Patent GB-1419675-A (GB)
Title: Apparatus for machining a trochoidal surface on a workpiece
IPC: B23Q27/00
Filed: 1973-10-10
Abstract: 1419675 Grinding trochoids; generating trochoids DORNIER SYSTEM GmbH 10 Oct 1973 [13 Oct 1972] 47299/73 Headings B3D B3K A device for working, such as grinding or milling, a trochoidal workpiece 4, Fig. la, comprsies a working tool 35 having its axis of rotation at right angles to the trochoid crosssection and contacting the workpiece on a generatrix G which, with the axis of the tool, lies in a plane, the workpiece, during rotation by a transmission 1, 3, being pivotable about the generatrix G by a disc 6 which is coupled to the transmission 1, 3 and is displaceable in the direction of a diamter of the disc parallel to the said plane. In an embodiment for producing a workpiece having a cardioid trochoid, an internally toothed housing 1 is mounted in a pivot 2, the axis of which is coincident with the generatrix G formed by the tool 35. A shaft 15, which is driven by a homokinetic joint, is mounted in the housing 1 for rotation about an axis a and has a cranked portion of excentricity E carrying a gear wheel 3 which rotates about an axis in engagement with the internally toothed gear. The workpiece is also mounted on the shaft 15 for rotation about the axis b and is secured by a pin 5 to the gear wheel 3. The shaft has a further cranked part of eccentricity 2E, relative to axis a, and is secured to the disc 6 which rotates in bearings 7 in a ring 8 having diametrically-opposed rods 9 slidable in guides 10 on the machine frame. Rotation. of the shaft 15 causes the gear 3 to roll around the internal teeth of the housing 1 with consequent rotation of the workpiece about axis b of the gear 3 and axis a of the shaft, the rotation of the disc 6 about the axis c causing straight line movement of the axis c whereby the axis a rotates relatively around the axis c to cause a swinging movement of the housing 1, and hence the workpiece, about the axis G of the pivot 2 and generatrix. With the ratio of the gear wheels equalling 2 : 1 and the eccentricity of the axis c relative to axis a being twice that of axis b, a carchoid trochoid is produced on the workpiece and the normal to the curve at the generatrix always passes through the axis of the tool. If the gearwheels have a ratio of 2 : 3 with a corresponding change in the eccentricities of the axis, a nephroid trochoid is produced on the workpiece. In another embodiment, the shaft 15, Fig. 2, is rotatably mounted in a member 16 for rotation about an axis b, the member 16 being rotatably mounted about an axis a in a frame 13 carried by a pivot 12<SP>1</SP> having an axis G coincident with the generatrix of the tool 35. The member 16 has a disc 6 having a centre on an axis c, the disc being rotatable in bearing 7 in a housing 8 having diametrical rods 9 slidable in guides 10. A receiving plate 17 is mounted in shaft 15 and has a centreing plate 18 for the workpiece 4 which is secured by a clamp 19. A gear 3 on the shaft meshes with an internal gear 14 in a housing 14 secured to the frame 13. In an alternative arrangement, the gears are replaced by a pair of discs which are mounted eccentrically in opposite directions in the shaft 15 and are recessed in respective slides guided for movement in directions at right angles to one another in the frame 13. The frame 13 may be slidably adjustable on a further frame mounted on the pivot 12 to vary the distance between the axes G and a. A balance weight counteracts the swinging movement of the frame. The tool 35 is adjustable in the direction of the arrow to vary the size of the trochoid.