Homework 2: Validity of "Combinations"

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1. Patent 3676638: Plasma Spray Device and Method (1972)

Summary: 1972 v. 1988 The some of the most prominent conditions which separate this earlier device from its later cousin (found in Homework 1: 1980-1990 Patent and hereby referred to as "the 1988 device") are as follows:

  • There are significantly more pieces used to assemble the 1972 device than in the 1988 device
  • The 1972 device takes the shape of a hand-held "gun" when fully assembled, whereas the 1988 device is meant to be used in an automated machine
  • The material powder is inserted into the gas flow at an earlier point than in the 1988 device
  • Plates with helical holes are used to drive the pattern of the flow of gas through the nozzle instead of creating a vortex
  • The electric arc is created directly at the end of the cathode, rather than at the end of the nozzle in the 1988 device (which has "extended arc" in the patent title)
  • The plasma spray gun can only spray powdered materials, whereas the 1988 device can spray both powders and wires/thin plates
  • Geometries of the nozzles and internal cavities vary dramatically between the two devices
  • The velocity of the gas/material in the 1972 device is significantly lower than in the 1988 device


2. Patent 4095081: Electric Arc Metal Spraying Devices (1978)


Summary: 1978 v. 1988 The some of the most prominent conditions which separate this device from the 1988 device are as follows:


Hotchkiss v. Greenwood

Under the court ruling in Hotchkiss v. Greenwood, inventions which are mere collection of "known" items are not considered patentable. In this specific case, it was in relation to a change in material.


A. & P. Tea Co. v. Supermarket Corp.

Under the court ruling in A. & P. Tea Co. v. Supermarket Corp., inventions which are collections of "known" items are considered to be patentable, provided that the combination performs a new or different function than it otherwise had, or the improvements made in the combination are significant enough.