GB2086948A

GB2086948A - Needle monitor for knitting machines

Info

Publication number: GB2086948A
Application number: GB8033327A
Authority: GB
Original assignee: SHEER Ltd
Current assignee: SHEER Ltd
Priority date: 1980-10-16
Filing date: 1980-10-16
Publication date: 1982-05-19

Abstract

The machine comprises a feeler (37) to detect a bent or broken needle head. The feeler is displaceable against a bias from a stop-motion position clear of the needles to engage the needle heads (13) of the needles as they rotate, to be maintained displaced from said position by successive engagement of the needle heads with the feeler. The feeler, however, is maintained displaced from said position only for as long as the time interval between the engagements with two successive undamaged needle heads is equal to the time interval between the passage of two immediately successive needles, whereby, when a needle head is bent or broken, the feeler has a sufficient time to move under the bias to the machine stop position, thereby to indicate the presence of the impaired needle and to cause the machine to be stopped. <IMAGE>

Description

SPECIFICATION Improvements in yarn knitting machines The present invention relates to a yarn knitting machine of the circular type and, more particularly, to the provision on such a machine of means to detect or sense a broken needle.

In a circular type knitting machine, the needles are arranged in a circle and, in use of the machine, are rotated at speeds of up to 17,000 revs per minute. Because of the high speed of operation of the machine, the breaking off of a needle head can give rise to a considerable amount of faulty knitted material unless, promptly, the broken needle is detected and the machine stopped.

Attempts have been made heretofore to provide means for sensing a broken needle, for instance, by a photoelectric sensor but have not proved satisfactory.

It is an object of the present invention to provide in a circular type yarn knitting machine, an efficacious means of sensing a broken needle.

It is explained in this connection that a needle comprises a head in the form of a hook portion and that bending, breaking, or breaking off, of the hook portion renders the needle useless. In practice, therefore, sensing a broken needle entails sensing a bent or broken hook portion.

In an embodiment of the invention, a feeler is biased to a position (hereinafter called the machine stop position) and is displaceable to engage the needle heads of the needles as they rotate, to be maintained displaced from said position by successive engagement of the needle heads with the feeler but the feeler is arranged so that it is thus maintained displaced from said position only for as long as the interval between a needle head engaging the feeler and the next following undamaged and intact needle head is equal to the interval between two immediately successive needles, whereby, when a needle hook portion is bent or broken, the feeler moves under the bias to the machine stop position.The assumption, during operation of the machine, of that position by the feeler is taken as being indicative of the presence of a broken needle; and accordingly, on the assumption of this position, the feeler may be used to actuate an alarm and/or to supply a control signal to stop the machine. For this purpose, the feeler may be of an electrically conductive material and mounted in electrical contact with ground or an electrical source and fixed contact may be arranged, connected to an electrical source or ground as the case may be, so that when the feeler assumes the machine stop position, it engages the fixed contact and grounds the electrical source, thereby providing a current flow to source as the alarm actuating signal or the control signal.A feeler re-set device may be provided by which the feeler can be mechanically displaced from the machine stop position into the path of the needle heads.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, in which like parts are indicated by the same reference characters, and in which: Figure 1 is a simplified diagram of a circular yarn knitting machine showing the relationship between the machine frame and the needles thereof; Figure 2 is a similar drawing showing further parts of the machine incorporating a feeler arrangement, according to the invention; Figure 3 shows in side elevation the feeler arrangement of Figure 2 in one condition thereof; and Figure 4 shows in side elevation the feeler arrangement in another condition.

Referring to the drawings, the knitting machine comprises a frame 3 of circular cross-section within which is arranged concentrically therewith a circular array 5 of knitting needles. Each needle, as appears from Figures 3 and 4, comprises a shank portion 11 terminating in a head generally indicated at 13, comprising a hook portion 1 5.

Although Figures 3 and 4 may suggest otherwise, the needles lie with their shank extending radially towards the machine frame.

The machine also comprises feeder heads 21 for feeding the fibre to be knitted to the needles: and the feeler arrangement indicated by the present invention is located between adjacent feeder heads; the feeler arrangement generally being indicated by the reference numeral 31.

The feeler arrangement comprises a base plate (not shown) the underside of which bears a recess 35 in which is secured a feeler constituted, in this instance, by a spring steel strip 37 so that part of the strip extends beyond the adjacent end of the base plate to be capable of flexing downwardly, as viewed in Figures 3 and 4, away from the casing.

At its free end the feeler strip bears a needle engagement members 39.

The base plate is itself mounted on the machine frame and supports a casing 41 in the top wall of which is mounted a boss 43 (indicated in outline in Figure 3). A terminal (not shown) for an electrical circuit is mounted in the boss and comprises a fixed contact 45 positioned so that when the feeler strip is unflexed it makes contact with the fixed contact to earth the electrical circuit. in this instance, the latter is that of the machine isolater. When the circuit is thus grounded, the machine is stopped. This position of the feeler strip constitutes the machine stop position thereof.

On depression of the terminal, the fixed contact acts against the feeler strip to flex it away from the casing, and the base plate is positioned so that, by this action, the feeler strip needle engagement member is brought into the path of rotation of the needle heads to enable it to engage under a hook portion thereof as shown in Figure 4.

The array and its speed of rotation are such that the repetition rate of engagement of a needle head with the feeler member 39 provides insufficient time to permit the feeler strip to return to the machine stop position after leaving engagement with a needle head before the head of the next following needle makes contact with the feeler member 39. Provided therefore all the needle heads are intact and undamaged, the feeler is maintained against its spring bias from the machine stop position; but, should a needle head be broken or bent, the feeler strip does have time to move clear of the path of the needle heads.

Consequently, it returns to the machine stop position and causes the knitting machine to be stopped.

In a typical circular knitting machine the needle array may contain up to 48 needles per 2.54 cm, it may be of some 1.22 m diameter and rotate at a speed of some 17,000 R.P.M.

When the machine is ready to be restarted, the terminal is again depressed to allow engagement, on rotation of the needles, of the feeler member therewith as described above. The terminal with its contact therefore also serves as a re-set device.

Claims

1. A yarn knitting machine of the circular type, having means to detect a needle impaired by breakage of the needle head or a part thereof or by bending of the needle head; said means comprising a feeler which is displaceable against a bias from a position (hereinafter called the machine stop position) lying clear of the needles, so as to engage the needle heads of the needles as they rotate, to be maintained displaced from the machine stop position by successive engagement of the needle heads with the feeler; the feeler being arranged so that and being such that it is thus maintained displaced from the machine stop position only for as long as the time interval between the engagement of one undamaged needle head with the feeler and the engagement therewith of the next following undamaged needle head is equal to the time interval between the passage of two immediately successive needles past any given station along the path of the needle heads; whereby when a needle head is bent or broken, the feeler has a sufficient time to move under the bias to the machine stop position, thereby to indicate the presence of the impaired needle.

2. A knitting machine as claimed in claim 1, wherein means are provided to generate a signal (hereinafter called the feeler signal) on the assumption by the feeler of the machine stop position during operation of the machine.

3. A knitting machine as claimed in claim 2, wherein an alarm is provided responsive to said feeler signal.

4. A knitting machine as claimed in claim 2 or 3, comprising a control system responsive to said feeler signal automatically to stop the machine.

5. A knitting machine as claimed in claim 2, 3 or 4, wherein the feeler is made of electrically conducting material and is mounted in electrical contact with ground or an electrical source; and a fixed contact is provided connected to the electrical source or ground as the case may be, so that, when the feeler assumes the machine stop position, the feeler engages the fixed contact and grounds the electrical source to provide a flow of current to constitute the feeler signal.

6. A knitting machine as claimed in any of the preceding claims, wherein a feeler re-set device is provided comprising means mechanically to displace the feeler from the machine stop position into the path of the needle heads.

7. A detector for use on a knitting machine of the circular type, for detecting a needle thereof impaired by breakage or bending of the needle head, the detector comprising a feeler, means mounting the feeler such as to permit the feeler to be stationed on the knitting machine in a position (hereinafter called the machine stop position) clear of the needles thereof but to be displaced against a bias from that position into the path followed by the needle heads on rotation of the needles so as to be engaged by the successive needle heads as they rotate; the feeler being arranged so that and being such that it is thereby maintained displaced from the machine stop position but only for as long as the time interval between the engagement of one undamaged needle head with the feeler and the engagement therewith of the next following undamaged needle head is equal to the time interval between the passage of two immediately successive needle heads past any given station along the path of the needle heads; whereby, when a needle head is bent or broken, the feeler has sufficient time to move under the bias to the machine stop position thereby to indicate the presence of the impaired needle.

8. A detector as claimed in claim 7, further comprising means to generate a signal (hereinafter called the feeler signal) on the assumption of said machine stop position by the feeler during operation of the knitting machine.

9. A detector as claimed in claim 8, wherein an alarm is provided to operate in response to said feeler signal.

10. A detector as claimed in claim 8 or 9, wherein the feeler is made of electrically conducting material and is mounted in electrical contact with ground or an electrical source; and a fixed contact is provided connected to the electrical source or ground as the case may be so that, when the feeler assumes the machine stop position, the feeler engages the fixed contact and grounds the electrical source to provide a flow of current to constitute the feeler signal.

11. A detector as claimed in any of claims 7 to 10, wherein a feeler re-set device is provided comprising means mechanically to displace the feeler from the machine stop position into the path of the needle heads.

12. A knitting machine of the circular type, substantially as hereinbefore described with reference to the accompanying drawings.

13. A detector for use on a knitting machine of the circular type, substantially as hereinbefore described with reference to the accompanying drawings.