US3755682A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Machine position detection and control devices
Assignee: National Research Development Corp UK
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Filing: 1971-07-01
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Granted: 1973-08-28
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Expires: 1991-07-01
Abstract
Abstract In a position indicating or measuring device, diffraction gratings are attached to relatively movable members and light fringes formed by the gratings are directed onto an array of at least eight photoelectric cells, such as an integrated circuit photocell array transducer, the outputs of the photocells being selected in cyclic order by scan pulses to produce a composite output signal having a cyclic waveform the timing of which is compared with a reference signal. In a position control device, data pulses, e.g. from a punched tape, may then be added to or subtracted from the scan pulses to alter the timing of the composite output signal with respect to the reference signal. The resulting error signal may be applied to a servomechanical system which can move a desired one of the movable members to a required position in accordance with the data pulses. The movable member may follow a predecided contour or move from point to point.
Inventors
- 👤 A Russell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 15:03
CPC Classifications
G; G01; G01D; G01D5/00; G01D5/26; G01D5/32; G01D5/34; G01D5/36; G01D5/38
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
177 words
Apparatus for indicating or measuring the relative position of two relatively movable members and comprising a first optical grating on one member and a second optical grating on the other member arranged to co-act with the first optical grating to produce a fringe pattern when illuminated by a light source, relative movement of the gratings causing apparent movement of the fringe pattern, a linear array of at least eight photocells which are arranged to be illuminated by the fringe pattern so that each individual photocell is illuminated by a different part of the fringe pattern, means for selecting sequentially in cyclic order the outputs of the photocells to provide a composite output having a cyclic waveform, there being sufficient photocells in the array to ensure that the shape of the cyclic waveform of their composite output is substantially unaffected by any change in position of the fringe pattern, and means for comparing the timing of the waveform of the composite output with the timing of a reference signal to indicate the relative position of the two members.
Claim 2
Dependent Claim
177 words
Apparatus for indicating or measuring the relative position of two relatively movable members and comprising a first optical grating on one member and a second optical grating on the other member arranged to co-act with the first optical grating to produce a fringe pattern when illuminated by a light source, relative movement of the gratings causing apparent movement of the fringe pattern, a linear array of at least eight photocells which are arranged to be illuminated by the fringe pattern so that each individual photocell is illuminated by a different part of the fringe pattern, means for selecting sequentially in cyclic order the outputs of the photocells to provide a composite output having a cyclic waveform, there being sufficient photocells in the array to ensure that the shape of the cyclic waveform of their composite output is substantially unaffected by any change in position of the fringe pattern, and means for comparing the timing of the waveform of the composite output with the timing of a reference signal to indicate the relative position of the two members.
Claim 3
Dependent Claim
20 words
Apparatus according to claim 1 in which the linear array of photocells is an integrated circuit photo-electric cell array transducer.
Claim 4
Dependent Claim
68 words
Apparatus according to claim 1 and comprising a clock pulse generator, means for deriving the reference signal from the clock pulse generator, and means for deriving from the clock pulse generator scan pulses which are used to select the outputs of the photocells in cyclic order, the frequency of the scan pulses being n times that of the reference signal, where there are n photocells in the array.
Claim 5
Dependent Claim
63 words
Apparatus according to claim 3 and wherein the said means for selecting sequentially in cyclic order the outputs of the photocells has a smoothing circuit to which the outputs are fed and which smooths out signal components having a frequency around that of the scan pulses, to produce a smoothed output having a waveform substantially in accordance with that of the fringe pattern.
Claim 6
Dependent Claim
70 words
Apparatus according to claim 3 and having means for generating a predetermined sequence of data pulses which may be used to control the position of one member relative o the other member and means for adding data pulses to or for subtracting data pulses from the sequence of scan pulses selecting the outputs of the photocells; thereby changing the timing of the waveform of the composite output of the photocells.
Claim 7
Dependent Claim
42 words
Apparatus according to claim 5 and having servo-mechanical means to which the output of the position indicating means are applied, said servo-mechanical means causing the two relatively movable members to move progressively towards a relative position as required by the data pulses.
Claim 8
Dependent Claim
32 words
Apparatus according to claim 5 in which the data pulses are added to or subtracted from the scan pulses through means to prevent coincidence of a data pulse and a scan pulse.
Claim 9
Dependent Claim
45 words
Apparatus according to claim 5 including means which can detect the timing difference between the waveform of the composite output and the reference signal and which can limit the rate of addition or subtraction of data pulses so that it cannot exceed a predecided value.
Claim 10
Dependent Claim
24 words
Apparatus according to claim 5 in which one data pulse corresponds to a relative movement between the two relatively movable members of 0.0001 inch.
Claim 11
Dependent Claim
15 words
Apparatus according to claim 1 in which the photocell array comprises at least 20 photocells.
Claim 12
Dependent Claim
15 words
APparatus according to claim 1 including means for attaching said apparatus to a machine tool.
Claim 13
Dependent Claim
46 words
Apparatus according to claim 1 and having a reflective optical grating a attached to one member and a light source, a photocell array and a transmitting optical grating attached to the other member, the light being arranged to illuminate the two gratings and the photocell array.
Claim 14
Dependent Claim
15 words
Apparatus according to claim 1 in which the photocell array comprises at least 32 photocells.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-08-27 | 1977-02-26 | 1977-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-08-27 | 1981-02-26 | 1981-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-08-27 | 1985-02-26 | 1985-08-28 | $7700.00 | Window Closed / Lapsed |