US3190043A

US3190043A - Apparatus for manufacturing electric resistor

Info

Publication number: US3190043A
Application number: US308805A
Authority: US
Inventors: Koumans Petrus Willem; Stal Henricus Petrus
Original assignee: NORTH AMERICAN PHILLIPS COMPAN
Current assignee: NORTH AMERICAN PHILLIPS COMPAN; NORTH AMERICAN PHILLIPS COMPANY Inc
Priority date: 1963-09-13
Filing date: 1963-09-13
Publication date: 1965-06-22
Anticipated expiration: 1982-06-22
Also published as: BE635969A

Description

J1me 1965 P. w. KOUMANS ETAL 90,043

APPARATUS FOR MANUFACTURING ELECTRIC RESISTOR Filed Sept. 13, 1963 4 Sheets-Sheet 1 INVENTOR.

PETRUS W. KOUMANS HENRICUS I? STAL June 22, 1965 P, w. KOUMANS ETAL 3,190,043

4 Sheets-Sheet 2 FIG.3

INVENTOR PETRUS W KOUMANS HENRICUS F. STAL BY APPARATUS FOR MANUFACTURING ELECTRIC RESISTOR 4 Sheets-Sheet 3 Filed Sept. 15, 1963 FIG.4

FIG.6

INVENTOR. PETRU S W. KOUMANS S$NRICUS R STAL J1me 1965 P. w. KOUMANS ETAL 3,190,043

APPARATUS FOR MANUFACTUR ING ELECTRI C RES I S TOR Filed Sept. 15, 1963 4 Sheets-Sheet 4 IN VEN TOR. PETRUS W. KOU MANS HENRICUS R STAL BY United States Patent 0 3,190,043 APPARATU FUR MANUFACTURWG REdlSTtlit Petrus Willem Kournaus, Emmasingel, Eindhoven, and Henricus Petrus Stal, Eindhoven, Netherlands, assignors to North American Philips Company, lnc New Yorir, N.Y., a corporation of Delaware Filed Slept. 13, 1%3, Ser. No. 368,805 7 Claims. (Cl. 51-67) The invention relates to apparatus for manufacturing resistors with a predetermined resistance value. Said apparatus is provided with means for rotating the resistors while held at their ends, and with at least one rotating grinding disc which is displaceable parallel to itself in a manner such that the grinding disc is capable of cutting a helical groove with a given pitch in a layer provided on electricallydnsulating material of the resistor body.

In known apparatus the grinding disc, during its parallel displacement, is held at right angles to the center line of the resistor. Since this angular condition of the cutter does not bear any relation to the pitch angle of the helical groove to be ground, an unfavorably shaped groove is obtained. Devices are also known in which the grinding disc is adjusted to a given angular position with respect to the center line through the resistor at which it is fixed for a given series of resistors. In this case a groove having the same pitch is ground in all resistors, a favorable shape of the groove being obtained so long as the angle of the grinding disc corresponds to the pitch angle. However, the resistance value of ungrooved resistors i.e. the layer which is to be grooved to provide a given resistance value, varies for almost each individual resistor, even if they are pre-graded. Therefore, if the helical groove for all resistors, through a given distance, is parallel to itself, and the groove length of all resistors is the same, the resistance values of the finished product will vary individually, and the tolerance with respect to the desired value may be inadmissibly large. Also, if the displacement of the grinding disc is continued, i.e. the length of the groove is varied until the desired resistance value is obtained, the groove will not extend through an equal portion of the surface in various resistors. For favorable heat distribution of a resistor operating in an electric circuit, this latter is disadvantageous. In addition, if a groove is ground with a variable pitch, the fixed grinding disc will again not be in the most favorable angular position with respect to the resistor for a favorable groove shape.

The object of the invention is to provide a device for manufacturing resistors, in which the above problems are avoided. For that purpose, according to the invention the shaft on which the grinding disc is mounted is swingably in a plane which extends parallel with the center line of the holding means or longitudinal axis of the resistor. Means are provided for adjusting the displacement of the grinding disc parallel to itself and also for adjusting the angle which the grinding disc makes with the center line through the holding means. These means are mutually coupled in a manner such that for any value of adjusted pitch, the angle which the grinding disc makes with the center line of the holding means corresponds to the pitch angle. Therefore, for any adjustment of the pitch for the groove to be ground in a resistor, the cutter will be at the correct pitch angle, as a result of which a sound, clean groove is obtained. The pitch is adjusted for each resistor having the same value so that the grooves are all the same length over equal parts of the surface of the resistor which is as favorable as possible. The correct adjustment of the cutter varies even if grooves are to be ground with a variable pitch.

The adjusting members for the parallel displacement of the grinding disc may consist, for example, of a spindle Ziglhhfidd Fatented June 22, 1%65 provided with screw-thread. in a preferred embodiment of the invention, the adjusting members, however, consist of two axially displaceable rods, the first of which is connected at one end to a stand which is movable parallel to itself and which carries the grinding disc, while the second rod is connected at one end to a lever mechanism which causes the grinding disc to swing when under the influence of a displaceable profiled member engaged by the other end of each rod. The profiled member may impart an axial displacement to the two rods, as a result of which a coupled adjustment of the two members is obtained.

The profiled member may be constructed, for example, as a cup-shaped disc. However, it is of advantage to use an embodiment in which the free ends of the rods cooperate with a plate, of which one side has the desired profile, said plate being capable of rotating in its plane around a shaft at right angles to the plane in a manner such that the angle which the profiled side makes with the center line through the holding means ofthe resistor is varied. In addition, the plate is movable parallel to itself and in a direction at right angles to the said centre line. In this embodiment a very simple coupling of the rods is obtained which serves for the parallel displacement and for the angular movement of the grinding disc. The profiled side is turned to the suitable position for obtaining the desired pitch and pitch angle. When the plate is displaced the grinding disc always corresponding to the pitch angle. In this case, a favorable effect is obtained if the free end of the rod is provided with a roller or stud located on the profiled side, in which, in the starting position of the profiled plate, the axis of rotation of this plate and the center point of the stud or roller of that rod, which when being displaced axially causes the movement of the grinding disc parallel to itself, are in alignment. The stud or roller of the second lever being located beside the first stud or roller on the profiled side. In the starting positon of the plate the desired angle adjustment of the grinding disc may be obtained without the grinding disc moving parallel to itself.

In a further embodiment of the invention two separately driven grinding discs are provided which are influenced by two axially displaceable rods, the rods which ensure the parallel displacement of the grinding discs being each connected pivotably to one end of a lever and the rods which ensure the angle adjustment of the grinding disc being connected to the ends of a second lever, said levers being rotatable around a common shaft, the rods located at one side of the axis of rotation being provided with rollers or studs which cooperate with the profiled side of the plate. In this construction two grooves can be ground on the resistor which end at a short distance from one another. For the best dissipation of heat of these resistors in an electric circuit this has a favorable elfect.

According to the invention, members may be provided for adjusting the angular position of the profiled side of the plate with respect to the center line through the holding means in accordance with the previously measured resistance value of a resistor to be processed and the desired final value of this resistor, and for holding the plate in its adjusted angular position. The resistance value of each of the resistors to be provided with grooves may be measured while in the device, after which the desired angle adjustment of the profiled side of the plate is made with reference to this measured result. Then the plate is held in this position, for example, by means of a magnet.

In a further embodiment according to the invention a rotatable cylindrical cage is provided, the end faces of which contain a number of opposed chucks or clamping devices, which are at regular distances from one another and lie in a circle with their center lines aligned. Each clamping devices can be moved in an axial direction tocord 17 for convenience.

arouses (.3 ward each other such that a resistor can be clamped at both ends therebetween, said clamping devices being electrically insulated with respect to the cage. This arrangement is excellently suitable for mass production. One of the grinding discs may be located outside and the other inside the cage.

In order that the invention may readily be carried into effect, it will now be described more fully, by way of example, with reference to the accompanying drawing, in which FIGURE 1 shows the diagrammatic illustration of the apparatus for grinding a helical groove into a resistor.

FIGURE 2 is a plan view of the device.

FIGURE 3 shows a structural detail of the profiled plate, the slide being in the starting position.

FIGURE 4 shows a detail taken on the line IV-IV in FIGURE 2.

FIGURE 5 shows part of the elevation in the direction of the arrow V in FIGURE 4.

FIGURE 6 shows a cross-sectional view taken on the line VI--VI in FIGURE 4, in which a few component parts are not shown for reasons of clarity.

FIGURE 7 shows the cage with clamping device for the resistors, in which also the driving is shown.

FIGURE 8 shows an elevation of the driving disc in the direction of the arrow VIII in FIGURE 7, and

FIGURE 9 shows the various positions of the resistor in the cage.

In the principal diagram shown in FIGURE 1, a resistor to be processed is indicated by 1. The resistor which comprises a resistance layer provided on electrically-insulating material, is clamped with its ends in a rotatable clamping member 2. A grinding disc 3 is connected to a shaft 4 which is driven by a motor 5. The grinding disc .is pivotable around a point 6 in a plane parallel to the center line of the resistor. An axially movable rod 7 which can slide in bearings 8 and 9 ensures the displacement of the grinding disc required for the pitch of the groove. In addition, a lever 11) is provided on the motor 5, against which one end of a second axially movable rod 11 is located. The rod 11 is capable of sliding in

bearings

12 and 13. The bearings i5, 9, 12and 13 are provided in a stand 14. In addition, a slide is provided which is capable of sliding in bearings 15 and which is shown by a At one end this cord is wound on the clamping member 2 with a few turns and can be displaced at its other end in the direction of the arrow by a driving means (not shown). On the slide or cord 17 a rod 13 is connected by means of a hinge 19. The ends 20 and 21 of the rods '7 and 11 engage the rod 18, the end 211 being in alignment with the center line of the hinge 19 in the starting position. In addition, a cam stud 2.2 is provided which is rotatable around a shaft 16 connected in the stand 14 which cam stud can be adjusted by means of a driving motor 23. An adjusting pin 24 is provided between the cam stud 22 and the rod 18 is slidable in a bearing 25. A spring 26 pulls the rod 18 against the adjusting pin 24.

The operation of the device above described is as follows:

Beforethe resistor 1 comes into position for grinding its value is measured in any suitable manner and the cam stud 22 is adjusted with reference to this value and the final value desired for the resistor to be ground. The adjusting pin 24 is moved by the cam stud, which movement istransmitted to the rod 18 which rotates or pivots around the hinge 19 to the desired position and is fixed in that position by any suitable means (not shown). As a result of the rotation of the rod 18, the rod 11 is moved axially as a result of which the shaft of the grinding disc swing around the pivot 6 through the lever 1t and the grinding disc is positioned at an angle with the center line of the resistor. This angular position of the grinding disc exactly corresponds to the pitch angle of the groove 4ito be ground into the resistor, as a result of which a favorable shape of the groove will be obtained. For each resistor the rod 18 is adjusted by the cam stud at that value at which a pitch is obtained of a size such that the groove extends over a portion of the resistor which is as favorable as possible. Now the slide or cord 17 is moved in the direction of the arrows by known means (not shown) while the grinding disc rotates. The resistor is rotated around its center line, while the rod 18 is simultaneously moved to the left in the drawing. Both the rod 7 and the rod 11 are moved axially, the axial distance moved being dependent upon the angular position of the rod 18. The grinding disc is therefore moved parallel to itself or parallel to the centerline of the resistor by the rod 7. A given pitch of the groove being obtained as a result of the rate of movement of the rod 7 and the rotation which the resistor experiences. The angular position of the grinding disc does not vary, since the rods 7 and 11 are of equal lengths and are moved through the same distance by the rod 18.

It is not necessary for the rod 18 to be straight. If, for example, it has a curved shape, the grinding disc, while grinding, will have an angular movement, while the axial displacement of the disc parallel to itself is also variable. Consequently, a groove will be ground with a variable pitch, the angular position of the grinding disc nevertheless being such that the disc has the correct pitch angle at any moment.

A machine will now be described with reference to FIGURES 2 and 6 which operates according to the principle of the diagrammatic appaartus shown in FIGURE 1 but in which two grinding discs are used, two grooves being ground on the resistor each extending over substantially one half of the resistor. A resistor 27 is held by clamping

members

28 and 29 which are provided in an electrically-insulated manner in a cage shown and de scribed in connection with FIGURE 7. The clamps are capable of rotating. Two grinding

discs

30 and 31 are each capable of cutting a groove on one half of the resistor 27 and are connected to

shafts

32 and 33. The driving means for the

shafts

32, 33 are indicated by 34. The driving means 34 are each connected to sleeves 36 by means of bifurcated arms 35. The sleeves 36 are each rotatable around its center line and are supported on plates or stands 37 and connected to the stands 37 by means of bearing braces 38. The bifurcated arm is connected to one end of each sleeve by means of a screw 39 (FIG. 6). As best seen in FIG. 6 the sleeves comprises bearings 4d and 41 in which a shaft 42 can slide. This shaft is provided at one end with an arm 43 which is connected by means of a pin 44 in a slot 45 of a supporting member 46 connected to the driving means 34. When the shaft 42 moves the driving means 34 will swing around the pivot provided by bifurcated arm 35, the grinding disc being made to engage or to disengage the resistor 27.

The stands 37 on which the sleeves 36 are supported are also provided with braces 48 comprising bearings. Shafts 49 extend through these hearings and are rigidly connected to supports 5% at each end. These supports 5% are connected to a base plate 51 of the device. By this assembly the stands 37 can be moved parallel to themselves, the bearings of the braces 48 sliding on the shafts 49. The end of the shaft 42 carries a block 53 which is provided with a slot. A pin 54 of a lever 55 is located in the slot. This lever is pivotally supported by a pivot shaft 56 which is supported on the stand 37 by means of a brace 57. Attached to the other end of the lever 55 is a soft iron core 52 which is attracted by an electro-magnet 73, the shaft 42 being thus moved or slid in the bearings 4d and 41. A spring 58 biases the lever 55 off the magnet. An adjustable stop member 5h prevents the lever from moving too far.

As seen in FIGS. 4 and 5 each of the sleeves 36 also has an arm 60 rigidly connected thereto. Attached to the end of the arm 6% is a pm 61 to which an arm 62 is pivotally connected. Each arm 62 is connected to a

rod

63 and 64 respectively (FIG. 2). The

rods

63, 64 are journalled so that they can be moved or slide axially in supports 65 mounted on the base plate 51. If the

rods

63, 64 perform an axial movement, the

arms

60 and 62 cause the sleeve 36 to rotate around its center line, which rotation is transmitted by the bifurcated arm 35 and thence to the grinding disc which, as a result, is caused to swing in an angle with the center line taken through the resistor.

Similarly rods 66, 67 are provided in a manner such that they. can be moved axially in supports 65. These

rods

66, 65"? are connected at one end to the stand 37. When the rods -65 and 67 are moved axially, the grinding discs 30 and Ell connected to the stand 37 are consequently moved parallekto themselves i.e. in planes parallel with the longitudinal axis of the resistors. One pair of the rods 64 and 67 are provided with adjusting rings 65a. Between these adjusting rings and an upright edge 68 of the support 65 springs 6Q, '70 are provided. The rods 63, 64-, 66, 6'? have a thickened

portion

71, 72 at one end which are slotted at '75, '74. A lever 75 is pivotally mounted on shaft '76 mounted on the base plate 51. The ends of lever 75 are provided with pins I? which extends into the slots 73 of the

rods

63, 54. A second lever 7% spaced from lever T5 is also pivotally mounted on shaft '76 and is provided with pins till which extend into the slots 74 of rods 65 and d7. The

rods

63 and 66 each have an extension member 823, 83, each of which is provided with a

roller

84 and 85. These rollers engage one side 36 of a profiled or cam plate 87 as a result of the force of the springs 69 and 7d acting through rods 64, 67 and levers i5, '79. in the embodiment shown, the side 86 of the plate has the shape of a straight line but may also have a different profile. The plate 37 is carried by a slide $8 which contains bearings 89 by which the slide is movable on shafts 96). These shafts are connected in supporting members 91, $2 which are rigidly connected to the base plate 51. An arm S 3 is provided on the slide 38 and an arm 94 is provided on the plate 87 (PEG. 3). These two arms are pivotally connected by means of the shaft 95. The profiled plate 87 is thus rotatable around the shaft 95. The plate is further provided with a projection 96 to which a roller $7 is connected. If the slide rests against the support 92 the roller may engage a rotatable cam $8 of which the driving means are not shown. The cam 3 is rotatable around the shaft 99 connected to the base plate. The profiled plate 87 can be held in the desired position with respect to the slide 88 after rotation around the shaft 95 by means of an electromagnet 1th? (shown below plate 37) connected on slide 83. Pins ltill and 102 are also provided on the slide 33. A cord M93 is connected to the pin 161 which cord is wound around a drum 104 which is coupled to a motor res by means of a coupling 1%. A spring lltll is connected to the pin 1% which spring is connected to a fixed point 108 of the base plate.

The operation of the device as illustrated in FIGS. 26. In the starting position the slide 88 with the plate 87 is in the position in which the slide engages the supporting member hi2. In this case the roller 9'7 presses against the cam 98 (shown in phantom) and the magnet we is switched off. The grinding discs are at the starting positions of the groove to be ground in the resistor and are swung outwards by means of the magnets is and associated linkage. The shaft of the roller 84 is located on the center line of the hinge shaft 95 (see FIG. 3). When the resistor is introduced into the clamping members 2% and 29, the resistance valve of the layer to be provided with a groove is measured. Having this measured value and knowing the desired resistance value to be ground, the cam 93 is turned to the desired position by any suitable means (not shown). The plate 8'7 (shown in its starting position in FIG. 2') is therefore rotated around the shaft 95, however, the roller 84, being coaxial with shaft 535 in the starting position, is not moved by rotation of the plate about pivot 95, whereas the roller 85 is moved. This can also be seen in FIG. 1 where the head of arrow 2i? corresponds with roller 84 and rod 18 corresponds with plate 37. The rod s3 and the rod 64 connected to roller 55 by the lever are consequently moved axially whereby the rotating grinding discs 30, Si. are moved to the correct pitch angle through the linkage including the arms tit) and 62, sleeve 3d and bifurcated arm 35. When the magnets 73 are switched off the circumference of the grinding disc comes into contact with the resistance layer by movement of the lever 55 and the shaft 42. Simultaneously the motor res becomes operative, in known manner, whereby the plate 37 with the slide 83 are moved on guides 99. The rollers 84 and are now displaced against the pressure of the springs so and 7t by the side as of the plate and the stands 37 are moved parallel to themselves by the axial movement of the rod 66 and the rod d7 coupled thereto by the lever "75 the desired pitch being thus cut on the resistor. In the embodiment shown in FIG- URE 2, in which the side 86 is straight, the roller 85 which displaces the rods and d4 axially is not necessarily moved during the parallel movement of the plate, so that the angular position of the grinding disc remains the same. When the resistor has been processed until the desired resistance value is reached, the motor 166 stops, the magnets '78 are energized, as a. result of which the grinding discs are swung away from the resistors, and a new resistor to be processed is put in its place. At the same time the slide 83 and the plate 87 move to the starting position and the magnet 1% is deenergized as a result of which the plates 3%, 37 can again be adjusted by the cam 98 to the correct position for processing the following resistor.

Consequently, for each resistor processed an adjustment is made to provide the correct pitch for the groove formed over a portion of the resistor which is as favorable as possible for minimizing rejects.

It is not necessary for the plate 87' to have the shape shown. The side 86 against which the

rollers

84 and 85 press, may also have other shapes, for example, convex or concave; the pitch of the groove on the resistor will then be varying.

FTGURES 7, 8 and 9 show the mechanism, which ensures the supply and adjustment of the resistor with respect to the grinding disc. The resistors are supplied to a cage lid which is provided with five positions a, Z), c, d, and e for receiving a resistor. These positions are provided by two rotatable circular discs 111, 112 the circumference of which is provided with gear teeth 113, 114. In these five positions are opposed clamping members 2%, 29 of known telescopic construction and operation. These members are mounted for movement in a direction at right angles to the discs ill, 112 in any suitable manner. The clamping members are electrically insulated with respect to the discs, as a result of which it is possible to measure the resistance value of the resistor at any desired moment while held in the chucks or clamping members. Discs 111, 112 are connected to shafts ll? and 113 which are each journalled into two supporting members H9 and 12%. A pinion 121 which is connected to a shaft 122 cooperates with the teeth 113. At the other side of the shaft 122 a similar pinion 12.3 cooperates with the teeth 114. The discs 111 and 1112 are driven by the shaft 118 on which a driving mechanism is provided in the form of a plate 125 which is provided with grooves 124. An arm 12 5 which can engage the grooves of the plate 125 is connected to a sleeve 127 which is connected, with a shaft 128, to a bearing 129 which is connected to the base plate The arm 32% and the plate 125 operate in the manner of at Geneva wheel. The sleeve 127 can rotate by means of the driving chain 133 and a sprocket wheel 131. In addition, two supporting members 132 are provided which are connected to the base plate. In these supporting members a shaft 133 is journalled which is provided with a toothed wheel 134 at both ends. These toothed wheels intermesh with the toothed wheels 135 to which the shafts 136 are rotatably connected, which shafts are each rotatable in a bearing of the supporting members 132. When rotating, the two toothed wheels 135 will rotate equally rapidly. prise a coupling disc 137 to which, for example, a friction disc 13% is provided. This disc may come into engagement with a disc 139 on the clamping

members

28, 29. A lever Mi) which is pivotal around a shaft 141 engages with one arm 14?. in a groove 143 on the shaft 136 and is connected with its other arm to a rod 144. This rod is passed through the base plate and its end engages a cam Wheel 145 which is connected to a shaft 146 which is again coupled to a sprocket wheel 147 with a chain 139.

' A resistor is supplied by means of a known chain conveyor 149 (FIGURE 9) and is deposited in a suitably shaped member 150 so that it enters into the space between the discs Ill and 112 of the cage. Then the clamping

members

28 and 29 are closed by any suitable means (not shown). The chain 130 causes the arm :26 to rotate as a result of which the plate 125 is moved to a next position, in which the discs 139 of the clamping members remain closed by a guide (not shown) and the clamps consequently remain holding the resistor. the position b the resistance value of the layer to be cut is determined. The measuring device (not shown) includes measuring

pins

151, 152 which resiliently engage the

insulated clamping members

28 and 29. Knowing this value and the desired value of the resistor to be ground, the required adjustment is made at the cam stud $8, (FIGURE 2) which ensures adjustment of the profiled plate $7. In the condition 0 (FIGURE 9) the cams 145 force the coupling discs 137 against the discs 139 of the clamping device through the rod 144 and the lever 140. Now a rotation is imparted to the resistor. The motor for obtaining the rotating movement of the resistor is not shown. This may be coupled, for example to the driving means of the profiled plate i.e. elements 194-166. The grinding

discs

30, 31 cut a helical groove with a given pitch into the resistor body in the manner already described. The measuring pins 151, 152 during grinding measure the value of the resistor. If this has reached the desired value, the magnets '78 (FIGURE 2) are energized, the grinding discs being thus moved away from the resistor. Somewhat later the rods 144 on cam 145 move downwards and the coupling 137 is opened. When turning to position a the discs 139 are decoupled by an arm 155 which is partially shown in FIGURE 7 and the processed resistor is conducted away. In the position 2 the clamping members remain opened.

It maybe clear that an adjustment cage with five positions is not necessary, although it has proved useful.

From the above it will be apparent that the device is suitable for grinding resistors on which at least one groove is provided and in which the grinding disc is adjusted to the most favorable pitch for each individual resistor.

We claim:

1. Apparatus for manufacturing resistors ofpredetermined value having a helical groove having a pitch angle comprising means for holding a resistor, means for rotating said resistor about its longitudinal axis, rotating cutter means, a first means for moving said cutter means in a plane parallel with the said axis of said resistor for cutting a helical groove in said resistor, a second means sup- The shafts 135 com- 3 a3 porting said cutter means for movement to the pitch angle of said helical groove, and a meansv operatively connected with both said first and second means for establishing the rate of movement of said cutter means as well as the angle of said cutter means.

2. Apparatus for manufacturing electric resistors having a predetermined value comprising at least one clamping means for holding a resistor to be processed, means for rotating said clamping means and said resistor, at least one grinding disc including means for driving said disc, at

least one slidable member mounting said grinding disc means for movement in a plane parallel with the longitudinal axis of said resistor, at least one means mounting said disc means for angular movement relafive to the longitudinal axis of said resistor, and adjustifig means operatively connected wtih said slidable member and said mounting means for angularly and slidably moving said disc whereby a helical groove is cut in said resistor and said disc is operated at the pitch angle of said helical groove.

3. Apparatus according to claim 2 wherein said adjusting means comprises at least two axially displaceable rods, one of said rods having one end connected with said slidable member for moving said slidable member in said plane, the other of said rods having one end connected with said mounting means, and a movable member having a profiled surface operatively connected with the other ends of each said rod for establishing the said pitch angle of said groove and said cutting disc and means for moving said profiled member in its starting position for selecting the pitch angle required. '4. Apparatus according to claim 3 wherein said profiled member is rotatable about an axis perpendicular to said surface in its starting position whereby the angle defined by said surface and the centerline of said resistor is varied, means for holding said profiled member in the selected position and means for linearly moving said profiled member in a plane substantially normal to the centerline of said resistor.

5. Apparatus according to claim 4 wherein the axis of rotation of said profiled member and the longitudinal axis of the rod for moving said slidable member intersect in the starting position of said profiled member.

6. Apparatus according to claim 3 wherein two separately driven grinding disc means are provided to form helical grooves in a resistor body, two slidable members mounting said grinding disc means, two means mounting said disc means for angular movement, two pair of rods connecting each said slidable member and mounting means for angular movement of said cutting discs, and a pair of levers interposed between said profiled member and each of said two pairs of rods, one said lever connecting the corresponding rod in each said pair with said profiled member and the other of said pair of levers connecting the remaining rods of said pairs of rods.

'7. Apparatus according to claim 2 with the adidtion of rotatable cage means supporting a plurality of said clamping means, said cage means comprising a plurality of axially movable clamping members, a pair of rotatably mounted parallel spaced wheels supporting said clamping members evenly spread in a circular array, and means for driving said clamping members in only one position thereof.

References Cited by the Examiner UNITED STATES PATENTS 1,660,468 2/28 Bath 51-50 2,669,811 2/54 Henderson 5l37 2,884,746 5/59 Rus et al 51-37 LESTER M. SWINGLE, Primary Examiner.

I. SPENCER OVERHOLSER, Examiner.

Claims

1. APPARATUS FOR MANUFACTURING RESISTORS OF PREDETERMINED VALUE HAVING A HELICAL GROOVE HAVING A PITCH ANGLE COMPRISING MEANS FOR HOLDING A RESISTOR, MEANS FOR ROTATING SAID RESISTOR ABOUT ITS LONGITUDINAL AXIS, ROTATING CUTTER MEANS, A FIRST MEANS FOR MOVING SAID CUTTER MEANS IN A PLANE PARALLEL WITH THE SAID AXIS OF SAID RESISTOR FOR CUTTING A HELICAL GROOVE IN SAID RESISTOR, A SECOND MEANS SUPPORTING SAID CUTTER MEANS FOR MOVEMENT TO THE PITCH ANGLE OF SAID HELICAL GROOVE, AND A MEANS OPERATIVELY CONNECTED WITH BOTH SAID FIRST AND SECOND MEANS FOR ESTABLISHING THE RATE OF MOVEMENT OF SAID CUTTER MEANS AS WELL AS THE ANGLE OF SAID CUTTER MEANS.