Apparel – Guard or protector – For wearer's head
Reexamination Certificate
1999-07-14
2001-11-20
Neas, Michael A. (Department: 3741)
Apparel
Guard or protector
For wearer's head
C002S412000, C002S416000
Reexamination Certificate
active
06317895
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to safety helmets, and particularly, to safety helmet assemblies providing protection against top impacts, lateral impacts and penetrating impacts.
BACKGROUND OF THE INVENTION
Many types of protective headgear or safety helmets are worn by individuals to protect against head injuries. For example, safety helmets providing protection from top impacts, lateral impacts and/or penetrating impacts typically include a rigid outer shell, a shock absorbing layer within the outer shell and a suspension system. An example of such a safety helmet is the SUPER V safety helmet available from Mine Safety Appliances Company of Pittsburgh, Pennsylvania. In such safety helmets, the outer shell, the shock absorbing layer, along with the suspension act to absorb the shock of any impact to the safety helmet.
Safety helmets providing protection from top impacts, lateral impacts and penetrating impacts are subjected to stringent testing requirements. Those safety helmets are tested under Impact Standard ANSI Z89.1-1997 in the United States and under CSA Z94.1-1992 in Canada. Under CSA Z94.1-1992, for example, safety helmets are subjected to a rigorous penetration test in which a heavily weighted, pointed projectile is accelerated to impact the helmet. To satisfy such penetration tests, manufacturers of safety helmets fabricate the outer shell of the safety helmet from a relatively thick layer of a high impact strength material. The thicker the layer, the heavier the helmet, which makes the helmet uncomfortable for the user to wear. This discomfort can result in fatigue and/or a reluctance to use the safety helmet, either of which can result in safety lapses. Furthermore, use of a relatively thick layer of a very high impact strength material results in substantial manufacturing expense.
It is very desirable, therefore, to develop a safety helmet that provides top impact protection, side impact protection and penetration protection that is lightweight and comfortable to wear, as well low cost and simple to manufacture.
SUMMARY OF THE INVENTION
Generally, the present invention provides a safety helmet assembly comprising:
(a) a rigid outer shell;
(b) a shock absorbing layer inside of the outer shell; and
(c) a shield layer positioned between the outer shell and the shock absorbing layer.
The shield layer assists in preventing an object that penetrates the outer shell from contacting the user's head. The shield layer is thus preferably fabricated from a relatively strong material that is also lightweight and inexpensive. In that regard, the shield layer is preferably fabricated from a polymeric material having a notched impact strength greater than 0.5 ft.lb./in. The polymeric material also preferably has a modulus in the range of approximately 150,000 to approximately 700,000 psi. Polymeric materials used in the present invention, when amorphous, preferably have a glass transition temperature (T
g
) of at least approximately 125° C. Semicrystalline or crystalline polymeric materials preferably have a crystalline melting point of at least approximately 95° C.
To minimize the size, weight and cost of the safety helmet assembly, the thickness of the shield layer is preferably minimized, particularly when using polymeric materials as described above. The thickness of the shield layer is preferably in the range of approximately 0.015 to approximately 0.040 in. More preferably, the thickness of the shield layer is preferably in the range of approximately 0.025 to approximately 0.035 in. In general, the stronger/more impact resistant the material used in fabricating the shield layer, the thinner the shield layer can be. Regardless of modulus, impact strength and thickness, an appropriate material for the shield layer and the thickness thereof is readily and easily determined using a known standard such as provided in CSA Z94.1-1992.
Similarly, the cost and manufacturability of the material are preferably taken into account since there are many strong, lightweight materials which are simply too expensive for use in a helmet or cannot be manufactured easily in a helmet.
Preferably, the shield layer is free to move relative to the outer shell in a direction toward the shock absorbing layer. It is believed that forcing the shield layer into the shock absorbing layer upon penetration of the outer shell absorbs some of the energy of the penetrating object and limits the extent of penetration.
The present inventors have discovered that placement of a relatively thin shield layer between the outer shell and shock absorbing layer of a safety helmet assembly greatly increases the penetration resistance of the safety helmet assembly. The incorporation of such a shield layer eliminates the need to fabricate the outer shell of the helmet from a thick layer of a relatively high strength material. The weight, size and cost of safety helmet assemblies can be reduced with the use of the shield layer of the present invention.
REFERENCES:
patent: 3616463 (1971-11-01), Theodore et al.
patent: 3946441 (1976-03-01), Johnson
patent: 4656667 (1987-04-01), Blake
patent: 5517691 (1996-05-01), Blake
patent: 5669079 (1997-09-01), Morgan
patent: 5898949 (1999-05-01), Barthold et al.
patent: 5956777 (1999-09-01), Popovich
patent: 6032297 (2000-03-01), Barthold et al.
Erth Richard A.
Wise Layton A.
Bartony, Jr. Henry E.
Mine Safety Appliances Company
Neas Michael A.
Ulber James G.
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