| 摘要 |
1282910 Feeding sheets XEROX CORP 18 Nov 1969 [19 Nov 1968] 56394/69 Heading B8R [Also in Division H2] Apparatus for moving a workpiece, particularly for raising a stack of sheets or a table 20, Fig. 3, to a predetermined height by means of a motor drive, controlled by a device 44 sensing the height of the stack, comprises a motor control circuit having paths for delivering either alternating current to the motor for fast movement, e.g. raising of the table or half-wave rectified current for slow movement, e.g. raising of the table, the particular arrangement being such that the table is first raised at a fast speed, then at a lower speed as the stack top nears the predetermined position, and finally is stopped when the predetermined position is reached. As applied to an arrangement wherein the sheets are separated one by one from the top of the stack by suction devices 16 and fed forward by rollers 18, the table 20 is guided for vertical movement by rollers 22 situated in vertical channels 24. A cable 26 attached to the table 20 passes over a pulley 28 fixed to a shaft 32 driven by worm gearing 36, 38, Fig. 2, from a reversible motor 42. Initially the table is lowered by operation of a "down" switch which causes the motor to rotate in a direction to lower the table, a switch in the motor circuit being opened when the lowest position is reached. To raise the table an "up" switch is operated which causes rotation of the motor at a high speed in a reverse direction and opening of the down switch. At a certain point in the upward movement, the top sheet of the pile contacts a detector member 44 of generally U-shape in plan. The member 44 is fixed to a pivot shaft 48 to which is also fixed an arm 50, Fig. 2, urged by a spring 52 anticlockwise to a position where it closes two normally open switches 6LS, 10LS, and holds the member 44 in its lowest position. When the member 44 is raised by engagement therewith of the top of the stack, the arm 50 is pivoted clockwise, and first opens the switch 6LS which causes half-wave rectified current to be supplied to the motor so that it continues to raise the table but at a slow speed. After further clockwise movement of the arm 50, the switch 10LS is opened and raising of the table is stopped. As sheets are fed from the stack, the switch 10LS is actuated to keep the top of the stack at the required height. When the stack has been depleted, a switch (4LS, Fig. 5) is operated to lower the table without the necessity to operate the "down" switch. During actual feed of a sheet, a cam operates on the arm to raise the arm 50, open the contacts 6LS, 10LS, and move the member 44 temporarily out of contact with the pile. |
