US2875571A - Machines for lapping insulating material on to electric conductors - Google Patents

Description

March 3, 1959 Filed Jan. 13, 1958 A. MACKENZIE EI'AL W. MACHINES FOR LAPPING INSULATING MATERIAL ON TO ELECTRIC CONDUCTORS 7 Sheets-Sheet 1 Inventors Wr'lliam #IexmJw/Iackenzie 8 William l/zrr y (larlnJlart A [form eys March' 3, 1959 w. A. MACK/ENZIE ET AL 2,875,571 V MACHINES FOR LAPPING INSULATING MATERIAL ON TO ELECTRIC CONDUCTORS Filed Jan. 13, 1958 '7 Sheets-Sheet 2 A ttorney:

March 3, 1959 Filed Jan. 15, 1958 w. A. MACKENZIE ETAL MACHINES FOR LAPPING INSULATING MATERIAL ON T ELECTRIC CONDUCTORS 7 '7 Sheets-Sheet 5 Inventor wilhim lie/tender Mackenzie a William A arm Clark: J'lar/r Attorneyx March 3, 1959 w. A; MACKENZIE ET MACHINES FOR L AL 2,875,571 APPING INSULATINGCMATERIAL ON TO ELECTRIC CONDUCTORS Filed Jan. 13. 1958 7 Sheets-Sheet 4 F/G, 2b,

. In ventor: William lie/lander flar /1Z1? 17 A ttomey:

w. A. MACKENZIE ETAL 2,875,571 MACHINES FOR LAPPING INSULATING MATERIAL ON TO March 3, 1959 A ELECTRIC CONDUCTORS Filed Jan. 13, 1958 '7 Sheets-Sheet 5 III 5 Inventor-s William Iletandrlbdenn? 9 William l/ary diaries ,SZark Bya5 V Attorneys March 3, 1959 w A. MACKENZIE ETAL 2,875,571

MACHINES FOR LAPPING INSULATING MATERIAL ON T ELECTRIC CONDUCTORS Filed Jan. 13, 1958 '7 Sheets-Sheet 6 1211091110725 William lkmaJerfimnzn" d William flan] (Zerkr ,S'fart A ttorne y:

March 3, 1959 w. A. MACKENZIE ETAL 2,875,571 MACHINES FOR LAPPING INSULATING MATERIAL ON TO ELECTRIC CONDUGTORS Filed Jan. 13, 1958 V 7 Sheets-Sheet 7 'F lG/O. o

w A O o 97 '92 99 F/GQ9. a

,4; Aim/9W A ttorn e 31.:

United States Patent MACHINES FOR LAPPING INSULATING MATE- RIAL ON TO ELECTRIC CONDUCTORS Application January 13, 1958, Serial No. 708,588

Claims priority, application Great Britain January 18, 1957 14 Claims. (Cl. 57-19) I This invention relates to machines for lapping insulatlng tape, e. g. paper strip, on to electric conductors over an open lapping of a spacing material, e. g. paper string, which spacing material may be, and generally will be, applied by the same machine immediately prior to the application of the insulating tape. For convenience the conductor will hereinafter be referred to as a wire.

The object of the invention is to provide a machine which works at high speed and which requires the minimum of supervision since it is automatically stopped when it requires attention.

In accordance with the invention the insulating tape applying machine is provided with automatic stopping means which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire to which the insulating tape is being applied and atleast one electric contact which is adapted to bear against the wire between the turns of the spacing material when the Wire ceases to be covered by the insulating tape, the contact or contacts being normally insulated from and held away from the wire by the insulating tape lapped thereon.

Where more than one contact is used the contacts are all electrically connected, e. g. they may form part of a single conducting member.

We prefer to use a conducting member comprising a pulley over which the wire passes in its path from the insulating tape lapping head, the pulley being so shaped as to provide a number of electric contacts which touch the wire if the insulating tape is no longer applied over the spacing material. The pulley may, for example, carry metal members which act as the contacts; the members may, for example, consist of conductive cylinders, e. g. copper cylinders, mounted transversely in the pulley groove and spaced apart around the periphery of the pulley by a distance which is not equal to or is not a multiple of the lay of the paper string. or other spacing material.

When the open lapping of spacing material is applied to the wire in the same machine an automatic stopping means may also be arranged to come into operation by the making of an electric circuit including the wire and an electric contact which is urged towards, but normally held out of contact with, the wire by the spacing material. This circuit may include a pair of coaxially mounted discs which are normally insulated from each other and are pressed lightly towards each other but are normally held apart by the lapping of spacing material applied to the wire. When the wire is bare the two discs press against it to complete the circuit. The discs are preferably free to rotate and arranged so that the wire passes along a chord near the outer edges of the discs.

Both the tape lapping head and the haul-off capstan ice electric motor and, when the spacing material is applied simultaneously with the tape, the head by which it is applied is preferably also driven by this motor. The head for applying the spacing material is conveniently mounted beneath and coaxially with the tape head so that the wire can pass vertically upwards through the two heads. The device for. detecting a break in the spacing material is then mounted between the two heads.

In order to attain rapid stopping of the machine we prefer to employ stopping means which when brought into operation, effects or effect a reversal of the power supply to the field coils of the motor for a controlled time.

The invention is particularly applicable to machines of the type in which the coil of tape being applied to the wire is mounted coaxially with the wire and the lapping head is driven by an electric motor with a hollow shaft through which the wire passes.

We prefer also to provide means for stopping the motor when the coil of tape from which tape applied to the wire is being withdrawn is almost exhausted. When, as is customary, the coil from which the tape is applied to the wire consists of a flat pad supported eoaxially with the motor shaft on or above a horizontal rotating table mounted on the motor shaft, the arrangement for stopping the motor when the pad is almost run out may include a first electric contact pressed on to the pad near its centre by a spring contact arm mounted on the cable and a second electric contact on the surface of the table immediately beneath the first contact. The first contact will normally be separated from the second contact by the pad but when the pad is almost run out it will be free to move downwards and make contact with the second contact. The first contact, mounted on the spring arm, may be earthed through the machine frame and the second contact insulated from the table and connected to the appropriate relay circuit through a slip ring and brush. The first contact may be associated with or form part of means for braking the pad to restrain its rotation relative to the table for the purpose of controlling the tension in the tape.

Means for stopping the motor when a predetermined length of wire has been passed through the machine may also be provided.

The invention will now be described by way of example with reference to the accompanying drawings wherein Figure l is a front elevation of a machine adapted to apply an open lapping of paper string and a lapping of paper tape to a wire;

Figures 2, 2a and 2b are together a sectional elevation of the machine of Figure 1, taken along the line Il-II for the insulated wire are preferably driven by a single and drawn to a larger scale, but with the top portion of the machine omitted; V

Figure 3 is a cross-section of the machine taken along the line III-III of Figure 2a;

Figure 4 is a cross-section of the machine taken along the line IV-IV of Figure 2a;

Figure 5 is a cross-section of means for detecting whether or not the open lapping of paper string has been applied tothe wire;

Figure 6 is a cross-section of a pulley for detecting whether or not the lapping of paper tape has been applied to the wire;

Figure 7 is a sectional elevation of the paper tape applying head taken perpendicular to the view of Fig ure 2;

Figure 8 is an electrical circuit for the machine;

Figure 9 is a sectional elevation of a switchforming part of the machine;

Figure 10 is a plan view of the tape applying head, partly broken away, and

Figure 11 is a diagrammatic elevation of means for actuating a switch by a counter.

The machine shown in Figure 1 is adapted to apply to a wire 1 an open lapping of paper string followed by a lapping of paper tape. It comprises a frame 2 which supports an induction motor 3 having a hollow spindle through which the wire passes. The wire to be covered, which may be stored on a supply drum (not shown) or any convenient means, passes around a pair of guide pulleys 4, 5 and upwardly through the hollow spindle of a string applying head 6. A sensing device 7 detects whether or not the string has been applied. From the sensing device 7 the wire passes upwardly through the hollow spindle of the motor 3, through the hollow spindle 5 of a paper tape lapping head 8 and over a pulley 9 which acts as a sensing device to detect whether or not the paper tape has been applied. The wire is then pulled downwardly by a capstan 10 and passes over a guide pulley 11 and between the fingers of a finger guide 12 to be wound on to a take-up drum 13.

The method by which the tape applying head, string applying head, capstan and take-up drum are all driven from the induction motor 3 will be described with reference to Figures 2, 2a, 2b, 3 and 4. Referring to Figure 2,

the hollow spindle 14 of the tape applying head is screwed at its lower end on to the upper end of the hollow spindle 15 of the motor and is thus driven directly. A hollow shaft 16 is keyed to the lower end of the motor spindle and is driven by the motor spindle. A gear train which is housed in a block 42 fixed to the sleeve 39. Relative rotation between the sleeve 39 and the shaft causes the block 42 and the blade 41 to rotate relative to the shaft 35 and the shaft 35 is constrained to move axially backwards and forwards a distance equal to the length of the superimposed screwthreads. The end portions of these threads are so arranged to guide the blade from the left hand thread to the right hand thread or vice versa and to reverse the shaft when the knife blade reaches the end portion of the appropriate thread. In this manner the take-up drum is rotated at the angular velocity of the pulley 33 and is reciprocated at a rate which depends on the ditference between the angular velocity of the two pulleys 33 and 34.

The sensing device 7 which detects whether or not the open lapping of paper string is being applied to the wire is shown in detail in Figure 5 and mounted on the machine in Figures 1 and 2a. It comprises a pair of coaxially mounted metal discs 43 which are normally insulated from each other and are pressed lightly towards each other by a spring 44 but held apart by the lapping of spacing material. When the wire is bare the discs press against it to complete a circuit described below. The discs are free to rotate and are arranged so that the wire passes along a chord near their outer edges.

The pulley 9 (see Figures 1 and 6), over which the wire passes after it has passed through the insulating tape applying head, is made of metal and is insulated from the frame of the machine. It carries copper cylinders 45 spaced apart around its periphery by a distance which is not equal to or is not a multiple of the lay of the paper string. The copper cylinders form part of the electric circuit described below and which is completed if the 1 wire comes into contact with one of the copper cylinders lower end of the hollow spindle 24 of the string apply- 1 ing head (see Figures 2a and 4) to drive the string applying head.

A wormed sleeve 25 is fastened to the outer surface of the hollow shaft 16 and forms a worm gear with a worm wheel 26 which is coaxially fixed to a rotatable shaft 27 (see Figures 2a and 3) which is thereby driven by the electric motor. At one end of the shaft 27 is the capstan 10. At its other end is a friction clutch comprising a pair of discs 28 faced with friction material29 and urged by a spring 30 to contact the outer faces of a double pulley 31. Two V-belts 32 running in the pulley grooves transmit the motor drive to two pulleys 33 and 34 (see Figure 2b) by which a shaft 35 carrying the take-up drum 13 is both rotated and also reciprocated along its axis to cause the wire to be evenly wound. The drum is coupled to the shaft 35 by a disc carrying pins 36.

The simultaneous rotation and reciprocation of the shaft 35 is achieved as follows. To the pulley 33 is fixed a member 37 which is provided with a stud which runs in a groove 38 in the shaft 35 so that when the pulley 33 rotates it rotates the shaft 35 with it, irrespective (within limits dictated by the length of the groove 38) of the longitudinal position of the shaft. The pulley 34 is fastened to a sleeve 39 surrounding the shaft 35, so that the sleeve rotates with the pulley 34. The diameter of the two pulley grooves in the double pulley 31 and the two diameters of the two pulleys 33 and 34 are so arranged that the pulley 33 rotates more quickly than the pulley 34 so that there is relative rotation between the shaft 35 and the sleeve 39, the angular velocity of relative rotation being equal to the difference between the angular velocity of the pulleys 33 and 34. The surface of the shaft 35 is provided with a double groove 46) comprising a left hand thread superimposed on a right hand thread and in this groove fits a knife blade 41 through not being covered with insulating tape.

The tape lapping head 8 (see Figures 2 and 7) includes a two- part head guard 46, 47, the taping head spindle 14 and a freely rotatable table or platform 48 which normally carries a pad or coil of paper 49. There is also provided a sensing device which detects when the pad of paper is nearly used up. This sensing device may be seen by referring to Figure 7. It comprises a spring arm 50 mounted at one end on a table or platform 7 51 which is fixed to and rotates with the motor spindle 15 and hence also with the taping head spindle 14. The other end of the arm 50 is provided with a contact member 52 which is normally pressed against the pad by flexing of the arm 50, this position being shown chain dotted in Figure 7. In thisposition the contact member 52 acts as a brake for the pad and its table 48 to restrain its rotation relative to the spindle of the taping head for the purpose of controlling the-tension in the tape. When the pad is nearly run out the contact member springs into contact with a contact member 53, located above and insulated from the table 51 (this position is shown in full lines in Figure 7). The contact member 53 is electrically connected to a slip ring 54 carried on the motor spindle, the connection between the contact member 53 and the slip ring 54 being electrically insulated from the body of the machine. A carbon brush 55 fixed to but insulated from the frame of the machine makes contact with the slip ring and is electrically connected to the electric circuit described below to stop the machine when the pad has nearly run out.

This circuit is shown in Figure 8 and functions as follows. The motor terminals 56 are connected to the power lines 57 through two heavy current relays 58, 59 the terminals 60, 61 of which are so arranged that if the relay 58 (the forward relay) is energized the motor rotates forward and if the relay 59 (the reverse relay) is energised the motor rotates in reverse. The actuating current for the two relays 58 and 59 is controlled by a double-acting relay comprising a coil 62 and switches derived through a transformer 63 from the power line independently of the actuating current supply for the forward and reverse relays. The secondary circuit of the transformer includes the coil 64 of an interlock relay the contacts 65 of which break the power supply circuit to the forward and the reverse relay when the coil 64 is deenergised, thus ensuring that neither of these relays can be energised until the transformer secondary is energised. A switch 66 in the transformer secondary circuit is operated by the head guard 46, 47 in such a way that none of the relays can function until the guard. is shut.

The coil 62 of the double-acting relay is so connected that when it is not energised its contects 67, 68 are in a position such that the power supply circuit to the coil of the forward relay 58 is closed and when its coil is energised this circuit is opened and the power supply circuit to the coil of the reverse relay 59 is closed. In Figure 8 the contacts 67 for the forward relay are closed and contacts 68 for the reverse relay are open.

One terminal of the transformer secondary is connected toone terminal of the coil 62 of the double acting relay through trip circuit contacts 85 which are closed by the forward relay 58 when it is energised and are opened by it when it is de-energised; a pilot light 103 indicates when the trip circuit contacts are closed. The other terminal of the transformer secondary is connected to the other terminal of the coil 62 of the double-acting relay through a switch 102, a rectifier 69 and one of a number of, paths. One of these paths 70 comprises the wire 1 to which the open lapping of string is being applied and the string sensing device 7. A second path 71 is through the spring arm 50 and contact members 52, 53 to the slip ring 54 and carbon brush 55. A third path 72 is through the wire and the pulley 9 over which the normally insulated wire passes. Across the terminals of the coil 62 of the double-acting relay are connected two capacitors 73 and, in parallel therewith, two leakage resistors 74, to form a timing circuit.

The actuating supply circuits to the forward and reverse relays 58, 59 are also under the control of a start push button 75, a stop push button 76 and an inc push button 77.

In operating the machine the guard switch 66 must first be closed by closing the two- part head guard 46, 47, and a main switch 101 must be closed by hand, thereby completing a circuit to a pilot light 78, indicating that the sensing circuits 70, 71, 72 are operable, and also energising the coil 64 of the interlock relay to close the switch 65. When the start button 75 is pressed the circuit to the forward relay 58 is completed by the closing of contacts 79 on the start button and through closed contacts 80 on the stop button. At the same time contacts 1% are opened. On releasing the start button the contacts 1% are closed and contacts 79 are opened but the forward relay is energised through contacts 81 forming part of the inch control, and a hold-on control 82 held in position by the forward relay 58.

On pressing the stop button, the contacts 80 are opened, thereby de-energising the forward relay 58 and hence also the hold-on control 32. The motor is no longer energised to rotate forward. Whilst the stop button is being pressed, the contacts 83 are held closed and complete a circuit to energise the reverse relay 59, thereby reversing the connection to the motor. On releasing the stop button, the contacts 83 are opened and contacts 80 are closed again but the motor is not energised forwards because the hold-on control 82 is not made. On pressing the inch button the circuit to the forward relay 58 is completed through contacts 84 and contacts 80 but the contacts 81 are opened when the contacts 84 are closed, and thus the hold on control is disabled so that the motor is energised only whilst the inch button is being pressed. Whenv the inch button is released the contacts 81 are closed and contacts 84 are opened thus disabling the clrcuit to the forward relay 58.

The automatic cut-out circuit acts as follows. Assuming that the motor is running forwards, that the switch 102 is closed and that the string applying head andtape applying head are functioning properly, if the tape breaks the wire makes contact with the pulley 9 and the coil 62 of the double-acting relay is energized through the rectifier 69 and at the same time the capacitors '73 commence to charge. Immediately the coil 62 of the double-acting relay is energised the contacts 67 are opened and the contacts 68 are closed, thereby deenergising the forward relay 58 and energising the reverse relay 59, and reversing the connections to the motor. The forward relay 58, when it is tie-energised, opens the trip circuit contacts 65 to break the power supply circuit to the double acting relay 62 and to the capacitors 73. The capacitors will now discharge through the leakage resistances 74 and through the coil of the double-acting relay, which will thus remain energised for a controlled time depending on the capacitance of the capacitors and the value of the leakage resistance. At the end of this period the contacts of the double acting relay will be reversed, thus de-energising the reverse relay 59 and stopping the motor.

At the same time as the forward reply 53 is de-energised, the hold on control 82 is disabled so that when the contacts of the double-acting relay reverse the motor will not be automatically restarted.

The circuit 71 for stopping the motor when the pad is almost run out is connected in parallel with the circuit 72 for stopping the motor when the tape ceases to be applied to the wire, thus a similar sequence of operation is initiated when the pad is almost run out. The circuit 70 operates similarly when a break occurs in the spacing materim. A counter is also provided which measures the length of wire passing through the machine This counter operates a switch 86 which is tripped when the length of wire to which the counter is set has been covered by the machine.

When one of the circuits for automatically stopping the machine is completed for too short a time to charge the capacitors, the forward relay 58 is de-energised, the trip circuit contacts are opened, the hold on the control 82 is disabled and the machine idles to rest without reverse braking.

As already mentioned, none of the relays can function until the two- part head guard 46, 47 is closed, thereby closing the contacts 66 of the guard switch which is shown in detail in Figure 9 and mounted on the head as seen in Figure 1. This switch comprises an upper and lower casing, the lower casing 87 being fixed to the fixed part 46 of the head guard and the upper casing 88 being fixed to the movable part 47 of the head guard. Within the lower casing are the contact 66 (see also Figure 8) one being connected to a terminal of the transformer secondary winding and the other being connected to a. terminal of the interlock relay 64. A plunger 89 in the lower casing is normally urged by a spiral spring 90 out of engagement with the contacts 66. On closing the movable part 47 of the head guard the end of an adjustable screw member 91 engages the top of the plunger and forces it into engagement with the: contacts which are thereby bridged by the bottom end of the plunger and complete the circuit for the transformer secondary winding.

The head guard includes a mechanical locking arrangement which may be seen by reference to Figures 2 and 10 and which prevents an operator opening the head guard until the speed of rotation of the motor spindle has fallen to a very low value. The lock comprises an actuating member 92 slidably mounted for longitudinal movement on the base of the lower part 46 of the guard in a direction towards and away from the motor. shaft. Its outer end is provided with a manually operable but,-

ton 93 fitting into a cover 94 ('see also Figure l). A.

spring 95 is fastened at one end of a bell crank lever 96, the other end of which fits into an indentation in the actuating member thereby locking the actuating member in the position shown in Figure 10. The actuating member has a T-shaped lug 97 which fits into a complementary T-shaped slot on a metal strip 98 fixed to the movable part 47 of the head guard when the actuating member is in its outer position. Thus in this position the movable part 47 of the head guard is locked to the fixed part. When the actuating member is in its inmost position the lug 97 is clear of the metal strip 98 and the movable part of the head guard may be opened. If the motor is rotating, the actuating member is prevented from being moved inwardly by a toothed wheel 99, coaxially fixed to the motor spindle, which makes contact with the pointed inner end of the member 92. Since the lock cannot be released until the pointed end of the actuating member is fitted between two of the teeth, the actuating member cannot be forced into the guard release position until the motor spindle and hence the tape lapping head is stationary or moving very slowly.

The means by which the counter which measures the yardage of wire passing through the machine closes the switch 86 when a desired length of wire has passed through is shown in Figure 11. The counter, which is of the kind comprising a number of interconnected drums each marked on its periphery with the numbers -9, is supported on the frame of the machine by a bracket 104 (see Figure 1) and is driven by a reduction gear coupled to the spindle of the pulley 9. Each drum 105 of the counter has a cam on its periphery which actuates an arm 106 of spring metal fixed at one end and having a contact 107 at its other end associated with a contact 108. The disposition of the cams is such that when a desired yardage of wire has passed through the machine all contacts 107, 108 are closed. The switch 86 comprises a circuit including all of the contacts 107, 108 in series and when all of the contacts are closed the switch is closed.

What we claim as our invention is:

1. A machine for applying an open lapping of spacing material to a bare wire and for lapping an insulating tape over the spacing material comprising a head for applying the spacing material, a head for applying insulating tape from a coil of said tape, means for driving the two heads, means for advancing the wire through the two heads, first automatic stopping means, brought into operation when the machine ceases to apply the spacing material, comprising a first electric circuit including the wire and electric contact means urged towards, but normally held out of contact with, the wire by the spacing material, second automatic stopping means brought into operation when the wire having an open lapping of spacing material ceases ,to be covered by insulating tape, comprising a second electric circuit including the wire and second electric contact means adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape and normally insulated from and held away from the wire by the insulating tape lapped thereon, third automatic stopping means brought into operation by the making of a third electric circuit when said coil of insulating tape is nearly used up, said third electric circuit including electric contact means normally held open by said coil of insulating tape and fourth automatic stopping'means comprising means for measuring the length of wire passing through the machine and an electric circuit rnade thereby when a predetermined length of wire has passed through the machine, each of said automatic stopping means being adapted to stop the means for advancing the wire through the two heads and the means for driving said heads.

2. A machine according to claim 1 driven by a single electric motor, wherein each automatic stopping means operates by reversing the power supply to the field coils of the motor for a controlled time.

3. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material comprising a head for applying the insulating tape from a coil of said tape, driving means for rotating the head, driving means for advancing the wire through the head and automatic stopping means for said driving means which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire and at least one electric contact which is adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape and which is normally insulated from and held away from the wire by the insulating tape lapped thereon.

4. A machine according to claim 3 driven by a single electric motor, wherein the automatic stopping means op crates by reversing the power supply to the field coils of the motor for a controlled time.

5. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material comprising a head for applying the insulating tape from a coil of said tape, driving means for rotating the head, driving means for advancing the wire through the head and automatic stopping means for said driving means which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire and a member of contacts which are electrically connected, which are carried by a single member and which are adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape, the contacts being normally insulated from and held away from the wire by the insulating tape lapped thereon;

6. A machine according to claim 5 driven by a single electric motor, wherein the automatic stopping means operates by reversing the power supply to the field coils of the motor for a controlled time.

7. A machine for lapping an insulating tape onto a wire over an open lapping of spacing material comprising a head for applying the insulating tape from a coil of said tape, driving means for rotating the head, driving means for advancing the wire through the head and automatic stopping means for said driving means which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire and a pulley over which the wire passes in its path from the insulating tape lapping head, the pulley being so shaped as to provide a number of electric contacts which touch the wire when the wire ceases to be covered by the insulating tape, the contacts being normally insulated from and held away from the wire by the insulating tape lapped thereon.

8. A machine according to claim 7 driven by a single electric motor, wherein the automatic stopping means operates by reversing the power supply to the field coils of the motor for a controlled time.

9. A machine according to claim 7 in which the pulle is provided with contacts consisting of conductive cylinders mounted transversely in the pulley groove and spaced apart around the periphery of the pulley by a distance which is not equal to and is not a multiple of the lay of the spacing material.

10. A machine for applying an open lapping of spacing material to a bare wire and for lapping an insulating tape over the spacing material, comprising a head for applying the spacing material, a head for applying insulating tape from a coil of said tape, driving means for the heads, driving means for advancing the Wire through the two heads, first automatic stopping means for. said driving means, brought into operation when the machine ceases to apply the spacing material, comprising a first electric circuit including the wire and electric contact means urged towards, but normally held out of contact with, the wire by the spacing material and second automatic stopping means tor said driving means, brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, comprising a second electric circuit including the wire and a number of contacts which are electrically connected, which are carried by a single member and which are adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape, the contacts being normally insulated from and held away from the wire by the insulating tape lapped thereon.

11. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material, comprising a head for applying the insulating tape from a coil of said tape in the form of a flat pad supported coaxially with the wire, driving means for the head, driving means for advancing the tape through the head, first automatic stopping means for said driving means, which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by the insulating tape, including a first electric circuit including the wire and at least one electric contact which is adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape and which is normally held away from the wire by the insulating tape lapped thereon and second automatic stopping means for said driving means comprising a second elect-ric circuit including a spring arm mounted at one end on a table, which is rotated about the wire, and formed at its other end with a contact member which is normally pressed on to the pad near its centre by the arm but which is adapted to engage an insulated contact on the table, when the pad is nearly used up, to complete the second electric circuit.

12. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material, comprising a head for applying the insulating tape from a coil of said tape, driving means for the head, driving means for advancing the wire through the head, first automatic stopping means for said driving means comprising means for measuring the length of wire passing through the machine and an electric circuit made thereby when a predetermined length of wire has passed through the machine and second automatic stopping means for said driving means, brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, comprising a second electric circuit including the wire and a number of contacts which are electrically connected, which are carried by a single member and which are adapted to bear against the wire between the turns of the spacing material when the wire ceases to 10 be covered by the insulating tape, the contacts being normally insulated from and held away from the wire by the insulating tape lapped thereon.

13. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material, comprising a head for applying the insulating tape from a coil of said tape, a single electric motor for driving the head, driving means for advancing the wire through the head, automatic stopping means for said motor which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire and at least one electric contact which is adapted to bear against the wire between the turns of the spacing material when the Wire ceases to be covered by the insulating tape and which is normally insulated from and held away from the wire by the insulating tape lapped thereon, and a head guard normally enclosing the insulating tape lapping head and formed of a fixed part and a movable part hinged to the fixed part and including an electric switch controlling the motor circuit in such a way that when the head guard is closed the switch is closed automatically and when the head guard is opened the switch is opened automatically.

14. A machine for lapping an insulating tape on to a wire over an open lapping of spacing material comprising a head for applying the insulating tape from a coil of said tape, driving means for rotating the head, driving means for advancing the wire through the head, automatic stopping means for said driving means which is brought into operation when the wire having an open lapping of spacing material ceases to be covered by insulating tape, the automatic stopping means including an electric circuit comprising the wire and at least one electric contact which is adapted to bear against the wire between the turns of the spacing material when the wire ceases to be covered by the insulating tape and which is normally insulated from and held away from the wire by the insulating tape lapped thereon and a head guard normally enclosing the insulating tape lapping head and formed of a fixed part and a movable part hinged to the fixed part, the two parts being adapted to be secured together by a lock which prevents the movable part from being moved firom its enclosing position to an open position until the speed for rotation of the tape lapping head has fallen to a low value.

References Cited in the file of this patent UNITED STATES PATENTS 621,735 Arnold Mar. 21, 1899 1,368,489 Crumley Feb. 15, 1921 1,782,403 Bouvier Nov. 25, 1930

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