Patent GB-169370-A (GB)
Title: Improved apparatus for grinding the teeth of hobs and like tools used for cutting pinions and gear wheels
IPC: B24B3/12
Filed: 1920-08-21
Abstract: 169,370. Mensforth, H., Cowell, F. A., and Metropolitan-Vickers Electrical Co., Ltd. Aug. 21, 1920. Milling-cutters, sharpening. - Apparatus forgrinding hobs and like tools comprises a holder for the hob adapted to be oscillated to the extent of the peripheral arc of a tooth and at the same time traversed axially and transversely to give lead and relief to the tooth; the grinding- wheel is set for each tooth, in any row of teeth, by means of length gauges. The hob 1, Fig. 7, has a number of teeth similar to a screw-thread mutilated by flutings 1<b>, which may be parallel to the axis of the hob, or spiral, and the teeth are ground to the outline CBAB<1>C<1>, Fig. 8, and also to have relief E, as shown in Fig. 7. The hob is rotatably mounted on an arbor 2, which is supported in V-blocks 3, 4, Fig. 1, and secured therein by screws 11 in hinged caps 7, 8; theblocks are secured to a table 6 movable on a bedplate 30. Axial movement of the arbor is prevented by a flange 13 thereon and a cup 13<a> secured thereto, which engage the faces of the block 4; the hub is pressed towards the block by a spring 3a. To obtain correct angular setting of the hob, an index-plate 16 is mounted on the arbor and is keyed to the hob. The plate. has peripheral radial slots 17 therein equal in number to the number of teeth in one convolution of the hob, the slots having an inclined face to ensure that the hob is correctly located when a slot is engaged by a manually movable spring plunger 18 mounted in a lever 20 carried on a bush 21 on the arbor. The lever is rocked by a cam 27 mounted on a shaft 28, whereby uniform oscillation is imparted to the hob to the extent of the peripheral length of one tooth. To obtain relief on the tooth, the hob is moved, as it oscillates, transversely of its axis by means of a cam 34 on the shaft 28 acting on the table 6. The grinding- wheel 40 is mounted in adjuutable bearings 42, 43 carried by a plate 51, which is rotatably adjustable, about an horizontal axis, on a plate 53, and this plate is vertically adjustable on a slide 54. The slide 54 is rotatably adjustable about a vertical axis 56 on a slide plate 57, which is movable horizontally on a slide 61, and this slide is movable on a plate 63 in a direction perpendicular to the movement of the slide 57. The plate 63 is mounted, on a carriage 65, to swivel about a vertical axis passing through the point of intersection of the centre lines of the slides 57, 63. The carriage 65 is mounted on a slide 68 on the base 30, and is movable parallel to the axis of the hob by a screw 70 having a fine-adjusting means 82. The longitudinal position of the grinding-wheel is determined in relation to individual teeth of the hob by a series of length gauges 72, 73 adapted to be placed between a stop 76 on the carriage and a lever 79 operating a micrometer indicating-device 77. The gauges 72 serve to space the grinder for individual teeth in any one row, and the gauges 73 correspond to the lead of the various teeth in one convolution. A diamond 87 is provided for trueing the wheel and also for use as a datum point, or positioning- gauge. for the wheel. It is adjustably mounted on a bracket 89 secured to the carriage 65. The hob is traversed axially and transversely by movement of the table 6, which is mounted on a plate 91 and is rotatably adjustable thereon. The plate 91 is slidable on a plate 91<a>, which is rotatably adjustable on the bed 30, so that the slidegroove 90 in the plate 91<a> can be set to the requisite angle f to the line KL, which is perpendicular to the hob axis, the axial direction of the hob remaining unchanged. In operation, a grinding-wheel having a curved face corresponding to the part BAB<1> of a tooth is first employed, and all the teeth of a row are ground by use of the gauges 72 and the appropriate gauge 73. The hob is then indexed to bring the next row of teeth into position and the process is repeated, using another gauge 73. The flanks BC, B<1>C<1> of the teeth are then ground by another wheel, which is set in a similar manner for the various teeth and which is positioned by rotating the plate 63 .on the carriage to make an angle d, Figs. 1 and 8, to the line MN. The face of the wheel is then moved into contact with the diamond by moving the slide 57 on the base 63, and the wheel, if necessary, is trued-up. It is then traversed, by movement of the slide 57, along the flank of the tooth. The opposite flanks are then similarly ground after re-setting the slides. Spirally fluted hobs may be ground by the use of a suitable index-plate and gauges 72, 73. Specification 162,457, [Class 106 (ii), Dynamometers &c.], is referred to.