset arm 46 to be pivoted downwardly by a reset actuator such as a solenoid 108. Such a pivoting action of the reset arm 46 brings a lower edge 110 of the lower finger 102 downwardly, thus engaging the projecting end of the driven member camming shaft 82 that extends from on side of the pawl 38 to pivot the pawl counterclockwise out of engagement with the ratchet 26.

While the invention has been described in. conjunction with a specific embodiment it is evident that many modifications and alterations not truly departing from the inventive concept residing therein will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace within the appended claims all such modifications and alternatives that reside within the inventive concept disclosed herein.

What is claimed is:

1. In combination with a unidirectionally rotatable driving member, the rotation thereof being in a first direction, a clutch mechanism for bi-directionally rotating a driven member within a predetermined arc, said mechanism comprising:

first biasing means associated with said driven member and effective for rotating said driven member in a second rotational direction opposite said first direction of rotation;

an engaging member bi-directionally rotatable with said driven member through said predetermined are said engaging member having a pivotally mounted engaging portion biased by a torsion biasing means into driving engagement with said driving member resiliently driving said driven member in the first;

second biasing means coupling said engaging member and said driven member and effective for rotating said driven member in said first direction of rotation as driven by said driving member and said engaging member; and

an engagement control member bi-directionally rotatable through said predetermined arc with said driven member and said engaging member, said control member being yieldably biased for resilient displacement in the second rotational direction with respect to the driven member, said control member having a camming sector cammably opposed to the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with said driving member, whereby the relative rotation of said engagement control member in the first rotational direction relative to said driven member and said engaging member releases the engaging portion of said engaging member into driving engagement with said driving member while the relative rotation of said driven member in the second rotational direction relative to said engagement member cammably displaces said engaging portion thereof out of engagement with said driving member, the combination of said elements effectively utilizing the said unidirectional rotation of said driving member to produce one of said bi-directional rotations of said driven member, said one direction rotation being defined as said first direction of rotation.

2. A clutch mechanism as defined in claim 1 further comprising first restraint means effective for displacing said engagement control member in said first rotational direction relative to said driven member and said engaging member, and said restraint means effective for restrainably limiting the first direction rotation of said driven member, such restraints being effective to respectively engage and disengage said engaging portion of said engaging member with said driving member.

3 A clutch mechanism as defined in claim 2 wherein said first restraint means is a first stop radially disposed in a predetermined location in the' rotational path of said engagement control member, and said second restraint means is a second stop disposed in a predetermined angularly displaced location with respect to said first stop, said second stop being radially disposed in the rotational path of said driven member, whereby the angular distance between said stops defines said predetermined are through which said driven member is bi-dire ctionally rotated.

4. A clutch mechanism as defined by claim 1 wherein said torsion biasing means for biasing said engaging portion of said engaging member into driving engagement with said driving member is a torsion spring.

5. A clutch mechanism as defined in claim 1 wherein the pivotal axis of said engaging portion is offset from the direction of driving force imparting to said engaging portion by said driving member so that said driving member creates a moment of force about said pivot point tending to maintain said engaging portion into engagement with said driving member.

6. A clutch mechanism as defined in claim 1 wherein the camming sector of said engagement control member in response to said bias of said control member.-

cams against a cam engaging means carried by the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with the driving member.

7. A clutch mechanism as defined by claim 6 wherein said cam engagingfmeans of said engaging portion is a roller joumaled by said engaging portion.

8. A clutch mechanism as defined in claim '7 wherein the camming sector of said engagement control member has a first step-like edge upon which said cam engaging means is biasly maintained during engagement of said engaging portion with said driving member, the disengaging pivotal motion of said engaging portion being effective to displace said cam engaging means over said first step-like edge onto a second contoured edge of said camming sector, said second contoured edge being effective to cam said biased engaging portion out of engagement with said driving member.

9. A clutch mechanism as defined in claim 8 wherein the disengaging pivotal motion of said engaging portion over the first step-like edge of said camming sector releases said engagement control member to its full first direction displacement so that said camming sector assists in maintaining said engaging portion disengaged from said driving member.

10. A clutch mechanism as defined in claim 1 wherein said engaging portion has a driven member cam disposed in abutable relationship with said driven member for cammably pivoting said engaging portion out of engagement with said driving member when said driven member is rotated in the second rotational direction relative to said engaging member.

11. A clutch mechanism as defined in claim 10 wherein said driven member cam is a shaft extending from said engaging portion so that rotation of said a bi-directionally rotatable driven member rotatable torsion biasing means into driving engagement with said driving member;

second biasing means coupling said engaging member and said driven member and effective for rotating said driven member in said first direction of rotation as driven by said driving member and said engaging member;

an engagement control member bi-directionally rotatable with said driven member and said engaging member, said control member being biased for resilient displacement in the second rotational direction with respect to the driven member, said control member having a camming sector cammably opposed to the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with said driving member;

first means for restraining said engagement control member in its second direction rotation; and

second means for restraining said driven member in its first direction rotation, such restraint being effective to engage said engaging portion with said driving member upon restraint of said engagement control member and to disengage said engaging portion from said driving member upon the restraint of said driven member, such that said driven member serves to lift the document while being rotated in the first rotational direction between said first restraining means and said second restraining means, said first biasing means being effective to return said driven member in the second rotational direction after the driven member is restrained by said second restraining means. 13. A clutch mechanism as defined in claim 12 wherein said first restraining means is a first stop radially disposed in a predetermined location in the rotational path of said engagement control member, and,

said second restraining means is a second stop disposed in a predetermined angularly displaced location with respect to said first stop, said second stop being radially disposed in the rotational path of said driven member wherebtyl the angular distance between said stops determines e vertical distance over which the document may be lifted.

14. A clutch mechanism as defined by claim 13 further including means engageable with said driven member for stopping said driven member in an intermediate position between said first and said second stops, the release of said driven member by said means being effective to enable said first biasing means to rotate said driven member in the second rotational direction.

15. A clutch mechanism as defined by claim 14 wherein said engageable means is characterized by a manually depressible keyed latch and a bail, said bail being restrainingly engageable with said driven member and said latch being effective to controllably actuate said bail.

16. A clutch mechanism as defined in claim 12 wherein said driven member, said engaging member and said engagement control member are bidirectionally rotatable about an axis common with the axis of said driving member,

17. A clutch mechanism as defined in claim 12 further comprising a ratchet wheel fixedly connected to the driving member for rotation therewith.

18. A clutch mechanism as defined in claim 17 wherein the engaging portion of said engaging member has a tooth for engagement with said ratchet wheel.

1: r a: 1: a:

32230 Uri-TED STATES PATENT OFFICE. CERTIFICATE OF CORRECTION Patent No. 3,7 3, 9 Dated November 28, 1972 Ronald H. Mack, Robert H. Wilozewski and Invenzofls) Nicholas Kondur, Jr.

It is certified that error appears in the-above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 7, lines 28 and 29, delete "resiliently driving said.

driven member in the first? Signed and sealed this 1st day of May 1973.

(SEAL) Attest:

EDEETARQM. FlElCHER, JR. ROBERT GOTTSCHALK At testing Officer Commissioner of Patents

Claims

1. In combination with a unidirectionally rotatable driving member, the rotation thereof being in a first direction, a clutch mechanism for bi-directionally rotating a driven member within a predetermined arc, said mechanism comprising: first biasing means associated with said driven member and effective for rotating said driven member in a second rotational direction opposite said first direction of rotation; an engaging member bi-directionally rotatable with said driven member through said predetermined arc said engaging member having a pivotally mounted engaging portion biased by a torsion biasing means into driving engagement with said driving member resiliently driving said driven member in the first; second biasing means coupling said engaging member and said driven member and effective for rotating said driven member in said first direction of rotation as driven by said driving member and said engaging member; and an engagement control member bi-directionally rotatable through said predetermined arc with said driven member and said engaging member, said control member being yieldably biased for resilient displacement in the second rotational direction with respect to the driven member, said control member having a camming sector cammably opposed to the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with said driving member, whereby the relative rotation of said engagement control member in the first rotational direction relative to said driven member and said engaging member releases the engaging portion of said engaging member into driving engagement with said driving member while the relative rotation of said driven member in the second rotational direction relative to said engagement member cammably displaces said engaging portion thereof out of engagement with said driving member, the combination of said elements effectively utilizing the said unidirectional rotation of said driving member to produce one of said bi-directional rotations of said driven member, said one direction rotation being defined as said first direction of rotation.

3. A clutch mechanism as defined in claim 2 wherein said first restraint means is a first stop radially disposed in a predetermined location in the rotational path of said engagement control member, and said second restraint means is a second stop disposed in a predetermined angularly displaced location with respect to said first stop, said second stop being radially disposed in the rotational path of said driven member, whereby the angular distance between said stops defines said predetermined arc through which said driven member is bi-directionally rotated.

6. A clutch mechanism as defined in claim 1 wherein the camming sector of said engagement control member in response to said bias of said control member cams against a cam engaging means carried by the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with the driving member.

7. A clutch mechanism as defined by claim 6 wherein said cam engaging means of said engaging portion is a roller journaled by said engaging portion.

8. A clutch mechanism as defined in claim 7 wherein the camming sector of said engagement control member has a first step-like edge upon which said cam engaging means is biasly maintained during engagement of said engaging portion with said driving member, the disengaging pivotal motion of said engaging portion being effective to displace said cam engaging means over said first step-like edge onto a second contoured edge of said camming sector, said second contoured edge being effective to cam said biased engaging portion out of engagement with said driving member.

11. A clutch mechanism as defined in claim 10 wherein said driven member cam is a shaft extending from said engaging portion so that rotation of said driven member in the second direction relative to said engaging member causes said driven member to cammably contact said shaft and to pivot said engaging portion out of engagement with said driving member.

12. In a printing machine having a paper strip feeding apparatus, including a unidirectionally rotatable driving member for vertically spacing the strip according to the printed lines thereon, a clutch mechanism cooperating with said paper strip feeding apparatus for likewise spacing a document within a predetermined vertical distance, said mechanism comprising: a bi-directionally rotatable driven member rotatable in a first direction for vertically spacing the document over the predetermined vertical distance according to a predetermined variable number of printed lines that are to be provided thereon; first biasing means associated with said driven member and effective for rotating said driven member in a second rotational direction; an engaging member bi-directionally rotatable wIth said driven member, said engaging member having a pivotally mounted engaging portion biased by a torsion biasing means into driving engagement with said driving member; second biasing means coupling said engaging member and said driven member and effective for rotating said driven member in said first direction of rotation as driven by said driving member and said engaging member; an engagement control member bi-directionally rotatable with said driven member and said engaging member, said control member being biased for resilient displacement in the second rotational direction with respect to the driven member, said control member having a camming sector cammably opposed to the engaging portion of said engaging member for maintaining said engaging portion out of driving engagement with said driving member; first means for restraining said engagement control member in its second direction rotation; and second means for restraining said driven member in its first direction rotation, such restraint being effective to engage said engaging portion with said driving member upon restraint of said engagement control member and to disengage said engaging portion from said driving member upon the restraint of said driven member, such that said driven member serves to lift the document while being rotated in the first rotational direction between said first restraining means and said second restraining means, said first biasing means being effective to return said driven member in the second rotational direction after the driven member is restrained by said second restraining means.

13. A clutch mechanism as defined in claim 12 wherein said first restraining means is a first stop radially disposed in a predetermined location in the rotational path of said engagement control member, and said second restraining means is a second stop disposed in a predetermined angularly displaced location with respect to said first stop, said second stop being radially disposed in the rotational path of said driven member whereby the angular distance between said stops determines the vertical distance over which the document may be lifted.

16. A clutch mechanism as defined in claim 12 wherein said driven member, said engaging member and said engagement control member are bi-directionally rotatable about an axis common with the axis of said driving member,