Price-Trawick, Inc. v. Gas Lift Corp.

101 F.2d 134, 40 U.S.P.Q. (BNA) 265, 1939 U.S. App. LEXIS 4351
CourtCourt of Appeals for the Fifth Circuit
DecidedJanuary 24, 1939
DocketNo. 8921
StatusPublished
Cited by18 cases

This text of 101 F.2d 134 (Price-Trawick, Inc. v. Gas Lift Corp.) is published on Counsel Stack Legal Research, covering Court of Appeals for the Fifth Circuit primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Price-Trawick, Inc. v. Gas Lift Corp., 101 F.2d 134, 40 U.S.P.Q. (BNA) 265, 1939 U.S. App. LEXIS 4351 (5th Cir. 1939).

Opinion

HOLMES, Circuit Judge.

This appeal is from a decree dismissing appellant’s bill for an injunction against infringement of Letters Patent No. 1,793,193, issued to Frederick Price. The decree sustained the validity of the patent but dismissed the bill for want of infringement. The patent is for an apparatus for starting the flow of flowing wells, and, in view of the prior art, only a part of the fifth and last claim need be considered on this appeal.

• The principal use of the devices under consideration is in producing oil from wells in which the natural or rock pressure is not sufficient to cause the oil to flow to the sur[135]*135face. Normally, an oil well consists of a large pipe, called a casing, extending from the surface of the land to the oil-bearing stratum. A flow-tube or pipe is disposed within the casing, extending to a point well below the level to which the oil rises under natural pressure. The space between the casing and the tube is sealed at the top, so that gas or air may be introduced under pressure. In shallow wells, or wells in which rock pressure brings the oil near the surface, production may be obtained by simply increasing tile pressure in the casing outside the tube until the level of the oil is forced downward to the bottom of the tube. At this point, the gas begins to flow up through the oil in the tube, producing bubbles or alternate columns of air and gas, or both. The oil thus displaced rises in the tube, and, the weight not being increased, the pressure causes it to flow from the well.

Where oil is to he produced from a great depth, the pressure necessary to start and maintain the flow causes great strain upon the casing and requires large and expensive machinery. To avoid these difficulties, gas-flow valves have been developed to admit gas from the casing to the tube at predetermined pressures. These valves are spaced along the tube at intervals, and operate by closing when the differential in pressure between the casing and tube has increased due to the absence of the proper quantity of oil in the tube above the valve.

In the original Price application, claim was made for a method of flowing wells. The claims were subsequently amended to cover the valve therein specified as an apparatus. Claim S recites a valve stem with two convex valves disposed thereon with convexities adjacent, so disposed that a double faced concave valve seat, fixed in the walls of the tube, is interposed between them with an opening through which the valve stem passes and through which the gas flows from the casing into the tube. The claim recites means yieldingly holding the valve in position and allowing the same to wabble with relation to its seat, whereby it is allowed to assume any position necessary to seat itself under pressure.

The means, yieldingly holding the valve in place and allowing the same to wabble, are described in the specifications of the patent, and illustrated by appellant’s exhibits introduced in evidence in the district court, as a flat or single leaf spring disposed outside the tube and extending parallel with the axis thereof to a point opposite the opening therein in which the valve seat is inserted, and joined to the valve stem by a flat-head screw passing through a hole in the spring and engaging the valve stem, but not being screwed into the stem a sufficient distance to bind the spring. Thus, we have a simple mathematical statement, avoiding the use of functions, that the ratio of the radius of the head of the screw to the length of the valve stem is the same as the ratio of one-half of the length of the screw from its head to the valve stem, less the thickness of the spring, to the distance the end of the valve stem may be varied from the perpendicular to the surface of the spring. Assuming values of one-fourth of an inch for the radius, one inch for the length of the valve stem, and one-sixteenth of an inch for one-half of the length of the screw from its head to the valve stem, less the thickness of the spring, we have a distance of one-fourth of an inch possible variation from the perpendicular; or, since the variation is in both or all directions, the above values allow a total movement in any plane (perpendicular to the spring and passing through the point of contact with the valve stem) of one-half of an inch or through an arc of one-half of a radian. Thus, under the assumed conditions, the wabble mentioned in the claim is a possible variation of approximately thirty degrees. If the length of the screw from head to valve stem, less thickness of the spring, is increased from one-eighth to one-fourth of an inch, the variation or wabble becomes one inch, one radian, or approximately sixty degrees.

The advantage claimed for this type of structure is that the convex faces are allowed to assume any position necessary to seat them properly in the concave faces. In the devices described, a distinction may be drawn between the function of the spring mounting of the valve and the manner in which the mounting is accomplished. The use of a flat single leaf spring satisfies the requirement of a means yieldingly holding the valve, since the spring yields to perpendicular, as well as to torsional, stresses. Wabble is the result of the loose mounting or connection between valve stem and spring, and is a true function of the limits of looseness employed, as illustrated above. The leaf spring mounting is old in the art, and the claim of infringement is confined to the arrangement permitting wabble.

Appellee’s device, which it is alleged infringes the patent in suit, consists of a [136]*136valve stem with valves integral therewith, disposed within a tubular housing in which three guides are mounted so as to hold the stem in the center of the housing but permit the entire member to move along the axis thereof. The' guides are positioned one at each end of the housing and one near the center. A coil spring is mounted at one end of the stem, and is so arranged that its tension ‘is against the pressure of the gas moving through the assembly. The valves are conical enlargements of the valve stem resulting from machining, and seat simultaneously in seats accurately machined on the edges of the middle guide-member and the guide member at the opposite end from the spring. The latter guide member is larger than the valve stem proper, so that the valve stem is machined with a triangular enlargement to be disposed within the member with only the points of the enlargement in contact with the member, leaving the space along the sides for the passage of the gas which has found its way through the valve opening.

.The wabble complained of is that appellee allows clearances between the guide members and the portions of the valve stem in contact therewith. Appellee admits clearances of as much as .015 of an inch, but says that these clearances are necessary to allow the valve to operate; that smaller clearances would cause the stem to bind and stick in the guides. It also points out that, in its manufacture, dimensions are held within tolerances of not less than .002 of an inch, and that stricter limits would make costs prohibitive.

However this may be, we do not think that clearances of .015 of an inch in valve stems three inches long, or more, can be said to permit wabble within the meaning of the patent claim. If we undertake to consider appellee’s device in the light of the mathematical analysis applied above to the Price valve, we find an entirely different ■ disposition of elements. Instead of the movement at point of clearance, i.

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Bluebook (online)
101 F.2d 134, 40 U.S.P.Q. (BNA) 265, 1939 U.S. App. LEXIS 4351, Counsel Stack Legal Research, https://law.counselstack.com/opinion/price-trawick-inc-v-gas-lift-corp-ca5-1939.