|Publication number||US2747233 A|
|Publication date||May 29, 1956|
|Filing date||Jul 25, 1952|
|Priority date||Jul 25, 1952|
|Publication number||US 2747233 A, US 2747233A, US-A-2747233, US2747233 A, US2747233A|
|Inventors||Virgil Hitt Ira|
|Original Assignee||Du Pont|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (17), Classifications (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
May 29, 1956 l. v. HlTT ADJUSTABLE STOP CRIMPER Filed July 25, 1952 Ira BY 7% 31 ATTORNEY United States Patent O ADJUSTABLE STOP CRIMPER Ira Virgil Hitt, Waynesboro, Va., assignor to E. L du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Application July 25, 1952, Serial No. 300,871
4 Claims. (Cl. 19-'"66) This invention relates I to an improved stutter box crimper for more uniformly crimping bundles or tows of filaments. More particularly this invention relates to means for controlling the uniformity and intensity of crimp imparted to a bundle of'continuous filaments to be out into staple for subsequently processing into spun yarn.
Inadequate and non-uniform crimp applied to bundles of continuous filaments of polyacrylonitrile or similar polymers subsequently cut into staple has been the cause of troublesome processing of the staple and non-uniform and low quality spun yarn therefrom. Variations in crimp and crimp intensity were often the cause of too great or too little mass cohesion or the cause of lap splittin-g, and in some cases a staple stock could not be processed at all satisfactorily. A thorough study of the many factors affecting satisfactory staple processing brought out the necessity for uniform and adequate crimp. The frequeney and uniformity of crimp is affected in many Ways and although highly satisfactory results were secured at times, reproductibility was most uncertain prior to this invention.
An object of this invention is to provide an improved means for crimping bundles of continuous filaments. Another object of this invention is to provide a means for controlling the action of the crimper to impart to the filaments passing thereinto a uniform crimp of the desired crimp intensity over long periods of time. Other objects will be apparent from the description that follows.
In the figures:
Figure 1 is a diagrammatic sketch of the apparatus and Figure 2 is taken on line 2-2 of Figure l to illustrate the nature of the crimp.
The objects of this invention are accomplished by modifying the crimper, as is described hereinafter. Briefly the improvement resides in limiting the movement of the pivotal feed roll so that it cannot contact the fixed roller and maintaining under all circumstances a clearance of at least a few thousandths of an inch therebetween. As shown in Figure l the adjustable stop comprises a shoe I mounted on an adjustable screw 2 through a fixed bar 3.
Earlier experiments had established the possibility of two types of crimp that could be formed in the tow depending on the precise conditions of operation. One type, which will be referred to as Type A for convenience, is desirable, being uniform and of the right frequency and intensity. This crimp is characterized by a herringbone appearance in the crimped tow in the box and as it comes from the box, and the crimp lies in a plane parallel to the faces of the crimper feed rolls, as is shown in Figure 2 and represented by reference number 4. On the other hand, a crimp may be obtained which takes place in a plane at right angles to that of Type A crimp; that is, the crimp is in a plane perpendicular to the faces of the crimper feed rolls. This crimp is undesirable in that it is random in its formation and is, therefore, difiicult to control and characterize. Hereinafter this crimp will be called type B crimp. One of the major requirements to produce crimp of the A type is relatively low pressure at 2,747,233 Patented May 29, 1956 2 the nip of the crimper feed rolls, whereas greater pressure between these rolls brings about crimp of the B type.
Normally a tow 5 of continuous filaments of 70,000 to 300,000 or more total denier is finished, steamed, and fed into a crimper such as that described in my U. S. Patent 2,311,174. With the tow of filaments fed under substantially optimum conditions as to speed, finish concentration, temperature, etc., the desired type A crimp may be secured, although a relatively slight increase in pressure on the tow passing between the feed rolls 6 and 7 will bring about production of type B crimp. For instance, with a pressure cylinder and piston combination (not shown) or a spring device 8 provided to exert a pressure of 10 pounds downward against the end of the pivot arm 9, thereby urging the movable roll 6 toward the fixed feed roll 7, type A crimp of the desired uniformity and intensity resulted; with a 50% pressure increase the crimp completely changed to type B. With the original pressure decreased by 50%, the feed rolls continually wrapped back and made operation impossible. Due to frictional changes with time, especially between the sides of the feed rollers and the insert members 10 and 11 (shown in Figure 2), it was unusual for the actual .pressure exerted at the nip of the rolls to vary widely without the primary force acting to urge the rolls together being changed in any way. In fact, the high frictional resistance to change in position of the movable roll caused an exaggerated movement of the roll when a movement occurred, resulting in bouncing and wide fluctuations in pressures. As a result, the tow of filaments passing through the crimper became crimpe'd in a haphazard manner being partly type A and partly type B crimp with the crimps varying widely in frequency and intensity. Such production, when out into staple for processing and converting into spun yarn, led to the numerous dilii'culties previously mentioned.
The provision of the limiting stop of this invention essentially eliminates variation in pressure at the nip of the rolls. The clearance adjustment will, of course, depend on the size of the tow being fed therethrough and the width of the crimper rolls. For an 85,000 denier tow of acrylonitrile polymer filaments of about 3 denier per filament in size fed between crimper rolls 1 inch in width, the stop should be adjusted for a minimum clearance of from 0.012 inch to 0.018 inch and preferably about 0.015 inch. With a smaller tow or wider feed rolls, the clearance should be reduced and vice-versa for a larger tow or narrower rolls, or both. Usually, however, this minimum clearance should be no less than 0.005 inch, nor more than 0.05 inch. Furthermore, with the limiting stop installed, the force imposed to urge the rolls together may be adjusted to a considerably higher value than that which must be used to produce the desirable type A crimp without the stop. The use of the greater pressures positively eliminates the sensitivity of the feed roll pressure and nonuniform crimp. Moreover, by operating with a higher force more rapid recovery of proper roll clearance is obtained after the passage of some extra thick portion of tow. This minimizes the tendency for the tow to wrap back on previous rolls because of a sudden loss of grip by the crimper rolls.
Example An 85,000 denier tow of about 3 denier acrylonitrile polymer filaments was prepared by evaporative spinning of acrylonitrile polymer dissolved in dimethylformamide, washing the filaments substantially free of solvent, drawing 4X and combining a number of strands. This tow was then led over a finish roll, through a steam cell, and over, under and between pin guides to shape the tow into a uniform bundle of proper width before introducing it into the bite of the feed rolls of the crimper. The crimper was preheated by the introduction of low pressure steam and a temperature of about 150 F. was maintained in the tow while it was being crimped. The crimper feed rolls, 1 inch in width, were adjusted to a minimum clearance of 0.015 inch by means of the stop device of this invention and the pressure cylinder was adjusted to impart a load of 15 pounds against the end of the pivot arm to hold the movable feed roll up against the stop. The tow was introduced into the crimper at the rate of 132 y. p. m. and emerged against the action of the weighted clapper plate 12 uniformly crimped with about 10 crimps per inch. After cutting this tow into 1%, 2, 2 /2 or 4 inch staple, it was further processed and spun without difficulty into uniform high strength yarn.
The use of the stop of this invention materially reduces the pressure applied on the tow in the nip of the crimper feed rolls and allows the crimp to form in a plane parallel to the faces of these rolls. Yet, there is suflicient squeezing action to feed the tow properly along into the crimper against the back pressure caused by the weighted clapper plate. If a heavy section of tow comes along, the rolls spread apart as before but because a greater force tending to close the rolls is being applied, the separation of the rolls is less frequent. As a consequence, repeated bouncing and oscillating of the pivot roller 6 is substantially eliminated and importantly the rebound from the more widely opened position is stopped short of pounding and compressing the tow so that the desirable A type crimp is not lost.
The apparatus of this invention permits the assured Any departure from the above description which conforms to the present invention is intended to be included within the scope of the claims.
1. In a crimper having cooperating feed rolls one of which is mounted on a pivot member so as to be capable of being moved away from the other roll, the improvement comprising a stop limiting the movement of said pivotal feed roll so that it cannot come in contact with said other roll.
2. In a crimper having cooperating feed rolls one of which is mounted on a pivot member so as to be capable of being moved away from the other roll, the improvement comprising a stop for maintaining a minimum gap between said feed rolls.
3. In a crimper having cooperating feed rolls one of which is mounted on a pivot member to form a nip with the other feed roll, the improvement comprising an adjustable stop comprising a shoe mounted on an adjustable screw and located on said pivot member to maintain a minimum clearance of at least a few thousandths of an inch between said feed rolls.
4. Apparatus in accordance with claim 3 wherein said clearance is between about 0.005 to about 0.05 inch.
References Cited in the file of this patent UNITED STATES PATENTS 2,044,135 Taylor June 16, 1936 2,090,669 Dreyfus Aug. 24, 1937 2,245,874 Robinson June 17, 1941 2,311,174 Hitt Feb. 16, 1943 2,698,970 Wicker Jan. 11, 1955 FOREIGN PATENTS 487,711 Great Britain June 24, 1938
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