Patent Grant
7273578
This invention relates to a method and apparatus for drawing fibers, yarns, or tapes formed from natural resin, synthetic resin, or combination of both. For the sake of convenience, in the description of this invention, which follows, the method and apparatus will be described in terms of drawing fibers. However, it is to be understood that the method and apparatus are equally usable for drawing any elongated body elements subject to such procedure. But for all that, the invented drawing method and apparatus will be described in terms of drawing of fibers in the form of coiled fiber loops. It is to be understood that the coiled fiber loops are a connected set of rings or twists into which the fiber can be wound.
In the production of most polymer fibers (e.g., nylon, polypropylene, and polyester fibers) a drawing stage is included subsequent to the spinning or extrusion stage. In the drawing stage the fiber is usually drawn by a drawing apparatus at elevated temperature to a length substantially exceeding (in some cases, several times) their original length. The fiber passes the drawing apparatus with a speed Vfiber which increases from the beginning to the end of the drawing stage, speed Vfiber being a linear speed along the fiber axis of fiber points in the drawing process (along the tangent to the fiber axis if the fiber drawing occurs on the curved surface, e.g., a curved hot plate or a roller). A fiber draw ratio λ, which is the extent of fiber drawing, is given by
λ=Vfiber2/Vfiber1, (1)
where
The drawing of the fibers enables them to achieve the required molecular orientation and structure by virtue of which they attain the necessary strength and other desired physical characteristics. As an example, typical λ for commercial nylon fibers is about 6 to 1. Usually, the higher λ, the higher molecular orientation and fiber tensile properties (tenacity and Young modulus in particular).
In case of a continuous multi-stage drawing process, Vfiber2 is the fiber linear speed at the end of the last fiber drawing stage, and Vfiber1 is the fiber linear speed in the beginning of the first fiber drawing stage.
The drawing has generally been hitherto effected on a commercial scale by passing the fiber from one set of rotating rollers to another. Each set of receiving rollers rotates at a surface speed, which is greater than that of the preceding set of feed rollers.
In case of drawing the fiber by the rotating rollers we get
Vfiber1=Vsurface1=Vinlet and (2)
Vfiber2=Vsurface2=Voutlet, (3)
where
Thus in conventional industrial drawing processes a ratio of fiber outlet speed Voutlet to fiber speed Vfiber2 is 1 to 1 (this ratio will be used for discussion below).
In case of conveying drawn fiber after the drawing stage to the receiving package we get
Vfiber2=Voutlet=Vtake-up, (4)
where
Outlet speed Voutlet and take-up speed Vtake-up determine the throughput of the drawing stage. Most conventional commercial processes, particularly in the area of melt-spun flexible-chain polymer fibers, have very high speed Vtake-up ranging from several hundred to several thousand meters per minute to provide high throughput. This means that in the high-throughput commercial processes speeds Vfiber2, and Voutlet are also high, i.e., ranging from several hundred to several thousand meters per minute.
Another parameter is used to characterize the fiber drawing process, i.e., a speed of drawing or a strain rate Vstrain, which is a relative deformation of the fiber (strain) in a unit time. Usually strain rate Vstrain is expressed in percent per second (%/sec) and is given by
Vstrain=λ/T, (5)
where
In conventional commercial processes strain rate Vstrain is high, i.e., several hundred percent per second.
In such conventional high-fiber-speed, high-drawing-speed processes the fiber is subjected to a very abrupt acceleration and rise in tension at the point where it leaves one roller to pass to the succeeding higher-speed roller. Care must be taken to ensure that the abrupt rise in tension does not break the fiber. Thus, this conventional technique may be termed “impulsive drawing” because the fiber experiences a sudden “impulsive” acceleration from its initial state to its final drawn state while traveling through the drawing machine. The “impulsive” acceleration and high tension result in frequent fiber breaks and equipment stops, high volume of waste, and preventing further fiber improvement.
Because of high fiber speed, time of drawing T is very short in most high-throughput industrial processes, i.e., less than a second for one-stage drawing and about 1-3 seconds for two- or three-stage drawing. This results in “non-equilibrium” drawing where the fiber does not have enough time to be heated to ambient elevated temperature while being drawn, and the drawing occurs at high temperature gradient in the fiber cross-section. This, in turn, results in reduced drawability and crystallinity, high gradient of morphology and physical properties in the cross-section, high local overstresses, reduced tensile properties, and dimensionally unstable fibers with high hot-air shrinkage. This is especially typical for fibers and yarns having high denier (denier is weight in grams of 9000 meters of fiber). To provide additional time for heat setting, the existing technology requires a separate, specialized, very expensive, and energy-consuming equipment to produce dimensionally stable fibers without decrease of their tensile properties (U.S. Pat. No. 5,522,161 to Vetter (1996), U.S. Pat. No. 5,588,604 to Vetter et al. (1996)—these patents are discussed below). More often, a different method for decreasing shrinkage is used in commercial processes. The fiber is subjected to restricted shrinkage while moving through a special stage, which follows the last drawing stage. In doing so, the initial modulus, intermediate moduli, and tenacity are reduced.
The commercial drawing processes mentioned above do not enable one to produce polymer fibers with tensile and other physical properties close to those made by lab-scale low-fiber-speed, low-drawing-speed, long-drawing-time, and non-impulsive drawing process. This lab-scale drawing may be termed “uniform” or “equilibrium” drawing, where drawing time T is long enough to heat the fiber to the ambient temperature, while it being drawn, with low temperature gradient in the fiber cross-section. This results in uniform morphology and physical properties in the cross-section. These lab-scale experiments achieve more effective morphological transition “low-oriented-high-oriented polymer system” and superior physical properties. For example, tenacity of lab-scale flexible-chain, regular-molecular-weight, melt-spun polymer samples is higher by a factor of about 1.5-2 and initial moduli are several times higher than those for conventional commercial fibers. (As an example, tensile properties of lab-scale polypropylene fibers can be seen in “Superdrawn Filaments of Polypropylene” by W. N. Taylor, J R. and E. S. Clark, Polym. Eng. Sci., 18, 518-526 (1978). A comparison of these results with tensile properties of commercial polypropylene fibers is presented in Table VI below). In order to overcome this large gap between the properties of lab-scale and commercial-scale polymer fibers, a new approach needs to be developed.
Moreover, within today's fiber industry there is another large gap, i.e., tensile properties of low-cost, low-performance, regular-molecular-weight, melt-spun, flexible-chain polymer fibers (e.g., polyethylene, polypropylene, polyester, nylon, etc.) are much lower than those of high-cost, high-performance, wholly-aromatic polymer fibers (e.g., Kevlar® 49, DuPont and Twaron®, Teijin) and ultra-high-molecular-weight, solution-spun, aliphatic polymer fibers (e.g., Spectra®, Honeywell and Dyneema®, DSM). The great challenge for fiber science and technology is to fill this gap by producing industrially a new generation of low-cost, high-performance polymer fibers (most probably, flexible-chain, regular-molecular-weight, melt-spun) with substantially improved tensile and other physical properties. This can be done by introducing the results of the lab-scale research efforts (mentioned above) to the industry. It would be extremely attractive to achieve in the high-throughput industrial process (i.e., with take-up speed Vtake-up ranging from several hundred to several thousand meters per minute) fiber tenacity of about 1-2 GPa (12-22 gpd) and initial tensile modulus of about 20-100 GPa (250-1000 gpd) for different flexible-chain, regular-molecular-weight polymer fibers having different theoretical values of tensile properties.
In the work of Taylor and Clark mentioned above, tenacity about 1 GPa (12 gpd) and initial modulus 22 GPa (270 gpd) where achieved for melt-spun, regular-molecular-weight polypropylene filaments in the lab-scale experiments (see Table VI below).
Any company that makes progress in this area will have a tremendous advantage in competition today and in the future. To the best of our knowledge, no significant progress in this area has been so far achieved by the American, Asian, or European fiber industries.
A few attempts have been made in the prior art to improve conventional industrial drawing methods.
A method and apparatus for incremental drawing of fibers on the industrial scale were introduced in U.S. Pat. No. 2,372,627 to Goggin et al. (1945), in U.S. Pat. No. 2,788,542 to Swalm et al. (1957) and in U.S. Pat. Nos. 3,978,192 (1976), U.S. Pat. No. 4,891,872 (1990), U.S. Pat. No. 4,980,957 (1991), U.S. Pat. No. 5,339,503 (1994), and U.S. Pat. No. 5,340,523 (1994), all to Sussman. The incremental drawing improves the conventional commercial drawing process by dividing it into small steps, typically 10-30, i.e., fibers are drawn on microterraced or smooth surfaces of a pair of conical rollers with canted axes.
U.S. Pat. No. 4,967,457 to Beck et al. (1990) disclosed an arrangement for stretching thermoplastic fibers. In this patent fiber moves through a plurality of non-driven rollers arranged between the delivery mechanism and the stretching mechanism inside the heat chamber. Some rollers have brakes providing several successive stretching zones.
Both invented methods provide longer drawing path and drawing time T as well as lower strain rate Vstrain in comparison with conventional methods. However, as in the conventional drawing methods the fiber, while being drawn, passes the drawing apparatuses at high speed and at the end of the drawing stage Vfiber2=Voutlet (in other words, the ratio of outlet speed Voutlet to fiber speed Vfiber2 is 1 to 1). If after the drawing stage the drawn fiber is conveyed to the receiving package, Vfiber2=Voutlet=Vtake-up. Economical reasons force to keep speeds Vfiber2, Voutlet, and Vtake-up as high as possible, i.e., in the range from several hundred to several thousand m/min, in order to provide high throughput.
For both methods the “impulsive” acceleration, although reduced, remains high at each drawing step or zone. In case of high-throughput processes, the drawing is “non-equilibrium”, i.e., it still has short drawing time (a few seconds), which is not enough to heat the fiber (especially high-denier fiber) to the ambient temperature in the process of drawing. In case of the incremental drawing, the fiber is drawn only between rollers and not on their surfaces while traveling through the drawing apparatus. This results in reduction of drawing time to the level, which can reach about half of the residence time in the apparatus. The drawing starts and stops while the fiber moves through the drawing apparatus. Thus, the incremental drawing is not uniform and may be termed “intermittent drawing”.
A technology for winding fiber into coiled loops around a conveyer device, conveying these fiber loops at a slow speed and high residence time through a heat chamber by this conveyer device, then unwinding these fiber loops, and taking up the fiber with high speed has been proposed for fiber heat setting in U.S. Pat. No. 3,426,553 to Erb (1969), U.S. Pat. No. 3,774,384 to Richter (1973), U.S. Pat. No. 4,414,756 to Simpson et al. (1983), U.S. Pat. No. 5,522,161 to Vetter (1996), and U.S. Pat. No. 5,588,604 to Vetter et al. (1996). However, the invented method and apparatuses were not designed for and capable of fiber drawing.
U.S. Pat. No. 2,302,508 to Sordelli (1942) disclosed an apparatus substantially in the form of a winding frame having the general form of a frustum of a cone, which upon being set rotating about its axis promotes the winding of the filament material in a series of helical turns distributed over the apparatus from its end having the minimum diameter towards the opposite end having the maximum diameter. The filament material winds up in a continuous manner onto the apparatus and unwinds therefrom after it has traveled along the said series of turns; during the movement the material undergoes a continuous progressive stretching action, whereby it increases in length to an extent which depends upon the structural characteristics of the apparatus. The winding frame comprises a carrier member rotating about a central axis and a plurality of cantilever rollers each rotatably mounted at one end at said carrier member, the axes of said rollers being both diverged and skewed with respect to the central axis. The skewed rotated rollers draw the fiber by expanding the helical turns while conveying these turns along the central axis.
In this invention, the fiber passes the drawing apparatus at low speed providing longer drawing path and drawing time T as well as lower strain rate Vstrain in comparison with conventional industrial drawing processes. However, this apparatus has some disadvantages with respect to implementation on the industrial scale. They are as follows:
(1) It is complicated in design having the diverged and skewed cantilever conveyer-drawing members (driven rollers) rotated about their exes and simultaneously about the central axis as a part of the winding rotating frame.
(2) The apparatus has a fixed angle of divergency of the conveyer-drawing members and is not capable to change the fiber draw ratio, if it is necessary, by changing the angle of divergency.
(3) The conveyer-drawing members (which are cantilever, diverged, and skewed with respect to the central axis) are not strong enough to sustain high drawing forces in the drawing process while drawing large number of the fiber loops (up to a few hundreds) especially in case of high draw ratios (e.g., 5× and higher), high denier filaments, and present-day high tenacity fibers. Large number of loops (100-200 and higher) is necessary to provide long drawing time T and low strain rate Vstrain at high outlet speed Voutlet and throughput [see equation (32) below ]. For the same reasons, Sordelli's apparatus has also limitations to be long to place large number of the loops. Sordelli's apparatus has also limitations to provide large angle of divergency of the conveyer-drawing members and large diameter (and circumference) of the leading fiber loop at the delivery ends necessary for high draw ratios (5× and higher) because of design of the driving mechanism (gear box) to drive the conveyer-drawing members and possibility of sliding down of the fiber loops along the conveyer-drawing members (see below).
(4) In Sordelli's apparatus, the conveyer-drawing members (rollers) have smooth surface covered with rubber or other materials to improve friction and to prevent sliding down of the fiber loops on the surface of the members. In that case, it would be difficult to find the coating that can operate inside a heat chamber at elevated temperatures necessary for effective hot drawing of the fibers. Without the coating, it is quite possible that the loops will slide down the conveyer-drawing members especially in case of (i) the higher divergency of the conveyer-drawing members necessary for higher draw ratios, (ii) some polymers with lower friction coefficient, and (iii) some finishes applied in the fiber making process.
(5) Sordelli's apparatus is not operator-friendly, i.e., it is difficult to load the fiber end into the apparatus to start the drawing process as well as to restart the apparatus after fiber breakage, and, in case of fiber breakage, the broken ends can be easily wound on the rotated conveyer-drawing members (rollers) resulting in significant operational problem.
Thus, the Sordelli's apparatus has substantial disadvantages to be industrially feasible.
This invention relates to a method and apparatus for low-fiber-speed, low-drawing-speed, high-throughput, uniform, continuous drawing of fibers, or like flexible elements formed from natural resins, synthetic resins, or combination of both, in the form of coiled fiber loops. As mentioned above, the coiled fiber loops are a connected set of rings or twists into which the fiber can be wound.
The fiber is fed at an inlet speed to the drawing apparatus, which comprises a conveyer-drawing structure comprising a plurality of conveyer-drawing members (e.g., rotating threaded spindles or circulating endless chains) disposed about a central axis. The conveyer-drawing members have receiving ends and delivery ends spaced along the central axis and diverge from this axis in such a way that the distance between the delivery ends and the central axis is greater than the distance between the receiving ends and the central axis. The coiled fiber loops are continuously laid on the receiving ends of the moving conveyer-drawing members. The conveyer-drawing members draw the fiber by expanding the circumference of the fiber loops while slowly conveying these loops along the central axis from the receiving ends to the delivery ends. Thus, a layer consisting of coiled fiber loops (e.g., circular or serpentine loops) is formed on the conveyer-drawing members. Preferably, the points of the fiber loops are moved along the fiber axis (e.g., the fiber circular loops are slowly rotated about the central axis) preventing the fiber loops from having permanent contact points with the conveyer-drawing members.
The coiled fiber loops, while being conveyed and drawn, are subjected to elevated temperature using a heat chamber supplied with hot air, hot inert gas, or superheated steam.
At the delivery ends, leading loops of the drawn fiber are successively removed. The fiber is conveyed either to a next stage of the fiber making process or to a receiving package at outlet speed Voutlet ranging from several hundred to several thousand meters per minute.
In comparison with existing industrial processes, the invented drawing process has one or more of following advantages: significantly longer drawing time T, lower strain rate Vstain, and lower tension in the drawing line at the same or higher fiber speeds Voutlet and Vtake-up and throughput. This opens the door for substantial improvement of physical properties of commercial fibers, less breaks, less equipment stops, and less waste in comparison with the prior art in industrial fiber technology.
It is an object of the present invention to provide a new method and apparatus for continuous drawing of polymer fibers that avoid the disadvantages of the prior art.
1. It is an object of the present invention to provide a new industrial method and apparatus for continuous fiber drawing which meet two requirements that are considered incompatible by the fiber industry, in particular in the area of melt-spun flexible-chain polymer fibers:
2. Another object of the present invention is to provide a new industrial method and apparatus for continuous drawing of polymer fibers (both flexible-chain and wholly-aromatic) capable of substantially improving fiber tensile properties (i.e., tenacity, Young modulus, intermediate moduli, breaking elongation, etc.) approaching those obtained in laboratory experiments at low strain rate Vstrain and long drawing time T. In particular, this will result in development of a new generation of low-cost, high-performance industrial polymer fibers (most probably melt-spun, regular-molecular-weight, flexible-chain) having tenacity of about 1-2 GPa (12-22 gpd) and initial tensile modulus of about 20-100 GPa (250-1000 gpd) for different polymer fibers having different theoretical values of tensile properties.
3. Another object of the present invention is to provide a more reliable industrial process for continuous fiber drawing without abrupt, “impulsive” acceleration. This process will result in lower tension in the drawing line, less breaks, less equipment stops, and less waste than in the prior art.
4. An additional object of the present invention is to provide a new industrial method and apparatus for continuous fiber drawing which will produce dimensionally stable, low-shrinkage fibers without using expensive and energy-consuming additional equipment, while retaining improved physical properties, such as initial modulus, intermediate moduli, and tenacity, mentioned above. This may result in substantial saving in capital expenses, energy consumption, and possibility of smaller industrial space.
5. A further object of the present invention is to develop a new industrial method and apparatus for continuous fiber drawing (a) providing, in some cases, a substantial increase in the throughput in comparison with the existing industrial processes by increasing outlet speed Voutlet and take-up speed Vtake-up and (b) maintaining existing or improved physical properties, such as initial modulus, intermediate moduli, tenacity, and shrinkage, mentioned above.
6. To accomplish the objects mentioned above, it is an object of the present invention to develop a new industrial method and apparatus for continuous fiber drawing which provide a ratio of outlet speed Voutlet to a fiber speed (Vfiber)max greater than 1 to 1 (i.e., preferably in the range from about 10 to 1 to about 9000 to 1), fiber speed (Vfiber)max being the highest value of fiber speed Vfiber in the drawing process. In the prior art discussed above, fiber speed (Vfiber)max is fiber speed at the end of the drawing stage Vfiber2 which equals Voutlet. Thus, in the prior art the ratio of Voutlet to (Vfiber)max is 1 to 1.
Still further objects and advantages will become apparent from the consideration of the ensuing description and drawings.
In the drawings, closely related figures have the same number but different alphabetic suffixes.
This invention is further illustrated by the following embodiments, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof, which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims.
One embodiment of the invention for continuous drawing of fibers in form of coiled fiber loops is illustrated in
(a) The conveyer-drawing structure comprises six spindles 54 comprising shaft portions 54a and 54b and a thread or a spiral groove. The spindles are disposed about a central axis and have receiving ends for receiving the fiber and delivery ends for delivering the fiber and both the receiving ends and the delivery ends are spaced along the central axis. The delivery ends are spaced further from the central axis than the receiving ends. Spindles 54 are arranged in an equilateral hexagon when viewed in the cross-section (
The conveyer-drawing structure comprises supporting housings 12 and 14, supporting bearings 16 and 18, bearings 13 and 15, bearings 52 and 53, drive shafts 20 and 21, a tubular support 32 (composed of two parts), and radial arms 46, 48, 62, 62′, and 62″ (six of each arm). The radial arms are arranged in an equilateral hexagon when viewed in the cross-section. Bearings 16 and 18, which are mounted in housings 14 and 12 respectively, support one end of shaft 20 and one end of shaft 21 respectively. Two bearings 13 and two bearings 15 are mounted in tubular support 32. They support shafts 21 and 20 respectively. Support 32 supports radial arms 46, 48, 62, 62′, and 62″. Arms 48 support bearings 52. Bearings 52 can be moved along and secured in guide slots 50 in arms 48, angle γ of spindles 54 being changed. Arms 62 support bearings 53. Bearings 53 and 52 support shaft portions 54a and 54b of spindles 54 respectively. Arms 62′ and 62″ support spindles 54 to prevent sagging.
The conveyer-drawing structure comprises a stabilizing mechanism which prevents rotation of the conveyer-drawing structure (to put it more precisely, its parts supported by tubular support 32) about the central axis. The stabilizing mechanism is located at the receiving ends of spindles 54. It comprises a planetary carrier 35, shafts 36 and 38, a pair of planetary pinions 40, a pair of planetary pinions 42, a first sun gear 34, and a second sun gear 44.
Planetary carrier 35 is secured to shaft 20, shafts 36 and 38 are mounted on carrier 35 for rotation, planetary pinions 40 are secured to shaft 36, planetary pinions 42 are secured to shaft 38, first sun gear 34 is secured to tubular support 32, and second sun gear 44 is secured to supporting housing 14.
(b) The feed device comprises a pair of driven feed rollers 26, a fiber-winding flyer 22, an outlet 22a, a first inner guide channel 20a, a second inner guide channel 22b, a polytetrafluoroethylene tube (not shown), carrier 35, and shaft 20 (carrier 35 and shaft 20 are also parts of the conveyer-drawing structure, see above). Flyer 22 is secured to carrier 35 at the receiving ends of spindles 54. Flyer 22 has outlet 22a at its free end and second guide channel 22b communicating with first guide channel 20a passing through the end portion of shaft 20 and planetary carrier 35. The polytetrafluoroethylene tube (not shown) is inserted into channels 20a and 22b up to outlet 22a, the fiber passing through the channels with very little friction.
(c) The take-off device comprises a pair of driven conveying rollers 28, a roller 28′, a weight 30, an fiber-unwinding flyer 24, an inlet 24a, a third inner guide channel 21a, a fourth inner guide channel 24b, a polytetrafluoroethylene tube (not shown), and shaft 21 (it is also a part of the conveyer-drawing structure, see above). Flyer 24 is secured to shaft 21 at the delivery ends of spindles 54. Flyer 24 has inlet 24a at its free end and fourth guide channel 24b communicating with third guide channel 21a passing through the end portion of shaft 21. Roller 28′ supports weight 30. The polytetrafluoroethylene tube (not shown) is inserted into channels 21a and 24b up to inlet 24a, the fiber passing through the channels with very little friction.
(d) The driving mechanism comprises electric motors 27 and 27a, driving gears 25 and 25a, shafts 20 and 21 (they are also parts of the conveyer-drawing structure, the feed device, and the take-off device, see above), six chain wheels 56, a chain wheel 60, a chain 58, universal joints 61, shafts 55, a shaft 59, and an adjustable transmission (not shown). Gear 25 is secured to shaft 20, and gear 25a is secured to shaft 21. Chain wheels 56 are secured to shafts 55 mounted in arms 46 for rotation. Chain wheel 60 is mounted on shaft 59 for rotation and connected by the adjustable transmission (not shown) to shaft 20 (
(e) Heat chamber 11 envelops the conveyer-drawing structure (besides supporting housings 12 and 14 and bearings 16 and 18), the winding and unwinding flyers, and the driving mechanism besides motors 27 and 27a and gears 25 and 25a. It is supplied with hot air, hot inert gas, or superheated steam.
Electric motor 27 rotates gear 25 and hence rotates shaft 20 in bearing 16 and two bearings 15. Shaft 20 rotates carrier 35 with flyer 22, shafts 36 and 38, and pinions 40 and 42 about the central axis. Pinions 40 and 42 roll on sun gears 34 and 44 preventing support 32 from turning about shaft 20 and the central axis. Thus the parts of the conveyer-drawing structure supported by tubular support 32 are prevented from rotation about the central axis. Electric motor 27a rotates gear 25a and hence rotates shaft 21 in bearing 18 and two bearings 13. Shaft 21 rotates flyer 24 about the central axis.
Spindles 54 are rotated by means of electric motor 27a, gear 25a, shaft 21, the adjustable transmission (not shown), wheel 60, chain 58, wheels 56, shafts 55, and universal joints 61. Shaft portions 54a and 54b of spindles 54 rotate in bearings 53 and 52, respectively.
Fiber G comes to feed rollers 26 at an inlet speed either from a previous stage of the fiber making process (e.g., spinning, previous stage of drawing, etc.) or from a feeder package. The fiber passes through channels 20a and 22b and comes out of outlet 22a. Flyer 22 rotates with shaft 20 and carrier 35 and lays successive, coiled equilateral hexagonal fiber loops about the receiving ends of rotating spindles 54. Spindles 54 are rotated in such a direction that the newly laid fiber loops travel to the left along the central axis, as viewed in
Both flyers 22 and 24 make one revolution while spindles 54 make one revolution. As this takes place, each fiber loop travels along the central axis one pitch of the fiber coil. Simultaneously the coiled fiber loops are slowly rotated about the central axis by the rotating spindles, and each point of the fiber loop passes along the loop circumference a distance equal to a spindle circumference (measured at inner diameter of the thread or spiral groove). The loops increase their circumference with each spindle revolution, the fiber gradually being drawn by rotating spindles 54 at the heat chamber temperature (
For the invented method and apparatus, the fiber draw ratio λ equals the ratio of the loop circumference at the delivery ends to that at the receiving ends. It can be changed by moving bearings 52 along guide slots 50 in arms 48 and securing them there, angle α of spindles 54 being changed. This results in changing the loop circumference at the receiving ends. Heights of arms 62′ and 62″ supporting spindles 54 are adjusted when angle α is changed. The fiber, while being fed to and taken off the spindles, is under tension and cannot shrink because feed rollers 26 and conveying rollers 28 with roller 28′ and weight 30 carry out tension control along with additional tension control devices (not shown) placed before and after the whole apparatus.
The embodiment illustrated in
All chains have a plurality of displacing members 76a and 76b. Each chain link has either displacing member 76a or displacing member 76b (
As shown in
This changes contact points between the fiber and the fiber displacing members thus resulting in better uniformity of dimensions and physical properties of the drawn fiber.
The chains are driven by means of electric motor 27a, gear 25a, shaft 21, the adjustable transmission (not shown), wheel 60, chain 58, wheels 56, gears 72 and 74, and wheels 68 and 68′ (
The embodiment illustrated in
Displacing members are mounted on the parallel chains. They comprise rollers 98 having circular circumferential grooves 98a, pins 106 and 106a, shafts 104, and ball bearings 102 (
Each shaft 82 mounted in arm 71 carries two wheels 68, a beveled gear 84, beveled gear 74, and supports one end of a shaft 88 (
Chains 80 are driven by means of electric motor 27a, gear 25a, shaft 21, the adjustable transmission (not shown), wheel 60, chain 58, wheels 56, gears 72 and 74, and wheels 68 (
The apparatus can be used with rollers 98 not being rotated by the driving mechanism. In this instance, the coiled fiber loops, supported by free-to-rotate rollers, are not rotated about the central axis. In some cases, this is sufficient to produce the drawn fiber having uniformity of the dimensions and physical properties along the fiber axis.
The embodiment illustrated in
In this embodiment shafts 55 are longer than in the embodiment of
The fiber displacement members, rollers 98, are mounted on chains 80 by the same way as illustrated in
In this embodiment, the conveyer-drawing structure is not stationary. The whole structure (comprising tubular support 32, radial arms 46, 49, 71, 71′, 71″ and 71′″, conveyer-drawing chains 80, chain wheels 68, beveled gears 72 an 74, shafts 82 and 88, gears 84 and 86, long gears 90, rollers 98 with gears 100, chains 58 and 58a, shafts 55, and supporting parts 96 and 97) is rotated about the central axis by means of electric motor 27 and gears 25 (
Chains 80 are driven by means of electric motor 27a, gear 25a, shaft 21, chain wheel 57, chain 58a, wheel 60, chain 58, wheels 56, gears 72 and 74, and wheels 68 [gears 72 and 74, and wheels 68 being mounted on both radial arms 71′″ (
The rotating conveyer-drawing structure promotes winding of fiber G on the receiving ends of conveyer-drawing chains 80 in the form of successive, coiled equilateral hexagonal fiber loops (
This embodiment is especially operator friendly. To start the process an operator turns driving motors 27 and 27a off, loads the fiber to the receiving ends (outside of the heat chamber) using an air gun, and clamps it to one of the fiber displacing members (rollers 98). The operator turns driving motors on, and the apparatus starts to lay continuously the successive fiber loops around the receiving ends of circulating conveyer-drawing chains 80, convey the loops along the central axis towards the delivery ends, and draw them. Thus, the apparatus loads all the fiber loops (possibly several tens or several hundreds) on rollers 98 mounted on chains 80 from the receiving to delivery ends. When the fiber end reaches the delivery ends (outside the heat chamber), the operator turns the driving motors off, unclamps the fiber, sucks the fiber end in the air gun, turns the motors on, and takes the fiber up to a winder or next stage of the fiber making process. Thus, the process of loading the fiber loops on the apparatus is semi-automatic. In case of broken fiber, the chains convey the broken ends to the delivery ends (outside the heat chamber) where the operator can easily handle them.
An embodiment of the invention for continuous drawing of fibers in form of coiled serpentine fiber loops (the coiled serpentine fiber loops are one of the form of the coiled fiber loops, according to the definition presented above) is illustrated in
(a) The conveyer-drawing structure comprises two conveyer-drawing members. Each conveyer-drawing member comprises a pair of parallel circulating endless chains 108 and a plurality of rollers 112, as displacing members, mounted on the conveyer-drawing members and placed between chains 108 (
Just as in the previous embodiments described above, the conveyer-drawing members are disposed about a central axis and have receiving ends for receiving the fiber and delivery ends for delivering the fiber and both the receiving and delivery ends are spaced along the central axis. The delivery ends are spaced further from the central axis than the receiving ends. The conveyer-drawing structure, as well as other parts of the drawing apparatus, is supported by a vertical supporting housing 110. Each chain 108 passes over two chain wheels 150 mounted on housing 110 (
There are two endless circulating chains 114 (each for one pair of chains 108). Each chain 114 passes over two chain wheels 118 and two rollers 120. One wheel 118 for each chain 114 is driven by an electric motor (not shown). Chains 114 are engaged with chain wheels 160 of rollers 112. Chains 114 slide along supporting parts 116 to prevent their sagging as well as sagging of chains 108 with rollers 112 under drawing forces. Parts 116 are stationary and are mounted on housing 110.
(b) The feed device comprises a pair of driven feed rollers 122, a roller 124, a roller 126, a weight 128, a feed flyer 132 with two free-to-rotate rollers 130, guide 134, two springs 136, two plungers 138, two solenoids 140 with cores 141, and four solenoids 142 (two for each solenoid 140) with cores 144.
(c) The take-off device comprises a pair of driven conveying rollers 122′, a roller 124′, a roller 126′, a weight 128′, a take-off flyer 132′ with two free-to-rotate rollers 130′, a guide 134′, two springs 136′, two plungers 138′, and two solenoids 140′ with cores 141′.
(d) The driving mechanisms for chains 108 comprise electric motors 146 (one motor per one pair of chains 108). Each motor 146 drives two chain wheels 150 (one wheel for each chain 108).
(e) The heat chamber 148 is supplied with hot air, hot inert gas, or superheated steam. It envelops the conveyer-drawing members, the serpentine fiber loops, and part of the feed and take-off devices.
Chains 108 are driven by means of electric motors 146 and gears 150 (
Fiber G (single end or parallel multiple ends) comes to feed rollers 122 at an inlet speed either from a previous stage of the fiber making process (e.g., spinning, previous stage of drawing, etc.) or from feeder packages. The fiber ends come to feed flyer 132, curve around roller 130, and come to rollers 112 (
Flyer 132 moves up and down along guide 134 by the same manner as in the weaving operation in textile industry, i.e., it is struck in turns by plungers 138 at the top and bottom of guide 134. Solenoids 140 draw in cores 141, compress springs 136, and lead up plungers 138 in percussive position. The springs are released by the solenoids in turns at certain time, the plungers hit the feed flyer, and the flyer moves along the guide carrying the fiber ends. Locking devices (not shown) can stop flyer 132 at the top and bottom of guide 134 allowing plungers 138 to hit the feed flyer at proper time. An assembly of parts of the feed device comprising solenoids 140, cores 141, springs 136, plungers 138, guide 134, and feed flyer 132 with rollers 130 has short-distance horizontal reciprocal motion by means of solenoids 142 (two on the top and two on the bottom of the apparatus) and cores 144. This combination of vertical and horizontal motions of flyer 132 provides more flexibility and precision in the apparatus operation.
Thus, feed flyer 132 lays successive coiled serpentine loops on rollers 112 at the receiving ends of chains 108. The fibers are placed in grooves 162. The newly laid fiber loops travel to the left along the central axis, as viewed in
The successive leading loops of drawn fibers are continuously taken off at the delivery ends by the take-off device operating by the same manner as the feed device described above besides that the take-off device does not have horizontal reciprocal motions. Motions of all parts of the drawing apparatus should be synchronized.
The rest of the operation is the same as in the case of the embodiments of
Calculations
As discussed above, the invented continuous drawing method provides that fiber linear speed (Vfiber)max the drawing process is lower than outlet speed Voutlet (the ratio of Voutlet to (Vfiber)max is greater than 1 to 1). At the same time, strain rate Vstrain is substantially lower and drawing time T is longer than those in the existing industrial processes without reducing, and in some cases even increasing, the throughput. The following calculations, made for the embodiments of
A speed of conveying the fiber loops along the central axis Vloop is given by
Vloop=d/ΔT and (6)
ΔT=d/Vloop, (7)
where
According to the mass conservation rule, in a continuous fiber making process equal fiber mass should pass through any cross-sectional plane (plane perpendicular to the central axis) in a unit time both inside and outside the apparatus. For the fiber having the same draw ratio λ, the fiber mass is in proportion to the fiber length.
Inside the apparatus, at the delivery ends, a fiber length L, which is a circumference of the leading fiber loop at the delivery ends, passes cross-sectional plane for time ΔT (see above). Outside the apparatus, while the fiber being conveyed either to the next stage of the fiber making process or to the receiving package, the same length L of the straightened fiber (having the same λ) should pass cross-sectional plane for the same time ΔT. Thus, outlet speed Voutlet is given by
Voutlet=L/ΔT, (8)
Thus, equations (7) and (8) lead to a ratio A
A=Voutlet/Vloop=L/d. (9)
(a) The Case of the Embodiments of
(Vfiber)max=VfiberK=VfiberP=QW/ΔT=(PW·cos φ1)/ΔT (10)
From isosceles triangle POK (
φ1=(180−φ)/2 (11)
In case where n conveyer-drawing members are arranged in an equilateral polygon, angle φ is given by
φ=360/n, (12)
From equations (11) and (12) we get
φ1=(180−360/n)/2=90·(1−2/n) (13)
From equations (10) and (13) we get
(Vfiber)max=PW·cos [90·(1−2/n)]1/ΔT (14)
From
PW=d·tgα and (15)
(Vfiber)=d·tgα·cos [90·(1−2/n)]˜1/ΔT (16)
From equations (6) and (16) we get
(Vfiber)max=Vloop·tgα·cos [90·(1−2/n)] (17)
From equations (9) and (17) we get
(Vfiber)max=Voutlet·d·1/L·tgα·cos [90·(1−2/n)] (18)
Thus, fiber speed (Vfiber)max is constant during the drawing at given Voutlet, d, L, n, and α
Equation (18) leads to a ratio B
B=Voutlet/(Vfiber)max=L/{d˜tgα·cos [90·(1−2/n)]} (19)
In case of rotation of the coiled fiber loops about the central axis by the rotating rollers or spindles (like in the embodiments of
Distance Lfiber is given by
Lfiber=Vrotation·ΔT (20)
From equations (8) and (20) we get
Lfiber=(Vrotation/Voutlet)·L (21)
During the drawing, while the fiber loop passes from the receiving to delivery ends, each point of the fiber loop in the process of the rotation of the loop about the central axis passes total distance designated as Ltotal, which is given by
Ltotal=Lfiber·(N−N′)=(Vrotation/Voutlet)·L·(N−N′), (22)
where
The draw ratio λ is given by
λ=L/L′ and (26)
Laverage=(L+L/λ)/2 (27)
From equations (22) and (24) we get
N′=N/(Laverage/Lfiber+1) (28)
One can see that the larger the ratio Laverage/Lfiber, the smaller N′ in comparison with N.
Thus, time of drawing T, which is time needed for each fiber point to pass from the receiving ends to the delivery ends, in a view of equation (9), is given by
T=(M−N′·d)/Vloop=[A·(M−N′·d)]/Voutlet=[L·(M−N′·d)]/(Voutlet·d) (29)
From definition of ΔT, that is, time needed for the fiber loop to pass distance d between adjacent loops along the central axis (see APPENDIX, page 52), and in case of N′=0 we get
ΔT=T/(N−1) (30)
From equations (8) and (30) we get
Voutlet=[L·(N−1)]/T (31)
At large N
Voutlet=(L·N)/T (32)
Equation (32) shows that Voutlet is directly proportional to L and N and inversely proportional to T.
L=π·D (33)
were
From equations (32) and (33) we get
Voutlet=(π·D·N)/T (34)
One can see that Voutlet is proportional to D (or L) and N.
Table I gives the results of calculations for the case: L=5500 mm, Voutlet=Vtake-up=3000 m/min (the fiber is conveyed to the receiving package after the drawing stage), n=6, λ=5 to 1 (400%), and d, M and A are variable. The coiled fiber loops are not rotated about the central axis by the rotating rollers or spindles. Take-up speed of 3000 m/min is typical take-up speed for the commercial process for multifilaments and yarns.
Table II gives results of calculations for the case: L=2000 mm, Voutlet=Vtake-up==500 m/min (the fiber is conveyed to the receiving package after the drawing stage), n=6, λ=5 to 1 (400%), and d, M and A are variable. The coiled fiber loops are not rotated about the central axis by the rotating rollers or spindles. Take-up speed of 500 m/min is typical take-up speed for the commercial process for tape yarns and monofilaments.
(b) The Case of the Embodiment of
Equations (10)-(32) derived for the case of the coiled equilateral polygonal fiber loops (embodiments of
Table III gives the results of calculations for the case: L=5500 mm, Voutlet=Vtake-up==2000 m/min (the fiber is conveyed to the receiving package after the drawing stage), n=2, λ=5 to 1 (400%), and d, M and A are variable. Fiber points of the serpentine fiber loops are not moved by rotating rollers along the fiber axis. As discussed above, this embodiment of the invention having the serpentine fiber loops can draw multiple ends.
Thus, in the cases examined in Examples 1-3, fiber linear speed (Vfiber)max is low, i.e., 0.1-8 m/min, time of drawing T can reach tens of seconds, strain rate Vstrain is low, i.e., 6-70%/sec, and the ratio of Voutlet to (Vfiber)max is greater than 1 to 1, i.e., varying from the ratio 250 to 1 to the ratio 9000 to 1 (the fiber drawing apparatus can be constructed and arranged to provide the ratio, if necessary, lower than 250 to 1 and greater than 9000 to 1). In case of conventional commercial drawing process having the same λ=400% and (Vfiber)max=Vfiber2=Voutlet=Vtake-up=3000 m/min., time of drawing T is about 1 second, and Vstrain is substantially higher, i.e., about 400%/sec.
In the invented method, time of drawing T in some cases is so long that it can be decreased by a factor of 1.5-2 remaining sufficiently long (20-40 sec) to perform uniform hot drawing of even high denier fibers. Thus, speeds Vloop, Voutlet, and Vtake-up can be also increased in these cases at least by a factor of 1.5-2, resulting in the 1.5-2-fold increase and more of the throughput. Thus, the take-up speed can be 4500-6000 m/min and more.
Experiment—Drawing of Polypropylene Fibers.
The first version of a prototype of the drawing apparatus was built. The drawing apparatus comprises two endless chains as the conveyer-drawing members, non-driven, free-to-rotate rollers as the guide members of the displacing elements, and a heat chamber supplied with hot air. The feed and take-off devices or mechanisms were not built at this first stage. However, this type of mechanisms was proved to be feasible and was successively used in the industrial processes for heat setting of polymer fibers discussed above. The heat chamber of this unit was 1000 mm. long.
Polypropylene commercial resin from Amoco Chemical Co. (grade 10-6345) was used. The resin had the following parameters: Melt Flow Rate −3.1 gm/10 min., Mw=370,000, and MWD=5.6. It was extruded at 220° C. through the 0.5 mm spinneret orifice at very low take-up speed and quenched in a water bath at room temperature. Wide-angle X-ray diffraction pattern revealed that the as-spun fiber produced was unoriented and low-crystalline.
The drawing process was performed in two separate stages using the drawing apparatus twice, at different temperatures. These two stages of drawing represent two different drawing mechanisms occurring on the molecular level. The initial drawing stage converts the undrawn spherulitic as-spun fiber into a fiber with fibrillar structure developed through a necking-down mechanism. The first stage can be rapid. It is followed by the second drawing stage, which is named superdraw. The second drawing stage orients the newly formed fibrillar structure. This stage needs to be much slower to produce polymer fibers with improved physical properties approaching those achieved in lab-scale experiments mentioned above (V. A. Marikhin and L. P. Myasnikova, “Nadmolekulyarnaya Struktura Polymerov”, St. Petersburg, Russia, Khimia (1977); V. A. Marikhin and L. P. Myasnikova, Progr. Colloid Polym. Sci., 92, 39-51 (1993); W. N. Taylor and E. S. Clark, Polym. Eng. Sci., 18, 518-526 (1978)). The first stage can be performed by both conventional and the invented drawing methods. The slower second stage needs to be performed by the invented method and apparatus.
The heat chamber was preheated to given drawing temperatures (see Tables IV and V below) with the chains at rest. The front door of the chamber was opened, several loops of polypropylene fibers were placed about the receiving ends of the chains and supported by the rollers inside the heat chamber, the chamber door was closed, and temperature was raised to given temperatures for 30-300 seconds (see Tables IV and V). Then the driving electrical motor was turned on, and the chains started to move conveying the fiber loops through the heat chamber and simultaneously drawing the fiber. When the fiber reached the delivery ends of the chains, the equipment was stopped, the chamber door was opened, and the drawn fiber was cooled down for 20-300 seconds (see Tables IV and V) before being removed.
Tensile properties were measured by an Instron tensile-testing machine. The breaking length was 30 mm, and the lower clamp speed was 50 mm/min. Results can be seen in Table VI along with results on shinkage. Each result is an average of three tests. Results for conventional commercial polypropylene fibers are presented for comparison.
Thus the results of the first experiments confirm that the invented method is capable of producing industrial polymer fibers with superior physical properties in comparison with the conventional industrial processes and approaching those generated in the lab-scale experiments. Our results are very close to laboratory results reported in paper of Taylor and Clark (see Table VI) for regular-molecular-weight polypropylene fibers, i.e., our samples have tenacity 0.9-1.2 GPa (11-14.5 gpd) and tensile initial modulus 17.7-20.5 GPa (214-248 gpd).
As presented in Tale VI, for polypropylene fibers tenacity is increased by a factor of 1.2-3.0, initial modulus is increased by a factor of 4.8-8.5, and breaking elongation is decreased by a factor of 1.54 in comparison with conventional industrial processes. This is accompanied by excellent dimensional stability, i.e., hot-air shrinkage is 0-3% at 132° C.
As an example, stress-strain behavior of the samples 1 and 4 from Tables IV-VI is presented in
From the descriptions, calculations, and results of experiments given above, one or more of following advantages of the invented drawing method and apparatus in comparison with the prior art in industrial fiber drawing processes become evident:
1. The invented method and apparatus provide the fiber drawing in industrial environment at low fiber speed Vfiber and, at the same time, maintain fiber outlet speed Voutlet and fiber take-up speed Vtake-up up to 3000-6000 m/min and more providing high throughput. The ratio of speed Voutlet to speed (Vfiber)max is greater than 1 to 1 ranging from about 10 to 1 to about 9000 to 1. This accomplishment results in some other advantages presented below.
2. The invented method and apparatus provide the uniform fiber drawing in industrial high-throughput process at low strain rate Vstrain, i.e., about 6-70%/sec, and high drawing time T, i.e., it can reach tens of seconds. This long drawing time is necessary to heat the fiber to the elevated ambient temperature with low temperature gradient in the fiber cross-section during the drawing in order to have uniform morphology and physical properties in the cross-section.
3. The low-strain-rate, long-drawing-time invented method and apparatus provide more reliable high-throughput industrial process for continuous uniform drawing of polymer fibers without abrupt, “impulsive” acceleration resulting in lower tension in the drawing line, less breaks, less equipment stops, and less waste than in the prior art.
4. The invented method and apparatus for continuous fiber drawing provide high-throughput industrial process producing dimensionally stable, low-shrinkage fibers without using expensive and energy-consuming additional equipment while retaining enhanced physical properties, such as initial modulus, intermediate moduli, and tenacity, mentioned above. This may result in substantial saving of capital expenses, energy consumption, and possibility of smaller industrial space.
5. The invented method and apparatus provide high-throughput industrial continuous process for drawing of polymer fiber (both flexible-chain and wholly-aromatic) capable of improving their tensile properties (i.e., tenacity, Young modulus, intermediate moduli, etc.) approaching those obtained in laboratory experiments. This method is the missing link in development of a new generation of low-cost, high-performance industrial polymer fibers (most probably made of melt-spun, regular-molecular-weight polyester, nylon, polypropylene, polyethylene, and other flexible-chain polymers) having tenacity of about 1-2 GPa (12-22 gpd) and initial tensile modulus of about 20-100 GPa (250-1000 gpd) for different polymer fibers having different theoretical values of tensile properties. Thus, for the new generation of industrial melt-spun, flexible-chain polymer fibers, tenacity can be 1.5-2.0 times higher and initial moduli can be several times higher than for conventional commercial flexible-chain polymer fibers.
6. Our invention can accomplish all of the above because it overcomes limitations and operational problems of Sordelli discussed above in section BACKGROUND OF THE INVENTION. The invented method and apparatus have advantages in comparison with Sordelli as follows:
Thus, the reader can see that the fiber drawing method and apparatus of this invention can be used to produce industrial fibers at fiber speed (Vfiber)max substantially lower than outlet speed Voutlet and take-up speed Vtake-up and at substantially lower strain rate Vstrain, lower tension in the fiber drawing line, and longer drawing time T than in the prior art without reducing throughput.
This provides a basis for achieving some unprecedented results, i.e., producing industrially polymer fibers with improved tensile and other physical properties approaching those obtained in laboratory experiments. This means that the development of a new generation of low-cost, high-performance, flexible-chain industrial polymer fibers is feasible. On the one hand, tenacity of the new fibers can be ⅓-½ of that of high-cost, high-strength, high-modulus fibers (Kevlar 49®, Twaron®, Spectra®, Dyneema®, et al.) discussed above. On the other hand, the tenacity can be one and a half times and more higher than that of low-cost, low-performance commercial flexible-chain polymer fibers. Initial modulus and intermediate moduli can be increased even greater.
Furthermore, this invented method offers additional advantages.
The invented method resolves another fundamental problem of the fiber technology—how to produce industrial fibers having substantially improved both tensile properties and dimensional stability (low shrinkage) in the high-throughput process without utilizing special heat-setting equipment. This may result in substantial saving in capital expenses, and possibility of a smaller industrial space.
It also provides a more reliable process, which has fewer breaks and equipment stops, and lower waste resulting in substantial saving.
While the above description contains many specifics, these should not be considered as limitations on the scope of the invention, but rather as an exemplification of the presented embodiments thereof. Many other variations are possible. For example:
1. In the embodiments of
2. The invented drawing apparatuses can be arranged in a series or other treating devices may be provided between two drawing apparatuses of the invention; a consecutive arrangement of two or more invented apparatuses is especially advantageous for achieving the total draw ratios 10 to 1 and higher, like in case of gel spinning of ultra-high molecular weight polymers, or providing different drawing temperatures at different stages of drawing.
3. A conventional stage of drawing using cylindrical draw rollers may precede or follow the invented apparatus; the rollers can be used for fine and minute adjustment of the total draw ratio; the draw rollers can be constructed with or without internal heaters.
4. In the embodiment illustrated in
5. In another embodiment of the invention, each conveyer-drawing member (e.g., the threaded spindle or the chain) consists of three sections. In section I the conveyer-drawing members are arranged in parallel to the central axis, in section II they diverge from the central axis (as in the embodiments illustrated in
6. In the embodiment of
7. In the embodiments of
8. In another embodiment of the invention, the conveyer-drawing members are cantilever having either the delivery or receiving ends free, with no support. This is an alternative design to the embodiments of
9. In the embodiment of
10. In the embodiment of
11. In the embodiments of
12. In the embodiments of
13. The fiber draw ratio can be changed, in addition to that presented in the embodiments of
14. The fiber draw ratio can be changed, in addition to that presented in the embodiments of
15. In the embodiments of
16. In the embodiment of
17. In the embodiment of
18. In the embodiment of
19. In the embodiments of
Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.
This is a continuation-in-part of a prior-filed application (application Ser. No. 09/978,346, filing date—Oct. 16, 2001, status—abandoned).
| Number | Name | Date | Kind |
|---|---|---|---|
| 2302508 | Sordelli | Nov 1942 | A |
| 2372627 | Goggin | Mar 1945 | A |
| 2788542 | Swalm | Apr 1957 | A |
| 3426553 | Erb | Feb 1969 | A |
| 3774384 | Richter | Nov 1973 | A |
| 3978192 | Sussman | Aug 1976 | A |
| 4414756 | Simpson | Nov 1983 | A |
| 4891872 | Sussman | Jan 1990 | A |
| 4967457 | Beck | Nov 1990 | A |
| 4980957 | Sussman | Jan 1991 | A |
| 5339503 | Sussman | Aug 1994 | A |
| 5340523 | Sussman | Aug 1994 | A |
| 5522161 | Vetter | Jun 1996 | A |
| 5588604 | Vetter | Dec 1996 | A |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09978346 | Oct 2001 | US |
| Child | 11155810 | US |
