Patent GB-1039209-A (GB)
Title: Device for indicating the amount of the displacement of a slide
IPC: B23Q23/00
Filed: 1964-05-14
Abstract: 1,039,209. Electric selective signalling. M. HENSOLDT UND SOHNE, OPTISCHE WERKE A.G. May 14, 1984 [May 18, 1963], No. 20126/64. Heading G4H. Electric or electronic means are provided to correct for the tilt of a position-indicating slide. Movement of the slide of a jigborer across the workpiece causes a sensing head on the slide to move along a measuring scale thus producing pulses which are counted to indicate the displacement. In Fig. 2 (not shown) tilt or rotation of the slide is detected by a pendulouslysuspended prism which reflects an optical image of a grid on to another grid which is divided into two halves mutually displaced by half a grid stroke. Light from the two halves goes to respective photocells, one of which thus produces pulses depending on the direction of tilt. These pulses, constituting correction pulses, are counted up or down by the counter together with those from the measuring scale. For a given angle of tilt, the number of correction pulses required will depend on the work. ing distance, i.e. that between the slide and the workpiece. In Figs. 3, 4 (not shown) a knob is manually positioned in accordance with this distance to energize 0 to 3 of 3 wires. Each correction pulse, besides being fed to the counter also produces three further pulses (with inversion of polarity to give mutual displacement in time) 0 to 3 of which are also fed to the counter depending on how many of the three wires above are energized. In order to prevent loss of correction pulses when the working distance is changed, the pulses on leaving the photocells are first stored and only permitted to proceed to the counter etc. when a button is pressed manually. Fig. 5 (not shown) shows an alternative arrangement (making the store redundant) in which the prism is attracted electromagnetically to a standard zero position prior to change of the working distance by closing a manual switch. Fig. 6 (not shown) shows a modification of this in which a locking arrangement prevents adjustment of the working distance knob referred to until the prism has been zeroized. Fig. 15 (not shown) shows another arrangement for compensating for change in the working distance in which, on closing of a switch, correction pulses are sent to trigger a multivibrator rather than to the counter. Each time it is triggered, the multivibrator holds open a gate for a period of time dependent on its time constant, thus allowing pulses from an oscillator to reach the counter. The working distance knob controls either the frequency of the oscillator or the time constant of the multivibrator. It is also mentioned that the pulses from the measuring scale itself could take the place of the correction pulses in the Fig. 15 arrangement and the corrections for tilt and for change in the working distance be done by controlling the multivibrator time constant and oscillator frequency. Fig. 13 (not shown) shows a further arrangement for compensating for change in the working distance, by feeding the correction pulses to a ring counter, one stage of which only is selected by a switch to provide pulses for the main counter. Fig. 14 (not shown) shows a modification of Fig. 13. Fig. 7 (not shown) shows a further embodiment of the tilt detection means, comprising a spirit level, an optical image of which is transmitted through a glass plate and a prism on to a pair of photo-cells. If tilt occurs, the photocell outputs become unequal thus actuating a follower device which moves a fulcrumed lever to tilt the glass plate until the illuminations of the photocells are equalized. The follower device simultaneously drives a bush-sensed marked disc to provide correction pulses. Change in the working distance is allowed for by altering the position of the fulcrum of the lever by a manual knob. Fig. 8 (not shown) shows a further embodiment in which an image of the measuring scale is projected on to a grid having two mutuallydisplaced halves as in the Fig. 2 arrangement backed by two photo-cells which feed the counter. Tilt detection means as in Fig. 7 (see above) are provided, with the follower means, however, now displacing the grid against a spring. Both the measurement pulses and the correction pulses now come from the two photo-cells. Figs. 9-12 (not shown) show a last embodiment comprising a decimally-coded measuring scale controlling number - indicating tubes through zeroizing switches which permute the leads to choose an arbitary zero position on the workpiece. The lowest order zeroizing switch also serves to correct for tilt being controlled for this purpose by a follower device as in Fig. 7 (see above).