The opinion of the court was delivered by: KNIGHT
This is a patent infringement suit involving Claims 20 and 24 of Letters Patent No. 1,675,760 issued to Charles W. Manzel on July 3, 1928, covering an improvement in hydraulic shock absorbers. Title in the plaintiff is admitted. It is also admitted that the accused shock absorbers were manufactured by defendant, Houde Engineering Corporation, sold by that corporation to the Ford Motor Company, and thereafter sold by the defendant last named.
We are concerned in this suit with shock absorbers as used on automobiles. It is well known that the function of the shock absorber is to check the rebound movement of the vehicle spring after it has been compressed by the wheels passing over an obstruction and retard the relative movement on the rebound stroke or downward movement of the spring. These checking movements have been brought about by two general types of shock absorbers: mechanical friction and hydraulic. The friction type is shown in what has been familiarly known as "snubbers" -- embracing a friction strap wound around a brake drum carried by the body with the strap connected with the vehicle axle and maintained taut. That type is not now involved. In the socalled hydraulic type the movement is controlled or retarded by resistance to the flow of a viscous fluid through a relatively small passage. This flow is induced by the movement of a piston or rotor in a fluid filled chamber or cylinder. The piston or rotor is connected for movement with the vehicle axle and the cylinder or chamber with the vehicle body.
Concededly hydraulic shock absorbers are not of recent origin and various types antedate the patent in suit. As pointed out by the plaintiff, the first patent was No. 845,088 issued to Hotchkin, February 26, 1907. As revealed by the prior art patents, there has been a gradual step by step development of shock absorbers since that time. The general principles of construction of the devices in suit have long been known. Manzel embodies the general type of structure of absorbers shown in Houde Patent No. 933,070 issued September 9, 1907, and Houde No. 1,087,017 issued February 10, 1914. With the exception of the valves, the Manzel and the present Houde structures are substantially similar.
In the Manzel shock absorber, a stator member is rigidly secured to the vehicle body. The casing of the absorber rotates about the stator member counter clockwise on the bound stroke and clockwise on the rebound stroke. Two oil filled chambers are formed between the stator and rotor by the stator blade and the rotor blade. A reservoir for replenishing the supply of oil in the above-described operating chambers is found between the outside of the rotor and the cover plate of the shock absorber. On the bound stroke, oil flows from one chamber as it becomes smaller upon the movement counterclockwise of the rotor vane, passes through a port into the reservoir and then through a ball check valve into the other chamber, which is becoming larger as the rotor vane moves.Some oil also flows through the valve into the enlarging chamber. There is a little resistance to the movement on the bound stroke because of the size of the ports through which the oil flows. On the rebound stroke the rotor moves clockwise. As the second chamber becomes smaller and the other larger as the result of this movement, the ball check valve is caused to close. The returning oil is forced to pass through the valve illustrated below:
[SEE ILLUSTRATION IN ORIGINAL]
The oil must pass between valve plug 65 and valve seat 60. Thence it passes through prescribed passages to the other chamber which is now enlarging. On the rebound stroke there is considerable resistance to the movement of rotor vane, because the passage between valve plug 65 and valve seat 60 is small. This builds up pressure in the chamber which is decreasing in size and tends to retard the movement of rotor vane and rotor. The degree of pressure and resistance depends upon the size of the opening.
Two types of Houde shock absorbers are alleged to infringe. One was put out in 1932; the other in 1934. The only difference between them is that the direction of the flow of the liquid through the valve of the absorber is reversed in the latter device. The two types show the same general flow of liquid in the chambers and the same general principle of structure of the chambers proper as in Manzel. Oil constantly fills the opposing chambers in the Manzel and Houde devices. On the bound stroke, the oil passes freely from one working chamber to the other through a ball check valved by-passage; on the rebound stroke, the by-pass ball valve automatically closes so that all oil must pass from one chamber to the other past the regulating valve plug. The rate of movement of the shock absorber rotor and the vehicle axle upon the rebound stroke depend upon the force applied upon the shock absorber and upon the position of the regulating valve plug relative to its seat.
Following are diagrammatic representations of the Houde shock absorbers:
[SEE ILLUATRATION IN ORIGINAL]
Two claims only are at issue. Claim 20 reads: "The combination with an hydraulic shock absorber having a passage for the discharge of fluid under pressure, of a regulating valve for controlling the discharge of fluid through said passage and including an adjustable head at one end, a valve-plug at its opposite end, and a normally neutralized yieldable element of a predetermined tension disposed between said head and said valve-plug for resisting the opening of the latter." Claim 24 is the same as Claim 20, except that it omits the requirements that the normally neutralized yieldable element shall be of a predetermined tension and that such element resists the opening of the valve plug, while it additionally provides that the yieldable element shall be disposed between the adjustable head and the valve to form a unitary structure.
The patent in suit describes an hydraulic shock absorber as an entire construction and includes various claims relative thereto. The claims in suit refer only to the regulating valve.
The Manzel patent describes a valve plug inserted in or in close proximity to a seat, a "normally neutralized" spring of predetermined tension and a screw threaded adjusting head, all making a unitary structure. "Predetermined tension" as described in the patent means the extent the spring will be compressed by pressure of a predetermined force. "Normally neutralized", as applied to a spring, means that it is normally neither under tension nor compression.
The Houde devices show what is described as thermostatic control. Its purpose is alleged to be to regulate, according to temperature, the width of opening of an orifice slit in the seat structure in which the valve plug is engaged. Houde claims that any change in the size of the arcuate slit is only to an extent caused by temperature changes. Thermostatic action is brought about by the bi-metallic material in the spring, heat causing the spring to ...