US3805419A

US3805419A - Safety footwear and manufacture thereof

Info

Publication number: US3805419A
Application number: US00360210A
Authority: US
Inventors: J White
Original assignee: Uniroyal Inc
Current assignee: UNIROYAL HOLDING Inc WORLD HEADQUARTERS MIDDLEBURY CONNECTICUT 06749 A CORP OF NEW JERSEY
Priority date: 1973-05-14
Filing date: 1973-05-14
Publication date: 1974-04-23
Anticipated expiration: 1991-04-23
Also published as: ATA394474A; AT353651B; CA992309A

Abstract

Disclosed are an article of safety footwear, a method of making the same, and a safety toe cap assembly adapted to be used in making such footwear. The article of safety footwear has a rigid, crush-resistant toe cap located in its toe region and having its outer surface bonded to the interior of the upper of the footwear article, a cushioning layer of resilient, compressible cellular (open-celled or closed cell or having both open and closed cells) cures elastomeric polymeric material, typically formed of opencelled cured cellular polyurethane, covering and being bonded to the inner surface of the toe cap, and a lining of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of the cushioning layer. The method of the invention is particularly characterized by the fact that it enables safety footwear to be manufactured at high production rates in marked contrast to conventional methods of making safety type footwear in which many hand fitting operations are normally involved.

Description

United States Patent 1191 White 1451 Apr. 23, 1974 SAFETY FOOTWEAR AND MANUFACTURE THEREOF Primary ExaminerAlfred R. Guest Attorney, Agent, or FirmRobert .1. Patterson [5 7] ABSTRACT Disclosed are an article of safety footwear, a method of making the same, and a safety toe cap assembly adapted to be used in making such footwear. The article of safety footwear has a rigid, crush-resistant toe cap located in its toe region and having its outer surface bonded to the interior of the upper of the foot-.

wear article, a cushioning layer of resilient, compressible cellular (open-celled or closed cell or having both open and closed cells) cures elastomeric polymeric material, typically formed of open-celled cured cellular polyurethane, covering and being bonded to the inner surface of the toe cap, and a lining of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of the cushioning layer. The method of the invention is particularly characterized by the fact that it enables safety footwear to be manufactured at high production rates in marked contrast to conventional methods of making safety type footwear in which many hand fitting operations are normally involved.

12 Claims, 6 Drawing Figures SAFETY FOOTWEAR AND MANUFACTURE THEREOF BACKGROUND OF THE INVENTION United States Patents Baird, U.S. Pat. No. 2,328,601, Sept. 7, 1943; Heckman, U.S. Pat. No. 2,426,211, Aug. 26, 1947; Shultz, U.S. Pat. No. 2,795,868, June 18, 1957; Hunting et al., U.S. Pat. No. 3,034,235, May 15, 1962;Rollman, U.S. Pat. No. 3,165,841,.Ian 19, 1965.

Foreign Patents British, 722,803, (Dunlop), Feb. 2, 1955; French,

1,193,781, (Hutchinson), May 4, 1959; French, 1,260,816 (Latchere), Apr. 14, 1961; French, 1,280,701, (Kleber-Colombes), Nov.'2l, 1961. The foregoing patents, which are believed to be representative of the state of the prior art, generally show safety shoes embodying metal toe caps incorporated in the toe area of the shoe. Some of them, such as Baird and Kleber-Colombes, show cushioning elements of sponge rubber on the inside of the metal toe cap. It is fair to say that prior art practice embodied a toe cap construction fabricated in situ using hand lay-up fabrication techniques designed to lock the toe cap into the article of footwear and involving many hand fitting operations. So far as the present inventor is aware, none has heretofore suggested a safety shoe fabrication technique like that disclosed herein which makes it possible to manufacture footwear having a safety toe cap of metal or other rigid, crush-resistant material, a cushioning layer on the interior of the cap which provides comfort and thermal insulation, and a lining of smooth slippery fabric which provides protection against chafing of the foot and facilitates donning and doffing and protects the cushioning layer agains abrasion, wear and other adverse influences, with a minimum of separate hand operations and in a manner adapting itself to high production rates.

SUMMARY OF THE INVENTION The invention has three principal aspects, namely a method of making safety footwear, a safety toe cap and lining assembly as an intermediate article of manufacture, and the resulting safety footwear.

In its method aspects, the invention broadly comprises inserting into contact and conformity with the toe region of the upper of an article of footwear a separately prepared safety toe cap and lining assembly comprising a rigid, crush-resistant toe cap, a cushioning layer of resilient, compressible cellular cured elastomeric polymeric material, typically open-celled cured polyurethane, covering and being bonded to the inner surface of the metal toe cap, as by means of a solvent based thermoplastic polyurethane adhesive of the type described more fully below, and a liner of stretchable fabric having a low coefficient of friction (so as to facilitate donning and doffing and prevent chafing of the toes) covering and being bonded in any suitable manner to the inner surface of the cushioning layer. The separately prepared safety toe cap and lining assembly is caused to be adhered to the inner portion of the toe of the article of footwear by means of an adhesive layer provided on the outside of rigid crush-resistant toe cap. Preferably this adhesive layer is formed on the outside of the toe cap prior to insertion of the toe cap and lining assembly into position in the toe of the footwear and is laid down from a solvent-based thermoplastic polyurethane adhesive, the adhesive layer being allowed to dry to the point where it becomes extremely tacky but is no longer really wet. Upon insertion of the resulting assembly firmly into the toe of the boot or other footwear article, the assembly becomes permanently bonded in position. Such bonding is facilitated by having the footwear article heated to an elevated temperature prior to insertion of the toe cap and lining assembly.

The safety toe cap and lining assembly of the invention is an intermediate article of manufacture adapted to be incorporated in an article of footwear during manufacture thereof by simply inserting it into the toe of the footwear article under appropriate conditions causing permanentbonding of the outer surface of the rigid, crush-resistant toe cap to the inner surface of the toe portion. This assembly comprises a rigid toe cap, a coating of activatable adhesive, preferably deposited from a solvent-based thermoplastic polyurethane adhe sive composition, on the outer surface of the cap, a cushioning layer of resilient, compressible cellular cured polymeric material, especially open-celled polyurethane, covering and being bonded to the inner surface of the toe cap, and a liner of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of the cushioning layer.

The construction of the safety footwear made according to the invention will be obvious from the descriptions herein of the method and of the toe cap and lining assembly.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: FIG. I is a vertical section of an article .of footwear made in accordance with the present invention;

FIG. 2 is a perspective view of a rigid crush-resistant toe cap of the type used in the practice of the invention. Toe caps of this type are well-known articles of com- .merce in the footwear industry;

FIG. 3 is a sectional view of the toe cap after having been provided on both sides with a layer of adhesive;

FIG. 6 is a perspective view of the complete toe-cap sub-assembly ready for insertion into the toe portion of the article of footwear.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The toe cap construction of the present invention is adaptable to provide toe protection for any kind of footwear whether it be a high boot, a boot of intermediate height or a low cut shoe such as an oxford. The toe cap comprises a rigid, crush-resistant toe cap provided with a lining consisting of a laminate of soft, resilient, compressible cellular elastomeric polymeric layer bonded to the toe cap and a stretchable fabric which is smooth in texture and has a low coefficient of friction bonded to the inner face of the cellular elastomeric cushioning layer in any suitable manner. The laminate of cellular elastomeric polymeric material and stretchable fabric is adhered to the inside of a toe cap, which typically is made of steel, in such a way that the smooth stretchable fabric on one side of the foam is exposed to the foot. This adhesion is typically achieved by means of a layer of solvent-based thermoplastic adhesive applied to the interior of the toe cap and allowed to dry by evaporation of solvent to a very tacky condition prior to application of the laminate. The outside surface of the toe cap is also provided with a layer of dried solvent-based thermoplastic adhesive preferably in the same operation as that wherein the inside adhesive layer is formed on the toe cap.

The toe-cap lining sub-assembly is placed directly into an otherwise finished footwear article under conditions such that adhesion of the exterior of the toe cap to the interior of the upper of the toe portion of the footwear is achieved by reason of the adhesive layer on the outside of the toe cap. The smooth interior fabric is preferably a nylon tricot of well-known type in the textile industry. It provides protection against chafing of the foot and also facilitates donning and doffing. The cellular elastomeric layer provides excellent cushioning and thermal insulation. I

In one embodiment, the present invention is utilized in conjunction with a slush cast polyvinyl chloride (PVC) footwear process wherein the finally fused article of footwear is made in a footwear-shaped mold in accordance with the well-known slush casting or molding procedure such as is described for example in U.S. patent to Streed et al. U.S. Pat. No. 2,974,373 dated Mar. 14, 1961. In this embodiment a plastisol is slush cast in a footwear-shaped mold, the mold is heated to fuse the plastisol in the mold and convert it to solid form, and the hot footwear article is then stripped from the hot mold. The safety toe cap and lining assembly is separately fabricated by applying a coating of a solventbased thermoplastic adhesive to both the inner and the outer faces thereof as by immersion in the solventadhesive solution removing the toe cap from the adhesive solution, allowing the layers of adhesive to dry by evaporation of solvent until they are very tacky and no longer truly wet, covering the inner face of the toe cap with a lining in the form of a laminate comprising the aforementioned cushioning layer of cellular cured elastomeric polymeric material and a liner of the stretchable fabric covering bonded to the inner surface of the cushioning layer, with the other surface of the cushioning layer in contact with the adhesive layer on the inner face of the toe cap, thereby causing bonding of the laminate to the toe cap as a result of tackiness of the adhesive on the inside of the toe cap, and then inserting the resulting toe cap and lining assembly into the toe region of the hot footwear article stripped from the hot mold and causing bonding of the toe cap and lining assembly to the footwear article as a result of tackiness of the adhesive on. the outer surface of the toe cap. Where available, residual heat in the footwear article may be used to expedite the bonding of the toe cap to the footwear article.

Now referring to the accompanying drawings, a toe cap 1, such as a steel toe cap of the type available commercially, as shown in FIG. 2 is employed. Toe cap 1 is coated on both sides with an adhesive layer, as by dipping the toe cap in a container of solvent-based thermoplastic adhesive such as a thermoplastic polyurethane, for example any of many such adhesives available on the market. The resulting toe cap is shown in FIG. 3 as having a coating 2 of adhesive on the outside and a coating 3 of adhesive on its inner face. This coated toe cap is allowed to partially dry to a tacky state and is then employed in both the assembly of the toe cap and liner assembly and in the fabrication of the finished article of footwear.

A laminate of the cured cellular cushioning material and the nylon tricot fabric bonded together in any suitable manner, for example with an adhesive, and of a type commonly available commercially, is die cut to form a piece 4 (FIGS. 4 and 5) of the proper shape to conform to the inside of toe cap 1. Notch 4a is provided in die cut piece 4 in order to obtain perfect conformity of piece 4 with toe cap 1. Piece 4 is shown as having a cushioning foam layer 5 faced with nylon tricot liner 6. The die cut laminate piece 4 is then inserted into the adhesively coatedtoe cap of FIG. 3 with the result that the piece 4 is firmly bonded to the inside of metal toe cap 1 as a result of the tacky adhesive layer 3. The result of this operation is the finished toe cap and lining assembly 7 shown in FIG. 6.

The toe cap assembly 7 having the tacky outer adhesive layer 2 is then inserted firmly into the toe portion of the still hot footwear article 8. The residualheat in the footwear article and the heat conducted into the metal toe cap 1 of the assembly from the footwear article combine to activate both adhesive coatings 2 and 3 and cause firm adhesion of the toe cap and lining assembly 7 in permanent position in the article of footwear after the entire assembly is allowed to cool. The result is the article of footwear 9 portrayed in FIG. 1.

The greatest advantage of the present invention is the manner in which it achieves the protective toe cap construction in the footwear article. The invention involves the complete pre-assembly of the toe cap and lining assembly externally with respect to the production of the article of footwear itself. As a matter of fact, fabrication of the articles of footwear and of the toe cap and lining assemblies would typically proceed simultaneously in mass production manufacture in accordance with the invention.

The technique of external prefabrication of the toe cap and lining assembly in accordance with the present invention greatly simplifies the manufacture of safety toe footwear by significantly reducing the number of steps and complexity of assembly normally required in conventional methods of making safety footwear. ln addition, in practicing the present invention the toe cap is not encased within plies of fabric and/or rubbers as in all other commercially used safety toe footwear constructions that the present inventor has seen. It is understood that the reason for this is that nonencapsulated constructions have not performed satisfactorily prior to the present invention. As a-matter of fact design experts associated with the present inventor did not feel that the mode of construction of the instant invention would be successful. However the performance of applicants technique and of the resulting footwear has been exceedingly satsifactory to the great surprise of all concerned.

It is believed that the present invention is the first that accomplishes insertion of a complete toe cap and lining assembly into an essentially finished footwear article of any type such as for example a molded footwear article or a machine-made shoe, in a manner that is so GENERAL The invention is not limited to the use of metal toe caps but is applicable with toe caps made of any other suitable material which provides the necessary crushresistance and impact-resistance. Examples of other types of toe caps which can be used arethose made from hard rubber, rigid ABS (acrylonitrile-butadienestyrene) resins, rigid PVC, glass fiber-reinforced polyester resins, and vulcanized fiber.

The invention is not limited to slush cast footwear but can be applied with any other type of footwear such as injected PVC footwear, compression-molded rubber footwear or conventionally made footwear.

The cushioning layer 4 can be made of any suitable cellular polymeric material which provides the necessary give and comfort to the wearer. While an opencelled material can be used, a closed cell material can be used. Cellular material having both an open-celled (intercommunicating cells) and a closed cell (notintercommunicating cells) structure can also be used. Layer 4 can be sponge rubber, if desired.

Laminates of cushioning cellular material 5 and lining fabric 6 suitable for use in the practice of the invention are available on the market. The fabric lining layer and the cellular layer of such laminates are bonded together in a manner known to the art. Instead of using a preformed laminate, in the practice ofthe invention fabric could be bonded to cellular polymeric material by use of a suitable adhesive, for example.

The polyurethane foam preferably used for cushioning layer 5 has a compression-deflection value of about 1.4 pounds per square inch at 25 percent deflection; a density of approximately 4 pounds per cubic foot, and a thickness of from one thirty-second to three thirtyseconds of an inch.

The preferred adhesive employed for forming adhesive layers 3 and 2, respectively bonding the cushioning layer 5 to the interior of the toe cap 1 and the toe cap to the interior of the toe portion of the footwear article, is a thermoplastic polyurethane polymer, for example Estane 5713 (trademark) available from the HF. Goodrich Company, dissolved in a solvent consisting of tetrahydrofuran and methyl ethyl ketone in suitable relative proportions. The total solids content of the resulting adhesive solution can vary widely but for dipping application preferably is approximately 25 percent by weight.

The invention is not limited to use of solvent-based thermoplastic adhesives for achieving bonding of the cushioning layer 5 to the toe cap 1 and bonding of the toe cap 1 to the interior of the upper of the footwear article 8, although such adhesives are most highly preferred. Any other suitable type of adhesive could be used in the practice of the invention, for example hot molten adhesive although their use would introduce certain complications.

Instead of using an immersion technique for applying adhesion layers 2 and 3 to the toe cap 1, other methods of application such as brushing, spraying, fluidized coating, etc., can be employed.

If desired, especially where a metal toe cap 1 is used, the toe cap could be pre-heated prior to application of adhesive layers 2 and 3 thereto and the residual heat in the toe cap 1 after such application could be utilized to expedite bonding of cushioning layer 5 of laminate 4 thereto and residual heat in toe cap 1' after such bonding could be utilized to expedite bonding of the toe cap to the inside face of the upper of the toe portion of the footwear article. However, such pre-heating of toe cap 1 is not required to get good adhesion on both sides thereof when a solvent-activated adhesive is used as described above.

It is preferred to carry out the present invention in such a way that the toe cap and lining is inserted in the footwear article while the latter is at an elevated temperature of say from l25 to 225F. If the footwear article is at. room temperature after manufacture, it is preferred to pre-heat it so that it is at a temperature of l25-225F. when the sub-assembly of toe cap and lining is inserted therein.

The insertion of toe cap assembly 7 into the toe portion of the footwear article 8 can be performed either manually or by machinery. Methods of effecting placement of assembly 7 in the toe portion will be readily apparent to those skilled in the art.

While the foregoing describes the preferred embodiments of the instant invention, it will be understood by those skilled in the art that many variations can be made therein without departing from the invention and the spirit thereof. For example bonding of the toe cap to the upper of the footwear article can be carried out other than by conducting heat derived from the residual heat in the footwear article in the particular manner described above. For example a metal toe cap and lining assembly 7 could be inserted into the toe of the footwear article after which heating of the metal toe cap could be carried out by induction heating or by microwave means to achieve bonding to the upper of the toe of the footwear. Less desirably a heater could be inserted within the subassembly 7 after insertion of the latter into the boot. Similarly, alternate means of bonding the toe cap 1 to the foam side of die-cut laminate piece 4 could be employed. Numerous other modifications and changes which can be made without departing from the spirit of the invention will be obvious to those skilled in the art.

I claim:

1. As an article of manufacture, a safety toe cap and lining assembly adapted to be incorporated in an aticle of footwear during manufacture thereof, said assembly comprising a rigid toe cap, a coating of adhesive on the outer surface of said cap, a cushioning layer of cellular cured elastomeric polymeric material covering and being bonded to the inner surface of said toe cap. and a liner of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of said cushioning layer.

2. An article of manufacture as set forth in claim 1 wherein said cellular cured elastomeric polymeric material is a polyurethane.

3. An article of manufacture as set forth in claim 2 wherein said adhesive is a solvent-based thermoplastic polyurethane.

4. An article of manufacture as set forth in claim 1 wherein said stretchable fabric is a nylon tricot.

5. An article of safety footwear comprising a footwear article, a rigid toe cap located in the toe region of said footwear article and having its outer surface bonded to the interior of the upper of said footwear article in the toe region thereof, a cushioning layer of cellular cured elastomeric polymeric material covering and being bonded to the inner surface of said toe cap, and a liner of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of said cushioning layer.

6. An article of safety footwear as set forth in claim 5 wherein said cellular cured elastomeric polymeric material is a polyurethane.

7. An article of safety footwear as set forth in claim 6 wherein said toe cap is bonded to the interior of said upper by a thermoplastic polyurethane adhesive and wherein said cushioning layer is bonded to the inner surface of said toe cap by a thermoplastic polyurethane adhesive.

8. An article of safety footwear as set forth in claim 5 wherein said stretchable fabric is a nylon tricot.

9. An article of safety footwear comprising a slush cast footwear article made of a fused plastisol, a rigid toe cap located in the toe regionof said footwear article and having its outer surface bonded to the interior of the upper of said footwear article in the toe region thereof, a cushioning layer of cellular cured elastomeric polymeric material covering and being bonded to the inner surface of said toe cap, and a liner of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of said cushioning layer.

10. An article of safety footwear as set forth in claim 9 wherein said cellular cured elastomeric polymeric material is a polyurethane.

l 1. An article of safety footwear as set forth in claim 10 wherein said toe cap is bonded to the interior of said upper by a thermoplastic polyurethane adhesive and wherein said cushioning layer is bonded to the inner surface of said toe cap by a thermoplastic polyurethane adhesive.

12. An article of safety footwear as set forth in claim 9 wherein said stretchable fabric is a nylon tricot.

Claims

2. An article of manufacture as set forth in claim 1 wherein said cellular cured elastomeric polymeric material is a polyurethane.
3. An article of manufacture as set forth in claim 2 wherein said adhesive is a solvent-based thermoplastic polyurethane.
4. An article of manufacture as set forth in claim 1 wherein said stretchable fabric is a nylon tricot.
5. An article of safety footwear comprising a footwear article, a rigid toe cap located in the toe region of said footwear article and having its outer surface bonded to the interior of the upper of said footwear article in the toe region thereof, a cushioning layer of cellular cured elastomeric polymeric material covering and being bonded to the inner surface of said toe cap, and a liner of stretchable fabric having a low coefficient of friction covering and being bonded to the inner surface of said cushioning layer.
6. An article of safety footwear as set forth in claim 5 wherein said cellular cured elastomeric polymeric material is a polyurethane.
7. An article of safety footwear as set forth in claim 6 wherein said toe cap is bonded to the interior of said upper by a thermoplastic polyurethane adhesive and wherein said cushioning layer is bonded to the inner surface of said toe cap by a thermoplastic polyurethane adhesive.
8. An article of safety footwear as set forth in claim 5 wherein said stretchable fabric is a nylon tricot.
9. An article of safety footwear comprising a slush cast footwear article made of a fused plastisol, a rigid toe cap located in the toe regionof said footwear article and having its outer surface bonded to the interior of the upper of said footwear article in the toe region thereof, a cushioning layer of cellular cured elastomeric polymeric material covering and being bonded to the inner surface of said toe cap, and a liner of stretchable fabric having a low coefficient of friction covEring and being bonded to the inner surface of said cushioning layer.
10. An article of safety footwear as set forth in claim 9 wherein said cellular cured elastomeric polymeric material is a polyurethane.
11. An article of safety footwear as set forth in claim 10 wherein said toe cap is bonded to the interior of said upper by a thermoplastic polyurethane adhesive and wherein said cushioning layer is bonded to the inner surface of said toe cap by a thermoplastic polyurethane adhesive.
12. An article of safety footwear as set forth in claim 9 wherein said stretchable fabric is a nylon tricot.