880,337. Melting glass frits. ZEISSSTIFTUNG, CARL., [trading as JENAER GLASWERK SCHOTT & GEN.]. March 17, 1960, No. 9477/60. Class 56. In melting a frit in a melting vessel with or without a stirrer, the tendency of the resulting glass melt to crystallise and for volatile constituents to escape from the vessel is prevented or retarded by providing a cover to seal the melt from the atmosphere and providing heat regulating means so that the temperature of any part of the vessel and stirrer is substantially the same as that part of the melt in contact therewith. Preferably a uniform temperature gradient is maintained, the upper part of the melt being up to 20‹C higher than the lower part. As shown in Fig. 4, a vessel 1 with stirrer 2 is provided with a cover 3 of platinum secured to the stirrer 2 to rotate therewith, the cover 3 having a heat insulating layer 4 and an electrical resistance heating coil 5 above. The shaft of the stirrer 2 may be separately heated and also coils may be provided round the top part of the vessel 1. For melts having a reaction with the atmosphere, a complete liquid seal may be provided for the cover 3. As shown in Fig. 6, the bottom of the vessel 1 may be recessed at 1a to take heating coils 9 round a tube 10 which may supply regulating cooling air. The stirrer 2 for this vessel may have a forked end 2a. 880,424. Grinding machines. JONES & SHIPMAN Ltd., A. A., and HOULDSWORTH, J. Sept. 30, 1959 [Oct 6, 1958], No 31829/58. Class 60. A grinding machine of the kind having a grinding wheel 4 with mechanism to provide a radial feed into a rotating workpiece 1, which may itself be reciprocated axially, has the feedmechanism drive effected through a transmission gear including a movable sine bar or ramp 40, the inclination of which is adjustable to vary the transmission ratio of the said drive and hence the feed. The feed may be applied either continuously or in separate increments at either or both ends of the stroke of a reciprocating workpiece. The work-carrying table 12 is traversed in either direction by hydraulic control mechanism 8, cylinder 5, and reversing lever 9 operated by dogs 10, 11, a manual control 13 being engagable at will by a lever 14 which is interlocked with the hydraulic mechanism to prevent simultaneous engagement with the power-operated traverse. The wheel-head 15 is movable in a direction normal to the traverse by a mechanism 18 comprising an hydraulic cylinder and piston 22, 21, and threaded member, 17 which is reciprocatable without rotation to impart a high rate of feed to, or withdrawal from, the workpiece. A nut 16 attached to the wheel-head 15 enables an additional feed, by rotation of the member 17, to be imposed on that provided by the mechanism 18. When this is required the member 17 is rotated by a wide-toothed gear wheel 24 meshed with a wheel 23 forming part of a compound train housed in a pivoted casing 33 having an extending arm and a roller 46 which bears upon the adjustable ramp 40 carried by a reciprocatable slider 39 so that longitudinal movement of the slider and ramp 40 by hydraulic mechanism 49 causes movement of the casing 33 about the axis of the wheel 23. Stops 47, 48 on the machine frame and the casing 33 limit the anti-clockwise rotation of the casing under the influence of its own unbalanced weight, as determined by the inclination of the ramp, until the roller leaves the ramp when the stops become effective to limit the infeed movement. At the completion of a workpiece the slide 39 moves to the right, causing the casing 33 to rotate clock-wise and thus to withdraw the wheel clear of the work, this movement being accompanied by a movement of the hydraulic mechanism 18 to effect the loading clearance. The casing 33 may be rigidly or loosely connected to a tube 27 carried in bearings 35 in the machine frame, the tube having co-axially located therein a shaft 26 to which a pinion 28 is rigidly fixed, the gear wheel 23 being freely mounted on the same shaft. Rotation of the shaft 26 effects a low-speed drive to the wheel 23 through the reduction gear train 28, 29, 30. The shaft 26 and tube 27 are locked together for automatic feed of the wheel-head 15, by a rod 37 extending from a hand wheel 25 to engage a slot 38 in a plate 31a secured to the end of the tube. For manual feed the hand wheel 25 effects rotation of the shaft 26 by the engagement of an irreversible worm 90 carried by the wheel with a worm wheel 91 on the end of the shaft; the angular position of the wheel 25 relative to the shaft 26 may thus be adjusted so that the rod 37 may engage the plate 31a to lock the shaft in any desired angular position relative to the shaft. The worm 90 may be manually rotated to provide a finer feed than by a direct rotation of the shaft by the handwheel. An abutment 31 on the plate 31a engagable by a pivoted member 32 carried by the hand wheel 25, limits the rotation of the feed via the hand wheel and shaft 26 but a cam 36 may be manually moved to bring the member 32 into or out of the path of the abutment 31. Almost a full revolution of hand wheel movement may thus be applied to bring the wheel-head 15 to a given forward position or to reverse it to accommodate the next workpiece. In the arrangement in which the casing 33 is freely mounted on the end of the tube 27, instead of fixed thereto, the shaft 26 is locked to the machine bed. The magnitude and rate of feed will be effected in this arrangement by the epicyclic action of the gear train rolling about the axis of the fixed pinion 28. The adjustment of the angle of the ramp 40, whereby the rotation of the casing 33 and the movement of the wheel-head 15 via the member 17 is determined, is effected by a hand wheel and shaft 45 and bevel gears 44, 42, the latter pair having one gear mounted on a splined shaft 43 to allow of adjustment during movement of the ramp with the slide 39. Control of the slide may be effected by two separate mechanisms, one under the influence of the hydraulic cylinder 49, as when the width of the wheel exceeds the length of the work, and the other by a rack-and-pinion 50, 51 when intermittent feed is necessitated by traverse of the work; feed-speed variation is provided for in both systems. Control of the rate of movement of the slide 39 is effected by solenoidactuated valves in the hydraulic system which control the rate of flow to and from the cylinder 49 in a known manner to effect the required feedspeed variation. Slow feed is introduced at a predetermined point of the grinding cycle by a pointer 56 carried by a steel tape 57 moved over pulleys, one of which, 55, is driven by the pinion 51 through an internal gear 53, 54. An abutment 60 of the pointer 56 operates a limit-switch 59 as it passes, the switch itself being adjustably clamped to a fixed part 86 of the machine and provided with a pointer 61; pointers 56, 61 bear upon a scale carried by a drum 58 which is rotated through chain and sprockets and worm gearing 62, 89 by the shaft 45. By setting the pointer 61 against a position on the scale at which it is desired to reduce feed rate a signal operates, as the limit-switch 59 is closed to restrict the flow to the slide-operating cylinder 49 whilst grinding is in progress. A control signal may, alternatively, originate from a gauge in contact with the workpiece or from a pre-set timing device. For intermittent feed the cylinder 49 operates only to withdraw the wheel-head 15 by movement of the slide 39 to the right, leftward or feeding movements being effected by a pair of ratchetoperated wheels 65, 66 which may be drivingly connected to the pinion-shaft 52 by a hydraulic clutch 67. An increment of radial feed may be applied at both ends of the workpiece travel or at one end only; when at both ends the amounts may be different. During feed, when the clutch 67 is operative, the ratchet-wheels 65, 66 are rotated by pawls 68, 69 until a switch 70 is operated to disconnect the clutch 67 as the slide 39 reaches the limit of its leftward movement and there is clearance between the roller 46 and ramp 40. The pawls are carried by rams 71, 72 which are operated alternately by reversals of fluid flow to the table-traversing cylinder 5; as the table moves in one direction the ram 71 moves inwards and the ram 72 moves outwards and vice versa. The stroke of each ram may be varied independently by hand controls 73, 74 which determine the angular positions of two cams 75, 76, which may be set to pick the required number of teeth on the associated ratchet wheel at each reversal of the table 12, thus varying the feed applied at opposite ends of the workpiece. Indicator dials show the number of teeth picked when adjusting the cams 73, 74. As the amount of feed associated with each tooth picked will vary with the inclination of the ramp 40, the drum 58 is provided with a circumferential scale 92 showing the extent of feed per tooth. Similar methods to those employed during continuous feeding may be used to vary the rate of feed at a given point of the cycle and a signal from one of the three sources indicated above may operate to control the movements of swing- ing links 77, 78, which may be brought into engagement with abutments on the rams 71, 72 by hydraulic cylinders 81 controlled by solenoidactuated valves in response to a gauging or timing signal transmitted thereto. Cams 82, 83 are manually operated to adjust the position at which the abutments engage the rams 71, 72 to limit their strokes. A further feed-speed control is provided by a limit switch 85, also operable by the abutment 60 of the pointer 56, which reduces the rate of flow to the cylinder 49, prior to the closure of the switch 59, to effect an intermediate reduction of flow, thereby providing three rates of movement of the slide 39 during feed, maximum, normal and slow, or finishing rates. The magnitude of the required feed and the progress during feeding is indicated