GB2036811A

GB2036811A - A Magnetic Device for Needle Selection in Automatic Knitting Machines

Info

Publication number: GB2036811A
Application number: GB7940017A
Authority: GB
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1978-12-13
Filing date: 1979-11-20
Publication date: 1980-07-02
Also published as: IT1164083B; IT7936228V0; IT7951029A0; FR2444100B1; FR2444100A1; GB2036811B; DE2948804A1; JPS5587385U; ES486560A1

Abstract

A needle selection device is provided wherein is used a torsion solenoid which assures an accurate needle selection in automatic knitting machines at a very high speed. The rotor (18) and the stator (15) of the torsion solenoid are made to contact each other directly when the solenoid is energised, for secure engagement, and, by reducing the current through a solenoid winding after the contact is established, the power consumption as well as heat generation of the solenoid is considerably reduced. <IMAGE>

Description

SPECIFICATION A Device for Needle Selection in Automatic Knitting Machines The present invention relates to a device for needle selection in automatic knitting machines, and, in particular, to a device for needle selection which utilizes a torsion solenoid in an advantageous manner.

In conventional needle selection devices, such as those disclosed in Japanese Patent Application No. 50-1001 5 (Laying-Open Publication No.

52-25157), the angular displacement of the rotor of a torsion solenoid is controlled by balancing the force generated in an electromagnet and the restoring force of a torsion rod. Therefore, to maintain the displacement of the rotor constant at all times, the electric current applied through the solenoid must be well controlled. And, since a transient oscillation often ensues after each selecting action, it is necessary to install a common damper or other damping device to compensate for such an oscillation.

Moreover, the position of the selector lever which is directly moved by the torsion solenoid tends to be unstable as it is determined by balancing the twisting force of the torsion solenoid and the restoring force of the torsion rod. Therefore, the driving stroke of the selector lever has to be set in excess so as to compensate for the tendency of the selector lever to become unstable.

One of the main objects of the present invention is to provide a needle selection device which does not require such a damping device and is still capable of performing accurate selecting actions at a very high speed.

Another object of the present invention is to provide a device for needle selection which requires relatively small power consumption and dissipates relatively little heat without sacrificing the accuracy and the speed of the selecting action.

It is another object of the present invention to provide a device which is capable of functioning properly even when the electric current supplied through the solenoid fluctuates to a certain extent.

The above and other objects are accomplished according to the present invention by providing a torsion solenoid, the rotor and the stator of which are made to directly contact each other for a secure engagement therebetween, and by reducing the current supply to the solenoid after the contact is established.

In order that the present invention may be better understood, one embodiment will now be described with reference to the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: Fig. 1 shows an essential part of a device for needle selection according to the present invention in a fragmentary side view, partly in cross-section; Fig. 2 is a perspective view of a part of the same device as shown in Fig. 1; Fig. 3 shows an example of a torsion solenoid used in the device of the present invention in a perspective view, partly broken; Fig. 4 shows two different positions of a selector shown in Figs. 1 and 2 resting on a needle cam (I) and being pushed away from the needle cam (II), respectively;; Fig. 5 shows two different positions of the rotor in the torsion solenoid shown in Fig. 3 in a cross-sectional view; and Fig. 6 is a graph showing the variation of the current applied through the solenoid with respect to time, in which the applied current is initially great but, after a short time, it is reduced to a smaller value.

With reference to Figs. 1 and 2, a plurality of knitting needles 2 and selectors 3, which are forming a plurality of vertically disposed pairs at a fixed pitch, are arranged on the outer circumference of a needle cylinder 1, and they are adapted to rotate in a body.

Below the selectors 3, a stationary circular needle cam 4 is disposed on a rigid support not shown in the drawings, and the selectors are moved in a generally vertical direction as the bottom end of the projection 5 which is provided in the lower part of each of each selector 3 and projecting outwardly is slid over the upper surface of the needle cam 5.

On appropriate places on the needle cam 5 surface, elevated sections 9, the number and the positions of which being determined by the number and the positions of corresponding knitting yarn feeding outlets which are not shown in the drawings, are provided in an upwardly projecting manner, and the bottom end of the projection 5 provided in the lower part of each selector 3 in an outwardly projecting manner slides over the needle cam 5 according to the cam profile which includes these elevated sections 9.

Radially outside of the needle cam 4, a selector lever 6 is supported by a guide member 7 so as to be slidable in its longitudinal direction or the radial direction with respect to the needle cylinder 1, and is adapted to make a reciprocating motion by means of a torsion solenoid 8 which is connected to the base end of the selector lever 6.

The torsion solenoid 8, the details of which will be described hereinafter, is capable of producing the motion of the selector lever 6 at a very high speed, and one example of such a torsion solenoid is illustrated in Fig. 3. Each selector may assume either a position where the free end of the selector lever 6 is completely removed from the projection 5 of the selector 3 which is nearest to the selector lever 6 as shown in Fig. 4 (1), or, alternatively, a position where the selector lever 6 is pushing the projection 5 of the selector 3 which is located nearest to the selector lever 6 sufficiently inwardly for the projection 5 to be disengaged from the needle cam 4 as shown in Fig. 4 (11).

Accordingly, when one of the selectors 3 passes over the elevated section 9 of the needle cam 4 as the needle cylinder 1 rotates, a projection 5 which is engaged to the needle cam 4 as shown in Fig. 4 (1) is pushed upward by the elevated section 9 and a corresponding knitting needle 2 is urged to project over the upper rim of the needle cylinder 1, or, in other words, to assume a knitting position. Alternatively, if a projection 5 is taking a position where the projection 5 is disengaged from the needle cam 4 as shown in Fig. 4 (11), a corresponding knitting needle 2 is not urged to project over the rim of the needle cylinder 1 and the needle 2 remains in a welting position.

As mentioned before, either the knitting or welting position is selected for each knitting needle 2 by the action of the selector lever 6 which is moved preferably at a very high speed in actual industrial applications. Normally, the time required for the selector lever 6 travelling from one end to another is desired to be in the order of 1 millisecond.

In Fig. 3 is shown an example of such a torsion solenoid which may be applicable to a needle selection device for knitting machines according to the present invention, wherein a pair of Cshaped cores 1 5 (the upper portion of which is made of magnetic material, while the lower portion is made of non-magnetic material) are arranged opposing each other with a pair of permanent magnets 1 6 attached to the upper ends of the pair of cores 1 5, respectively. The permanent magnets 16 are magnetically connected by a connecting piece 1 7 which is made of an iron plate. Within a statorthus formed, a rotor 18 and a solenoid 14 are installed so that the former may be magnetized when the iatter is energized by electric current applied therethrough.

One end of the shaft 11 of the rotor 18 is projecting outwardly and the opposing end is connected to a torsion rod 1 2 whose base end 1 3 is rigidly connected to a base so as to impart restoring force to the rotor 1 8 when the rotor 1 8 has made an angular displacement.

When electric current having a sufficient amplitude is supplied to the solenoid 14, the rotor 1 8 becomes magnetized and rotates in the direction indicated by an arrow shown in Fig. 3 overcoming the restoring force of the torsion rod 12 until it comes in contact with one of the Cshaped cores 1 5. Then, the shaft 11 along with an arm 10 rigidly attached thereto rotates in a body with the rotor 18, and the push rod attached to the free end of the arm 10 moves along the direction indicated by an arrow in Fig. 3.

Accordingly, the position of the selector lever 6 may be used for needle selection by connecting the previously mentioned selector lever 6 to the rod 19 or by using the rod 1 9 as the selector lever 6.

Fig. 5 (1) shows the torsion solenoid 8 when the rotor has rotated overcoming the restoring force of the torsion rod 12 until it comes in contact with one of the pair of C-shaped cores 1 5 by applying electric current through the solenoid 14 with a sufficient amplitude.

Fig. 5 (Il) shows the torsion solenoid 8 when the rotor 1 8 has rotated in opposite direction overcoming the restoring force of the torsion rod 1 2 until it comes in contact with the other one of C-shaped cores 1 5 by applying current through the solenoid 14 in opposite direction.

As clearly seen in the present embodiment, according to the present invention, the rotor 1 8 and one of the C-shaped cores 1 5 are made to directly contact each other. Therefore, the engagement between the rotor 1 8 and the stator (or one of the C-shaped cores 1 5) is relatively secure and, furthermore, a transient oscillation of the stator 18 after each selecting action may be prevented to a considerable extent. It should be noted that these advantages are attained from the fact that the magnetic attracting force between a magnet and a piece made of magnetic material is inversely proportional to the square of their distance (Coulomb's Law). In other words, the attracting force between the stator and the rotor becomes very great when they are contacting each other.

From above considerations, electric current to be supplied through the solenoid 14 is varied as indicated in the graph of Fig. 6 according to the present invention. Since the initial current is so great that the motion of the torsion solenoid may be considerably speeded-up. However, the current is immediately reduced, after the contact is established, to a minimum enough to maintain the contacting state of the rotor and the stator.

Therefore, the overall power consumption as well as the overall heat dissipation of the torsion solenoid will be considerably reduced. Moreover, since the initial current supply is so great the torsion rod 12 may be selected to be of a relatively higher rigidity for quick restoring of the rotor displacement.

As a result, according to the present invention, a device for needle selection in automatic knitting machines having a higher operating speed yet requiring less power consumption becomes possible. Also, after each selecting action, there arises little transient oscillation according to the present invention.

The device according to the present invention is not limited to the above described embodiment.

For example, instead of reversing the direction of electric current applied through the solenoid for positioning knitting needles either to knitting or welting position, the same end may be attained by supplying the current only in one direction.

To be specific, it also is possible to give some initial twisting to the torsion rod so as to make the rotor contact one of the C-shaped cores when no current is applied through the solenoid. And, when some electric current is applied through the solenoid, the rotor rotates overcoming the restoring force of the torsion rod until it comes in contact with the other one of the C-shaped cores.

To maintain the torsion solenoid in this state, some electric current must be applied through the solenoid but the amplitude of the current may be reduced after the contact has been established as was the case with the previously described embodiment.

When the electric current is completely turned off, the rotor of the torsion solenoid will return to its former state and maintain the state solely by the restoring force of the torsion rod which is given some initial twisting.

In this embodiment, the power consumption will become slightly greater than in the previously described embodiment, but, since the direction of the electric current needs to be only one, the control circuit for the solenoid may be considerably simplified.

If three control positions (knitting, tucking and wetting) are desired, an additional neutral position where neither twisting force to the solenoid nor energization current to the solenoid is applied, may be placed in addition to the two positions where the rotor is contacting either one of the Cshaped cores by means of electromagnetic force.

In other word, there are provided three positions; a position where the rotor is made to rotate and contact one of the C-shaped cores by means of electromagnetic force overcoming the restoring force of the torsion rod, a position where, by reversing the current through the solenoid, the rotor is made to rotate and contact the other one of the C-shaped cores, and, lastly, a position where no energization current is applied through the solenoid and the rotor assumes a neutral position without any force opposing the restoring force of the torsion rod. However, in this embodiment, a transient oscillation may occur immediately after the last neutral position is selected. Therefore, without any restraining means present, a damping device may become necessary.

Thus, according to the present invention, all of the afore-mentioned objects may be accomplished. Moreover, the device according to the present invention may be made much smaller in size than conventional devices intended for the same purpose. Therefore, combined with saving in power consumption and elimination of a damping device, the device according to the present invention may be manufactured and used at a smaller cost than equivalent conventional devices.

Although the present invention has been shown and described with respect to preferred embodiments thereof, it should be understood that various changes and modifications could be made therein by a person skilled in the art without departing from the scope of the invention. For example, the present invention has been described concerning its application to a rotary knitting machine, but, to a person skilled in the art, it is obvious that the device according to the present invention may be applicable to flat knitting machines and other machineries of similar sorts.

Claims

1. A device for needle selection in automatic knitting machines, comprising; a rotary needle cylinder; a plurality of knitting needles and selectors forming vertically arranged pairs and being rotatable with said needle cylinder in a body; a stationary needle cam over which each of said selectors may be slidably engaged or disengaged and which is disposed closely surrounding said needle cylinder; a selector lever which selectively allows or forbids the engagement of said selectors to said needle cam; and a torsion solenoid which is capable of rotatory displacement for driving said selector lever, said torsion solenoid being supplied with electric current corresponding to a specific knitting pattern; characterized in that: the rotor of said torsion solenoid is imparted with magnetic force sufficiently great to overcome twisting restoring force of a torsion rod connected to the shaft of said rotor and to contact one of cores of the stator of said torsion solenoid.

2. A device according to claim 1, characterized in that: the direction of the electric current for energization of said torsion solenoid is selectively inverted so as to rotate the rotor of said torsion solenoid either clockwise or counter-clockwise in accordance with the direction of said electric current until said rotor comes in contact with either one or the other one of a pair of cores in the stator of said torsion solenoid.

3. A device according to claim 1, characterized in that: said torsion rod connected to the shaft of the rotor of said torsion solenoid is given with some initial twisting so as to have said rotor pressed against one of said pair of cores in the stator of said torsion solenoid in absence of said energization current and, upon application of said energization current, the rotor of said torsion solenoid is made to rotate overcoming the twisting restoring force of said torsion rod until it comes in contact with the other one of said pair of cores.

4. A device according to claim 1, characterized in that: the rotor of said torsion solenoid is capable of assuming three possible positions; the first and the second positions corresponding to states when the rotor of said torsion solenoid is made to rotate either clockwise or counter-clockwise until said rotor comes in contact with either one or the other one of a pair of cores in the stator of said torsion solenoid, and the third position corresponding to a state when said rotor is assuming a neutral intermediate position without supply of energization current to the solenoid of said rotor.

5. A device according to any of preceding claims, characterized in that: energization current supplied to the solenoids of the rotor of said torsion solenoid is initially given with a large amplitude, and after the contact between the rotor and the stator of said torsion solenoid is established, said current is reduced to a smaller value.

6. A needle selection device substantially as described herein with reference to the accompanying drawings.

7. The features as herein described, or their equivalents, in any novel selection.