US3680753A

US3680753A - Constant tension strand feeding system

Info

Publication number: US3680753A
Application number: US73828A
Authority: US
Inventors: David E Shaw-Stewart
Original assignee: GOLDSWORTHY ENG Inc
Current assignee: GOLDSWORTHY ENG Inc
Priority date: 1970-09-21
Filing date: 1970-09-21
Publication date: 1972-08-01
Anticipated expiration: 1989-08-01

Abstract

A system for feeding a roving strand to a demand point where the system employs a driven capstan roller for receiving the strand from a strand supply. The strand is also passed around a dancer roller which is mounted on a pivotal arm, and then over a resin applicator to the demand point. The pivotal arm is mounted at a pivot and operatively actuates a rotary transducer which, in turn, controls the speed of the motor operating the capstan. Accordingly, as the demand for the strand increases, the pivotal arm is biased upwardly which, in turn, causes the rotary transducer to increase the speed of the motor operating the capstan. Constant tension is maintained on the pivotal arm by means of a cord which is connected to the arm and to the piston of a pneumatic cylinder. Air biases the piston in one direction causing the arm to be urged downwardly. Thus, by changing the air pressure against the piston, it is possible to change the tension maintained on the pivotal arm.

Description

United States Patent Shaw-Stewart [54] CONSTANT TENSION STRAND FEEDING SYSTEM [52] U.S. Cl. ..226/25, 226/42, 226/44, 226/195, 242/45, 318/6 [51] Int. Cl. ..B65h 25/08 [58] Fieldof Search ..226/42, 44, 195, 25, 30; 242/45, 147

[5 6] References Cited UNITED STATES PATENTS 1/1971 Ferguson ..226/195 X 6/1967 3,556,369 3,326,436 3,240,058 3/1966 Foster ..226/195 UX 2,981,491 4/1961 Eans ..242/45X Primary ExaminerAllen N. Knowles Assistant Examiner-Gene A. Church Attorney-Robert J. Schaap, John D. Upham and Neal E. Willis Huck ..226/44 X [4 1 Aug. 1,1972

[5 7] ABSTRACT A system for feeding a roving strand to a demand point where the system employs a driven capstan roller for receiving the strand from a strand supply. The strand is also passed around a dancer roller which is mounted on a pivotal arm, and then over a resin applicator to the demand point. The pivotal arm is mounted at a pivot and operatively actuates a rotary transducer which, in turn, controls the speed of the motor operating the capstan. Accordingly, as the demand for the strand increases, the pivotal arm is biased upwardly which, in turn, causes the rotary transducer to increase the speed of the motor operating the capstan. Constant tension is maintained on the pivotal arm by means of a cord which is connected to the arm and to the piston of a pneumatic cylinder. Air biases the piston in one direction causing the arm to be urged downwardly. Thus, by changing the air pressure against the piston, it is possible to change the tension maintained on the pivotal arm.

2 Claims, 4 Drawing Figures PATENTED B 1 I973 SHEEI 1 [IF 2 FIG.

INVENTOR DAVID E. SHAW- STEWART BYW%MW ATTORNEY FIGZ PATENTEDAUE 1 m2 SHEET 2 OF 2 ATTORNEY FEEDWG SYSTEM This invention relates in general to certain new and useful improvements in filament feeding systems and more particularly to a system which is capable of feeding filament at a relatively constant tension regardless of the demand thereon.

In recent years, the art of filament winding has received increased recognition. There appears to be an ever-increasing number and type of filament winding devices which are commercially available to producers of reinforced plastic products. However, it is well recognized in this industry that proper payout and careful control over the amount of tension maintained on this filament at all times in the operation are parameters which materially affect the quality of the final product.

In many winding operations, it is necessary to change the tension on the filament in accordance with the requirements in the final reinforced plastic product to be produced. Furthermore, the various winding systems impose limitations on the presently available feeding systems by constant tension changes imposed on the filament throughout the winding operation. Furthermore, surges of tension are created on the feeding device and these surges materially interfere with the quality of the filament wound.

It is, therefore, the primary object of the present invention to provide a filament feeding system to be used in filament winding devices and the like, where constant tension is to be maintained on the filament strands at all times.

It is another object of the present invention to provide a system of the type stated which employs a pneumatic device in order to maintain a constant tension in the filament feeding system.

It is a further object of the present invention to provide a system of the type stated which is highly efficient in its operation and relatively economical to manufacture.

With the above and other objects in view, my invention resides in the novel features of form, construction, arrangement and combination of parts presently described and pointed out in the claims.

In the accompanying drawings:

FIG. 1 is a schematic view of a filament feeding system constructed in accordance with and embodying the present invention;

FIG. 2 is a fragmentary horizontal sectional view taken along line 2-2 of FIG. 1;

FIG. 3 is an enlarged vertical sectional view showing a junction box which forms part of the filament feeding system of FIG. 1; and

FIG. 4 is a schematic view of an electrical circuit which forms part of the feedback controller illustrated in FIG. 1.

Referring now in more detail and by reference characters to the drawings, which illustrate a preferred embodiment of the present invention, A designates a filament feeding system of the type used with filament winding devices for winding of filament about a mandrel M. By reference to FIG. 1, it can be seen that the mandrel M, in this case, is rotated about an axis which is perpendicular to its longitudinal central axis. Thus a series of longitudinal layers or strands of filament or socalled roving S are supplied to the mandrel.

The filament feeding device generally includes a supply spool l of roving which is mounted on a pintle 2. Conventionally, the spool 1 is removably disposed on the pintle 2 for convenient changing of the supply of roving S. The roving S which is surface-pulled from the spool l, is trained about a capstan 3 and which is mounted on a shaft 4. A conventional D.C. electrical motor 5 drives the shaft 4 and capstan 3 in the manner as illustrated in FIG. 1. A conventional brake mechanism b is operatively connected to the shaft 2 in the manner as illustrated in FIG. 1 to maintain tension on the pintle 2.

The roving S is thereafter trained about a sensing roller 6 or so-called dancer pulley which is pivotally mounted on the free end of a pivotal bar or so-called dancer arm 7, the latter being pivoted intermediate its ends by means of a pivot pin 8 through a pivot joint 9. The pivot pin 8 is operatively connected to and operates a rotary transducer 10 which is essentially a variable transformer and which, in turn, controls the speed of the motor 5 through a feedback controller 1 1.

The roving material may be resin impregnated by means of a resin applicator 12 having a resin transfer roller 13 and which has a suitable surface for applying a resin matrix to the roving material S. The resin transfer roller 13 is, in turn, disposed in either slightly spaced relation to or contact with a pick-up roller 14, the latter being disposed within a resin tank 15. The gap between the transfer roller 13 and the pick-up roller 14 can be varied to control the amount of resin transfer. Any suitable resin matrix normally employed in reinforced plastic materials may be used in the resin tank 15. By further reference to FIG. 1, it can be seen that the pickup roller 14 is driven through a conventional D.C. electric motor 16, the speed of which is controlled by a tachometer 17, the latter being connected to the transfer roller 13. The transfer roller 13 is rotated through the action of the strand S passing over the roller 13. Thus, the speed of the pick-up roller 14 is also controlled to coincide with the rate of movement of the strand S through the tachometer l7 and the rate of speed of the D.C. electric motor 16.

Any continuous material or synthetic filament capable of being bent to conform to a desired shape can be employed in the present invention. The most preferred filament employed in the present invention is that made of glass. However, it should be recognized that boron filaments, carbon, and graphite filaments and filaments from lithium and other grown-whisker crystals can be employed. In addition, metal wire may be interspersed with the glass filaments in the event that it is desired to add some type of metallic body to the fiberglass reinforced structure which is produced, such as for electrical conductivity. Furthermore, quartz filaments may also be employed.

Any material which is normally liquefied or which is capable at some stage of the process of being liquefied and softened for a period of time may be employed as the resin hinder or so-called matrix." The matrix should be sufficient to flow into the filament and fill the interstices between adjacent filaments and layers thereof achieving a rigid state or completing polymerization to become a rigid solid. Furthermore, the matrix should possess the ability to adhere to the reinforcement. Some examples of the suitable binders or matrix which can be employed in the present invention are various thermo-plastic resins, such as nylon, polyethylene, polypropylene, many of the polycarbonates, etc. In addition, therrnosetting resins such as polyesters, many of the phenolics and epoxys, etc. can be used. Generally, the thermosetting resins should be capable of being fused into an insoluble, nonheat softening mass upon application of heat or similar method of triggering the catalytic system. Other binders or matrices are hard waxes, eutectic metals, synthetic rubbers, etc.

While the present invention has been described in terms of feeding roving material, it should be recognized that this feeding system is also useful in feeding any other types of materials where cyclic variations or surges may occur in the feeding line or in the demand requirements of the material.

The roving, which is unwound from the spool 1, is passed through a roving guide 18 which is more fully illustrated in FIG. 2 and which includes a pair of somewhat triangularly shaped blocks 19. It can be seen that the roving can be unwound from the spool at various points intermediate the two transverse ends of the spool 1. Accordingly, the roving is essentially guided into a straight path prior to training about the capstan 3 through the action of the roving guide 18. A second roving guide 18' is located between the transfer roller 13 and the mandrel M in order to guide the strands onto the mandrel M.

The dancer arm 7 is biased downwardly in a counterclockwise direction, reference being made to FIG. 1, about the pivot pin 8 by means of a cable 20, which is trained about a roller 21 and connected to a piston 22 forming part of a pneumatic cylinder '23. The cylinder 23 is connectedto a pneumatic junction box 24 which holds the roller 21 in the manner as illustrated in FIG. 1. The junction box 24 is provided with an air fitting 25 receiving air under pressure from a source (not shown). A fitting 25 is connected to the cylinder 23 so that the air biases the piston 22 to the right, reference being made to FIG. 1, thereby creating a tension on the cable 20.

The piston 22 is loosely fitted within the cylinder 23 so that the air can flow around the peripheral annular surface of the piston 22, but nevertheless, bias the piston 22 in the direction of the air exit from the cylinder 23. By virtue of the loose fit of the piston 22 within the cylinder 23, a high degree of sensitivity is achieved. Furthermore, the air flowing past the piston 22 creates an air-bearing effect. The air is fed to the cylinder 23 from an air reservoir which 'is large in volume with respect to the volume of the cylinder in order to reduce piston fluctuations.

The junction box 24 is more fully illustrated in the enlarged sectional view of FIG. 3. It can be seen that the junction box 24 comprises an outer housing 26 which receives one end of the cylinder 23 in the air duct 27. The fitting 25 is threadedly secured to an air duct 28 formed in the junction box 24 in the housing 26 and which communicates with the air duct 27. The roller 21 is disposed within a large central bore 29 and has the cable trained therearound in the manner as illustrated in FIG; 3. Furthermore, the cable extends around the roller 21 and into the duct 27 through a small aperture 29' and enables communication between the duct 27 and the large bore 29. The cable 20 should preferably be formed of steel and may be provided with a vinyl sleeve or Teflon sleeve, or at least Teflon coated in the area of the aperture 30. In this manner, the cable 20 is capable of sliding through the aperture 30 and also maintaining somewhat of an air seal between the bore 29 and the cylinder 23.

A conventional break spring tension motor t is also connected to one end of the arm 7 in order to maintain a proper bias on the arm 7. Inasmuch as the arm 7 with the various components suspended thereon has some appreciable weight, the spring motor t will maintain the arm in somewhat of a freely suspended state on the pivot pin 8. Accordingly, only the demand created by the strand S will afiect the movement of the arm 7.

The feedback controller 11 is more fully illustrated in FIG. 3 and includes the rotary transducer 10, which is illustrated as being operatively connected to the arm 7. The transducer 10 receives a 500 cycle per second signal from a conventional oscillator 30' and is capable of introducing a position signal from the transducer 10 to a phase detector 31. The transducer 10 includes a primary transformer winding and a secondary transformer winding (not shown). The oscillator feeds the input signal into the primary winding.

The output of the secondary winding of the transducer 10 would normally be in phase with the input to the primary winding at zero speed of the motor 5 which will result in a zero voltage output from the transducer 10. As the arm 7 lifts due to an increased demand on the strand S, a lag or lead will occur between the signal from the primary and secondary windings of the transducer 10 and this lag or lead will be detected by the phase detector 31. Furthermore, the change in position of the arm 7 will also change the voltage generated by the transducer 10. The amplitude of the voltage in this leading or lagging signal will be proportional to the required change of speed in the capstan 3. The lag or lead of the signal provides an indication of the direction of movement of the arm 7 and the amount of voltage of the signal is proportional to the amount of movement of the arm 7, which is, in turn, proportional to the speed of the motor 5.

A tachometer sample amplifier 32 is connected to the motor 5 in the manner as illustrated in FIG. 3. The tachometer sample amplifier 32 also has an output connected to an integrating amplifier 33 which receives an input from the phase detector 31. If the motor 5 is operating at a higher rate of speed, the integrating amplifier 33 will subtract the signal from the phase detector 31 with respect to the signal from the tachometer sample amplifier 32. In like manner, if the motor is running at a slower speed the integrating amplifier 33 will add the signal from the phase detector 31 with respect to the signal from the tachometer sample amplifier 32. The signal from the integrating amplifier 33 is then inverted by means of an inverter 34 and transmitted to a timing generator 35.

The timing generator 35 also is connected to the tachometer sample amplifier 32 and receives an input from a zero crossing detector 36. The zero crossing detector 36 is connected to a line voltage such as a 60 cycle A.C. voltage source. Finally, the timing generator 35 has an output connected to a forward-reverse direction flip-flop 37 which has two outputs connected to an SCR motor driving circuit 38. The two outputs from the flip-flop 37 provide both the forward and reverse direction signals to the motor driving circuit 38. By further reference to FIG. 3, it can bee seen that the output from the motor driving circuit 38 is, in turn, connected to the motor 5 to enable operation of the motor 5 at the desired speed.

The motor driving circuit 38 also has an inhibit line 39 which may be connected to the equipment (not shown) in which the filament feeding circuit of the present invention is associated. Thus if the equipment is de-energized, the motor driving circuit 38 will automatically de-energize the motor 5.

It should be observed that when the motor 5 is operating the voltage input, the motor 5 will actually drive the capstan 3. When no voltage is imposed on the motor S, that is at a time when the driving circuit 38 is not firing, the motor 5 will still operate the capstan 3 but will partially act as a generator. A sampling of the voltage on the terminals of the motor 5 is made by the tachometer sample amplifier 32 at the time when the motor driving circuit 38 is not operating. The timing generator 35 will generate a series of ramp wave pulses and each of these pulses will be initiated at the time of zero crossings of the sine wave in the zero crossing detector 36. Furthermore, the signal from the transducer 10, as it passes through the inverter 34, will be either rising or falling in a linear manner. As long as this signal from the inverter 34 is above the peak of the ramp waves generated in timing generator 35, the motor driving circuit 38 will not fire. However, when the level of the signal from the inverter 34 falls below the peak of the ramp waves generated in the timing generator 35, then the motor driving circuit 38 will be caused to fire the SCR drive to the motor 5.

It can be observed that the forward-reverse direction flip-flop 37 is also connected to the phase detector 31 in the manner as illustrated in FIG. 3. This connection enables the forward-reverse direction flip-flop to energize either one of the lines connected to the motor driving circuit 38. Thus, as a lag is occurring from the transducer 10, the signal will be transmitted from the flipflop 37 over one of the lines to the motor driving circuit 38. On the other hand, if a lead occurs in a signal from the transducer 10, the signal from the flip-flop 37 will be transmitted over the other of the lines to the motor driving circuit 38.

It can thus be seen that the capstan 3 will rotate at a particular rate which is consistent with the demand for the filament strands S. Thus, if the demand should increase, the feedback controller 11, which is actuated by the arm 7 will cause an increase in the rotation of the capstan 3. Accordingly, a greater amount of strand per unit time will be removed from the spool 1 and supplied to the mandrel M. In like manner, if the demand for the strands S should decrease, the feedback controller 1 1 will cause the motor 5 to reduce the speed of the capstan 3. In this manner, the amount of strands removed from the spool 1 will decrease. It can thus be seen that the position of the arm 7 will regulate the speed of the capstan 3, and hence, the amount of strand supplied to the mandrel M. Furthermore, the amount of tension maintained on the arm 7 can be carefully te 7thr th bl 20.

lifiibfild u iiiiersto at clianges and modifications in the form, construction, arrangement and combination of parts presently described and pointed out may be made and substituted for those herein shown without departing from the nature and principle of my invention.

Having thus described my invention, what I desire to claim and secure by Letters Patent is:

1. An apparatus for supplying a strand of material with relatively constant tension maintained thereon pursuant to demand for said strand, said apparatus comprising means for supplying said strand, motive means for moving said strand from said source to a point of demand, a pivotal member operatively associated with said strand and being urged in a first direction when demand for said strand increases, said pivotal member being comprised of an arm pivoted centrally of its ends, and a roller mounted on one end of said arm and having said strain trained thereabout to bias said arm in said first direction, control means operatively connected to said pivotal member and motive means for controlling the rate of movement of said strand pursuant to demand thereon, and fluid power means operatively connected to said pivotal member and urging same in a second direction to maintain a relatively constant tension on said strand, said fluid power means comprising a pneumatic cylinder with a piston movable therein, a cable connecting said arm on the same side of the pivot point of said arm as said roller to said piston and means for supplying air under pressure to said cylinder to urge said piston in such manner to bias said pivotal member in said second direction.

2. An apparatus for supplying a strand of material with relatively constant tension maintained thereon pursuant to demand for said strand, said apparatus comprising means for supplying said strand, motive means for moving said strand from said source to a point of demand, a pivotal member operatively associated with said strand and being urged in a first direction when demand for said strand increases, control means operatively connected to said pivotal member and motive means for controlling the rate of movement of said strand pursuant to demand thereon, said control means comprising a transducer which measures the positional change of said pivotal member as it pivots about its pivot point, means for introducing a first electrical signal representative of a first position of said pivotal member, means for generating a second electrical signal from pivotal movement of said pivotal member, means for comparing the phase difference of said first and second signals, and means for generating a corrective signal to said motive means in response to the phase difference and fluid power means operatively connected to said pivotal member and urging same in a second direction to maintain a relatively constant tension on said strand.