GB1593282A - Measuring apparatus - Google Patents

Measuring apparatus Download PDF

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Publication number
GB1593282A
GB1593282A GB583177A GB583177A GB1593282A GB 1593282 A GB1593282 A GB 1593282A GB 583177 A GB583177 A GB 583177A GB 583177 A GB583177 A GB 583177A GB 1593282 A GB1593282 A GB 1593282A
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GB
United Kingdom
Prior art keywords
measuring apparatus
metering wheel
pulses
count
counter
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
GB583177A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Taylor G M
Original Assignee
Taylor G M
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Taylor G M filed Critical Taylor G M
Priority to GB583177A priority Critical patent/GB1593282A/en
Publication of GB1593282A publication Critical patent/GB1593282A/en
Expired legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C22/00—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
    • G01C22/02—Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers by conversion into electric waveforms and subsequent integration, e.g. using tachometer generator
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B3/00—Measuring instruments characterised by the use of mechanical techniques
    • G01B3/12—Measuring wheels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D11/00—Component parts of measuring arrangements not specially adapted for a specific variable
    • G01D11/24—Housings ; Casings for instruments
    • G01D11/245—Housings for sensors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/244—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains
    • G01D5/245—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing characteristics of pulses or pulse trains; generating pulses or pulse trains using a variable number of pulses in a train
    • G01D5/2451—Incremental encoders
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/36—Forming the light into pulses

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Length Measuring Devices With Unspecified Measuring Means (AREA)

Description

(54) IMPROVEMENTS IN OR RELATING TO A MEASURING APPARATUS (71) We, GERALD MARTIN TAYLOR, a British Subject of 57 Blakesley Walk, Anstey Heights, Leicester and STANLEY TAYLOR, a British Subject of 107 Main Street, Ratby, Leicester, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: The present invention relates to measuring apparatus for determining the distance travelled along a surface, for example the distance travelled by a first member along the surface of a second member. The invention is intended particularly but not exclusively for use with machine tools such as lathes or milling machines where the apparatus may be used to measure the relative travel between a cutting tool and a workpiece, for example.
According to the present invention, there is provided measuring apparatus comprising a housing, a rotatable metering wheel contained within the housing such that only a small part of its periphery projects therefrom for frictional rolling engagement with a measurement surface in use, transducer means arranged to correct rotational movement of the metering wheel into electrical signals representing the amount of such movement, the transducer means including an optical sensor, and digital display means responsive to the electrical signals produced by the transducer means and arranged to provide in accordance with said signals a numeric display which represents the distance travelled by the metering wheel along said measurement surface, the transducer means and the digital display means being contained within or provided on said housing so that the measuring apparatus forms a self-contained unit.
The invention will now be described further by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of measuring apparatus in accordance with the present invention, Figure 2 is a side elevational view, partly in section, of the apparatus shown in Figure 1, Figure 3 is a front elevational view of the apparatus shown in Figures 1 and 2, Figure 4 is a plan view of an encoder disc used in the apparatus of Figures 1 to 3, Figure 5 is a sectional view of part of the apparatus shown in Figure 2, showing an optical sensor for detecting graduations on the disc of Figure 4, Figure 6 and 7 are block diagrams of suitable electrical circuitry for use with the apparatus shown in Figures 1 to 5, Figure 8 is a circuit diagram of a quadrature direction sensing unit which forms part of the circuitry shown in Figure 6, and Figure 9 is a circuit diagram of a count and direction control unit which also forms part of the circuitry shown in Figure 6.
The measuring apparatus illustrated in the drawings includes a housing 2 which partially encloses a metering wheel 1. The periphery of the wheel has a roughened or other form of friction surface, a small part of which projects through the housing 2, as may best be seen from Figure 1. The exposed portion of the metering wheel is arranged to roll frictionally along a surface to be measured which is illustrated diagrammatically at 3 in Figure 2. The metering wheel is fixed to a shaft 5 which is rotatably mounted in the housing 2 by means of bearings. Digital display devices 32 are disposed on an exterior surface of the housing 2, as shown in Figure 1.
A gear train 7 comprising gears 10 and 11 is coupled between the shaft 5 and a second rotatable shaft 8 which is also mounted in the housing by bearings. The gear train 7 amplifies the rotation of the shaft 5 by an amplification factor determined by the gear ratio of the gear train 7. The amplified movement appears as additional rotational movement of the shaft 8 over that of the shaft 5.
In a preferred embodiment of the invention the circumferential surface 4 of the metering wheel 1 is 6" (152.4mm) and the gear ratio of the gear train 7 is 12 to 1.
Hence, the shaft 8 rotates exactly 12 times for each rotation of the metering wheel.
An anti-backlash gear train is provided on the shaft 5 to ensure that the shaft 8 rotates immediately in response to rotation of the metering wheel in either direction and has a gear ratio equal to that of the gear train 7.
The anti-backlash gear train includes a gear 9 journaled coaxially with the shaft 5 and biased relative to the corresponding gear 10 of the train 7 by means of a tension spring (not shown). Hence, the two gear trains are continuously loaded against each other so that there is no play between them.
An encoder disc 13 (shown in detail in Figure 4) is fixedly mounted upon the shaft 8 and has two sets of graduations, one set 14 being metric and the other set 15 being imperial. The encoder disc has radial translucent and opaque portions arranged alternately, the translucent and opaque portions being of equal angular extent.
A reading head shown in detail in Figure 5) is mounted about part of the encoder disc and includes means for reading the graduations upon the disc. In the illustrated embodiment of the invention, the reading head 18 has four light-emitting diodes 19, two for each set of graduations. The two diodes of each diode set are set angularly one relative to the other. A lens 20 is mounted above each light-emitting diode and serves to focus the light onto a respective photo-electric cell 21.
As the encoder disc 13 is rotated upon rotation of the metering wheel 1, the light from the light-emitting diodes is blocked intermittently. When light from the lightemitting diodes does fall upon the photocells, electric current is caused to flow into a two input amplifier and signal generator 22 (see Figure 6) through an inch/metric selector switch 23. Switch 23 is of the double pole, double throw type.
The amplifier and signal generator 22 amplifies the current produced by the photo-electric cells and produces sinusoidal waveforms 24 and 25 respectively which are 90 electrical degrees out of phase with each other. These two waveforms are passed to a double input Schmitt trigger 26 which changes the wave forms 24 and 25 to square pulse waveforms 27 and 28 respectively, these waveforms again being 90 electrical degrees out of phase. The squared waveforms are then passed to a quadrature direction sensing unit 29, the function of which is to ascertain whether the metering wheel 1 is rotating clockwise or anticlockwise.
The quadrature direction sensing unit (shown in detail in Figure 8) contains a NOT gate 40, a pulse generator 42 and two AND gates 44 and 45. Waveform 27 is fed directly to the NOT gate 40 and one input of the AND gate 44. The NOT gate inverts the waveform 27 and that signal then passes to one input of the other AND gate 45. The waveform 28 is fed to the pulse generator 42 which produces a short duration pulse on the positive edge of the input pulse, which is then fed to the other inputs of both AND gates 44 and 45.
It is assumed that clockwise rotation of the metering wheel produces a count of positive direction (UP), which is displayed on the display devices 32 when clockwise rotation is recorded. The waveform 27 and the waveform 28 from the pulse generator arrive at the AND gate 44 when the gate operates to pass a short duration pulse from the pulse generator as an UP pulse.
When the shaft carrying the metering wheel rotates in the opposite direction a pulse from the NOT gate is passed to the AND gate 45 along with waveform 28 from the pulse generator, and the gate 45 operates to pass a DOWN pulse.
The electrical pulses are then passed to a count and direction control unit 30 which splits them up into two parts (i.e. instruction and decoder pulses). The count and direction control unit (shown in detail in Figure 9) consists of one OR gate 46 and one parallel connected set-reset flip flop 48, i.e.
a bistable multivibrator. Both the UP and DOWN signals received from the sensing unit 29 are fed to the OR gate 46 which allows either signal to pass through it to the count input of a bi-directional counter. The UP and DOWN pulses are fed respectively to the inputs of the set-reset flip flop 48.
When UP pulses are produced and received by the flip-flop an UP instruct line is energised, and when DOWN pulses are produced and received by the flip flop a DOWN instruct line is energised. It will thus be apparent that three signal lines pass from the unit 30 to the counter (which forms part of a counter decade decoder 31) : the signal line from the output of the OR gate 46 passes to the count input of the counter, and the signal lines from the outputs of the flip flop 48 pass respectively to UP and DOWN control inputs of the counter. In Figure 6, these signal lines are represented by wareforms a to d, the wareforms a and b being produced at the output of OR gate 46 according to whether the metering wheel is being rotated clockwise or anticlockwise.
Wareform c instructs the counter to count the pulses in wareform a additively, while wareform d instructs the counter to count the pulses in wareform b subtractively.
The counter decade decoder 31 operates to count the pulses UP or DOWN in dependence upon the nature of the instructing pulses. The counter decade decoder 31 is made up of a bi-directional decade counter and a binary to decimal converter which is connected to the digital display devices 32.
Binary coded up/down pulses received from the count and direction control unit 30 are converted to decimally coded signals for operating the display devices 32.
In Figure 7 the display devices 32, from right to left, have values of thousandths, hundredths, tenths, units, and tens of inches or hundredths, tenths, units, tens and hundreds of millimeters respectively of travel of metering wheel along the measurement surface. The digital display thus, has a measurement range from 00.000 to 99.999 inches and 000.00 to 999.99 millimetres. The digital display includes at its extreme left, i.e the sixth decade, an indicator for showing when the distance being measured passes through zero. In the case illustrated in Figure 1 the distance is a positive one, as indicated by the plus sign. A reset switch 33 enables all the numbers to be returned to zero upon completion of a measurement operation.
As mentioned, the digital display devices are mounted on an exterior surface of the housing 2, for example on the top of the housing. The inch/metric switch 23 and reset switch 33 are also mounted exteriorally, at the front of the housing, as may be seen from Figure 3.
The housing 2 includes a dovetail 6 which enables the measuring apparatus to be slidably engaged with a female dovetail contained on a mounting mechanism (not shown) which carries the apparatus at a location adjacent a surface to be measured.
The mounting mechanism includes means for biasing the metering wheel with a force of approximately 30 pounds per sq. inch into firm contact with the surface to be measured. It is to be understood however that the force must only be sufficiently large to maintain the metering wheel in non-sliding contact with the surface to be measured. In practice, forces of between 20 and 40 pounds per sq. inch have been found suitable.
WHAT WE CLAIM IS: 1. Measuring apparatus comprising a housing, a rotatable metering wheel contained within the housing such that only a small part of its periphery projects therefrom for frictional rolling engagement with a measurement surface in use, transducer means arranged to convert rotational movement of the metering wheel into electrical signals representing the amount of such movement, the transducer means including an optical sensor, and digital display means responsive to the electrical signals produced by the transducer means and arranged to provide in accordance with said signals a numeric display which represents the distance travelled by the metering wheel along said measurement surface, the transducer means and the digital display means being contained within or provided on said housing so that the measuring apparatus forms a self-contained unit.
2. Measuring apparatus as claimed in Claim 1, wherein the transducer means includes an up-down counter connected to the digital display means and arranged to count pulses produced by the optical sensor in accordance with the amount of rotation of the metering wheel, a direction sensor arranged to sense the direction of rotation of the metering wheel, and a count control arranged to cause the counter to count said pulses additively or subtractively according to the direction sensed by the direction sensor.
3. Measuring apparatus as claimed in Claim 2, wherein the direction sensor is arranged to pass the pulses produced by the optical sensor to a first output when the metering wheel rotates in one direction and to a second output when the metering wheel rotates in the opposite direction, and the count control includes a bistable multivibrator whose inputs are connected respectively to said first and second outputs of the direction sensor and whose outputs are connected respectively to UP and DOWN control inputs of the counter.
4. Measuring apparatus as claimed in Claim 3, wherein the count control also includes a logic OR gate having two inputs which are connected respectively to said first and second outputs of the direction sensor and an output which is connected to a count input of the counter.
5. Measuring apparatus as claimed in Claim 2, 3 or 4 wherein the optical sensor is arranged to supply respectively to first and second outputs thereof two series of square wave pulses which are 90" out of phase, and the direction sensor includes a pulse generator connected to the first output of the optical sensor and arranged to produce an output pulse on a predetermined edge of each square wave pulse supplied thereto, a first logic AND gate having a first input connected directly to the second output of the optical sensor and a second input which receives the output pulses produced by the pulse generator, and a second logic AND gate having a first input connected to the second output of the optical sensor via an inverter and a second input which receives the output pulses produced by the pulse
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (1)

  1. **WARNING** start of CLMS field may overlap end of DESC **.
    the pulses in wareform a additively, while wareform d instructs the counter to count the pulses in wareform b subtractively.
    The counter decade decoder 31 operates to count the pulses UP or DOWN in dependence upon the nature of the instructing pulses. The counter decade decoder 31 is made up of a bi-directional decade counter and a binary to decimal converter which is connected to the digital display devices 32.
    Binary coded up/down pulses received from the count and direction control unit 30 are converted to decimally coded signals for operating the display devices 32.
    In Figure 7 the display devices 32, from right to left, have values of thousandths, hundredths, tenths, units, and tens of inches or hundredths, tenths, units, tens and hundreds of millimeters respectively of travel of metering wheel along the measurement surface. The digital display thus, has a measurement range from 00.000 to 99.999 inches and 000.00 to 999.99 millimetres. The digital display includes at its extreme left, i.e the sixth decade, an indicator for showing when the distance being measured passes through zero. In the case illustrated in Figure 1 the distance is a positive one, as indicated by the plus sign. A reset switch 33 enables all the numbers to be returned to zero upon completion of a measurement operation.
    As mentioned, the digital display devices are mounted on an exterior surface of the housing 2, for example on the top of the housing. The inch/metric switch 23 and reset switch 33 are also mounted exteriorally, at the front of the housing, as may be seen from Figure 3.
    The housing 2 includes a dovetail 6 which enables the measuring apparatus to be slidably engaged with a female dovetail contained on a mounting mechanism (not shown) which carries the apparatus at a location adjacent a surface to be measured.
    The mounting mechanism includes means for biasing the metering wheel with a force of approximately 30 pounds per sq. inch into firm contact with the surface to be measured. It is to be understood however that the force must only be sufficiently large to maintain the metering wheel in non-sliding contact with the surface to be measured. In practice, forces of between 20 and 40 pounds per sq. inch have been found suitable.
    WHAT WE CLAIM IS:
    1. Measuring apparatus comprising a housing, a rotatable metering wheel contained within the housing such that only a small part of its periphery projects therefrom for frictional rolling engagement with a measurement surface in use, transducer means arranged to convert rotational movement of the metering wheel into electrical signals representing the amount of such movement, the transducer means including an optical sensor, and digital display means responsive to the electrical signals produced by the transducer means and arranged to provide in accordance with said signals a numeric display which represents the distance travelled by the metering wheel along said measurement surface, the transducer means and the digital display means being contained within or provided on said housing so that the measuring apparatus forms a self-contained unit.
    2. Measuring apparatus as claimed in Claim 1, wherein the transducer means includes an up-down counter connected to the digital display means and arranged to count pulses produced by the optical sensor in accordance with the amount of rotation of the metering wheel, a direction sensor arranged to sense the direction of rotation of the metering wheel, and a count control arranged to cause the counter to count said pulses additively or subtractively according to the direction sensed by the direction sensor.
    3. Measuring apparatus as claimed in Claim 2, wherein the direction sensor is arranged to pass the pulses produced by the optical sensor to a first output when the metering wheel rotates in one direction and to a second output when the metering wheel rotates in the opposite direction, and the count control includes a bistable multivibrator whose inputs are connected respectively to said first and second outputs of the direction sensor and whose outputs are connected respectively to UP and DOWN control inputs of the counter.
    4. Measuring apparatus as claimed in Claim 3, wherein the count control also includes a logic OR gate having two inputs which are connected respectively to said first and second outputs of the direction sensor and an output which is connected to a count input of the counter.
    5. Measuring apparatus as claimed in Claim 2, 3 or 4 wherein the optical sensor is arranged to supply respectively to first and second outputs thereof two series of square wave pulses which are 90" out of phase, and the direction sensor includes a pulse generator connected to the first output of the optical sensor and arranged to produce an output pulse on a predetermined edge of each square wave pulse supplied thereto, a first logic AND gate having a first input connected directly to the second output of the optical sensor and a second input which receives the output pulses produced by the pulse generator, and a second logic AND gate having a first input connected to the second output of the optical sensor via an inverter and a second input which receives the output pulses produced by the pulse
    generator.
    6. Measuring apparatus as claimed in any preceding claim, herein a graduated encoder disc is mounted within the housing for rotation in response to rotation of the metering wheel and has alternate opaque and light-transmitting graduations arranged circumferentially thereof, and the optical sensor includes a light source and a lightsensitive detector disposed on opposite sides of both the encoder disc, such that the opaque and light-transmitting graduations alternatively prevent and allow light from the light source reading the light-sensitive detector as the encoder disc is rotated.
    7. Measuring apparatus as claimed in Claim 6, wherein two sets of graduations corresponding respectively to metric and imperial measure are provided in radially spaced relation on the encoder disc, a respective light source and a respective light-sensitive defector are provided for each said set of graduations, and a selector switch is operable to determine which of the light-sensitive detectors is operative at a given time.
    8. Measuring apparatus as claimed in Claim 6 or 7, wherein electrical signals produced by the light-sensitive detector are supplied to an amplifier and signal generator which produces an amplified sinnsoidal wareform therefrom, the amplified sinnsoidal wareform being converted to a square wave by a Schmitt trigger.
    9. Measuring apparatus as claimed in any preceding claim, wherein the digital display means includes an indicator for indicating when the distance being measured passes through zero.
    11. Measuring apparatus as claimed in any preceding claim, wherein the digital display means includes means operable to re-set the numeric display to zero.
    12. Measuring apparatus substantially as hereinbefore described with reference to the accompanying drawings.
GB583177A 1978-01-26 1978-01-26 Measuring apparatus Expired GB1593282A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB583177A GB1593282A (en) 1978-01-26 1978-01-26 Measuring apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB583177A GB1593282A (en) 1978-01-26 1978-01-26 Measuring apparatus

Publications (1)

Publication Number Publication Date
GB1593282A true GB1593282A (en) 1981-07-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB583177A Expired GB1593282A (en) 1978-01-26 1978-01-26 Measuring apparatus

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2419949A (en) * 2004-11-02 2006-05-10 Trumeter Company Ltd Distance Measuring Apparatus
US10898397B2 (en) 2016-02-04 2021-01-26 Jeffrey Turitz System for measuring distances traveled by a mobility assistance device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2419949A (en) * 2004-11-02 2006-05-10 Trumeter Company Ltd Distance Measuring Apparatus
US10898397B2 (en) 2016-02-04 2021-01-26 Jeffrey Turitz System for measuring distances traveled by a mobility assistance device

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