US2594741A

US2594741A - Electronic control for filament wrapping machines

Info

Publication number: US2594741A
Application number: US9887A
Authority: US
Inventors: Jr Albert M Dexter
Original assignee: Niles Bement Pond Co
Current assignee: Niles Bement Pond Co
Priority date: 1948-02-20
Filing date: 1948-02-20
Publication date: 1952-04-29
Anticipated expiration: 1969-04-29

Description

April 29, 1952 A. M. DEXTER, JR 2,594,741

ELECTRONIC CONTROL FOR FILAMENT WRAPPING MACHINES Filed Feb. 20, 1948 INVENTOR.

AFOR/VEY Patented Apr. 29, 1952 ELECTRONIC CONTROL FOR FILAMENT WRAPPING MACHINES Albert M. Dexter, Jr., Farmington, Conn., as-

signor to Niles-Bement-Pond Company, West Hartford, Conn., a corporation of New Jersey Application February 20, 1948, Serial No. 9,887

3 Claims. (01. 153-67) This invention relates to winding machines and moreiparticularly to a winding machine for tungsten wire in which a fine filament of tungsten is continuously wrapped about a core of wire of small diameter such as of steel while the wire forming the core is advanced at a uniform rate and maintained under tension.

An object of the invention is to promptly indicate breakage of the filament as it is being wrapped so that the machine may be promptly and automatically stopped as soon as a breakage occurs.

A feature of importance of the invention is that 'thebreakage indicator forming the present invention requires no mechanical connection to the winding mechanism but depends upon light flashes reflected from a mirror rotated with the wrapping mechanism falling periodically on a photoelectric tube. By means of an electronic circuit; within which the photoelectric tube is in cluded, constant light flashes, or no light, falling on the photoelectric tube as the wrappingmechanism rotates maintain a stop motion device relay energized to open the main circuit contacts for the machine and stop its operation. Variable flashes occurring periodically during normal operation 'serve to deenergize the relay coil and maintain the main circuit contacts for the machine closed.

In forming tungsten filaments for high and low wattage light bulbs, it is the usual custom to wrap the filament around a mandrel Or core of steel wire, the steel wire being continuously advanced under-tension during the wrapping operation so that successive convolutions of the filament along the core will be equally spaced. After wrapping thefilament the steel core is dissolved in an acid bath which effectively removes the steel and leaves the helically wound filament ready for outting into proper lengths for assembly within the bulb.

As the filament is extremely fine, it is very difficult for the operator to determine when a break occurs in the filament duringthe Winding or wrapping operation. Continued operation of the machine after breakage of the filament is wasteful. It is therefore a desirable feature of the invention to stop operation promptly when the filament breaks, and without the addition of mechanism increasing the tension on the filament.

To effect this stoppage advantage is taken of the difference in speed of the guide member for the filament and the filament carrying spool rotated with the guide member. The rotation of the spool is at a different and slightly increased speed from that of the guide member by reason of the unwinding of the filament from the spool. After a break occurs in the filament the spool will rotate with the guide carrying member and at the same speed.

During normal operation of the wrapping mechanism due to the difference in speedof rotation of the guide member and spool, a mirror rotating with the guide member is periodically exposed to a light source through an opening in a member rotating with the spool. Reflected flashes from the mirror fall on a photoelectric tube and render this tube momentarily conducting to pass current through an electronic circuit. These flashes will vary in intensity due to the mirror slowly passing the opening, the flashes first increasing and then decreasing. After a break in the filament the spool and guide member will rotate at the same speed so that there will be equally timed flashes of equal intensity With each revolution of the guide member or if the mirror is concealed there will be no flashes whatever. This is due to the relative positions of the mirror and opening remaining unchanged. If the break occurs when the opening is above the mirror there will be a continuous series of flashes of equal intensity and at equal intervals, one with each rotation of the guide member and spool. If the break occurs when the mirror is concealed by the flange, there will be no light flashes at all. This will be obvious by an inspection of Fig. 2 of the drawing. By the electronic circuit including the photoelectric tube the relay operating the stop motion is not affected by the periodic varying se;- ries of flashes of different intensity but is caused to be operated and open the main circuit for the machine by equal flashes equally timed or by no flashes at all falling on the tube. I

It is therefore a primary object of the invention to provide an electronic circuit responsive to flashes of difierent types falling on a photoelectric tube included Within the circuit.

In the accompanying drawing annexed hereto and forming a part of this specification, I have shown the invention embodied in a simple form of filament wrapping device but it will be understood that the invention can be otherwise embodied and that the drawing is not to be construed as defining or limiting the cope of the in vention, the claims appended to this specification beingrelied upon for that purpose.

In the drawing:

Figure l is a side elevation in section showing the principal parts of a simple filament wrapping machine.

Fig. 2 is a front elevation in section taken on the line 22 of Fig. 1, and

Fig. 3 is a diagram showing a preferred circuit for controlling a motor operating relay for the machine.

In the above mentioned drawing there has been shown but one embodiment of the invention which is now deemed preferable, but it is to be understood that changes and modifications may be made within the scope of the appended claims without departing from the spirit of the invention.

In Fig. 1 are shown the operative parts only of a winding machine which may have the stop motion relay controlling circuit forming the present invention. The rotating member includes a hollow shaft It and arm {2. The base for supporting this member and its rotating means are not shown, the rotating member being shown extending from a fixed member I which may be attached to a suitable base. The shaft It supports a spool to freely rotatable on the shaft on which is wound the filament 18. The arm 12 supports guides 20 in the form of rolls over which the filament 18 passes from its spool H to the wire 22 around which it is being wrapped.

The shaft is supporting the arm I2 is hollow and the steel wire for the core 22 is advanced by means (not shown) axially through the shaft, and after being wrapped by the filament I8 is wound upon a suitable drum 24 which may be rotated at a uniform speed by any appropriate means. The spool I6 is freely rotatable on its supporting shaft is so that it may rotate relatively to as well as with the shaft while the shaft and arm 52 are rotated to permit the filament I8 to unwind while the spool is rotated with the guiding member 12.

As shown in Fig. 1 the arm forming the guiding member :2 is keyed directly to the shaft and has mounted thereon a disc 26 .on the periphery of which is mounted a small mirror 28. The spool it on one of its faces is provided with a flanged member 30 fixed to the spool for rotation therewith, there being an opening 32 in the flange 3G aligned with the mirror 28.

From the above description it will be seen that during rotation of the shaft Ill andspool It at different speeds the mirror 23 will be directly below the opening 32 in the flange 30 after a number of revolutions of the shaft It). Just before and after the mirror 28 is directly below the opening 32 for several revolutions, the mirror 28 will be partially below the opening. These phases increase as the mirror 28 slowly moves toward the position directly below the opening and then decrease as the mirror moves away from the opening. In the event of a breakage of the filament the spool l6 and shaft IE] will rotate together at the same speed and the relative positions of the mirror 28 and opening 32 will not change. The mirror 28 may be visible below the opening 32, partially visible, or completely out of sight by being hidden by the flange 3B.

Adjacent the spool 16 and shaft H! is a source of light 34 such as a small light bulb. A lens 36 is preferably mounted between the bulb and mirror 23 so that the light rays may converge upon the flange 38. When the mirror 28 is visible below the opening 32 in the flange, light from the bulb 34 will be reflected to a photoelectric tube 38 positioned adjacent the light source 34. The reflected flashes of light falling on the photoelectric tube 38 will increase as the mirror 28 slowly comes into a position below the opening 32 and will then decrease as the mirror passes the opening. The passage of the arm 12 at each revolution does not produce any interruption of these light flashes for the reason that the mirror 23 is angularly'disposed relative to the position of the arm 12.

To actuate a stop motion or motor control- 1 ling relay 4!! by means of the flashes of reflected light from the mirror 28 to the photoelectric tube 38 the following circuits have been devised, the diagram for the circuit being indicated in Fig. 30f the drawing.

These circuits control energizing of relay Ml opening and closing the contacts of a motor circuit for operating the machine. With the relay 40 energized the motor circuit contacts are opened and the machine is thus stopped. So long as the coil 'of relay 49 is not energized the motor circuit contacts are closed to continue the normal operation of the machine. The function of the circuits shown in Fig. 3 is to energize the .coil of relay .159 as soon as a break in the filament 18 occurs, and to maintain the coil of relay 40 deenergized during normal operation of the machine.

T1 is a power transformer connected as an auto-transformer with primary and secondary connected series windings. The first section of tube V1 is a diode rectifier. Following the current from one side of the line indicated at A. C., it flows to the plate of diode of D1 (which forms a part of tube V1) through diode D1, to the cathode of D1, through resistances R3, R2 R1; and potentiometer P1. and back to the end of transformer secondary 42. Due to the half wave rectification action of tube D1, no current flows through this tube on alternate halfcycles. A pulsating uni-directional current therefore'flows through tube D1, and due to the filtering action of condensers C1, C2 and resistance Rs. 2. .steadyD. C. voltage appears across the network consisting of resistances R2, R1, and potentiometer P1, the polarity of which is indicated in ,Fig. 3. This voltage may be called the 13 voltage supply.

T2 an audio coupling transformer with one end of its primary connected to the terminal of the B voltage supply and the other end connected to the plate of the second, or triode', section of tube V1. The cathodeof the triode section of t be V1.13 connected t t e s i r of pot no eter P1 n th B vol a e s pp y n w rk. Condenser Q3 forms a by-pass from the cathode of t e tri de ion f tu V1 to the m us end of B voltage supply network to prevent degeneration in the cathode circuit as is the practice in amplifying stages. The grid of the triode section of tube V1 is connected through resistance R4. to the minus end of the B voltage supply. It will be seen, therefore, that the triode section of tube V1 is biased to the extent of the voltage from the slider on potentiometer P1 to 3 minus, and this slider should be adjusted until the triode section of tube -V1 is just drawing current, that is, not quite to cut-off.

Photoelectric tube 38 referred to above is connected between grid of triode in tube V1 and a positive tap on thenetwork formed by resistances Psalm, and potentiometer P1. When this photoelectric tube 38 is illuminated; it becomes more conducting, and the current in flowing from the tap on the B voltage network through photoelectric tube 38, through resistance R4 to the minus end of B voltage network, makes the grid less negative;.in other words, the triode D1 is no'longer biased negatively. Current flows from the plate of the triode section of tube V1 to the cathode, therefore, whenever the photoelectric tube 38 isv illuminated.

At this point it is well toconsider the function of the-rotating mirror 28, which is on the disc 26 attached to the shaft 0, and the flange 30 with the opening 32 which is attached to the spool Hi. If the mirror 28 and the flange 30 are travelling at the same speed (a condition which exists only when the tungsten filament has been broken), one of two conditions can take place, either the mirror 28 will be totally or partially in register with the opening 32, in which case a flash of light will strike the photoelectric tube 38 with every revolution, or alternatively the mirror 28 will be obscured completely by the flange 30 and no flashes of light whatsoever will reach the photoelectric tube 38. In any case, the photoelectric tube 38 will receive either constant flashes of light or no light at all.

Consider now the condition where the tungsten filament l8 has not been broken and the machine is operating normally. The mirror 28 and the flange 30 will not be travelling at the same speed, the flange will be travelling at a higher speed'due to the spools paying-off of the tungsten filament. Flashes of light will therefore reach the phototube 38, but these flashes will not allbe of the same intensity. A beat will occur at a frequency equal to the difference in speed of the mirror 28 and flange opening 32, as for example, the mirror 28 one time around will be obscured by the flange 3B; the next time the opening will just slightly uncover the mirror allowing a very weak flash to strike the phototube; each successive time around the opening will uncover more of the mirror, passing a slightly stronger flash, and so on until the entire mirror 28 is reflecting light to the photoelectric tube 33. The opening 32 will then progressively advance so that with each revolution less and less of the mirror 28 will be visible to the photoelectric tube 38, until again it is totally obscured by the flange 30. This heat will, of course, be at a low frequency compared to the speed of the mirror itself, and it is this beat which causes the circuit to operate.

Going back to Fig. 3, consider first the case of the broken tungsten wire. If the mirror 28 is obscured by the flange 39, no light at all strikes the photoelectric tube 38, therefore the triode of tube V1 continues to pass just a slight D. C. current through the primary of transformer T2 and because a transformer will pass from primary to secondary only an alternating voltage, no voltage will appear at the secondary of this transformer. On the other hand, if the mirror 28 happens to be totally or partially in register with the opening 32 in the flange 3B and is travelling at the same speed, a flash of light will strike the phototube 38 with each revolution, but each flash will be of equal intensity, and the frequency of these flashes will be equal to the speed of the mirror and flange. These flashes will cause, as explained before, the triode section of tube V1 to pass current through the primary of transformer T2, and since the light is in the form of flashes, the current through the primary of transformer T2 will be in the form of pulses at a frequency equal to the speed of the mirror. Transformer T2 will cause an A. C. voltage to appear across its secondary winding and across potentiometer P2. Considering for a moment that 6 the upper end of transformer T2 secondary is momentarily positive, current will flow to the diode plate of tube V3 to cathode of tube V3, through resistance R5 and back to the other end of potentiometer P2. On the alternate half cycle when the upper end of transformer T2 secondary is momentarily negative, due to the rectification of the diode section of tubeVz no current will flow through resistance R5. A uni-directional current therefore flows through resistance R5, and due to the filtering action of condenser C4 it is substantially D. C. of polarity as indicated and its magnitude depends upon the intensity of the light flashes. Since we are at the moment considering that the filament is broken and the flashes striking the photoelectric tube 38 are all of equal intensity, a D. C. voltage of constant magnitude appears across resistance R5. Since the grid of the triode section of. tube V3 is connected to the minus end of resistance R5, the triode section of tube V3 may or may notbe passing plate current through the primary of transformer T3 depending upon the magnitude of the equal light flashes. In any case, the voltage on the grid of tube V3 is D. 0., therefore the plate current, if any, through the triode section of this tube will be D. C. As before, a transformer will develop a voltage across the secondary only if a varying current flows in its primary. In the case' under discussion, therefore, no voltage appears 'across the secondary of transformer T3, andby the same reasoning applied to the first or diode section of V4, Re, and C5 as was applied to the diode section of .V3, R5, and C4, no voltage appears across R6. The grid of tube V4 has no biasing voltage on it, therefore, and it draws plate current through and energizes the coil of relay 4U. Condenser Ce serves to filter out the supply frequency pulsations across the coil of relay 40.

We have seen up to this point that if the tungsten filament is broken, there are two situations that can exist: First, the mirror 28 may be completely obscured by the flange 30 so that no flashes at all reach the phototube. In this case no voltage appears across resistance R5, no voltage appears across resistance Re, and relay 40 is energized and its contacts will be held open. Secondly, the mirror 28 may be only partially or not at all obscured by the flange 30 so that light flashes of constant magnitude strike the phototube, a steady D. C. voltage does appear across R5, but no voltage can appear across Rs, so that again relay 40 still remains energized with contacts open.

Consider now the case of the tungsten filament l8 not being broken and the device being operated normally, a beat of comparatively low frequency strikes the phototube 38. This is due to the relatively small difference in speed of rotation of the mirror and the opening in the flange. The mirror 38 is uncovered by the opening 32 in the flange 30 only after a large number of rotations of the mirror and flange. A voltage will appear across R5 but it will not be aconstant. It will, rather, be a voltage whose magnitude varies with the beat frequency, since the time constant of R5 and C4 is insuflicient to filter this low frequency. The bias on the triode section of tube V3 will therefore vary with the beat frequency, current will flow in low frequency pulses through the primary of transformer T3, and low frequency voltage pulses will appear across the secondary of transformer T3 and will be rectified by the first (or diode) section of tube V4, and a voltage will appear across Re. The values of Re and C are such as to give a time constant equal to or greater than this low frequency pulse, so a substantially pure D. C. appears across Re. Sinceuthe grid of the triode section of V4 is connected to the minus end of Re, it will be biased to cut-off, the relay will no longer be energized and the contacts for the motor circuits will be closed, This is the case of the machinecontinuingto run.

What I claim is:

1. A control for filament wrapping machines in which a filament carrying spool during normal operation rotates with and at a different speed from guiding means therefor, an electronic circuit, a photoelectric tube therein, a mirror-carried by said guiding means, a shield having an opening therein rotating with said spool whereby increasing and decreasing light flashes are imposed on said photoelectric tube, said photoelectric tube receiving said variable flashes of light from said mirror-during normal operation, and said circuit operating a relay to stop said machine when said flashes cease or become constant,

'2. A control for filament wrapping machines in which a :filament carrying spool rotates with and ata difierent speed from guiding means therefor during operation, an electronic circuit having a photoelectric tube therein, a mirror carried by one of said rotating means, a shield having an opening therein carried by the other memher, said photoelectric tube receiving periodic variable flashes of light as said mirror is variably uncovered by the opening in said shield at each chine, and said circuit operating a relay to stop said machine when said flashes cease or become constant.

3. A control for filament wrapping machines comprising, filament guiding means, rotating means for said guiding means, means to feed a core wire axially of said guiding means, a spool rotatable with and relatively of said guiding means, a mirror mounted for rotation with said guiding means, a flange rotatable with said spool having an opening therein through which said mirror may be viewed during relative rotation of the shaft and spool, a light source, a. photoelectric tube positioned to receive light from said source as reflected by said mirror, and an electroniccircuit controlled by the flashes of light reflected by said mirror upon said photoelectric tube for controlling operation of said wrapping machine.

ALBERT M. DEXTER, JR.

REFERENCES CITED The following references are of'record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,971,191 Lord Aug. 21, 1934 2,101,382 Donovan Dec. 7, 1937 2,211,320 Efron Aug. 13, 1940 2,340,547 Mikami Feb. -1, 1944 2,383,313 Hoffman Aug. 21, 1945 2,416,595 Reynolds Feb. 25, 1947