GB2037821A - Knitting Machine Cam - Google Patents

Abstract

A knitting machine cam serves to control knitting tools each having at least one butt (10) and is provided with a plurality of draw-down cams (21) acting on the butts (10) of the knitting tools and having draw-down faces with a negative pitch or inclination. To enable a considerable increase in the knitting speed with low manufacturing costs each draw-down cam (3) is associated with a counterguide element (4) with a striking zone (A) for the knitting tool butts (10) controlled by the draw- down cam (3) and all the striking zones (A) have positive pitches compared with the draw-down faces (21). The pitch angles (B) of these positive pitches are preferably between 8 DEG and 27 DEG . <IMAGE>

Description

SPECIFICATION Knitting Machine Cam The invention relates to a knitting machine cam for controlling knitting tools each having at least one butt and with a plurality of cammingdown elements acting on the butts of the knitting tools end having camming-down faces with a negative pitch, or inclination.

Cams of this type have a plurality of cammingdown elements with camming-down faces which act on the butts of knitting needles, sinkers, jacks or their auxiliary parts and lower these members from a relatively high clearing or tucking position reached with the aid of a camming-up element into a lower position, for example the run-through position or the knocking-over and loop-sinking position. In dependence upon the kind of control, the butts encounter the camming-down elements at the level of the clearing, tucking or run-through positions.Those camming-down elements which act directly on knitting needles or parts fixedly coupled thereto and lower them into the knocking-over and loop-sinking position also have as a rule, immediately after the lowest point of the camming-down face, a short ascending cam face portion which renders possible a slight lifting of the knitting needles and thereby a release of the tension of the loops suspended therein. Moreover, the camming-down elements frequently have counterguide elements associated with them which serve as counterguides for the butts during their movement into the lowest position and comprise short ascending portions arranged immediately after the lowest point of the camming-down face and by means of which the needles are raised slightly to release the tension of the loops, the corresponding cam face portion of the cammingdown element being able to act as a counterguide.Sometimes, these counterguide elements are also completely absent, however, so that after being cammed down the butts immediately strike against the camming-up elements again and are raised by them into the tucking or clearing position.

Depending upon the position from which and the angles and the speed at which the butts of the knitting tools strike against the camming-down face of the camming-down element, the butts rebound with greater or lesser force from the camming-down face and are then taken over more or less abruptly on their further course by a counterguide element or a camming-up element, this process being also affected by opposing forces, for example frictional forces or the retaining forces exerted by the loops disposed in the needle hooks. For these reasons, it is generally not possible to indicate any definite place at which the impact against the counterguide path takes place. On the contrary, it is appropriate to speak of a striking zone within which the impact will take place irrespective of a particular case.

It has long been assumed that the impact of the butts against the camming-down and/or counterguide elements is somehow connected with various symptoms of wear in the knitting tools, in particular breakages of needle heads or butts. For example, in the journal 'Deutsche Textiltechnik' 22 (1972), No. 7, it is pointed out on page 442 that the direct impacts frequently occurring at the loop-sinking point cause breakages of needle heads.

In order to avoid such disturbances, which make any further increase in the knitting speed which can be achieved today impossible, it is known to provide cam tracks for the butts of the knitting tools which are substantially closed over their entire length, by reason of their shape allow "soft" running of the butts up against the camming-down and/or counterguide elements or have supplementary parts which have a favourable effect on the movement of the butts (see, for example, German Laid-open Patent Specification 1,585,439 or German Laid-open Pending Patent Applications 17 60 332, 23 57 053, 26 06 585, 23 36 020, 26 43 185 and 27 33 012). All the known proposed solutions do not, however permit any satisfactory increase in knitting speeds. Apart from this, some known proposed solutions entail an undesirably high design expenditure.

The present invention is defined in the appended claims, to which reference should now be made.

The invention is based on the discovery that to achieve high knitting speeds it is necessary to associate a counterguide element with a striking zone having a positive pitch with each cammingdown element. In this way, an increase in efficiency by about 25% is obtained compared with cams of conventional type. Moreover, the invention does away with a widespread preconception which consists of the assumption that the striking zone of the counterguide elements, so far as counterguide elements are considered necessary at all in connection with the avoidance of needle breakages, should either have a negative pitch, like the camming-down elements, or at least extend horizontally. No indication can be gathered from the entire state of the art that the specialist world has ever related the number of needle breakages that occur with the pitch of the counterguide elements.

According to the invention, moreover, a counterguide element is always associated with all the camming-down elements present on the machine, since otherwise needle breakages would occur preferentially where no counterguide element according to the invention is provided.

As regards the angle of the positive pitch of the counterguide elements, it has been proved that angles between 8 and 270, in particular between 100 and 250, are most suitable. The result of larger angles is that the butts of the knitting tools undergo a too abrupt change in their direction of movement on their impact against the counterguide element and therefore, for example, are braked too sharply, as would also be the case if the counterguide element were absent and the butts would strike instead against a following camming-up element, since the camming-up elements employed for camming upwards into the tucking or knitting position normally have pitch angles of far more than 300.On the other hand, angles smalier than 80 have the result that the butts of the knitting tools, similarly to what occurs in impact against a straight counterguide element, rebound from the striking zone or are thrown back by it, which is likewise undesirable.

The invention is described in detail hereinafter by way of example, with reference to the embodiments in conjunction with the drawings. In the drawings: Figs. 1 and 2 show cams with camming-down elements of conventional type; and Figs. 3 and 4 show cams embodying the invention.

Fig.1.shows a knitting cam of known type with a camming-up element 1, with which a guide element 2 is associated, and with a cammingdown element 3, with which a counterguide element 4 is associated and which serves to cam down knitting needles into a knocking-over and loop-sinking position. The camming-down element 3 has a substantially linearly descending camming-down face 5, that is a camming-down face with a negative pitch, which is followed after the lowest point 6, the loop-sinking point, by an initially horizontally extending, then linearly ascending and thereafter again horizontally extending cam face 7 which serves to release the tension of the loop formed at the loop-sinking point and locating in the hook of the needle.Correspondingly, the counterguide element 4 has a counterguide path 8 associated with the camming-down face 5 and the cam face 7 and which has a negative pitch as far as a point located in advance of the lowest point 6, then changes over into a horizontal section 9, which terminates approximately at the same point as the first horizontal section of the cam face 7, and then has another horizontal section after a short linearly ascending section. The first horizontal section of the counterguide cam face 8 may be described as the "striking zone" for the butts 1 0, which are indicated by shading, of the knitting tools, for example knitting needles, because irrespective of the point at which and the speed with which the butts 10 have run up against the camming-down face 5 they can always strike against the counterguide cam face 8 within the section 9.

During the sliding of the butts 10 against the cam faces 5 or 8, either the associated knitting tools together with their support move to the right in the direction of the arrow or the cams formed by the elements 1 to 4 move to the left in the opposite direction to that of the arrow. The result of this is that the knitting tools, which are arranged in guide channels (tricks) or grooves 11 in their support, bear against one side wall of the associated guide channel 11, i.e. its left-hand side wall in Fig. 1, at one long side at least as long as the associated butts slide along the cammingdown face 5, and then strike against the horizontal section 9 of the counterguide path 8 with their horizontally extending lower edge, which is described as a direct impact and is indicated by an arrow 12 in Fig. 1.On striking against the section 9, the knitting tool is either lifted away completely from the one side wall of the associated guide channel 11 or at least slightly tilted. The butt 10 thereafter runs up onto the slightly ascending part of the counterguide cam face 8 until a direct impact takes place again, this time when the butt strikes against the second section, acting as a counterguide, of the cam face 7 at the point indicated by an arrow 13. It is accepted that the tilting or shifting movements of the knitting tools in their guide channels 11 which are unavoidable on direct impact are a material cause of the mentioned wear symptoms.

Fig. 2 shows a known cam wherein the parts corresponding to those of the cam according to Fig. 1 are provided with the same reference numbers and which, in contrast to the cam according to Fig. 1, has a curved camming-down face 14 which initially has a relatively small negative pitch in its first section on the left in Fig.

2, so that the striking angle for the butts 10 is small, them changes over into a section with a relatively large negative pitch and finally opens along an arc into a cam face 1 5 with a positive pitch which serves to release the tension of the loops formed. A counterguide cam face 1 6 associated with the cam faces 14 and 1 5 has a similar shape. It is characteristic of cams of this type that as long as the butts 10 slide along the descending section of the camming-down face 14 they abut the camming-down face 14 at their corner at the top on the right in Fig. 2, as can be seen clearly at the point marked by an arrow 17.

When, on the other hand, in its further course, the butt 10 strikes against the counterguide cam face 1 6 at the location of the arrow 17 or else not till at a point marked by the arrow 18, then it comes into contact with the counterguide cam face 1 6 with its lower left-hand corner in Fig. 2.

Correspondingly, in the region of the arrow 1 9 the butt knocks against the ascending portion of the counterguide cam face at its lower right-hand corner and a little later against the cam face 1 5 of the camming-down element, which face acts as a counterguide, at its upper left-hand corner. It is assumed that these constant changes in the point of contact, in conjunction with the movement components present in the direction of the arrow and perpendicularly thereto, result in undesirable tilting or swinging movements of the knitting tools in the guide channels 11 and that the moments thereby exerted on the knitting tools are the cause of the mentioned wear symptoms, in particular needle head breakages.

In the knitting cam according to Fig. 3, on the other hand, in which like parts are again provided with the same reference numbers, a counterguide element 4 is provided with a counterguide path 20 which ascends linearly continuously, that is has a constant positive pitch.An essential difference compared with the counterguide cam faces 8 and 16 according to Figs. 1 and 2 results from the fact that, irrespective of the point at whichzthe butts 10 of the knitting tools strike against the counterguide cam face 20 after sliding off a camming-down face 21 they always come into contact with the counterguide cam face 20 at their lower right-hand corner (arrow 23), while when they are sliding along the camming-down face 21 they are always in contact with the camming-down face 21 at their upper right-hand corner. the striking of the butts 10 against the camming-down and guide faces 21 and 20, respectively, consequently always takes place on the same side, that is from the right in Fig. 3, so that the knitting tool already bearing in any case against the left-hand side wall in Fig. 3 of the associated guide channel 11 is at most pressed stiil more strongly against this side wall, but cannot be subjected to uncontrolled tilting or swinging movements as in the cases explained with reference to Figs. 1 and 2. Tests with knitting needles have shown that, when the counterguide path 20 is employed, needle head breakages in particular occur considerably more rarely and that it is possible to operate at substantially higher knitting speeds, that is, for example, at greater speede of rotation in the case of a circular knitting machine or at higher carriage speeds in the case of a flat knitting machine.

The cam face 22 of the camming-down element 3 following on the camming-down face 21 and intended to release the tension of the loops has the same positive pitch as the counterguide path 20 and terminates at the level of the run-through position. This embodiment also makes possible particularly simple adjustment of the cam elements 3 and 4 relative to one another.

As shown in fig. 3, the camming-down face 21 changes abruptly at its lowest point indicated by the arrow 23 into the cam face 22. Tests have shown that roundings of the two cam faces 21 and 22 at this point of transition are not necessary. Alternatively, the cam face 22 could first have a horizontal section, which may be advantageous for reasons of knitting technique.

The embodiment according to Fig. 3 can be modified in various ways. For example, it is possible to give the counterguide path 20 a varying positive pitch. In particular, the positive pitch could also change within the striking zone for the butts 10.

A constant pitch of the counterguide path 20 in the region of the striking zone would, of course, have the advantage that the butts 10 will always encounter the same pitch irrespective of where they strike against the striking zone.

Apart from this, the first and the last section of the counterguide path 20 could also be given negative pitches, provided that the middle section against which the butts 10 controlled by the camming-down face 21 strike has a positive pitch. An angle of 200, for example, is suitable as the pitch angle. The best results can be achieved with angles of 80 to 270. Below and above these values, on the other hand, the results become increasingly poorer. The shape chosen in a particular case for the camming-down face 21 is not critical, that is the camming-down face may be formed both in accordance with Fig. 1 and in accordance with Fig. 2.

The application of the invention is not limited solely to a knitting cam with an enclosed full camming-up arrangement (Fig. 3). In the embodiment according to Fig. 4, on the contrary, the butts 10 can also be brought up to the cammingdown face 21 along paths 24,25 and 26, the path 24, for example, being associated with a needle raised as far as the clearing position, the path 25 being associated with a needle raised as far as the tucking position, and the path 26 being associated with a non-knitting needle remaining in the run-through position. The striking zone A embracing all three cases of use (straight runthrough, tucking and full camming-up) is indicated by a broadened line within the counterguide cam face 20.

Finally, the invention is not restricted to cam elements 3 and 4 with cam faces 20 and 22 extending obliquely with respect to the remaining lateral faces. On the contrary, the cam faces 21 and 22, on the one hand, and the cam face 20, on the other hand, could also be realized with cam elements which, for example, have an essentially rectangular outer contour, but are so fixed to a support plate that one lateral face extends obliquely as shown in Figs. 3 and 4 for the cam faces 20,21 and 22.

A cam face with a "negative" pitch or inclination within the meaning of the invention is a cam face which encloses with the direction of the arrow according to Fig. 4, that is with the direction of movement of the knitting tool support (or with the direction opposite to the direction of movement of the cam support) an angle a which would be located in the fourth quadrant of a cartesian coordinate system placed through the vertex of the angle a. Accordingly, a cam face with a "positive" pitch is defined by an angle p enclosed between the cam face and the direction of the arrow and which would be located in the first quadrant of a cartesian coordinate system placed through its vertex (see Fig. 4).

The invention can be applied both to flat knitting machines and to circular knitting machines with rotatable needle cylinders or rotatable cam boxes and in particular both to large circular knitting machines with cylinder diameters of thirty inches and so-called underwear machines with cylinder diameters of fourteen to twenty-two inches and also to automatic stocking machines with cylinder diameters of about four to eight inches. The invention is applied with special advantage in very high-speed large circular knitting machines having, for example, up to 144 feeds, for instance rib machines or interlock machines.It is moreover provided that a counterguide cam face in accordance with the invention be associated with each of the camming-down faces or cammingdown elements of every individual feed, since otherwise in view of the high speeds of rotation of the needle cylinders or cams which can be achieved needle breakages would always occur at that feed having a camming-down element with which no counterguide element with a positive pitch is associated. The same would also apply in the event of camming-down elements being provided which do not serve to convey the knitting tools into the loop-sinking position, but, for example, cam down knitting needles from a high non-knitting or miss position into a low knitting, tucking or run-through position, as is necessary in certain automatic stocking machines having reciprocating devices during or after completion of the reciprocating movement.

Furthermore, the pitches of the counterguide elements are preferably chosen independently from the pitches of following camming-up faces which move the knitting tools into a tucking or knitting position. This can be achieved in particular by producing the counterguide elements 4 according to Figs. 3 and 4 from separate pieces independent from the cammingup elements 1 and brings with it the advantage that the pitches both of the counterguide elements 4 and of the camming-up elements 1 can be designed in each case in optimum manner in accordance with their different functions.

Moreover, it is, of course, advantageous also to provide in the counterguide elements 4, behind the striking zones in the direction of movement of the needles, those short cam portions acting in the camming-up direction which serve to raise the needles slightly for releasing the tension of the loops suspended from the needle hooks before the needles of a following knitting feed are cammed up again into the tucking or knitting position.

Claims (7)

Claims

1. A knitting machine cam for controlling knitting tools each having at least one butt and with a plurality of camming-down elements acting on the butts of the knitting tools and having camming-down faces with a negative pitch, in which with each camming-down element there is associated a counterguide element with a striking zone for the knitting tool butts controlled by the camming-down element, and all the striking zones have positive pitches compared with the camming-down faces.

2. A Cam according to claim 1, in which the striking zones have a constant positive pitch.

3. A Cam according to claim 1 or 2, in which the counterguide elements are provided with counterguide paths which have a continuously constant positive pitch.

4. A Cam according to claim 3, in which immediately after the camming-down faces, the camming-down elements are provided with cam faces having pitches coinciding with the pitches of the associated parts of the counterguide paths.

5. A Cam according to any of claims 1 to 4, in which the positive pitches of the counterguide elements have a pitch angle of 80 to 270.

6. A Cam according to any of claims 1 to 5, in which the pitches of the counterguide elements are chosen independently from the pitches of following camming-up elements intended to cam up the knitting tools into a tucking or knitting position.

7. A knitting machine cam substantially as herein described with reference to Figs. 3 or 4 of the drawings.