DESC:FIELD OF INVENTION

[0001] The present invention relates to the technical field of textile machinery. Particularly, the present invention relates to a drafting apparatus of a spinning machine.

BACKGROUND OF THE INVENTION

[0002] The subject matter discussed in the background section should not be assumed to be prior art merely because of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may correspond to implementations of the claimed technology.
[0003] A spinning machine of a textile mill typically includes mechanisms for fibre material feeding, drafting, twisting and winding to convert roving material into yarn. One of the important components of the spinning machine is drafting apparatus, where fibres in the form of roving or sliver strands are stretched and parallelized to reduce diameter thereof. A 3/3 drafting apparatus or a 4/3 drafting apparatus are conventionally used in spinning mills. Normally, the 3/3 drafting system consists of two drafting zones, i.e. a pre/break-drafting zone and a main drafting zone. The pre-drafting zone is a space between a nip of a back roller pair and a middle roller pair. The main drafting zone is a space between the nip of the middle roller pair and a front roller pair. The fibres are firmly nipped between a steel bottom roller and a top roller formed of pressurized rubber cot material. The drafting rollers are rotated in such a way that their peripheral speed in a flow direction increases from roller pair to roller pair leading to the drawing of fibres from roving strands.
[0004] A double apron system is widely used to control movement of short fibres and to improve uniformity of strands with greater draft at the main drafting zone. In a conventional double apron system, a top apron is rotated over a top middle roller which is tensioned and guided by an apron cradle. Further, a bottom apron is rotated over a bottom middle roller which is tensioned by a nose bar and tensioning fork. Spacers are fixed on the cradle to provide a gap between the top apron and the bottom apron, which is necessary for passage of fibres from the pre-drafting zone to the main drafting zone. Size of the spacer is chosen according to count of the yarn to be produced.
[0005] In existing technology, a closer setting between the front roller pair and the middle roller pair is not possible due to a geometry of front edge of the cradle. Due to existing profile of conventional cradles, the apron hinder over the front top roller if a tip of the cradle is extended further, which affects deflection of the fibre strands. Fig. 1 illustrates a side view of a drafting apparatus in accordance with prior art. In existing design of cradle (10), slackness of top apron (8) occurs due to presence of hump in rear side of the cradle (10). The rear side hump of the cradle (10) also has small area of contact, i.e. line contact (11), between the apron (8) and the cradle (10) only at two points, as shown in Fig. 1. The two-point line contact (11) of the cradle (10) with the top apron (8) causes buckling of the apron (8) in the main drafting zone. Normally 15 to 20 mm gap is maintained between this unsupported area (12) present between the nip of top and bottom apron (8, 9) and the front roller pair (6, 7). A front edge of the top apron cradle (10) cannot be extended since the top apron (8) hinders the top front roller (6), which affects deflection of the fibre strands in the main drafting zone. Also, closer setting between the front top roller (6) and the nip of the middle apron (8) is not possible due to geometry of the conventional cradle (10). Due to this, the apron (8) freely rotates over the roller (4), and buckling of the apron (8) is caused by limited area of contact, thereby disturbing movement of the roving strands in the main drafting zone due to increase in the unsupported area (12) of the fibre strands.
[0006] As a background of the existing technology, in Indian patent IN339930 (330/KOL/2010), movement of fibre strands at the main drafting zone is well controlled by an additional guiding or deflection element fixed with a spacer (13), as shown in Figs. 2 and 5. The spacer (13) and the guiding element are affixed to one another in a releasable way and are arranged to the cradle. The spacer (13) is fixed on the cradle (10) to create a gap between the top apron (8) and the bottom apron (9) for the passage of fibre strands (1) from the pre-drafting zone to the main drafting zone. Metal strip of the spacer (13) prevents scattering of short fibres and improves coherence of the fibre strands (1) at the unsupported area (12). Though the requirement of fibre strands is to be passed below the deflection element fixed with the spacer (13), as shown in Fig. 5, the strands sometimes undergo a slight change in direction by passing above the deflection element, as shown in Fig. 2, which is disadvantageous. The fibre strands (1) passing above the metal strip of the spacer (13) causes an increase in friction between the fibre strands (1) and the spacer (13), and leads to deterioration in yarn quality.
[0007] The change in fibre passage deteriorates yarn quality and creates more end breaks in the fibre strands. Also, the guiding/deflection element exerts a guiding force on the fibre strands in the drafting zone. Likewise the fiber strands exert a force on the guiding element, which introduces a friction between the fiber strands and the guiding element. The two forces that act on the guiding element at a distance from one another are different, which creates a negative effect in the yarn quality. Furthermore, optimal determination of the nip of the apron (8) and height of the spacer (13) is cumbersome. The deflecting/guiding element (pin) of the spacer (13) also sometimes touches the apron (9) encircling the bottom roller (5) due to improper setting of the middle roller pair (4, 5). In addition, a top arm pin position of a load distribution unit must be changed with respect to a nipping point of the fibre strands while using the additional guiding element (pin) with the spacer (13), together known as “pin spacer”.
[0008] In the conventional cradle (10), extending the tip portion to reduce unguided fibre length in the main drafting zone, is known from United States patent US5479680, which mentions a distance t2 in which fibre flow is not guided. However, the same is not proven to be implemented.
[0009] Another Indian patent, IN241090 (85/KOL/2006) discloses a cradle in the form of a pressure plate which exerts downward force towards a bottom portion. The cradle discloses surface contact type top surface with apron lower face instead of line contact at two hump like portions. However, in this type of cradle, a downward portion of the pressure plate exerts more thrust on a nose bar by complete contact, which is disadvantageous in terms of fibre quality.
[0010] There exists a need to overcome the above mentioned disadvantages, to which the present invention provides an improved solution.

OBJECTS OF THE INVENTION

[0011] The main object of the present invention is to provide an improved drafting apparatus for a spinning machine comprising a top roller apron cradle which reduces uncontrolled fibre passing area at a main drafting zone.
[0012] It is another object of the present invention to prevent movement and slippage of fibres above a guide element of a pin spacer in order to improve yarn quality.
[0013] Further object of the present invention is to reduce thickness of the apron by replacing a hump of regular cradle profile with an improved cradle profile.

SUMMARY OF THE INVENTION

[0014] In order to achieve the above-mentioned objects, according to an aspect of the present invention, a drafting apparatus of a spinning machine is disclosed. The drafting apparatus includes a plurality of drafting roller pairs including top drafting rollers arranged over bottom drafting rollers. The drafting roller pairs include a back roller pair, a middle roller pair and a front roller pair. A top apron rotates over at least one top drafting roller for controlling movement of one or more fibre strands passing through the at least one top drafting roller and a corresponding bottom drafting roller. The drafting apparatus also includes a cradle coupled to the at least one top drafting roller for guiding and tensioning the top apron rotating over the at least one top drafting roller. The cradle may be fixed on a middle top roller to improve stiffness of the top apron. The cradle includes at least one guiding surface having a profile to increase contact area between the top apron and a top surface of the cradle through surface contact. A radius of the top surface of the cradle is optimized to improve tension and stiffness of the top apron. The circumference of the top surface of the cradle with two different radius is achieved for smooth guidance of the top apron. The top profile of the cradle is optimized such that increased contact area is created between the bottom surface of the top apron and the top surface of the cradle at fibre movement area, through surface contact. The front edge of cradle profile is extended to shorten floating or unsupported area of a main drafting zone, i.e., area between nip of the middle roller pair and a front roller pair. The unsupported area is reduced from the existing range of 15-20mm to 8.5-10mm. As a result, a fibre shifting point in the main drafting zone becomes very closer to the nip of the front roller pair. Due to this, the fibre strands are well controlled from the middle roller pair to the front roller pair without changing an offset of the middle top roller. The profile of the cradle enables a closer setting between the front top roller and the front bottom roller which can obtain more stable pressing force, and also intensifies traction of the fibre strands.
[0015] According to an embodiment of the present invention, the drafting apparatus may include at least one pin spacer arranged on the cradle for creating a gap between the top apron and the bottom apron for passage of the one or more fibres passing through the at least one top drafting roller and the bottom drafting roller. The at least one pin spacer may be fixed at center of the cradle to provide the gap between the top apron and bottom apron for smooth passage of fibre strands passing to the main drafting zone. A front edge of cradle guides the fibre strands correctly below a metal strip (pin) of the at least one pin spacer. Advantageously, the pin spacer is not required and can be eliminated, thereby effectively reducing draft wave in the unsupported area, which is very beneficial to stabilize the yarn quality.
[0016] According to an embodiment of the present invention, the profile of the at least one guiding surface decreases distance between a nip of the top apron and a nip of a subsequent top drafting roller of the plurality of top drafting rollers.
[0017] According to an embodiment of the present invention, the at least one guiding surface has a plurality of ridges to reduce friction between the top apron and the top surface of the cradle. The plurality of ridges are formed on the at least one guiding surface by a knurling process. As the top apron guiding surface is knurled, it further improves the stiffness and life span of apron. The modified profile of the cradle can be applied to both 3 over 3 and 4 over 4 drafting apparatuses of textile spinning machine.
[0018] According to an embodiment of the present invention, the profile of the at least one guiding surface increases tension of the top apron rotating over the at least one top drafting roller.
[0019] According to an embodiment of the present invention, the cradle reduces an unsupported area between an apron pair and a front roller pair without changing an offset of the top drafting roller. Also, short fibres are well controlled from a middle roller pair to the front roller pair. The distance of the unsupported area is reduced to 8.5 to 10 mm.
[0020] According to an embodiment of the present invention, adequate load can be given to cradle without changing the middle roller existing setting.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0021] Fig. 1 illustrates a side view of a conventional drafting apparatus of a spinning machine, in accordance with prior art.
[0022] Fig. 2 illustrates an incorrect sliver path at a main drafting zone of a conventional drafting apparatus using a pin spacer, in accordance with prior art.
[0023] Fig. 3 illustrates a side view of a drafting apparatus of a spinning machine, in accordance with an embodiment of the present invention.
[0024] Fig. 4 illustrates an amplified view of a main drafting zone of the drafting apparatus, in accordance with an embodiment of the present invention.
[0025] Fig. 5 illustrates a correct sliver path at the main drafting zone of the drafting apparatus while using pin spacer, in accordance with prior art.
[0026] Figs. 6A and 6B illustrate modified profile of a cradle of the drafting apparatus, in accordance with an embodiment of the present invention.
[0027] Fig. 7 illustrates a representation of distribution of load applied to the cradle of the drafting apparatus, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0028] The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the present invention and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
[0029] The terms “or” and “and/or” as used herein are to be interpreted as inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B and/or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B and C.” An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.
[0030] Some embodiments of this disclosure, illustrating all its features, will now be discussed in detail. The words “comprising”, “having”, “containing”, and “including” and other forms thereof, are intended to be equivalent in meaning and be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items.
[0031] The present invention provides an improvement in a drafting apparatus of a spinning machine. The drafting apparatus includes a rear drafting roller pair, a middle drafting roller pair and a front drafting roller pair. A roving or sliver strands are fed to the rear roller pair from which the strand is conveyed to the middle roller pair and then to the front roller pair. A top apron is rotated over the middle top roller and a bottom apron is rotated over the middle bottom roller. A cradle is arranged around the middle top roller and is in contact with the top apron, for guiding and tensioning the top apron.
[0032] A twist imparted to the roving strands is untwisted at a pre-drafting zone, i.e., a drafting area between a nip of the rear and the middle roller pairs. The fibres of untwisted roving strands are stretched and parallelized at a main drafting zone, i.e., a drafting area between a nip of the middle and the front roller pairs. A geometry of the cradle is optimized in the present invention to improve tension and stiffness of the top apron, and increase a contact area between a bottom surface of the top apron and a top surface of the cradle, through surface contact, instead of a contact at two points only in existing hump type cradle of the prior art as shown in Fig. 1.
[0033] Referring to Figs. 3 and 4 showing drafting apparatus according to the present invention, the roving or sliver strand (21) is fed to feed/back/rear roller pair (22, 23) from which the fibre strand (21) is conveyed to the middle roller pair (24, 25) and finally reaches the delivery or front roller pair (26, 27). The back roller pair comprises back bottom roller (23) and back top roller (22). The middle roller pair comprises middle bottom roller (25) and middle top roller (24) and the front roller pair comprises front bottom roller (27) and front top roller (26). The top apron (28) is rotated over the middle top roller (24) and the bottom apron (29) is rotated over the middle bottom roller (25). The top apron (28) is tensioned and guided by a cradle (30) coupled to middle top roller (24). The top apron (28) and the bottom apron (29) control movement of the short fibres (21) at the main drafting zone. The drafting apparatus may include a tensioning assembly for generating tension in the bottom apron (29) rotating over the bottom drafting roller (25).
[0034] According to the present invention, as shown in Figs. 3 and 4, a top profile of the cradle (30) is optimized such that increased contact area is created between the bottom surface of top apron (28) and the top surface of the cradle (30) through surface contact. The cradle (30) includes at least one guiding surface having a profile to increase the contact area between the top apron (28) and the top surface of the cradle (30).
[0035] The main drafting occurs between the nip of middle roller pair (24, 25) and the nip of front roller pair (26, 27). The part numeral (31) in Fig. 4 indicates unsupported area of fibre strand between the nip of apron pair (28, 29) and the front roller pair (26, 27). Quality indicators such as yarn evenness, hairiness and strength depends upon coherence of short fibres along with the axis of fibre strand at the unsupported area (31) of the main drafting zone. Fig. 4 illustrates a distance between the nip of middle top roller apron (28) and the front roller pair (26, 27) according to the present invention. According to the design of the cradle (10) of present invention, the distance between the front top roller (26) and the nip of the middle roller apron (28) is reduced. Due to this, the unsupported area (31) is reduced without changing an offset of the middle top roller (24), and the short fibres are well controlled from the middle roller pair (24, 25) to the front roller pair (26, 27). The unsupported area (31) is reduced to 8.5 to 10 mm because of front portion of cradle geometry according to the present invention. The top radius of the cradle (30) is optimized to improve stiffness and tension of the top apron (28). The circumference of the cradle (30) with two different radius is achieved to enhance smooth guidance of the top apron (28), while improving the coherence of the final yarn. The cradle geometry of present invention increases area of contact between the top surface of cradle (30) and the bottom surface of top apron (28) through surface contact, by elimination of line / two point contact (11) of cradle design in conventional drafting apparatuses as shown in Fig. 1.
[0036] The conventional drafting apparatuses employ pin spacers (13) as shown in Figs. 2 and 5, which often lead to flow of sliver strands along an incorrect sliver path at the main drafting zone as shown in Fig. 2. The pin spacer (13) is arranged on the cradle (10) for creating a gap between the top apron (8) and the bottom apron (9) for a passage of the one or more fibres passing through the middle top roller (4) and the middle bottom roller (5). Due to some uncertain factors, fibre strand (1) sometimes passes above the pin spacer (13) which causes friction between the fibre strand (1) and the pin spacer (13) to increase, thereby leading to deterioration of yarn quality. This incorrect passage of fibre strand is continued unless it is noticed and corrected manually by the operators to attain correct sliver path as shown in Fig. 5. This disadvantage can be eliminated by using the cradle (30) according to the present invention as illustrated in Figs. 3 and 4. Advantageously, usage of the pin spacer (13) can be eliminated while using the cradle (30) according to the present invention.
[0037] Figs. 6A and 6B illustrate modified cradle profile according to present invention. The increase in area of contact between the cradle (30) and the top apron (28) increases abrasion of the top apron (28) and may result in wear and tear of the top apron (28) over a period of time. This leads to frequent replacement of the top apron (28). In order to overcome this disadvantage, a top apron guiding surface (33) of the cradle (30) is knurled or profiled. Since the guiding surface (33) is knurled, the frictional force action on the top apron (28) is reduced and the life span of the top apron (28) is enhanced. The guiding surface (33) may be knurled by forming a plurality of ridges through a knurling process.
[0038] Fig. 7 illustrates a representation of distribution of load applied to the cradle (30) according to the present invention. Out of the total load applied to the cradle (30), 75% of the load is distributed to a nip (34) of the top middle roller (24) and 25% of load is distributed to a front nip (35) of the cradle (30). Thus, adequate amount of load is supplied to cradle (30) without changing the roller and top arm settings.
[0039] It would be appreciated by a person skilled in the art that the drafting apparatus of the present invention is not only restricted to drafting apparatuses of ring spinning machine but also applicable to drafting apparatuses of roving frame machine and pneumatic spinning machine, and the like.
[0040] In view of the present disclosure which describes the present invention, all changes, modifications and variations within the meaning and range of equivalency are considered within the scope and spirit of the invention. It is to be understood that the aspects and embodiment of the disclosure described above may be used in any combination with each other. Several of the aspects and embodiment may be combined together to form a further embodiment of the disclosure.
,CLAIMS:We Claim:
1. A drafting apparatus of a spinning machine, comprising:
a plurality of top drafting rollers (22, 24, 26) arranged over a plurality of bottom drafting rollers (23, 25, 27);
a top apron (28) rotating over at least one top drafting roller (24) of the plurality of top drafting rollers (22, 24, 26) for controlling movement of one or more fibre strands (21) passing through the at least one top drafting roller (24) and a bottom drafting roller (25) of the plurality of bottom drafting rollers (23, 25, 27); and
a cradle (30) coupled to the at least one top drafting roller (24) for guiding and tensioning the top apron (28) rotating over the at least one top drafting roller (24), wherein
the cradle (30) comprises at least one guiding surface (33) having a profile to increase contact area between the top apron (28) and a top surface of the cradle (30) through surface contact.

2. The drafting apparatus as claimed in claim 1, wherein the profile of the at least one guiding surface (33) decreases distance between a nip of the top apron (28) and a nip of a subsequent top drafting roller (26) of the plurality of top drafting rollers (22, 24, 26).

3. The drafting apparatus as claimed in claim 1, wherein the at least one guiding surface (33) comprises a plurality of ridges to reduce friction between the top apron (28) and the top surface of the cradle (30).

4. The drafting apparatus as claimed in claim 3, wherein the plurality of ridges are formed on the at least one guiding surface (33) by a knurling process.

5. The drafting apparatus as claimed in claim 1, wherein the profile of the at least one guiding surface (33) increases tension of the top apron (28) rotating over the at least one top drafting roller (24).

6. The drafting apparatus as claimed in claim 1, wherein the cradle (30) reduces an unsupported area (31) between an apron pair (28, 29) and a front roller pair (26, 27) without changing an offset of the top drafting roller (24), and short fibres are well controlled from a middle roller pair (24, 25) to the front roller pair (26, 27).

7. The drafting apparatus as claimed in claim 6, wherein a distance of the unsupported area (31) is reduced to 8.5 to 10 mm.

Dated this: March 30, 2022

[JAYANTA PAL]
Patent Agent Number: IN/PA 172
of Remfry & Sagar
ATTORNEY FOR THE APPLICANT[S]