US2144771A - Device for working sectional shapes for shafts and bores - Google Patents

Description

Jan. 24, 1939. M D RF 2,144,771

DEVICE FOR WORKING SECTIONAL SHAPES FOR SHAFTS AND BQRES Filed July 20, 1935 4 Sheets-Sheet l Jan. 24, 1939. R. MOSSDORF DEVICE FOR WORKING SECTIONAL SHAPES FOR SHAFTS AND BORES 4 Sheets-Sheef 2 Filed July 20, 1935 R. MOSSDORF Jan. 24, 1939.

DEVICE FOR WORKING SEGTIONAL SHAPES FOR SHAFTS AND BORES Filed July 20, 1935 4 Sheets-Sheet 3 R. MOSSDORF Jan. 24, 1939. 2,144,771

DEVICE FOR WORKING SECTIONAL SHAPES FOR SHAFT-S AND BORES Filed Jfily 20, 1955 4 Sheets-Sheet 4 lnvenfor': I 11 144 7 Patented Jan. 24, 1939 DEVICE FOR WOBKING SEO'I'IONAL SHAPES FOR SHAFTS AND BOBES Richard Molsdori, Ohemnita, Germany,- assignor to Ernst Krause a Go. A.-G., Vienna, Austria 1 Claim.

For connecting machine parts, especially shafts and the like, the shaft connection is recently made of square or similar cross-sectional shape instead of as hitherto by keys.

The production of such cross-sectional shapes presents, however, considerable diiliculties, owing to the fact that the contour of the shaft must be produced with other tools and according to another method than the internal cross-sectional shape of the corresponding hub. The shaft can be milled and ground, whereas the hub can only be slotted, an essential condition for the smooth running of the connection without play and shock being that the surfaces of the two cross-sectional shapes absolutely correspond as regards distance, parallelism and correct angular position. .Owing to the different methods of production the attainable degree of accuracy is. however, far inferior to that of round working in which both the external and internal cross sectional shapes can be produced by the same method with the same or similar tools (grinding wheels) with a degree of accuracy which renders unnecessary all subsequent work both on the shaft and on the hub. The accuracy limit in the case of square sectional shape decreases considerably more when the hub is hardened because it is then not possible to eliminate the distortions caused by hardening by subsequent shaping. These drawbacks and the considerable amount of time and expense which the production entails have resulted Application July 20, 1935, Serial No. 32,417

Germany May 4, 1933 in the abandonment of these cross-sectional shapes and the introduction of star-wedge sections chiefly employed to-day.

The star wedge section does not overcome the drawbacks. The condition, that the interengaging wedge faces of both parts absolutely correspond as regards spacing, pitch, parallelism and correct angular position, in order to ensure an accurate concentric fitting, can likewise not be fulfilled in this instance. especially in the case of hardened hubs in which it is practically impossible to eliminate by subsequent shaping the distortions caused by hardening.

The invention relates to a method and device by which the connecting part of the shaft and the bore of the corresponding machine element are worked with the same tool and by the same method to produce a cross-sectional shape the contours of which extend according to the law of cyclic curves.

The perfect drive of the machine element placed on the shaft is ensured by-the departure from the hitherto generally employed concentric cross-sec tion, this element being either rigid or slidable in longitudinal direction on the shaft. The machining of the parts is considerably simplified because for the former'round machining of the shaft and of the bore merely the cross-sectional shaping of them is substituted.

The development of the cross-sectional shapes and the method for producing congruent internal and external shapes are illustrated by way of example in the accompanying drawings in which:-- 1

Figs. 1 and 2 show the crank gear system.

Fig. 3 shows in side elevation a grinding machine for working external profiles and F'g. f1 shows a horizontal section through the work head stock ofthis machine. 15

Fig. 5 shows on larger scale the reciprocating rotary gear which is arranged instead of the two rolling circles and therefore the application of the manner of operation illustrated in Fig. 2 upon the constructional form of this gear.

If the circle I (Fig. 1) rolls in the stationary circle 2, the point 3, which is located at a predetermined distance on the extension 4 of a radius of the circle I, describes an extended hypocycloid 5, which represents a special variety, be- 25 cause the generating point is situated outside both the rolling circle and the base circle and which, according to the selection of the transmission. can repeat itself once, twice or several times during a revolution, whereby polygons with two, three 30 or more rounded corners are produced. The normal to any desired point of the produced curve always extends through the point of contact of the rolling circle and the stationary circle. The normal can therefore be effectively represented 35 by the link of a 'slot and crank which swings about the point 8, the radius of the circle 2 serving as crank radius, As the centre I of the circle I circulates at the same angular speed about the centre 8 of the circle 2 as the common contact 40 point 9, the point 1' remains unchanged on the crank ill and at a constant distance from the point 3. The slot and crank system shown in Fig. 1 therefore produces when the circle 2 is stationary the desired polygon shape at the same time positively determining the actual contact normal.

A condition is thatthe engaging point of the tool lies on this normal; that, for example. when employing grinding wheels, their centre is situated always in this normal or the extension thereof, and the tool is likewise fed in the direction' 'of this normal. The result is, that accurately the same sectional shape is produced, no 5 matter whether the tool is outside or inside the curve.

Instead of the arrangement illustrated in Fig. 1, in which the circle 2 and the profile 6 connected with the same are stationary and the crank gear revolves around the centre of the profile, the link of the crank gear may be stationary and the crank gear revolve on the stationary link, the other parts of the crank gear oscillating at both sides of the link.

Such an arrangement is illustrated in Fig. 2. The linkis in a horizontal non-variable position in which therefore also the point 3 is permanently fixed. In the position of the crank gear corresponding to the curve 5 crank l6 and connecting rod 4 coincidewith the link 6, the distance 3-l5 corresponding to the connecting rod 4 and the distance 4-| 6 to the crank I. -By turning the crank ID in the direction of the arrow the point 3 slides on the link 6 from l4 to 9. The point 1 is lifted by the distance'lS-l and the centre 3 by the distance |66. :If the rotation continues, the points descend finally and oscillate then to the opposite side of the link and so forth.

For the following explanation it has to be observed that the angle of rotation at between crank l6 and connecting rod 4 relates to the angle 5 between crank I6 and profile middle 6-|| as the diameter of the circle 2 to that of the circle I.

Fig. 3 shows the usual construction of a circular grinding machine, in which on a stationary bed 33 a plate 35 destined to hold the work 34 slides to and fro in the usual manner.

The grinding wheel 36 is mounted in a grinding upright 31 which is adapted to be adjusted on the guide way 36 in perpendicular direction to the path of the table and consequently also relative to the work 34 in order to obtain the desired size of the workpiece. The adjusting is effected by means of the screw spindle 39 which engages in the nut 46 rigidly connected with the bracket 31 and can be rotated by the hand wheel 4|. The grinding wheel 36 can be driven by a belt 42 from an overhead transmission gear or directly by a motor.

On the reciprocating table 35 the head stock 43 (see also Fig. 4) is mounted. By a belt 44 of the overhead transmission gear or of a motor the driving disc 45 is driven in such a manner that the eccentric shaft 46 and through the intermediary of the gears 26, 2|, 22 also the eccentric shaft 41 are rotated in always corresponding manner.

I The eccentric centres 3 and 46 are rotatably mounted in the sliding blocks 49 and 56 which are slidably arranged in the guide ways 5| and 52 so that the centres 9 and 48 of the eccentric shafts and the centre I2 of the grinding wheel are always situated on the same straight line which in turn extends parallel to the 'guide way 33 of the feed plane.

The eccentric shafts are journalled at their second eccentric centre 6 and 53 in a common oscillatable body 54 which further carries the clamping spindle 55 in such a manner that the centre |6 of the same and the eccentric centres 3 and 53 are always situated in a straight line. Herefrom results that the centres 6, I6 and 53 describe always similar paths during the oscillation of the bearing 54.

The eccentric shaft 46 carries the other eccentric centre I around which the link piece 56 is arranged oscillatably which is hingedly mounted 36 at its middle 3 but otherwise fixed in the holding head stock 43. This centre 3 is always situated unchanged on the connecting straight line through the centres 3, 43 and I2.

A comparison of the Fig. 3 with the Fig. 2 shows the conformity of the arrangement of the crank gear, the distances 3-9 corresponding to the crank radius l3 and 1-3 to the connecting rod line 4- and 5| corresponds to the link 6 which in this example is stationary.

In the point 3 (Fig. 3) the curve around the centre 6 would be produced by rolling of the crank gear according to Fig. 2. The same curve is produced around the centre |6 if the point of contact 32 between tool and work is spaced from the point 3 by the distance 6-|3.

A gear wheel 23 centred with the centre 1 is rigidly connected with the eccentric shaft 46 and rotates the gear 24, the latter is rigidly connected with the gear wheel 25 and runs loosely on the bolt 21 which is mounted in the joint piece 56. The gear wheel 25 drives the gear wheel 26 loosely rotating around the centre I of the eccentric shaft.

The transmission in the wheels 23 to 26 is selected so that at an angle of rotation on of the crank l6 (Fig. 5 and Fig. 2) relative to the connecting rod 4 the wheel 26 rotates by the angle oc--fl relative to the connecting rod, the angles a and 5 relating like the diameters of the two rolling circles I and 2 (Fig. 2). At a complete revolution of the gear 23 the gear 26 then turns angularly a distance governed by the amplitude of a curve period and at a number of revolutions of the gear 23 corresponding to the period number of the profile the gear has completed one rotation.

The grooved disc 51 in which the ribs 56 of disc 26 engage, is rigidly connected with the gear 26. The ribs 59 of disc 26 displaced by 90 engage in the corresponding grooves of the gear wheel 29 loosely rotating around the centre 6 of the eccentric shafts, whereby the rotating movement of gear 26 is transmitted at the same angular speed upon the gear wheel 29 and consequently also from centre 1 to centre 6. Wheel 29 rotates wheel 3| through the intermediary of the intermediate wheel 36 loosely rotating around bolt 66 in the oscillatable bearing 54. This wheel 3| is keyed on the clamping spindle 55 and is thereby connected also with the profile 34. The revolving movement of wheel 26 is therefore transmitted unchanged upon the profile so that also here the angle of rotation is between crank I6 and connecting rod 4 and the angle s between crank i6 and the profile are in the same proportion as with wheel 26.

The mathematical conditions for the rolling of the two circles and 2 according to Fig. 2, which, however, owing to their very small dimensions cannot be practically obtained directly, are fulfilled in the same measure by means 01' the gear wheels 23-26 and an accurate curved production is obtained according to the conditions of Fig. 2.

In Fig. 5 instead of the outer grinding wheel 36 an inner grinding wheel 6| is provided. Its centre I3 is always situated upon the straight connecting line through the centres 9, 3 and 46. The inner grinding disc touches therefore the profile curve from the inner side at the same point 32 at which the outer grinding wheel would touch the curve from the outer side (Fig, 2).

As these contact points of the tools with the curved profile coincide always with the point 3,

the produced external and internal profiles are also congruent. I

Instead of the form of construction just described, in which the link of the crank gear is stationary and the crank gear rolls on the link, the arrangement shown in Fig. 1 may also be employed in which the profile, i. e. the workpiece is stationary. Around the workpiece then rotates the crank gear and therefore also the link with the tool on thesame.

The connecting rod 4 might also be stationary. In this instance the link with the tool carries out an oscillating movement around the end point of the connecting rod, whereas the crank rotates around the other end point and communicates to the workpiece the corresponding rotar! movement.

If the centre of the workpiece is made stationary, so that this workpiece can turn around it, an always parallel upwardly and downwardly directed oscillating movement may be imparted to the link in an ordinary arrangement shown in Fig. 3, the connecting rod 4 oscillating then relatively at both sides of the link and imparts to the workpiece the corresponding rotation.

In order to attain the highest possible efliciency of the method, the provision commonly used for grinding, turning or milling is maintained to give to the tool any desired width which besides can carry out in the longitudinal direction of the work axis the usual reciprocating feeding movement. This longitudinal movement may also be communicated to the work. Instead of the above mentioned point contact between tool and work a line contact takes place along a common wall line and instead of the contacting tangent there is a common tangential plane. As the contact line and the workpiece centre are parallel the one to the other, the same is valid also for every point of the contact line as regards the profile movement. By this arrangement is obtained that the efficiency remains the same as in the otherwise usual round working so that the omission of the wedge working has to be considered as profit in the total efllciency.

For producing conical seats a. convergent position relative to the centre of the workpiece can be given to the common contact line so that both lines intersect or approximately intersect.

I claim:-

In a machine of the type described, a cutting tool, a work support, means for efiecting a relative feeding movement between said tool and said support, a bearing member mounted on said support, a work rotating spindle journalled in said bearing member, a pair' of shafts rotatably journalled in said bearing member parallel to said spindle and adapted to support said bearing member, means for mounting each of said shafts eccentrically of its axis in bearings slidable in said support, and means for differentially rotating said spindle and said shafts,

RICHARD MOSSDORF.

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