| 摘要 |
1,195,453. Screw-and-nut mechanism; controlling clutches. RESEARCH INSTRUMENTS Ltd. 28 Jan., 1969 [5 Feb., 1968], No. 5632/68. Headings F2L and F2Q. [Also in Division G1] An indexing mechanism for linearly moving a workpiece 122 in a series of steps comprises a shaft 36 coupled to a lead-screw 106 engaging an internally threaded barrel 110 secured to a support 112, and control means including sensing means which is adapted to sense references markings on a drum 44 driven from shaft 36 whereby the drum 44 is adapted to undergo intermittent single complete revolutions each corresponding to a predetermined linear movement of the workpiece. The drum 44 is mounted on a shaft 54 carried by a frame 42 pivotally mounted on shaft 36, a gear-wheel 70 being secured to shaft 54 and being driven from shaft 36 by gears 68, 72. The gear-wheel 70 may be replaced by another gear-wheel having a different number of teeth. The end of shaft 54 remote from gear-wheel 70 is coupled via a spline shaft 82 to a shaft 86 forming part of an electromagnetic brake 88. Shaft 36 is driven from an electric motor 10 through a gear-box 18, an electromagnetic clutch 30 and a spline shaft 38. The drum 44 contains slots 56, 58 which are adapted to pass between lamps 60, 62 and photo-cells 64, 66 connected to amplifiers 130, 132 controlling the brake 88 and clutch 30 respectively. An over-ride circuit 134 is connected to the amplifiers 130, 132. When the drum 44 is at rest, an enlarged portion 136 of slot 56 is aligned with lamp 60 and photo-cell 64 so that a brake solenoid 98 is energized and brake 88 engaged, the clutch 30 being in a disengaged condition. On the application of a start pulse S to the over-ride circuit 134, a cutoff pulse is applied to amplifier 130 thereby disengaging the brake 88 and a switch-on pulse is applied to amplifier 132 thereby engaging clutch 30 and causing rotation of shaft 36 and drum 44 for one revolution until slots 56, 58 cause the brake 88 to be applied and the clutch 30 to be disengaged. Due to lead-screw 106, the shaft 36 is caused to move axially and carries with it gears 68, 70, 72 and frame 42 which is supported at one side on a bearing plate 50 which may be horizontal or inclined. In a modification, the slots 56, 58 are replaced by magnetic marks and the lamps 60, 62 and photocells 64, 66 replaced by magnetic transducing heads. Alternatively, the reference marking could be carried by gear-wheel 70. Further modifications include the use of a chain band or friction drive, a cluster of gears, a plurality of pairs of reference slots in the drum, replacement of a drum of different inertia in accordance with a change of gear ratio, and the application of braking action to the shaft 36 instead of to the spindle 54. |
