US2985944A

US2985944A - Control apparatus for bias-cutting machine

Info

Publication number: US2985944A
Application number: US578792A
Authority: US
Inventors: David N Judelson
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-04-17
Filing date: 1956-04-17
Publication date: 1961-05-30
Anticipated expiration: 1978-05-30

Description

May 30, 1961 D. N. JUDELSON CONTROL APPARATUS FOR BIAS-CUTTING MACHINE Filed April 17, 1956 AAAAA nun-nu IN VEN TOR.

5 5 mm T w M m V M.

CONTROL APPARATUS FOR BIAS-CUTTING MACHINE The present invention relates generally to machines for cutting material on the bias, and in particular to an improved method and apparatus for feeding a seamed tube of material through a bias-cutting machine. This application is a continuation-in-part of my earlier filed application Serial No. 446,374, filed July 28, 1954, now United States Patent No. 2,772,734 of December 4, 1956.

Known machines for bias-cutting material usually include a mandrel over which a seamed tube of material is drawn in a spiral path past a cutting knife which severs the tube into a continuous length of material cut on the bias. The tube of material is pulled over the mandrel and past the knife by appropriate pulling mechanisms, which usually serve as the windup device for the continuous length of bias-cut material. The material is fed to the mandrel from a material supply, which may take the form of a roll of material carried on a rotatable turn buckle, or similar rotary feeder which is intended to present the tubular material to the mandrel in correct rotational orientation. The spiralling of the material about the mandrel, which is a function of the take-off rate as established by the pulling or windup mechanisms, determines the rate of rotational presentation of the material at the input end to the mandrel.

In an attempt to achieve substantial automatic operation, it has been suggested in the prior art that a variable speed drive be used in conjunction with the conventional rotatable feeder for presenting the tubular mandrel in correct rotational alignment. Such variable speed drive, apart from its inherent complexity, requires very precise and critical adjustment to obtain delivery of the tube of material in substantial synchronism with take-01f of the bias-cut material. That is, the pull exerted by the windup mechanism produces a spiral movement of the tubular material about the mandrel, which spiral movement manifests itself as a linear component of advance along the mandrel and a rotational component of displacement about the mandrel. The tubular material must ,be presented at the input end of the mandrel in untwisted condition to prevent the formation of wrinkles in the material and/or the creation of drag and other distorting forces. When the take-oflf rate varies, as when the degree of biasing is changed, it is necessary to readjust the rotational feed rate of the variable speed drive. Practical experience indicates that variable speed drives are exceptionally difiicult to use for this type of operation, in part because of the required preciseness of adjustment. Too frequently, the most precise adjustment of the variable speed drive is to no avail in that the smallest rotational error in initial adjustment becomes cumulative with successive rotations. For example, if there is a 1 overfeed or underfeed of the material in a single cycle, within three hundred sixty revolutions of the rotary feeder, the error is compounded I to the point where the material is one whole turn leading or lagging the travel of the material about the mandrel. Despite the alleged eflicacy of variable speed drives for all practical purposes they are to no avail United States Patent 2,985,944 Patented May 3Q, 1961 in that an operator is required to constantly readjust the drive to obtain proper feed of the material to the bias-cutting machine.

Broadly, it is an object of the present invention to provide an improved feeding and control mechanism for bias-cutting machine which obviates one or more of the sion.

It is a still further object of the present invention to provide means for rotationally presenting material to a bias-cutting machine at a rate which may be corrected in accordance with variations in the take-off or windup of the bias-cut material. I

In my copending application, there is disclosed a feeding and control mechanism for bias-cutting machines in which the occurrence of seams in the bias-cut material is used as a standard or monitor for controlling the ro tational feed or presentation of material to the mandrel. As detailed in said copending application, for each spiral or revolution of the feed tube of material about the mandrel, a segment of the seam appears angularly across the width of the bias-cut material. That is, for each revolution of the tubular stock about the mandrel, "a seam extending angularly across the bias-cut material is presenting at or moving toward the windup mechanism. This principle was employed in said copending application to correct the rotational presentation of the material during each spiral or revolution of the tubular stock about the mandrel. Specifically provision was made to interrupt the drive to the turn buckle during each cycle of operation, the drive being restored upon sensing of a seam as a measure of the take-ofi rate.

.By making the rotary feeder or turn buckle turn at a rate slightly faster than the rotational displacement of the tube about the mandrel under control of the takeoff mechanism, during each cycle of operation the turn buckle would wait for the sensing of a seam to be recycled.

In accordance with the present invention, the principle of sensing the seams to determine the rate of takeoff of the bias-cut material is used to advantage to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of the take-ofif mechanism. Specifically, corrections in the rotational feed of the material are made when a prescribed error limit is exceeded. That is, when a permissible range of variation between the presentation and take-off of the material is exceeded, an automatic control responsive to seam detection is effective to correct the rotational feed.

The above brief description, as well as further objects, features, and advantages, of the present invention will be best appreciated by reference to the following detailed description of a presently preferred embodiment, when taken in conjunction with the drawings, wherein:

The single figure is a diagrammatic and schematic showing of an improved feed and control system for a bias-cutting machine demonstrating features of the present invention.

Referring now specifically to the drawing, there is shown diagrammatically a bias-cutting machine, which is cludes an elongated relatively flat mandrel 22, material delivery or presenting apparatus 24 adjacent the leading for forward end of the mandrel 22, a cutter 26 at one side of and adjacent the trailing or rear end of the mandrel 22, and an angularly disposed windup or pulling mechanism 28 extendingangularly across the mandrel 22.

The delivery or presenting mechanism 24 includes a turnbuckle 30 which is supported on a shaft 32 connected to a turn buckle motor 34 having a speed control unit '36. The motor and

speed confrol unit

34, 36 may take the form of any one of a number of conventional A.C. drive motors and magnetic clutch controls. One unit found to be particularly useful is known as the Dynamatic which is sold by Eaton Manufacturing Company of Kenosha, Wisconsin. The details of the control circuit may be found in said manufacturers catalogue dated May 1955. Briefly the A.C. motor 34 hasa normal armature and field. The armature is mounted on an internal shaft which carries a small generator and one section of an electromagnetic slip clutch. The other section of the slip clutch is connected to the output shaft 32. Between the clutch sections, there is provided a clutch excitor winding. The slip between the clutch sections is proportional to the current through the excitor coil. If there is no current through the excitor coil, the clutch is completely disengaged and the output shaft 32 is stationary although the motor 34 is running at its normal speed.

'The rotor is energized by application of an appropriate line voltage to the terminals 14, 20; while the exciter coil or winding which determines the torque transmitting force is energized by appropriate connections to the terminals 17, 18, 19. The excitation current internally of the control unit 36 is determined by the plate current applied to a thyratron tube and associated circuitry. The voltage supply of the thyratron tube controls the plate current output of the thyratron which in turn determines the amount of slip and the speed of the output shaft 32. Accordingly, as the current increases to the exciter coil, the speed of the output shaft 32 is proportionately increased. It follows that speed control for the

unit

34, 36 may be achieved quite readily by merely applying selected voltages to the control grid of the thyratron tube.

The cutting mechanism 26 is seen to include a rotary cutting blade or knife 38 supported on the output shaft 40 f a motor 42 having energizing connection 42a, 42b.

The take-ofi mechanism 28 includes a take-pit shaft (not shown) which is connected to the drive shaft 44 of the motor 46 having energizing connections 46a, 46b.

Detailed reference will now be made to the schematic diagram of the control circuit in conjunction vwith the several component parts of the bias-cutting machine 21. Specifically, input is derived from a conventional A.C. supply via the input lines 50, 52. A pair of lines 54, 56 are connected to the main or input lines 50, 52 and extend through a triple-pole, single-throw master switch 58 which includes switch blades or contacts 58a, 58b, 58c. Upon closing of the switch 58, a circuit is completed for the take-up motor 46 which includes the terminal 46b, the contact 58b, the line 56 and the terminal 46a, the contact 58a and the line 54. Provision is made for temporarily energizing the take-up motor 46, for example, when the windup is to be used to initially feed through a lengthof material for threading up the machine, or for winding up an end of bias-cut material at the completion of a run. This auxiliary control includes a single-throw, double-pole foot switch 60 having contacts 60a, 60b connected by leads 62, 64 to the terminal 46a, 46b of the motor 46. It will be appreciated that upon closing of the foot switch 60 the terminals 46a, 46b are 4 connected to the lines 54, 56 via the lines 62, 64 and the switch contacts 60a, 60b, the main switch 58 being by-passed.

The knife motor 42 is energized from lines 66, 68 connected respectively to the main lines 50, 52 via a single-throw, double-pole switch 70 having contacts 70a, 70b. Upon closing of the switch 70, the energization circuit for the motor 42 is completed via the terminal 42a, the contact 70a and the line 66, and the terminal 42!), the contact 70b and the line 68.

The turn buckle motor is energized from lines 72, 74 via a single-throw, double-pole turn buckle switch 76 having contacts 76a, 76b. The energization circuit for the turn buckle motor 34 will be seen to include the terminal 34a, the contact 76a, and the line 72 connected to the line 66, and the terminal 34b, the contact 76b, and the line 74 connected to the line 68.

Turning now to the several connections to the turn buckle motor control 36, the terminals 14, 20 are connected via

lines

78, 80 to the contact or blade 580 of the main switch 58 which is closed at the start of operation. With the switch blade or terminal 580 open, the output shaft 32 of the turn buckle motor 34 is completely inactivated; when the contact 58c is closed, the speed of turning may be controlled by appropriate provision at the terminals 17, 18 and 19. Specifically, a speed-control potentiometer 82 is connected cross the terminals 17, 19 which includes a speed-trimming resistor 84 and a speedcontrol resistor 86. The terminal 17, is connected via a tap 88 to the speed-trimming resistor 84. The terminal 18 is connected to an adjustable tap 90 which is movable, as in a conventional potentiometer, to provide varying voltage to the thyratron grid in the internal control circuit. The terminal 19, which corresponds to an internal ground within the control unit 36, is connected to the speed-control resistor 86 via the lead 92. The internal arrangement within the control unit 36 is such that as the resistance between the terminals 17 and 18 is decreased, the turn speed of the turn buckle is proportionately increased. Thus, as the potentiometer slider or tap 90 moves to the left along resistance 86, the turn speed is increased; correspondingly, as the slider tap 90 moves toward the right, the resistance is increased and the speed of turning is decreased.

The circuit which is now to be described and is controlled by a seam sensing unit, is arranged to periodically bring the speed-trimming resistor 84 into the circuit, is connected between the tap 88 and the tap 94 at the junction of the resistors 84, 86. By shorting out the resistance 84, the speed of turning may be increased by an increment, which is determined by the value of the resistance between the

points

88, 94.

Normally the trimmer resistor 84 is shorted out of the circuit by leads 96, 98 which are connected together over a closed circuit provided by a control relay 100. The relay 100 includes a normally-closed contact 100a, a normally-open contact 100b, and a relay coil 1000. In response to energization of the relay 100, as indicated by the light 100d, the contact 100a opens and breaks the short circuit connection over lines 96, 98 to opposite ends of the trimmer resistance 84; the contact 10% closes to provide a holding circuit for the relay coil 1000, as will subsequently be described.

The main energization circuit for the relay coil 100a includes line 102 connected to the input line 52 and to one end of the relay coil; line 104 connected to the seam-detecting unit 106; line 108 connected via line 110 and brush contact 112 to the collector ring 114 which is connected by jumper connection 116 to the collector ring 118 having gap 118a, the collector ring 118 being contacted by a brush 120; and a normally closed synchronization switch 122 connecting brush 120 through the lines 72, 66 to the input line 50.

The seam-detecting unit 106 is usually in the form of a microswitch having a switch contact or blade 106a mechanisms 28) seam in the windup mechanism 28' of the bias-cutting machine 21. The main energization circuit for the relay coil 1000 is put in condition for operation by closing of the switches 70, 122. In operation, upon sensing of a seam and closing of the contact or switch element 106a, the energization circuit for the relay coil 1000 is completed which opens contact 100a and closes contact 1001:. Opening of the contact 100a removes the short circuit across the trimmer resistance 84 and slows down the motor by a fixed increment determined by the initial setting of the tap 88. Closing of the contact provides an auxiliary holding circuit for maintaining the relay 100 energized despite the fact that the seam detector only closes momentarily in response to the passage of a seam. This holding circuit includes the contact 100b, lead 110, brush 112, commutator or collector rings 114 and 118, the brush 120, the normally-closed switch 122, and the lines 72, 66. This holding circuit remains activated or closed as long as the brush 120 is on a continuous portion of its collector ring 118; that is until the insulation or gap 118a passes beneath the brush 120 to open the holding circuit.

A typical sequence of placing the control in operation, and an illustration of the control function will now be described in detail to facilitate a more thorough understanding of the invention:

The knife switch 70 is closed to start the knife motor 42 and the turn buckle switch 76 is closed to start the turn buckle motor 34. No rotation is imparted to the output shaft 32 since the control unit is disabled by the still open connection 580 across the terminals 14, 20. The synchronization switch 122 is opened to allow for initial adustment of the speed of shaft 32' and the rotary feed by turn buckle 30. Opening of switch 122 keeps the seam detecting and relay control out of the circuit. The switch 58 is closed which completes the necessary internal connections via

lead

78, 80 and terminals 14, to place the speed control unit 36 in operation. This starts the drive of the take-up mechanism 28. The speed of the turn buckle is then varied by adjusting the slider or tap 90. Adjustment of the slider 90 to the left along resistance 86 decreases the resistance between the terminals 17, 18 and increases the turn speed for material feed. The initial speed is adjusted to impart a slight overtwist to the material being fed to the mandrel .22 in that the illustrative form of the invention provides for periodic increase of the resistance between the terminals 17, 18 to slow down the material feed. Initial conditions are established so that the insulation or gap 118a is past the brush 120 in the direction of turn when the seam S is sensed. Accordingly, as the seam S is sensed at the unit 106a, the energization circuit for the relay 100 is closed opening the switch 100a and removing the short circuit from the trimmer resistance 84. In a typical practical embodiment, the insulation or gap 118:: is between ten to fifteen degrees, which allows for a fairly broad range of error between the rotational feed (as determined by the drive of the turn buckle) and the take-01f rate (as determined by the pull of the windup If the brush 120 is within the arcuate extent of the gap or insulation 118a when the seam detector 106 closes, the energization circuit for the relay 100 is disabled and no speed correction is made for the particular cycle of operation. Only when the error accumulates so that the lead of the material feed. to the bias-cutting machine is greater than the gap width, will the machine automatically correct its speed by the fixed increment.

Although the illustrated control is for adjusting the speed under conditions where the initial turn buckle speed is faster than the take-oil? rate, it will be appreciated by those skilled in the art that essentially the same control may be employed to periodically speed up the turn buckle for correction under control of the seam 6 detecting unit. For this latter type of control, the trimmer resistance would normally be in the circuit and shorted out upon sensing of a seam S. Further within the contemplation of the present invention is a control which has provision for correcting for deviations beyond a permissible range, both in the slow and fast direction. However as a practical matter, corrections to either slow down or speed up the rotary presentation are the only ones that are required in that errors or deviations are cumulative in one direction.

A latitude of modification, substitution and change is intended in the foregoing disclosure and in certain instances some features of the invention will be used without a corresponding use of other features. Accordingly, it is appropriate that the claims be construed broadly within the spirit and scope of the present invention.

What I claim is:

1. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-off mechanisms for removing the bias cut material from said mandrel at a prescribed rate, means including a variable speed drive for rotationally presenting the material to said mandrel for pull along and about said mandrel by said take-off mechanisms, means at a point along the path of travel of the material through said machine for sensing the passing of seams as a measure of the travel of the material about said mandrel, and correcting means under control of said sensing means and operative to change the speed of said variable speed drive to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said take-off mechanisms.

2. In a bias-cutting machine for material in tubular form, a mandrel, take-otf mechanisms for removing the bias cut material from said mandrel at a prescribed rate, means including a variable speed drive for rotationally presenting the material to said mandrel for pull along and about said mandrel by said take-off mechanisms, means for sensing the rate of travel of the material about said mandrel, and correcting means under control of said sensing means and operative to change the speed of said variable speed drive to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said ta ke-ofi mechanisms.

3. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-off mechanisms for removing the bias cut material from said mandrel, and means including a variable speed drive for rotationally presenting the material to said mandrel for pull along and about said mandrel by said take-off mechanisms, the improvement comprising seam-detecting means at a point along the path of travel of the material through said machine for sensing seams passing'said point, and correcting means under control of said seam-detecting means and operative to change the speed of said variable speed drive to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said take-off mechanisms.

4. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-off mechanisms for removing the bias cut material from said mandrel at a prescribed rate, variable speed means for rotationally presenting the material to said mandrel for pull along and about said mandrel by said take-off mechanisms, means for sensing the passing of seams as a measure of the travel of the material about said mandrel, and correcting means under control of said sensing means and operative to change the speed of said variable speed means to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said take-off mechanisms.

5. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-oil mechanisms for removing :t-he bias .cut material from said mandrel at a :prescribed rate, a turnbuckle for rotationally present- --ing the material to said mandrel for pull along and about said mandrel by said take-off mechanisms, sensing the rate of .travreltof the material about said mandrel .during each rotation of saidturnbuckle, a variable speed drive, and a control for said drive operated by said sensing means and periodically effective to change the speed of said drive to maintain a prescribed rotational orientation between the presentation of material and .its travel about the mandrel under the pull of said take- ,oflmechanisms, said control including a slip clutch connected tosaid ,drive and having an excitor coil, the slip of said clutch being proportional to the current through said excitor coil, a speed control potentiometer connected in circuit with said excitor coil and having series connected speed-trimming and speed-control resistors, means for varying the resistance of said speed-control resistor, means normally providing a short circuit across said speed-trimming resistor, and means for periodically removing the short circuit across said speed-trimming resistor.

6. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-oif mechanisms for removing the bias cut material from said mandrel at a prescribed rate, a turnbuckle for rotationally presenting the material to said mandrel for pull along and about 1said mandrel by said take-off mechanisms, a sensing switch at a point along the path of travel of the material through said machine which is closed by the passage of successive segments of the seam for sensing the rate of travel of the material about said mandrel during each rotation of said turnbuckle, a motor, and a control for said motor operated by said sensing switch and periodically effective to change the speed of said motor to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said take-ofl? mechanisms, said control including a slip clutch connected to said motor and having an excitor coil, the slip of said clutch being proportional to the current through said excitor coil, a speeed control potentiometer connected in circuit with said excitor coil and having series connected speed-trimming and speed-control resistors, a normally-closed shorting switch across said speed-trimming resistor, and a relay control responsive to closing of said sensing switch for periodically removing the short circuit across said speedtrimming resistor.

7. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-off mechanisms for remo'ving the bias cut material from said mandrel at a prescribed rate, a turnbuckle for rotationally presenting the material to said mandrel for pull along and about said mandrel by said take-E mechanisms, a sensing switch at a point along the path of travel of the material through said machine which is closed by the passage of successive segments of the seam for sensing the rate of travel of the material about said mandrel during each rotation of said turnbuckle, a motor, and a control for said motor operated ,by said sensing switch andperiodically effective to changethe speedof said motor to maintain a prescribed rotational orientation between the presentation of ,material and its travel, about the mandrel under the pull of said take-off mechanisms, saidcontrol including a slip clutch .connected to said motor and having an excitor coil, theslip of saidclutch being proportional to the current through said excitorco'il, a speed-control potentiometer connectedin circuit with saidexcitor coil andhaving series connectedspeed-trimming and speed-control resistors, said potentiometer being connected so that increases in resistance cause corresponding increases in the currentthrough said excitor coil, a shorting switch across said speed-trimming resistor and having a relay control for periodically removing the short circuit across said speed-trimming resistor, a conductive commutator ring havinglan insulated section and rotatable with said turnbuckle, a brush in contact with said commutator ring, and an energization circuit for said relay control including said conductive commutator and brush, said relay control being effective to removesaid short circuit from said speed-trimming resistor when said brush is in the conductive section of said commutator ring and said sensing switch is closed by the passage of a seam to increase the resistance of said potentiometer.

8. In a bias-cutting machine for material in seamed tubular form, a mandrel, take-0E mechanisms for removing the bias cut material from said mandrel at a prescribed rate, a turnbuckle forrotationally presenting the said machine which is closed by the passage of successive segments of the seam for sensing therate of travel ofthe material about said mandrel during each rotation of said turnbuckle, a motor, and a controlfor said motor operated by said sensing switch and periodically effective to change the speed of said motor to maintain a prescribed rotational orientation between the presentation of material and its travel about the mandrel under the pull of said take-0E mechanisms, said control including a slip clutch connected to said motor and having an excitor coil, a speed control potentiometer connected in circuit with said excitor coil and having series connected speed-trimming and speed-control resistors, means for varying the resistance of said speed-control resistor, a shorting switch across said speed-trimming resistor and having a relay control for periodically removing the short circuit across said speed-trimming resistor, a conductive commutator ring having an insulated section and rotatable with said turnbuckle, a brush in contact with said commutator ring,

References Cited in the file of this patent UNITED STATES PATENTS 2,772,734 Judelson Dec. 4, 1956