US3548544A - Device for cutting helical groove on metallized resistors - Google Patents

Description

DEVICE FOR CUTTING HELICAL GROOVE ON METALLIZED RESISTORS Filed Nov. 7, 1967 A. S. AMELCHENKO ET AL Dec. 22, 1970 3 Sheets-Sheet 1 Dec. 22, 1 970 A. s. AMELCHENKO ET AL 3,548,544

DEVICE FOR CUTTING HELICAL GROOVE ON METALLIZED RESISTORS Filed Nov. 7,. 19 67 5 Sheets-Sheet 2 v mI;

Dec. 22, 1970 AMELCHENKQ ETAL 3,548,544

' DEVICE FOR CUTTING HELICAL GROOVE ON METALLIZF ZO RESISTORS Filed Nov. 7, 1967 s Shets-Sheet 5 United States Patent 3,548,544 DEVICE FOR CUTTING HELICAL GROOVE 0N METALLIZED RESISTORS Alexei Semenovich Amelchenko, Varshavskaya ul. 58, kv. 37; Jury Lukich Muzyka, Prospekt Lenina 133, kv. 64; Nikolai Zakharovich Amelichev, Ul. Bratiev Vasilievykh 6, kv. 8; and Vladimir Petroviclr Myadzel, Prospekt Grazhdansky 9, korpus 4, kv. 39, all of Leningrad, U.S.S.R.

Filed Nov. 7, 1967, Ser. No. 681,227 Int. Cl. B23g 1/38 US. Cl. 51-50 Claims ABSTRACT OF THE DISCLOSURE A resistor is supported in holders for being cut with a helical groove by a tool supported in a tool head such that the tool undergoes reciprocatory movement while the resistor is driven in rotation. The pitch of the groove is controlled by a hinge supported on a pivotal lever for movement therealong, one end of the lever riding on a cam with two mirror image profiles and the other end of the lever being coupled to the tool to effect reciprocating movement thereof. Movement of the hinge along the lever provides a variation of the length ratio of the lever arms to thereby control adjustment of the grooving pitch.

This invention relates to devices for cutting a helical groove on metallized resistors.

Known in the art is a device wherein grooving of a resistor with a pitch discretely determined by interchangeable gears is accomplished while said resistor is moving in holders in relation to the axis of a rotating cutting tool. The cutting tool is mounted on an oscillating tool head and is brought in engagement with the resistor to be grooved by means of an advance mechanism. The reverse stroke of the holders to the position initial for grooving is an idle one (ref., for example authors certificate of the USSR. No. 172,644).

The conventionally known device ensures the cutting of a helical groove on a resistor in the course of the resistor translational movement in one direction only, which reduces the efficiency of the device.

To utilize the reverse stroke of the holders for cutting the helical groove on resistors would call for the provision of an additional loading mechanism resulting in a more complicated design of the device.

Further, in the conventionally known device the groove pitch cannot be varied within the limits of two adjacent discrete values, which adversely affects the possibility of obtaining a specified accuracy of the nominal resistance of the resistor to be grooved.

Anobject of this invention is to provide a device free from the above-mentioned disadvantages.

The above-specified and other objects of the invention are achieved owing to that in the device the tool head intended to ensure reciprocating movement in the course of cutting a helical groove in both directions is spring-loaded along the axis of the holders, and is hinged to one of the ends of an oscillating lever, the opposite end of said lever resting on a rotary cam of a drive mechanism, said cam imparting reciprocating movement to the tool head, said lever being supported by a movable hinge ensuring stepless variation of a specified pitch of grooving within the limits of its adjacent discrete values, which is effected by varying the length ratio of the lever arms.

The tool head should preferably be rigidly fixed on a shaft which bears by its end face against a spring and is coupled with the oscillating lever.

The body'of the tool head can be spring-loaded and hinged to the oscillating lever.

The specific features and advantages of this invention will appear more clearly from the following description of a typical embodiment thereof which is given by way of example with reference to the accompanying drawings in which:

FIG. 1 is a gearing diagram of the device.

FIG. 2 is a gearing diagram of the tool head.

FIG. 3 is a gearing diagram of the device in which the oscillating lever is hinged to the spring-loaded body of the tool head.

FIG. 4 is a gearing diagram of the tool head installed in the device, according to FIG. 3.

The device for cutting a helical groove on a resistor (FIG. 1) is mounted on two plates separated by posts, and is installed on a base frame (not shown in the drawings).

An electric motor 1 is connected by a V-belt transmission 2 to a shaft 3 which is connected by a rigid coupling 4 to a shaft 5 coupled by means of worm-andgear pairs 6, 7, 8 and 9 with shafts 10, 11, 12 and 13.

The shaft 10 supports cams 14, 15, 16', 17, 18 and 19 Which, acting through contacts 20, 21, 22, 23, 24 and 25 and an electronic instrument 26- connected to them perform automatic control of the device as a whole.

The same shaft 10 supports a cam 27 which controls a resistor loading mechanism 28.

The shaft 11 and 13 support cams 29 and 30 which, acting through respective levers 31 and 32 and springs 33 and 34, impart reciprocating movement to driving and driven collets 35 and 36. A resistor a to be grooved is fixed in collets 33 and 36 and is ejected after a helical groove is cut on its surface by a grinding wheel 37 of a tool head 38.

The tool head 38 is fixed on a shaft 39 and reciprocates in relation to the longitudinal axis of the collets 35 and 36 in which the resistors a to be grooved are successively secured.

To ensure the reciprocating movement of the tool head 38, the shaft 12 is provided with a cam 40 actuated by the worm-and-gear pair 8 and connected through a lever 41 to the shaft 39 whose end face bears against a spring 42.

The cam 40 has two mirror-image profiles intended to ensure a uniform and identical movement of the tool head 38 in both directions, the movement of said tool head in one of the two directions being ensured by the force produced by the cam 40 through the lever 41. At this stage the cam 40 in combination with the lever 41 and shaft 39 compresses the spring 42. Movement of the tool head 38 in the opposite direction is caused by the force of the compressed spring 42 which pushes the shaft '39, thus making the roller 43 of the lever 41 roll over the oppositely shaped profile of the cam 40 in this way copying its profile.

The lever 41 is provided with a movable hinge 44 which is set in motion by manually rotating a dial 45 through a bevel gear pair 46 by means of a screw 47.

As a result of movement of the movable hinge 44, the pitch of the grooving of a resistor is steplessly varied within the limits of two adjacent discrete values of a specified pitch.

The discrete values of the pitch of the helical groove are set by a stepped variation of the speed of rotation of the collet 35 which drives the resistor (1.

Speed control is accomplished through the coupling 48, gears 49, 50 and 51, by causing a gear 52 of a carriage 53 to mesh with one of the gears of a cluster gear 54.

After being moved the carriage 53 is fixed in position with a retainer 55.

The difference of two adjacent discrete values of the groove pitch is equal to 0.1 mm.

The shaft 39 of tool head 38 (FIGS. 1 and 2) carries a section 56 rigidly fixed on the shaft 39 and a section 57 free-mounted on said shaft, said section 57 carrying the grinding wheel 37.

The sections 56 and 57 are interconnected by a spring 58, and are forced apart by a screw 59.

In case the diameter of the grinding wheel varies as a result of its wear, the screw 59 must be loosened and under the action of the spring 58, the section 57 with the grinding wheel 37 is moved towards the resistor through a distance equal to the amount of wear.

The force necessary for pressing the grinding wheel 37 against the resistor a being grooved is provided by a spring 60 and is adjusted by a nut 61 with a screw 62.

The section 56 of the tool head is provided with a roller 63 which runs over a spool 64 thus feeding the grinding wheel 37 towards the resistor a to groove the same.

The drive of the grinding wheel 37 (FIG. 1) comprises an electric motor 65 and belt transmissions 66 and 67.

To prevent the resistor a from seizing in the collets the collet 36 when there is no resistor therein, a screw stop 68 is provided.

To prevent the resistor a from seizing in the collets 35 and 36 on completion of grooving, stops 69 and 70 are provided.

In the course of adjustment of the device, the earns 14, 15, 16, 17, 18, 19, 27 and 29 and 30 are set in accordance with a cycle diagram.

The device functions as follows.

The loading mechanism 28 automatically supplies the resistors a to the collets 35 and 36.

The collets 35 and 36 controlled by the levers 31 and 32 clamp a resistor, while the lever 32 which bears against a screw 71 fixes the resistor in the starting position.

At the moment of clamping of the resistor, the cam 14 acting through the contact 20 connects the electronic instrument 26 to the collets 35 and 36. After the electronic instrument is connected as described, the cam 15 through the contacts 21 checks for the actual presence of the resistor a in the collets 35 and 36. If there is no resistor in the collets, the device is automatically stopped.

Before the clamping of the resistor in the collets, the cam 40 by means of lever 41 commences moving the tool head 38 along the axis of the collets 35 and 36.

Further, the roller 63 rolling over the surface of the spool 64 copies its profile. Owing to this arrangement, the rotating grinding wheel 37 is engaged with the resistor a which by that time has been clamped in the collets 35 and 36, after which said grinding wheel cuts a helical groove on the surface of the resistor with a pitch discretely set by the cluster gear 54. Corrections of the pitch within the limits of the adjacent discrete values, for the purpose of obtaining the predetermined degree of accuracy of the rated nominal value of resistance of a resistor to be grooved are made by varying the speed of movement of the tool head 38, through changing the length ratio of the arms 41 and 41" of the lever 41, which is achieved by shifting the movable hinge 44 along the axis of the lever 41.

In the course of grooving the resistor a, the earns 16, 17 and 18 succesively close the respective contacts 22, 23, and 24, thus through the medium of the electronic instrument 26 controlling the electromechanical calibrator (not shown in the drawing) which classifies the grooved resistors a depending upon the obtained rated value of their resistance, for subsequently dropping them into respective containers, according to the following classification: serviceable (that is, the resistors grooved throughout the entire active length), rejected (that is,

the resistors grooved over 80% of the active length), and faulty (that is, the resistors grooved throughout their entire length but having a resistance other than nominal).

Upon obtaining the nominal value of resistance, an electromagnet 72 by means of a lever 73 retracts the grinding wheel 37 from the resistor a over a short distance, while further movement of the grinding Wheel away from the resistor is accomplished as a result of the roller 63 rolling over the respective section of the profile of the spool 64.

When the nominal value of resistance in the resistor being grooved is not obtained because the resistor which has been fed for grooving had a resistance other than the specified initial value of nominal resistance, the grinding wheel 37 is retracted from the resistor only when the roller 63 rolls over the respective section of the profile of the spool 64.

On completion of grooving, the cam 19 by means of the contact 25 brings the elements of the electric circuit back to the initial position.

Following this, the feed mechanism 28 places the next resistor a in the collets, while the tool head 38 actuated by the spring 42 moves in the reverse direction thus performing grooving by the grinding wheel 37 in the sequence described above.

By making use of the reciprocating movement of the tool head 38 for grooving the resistors without an idle stroke the efficiency of the device is greatly increased, while the employment of the movable hinge 44 as a support for the lever 41 ensures stepless variation of the grooving pitch within the limits of adjacent discrete values of the pitch, which guarantees accurate adjustment of the nominal value of resistance of a resistor to be grooved.

However, the device described above is not sufiiciently sensitive to radial run-out of the resistor which may occur during grooving due to a certain deviation of said resistor from the correct geometry, resulting in a non-uniform width of the heilcal groove and adversely affecting the wear-resistance of the grinding wheel.

Therefore it is desirable that the collets be made so that they could be advanced towards the grinding wheel, innstead of advancing the grinding wheel towards the resistor to be grooved. Besides, the collets should be made as light as possible.

According to this embodiment of the invention, collets 74 and 75 (FIG. 3) mounted on brackets 76 and 77 are installed in guides 78 and 79 rigidly coupled with a shaft 80, said collets being capable of moving towards and away from the grinding wheel 37 this being effected by turning a shaft 80 by the collet control mechanism (not shown in the drawing).

In the course of cutting the helical groove, the resistor is held against the grinding wheel with a certain force maintained by means of a spring mechanism 81.

A grinding head 82 (FIG. 4) consists of a section 83 movable on balls 84 in guides 85, 86 and a section '87 carrying the grinding Wheel 37.

In case of variation of the diameter of the grinding wheel 37 as a result of its wear, the section 87 is moved by a screw 88 along guides (not shown in the drawing) of the section 83- towards the resistor a through a distance corresponding to the amount of wear of the grinding wheel.

Prior to shifting the section 87 with the purpose of compensating for the wear of the grinding wheel, a screw 89, should be loosened and tightened again after making the necessary adjustment, in order to ensure tight mating of the section 87 with the section 83.

The lever 41 hinged to the section 83, owing to the action of the cam 40, imparts reciprocating movement to the tool head 38. The reversal movement of the tool head 38 is accomplished by a spring 90 fastened by one of its ends to the body of the tool head 82.

To ensure rotary motion of the collet 74 the latter is connected through a splined bushing 91 to the gear 49 by means of a universal-joint shaft 92.

The electronic instrument 26 is connected to the collets 74 and 75 after a disc 93 touches a contact 94 in the course of clamping the resistor a in the collets 74 and 75.

The electromagnet 72 is intended for retracting the resistor a held in the collets 74 and 75 through a short distance when the nominal value of resistance in the processed resistor is obtained.

When there is no resistor a in the collets 74 and 75, the lever 31 bears by its roller 95 upon the cam 29 thus preventing the grinding wheel 37 from cutting into the collet 75.

The cam 96 by means of the contact 97 connects the eleetromagnet 72 to the electronic circuit (not shown in the drawing) of the device, thus making said device ready for operation.

The functioning of the device is similar to that described above.

The employment of the device according to this invention ensures high-quality cutting of a helical groove on resistors, provides for ready adjustment of the pitch in the process of grooving for the purpose of precise setting of the nominal value of resistance of a resistor to be grooved, and greatly improves the manufacturing efficiency.

What is claimed is:

1. A device for cutting a helical groove on metallized resistors, said device comprising first and second holders for cooperatively fastening a resistor to be processed along an axis of said holders, a tool head with a cutting tool which is brought into engagement with said resistor to form grooving therein, said tool head being spring-loaded along the axis of said holders, an advance mechanism connected to said tool head for advancing the cutting tool towards the resistor to be processed, means for rotating the holders, a driving mechanism for effecting reciprocating movement of the tool head along the longitudinal axis of said holders, said driving mechanism including means for adjusting the pitch of the grooving comprising a rotatable cam with two mirror-image shaped profiles, a pivotal lever having one end hingeably coupled with said tool head and an opposite end resting upon said rotatable cam with two mirror-image shaped profiles and a hinge supporting said lever and movable therealong to provide a variation of the length ratio of the arms of the lever to control adjustment of the grooving pitch.

2. A device as claimed in claim 1, wherein said means for rotating the holders comprises a device for stepped adjustment of the speed of rotation of the holders.

3. A device as claimed in claim 1 comprising an advance means connected to said holders for feeding a resistor to be processed to said cutting tool.

4. A device as claimed in claim 1 comprising a shaft supporting said tool-head, and spring means acting on said shaft to spring-load the tool head, said one end of said pivotal lever being connected to said shaft.

5. A device as claimed in claim 1 comprising spring means acting on said tool-head to spring-load the same, said one end of the pivotal lever being connected to said tool-head.

References Cited UNITED STATES PATENTS 1,967,118 7/1934 Glasgow 51-48 2,884,746 5/1959 Rus 51-50X 3,357,139 12/1967 Ianuzzi 51-50 3,408,896 11/1968 Mandonas 5l50X ROBERT C. RIORDON, Primary Examiner D. G. KELLY, Assistant Examiner

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