Method And Apparatus For Unit Molding

Abstract

A method of lasting shoe uppers and sole-attaching devices to carry out the method.

Parent Case Text

This application is a continuation-in-part of our copending application Ser. No. 78,412, filed Oct. 6, 1970.

Description

BACKGROUND OF THE INVENTION

It is customary to last shoe uppers of material such as leather on wooden lasts to obtain the stretching of the leather for the desired permanent fit. The so prepared upper often must be transferred to a metal last for sole-attaching (securing a sole to the shoe upper), be it by cementing, vulcanizing, or molding sole material. Frequently sole-attaching machines are used having a turret with several arms, each carrying a last, with a single sole pressure plate fitting all lasts on the turret located beneath the turret. The operator has access to one last for mounting an upper while another last with its upper is in contact with the sole pressure plate, which frequently is combined with a side frame determining the side contour of the sole.

SUMMARY

The placing and lasting of the shoe upper on the last of the sole-attaching device requires skilled operators as great care is needed to assure that the back seam and the instep of the shoe is in the right location and is straight.

According to the invention, satisfactory lasting is facilitated by providing means for the operator to control the correct position of the upper on the last, before moving the lasted upper to the sole-attaching position.

The side-frame, hitherto located in relation to the sole pressure plate, is located now directly against the last and secured to the last before moving the upper into the sole-attaching position. This allows the operator to see the shoe bottom pressed against the side frame and to discover any irregularity which might exist. A correction is then possible before a sole is attached. This is of great advantage not only for weltless uppers, but also for prewelted uppers where the closing of the usually divided side frame can be used to push the welt inwardly and thereby tension additionally the upper on the last.

As shoes are sold and shipped from the factory in assortments (cases) composed of many sizes and each size often in several widths, with several pairs of shoes in the most commonly sold sizes and only one pair in rarely sold sizes and widths, then the necessity of having three identical lasts for each mold increases the already high mold costs as well as the costs of the many mold changes needed to cover the entire range of sizes and widths.

For sole-attaching by cementing or by molding of elastomeric material directly to the shoe bottom, sufficient time has to be allowed for the vulcanization of the rubber sole or for the cooling of the thermoplastic, molten elastomer.

To satisfy this need, sole-attaching machines are widely used which have a three or four arm turret above a single sole pressure plate or sole piston, so that the operator can use the vulcanization or cooling time to remove from a second last on a second arm a finished shoe and to place and last an upper on the second or a third last on a third arm. All lasts mounted at a given time on such turret are identical to fit the single sole pressure plate or sole mold. This has the drawback not only of doubling or tripling the last costs, but also that every time the size or width of the shoe is to be changed, two or three lasts have to be changed for every change of the sole cavity determined by the side frame and the sole plate.

One object of the invention is to reduce the mold costs by using only a single last for each mold without reducing the output per machine. Another object of the invention is to reduce the number of mold changes per machine.

Other features and advantages of the invention will be apparent with reference to the following specification and drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic view showing a turret machine with four arms;

FIG. 2 shows in larger scale a view of the device according to the invention of a last with attached side frame and means to position and lock the side frame in relation to the upper on the last;

FIG. 3 shows a first piston;

FIG. 4 shows a second piston for use with the device of FIG. 2;

FIG. 5 shows a unit mold comprising the unit of FIG. 2 with attached sole piston; and

FIG. 6 shows a cross section of the unit of FIG. 2 with the side frame secured to the last.

DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the invention, each arm 2 of the turret 1 carries a last 3 differing in dimensions, such as right or left, width or size, from the last carried by the next turret arm. The operator places an upper 5 on the last carried by the turret arm in mounting position 6. When the turret 1 is indexed (manually or by power means), the upper 5 moves into the molding position 7 where the molding compound is injected into the cavity formed by the mold 8, the usually split side frame 9 and the piston 10 with the configuration of the sole bottom. The piston or sole pressure plate 10 rests on the molding table 11, which might be chilled to reduce the time needed for the sole compound to solidify.

The invention provides further that the side frame 9 fitting the specific last is placed into the desired final position in relation to the last and the upper placed thereon while the turret arm is still in the mounting position. This allows not only easy visual inspection of the seating of the upper on the last but also lengthens the cooling time in the molding position. The last carries correspondingly the side frame 9 as well as last support extensions 13 to locate the side frame 9 as well as locking means 14 to maintain the relative position of last 3 and side frame 9 while moving from the mounting position into the molding position. There the side frame 9 surrounds the piston 10 resting on the molding table 11, placed there manually or by power means. It is understood that always the piston fitting the side frame and last coming into the molding position has to be brought into the correct position on the molding table. The ease with which this can be done allows, in further improvement of the method of the invention, to provide a first piston 15, as shown in FIG. 3, to mold a relatively flat, heel-less first sole layer to the upper, and to mold without further indexing of the turret, a heel or outer sole and heel to said first sole layer. If desired, the turret can be indexed as usual until the upper with the first sole layer reaches the mounting position again. Then inserts for the heel or sole, or both, can easily and accurately be placed onto the first sole layer before indexing again into the molding position. The division of the sole into a first and a second layer, be they the same or different thermoplastic material, will always bring a reduction in required cooling time because of the poor heat conductivity of such material.

The aforementioned improvement of placing not only the last but also the side frame on the turret arm, and have it travel together, is further broadened by connection also the mold component forming the sole bottom to the last traveling with the turret arm. Then the entire closing of the mold occurs before the indexing into the molding position. As the last and the side frame as well as the locating means 13, 18 and the locking means 19 are interconnected, the entire unit can be adjusted off the machine and instantly exchanged. In such case, as shown in FIG. 5, the sole bottom plate 16 can be exchangeably fastened to the turret arm 17 or the entire unit mold can be exchangeably mounted with the last locked to the turret arm 17. A machine with 2 turrets with four arms each equipped according to the invention takes care of four complete sizes, right and left, compared to production of a single size with the customary equipment.

These advantages are important not only for injection molding of soles, but also for molding of heat setting elastomers, such as rubber ornaments.

As shown in FIG. 5, the locking means 13, 18 are posts extending both from the last carrier and from the frame with locking means where these posts meet. This allows to set the contact between upper and frame lip independently from the action of the closing device 19 or other pressures.

FIG. 6 shows how the posts 13 hold the lip 24 of the side frame in the desired, spaced relation to the last 5 to push the welt 26 inwardly and tighten thereby further the upper 5 to which the welt is secured by the stitching 27. The side frame 9 has not only the cavity wall 21 mating the contour of the sole piston (not shown in FIG. 6) but also guide surfaces 22 to bring the piston into the exact alignment with the side frame.

The threaded posts 13 allow the exact adjustment of the side frame in relation to the last to suit different thicknesses of the material of the upper before placing the unit of last and frame onto the arm of the turret 1, thereby saving costly machine time. The locking means 23, which might use cam surfaces as shown, assure the rigid maintenance of the frame position also during the travel from the lasting position to the sole-attaching or molding position. The sole pistons, unencumbered by other cavity or locating parts, are easily moved by hand or mechanical means to have always the piston fitting under the frame (and last) when the unit arrives in the molding position.

The absence of any mechanical connection between the unit of last and frame on the one hand and the piston on the other hand allows in further improvement of the method according to the invention to mold closed cell elastomeric soles to the upper by providing a sequence of decreasing, increasing, and again decreasing the cavity volume by the relative movement between last and piston.

Claims

What is claimed is:

1. The method of manufacture of footwear which includes the steps, in sequence, of placing an upper upon a last, positioning a sideframe in proper position relative to the upper and last to hold the upper in its proper position on the last, locking the sideframe in its proper position, the last, upper and sideframe constituting a movable unit, thereafter moving the unit in relation to a sole plate to form a sole molding cavity, placing an elastomeric material in the cavity and molding a sole to the upper.

2. The method of manufacture of footwear as set forth in claim 1 wherein a plurality of lasts and side frames are mounted upon a conveyor and moved relative to the sole plates.

3. The method of manufacture of footwear as set forth in claim 2 wherein said lasts and side frames are of different configurations to manufacture in sequence footwear of different sizes.

4. Apparatus for manufacture of footwear comprising a last, an adjustable side frame, means for locking said side frame directly to said last in its adjusted position, said last, side frame and locking means forming a unitary structure, a separate sole plate forming with said unitary structure a mold cavity, and means for exerting relative movement between said sole plate and said unitary structure to mold a sole to an upper.

5. Apparatus for manufacture of footwear comprising a plurality of lasts, an adjustable side frame for each last, means for locking each said side frame directly to its respective last in its adjusted position, said last, side frame and locking means forming a unitary structure, a plurality of said unitary structures being mounted on a conveyor, said unitary structures being of different configurations, sole plate means forming with each unitary structure a mold cavity, and means for exerting relative movement between said sole plate means and each said unitary structure to mold a sole to an upper.