US3541828A - Spring forming apparatus and process - Google Patents

Description

Nov. 24, 1970 H. H. NORMAN SPRING FORMING APPARATUS AND PROCESS Filed Aug; 21, 1967 7 Sheets-Sheet 1 @z N: on

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BY w; 7% We Nov. 24, 1970 H. H. NORMAN SPRING FORMING APPARATUS AND PROCESS 7 Sheets-Sheet 2 Filed Aug. 21, 1967 INVENTOR.

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Harem H. NOQMAM/ m mm N9 .0 mm 02 5 :2 a 03 m9 wm mm H 0mm Nov. 24, 1970 H. H. NORMAN SPRING FORMING APPARATUS AND PROCESS 7 Sheets-Sheet 4 Filed Aug. 21, 1967 INVLNIOR HHQQY .H. NOEMAA/ Nov. 24, 1970 H. H. NORMAN 3,541,828

SPRING FORMING APPARATUS AND PROCESS Filed Aug. 21, 1967 '7 Sheets-Sheet 5 DIFFEENTIAL COUPLING coN'rQaL MEANS m Haeev H. NOEMIQ/L/ d INVENTORA O I :4 BY 4% S Nov. 24, 1970 H. H. NORMAN 3,541,828

SPRING FORMING APPARATUS AND PROCESS Filed Aug. 21, 1967 7 Sheets-Sheet 6 I68 an 2:3 20 203 1220 (O) 1 "1 :2 :11. I1] I L [I l 4 J 412219 fi 222a 52252 b L f I 5 52 INVENTOR.

HHEQY H, NOAQMAA/ Nov. 24, 1970 H. H. NORMAN 3,541,323

SPRING FORMING APPARATUS AND PROCESS Filed Aug. 21, 1967 7 Sheets-Sheet 7 fin/22v H. Noe/wald- United States Patent T 3,541,828 SPRING FORMING APPARATUS AND PROCESS Harry H. Norman, Los Angeles County, Calif., assiguor of one-half to Stephen Baliski, Gardeua, Calif. Filed Aug. 21, 1967, Ser. No. 661,948 Int. Cl. 321E 3/02, 3/04, 3/10, 7/00, 23/00, /00 US. Cl. 72-140 35 Claims ABSTRACT OF THE DISCLOSURE coaxially below the platen twists the incoming wire, which then is guided through a passageway and around the feed wheel toward a stationary stanchion. Control rollers mounted on the platen restrain the natural wire curvature, imparted by twisting, to form the spring. A mechanical feedback system may be used to control the planetary ratio so as to keep the spring from rotating as it is being formed.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to an apparatus and process for producing a spring from a wire. More particularly, the invention relates to fabrication of compression or extension springs by twisting a wire about its longitudinal axis, and restraining the natural pitch and curvature resultant when the twisted wire is released.

Description of the prior art As is well known, coil springs are of two major types, compression and extension. Compression springs, exemplified by bed springs or automobile valve springs, act to oppose a compressional force tending to reduce their length. Extension springs, such as garage door springs, act in opposition to loads tending to elongate them.

In the past, virtually all extension and compression springs have been fabricated by first forming a coil from a wire. Initially, the wire is forced against a tool or wound around a mandril, longitudinally stressing the outer edge of the wire in tension, while stressing the inner edge (with respect to the diameter of the coil) in compression. Of course, the elastic limit of the wire was exceeded during this step, otherwise the wire would unwrap immediately when the force used to wind the coil was removed.

To fabricate a prestressed spring, the coil initially was wound with a length greater than that desired for the final product. This coil then was compressed in length, thereby forming a prestressed spring having a final length less than that as originally wound. Typically, to make a three inch spring, a coil having a predetermined length of about six inches first was wound. After the coil was prestressed by compression, it assumed the desired three inch length. Of course, the diameter of the final spring also differed from that of the coil as originally wound. To compensate for this, the coil initially was wound to a different but predetermined diameter so that subsequent to prestressing, it would resume the desired dimension.

Note that by stretching the original coil, the wire forming the coil itself was twisted beyond the elastic limit, prestressing it circumferentially. Thus, if the original coil were wound clockwise around the mandril, when stretched, the wire became prestressed counterclockwise.

3,541,828 Patented Nov. 24, 1970 It is this substantially circumferential prestressing, resultant from crystallographic restructuring within the wire when its elastic limit is exceeded, which makes the coil act as a compression spring.

Recall that as the coil originally was wound, the wire was stressed substantially longitudinally, its outer portion in tension, its inner portion in compression. The circumferential stress resultant from stretching the coil is additive with the tension stress introduced during winding, but generally is opposite in direction to the compression stress over the remainder of the cross section. Thus, the net twist or circumferential prestress obtained by stretching is substantially less than that which could have been achieved had the wire not previously been forced into a coil.

As in the case of a compression spring, the circumferential prestress introduced during formation of an extension spring generally was additive with the tensional stress due to coiling, but was opposed by the compression stress present over the inner portion of wire cross section. Consequently, the net circumferential prestress (twist) obtained was substantially less than could have been obtained if the wire had not previously been coiled.

Yet another factor, the degree to which the initially wound coil could be reduced in length, limited the maximum circumferential prestress obtainable in prior art springs. Clearly, the coil could not be compressed much beyond the point where adjacent turns of wire are touching unless special overlay techniques were used. This has meant that in the past, extension springs had to be made substantially longer than theoretically should be necessary to obtain a spring of desired characteristics.

Other techniques used in the prior art included the ap plication of tools or dies, with which or against which the wire is forced to produce pitch and/or diameter. The tool or die may be stationary, or rotatable to obtain compound angles of the wire for pitch and diameter control. Such die forming techniques also produced undesired tension and compression on opposite sides of the wire formed into a spring.

As represented by the peak in the Youngs modulus of elasticity curve for the wire used to make the spring, there exists a maximum limit to the total amount of force per unit area which the wire can undergo before becoming plastic or breaking. Thus, it will be appreciated from the foregoing discussion, that if the Youngs modulus maximum force were applied during compression or stretching of the initially wound coil, the portion of the wire which had been stressed in tension would exceed the stress limit of the material and fracture. Thus, a lower force had to be used to generate'the circumferential stress, and as mentioned, this stress was reduced by the subtractive effect of the prior compression of the wire adjacent the inner periphery of the coil.

Thus, the prior art method of making either compression or extension springs placed an inherent limitation on the maximum working stress obtainable with a spring fabricated of a given material and spring index (ratio of coil diameter to wire diameter). These maximum values of working stress are reflected in the standard tables of spring characteristics, such as those contained in the Tool Engineers Handbook. These maximum working stress values are substantially less than those which could be obtained were the springs formed without first coiling the wire.

Springs fabricated in accordance with the prior art sutfer various other shortcomings. Because of the limitations previously noted, to obtain a particular working stress often requires use of a spring of considerable physical size. Moreover, with some prior art springs, the full working stress is not obtained until the spring has been elongated or compressed for some length.

Thus, there are situations where a spring of particular working stress is required, but where there is insufficient space for a spring of the minimum size capable of providing that Working stress. Alternatively, there may be sufiicient space to mount the spring, but insufficient space to expand the spring in length sufficiently to obtain the required working stress.

Springs manufactured in accordance with the prior art have another shortcoming. The substantially longitudinal tension stresses introduced in the wire along the outer periphery of the intially wound coil made the wire susceptible to surface fractures, and subsequent breakdown of the spring. This is a major factor limiting the fatigue life, and hence the useful lifetime of a spring.

While some of the problems noted above are reduced by annealing of the spring, such annealing still does not permit use to be made of the maximum stress capability of the spring material. Annealing is common and in the past has been necessary for stability of the spring.

Prior art spring winding machines themselves have various shortcomings, often resulting from the basic method employed. For example, often no provision was made to isolate the coil winding forces from the source spool of wire. Thus, if the wire came off the reel irregularly (which normally was the case), the occasional tugging of the wire was reflected as an irregularity in the finished coil. Then too, random variation in the natural cast of the wire entering the prior art winder mechanisms affected the degree of compression or tension experienced by the wire being coiled. This irregularity adversely affected the uniformity of the springs produced.

Yet another problem is that some slippage often occurred in the prior art winder mechanism. This affected the amout of bending achieved by the fixed forces employed in the prior art devices, and often affected the diameter, pitch, or working stress of the resultant spring.

Yet another shortcoming of prior art winders is that, as produced, the coil or spring is rotating. Thus, often the coil has to be cut and removed from the winder before it can be subjected to further processing. While in many industries this is not objectionable, it is a problem in applications, for example, where very long coils are required. In the air conduit field, this rotation of the coil prevents the outer nylon or cloth jacket from being applied to the coil directly as it comes from the machine. Clearly, this limits the maximum length of conduit which can be manufactured conveniently.

The spring winding method and apparatus of the present invention facilitates the manufacture of compression or extension springs having very closely controlled pitch, diameter, and working stress. This is accomplished by fabricating the springs by a unique twisting process which does not require initial coiling. The inventive process thus eliminates the detrimental stressing of the wire which resulted when, in the prior art, the wire was forced into a coil.

The present invention permits the manufacture of springs which can be initially circumferentially stressed up to the maximum limits set by the Youngs modulus curve for the wire material used. Either extension or compression springs can be made, which may exhibit working stresses greater than those obtainable by the best springs of the same dimensions fabricated in accordance with the prior art. Moreover, such springs may exhibit maximum force with very slight displacement. Thus, for example, extension springs made in accordance with the present invention may be used in applications where very limited space exists for elongation of the spring.

SUMMARY OF THE INVENTION In accordance with the present invention, there is set forth a technique and apparatus for forming a spring from a wire by initially twisting the wire, beyond its elastic limit, about its longitudinal axis. The twisted wire is mo ded nto a spring having a desired pitch and diameter obtained by restraining the natural pitch and curvature produced by the twisting. The technique permits fabrication of springs having unique stress characteristics.

The inventive apparatus utilizes a rotating platen on which is provided a feed wheel which experiences planetary motion with respect to the platen. A twisting mechanism, extending coaxially below the platen, twists the in coming wire about its longitudinal axis in rotational correspondence with the platen.

The twisted wire is guided around a portion of the periphery of the feed wheel. The natural pitch and curvature of the twisted wire coming from the feed Wheel then are restrained to the desired values using pitch and diameter control rollers mounted on the platen. The spring is formed about a stationary stanchion which extends coaxially above the platen.

A unique gearing system enables continuously variable control of the planetary ratio (that is, the number of revolutions of the feed wheel about its own axis for each revolution of the platen). If desired, the planetary ratio may be selected to insure that the spring being produced does not rotate about the stanchion. When so used, undesired rotation of the coil about the stationary platen is sensed and used to control a feedback mechanism which correctively alters the planetary ratio, thus eliminating the rotation.

The inventive apparatus may be used for winding either tension or compression springs by appropriately selecting the relative directions for twisting the wire and for molding the twisted wire into a spring.

A pre-feed constant demand mechanism and a twist isolator apparatus function to isolate the coiler mechanism from the tugging and bending variations experienced by the Wire as it comes off its spool.

Other embodiments of the invention facilitate the manufacture of either extension or compression springs, the winding pairs of identical leftand right-handed springs, and the production of springs having programmatically controlled variations in pitch and diameter.

Thus, it is the primary object of the present invention to provide a method and apparatus for producing springs.

It is another object of this invention to provide a technique and apparatus for fabricating a spring by the controlled twisting of a wire.

Another object of this invention is to provide a spring winding apparatus wherein the desired spring pitch and diameter are achieved by restraining the natural pitch and curvature imparted by twisting a wire about its longitudinal axis.

Still another object of this invention is to provide a method and apparatus for fabricating a spring from a wire without initially coiling the wire.

It is another object of this invention to provide an apparatus for fabricating a spring from a wire by twisting the wire, and then directing the twisted wire into the form of a spring by utilizing a feed wheel and restraining rollers mounted on a rotating platen.

A further object of this invention is to provide a spring Winder employing a feed Wheel experiencing planetary motion on a rotating platen, about a stationary stanchion, and wherein the planetary ratio is continuously controllable.

It is another object of this invention to provide a spring fabrication apparatus in which the spring being formed does not rotate.

It is a further object of this invention to provide a novel feedback system for controlling the planetary ratio of a pair of rotating members such as a platen and a feed wheel in a spring fabrication apparatus.

Another object of this invention is to provide a spring forming apparatus capable of producing springs having programmatically controllable variations in pitch and diameter.

A still further object of this invention is to provide a spring making apparatus having pre-feed mechanism for supplying wire to the apparatus at a constant rate free of tugging effects due to the wire irregularly leaving the spool.

Yet a further object of this invention is to provide a method of producing extension springs having up to 100% preload.

Still a further object of this invention is to provide a method and apparatus for producing springs having unique stress characteristics.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The present invention, both as to its organization and manner of operation, together with further ob jects and advantages thereof, may best be understood by reference to the following description, taken in connec tion with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a preferred embodiment of the inventive spring forming apparatus; the two iden' tical mechanism illustrated may be used simultaneously to produce rightand left-handed springs having identical characteristics;

FIG. 2 is a side elevation view of the inventive spring forming apparatus, a top View of which is shown in FIG. 1. The overall appearance of the pre-feed mechanism, the twist isolator, the spring forming mechanism and the primary drive train, is evident;

FIG. 3 is a sectional view of the loop diameter sensing portion of the pre-feed mechanism as seen along line 33 of FIG. 1;

FIG. 4- is a sectional view showing portions of the planetary gear system used to drive the feed wheel, as viewed along line 44 of FIG. 1;

FIG. 5 is a sectional view showing portions of the planetary gear system used to drive the stanchion, as viewed along line 55 of FIG. 1;

FIG. 6 is a sectional view showing portions of the feedback mechanism used to alter the planetary ratio of the gear system used to drive the feed wheel, as viewed along line 6-6 of FIG. 7;

FIG. 7 is a sectional view showing the planetary gear systems for both the feed wheel and the stanchion as well as the feedback gear system, as viewed along line 7-7 of FIG. 4;

FIG. 8 is a fragmentary top plan view, in partial section, of the spring forming mechanism illustrated in FIG. 1. Details of the feed wheel, bias wheel and upper platen are evident;

FIG. 9 is a fragmentary perspective view of a portion of the spring forming mechanism shown in FIG. 8. The pitch and diameter control rollers, the stanchion about which the spring is formed, and the spring diameter size sensing apparatus are illustrated;

FIG. 10 is a fragmentary sectional view of a scraper device for cleaning particles on the periphery of the feed reel, as seen along line 1010 of FIG. 8;

FIG. 11 is a fragmentary sectional view of the coupling used to guide the wire through the upper platen, as seen generally along line 11-11 of FIG. 8;

FIG. 12 is a fragmentary top plan view of another embodiment of the inventive spring forming mechanism adapted to vary periodically the pitch and diameter of the spring being formed;

FIG. 13 is a fragmentary sectional view of the cylindrical cam and cam follower apparatus used to vary periodically the pitch of the spring being wound, as viewed along line 13-13 of FIG. 12;

FIG, 14 is a fragmentary sectional view of the pitch control roller lever arm, as seen along line 14-14 of FIG. 12;

FIG. 15 is a side elevation view of a spring which may be produced using the embodiment of the invention spring forming apparatus illustrated in FIG. 12;

FIG. 16 is a diagrammatic cross section View of a wire formed into a spring in accordance with the present invention illustrating the internal stress pattern thereof;

FIG. 17a is a diagrammatic cross sectional view of a wire formed into a spring prior to prestressing, in accordance with the prior art, illustrating the internal stress pattern thereof; and

FIG. 17b is a diagrammatic cross sectional view of a wire formed into a spring, subsequent to prestressing, in accordance with the prior art, illustrating the internal stress pattern thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a preferred embodiment of the inventive apparatus for making coil springs. The apparatus illustrated in FIG. 1 is configured to produce compression springs using a method, in accordance with the present invention, wherein a wire is twisted about its longitudinal axis. The twisted wire then is molded into a coil of desired diameter and pitch by restraining the natural pitch and diameter imparted by twisting.

Two identical spring fabrication machines are evident in FIG, 1. The two machines permit simultaneous winding of clockwise and counterclockwise springs having identical characteristics; such pairs of springs are used extensively in the bedding industry. It should clearly be understood, however, that for most applications only a single spring winding apparatus would be used. For this reason, and for ease of exposition, the operation of the inventive apparatus herein will be described for a single unit, except as required to describe the inter-relationship of the dual winders shown in FIG. 1.

The overall appearance of the inventive spring fabrication apparatus is shown in FIGS. 1 and 2. As indicated therein, the apparatus is mounted on a frame 20 which includes a lower horizontal portion 21 adapted for mounting on a floor, an upper table 22 on which various components of the spring winder are mounted, and appropriate vertical support members 23. The spring fabrication apparatus accepts wire 18 from a reel or spool 24 which is fastened to the floor 19 by mounting 25 which permits reel 24 to rotate as wire 18 is pulled into the coil winder.

Referring again to FIGS. 1 and 2, wire 18 first passes through vertical straightener 27 and horizontal straightener 28. Straighteners 27 and 28 are of conventional design, each employing a plurality of straightening rollers 29 and 29' arranged in parallel rows, and serve to eliminate bends in incoming wire 18.

Wire 18 next enters a constant demand pre-feed mechanism 30 which functions to pull wire 18 off spool 24 and to feed wire 18 to the remainder of the spring forming mechanism in a uniform demand. Pre-feed mechanism 30 is powered by motor 31 which is mounted to frame 20 by bracket 26, Motor 31 drives feed rollers 32 and 33 via belt 34 and AC coupling 35; motor 31 also may drive feed rollers 32 and 33, in pre-feed mechanism 30', via a second belt 34' (shown in phantom in FIG. 2) and a second AC coupling (not shown).

Wire 18 is coiled into three or four large horizontal loops within housing 36, which housing is supported by arms 37. As shown most clearly in FIGS. 1 and 3, a pivotally mounted sensing arm 40 is spring biased to rest against the inside of the loops of wire 18 within housing 36. Vertical member 41 of sensing arm 40 extends through slot 38 in housing 36, which slot is curved to conform to the angle of travel of sensing arm 40. This prevents wire 18 from slipping over the top of member 41 into the center of housing 36.

Sensing arm 40' is connected by shaft 42 to control means 43. Control means 43 in turn controls AC coupling 35 in such a manner as to adjust the speed of rotation of feed rollers 32 and 33. For example, control means 43 may comprise a rheostat which adjusts the voltage applied to coupling 35, and hence the rate at which power is transmitted from belt 34 to feed rollers 32 and 33.

Should the diameters of wire 18 loops within housing 36 become smaller, as may happen when wire 18 is coming off spool 24 at a rate slower than the uniform rate being demanded by the remainder of the spring winder, member 41 of sensing arm 40 will be pulled toward the center of housing 36. The resultant operation of control means 43 causes coupling to make feed rollers 32 and 33 rotate more rapidly. Conversely, when wire 18 is coming olf spool 24 too rapidly, the loops within housing 36 will increase in diameter, sensing arm 40 will pivot away from the center of housing 36, and control means 43 in conjunction with coupling 35 will cause feed rollers 32 and 33 to slow down.

It will be appreciated that the function of pre-feed mechanism 30 is to pull wire 18 off spool 24 and to supply wire 18 to spring forming mechanism 50 at a constant rate. In addition, pre-feed mechanism 30 prevents the distortion due to tugging which would occur in the final product if spring forming mechanism 50 itself had to pull wire 18 off spool 24.

As in all wire, there is a natural cast to wire 18. Due to this natural cast, the span of wire between spool 24 and straightener 27 will not be a straight line, but rather a free form coil ever changing as the spool 24 attempts to keep up with the coiler. Moreover, wire 18 is coming off spool 24 at a changing angle. If pre-feed mechanism 30 were not used, a varying amount of tugging would be exerted as wire 18 was pulled into spring forming mechanism 50. This tugging would be reflected as distortion in the spring being produced, which distortion is eliminated by use of pre-feed mechanism 30.

From pre-feed mechanism 30, wire 18 passes through table 22 via chute 45 and then is wrapped around grooved wheel 46, which is free to rotate about shaft 47. Shaft 47 is mounted to lower horizontal portion 21 of frame 20 by support member 48 in such a manner that wheel 46 cannot rotate about a vertical axis. Preferably, there are three or four wraps of wire 18 in the groove of wheel 46. Wheel 46 in effect serves as an isolator between pre-feed mechanism 30 and spring forming mechanism 50 in that no twisting of wire 18 which is performed by spring forming mechanism 50 is detectable in that portion of wire 18 between chute 45 and wheel 46. Although some twist feedback may be present within one or two wraps around wheel 46, it will be uniform and will not affect the final product.

Referring still to FIGS. 1 and 2, it may be seen that spring forming mechanism 50 is supported on table 22 by stationary base 51. Upper platen 52, lower platen 53, and oil tray 54 rotate in unison with respect to base 51 under power supplied by motor 60. Motor is mounted to base 51 by support bracket 63. Drive shaft 64, from motor 60, extends through base 51 via cartridge bearing and includes coupling 61 and sprocket wheel 68. Belt 62 transmits power from pulley 68 to lower platen 53.

Tubular shaft 55 is suspended from lower platen 53 by tripod legs 56, hence shaft 55 and legs 56 rotate with platen 53. Shaft 55 is coaxial with platen 53 and is tangentially aligned with grooved wheel 46 so that wire 18 from wheel 46 goes directly vertically through a portion of tubular shaft 55. Tubular shaft 55 also includes a curved tubular passageway 69 which guides wire 18 from a position within and substantially coaxial to shaft 55, through the wall of shaft 55, and to a location adjacent platen 53, but spaced apart from its axis. As will be explained hereinbelow, rotating tubular shaft 55, passageway 69 and grooved wheel 46 function as the mechanism for imparting a longitudinal twist to wire 18.

Extending coaxially upward from platen 52 is stanchion 59, about which spring 18' is guided. As will be described more fully hereinbelow, stanchion 59 is appropriately geared to remain stationary with respect to base 51 (and hence with frame 20) despite rotation of platen 52. Also extending from the top of platen 52 (see FIG. 1), are teed wheel 57 and bias wheel 58. The motion of whee 57 is generated by rotation of platen 52 via a planetary gear system to be described in detail below. Pulleys 112 and 117 and belt 118 function as part of a feedback system to alter the planetary ratio between feed wheel 57 and platen 52. Bias wheel 58 is driven by wheel 57 and platen 52. Bias wheel 58 is driven by wheel 57 via band 145, which also serves to guide twisted Wire 18 around a portion of the peripehry of feed wheel 57. While, in the inventive apparatus, wire 18 is directed around feed Wheel 57, the line force (i.e., the force per unit length) exerted on wire 18 by feed wheel 57 is exceptionally small, certainly less than the elastic limit of the wire. Thus, feed wheel 57 does not cause wire 18 to be bent or longitudinally stressed in compression and tension as in the case of a wire coiled in accordance with the prior art.

The various components of mechanism 50 are identical to those of spring former 50. Various design features of spring forming mechanism 50 may be understood by reference to FIG. 4. Note that lower platen 53 contains teeth (indicated generally at 66) around its outer periphery which engage timing belt 62. Belt 62 also engages sprocket wheel 68, which, as noted above, is driven by motor 60 via shaft 64 and coupling 61. These items thus function as the primary drive train to rotate platen 53.

As lower platen 53 rotates, it carries with it tripod legs 56 (mounted to platen 53 by spacer 71), passageway 69, and shaft 55. Lower platen 53 is fixedly connected to upper platen 52 by shaft 73 and by blocks (not shown) attached between platens 53 and 52; thus platen 52 rotates in unison with, and is driven by, platen 53. Platen 52 is free to rotate with respect to base 51, being mounted thereto by ball bearing raceway 71. Lower platen 53 also is rigidly attached to oil pan 54 by spacer 74, hence pan 54 also rotates with platen 53. Note that lip 75 of oil pan 54 is free to rotate within corresponding groove 76 of base 51.

Referring still to FIG. 4, note that bias Wheel 58- is supported by shaft 76 which projects from, and is free to rotate with respect to slidable block 78; shaft 76 does not extend into upper platen 52. Block 78 itself seats within slot 79 in platen 52, and is free to slide radially of platen 52 along track 80. Spring 81 is provided to bias block 78, and hence wheel 58, away from the axis of platen 52.

Note also in FIG. 4 that ring gear is rigidly attached to base 51 by support member 82. Ring gear 90, which has teeth only on its inner periphery, thus is stationary, and does not move when platen 52 rotates. Attached to the outer periphery of gear 90 is thin-line ball bearing roller 83, which supports ring gear 100 by means of retainer 84. Ring gear 100, which has teeth on both its inner and outer peripheries, thus is free to rotate with respect to and coaxial with, upper platen 52.

Operation of the gear train associated with stationary ring gear 90, and used to maintain stanchion 59in a fixed relationship with base 51, may be understood by reference to FIGS. 5, 6 and 7. As seen therein, spur gear 91 is mounted on shaft which extends between lower platen 53 and upper platen 52. Gear 91 meshes with the teeth on the inner periphery of stationary gear 90. Since shaft 95 rotates with platens 52 and 53, gears 90- and 91 form a planetary system such that spur gear 91 Will rotate about an axis through shaft 95 in a direction (for example, counter-clockwise) opposite that direction (for example, clockwise) in which platens 52 and 53 are rotating.

Gear 91 is fixed or keyed to gear 92 (also on shaft 95). Gear 92 itself meshes with pinion gear 93 which is free to rotate about shaft 96 extending from upper platen 52 (see FIG. 6). Pinion 93 also meshes with spur gear 94 which is connected to stanchion 59 via shaft 97. Platen 52 is separated from shaft 97 by way of double-rowed ball bearing 98, hence platen 52 may rotate independent of the motion of shaft 97 and stanchion 59. Of course, stanchion 59 and upper platen 52 are coaxial.

It will be appreciated by study of FIG. 7 that shaft 97 will rotate in a direction opposite that of platen 52. That is, if platen 52 is rotating clockwise, shaft 97 will rotate counterclockwise. In a preferred embodiment of spring forming mechanism 50, gears 90, 91, 92, 93 and 94 are selected (in a manner Well known to those skilled in the art) to have appropriate ratios so that shaft 97, and hence stanchion 59, will remain stationary with respect to base 51. That is, stanchion 59 will rotate at the same rate with respect to a reference point on platen 52, but in opposite direction, as platen 52 itself is rotating with respect to stationary base 51.

A second planetary gear train, independent of that used to drive stanchion 59, is used to drive feed wheel 57. This second planetary system. may be understood by reference to FIGS. 4, 5, 6 and 7.

Referring first to FIG. 5, notice that spur gear 101 meshes with the teeth on the inner periphery of rotatable ring gear 100. Gear 101 is supported on the same shaft 95 as is gear 91; however, gear 101 is free to rotate independently of gear 91. Spur gear 101 is fixed or keyed to pinion gear 102, which also is mounted on shaft 95. If ring gear 100 were held stationary with respect to base 51 while platen 53 was rotated, shaft 95 would experience relative motion with respect to ring gear 100. This would cause spur gear 101, and hence pinion 102 to rotate about their own axes (i.e., shaft 95) at the same time that shaft 95 itself was rotating about the center of platen 52. Thus, gears 100 and 101 comprise a second planetary system.

Referring to FIGS. 6 and 7, note that pinion gear 102 meshes with spur gear 103 on shaft 106. Shaft 106 extends between platens 52 and 53, and also contains pinion gear 104 which is keyed or fixed to spur gear 103. As shown in FIGS. 4 and 7, pinion gear 104 meshes with gear 105 which is keyed to drive shaft 73. Drive shaft 73, itself mounted to platens 52 and 53 by means of ball bearings 108 and 109, respectively, transmits the rotational motion of gear 105 to feed wheel 57.

If ring gear 100 is held stationary, then the number of revolutions made by feed wheel 57 to each revolution of platens 52 and 53 will be determined by the diameters of gears 100, 101, 102, 103 and 104. Selection of the desired planetary ratio between the number of revolutions made by platen 52 for each revolution of feed wheel 57 is discussed in detail hereinbelow.

Spring forming mechanism 50 also includes a system for altering the planetary ratio (i.e., for altering the number of revolutions traversed by platen 52 for each revolution of feed wheel 57). Referring to FIGS. 6 and 7, it will be seen that gear 107 meshes with the teeth on the outer periphery of ring gear 100. Gear 107 is fixed or keyed to pinion gear 108', which, together with gear 107, is mounted on shaft 110. As evident in FIG. 6, shaft 110 extends downwardly from base 51, and hence is stationary with respect to platen 52. Pinion gear 108 itself meshes with spur gear 109.

Gear 109 (see FIG. 6) is mounted on, and keyed to drive shaft 111, which shaft is tied to pulley 112. The lower end of shaft 111 is mounted to base 51 via ball bearing 113, while a portion of shaft 111 above gear 109 is supported to base 51 by retainer 115 and ball bearing 114. As shown in FIG. 1, pulley 112 is driven by differential coupling means 120 via shaft 116, pulley 117, and belt 118. Differential 120 itself is driven by motor 60 via belt 67 connected to drive shaft 64. The rate at which differential 120 drives pulley 112 may be set at a constant value, or may be controlled by a feedback system, as described hereinbelow.

It is evident that rotation of pulley 112 will result in rotation (in the same direction) of ring gear 110. Thus, if pulley 112 is driven while platen 52 is rotating, the number of revolutions of platen '52 for each revolution of feed wheel 57 (i.e., the planetary ratio) will be decreased if pulley 112 is rotating in the same direction as is platen 52. Conversely, if pulley 112 is rotating in the opposite direction as platen 52, the planetary ratio will be increased.

For lubrication purposes, the gear trains located between upper platen 52 and lower platen 52 are immersed in oil. As indicated in FIGS. 4 and 5, this oil is contained by oil pan 54. Note that lip 75 of pan 54 forms an oil labyrinth seal with base 51 and that ridge 121 prevents oil leakage via ball race 71.

During rotation of platens 52 and 53, centrifugal force tends to force the lubricating oil therebetween toward periphery regions 122 of pan 54. A pump mechanism, indicated generally by numeral in FIG. 5, is provided to drive oil scooped from regions 122 back toward the axis of platens 52 and 53. Pump 120 is powered by drive shaft 124 and gear 125, which gear (see FIG. 7) meshes with stationary ring gear 90.

Recall (from FIG. 1) that wire 18, after arriving via passageway 69 passes through lower platen 53 via oil proof coupling 130. As shown in FIG. 8, wire 18 then is channeled through the area between platens 52 and 53 within chute 136. Wire 18 emerges from chute 136 through upper platen 52 via a second oil proof coupling 131 (also evident in FIG. 5). Couplings and 131, and chute 136 insure that wire 18 is not immersed in or exposed to the lubricating oil contained between platens 52 and 53.

A preferred embodiment of coupling 131 is shown in FIG. 11; coupling 130 is of substantially identical design. Coupling 131 comprises face plate 132 which is fastened to platen 52 by means of screws 133. A tube 134 having an inside diameter just slightly larger than the diameter of wire 18 extends at an angle through face plate 123 and platen 52. The angle of tube 132 corresponds to that required to supply wire 18 to feed wheel 57.

Referring again to FIG. 8, when wire 18 emerges from coupling 131 it next passes through guide 135 which directs the wire into groove of feed wheel 57. As best shown in FIG. 9, groove 140 extends around the entire periphery of wheel 57 approximately midway its top and bottom. Groove 140 is sufiiciently deep so that wire 18 will ride therein, but not so deep that wire 18 might become embedded within it.

Note that in FIG. 9, groove 140 is located within a wider trough 141 around the periphery of feed wheel 57. Trough 141 is defined by ridges or lips 142 and 142' around the upper and lower periphery of wheel 57. Bias wheel 58 (see FIGS. 4 and 8) has a similar trough 143 about its periphery.

A flat, continuous band 145, having a width corresponding to the width of troughs 141 and 143, extends between bias wheel 58 and feed wheel 57. As shown in FIG. 8, band 145 engages approximately half of the periphery of each of wheels 57 and 58. Wire 18 is directed by guide 135 into groove 140 where it is trapped between the outer periphery of feed wheel 57 and band 145. The bias on wheel 58 provided by spring 81 (see FIG. 4) insures that band 145 will be held tightly against wire 18.

Scraper 146 serves to clean particles of metal or other material from the inner surface of band 145. Similarly, scrapers 148 and 1 49 are provided to insure that trough 141 is free of particles of metal or other material which might prevent wire 18 from seating in groove 140.

As shown in the detail of FIG. 10, scraper 149 (similarly, scraper 148) is mounted to platen 52 and includes scraper arm 150. Arm 150 is equal in Width to trough 141, and rides therewithin. In addition, arm 150 includes scraper finger 151 which extends into groove 140 to insure that it is free of particles.

Upon leaving feed wheel 57 (see FIG. 8) wire 18 passes through another chute or guide 147 toward stanchion 59. As will be described in detail hereinbelow, wire 18 tends by itself to form into a coil or spring, the diameter of which is limited or restrained by diameter guide rollers 161, 162 and 163. In the embodiment illustrated in FIGS. 8 and 9, diameter guides 161 and 162 are mounted at fixed locations, while the location of guide rollers 163 may be adjusted to set the desired diameter. Alternatively, all three guides 161, 162 and 163 may be 1 1 provided with eccentric position adjustments. Each of guide rollers 161, 162 and 163 are free to rotate on their respective shafts 164, 164 and 164" and each has a peripheral groove 165 for guiding wire 18.

As platen 52 rotates, shaft and passageway 69 (see FIG. 1) act in conjunction with grooved wheel 46 (which does not rotate with platen 2) to twist wire 18. In effect, wheel 46 holds an end wire 18 and prevents it from rotating while the rotation of shaft 55 twists wire 18 about its longitudinal axis as it leaves wheel 46. As noted earlier, this twist is not fed back through the three or four turns of wire on wheel 46. Thus, the twist is isolated to the spring forming mechanism 50 by wheel 46 and is completely determined by the rotation of shaft 55.

As is evident, this twisting is accomplished in rotational correspondence to the rotaton of platen 52; that is, one complete longitudinal twist of about 360 is accomplished for each revolution of platen 52. Although not required, the length of wire fed from grooved wheel 46 in the time required to perform one complete twist (i.e., one revolution of platen 52) may equal the desired circumference of the coil being formed.

Referring again to FIGS. 2, 8 and 9, note that wire 18 is guided in a narrow passageway (compising members 55, 69, 136, 135, 57 and 147) for substantially the entire distance between the region adjacent isolator 46 where twisting was accomplished and the end of chute 147. Upon emerging from the end of chute 147, twisted wire 18 tends to assume a natural pitch and curvature imparted by the twisting. This natural pitch and diameter normally will be greater than that desired for the compression spring 18 being fabricated.

The function of diameter control rollers 161, 162 and 163, which rollers are mounted to and hence rotate with platen 52, is to limit the diameter of twisted wire 18. By guiding wire 18 around the base of stanchion 59, rollers 161, 162 and 163 control the diameter of the spring 18' being formed by restraining the natural outward force of the wire.

Referring still to FIGS. 8 and 9, it now may be understood that rollers 167 and 168 act as anti-pitch controllers. That is, rollers serve to restrain the natural tendency of the turns of wire 18 to spread apart. In particular, rollers 167 and 168 are adjusted to limit the pitch of wire 18 to correspond to the desired spacing between adjacent turns of compression spring 18. Note that this function accounts for the placement of rollers 167 and 168 on top of wire 18.

To review, compression spring 18 is formed by twisting wire 18 about its longitudinal axis as it leaves isolator 46. Twisted wire 18 is guided through a passageway including feed wheel 57 and emerges from chute 147 which is revolving on platen 52 about stanchion 59. As it emerges, wire 18 assumes a natural pitch and curvature (imparted by the twisting) which are restrained to the desired spring diameter and pitch by ap ropriate control rollers mounted on platen 52.

Since platen 52 is rotating in the same direction as that in which the twisting of wire 18 was accomplished, a compression spring is produced. When viewed from the top of spring forming mechanism 50 (see FIG. 8), a counterclockwise spring 18 will result from clockwise rotation of platen 52. Since wire 18 was twisted clockwise about its longitudinal axis (as viewed from the end of spring 18' emerging from mechanism 50) the requirements for a compression spring have been met.

Note that spring 18' is not formed by forcing wire 18 into a coil about stanchion 59, and in fact, spring forming apparatus 50 would work even if stanchion 59 were omitted. Howver, stanchion 59 does provide a convenient guide for the spring 18 being formed, insuring that spring 18 does not bend over and get caught in mechanism 50. In this regard, it is important to note that since wire 18 is not forced into the shape of a coil, the spring 18 which is produced does not have the undesired tension on the outer periphery and compression on the inner periphery, typical of prior art springs.

As formed, spring 18' may be either rotating about, or stationary with respect to stanchion 59. Spring 18' will be stationary if the amount of wire fed from feed wheel 57 during one revolution of platen 52 corresponds exactly to the diameter of spring 18' being formed. In this instance, the wire in a single turn of the spring will contain one complete longitudinal twist of 360.

If a length of wire greater than the spring diameter is supplied by feed wheel 57 during one revolution of platen 52, spring 18 as produced will rotate about stanchion 59 in the opposite direction from platen 59. If a length of wire less than the diameter of spring 18 is supplied during one revolution of platen 52, the spring will rotate about stanchion 59 in the same direction as platen 52.

In view of the foregoing, it is evident that there is wide latitude in selection of the relative diameters of platen 52 and feed wheel 57, as well as in selection of the planetary ratio (ie the ratio of the number of times feed wheel 57 rotates about its oWn axis for each revolution of platen 52). However, to produce a Spring 18 which does not rotate with respect to stanchion 59 as it is being produced, the planetary ratio must equal the ratio of the diameter of feed wheel 57 to the diameter of spring 18. For other planetary ratios, spring 18 will rotate as it is produced.

For some applications, it is desirable to have spring 18' stationary as it is being produced, since this permits subsequent work to be performed on spring 18' as it emerges from spring forming apparatus 50. As just noted, this necessitates that the planetary ratio equal the diameter ratio between feed wheel 57 and spring 18. This required planetary ratio can be achieved in two ways. First, ring gear may be kept stationary, and gears 101105 selected to achieve the desired planetary ratio for feed wheel 57 of specified diameter. Alternatively, gears 101 105 may be selected to give approximately the correct planetary ratio, and ring gear 100 rotated (by applying an appropriate rotational force to pulley 112, as described hereinabove) to correct the planetary ratio to the desired value.

The rate of rotation of ring gear 100 required to produce a planetary ratio equal to the diameter ratio between feed wheel 57 and spring 18 can be calculated by techniques well known to those skilled in thhe art. Differential coupling then may be adjusted to rotate shaft 116 (and hence pulley 112) constantly at the correct value to provide the required rotation of ring gear 100. For example, gears 101-105 may be selected to rotate feed wheel 57 about ten percent slower than required to obtain stationary production of spring 18'. Pulley 112 then may be rotated (by appropriate control of differential coupling 120) to provide, on a constant basis, the additional required rotation of ring gear 100 to achieve the required planetary ratio.

Recall that wire 18 has a natural cast, typical of all wire. As changes occur in the cast (some regions of the wire being slightly harder than others), the amount of pitch and/ or curvature produced by twisting wire 18 about its longitudinal axis may vary slightly. This may result in a slight variation in diameter of the spring 18 produced with a given setting of pitch and diameter control rollers 161, 162, 163, 167 and 168. This variation may result in rotation of the spring 18 being produced. Similarly, slight slippage of wire 18 as it goes through spring forming mechanism 58 may cause spring 18' to rotate slightly, even though the planetary ratio has been selected to equal the diameter ratio between feed wheel 57 and spring 18'.

To correct for such variations, and hence to provide an embodiment of the invention which will insure that spring 18 will not rotate with respect to stanchion 59, a feedback system may be provided. Such a feedback may include the sensor mechanism, illustrated in FIG. 9, to detect rotation of spring 18. The feedback system then 13 correctively alters the rate of rotation of ring gear 100, and hence the planetary ratio, so as to halt rotation of spring 18'.

Referring to FIG. 9, note that spring forming mechanism 50 is provided with a pair of sensing plates 175 connected by crossed arms 176. Arms 176 are adapted to pivot in scissor-like fashion about shaft 177 which itself is fixedly mounted to table 22. Arms 176 terminate in members 178 and 179 between which is mounted sensing means 180. Means 180 may comprise, for example, a pressure sensitive switch or alternatively, a rheostat, adjustable by changes in distance between members 178 and 179. Sensing means 180 is electrically connected to differential coupling means 181, shown in Phantom in FIG. 9. Control means 181 is of a type well known to those skilled in the art and functions to energize difierential coupling means 120 (see FIG. 1).

It should now be apparent that coil rotational sensing plates 175, sensor 180, control means 181, coupler 120, pulleys 117 and 112, gears 108, 109, and 110, and rotata- 'ble ring gear 100 comprise a mechanical feedback system, capable of correcting for undesired rotation of spring 18.

In a preferred embodiment, sensing plates 175 are biased to exert a slight pressure on spring 18'. Thus, if the portion of spring 18 below sensor plates 175 begins to rotate, this will cause a slight diameter growth of spring 18' where it is gripped between plates 175. In turn, sensing plates 175 will spread apart and effect corresponding change in sensor means 180.

As an example, suppose that spring 18' begins to rotate counterclockwise (due to feed wheel 57 supplying a length of wire 18 greater than the circumference of spring 18' during a single revolution of platen 52). As a result, plates 175 will spread apart, sensor means 180 will initiate an electrical signal to differential coupling means 181. Control means 181 in turn will cause differential coupler 120 to rotate shaft 116 in a clockwise direction. As noted earlier, this will cause ring gear 100 to rotate counterclockwise with respect to base 51,

and hence will cause feed wheel 57 to make slightly fewer turns about its own axis per revolution of platen 52. The rate of rotation of ring gear 100 is controlled by the feedback system in such a way as to adjust the planetary ratio to that required to eliminate rotation of spring 18'.

The spring 18' produced by inventive spring forming apparatus 50 can be of any length, limited only by the length of wire on spool 24. However, in some applications, it is desirable intermittently to stop apparatus 50, to permit the length of spring '18 previously formed to be cut, or to permit additional work to be performed on spring 18. To accomplish this, drive shaft 64 (see FIG. 4) may be provided with an appropriate dwell cam arrangement (not shown in the figures) whereby platens 52 and 53 are rotated for only a portion of one revolution of the cams. Thus, the cam on drive shaft 64 may be adjusted to stop spring forming apparatus 50 for a predetermined period each time platens 52 and 53 perform a selected number of revolutions.

In some applications, advantages are to be gained by having spring 18' rotate as it is produced. For example, a bed spring having, for example 3 /2 turns and an hour glass shape (see FIG. may be fabricated in a single revolution of platen 52 using the embodiment of the invention shown in FIGS. 12, 13 and 14.

As described hereinabove, the position of adjustable diameter control roller 163 determines the diameter of spring 18, while the vertical location of adjustable pitch control roller 168 adjusts the pitch of spring 18.. Apparatus such as that illustrated in FIGS. 12, 13 and 14 'may be incorporated in the inventive spring forming mechanism 50 to facilitate winding of springs having programmed variations in pitch and/or diameter. For example, the apparatus shown in FIGS. 12, 13 and 14 14 may be employed to produce springs 218 of the shape shown in FIG. 15.

Referring to FIGS. 12 and 13, note that diameter control roller 163' is mounted by shaft 20-1 to rocker arm 202. Rocker arm 202 is pivotally mounted to upper platen 52 by shaft 203 and is free biased in contact with cam 208 by spring 210. Pivotally attached at elbow 203 of rocker arm 202 is cam follower arm 204, at the other end of which is mounted cam follower roller 205. The angle between follower arm 204 and rocker arm 202 may be adjusted by loosensing fastener 206, pivoting follower arm 204 to the desired orientation, then retightening fastener 206. The extent of adjustment of follower arm 204 is limited by the extent of slot 207.

As feed wheel 57 rotates, roller 205 follows diameter control cam 208, which cam is mounted on drive shaft 73 atop feed wheel 57. When roller 205 traverses a wide region 209a of cam 208, the resultant motion of follower arm 204 and rocker arm 202 moves control roller 16-3 away from stanchion 59, resulting in spring -segments having a larger diameter. (See, for example, the large diameter segments 218a of spring 218 in FIG. 15.) Conversely, when roller 205 dwells on the narrow regions 2091; of cam 20 8, diameter control roller 202 is nearest stanchion 59, resulting in the small diameter turns 218k of spring 21 8 (see FIG. 15).

Variable pitch also may be achieved using the mechanism illustrated in FIGS. 12, 13 and 14. Note that pitch control roller 168 is mounted on shaft 211 which extends through circular housing 2'12. Pitch cam follower roller 213 also is mounted on shaft 211. Housing 212 is rigidly mounted at one end of lever arm 214, which arm has an L-shaped cross-section and is pivotally mounted at shaft 215. Shaft 215 is supported by mounting block 216 which itself is secured to upper platen 52. Bias spring 217, on retaining peg 217 serves to pivot lever arm 214 about shaft 215 to insure positive contact of roller 213 with cylindrical pitch control cam 220. Leg 219 prevents lever 214 from dropping down so far as to strike rocker arm 202.

Pitch control cam 220 is a cylindrical cam securely mounted coaxially with feed wheel 57 and separated therefrom (see FIG. 13) by diameter control cam 208 and spacer 221. The height of cam 220 determines the pitch of the corresponding portion of spring 218. Thus, when roller 213 dwells on a high portion 222a, pitch control roller 168' will be a relatively high location with respect to the plane of platen 52; the corresponding portion 222b' of spring 218 (see FIG. 15) will have a wide pitch spacing. Conversely, when pitch roller 213 dwells on low attitude cam region 222b, pitch control roller 168' will be closer to platen 52, and the narrow pitch spacing 222b' of spring 21 8 (see FIG. 15) will result.

It is evident that simultaneous variations in pitch and coil diameter is achieved with the setup of FIGS. 12, 13 and 14 and that springs of desired diameter and pitch may be programmed by appropriate selection of cams 208 and 220. Other techniques for controlling the location of diameter control roller 163 and of pitch control roller 168 may be provided to permit programmed variations in the size and shape of spring 18' over more than the number of turns produced during a single revolution of platen 52. By so controlling rollers 163 and 168, it is possible to produce, for example, hourglass springs of the type common to the bedspring industry.

Clearly, the inventive spring forming apparatus 50 illustrated in FIGS. l-14 can wind either clockwise or counterclockwise compression springs, depending on the direction of rotation of platen 52. Thus, in the embodiment of FIG. 1, mechanism 50 could be adapted to wind righthanded springs. By providing an appropriate control system between differential coupling (in spring forming machanism 50) and the corresponding differential coupling in mechanism 50', the two spring forming appartuses can be made to produce spring pairs of identical character- 1 5 istics but opposite coil direction. Such spring pairs are particularly well suited for use as bedsprings or in mattresses.

As described hereinabove in conjunction with the embodiment of FIGS. 1-14, platen 52 rotates about its own axis in the same direction as that in which wire 18 is twisted about its longitudinal axis as it leaves isolator 46. This configuration will produce a compression spring. By providing an appropriate gear system to rotate platen 52 in the opposite direction as that in which twisting of wire 18 is accomplished, a pre-loaded extension spring can be produced. In such an apparatus, the twisted wire naturally Will tend to form into a spring having small diameter and pitch. Thus pitch control rollers 167 and 168 would be placed below wire 18 (instead of above, as shown in the compression spring apparatus of FIG. 9) to restrain the tendency of wire 18 to assume minimum pitch. Similarly, diameter control rollers 161, 162 and 163 would be placed on the opposite side of wire 18 from that shown in FIG. 8, so as to restrain the tendency of wire 18 (when being fashioned into an extension spring) to assume a small diameter.

As in the case of the compression spring forming mechanism ilustrated, either clockwise or counterclockwise extension springs can be produced in accordance with the present invention. Of course, to form extension springs, the spring must be molded (i.e., platen 52 must revolve) in the same direction to that in which the wire is twisted.

Springs manufactured using the inventive spring forming apparatus exhibit unique properties not common to springs wound with conventional equipment. In prior art winders, a wire was forced into a coil-like shape by abruptly bending the wire. This bending simultaneously subjected one side of the wire to considerable internal tension forces, the other side to internal compressional forces. The resultant disorientation of the wire crystallographic structure effectively placed an upper limit on the amount of working stress which could be achieved by such a spring.

In contrast to prior art spring winders, the inventive spring forming mechanism does not exert large forces to bend a wire into a coil; rather, the apparatus acts to restrain to the desired values the natural pitch and curvature imparted by twisting wire about its longitudinal axis. The present technique appears to result in considerably less distortion of the wire crystallographic structure and hence more uniform circumferential stressing, than does the abrupt bending of the prior art.

The uniform circumferential stress characteristic of springs produced in accordance with the present invention and utilizing the apparatus described hereinabove typically may have the appearance shown in FIG. 16. Note in this cross sectional view that the stress has been shown diagrammatically as a series of arrows 231 which extend circumferentially about the wire 230. Note that the stress imparted to the wire is circumferentially uniform but decreases gradually toward the center of the wire. Such a uniformly stressed spring 230 is to be distinguished from the stress pattern typical of springs wound in accordance with the prior art and illustrated diagrammatically in the typical cross section view of FIG. 17.

As may be seen in FIG. 17, the prior art wire 240 initially was stressed in tension along the outer periphery of the spring, as represented by crosses 241 in FIG. 17. At the same time, the forced coiling of wire 241 in the prior art caused stressing in compression (represented by circles 242 in FIG. 17) along the inner periphery of the spring. Wire 240 exhibited a line 243 of no stress running through the center of the wire between the tension and compression sides.

When the prior art spring (see FIG. 17a) was subjected to pre-stressing (by stretching or compressing the previously wound coil) the resultant circumferential stress generally assumed the shape illustrated by arrows 245 in FIG. 17b. Comparison with FIG. 17a indicates that the prestress generally was additive with the portion 241 of wire 240 previously stressed in tension, but was subtractive with the compressed portion 242.

Comparison of FIGS. 15 and 17b clearly indicates the improved uniformity of the circumferential stress of springs 230 would in accordance with the present invention as compared with the stress typical of prior art springs 240. It will be appreciated that such inventive springs 230 are capable of providing higher values of working stress for a given spring index than are springs of the same size manufactured in accordance with the prior art. In addition, the uniform circumferential stress (see FIG. 16) significantly decreases the likelihood of fracture of the wire and hence significantly increases the fatigue life of spring 230.

Additional benefits are derived from the uniform circumferential stress exhibited by springs formed in accordance with the present invention. For example, extension springs can be produced in which the adjacent turns are touching, and which will exert almost their maximum working stress with very little displacement of the spring. Such springs would be useful in applications where very little space is available for spring extension.

As another example, a spring having a given value of working stress when manufactured in accordance with the present invention will require less wire (-i.e. either less length, or a smaller diameter wire, or both) than will a spring of the same working stress manufactured using prior art techniques. Thus, utilization of the present invention can result in considerable reduction of the amount of metal, and hence the cost, of a spring. In industries where many springs are used (for example, the bedding industry) it could result in reduction in cost of the final product.

Moreover, the present permits excellent control of the stress characteristics of a spring. It thus permits manufacture of sets of springs with matched, uniform characteristics, desirable, for example, as automotive valve springs.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects, and, therefore, the aim in the appended claims is to cover a1 such changes and modifications as fall within the true spirit and scope of this invention.

What is claimed is:

1. A machine for producing a spring from a wire supplied from a source, said machine including a stationary frame and comprising in combination:

a platen mounted to rotate with respect to said frame;

twist means for twisting said supplied wire about its longitudinal axis to substantially circumferentially stress said wire;

a feed wheel mounted non-coaxially on said platen to rotate about its own axis in a plane parallel to said platen;

first gear means for imparting planetary motion to said feed wheel;

drive means for driving said first gear means and for rotating said platen; and

guide means for guiding said twisted wire from said twist means about a peripheral portion of said feed wheel; whereby twisted wire released from said feed wheel forms a spring.

2. The machine as defined in claim 1 wherein said twist means comprises:

a tubular shaft fixedly attached to said platen, coaxially thereof; and

means for guiding said wire first through a longitudinal portion of said shaft, and then to said platen at a location spaced apart from its axis.

3. The machine as defined in claim 2 wherein said twist means further comprises isolator means for preventing twisting of said wire prior to engaging said twist means.

4. The machine as defined in claim 3 wherein said isolator means comprises a grooved wheel adapted to rotale only in a. plane perpendicular to said platen, said grooved wheel being fixedly mounted to said frame in tangential, spaced apart relationhip with said shaft.

5. The machine as defined in claim 1 further compnsmg:

a stanchion extending coaxially from said platen; and

means for maintaining said stanchion stationary with respect to said frame during rotation of said platen.

6. The machine as defined in claim 5 wherein the diameter of a portion of said stanchion corresponds to the diameter of said coil.

7. The machine as defined in claim 6 wherein said means for maintaining comprises a second planetary gear system driven by said platen and including a ring gear mounted in fixed relationship to said frame.

8. The machine as defined in claim 1 wherein said feed wheel includes a groove around its periphery, and wherein said guide means comprises:

a bias wheel rotatably mounted non-coaxially on said platen, diametricaly opposite said feed wheel, said bias wheel being adapted to move radially of said platen;

a continuous band adapted to engage a portion of the periphery of said feed wheel and a portion of the periphery of said bias wheel; and

spring means for biasing said bias wheel away from said feed wheel.

9. The machine as defined in claim 8 further comprising:

chute means for guiding said twisted wire into said groove between said feed wheel and said band.

10. The machine as defined in claim 8 further comprising:

passageway means for guiding said wire from said twist means into said groove between said feed wheel and said band, and for guiding said wire from said groove to a location adjacent said means for controlling.

11. The machine as defined in claim 6 wherein the planetary ratio of the planetary motion of said feed wheel corresponds to the ratio of the diameter of said feed wheel to the diameter of said spring, whereby said spring, as formed, does not rotate with respect to said stanchion.

12. The machine as defined in claim 6 wherein the planetary ratio of the planetary motion of said feed wheel does not correspond to the ratio of the diameter of said feed wheel to the diameter of said spring, whereby said spring, as formed, rotates with respect to said stanchion.

13. The machine as defined in claim 1 further comprising means for restraining the diameter of said twisted wire fed from said feed wheel.

14. The macihne as defined in claim 1 further comprising means for restraining the pitch of said twisted wire fed from said feed wheel.

15. The machine as defined in claim 6 further comprising diameter control means for rstraining the diameter of said twisted wire fed from said feed wheel; and pitch control means for restraining the pitch of said twisted wire fed from said feed wheel.

16. The machine as defined in claim 15 wherein said diameter control means comprises at least one roller mounted on, and rotatable parallel to said platen, wherein said pitch means comprises at least one roller mounted on, and rotatable perpendicular to, said platen.

17. The machine as defined in claim 16 further comprising:

means for programmatically adjusting the location of each of said diameter control means and said pitch control means.

18. The machine as defined in claim 13 wherein said means for restraining the diameter comprises at least one roller mounted on, and adapted to rotate about its own axis in a plane parallel to said platen, said machine further comprising means for programmatically adjusting the di- 18 ameter of said spring, said means for programmatically adjusting comprising:

a cam adapted to rotate in unison with said feed wheel;

and

follower means for altering the location of said roller radially of said platen in response to the radial eX- tent of said cam.

19. The machine as defined in claim 14 wherein said means for restraining the pitch comprises at least one roller mounted on, and adapted to rotate about its own axis in a plane perpendicular to said platen, said machine further comprising means for programmatically adjusting the diameter of said spring, said means for programmatically adjusting comprising:

a cylindrical cam adapted to rotate in unison with said feed wheel; and

follower means for altering the height of said roller above said platen in response to the vertical extent of said cylindrical cam.

20. The machine as defined in claim 11 further comprising:

feedback means for adjusting said feed wheel planetary ratio in response to rotation of said spring about said stanchion.

21. The machine as defined in claim 20 wherein said feedback means comprises:

sensing means for determining the relative rotation of said spring and said stanchion, and for providing an output indicative thereof; and

adjustment means for altering said planetary ratio in response to said output.

22. The machine as defined in claim 21 wherein said sensing means comprises:

means for gripping said spring and for moving in response to the coil diameter growth caused by rotation of said gripped spring; and

sensor means for providing an output indicative of said moving.

23. The machine as defined in claim 22 wherein said second planetary system includes a ring gear rotatable with respect to said frame, and wherein said adjustment means comprises:

means for rotating said ring gear at a rate responsive to said output.

24. The machine as defined in claim 23 wherein said means for rotating comprises:

a drive gear adapted to rotate about an axis fixed with respect to said frame and further adapted to mesh with said rotatable gear; and

differential coupling means adapted to transmit rotational energy from a source to said drive gear at a rate responsive to the output of said sensor means.

25. The machine as defined in claim 1 wherein said platen rotates in a direction opposite the direction of rotation of said twist means, thereby producing an extension spring.

26. The machine as defined in claim 1 wherein said platen rotates in the same direction as the direction of rotation of said twist means, thereby producing a compression spring.

27. In combination, first and second machines, each as defined in claim 1, wherein:

said platen of said first machine rotates clockwise, wherein said platen of said second machine rotates counter clockwise, and further comprising:

means for synchronizing said first and said second machines, whereby said machines simultaneously produce substantially identical rightand left-hand spring pairs.

28. The machine as defined in claim 7 further comprising:

an oil pan surrounding said gear systems and adapted to rotate with said platen; and

pump means driven by coaction with said fixed ring for pumping oil from the inner periphery of said pan to a location adjacent the center of said pan.

29. The machine as defined in claim 9 further comprising:

scraper means for cleaning particles from said band and the periphery of said feed wheel.

30. A machine for producing a spring from a wire, said machine including a stationary frame and comprising, in combination:

a platen adapted to be rotated with respect to said frame;

pre-feed means for pulling a Wire and for delivering said wire at a constant rate;

an isolator wheel adapted to rotate about its axis only, the periphery of said wheel containing a spiral groove adapted to receive said wire from-said pre-feed means, said isolator wheel mounted to said frame with its periphery tangential to the axis of said platen;

twist means for twisting said wire in rotational correspondence with said platen, thereby to produce substantially uniformly circumferential stress in said wire, said twist means comprising;

a tubular shaft extending from the bottom of said platen coaxially thereof;

means for guiding said wire from said isolator wheel first through a longitudinal portion of said shaft and then to said platen at a location spaced apart from its axis;

a feed wheel including a groove around its periphery, said feed wheel mounted non-coaxially on said platen and adapted to rotate about its own axis in a plane parallel to said platen;

means comprising a spring biased band engaging a portion of the periphery of said feed wheel for guiding said twisted wire received from said means for guiding about a peripheral portion of said feed wheel;

a stanchion extending coaxially from the top of said platen, and means for maintaining said stanchion stationary with respect to said frame;

diameter control means, comprising at least one roller mounted on and rotatable parallel to said platen, for restraining the diameter of said twisted wire fed from said feed wheel; and

pitch control means comprising at least one roller mounted on, and adapted to rotate about its own axis in a plane perpendicular to said platen, for restraining the pitch of said twisted wire fed from said feed wheel.

31. The machine as defined in claim 30 wherein said platen is adapted to rotate in the same direction as said tubular shaft thereby producing a compression spring.

32. The machine as defined in claim 30 further comprising:

means for rotating said tubular shaft in a direction op- 2 0 posite the direction of rotation of said platen, thereby producing an extension spring.

33. The machine as defined in claim 30 and adapted to produce a spring which as formed, does not rotate with respect to said stanchion, said machine further comprising:

means for sensing rotation of said spring with respect to said stanchion; and

means for adjusting the relative ratio of rotation of said platen and said feed wheel in response to said sensed rotation of said spring.

34. A machine for forming a spring from a wire supplied from a source, said apparatus comprising:

an isolator wheel mounted to rotate about its own axis only, the periphery of said wheel being adapted to receive several turns of wire from said source,

a planetary system including a platen revolving about a first axis substantially tangential to the periphery of said isolator wheel, and a driven feed wheel mounted on said platen and rotating about a second axis substantially parallel to but spaced from said first axis, wire provided from said isolator wheel being directed around a portion of and pulled by the periphery of said feed wheel, revolution of said platen imparting a substantially circumferential twist to the portion of said wire isolated between said isolator wheel and said feed wheel, twisted wire emergent from said feed wheel releasing into a coil spring.

35. A machine as defined in claim 34 further comprising:

means for adjusting the planetary ratio of said planetary system so that said emergent spring does not rotate.

References Cited UNITED STATES PATENTS 475,194 5/1892 Burton et a1. 72135 642,339 1/ 1900 Krummel 72-140 1,453,431 5/1923 Blount 72-138 2,404,424 7/1946 Balla -r 72145 2,567,537 9/1951 Workman 149 2,631,639 3/1953 Palmer l40l49 2,705,932 4/1955 Beaumont 7266 2,793,672 5/1957 Duif 72-145 3,251,384 5/1966 Vanzo 140-149 3,319,447 5/1967 Wise 72l40 3,351,104 11/1967 Kitselman 140--149 CHARLES W. LANHAM, Primary Examiner E. M. COMBS, Assistant Examiner US. Cl. X.R.

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