Boots of Injection Molded Plastic and Process Therefor

The present invention relates to the manufacturing of boots made from injection molded plastic material, and more particularly to a process, and a boot resulting therefrom, wherein a reinforced arch and heel member is incorporated into the boot during the injection molding process.

Boots made entirely from injection molded plastic material have been used for some time as a substitute for traditional leather boots. The plastic material may be made to resemble the appearance of leather, and such boots have the advantage of being more economical than leather and are completely waterproof. However, they have had certain disadvantages such as the lack of rigidity of the heel in relation to the sole and a lack of resiliency. These disadvantages are a particular problem in the case of ladies' boots with rather high heels.

It is the purpose of the present invention to provide a process which overcomes these disadvantages simply and effectively and which produces improved boots having rigid arch and heel structures.

The present invention involves the use of a rigid arch and heel structure which is incorporated into an injection molded plastic boot during manufacture to act as a reinforcement between the sole and heel resulting in an improved boot construction.

In one embodiment a rigid reinforcement member, consisting of an arch portion and a heel portion formed from a single integral piece of rigid plastic or suitable metal, is disposed within the injection mold and incorporated into the plastic material injected into the mold during the initial stage of the process when the entire upper of the boot is formed including the foot from which the heel portion, which is part of the reinforcement member, projects. During the second stage of injection of plastic material for the purpose of molding the sole and the heel covering, the plastic material covers the underside of the arch portion and the outside of the heel portion of the reinforcement member. Suitable passages are provided in the reinforcement member to accommodate and achieve satisfactory union with the extruded material and the subsequently attached lift.

An alternative embodiment incorporates the reinforcement member into the boot during the second stage of injection molding, that is, during molding of the sole and heel covering. The reinforcement member is secured to the insole of the boot, which has already been molded in the initial production stage, by means of suitable passages arranged in the instep part of the arch portion and by means of longitudinal grooves in the body of the heel portion, the plastic material being injected into these passages and grooves in the course of the second stage of injection molding. The lift is inserted into the heel portion by means of projections extending from the lift into blind holes in the bottom of the heel body.

A third embodiment comprises a reinforcement member in the form of a rigid arch portion having a threaded screw therethrough, which screw acts as the heel portion of the reinforcement member. This member is suitable for incorporation in a boot after completion of the conventional injection molding process. The screw is screwed into a synthetic resin core inserted into the heel and the screw head is covered by a leather lining which is glued to the insole and over the arch portion to protect the wearer's foot.

It will be seen that the reinforcement member and processes of the present invention have been described in connection with the manufacturing of the injection molding of plastic boots, but they may be found equally applicable to the manufacture of other injection-molded footwear.

FIG. 1 is a side elevation in cross section of a reinforcement member in accordance with the present invention consisting of integral arch and heel portions;

FIG. 2 is a plan view of the reinforcement member shown in FIG. 1;

FIG. 3 is a side elevation partly in cross section of a boot made by the process of the present invention and using the reinforcement member of FIG. 1;

FIG. 4 is a side elevation in cross section of another reinforcement member in accordance with the present invention;

FIG. 5 is a plan view of the reinforcement member of FIG. 4;

FIG. 6 is a side elevation partly in section of a boot made in accordance with the present invention and using the reinforcement member of FIG. 4; and

FIG. 7 is a side elevation partly in section of a boot made in accordance with a further embodiment of the present invention.

A reinforcement insole member in accordance with the present invention is shown in detail in FIG. 1 and may be constructed of a suitable rigid plastic material or of a suitable metal or metal alloy or a combination of both. In this embodiment, which is intended for use in high heel boots, the member M comprises a heel portion 1, having an internal cavity 3 which may be of truncated conical shape to accommodate a lift for the heel, and an integrally formed arch portion 2. The forwardly disposed arch portion 2 is designed to support the boot instep, that is, the part of the sole of the boot extending between the heel and the ground-contacting portion of the sole. Arch portion 2 is provided with a series of holes 4 designed to accommodate plastic material injected therein during the initial phase of the process of forming the boot. As seen in FIG. 2 the holes may suitably be formed in two parallel series along the length of the arch portion 2.

In accordance with the process of the present invention, the reinforcement insole member M is disposed within the injection mold before it receives the plastic material in the initial stage of the molding process during which the entire upper U of the boot is formed. As a result, upon injection of the plastic during this stage, the upper of the boot assumes its shape as shown in FIG. 3 complete with foot 5 and including the reinforcement member M which is incorporated therein, by accommodating the plastic material in the holes 4 of the arch portion 2, with the heel portion 1 projecting from the foot 5. Cooperation of the plastic material and the reinforcement member produces a union between the two. The configuration of the mold typically used for this first phase of the injection molding operation is such that the reinforcement member normally will have to be supported within the mold cavity by a suitable pin, as will be appreciated by those skilled in the art.

In the second production phase additional plastic material, again of a suitable type, is injected into the mold to form a sole 6 and the outer covering 7 of the heel. The various plastic materials are joined and an integral boot and heel is accordingly formed.

Upon removal of the boot from the mold, all that then remains to complete the construction is to insert a lift into the base of the heel. A suitable lift 8, provided with an upstanding truncated conical pin 9, may be pressed into cavity 3 in the heel portion of the reinforcement member. Pins 10 may also be formed on the upper surface of the lift 8 to cooperate with corresponding holes in the lower surface of the heel portion and thus improve the stability of the cooperation between the heel portion and the lift.

A reinforced boot will thus have been constructed, that is of great mechanical strength since the arch or insole is rigidly integral with the body of the heel which ensures increased stability and rigidity of the heel in relation to the sole while at the same time improving the resiliency of the heel. Further the process has economic advantages derived from the fact that the reinforcement member is placed directly into the mold used during the initial injection molding phase, thus eliminating the need for any additional operations in securing the reinforcing element within the boot. As a result, improved boots are produced which have characteristics of stability and resilient deformation clearly better than existing plastic boots and which boots may be economically produced.

An alternative embodiment to the process and boot disclosed in connection with FIGS. 1-3 is shown in FIGS. 4-6. This embodiment is directed to avoiding the possible need with the first embodiment for a complex modification of mold construction in order to support the reinforcement member during the initial phase of injection molding. Accordingly, a reinforcement member M' may alternatively be incorporated into the boot during the course of the second stage of injection molding when the sole and heel covering are being produced. In this embodiment during the first molding phase the upper portion U' of the boot is injection molded from plastic material to include, as shown in FIG. 6, an insole portion 20. The reinforcement member M', which may be of a somewhat different construction, is joined to insole portion 20 during the second molding phase.

As shown more clearly in FIGS. 4 and 5, the arch portion 12 of the reinforcement member M' is provided with holes 14 through which the plastic material, injected during the second molding phase, may pass. As a result, this plastic material unites the arch portion 12 with the already-formed insole 20 and the insole with the sole 16 and with the heel covering 17. In addition, lateral grooves 26, 27, and 28 are formed on the sides of the heel portion 11 to provide a better hold between the plastic material forming the heel covering 17 and the sides of the heel portion.

To obviate any need for complicated mold structure modification, the heel portion 11 may also be provided with a cavity 13, preferably rectangular in shape, which may serve to accommodate a suitable guiding and supporting pin. Such a pin can readily be formed on the molding equipment to support the reinforcement member M' during the second phase of injection, as will be appreciated by those skilled in the art. Small cavities 21, 22, and 23 are located laterally on the lower surface of heel portion 11 and accommodate lateral projections 25 extending upwardly from a lift 18 so that the latter may be easily secured to the heel portion 11 when completing boot construction. Cavity 13 may be left empty, if desired, in order to reduce the weight of the boot.

It will thus be seen by those skilled in the art that the mold structure modification required to support the reinforcement member in the mold during the second injection molding phase may be fairly simple, but yet ensures the obtaining of a boot in which the stability and resiliency of the heel in relation to the sole are improved over hitherto known plastic boots. The boot also has a substantial production cost advantage and is considerably easier to assemble as compared with prior processes and even the process of the first-mentioned embodiment.

A third embodiment, shown in FIG. 7 is particularly suitable for incorporating an improved reinforcement member in an already-constructed boot. This embodiment comprises a reinforcement member M" in the form of two pieces. The member M" has an arch portion 32 of a rigid material, which may, for example, have a metal reinforcement 32', running from the boot heel 35 to over about one-third of the sole 36. The arch portion 32 is disposed over the boot insole and secured to the heel by means of a screw 31 of the self-tapping type that acts as the rigid heel portion of the member. This member M" may be secured to the boot heel 35 by screwing the end of the screw 31 into a resin core 33 fitted to the internal cavity 38 in the heel. Resin core 33 may be introduced into the heel cavity through an aperture 38' in the bottom thereof and the cavity may be closed off by a lift 34 formed by molding the same resin. A leather lining 39 for covering the head 31' of the screw 31 may be glued to the insole in order to protect the wearer's foot. This process and combination produces the advantages that the inserted reinforcement insole member may be securely held to the heel by means of a simply-inserted screw which is screwed into a synthetic resin core that may be inserted into the heel by an extremely simple and economical procedure. This procedure produces an improved structural and functional arrangement since it imparts maximum stability to the heel and stiffens the heel-sole structure of the boot which thus no longer becomes deformed in use. The design of the boot may therefore be modified such that the heel may be formed separate from the sole, whereas the prior art ladies' plastic boots it has hitherto been necessary to construct the heels integral with the sole.

While the various embodiments are described in connection with the manufacturing of plastic boots, and particularly ladies' boots with rather high heels, it will be seen that the invention is readily applicable to the manufacture of other injection-molded plastic footwear.