GB2149093A

GB2149093A - Measuring dimensions

Info

Publication number: GB2149093A
Application number: GB08326703A
Authority: GB
Inventors: Percival Henry Edwar Parkinson
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-10-06
Filing date: 1983-10-06
Publication date: 1985-06-05
Also published as: GB8326703D0

Abstract

Apparatus for measuring a dimension of a member (10) comprising mounting means (12, 13) for mounting the member (10) in a predetermined position; at least one grating (20); at least one light source (14); at least one projecting means (15, 16) for projecting light from said light source or sources (14) onto the or each said grating (20) so as to produce thereon a magnified image (22) of a member (10) carried by said mounting means (12, 13); photo-electric means (26) movable along the grating (20) arranged to receive light which has passed through a portion of the or each grating (20) which is not obscured by the, or the respective, magnified image (22); and measuring means controlled by the output of said photo-electric means (26), for measuring said dimension. <IMAGE>

Description

SPECIFICATION Method and apparatus for measuring a dimension of a member This invention concerns a method and an apparatus for measuring a dimension of a member and, although the invention is not so restricted, it is more particularly concerned with a method and apparatus for measuring the diameter or width, or the average diameter or width, of a longitudinally moving yarn, thread or wire, e.g. a hot metallic wire.

Such a yarn, thread or wire may move during manufacture at speeds of up to 5,000 metres a minute and it is desirable to be able to measure its average diameter or width by means which do not contact the yarn, thread or wire.

Although, therefore, the invention is primarily directed to any novel integer or step, or combination of integers or steps, as herein disclosed and/or as shown in the accompanying drawings, nevertheless according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided apparatus for measuring a dimension of a member comprising mounting means for mounting the member in a predetermined position; at least one grating; at least one light source; at least one projecting means for projecting light from said light source or sources onto the or each said grating so as to produce thereon a magnified image of a member carried by said mounting means; photo-electric means arranged to receive light which has passed through a portion of the or each grating which is not obscured by the, or the respective, magnified image; and measuring means, controlled by the output of said photo-electric means, for measuring said dimension.

There may be a plurality of angularly spaced apart gratings and of angularly spaced apart projecting means.

Movement effecting means are preferably provided for moving the photo-electric means across the or each grating so as to scan the latter, the output of the photo-electric means varying between a maximum and a minimum value as it scans across the spaces and lines of the grating.

The movement effecting means may comprise means for reciprocating the photo-electric means across the or each grating. Alternatively, the movement effecting means may comprise means for rotating the photo-electric means around the or each grating.

The projecting means may comprise at least one objective lens for forming the said magnified image or images, and at least one condenser lens for directing light from the or each light source onto the or each objective lens.

There may be a respective condenser lens and objective lens associated with each grating, light-conducting means being provided for directing light from a single light source onto all the condenser lenses.

Adjusting means are preferably provided for adjusting the position of the mounting means so that the centre of the said member, irrespective of the size of the member, may be maintained at a substantially fixed distance from the grating or gratings.

The adjusting means may comprise a settable part which is provided with surfaces or carries or is associated with indicia indicative of the expected dimension of the said member; the settable part, when set at the expected dimension, causing the mounting means to be set at a distance from the grating or gratings such that the centre of a said member mounted in the mounting means which has the said expected dimension will be at the said substantially fixed distance.

The settable part may be a cam having a plurality of different cam surfaces.

Alternatively, there may be computerised means for adjusting the measured dimension to take account of any variation in the distance of the centre of the said member from the grating or gratings.

The measuring means may comprise means for determining the said maximum value, means for producing from the maximum value at least one reduced output, and counting means which counts the number of times that the instantaneous output from the photo-electric means equals the said maximum value or equals the or each reduced output.

The means for determining the said maximum value may comprise a reference photocell which is arranged to receive light from the or a light source. Alternatively, the means for determining the said maximum value may comprise a sample and hold amplifier connected to receive the output of the said photoelectric means.

Means are preferably provided for adjusting the measurement produced by the measuring means so as to compensate for variations in the tension of the said member and/or to compensate for ambient conditions.

The invention also comprises a method of measuring a dimension of a member comprising mounting the member in a predetermined position; projecting light from at least one light source onto at least one grating so as to project a magnified image of said member onto the or each grating; employing photoelectric means to receive light which has passed through a portion of the or each grating which is not obscured by the, or the respective, magnified image; and employing the output of said photo-electric means to measure said dimension.

A plurality of angularly spaced apart gratings may be employed onto which are respectively projected magnified images of the mem ber taken frcm different directions, the output of the photo-electric means being employed to measure the average diameter or width of the member.

The invention is illustrated, merely by way of example, in the accompanying drawings, in which: Figure 1 is a diagrammatic view of a first embodiment of an apparatus according to the present invention for measuring the diameter of the yarn, Figure 2 is a diagrammatic broken away view taken in the direction of the arrow 11 of Figure 1 and illustrating a projected image on a grating which forms part of the apparatus of Figure 1, Figures 3 and 4 are circuit diagrams, and Figure 5 is a diagrammatic view of a second embodiment of an apparatus according to the present invention for measuring the diameter of a yarn.

Terms such as "left" and "right", as used in the description below, are to be understood to refer to directions as seen in the accompanying drawings.

In Figure 1 there is shown a first embodiment of an apparatus according to the present invention for measuring the diameter of a yarn 10. The yarn 10 is caused to move longitudinally (by means not shown) in the direction of an arrow 11, the yarn 10 being mounted in a predetermined position by reason of passing over control guides 1 2 and passing through V-shaped notches of yarn guides 1 3.

Disposed on the left hand side of the yarn 10 is a light source 14 and a condenser lens 1 5. Disposed on the right hand side of the yarn 10 is a short focus objective lens 1 6 and a screen 1 7 provided with a grating 20, the screen 1 7 being disposed at a substantially greater distance from the short focus objective lens 1 6 than the distance between the latter and the yarn. The grating 20 is provided with a known number of grating lines or marks 21, the grating 20 having a constant mark-space ratio.

The condenser lens 1 5 focusses the light from the light source 14 onto the short focus objective lens 1 6 and, since the yarn 10 passes between the lenses 15, 1 6 and the distance from the yarn 10 to the short focus objective lens 1 6 is substantially less than the distance of the latter from the screen 17, the short focus objective lens 1 6 projects a magnified image 22 (Figure 2) of the yarn 10 onto the grating 20 so as to obscure a number of grating lines 21. Although it is convenient to arrange the grating scaling and the magnification of the system in a convenient known ratio to each other, this is not essential.Thus the system can be standardised by using a known diameter master or series of masters (e.g. standard diameter wires and in particular ones of similar size to that of the yarn to be measured) and then referring the yarn count to this standard.

Disposed on the right hand side of the screen 1 7 is a table 23 on which are mounted a slit member 24 having a measuring slit (not shown), a lens 25, and a scanning photocell 26. The width of the measuring slit is equal to or less than the width of a grating line 21.

The table 23 is connected to an electric motor 27 (or to a crank, not shown, or a cam, not shown) so that the slit member 24, lens 25 and scanning photocell 26 are longitudinally reciprocated completely across the grating 20 from one side thereof to the other Light from the light source 14 which passes through the portion of the grating 20 which is not obscured by the magnified image 22 is received by the scanning photocell 26 in the course of the scanning movement of the latter. Thus the total output of the scanning photocell 26, in the course of one scanning traverse of the grating 20, will be representative of the diameter of the yarn 10.As will be appreciated, the output of the scanning photocell 26 varies periodically between a maximum value, which occurs when a space between adjacent grating lines 21 is aligned with the said measuring slit, and a minimum value, which occurs when a grating line 21 is aligned with the said measuring slit.

The diameter of the yarn 10 could be determined merely by connecting the photocell 26 to means (not shown) which would count the number of changes in the output of the scanning photocell from its maximum to its minimum value and vice versa in the course of one scanning traverse of the grating 20. Thus the arrangement could be equivalent to counting the number of grating lines 21 left illuminated, subtracting these from the known number of grating lines 21 in the grating 20, and then correcting this count by allowing for the magnification produced by the lens 1 6 and the grating line width, together with the tension in the yarn.

Preferably, however, use is made of a reference photocell 30 whose construction and sensitivity etc is the same as that of the scanning photocell 26 but which is arranged to receive light from the light source 14 by way of a slit member 29 (whose slit is the same size as that of the slit member 24) and a lens 31 whose light absorption properties are so related to those of the lenses 15, 16, 25 that the reference photocell 30 will at all times produce a reference output which is the same as the said maximum output of the scanning photocell 26. As shown in Figure 3, the reference photocell 30 is connected by way of an amplifier 32 to a resistor chain 33 which comprises any desired number of equal resistances, e.g. three equal resistances 34, 35, 36 as shown so as to produce at a comparator 37 outputs V1, V2, V3 and V4 which correspond respectively to the maximum output of the scanning photocell 26, 2/3rds of said maximum output, 1/3rd of said maximum output, and the minimum output of the scanning photocell 26. Although the resistances 34, 35, 36 are referred to above as being equal resistances, this is not essential since the resistances could have any desired relative values. It is convenient, however, to choose resistances whose values are appropriate in relation to the waveform of the output from the photocell 26.

The comparator 37 is also connected to the scanning photocell 26 by way of an amplifier 40. The arrangement is such that, whenever the instantaneous voltage V5 which is transmitted by the scanning photocell 26 is equal to one of the voltages V1, V2, V3, V4, the comparator 37 transmits an output to a counter 41 whose count constitutes a measurement of the diameter of the yarn 10. The counter 41 may, as shown be connected by way of adjustment means 39 to a display 42 which indicates the value of the diameter of the yarn 10, or it may be connected to a control (not shown) or an alarm (not shown) which stops or otherwise controls the production of the yarn 10, or gives warning of a malfunction, if the measured value of the diameter is outside a given tolerance range.

The adjustment means 39 adjust the measurement produced by the counter 41 so as to compensate for variations in the tension in the yarn and/or to compensate for ambient conditions such as temperature and humidity.

In the embodiment of Figure 3, since a count is obtained whenever the output of the scanning photocell 26 equals any of the four voltages V1, V2, V3, V4, this enables the accuracy of the measurement of the diameter to be twice as good as would be obtained by merely producing a count whenever the scanning photocell 26 produced its maximum or minimum output.

In Figure 4 there is shown an arrangement which is generally similar to that of Figure 3 and which, for this reason, will not be described in detail, like reference numerals indicating like parts. In the Figure 4 arrangement, however, the reference photocell 30 is omitted and is replaced by a sample and hold amplifier 43 which is connected to receive the output from the amplifier 40 so that the output from the sample and hold amplifier 43 always corresponds to the previous maximum output of the scanning photocell 26.

In Figure 5 there is shown a second embodiment of an apparatus according to the present invention for measuring the diameter of a yarn. The embodiment of Figure 5 is generally similar to that of Figures 1-4 and for this reason will not be described in detail, like reference numerals indicating like parts.

In the embodiment of Figure 5, however, the yarn 10, which is located in V-grooves 43 of the yarn guides 1 3 (only one shown), is disposed at the centre of a cylinder 44 and passes axially through the latter, the yarn 10 having been introduced into the cylinder 44 through a radially extending yarn entrance slot 45. The cylinder 44 is provided with two angularly spaced apart gratings 20, the cylinder 44 being transparent or being apertured in the regions of the gratings 20 so that light may pass through the latter.

A light source 14 directs light onto an arcuate light pipe, or other light-conducting member, 46 having radial arms 50, 51, 52.

Light from the arms 50, 51 is directed through angularly spaced apart condenser lenses 1 5 and objective lenses 1 6 onto the respective gratings 20 so that a magnified image of the yarn 10 taken from different directions will be projected onto the respective gratings 20. Thus the arrangement is such that light from a single light source 14 is directed onto both the condenser lenses 1 5.

Mounted concentrically with the cylinder 44 is a rotatable arm 53 which carries at least one slit member 24, scanning photocell 26 and amplifier (not shown) corresponding to the amplifier 40. The output from this amplifier 40 may be fed out via slip rings or an inductive rotary coupler (not shown). Means (not shown) are provided for rotating the arm 53 around the cylinder 44 and thus around the angularly spaced apart gratings 20 so that the scanning photocell 26 may scan both the gratings 20 during the rotation of the arm 53.

If the cylinder 44 is transparent, means (not shown) are provided for shielding the scanning photocell 26 from any light from the light source 14 other than light which passes through the gratings 20. The output of the scanning photocell 26 is thus representative of the average diameter of the yarn 10, whereby to reduce any error in determining the diameter of a yarn which is not perfectly round.

In the Figure 5 construction, a reference photocell 30 receives light from the radial arm 52 by way of a respective slit member 29 and lens 31. The reference photocell 30 and the scanning photocell 26 are arranged in a circuit corresponding to that shown in Figure 3, or the reference photocell 30 is replaced by a sample and hold amplifier 43 by employing the circuit shown in Figure 4.

Air jets 54 are employed to keep the yarn guides 1 3 and the gratings 20 free from dust or debris.

The rate of reciprocating movement of the scanning photocell 26 in the Figure 1 embodiment or rotary movement thereof in the Figure 5 embodiment can be related to the rate at which it is necessary to determine the diameter of the yarn 10, but in practice the faster the scan rate the better up to the safe response time of the photocell 26 and of the electronics employed.

The degree of magnification of the image 22 depends upon the position of the yarn 10 with respect to the gratings 20 and will therefore normally vary with the diameter of the yarn 10. In operation, the yarn 10 is urged towards the bottom of the V-grooves 43 so that if the yarn guides 1 3 remain still, as the diameter of the yarn 10 reduces, the distance of the centre of the yarn 10 from the respective grating 20 increases, and as the said diameter increases its said distance reduces.

Consequently if the diameter of the yarn 10 is to be measured accurately it is necessary to provide means for adjusting the positions of the yarn guides 1 3 so that the centre of the yarn 10, irrespective of the size or denier of the yarn, is maintained at a substantially fixed distance from the gratings 20. In the embodiment illustrated in Figure 5 this is achieved by mounting each yarn guide 1 3 on a rod 55 which passes freely through fixed structure 56, the rod 55 being urged radially outwardly by a spring 57. The radially outer end of the rod 55 engages a disc-shaped cam 60 which is mounted on a cam indexing shaft 61. The cam 60 is provided with a plurality of flats or other surfaces (not shown) which respectively correspond to the expected diameter of denier of the yarn 10.Thus the cam indexing shaft 61 may, for example, have a graduated knob (not shown) whose graduations indicate various diameters or deniers of the yarn, the graduated knob being manually turnable to bring a particular graduation into alignment with a fixed index mark (not shown). Thus when the graduated knob, and consequently the cam 60, is set at an expected dimension of the yarn 10, this will cause the yarn guides 1 3 to be set at a distance from the gratings 20 such that the centre of the yarn 10 which has the said expected dimension and which is mounted in the yarn guides 1 3 will be set at a substantially fixed distance from the gratings 20.

Alternatively, instead of moving the yarn guides 1 3, the count produced by the counter 41 may be adjusted by an appropriately programmed computer or calculator circuitry (not shown) in relation to the actual measured diameter so as to produce the true diameter.

The computer or calculator circuitry may also be so programmed as to produce the mean diameter of a yarn or other member whose diameter varies lengthwise, and may be so programmed as to compensate for diameter variations due to changes in temperature, tension, humidity etc.

As will be appreciated, for those materials where the cross-sectional shape is likely to be of a regular diameter, apparatus for effecting a single measurement of the material, as in the apparatus illustrated in Figure 1, is satisfactory. However in the case of a textile yarn or thread it is desirable to take multiple diagonal readings and to average these to arrive at the mean diameter, as is achieved by the apparatus of Figure 5. It will be noted that the apparatus of Figure 5 achieves such multiple diagonal readings with the minimum of parts, whereby to reduce cost and increase reliability.

Claims

1. Apparatus for measuring a dimension of a member comprising mounting means for mounting the member in a predetermined position; at least one grating; at least one light source; at least one projecting means for projecting light from said light source or sources onto the or each said grating so as to produce thereon a magnified image of a member carried by said mounting means; photoelectric means arranged to receive light which has passed through a portion of the or each grating which is not obscured by the, or the respective, magnified image; and measuring means, controlled by the output of said photoelectric means, for measuring said dimension.

2. Apparatus as claimed in claim 1 in which there are a plurality of angularly spaced apart gratings and of angularly spaced apart projecting means.

3. Apparatus as claimed in claim 1 or 2 comprising movement effecting means for moving the photo-electric means across the or each grating so as to scan the latter, the output of the photo-electric means varying between a maximum and a minimum value as it scans across the spaces and lines of the grating.

4. Apparatus as claimed in claim 3 in which the movement effecting means comprises means for reciprocating the photo-electric means across the or each grating.

5. Apparatus as claimed in claim 3 in which the movement effecting means comprises means for rotating the photo-electric means around the or each grating.

6. Apparatus as claimed in any preceding claim in which the projecting means comprises at least one objective lens for forming the said magnified image or images, and at least one condenser lens for directing light from the or each light source onto the or each objective lens.

7. Apparatus as claimed in claim 2 and in claim 6 in which there is a respective condenser lens and objective lens associated with each grating, light-conducting means being provided for directing light from a single light source onto all the condenser lenses.

8. Apparatus as claimed in any preceding claim comprising adjusting means for adjusting the position of the mounting means so that the centre of the said member, irrespective of the size of the member, may be maintained at a substantially fixed distance from the grating or gratings.

9. Apparatus as claimed in claim 8 in which the adjusting means comprises a settable part which is provided with surfaces or carries or is associated with indicia indicative of the ex pected dimension of the said member; the settable part, when set at the expected dimension, causing the mounting means to be set at a distance from the grating or gratings such that the centre of a said member mounted in the mounting means which has the said expected dimension will be at the said substantially fixed distance.

10. Apparatus as claimed in claim 9 in which the settable part is a cam having a plurality of different cam surfaces.

11. Apparatus as claimed in any of claims 1 to 7 comprising computerised means for adjusting the measured dimension to take account of any variation in the distance of the centre of the said member from the grating or gratings.

1 2. Apparatus as claimed in claim 3 or in any claim dependent thereon in which the measuring means comprises means for determining the said maximum value, means for producing from the said maximum value at least one reduced output, and counting means which counts the number of times that the instantaneous output from the photo-electric means equals the said maximum value or equals the or each reduced output.

13. Apparatus as claimed in claim 12 in which the means for determining the said maximum value comprises a reference photocell which is arranged to receive light from the or a light source.

14. Apparatus as claimed in claim 12 in which the means for determining the said maximum value comprises a sample and hold amplifier connected to receive the output of the said photo-electric means.

1 5. Apparatus as claimed in any preceding claim in which means are provided for adjusting the measurement produced by the measuring means so as to compensate for variations in the tension of the said member and/or to compensate for ambient conditions.

1 6. Apparatus for measuring a dimension of a member substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 7. A method of measuring a dimension of a member comprising mounting the member in a predetermined position; projecting light from at least one light source onto at least one grating so as to project a magnified image of said member onto the or each grating; employing photo-electric means to receive light which has passed through a portion of the or each grating which is not obscured by the, or the respective, magnified image; and employing the output of said photo-electric means to measure said dimension.

1 8. A method as claimed in claim 1 7 in which the member is a longitudinally moving member whose diameter or width, or average diameter or width, is to be measured.

19. A method as claimed in claim 18 in which the member is a yarn, thread, or wire.

20. A method as claimed in any of claims 1 7 to 1 9 in which a plurality of angularly spaced apart gratings are employed onto which are respectively projected magnified images of the member taken from different directions, the output of the photo-electric means being employed to measure the average diameter or width of the member.

21. A method of measuring a dimension of a member substantially as hereinbefore described with reference to the accompanying drawings.

22. Any novel integer or step, or combination of integers or steps, hereinbefore described and/or as shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.