mechanism necessarily requires a continuous flow of liquid from the pump as long as the clamps are in action. In other words, the clamping pistons operate by direct and continuous application of force from the pump. It will be recalled also that the clamping pressures exerted by these pistons vary and the differential is maintained by relief valves which allow the liquid to escape when the pressure reaches a certain point. It is obvious there is a diversion of part of the external force from drawing or plunging purposes to the clamping function and that a part of the force diverted is entirely lost or wasted, namely, that represented by the liquid which escapes through the relief valves. Appellee says this constitutes a "diversion of drawing force" within the meaning of appellants' claims.

It should be mentioned also that Ferris' clamping mechanism is a complicated one, consisting of numerous pistons to each of which, through a cylinder, a portion of the clamping force is applied. In other words, after the liquid which supplies the clamping force is diverted from that which supplies the drawing force and has traveled a considerable distance to its work, the pipeline through which it runs is again divided into a number of smaller or separate ones, each of which leads into a cylinder from which a clamping piston is operated. Appellants characterize this general scheme of separating drawing force or liquid from clamping force out of the total external force supplied from the pump as being one of "independent fluid lines" or "parallel flow arrangement."

The method of separating the two forces, and especially of applying the clamping force, in Ernst is as follows. As in Ferris, the external force (liquid) leaves the pump at one point and travels a short distance through a single pipe. This leads to a four-way valve. From this valve, the liquid which creates the drawing force runs through a pipe into the drawing cylinder where it exerts downward pressure upon the drawing piston head. As in Ferris, this creates the drawing force which performs the molding operation directly on the work piece. But, as will appear, it also has a part in the clamping operation. In other words, the downward application of the drawing force has two functions in Ernst, namely, the primary one of performing the drawing operation which molds the work piece, and a secondary one to assist in the clamping operation which holds it in place.

Understanding of the latter requires further detailed description of the clamping process and arrangement as a whole. Two features are outstanding, the arrangement of the clamping mechanism in coordination with the drawing mechanism and the method of introducing and applying the liquid used for clamping purposes. The former will be described first, as it supplies a basis for clear understanding of the latter.

In a very general way it can be said that the drawing and clamping functions are performed by the same machinery, but with the application of different forces at different intervals. More specifically, both drawing and clamping operations are performed by successive operations of the upper part of the press, that is, all except the stationary member or die at the bottom upon which the work piece is laid and to which it is clamped down for molding by depression into the cavity at the center of the die. This upper portion all moves downward, except the inverted cylinder at the top, which is stationary.

The movable apparatus consists principally of four parts, connected with each other in the following order from top to bottom: (1) the drawing piston which moves downward from the inverted cylinder when the drawing force is applied above the piston head; (2) a platen (or heavy metal block) which is attached firmly to the piston at its lower end, just outside the bottom of the inverted cylinder, and moves up and down exactly as the piston does; (3) a second, but much less thick metal block, otherwise of the same dimensions as the platen, which is called the clamping member and is movably, not firmly, attached to the platen just above it; and (4) a pressing member, which is shaped on its bottom to conform to the cavity in the die and does the immediate work of molding the work piece by pressing it down into this cavity. The pressing member is attached firmly to the bottom of the platen in the center and moves up and down in exact coordination with the platen's motion. It does this through a hole in the center of the movable clamping member.

This somewhat complicated description of the whole movable upper portion of the press can be simplified somewhat by pointing out that the piston proper, the platen and the pressing member are all firmly attached together and move with one motion when pressure is applied from above or is released. Their principal function is the drawing operation. On the other hand, the clamping member is attached to the platen, not firmly, but movably, and therefore does not move with the identical motion which actuates the other parts, but moves with them in the same direction at a different rate. Its function is primarily in connection with the clamping operation.

The attachment of the clamping member to the platen is peculiar and important. It is accomplished by means of cylinders and pistons. The cylinders are located within the body of the platen and are inverted, as is the drawing or pressing cylinder. They may be called the clamping cylinders. Attached firmly to the top of the clamping member are two upright pistons which operate up and down within the clamping cylinders. They may be called the clamping pistons. When hydraulic pressure is applied within the clamping cylinders to the heads of the clamping pistons, the latter move downward and take

with them the clamping member, which holds the work piece in place on the die.

Introduction of liquid into the clamping cylinder takes us back to the four-way valve, from which liquid also is introduced, as has been shown, through one outlet into the drawing cylinder chamber above the drawing piston head. Through another outlet from the valve liquid is carried by another pipe line into the drawing cylinder, but at a point near its bottom. Below its head the piston is somewhat smaller in diameter than the cylinder and in this space between the piston and the cylinder wall the liquid flows upward to a point just below the piston head. There it enters an aperture in the piston itself, which first leads horizontally to the center of the piston and thence downward through its length and into the platen to a point about level with the tops of the clamping cylinders. From this point the liquid flows through horizontal apertures or "pipes" in the platen to the clamping cylinders and fills them. Check valves in the horizontal lines of flow prevent the liquid from returning in the direction of the pump when clamping pistons exert pressure upward against the liquid in the tops of the clamping cylinders. Apertures also lead outwardly from the clamping cylinders to the relief valves and thus allow escape of liquid from the cylinders when the clamping pressure reaches the desired point. This substantially completes the detailed description of the parts and arrangement of the mechanism and the manner in which the liquid is introduced for the work both of drawing and of clamping. It remains to describe briefly the coordinated operation of the process as a whole.

It is obvious that the clamping member, with its upright pistons resting against the liquid in the clamping cylinders contained in the platen, forms a kind of cushion between the die beneath and the movable upper portion of the press. The cushioning effect is useful chiefly in the clamping operation. This takes place, as in Ferris, just before the drawing operation. The whole process of clamping and drawing occurs, in a general way, as follows.

The clamping cylinders being filled with liquid (which takes place during upward recession of the drawing piston), liquid is pumped through the four-way valve into the drawing cylinder, and this creates pressure upon the drawing piston head driving the piston and the platen downward. As they descend, they meet resistance first from the action of the clamping pistons against the liquid in the clamping cylinders. This creates pressure in the latter, which continues until the point is reached at which the relief valves function to allow escape of liquid from the clamping cylinders. When this takes place, the clamping operation is completed and the work piece is held firmly in place between the clamping member and the die, ready for the draw

ing operation. Continued pressure then is applied to the drawing piston head, and this forces the drawing-piston-platen-pressingmember combination further down, so that the pressing member descends through the aperture in the clamping member, makes contact with the work piece, and presses it down into the die cavity, thus molding it to the desired shape. When this is finished, the pressure on the drawing piston is removed, the drawing piston and other firmly connected parts return upward, thus releasing the pressure upon the clamping member, which then releases the molded work piece from its grasp. During the return stroke of the drawing piston upward, liquid again enters the clamping cylinders from the four-way valve, as above described, and fills them. The press is then ready to begin another clamping and drawing operation.

As has been said, Ernst and Ferris are alike in using a single pump which supplies the total external force and expels this for a short distance through a single pipe.

From that point there is difference. In Ferris the pump, moving at constant speed, supplies continuous pressure which is applied directly for both clamping and drawing. In Ernst there is likewise a separation of the drawing fluid pipe from the clamping fluid pipe, at the four-way valve. But the liquid does not flow through these pipes at the same time, as in Ferris, in a continuous column of pressure. As we understand the process, the liquid flows from the valve first through one, then through the other. It is only when the drawing piston is moving upward, and therefore no liquid is flowing to the head of the drawing piston, that fluid enters the clamping cylinders. Conversely when liquid is moving to the head of the drawing piston, and it is moving downward, the resulting pressure created by this movement in the clamping cylinders prevents entrance there of any liquid from the four-way valve. Thus, while in Ferris the pump supplies a direct, continuous and simultaneously working pressure through both the drawing fluid pipes and the clamping fluid pipes to the drawing piston and the clamping pistons respectively, in Ernst the pump supplies pressure which, after it leaves the four-way valve, is applied alternately, first to fill the clamping cylinders, then to drive the drawing piston down. Hence, the liquid in the clamping cylinders supplies the first resistance to the downward motion of the drawing piston, and this in turn creates a pressure of resistance in the clamping cylinders to the downward motion, which then continues its downward pressure for the drawing operation.

As distinguished from Ferris, therefore, the two liquid flow lines to the drawing and clamping cylinders operate in alternate intervals to conduct the liquid for its work; the liquid introduced into the clamping cylinders acts directly in opposition to the force of the liquid

applied to the drawing piston head; the entire external force of the pump is available to apply to the drawing piston head as it moves downward for the work; both clamping and drawing operations are accomplished with a single downward movement of the drawing piston; and the liquid introduced into the clamping cylinders during the previous return stroke of the drawing piston acts in performance of the clamping operation, not as a direct and continuous application of force from the pump (as it is in Ferris), but as a cushion creating resistance against the down stroke of the drawing piston. This arrangement and action appellants characterize as an application of force "in series" in contradistinction to the "parallel flow" arrangement of Ferris. In these features they now find the invention, though the claims were much broader when the proceedings in the Patent Office began.3

It may be that these features of improvement are inventive. But, as the case is before us, the issue is whether the invention as described in claims 4, 5, and 7 shows patentable features not disclosed in Ferris. The claims must be read therefore, not merely with a view to whether the allegedly patentable features they describe are disclosed in appellants' process, but whether Ferris also discloses them. Appellants insist the claims disclose invention beyond Ferris in the following features: (1) the diversion of a portion of the drawing force; (2) to generate hydraulic pressure; (3) during the drawing operation; and (4) apply the pressure so generated to produce the clamping action (claims 4 and 5); and (5) release the excess pressure at a predetermined maximum (claim 5); or (claim 7) to apply the pressure so generated to assist the clamping action, (a) applying a retracting force to the member applying the drawing force, (b) diverting a portion of the retracting force to generate pressure, and (c) applying the pressure thus generated to maintain the clamping pressure during retraction.

The application came successively before several Examiners. The original ten claims were rejected first as being directed "to the method of drawing metal," which the Examiner held is the same regardless of the source of pressure fluid; he therefore rejected them twice on Ferris, basing the second rejection on the ground that "the source or manner of developing the clamping pressures is not a material and patentable limitation in the method of drawing metal." [Italics added.]

Ernst then cancelled all claims except 4, 5, 6, and 7, and requested reconsideration for them stating: "These claims have been amended so that they are no longer directed to a method of drawing articles but are now directed to a method of generating and utilizing hydraulic power for clamping articles being drawn." [Italics added.] The amended claims were again rejected: (1) as misleading, inaccurate and not readable on the instant disclosure; (2) on Ferris, as containing no more than functional limitations over that disclosure; and (3) as disclosing only the function of an apparatus, though purporting to be directed to a method. Claim 6 was then cancelled, and on reconsideration claims 4, 5, and 7 were again and finally rejected on Ferris. The Board of Patent Appeals affirmed the Examiner's decision, holding that "insofar as the claims recite true methods they do not distinguish in any patentable respect from the reference [Ferris]." This suit then followed.

4 Cf. text infra.