US3732771A - Knives for fiber tow-cutting apparatus - Google Patents

Abstract

In knives for the fiber tow-cutting for manufacturing staples by cutting synthetic tows, the improvement comprising I. MAKING THE BLADE BODY OF SUCH KNIVES OF A STEEL MATERIAL HAVING THE FOLLOWING COMPOSITION: Content of C0.08 - 1.10% by weightContent of Si0.15 - 0.80% by weightContent of Cr0.40 - 1.80% by weight Total content of Mn, P and S0 - 1.75% by weightContent of metallicimpurities otherthan Fe and theabove components0 - 5.00% by weightContent of Eeremainder of a total of 100% by weight; and II. PROVIDING ONLY ON ONE SIDE OF SUCH KNIVES A METALLIC COATING LAYER A THICKNESS RANGING FROM 2 MICRONS TO 50 MICRONS AND A Vickers hardness of above 700.

Description

United States Patent 1 Kinoshita et al.

[ 1 May 15, 1973 KNIVES FOR FIBER TOW-CUTTING APPARATUS [75]' Inventors: Saijiro Kinoshita; Kats'unobu Shinmura, both of Matsuyama-shi, Ehime-ken, Japan [73] Assignee: Teijin Limited, Osaka, Japan [22] Filed: July 7, 1971 [21] Appl. No.: 160,293

[30] Foreign Application Priority Data Aug. 26, 1970 Japan 45/748123 [52] US. Cl.' .l..83/663, 83/355, 83/701 [51] Int. Cl. ..B26d 1/28 [58] Field of Search ..83/675, 673, 403, 83/592, 355, 663, 70]; 29/95 D, 95 R; 76/161 A [56] References Cited UNITED STATES PATENTS 2,747,663 5/1956 Cook 2,792,887 5/1957 Midde|hof.. 3,387,521 6/1968 Okamoto ..83/355 above components Primary ExaminerFrank T. Yost A ttorney-Sherman & Shalloway [57] ABSTRACT In knives for the fiber tow-cutting for manufacturing staples by cutting synthetic tows, the improvement comprising i. making the blade body of such knives of a steel material having the following composition:

Content ofC 0,08 1.10% by weight Content of Si 0.15 0.80% by weight Content of Cr 0.40 1.30% by weight Total content of Mn, P and S 0 1.75% by weight Content of metallic impurities other than Fe and the 0 5.00% by weight remainder of a total of I00% by weight; and

Content of Be ii. providing only on one side of such knives a metallic coating layer a thickness ranging from 2 microns to 50 microns and a Vickers hardness of above 700.

9 Claims, 5 Drawing Figures I PATENTED HAY 1 $1973 l KNIVES FOR FIBER TOW-CUTTING APPARATUS This invention relates to improvements in knives used for cutters which are employed in the manufacture of staple fibers by cutting synthetic tows and, in particular, knives used for cutters heretofore known as a so-called Gru-Gru cutter. The use of the improved knives in the invention not only prevents synthetic tows from being miscut but also greatly reduces occurrence of fused end fibers in cutting, accordingly sharpness of the cutter knives can be maintained stably for a long time, and marked improvements in the operating efficiency and productivity are made possible. The term fused end fibers refers to a state wherein at least two adjacent monofilaments are in intimate cohesion at the cut plane.

More specifically, the invention relates to knives for a cutter in used in manufacturing staple fibers by cutting a synthetic tow, and the knives are characterized by as follows:

i. The blade of the knives is made of steel having the following composition:

Content ofC 0.08 1.10 by weight,

preferably 0.45 1.10% by weight, still more preferably 0.80 1.10% by weight, particularly 0.95 1.10% by weight (SUJ designated in .115) Content of Si 0.15 0.80% by weight,

preferably 0.15 0.70% by weight 0.40- 1.80% by weight, preferably 0.50 1.60% by weight, still more preferably 0.90 1.60 by weight 1.75% by weight, preferably Content of Cr Content of Fe and the ii. A layer of metallic coating is provided only on one side of the knife, such layer having a thickness ranging from 2 to 50 microns, and preferably 2 25 microns, and a Vickers hardness of above 700.

The conventional knife material in the Gru-Gru cutter has been disclosed, for example, in US. Pat. No. 2,792,887. The knives used in this type of cutter have previously been made of steel materials such as high speed steel, stainless steel or carbon tool steel and have been given a suitable heat treatment to the edges thereof. These knives have been used mounted on the knife-head of the Gru-Gru cutter.

However, when staple fibers have been manufactured by cutting synthetic tows as, for example, polyester type, polyamide type or polyolefin type, using the Gru-Gru cutter equipped with knives made of the steel materials such as beforementioned, the edges of the knives lose their sharpness in a very short time in continuous use, for example, as short as about 20 minutes. Now, if those dulled knives are forced to be used, either fused end fibers or imperfect cuttings finally make it impossible to continue the cutting operation.

Therefor, it becomes necessary to perform the operation of exchanging the knives at very short intervals of operation. There is not only the disadvantage from operative standpoints that the troublesome exchanging operation must be performed frequently and that labor is required for this purpose but also the result that the low productivity is inevitable.

Further, the edges of the knives are susceptible to chipping during the cutting of a tow. Therefore, these chips may be mixed in the staple fibers and cause problems in the subsequent treatment steps of the spinning process. Still further the nicked edges entail problems such as miscutting or fusing of the tow which occurs in the case of the use of dulled edged knives as hereinbefore described.

Knives for fiber tow-cutting apparatus have been studied in an attempt to overcome these drawbacks of the prior art. As a result, it has been have found that the knives for the Gru-Gru cutter whose properties have been markedly improved can be obtained by making the blade body of the knives with the steel material of the hereinbefore described composition, i.e., one belonging to the category of bearing steels which have been heretofore used in an area different from that of cutlery such as knives of the Gru-Gru" cutter, and by providing the blade body, on one side only, with a layer of metallic coating, and preferable chromium plating layer ofa thickness between 2 microns and 50 microns and a Vickers hardness of about 700, preferably above 800.

An object of the present invention therefore is to overcome the drawbacks in the conventional knives for the Gru-Gru cutter and to provide knives for the Gru-Gru cutter whose excellent cutting ability can be stably maintained for an especially prolonged period of time without miscutting tow or fused end fibers, thereby making it possible to demonstrate a pronounced improvement in the working efficiency and productive capability in the manufacture of staple fibers.

Other objects and advantages of the invention will become apparent to those skilled in the art from the following description.

It has been known to apply chromium plating to the entire blade portion of knives in the case of paring knives and other knives for home use to impart rust resistance and surface luster and smoothness to the knives, or to apply chromium plating to such tools for machining metals as drills, cutters, taps, reamers and tools to reduce the surface coefficient of friction of the edge portion and prevent adhesion of the tool to other metals.

The present invention departs from the conventional conception of using cutlery steel as the steel material of knives for the Gru-Gru cutter which is used specifically for cutting synthetic tows, and instead uses the steel material which has hitherto been used principally for bearing purposes in view of its suitability therefor. The knives according to the invention are made of bearing steel and are provided on one side only with a thin layer of a metallic coating preferably a chromium plating layer of less than 50 microns in thickness and preferably a thin layer within specified limits, and of Vickers hardness of above 700. Thus, in carrying out cutting of synthetic tows, the distal portion of the metallic chromium coating layer exposed at the knife edge participates directly in the cutting operation. Therefore, since the blade with a major portion of the knife, is made of the steel material as hereinabove described and this is covered only on.one side with the aforesaid metallic coating, the dulling of the knives in an extremely short period of time carrying out cutting of synthetic tows has not only been ingeniously avoided but also such other drawbacks as the entry into the staple fiber stock of chips resulting from the nicking of the edge has been conveniently overcome, and the occurrence of miscuts and fusing of the tows during their cutting have also entirely been overcome. Thus, the invention has succeeded in achieving remarkable improvements in increasing the life of knives as well as working and productive efficiency of the operation of cutting the synthetic tow. This surprising improved effect will be readily appreciated in connection with the results of the hereinafter given examples and comparative data.

Next, for easier understanding of the invention, the improved knives for the Gru-Gru cutter will be described with reference to the accompanying drawings in which; FIG. 1 is a plan view of one embodiment of the knives of the present invention, a plurality of which are exchangeably mounted and secured to the knifehead ofa Gru-Gru cutter; FIG. 2 is a enlarged crosssectional view taken along line AA of FIG. 1; FIG. 2' is a cross-sectional view of a conventional knife similar to that of FIG. 2; FIG. 3 is a cross-sectional view similar to that of FIG. 2 illustrating that of another embodiment of the invention; and FIG. 4 is a similar enlarged cross-sectional view partly cut away illustrating the edge portion of the knife of the invention.

Referring now to FIG. 1, an arm 4 by which the knife is mounted to the knife-head is provided with a mounting hole 5. The knife portion extends from the arm 4 in angular relationship to the planar axis of the arm.

The blade body 1 extended usually is provided with a face 1' at the edge portion of the blade body just before arriving at the knife edge, and a face 2' of the terminal portion of the coating of the layer 2 of metallic coating (see FIG. 2) appears at the terminal portion of the edge. This forms an extremity 3 of the edge. FIG. 2 shows the edge by means of a cross-sectional view taken along line A-A of FIG. 1. In FIGS. 1 and 2 the blade body 1 inclusive of the face 1 is made ofa steel material having the composition given in (i), beforementioned. The blade body 1 is provided only on its one side with a metallic coating layer of a thickness ranging from 2 microns to 50 microns, preferably 2 25 microns, especially 5 25 microns, and ofa Vickers hardness of above 700, preferably above 800. The terminal portion of this metallic coating layer appears beyond the terminal edge portion of the blade body 1 to form the edge of the knife. Therefore, in the knife of the invention the material of which this metallic coating layer is made plays a direct role in determining the cutting life of the knife when used in the operation of cutting synthetic tows.

On the other hand, in the case of the conventional knife, as shown in FIG. 2', the material such, for example. as high speed steel of which the blade body 1 is made extends to the terminal portion of the edge. Therefore, since the blade body and the terminal portion ofthe edge are made of the same material, the material of which the blade body is made plays a direct role in determining the tow cutting ability of the knife.

In the knife ofthe invention, as materials for forming the aforesaid metallic coating layer, the metallic materials such, for example, as chromium, tungsten or tungsten carbides can be used, and chromium is most preferable.

The methods of forming the metallic coating layer are already known. Any of'the various methods by which the blade body and the metallic coating layer can be firmly bonded can be employed. As to forming methods the electroplating method, the flame plating method and the soldering or bonding method can be mentioned.

FIG. 3 illustrates a modification of a knife similar to that shown in FIG. 2. This embodiment is provided with a face 1" in addition to the face 1. The edge angle a of the knives according to the invention is preferably 5- 40, especially 10- 30. The edge angle a, as here used, denotes, as shown in FIGS. 2 and 3, an angle made in the A-A line section, at right angles to the axis of the knife, by the face 1' extending directly to the tip 3 of the blade and a tangent to the curvilinear surface of the metallic coating layer.

In the invention the surface of the metallic coating layer should preferably have a Vickers hardness of above 800, and this should preferably be at least 50 higher in the Vickers hardness than the surface of the steel material of which the blade body is made.

FIG. 4 is a partly cutaway cross-sectional view of the knife edge terminal portion. In FIG. 4, owing to the presence of such a difference in Vickers hardness as indicated above, the face 1', though originally of the form shown by the dotted line in the figure, abrades at all times ahead of the face 2 of the terminal portion of the coating formed at the knife edge. As a result, the face 1' becomes as shown by 1 in the figure and, as a consequence, promotes the maintenance of the face 2', including the knife edge extremity 3, continually in a sharp state. In the conventional knife such as shown in FIG. 2 the knife edge terminal portion, including the knife edge extremity 3, abrades at the same rate as the blade body material, with the consequence that the edge becomes dull.

In the case of the knives for the Gru-Gru cutter of the present invention, their cutting ability is thus maintained for an exceptionally prolonged period of time. The following test is carried out for determining this improved durability.

DURABILITY IMPROVEMENT RATE TEST.

A Gru-Gru cutter whose knife-head is mounted with the knives to be tested is used, and the cutting of synthetic tows is carried out at a cutting speed of I00 meters per minute.

After the cutting operation has been started, sampling is carried out every S-minutes, taking 10 grams of the cut staple fibers in each sampling. From the obtained samples one gram thereof is taken at random and from the obtained 1 gram of sample I milligram sample is further taken at random. For example, in the case of 1.4 denier nylon filament tow about 120 I ends of monofilaments are contained in the final sample.

The foregoing sample which has been taken at random, as hereinabove described, is observed under a microscope (magnification: I40 times) and the time (min.)at which of the number of filaments contained in the final sample the cut ends of 20 percent become fused is determined and this time is designated the durability time X.

Separately, standard knives made of a high speed steel (JIS G4403 SKTT4B) of the following composition:

Component Weight 71 0.70 0.85 Si not more than 0.35 Mn do. 0.60 P do. 0.03 S do. 0.03 Cr 3.50 4.50 W 18.00 20.00 V 1.00 1.50 Co 1400 16.00 Impurities not more than 0.50

(impurities must not contain more than 0.25 "/1 Cu and 0.25 Ni) Fe remainder of 100 weight '70,

Durability improvement rate [(X Y)/Y] X 100 v The following examples are given for further illustration of the invention.

EXAMPLES I 111,CONTROL AND COMPARISONS I VIII Several classes of knives for Gru-Gru cutter use were made, some of which satisfied and some of which did not satisfy the steel composition of the knife blade body and the metallic coating layer conditions of the invention. The test for the durability improvement was carried outwith the results shown in Table l. The steel compositions of the blade body materials indicated in Table 1 under the experiment numbers are as follows:

Blade Composition of Steel Material (wt.

Body Impurimaterial C Si Cr Mn+P+S ties Fe No. l 0.900.55 1.55 0.88 0.60 remainder No. 2 000.25 1.40 0.35 0.45 do No. 3 0.850.60 1.60 1.45 0.52 do No.4 0.850.20 0.35 0.30 1.80 do No. 5 1.00030 4.55 0.65 1.50 do No.6 0.300135 13.00 0.80 0.50 do Note.

No. 1 ASTM 52100 Model 1 No 2 SU] 2(J1S) No.3 ASTM 52100 Model 2 No.4 SKD 42 (.115) No.5 SKD 12 (113) No. 6 SUS 53(J1S) The test was carried out using a tow of total denier of 500,000 consisting of polyester synthetic fibers (drawn) of monofilament denier of 1.4. The knives had an edge angle of 27.

TABLE 1 Experi- Blade Metallic Coating Layer Durability iment Body Thickness Vickers Improve- No. Material Metal (micron) Hardness ment Ex. 1 No. 1 Cr 800 1400 Ex. 11 No. 2 Cr 5 820 2900 Ex. 111 No.3 Cr 15 790 1300 Control high speed steel 0 for use in standard knives Comparison 11 No.5 60 111 .No. 6 40 1V No. 2 Cr 1.5 820 2000 V No. 2 Cr 20 650 1000 VI No. 2 Cr 55 820 500 VII No. 2 10 820 150 *Both sides of knife were applied a chromium plating.

EXAMPLE 1V AND COMPARISONS VIII 1X Blade body'materials of the following two classes of compositions were used and knives of identical shape were made in each case. The durability improvement test was then carried out in accordance with the hereinbe'fo r'e described method to determine their respective durability times X. The average durability time of the 100 knives, the durability improvement rate and the number of knives in which damage of the knife edges were noted in the case of each of these classes of knives are shown in Table 2. The tow used in this test was the same as that used in Example 1,

No.8 SKH 2 (.118)

EXAMPLE V AND COMPARISON X Blade body materials of the following two classes of compositions were used, and 100 knives each of the same shape were made. These knives were tested as in Example IV with the results shown in Table 3, below. 7 1. 8 2

Blade Composition of Steel Materials (wt. 7:) Body Impuri- Material C Si Cr Mn+P+S ties Fe No. 9 0.45015 0.45 0.86 0.97 remainder No. 10 0140.40 12.50 0.75 0.55 do.

The tow used was of total denier 500,000 consisting of polyester synthetic fibers (drawn) of monofilament denier of 1.4.

TABLE 3 Metallic Coating Layer (plated on one side only) Average Knife Dur- Edge Blade ability Damaged Exper. Body Thickness Vickers Time (per 100 No. Material (micron Hardness (min.) knives) metal Example V No. 9 Cr 5 830 240 Comparison X No. 10Cr 5 830. 60

The results of the durability improvement tests of the foregoing Examples IV and V and Comparisons V111, IX and X are shown in Table 4, below.

TABLE4 Experiment Durability Improvement No. Example IV 1700 do. V 1 100 Comparison Vlll 350 do. lX 100 do. X 200 We claim:

1. In knives for fiber tow-cutting apparatus for manufacturing staples by cutting synthetic tows, the improvement wherein i. the blade body of the knife is formed ofa steel material having the following composition:

Content of C 0.08 1.10 7: by weight Content of Si 0.15 8.80 by weight Content of Cr 0.40 1.80 by weight Total content of Mn, 1.75 '74 by weight P and S Content of metallic impurities other than Fe and the above components Content of Fe 0 5.00 by weight remainder of a total of 100 7! by weight; and

ii. one side of said knife is provided with a metallic coating layer of a thickness ranging from 2 microns to 50 microns and of Vickers hardness of above 700.

2. The knife of claim 1 wherein i. the composition of said steel material is as follows:

Content of C Content'of Si Content of Cr Total content of Mn,

P and S Content of metallic impurities other than Fe and the above components 0.45 1.10 by weight 0.15 0.70 by weight 0.50 1.60 by weight 0 1.21 7t by weight 0 2.20 7: by weight remainder of a total of 100 by weight, and

Content of Fe of the surface of the coating layer on one side of said blade is at least 50 higher than that of the surface of the said blade portion made of steel material.

I 6. The knife of claim 1 wherein i. the composition of said steel material is as follows:

Content of C 0.80 1.10 by weight Content of Si 0.15 0.70 by weight Content of Cr 0.90 1.60 by weight Total content of Mn, 0 1.21 by weight P and S Content of metallic O 0.50 by weight impurities other than Fe and the above components Content of Fe remainder of a total of 100 by weight; and

ii. a metallic coating layer of chromium of thickness of 5 25 microns and Vickers hardness of above 700 is provided only on one side of said knife, and the edge angle a of said knife is 10 30.

7. The knife of claim 2 wherein the edge angle a of said knife is 5 044071405 40.

8. The knife of claim 2 wherein the metal forming said coating layer on one side of said blade is chromium.

9. The knife of claim 2 wherein the Vickers hardness of the surface of the coating layer on one side of said blade is at least 50 higher than that of the surface of the said blade portion made of steel material.

Claims (8)

1. 2. The knife of claim 1 wherein i. the composition of said steel material is as follows: Content of C 0.45 - 1.10 % by weight Content of Si 0.15 - 0.70 % by weight Content of Cr 0.50 - 1.60 % by weight Total content of Mn, 0 - 1.21 % by weight P and S Content of metallic impuri- 0 -2.20 % by weight ties other than Fe and the above components ContEnt of Fe remainder of a total of 100 % by weight, and ii. the thickness of said metallic coating layer is 2 - 25 microns.
2. 3. The knife of claim 1 wherein the edge angle Alpha of said knife is 5*- 40*.
3. 4. The knife of claim 1 wherein the metal forming said coating layer on one side of said blade is chromium.
4. 5. The knife of claim 1 wherein the Vickers hardness of the surface of the coating layer on one side of said blade is at least 50 higher than that of the surface of the said blade portion made of steel material.
5. 6. The knife of claim 1 wherein i. the composition of said steel material is as follows: Content of C 0.80 - 1.10 % by weight Content of Si 0.15 - 0.70 % by weight Content of Cr 0.90 - 1.60 % by weight Total content of Mn, 0 - 1.21 % by weight P and S Content of metallic 0 - 0.50 % by weight impurities other than Fe and the above com-ponents Content of Fe remainder of a total of 100 % by weight; and ii. a metallic coating layer of chromium of thickness of 5 - 25 microns and Vickers hardness of above 700 is provided only on one side of said knife, and the edge angle Alpha of said knife is 10* - 30*.
6. 7. The knife of claim 2 wherein the edge angle Alpha of said knife is 5* - 044071405 40*.
7. 8. The knife of claim 2 wherein the metal forming said coating layer on one side of said blade is chromium.
8. 9. The knife of claim 2 wherein the Vickers hardness of the surface of the coating layer on one side of said blade is at least 50 higher than that of the surface of the said blade portion made of steel material.

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