Boots – shoes – and leggings – Toe caps and tips
Reexamination Certificate
2000-02-18
2002-05-21
Kavanaugh, Ted (Department: 3728)
Boots, shoes, and leggings
Toe caps and tips
C036S07200R
Reexamination Certificate
active
06389715
ABSTRACT:
FIELD OF THE INVENTION
This invention is concerned with improvements in or relating to toe box and/or metatarsal protectors as used in safety footwear, namely boots and shoes that are worn in locations where there is danger of impact or compression forces being applied to and injuring the feet of the wearers.
BACKGROUND OF THE INVENTION
Many industries now require that at all times workers wear safety footwear to protect their feet against injury caused, for example, by blows from falling objects, or crushing such as may be caused by a vehicle wheel rolling over the foot. Almost all safety footwear currently available comprise a toe protector, usually of steel, alternatively called a box toe or a toe box, providing a protective arch above the toes through which any compression or impact force applied to its top surface is transmitted to the insole on which it rests, and through the insole to the outsole and the ground. It is a requirement for official certification (more details of which are given below) that the toe box is incorporated into the footwear during its manufacture so as to be an integral part thereof. Also, provision is now commonly made to protect the metatarsus, namely the five long bones of the instep extending from the toes to the remainder of the bones of the foot. Many of the prior proposals for metatarsal protection comprise a guard that is applied to the exterior of the boot, but increasingly the protector is incorporated into the footwear as an integral part, it also being arranged so that forces applied to it are transmitted through the insole and outsole to the ground.
The Occupational Health & Safety Association (OHSA) specifies test and performance standards that have been established by American National Standards Inc. (ANSI) which safety footwear must pass if they are to be certified by them. The current standards are identified as ANSI 241/1999. The Canadian Standards Association (CSA) have adopted equivalent standards. In commercial practice these standards are sufficiently important that a safety boot is virtually unsalable unless it is entitled to and carries at least the minimum standard designation, i.e. I30 for toe impact force. Preferably, it is also certified as to its resistance to compression, the minimum designation being C30 for toe compression force, although for many jurisdictions and industries such certification is not a requirement. If a metatarsal protector is included then preferably it will at least meet the minimum standard of Mt30 for metatarsal impact force. The maximum standards available using the ANSI system are designated C75 and I75, with or without Mt75; there are also intermediate standards C50 and I50, with or without Mt50. The tests required and the standards indicated by these designations are explained below.
In the compression force test procedure for the toe box protector (there is no equivalent test procedure for a metatarsal protector) it is subjected to a crushing force using any standard compression testing apparatus that is applied at a rate of approximately 22.7 Kg per second (50 lbs; 222.4 Newtons) after an initial load of 227 Kg (500 lbs; 2224 Newtons) has first been applied. The vamp and upper of the test boot is cut away to allow insertion of a cylindrical steel test gauge into the toe box interior, the gauge being slid back and forth on the insole as the pressure is increased. The diameter of the gauge is 12.7 mm ({fraction (16/32)} in) for men's footwear and 11.9 mm ({fraction (15/32)} in) for women's footwear, and the compression resistance of the specimen is the compressive load that reduces the internal clearance in the toe box until movement of the gauge either forward or backward is first prevented. The three certifications available are designated C/30 or C/50 or C/75 and indicate respectively that the footwear will withstand a compression force of 455 Kg (1,000 lbs; 4,448 Newtons), or 795 Kg (1,750 lbs; 7,784 Newtons), or 1,134 Kg (2,500 lbs; 11,121 Newtons).
The test procedure for toe box impact force resistance involves dropping a standard weight of 22.7 Kg (50 pounds)with a cylindrical impact nose of 51mm (2 ins) length and 25.4 mm (1 in) diameter on to the toe portion of a specimen boot (size 9D for men's footwear and 8B for women's footwear) selected at random from stock after at least 14 days have elapsed from the time of completion of its manufacture. The impact occurs at a point at the approximate centre of the toe box and 13 mm (0.5 in)in front of its back edge, the weight being dropped from a height such that it exerts an impact force of the selected one of the three values, namely 40.7 Joules (30 foot pounds), or 67.8 Joules (50 foot pounds), or 101.7 Joules (75 foot pounds). The maximum downward compression suffered by the toe box during the impact, and the corresponding minimum internal clearance available to the wearer's toes, is measured by a cylindrical lump of modelling clay or wax placed inside the box under the impact zone, the lump not exceeding 25.4 mm (1 in) in diameter and being shaped to extend between and make contact with the dome of the toe box and with the insole. After impact the cylinder is removed and its height measured at its lowest point to the nearest 0.794 mm ({fraction (1/32)} in). The required minimum internal clearance in the toe box interior during and after impact, as indicated by measurement of the compressed lump, is 12.7 mm ({fraction (16/32)} in) for men's footwear and 11.9 mm ({fraction (15/32)} in) for women's footwear. The footwear is certified according to the standard reached, and can be labelled with the designation I/30, I/50 or I/75 respectively.
The equivalent impact force test for a metatarsal protector employs similar equipment to that used to test the toe box, with the difference that the impactor at the bottom of the weight is a cylindrical bar extending transversely of the length of the boot. The test again requires an impact force of specified value, and this force is applied at a point 8.9 cm (3.5 in) from the outside tip of the 9D boot toe and 8.6 cm (3.375 in) for the 8B boot. A wax body of specified shape and composition is held in place within the boot beneath the impact zone, the required minimum internal clearance beneath the protector after the impact, as indicated by the height of the deformed body being 2.5 cm ({fraction (32/32)} in) for the male 9D boot and 2.4 cm ({fraction (30/16)} in) for the female 8B boot. The impact forces employed are again of nominal value 30 foot pounds (40.7 Joules), or 50 foot pounds (67.8 Joules), or 75 foot pounds (101.7 Joules), footwear that passes the respective test being certified with the designation Mt/30, Mt/50 or Mt/75 respectively.
Box toes of plastics materials are available, but they are significantly thicker than the commonly used steel box toe, so that it is more difficult to incorporate them into the boot construction without the resultant boot toe appearing much more bulky, especially in side elevation. Moreover, most safety footwear is manufactured by molding the outsole to the remainder of the boot and a box toe that is significantly thicker makes it impossible to use existing molds used with steel box toes, so that expensive new molds are required for each size of boot. Metatarsal protectors of plastics material, e.g. high density polyethylene or polypropylene (HDPE or HDPP), ABS and various proprietary nylons, are also available and again, if the above described impact standards are to be met the protector is such thickness that, even if the more expensive high modulus plastics materials are used, it is difficult to incorporate in safety footwear of standard sizes. The manufacture of both box toes and metatarsal protectors from plastics material has the advantage that even if of complex shape they can be molded in a single relatively inexpensive operation. There is also the possibility that protectors that are lighter in weight can also be produced. Manufacturers of safety footwear face an inherent marketing problem that whether the footwea
Kavanaugh Ted
Rogers Stanley J.
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