US3182426A - Helixing lathe having automatically changeable chucks - Google Patents

Description

May 11, 1965 A. J. vRsl-:CKY D 3,182,425"

HELIXING LATI-IE HAVING AUTOMATICALLY CHANGEABLE CHUCKS y Filed June 15, 1962 .2 Shets-Sheet l l INVENTO aib/1 y I 715196.35 y

A'IITORNEY May 11, 1965 A. J. vRsEcKY HELIXING LATI-IE HAVING AUTOMATICALLY CHANGEABLE CHUCKS Filed June-15, 1962 2 Sheets-Sheet 2 United States Patent O 3,182,426 HELIXING LATHE HAVING AUTOMATICALLY CHANGEABLE CI-IUCKS Anthony J. Vrsecky, Winston-Salem, N.C., assigner to Western Electric Company, Incorporated, New York,

N.Y., a corporation of New York Filed June 15, 1962, Ser. No. 202,725

6 Claims. (Cl. 51-95) This invention relates to a helixing lathe having automatically changeable chucks, and more particularly to a helixing lathe having special chucks which are automatically changeable for accommodating workpieces of different sizes and diameters. This invention finds special utility in helixing, that is forming a spiral conductive path on, electrical resistors of the type including a thin conductive film deposited on an insulating core.

In the manufacture of electrical resistors, such as deposited carbon resistors, it is customary to provide a resistor blank having a nonconductive, cylindrical core body on which is deposited a thin, conductive lm of carbon. A helical groove is progressively cut through the carbon lilm unti-l the resistor has been helixed to desired resistance value. Resistors of this sort vary in physical size, usually those of higher power ratings being larger in over-all size and diameter than those of smaller power ratings. Where resistors of different power ratings are to be helixed, it is desirable to provide a helixing lathe the chucks of which are readily changeable to accommodate resistor blanks of different sizes and diameters.

An object of this invention is to provide a new and improved helixing lathe having automatically changeable chucks.

Another object of this invention is to provide a helixing lathe having automatically changeable chucks for accommodating resistor blanks of different sizes and diameters.

It is a further object of this invention to provide a new and improved chuck having a plurality of work holding faces which are selectively presentable in work engaging position.

Apparatus illustrating certain features of this invention may include a pair of opposed chucks for supporting a workpiece which is to be helixed. Each of the chucks has a plurality of Work holding faces, which may, for example, be suitable in size and shape to accommodate resistor' blanks of ditIerent diameters. Means are provided for selectively presenting a work holding face of each chuck in a workpiece engaging position. Also provided are means for cutting a helix in the workpiece which is supported between the chucks. y

A complete understanding of this invention may be obtained from the following detailed description of a specie embodiment thereof, when read in conjunction with the accompanying drawings, wherein:

FIG. l shows a deposited carbon resistor partially in section which has been helixed to desired resistance value in a helixing lathe according to this invention;

FIG. 2 is a schematic elevation of a speciiic embodiment ofr` this invention showing a resistor blank supported between chucks for rotation and for longitudinal motion .relative to a cutter whereby the blank may be'helixed to resistance value;

V3 and 4; and

FIG. 6 shows a resistor blank supported between work holding faces of the chucks shown in FIGS. 2,-5, and

ICC

also the line of approach of the blank, so supported, toward the cutter.

In FIG. 1, there is illustrated a deposited carbon resistor including a core body 16 having a conductive carbon coating 17 deposited thereon. A pair of conductive caps 1S are secured about the core body in electrical contact with the carbon coating, and a pair of leads 19 are electrically connected to the caps, as by welding. -In the embodiment of this invention described in detail below, it will be seen that this invention produces a helical cut 2t? in the carbon coating 17 thereby determining the electrical resistance between leads 19.

/Jhile this invention will be described with particular reference to the helixing of deposited carbon resistors similar to that illustrated in FIG. 1, it will be understood that the helixing lathe according to this invention is a tool of generally applicability in helixing.

Referring to FIG. 2, an unhelixed resistor blank 21 is supported between a pair of chucks 23 and 24 which are journaled forl rotation within bearings 26 and 27, respectively. Bearings 26 and 27, in turn, are supported on arms 2S and 29, both of which are mounted so as to be slideable along, but not rotatable about, splined guide rod 31. A pair of bearing members 32 and 33, which are mounted on frame 34, support guide rod 31 allowing it free rotation about and translation along its longitudinal axis.

The separation of chucks 23 and 24 is determined by the separation of arms 28 and 129. This separation is controllable by rotating rotatable arm 36 by means of pivot shaft 37 to drive links 38 and 39 outwardly. Links 38 and 39 are pivotally connected to arms 2S and 29, respectively. Pivot shaft 37 may be rotated in either direction by power means (not shown) within a link connector 40, which is fixed to splined guide rod 31.

A pair of supports 41 and 42 are mounted for free r0- tation about guide rod 31. This mounting is such as t0 prevent longitudinal sliding on the guide rod. Chucks 23 and 24 include shafts 43 and 44, respectively, these shafts, in turn, being coupled to telescoping joints 46 and 47 by means of universal joints 48 and 49, respectively. The telescoping joints are connected by means of universal joints 51 and 52 to stub shafts 53 and 54, respectively. Stub shafts 53 and 54 are journaled 'for rotation within supports 41 and 42. Thus, it will be seen that rotation may be imparted to the chucks by rotating shafts 53 and 54. Also, due to the action of telescoping joints 46 and 47 asthey are connected between universal joints 51 and 48, and 49 and 52, respectively, chucks 23 and 24 may be swung into and out of the plane of FIG.` 2 without interfering with the rotation of the chucks.

A motor 61 is arranged to drive an elongated gear 62 which is in -mesh with a gear 63. Gear 63 is fixed to stub shaft 54, and when revolved, imparts rotation to chuck 24. Gear 63 is in mesh with a gear 66 fixed to a shaft 67, and shaft 67 is .journaled at its ends Within supports 41 and 42. AV gear 68 is iixed on the other. end of shaft 67 in driving engagement with a gear 69. Gear 69 is fixed on stub shaft53; thus, rotation imparted to elongated gear 62 by motor 61 turns chuck 24 and also drives the above-descrlhedgear train, gears 63 and 66, shaft 67, and gears 68 and 69 to drive stub shaft S3. As mentioned above, the turning of stub shaft 53 imparts rotation to chuck 23.- This driving :arrangement for the chucks causes them to turn in the same direction to impart rotation to resistor blank 21 supported therebetween.

A reversible motor 71 is provided with a threaded drive shaft 72 which threadedly engages nut 73. A drive bracket 74 is `fixed at one end to nut 73 and at its other end to support 41. Means (not sho-Wn) are provided for energizing motor 71 alternately in either direction for a given number of revolutions. It will be seen that enercarriage 84 into and o-ut of the plane of FIG. 2. Carriage 84 is slideably supported on the upper face of base 85.

Threaded shaft 86 threadedly engages dovetail 83, and when rotated (by means not shown), controls the position of cutter S1 toward and away from blank 21'.

Carriage 84 is provided with a pair of depending threaded members 87 and 88which engage threads on'a threaded shaft 89. A reversible motor 91 is connected to threaded shaft 89 so that energizing motor 91 in one direction or the other controls the position of carriage $54,;

and therefore the position of cutter 81, along the longitudinal axis of blank 21V.

Carriage 84 is provided with aprojection 96 which extends in the longitudinal direction of resistor-blank 21..

Projection 96 is provided with a series of apertures 97 spaced along its length into one -of which a pin 8 may be` inserted. Avpair of microswitches 101 and 102,-are

mounted on base 8S'so as to be actuable byfpinv 98.

Microswitches 191 and 102 may be spaced on base 85 under projection 96 'as desired.

As will be more fully understood by referring to U.S. Patent 3,063,346, and assigned to the same assignee as this application, a pair of electro-magnets 111 and 112,' shown schematically in FIG. 2, are arranged on either side of anar-mature (not shown) on arm 28. Energizing electromagnet 111 attracts the armature Vand v,Swings arm 28 toward the observer of. FIG. 2; energizing electromagnet 112 attracts the armature and swings arm 28V awayY from the observer of FIG. 2, thus separating resistorz blank`21` and cutter 81.' Also as will be understood by referring to the above-mentioned copending application, the energizing of *.electromagnet 112 to separate the core body and the cutter is controlled by means (not shown) which are sensitive to the resistor blankv Since having been helixed to a desired resistance value.

arms 28 and 29 engage the splines of splined guide rod 31, rotation imparted to `arm 28 by means of electromagnets 111 and 112 is simultaneously imparted to both'chucks Y23 and'24. y

Chucks 23 and 24 are mirror imagesV of one another; hence, the detailed description yof chuck 23 withreference to FIGS. 3 6, will apply equally tofchuck'24, and aV detailed description of chuck24 will be unnecessaryg. l

Chuck 23 comprises an outer lsleeve or chucking member 121 including` an enlarged portion 122 having an annularfflangel 123 thereabout. Shaft 43` suitable for reception within bearing 26 extends from enlarged portion 122. A snap ring 126-which engages a groove in shaft 124Vlocks`ichuck 23 within bearing 26.

within bore y132 and extendswithin enlarged portion 122. a

As best seen'in FIG. 3, when inner chucking member 136 `is in yits leftmost position, the'inner `and Vouterwork holding-faces have a common vertex and cooperate'to form-7,

a single, continuous, conical work holding face. though work-holding faces 131 and 137 are shown-as being conicaldepressions,y it will be understood that the shape of these work holding facesmay .be of a shapeA .suitable for engaging-any desired-workpiece. f A" spring v141 is arranged 1within bore 132 to bias inner chucking member'136 to the right as viewedin FIG. 3.

lInner chucking member 13.6 isprovided with a radially movement of cam follower pin 146 ywhile preventingY .inner chucking member 136 from rotating relative to outer chucking'member 121. Y

VAs best seen in FIG. 5,` cam track 148 is provided with two locking portions, rear locking portion 156 and forward locking portion 157. The locking portions extend in planes perpendicular'to the longitudinal axis of the chuck and are spaced along that axis. A diagonal position shiftingportion 158 of the cam track connects the rear and forward locking portions of the cam track.

Sleeve 147 (FIG. 3) is provided with a bore 161 into which is placed a detent ball 162 jand detent spring 163. A set screw 164 threaded Withinbo-re 161 applies `pressure to the detent spring to bias detent ball 162 to the left. as viewed in FIG. 3. Enlarged portion 122 is provided` with an indentation 166 for receiving detent ballv 16.2 Y. Indentation 166 is placed so as tofreceive detent ball 162 when sleeve 147 yhas 'been rotated .to place cam follower `pin `146` in rear locking portion 156. Another indentation (not shown) is provided .in enlarged portion 122 to receive detent ball 162 when sleeve 147 has been rotated to place cam follower pin y146 injforward locking portion` 157. Thus, theV detent ball 162 serves to yieldably lock sleeve 147 against'rotation when it is in either of the extreme degrees of rotation permitted'by cam follower pin 146.

As best seen in FIGS. 3 and 4, outer chucking member 121 is divided along a portion of its length by a liared slot 168and inner chucking member 136 is divided along a portion of its length by a ared slot 169. These slots are maintained in' alignment as shown in FIG. 4 by the sides of slot 151 acting on cam-follower pin 146.

Referring to FIGS. 2 .and 4,V a pairof chuck `shifting disks 171 and 172',` having respective drive elements 17,3 and 174 "on the peripheries thereof, `are VVmounted to be rotated by reversible motors 178' and V179, respectively. Rotation of the chucking shifting disks bringsthe drive elements 173 and 174 linto driving contact with sleevesV 147 impartingV rotation thereto*y In FIG.` 4 it may be seen that drive element 173 (drive element 174 is identical thereto), which may, for example, be madefof rubber, is providedy with a driving surface 177 V-having a length somewhat greater than;the length of the arc connecting the extremes of rear and forwardV locking portions 156 and 157 of cam track 148. Since motors 17S and 179,

are reversible, energizing these motors to turn'at least oney revolution in either ,direction fwill' impar-t rotation to sleeves 147 causingthernovement ofcam tracks 14S to Y' their extreme `positions in either, direction. e

' Operation I AssumeA that-itis desired to v*helixga `deposited carbon"l resistorjblank (hereinreferredfto 'asV a large resistor blankijthe caps18 of whichare larger than the diameter!- of inner-work holding faces;-137. v Reversible' motors 178l f and 179 are actuated to turn one revolution in the clockwise direction as Vviewed in FIG'. 4, causing drive elements 173 andf174to` turn sleeves 147.. CamV tracks 143` act upon cam follower pins 114610 position inner clucking members 136 in their retracted positions.V (solid linesV The enlarged portion 122of the outer chucking to bring carriage 84 to a leftmost position. Motor 91 is vthen reversed and carriage 84 is driven rightward until microswitch 101 is actuated by pin 9S to provide a control signal for stopping motor 91. Microswitch 101 has previously been positioned so that this control signal occurs at a point which stops the cutter in the desired position for starting a helixing cut on a large resistor blank.

Motor 71 is energized to drive nut 73 to the right as viewed in FIG. 1, thereby bringing the large resistor blank into proper alignment with cutter 81 for starting a helixing Cut.

Rotatable arm 36 is rotated with pivot 37 by link connector 40 to drive links 38 and 39 and close chucks 23 and 24 about the resistor blank presented therebetween by feeding means (not shown). The alignment of slots 168 and 169 (FIGS. 3 and 4) permits leads 19 to t within the chucking members and also facilitates the feeding of the large resistor blank between the work holding faces 131 and 137. The flare of these slots (FIG. 4) facilitates the insertion of the leads within these slots.

With the resistor blank chucked, motors 61 and 71 and electromagnet 111 are energized simultaneously. Motor 61 imparts rotation to chucks 23 and 24 and the large resistor blank; motor 71 moves chucks 23 and 24 to the left as viewed in FIG. 2; and, electromagnet 111 swings the large resistor blank into engagement with cutter 81. Means (not shown) monitor the resistance of the resistor blank as it is being helixed, and energize electromagnet 112 tovwithdraw the large resistor blank from engagement with the cutter 81 when the blank has been cut to the desired resistance value. This withdrawing function is described in detail in the above-mentioned, copending application. Finally, rotatable arm 36 is pivoted in a clockwise direction to separate chucks 23 and 24 and release the helixed resistor.

This process may be repeated to helix any desired number of large resistor blanks. However, since the diameter and length of the large resistor blanks is uniform from blank to blank, it will not be necessary to readjust the position of cutter 81 or to re-energize motors 178 and 179 prior to chucking each succeeding large resistor blank. Furthermore, the action of detent balls 162 in identations 166 prevents the rotation of sleeves 147 until motors 17S and 179 are energized in the counterclockwise direction as viewed in FIG. 4.

Assume now that it is desired to helix a resistor blank of smaller wattage rating (hereinafter referred to as a small resistor blank), the caps 1S of which are of a diameter less than the outside diameter of inner work holding face 137.

Referring to FIG. 6, the position of the outer work holding face 131 is shown in phantom in alignment with inner Work holding face 137. This, it will be remembered, is the position which the work holding faces assumed during the previous operation in supporting large resistor blanks. If a small resistor blank, for example, blank 201, were positioned within the chucks so arranged, then outer work holding face 131 would extend over an appreciable portion of blank 201. Outer work holding face 131 would also extend beyond point 202 on the surface of blank 201, this point representing the spot at which it is desirable to start the helixing cut. A path 203 represents the approach of point 202 toward the fixed cutter position. This path is angular with respect to the longitudinal axis of the chucks as it is the resultant of two motions, one motion being that of the chucks moving toward the cutting wheel, the other being longitudinal motion imparted to the chucks by motor 71. It may readily be seen in FIG. 6, that path 203 passes through the outer work holding surface 131 as shown in phantom. Thus, if the inner and outer work holding faces were to remain in alignment during the commencement of helixing blank 201, outer chucking member 121 of chuck 23 would interfere with the desired approach of the resistor blank to the cutter, or, alternatively, the initial cut would have to commence at a point on the blank undesirably nearer the center of the blank. A corresponding problem would also arise when the small resistor blank is withdrawn from the cutter 81 after termination of a helixing cut near right cap 18 (FIG. 6).

In accordance with this invention, this problem is overcome by automatically changing the size of the work holding faces which engage a small resistor blank; inner work holding faces 137 are projected beyond outer work holding faces 131 as shown in FIG. 6.

In order to change the chucks, reversible motors 178 and 179 are energized at least one revolution in a counterclockwise direction as viewed in FIG. 4 and rotation is imparted to sleeves 147 by means of drive elements 174. Cam tracks 148 move relative to caml follower pins 146 until the cam follower pins rest in forward locking portions 157 and the inner chucking member is moved into the positions shown in FIG. 6 (solid lines) and in phantom in FIG. 3.

Since resistor blank 202 is of smaller diameter than that previously helixed, it is necessary to move cutter 81 into the plane of FIG. 2. This is accomplished by turning threaded shaft 86 as by means of a reversible motor (not shown). In order to position cutter 81 at the proper point along the longitudinal axis of blank 202, motor 91 is energized to move the cutter leftward as viewed in FIG. 2 until pin 98 is left of microswitches 101 and 102 and then reversed to drive the cutter r-ightward until microswitch 102 is engaged to produce a control signal for stopping motor 91. Microswitch 102 (FIG. 2) has previously been placed on base so that motor 91 stops to position cutter 81 at the proper position for commencing a helixing cut on a small resistor blank.

Motor 71 is energized to drive the chucks to the right, then deenergized to properly position the chucks relative to the cutter. For convenience of control, this starting position may be the same regardless of the size of the resistor blank being helixed. Rotatable arm 36 is turned in the counterclockwise direction (FIG. 2) causing chucks 23 and 24 to engage blank 201 from the feed means (not shown). Motors 61 and 71 and electromagnet 111 are simultaneously energized to bring blank 201 into helixing engagement with cutter 81. As described above, helixing continues until blank 202 has been cut to the desired resistance value and is interrupted by the action of electromagnet 112 when this occurs.

.Successive resistor blanks 2011 may be helixed by repetition of this process, it being unnecesary to change the position of the cutter or adjust the chucks until it is desired to helix a resistor of a different size. Detent balls 162 maintain the adjustment of the chucks until it is desired to change this adjustment.

It is to be understood that the above-described apparatus and construction of elemental parts, are simply illustrative of an application of the principles of this invention and that any other modifications may be made without departing from the invention.

What is claimed is:

1. In a lathe for helixing cylindrical resistor blanks of varying diameters,

a pair of opposed chucks spaced along a longitudinal axis for supporting a blank to be helixed, each chuck including an outer chucking member having an axial bore therein and a concave outer work holding face thereon,

ank inner chucking member having a concave inner work holding face thereon slidably positioned Within the bore with the inner work holding face facing the same direction as the outer work holding face, and

means for imparting relative movement between the inner and outer chucking members to selectively '27 i project or retract the inner work holding face relative to the outer work holding face;

a cutter; and

means for imparting simultaneous longitudinal and transverse movement to the chucks to engage and disengage the cutter with a blank supported between the chucks. Y

2. In a chuck for supporting cylindrical workpieces of different diameters,

an elongated outer ychucking member having a longitudinally extending bore therein and a concave, conical work holding face on one end thereof,

an inner chucking member having a concave, conical inner work holding face on one end thereofv and slidably positioned within the bore with the inner work holding face facing in `the same direction as the outer work holding face,

means for preventing relative rotation between the inner and outer chucking members,

a cam follower fixed to the inner chucking member and projecting radially therefrom,

a rotatable `sleeve surrounding the vouter chucking member and having a cam track thereon the camming surface of which engages the cam follower, the carn track having angularly disposed camming surfacesthereon for moving the inner'chucking member relative to the outer chucking member, and Vhaving locking surfaces there.

on Vfor retaining either the inner work holding face or both the inner and outer work holding faces in a work engaging position.

3. A chuck according to claim 2 wherein the sleeve is provided with detent means for yieldably locking the sleeve against rotation relative to the inner chucking f member when the cam follower is in engagement with either of the locking surfaces of the cam track.

the outer chucking member, which sides engage the cam follower.

6. A chuck comprising an vouter sleeve having an inwardly extending conical end surface,

an inner sleeve slideably mounted within the outer sleeve and having an inwardly extending conical end surface,

means for positioning the inner sleeve within the outer Vsleeves so that both conical end surfaces `have a common vertex,V

and means for shifting the inner sleeve relative to the outer sleeve to move theVV conical end surface of the inner sleeve beyond the end of the outer sleeve.v

References Cited by the Examiner UNITED STATES PATENTS 1,443,651 1/23 Runge 51-237 XR 2,724,306 11/55 WOOdll 90f-11.46 2,773,332 12/56 VBuchman et al.x 51-15 2,869,596 1/59v Latimer 1 144-209 2,959,202 11/60 Sprillgae 1447-209 3,052,272 9/62 YOCk V144---2j9 3,073,363 1/63 LOfSCdt 144-209 WILLIAM W.' DYER, In., Primary Examiner.y

Claims (1)

1. IN A LATHE FOR HELIXING CYLINDRICAL RESISTOR BLANKS OF VARYING DIAMETERS, A PAIR OF OPPOSED CHUCKS SPACED ALONG A LONGITUDINAL AXIS FOR SUPPORTING A BLANK TO BE HELIXED, EACH CHUCK INCLUDING AN OUTER CHUCKING MEMBER HAVING AN AXIAL BORE THEREIN AND A CONCAVE OUTER WORK HOLDING FACE THEREON,

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