US3108461A - Zahradka - Google Patents

Description

Qct. 29, 1963 P. ZAHRADKA 3,108,461

. SELECTOR MECHANISM FOR A YARN-CHANGE DEVICE IN A CIRCULAR KNITTING MACHINE Filed Feb. 27, 1961 4 Sheets-Sheet l U L IT INVENTOR. a ve/ YaArJL/A a Oct. 29, 1963 P ZAHI'QADKA 3,108,461

SELECTOR MECHANISM FOR A YARN-CHANGE DEVICE IN A CIRCULAR KNITTING MACHINE Filed Feb. 27, 1961 IN VEN TOR. fave/ 221% Fad/Va 4 Sheets-Sheet 2 AAAAAAAAAA CHANISM FOR A YARN G E Sdrnzeni podniltu textiiniho strojirenstni, Liherec, Czechoslovakia Filed Feb. 27, 1961, Ser. No. $2,001 Claims priority, application Czechoslovakia Mar. 11, 1962 11 Claims. (Cl. 66l38) The present invention relates to a selector mechanism for a feed-changing device in a circular knitting machine, and is more particularly concerned with an improvement in a selector mechanism for multiple yarn feeders of the type disclosed in US. Patent No. 1,838,651 to Bentley et al.

The known selector mechanism is intended for use in a circular knitting machine having superposed needle cylinders. Its operating elements are cam discs, ratchet wheels, pawls and a selector bar. Each cam disc actuates a respective yarn feeder or guide and is rigidly connected to a ratchet wheel having circumterentially alternating long and short teeth engaged by a pawl during oscillatory movement of the latter when the pawl is suitably positioned by the selector bar. The bar is longitudinally slidable and provided with longitudinally spaced slots. Engagement of the pawls with the slots during bar movement controls the position of the pawls. Each feeder control unit thus has a single ratchet wheel and a single pawl. This arrangement has been found to be disadvantageous. When accidentally a feed changing operation is initiated twice, as may occur by an operators mistake, the cam disc involved is rotated because the corresponding pawl hook engages a ratchet wheel tooth. Such rotation, however, causes withdrawal of the operating yarn guide into a position out of needle range and cutting of the yarn by an associated cutting device, which results in dropping of the hosiery from the needles and damage to the sensitive needle latches. It is necessary then to rethread the machine, which involves an undue Waste of material.

It is an object of the present invention to provide a selector mechanism wherein upon an accidentally repeated feed changing operation involving the same operating yarn guide, a renewed engagement bet-ween the pawl tip and the ratchet wheel tooth of any control unit is avoided, and the resulting withdrawal of the operating yarn guide out of reach of the needles is positively prevented.

According to the primary feature of the present invention, each control unit which alctuates a respective yarn guide comprises a cam disc and coordinated twin ratchet wheels respectively cooperating with two pawls. The pawls have respective operating arms of different thickness, the arm of one pawl serving for positioning the corresponding inoperative yarn guide range of the needles, while the other pawl arm actuates the removal of the operative yarn guide from the range of the needles.

According to a further feature of the invention each ratchet wheel of the mechanism is equipped with teeth of the same size, the coordinated ratchet wheels being arranged so that their teeth are angul-arly offset relative to the common axis.

The invention also comprises novel details of construction and novel combinations and arrangements of parts as Will more fully appear in the course of the following description. However, the drawings merely show and the following description merely discloses preferred embodiments of the present invention which are given by way of illustration or example only.

Ziyliilifidl Patented Get. 29, 19%3 In the drawings:

FIGURE 1 is a sectional plan view of a selector mechanism for a feed changing device, the section being taken along the line II in FIGURE 2;

FIGURE 2 shows the selector mechanism of FIG. 1 in elevational section on line IIII in FIGURE 1 and associated motion transmiting means;

FIGURE 3 is a perspective view of the several ratchet wheels of the apparatus of FIGURE 1 in their basic position or position of rest;

FIGURE 4 shows the wheels of FIGURE 3 in the position assumed when two yarn guides are being exchanged;

FIGURE 5 shows the wheels of FIGURE 4 in the position assumed after the guide change has been completed; and

FIGURES 6-6e respectively illustrate diagrammatically the cooperation of a selector rod with pawls of the mechanism of FIG. 1, the selector rod being shown in the several figures in its basic position and in various operative positions.

As apparent from FIGURE 1, a stationary shaft 4 provided with a terminal flange 5 is mounted on a supporting firame 3 by means of two sleeves l, 2. The shaft 4 carries six control units I to V1 which are arranged freely rotatable thereon in axially juxtaposed relation. The control unit I controls auxiliary movements of the knitting machine not directly relevant to this invention. The units II to VI actuate movement of yarn guides in the known manner. The control unit I comprises a ratchet wheel 6 and a cam disc 7 which are fixedly connected by means of screws 8 and registration pins 9'. The ratchet wheel 6 is equipped with six teeth 10 of equal size (FIGURE 3), which are distributed uniformly over its periphery. The control unit II (FIGURE 1) which may actuate movements of a rubber yarn guide comprises a ratchet wheel 11 and a cam disc 12, which are fixedly connected by means of screws 3 and registration pins 9. The ratchet wheel 11 is also provided with six teeth 13 of equal size (FIGURE 3), which are uniformly distributed on its periphery. The other control units III to VI which actuate movements of respective yarn guides in the manner disclosed in the aforementioned patent, have respective twin ratchet wheel-s 14-45, l8-19, 2223, 2.627, and corresponding respective cam discs 16, 2t), 24, 28. Each pair of ratchet wheels and the correspondingcam disc are rigidly connected by means of screws 8 and registration pins 9.

Each ratchet wheel of units III to V1 is equipped with three teeth of equal size 17, 17a, 21, 21a, 25, 25a, 29, 2.9a (FIGURE 3) spaced apart; however, the teeth of each ratchet wheel are offset 60 from the teeth of the twin wheel. The successive ratchet teeth of each control unit are thus spaced 60 from each other on the peripher of the ratchet wheel pair, and placed alternatingly on the twin wheels. Friction washers 3d are mounted on the shaft 4 and secured against rotation in a conventional manner. A compression spring 33 is mounted on the threaded terminal portion of the shaft 4 remote from the flange 5 between a Washer 31 which abuts against the sleeve 2 and a nut 32 which threadedly engages the shaft 4. The spring 33 urges the individual control units I to VI towards one another.

The sleeves 1 and Z of the supporting frame 3 rotatably support a pawl carrying frame 34. The frame 34- is oscillated in a known manner through an angle of 65 by means of a not illustrated eccentric on a countershaft of the knitting machine. Ten pawls 36 to 45 are freely rotatable on a shaft 35 which is mounted on the frame 34 parallel to the shaft 4. The pawls are twoarmed levers having corresponding arms of identical length. One arm of each pawl is hook shaped, and is operated by means of the other arm. The hooks of the pawls bear on the peripheries of respective ratchet wheels under the pressure of flat springs 46 which are secured on the pawl carrying frame 34 (FIGURE 2). The movement of each cam is transmitted to an associated yarn feeder in a conventional manner disclosed in the aforementioned patent to Bentley.

A lever 75 a'buts against the end of a partly illustrated yarn feeder '73 which is movably mounted on the machine frarne in a known manner not further illustrated. A cam follower 76 mounted on the lever 75 by means of a pivot pin 77 engages the face of the cam 16. The cam follower is adjustable on the lever 75 by means of a screw 7 8 for varying the position of the yarn feeder 73. The several levers swing on a common shaft 74. An elongated selector rod 47 of circular cross section is mounted on the supporting frame 3 parallel to the shafts 4 and 35, and slidable on the supporting frame 3 in a longitudinal direction. The rod 47 has eight axially spaced annular slots or grooves 48 to 55. The grooves are of identical radial depth, but differ in axial width (FIGURE 1). Depending on the position of the selector rod 47, individual operating arms 56 t 65 of the pawls 36 to 45 which differ in width may selectively engage the above mentioned grooves 48 to 55. The narrow arm 57 of the pawl 37, for instance, can engage the groove 49 (FIGURE 6a), while the wider extension 59 of the pawl 39 can only engage the Wider groove 50 (FIGURE 6b). Similarly, the wider extension 61 of the pawl 41 can enter the groove 52 (FIGURE 60), the wider extension 62 of the pawl 42 can enter the groove 53 (FIGURE 6d), and the wider extension 64 of the pawl 44 can enter the groove 55 (FIGURE 6e) upon suitable longitudinal displacement of the selector rod 47 from the rest position shown in FIG. 6 over axial distances t, 2t, 3t, 4t and t as shown in FIGURES 6a to 6e.

One end of the selector member 47 is equipped with a knurled knob 66 which permits manual displacing of the selector rod in a longitudinal direction, while the other end of the selector rod carries a screw 67 threadedly engaging an axial bore in the rod 47, and secured in an axially adjusted position by a lock nut 68 (FIGURE 1). A compression spring 70 is mounted between an integral collar 69 of the selector member 47 and the frame 3. The compression spring '70 urges the aforementioned other end of the selector rod against the head of an adjusting screw 71 threadedly engaging the supporting frame 3. The axial position of the screw 71 is secured by means of a lock nut 72. The longitudinal displacement of the selector rod 47 from its basic position (FIG- URE 6) over respective distances 1, 2t, 3t, 4t or St (FIG- URES 6a, 6b, 6c, 6d, 6e) into five different operative positions is actuated in a conventional manner by studs of different height arranged on the links of a nonillustrated pattern chain of the knitting machine by means of levers or a Bowden cable acting on the head of the screw 67 against the force of the spring 70.

The afore-described selector mechanism operates as follows:

When all yarn guides (not illustrated) of the knitting machine are inoperative, the ratchet wheels 6, 11, 14, 15, 18, 19, 22, 23, 26, 27 of the control units I to VI (FIG- URE 1) are in the basic position shown in FIGURE 3 relative to respective points of engagement Z (as shown in FIGURE 2). In this basic position, the teeth 10, 13, 17a, 21a, 25, 29 of the ratchet wheels 6, 11, 15, 19, 22, 26 are aligned for engagement by corresponding pawls, while the teeth 17, 21, 25a, 29a of the remaining ratchet wheels 14, 18, 23, 27 are offset from the point of engagement by at least an angle of 60.

The selector member 47 is also in its basic position (FIGURE 6), in which all operating arms 56 to 65 of the pawls 36 to 45 bear against the outer periphery of the selector member 47 between the several slots so that the pawl hooks are kept out of engagement with the ratchet wheel teeth.

When one of the not illustrated yarn guides, for example the yarn guide of the control unit III (FIGURE 1), is to be brought from its inoperative into its operative position for a feed change, the selector rod 47 is displaced from its initial position (FIGURE 6) in a longitudinal direction over a distance 2t (FIGURE 61;) into an operative position by means of the pattern chain.

The respective arms 56, 59, 60, 63, 65 of the pawls 36, 39, 40, 43, 45 can enter the grooves 48, 50, 51, 53, 55 in the selector rod 47 under the urging of flat springs 46, during movement of the frame 34, whereby the hooks of the afore-mentioned pawls are moved into contact with the corresponding ratchet wheels 6, 15, 18, 23, 27 (FIG. 1). It will be remembered that the ratchet wheel 6 and the ratchet wheel 15 have teeth 10, 17a at the point of engagement Z in the basic position. The ratchet wheels 6 and 15 are rotated through an angle of 60 during the next oscillating motion of the pawl frame 34. The cam disc 16, which is rigidly connected to the ratchet wheels 15 and 14, is turned by the same, and moves the thread guide of the control unit III in the conventional manner into its operative position i.e. within reach of the knitting needles. The cam disc 7 which is rigidly connected to the ratchet wheel 6 is also rotated at the same time, and causes a change in the density of the fabric during the operation of the newly engaged thread guide.

When the ratchet wheel 15 rotates from its basic position (FIGURE 3) through an angle of 60 in the direction of the arrow, it reaches the position shown in FIG- URE 4 in which the ratchet wheel 15 has no tooth 17a at the point of engagement Z. The ratchet wheel 14 rotates together with the ratchet wheel 15 in the direction of the arrow, and the tooth 17a of the ratchet wheel 15 is replaced at the point of engagement Z by the tooth 17 of the ratchet wheel 14. When the selection of the thread guide of the control unit III is completed, the selector rod 47 is returned to its basic position by the act-ion of the spring 70. In this position of the rod 47, the operating arms of the pawls cannot enter the respective grooves in the selector member 47, and the pawl hooks are held out of engagement with the ratchet wheel teeth.

During a feed change in which the yarn guide of the control unit III is to be replaced in the feeding position by the yarn guide of the control unit IV, the operation of the selector mechanism is as follows:

Upon impulse generated by the pattern chain, the selector rod 47 is moved from its basic position (FIG- URE 6) over the distance 3t to an operative position shown in FIG. 6c. Thus the arms 56, 58, 61, 63, 65 of the pawls 36, 38, 41, 43, 45 are released from their inoperative positions and enter the grooves 48, 50, 52, 53, 55 of the selector rod 47 under the pressure of the flat springs 46. The hooks of said pawls contact the corresponding ratchet wheels 6, 14, 19, 23, 27. Only the three ratchet wheels 6, 14, 19 have teeth 10, 17 and 21a at the point of engagement Z, and these three ratchet wheels together with wheels 15 and 18 are turned simultaneously through an angle of 60 in the direction of the arrows from the position shown in FIGURE 4 to the position according to FIGURE 5 during the next oscillatory movement of the pawl frame 34.

The cam disc 16 which is rigidly connected to the ratchet Wheel 14 turns with the wheel and shifts the yarn guide of the control unit III from operative position into its inoperative position, while the cam disc 20, rigidly connected with the ratchet wheel 19, moves the previously inoperative yarn guide of the control unit IV into its operative position i.e. within range of the needles. The cam disc 7 which is rigidly connected to the ratchet wheel 6 and rotates therewith, causes a change in the density of the fabric during initial operation of the yarn guide.

When the two yarn guides of the control units V and VI are substituted for other yarn guides, the mechanism operates in an analogous manner. As is evident from FIGURES 6b to 6e, the wider arms 59, 6 1, 62 and 64 of the pawls engage corresponding wider grooves 50, 52, 53, 55 of the selector rod 47, and cause their respective yarn guides to be brought from an inoperative position within reach of the needles, while the narrower arms 53, 60, 63, 65 of the pawls, which enter the grooves 50 to 55 of the selector member 47, effect the removal of the corresponding operative yarn guides to the inoperative position out of reach of the needles, it the teeth of the cooperating ratchet wheels are at the point of engagement Z.

If accidentally a feed change from the yarn guide of control unit III to that of unit IV is again initiated while the ratchet wheels already are in the position shown in FIG. the selector rod 47 is again shifted from its basic position (FIGURE 6) through the distanoe 3t to its operative position shown in FIG. 60. The arms 56, 58, 61, 63, 65 of the pawls 36, 38, 41, 43, 45 again enter the grooves 43, 50, 52, 53, 55 in the selector rod 47 under the action of fiat springs 46, and the hooks of the pawls again bear against the corresponding ratchet wheels 6, 14, 19, 23, 27. It will be recalled that during the previous movement of the yarn guide of the control unit IV into its operative position, the ratchet wheel pair 13, 19 was rotated through an angle of 60 in the direction of the arrow from the position shown in FIGURE 4 to the position according to FIGURE 5 a tooth 21 of the ratchet wheel 18 is now at the point of engagement Z, while the ratchet wheel 19 has no tooth at the point of engagement Z."

The pawl 41 therefore cannot rotate the corresponding ratchet wheel 19. In the position of FIG. 60, the arm 60 of the pawl 4d abuts against the outer periphery of the selector rod 47, and the pawl 40 cannot engage the tooth 21 of the ratchet wheel 18. The cam disc 26 rigidly connected to the ratchet wheels 18, 19 remains stationary, and so does the yarn guide of the control unit TV, which is already in the operative position. Similarly the inoperative yarn guide of the control unit 111 remains stationary during an accidentally repeated feed change movement of the selector mechanism although the arm 58 of the pawl 38 enters the groove 50 of the selector rod 47, because the ratchet wheel 14 has no tooth 17 at the point of engagement Z (FIGURE 5).

The pawl 36 however engages a tooth of the ratchet wheel 6 at the point of engagement Z, and the ratchet wheel 6 and the connected cam disc '7 are rotated through 60", said rotation causing only a temporary change in the density of the fabric.

A change of the four individual yarn guides belonging to control units III to V1 is effected with the aid of cam discs 16, 20, 24-, 28, while the insertion of the rubber thread guide of the control unit H within reach of the needles is caused by the cam disc 12, irrespective of which of the four yarn guides of the control units 1511 to V1 is just in operation. When the selector member 47 is moved from its basic position '(FIGURE 6) into the operative position of FIG. 6a over the distance t, the arm 57 of the pawl 37 enters the groove 49 in the selector rod 47. Consequently, the pawl 37 engages a tooth 1 3 of the ratchet wheel 11, and the cam disc 12 which is rigidly connected to the ratchet wheel 11 is rotated through an angle of 60. As the ratchet wheel 6 is provided with six teeth 19 spaced 60 apart, the ratchet wheel together with the cam disc 7 fixedly connected thereto is rotated during every selection of the rubber thread guide. During this selection all yarn guides of the control units III to V1 remain in the positions which they assumed prior to the selection of the rubber thread guide because the arms 53 to 65 of pawls 38 to 45 bear 6 against the outer periphery of the selector rod 47 so that the hooks of these pawls cannot cooperate with the teeth of the corresponding ratchet wheels.

While the arm 57 of the pawl 37 enters the groove 49 in the selector rod 47, the operating arm 56 of the pawl 36 enters the groove 48 causing the pawl 36 to engage a tooth 10 of the ratchet wheel 6 whereby the cam disc 7 is rotated for a change in the density of fabric.

The single selector member rod 47 has grooves of different Width for receiving the under arms 59, 61, 62, 64 of a group of pawls 39, 4 1, 4-2, 44 which actuate movement of yarn guides into the operative position, and for receiving the narrower arms 58, 6t), 63, 65 of another group of pawls 38, 4t 42, 45 which return the yarn guides to the inoperative position. This single rod may be replaced, if so desired, by two selector members, which respectively actuate the two groups of pawls.

It will be appreciated that the ratchet wheel pairs having offset teeth and cooperating with separate pawls having operating arms of different thickness to rotate cam discs which actuate the respective yarn guides of the control units III to VI, prevent the accidental repeated selection of a yarn guide which is already in the operative position.

I claim:

1. In a selector mechanism for actuating feed changes in a knitting machine, in combination,

(a) a support;

(lb) ratchet wheel means rotatable on said support about an axis; said ratchet wheel means having two axially spaced sets of teeth, the teeth of each set being angularly spaced about said axis, and each tooth being angularly spaced from the two circumferentially adjacent teeth of the other set;

(0) two pawl means respectively corresponding to said sets;

(d) actuating means mounted on said support for actuating joint reciprocating movement of said pawl means and rotation of said ratchet wheel means by said reciprocating movement of said pawl means when the same engage a tooth of a corresponding set of said teeth;

(e) control means movable on said support between a plurality of positions, said control means in a first one and a second one of said positions respectively engaging said pawl means for urging the engaged pawl means into a position of engagement with a corresponding one of said sets of teeth while maintaining the other pawl means out of a position of engagement with the other set of teeth of said ratchet wheel means; and

(f) motion transmitting means for transmitting the movement of said ratchet wheel means to a yarn feeder of said knitting machine.

2. In a mechanism as set forth in claim 1, the teeth of said two sets being of substantially uniform size.

3. In a mechanism as set forth in claim 1, said ratchet wheel means including two ratchet wheels, each wheel carrying a set of said teeth, and means fixedly connecting said wheels for joint movement.

4. In a mechanism as set forth in claim 1, said actuating means including a pawl carrier pivotally mounted on said support for reciprocating movement about said axis, said pawl means being mounted on said carrier in axially spaced relationship.

5. In a mechanism as set forth in claim 1, said control means including a control member movable in a direction substantially parallel to said axis and formed with a plurality of grooves, transverse to the direction of elongation, each pawl means having an arm selectively engageable with a groove of said control member, and

resilient means urging said pawl means into a position in which said arm engages said groove and said pawl means engages the corresponding set of teeth.

6. In a mechanism as set forth in claim 1, said motion '2 transmitting means including rotary cam means fixedly connected to said ratchet wheel means for joint rotation therewith about said axis.

7. In a selector mechanism for actuating feed changes in a knitting machine, in combination,

(a) a support;

(12) ratchet wheel means rotatable on said support about an axis, said ratchet wheel means having two axially spaced sets of teeth, the teeth of each set being angularly spaced about said axis, and each tooth being angularly spaced from the two circumferentially adjacent teeth of the other set;

(c) a pawl carrier reciprocally pivotable on said frame about said axis;

(d) two pawl means mounted on said carrier for pivoting movement therewith, and movable on said carrier between an operative position in which each pawl means is adapted to engage a tooth of a corresponding one of said sets for rotary movement of said wheel means about the axis thereof during one stroke of the reciprocating movement of said pawl carrier, and an inoperative position in which said pawl means is removed from the corresponding set of teeth;

(e) control means for selectively moving one of pawl means into the operative position thereof while maintaining the other pawl means in the inoperative position thereof; and

(f) motion transmitting means for transmitting the movement of said ratchet means to a yarn feeder of said knitting machine.

8. In a selector mechanism as set forth in claim 7, each of said pawl means including a pawl member pivoted on said carrier for movement between operative and inoperative positions, and said control means including resilient means permanently urging said pawl member into the operative position thereof, and a control member selectively engageable with one of said pawl members for maintaining the same in said inoperative position against the urging of said resilient means.

9. In a selector mechanism as set forth in claim 8, each of said pawl members having an arm portion of predetermined dimensions different from the dimensions of the arm portion of the other pawl member and spaced from said other arm portion, and said control member being formed with a plurality of recesses of different dimensions, one of said recesses being of dimensions sur'licient to receive one of said arm portions only, the corresponding one of said pawl members being in the operative position when the arm portion thereof is received in said one recess.

10. In a selector mechanism for actuating feed changes in a knitting machine in combination,

(a) a support;

([2) a plurality of ratchet wheel means rotatable on said support about a common axis, said ratchet wheel means being axially spaced from each other;

(0) two axially spaced sets of teeth on each of said ratchet wheel means, the teeth of each set being angularly spaced about said axis, and each tooth being angularly spaced from the two circumferentially adjacent teeth of the other set;

(d) a pawl carrier reciprocably pivotable on said frame about said common axis;

(e) a plurality of pawl means mounted on said carrier for pivoting movement therewith, each of said pawl means being coordinated with one of said sets of teeth, and movable on said carrier between an operative position in which said pawl means is adapted to engage a tooth of the coordinated set, and an inoperative position in which said pawl means is remote from said coordinated set;

(f) control means for moving a selected pawl means into the operative position thereof while maintaining the pawl means coordinated with the other set of teeth of the same ratchet wheel means in the inoperative position; and

(g) motion transmitting means for transmitting the movement of said ratchet means to a yarn feeder of said knitting machine.

11. In a selector mechanism as set forth in claim 10, said control means including means for moving a pawl means coordinated with another ratchet wheel means from the inoperative to the operative position thereof while said selected pawl means is being moved to the operative position thereof.

References Cited in the file of this patent UNITED STATES PATENTS 1,838,651 Bentley et al. Dec. 29, 1931 2,180,708 Houseman Nov. 21, l939 2,625,808 Green et al. Jan. 20, 1953 2,709,351 Bouthillette et a1. May 31, 1955 3,022,652 Wainwright et al. Feb. 27, 1962

Claims (1)

1. IN A SELECTOR MECHANISM FOR ACTUATING FEED CHANGES IN A KNITTING MACHINE, IN COMBINATION, (A) A SUPPORT; (B) RATCHET WHEEL MEANS ROTATABLE ON SAID SUPPORT ABOUT AN AXIS; SAID RATCHET WHEEL MEANS HAVING TWO AXIALLY SPACED SETS OF TEETH, THE TEETH OF EACH SET BEING ANGULARLY SPACED ABOUT SAID AXIS, AND EACH TOOTH BEING ANGULARLY SPACED FROM THE TWO CIRCUMFERENTIALLY ADJACENT TEETH OF THE OTHER SET; (C) TWO PAWL MEANS RESPECTIVELY CORRESPONDING TO SAID SETS; (D) ACTUATING MEANS MOUNTED ON SAID SUPPORT FOR ACTUATING JOINT RECIPROCATING MOVEMENT OF SAID PAWL MEANS AND ROTATION OF SAID RATCHET WHEEL MEANS BY SAID RECIPROCATING MOVEMENT OF SAID PAWL MEANS WHEN THE SAME ENGAGE A TOOTH OF A CORRESPONDING SET OF SAID TEETH; (E) CONTROL MEANS MOVABLE ON SAID SUPPORT BETWEEN A PLURLITY OF POSITIONS, SAID CONTROL MEANS IN A FIRST ONE AND A SECOND ONE OF SAID POSITIONS RESPECTIVELY ENGAGING SAID PAWL MEANS FOR URGING THE ENGAGED PAWL MEANS INTO A POSITION OF ENGAGEMENT WITH A CORRESPONDING ONE OF SAID SETS OF TEETH WHILE MAIN-

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