US2779860A - Apparatus for making, sizing, and electrically treating a wire coil - Google Patents

Description

Jan. 29, 1957 w. CONRAD 2,779,860

APPARATUS FOR MAKING, SIZING AND ELECTRICALLY TREATING A WIRE COIL. Filed Nov. 10, 1955 2 Sheets-Sheet l INVENTOR. IUIUDLLT' Conrad.

ATTORNEY Jan. 29, 1957 W. CONRAD APPARATUS FOR MAKING, SIZING AND ELECTRICALLY TREATING A WIRE COIL 2 Sheets-Sheet 2 Filed Nov. 10, 1955 INVENTOR. Ufilbur Conrad.

BY QE- a LW ATTORNE Y through a segment of the wire.

United States Patent APPARATUS FOR MAKING, SIZING, AND ELEC- TRICALLY TREATENG A WIRE COIL Wilbur Conrad, Unionville, Conn. Application November 10, 1955, Serial No. 546,189 7 claims. or. 219-153 This invention relates to wire coiling machines, and more particularly to a structure for accurately sizing the free length of the spring and reducing the coiling stress therein.

A compression spring made of helically coiled wire is often required to be used at the top allowable stress which each particular type of spring metal is capable of withstanding, and the spring length should be accurate. Heretofore, springs have been made by coiling the wire on a conventional wire coiling machine and cutting off the spring in a length which is longer than the desired finished length. They are then heat treated in a furnace, after which they are cold set by compressing the springs until the coils are in close contact. Such a compressed cold set spring will not return to its original free length but will have a length somewhat nearer the desired measurement. Some springs are ground at their ends to provide bearing surfaces, and at that time the total length of the spring may be shortened to a uniform required length. It is desirable to avoid this need for an excessive grinding operation to control the length of the spring.

It is common practice to normalize the stressed wire by placing a group of the coiled springs in a basket and heating them in a large furnace or oven. The springs are heated for a considerable time, such as from one-half to five or six hours, according to the spring requirements. The length of heattreatment and the temperature are, however, determined largely by trial and error. The heat treatment is uneven, because of the large number of springs held in the basket, and the heating conditions are therefore set to give an average treatment in which the outer layer of springs may be overheated and the less exposed springs undertreated.

Another normalizing and sizing treatment involves clamping a set of springs between parallel plates and heat treating them in that. condition while the spring lengths are held uniform. This expensive and laborious operation does not prevent a detrimental grain growth at the surface as is caused by the prolonged heating procedure. .Also, the coiled spring has previously recoiled to a larger size and so is heat set in the recoiled condition and not in the coil dimensions and shape imposed by the tools of the coiling machine.

In accordance with my copending application Serial No. 546,142 filed on even date herewith, a wire may be electrically treated during the entire coiling operation by passing a current of uniform characteristics continuously No provision is therein made, however, for setting a finished coil of normalized wire in a standard length.

The primary object of my invention is to provide apparatus whereby each spring may be treated at the end of the coiling operation and prior to its being severed from the in-feeding wire in order both to reduce the coiling stress therein and at the same time accurately size the spring. I

A further object is to electrically treat a coiled spring ice in the coiling machine to relieve the coiling and other stresses therein while the spring shape is held substantially fixed and its length is held according to a desired adjustment, as by stretching or compressing the coil. Other objects will be apparent in the following disclosure.

In accordance with this invention, I form a wire coil by means of suitable coiling tools, such as the wire guide block, the arbor, the coiling point and the pitch control member of a universal coiling machine shown in the U. S. Patent Blount and Fisher No. 2,175,426 of October 10, 1939. When a desired length of coil has been formed, the wire feeding is stopped and the coil is brought to a required length, and while its dimensions are thus fixed and before the coil has been severed from the Wire, it is subjected momentarily to an alternating electric current of required voltage and amperage to reduce various stresses in the coil. A standard type of compression spring may be compressed to a desired length against the coiling tools, and while its shape and stressed condition are thus substantially fixed, it is treated by an alternating current having a low voltage related to the wire resistance which is applied for a short period and will not heat the wire detrimentally. Thus, the coil is normalized at a desired length.

Although the invention is applicable to various types of wire coiling machines, it has been illustrated as applied to the machine described in my prior application Serial No. 447,278 filed August 2, 1954, and to which reference may be had for further description of the mechanism thereof.

Referring to the drawings bodiment of this invention:

Fig. 1 is a fragmentary elevation of a wire coiling machine which embodies mechanism for electrically treating the wire coil after its formation and prior to its severance from the in-feeding wire, the lower feed roll being omitted for clarity of showing of the coil pressure mechanism;

Fig. 2 is a fragmentary diagrammatic view of the spring compressing and coiling mechanisms and showing the electric circuit for applying an alternating current to the cor Fig. 3 is a fragmentary perspective view of parts of the coiling mechanism and the cam control for the wire cutter;

Fig. 4 is a diagrammatic view of the coiling tools and wire feeding rolls; and

Fig. 5 is a sectional view illustrating the cam control for the cutter.

As more fully set forth in In supply of wire 1 is fed forward feed rolls 2 and 3 and between pairs of guide blocks 4 and 5 on opposite sides of the rolls and thence to a position beneath or above a grooved guide block 6 located close to a coiling arbor 8. that arbor in the required coil shape as determined by the position of the grooved end of a coiling point 9 which is adjustably and movably supported by means of a clamping block ll). A cutting tool 11 suitably mounted on a pivoted support 12 serves to sever the wire coil from the iii-feeding wire 1. A pitch controlling tool 13 is also suitably mounted adjacent the arbor and arranged at the side of the convolution of the first coil to determine the spacing of the coils of the helix. These elements determine the shape and size of the coil in accordance with standard practice, and at the required time the cutting tool 11 is brought forward to sever the coil from the wire.

Prior to severing the coil, the longitudinally movable compression tool 15 moved forward by a suitable controlling device, such as a cam, solenoid or fluid pressure operated mechanism, to engage the free end of the wire illustrating the preferred emy prior application, a by means of grooved the wire passes around coil and force it back towards the coiling tools to provide an exact coil length. When the length has been adjusted and while the coil is held fixed, an alternating current of required voltage is applied momentarily, such as for a small fraction of a second, to the fully made coil 16 so as to reduce a stress therein.

The pressure applying mechanism which serves to compress the completed coil against the forming tools comprises the cylindrical body which is slidably mounted between the split arms 17 of an upstanding lug carried by the slide 18. The body 15 carries a cylindrical reduced portion 19 sized to fit within the end of the coil. This part 19 may be adjustably and removably mounted in a socket in the body 15 for replacement according to the size required. The body 15 is adjustably mounted within an insulating bushing 29 made of fibre, rubber or other suitable material, which supports and electrically isolates it from the upstanding arm 17 on the slide. The body 15 may be clamped in place by means of a bolt 22 passing through the two spilt arms 17. The slide 18 is suitably mounted on a dove-tailed slideway 23 supported by a bracket 24 on the machine frame 25.

In order to move the pressure members 15, 19 into engagement with the coil and to compress the latter to a required coil length, a suitable mechanism comprises a cam mounted on the camshaft 31 which is shaped to provide a high spot 32 for engagement with the roller 33 on an arm 34 pivoted at 35 on the bracket 24. The upper end of this arm 34 carries an adjustment screw 36 which is adapted to engage the left hand side of the slide support 18 and move the latter toward the right. A spring 38 suitably mounted beneath the slide body and engaging a depending member 39 thereof serves to hold the slide body toward the left and in engagement with the rocking arm 34.

As more fully described in my prior application Serial #447,278, the upper feed roll 2 is supported by a bearing box 40 and its shaft 41 is pivotally mounted at its right hand end (not shown). Two lifting cams 43 and 5-4 (Fig. 3) mounted on the shaft 41 and rotating with the upper feed roll 2 are arranged to be engaged at controlled times by a cam follower ring 45 mounted to rotate with the shaft 46 which carries the lower feed roll 3. The front cam 43 is shaped to lower the upper feed roll onto the wire to start the feeding operation and the rear lifting cam 44 serves to remove the upper feed roll from its driving engagement with the wire, so that depending upon the operation of these cams the wire is fed to make the coil or it is stopped to permit electrically treating and severing the coil. 7

The follower ring 4-5 is moved to its various positions by means of a yoke arrn 4-8 suitably mounted and spring pressed toward the left, which is moved towards the right by means of the high point 49 on a barrel cam 50 carried by the camshaft 31. That cam 50 is so shaped and coordinated with the lifting cams that when the follower 52 on the yoke arm 43 engages the low portion thereof, the follower ring 45 engages the feed roll lowering cam 43. When the high point 49 of cam 50 comes into contact with the follower 52, the follower ring 45 is moved to engage the lifting cam 44 which removes the feed rolls from driving engagement with the wire. An intermediate level 54 on the cam 5 provides for the follower ring 45 being located between the two cams 43 and 44 and thus inoperative. A further adjustably shaped holding cam 56 on the shafts 31 serves through a cam follower 57 carried by a bar 58 depending from the housing 40, and acting in timed relation with the operation of the high part of cam 56, to hold the upper feed roll from the wire until the electrical treatment and cutting operations have been effected.

Governed by the camshaft 31 is a further cam 60 (Fig. 3) which serves through a cam follower 61 on the rocking lever 62 to draw down on a pitman rod 63 of adjustd able length and thus rock the cutting tool 11 about its supporting shaft 64 to sever the wire.

The various cams are so positioned and timed relatively that the feed rolls will feed an exact length of wire to form a coil, and when that predetermined length has been made, the cam follower 45 shifts toward the right to cause the upper cam 44 to lift the upper feed roll from the wire, and immediately thereafter the holding cam 56 causes the feed roll to be held in that lifted position. Then, the cam 3'9 (Fig. 1) causes the plunger 15, 19 to move forward and compress the spring to an exact length.

The alternating electric current is applied momentarily to the coil, immediately after the coil length has been sized by the plunger 15, by means of a further cam 79 on the periphery of the cam 39 or on a separate cam, if desired, which operates a control switch to make the electric circuit. This switch, in the embodiment illustrated in Fig. 2, has a contact bar 72 normally held open or away from the line terminals by means of a compression spring 73, and an arm 74- of suitable construction is moved to close the switch by means of a lever 75 pivoted at 76 on the base of the machine. A cam follower roller 77 on the end of the lever normally rests against the cylindrical periphery of the cam 39, but is elevated to close the switch momentarily by means of a short rise 78 on the cam periphery. This cam rise is so located that the cam roller 33 will have reached the height of its associated cam 32 and compressed the coiled spring 16 to its minimum length just prior to the closing of the switch 72. The cam rise 32 which moves the coil compressing lever is long enough to hold the spring compressed while the roller 77 is passing over the cam rise 78, so that the spring is held at a fixed length during the period of the introduction of the electric current to the spring.

The source of low voltage alternating current controlled by the switch 72, as shown in Fig. 2, may be a step-down variable voltage transformer 80, such as a stepless Variac auto-transformer. This comprises a transformer winding 82 coiled on a laminated ring core 83 of magnetic metal. The power line 84 of suitable voltage, such as 110 volts, is connected to the ends or suitably spaced terminals of the coil 82. One side of the power line is connected through switch 72 with a transformer terminal 85 and the other side of the power line is connected to the opposite transformer terminal 86 so that the transformer winding comprises the load on the power line. The transformer may be connected directly to the load represented by the coiled wire 16; but in the illustration an intermediate step-down transformer comprising the primary and secondary coils 87 and 88 are inserted between the variable transformer and the coiled wire load 16. One terminal of the primary coil 87 is connected to the terminal 85 of the variable transformer and the other terminal of the primary winding 87 is connected to a movable arm 89 pivoted at the center 'of the variable transformer coil and which has a sliding contact with that coil. Thus the voltage applied to the primary coil 87 is a proportionate .part of the volts applied to the variable transformer as determined by the position of the movable arm 89. The switch 72 is preferably located in the primary circuit, but may be arranged in the ultimate load circuit which comprises the wire coil 16.

This auto-transformer involves the induction of a counter E. M. P. which materially limits the no-load current flow, and the voltage that is derived therefrom is determined by the ratio of the variable transformer turns picked off by the movable arm 89 relative to the total number of'turns in the transformer. Thus, the current flow is limited primarily by the load resistance of the wire coil produced by the coiling tools. It will be appreciated that the low resistance of the formed wire coil 16 for the ordinary sizes of wire requires a very low voltage in-put to give the desired heating and electrical effect. Since the current is applied momentarily within the entire wire coil 16, the heating effect is uniform and does not produce a grain growth or other skin efi'ects involved in heating the wire from an external heat source. Moreover, the current is applied for only a very short period of time, such as & second, and any high temperature condition applied momentarily to the wire need not cause an overheating of the wire. The voltage may be accurately controlled to avoid any dertimental effect.

The current is to be controlled for heating the wire momentarily to that temperature at which the metal is normalized and the molecular orientation accomplished to relieve the stressed condition. The repeated reversal of the alternating current is thought to apply a reversing polarity to the molecules just as a reversal of magnetism will neutralize a magnetized body. After the coil has been made and compressed to the required length, the current may be applied momentarily to it, as herein described. I may use a voltage of from 5 to 6 volts for a No. 21 spring wire (0.032 inch diameter) to relieve the stresses involved in cold working the metal. Wide variations may be made in the characteristics of the current. Nevertheless, it is desirable that an alternating current be used and that the wire be not heated excessively and to such an extent as to produce the undesired characteristics heretofore had when the wire is heated in a furnace. That is, overheating the wire such as spring metal may reduce the hardness or cause a growth of the grain structure at the surface and so change the wire structure to a detrimental extent. Any weakening of the molecular cohesions and a reduction of the resistance of the spring metal against bending and fracture is of course to be avoided.

It is also to he noted that the coil 16 is compressed to a fixed length between the slidable body 15 and the coiling tools comprising the grooved coiling point 9, the pitch controlling tool 13 and the grooved guide 6 which retain their functions of positioning the wire for coiling until after the electricity has been applied. Immediately after the introduction of the low voltage alternating electric current and the breaking of its circuit, the cam 60 is operated in its controlled timing cycle to cut off the coil. Thereafter, the lifting cam 43 lowers the upper roll 2 onto the wire and a new coiling process starts.

It will now be appreciated that various modifications may be made in the apparatus and that the above disclosure is to be interpreted as a description of the underlying principles of the invention and one embodiment of the same and not as imposing limitations on the appended claims.

I claim:

1. Apparatus for coiling wire comprising mechanism for feeding a wire progressively, tools including a coiling arbor for making a coil on the wire, cutter mechanism for severing the coil from the wire, mechanism operating prior to the coil severance for subjecting the coil to a force which holds it at a predetermined length and means for introducing an electric current of controlled voltage into the non-severed coil while subjected to said force to reduce a stressed condition resulting from the coiling operation.

2. Apparatus for coiling wire comprising mechanism for feeding a wire progressively, tools including a coiling arbor for making a coil on the wire, cutter mechanism for severing the coil from the wire, mechanism operating prior to the coil severance for compressing the coil to a predetermined shorter length and means for introducing into the compressed non-severed coil an alternating current of a low voltage related to the wire resistance to reduce the coiling stress.

3. Apparatus for coiling wire comprising mechanism for feeding a wire progressively, tools including an arbor, a coiling point, a wire guide and a pitch controlling tool for coiling the wire helically on said arbor, mechanism for compressing the coil axially against said tools to a predetermined length, means acting while the coil is thus compressed for introducing an alternating current of a voltage related to the wire resistance which reduces a coiling stress therein, and switch mechanism acting in timed relation with the coil compression to introduce said current to the coil only while it is compressed.

4. Apparatus for coiling wire comprising mechanism for feeding a wire progressively, coiling tools which form a coil on said wire, a cutter mechanism for severing the coil from the wire, mechanism for compressing the coil against the tools and maintaining it at a predetermined length, means providing an alternating current of voltage related to the Wire resistance for reducing a coiling stress in the wire, and cam control mechanism which causes the wire coil to be compressed and electric current to be introduced momentarily prior to the severance of the coil from the wire.

5. Apparatus for coiling wire comprising wire feeding rolls for moving a wire forward, coiling tools including an arbor for forming a coil on the end of said wire, cutter mechanism for severing the coil from the wire, power mechanism for compressing the coil to a predetermined length prior to its severance, means including a variable voltage transformer for introducing an alternating current into the compressed coil and timing mechanism which insures that the coil is compressed and the electric current applied momentarily prior to the sever ance of the coil from the wire.

6. Apparatus according to claim 5 comprising cam con trol mechanism which causes a predetermined length of wire to be fed to the coiling tools and a cam governing the timing mechanism.

7. Apparatus for coiling wire comprising power feed rolls, cam mechanism controlling the rolls which causes a predetermined length of wire to be fed forward and the wire to be stopped, coiling tools to coil the moving wire progressively, power mechanism to compress the com pleted coil to a predetermined length after the wire has stopped, electrical apparatus supplying a low voltage alternating current related to the wire resistance, cam controlled timing means to apply the current momentarily to the coil while it is held compressed and cam controlled cutter mechanism acting after the application of the current to sever the coil from the wire.

References Cited in the file of this patent UNITED STATES PATENTS 458,115 Thomson Aug. 18, 1891 469,943 .Tefiery Mar. 1, 1892 2,667,204 Jaycox Jan. 26, 1954

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