GB2122653A - Circular knitting machine for producing knitted articles with combed-in fibres - Google Patents

Abstract

Around the needle cylinder 3 are several combing-in stations each having a carding device 18 with a blowing nozzle 14. A suction hood 25 over the needle cylinder leads to an extraction pipe 26. A second conical suction hood 28 is supported at a uniform spacing b within the hood 25 by support arms 30 to define a suction passage 29. The arms 30 are hollow and of streamlined profile and are supplied with compressed air from a ring conduit 36. The air emerges through a leading edge slot 32 and a trailing edge slot 38 to prevent accumulation of fibres on the support arms. <IMAGE>

Description

SPECIFICATION Circular knitting machine for producing knitted articles with combed-in fibres The invention relates to a circular knitting machine of the general kind set forth in the classifying portion of claim 1.

In a known circular knitting machine of this kind (US patent specification No 3 014 355), the member which is arranged within and/or below the suction hood comprises a bottom plate member which substantially covers the lower suction opening and which leaves free only a narrow annular suction gap. It is also known (US patent specification No 3 968 662) for a second suction hood to be disposed within and below a first suction hood which is arranged above the needle cylinder and which is adapted to suck away loose fibres in the region of the carding means, the second suction hood projecting far into the needle cylinder and serving also to suck away the loose fibres which are within the needle cylinder and on the front face of the knitted article produced.Also known are complicated blowing and suction devices which have blowing nozzles, suction hoods and plates covering the needle cylinder (DOS No 23 07 111) and which are intended on the one hand to improve the combing-in operation and on the other hand to reduce the level of fibre losses. Finally, circular knitting machines are known (DOS No 2633 912) in which the member arranged below the suction hood comprises two fibre or fibre and material guide devices which are arranged one below the other.

In the case of the circular knitting machines first mentioned above, the member is secured to the suction hood by means of respective support arms These represent obstacles in the suction removal flow, and the loose fibres which are to be sucked away rapidly accumulate at such obstacles, form lumps and reduce the flow crosssection, which gives rise to the necessity for frequent maintenance work. This effect is further increased by the amounts of oil and water (needle oil, condensed water or the like) which are produced in operation of the circular knitting machine and which greatly increase the tendency of the loose fibres to cling to the support arms.

Corresponding problems would arise if the member were secured to another fixed part of the circular knitting machine, instead of being secured to the suction hood.

In the last-mentioned circular knitting machine (DOS No 26 33 912), in an effort to overcome that disadvantage, the member which is arranged below or within the suction hood is secured to a shaft which is arranged coaxially in the needle cylinder and which is secured thereto, so that the member rotates with the needle cylinder. By virtue of this arrangement, the knitted article has to be cut up in the longitudinal direction in the circular knitting machine, and this is frequently undesirable.

Apart from the rapid rate at which the support arms become fouled, the above-mentioned suction means are distinguished by a low level of suction removal efficiency or by a high level of power consumption. A primary reason for this lies in the conical or frustoconical configuration of the suction hood which has its largest cross-section and therefore its lowest suction force, at the position where the loose fibres are to be picked up and removed, because the cross-section of the bottom suction opening of the suction hood is usually about 9 times the cross-section of the upper suction pipe.This disadvantage also cannot be substantially eliminated by substantially covering the bottom suction opening or by mounting additional air guide plates (US patent specification No 3 014 355, DOS No 23 07 111), as any additional member possibly increases the tendency to fouling and thereby further reduces the suction removal capability.

In practice therefore, simple, frustoconical or conical suction hoods have been used hitherto, and the resulting low levels of suction efficiency have been tolerated.

Because of the low levels of efficiency of the known suction arrangements, it is also necessary for at least one blowing nozzle to be provided at each knitting location, in order to hold the fibres which are to be combed in securely in the hooks of the knitting needles, during the combing-in operation and before the stitch formation operation. It will be appreciated that such nozzles, in conjunction with the air currents caused by the rotary movement of the needle cylinder, give rise to considerable turbulence and eddy phenomena which detrimentally affect the suction removal process and which even further reduce the level of efficiency of the suction device.The use of blowing nozzles also has the undesirable consequence that they frequently blow fibres which are already laid into the knitting needles out of the needles again before those fibres are bound into the ground knitting, so that the level of fibre losses is increased, and also that the blowing pressure has to be set at a higher level in proportion to increases in the desired fibre density, and this increases the formation of turbulence and eddy currents and increases fibre losses.

Therefore, the invention is based on the problem of increasing the operational efficiency of the known suction devices, while having a reduced power consumption and a reduced level of fibre losses, and in particular substantially eliminating the danger of loose fibres accumulating on the support arms.

The characterising features of claim 1 are provided to solve the above-defined problem.

Further advantageous features of the invention are set forth in the subsidiary claims.

On the one hand, the invention gives the advantage that a boundary layer comprising an air cushion may be formed in the region of the leading edge of the support arms, the boundary layer keeping the sucked-away fibres away from the leading edge of the support arms and therefore making it substantially impossible for fibre accumulations to occur. For this purpose, the speed of the pressure medium issuing from the hollow body needs to be only slightly higher than that of the air flow which surrounds the hollow body and which is produced by the suction process. On the other hand, mounting any components within and/or below the suction hood, in a non-fouling manner, opens many possiblities in regard to improving the air flow conditions in the region of the knitting locations and thereby substantially reducing the level of fibre losses.

The invention is described in greater detail hereinafter in embodiments, with reference to the accompanying drawings in which: Figure 1 is a diagrammatic perspective view of a circular knitting machine for producing knitted articles with combed-in fibres, Figure 2 is a diagrammatic side view of a knitting location of a circular knitting machine according to the invention, Figure 3 shows a front view of a support arm of the circular knitting machine shown in Figure 2 and, in diagrammatic form, the air currents produced thereby, and Figure 4 shows a diagrammatic side view of a knitting location of an alternative embodiment of the circular knitting machine according to the invention.

Referring to Figures 1 and 2, a circular knitting machine for the purposes of producing a knitted article 1 with combed-in fibres has a needle cylinder 3 which is provided with knitting needles 2, and a sinker ring 5 which is provided with sinkers 4. The needle cylinder 3 and the sinker ring 5 are both mounted rotatably in a machine frame structure. The knitting needles 2 and the sinkers 4 are controlled in the usual manner by cam members 7 secured to a cylinder cam 6 and cam members 9 secured to a sinker cam 8. Arranged at the periphery of the needle cylinder 3 are a plurality of spaced knitting locations or knitting systems 10 to 1 3 which may each include a respective pattern device by means of which the knitting needles are selected for knitting or not knitting, in accordance with the pattern.Also associated with each knitting system is a blowing nozzle 14 to 1 7 which is intended to align the fibres.

Also provided at each knitting system 10 to 1 3 is a respective carding means 18 to 21 which serves to supply the knitting needles which are selected for knitting with fibres having a given attribute, for example colour. Each carding means comprises for example a drum 22 with a carding fitment to which fibres are supplied in the form of a sliver by means of a pair of feed rolls, and a doffer or combing-in roller 23 having a carding fitment by means of which the fibres taken from the drum 22 are offered to the knitting needles selected for knitting.

Arranged above the needle cylinder 3 is a suction removal means 24 which has a conical or frustoconical suction hood 25 which is intended to suck away loose fibres and whose upper end is connected to a suction pipe 26 which leads to a suction source (not shown).

The direction of rotation of the needle cylinder 3 is indicated by arrow 27. The air flows in the blowing nozzles 14 to 1 7 which are connected to compressed air sources (not shown) and within the suction hood 25 are indicated by the other arrows.

Circular knitting machines of the abovedescribed type are known for example from US patent specifications Nos 3 014 355 and 3 968 622 and DOS Nos 23 07 111 and 26 33 912 to which reference is hereby expressly made.

According to the invention, arranged within the suction hood 25 is a second suction hood 28 which is also of a frustoconical or conical configuration. The second suction hood 28 is arranged in the first suction hood substantially coaxially and in such a way that a suction passage or gap 29 is formed between the two suction hoods 25 and 28. The suction gap 29 tapers substantially conically and extends approximately from the upper edge of the needle cylinder to the suction pipe 26 and is of a substantially constant width b throughout. This arrangement substantially increases the suction capability and restricts and concentrates the suction opening to an annular area adjacent the upper edge of the needle cylinder.

At least one support arm 30 is provided for securing the second suction hood 28 to the first suction hood 25. The support arm 30 comprises a hollow body having a flow-entry or leading edge 31 which is towards the needle cylinder. The edge 31 has an outlet opening 32 (see Figure 3) for a pressure medium, for example air, which is introduced into the hollow body. The outlet opening 32 desirably comprises a slot which extends over the entire width of the hollow body or the suction passage 29. In a lateral portion, the support arm 30 has a bore 33 which is aligned to a corresponding bore 34 which is formed in the suction hood 25 and to which a pressure medium source 36 is connected by means of a pipe 35.

The pressure medium source 36 may comprise for example a ring conduit which is connected to a compressor and to which all other corresponding support arms (not shown in the drawing) are also connected.

In a preferred embodiment of the invention, the flow-exit or trailing edge 37 of the support arm 30 comprising a hollow body is also provided with an outlet opening 38 for the pressure medium, in the form of a slot extending over the entire width thereof. It will be appreciated that the width of this slot should desirably be less than that of the outlet opening 33 so that a smaller amount of pressure medium issues at the trailing edge. In addition, as shown in particular in Figure 3, the support arms 30 have an external contour in the nature of an aerofoil configuration, resulting in particularly favourable flow conditions in the region of the support arms.

The arrows shown in the region of the support arm 30 in Figures 2 and 3 indicate the flow conditions in operation of the arrangement. As shown by the arrows, loose fibres, particles of dust or the like in the region of the upper edge of the needle cylinder are sucked into the suction shaft 29 by the combined suction and blowing pressure and are transported from the suction shaft 29 towards the suction pipe 26. If the air speed caused by the pressure medium at the position of the outlet opening 32 is slightly higher than the air speed which would occur at that point without the presence of the pressure medium, then an air cushion is formed in front of the outlet opening 32 and substantially prevents the loose fibres from approaching the edge 31. Therefore, as shown in Figure 3, the fibres are guided around the support arms 30 without coming into contact therewith.The aerofoil or streamline configuration of the support arms 30 enhances that phenomenon so that even when oil and water residues are present on the side surfaces of the support arms 30, no fibres are accumulated thereon. There is also no accumulation of fibres in the region of the trailing edge. There too the speed of the flow of pressure medium should be higher than that of the rest of the flow.

By virtue of the arrangement of the second suction hood 28 in the first suction hood 25, it is possible for the lower ends of both suction hoods to be formed as flow guide surfaces and to be so shaped that the flow conditions which are desired in the specific case in point are produced. As shown in Figure 2, for example the lower end 42 of the first suction hood 25 terminates, corresponding to the frustoconical shape, above the upper edge of the needle cylinder approximately at the level of the maximum cammed-up height of the knitting needles 2, while the lower end 43, also corresponding to the frustoconical shape, is taken to a position close to the knitted article 1 and terminates below the upper edge of the needle cylinder and below the axes of the nozzles 14, whereby eddy and turbulence phenomena are substantially eliminated.Alternatively, as shown in Figure 2 in broken lines, the lower ends 42a and 43a of the suction hoods 25 and 28 may also be bent away radially outwardly. In this respect, in particular the end 42a may be connected to an outer cover means 44 for the drum 22 and the combing-in roller 23 so that the space in the needle backs is completely covered. In comparison with the virtually perpendicular arrangement of the ends 42a and 43a relative to the axis of the nozzle 14, the above-described arrangement gives the advantage that the fibres are diverted on to the ends 42a and 43a in an inclined or almost tangential manner and scarcely remain clinging thereto even when the ends 42a and 43a are covered with a sticky deposit of oil or water residues.A further advantage is that, with the ends 42a and 43a being of such a configuration, the blowing pressure of the nozzle 14 can be greatly reduced or the nozzle 14 can even be entirely omitted because the suction force developed by the suction shaft 29 can be made of sufficiently great magnitude to align the combed in fibres and for sucking away the loose fibres, without a high level of energy expenditure.

A further embodiment of the invention is shown in Figure 4 in which the same components are denoted by the same reference numerals and only the two suction hoods 25 and 28 are replaced by a first outer suction hood 45 and a second inner suction hood 46.

In contrast to Figure 2, in the embodiment shown in Figure 4, the inner suction hood 46 is provided with a lower end 47 which projects relatively far into the needle cylinder and which is curved approximately from the upper edge of the needle cylinder along an arc which gradually extends radially inwardly so that the lower edge 48 thereof is of a cross-section which is equal to or smaller than the cross-section of the suction hood 46 in the region of the upper edge of the needle cylinder. In addition, the lower crosssection of the suction hood 46 is covered with a cover means 49 and the upper cross-section of the suction hood 46 is covered with a cover means 50. It will be appreciated that a narrow annular gap 51 and 52 respectively is left free between the respective cover means 49, 50 and the suction hood 46.Finally, the side of the support arm 30 which is opposite the bore 33 has a further bore 53 which is aligned to a corresponding bore 54 in the suction hood 46 so that the pressure medium can also pass into the interior of the suction hood 46 and can flow in the direction of the arrows shown in Figure 4.

The purpose of the gap 51 and the bores 53 and 54 is to produce an air flow, in particular in the region of the lower curved end 47 of the suction hood 46 and on the outside thereof, the air flow extending parallel to the front side of the knitted article 1 and sucking undesired loose fibres away from the front ot the knitted article 1, thereby facilitating subsequent handling of the article 1. As in the case of the embodiment shown in Figure 2, not only can the airflow be easily adapted to the requirements of any particular case and precisely controlled and regulated, by the size of the gap 51 and the bores 53 and 54 and the pressure of the pressure medium being selected at suitable values, but in many cases it is also possible to provide that the blowing nozzle 14 can be omitted or left unused.

In contrast, the purpose of the gap 52 in conjunction with the bores 53 and 54 is to control the flow in the region of the outside of the upper end of the second suction hood 46 and prevent undesirable and energy-consuming turbulence and eddies from being formed. For this reason, in comparison with the upper end of the suction hood 28 shown in Figure 2, the upper end of the suction hood 46 is also not of a pointed configuration, corresponding to a cone, but is flattened so as to correspond to a truncated cone.

The invention is not limited to the abovedescribed embodiments but may be modified in many respects. This applies in particular in regard to the particular configuration of the two suction hoods and the shape thereof in the lower region, which can be adapted to the conditions desired in a particular situation. In addition, the inner suction hood 46 shown in Figure 4 may be provided with a separate pressure medium connection which is independent of the pressure medium source 36.

There is also no necessity for the two suction hoods 25, 28 and 45, 46 respectively to be arranged coaxially with respect to each other and coaxially with respect to the needle cylinder axis, although an arrangement of this kind is preferred for reasons of symmetry and for providing the same conditions at all knitting systems. Finally, the support arms 30, as set forth in the foregoing description, may also be provided for mounting other components than inner suction hoods and for securing the inner suction hoods or other components at other stationary parts of the circular knitting machine than the outer suction hoods.

As regards the external shape of the support arms, they are desirably only provided with smooth large-area wall surfaces to which the fibres have only a poor adhesion capability, even without the outlet openings according to the invention. In this connection, in place of streamlined profiles other profiles, for example circular, may be used.

There may be any number of support arms, at least three support arms being preferred.

Claims (14)

1. A circular knitting machine for producing knitted articles with combed-in fibres, comprising a needle cylinder supporting knitting elements, at least one carding means for combing the fibres into the knitting elements, a suction removal means which is intended for sucking away loose fibres and which has a first suction hood arranged above the needle cylinder, and at least one member which is arranged within and/or below the suction hood and which is secured by means of at least one support arm to a stationary part of the circular knitting machine, characterised in that the support arm (30) comprises a hollow body which is connected to a pressure medium source (36) and whose leading edge (31), which is towards the needle cylinder (3), has an outlet opening (32) for the pressure medium, which outlet opening is intended to avoid the accumulation of fibre.

2. A circular knitting machine according to claim 1 characterised in that the trailing edge (37) of the support arm (30) also has an outlet opening (38) for the pressure medium.

3. A circular knitting machine according to claim 1 or claim 2 characterised in that said member comprises a second suction hood (28, 46) which is arranged within the first suction hood (25, 45).

4. A circular knitting machine according to claim 3 characterised in that the second suction hood (28, 46) is arranged coaxially in the first suction hood (25, 45).

5. A circular knitting machine according to claim 3 or claim 4 characterised in that the suction hoods (25, 45 and 28, 46 respectively) are of a conical or frustoconical configuration.

6. A circular knitting machine according to claim 5 characterised in that both suction hoods (25, 45 and 28, 46 respectively) have the same apex angle and form a suction gap (29) of constant width (b).

7. A circular knitting machine according to one of claims 3 to 6 characterised in that the portion of the leading edge (33) of the support arm (30), which portion extends between the two suction hoods (25, 45 and 28, 46 respectively) has an outlet opening (32) in the form of a slot which extends over the width (b) of the suction gap (29).

8. A circular knitting machine according to one of claims 1 to 7 characterised in that the outer contour of the support arm (30) is formed in the manner of an aerofoil member.

9. A circular knitting machine according to one of claims 3 to 8 characterised in that the lower ends (42, 42a, 43, 43a) of the suction hoods (25, 45) are formed as flow guide surfaces.

10. A circular knitting machine according to one of claims 3 to 9 characterised in that the lower end (43a) of the second suction hood (28) terminates within the needle cylinder (3) and approximately at the level of the upper edge of the needle cylinder, while the lower end (42) of the first suction hood (25) terminates above the upper edge of the needle cylinder.

11. A circular knitting machine according to claim 10 characterised in that the lower end (43a) of the second suction hood (28) is formed as a radially outwardly extending arc which terminates close to the upper edge of the needle cylinder.

12. A circular knitting machine according to one of claims 3 to 11 characterised in that the carding means has a combing-in roller (23) which is provided with a radially outwardly disposed cover means (44), and that the lower end (42a) of the first suction hood (25) terminates at the lower end of said cover means (44).

13. A circular knitting machine according to one of claims 3 to 12 characterised in that the lower end (47) of the second suction hood (46) terminates below the upper edge of the needle cylinder and ends in the form of a radially inwardly curved arc.

14. A circular knitting machine according to one of claims 3 to 1 3 characterised in that the interior of the second suction hood (46) is connected to a pressure medium source (36).

1 5. A circular knitting machine according to claim 14 characterised in that the lower end (47) of the second suction hood (46) is covered with a plate (49) of corresponding cross-section, but a narrow gap (51) is left free between the lower edge of the second suction hood (46) and the plate (49).

1 6. A circular knitting machine according to claim 14 or claim 1 5 characterised in that the second suction hood (46) is of a frustoconical configuration and that its upper end is covered with a further plate (50) of corresponding cross section, but a narrow gap (52) is left free between the upper edge of the second suction hood (46) and the further plate (50).

1 7. A circular knitting machine according to one of claims 14 to 1 6 characterised in that the second suction hood (46) has a bore (54) which is in flow communication with the interior of the support arm (30).