GB2225210A - Last for footwear - Google Patents

Abstract

A method of making a footwear last of the type comprising a standard backpart 1 and a toe part 2. The method involves moulding the backpart and an oversize toe part in moulds whose shape is defined by a plurality of spatial co- ordinates positioned in space with reference to a common datum point. The toe part is later machined down to the required shape using computer controlled machines utilising the same datum point as a reference. In the illustrated last, the backpart is split into a heel part 3 and fore part 4 separated by an arcuate surface 5 to provide a "broken" type of last. <IMAGE>

Description

"MANUFACTURE OF LASTS FOR FOOTWEAR" This invention relates to a method of manufacturing lasts for footwear.

With the growing demand for the automation of shoe manufacturing, emphasis is being placed on the need for lasts to be more accurate and which can be accurately located on the associated shoe making machinery. These conditions cannot be met by the conventionally turned lasts currently in use.

Our copending British Patent Application No.

8724904 describes a method of last manufacture to meet these exacting requirements. It refers in the main to the manufacture of a complete last, and where the number of lasts required to be produced in each mould is sufficient to cover the cost of the mould to be commercially attractive then this is an eminently suitable way to proceed. Where however, the quantity of lasts required is small, for instance for the production of so-called fashion shoes, then it becomes more difficult to absorb the mould cost price of each last.

It is common practice for shoe manufacturers, when laying down a new last plant, to retain a previously used backpart shape and have modelled on to it a required new toe shape. This practice is referred to in the shoe industry as the use of "Standard Backparts". Different manufacturers may have their own standards, or adopt one offered by the last manufacturer. Thus many different designs of shoe may be created from a single standard backpart. The shoe manufacturer then has to keep in stock a relatively small number of standard backparts one for each shoe size, and one for each different heel height required, although it is sometimes the case that the shoe manufacturer will require more than one backpart shape for a given size and heel height in order to cover differing styles of shoe and to achieve good fitting qualities for varying foot shapes.The use of standard backparts in this way has many advantages, proven fit qualities of the shoe will be retained, common components such as insole backers, shanks, heels and heel stiffeners may be used.

For reference purposes, as a general rule, the standard backpart is that portion of the last which extends rearwardly from the ball joint or last ball break.

The present invention seeks to provide a method of making lasts of the type comprising a standard backpart and a toe part of variable shape. In the method of the invention a mould is made, preferably by means of the techniques described in the aforementioned Application 8724904, which mould will fabricate not the whole last, but just the standard backpart of the last.

After moulding of the backpart, the required shape of toe part is attached to the backpart to fabricate the full last of the required style.

The moulded backpart is equipped with location means for accepting the toe part, for example two spigot holes in the front face of the backpart which accept spigots on the adjoining face of the toe part.

Regardless of the type of location means used for the joining of the toe part to the backpart, both parts are produced with reference to a datum point whose position is defined three dimensionally in space, and is preferably computer software generated and digitised with respect to the digital lasts produced by the method described in Application 8724904.

The preferred way of producing the toe part is to machine it, preferably on a computer numerical controlled milling machine or similar, from an oversize blank which has the location arrangement incorporated.

The blank may be moulded in the same material as the backpart or in some other suitable material, for example the backparts may be moulded in polyurethane and the toe part in nylon.

If the moulded blank is intended only to cover various toe styles for a given backpart then the last bottom surface contour could be finish moulded. If however, it is preferred that the toe part blank is to cover a variety of sizes and/or differing backpart shapes then the last bottom area could also be machined. The decision of which of these two alternatives to use will depend on the economics of mould cost versus machining and wasted material cost.

Joining the toe part to the backpart may be by merely mechanical means, such as locking one to the other, or may be achieved by adhesives either alone or in addition to such mechanical means.

In order that the invention may be better understood, an embodiment thereof will now be described by way of example only and with reference to the accompanying drawings in which: Figures 1 and 2 are plan and side views respectively of a last constructed in accordance with the present invention; Figure 3 is a perspective view of the last of Figures 1 and 2; and Figure 4 is a diagrammatic side view of a last outline, showing an alternative position of the dividing line between the standard backpart and the toe part of the last.

Referring to Figures 1 to 3, the last comprises a backpart 1 and a toe part 2. The last is of conventional shape, and is of the "broken" type in which the backpart 1 is itself formed of two parts: a heel part 3 and a fore part 4. The heel part and fore part are separated by an arcuate surface 5 which allows arcuate sliding movement between the heel and fore parts in order to shorten the length of the last during shoemaking. The heel and fore parts of the backpart are held together by a tongue and groove joint,as is well known in the art. Inserts 7 and 8 are moulded into the heel part 3 and fore part 4 respectively. The insert 8 provides means for the accurate location and locking of the last to associated footwear-making machinery (not shown).

The backpart 1 and the toe part 2 are separated by a surface 9, usually planar, and postioned somewhat as shown. An alternative position is illustrated under reference 9 in the sketch outline of a last shown in Figure 4. The position shown in Figure 4 enables more fittings to be achieved with a given backpart 1 but, on the other hand, results in increased cost in producing the toe part 2. The exact position and orientation of the surface 9 with respect to the last varies from manufacturer to manufacturer, and those shown should be considered exemplary.

The backpart 1 is of a standard shape for any particular shoe size and heel height. Thus the manufacturer need keep in stock only a relatively small number of different standard backparts to cover his full range of shoe styles. It is preferred that the standard backpart 1 is moulded from, for example, polyurethane in the form of a solid or blown elastomer, nylon or polyproylene, using the techniques described in our copending Patent Application 8724904.

The toe part 2, on the other hand can be made entirely separately and may conveniently be formed by moulding, with the same choice of materials as above.

The toe part and the heel part are joined together by any convenient means. In the illustrated embodiment, the backpart 1 is formed during moulding with blind bores 10 which co-operate with corresponding projections 11 formed on the toe part 2, also during moulding.

It is preferred that the toe part is initially moulded to a shape approximately to that shown, but somewhat larger so that a single toe part, as moulded, can cover several different sizes and styles. The final shape of the toe part 2, as shown in the drawings, is obtained by computer controlled machining of the moulded toe part. As moulded, the toe part may be equipped with an appropriately shaped and positioned surface 12 to abut the surface 9 and also a pair of projections 11 protruding therefrom, since these items are likely to be standard. Likewise, it is possible that the undersurface 13 of the toe part will also be standard and this may also therefore be moulded to shape right from the start, in order to reduce the amount of machining necessary. The upper, side and front surfaces of the toe part are all variable, according to the style required, and can be machined to shape.

Thus the last manufacturer need only supply a relatively small number of standard backparts and a relatively small number of oversize toe parts to enable a shoe manufacturer to fabricate a vast number of different last styles. Alternatively, the last manufacturer can supply a ready-prepared last, complete with a moulded backpart and a toe part machined in accordance with a customers requirements. It will be seen that the use of the techniques of the invention greatly reduce the number of components necessary to manufacture many styles of last.

The toe part and back part may be fitted together by force fit between the pins 11 and their respective bores 10. This enables the two to be separated so that the backpart can be re-used.

Alternatively, adhesive may be applied to permanently attach the two parts.

Claims (10)

1. A method of making footwear lasts of the type comprising a standard backpart and a toe part of variable shape, said method comprising moulding the standard backpart and thence attaching to the backpart a toe part of a required shape.

2. A method as claimed in claim 1 including moulding into the backpart location means whereby the toe part may be accurately positioned with respect thereto.

3. A method as claimed in either one of claims 1 or 2 wherein the toe part is made by moulding oversize and thence machining down to a required shape prior to attachment to the standard backpart.

4. A method as claimed in any one of claims 1 to 3 wherein the shape of the standard backpart is defined by a plurality of spatial co-ordinates positioned in space with reference to a datum point.

5. A method as claimed in claim 4 wherein the coordinates are computer generated.

6. A method as claimed in claim 3 and either one of claims 4 or 5 wherein the shape of the oversize toe part is defined by a plurality of co-ordinates defined in space with reference to said datum point.

7. A method as claimed in claim 6 wherein the machining of the toe part is carried out by computer controlled machinery utilising said datum point as a reference.

8. A method as claimed in any one of the preceding claims wherein said standard backpart is itself moulded in two parts which may be separated to provide a "broken" last backpart.

9. A last when manufactured by the method of any one of claims 1 to 8.

10. A last as claimed in claim 9 substantially as hereinbefore described with reference to the accompanying drawings.