US3150552A

US3150552A - Apparatus for producing staple fibers

Info

Publication number: US3150552A
Authority: US
Inventors: James W I Heijnis
Original assignee: American Enka Corp
Current assignee: Akzona Inc
Priority date: 1961-02-20
Filing date: 1962-02-08
Publication date: 1964-09-29
Anticipated expiration: 1981-09-29
Also published as: GB926748A

Description

Sept. 29, 1964 Filed Feb. 8, 1962 J. W. l. HEIJNIS APPARATUS FOR PRODUCING STAPLE FIBERS FIG. 1

3 Sheets-Sheet l INVENTOR.

JAMES WATT IJSBRAND HEIJNIS TO NEY Sept. 29, 1964 J. w. 1. HEIJNIS APPARATUS FOR PRODUCING STAPLE FIBERS 5 Sheets-Sheet 2 Filed Feb. 8, 1962 INVENTOR.

JAMES WATT JJSBRAND HEIJNIS A on EY Sept. 29, 1964 J. w. l. HEIJNIS 3,150,552

APPARATUS FOR PRODUCING STAPLE FIBERS Filed Feb. 8, 1962 3 Sheets-Sheet 3 FIG. 3

INVENTOR.

JAMES WATT IJSBRAND HEIJNIS BY M 6 TTO NEY United States Patent 3,156,552 APPARATUS FOR PRQDEUCING STAPLE FHBERS lames W. I. Heijnis, Arnhem, Netherlands, assignor to American Enlra (Torporation, Enka, N.C., a corporation of Delaware Filed Feb. 8, 1962, Ser. No. 171,920 Claims. (Cl. 83-337) This invention relates to an apparatus for cutting a tow of continuous filaments into loose fibers and relates more particularly to the severing of a tow of continuous filaments by a cutting means which has both a chopping and a cutting component With respect to the tow. This invention further relates to a cutting device which produces loose fibers having controlled inequalities in length.

Various structures have been used heretofore for cutting continuous filaments into loose fibers. In such prior art structures, the filaments are bundled into a ribbonlike tow having a flat elongated cross-section and are engaged by pairs of clamping teeth located on the peripheral surfaces of mating draw wheels which function to continuously clamp the tow of filaments at equally spaced positions and draw the same into operative relationship with a knife or a cutterhead having a plurality of knives on its peripheral surface. The cutting edge of the knife is passed through the space between consecutive pairs of the clamping teeth, thereby continuously severing the tow and reducing the continuous filaments into loose fibers.

The cutters utilized in the prior art normally comprise two draw wheels having clamping teeth spaced at approximately equal intervals around their circumferential rim, the two draw wheels revolving about their axes in opposite directions in the same plane, so that the mating clamping teeth form a bight which clamps and draws the tow of continuous filaments. Rotation of the cutterhead, on which the plurality of knives is mounted, is synchronized with the movement of the draw wheels to successively pass a knife blade through the space between consecutive pairs of clamping teeth at the bight of the draw wheels to sever the tow.

Prior art tow cutters have suffered from numerous disadvantages. For example, they have been relatively limited in the thickness of the tow which they could successfully sever, and the speed with which the cutting action could be accomplished. Moreover, the life of the cutting edge of the knives has been limited, requiring frequent shut-downs for replacement and excessive expense for regrinding the cutting surfaces. A poor cutting edge will produce low quality loose fibers having irregular or fused fiber ends. In the cutting of thermoplastic materials with a blunt knife, the cut ends will often tend to adhere to each other. A further disadvantage of the cutters used eretofore is that it has not been practical to increase the number of knives in the cutterhead, in that the employment of a larger number of knives have required the draw wheels to have extremely large dimensions in order to maintain a free path of the knives relative to the draw wheels. By increasing the number of knives on the cutterhead, the time interval between shut-downs can be proportionately increased because of the fewer number of cuts which an individual knife edge must make in a unit of time. Moreover, prior art structures have always comprised a cutter whose clamping teeth and knives were placed at equispaced intervals so that each knife edge would always hit the tow exactly half-way between the two points at which it was clamped. This was necessary because if the knife edge hit the tow at a point which was not equidistant from the two clamping points, the knife would scrape along the bending tow before it would out. As a result of this, the knife edges would wear very rapidly and cause a poor cutting action on the tow. Apparatus of this type produced staple fibers, all of which were exactly the same length. However, yarns spun from such fibers appeared artificial since naturally occurring fibers have small variations in length.

To overcome these disadvantages, cutters have been developed in which the tow was passed through an ejector by a jet of gas or liquid which ensured the smooth transport of the tow. Located at the outlet of the ejector was the cutterhead, the knives of which would shear past the outlet, cutting the tow into staple fibers. However, in such structures the tow was supported at one end only while it was being cut. While this would provide staple fibers of unequal length, more like natural fibers, the unpredictability of apparatus of this type frequently produced loose fibers having a length two or three times the average. It is clear that such gross inequalities were very undesirable in further processing. Moreover, an excess of cutting energy is necessary in these cutters in order to clearly shear the tow.

It is therefore an object of the instant invention to provide an apparatus for cutting continuous filaments into loose fibers which are free from the foregoing and other disadvantages.

A further object of this invention is to provide a cutter, wherein the movement of the knives relative to the tow has a chopping as well as a cutting component.

It is a further object of the instant invention to provide a cutter capable of cutting a tow into staple fibers having slight inequalities in length.

Another object of this invention is the provision of a cutter which will provide staple fibers having controlled inequalities while the knives of said cutter remain sharp for an extended period.

Other objects and advantages of the instant invention will be seen from the following detailed description, and will be particularly pointed out in the appended claims.

According to the instant invention, a cutter of the type comprising two draw wheels and a cutterhead is employed wherein the knives on the cutterhead are moved along with the tow of continuous filaments in the direction of travel of the latter, so that the movement of the knives relative to the tow has a chopping as well as a cutting component, which components are of approximately the same magnitude. Moreover, the knife, which moves through its own plane, severs the tow by hitting the full width of a tow section clamped between consecutive pairs of clampin teeth with the knife edge.

Although the use of chopping and cutting components for cutters has been suggested before, the particular movement of the knives which is the subject of the instant invention has not been contemplated previously. It has now been found that this specific movement to be described more fully hereinafter is essential in order to obtain a satisfactory cutting of the tow.

The reason for the excellent results obtained by means of the novel method and apparatus of the instant invention is that by moving the cutting knife along with the tow in the direction of its travel, the knife does not scrape along the tow surface While the contact pressure is built up to the point of severance. By causing the knife to cut the tow while the former passes through its own plane, the friction between the sides of the knife and the cut fiber ends is restricted to a minimum. By reducing this friction, the generation of heat and the possibility of adhesion of individual fiber ends is eliminated. Furthermore, the cutting edge is not subjected to as much abrasion and will not be blunted as quickly.

It is of importance that during the cutting process,

this end, the cutting edge of the knife should hit the tow across the full width of the section clamped between the two pairs of clamping teeth. In order to require a minimum amount of energy for a good clean severance of the tow into loose fibers, it has been found desirable that the chopping and cutting components of the knife movement are of approximately the same magnitude.

According to a further feature of the instant invention, the tow feeding means consists of two draw wheels which are provided at their peripheries with clamping teeth having a pitch which is uneven. The term pitch is meant to define the distance between successive teeth. While the pitch of the teeth on each draw wheel varies throughout its circumference, the pitch between each pair of mating teeth on the two draw wheels is the same so that good clamping of the tow will result. In accordance with this feature of the instant invention, a cutterhead is provided having knives spaced around its periphery which have an uneven pitch therebetween which corresponds to the uneven pitch on the draw wheels and is synchronized so that each knife contacts the tow midway between successive clamping teeth. In this manner, a tow can be cut into staple fibers of controlled inequalities in length While the tow is supported and clamped at both ends. Thus, this construction makes it possible to cut a tow into loose fibers having any variation in length desired while avoiding all of the aforementioned drawbacks.

In order to more clearly disclose the instant invention,

reference is made to the accompanying drawings and to the following descriptive matter which shows a preferred embodiment of the instant invention.

In the drawings,

FIGURE 1 is a plan view of two draw wheels and a cutterhead in accordance with the preferred embodiment of the instant invention;

FIGURE 2 is a side elevation of the same;

FIGURE 3 is an enlarged cross-sectional view of the portion of the apparatus where the tow is cut;

FIGURE 4 is an enlarged cross-sectional view of a portion of the apparatus as seen in FIGURE 1;

FIGURE 5 is a cross-sectional view taken along 5-5 of FIGURE 4.

Like reference numerals indicate like parts throughout the several views of the drawings.

Referring now to the drawings, and particularly to FIGURES 1 and 2,

reference numerals

1 and 2 designate two draw wheels which are secured to shafts 3 and 4, respectively. Shaft 3 is rotatably supported in the bearings 5 and 6, and shaft 4 is rotatably supported in the bearings 7 and 8. In accordance with this invention the draw Wheel 1 is fiat and is provided at its periphery with a plurality of fiat clamping teeth 9. The second draw wheel 2 is conical in shape and has at its circumferential rim a plurality of conical clamping teeth 10. The shafts 3 and 4 are positioned in the same plane so that the clamping surface of the conical clamping teeth It) of draw wheel 2 rotates about its axis while coming into true mating contact with the clamping surface of the flat clamping teeth 9 on draw wheel 1. Clamping teeth 9 and 10 do not intermesh, but are in clamping contact with one another. In one embodiment of the instant invention every two pair of mating clamping teeth 9 and 10 rolling in contact with each other have the same pitch. According to a further embodiment to be set forth in detail hereinafter, the pitch of the teeth around the periphery of the draw Wheels may be unequal but coordinated.

Any means may be used to insure that the peripheral speeds of the

draw wheels

1 and 2 are the same. A preferred means for accomplishing this end is shown in FIGURE 1. A tooth rim 11 located centrally of the flat draw wheel 1 and a conical toothed wheel 12 on the end of the shaft 4 remote from the draw wheel 2 are provided which intermesh and directly couple the two wheels. Various other means for insuring synchronized rotation of the two draw wheels may be employed such as two belts or synchronized electromotors will be obvious to one with normal skill in the art. When the shaft 3 is driven in the embodiment of FIGURE 1 (by means not shown) the two draw wheels are rotated at the same peripheral speed. Reference numeral 29, FIGURE 2, shows the tow of continuous filaments as it is fed into the bight between the

draw wheels

1 and 2. The loose fibers, after they have been cut, are not shown.

A disc-shaped cutterhead 13 is provided which is secured to a shaft 14- The shaft 14 is rotatably supported in the bearings 15 and 1-5, and runs parallel to the plane through the shafts 3 and 4, crossing the shaft 3 at an angle of 45 (note FIGURE 1). By means of a gear wheel transmission (not shown) the shaft 14 can also be coupled to the shaft 3. As clearly shown in FIGURE 1, a plurality of knives 17 are mounted in the rim of the cutterhead 13 in such a way that they are at an angle of approximately 45 to the shaft 14.

Referring now particularly to FIGURES 3 and 4, at the point where the path of a knife 17 coincides with a tangent line between the conical clamping teeth 10 and the fiat clamping teeth 9, the cutting edge of said knife coincides with this tangent line, and said knife 17 lies in the plane through the shafts 3 and 4. This is the position of the apparatus immediately preceding the cutting of the tow. It will be seen that where the knife edge coincides with the aforementioned tangent line, the surface described by the edges of the knives makes an acute angle with the plane through the shafts of the draw wheels, and the plane of the knives themselves coincides with the plane passing through the shafts of the draw wheels. Not only is this the most favorable position for the knives to sever the tow, but the knives are arranged so that a knife edge hits the piece of clamped tow approximately midway between the two pairs of clamping teeth. By this arrangement, the clamped tow is symmetrically pressed out of its path and does not exert any force on the knife in a direction transverse to the plane of the knife. Moreover, it will be noted that this particular arrangement of the elements of the cutter allows the knife to move along with the tow in the direction of travel of the latter so that the movement of the knives relative to the tow has a chopping as well as a cutting component, the magnitude of each of these components being approximately the same.

The flat clamping teeth 9 and the conical clamping teeth It) are preferably covered with an elastic material which is designated by the

reference numerals

18 and 19, respectively, in FIGURE 3. In accordance with this invention, the elastic material 19 used on the surface of the conical clamping teeth It) is tougher than that used on the surface of the fiat clamping teeth 9. Thus, the depression caused in the

elastic material

18 and 19 by the clamped tow is deepest in the elastic material 18 on the flat draw wheel I. No variation will occur in the radius between the shaft 3 of the fiat draw wheel 1 and the point at which the tow is pressed against this wheel by the depression of the tow, so there will be little or no change in the traveling speed and the tension on the tow. It will be noted that a large depression in the surface of the conical clamping teeth It) might cause such a variation.

In FIGURE 5, a preferred means for mounting the knife 17 and the cutterhead 13 is shown. Reference numeral 22 designates a blade holder which is dovetailed and fits in corresponding recesses provided both in the rim of the cutterhead 13 and in a clamping block 23. The knife 17 is rigidly secured in its position by turning to the right (as viewed in FIGURE 5) the clamping block 23 by means of a blot 24 which presses against a supporting ring 25.

The particular number of clamping teeth on each draw wheel and the particular number of knives on the cutterhead may be varied to suit the specific cutting operation.

The only requirement in order to provide a structure in accordance with the instant invention is that the number of clamping teeth on one draw wheel is equal to, or a multiple of, the number of clamping teeth on the other draw wheel and the number of knives on the cutterhead. It has been found that a favorable number of knives is obtained if the number of clamping teeth and the number of knives of the fiat draw wheel 1, the conical draw Wheel 2 and the cutterhead 13 are approximately in the ratio of 3:111. The preferred arrangement is to have a flat draw wheel such as 1 which has ninety flat clamping teeth 9 around its periphery and a conical draw wheel such as 2 which has thirty conical clamping teeth It) around its rim. The cutterhead would then have thirty knives 17 placed around its periphery. Preferably, the average pitch of the clamping teeth 9 and 10 is about 37 millimeters.

To provide controlled inequalities in the cut fibers, the pitch of the clamping teeth and the knives must be irregular and coordinated. With such an arrangement the preferred maximum and minimum pitch distances would be 41 and 33 millimeters, respectively. The thirty knives in the cutterhead would then be on a pitch circle of about 1110 millimeters.

It is advantageous, in certain applications, to have the pitch progressively increase from the minimum to the maximum and then return to the minimum in a wavelike arrangement. Of course, in the preferred embodiment of the instant invention the conical draw wheel 2 and the cutterhead 13 would vary about the average pitch distance in a single wave and the fiat draw wheel 1 would vary in three waves so that the clamping teeth 9 and 10 would always roll in true mating contact with other. The variation about the average is chosen to most closely simulate the variations in length of natural fibers. The apparatus is preferably driven at a speed of approximately 117 revolutions per minute for the cutterhead 13 and the conical draw wheel 2, and the Hat draw wheel 1 is driven at an approximate speed of 39 revolutions per minute. Apparatus of the instant invention has been found to satisfactorily process a 210,000 denier crimp tow having a basis of a polyester. The loose fibers prepared on such an apparatus even after long uninterrupted use appear to show a very clean cut surface.

While specific details of preferred embodiments have been set forth above it will be apparent that many changes and modifications may be made therein without departing from the spirit of the invention. It will therefore be understood that what has been described herein is intended to be illustrative only, and is not intended to limit the scope of the invention.

What is hereby claimed and desired to be secured by Letters Patent is:

1. An apparatus for cutting a tow of continuous filaments into loose fibers comprising a cutterhead provided with a plurality of knives mounted around the periphery thereof, a draw wheel provided with a plurality of clamping teeth spaced around its periphery, said clamping teeth each having a fiat radially extending clamping surface, a conical wheel with a plurality of conical clamping teeth spaced around its periphery, said conical wheel having a smaller number of clamping teeth than said draw wheel, and means for driving said cutterhead and said wheels so that said flat clamping teeth and said conical clamping teeth roll in true mating contact with each other and with the pitch between mating flat and conical clamping teeth being the same, said cutterhead and said wheels being driven in synchronism so that one of said knives passes approximately midway between each two successive pairs of mating flat and conical clamping teeth, said wheels being fixed to rotatably supported shafts lying in the same plane, said cutterhead being fixed to a rotatably supported shaft which runs parallel to the plane through the shafts of the wheels and crosses the shaft of said draw wheel at an angle of about 45 the knives of said cutterhead being mounted at an angle of approximately 45 with regard to said cutterhead shaft.

2. An apparatus in accordance with claim 1 wherein said clamping teeth and said knives are spaced at irregular intervals around the periphery of said two wheels and said cutterhead respectively, the irregular intervals of said knives corresponding to the irregular intervals of said clamping teeth.

3. An apparatus in accordance with claim 1, wherein said knives have a cutting edge which coincides with a tangent line between the surface of said flat clamping teeth and the surface of said conical clamping teeth when the knife is in cutting position.

4. An apparatus in accordance with claim 3, wherein, at the point of coincidence between the cutting edge and said tangent line, the surface described by the edges of the knives makes an acute angle with the plane through the shafts of said draw wheels.

5. An apparatus in accordance with claim 4, wherein at the point of coincidence between the cutting edge and said tangent line, the plane of the knives coincides with the plane through the shafts of said draw wheels.

6. An apparatus in accordance with claim 1, wherein the number of clamping teeth and the number of knives of the draw wheel, the conical wheel and the cutterhead, respectively, are in a ratio of approximately 3:1:1.

7. An apparatus in accordance with claim 6, wherein said draw wheel has approximately clamping teeth.

8. An apparatus in accordance with claim 1, wherein said wheels are driven at the same speexl by intermeshing teeth which lie on a flat surface centrally of said draw wheel and on a conical surface on the shaft of said conical wheel.

9. An apparatus in accordance with claim 1, wherein said fiat clamping teeth are covered with a first elastic material and said conical clamping teeth are covered with a second elastic material, said second elastic material being tougher than said first elastic material.

10. An apparatus for cutting a tow of continuous filaments into loose fibers of unequal length comprising a rotatable cutterhead having a plurality of knives around the periphery thereof, and two draw wheels cooperating with said cutterhead, each of said draw wheels having a plurality of clamping teeth around the periphery thereof, the clamping teeth of said draw wheels rolling in contact with each other to continuously clamp said tow and transport the same into operative engagement with the knives of said cutterhead for severance midway between successive cooperating clamping teeth, said knives and said clamping teeth being spaced at corresponding irregular intervals around the periphery of said cutterhead and said two draw wheels, respectively.

References Cited in the file of this patent UNITED STATES PATENTS 1,617,511 Balch Feb. 15, 1927 2,173,789 Nikles et a1. Sept. 19, 1939 2,221,716 Morton Nov. 12, 1940 2,792,887 Middelhof May 21, 1957 2,851,103 Anthony et a1 Sept. 9, 1958 FOREIGN PATENTS 792,266 France Dec. 26, 1935

Claims

1. AN APPARATUS FOR CUTTING A TOW OF CONTINUOUS FILAMENTS INTO LOOSE FIBERS COMPRISING A CUTTERHEAD PROVIDED WITH A PLURALITY OF KNIVES MOUNTED AROUND THE PERIPHERY THEREOF, A DRAW WHEEL PROVIDED WITH A PLURALITY OF CLAMPING TEETH SPACED AROUND ITS PERIPHERY, SAID CLAMPING TEETH EACH HAVING A FLAT RADIALLY EXTENDING CLAMPING SURFACE, A CONICAL WHEEL WITH A PLURALITY OF CONICAL CLAMPING TEETH SPACED AROUND ITS PERIPHERY, SAID CONICAL WHEEL HAVING A SMALLER NUMBER OF CLAMPING TEETH THAN SAID DRAW WHEEL, AND MEANS FOR DRIVING SAID CUTTERHEAD AND SAID WHEELS SO THAT SAID FLAT CLAMPING TEETH AND SAID CONICAL CLAMPING TEETH ROLL IN TRUE MATING CONTACT WITH EACH OTHER AND WITH THE PITCH BETWEEN MATING FLAT AND CONICAL CLAMPING TEETH BEING THE SAME, SAID CUTTERHEAD AND SAID WHEELS BEING DRIVEN IN SYNCHRONISM SO THAT ONE OF SAID KNIVES PASSES APPROXIMATELY MIDWAY BETWEEN EACH TWO SUCCESSIVE PAIRS OF MATING FLAT AND CONICAL CLAMPING TEETH, SAID WHEELS BEING FIXED TO ROTATABLY SUPPORTED SHAFTS LYING IN THE SAME PLANE, SAID CUTTERHEAD BEING FIXED TO A ROTATABLY SUPPORTED SHAFT WHICH RUNS PARALLEL TO THE PLANE THROUGH THE SHAFTS OF THE WHEELS AND CROSSES THE SHAFT OF SAID DRAW WHEEL AT AN ANGLE OF ABOUT 45*, THE KNIVES OF SAID CUTTERHEAD BEING MOUNTED AT AN ANGLE OF APPROXIMATELY 45* WITH REGARD TO SAID CUTTERHEAD SHAFT.