US3106728A - Plastic hinged shoe last - Google Patents

Description

Oct. 15, 1963 w. OTTO 3,106,728

PLASTIC HINGED SHOE LAST Filed July 20, 1962 iWiI" United States Patent 3,106,728 PLASTIC HHNGED SHOE LAST Wiili @tto, Alfeld (Leine), Germany, assignor to Fagus- Work Karl Benseheidt, Alfeld (Leine), Germany, a

firm

Filed July 20, 1962, Ser. No. 211,214 Claims priority, application Germany Aug. 3, 1961 laims. (Cl. 12-136) In recent times shoe lasts have often been made from thermoplastic or duroplastic synthetic materials, because synthetic plastic material offers noteworthy advantages over wood, i.e., the material formerly used exclusively for the making of shoe lasts. These advantages consist primarily in the increased mechanical strength and the resultant greater durability of the shoe lasts as well as in the fact that plastic shoe lasts absorb no moisture from the air and are less liable to deformation under changes in temperature than shoe lasts made from wood. Plastic shoe lasts are remarkable for their nondeformaoility, which is urgently necessary for making footwear to measure, but is not attainable in a fully satisfactory manner with shoe lasts made from wood.

In the known plastic hinged shoe lasts the front part of the last made from thermoplastic or duroplastic material and the rear part of the last made either from the same material or from wood are connected to fold in the manner known from hinged lasts made from wood, i.e., a bolt passes transversely through the body of the shoe last or a beaded edge formed on one part of the shoe last and rounded in the shape of a semicircle, engages in a cup-shaped recess in the other part of the shoe last and thus forms the hinge. The clamping element which connects the two parts of the shoe last, holds them in extended position and guides them during the folding movement, is fitted in a milled slot on the opposite sides of the two shoe last parts and secured in position by bolts inserted in bores in the last parts. With this known type of connection the pivot must be arranged at a relatively great distance from the sole surface of the last because the slot-shaped milled out portions provided in the two parts of the last for receiving the connecting members must terminate at a certain distance from' the sole surface of the shoe last parts. The fact that the pivot is located at a relatively great distance from the sole surface is of disadvantage because the shoe last in folded state only produces a slight shortening, if any, as compared with the length of the last in extended state.

The lower the pivot can be arranged the greater will be the shortening of the folded shoe last and the easier the shoe last can be removed from the shoe. Rapid and easy extraction of the shoe last is, however, an important factor for use in mechanical shoe manufacture, which in the case of the folding lasts hitherto known has not been taken into consideration in a satisfactory manner to meet the requirements in practice.

A further disadvantage of the conventional assembly of hinged plastic lasts is that the hinge or joint is subject to great stresses which lead to considerable wear of the hinge or joint so that the durability of the shoe last resulting from making the parts thereof from plastic material is not usually fully utilized.

An object of the invention is to overcome these disadvantages of the plastic shoe lasts hitherto used and to simplify and reduce the cost of production of hinged shoe lasts of synthetic material.

This object is attained according to the invention by the provision of a plastic hinged shoe last which comprises a front part and a rear part, a cavity formed in each of said parts, the cavity in each part being open towards the abutting face of the other part and defining in cross section a substantially fiat bottom and an arc- 2 shaped upper portion, lateral bearing flaps of substantially semicircular shape projecting from the abutting face of one of the parts in the vicinity of the bottom and of a thickness corresponding substantially to the thickness of the arc-shaped upper portion of said one part, recesses corresponding substantially to the shape of said flaps and formed in the other part to guide said flaps, raised portions extending between said flaps and said recesses respectively on the bottoms of the cavities at the open ends thereof, a channel-she ed recess in the inner side of each of said raised portions, and a U-shaped clamping bow with rounded ends engaging in the channel-shaped recesses in the raised portions of said parts and exerting pressure towards the hinge axis of the shoe last.

In a hinged shoe last constructed in this manner, the pivot can be arranged considerably lower down than heretofore because no bolts are required for fixing the clamping bow. As a result, the advantage of the desirable considerable reduction in length of the folded last is attained.

Another advantage consists in that the mutual lateral guiding of the front part and the rear part of the shoe last is effected not in the manner hitherto customary by the connecting element, but by the lateral substantially semicircular bearing flaps provided on one of the parts and engaging in the recesses in the other part of the shoe last. In this manner large lateral sliding surfaces are produced where plastic is in contact with plastic and not as heretofore steel in contact with plastic or wood.

The lateral substantially semicircular bearing flaps can be relieved to a great extent from the pressure forces exerted by the clamping bow when the shoe last is in extended state, in that the raised portions of the bottoms hear one against the other with flat adjoining surfaces of the front and the rear parts of the shoe last so that the pressure forces of the clamping bow are taken up by these flat surfaces.

Whereas in the hinged folding lasts hitherto known the connecting elements are located in recesses which have to be subsequently milled in the front and rear parts of the shoe last, the two parts of the proposed plastic hinged shoe last are produced from the outset with large wide cavities.

Another object of the invention is to construct a plastic hinged shoe last in which the shape of one or both parts, preferably the front part thereof, can be changed by merely fitting other members, when a change in-fashion of the shoe shape requires this.

Several preferred embodiments of the invention will now be described by way of example and with reference to the accompanying drawing, in which:

FIG. 1 is a vertical longitudinal section through a plastic hinged shoe last as proposed by the invention, with the front and rear part thereof in extended position;

FIGI 2 is a vertical longitudinal section through part of the hinged shoe last with the front and rear part thereof in bent or folded position at the moment of fitting a clamping bow;

FIG. 3 is a horizontal section taken on line IIIIII of FIG. 1;

FIG. 4 is an inner end view of the front part of the shoe last;

FIG. 5 is an inner end view of the rear part of the shoe last, and

FIG. 6 is a vertical longitudinal section through the middle of the front part of the shoe last with a screwed-on toe-piece.

FIG. 1 shoes a plastic hinged shoe last consisting of a front part 1 and a rear pant 2 produced by injection molding from thermoplastic or duroplastic material and provided with cavities 3 and 4, respectively, which are open at the two ends facing each other when the parts 1 and 2 are fitted together. The two side walls of the rear part 2 of the shoe last are extended to form two projecting bearing flaps 5 of substantially semicircular shape. These flaps 5 have the same wall thickness as the side walls of the rear part 2 of the shoe last. Recesses 6 of corresponding shape but with a slightly shorter circular path are formed in the side walls of the front part 1 of the shoe last for receiving the bearing flaps 5.

The bottom 7 below the cavity 3 in the front part 1 and the bottom 8 below the cavity 4 in the rear part 2 of the shoe last are provided with raised portions 9 and it) respectively at the adjacent end faces of the bottoms 7 and 8. The raised portions 9 and It) are flush with the end faces of the bottoms 7 and 8, respectively, and extend over the entire width of the cavities 3 and l, respectively. In the inner sides of the raised portions 9 and i ascending slightly towards the interior of the cavities 3 and 4 respectively, channel-shaped recesses 17. and 12 are provided which extend across the entire width of the raised portions h and 1t}, respectively. In each of these, channcl-shaped recesses 11 and 12 engages one end leg 14 of a U-shaped clamping bow 13. Onto the rounded end of each of the legs 14 of the clamping bow 13 a sleeve 15, preferably of metal and provided with a central engagement hole 16 is slipped so that the sleeves 15 extend transversely to the clamping bow 13. The sleeves 15 are slightly shorter than the channel-shaped recesses 11 and 123 provided for their accommodation.

The clamping how 13 is fitted in such a manner that the sleeve 15 on one of its legs 14 engages in one of the channel-shaped recesses, for example in the recess 11 of the front part 1 of the shoe last, as shown in FIG. 2, and the bearing flaps of the rear part 2 of the shoe last loosely engage in their circular recesses 6 in the front part 1 of the shoe last. In FIG. 2 the two shoe last parts 1 and 2 are turned in relation to each other so as to leave open a small gap. When, while the parts 1 and 2 are held together in this position a strong pressure is exerted from the outside on the web of the clamping bow 13, for example with the aid of a hydraulic tool, the clamping how 13 will slightly bend so that the sleeve 15 on the other leg 14 can slide or snap into the channel-shaped recess 12 of the rear part 2 of the shoe last. The two last parts 1 and 2 are then pressed tightly one against the other by the clamping bow 13 yet can be turned towards each other until the end faces of the bottoms 7 and a come into contact (see FIG. 1). When the two last parts 1 and 2 are in this extended position the central axes of the two sleeves 15 have moved downwardly beyond the center of the pivot axis of the two last parts passing through the centers of the bearing flaps 5, so that the U- shaped clamping bow 13, now under tension, reliably holds the two last parts 1 and 2 firmly in extended position. The raised portion 9 of the front part 1 located between the bearing flaps 5 of the rear part 2 prevents any lateral displacement between the two parts It and 2 during the turning movement.

In order to increase the resistance to impact and bending of the two parts 1 and 2 of the plastic hinged shoe last, bent steel plates 17 can be embedded at particularly heavily stressed points, such as at the toe of the front part 1 of the shoe last, as shown in FIG. 1. The heel of the rear part 2 of the plastic hinged shoe last as well as the bearing flaps 5 of the rear part 2 can also be reinforced in a similar manner by means of bent or fiat steel plates.

FIG. 6 shows a front part 1 which has a screwed-on toe-piece 13 of plastic material. The plastic toe-piecc 13 is detachably held on the front part 1 by means of a socket head cap screw 19 screwed in from the cavity 3 in the front part 1 and engaging in a screw threaded bore 20 in the toe-piece 18.

This screw connection enables the plastic toe-piece 18 to be exchanged easily and quickly, should it become damaged in the course of working in shoe manufacture, or if the shoe last is to be changed in shape by fitting another toe-piece.

it is obvious that the plastic hinged shoe last may be provided with detachable fitted members of the same material as that of the plastic last par-ts, or even of other i iaterial, with the object of giving the shoe last a different shape when necessary in a simple and economical manner while re ining the main components of the shoe lasts.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all aspects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

I claim:

1. A plastic hinged shoe last comprising a front part and a rear part, a cavity formed in each of said parts, the cavity in each part being open towards the abutting face of the other part and defining in cross section a substantially flat bottom and an arc-shaped upper portion, lateral bearing flaps of substantially semicircular shape projecting from the abutting face of one of the parts in the vicinity of the bottom and of a thickness corresponding substantially to the thickness of the arc-shaped upper portion of said one part, recesses corresponding substantially to the shape of said flaps and formed in the other part to guide said flaps, raised portions extending between said flaps and said recesses respectively on the bottoms of the cavities at the open ends thereof, a channel-shaped recess in the inner side of each of said raised portions, and a U-shaped clamping bow with rounded ends engaging in the channel-shaped recesses in the raised portions of said parts and exerting pressure towards the hinge axis of the shoe last.

2. A plastic hinged shoe last as claimed in claim 1, wherein the raised portions completely fill the width between the respective bearing flaps and recesses of the two last parts and their outer upwardly extending transverse surfaces are located in the same planes as the transverse edges of the bottoms in contact when the plastic hinged shoe last is in extended position.

3. A plastic hinged shoe last as claimed in claim 1, wherein sleeves are provided on the ends of the U-shaped clamping bow and extend transversely to said how, said sleeves engaging in the channel-shaped recesses in the raised portions of the two last parts.

4. A plastic hinged shoe last as claimed in claim 1, wherein at least one of the two parts of the shoe last has a fitted member secured in position by means of a screw engaging a bore extending outwardly from the cavity of the last body.

5. A plastic hinged shoe last as claimed in claim 4, wherein the fitted member is made from the same material as the part of the shoe last to which it is secured.

6. A plastic hinged shoe last as claimed in claim 4, wherein the fitted member is made from a material different from that of the part of the shoe last to which it is secured.

References Cited in the file of this patent UNITED STATES PATENTS 2,521,072 Lovell Sept. 5, i950 2,602,193 Korkatti July 8, 1952 FOREIGN PATENTS 863,771 Germany Jan. 19, 1953 491,968 Great Britain Sept. 13, 1938

Claims (1)

1. A PLASTIC HINGED SHOE LAST COMPRISING A FRONT PART AND A REAR PART, A CAVITY FORMED IN EACH OF SAID PARTS, THE CAVITY IN EACH PART BEING OPEN TOWARDS THE ABUTTING FACE OF THE OTHER PART AND DEFINING IN CROSS SECTION A SUBSTANTIALLY FLAT BOTTOM AND AN ARC-SHAPED UPPER PORTION, LATERAL BEARING FLAPS OF SUBSTANTIALLY SEMICIRCULAR SHAPE PROJECTING FROM THE ABUTTING FACE OF ONE OF THE PARTS IN THE VICINITY OF THE BOTTOM AND OF A THICKNESS CORRESPONDING SUBSTANTIALLY TO THE THICKNESS OF TH ARC-SHAPED UPPER PORTION OF SAID ONE PART, RECESSES CORRESPONDING SUBSTANTIALLY TO THE SHAPE OF SAID FLAPS AND FORMED IN THE OTHER PART TO GUIDE SAID FLAPS, RAISED PORTIONS EXTENDING BETWEEN SAID FLAPS AND SAID RECESSES RESPECTIVELY ON THE BOTTOMS OF THE CAVITIES AT THE OPEN ENDS THEREOF, A CHANNEL-SHAPED RECESS IN THE INNER SIDE OF EACH OF SAID RAISED PORTIONS, AND A U-SHAPED CLAMPING BOW WITH ROUNDED ENDS ENGAGING IN THE CHANNEL-SHAPED RECESSES IN THE RAISED PORTIONS OF SAID PARTS AND EXERTING PRESSURE TOWARDS THE HINGE AXIS OF THE SHOE LAST.

Images