US3797420A - Thread overwrap mechanism - Google Patents

Abstract

Mechanism usable with a book cleat sewer which is actuatable upon completion of thread sewing across a cleat in the spine of a book being sewn to positively ensure thread over-wrap completely about the last end sheet in the cleat being sewn.

Description

United States Patent Streeter Mar. 19, 1974 THREAD OVERWRAP MECHANISM 2,800,095 7/1957 Schramm 112/21 [75] Inventor: Daniel I. Streeter, Glastonbury,

Conn- Primary Examiner-Geo. V. Larkin [73] Assigneez The Smyth Manufacturing Attorney, Agent, or Firm'-Prutzman, Hayes, Kalb &

Company, Bloomfield, Conn. chlton [22] Filed: May 24, 1973 Appl. No.: 363,666

us. c1. 112/21 1m. (:1 B42b 1/02 Field of Search 11/1 R, 1 CP; 112/21, 22

References Cited UNITED STATES PATENTS 7/l9l7 Bischof 1. 112/21 [57] ABSTRACT Mechanism usable with a book cleat sewer which is actuatable upon completion of thread sewing across a cleat in the spine of a book being sewn to positively ensure thread over-wrap completely about the last end sheet in the cleat being sewn.

12 Claims, 8 Drawing Figures PATENT) MR 1 9 ISM SHEET 5 [IF 6 1 THREAD OVERWRAP MECHANISM This invention relates to machines for sewing cleats on a spine of a book and particularly concerns the sewing head portion of such a machine.

A primary object of this invention is to provide a cleat sewing machine having a new and improved thread over-wrap machanism which positively ensures thread wrap about the end sheets of each cleat to be sewn on a spineof the book.

Another object of this invention is to provide such a new and improved thread over-wrap mechanism which not only significantly improves the quality of a cleat sewn book, but consumes virtually no added time requirements relative to a conventional cleat sewing operation and utilizes a minimum number of operating components.

Other objects will be in part obvious and in part pointed out in more detail hereinafter.

A better understanding of the objects, advantages, features, properties and relationships of the invention will be obtained from the following detailed description and accompanying drawings which set forth an illustrative embodiment and are indicative of the way in which the principles of this invention is employed.

In the drawings:

FIG. 1 is an isometric view, partly broken away, of a cleat sewer incorporating this invention;

FIG. 2 is a plan view of a portion of a sewing head of the cleat sewer of FIG. 1;

FIG. 3 is an end view, partly broken away, of the sewing head of FIG. 2;

FIG. 4 is an enlarged partial plan view, partly broken away, of the sewing head of FIG- 2;

FIG. 5 is. an isometric view showing part of a book spine having a pair of sewn cleats;

FIG. 6 is a schematic illustration of the path of needle movement during sewing of a cleat;

FIG. 7 is a side view, partly broken away and partly in section, of a needle rod shown from an end of the sewing head of FIG. 1; and

FIG. 8 is a schematic illustration of a portion of a control system for the sewing head.

Referring in detail to the drawings, a sewing head 10 of a cleat sewer 12 is shown incorporating a preferred embodiment of this invention. A suitable book clamp 14 and indexing means, not shown, are provided for holding and indexing a book.16 to be sewn. The book 16 is transported from a book loading and unloading station 17 on a slide 18 in a direction parallel to the spine of the book 16 through a saw station 20, wherein cleats such as at 22 are formed in the spine 23 of the book 16, and a sew station 24 for sewing the cleats. As seen in FIG. 1, the book spine 23 is fed from the book loading and unloading station 17 (wherein the book 16 is shown in broken lines) with the spine 23 down and disposed in a plane overlying the saw and sew stations and 24. Thereafter, the book is further advanced to an extreme limit position and subsequently returned to station 17 for unloading.

The sewing head 10 has a needle rod 26 (best seen in FIG. 7) operatively mounted on a spindle 28. The spindle 28 is fixed on a pair of shafts 30 and 32 extending perpendicular to the needle rod 26 as best seen in FIGS. 2 and 4 with the shafts 30, 32 mounted for reciprocable movement on spaced end plates 34 and 36 secured to side plates 38 and 40 of a spindle carriage 42.

The spindle carriage 42 is in turn supported for reciprocable movement on a cross shaft 44 fixed to a stationary frame 46 and a cam shaft 48 suitably mounted on that frame 46 for rotation.

The spindle 28 is reciprocable relative to and parallel to the carriage side plates38, for reciprocating a needle 50 of the needle rod 26 in a direction normal to the longitudinal axis of the needle rod 26. This direction of movement is hereafter called a longitudinal direction which is to be understood to be parallel to the longitudinally extending spine 23 of the book 16 which is to be positioned by book clamp 14 in overlying relation to the needle rod 26 of the spindle 28. Each cleat 22 is sequentially indexed into overlying parallel relation to the spindle 28 for sewing by the needle 50. As seen in FIG. 5, each cleat 22 is defined by inwardly sloping pairs of saw cuts 52 and 54 suitably formed in the book spine 23 at saw station 20. The saw cuts or slits 52, 54 extend laterally across book spine 23.

To reciprocate spindle 28 in the longitudinal direction parallel to the carriage side plates 38 and 40, the shafts 30 and 32 arefixed to and interconnected by bracket 56 having a cam follower 58 which will be understood to engage a contoured internal cam path, not shown, on a spindle cam 60. The latter is fixed to a cam drive assembly 62 mounted on cam shaft 48 between the carriage side plates 38 and 40. Cam drive assembly 62 is splined to cam shaft 48 for transmitting rotary motion upon rotation of cam shaft 48'while permitting movement of cam drive assembly 62 axially of cam shaft 48 upon operation of a four way valve 64 controlling a reversible sewing head feed cylinder 66 which is connected to a suitable source of power, not shown,

such as compressed air. The cylinder 66 has an extendible and retractable piston rod 68 (FIG. 4) fixed to a bracket 70 which will be understood to be secured to end plate 36 of carriage 42 for reciprocating it on frame 46. Carriage 42 is sequentially indexed intermittently in a feed direction. The feed direction of carriage 42 (and drive cam assembly 62) is from left to right, as

viewed in FIGS. 24. A rack and pawl escapement '71 (FIG. 3) between frame 46 and spindle 28 cooperates with feed cylinder '66 in the feed direction to provide controlled intermittent indexing of carriage 42 in timed relation to cam shaft rotation and longitudinal movements of spindle 28 to provide a desired sewing pattern. It will be understood that cam shaft 48 extends through oversize openings, not shown, within side plates 38 and 40 of carriage 42, permitting its lateral movement relative and parallel to cam shaft 48.

To also provide limited needle movement relative to the carriage 42 itself, crosswise to the book spine 23 to be sewn, needle rod 26 is shown (FIG. 7) drivingly con nected by a depending lug '72 of a tubular connector 74 to a spindle oscillating block 76 supported for reciprocating movement on a pair of shafts 78 and 80 (FIGS. 2 and 4) in parallel overlying relation to end plates 34 and 36. As described more specifically below, needle rod 26 is telescopically mounted within tubular connector 74 and is normally driven in unison with spindle oscillating block 76 and spindle 28. Needle rod 26 is provided a suitable bearing 81 on spindle 28 which also permits needle rod 26 to move axially relative to spindle 28. To reciprocate spindle 28 and needle rod 26in unison relative to carriage 42, a follower arm 82, integrally formed on spindle oscillating block 76, is provided with a cam follower 84 (FIG. 3) received for following movement in a cam path 86 of a spindle barrel cam 88 fixed to cam drive assembly 62 for moving needle 50 relative to spindle carriage 42 and crosswise to book spine 23 to be sewn.

Spindle oscillating block 76 is provided with a slot 90, extending in the so-called longitudinal direction, for receiving depending lug 72 of tubular connector 74 within which needle rod 26 is mounted. Such construction provides for driving both spindle oscillating block 76 and needle rod 26 in unison, axially of needle rod 26 and transversely to book spine 23, while permitting following movement of needle rod 26 longitudinally and also angularly of book spine 23.

To prove yet another motion, more specifically, an angular motion to needle 50, a needle rod gear 92 is mounted on an end of needle rod 26 for meshing engagement with an intermediate gear 94 (FIG. 7) mounted on a spindle side plate 96. Gear 94 in turn engages rack 98 drivingly connected by connecting rod 100 to a cam follower 102 in engagement with an internal cam path, not shown, on a rack cam 104 fixed to cam drive assembly 62 on cam shaft 48. Reciprocable movements of rack 98 in following relation to rack cam 104 and in timed relation to the other motion producing cams 60 and 88 provides for desired angular movements of needle 50 in opposite angular directions about the axis of needle rod 26 during cleat sewing, to ensure needle alignment with the angularly disposed saw cuts 52, 54 of cleat 22, and permits needle 50 to be inserted into and withdrawn from book spine 23.

To determine thickness of the book being sewn for purposes of terminating the sew cycle on a cleat, a sensor block air cylinder 106 is mounted on stationary frame 46 of sewing head 10 with a piston rod 108 which drivingly connects with and positions a sensor block 110, movably mounted on shaft 44 of frame 46. Cylinder 106 positions block 110 against a movable jaw 112 of book clamp 14 upon it being suitably dogged, by means not shown, in position for the sewing of each cleat. With sensor block 110 positioned in preselected relation to book clamp 14 and in fixed relation to carriage 42, a predetermined indication of the thickness of each book 16 being sewn is thus provided, and a switch actuator 114 is mounted on sensor block 110 for engaging a limit switch 9LS to commence termination of the sewing cycle for each cleat 22 as specifically described below.

The three described cams 60, 88 and 104 and their driving connections to needle rod 26 accordingly provide a complex compound motion for progressively sewing each cleat in spine 23 of book 16 in successive sections proceeding crosswise across the spine of the book, preferably in a progressive series of so-called figure 8 patterns. As best seen in FIG. 6 (which is to be understood as a bottom view projection of the cleat being sewn), needle 50 starts from a rest position A with carriage 42 positioned adjacent frame side plate 116 and with spindle 28 adjacent carriage end plate 34 to align needle 50 with the leading saw cut 52.

Driven by spindle barrel cam 88, needle 50 will move crosswise toward book spine 23 into home position A and thereafter longitudinally outside cleat 22 between saw cuts 52 and 54 under the influence of spindle cam 60 while needle 50 is also being rotated, by the modifying action of the rack and gear train drive connection between rack cam 104 and needle rod 26, into a position parallel with line XX (FIG. 5) in entering relation to trailing saw cut 54.

A progressive sewing pattern then continues as an advancing figure 8 as seen in FIG. 6 across spine 23 between saw cuts 52 and 54. Longitudinal needle movement is provided by spindle cam 60 and modified by rack cam 104. The rack and pawl escapement 71, such as seen in FIG. 3, will be understood to cooperate with spindle cam 60 and the reversible feed cylinder 66 to intermittently feed carriage 42 and cam drive assembly 62 in unison transversely or cross-wise of the book spine. That is, cylinder 66 provides intermittent feeding motion from left to right as viewed in FIG. 6 as controlled by escapement 71 in timed relation to rack cam 104 during the time needle 50 is below book 16. The air cylinder feed is modified by the barrel cam 88 to provide a desired direction and distance of needle travel crosswise of the book.

To initiate termination of the sew cycle near the end of the sewing traverse of needle 50 across book spine 23, the switch 9LS on carriage 42 contacts actuator 114 to condition the sewing head 10 for thread overwrap in accordance with this invention.

Positive thread overwrap about the last sheet of each cleat 22 is assured by providing a suitable needle rod drive to thrust needle 50 through the trailing saw cut 54 and beyond the last end sheet of book 16 to positively wrap thread around that last end sheet.

In the specifically illustrated embodiment of this invention, a normally de-energized air cylinder 118 is provided with a piston rod 120 coaxially secured to needle rod 26 as seen in FIG. 7. Spindle oscillating block 76 is drivingly engaged with depending lug 72 of tubular connector 74 which telescopically houses an end of the needle rod 26, and the tubular connector 74 is threadably connected with an end of cylinder 118. Rod 120 of piston 122 is screwed into an end of needle rod 26 and secured by a lock nut 124 within connector 74.

Tubular connector 74 normally serves to impart movement to the needle rod 26 in direct relation to spindle 28, axially of the needle rod 26 and crosswise of book 16 being sewn. In the preferred embodiment, a drive pin or dowel 126 is fixed to connector 74 to extend through an elongated slot 128 in needle rod 26 and is normally maintained in sew position by a compression spring 130 received in cylinder 118 on its rod side urging piston 122 toward the left with dowel 126 in abutting driving engagement with needle rod 26 at the right hand side of its elongated slot 128 as viewed in FIG. 7. Spindle 28 (which is in fixed relation to the tubular connector 74 and its lug) and the needle 50 are thus normally driven directly by the lug 72 as it follows the movements of the cam follower 84 laterally of the book spine.

As spindle carriage 42 traverses across book spine 23 from its starting or first traversing position, with the needle 50 adjacent the first end sheet of the book 16, to a terminal or second traversing position established by sensor block 110, needle 50 is adjacent the last end sheet to be sewn. With the carriage switch 9LS engaging actuator 114 on frame 46 and with needle 50 approaching needle position B (FIG. 6), e.g., near the end of its sewing traverse, any further lateral feed movement will be limited to the throw of the needle 50 by the cam follower 84 once needle 50 reaches position B with carriage 42 engaged with the sensor block 110. Depending on the timing of the arrest of spindle carriage 42 relative to the needle position upon carriage engagement with sensor block 110, it will be seen that such lateral feed movement frequently is insuffcient to ensure complete thread overwrap of the last sewn end sheet if the normal figure 8 pattern were merely repeated. However, in accordance with this invention, cylinder 118 is energized in response to actuation of switches 9LS and 12LS once needle 50 is aligned with trailing saw cut 54 as in position B to di rect air through a common supply and exhaust passage 132 into the piston side of cylinder 118.

As needle 50 is being driven out of trailing saw cut 54 to the right in FIG. 6 by the follower 84, the resilient drivig connection maintaining needle rod 26 in its normal full line or sew position illustrated in FIG. 7 is overcome, and needle rod 26 is thrust an additional distance a (FIG. 6) further to the right into a thread overwrap position C to depart from the sewing of the normal figure 8 stitch in the above described advancing repetitive pattern. The needle rod 26 is thus shifted axi ally to the right relative to the spindle 28 through the disclosed lost motion drive whereby the drive pin 126 is relatively positioned at the left side of needle rod slot 128. This slot 128 is suitably dimensioned to permit needle 50 to depart a sufficient distance from its normal figure 8 stitch to ensure complete thread overwrap about the end sheet without merely backstitching the thread through the end sheet as conventionally done upon return movement of the oscillating block 76 and the spindle 28 to the left as viewed in FIG. 7.

. More specifically, a portion of a suitable control circuit is schematically shown in H6. 8 with only certain significant controls being illustrated. Upon being indexed into position at the sew station 24, book 16 trips a swith 8LS to energize sewing cycle relay 4CR, which is held in by its contacts 4CR-2, and opens its contacts 4CR-1 to de-energize indexing relay 2CR which in turn opens its contacts 2CR-l to de-energize solenoid 4SOL to dog book clamp 14 of slide 18 in position for sewing. With clamp 14 dogged, limit switch llLS closes, energizing a sewing interlock relay. SCR causing sewing head to traverse in a feed direction. Relay contacts SCR-l and 5CR-3 reverse upon energization of relay SCR to energize a clutch and de-energize a brake of a conventional electric clutch and brake unit 135 on cam shaft 48. Sewing head feed releases switch 4LS thereby holding indexing relay 2CR de-energized until the sewing head 10 returns to starting position.

Near the end of the sewing traverse when switch 9L8 is actuated, it contacts 9LS-l opens and its other contacts 9LS-2 close. However, sewing cycle relay 4CR remains energized, being held in by contacts 6CR-l of a wrap cylinder relay 6CR and switch 10LS, a normally open switch held closed by a timing cam 134 on cam shaft 48.

After closing of contacts 9LS-2 timing cam 136 actuates switch 12LS upon alignment of needle 50 in trailing saw cut 54 to energize wr'ap cylinder relay 6CR through a normally closed contact 2CR-2 of indexing relay 2CR with the wrap cylinder relay 6CR being held in by normally closed contacts 2CR-2 until indexing relay 2CR is later energized upon return of sewing head 10 to starting position. Wrap cylinder relay tSCR in turn energizes solenoid valve 9SOL, through contacts 6CR- 2, which directs air to the needle rod air cylinder 118 to positively thrust needle 50 out of its repeating figure 8 pattern into its overwrap position C beyond the end sheet of the cleat 22.

With wrap cylinder relay 6 CR energized and upon further angular movement of cam shaft 48, the cams 60, 88 and 104 drive needle 50 alongside the outside end sheet of cleat 22 from position C" into position D" and timing cam 134 opens switch IOLS to deenergize sewing cycle relay 4CR and the sewing interlock relay SCR upon opening of contacts 4CR-2. Relay SCR reverses the valve solenoids 7SOL and SSOL via relay contacts 5CR-3 and 5CR-4 controlling the sewing head feed cylinder 66 to reverse the direction of the sewing head 10 to return needle 50 toward home through leading saw cut 52 of cleat 22 and return switch 9L5 to normal position upon disengaging actuator 114. It will be understood that switch 10LS may be adjusted so that the brake of the electric clutch and brake unit 135 mounted on cam shaft 48 may be applied at the proper time to ensure alignment of needle 50 with leading saw slot 52 through which needle 50 returns.

Upon approaching home, sewing head 10 closes switch 4L5, energizing indexing relay 2CR through contacts 4CR-1, and also energizing valve solenoid 4SOL which will be understood to undog book clamp 14 through a suitable air cylinder, not shown, and effeet operation of an indexing air clutch, not shown, to index book 16 to the next cleat, if there is one, and also provide a further overwrap on the first sewn end sheet of cleat 22 and return needle 50 from wrap to sew position by de-energizing the wrap cylinder relay 6CR. If there are more cleats to be sewn, these steps are repeated, but if all cleats have been sewn, the transport slide 18 passes out of the sew station 24 to commence termination of the cleat sewing cycle.

By virtue of the above described construction, the disclosed sewing head operates to ensure positive overwrap of thread around each cleat of a cleat sewn book on both sides of its spine to prevent any undesired loosening and provide a significantly improved, quality sewn book. This positive overwrapping action is ensured in a quick efficient cleat sewingoperation with a minimum number of additional required components and by means of a compact unit which can be utilized in either new or existing machines.

As will be apparent to persons skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without de-' parting from the teachings of the present invention.

1 claim:

1. A book sewing mechanism for use in progressively lacing thread in a repetitive advancing pattern across a cleat formed by a pair of slits extending laterally across a spine of a book and comprising a movable spindle, a needle rod having a needle thereon, the needle rod being mounted on the spindle to be driven thereby, a lost motion drive between the driving spindle and the driven needle rod for driving the needle rod in unison with the spindle laterally of the book spine, and a needle rod actuator for shifting the needle rod relative to the spindle to reposition the needle for thread overwrap in laterally offset relation to the cleat upon sewing of its last end sheet.

2. The mechanism of claim 1 wherein the needle ro d actuator is a power cylinder having an extendible and retractable piston rod drivingly connected to the needle rod for positioning the needle relative to the spindle for thread overwrap of the last sewn end sheet of the cleat I 3. The mechanism of claim 1 further including sensing means for sensing the last end sheet of the cleat, and control means response to the sensing means for operating the needle rod actuator upon sewing of the last end sheet of the clcat.

4. The mechanism of claim 3 wherein the sensing means is adjustable for sensing the last end sheet of books of varying thickness.

5. The mechanism of claim 1 wherein the lost motion drive includes a cam controlled oscillating block, a tubular connector fixed to both the oscillating block and the spindle for moving the spindle laterally of the book spine, the needle rod being in telescoping relation to the tubular connector, and a pin and slot lost motion connection between the needle rod and the tubular connector.

6. The mechanism of claim 5 wherein the needle rod and the tubular connector are movable between first and second relative positions respectively establishing through the pin and slot connection a normal sew position and a thread overwrap position.

7. The mechanism of claim 6 wherein the needle rod actuator includes a power cylinder with a reciprocable piston therein having an extendible and retractable piston rod coaxially fixed to the needle rod for selectively shifting it between said sew and overwrap positions.

8. The mechanism of claim 7 wherein the power cylinder is normally de-energized, wherein a spring is received in the power cylinder engaging the piston for biasing the needle rod toward said sew position, and wherein the power cylinder is selectively energizable to overcome the bias of the spring to reposition the needle in said thread overwrap position.

9. The mechanism of claim 1 further including a spindle carriage, the spindle being mounted for movement on the spindle carriage in a plane parallel to the spine of the book to be sewn andbeing reciprocable relative to the carriage both laterally and longitudinally of the spine of the book, the spindle carriage being reciprocable laterally ofthe book spine between a first traversing position, wherein the needle is adjacent a first end sheet of the book to be sewn, and a second traversing position wherein the needle is adjacent a last end sheet of the book to be sewn, the needle rod actuator being operable for shifting the needle rod for thread overwrap when the spindle carriage is in said second traversing position.

10. The mechanism of claim 9 further including a frame, the spindle carriage being supported on the frame for movement laterally of the spine of the book to be sewn, feed means for driving the spindle carriage between its first and second traversing positions, the frame having an adjustable sensor movably mounted on the frame for signaling sewing of the last end sheet of the book, the spindle carriage having a limit switch mounted thereon for actuation by the sensor, and the needle actuator being operable responsive to actuation of the limit switch when the needle is disposed in one of said pair of slits to reposition the needle for thread overwrap.

11. A thread overwrap mechanism usable in a machine for sewing a spine of a book and comprising a spindle carriage, a spindle mounted for movement on the spindle carriage in a plane parallel to the spine of the book to be sewn and being movable relative to the carriage both laterally and longitudinally of the spine of the book, a needle rod mounted on the spindle and having a needle for sewing the book spine between its end sheets, the needle rod being movable relative to the spindle between a normal sew position and an extended thread overwrap position, the spindle carriage being reciprocable laterally of the book spine between first and second traversing positions wherein the needle is respectively adjacent the first and last end sheets of the book to be sewn, means including a power cylinder for moving the needle rod relative to the spindle, the power cylinder having an extendible and retractable piston rod drivingly connected to the needle rod, the needle rod being movable by the piston rod, when the spindle carriage is in said second traversing position, to shift the needle from said normal sew position to said extended thread overwrap position to positively ensure thread overwrap about the last sewn end sheet of the book. I

12. A thread overwrap mechanism usable in a machine for sewing a spine of a book and comprising a spindle carriage, a spindle mounted for movement on the spindle carriage, a needle rod having a needle fixed thereto, the needle rod being supported on the spindle for movement relative to the spindle and laterally of the spine of the book between a normally retracted sew position and an extended thread overwrap position, drive means mounted on the spindle carriage and connected to the spindle for reciprocating the needle rod both longitudinally and laterally of the spine of the book, feed means for reciprocating the spindle carriage laterally of the book spine between first and second traversing positions wherein the needle is respectively adjacent the first and last end sheets of the book to be sewn, a lost motion drive connection between the spindle and needle rod for moving the needle rod relative to the spindle, and operating means connected to the lost motion drive for moving the needle rod from its normally retracted sew position to extended thread overwrap position when the feed means is in its second traversing position to positively drive the needle laterally of the book spine a sufficient distance to ensure complete thread overwrap about the last sewn end sheet of the book.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,797,420 Dated March 9.19%

Inventor(s) Daniel I, Streeter It is certified that error appears in the above-identified. patent and that said Letters Patent are hereby corrected asshown below:

Page 4, line 1, cancel "book spine 23" and substitute therefor --book 16- Signed and sealed this l7th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents uscoMM-oc scan-Poe Y U.S. GOVFRNHEITPRINT IG OFFICE II. OJ$"3) l-

Claims (12)

1. A book sewing mechanism for use in progressively lacing thread in a repetitive advancing pattern across a cleat formed by a pair of slits extending laterally across a spine of a book and comprising a movable spindle, a needle rod having a needle thereon, the needle rod being mounted on the spindle to be driven thereby, a lost motion drive between the driving spindle and the driven needle rod for driving the needle rod in unison with the spindle laterally of the book spine, and a needle rod actuator for shifting the needle rod relative to the spindle to reposition the needle for thread overwrap in laterally offset relation to the cleat upon sewing of its last end sheet.

2. The mechanism of claim 1 wherein the needle rod actuator is a power cylinder having an extendible and retractable piston rod drivingly connected to the needle rod for positioning the needle relative to the spindle for thread overwrap of the last sewn end sheet of the cleat.

3. The mechanism of claim 1 further including sensing means for sensing the last end sheet of the cleat, and control means response to the sensing means for operating the needle rod actuator upon sewing of the last end sheet of the cleat.

4. The mechanism of claim 3 wherein the sensing means is adjustable for sensing the last end sheet of books of varying thickness.

5. The mechanism of claim 1 wherein the lost motion drive includes a cam controlled oscillating block, a tubular connector fixed to both the oscillating block and the spindle for moving the spindle laterally of the book spine, the needle rod being in telescoping relation to the tubular connector, and a pin and slot lost motion connection between the needle rod and the tubular connector.

6. The mechanism of claim 5 wherein the needle rod and the tubular connector are movable between first and second relative positions respectively establishing through the pin and slot connection a normal sew position and a thread overwrap position.

7. The mechanism of claim 6 wherein the needle rod actuator includes a power cylinder with a reciprocable piston therein having an extendible and retractable piston rod coaxially fixed to the needle rod for selectively shifting it between said sew and overwrap positions.

8. The mechanism of claim 7 wherein the power cylinder is normally de-energized, wherein a spring is received in the power cylinder engaging the piston for biasing the needle rod toward said sew position, and wherein the power cylinder is selectively energizable to overcome the bias of the spring to reposition the needle in said thread overwrap position.

9. The mechanism of claim 1 further including a spindle carriage, the spindle being mounted for movement on the spindle carriage in a plane parallel to the spine of the book to be sewn and being reciprocable relative to the carriage both laterally and longitudinally of the spine of the book, the spindle carriage being reciprocable laterally of the book spine between a first traversing position, wherein the needle is adjacent a first end sheet of the book to be sewn, and a second traversing position wherein the needle is adjacent a last end sheet of the book to be sewn, the needle rod actuator being operable for shifting the needle rod for thread overwrap when the spindle carriage is in said second traversing position.

10. The mechaNism of claim 9 further including a frame, the spindle carriage being supported on the frame for movement laterally of the spine of the book to be sewn, feed means for driving the spindle carriage between its first and second traversing positions, the frame having an adjustable sensor movably mounted on the frame for signaling sewing of the last end sheet of the book, the spindle carriage having a limit switch mounted thereon for actuation by the sensor, and the needle actuator being operable responsive to actuation of the limit switch when the needle is disposed in one of said pair of slits to reposition the needle for thread overwrap.

11. A thread overwrap mechanism usable in a machine for sewing a spine of a book and comprising a spindle carriage, a spindle mounted for movement on the spindle carriage in a plane parallel to the spine of the book to be sewn and being movable relative to the carriage both laterally and longitudinally of the spine of the book, a needle rod mounted on the spindle and having a needle for sewing the book spine between its end sheets, the needle rod being movable relative to the spindle between a normal sew position and an extended thread overwrap position, the spindle carriage being reciprocable laterally of the book spine between first and second traversing positions wherein the needle is respectively adjacent the first and last end sheets of the book to be sewn, means including a power cylinder for moving the needle rod relative to the spindle, the power cylinder having an extendible and retractable piston rod drivingly connected to the needle rod, the needle rod being movable by the piston rod, when the spindle carriage is in said second traversing position, to shift the needle from said normal sew position to said extended thread overwrap position to positively ensure thread overwrap about the last sewn end sheet of the book.

12. A thread overwrap mechanism usable in a machine for sewing a spine of a book and comprising a spindle carriage, a spindle mounted for movement on the spindle carriage, a needle rod having a needle fixed thereto, the needle rod being supported on the spindle for movement relative to the spindle and laterally of the spine of the book between a normally retracted sew position and an extended thread overwrap position, drive means mounted on the spindle carriage and connected to the spindle for reciprocating the needle rod both longitudinally and laterally of the spine of the book, feed means for reciprocating the spindle carriage laterally of the book spine between first and second traversing positions wherein the needle is respectively adjacent the first and last end sheets of the book to be sewn, a lost motion drive connection between the spindle and needle rod for moving the needle rod relative to the spindle, and operating means connected to the lost motion drive for moving the needle rod from its normally retracted sew position to extended thread overwrap position when the feed means is in its second traversing position to positively drive the needle laterally of the book spine a sufficient distance to ensure complete thread overwrap about the last sewn end sheet of the book.

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