Ballet Slipper and Method of Manufacturing a Ballet Slipper

The present invention relates to footwear, and particularly to ballet slippers and a method of manufacturing the same.

The design and materials of the ballet slipper used by a dancer performing "sur les pointes" have generally been unchanged since the original conception of such "pointe shoes" or "toe shoes". The traditional blocked ballet slipper is made by hand on a last, using layers of fabrics, cardboard, paper or leather saturated with glue to form a reinforced toe box joined to a leather or cardboard shank. A reinforcing stiffener is frequently included in the shank. Usually the outer sole is made from leather. An outer fabric or "upper" is sewn to the sole and usually gathered in pleats under the toe. This type of slipper is labor intensive and expensive to produce, although some improved casting methods have been developed to speed the laminating steps, for example as disclosed in U.S. Pat. No. 4,453,966 to Terlizzi.

The traditional ballet slipper requires extensive breaking-in before it is comfortable for use. Typically, a ballerina will break in the slipper by manually flexing it, or applying force by way of slamming the slipper in a door or bashing it with a hammer, or soaking it in warm water or alcohol. It can take as much as three hours to prepare a single pair of slippers for a performance if they have been manufactured using an epoxy or other durable glue as a laminant. Once the slipper is broken in, it will have an extremely short useful life, usually no more than twenty to forty-five minutes during a performance. The short useful life is attributable to the deterioration of the toe box and or shank caused by the rapid breakdown of the glue used to form the laminates of the toe box. The breakdown can be accelerated by perspiration during energetic dancing. Once the shank and/or toe box have deteriorated, the slipper is useless, because there will be no support for the dancer.

A further problem encountered with the traditional ballet slipper is that the outer covering (typically a satin material) is slippery, and can contribute to slips and falls when the ballerina is rising to the pointe position. The ballerina will usually darn the toes of the slipper and rub the tips in resin to minimize the chances of slipping. Nevertheless, falls do occur.

The traditional ballet slipper is uncomfortable. The toe box compresses the side of the feet, and may exacerbate problems of tendonitis, bunions and stress fractures associated with the hopping and leaping on pointe required by ballet choreography. In addition, the ballet slipper is noisy: the sound caused by the hard toe box striking a floor can detract from the illusion of effortless grace for which a dancer always strives. Efforts by the ballerina to soften the impact of the slipper on the floor can detract from the continuity and flow of a performance and also may promote strains and other injuries.

In recent years several designs for a sturdier ballet slipper formed from polymeric materials have been proposed. U.S. Pat. No. 3,797,137 to Harkness discloses a unitary plastic base having a foot supporting section and a toe box. A fabric upper is attached to the base section, but leaves the plastic toe exposed. It has been found that such exposed plastic toe boxes are extremely noisy in use, and that the exposed plastic toe can be very slippery. Furthermore, the base is disclosed as being formed from polyvinylchloride, which to be comfortable, must be specifically molded for a particular dancer's foot. The manufacture of individual molds and lasts for a particular dancer can be very expensive. In addition, the plastic base cannot be broken in like the traditional ballet slipper, and thus this design for a ballet slipper is extremely uncomfortable, even when properly molded to a particular dancer's requirements.

U.S. Pat. No. 4,026,046 to Clark discloses a relatively rigid polymeric shank and toe box unit having an open toe into which is fitted a moldable toe insert. The disclosed slipper does not address the problems of noise associated with the use of plastic materials.

U.S. Pat. No. 4,199,878 to Wossner shows an integral shank and toe box unit in a plastic ballet slipper. This slipper suffers the same drawbacks of the other plastic slipper designs, namely, it is noisy, uncomfortable, and once molded, cannot be broken in to provide a more comfortable fit. Further, certain virtuoso steps such as hopping on pointe are very difficult to perform in these shoes because of the rigidity and small size of the section connecting the platform at the front of the toe box and the shank, and further because of the insufficient support provided in the top of the toe box.

Therefore, it can be seen that there no ballet slipper known or available which combines the virtues of durability with comfort and adjustability to the shape of a dancer's foot, and quietness on impact.

It is an object of the present invention to provide a ballet slipper which is durable and comfortable, and which reduces the noise caused by the slipper impacting on a dance floor. It is a further object of the present invention to provide a slipper which can be adjusted by the dancer to fit the dancer's foot.

These objects, and other objects which will become apparent from the description that follows, are achieved by a ballet slipper comprising an integral shank and toe box formed from a flexible thermoplastic polymeric material. The toe box includes a platform at its forward end and a curved radius joining the platform and the shank. The curved radius is rounded and larger than the edge joining the platform to the toe box in prior art slippers. A soft, resilient polymeric material lines the upper portion of the toe box and extends backwardly from the edges of the toe box. A shock absorbing material covers both the upper and lower surfaces of the shank, and the exterior surface of the curved radius and the platform of the toe box. A stiffener may be mounted in a cavity formed in the underside of the shank.

Preferably, the thermoplastic material forming the integral shank and toe box has a softening point between about 120.degree. F. and 220.degree. F., and is either an ionomer resin, an ethylene-vinyl acetate copolymer or a polyurethane. Most preferably it comprises an ionomer resin. Preferably the soft resilient lining is a foam comprising a polyurethane, a cross-linked polyethylene, a polyvinylchloride and nitrile rubber blend or a ethylene-vinyl-acetate (EVA) copolymer. The shock absorbing covering is a foam comprising a ethylene-vinyl acetate copolymer, a neoprene rubber or a polyurethane. Most preferably, the shock absorbing covering comprises an open celled polyurethane foam. An outer covering is fitted over the shank and toe box. The outer covering has a panel formed from a durable non-slip material, preferably canvas, to cover the platform and curved radius of the toe box. The outer covering has an elasticized throat to hold the slipper onto the dancer's foot, and may have at least one elasticized panel in one side or end to insure a secure fit. An outer sole formed from a shock absorbing material, preferably an ethylene-vinyl acetate copolymer, is secured to the outer covering adjacent to the underside of the shank.

Another aspect of the present invention is a method of manufacturing a ballet slipper, comprising the steps of molding an integral shank and toe box from a flexible thermoplastic polymeric material, the toe box having a platform at its forward end and a curved radius connecting the platform with the shank; lining the interior of the upper portion of the toe box with a soft, resilient material sized to extend backwardly from the edges of the toe box; and attaching a shock absorbing material to the upper and lower faces of the shank, and to the curved radius and platform. Preferably, the thermoplastic polymeric material has a softening point between about 120.degree. F. and 220.degree. F. and is an ionomer resin, an ethylene-vinyl acetate copolymer, or a polyurethane. The resilient material lining the inside of the toe box is a foam comprising a polyurethane, a cross-linked polyethylene or a polyvinylchloride and nitrile rubber blend, or an EVA. The shock absorbing underside is preferably a foam comprising a ethylene-vinyl-acetate copolymer, a neoprene rubber or a polyurethane. Most preferably the shock absorbing material is an open-celled polyurethane foam. A stiffener may be mounted on the underside of the shank. An outer covering having a panel formed from a durable non-slip material, preferably canvas, for covering the platform and curved radius is then fitted over the toe box and shank; and an outer sole formed from a shock absorbing material is then secured to the outer covering adjacent to the underside of the shank. Preferably, the shock absorbing outer sole material comprises an ethylene-vinyl acetate copolymer.

FIG. 1 is a cross-sectional view of the ballet slipper of the present invention without an outer covering.

FIG. 2 is a top plan view of the ballet slipper of the present invention before fitting of the outer covering.

FIG. 3 is a side view of the ballet slipper without an outer covering.

FIG. 4 is a bottom plan view of the ballet slipper showing the paddle shaped stiffener.

FIG. 5 is a perspective view of the assembled ballet slipper.

FIG. 6 is a cross-sectional view of the assembled ballet slipper.

The invention will now be illustrated further with respect to the drawings. Although the description and drawings generally describe a ballet slipper which can be fitted to either the left or right foot, it is to be understood that the present invention encompasses ballet slippers whether made as a pair for a left and right foot or as individual slippers made for use on either foot.

With reference to FIG. 1, 2, 3 and 4, the ballet slipper 10 comprises an integral toe box 12 and shank 14 formed from a flexible thermoplastic polymeric material. The thermoplastic polymeric material should be selected to have a softening point above the temperature which the shoe reaches during a performance due to the heat of friction of the shoe on a dance floor, stage lights, and body heat. The thermoplastic material should have a softening point which will allow the dancer to easily adjust the shank and toe box to the shape of her foot, for example, by using a conventional blow drier to heat the material until it is malleable, and then applying manual pressure to shape the shank and toe box to the shape of her foot. Preferably the thermoplastic material will have a softening point between about 120.degree. F. to about 220.degree. F. Preferably, the thermoplastic material comprises an ionomer resin, an ethylene-vinyl acetate copolymer ("EVA") or a polyurethane. Most preferably the thermoplastic material is an ionomer resin such as that manufactured and sold by the E.I. duPont deNemours Co. under the registered trademark Surlyn. Surlyn has a published softening point of about 160.degree. F. It is to be understood that other materials having the desired thermoplastic properties may be used within the scope of the invention, and further that mixtures of the above resins may be used to achieve the desired results.

In contrast to the traditional ballet slipper which can only be broken in by considerable time and effort, the present invention allows a dancer to quickly and easily break in and customize the slipper. In contrast to the prior art plastic ballet slippers which could not be broken in at all, the present invention provides a durable ballet slipper which can be fitted comfortably to a dancer's feet, eliminating the need for costly individual molds and lasts for each dancer.

The toe box 12 has at its forward end a platform 16 which provides a flat surface for the dancer's maneuvers on pointe. A curved radius 18 joins the platform 16 to the shank 14. The curved radius 18 improves over the sharp edge which connects the platform to the shank in prior art slippers, as it allows for better control by the dancer of the speed and motion of the foot as the dancer rises from a flat footed stance to the pointe position and vice-versa. In addition, the broad curve of radius 18 makes it easier to perform steps such as hopping on pointe.

Toe box 12 is generally wedge shaped as shown in FIG. 1, so as to support the dancer's foot primarily from the top and bottom of the foot when on pointe, rather than primarily from the sides as in the uncomfortable cylindrical toe box of the traditional ballet slipper design. Preferably a groove 15 is provided in the outer surface of toe box 12 surrounding platform 16.

Shank 14 is preferably a full shank, which is sized to extend backwardly from the toe box 12 for a distance equal to the length of the dancer's foot. However, a half shank or three-quarters shank may also be utilized within the scope of the invention. Shank 14 preferably has formed in its lower surface a cavity 19 which is generally paddle-shaped and which extends forwardly to curved radius 18 as shown in FIG. 4. The stiffener can likewise be of half or three-quarter size.

A layer of resilient polymeric material 20 lines the interior of the upper portion of toe box 12. Resilient material 20 extends backwardly from the edges of the toe box 12 in area 21, as can be seen in FIGS. 2 and 3. The resilient material in area 21 provides critical cushioning for the bunion joint which supports much of the dancer's weight in the pointe position. Preferably, the resilient material 20 comprises a foam formed from a material selected from the group consisting of polyurethane, cross-linked polyethylene, a polyvinylchloride and nitrile rubber blend or EVA. Resilient material 20 is about 1/16 inch thick, and may either be molded to fit into the toe box 12, or die cut from a flat sheet of material and fitted into toe box 12. Resilient material 20 may be either glued in place, or it may be removably mounted in the toe box 12.

A first layer of shock absorbing material 22 covers the upper surface of the shank 14 and may extend to cover the interior of the toe box 12 adjacent the platform 16 and radius 18. A second layer of shock absorbing resilient material 24 covers the lower surface of the shank 14. The shock absorbing material 24 may cover the entire underside of the shank 14 or may cover only portions of the underside of the shank 14. For example, as shown in FIG. 6, the shock absorbing material 24 can be applied only to the tip, heel, and ball areas of the shank to provide cushioning and sound reduction at the critical areas while at the same time providing an aesthetically pleasing arched look to the foot. Shock absorbing material 24 extends to cover the platform 16 and curved radius 18. The shock absorbing material 24 located on the outside of the slipper provides additional cushioning for the foot and reduces noise from the impact of the slipper on a dance floor. Shock absorbing material 24 also increases the size of the curved radius 18 in the finished slipper 10, enhancing the ease of ascent and descent on pointe. Preferably, the shock absorbing materials 22 and 24 comprises a foam formed from a material selected from the group consisting of EVA, neoprene rubber or a polyurethane. Most preferably, shock absorbing materials 22 and 24 are an open-celled polyurethane foam.

A stiffener 26 may be mounted on the shank 14 to provide additional support for the dancer, as shown in FIG. 4. In the preferred embodiment, the stiffener 26 is generally paddle-shaped and is glued to the shank 14 in cavity formed in the underside of the shank 14, so that the exposed surface of the stiffener 26 is flush with the underside of the shank 14. Preferably the cavity 19 is larger in size at its forward end than stiffener 26. The stiffener 26 may be formed from a stiffer grade of the same material which forms the integral toe box 12 and shank 14, and is preferably formed from an ionomer resin, EVA, or polyurethane.

An outer covering 28, as shown in FIGS. 5 and 6, is made from a silk, satin or canvas material and encloses the shank 14 and toe box 12. The outer covering 28 fits snugly over the shank 14 and toe box 12. An elasticized throat 30 holds the slipper to the dancer's foot. Elasticized throat 30 may be a single loop of elastic material or may be an elastic drawstring. If an elastic drawstring such as shown in FIG. 5 is selected, the free ends of the drawstring are preferably located at or near the rear end of the slipper, instead of near the front as in the traditional slipper design, to reduce the painful digging of laces into the foot when the laces are tucked into the slipper as required by aesthetics and custom.

Outer covering 28 has sewn into it a panel 32 made from a durable non-slip material, preferably canvas, which covers the platform 16 and curved radius 18 of the toe box 12. Panel 32 obviates the problems of a bare plastic toe platform found in the prior art molded plastic slippers which can induce slips and falls. Panel 32 also eliminates the need to darn the tips of the slippers as is done with traditional satin-covered slipper designs. The stitching and excess fabric joining panel 34 to outer covering 28 on the upper portion of the slipper 10 fits into groove 15 to eliminate an undesirable ridge in the outer appearance of the finished slipper. Similarly, the stitching and excess fabric joining panel 34 to outer covering 28 on the lower portions of slipper 10 fits into cavity 19 surrounding stiffener 26 to provide a smooth lower surface for attaching an outer sole 36. To insure a snug fit, the outer covering 28 preferably has at least one elasticized panel 34 to hold the outer covering 28 onto the dancer's foot, the toe box 12 and shank 14. Preferably the elasticized panel 34 is located along at least one side of the slipper 10; most preferably there are two such panels 34.

Outer sole 36 is formed from a flexible shock absorbing material, preferably an EVA foam, and is secured to the outer covering 28 adjacent to the underside of the shank 14 by gluing or sewing. The outer sole 36 provides an additional cushioning layer to increase comfort and reduce noise during a performance.

A method of manufacturing a ballet slipper in accordance with the foregoing description comprises the steps of molding an integral shank and toe box from a thermoplastic polymeric material, the toe box having a platform at one toe end and a curved radius connecting the platform with the shank; lining the interior of the upper portion of the toe box with a soft resilient material sized to extend backwardly from the edges of the toe box; and attaching a shock absorbing material to the upper and lower surfaces of the shank, and the outer and inner surfaces of the curved radius and platform. Preferably, the molding of the toe box and shank is accomplished by injection molding. An additional step which may be performed to increase the rigidity of the shank is the step of mounting a stiffener on the shank. The slipper is finished by the fitting of an outer covering having a panel formed from a durable non-slip material for covering the platform and curved radius over the toe box and shank; and securing an outer sole formed from a shock absorbing material to the outer covering adjacent to the underside of said shank.

The present invention provides a durable and comfortable ballet slipper designed to be adjusted by the dancer to conform to the dancer's feet, and provides a slipper which greatly reduces the noise caused by the various aerial ballet maneuvers called for by both traditional and modern choreography, and which provides an ease in rising up to and descending from pointe not available in prior art designs.