WO2010004463A2

WO2010004463A2 - Selector lever for selecting the jacks of a textile knitting machine

Info

Publication number: WO2010004463A2
Application number: PCT/IB2009/052677
Authority: WO
Inventors: Franco Caliari
Original assignee: Sys Tec S.R.L.
Priority date: 2008-07-09
Filing date: 2009-06-22
Publication date: 2010-01-14
Also published as: WO2010004463A3; ITBS20080131A1; IT1393024B1; CN102124154A

Abstract

The invention regards a selector lever for pushing down the jacks of a textile knitting machine, comprising a cam contact surface able to push the jacks into a rearward position, that on such contact surface there is an upper lever repelling chamfer facing upwards and a lower working chamfer facing downwards. Said chamfers converging towards the heel so as to form a coupling ridge of the heel so that when the heel moves over said ridge the lever is repelled downwards and when the heel passes under said ridge the lever is pushed upwards into the working position.

Description

"Selector lever for selecting the jacks of a textile knitting machine"

[0001] The present invention regards a selector lever for selecting the jacks of a textile knitting machine, a selector unit comprising a plurality of selector levers, and a related textile knitting machine.

[0002] Within the scope of these machines, increasingly- complex designs are required on the knitwear, and knit a high number of yarns of different colours with each other .

[0003] As is known, the yarns in a knitting machine are processed by a plurality of needles arranged in grooves on a cylinder (in the case of a circular knitting machine) or a bed of needles (in the case of a straight knitting machine) . In order, to obtain special processes, such as a design with several colours, or to obtain special knitting effects, the needles involved in the work are mechanically selected by matching underneedles , also known as Jacks, with a tooth, also known as the tongue heel .

[0004] The jack, appropriately selected, allows the related needle to rise to a specific position of the machine where it hooks a yarn from a reel and placed in position by a thread guide. Subsequently, the needle is lowered by an appropriate cam so that the hooked yarn is knitted with another yarn.

[0005] In turn, each, jack is selected from a selector unit comprising a plurality of selector levers or selector levers superimposed in height, which act on their respective jack heels by means of actuators, for example, by a computer in which is stored the design or process to be performed. [0006] As will be explained better below, all the selector devices currently used have technical limitations. The main one being the implementation speed, which is determined by the time needed by the selector tip to enter and select the jack corresponding to the tip of the desired colour or knit and the time needed to exit when the selection of the jack is not required.

[0007] This time can vary, depending on the various electrical solutions used, from 5/6 to 10/15 ms. [0008] In the pinch selection mode of the jacks, every jack is pinched by the selector lever into the groove in which it is housed. This is made to oscillate by means of the actuators between a lowered position not interfering with the heel and a raised interference position, which performs the pinch action of the jack. The jacks that are not pinched, therefore not selected, are raised by a fixed cam so that its needles can hook the yarn. [0009] To increase the selection speed and enhance the production, the use of traditional lever activation electromagnets has been replaced with solutions using piezoelectric ceramics, thus reducing both the implementation time as well as the consumption from the spools .

[0010] These actuators are equipped with piezoelectric lamina that, depending on the electric polarization to which they are subjected, move high or low, mechanically moving the lever, usually steel, which has its fulcrum on a pin that supports the mechanical impact with the jack. An example of a pinching selector unit 1 employing piezoelectric actuators, is illustrated in an exploded view in Figure 1. In this diagram, 10 shows the selector levers, while the piezoelectric laminae are illustrated by 12. Also noted are pins 15 on which the levers 10 fulcrum and the proximal ends 16 of these are shaped to receive the distal ends of the piezoelectric laminae 12. These laminae are made to oscillate on their respective pins 18 fixed to the body 2 of the selector unit.

[0011] The selector lever must be very light so that it can be moved by the piezoelectric ceramics lamina. [0012] The energising time of the piezoelectric ceramic is up to 5 times faster than the electromagnets solution (one ON/OFF cycle lasts approximately 6 mS) . [0013] The implementation speed of the piezoelectric ceramic permits the use of fewer levers, increase the working speed of the machine and reduce the mechanical dimensions of the cylinder in height, reducing the rotating masses of the machine.

[0014] However, the pinch selection mode using piezoelectric actuators, also presents some disadvantages . [0015] The piezoelectric actuators have to perform the entire mechanical stroke needed for the selector lever to oscillate between a position of non-interference and a position of interference with the heel of the jacks. In particular, the selector levers must be able to perform strokes of + lmm with positive excitation and - 1 mm with negative excitation, compared to a central position of 0 in the absence of voltage.

[0016] The stroke for distortion on electrical stimulation of the piezoelectric ceramics levers is limited by the actual structure of the ceramics and is directly proportional to the drive voltage.

[0017] The selector levers must be extremely thin and light due to the small force of a few grams developed by the piezoelectric ceramics . This leads to premature wear of the selector heels as well as to the levers themselves. [0018] The present DC drive voltage uses a range from +/- 50 V to +/- 100 V, and the piezoelectric ceramics uses a terminal voltage of 100V/200V or more.

[0019] Lower voltages limit the extent of the selector lever's travel and also increases the time required for switching, which can vary from 3 mS to 5 mS. Higher voltage require suitable cables and connectors for isolation and safety.

[0020] At present the work of the jack heels is designed in such a manner so as to work with a flat surface that runs against a corresponding flat surface acting as cam obtained in the distal end of the selector lever. [0021] The movement of the heel on the cam profile of the lever forces the jack to be pinched and then to fall into place. Figures 2, 2a and 2b show how the lever 10 is positioned in relation to the heel 11. In particular, compared to a neutral position in which the piezoelectric lamina is not energized (Figure 2) , the lever 10 may be moved into the upper position to interfere with the heel and thereby pinch the jack (Figure 2a) , or lower position not interfering with the heel (Figure 2b) .

[0022] To obtain the correct interference with the heel, the selector lever must be in the right position to present its flat working surface in correspondence with the flat side of the heel. [0023] The lever therefore has to complete the entire travel to achieve the correct working position, that is to say sent against the upper side 13 (or lower, depending on the design) of the aperture in which it oscillates. If this position is not reached in time before the arrival of the heel, the lever itself can be rejected by the heel, resulting in a selection error. This entails a process rejection.

[0024] The reasons which in time may affect the proper positioning of the selector lever are many, such as: • friction,

• mechanical hindrance arising from the dust or dirt that is formed,

• inadequate lubrication,

• expansion, even minimal, caused by the heat generated, • electrical degradation of the piezoelectric ceramic or implementation coils,

• mechanical wear

• mechanical play.

[0025] To reduce the necessary time and to avoid the possible causes of incorrect selection described above, the excitation voltage of the piezoelectric ceramics has been increased.

[0026] This solution creates another problem because the lever, pushed with greater speed against its mechanical stop, bounces generating greater oscillation and starts a swinging cycle before dampening and stopping. It follows that if the heel of the jack arrives while the selector lever is not motionless and fully against its stop on rebound, the lever itself can be rejected by the heel, generating a selection error.

[0027] The same problem can also occur when the selection lever must be in the idle position. The thrust generated by the piezoelectric ceramics can bounce the tip that can interfere with the arriving jack, hook it and thus generating an unwanted selection.

[0028] The purpose of the present invention is to contrive and make available a selector lever and a textile knitting machine that can at least partially overcome the disadvantages indicated above with reference to the prior art .

[0029] This aim is achieved by a selector lever wherein, at least two opposite angled chamfers are made on its contact surface used to pinch and push the heel in place that, also made on the heel of the jack, allow to impose a slight movement on the lever acting as consent to perform the selection, which will be mechanically completed by the machine itself with the heels of the jacks. [0030] This particular profile of the lever and heel stops the piezoelectric ceramics from carrying out the entire travel to the lever to reach the two stop positions, but used as a selection consent by making the lever move less, this movement being such as to automatically bring the heel, thanks to its specific profile, to complete the movement of the selector lever.

[0031] With the selector lever activated downward, the heel of the jack, while travelling with its profile, pushes the lever down that, being free, allows the heel to pass over them without being pinched and then selected. [0032] The contact profile of the lever used to generate its movement (or displacement) can run across the full width of the lever's contact surface or only on a first section of the contact surface (facing the arrival side of the heel) to ensure the desired effect. [0033] With the selector lever activated upward, the interference with the heel will mechanically take it into contact with the stop, forcing the heel of the jack to return and pinch in its seat . [0034] Therefore, with this particular profile it is no longer necessary to move the selector lever up or down to the mechanical stop.

[0035] This allows the use of the piezoelectric ceramics to enable the selection only, moving the selector lever almost imperceptibly so that it is auto-locked and pushing down or up directly by the heel of the jack during its rotation.

[0036] The selection is then performed by means of this reduced amplitude displacement that, once enabled, makes the selector lever interfere with the heel exploiting the movement and the force of the heel that auto-locks and makes the selector lever perform the necessary travel to arrive to its rest point.

[0037] The approval of this interference determines the consent or not to selection and is controlled directly by the piezoelectric ceramic.

[0038] Thanks to this technical solution, the implementation time of the ceramic is less than or equal to 1 ms . The physical movement of the selector lever is carried out mechanically by the heel of the jack. [0039] The resulting selection speed is no longer determined by the time required for the total movement of travel of the selector lever against its mechanical stop. [0040] Further characteristics and advantages of the lever and the machine according to the invention result from the description below of a preferred indicative and not limitative embodiment thereof, with reference to the attached figures, wherein:

- figure 1 illustrates an exploded view of a pinching selector unit employing piezoelectric actuators according to the prior art; - figures 2, 2a and 2b schematically illustrate the pinching selection method according to the prior art; figure 3 schematically illustrates a portion of a cylinder of a circular textile machine and a selector unit according to the invention;

- figures 4, 4a and 4b schematically illustrate a lever and a jack according to the invention in various positions of use, and

- figure 5 schematically illustrates a selector lever according to the invention in a alternative embodiment.

[0041] These drawings schematically illustrate a part of a textile knitting machine, comprising a plurality of selectable needles through their related jacks 60, each fitted with a selector heel 64. Each jack 60 is oscillating in a respective seat 61, obtained in a cylinder 62 for example in the case of a circular machine, between a forward position and a rearward position. The machine includes jacks selector unit 100 comprising a plurality of selector levers 50, each oscillating between a lower position not interfering with the heel 64 of the jack, and a upper position of interference with the heel to perform the pinching of the jack inside its seat 61. [0042] Each lever 50 includes a cam contact surface 51 suitable to push the jacks 60 in a rearward position. For cam contact surface 51 is intended that this surface extends along a direction having a component transverse to the movement direction of the jacks. [0043] The contact surface 51 has an upper repelling chamfer 52 facing upwards and a lower working chamfer 53 facing downwards. The said chamfers 52, 53 converging towards the heel so as to form a coupling ridge 54 of the heel 64 , so that when the heel 64 moves over the said ridge 54 the lever 50 is repelled downwards and when the heel 64 passes under said ridge 54 the lever is pushed upwards into the working position.

[0044] In other words, the contact surface 51 of the lever is not a flat surface as in the prior art, but is formed by two inclined planes 52, 53 converging before or toward the heel 64. The lever 50 therefore ends with a pointed profile culminating with the coupling ridge 54. [0045] In a complementary manner, the heel 64 of the jacks 60 also presents, on the side facing the lever 50, a pointed profile formed by a lower repelling chamfer 65 and a higher working chamfer -66.

[0046] These chamfers converge to form a heel ridge 67. The lower chamfer 65 of the heel is substantially parallel to the upper chamfer 52 of the lever, while the upper chamfer 66 of the heel is parallel to the lower chamfer 53 of the lever. [0047] In other words, the heel 60 of the jack and the contact surface 51 of the lever have pointed profiles so that, depending on whether the ridge 67 of the heel tip passes above or below the coupling ridge 54 of the lever tip, which is pushed in the lowered position or in the lifted position, respectively, by the passage of the heel itself.

[0048] Since the lower working chamfer 53 of the lever comprises the thrust surface of the heel in the rearward position, the lower chamfer 53 of the lever and the upper chamfer 65 of the heel are wider than the other two chamfers .

[0049] In accordance with an embodiment, the upper repelling chamfer 52 of the lever only extends to ^"an end portion of the contact surface 51 facing the arrival side of the jack heel (Figure 5) .

[0050] Aside from the shape of the contact surface 51, the selector levers 50 may be part of a selector unit 100 such as that illustrated in Figure 1 with regard to the selector units of the prior art .

[0051] In particular, each lever 50 protrudes from the body of the unit through a relative window 70 defining a lower stop 71 and an upper stop 72 for the oscillation of the lever . [0052] Each lever 50 is likely to oscillate a respective actuator acting on the proximal end of the lever. [0053] Preferably, said actuator includes a piezoelectric lamina 12 suitable to oscillate its end onto the proximal end of the lever. [0054] Thanks to the proposed technical solution, the selector lever is not controlled by the respective actuator to perform its entire travel between the two lower and upper stops. Instead, the actuator has to make the lever perform a much lesser movement, just enough to make the ridge of the heel pass below or above the ridge of the lever .

[0055] This small displacement is used as the consensus to the selection. In fact, as soon as the lever is raised or lowered just enough so that the edge of the heel passes under or above, respectively, it is the heel itself that, during its travel in contact with the chamfer of the upper or lower lever, completes the movement by pushing further up to the upper stop (performing the pinching of the jack) or further down (passing over without making the selection) .

[0056] The advantages that can be obtained thanks to the innovative profile of the lever and the heel of the jacks can be summarized as follows:

Selection speed no longer determined by the implementation time of the actuator, as a lesser movement of the- selector lever it required;

- the high speed is linked to the time required to enable the consent to the selection only;

- the high speed allows to reduce the number of selector - this also allows us to obtain much . lower cylinders, less inertia and lower electrical consumption;

- not having to make the complete travel, the lever can also be heavier, it can therefore have a greater thickness, enabling a better work and less wear of the jacks;

- reduction of the driving voltage of the piezoelectric ceramics according to the actual travel;

- non-existent electrical and polarity deterioration of the piezoelectric ceramic; - less wear on the heels and selector levers;

- improved mechanical reliability of the machine;

- increased production and reduction of discarded product due to incorrect selections;

- new machines equipped with a larger number of actuators that allow new technical solutions with a greater number of selectable colours on the same rank, higher number of drops and new ways of knitting.

[0057] It must also be stressed that the work carried out mechanically by the heel of the jack is currently performed using appropriate energy systems, mentioned above and assessed according to:

• weight of the lever

• Total travel required for the selection

• Minimum time required [0058] These three variables are linked together in a logical and functional manner in as much that increasing the weight of the lever increases the time needed for the movement, which therefore requires more energy to make the selection in the same implementation time. [0059] Also, increasing the travel requires more time to make the movement and therefore a lighter lever or more energy is required to maintain a time constant. [0060] In any case, it is the time required to move the lever that determines the selection speed and hence the productivity of the machine.

[0061] With the new proposed solution, the three variables weight, travel and time are no longer influenced by one another in that the displacement (travel) is the minimum necessary to trigger the actual work that is done by the heel of the underneedle or Jack.

[0062] The proposed technical solution is not affected by.

• the minimum time required, as it is the jack, with its specific speed, that determines the cycle time;

• the travel required for selection, as it is the heel that makes the lever perform the travel it requires to be selected or not selected;

• the weight or shape of the selector lever in as much that the work or energy required to move the lever in its working/not working extremes is the same that moves the mechanisms of the machine and not needed to implement the lever itself.

[0063] This allows you to use, to perform the small movement of the selector lever as consent or enabling, any means of implementation currently suitable to generate sufficient force to cause this movement . For example, the following can be used:

• a mechanical force from a spring;

• an electromagnetic force;

• a magnetic force for attraction or repulsion; • piezoelectric ceramic;

• electroactive Polymers (EAP) ;

• a force derived from organic synthesis.

[0064] To the embodiments of the selector unit described above, a man skilled in the art may make several changes and adjustments and replacements with others similarly functional parts in order to meet specific and incidental needs, all falling within the scope of protection defined in the following claims. Each of the characteristics described as belonging to a possible embodiment can be achieved independently from other embodiments described.

Claims

1. Selector lever for pushing down the jacks of a textile knitting machine, comprising a cam contact surface able to push the jacks into a rearward position, characterised by the fact that on such contact surface there is an upper lever repelling chamfer facing upwards and a lower working chamfer facing downwards, said chamfers converging towards the heel so as to form a coupling ridge of the heel so that when the heel moves over said ridge the lever is repelled downwards and when the heel passes under said ridge the lever is pushed upwards into the working position.

2. Lever according to claim 1, wherein the lower working chamfer constitutes the thrust surface of the heel in a rearward position.

3. Lever according to claim 2 , wherein the lower chamfer is more extended in height than the upper chamfer .

4. Lever according to claim 3, wherein the upper lever repelling chamfer extends solely to an end portion of the contact surface facing the side which the jack heel arrives at.

5. Selector unit for pushing down the jacks of a textile knitting machine, comprising a plurality of selector levers according to any of the previous claims .

6. Selector unit according to claim 5, wherein each lever protrudes through a relative window made in the body of the actuator and defining a lower mechanical beat and an upper mechanical beat for the oscillation of the lever .

7. Selector unit according to claim 5 or 6 , wherein each selector lever is able to oscillate by means of a respective actuator acting on a proximal end of the lever.

8. Selector unit according to claim 7, wherein said actuator comprises a piezoelectric lamina able to make

( one of its ends, acting on the proximal end of the lever, oscillate.

9. Textile knitting machine, comprising a plurality of needles selectable by means of their respective jacks, in which each jack has a selector heel and oscillates in its respective seat between a forward and rearward position, and a jack selector unit comprising a plurality of selector levers, in which each lever oscillates between a lowered position in which it does not interfere with the heel of the jack and a raised position in which it interacts with the heel to push the jack rearward, and wherein said selector lever terminates towards the heel with a cam contact surface able to push the jack when the lever is in a raised position, characterised by the fact that the heel of the jack and the contact surface of the lever have complementary shaped tip profiles so that depending on whether the ridge of the tip of the heel passes above or below the ridge of the tip of the lever, this is pushed into a lowered or raised position, respectively, by the passage of the same heel .

10. Textile machine according to claim 9, wherein on the contact surface of each lever there is an upper repelling chamfer and a lower working chamfer converging towards the heel so as to form a ridge of the lever, and in which each selector heel has, on the side facing the levers, a lower repelling chamfer and an upper working chamfer converging so as to form a ridge of the heel, the lower chamfer of the heel being parallel to the upper chamfer of the lever, the upper chamfer of the heel being parallel to the lower chamfer of the lever.

11. Textile machine according to claim 10, wherein the lower working chamfer of the lever constitutes the thrust surface of the heel in a rearward position.

12. Textile machine according to claim 11, wherein the lower chamfer of the lever and upper chamfer of the heel are more extensive than the upper chamfer of the lever and the lower chamfer of the heel .

13. Textile machine according to claim 12 , wherein the upper repelling chamfer of the lever extends solely to an end portion of the contact surface facing the part which the jack heel arrives at.