GB2052747A - Improvements in or relating to measuring apparatus - Google Patents

Abstract

There is described a measuring apparatus for providing a set of cartesian co-ordinates defining the shape of an article such as a shoe. A table 42 with an aperture 41 for a carrier for the article 10 has two holes to receive a pivot pin for each of three arms 43, 44, 45, enabling each arm to be pivoted at 47 about either of its ends, and each arm carries a rod 48 mounting a contact element 49 which is laterally movable relative to the arm in a direction normal to the lengthwise dimension of the arm. Displacements of the contact elements, which are used to touch points on the surface of the articles, are transmitted to a computer capable of defining any position of any one of the contact elements in cartesian co-ordinates relative to a common origin. The carrier is guided for movement normal to the plane of the table and parallel to the X axis, and the Y and Z co- ordinates are measured in the plane of the table. From these co-ordinates, duly recorded, a screen image of the article can be derived. <IMAGE>

Description

SPECIFICATION Improvements in or relating to measuring apparatus This invention relates to measuring apparatus and has a particularly useful but by no means exclusive application in an apparatus for measuring and recording co-ordinates defining the three-dimensional shape of a last.

According to this invention there is provided measuring apparatus comprising a base providing a plurality of pivot mountings for one or more measuring heads, the respective pivot axes provided by said mountings being parallel, the or each measuring head comprising an arm mounted for swinging movement about one of said pivot mountings, a probe mounted on the arm for guided movement relative to the arm in a direction at right angles to the lengthwise dimension of the arm, a workpiece carrier mounted for rectilinear movement along a fixed path passing between the pivot mountings in a direction parallel to the pivot axes provided by the pivot mountings, means for measuring displacement of the carrier from a fixed datum thereby to provide one cartesian coordinate and for measuring angular displacement of the arm about its pivot with respect two a datum direction, and the displacement of the probe in said direction at right angles to the lengthwise dimension of the arm with respect to a datum position, and means for processing the two lastmentioned displacements for obtaining the two other cartesian co-ordinates of any point on the surface of the workpiece touched by the probe.

In a preferred embodiment of the invention, an alternative pivot point is provided for the arm or each arm enabling the arm to pivot about either end selectively, and the processing means is capable of converting the values to provide the coordinates based on the common origin.

One embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 shows a shoe-making last in side elevation and illustrates the determination of a datum point for measurement of XYZ coordinates; Figure 2 shows the last in cross-section on the plane 2-2 of Figure 1; Figure 3 shows the last mounted on a subbase; Figure 4 illustrates how the position of the centre-line of the last is determined; Figure 5 shows a scriber frame for marking the last centre-line on the last, and Figure 6 shows a plan view of a measuring apparatus according to the invention.

in order to provide an acceptable record of a series of sets of cartesian co-ordinates defining the three-dimensional shape of a shoe-makers last 10. a series of parallel vertical planes are firstly envisaged extending at right angles to the centre line of the last. The designer of the last marks a heel/ball point 11 on the last and the point where a vertical plane 12 containing the heel/ball point intersects a vertical plane containing the centreline at the bottom face 13 of the last constitutes a datum from which co-ordinates XYZ are measured, for example in millimetres. Thus the vertical planes shown in Figure 1 represent X coordinates forward and rearward of the zero section 12 containing the heel/ball point. The drawings shows the last in its predetermined attitude, corresponding to a womans shoe having a heel of medium height.

Figure 2 shows a cross-sectional view of the last at the X co-ordinate of -60, i.e. 60 mm behind the heel/ball point, and indicates that for present purposes the vertical height of the last at each of the X section planes is divided to provide seven equal increments of the Y co-ordinate. The 7 co-ordinates are measured to the left and right of the centre line 14 shown in Figure 2.

Referring now to Figures 3 and 4, in order to determine and mark the longitudinal centre-line of the last, the last is mounted in its correct pitch attitude on a sub-based 1 7 which is in turn mounted adjustably on a slide 1 8 to permit the last to be swung about either end to adjust the position of the last and sub-base relative to the slide. The assembly of the last, sub-base and slide is mounted on a setting table 1 9 shown in Figure 4, the slide being engaged in a slot in the table so that the point of contact of the last with the subbase is in the plane of the table The slide is firmly secured to the table and a card is then secured to extend over the surface of the table.Two tangents 20, 21 are then drawn as shown in Figure 4 touching the two convex curves of the outline of the last 10 projected on to the card. Where the two tangents meet behind the last is the centre 24 for two arcs 25 of equal radius marked on the two tangents respectively forward of the last and the two points thus defined are the centres of two further arcs 26 of equal radius, and a line 27 is drawn between the intersection of these two arcs and the centre 24 behind the last. This line 27 is a projection of the centre-line of the last on the card and is of course the bi-sector of the angle between two tangent lines 21. This line is equivalent to the focal angle bisector used in anatomical measurement. To transfer the centre line to the last, a scribing frame and scriber as shown in Figure 5 is employed.The scribing frame has a main frame 30 mounted on two feet 31 interconnected by a cross-member 32 and has a large aperture 33 enabling it to extend from front to rear over the largest last. A sub-frame 34 is placed against one side of the main frame is slotted to extend over the particular last being dealt with. The feet 31 of the frame project a distance d, beyond the surface of the sub-frame 24. The scriber 35 is mounted in a small slide block 36 and the tip of the scriber is offset by a distance d, from the plane of each side face 37 of the slide block. Thus when the front edge 38 of the feet are set to the centre line 27 on the card and the slide block is slid over the surface of the sub-frame 34 the tip of the scriber is precisely located over the centre-line.The scribing frame and scriber is now used in conjunction with the centre line marked on the card to scribe a centre line on the last and particularly under the toe and heel of the last. Using adjusting slots and set screws on the sub-base these marks are brought into alignment with fixed setting marks on the slide, after the sub-base and last assembly has been removed from the table.

The assembly is now secured to a vertical slide mechanism (not shown) using a locating bush 40 at the rear edge of the slide, the toe end of the last projecting upward. Referring now to Figure 6, the toe end of the last projects upward through an aperture 41 in a measuring table 42, the slide mechanism being disposed under the table.

Mounted on the table 42 and disposed about the last are three measuring heads 43, 44, 45, each comprising an arm 46 having a vertical pivot busg 47 at each end, and a rod 48 mounted for sliding movement lengthwise of itself in the arm and carrying a probe 49 at its end. Each arm is pivotally mounted on the table by a dowel engaged in one of the bushes 47 in the arm and secured in a hole in the table 42. A second hole is provided in the table for each arm for the pivotal mounting of the arm by its other end, for a reason which will be explained presently.

The vertical movement of the last is measured by the vertical slide mechanism, and the mechanism is operated to bring each of the planes indicated in Figure 1 in succession into the plane of movement of the probes and to hold it there whilst a series of measurements are taken by means of the heads 43, 44, 45. The probes have associated with them a microprocessor 50 for converting the swinging movements of the arms 46 and the lengthwise movements of the rods and probes relative to the arm into YZ cartesian coordinates. The microprocessor also enables the same conversion to be made by whichever end of the arm is pivoted, provided that the appropriate program is put into effect.The correct alignment of the heads 43, 44, 45 is first checked by manipulating each probe 49 in turn to place it at two predetermined marked positions 52 on the table and zeroing the microprocessor so that the positional interrelationship of the probes is correct. This having been done, one of the probes, say the probe of head 43, is placed in contact with the top and bottom of the last at the centre line, and the microprocessor is arranged to divide the resulting distance in the Y direction into 7 equal increments. The probe is then moved round the last from one to the other of these two positions at the top and bottom of the last, and the microprocessor records the Z co-ordinate and the corresponding Y co-ordinate at each of the 7 increments of the Y co-ordinate.The head 44 is now used in the same way, with the same incremental values of Y. The heads 43, 44 thus deal with the upper parts of the last on opposite sides of the centre-line respectively. Head 46 measures the co-ordinates of the bottom of the last. It will be clear that in the toe region of the last the movements of the probes of heads 43 and 44 in the vicinity of the centre-line in the Z direction are large in relation to those in the Y direction, and for measuring the co-ordinates in these regions the arms 46 are arranged to pivot about their other ends as indicated in broken lines in respect of the arm of head 43, so as to increase the accuracy of measurement. The procedure is repeated with the third head 45, the appropriate instruction being fed into the microprocessor at each change of head, or arm pivot.When the full set of YZ co-ordinates for the first X co-ordinate has been recorded, the slide mechanism is operated to raise the next X plane into alignment with the probes, and the measuring process is repeated. The slide mechanism may be motoroperated and may be automatically actuated to move into the next vertical position after the final measurement in one vertical position. At the conclusion of operations, the microprocessor has produced a record of a complete set of cartesian co-ordinates defining the three-dimensional shape of the last, and the record enables a representation of the last to be shown on a screen.

The microprocessor is conveniently programmed to enable the representation to be rotated to provide an image equivalent to looking at the last from different viewpoints. Associated apparatus may permit a designer to draw a shoe and for the image of the shoe simultaneously to appear superimposed on the image of the last on the screen, so that in effect the designer draws on the screen. Further apparatus may enable a printed copy of the image on the screen to be obtained.

in one modified construction, the vertical movement of the last is detected by a probe similar to those used in measuring the last and a corresponding co-ordinate can be recorded on the tape and, if desired indicated on a visual display unit.

The last support may be mounted for rotational movement about a vertical axis in the aperture as well as for vertical movement, and a single probe and arm as described above and as illustrated in Figure 6 is employed to touch the points on the last surface whose co-ordinates are required. The microprocessor will in this instance provide the cartesian co-ordinates from the angular displacement of the last about its vertical axis relative to a datum angular position.

In an important modification of the apparatus the division of the vertical height of the last at any section is obtained optically. A plate has alternate transparent and opaque bands, say seven bands, all of equal width. Using a projector, an image of these bands is projected on to the last and the total width of the bands is adjusted to the correct magnification, by adjustment of the projector, to cover the height of the last (i.e. in the Y direction): The required positions at which the measurements are to be taken, at the section are now visible. The disadvantage of using a transparent plate with parallel lines is avoided in that there are no lines whose thickness is magnified. The measuring position is art the line of division between a light band and a dark band, and a probe may be used incorporating a light sensitive device which automatically actuates a measuring operation each time the probe traverses one of the lines of division, so that the operator has then only to traverse the probe around the last.

Claims (8)

1. Measuring apparatus comprising a base providing a plurality of pivot mountings for one or more measuring heads, the respective pivot axes provided by said mountings being parallel, the or each measuring head comprising an arm mounted for swinging movement about one of said pivot mountings, a probe mounted on the arm for guided movement relative to the arm in a direction at right angles to the lengthwise dimension of the arm, a workpiece carrier mounted for rectilinear movement along a fixed path passing between the pivot mountings in a direction parallel to the pivot axes provided by the pivot mountings, means for measuring displacement of the carrier from a fixed datum thereby to provide one cartesian coordinate and for measuring angular displacement of the arm about its pivot with respect to a datum direction, and the displacement of the probe in said direction at right angles to the lengthwise dimension of the arm with respect to a datum position, and means for processing the two lastmentioned displacements for obtaining the two other cartesian co-ordinates of any point on the surface of the workpiece touched by the probe.

2. Measuring apparatus as claimed in claim 1, wherein an alternative pivot point is provided for the arm or each arm enabling the arm to pivot about either end selectively, and the processing means is capable of converting the values to provide the co-ordinates based on the common origin.

3. Measuring apparatus as claimed in claim 1 or claim 2 further comprising means for recording the said co-ordinates of a series of predetermined points on the surface of a workpiece.

4. Measuring apparatus as claimed in claim 3, wherein the probe is equipped with a triggering device for automatically actuating a measuring operation at some at least of said predetermined points and recording of the co-ordinates of said points.

5. Measuring apparatus as claimed in claim 4 wherein said triggering device actuates a measuring and recording operation in response to a change in infra-red radiation falling on a sensor attached to the probe.

6. Measuring apparatus as claimed in any one of the preceding claims, wherein motor means is provided for moving the workpiece carrier along said fixed path.

7. Measuring apparatus as claimed in any one of the preceding claims, wherein said means for measuring the displacement of the carrier comprises a probe for engaging an end of the article which probe is coupled to the processing means.

8. Measuring apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 3 and 6 of the accompanying drawings.