CA1160748A - Method and apparatus for the design and manufacture of footwear - Google Patents

Abstract

ABSTRACT.

METHOD AND APPARATUS FOR THE DESIGN
AND MANUFACTURE OF FOOTWEAR

A method of deriving patterns for shoe manufacture, whereby leather pieces can be cut in accordance with the derived patterns for making the shoes. The method consists in using a computer to operate on three-dimensional co-ordinate information concerning (a) the shape of the shoe last and (b) the shape of style lines to produce three-dimensional co-ordinate information which is subjected to a grading program. The grading program produces three-dimensional co-ordinate information for different sizes which may be displayed in three-dimensional form and possibly modified. The individual graded co-ordinate information for each size is subjected to a flattening program to produce respective patterns.

Description

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METElO~ ~ND APPARATIJS FOR THE DESIGN
t-~ND ~NUFACT'JRE OF FOOrWEhR
The invention relates to a method and apparatus for the design and manufacture of ootwear. It will be helpful firstly to describe briefly a design procedure for a sho~, in which definitions for various terms will be given.
Firstly, a MODEL LAST is produced, which is a solid last of a particular shoe size, the exterior shape of which forms the interior shape of the shoe A DRAPE is formed on the model last, being a plastics skin tightly conforming to the shape of the last. The stylist draws STYLE LINES on the drape, which are lines defining the top line of the shoe and other lines such as where separate pieces of leather will join or where there is a line of stitching, for example. D~SIGN SHAPES such as bows, diamond shapes etc., may be added. The shoe dra~n on the drape has certain LAST PARAMETERS. These are dimensions or MEAS~RES, such as heel height; length of shoe;
curvilinear distance between defined pairs of points;
and cross-sectional areas of defined curves such as those defining the throat and waist of the shoe9 for example.
Next, the drape is cut from the model last and flattened between rollers. The flattened drape gives the shape of the NETI LASI PATTERN and this, when carrying the correspondingly shaped PATTERN LINES, whlch are the flattened style lines, is the NET~
PATTERN.

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In order to be able to cut pieces of leather which may be stitched together to form the shoe upper it is necessary to add overlap margins to the nett pattern shapes and this gives the GROSS PATTERN.
From the gross pattern cutting knives are formed to cut the required leather shapes. The stitched leather shapes are pulled on a LAST, which is a copy of the model last, to assume the required form and are ~ixed to the snoe sole or UNIT.
In order to make shoes of the same style in other sizes, GRADING is necessary. Thus, lasts are copies from the model last on a-last-making marhine ; which alters dimensions differentially in a pre-determired manner so that a desired non proportional scaling is achieved. A grading is necessary al~o on the nett pattern shapes. This is carried out by scaling the flat nett pattern shapes in a predetermined manner and adding the overlap margins. Different sets of cutting knives are thus made from the different gross patterns for the different sizes.
The mechanical flattening procedure described above has certain disadvantages and it has been proposed in British patent specification No. 1375822 to use a com~
outer program to derlve the nett pattern from th~ model last. British patent specification No. 1414298 describes an improved method of deriving the nett pattern, a~ain preferably using a comput~r. In these systems it is necessary to feed information to the computer tlhich defines the shape o the model last.
Such info~nation can be derived from a probe t~hich is 074F~

placed in turn on selected points on the last and which gives the three~dimenslonal x,y7z co-ordinates of those points in digitized form. The selected points lie on ~RINCIPAL LINES, which are defined as ]ines on the last surface ~hich join the digitized points.
These lines may be, for example, cross-sectional lines equally spaced along the last, OL' conventional reference lines such as the heel curve, the cone centre line and inner and outer feather lines.
Existing design procedures have disn-lvantages.
In particular, the problem of grading a design for different shoe sizes presents difficulties. A particuiar style can loo~ well in one size and yet be very unsatisfactory .n another. With current practice it is difficult to assess the effect of grading a design without making several prototypes in different sizes.
Furthermore, the existing practice of grading the nett patterns gives rise to discrepancies as size changes and it is found that further unpredicted modifications must be made to make the stitched uppers fit the graded lasts.
The present invention seeks to alleviate these difficulties.
According to one aspect of the invention there is provided a method of producing a pattern for a shoe comprising: applying as input to a computer (a) information defining the three~dimensional shape of a model last and (b) information defining the three-dimensional shape of style lines on the model last;
operating on the shape information (a) and (~) with a grading program to derive correspondin~ Iast and style line three-dimensionalshape lnformation ~c) for at ., .
least one ot~ler sho-e size; and operating on the information (c) for the said ot~er shoe size ~ith a flattening program to derive a ~espective shoe pattern.
~ith this arrangement, grading is performed on the three-dimensional information of both the last and the style lines, ~nd not merely on the two-dimensional nett pattern as before. This grading "in the round" aids better fitting and appearance and, furthermore, enables the effect of grading of a style to be examined and perhaps modified for different sizes without recourse to making graded lasts or shoes.
Preferably the shape information (a), (b) ' or (c) is capable of being modified before the operation of the grading or flattening program respectively by manual interactive use of a grapllical input device to the computer, in conjunction with a display of the shape information to be modified.
~ Preferably, for ~he purposes of modification, the three-dimensional information (a), (b) or ~c~ is subjected to a flattening program and the flattened nett pattern Ls displayed, the input device interacting with the display so that manually applied modifications are subjected to the inverse of the flattening program, thereby producing a three-dimensional modification.
The display device may be a storage cathode-ray tube which displays the model last in the form of skeletal lines. Alternatively, and prefera~ly in ~ddition~ the disp~y device comprises a television display sho~ing the model last in full perspective, preferably in colour.
~ en a storage tub~ is used there may be associated with it a writing tablet having cross-wires or a pen mova~le across it. The pen or cross-wire arrangement constitutes the input device andmay be used to modify the display. A required style line may be selectively p~esented at the tablet for modification and this is re-drat~ by appropriate manipulation. In addition to the perspective display there may be provided a representation (displayed or printed) of the nett pattern corresponding to the displayed model last and style lines. The required modifications can be made with reference to the nett pattern while observing the effect on the perspective view. Thus it will be appreciated that there is pro--vided an immediate visual representation of sketched modifications not only of style lines but also of principal lines of the model last.
When a television display is used, modifications may be made by means of a light pen interacting with the screen of the display. However, unlike the situation when the re-drawing is being carried out in the flat on a representation of the nett pattern, in this case distinction must be made between the front and the back of the displayed perspective. Thus, it is proposed to change the perspective view displayed by the television so as to present the line being modified on the near side. This may be done by manual or automatic selection of one of a number of stored perspective views.

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Tlle modification procedure outlined above allows changes to be made freely in the model last shape and the style lines. However, if unrestricted changes were allowed, many of the shoes produced would be unt~earable~ There are certain constricti.ons ; on the choices available for many oE the last para-meters. Thus, in accordance with another aspect of the invention there is provided a method of designing a piece of footwear consisting in applying as input to a computer (a) information defining the shape of . the model last and (~) information defining the shape of s,tyle lines on the model last; providing means for manual modification of lines of the model last or ~tyle li.nes; programming the computer to derive from the last shape so modified certain pre-i determined last parameters and.provide an output thereof; and comparing the said output with acceptable range limits for the parameters. In this way design modifications can be kept within the required limits 20 , for shoe comfort.
Preferably the flattening program is basedon the triangulation program described in patent specification No. 1414298. The information necessary to define the last shape and style line shape~ is preferably derived from a digitizing probe arrangement, the probe being placed in turn on selected points on the principal lines. A splining or fairing program ~s necessary to produce the best smooth curve joining the points and this program is preferably th,~t knot~n as 'i'4~

Polysurf, which defines the points in terms of a co-ordinate and two tangents and which constructs the intervening curves from syn-thesised cubic curve components. In this way the required surfaoes and curved lines are smoothly and continuously defined. "Polysurf"*
is described in pages 150 to 158 of CAD 76 Proceed mgs of the CAD
Centre, Cambridge.
In the flattening program each selected point on the last surface will have a corresponding point in the net pattern. Thus, in drawing modified lines on the net pattern a reverse corelation is established whereby the modified lines can be produced for display in perspective.
In practice the raw last data is read in from paper-tape and used to produoe a Polysurf model of the last. The simplest way to do this is to use the Polysurf splining algorithm to generate curves between the node points and then to use the Polysurf fitting algorithm to fit the additional points.
The raw style-line data can be converted into a 'last-independentl style-line by translating the digitized x, y, z data into parameterised data (u, v). A style line drawn on one last could then rapidly be displayed on another similar last. Whether the style line is held as x, y, z or u, v co-ordinates it is neces-sary to interpolate between these co-ordinates. If linear inter-polation is used the style-line may be unacoeptably polygonal. me alternative is to use a curve fitting algorithm. If the Polysurf splining algorithm is used the style line could be *Trade Mark - 7 -~... p, ,.~

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stored as a series of smooth cubic curves. The style line data would then be a series of points each with its associated tangent. This could be done in u, v or x, y, z space.
The invention will further be described with reference to the accompanying drawings, of which :
Figure 1 is an elevation of a model last with style lines;
Figure 2 is a block diagram of a system embodying the present invention for the design of shoes;
Figure 3 is a schematic diagram illustrating a grading process in accordance with the invention;
and Figure 4 is a schematic d 3gram illustrating a modific&tion of the process described with reference to Figure 3.
Referring to Figure 1 there is shown a model last 1 wlth style lines 2 drawn on it. A number of measures, or last parameters are shown, these being used in a manner to be described to place restrictions on the allowable design variations.
Figure 2 shows a system whereby the design methods of the present invention may be put into effect.
A model last digitizer 3 is used to take co ordinate measurements in digital form of points on the model last around parallel section lines. The information is stored on paper tape and applied to a computer 4. In another measuring operation~ after a stylist has dra~ the style line, points on these lines are digitized by a style line digitizer 5 and applied via paper tape to .. ., ~i~iO7~F~

the ccmputer 4. me input data is acted on by a Polysurf program unit 6 to p mduoe a Polysurf m~del of the last. A Polysurf model consists of a rectangular mesh of nodes where each node is repre-sented by 3 vectors; a point and two directions. Between each pair of adjacent nodes, a c~bic curve is faired with its end points and end directions determined by the node values. Between each group of four nodes a bic~bic patch is faired.
rrhe output frcm unit 6 is applied to a store 7 and thenoe to a (Tektronix)* storage tube display 8, which shows a perspective skeletal line view of the last. The output from store 7 is applied also to a flattening program unit 9. rrhe flattening program acoepts data as a series of cross-sections, each section defined by a string of co-ordinates. These need to be about 30-50 sections and about 30 -50 points per section. me Poly Æ f last will hold 11 sections with 13 nodes per section (6 on each faoe and 1 on the bcttcm). me intermediate sections and points will need to be derived.
The flattening program will then 'triangulate' the mesh of points so that between every pair of a~jaoent sections there is a strip of surfaoe composed of a string of triangles. m e flattening prooe ss then consists of locating one end of each string (Qn the cone oe ntre line) and flattening them.
rrhe outer edge of the end triangle of each strip will be located Qn a reference line. If springing has been selected, this reference line will be the straight cone oentre line. Each strip will then *rrrade Mark ~ 9 ~

~ ~0 7 4 8 be independently flattened by hinging the triangles along their cornmon edges so that they ~]1 lie in a single plane. (The plane containing the re~erence line).
The result of this procedure is therefore a set of flattened strips all having one end fixed to the reference line. The strips will normally overlap one another and/or have gaps between them (except where they all connect to the reference line).
To produce the Polysurf flattened last, all that is necessary is to find from amongst the flattened triangles those points which correspond with the Polysurf mesh. These node points will be splined to produce the Polysurf 1attened last. The output from unit 9 fed to a plotter 10 and t~e plotted output i9 applied to a writing tablet 11 for modification purposes.
By drawing with a pen over the writing tablet, using the plotted nett pattern as a guide, information concerning required modifications to the displayed shape is fed back to the Polysurf unit 6. These modifications are put into effect by the program and the changes are displayed and stored. A full colour perspective view of the modified last is obtained on a colour television screen 12. When the final design has been achieved this is passed to a library store 13 and a print out via plotter 10 is given to provide the final nett pattern. A gross pattern program (not sho~n) may be applied to add stitching margins and provide the final pattern for the cutting knivesO

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Alternatively the leather pieces may be cut by a numerically controlied cutter responsive to the output from unit 9. Also, the m~nufacturing last can be made by a numerically controlled machine 1~ responsive to the output from the store 7.
The library may ultimately provide all necessary basic last shapes in categorical form so that by calling up a desired basis shape and modifying it as described there will be no need for a physical model last. The library 13 also includes design shapes wnich may be added to the last and manipulated in place by manual adjustment of display controls.
In order to provide graded sizes a grading -program unit 15 is provided. This acts on the model last shape information in a predetermined manner to produce in the store 7 different data corresponding to last shapes of different sizes. There are flattened individually by the flattening program unit 9 to produce plotted nett or gross patterns.
In order to restrict the design variations to limits tolerated by the allowable last parameter ~ariations a measure program unit 16 is pro~-ided.
This is programmed to take the measures indicated in Figure 1 from the data in the store and to print out the parameters by a printer 17. It can then be detennined whether the modified or graded last is acceptable.
It is envisaged that a modification program will be included which will allow corelated changes to be made in the last by specifying a dimensional change in a last parameter - e.g. ~" add to heel height Once las~s have been modified (designed) usin~ the computer procedures described in earlier sections lt will be necessary to manufacture a model last both for further evaluation and ultimately for production use.
! One method of producing the new model last is to use a numerically controlled cuttin~ machine.
An alternative method -~hich s described below is to assemble the new model last from a series of stout-board sections. The computer can produce a series of cross-se~tions of the last at 1/10" intervals (the thickness of the stout-board), and pass them to the water jet cutter. The cutter can cut the sections to produce a series of about 100 templates. Each such template will have a series of locating holes w~ich serve as dowel holes for assembling the model last.
The designer may choose to view the last from any direction and with the apparent light source at any position. However, it is currently estimated that each new view will take between ~0 and 20 seconds to generate, and this is likely to be an unacceptable delay in the middle of the desi~n process. It is therefore proposed that various standard pictures of the selected last should be stored by the computer as a batch process. If new views are subsequently requested, thesewill be added to those stored.
~7hen a sty3e has been sketched, it will be necessary to give further infor~ation to fully classify .

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~4 it. The stylist may give the line a name of his own choosing; if he does not, a system name ~ill be generated. The unction of the line should also be given; e.g. raw edge of leather, closed seam ~ine, top sti~ching, and so on. When this has been done the line can be displayed using an appropriate representation on the television and the Tektronix.
lt is hoped to keep these representations as close to current practice as possible; i.e. pinked solid line for closed seams, broken line for top stitching, and solid line for edge of leather. Other represent-ations may be added as desired; being possible to give a good visualisation of brogue lines, fancy ~titching, etc.. In this case the d~,igner is saved lS a lot of work; he need only input the centre-line of the style line and the type of representation required.
Referring to Figure 3 there is sho~7n a schematic illustration of the process ~7hereby graded styles are produced for different shoe sizes. Digital information deferring the three-dimensional shape of the model last is applied from a model last unit 30 to a comb combining unit 31, which also receives, from a style line unit 32, digital information concerning the three-dimensional shape of the style lines of the intended shoe design. Unit 31 produces a combined three-dimensional digital output of the style lines and model last shape. Modifications can be made manually by a graphical input device and display as described above.
The output from unit 31 may be sub~ected ~L1~7~8 to a 1attening program at 33 to produce a flattened nett pattern ofi the model size. This may be subject to a gross pattern program 34 which adds margins for seams to the nett pattern pieces, thereby producing gross pattern piece shapes.
The output from unit 31 is applied also to a grading program 35 which multiplie~ the length and girth of the model last and style line dimensions by predetermined fa.ctors to produce non-proportionally reduced or enlarged versions of the three-dimensional - shape information, the~e corresponding to different shoe sizes (length and fitting). Three outputs from grading unit 35 illustrate the sizes, although in practicc there ~ould usually be more.
; 15 The sets of three-dimensional co-ordinates for the different sizes are each subjected to the flattening program at 36 and the gross program at 37.
T~e individual sizes may be modified 'oy displaying the three-dimensional graded information and graphically changing the style lines as described above.
The model last information may be taken directly from the last digitizer 3~ or from the library 3 of last dimensions.
Figure 4 illustrates a modif;.cation which makes use of last shape information stored in a lib-rary, not only in respect of the model last but also in respect of graded lasts. In Figure 4 ~he model last information from unit 30 is subjected to the grading program at 41 and three (for example) sets of graded last information is stored in library 3. ~hen ~ 1 ~Q~4 - lS -a style is to be graded the style line information is subjected to the gr~-~c~ing program at 42 and produces three corresponding sets of style line co-orclinates.
The respective co-ordinates are combined ~ith the inormation for those sizes on the required last retrieved from the library. The combination is sugg-ested schematically at 43. The flattening program is applied at 44 to the three-dimensional information.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method of producing a pattern for a shoe, comprising: applying as input to a computer (a) information defining the three-dimensional shape of a model last and (b) information defining the three-dimensional shape of style lines on the model last; operating on the shape information (a) and (b) with a grading program to derive corresponding last and style line three-dimensional shape information (c) for at least one other shoe size; and operating on the information (c) for the said other shoe size with a flattening program to derive a respective shoe pattern.

2. A method as claimed in Claim 1 wherein the grading program applies predetermined magnifications (positive or negative) of the length and girth of the shoe represented by information (a) and (b) to produce information (c).

3. A method as claimed in Claim 1 wherein the grading program is applied to information (a) and (b) in the same program operation.

4. A method as claimed in Claim 3 wherein information (a) is derived from a library of model last shapes stored in digital form and the style line information (b) is added manually by means of a graphical input device.

5. A method as claimed in Claim 1 or Claim 2 wherein the grading program is applied to information (a) initially and the graded last information for a range of sizes is stored in digital form in a library of last shapes, the required graded last size being selected from the library for combination with the graded information (b) before applying the flattening program.

6. A method as claimed in Claim 1 or 2 or 3 wherein the flattening program produces a nett pattern represented by information which is subjected to a gross pattern program whereby the required gross pattern is produced.

7. A method as claimed in Claim 1 wherein the shape information (a), (b) or (c) is capable of being modified before the operation of the grading or flattening program respectively by manual interactive use of a graphical input device to the computer, in conjunction with a display of the shape information to be modified.

8. A method as claimed in Claim 7 wherein, for the purposes of modicica-tion, the three-dimensional information (a), (b) or (c) is subjected to a flattening program and the flattened nett pattern is displayed, the input device interacting with the display so that manually applied modifications are subjected to the inverse of the flattening program, thereby producing a three-dimensional modification.

9. A method as claimed in Claim 7 or Claim 8 wherein a three-dimensional display representation of information (a), (b) or (c) may be produced for visual appraisal.