US2942303A

US2942303A - Control for drafting apparatus

Info

Publication number: US2942303A
Application number: US641410A
Authority: US
Inventors: David A Bossen; Glenroy W Barnett
Original assignee: Industrial Nucleonics Corp
Current assignee: Industrial Nucleonics Corp
Priority date: 1957-02-20
Filing date: 1957-02-20
Publication date: 1960-06-28
Anticipated expiration: 1977-06-28
Also published as: GB887266A

Description

June 28, 1960 D. A. BOSSEN ETAL 2,

CONTROL FOR DRAFTING 'APPARATUS Filed Feb. 20, 1957 30 44 HEN- 32 TRANSMISSION 34 ll IQ 8 I7 INVENTORS DAVID A. BOSSEN GLENROY W. BARNETT United States Patent 2,942,303 CONTROL FOR DRAFTING APPARATUS David A. Bossen and Glenroy W. Barnett, Columbus,

Ohio, assignors to Industrial Nucleonics Corporation Filed Figaro, 1957, Ser. No. 641,410

. 6 Claims. (CI. 19-70) This invention relates to an apparatus for drafting textile fibers, as in a sliver or roving, and more particularly it relates to an automatically controlled drafting mechanism whereby the weight per unit length of the output sliver is maintained substantially constant.

duction in Weight per unit length is effected by running the draft rolls with a. peripheral speed which is faster than the speed of the fallers.

As is generally the case in the usual drafting operation,

the weight of the outgoing sliver is established with respect to the weight of the incoming slivers by setting up a suitable fixed ratio between the speed of the fallers and that of the draft rolls. While this results in a fairly constant predetermined reduction in the weight of the outgoing sliver with respect to the incoming slivers, the output sliver reflects all of the variations in the weight per unit length of the input slivers.

More specifically, the fixed ratio of speed between the draft rolls and the fallers does not compensate for variations in the weight per unit length-of the input slivers; hence, corresponding variations in weight are retained in the output sliver.

In accordance with the teachings ofthe present invention, it has now been found possible to achieve excellent control of weight uniformity by means of an improved automatically controlled drafting apparatus employing a nuclear radiation gauge as the weight-measuring element. Furthermore, the system of this invention may be incorporated into a variety of presently existing machines, and without extensive modifications thereto.

According to this invention, a source of penetrative radiation and a radiation detector are'provided for producing a signal indicative of the actual weight per unit length of the sliver issuing from the gill box. Means are provided for makingavailable a continuously variable speed ratio between the fallers and the draft rolls and this speed ratio is continuously and automatically readjusted as necessary by a feedback control device responsive to any deviation in the output sliver weight from the desired value. j

It is therefore a primary object of this invention to provide a new and improved textile fiber drafting apparatus whereby the weight per unit length of a processed sliver, roving and the like can be maintained constant at any desired value. i

It is another object to provide an automatic gauging device capable of continuously and accurately indicating the weight per length "of a traveling stream of textile V Patented June 28, 1960 ice It is a further object to provide aneffective and reliable means for automatically regulating the draft of a textile fiber processing machine.

It is again an object to provide an automatic draft regulating system whereby sliver uniformity is accurately maintained despite unavoidable variations in slip between the fibers and the draft rolls or other cooperating machine elements. 7 f

'It is' a still further object to provide an automatic draftregulating system employing a speed variation device wherein the accuracy of control does not depend on reproducibility of speed output versus control setting of the speed variation device.

It is also an object to provide means for continuously and accurately measuring the weight per unit length of a traveling sliver issuing from a drafting apparatus, and to provide-an automatic control system responsive to the output of the measuring device for maintaining the weight per unit length of the sliver constant at any desired predetermined value.

Likewise it is an object to provide measuring and control apparatus in accordance with the aforesaid objects which may be readily adapted for installation on existing machines without extensive modifications thereof.

It is an additional object to provide apparatus capable of fulfilling the above objects which is relatively inexpensive to manufacture, simple to operate, and which requires a minimum of adjustment and maintenance.

These and further objects and advantages of the invention will become more apparent upon reference to the following specification and appended drawings in which:

Figure l is a schematic diagram of the mechanical and electrical elements of a typical apparatus in acrolls 11 and 12, a faller section indicated generally by the numeral 13, anda set of delivery rolls 14 and 15. The fallers comprise a plurality of faller bars as at 16, each of which is equipped with a plurality of protruding pins or quills as at 17 which are employed to mix, comb, parallel and draw the fibers which constitute the slivers 10. The fallers are divided into an upper and a lower set, whichare driven respectively bytwo upper pairs of axially parallel, rotating screws 18 and 19', and two lower pairs of similar screws 20- and 21. i The slivers 10 entering the gill box between feed roll 11 and 12 are engaged by the downwardly extending pins on the faller bars driven by the pair of screws 19, and are also engaged by the upwardly extending pins on the faller bars driven by the pair of screws 20. The rotations of the screws 19 and 20 carry the fallers engaging the slivers to the right until they reach the output endof the faller section, at which point the upper fallers are lifted in succession by suitable cams (not shown) in the manner of the faller 22, shown'moving vertically in :the direction of the arrow 23. Also the lower fallers are allowed to fall in succession out of engagement with the slivers in the manner of the faller 24 shown moving vertically downward in the direction of the arrow 25. The fallers in the extreme upper and lower levels are then returned to the feed end of the faller section by the

rotating screws

18 and 21, whereupon the fallers in the extreme 'upper level are allowed to fall again into enof raw slivers gagement with the slivers 10. Also, suitable cams lift the fallers in succession from the extreme lower level back into engagement with the slivers 10. In this manner there is a continuous recirculation of the fallen: in the upper and lower faller sets. 7

A source of mechanical power, here represented as a motor 30, is utilized to drive thefaller section 13 and the feed rolls 1 1 and '12 through suitable couplings rep- =resentcd by the

dotted lines

32 and 34. By-suitable-selection of fixed gear ratios or other means, thereis provided a speed differential between the surface speed of the feed roils l1 and 1-2 and the surface-speed f the fallers engaging the slivers, so that the fathers travel faster than the feed rolls. The ratio of the speed of'the .fallers to that of the feed rolls 11 and 12 is referredto as the back draft. The delivery rolls '14 and 15 are driven at a faster surface speed than that of the fallers. The ratio of these'two speeds is referred to as the front draft.

:In the illustrative drafting apparatus shown in the figure, the sliver exiting from the delivery rolls l4. and I is drawn through a set of calender rolls 37 and 38 and into a coiler, represented as a coiling can. 40. The calender rolls and the coiler are coupled directly to the delivery rolls Y14 and 15 as indicated by the

dotted lines

35 and 36, and in order to secure good loading into the can the coiler takes up the sliver at a slightly greater linear speed than that of the delivery roll periphery. There is thus a very slight reduction in the weight of the sliver between the delivery rolls and the sliver can.

Of great importance in a drafting operation as herein exemplified is the total material draft; that is, the ratio of the weight per unit length of the input slivers to the weight per unit length of the output sliver entering the coiler 40. While the material draft 'is dependent on the mechanical speed ratios of back draft, front draft and coiler draft, it is not necessarily a simple positive function thereof, primarily due to varying degrees of slippage between the slivers and the tractive machine elements, which is in turn dependent on the characteristics of. the fibers, the preparation of the inputslivers and the characteristics and mechanical condition of the drafting machinery.

Therefore, item be seen that the main factors causing the output sliver to deviate from the desired weight are the variations in material draft with a given mechanical draft and the reappearance of input sliver weight variations in the weight of the output sliver, as pointed out h'ereinabove.

According'to this invention, it is found that these deviations can be substantially eliminated if the draft is made variable and continuously readjustable by an automatic feedback controller responsive to the actual weight per unit length of the sliver as measured by an accurate weight gauge installed on the output side of the delivery "rolls. The preferred forms of the invention include .a variable ratio transmission supplementing the conventional change gears or other means whereby the mechanical draft ratio is fixed in the usual apparatus. A number of suitable transmissions providing for a continuously variable speed ratio between an input and output shaft are available. As an example, a transmission which is manufactured and marketed by the Cleveland Worm and Gear Company of Cleveland, Ohio, under their trade name of Speed Variator, has been :found satisfactory for this application. In Figure 1, the transmission 42 is equipped with a control shaft 44 whereby the speed of the output shaft 46 may be adjusted over a continum with relation to the speed of the input shaft 48. In this figure, it is seen that the feed rolls l1 and 12 and the faller section 13 are coupled directly to the power source represented by the m0tor30 so as to be driven at an cssentially constant speed, whereas the delivery rolls 14 and 15, the calender rolls 37 and 38, and the coder 40 are driven through transmission 42 whereby the speeds of these latter machine elements may be adjusted over a 4 continum by means of the control shaft 44 of the transmission 42. h

It should be particularly pointed out here that it is entirely a matter of choice that the functional location of the transmission 42 is as herein illustrated, since equal- 13/ satisfactory results have been obtained by coupling the motor 30 directly to 'the "

shafts

35 and 36 while driving the shaft 32 through the variable transmission. Therefore the choice is governed mainl-yby the relative amount of driving torque imposed'on the transmission 42 and the mechanical inertia and momentum of the machine elements driven thereby. For example, in at least on well-known type of gilling'mac hine the feed rolls 11 and 12 are not used, but rather the slivers 10 are fed directly into the faller section 13. In this case, it has been found that the power required to drive and to accelerate the fallers is so much less than the power required to drive and accelerate the draft rolls, calender rolls, and the coiler, that a much lighter and less expensive transmission may be utilized when the faller speed is made variable, thereby decreasing the cost of the control system without affecting the quality of its performance.

Located adjacent to the exit side of the delivery rolls l4 and 15 there is located a weight sensing element utilizing a radiation source 50 and a radiation detector 52. The radiation source 50 maybe any suitable radioactive source of penetrative radiation, but is preferably a source of beta rays which are emitted by an isotope such as strontium-90. The detector 52 may comprise an ionization chamber, Geiger-Mueller tube, scintillation counter or crystal detector, although the ionization chamber is preferred for this type of measurement. The source and detector are preferbaly arranged on opposite sides of a pass tube '54 through which the sliver travels on its Way to the coiling can 46. The pass tube '54 is designed to form a continuous metal surface surrounding the sliver on the side adjacent the source 50 as one of a'number of safeguards against the possibility of contamination of the sliver in the event of damage to the hermetically sealed capsule containing the radioactive substance. Since beta radiations are characterized by relatively low penetrating power, the pass tube 54 may have externally milled thin-walled sections at the diametrically opposite sides adjacent the source and detector to permit passage of a substantial quantity of radiation through the pass tube and the fibers passing therethrough, as is best shown in Figure 3.

At 56 is a suitable inlet guidefunn'el or trumpet which gathers the incoming fibers composing the sliver into a bundle of circular cross-section for transit through the pass tube 54, and at 58 an output guide funnel prevents spreading of the fibers in the pass tube. The respective orifices in the

guides

56 and 58 are of smaller diameter than the interior of the pass tube 54- in order to prevent the abrasive action of the fibers from producing excessive wear on the pass tube which could otherwise result in a change in its necessarily constant radiation absorption characteristics, thereby adversely affecting the accuracy of the gauge calibration.

In the schematic diagram of Figure l, for clarity the positions of the source 50 and the detector 52 have been rotated degrees from the positions they occupy in the actual apparatus. Figure 2 is a properly oriented elevation of the source/detector unit looking into the outlet guide funnel 58, and Figure 3 is a section on the line 3-3 of Figure 2.

The guide funnels 56 and 58 preferably are replaceable members secured in the housing 57 which contains the source 50, detector 52 and the pass tube 54. These funnels extend only part way of the length of the pass tube, leaving an open area in the center thereof to permit passage of beta radiation from the source 50 to the detector 52. It hasbeen found advantageous to provide an opening 59 in the bottom of the housing 57 and the pass tube 54 to allow dirt or loose fibers carried by the sliver to fall out and preventtheir collection in the pass tube to the detriment of accurate measurement of the sliver per se. V

The gauge includes the source 50, detector -2, resistor 60, a feedback amplifier 62, a calibrating and standardizing network 68 and an indicating device 72.

The automatic controller comprises a comparator network 84, and an integrating velocity servo system 102-114 including a gear reducer 106 through which the servo motor 104- may drive the-control shaft 44 which regulates the speed ratio of transmission 42.

.It is well known that the absorption of penetrative radiation is a function of the mass of a material interposed in the path of the radiation beam. The measured unit length of the sliver is constant, and is determined bly the length of the detector disposed parallel to the s rver.

The amount of radiated energy received by the detector is an inverse function of the weight per unit length of the sliver, and therefore the response 'of the detector is a reliable measure of weight per unit length.

The electrical output signal developed by the detector is a minute current which flows through a resistor 60 having a veryhigh impedance. A voltage proportional to current through the detector 52 is thereby developed across resistor 60, and this signal is utilized by the measuring system of the gauge to provide an indication of the weight of the fibers passing between the source 50-and the detector 52.

The measuring system comprises a feedback amplifier 62 with an input on line 64 and ground reference 66, a calibrating and standardizing network indicated generally at '68, and the weight indicator 72. In operation the signal voltage developed across resistor 60 is compared with a fixed voltage from the network 68, this latter voltage always being subtracted algebraically from the signal voltage so that the amplifier responds to the difference. The output of the amplifier on line 70 is coupled back to the input 64 through the network 68 and resistor 60, so as to maintain the amplifier input at substantially zero or ground potential at all times. Thus the amplifier output voltage between line 70 and ground isautomatically maintained equal to the algebraic. difierence between the voltage developed across resistor 60 and the fixed voltage from the network 68. The amplifier 62 therefore performs an impedance matching function in transforming a high impedance signal into a robust signal for operating the controller and the indicating meter 72, and. this is accomplished without appreciable distortion of the signal, through the agency of the substantially total inverse feedback arrangement. The indicator 72 is responsive to any output voltage from the amplifier 62, and its pointer will be deflected to either side of its zero center position depending on the polarity of this output.

It can be seen that the calibrating potentiometer 74 provides an adjustment whereby the zero center position of the indicator can be made to correspond to any selected value of fiber weight which it is desired to place at the center of the scale associated with the indicator. Potentiometer 76 is provided to allow an adjustment of the span of weight deviations, on each side of the center value, which are readable on the indicator scale. Thus the indicator scale may be calibrated directly in any desired units of weight per unit length such as grains per yard or ounces per 5 yards. Potentiometer 78 and resistor 80 determine the portion of the voltage from the voltage source 82 which is available across potentiometer 74 to provide the opposing voltage in the measuring system. Potentiometer 78-is therefore the means of standardizing the gauge so that the total voltage available across potentiometer 74 may be restored at any time to the exact value of the maximum voltage developed across resistor 60 when no material is interposed between the source 50 and the detector 52.

The measuring system briefly described above is the *6 subject of a co-pending application Serial No. 628,999, filed December 18, 1956, by Sidney A. Radley and accordingly the full details thereof are not included in this specification.

The voltage output of the amplifier 62 which appears on line 70 is indicative of the weight of the sliver passing between the source 50 and the detector 52. This signal, which energizes the weight indicator 72, also provides the input to the automatic controller. The network 84 provides a voltage signal representative of the desired weight of the sliver. This voltage is continuously subtracted from the voltage signal representing the measured weight of the sliver, so that the difference voltage appearing on line 86 at the junction of

resistors

88 and 90 is a signal representing the direction and magnitude of the error in the measured weight of the sliver.

The selected weight of the sliver which is desired to be maintained constant by the automatic controller may be preset by means of potentiometer 92 in the'network 84, that is, the setting of this potentiometer determines the direction and magnitude of the comparison voltage representing the desired weight. The bridge circuit 84, comprising potentiometer 92 and a pair of

identical precision resistors

94 and 96, is energized by a voltage source represented bythe battery 98. The voltage available across the bridge is adjustable by means of potentiometer 100. The potentiometer 92 may therefore be equipped with a graduated dial and calibrated directly in any desired units of weight per unit length to agree with the scale of the weight indicator 72. This provides a direct reading indication of the setting of the control point, independent of the calibration of the weight indicator 72.

The error signal appearing on line 86 provides an input voltage to the servo amplifier 102 which energizes the servo motor 104. The motor 104 drives the control shaft 44 of the variable ratio transmission 42 through reduction gears 106. The servo motor 104 also drives a tachometer generator 108 which develops a DC. voltage having a polarity in accordance with its direction of rotation and a magnitude proportional to its speed. The tachometer .output voltage appears across the voltage divider network of potentiometer3110 and resistor 112. Depending on the setting of potentiometer 110, a portion of the tachometer voltage is fed back through resistor 114 to the input of the servo amplifier 102 in opposition to the error signal voltage.

The servo amplifier 102 is designed to have an almost infinite forward gain so as to saturate on a very small input signal. If the input voltage representing an error in measured sliver weight has a certain polarity, the servo motor 104 will be driven with full acceleration in one direction. If the error voltage has the opposite polarity, the motor will accelerate in the opposite direction. The motor will continue to accelerate until the voltage derived from the tachometer becomes equal and opposite to the error signal, at which time the input to the servo amplifier on line 86 is reduced to zero. At any greater speed the tachometer output through resistor 114 would become larger than the error signal, so that the input to the servo amplifier 102 would have the opposite polarity, tending to energize the servo motor 104 to drive in the opposite direction. It can be seen that by this means the speed of the servo motor 104 and the rate of readjustment of the speed ratio between delivery rolls 14 and 15 and the faller bar section 13 is maintained instantaneously proportional to the magnitude and direction of the error in the measured weight of the sliver. Therefore, over any given period of time, the total amount of adjustment applied to the control shaft 44 is proportional to the time integral of the error signal receivedover the same period of time. V The rate of. correction to the control shaft 44 per unit of error in measured sliver weight. is referred to as'the gain of the control system. The maximum available gamma gain of the system is dependent on the ratio selected for the speed reduction gears 106. The gain is variable. over a suitable range by adjusting potentiometer 110;- which determines the portion of the tachometer voltage which is fed back to cancel the" error'signal. Potentiometer 110 therefore determines 'the' speed of the servo motor 104 which will be' maintained for a given amount of error in sliver weight; a V r The maximum permissible gain of the control system is definitely limited by transportation lag, that is; the length of time required for the effect of a step' change in the setting of shaft 44' to be observed as a change in weight of the sliver passing between the" source 50 and the detector 52. If the gain is set too high, an existing error will be over-corrected before the gauge is able to see that sufficient correction has already been applied". Hence the drawing process is caused to cycle or perform forced oscilla'tions around the desired sliver weight. On the other hand, it is desirable to keep the gain as high as possible to secure optimum performance from the controller.

The control system briefly described above is the subject of a co-pending application Serial No. 641,414, filed February 20, 1 957, by Philip Spergel and Sidney A. Radley and accordingly the full details thereof are not included in this specification.

The present invention has been herein illustrated in a specific embodiment, namely, in conjunction with a particular form of gilling apparatus normally'used in the woolen industry. However, it willbe evident that the spirit and scope of the invention not only embraces the use of the disclosed principles in other forms of fiber drafting apparatus also in common use in the woolen industry, but is equally well applicable to other textile or related industries.

Obviously most conventional cotton drawing frames or synthetic fiber drafting apparatus may be readily modified to incorporate the advanced control techniques herein exemplified. For instance, either a single set of rolls or a plurality of roll. sets may be employed in place of the taller bar. section 12, with the control system of the present invention utilized to vary the speed of one or more sets of rolls at the drafting or the entry end of the system or in an intermediate location. Many other modifications can be made without departing from the scope of the invention as set forth in the letter and range of equivalency of' the appended claims.

Whatis claimed is:

1. An apparatus for measuring the weight per unit length of a traveling workpiece of mingled textile fibers, comprising aradioactive source of penetrative radiation and a radiation detector disposed on opposite sides of said workpiece; confining means encircling said workpiece for guiding the same between said source and said detector, said confining means having a central aperture for shaping the cross-section of that portion of said workpiece passing in measuring relation between said source and said detector; a pass tube encircling said workpiece adjacent said confining means, said pass tube having a larger cross sectional area than said aperture in said confining means and having two diametrically opposite radiation-transmitting thin-walled portions respectively adjacent said source and said detector, a downwardly opening exit passage piercing said pass tube for preventing the accumulationtherein of loose material particles carried by said workpiece, and means for registering the output of said detector.

2. Apparatus for drafting an elongated workpiece of mingled fibers, wherein said workpiece passes in succession through first and second machine elements in tractive engagement with said workpiece for drafting the same, comprising afirst driving means for driving said first machine element at a predetermined speed, a second driving means for driving said second machine element at a speed not lessthan the speed of said first machine element thereby to effect an increase in the length of said workpiece and a concomitant decrease in its weight per unit length, means for adjusting the ratio of the speeds ofsa'id first and second driving means, a source of penetrative radiation and-a radiation detector mounted adjacent the workpiece output side of said s'eco'nd machine "element; confining means encircling said workpiece for guiding the same between said source and said detector, said confining means having a central aperture for shaping the crosssection of that portion of said workpiece passing, in measuring relation between said source and said detector; a pass tube encircling said workpiece adjacent said confining. means, said pass tube having a larger cross sectional area; than said aperture in said confining means and having two diametrically opposite radiation-transmit tin'g thin-walled portions respectively adjacent said source and said detector; means utilizing the output of said detector for generating an electrical signal indicative of the weight per unit length of said workpiece, and control means responsive to said electrical signal for actuating said speed ratio adjusting means so as to maintain the weight per unit length of said workpiece substantially constant.

3. Apparatus as in claim 2 wherein said source of penetrative radiation comprises a radioactive emitter of beta rays.

4. Apparatus asin claim 2 wherein said electrical signal generating means comprises electrical impedance means connected to said detector for producing a first voltage proportional to electrical current through said detector, an electrical network including a' voltage source for producing a second voltage opposing said first voltage; a feedback amplifier responsii e to the diiference between said first and second electrical signals, said amplifier having an input, an output, and a feedback loop including said high impedance and said electrical network connecting'the output of said amplifier to the input thereof so as to maintain said input at substantially zero potential; said amplifier output providing said electrical signal.

5. Apparatus as in claim 4 wherein said network includes first. potentiometer means for calibrating said op posing voltage and second potentiometer means for standardizing said calibrating means.

6. Apparatusas in claim 2 wherein said electrical signal comprises an output voltage, and wherein said control means comprises adjustable means for selecting a value of said output voltage corresponding to a desired value of the weight per unit length of said workpiece, circuit means for comparing" said output voltage with said selected value to derive a control voltage indicative of the difference therebetween, a servo motor, means connected to said servo motor for generating a rate signal voltage indicative of the direction and speed of operation of said servo motor, a servo amplifier having an output adapted to drive said servo motor and a control input for regulating said driving output so as to control the direction of operation of said servo motor, adjustable circuit means for connecting said control voltage and said rate signal voltage'in mutual opposition to said control input of said servo amplifier, and mechanical means connecting said servo motor to said speed ratio adjusting means for said first and second machine element driving means.