Reporter's Statement of the Case control the operation of the pumping engine is directly effected by means of a pair of auxiliary steam-driven pistons operating in the valve chamber, instead of by a mechanical linkage of the valve to some moving part of the engine. The construction of the valve mechanism disclosed in the patent is well illustrated by figure 1 reproduced herewith and by figures 3 and 4 on page 4. The valve itself is best described as a rocking slide valve the working face of which is a portion of a cylindrical surface having a roughly rectangular cavity inside its working edges. A typical valve is in evidence as plaintiff's exhibit V. Reporter's Statement of the Case In the operation of the valve mechanism, as disclosed in the patent in suit, the valve is reciprocated longitudinally along its cylindrical axis and by such action controls the flow of steam to the pumping engine pistons through the conventional arrangement of three linearly aligned ports. In addition to controlling the flow of steam to and from the pumping engine pistons, the valve also controls the flow of steam to and from the valve pistons. This is accomplished by providing a pair of ports, which have their inlet openings on opposite sides both longitudinally and transversely of the valve seat axis, and their outlet openings at opposite ends of the valve cylinders. Control of steam to the valve pistons is effected by the combined reciprocation of the valve and a rotary or rocking motion imparted to it by mechanism hereafter to be described. Uncovering or opening of one of the auxiliary ports is effected by the rotary or rocking motion of the valve, thus admitting steam behind the valve piston and moving the valve longitudinally. At some point in the valve travel, before the end of its stroke, the port from which steam is being exhausted is overrun by the valve as a result of its longitudinal motion, thereby closing the cylinder and trapping a certain amount of steam therein, which cushions the end of the valve stroke. If such cushioning were not provided the mechanism would soon batter itself into a state of inoperativeness. 5. The particular construction and arrangement of the valve with reference to the auxiliary ports are set forth in claims 1 and 2, which read as follows: 1. In a valve mechanism for steam pumps, the combination of a valve chest having a line of supply and exhaust ports arranged longitudinally, a double ended piston in said valve chest, a valve carried by said piston having an exhaust cavity of substantially rectangular form, with lateral working edges substantially parallel with the axis of the chest, means for oscillating the valve laterally at the end of each stroke, an auxiliary port connecting with one end of the steam chest, formed at each side of the line of main ports, said auxiliary ports being so placed as to be alternately opened to the steam space and the exhaust space as the valve oscillates laterally, and to be Reporter's Statement of the Case alternately overrun by the ends of the valve at or near the end of its longitudinal stroke. 2. In a valve mechanism for steam pumps the combination of a valve chest having a line of supply and exhaust ports arranged longitudinally, a double ended piston in said valve chest, a valve carried by said piston having an exhaust cavity with lateral working edges substantially parallel with the axis of the valve chest, means for oscillating the valve laterally at the end of each stroke, an auxiliary port formed in the valve chest on each side of the longitudinal and transverse centers, each of said auxiliary ports being connected with the farthest end of the valve chest and so located as to be alternately opened to the steam space and exhaust space by the lateral working edge of the valve, as the latter oscillates, and to be cut off from exhaust by the end of the valve at or near the end of its longitudinal stroke. 6. Oscillation or rotary motion of the valve is obtained by means of a yoke 5, connected by rod 10, which may be given a reciprocating motion "by the usual reducing motion lever and tappets from a crosshead on the piston rod 11." This yoke has its inner faces, which bear upon the valve stem, rounded off to provide a rolling contact with the stem and permits free longitudinal movement of the valve without interference with its oscillatory or rocking motion. Claims 3 and 4 are directed to this latter feature and are as follows: 3. In a valve mechanism for steam pumps the combination of a steam chest, a double ended piston therein, a laterally rocking valve carried by said piston, main ports being formed in said valve chest, controlled by the longitudinal reciprocation of said valve, and auxiliary ports controlled by its lateral oscillation, a pin projecting from said valve, a valve stem adapted to reciprocate longitudinally of its own axis and a yoke on said valve stem having a substantially rectangular opening embracing said pin and adapted to oscillate the valve laterally. 4. In a valve mechanism for steam pumps the combination of a valve chest, a double ended piston therein, a laterally rocking valve carried by said piston, main ports being formed in said steam chest, controlled by the longitudinal reciprocation of said valve, and auxiliary ports controlled by its lateral Reporter's Statement of the Case oscillation, a pin projecting from said valve, a valve stem adapted to reciprocate longitudinally of its own axis, and a yoke on said valve stem having a substantially rectangular space through which said pin passes, said space having a length sufficient to allow the pin to move through the longitudinal stroke of the piston and a width sufficient to allow contact with the pin on each side, the contacting surface on each side being cut away to present a rolling contact. 7. The plaintiff entered the service of the defendant on February 13, 1903, as a marine engineer and boiler draftsman and was immediately placed in charge of the drafting room of the Bureau of Steam Engineering at the Navy Yard, Boston, Massachusetts. At the time plaintiff entered the service of the defendant he was skilled in the construction of pumps and his stated purpose in entering the defendant's service was to increase such knowledge. 8. On June 1, 1905, Capt. (then Lieutenant) William S. Moore was placed in charge of the Bureau of Steam Engineering section at the Boston Navy Yard and made plaintiff his technical assistant, with the duties of conducting the technical correspondence as well as determining the drawings required for the manufacture and repair of devices cared for by the Bureau. 9. During and for some time prior to 1905, at which time internal combustion engines had not reached their present state of development, the Navy launches were largely, if not entirely, steam operated, and the Navy was encountering a great deal of difficulty and trouble in the operation of such launches. Naval regulations forbade the use of lubricating oil in the boiler feed pumps because such oil collected in the boilers and caused rapid deterioration thereof. The pumps which were then in use on such launches would not operate satisfactorily without lubricating oil and in order to obtain any degree of service from such pumps it was in fact necessary to provide them with lubricating oil even though this involved deterioration and increased expense in maintaining the boilers. 10. The officers in charge of the Boston Navy Yard at about this time conceived the desirability of manufacturing pumps at the Boston Navy Yard to keep their force of |