Cutlery – Cutting tools – Plural cooperating blades
Reexamination Certificate
2001-02-26
2002-04-30
Watts, Douglas D. (Department: 3724)
Cutlery
Cutting tools
Plural cooperating blades
C030S350000
Reexamination Certificate
active
06378215
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a hand operated device for severing heavy duty electrical conductor(s) carrying potentially lethal voltage/current with safety to the operator, the device and the environment. Use of this invention in cutting such electrical conductor(s) protects the operator from electric shock, protects the cutting device from melt/weld damage and minimizes the potential for spark or flame production and hence for ignition of explosive or flammable ambient environmental hazards such as natural gas, propane, methane and gasoline fumes. Further, use of this invention in cutting high voltage/current conductors minimizes the risk of ignition of low flammability materials associated with an ambient high oxygen environment.
Previous art designed for severing heavy duty high voltage/current conductors have used iron or steel alloy cutter blades or surfaces. Typically, other structural elements of such devices of previous art, most specifically handles and fulcra mechanisms, are stamped or forged from iron or steel alloy as well. Thus, all essential structural components of such tools may be electrically conductive. Attempts to minimize electric shock hazard to the operator using such metalic tools have taken two forms. The first has been to electrically insulate the handles of such cutting devices with coatings or sleeves of high resistance materials such as rubber or plastic. Second, and rarely, the handles of such devices have been fabricated from a structurally rigid and electrically resistive material such as fiberglass. Fiberglass, if well maintained and free of conductive contaminants such as grease and oil, provides excellent operator protection from electric shock. Cutting device handles insulated with rubber or plastic coatings or sleeves are very difficult to maintain and represent a potential hazard to the operator. Damage to the insulating materials due to workplace abuse such as cuts and abrasions may sometimes be visually detected before operator injury occurs. However, such insulative materials are subject to degradation through contact with chemical solvents in the workplace and to cracking and micropores due to ultraviolet and ozone exposure. Such degradation is usually not visually detectable and thus may constitute an unknown and potentially lethal hazard to the operator.
Aside from issues of operator safety regarding the quality of cutting tool handle insulation, the use of tools with metalic cutting blades or surfaces poses another, and potentially greater, hazard. In emergencies resulting from fires, floods, hurricanes/tornados and earthquakes high voltage/current power lines, service trunks and feeder legs must often be severed to terminate electrical power to damaged structures. Such cutting is required because of electrocution hazard and often appropriate breakers or switches cannot be located or accessed. Concurrently, such natural or man made disasters often rupture natural and propane gas service lines and may damage storage tanks for gasoline and other flammable or explosive chemicals. Such damage may result in ambient concentrations or pockets of potentially explosive gases or vapors which are easily ignited by sparks or flame. If electrical power lines are severed in such flammable environments, metalic bladed/surfaced cutting devices may ignite them.
A single high voltage/current conductor may be safely severed with a conventional metalic cutting blade, of previous art, if (a) appropriate intact insulation protects the operator from electrical ground potential and (b) the metalic aspects of the cutting device do not themselves contact ground potential while in contact with the conductor to be cut. Provision (a) protects the operator from electric shock and provision (b) assures that no spark or flame will occur by ground potential contact through the cutting device. Most commercial service lines do not have common buss grounding and such lines are composed of multiple, individually insulated, conductor packages of both high and low electromotive force potential. These are commonly represented by the ROMEX style cable and typically carry 110 to 440 volts AC with current potentials of hundreds of amperes. The severing of any such multiple conductor package or cable with a metalic blade cutting device will result in spark and flame. While the operator may not sustain electric shock injury, the cutting device will be distroyed through melting and welding. If ambient explosive gases, fumes or vapors are present, a violent explosion may be anticipated. Many deaths occur annually due to spark ignited gas explosions following natural and man made disasters.
Accordingly, the need exists for a high voltage/current cutting device which provides safety to the operator from electric shock injury, protects the cutting device from damage and minimizes the potential for spark and flame production when severing single and multiple high voltage/current conductors.
SUMMARY OF THE INVENTION
According to the present invention, the foregoing and other objects are attained by providing an electrical conductor cutting device including a first handle having first and second ends and a second handle moveably coupled to the first handle, having, as well, first and second ends. The cutting device further includes a first high electrical resistance ceramic cutting blade coupled to the second end of the first handle and a second high electrical resistance ceramic cutting blade coupled to the second end of the second handle in cutting alignment with the first blade. The first and second handles are adapted to be operated to move the first and second ceramic cutting blades into a contacting relationship to provide a cutting force.
Unlike metalic cutting blades of previous art, the cutting blades of this invention are constructed of a ceramic material possessing the properties of very high electrical resistance, tensile and shear strength and thus, in operating practice, protects the operator from electric shock injury while protecting the cutting device from weld damage and minimizing the potential for spark or flame production while severing multiple or single high voltage/current conductors. Unlike previous art employing ceramic cutting surfaces, embodiments of this invention specify cutting blades and mechanisms of sufficient torque, shear and tensile properties to effectively sever electrical conductors up to size 4/0 AWG carrying potentially lethal voltages/currents.
Additional objects, advantages and novel features of this invention will be set forth in part by the descriptions which follow and, in part, will become apparent to those skilled in the art upon examination of the following, or may be learned from practice of this invention.
The invention, having now been briefly summarized, may be further appreciated by an illustrative embodiment through the following explanations and drawings.
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patent: 5528833 (1996-06-01), Sakuma
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