US3875425A

US3875425A - Apparatus for the selective holding of a to-and-fro driven control element of a textile machine in one of its terminal position

Info

Publication number: US3875425A
Application number: US427625A
Authority: US
Inventors: Franz Speich
Original assignee: IMB INGENIEURBURS fur MASCHINENBAU JAKOB MULLER
Current assignee: IMB INGENIEURBURS fur MASCHINENBAU JAKOB MULLER
Priority date: 1973-01-10
Filing date: 1973-12-26
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01
Also published as: CH543127A; JPS598052B2; JPS505633A; GB1429154A; FR2215821A5; DE2359135C3; CS195267B2; ES421359A1; IT1002346B; DE2359135A1; DE2359135B2

Abstract

An apparatus for the selective holding of a to-and-fro driven control element of a textile machine in one of its terminal positions, wherein there is provided a holding element constructed as an armature of a selectively energizable electromagnet, this holding element, when the electromagnet is not energized, moves from a first position, in which it bears against the electromagnet into a second position and that in one of its positions blocks the control element located in the one terminal position. An actuation mechanism or device acts upon the holding element in order to bring the holding element from its second position into its first position and/or to raise the holding element bearing against the electromagnet from such electromagnet when it is not energized.

Description

United States Patent Speich Apr. 1, 1975 3.749.935 7/l973 Warren 307/ l4) Primary ExuminerL. T. Hix Attorney. Agent, or Firm-Diller, Brown Ramik 84 POSITION Wight [75] Inventor. Franz Speich. Frick, Switzerland 57 ABSTRACT I73] Assignee: 1MB lngenleurburs fur l 1 Maschinenbau Jakob M ll r, F i k An apparatus for the selective holding of a to-and-fro Swi l d driven control element of a textile machine in one of its terminal positions wherein there is provided a [221 1973 holding element constructed as an armature of a selec- [21] A l No; 427,625 tively energizable electromagnet, this holding element when the electromagnet is not energized, moves from a first position, in which it bears against the electro- Forelgn Apphfamm Prmmy Dam magnet into a second position and that in one of its J'tIlL IU, SWIIZCl'IUnd t t t i t t t positions blocks the ontrol element lgcated in [he one terminal position. An actuation mechanism or de- L.S. (,I. t t t v t t ricg acts upon the holding element in rder to bring 'f Cl H05 the holding element from its second position into its Field of SlalTh 317/262 R3 307/l49- 154 first position and/or to raise the holding element bearing against the electromagnet from such electromagl l Rtfferences cued net when it is not energized.

UNITED STATES PATENTS mien: 7/1933 Paris 317/262 R 13 8 Drawmg figures 7- 4 2 3 70 l} l l 2% 5 l r' 'p 3 7\ l! 2 a I I 5 m- AN H.575

SILU 2 6F 5 A 13cB APPARATI'S FOR THE SELECTIVE HOLDING ()F A TO-AND-FRO DRIVEN CONTROL ELEMENT OF A TEXTILE MACHINE IN ONE OF ITS TERMINAL POSITION BACKGROUND OF THE INVENTION The present invention relates to a new and improved construction of apparatus for selectively fixedly holding a to-and-fro driven control element of a textile ma chine in one of its terminal positions.

SUMMARY OF THE INVENTION It is a primary object of the present invention to provide an apparatus of the previously mentioned type which is simple in construction. operates in a relatively disturbance-free manner and which is not associated with any undesired limitations in the operating speed of the textile machine.

Another object of the present invention aims at the provision of an improved construction of apparatus for the selective holding of a to-and-fro driven control element of a textile machine in one of its terminal positions. wherein such apparatus is relatively simple in construction and design. extremely reliable in operation. and not readily subject to malfunction or breakdon it.

Now in order to implement these and still further objects of the invention. which will become more readily apparent as the description proceeds. the apparatus of the previously mentioned type and as contemplated by the invention comprises a holding element constructed as an armature of a selectively cnergizable electromagnet. wherein when the electroniagnet is not energized this holding element is moved from a first position. where it bears against the electromagnet. into a second position. and that in one of its positions blocks the control element located in a terminal position. An actuation mechanism or device acts upon the holding element in order to bring the holding element from its second position into its first position and/or to raise the holding element bearing against the electromagnet when the electromagnet is not energized from such electromagnet.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will he better understood and objects other than those set forth above. will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. I is a schematic view. partially in cross-section. of a first exemplary embodiment of apparatus designed according to the invention;

FIG. 2 depicts the embodiment of FIG. I in a different position of the components thereof.

FIG. 3 is a second exemplary embodiment of apparatus designed according to the invention.

FIG. 4 illustrates the apparatus of FIG. 3 in a different position of the components thereof;

FIG. 5 is a schematic view of a third exemplary embodiment of the invention;

FIGS. 6 and 7 depict the apparatus of FIG. 5 with the components thereof in respectively different positions; and

FIG. 8 is a schematic view depicting a fourth exemplary embodiment of the invention DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The exemplary embodiments of apparatus depicted in FIGS. I to 7 will be understood to each comprise and electromagnet 2 which is mounted at a schematically depicted holding or holder mechanism I. The nonvisible coil of each such electromagnet 2 is selectively connected via two coil terminals 3 with a not particularly illustrated suitable voltage source. Excitation of each electromagnet 2 occurs in accordance with a control program.

The armature 4 ofthe electromagnet 2 is constructed as a retaining or holding hook member or element which is pivotably mounted about an axle or shaft 5 at the holding or holder device I. A resilient element. such as the spring 6 engages with the armature 4. this spring 6 being secured at one end to the holding mechanism or device I. as shown. Spring 6 moves the armature 4. when the electromagnets are not energized. out of a first position where it bears against the associated electromagnet 2, as best seen by referring to FIGS. I. 3 and 5, into a second position. as best seen by referring to FIGS. 2. 4 and 6. where it engages with a recess 7a of a control element 7 and fixedly holds the latter in a first terminal or end position. This control element 7 is driven to-andtro in synchronism or cycle with a textile machine and between two terminal positions in any suitable manner. The second terminal position of the control element 7 has been indicated in phantom lines. This control element 7 can serve. for instance. to actuate a yarn guide device of a textile machine. as the same has been described in German patent application P 22 ()4 814 incorporated herein by reference.

The armature 4 is provided with a nose or dog mem ber 4a with which cooperates an actuation de\ice. which for the exemplary embodiments depicted in FIGS. 1 and 2. 3 and 4 as well as S to 7 respectively. is differently constructed.

In particular. with the exemplary embodiment depicted in FIGS. and 2 this actuation device or mechanism incorporates a lever 8 which is rotatably mounted at one end about a shaft or axle l0 and at its other end is supported through the agency of a spring II at the holding mechanism or device 1. Approximately at the center of the lever 8 there is rotatably secured thereat a roller or roll 12 which cooperates with a rotatably driven control disk or cam I3. By means of the spring I1 there is achieved the result that the roller 12 will bear against the control cam surface of the control cam 13. At the end of the lever 8 which is rotatable about the shaft II] this lever 8 carries an actuation ledge member or rail 9 which acts upon the nose or dog 41:.

The control cam 13 rotates in accordance with the movement ofthe control element 7 in cycle or synchronism with the textile machine. If. as shown in FIG. 1. the roller 12 cooperates with the protruding portion 13a of the control cam I3, then the lever 8 is raised and rotated into a position in which the actuation ledge or rail 9 acting upon the nose or dog 4a presses the armature 4 against the electromagnct 2 FIG. I J. During further rotation of the control cam or disk I3 the lever 8 is downwardly pressed by the spring II and the actuation ledge 9 rotates in clockwise direction out of the position depicted in FIG. I into the position illustrated in FIG. 2. If at this point in time the electromagnet 2 is not energized. then the spring 6 pulls the armature 4 into its position where it has dropped or moved away from the electromagnet 2. and which has been shown in FIG. 2. In this position the armature 4 engages with the control element 7 which. at this point in time. is located in its lower end or terminal position and fixedly retains this control element in such terminal position IFIG. 2).

Now as soon as the portion or part 13a of the control cam 13 again becomes effective at the roller 12. then the lever 8 is again raised and the actuation element 9 is rotated in the counterclockwise direction. In so doing. the actuation element 9 impacts against the nose or dog 41:. with the result that the armature 4 is again brought to bear against the associated electromagnet 2.

With the electromagnet 2 energized the armature 4 which bears thereagainst is fixedly held and cannot be moved by the spring 6 away from the electromagnet. The control element 7 is therefore not fixedly held in its lower terminal or end position. rather carries out its to-and-fro movement without obstruction.

Since the armature 4 is brought to bear against the electromagnet 2. out of its position depicted in FIG. 2, by means of the actuation ledge or rail member 9, this electromagnet must not attract the armature 4 out of its dropped-off position. rather must only fixedly hold the armature 4 contacting there-against. Hence. the electromagnet. because it must not carry out any actual stroke or displacement work. can be correspondingly smaller dimensioned.

With the exemplary embodiment depicted in FIGS. 3 and 4 the actuation mechanism. analogous to the embodiment depicted and described above with regard to FIGS. I and 2, possesses an actuation lever 8 which is rotatable about a shaft or axle 10, this lever 8 hearing at one end through the agency of a spring 11 at the holding or holder mechanism 1. At the lever 8 there is again rotatably mounted a roller 12 which is pressed by spring 11 against the control cam surface or curve of the control disk or control cam 13 which is rotatably driven in synchronism or cycle with the textile machine.

At the end ofthe lever 8 which is rotatable about the shaft N) there is mounted at this lever 8 an actuation ledge or rail member i.e.. an actuation member 14. This actuation ledge or rail member 14, analogous to the actuation ledge or rail member 9 of FIGS. 1 and 2, acts upon the nose or dog member 4a of the armature 4.

how ever in this instance is arranged at the other side of such nosc 40 than was the case for the actuation ledge member 9 of FIGS. 1 and 2.

If the armature 4 is located in a position where it has dropped-off or moved away from the electromagnet 2 (FIG. 4]. then it blocks the control element 7 located in its lower terminal or end position. In this position the armature 4 is held by the spring 6. Ifthe electromagnet 2 is energized. then such attracts the armature 4. so that this arntaturc. as best shown by referring to FIG. 3. comes to bear against the electromagnet.

As long as the roller I2 bears against the portion or part [3/1 of the control cam surface or control curve. which is defined by the points A and B. then the actuation ledge or rail member 14 does not act upon the nose or dog 44: (FIG. 3). On the other hand, if the roller 12 is located in the recess 13 of the control cam 13. then the lever 8 is rotated by the spring II, with the result that the actuation ledge or rail member 14 rotates in clockwise direction and pushes against the nose or dog member 4a. The actuation mechanism or device 8. 11,

l2. l3. I4 is constructed in such a way that the actuation ledge member I4 then pushes against the nose when the armature 4 bears against the electromagnet 5 2. Since this electromagnet 2. at this point in time, is not energized. the armature 4 is pushed away from the electromagnet by means ofthe actuation ledge member 14 and is rotated by the spring 6 into the position depicted in FIG. 4.

Depending upon whether the electromagnet is energized or not, the armature 4 is located in the one or other position and blocks the associated control ele ment 7 or does not influence such control element respcctively.

The pushing away fo the armature 4 from the nonenergized electromagnet 2 by means of the actuation ledge or rail member 14 is particularly of significance in the case of direct-current magnets, since the armature, after de-energizing the excitation coil of the elec tromagnet, remains adhering at the electromagnet owing to remanence. Now in order to avoid erroneous actuation brought about by the undesired adherence of the armature 4, this armature is raised or moved from the electromagnet when the latter is not energized by means of the actuation ledge or rail member 14.

With the exemplary embodiment depicted in FIGS. 5 to 7 the actuation mechanism is constructed as a combination of the actuation mechanisms of FIGS. 1 and 2 and that of FIGS. 3 and 4. The actuation lever 8 which bears at one end via a spring II at the holding mechanism or device 1 is rotatably mounted at its other end about the shaft or axle 10 and at this end possesses two actuation ledge or rail members i.e..

actuation members

9 and 14. These members accommodate therebetween the nose or dog 41:. upon which they act depending upon the position of the lever 8. The position of the actuation lever 8 is determined by the control cam or disk 13 which is rotatably driven in synchronism with the textile machine, this control cam 13 cooperating with a roller 12 which is rotatably secured at the lever 8.

FIG. 5 illustrates the armature 4 in its position where it bears against the electromagnet 2, and in which position the armature 4 is moved by the actuation ledge member or rail member 9 which acts upon the nose 4a. The lever 8 is located in its raised position in which it is rotated by means ofthe protruding portion 13a of the control cam 13.

During further rotation ofthe control cam 13 the roller l2 arrives so as to bear against the portion or part 13b of the control cam 13. resulting in rotation of the lever 8 under the action of the spring 11.

Now if the electromagnet 2 is energized. when the armature 4 bears thereagainst. then this armature 4 is fixedly held in this position and does not influence the to-and-fro movement of the control element 7.

On the other hand. ifthe electromagnet 2 is not energized when the armature 4 bears thereagainst. when the cam surface portion or part 13b cooperates with the roller 12, then the armature 4 under the action of the spring 6 can follow the actuation ledge or rail member 9 rotating in clockwise direction and such armature rotates into a position where it drops off. i.e., moves away from the magnet as such has been depicted in FIG. 6. In this position the armature 4 fixedly holds the control element 7 in its lower terminal or end position.

Ill

With further rotation of the control cam I3 the roller 12 drops into the recess I34 (FIG. 7). As a result. the lever Sis still further rotated and the actuation ledge or rail member 14 presses against the nose or dog 41:. in the event that after deenergization of the magnet 2 the armature 4 is fixedly held owing to the rcmancnce of the magnet and is hindered in its rotational movement. Due to the action of the actuation ledge or rail member 14 upon the nose or dog 4a. the armature 4 is pushed away from the electromagnet 2 and under the action of the spring 6 is rotated into its position where it has dropped-off the electromagnet (FIG. 7).

During further rotation of the control cam or disk I3 the roller 12 again travels onto the portion or part 13!) of the control cam 13. bringing about a rotation of the actuation lever 8 in the counterclockwise direction. In so doing. the lever 8 assumes the same position as shown in FIG. 6. The actuation ledge or rail members 9 and I4 respectively. do not act upon the nose or dog member 4a oI- the armature 4.

As soon as the roller or roll 12 again travels onto the protruding portion 13a of the control disk I3, then the lever 8 together with the

actuation ledge members

9 and 14 are further rotated in the counterclockwise direction. The actuation ledge member 9 begins to press against the nose or dog 41:. Consequently. the armature 4 is rotated towards the electroniagnet 2 until it comes to bear against the magnet. Then during further rotation ofthc cam disk I3 the previously described course of movement repeats.

FIG. 8 illustrates a different exemplary embodiment of the invention apparatus. An clectromagnet I6 is attached to a holding device or mechanism IS. The armature 17 of the electromagnct is constructed to possess a substantially plate-shaped configuration and carries a plunger 18 which is displaceably guided in the holder or holding mechanism I5. At the plunger 18 there engages a spring [9 which is attached to the holding mechanism 15. this spring I9 strives to pull the plunger I8 together with the armature plate 17 away from the electromagnet.

At the plunger 18 there is mounted a nose or dog member I811 which engages in a groove 20a of an actuation lever 20 which is guided in the holding or holder mechanism IS. The groove 20 is bounded or delimited by two stops 20b and 200 which act upon the nose or dog I811.

The actuation lever or lever member 20 is supported at one end at a spring 21. At the other or opposite end this lever 20 carries a roller 22 which is urged by the spring 21 against the control cam surface of a control cam or disk 23 which is rotatably driven in cycle or synchronism with the textile machine.

The apparatus depicted in FIG. 8 operates in the same manner as the apparatus depicted in FIGS. 5 to 7.

If. as shown in FIG. 8. the protruding cam surface portion or part 2311 of the control cam 23 acts upon the roller 22. then the lever 20 is displaced against the force of the spring 21 and the stop 20h presses against the cam 18a. with the result that the armature I7 is pressed against the electromagnet 16.

In this position of the armature 17. in which it bears at the electromagnct 16. the free end of the plunger 18 is located externally of the path ofmovement of a nonillustrated to-and-fro moving driven control element. which corresponds to the control element 7 of FIGS. 1

to 7 inclusive. Consequently. the to-and-fro movement of this control element is not influenced.

If the control cam 23 rotates further. then the roller 22 comes to bear against the surface portion 23b of the control disk 23. resulting in an axial displacement of the actuation lever 20 brought about by the spring 2I.

If at this point in time the electromagnet I6 with the armature I7 bearing thereagainst. is energized. then the armature is fixedly held and does not follow the movement of the actuation lever 20.

If. however. the elcctromagnet I6 is not energized. then the armature I7 and the plunger 18. under the tractive effort or pulling force of the spring [9. follows the displacment movement ofthe actuation lever 20. If. however. the armature I7 remains caught owing to the remanence at the electromagnet 16, then the stop or impact member 20 presses against the nose 18a as soon as the roller 22 falls into the recess 230 of the control cam 23. This brings about lifting-off of the arma ture I7 and permits axial displacement of the plunger 18.

The actuation lever 20 and also the plunger I8 are shifted until assuming the phantom line depicted position. in which the plunger blocks the previously mentioned. although not here particularly illustrated. control element in its one terminal position. as such has been described in conjunction with the embodiments of FIGS. I to 7.

With the embodiment depicted in FIG. 8 it would be also conceivable to construct the plunger 20 at its end in such a way that it blocks the control element in its one terminal position when the armature I7 bears against the electromagnet I6 and in the dropped-off or shifted away position of the armature I7. which has been shown in phantom lines. the movement of the control element is not influenced.

If necessary. the one or the other of the stops or im' pact members 20/] and 20( can be omitted at the actuation lever 20 in order to only bring about a lifting-off or a contact i.e.. pressing-on of the armature 17.

It should be understood that with all ofthe evemplary embodiments the point in time of energization and deenergization respectively. of the

relevant electromagnets

2 or 16 respectively. must be accommodated to the movement of the control element 7 and the corresponding rotation of the associated control cam or disk I3 and 23 respectively. As already previously mentioned, both the to-and-fro movement of the control element 7 as well as also the rotation ofthe

control cam

13 or 23 respectively. occurs in synchronism or cycle with the textile machine.

With the described apparatuses it is thus possible to influence selectively the movement of a control element in the described manner. Depending upon whether the electromagnet is energized or not at predetermined points in time. the holding element which is constructed as the armature of the clectromagnet selectively blocks the control element. for instance a notched bar. in one terminal position.

By means of the actuation device. and as already de scribed. the armature is moved against the elcctormag net and/or raised-off the dc-energized electromagnet.

If the armature is pressed against the magnet by the actuation mechanism. then such magnet must not be constructed as a stroke or displacment magnet. rather only as a holding magnet.

Due to the tnechanical lifting-off of the armature with the electromagnet not energized there are amided disturbances in operation. which can be brought about b the adherence of the armature at the electromagnet owing to retnancnce.

While there is show it and described present preferred embodiments of the invention. it is to be distinctl un derstood that the invention is not limited thereto. but ma be otherwise varioush embodied and practiced within the scope of the following claims. Accordingly What is claimed is:

1. An apparatus for selectively fixedly holding a substantially to-andtro tnoving and driven control element of a textile machine in one oftwo of its possible terminal positions. comprising a holding element defined by an armature of a selectively energizablc electromagnct. said holding element when the electromagnet is deenergized being movable from a first position in which it bears against the electromagnet into a second position and wherein in one of its positions said holding ele ment blocks the control element which is located in one terminal position. an actuation mechanism acting upon the holding element for selectively either bringing the holding element from its second position into its first position. lifting-off the holding element which bears against the electromagnet when the electromagnet is decnergized. or carrying out both ofsuch operations.

2. The apparatus as defined in claim 1. further in eluding at least one spring engaging with the holding element in order to move the holding element into its second position when the electromagnct is not energized and in which second position it blocks the control element.

3. The apparatus as defined in claim 1, further including a shaft for rotatablv mounting the holding element so as to be movable from the one position itito the other position. the actuation mechanism comprising a lever which is pivotable about said shaft. a control mechanism for adjusting the pivotal position of the lever. at least one actuation element carried by said lever. said actuation element in predetermined pivotal positions of the lever acting upon the holding element.

4. The apparatus as defined in claim 3, wherein the actuation element. with the holding element located in its second position, acts upon the holding element and upon pivoting the lever brings about a rotation of the holding element into its first position.

5. The apparatus as defined in claim 3, wherein the actuation element. when the holding element bears against the electromagnet. acts upon the holding ele' ment and with the electroniagnet tie-energized during pivoting of the lever lifts-off the holding clement front the electromagnet.

6. The apparatus as defined in claim 5, wherein a respective actuation element is mounted at the lever rotation of the holding element into its first position and for lifting-off the holding element from the electromagnet respectively.

7. The apparatus as defined in claim 1. wherein the holding element is movable in a substantially translator v manner from the one into its other position. and wherein the actuation mechanism possesses an actuation lever which is displaceable in the direction of its lengthwise axis. a control mechanism for adjusting the position of the actuation lever. the actuation lever carrying at least one actuation element which in a predetermined position of the actuation lever acts upon the holding element.

8. The apparatus as defined in claim 7, wherein the actuation element with the holding element located in its second position acts upon such holding element and during axial displacement of the actuation element brings about a displacement ofthe holding element into its first position.

9. The apparatus as defined in claim 7. wherein the actuation element, with the holding element bearing against the electromagnet. acts upon such holding element. and with the electromagnet de-energized during axial displacement of the actuation lever liftingoff the holding element from the electromagnet.

It). The apparatus as defined in claim 9. wherein a respective actuation element is mounted at the actuation lever for respectively displacing the holding element into its first position and for lifting-off the holding eletnent from the electromagnet.

11. The apparatus as defined in claim 3. wherein the control mechanism comprises a rotatabl driven control cam.

12. The apparatus as defined in claitn 7, wherein the control mechanism comprises a rotatably driven control cam.

13. The apparatus as defined in claim 1, wherein the holding element is constructed as a holding hook member which is intended to engage with a recess at the control element.

Claims

1. An apparatus for selectively fixedly holding a substantially to-and-fro moving and driven control element of a textile machine in one of two of its possible terminal positions, comprising a holding element defined by an armature of a selectively energizable electromagnet, said holding element when the electromagnet is de-energized being movable from a first position in which it bears against the electromagnet into a second position and wherein in one of its positions said holding element blocks the control element which is located in one terminal position, an actuation mechanism acting upon the holding element for selectively either bringing the holding element from its second position into its first position, lifting-off the holding element which bears against the electromagnet when the electromagnet is de-energized, or carrying out both of such operations.

2. The apparatus as defined in claim 1, further including at least one spring engaging with the holding element in order to move the holding element into its second position when the electromagnet is not energized and in which second position it blocks the control element.

3. The apparatus as defined in claim 1, further including a shaft for rotatably mounting the holding element so as to be movable from the one position into the other position, the actuation mechanism comprising a lever which is pivotable about said shaft, a control mechanism for adjusting the pivotal position of the lever, at least one actuation element carried by said lever, said actuation element in predetermined pivotal positions of the lever acting upon the holding element.

4. The apparatus as defined in claim 3, wherein the actuation element, with the holding element located in its second position, acts upon the holding element and upon pivoting the lever brings about a rotation of the holding element into its first position.

5. The apparatus as defined in claim 3, wherein the actuation element, when the holding element bears against the eLectromagnet, acts upon the holding element and with the electromagnet de-energized during pivoting of the lever lifts-off the holding element from the electromagnet.

7. The apparatus as defined in claim 1, wherein the holding element is movable in a substantially translatory manner from the one into its other position, and wherein the actuation mechanism possesses an actuation lever which is displaceable in the direction of its lengthwise axis, a control mechanism for adjusting the position of the actuation lever, the actuation lever carrying at least one actuation element which in a predetermined position of the actuation lever acts upon the holding element.

8. The apparatus as defined in claim 7, wherein the actuation element with the holding element located in its second position acts upon such holding element and during axial displacement of the actuation element brings about a displacement of the holding element into its first position.

9. The apparatus as defined in claim 7, wherein the actuation element, with the holding element bearing against the electromagnet, acts upon such holding element, and with the electromagnet de-energized during axial displacement of the actuation lever lifting-off the holding element from the electromagnet.

10. The apparatus as defined in claim 9, wherein a respective actuation element is mounted at the actuation lever for respectively displacing the holding element into its first position and for lifting-off the holding element from the electromagnet.

11. The apparatus as defined in claim 3, wherein the control mechanism comprises a rotatably driven control cam.

12. The apparatus as defined in claim 7, wherein the control mechanism comprises a rotatably driven control cam.