US2919794A - Tow brake - Google Patents

Description

Jan. 5, 1960 'w. A. BURN, JR

TOW BRAKE Filed July 28, 1958 2,919,794 Patented Jan. 5, 1960 TOW BRAKE William A. Burn, Jr., Rock Hill, S.C., assignor to Cellanese Corporation of America, New York, N.Y., a corporation of Delaware Application July 28, 1958, Serial No. 751,198

8 Claims. (Cl. 20312) The present invention relates to the severing of continuous filament tows to produce staple fiber and more particularly to the provision of simple and eifective means for braking the tow with sufficient accuracy and rapidity to prevent the tail of the tow from passing through the staple cutter to thereby permit the tow to be severed into staple at high speed while simultaneously eliminating long cuts in the staple fiber thereby to improve staple uniformity.

In the conventional severing of continuous filament tows to produce staple fiber, it is necessary to brake the tail of the tow to prevent the same from passing through the staple cutters resulting in long cuts. When the tow moves at high speed this braking operation makes it difficult to achieve high production rates from a single staple cutter. In the past it has been necessary either to cut back production speed by slowing the feed velocity of the tow to the cutter or to tolerate lowered staple quality due to the presence of long cuts resulting from tails passing through the cutter.

In the invention a simple and effective braking system is provided for the purpose of automatically stopping the tow close to the staple cutter to reduce waste and prior to the passage of the tail through the cutter. In this manner high tow feed velocities are utilized, yet a quality staple product is produced.

In accordance with the present invention, the tow is tensioned and then passed over a slide member or pin. Means are positioned within the pin, this means being retained within the pin by the tensioned tow. When the tail of the tow is released the tension on the tow drops and the member previously held within the pin by the tensionof the tow is urged outwardly either by gravity, spring urging, a weight, or the like. The tow in its passage to a cutter passes a dragging or further tensioning element which regulates the velocity of the tow to the staple cutter. In the invention, when the member within the pin emerges therefrom upon passage of the tow tail it actuates means to prevent advance of the tow, e.g. an air-operated clamp which is positioned between the drag element and the cutter to grasp the tail of the tow before the velocity of the same can increase which would produce long cuts. The air-operated clamp can be actuated by an air valve, a microswitch, or the like, which is rendered operative when the member within the pin emerges therefrom.

The invention will be more fully understood from the description which follows taken in conjunction with the accompanying drawings in which:

Fig. l is a partial perspective view of apparatus constructed in accordance with the invention;

Fig. 2 is a side elevation of a pin constructed in accordance with the invention and showing the member which is free for movement when the tow end passes the pin to release the tension upon this member and also the microswitch-operating lever;

Fig. 3 is a cross-section of the pin of Fig. 2 illustrating the action which takes place when the tension supplied by the tow is removed; and

Fig. 4 is a detailed view of the tow clamping means illustrating the clamp, the air piston which operates the same, the solenoid which actuates the air cylinder and the electrical circuit including the microswitch which operates the solenoid.

Referring to Fig. 1, a continuous filament tow 10 which is normally supplied from a drier (not shown) is directed to guide pins 11, 12 and 13, the tow 10' passing over the pins 11 and 13 and under the pin 12. Because of the high speed with which the tow is moved and since the direction of movement of the tow is altered by the pins 11, 12 and 13, the tow presses against the pin 13 until the tail of the tow passes the same. Accordingly, the instant of time in which the tail passes the pin 13 is accurately sensed by the release of tension against the pin.

After passing the guide pins 11, 12 and 13, the tow 10 is bundled together as indicated at 14 and is then passed to a drag element constituted in the form of the invention which is illustrated by drum 15 which is wrapped in the manner illustrated in the drawing. The tensioned tow is then passed to a conventional staple cutter 16 where it is cut into staple fiber lengths 17.

In accordance with the invention, a clamp 18 is' interposed in the path of the tow 10- between the staple cutter and the drum 15. The clamp 18 is normally open to permit the free passage of the tow therethrough. The

normally open clamp 18 comprises a movable clamp member 19 which is connected by a shaft 29' to an air cylinder 21. The air cylinder 21 is connected by means of conduits 22 and 23 and an intervening normally closed valve 24 to a source of fluid under pressure.

The pin 13 is provided with means for sensing the release of tension applied by the tow in its passage over the pin. This sensing means is interposed in a longitudinal channel 25 and operates to open the valve 24 and permit air to pass through the conduit 22 to close the clamp 18.

Operation of the sensing means in the channel 25 and of the clamp 18 will be described more fully hereinafter.

At this point it is desired to emphasize that the invention relies upon an accurate sensing of the passage of the tail of the tow over a given point up stream from the cutter in order to operate a clamp adjacent the cutter in time to grasp the tail of the tow so that this tail is prevented from passing through the staple cutter to improve the uniformity of the staple product which is produced while at the same time reducing waste represented by the uncut tail portion of the tow to a minimum. To this end the time interval between movement of the sensing means out of the position shown in Fig. 2 and clamping of the tow end is correlated to the distance between the sensing means and clamp so that the length of-the tow between the clamp and dragging or tensio-ning element will be a minimum.

The staple cutter 16 which is used is of conventional type and is not shown in detail in the drawing. It is sufficient to point out that the length of the staple is governed by the velocity of the tow. When the tail of the tow passes the drum 15, the frictional drag is eliminated and the velocity of the tow increases so that the staple cutter produces staple of excessive length, e.g. long cuts are produced. The invention by clamping the tow between the staple cutter and the mechanism employed to create a frictional drag upon the tow causes the tow to be caught before its speed has increased unduly.

The sensing mechanism of the invention is more clearly shown in Figs. 2 and 3 where it will be seen that a lever 26 is mounted in the channel 25, the lever 26 being pivoted at 27 for movement into and out of the channel 3 25. In the preferred construction illustrated, the lever 26 comprises an arm 28 which fits within the channel 25 and an extension 29 which bears against a sensing arm 30 operatively connected with valve 24.

As will be evident in Figs. 2 and 3, the pin 13 is formed with a cylindrical bore 31 which receives a compression spring 32. When the arm 28 of the lever 26 is forced into the channel 25 by the tension of the tow (this tension created by the undulating path of the tow effected by the combination of pins ll, 12 and 13) the spring 31 is compressed within the bore 31. As soon as the tow tail passes the pin 13, the tension on the arm 28 is relieved and the pin 13 ejects the arm 28 from the channel 25 as indicated in phantom in Fig. 3. As a result, extension 29 displaces sensing arm 30 to open valve 24.

Preferably the opening of valve 24 is effected by direct mechanical connection of this valve with sensing arm 3t). Alternatively, it can be effected electromechanically as illustrated in Fig. 4. The sensing arm 3% (not shown) controls a rnicroswitch 33 which is interposed in an electrical circuit in series with the armature of a solenoid 34. The electrical circuit may include a manual switch 35 which is closed to activate the electrical circuit.

As can be seen in Fig. 4, and assuming the manual switch 35 to be closed, operation of the microswitch 33 draws the core 36 of the solenoid upwardly within the solenoid to open the valve 24 and to thereby permit air to pass from a supply thereof through the conduits 23 and 22 to the air cylinder 21. As will be evident, the application of air pressure to the cylinder 21 will move the shaft 20 forwardly to force the movable platen 19 against the stationary platen 37 of the clamp 18.

In the construction of Fig. 4, a guide 38 is welded to the clamp support 39 to facilitate threading of a fresh tow through the clamp 18. The clamp support 39 is formed with a depending flange 40 which is formed with openings 41 to facilitate securement of the clamp structure to the support means which carry the drum 15 and its associated guides.

The details of construction of the valve 24 and the air cylinder 21 as well as the conduits which interconnect the same to permit projection and retraction of the shaft 20 have not been discussed as these are conventional.

Referring to Figs. 1, 2 and 3, the pins 11, 12 and 13 are mounted upon a plate 42 (see Fig. 1), these pins being secured to a support position behind the plate 42 as by the threaded extensions 43. It will be observed that the extension 29 of the lever 26 extends through a slot 44 in the plate 42, the sensing arm 30 being positioned behind the plate 42 and hence not seen in Fig. 1.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of my invention.

Having described my invention what I desire to secure by Letters Patent is:

1. Apparatus for severing continuous filament tows at high speed to produce staple fiber comprising a staple cutter for severing said tow, means for placing said tow under tension while moving to said cutter, means for sensing an end of said tow before said end reaches said tensioning means, and means for preventing advance of said tow, said advance preventing means being disposed intermediate said tensioning means and said cutter, said sensing means and said advance preventing means being operatively connected, whereby when an end of said tow 41 is sensed by said sensing means said advance preventing means is actuated and advance of said tow is prevented with the end between said tensioning means and said cutter thereby to prevent said end from passing to said cutter.

2. Apparatus as recited in claim 1 in which the time interval between sensing of said tow end and the time when advance of said tow is prevented is correlated to the distance between said sensing means and said advance preventing means so that the length of tow from said advance preventing means to said tow end is a minimum.

3. Apparatus for severing continuous filament tows at high speed to produce staple fiber comprising a staple cutter for severing said tow, spaced first and second means for placing said tow under tension while advancing to said cutter, means for sensing an end of said tow between said first and second tensioning means, means for clamping said tow disposed intermediate said second tensioning means and said cutter, said sensing means and said clamping means being operatively connected, whereby when an end of said tow is sensed by said sensing means said clamping means is actuated and advance of said tow is prevented with the end between said second tensioning means and said clamping means thereby to prevent said end from passing to said cutter.

4. Apparatus for severing continuous filament tows at high speed to produce staple fiber comprising a staple cutter for severing said tow, means for placing said tow under tension while advancing to said cutter, sensing means urged into a first position, said sensing means contacting said tow and being maintained in a second position by the tension on said tow, and clamping means including a displaceable member normally spaced from said tow and disposed intermediate said sensing means and said cutter, said sensing means and said member being operatively connected, whereby when an end of said tow passes said sensing means said sensing means moves from its second position into its first position 7 thereby to actuate and displace said member to clamp said tow and prevent said end from passing to said cutter.

5. Apparatus as recited in claim 4 in which said clamping means includes a stationary platen toward which said member moves to clamp said tow therebetween.

6. Apparatus as recited in claim 4 in which said sensing means includes a pin formed with a longitudinal channel and said portion of said sensing means includes a lever pivotally mounted within said channel, said sensing means further including an extension arm movable with said lever and projecting from said channel at a point spaced laterally from the path of said tow, resilient means for ejecting said lever from said channel in the absence of tension from said tow, and a sensing arm positioned in the path of said extension arm operatively connected with said clamping means.

7. Apparatus as recited in claim 4 including a plurality of horizontally offset pins about which said tow passes before contacting said sensing means, thereby being placed under tension.

8. Apparatus as recited in claim 4 in which the operative connection between said sensing means and said member includes an air cylinder connected to said member, air supply means connected to said air cylinder, and a valve controlling said air supply means.

No references cited.

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