The

It has two sides which are duplicates, the supply side and the exhaust side. The supply side has a passage from the supply pipe to the motor cylinder, and the exhaust side has a passage from the exhaust pipe to the motor cylinder. These passages to the motor cylinder are opened or closed by the movements of the pilot valve stem. elevator is started in its upward or downward movement by opening the supply or the exhaust passage, and it is stopped in its upward or downward passage by closing the supply or the exhaust passage. The speed with which the elevator starts or stops is governed by the quantity of water which is permitted to flow through these passages. If, therefore, these passages are what are termed "enlarged passages," the elevator will start and stop quickly. If they are what are termed "restricted passages," the elevator will start and stop slowly. If one of the passages is an enlarged passage and the other a restricted passage, the elevator will start quickly and stop slowly in one direction. and start slowly and stop quickly in the other direction. It was common in the art to restrict the pilot valve passages by means of throttling devices such as throttling screws, in order to effect a slow start and a slow stop, as distinguished from a quick start and a quick stop. It was also old in the art to accomplish a gradual start and a gradual stop by what are termed "graduated ports" in the pilot valve or in the main valve.

The purpose of the Cole invention was to secure an automatic slow stop of the elevator in both directions without affecting the rate of speed in starting.

Cole accomplished this purpose in the following way: He first constructed his pilot valve with a restricted and enlarged passage for the supply, and a restricted and enlarged passage for the exhaust. He then provided an auxiliary piston valve with a throttling plug on each end of the stem. He then provided means whereby one of the enlarged passages was automatically closed by the throttling plug when the elevator was stopped. These means consisted in connecting the auxiliary pilot valve stem with the main valve stem in such a manner that, when the main valve moved in one direction, the throttling plugs moved in the opposite direction, with the result that on the outward movement of the main valve to start the elevator the throttling plugs closed one of the enlarged passages, so that on the return movement of the main valve to stop the elevator the flow of water was confined to the restricted passage, and hence the main valve moved slowly, thereby causing the elevator to stop slowly. We have, then, in the Cole organization a pilot valve with enlarged and restricted passages, which are open to start the elevator, and with only the restricted passage open to stop the elevator.

The pilot valve mechanism and the nature and scope of the Cole improvement will be better understood by a fuller description of the plunger elevator and its mode of operation. In the plunger elevator 2 cylinder is sunk in the ground to the same depth as the height to which the elevator is to be raised. A plunger slides in this cylinder. and upon the upper end of the plunger is supported the elevator car. When water is introduced into the cylinder, the water pressure raises the plunger, and consequently the elevator. When water is permitted to flow out of the cylinder, the weight of the plunger and the car

causes the elevator to descend. When no water is permitted to flow into or out of the cylinder, the plunger and the car remain stationary. The regulation of the flow of water into and out of the cylinder, and the cutting off of the water from the cylinder, are accomplished by a somewhat elaborate system of piston valves. This system comprises the main valve, the motor, the pilot valve, and their connecting mechanisms. The main valve controls the movements of the plunger, which supports the elevator car, the motor valve controls the movements of the main valve, and the pilot valve, which is connected with the operating lever in the elevator car, controls the movements of the motor valve.

The valve mechanism of the plunger elevator is shown in figures. 3 and 4 of the Cole patent. These drawings also illustrate the pilot valve mechanism covered by the patent, and its mode of operation.

The middle part of each of these drawings shows the main valve, the lower part shows the motor, and the upper part shows the pilot valve. The main valve is a three-way piston valve. It has a passage to the source of supply, a passage to the main cylinder, and a passage to the exhaust. It opens the supply to allow the water to flow into the main cylinder to move the elevator upward, it shuts off the supply and the exhaust to stop the elevator, and it opens the exhaust to allow the water to flow out of the main cylinder to permit the elevator to descend. When the elevator is stopped, the main valve occupies its central or neutral position, which is seen in figure 3. In this position the port to the main cylinder is closed, and consequently the water cannot flow into or out of the cylinder.

The main valve is moved from its central position outward to start the elevator, and from its outward position back to center to stop the elevator. When the main valve moves from the center to the right, the main cylinder is connected with the supply, and the elevator ascends, and, when the main valve moves back to center, the supply is cut off, and the elevator stops. When the main valve moves from the center to the left, the main cylinder is connected with the exhaust, and the elevator descends, and, when the main valve moves back to center, the exhaust is cut off, and the elevator stops. If the main valve moves quickly in its outward movements and in its movements back to center, the elevator will start quickly and stop quickly. If the main valve moves slowly in its outward movements and in its movements back to center, the elevator will start slowly and stop slowly. On the other hand, if the main valve moves quickly in its outward movements and slowly in its return movements back to center, the elevator will start quickly and stop slowly.

The motor consists of a cylinder with two pistons. As the drawings show, the motor stem and the main valve stem are so connected that the movements of the motor pistons and of the main valve pistons must be the same. The movements of the motor pistons are controlled by the pilot valve. When the supply and exhaust of the pilot valve are cut off from the motor, the motor pistons are at their central or neutral position, as shown in figure 3. When the supply of the pilot valve is open, the motor pistons move from their central position to the right, as shown in figure 4, and the elevator ascends. When the supply of the pilot valve is cut off and the exhaust is open, the motor pistons move back to center, and the elevator stops. On the other hand, when the exhaust of the pilot valve is open, the motor pistons move from their central position to the left, and the elevator descends. When the exhaust of the pilot valve is cut off and the supply is open, the motor pistons move back to center, and the elevator stops. If the pilot valve has enlarged supply and exhaust passages, the outward movements and the return movements of the motor pistons, and therefore of the main valve, will be quick, and the elevator will start and stop quickly. If the pilot valve has contracted supply and exhaust passages, the outward movements and the return movements of the motor pistons, and therefore of the main valve, will be slow, and the elevator will start and stop slowly. On the other hand, if the pilot valve has a contracted passage and an enlarged pass

age for the supply, and a contracted passage and an enlarged passage for the exhaust, and both these passages are open on the outward movements of the motor pistons, and only the contracted passage is open on the return movements of the motor pistons, the elevator will start quickly and stop slowly.

The pilot valve, as the drawings show, has two sides which are alike the supply side, which connects with the supply pipe, and the exhaust side, which connects with the exhaust pipe. When the pilot valve is in its central or neutral position, as shown in figures 3 and 4, both the supply and the exhaust are cut off from the motor. The movement of the pilot valve to the left opens the supply to the motor cylinder, and the movement of the pilot valve to the right opens the exhaust to the motor cylinder. The pilot valve is so connected with the main valve that the movement of the main valve in either direction or back to center moves the pilot valve back to its central position. In other words, the pilot valve is automatically returned to its central position by the movement of the main valve. When the operator presses the lever down, as shown in figure 4, the pilot valve moves to the left and opens the supply, which causes the motor pistons to move to the right, and therefore the main valve, and the elevator starts in its upward movement. This outward movement of the main valve returns the pilot valve to its central position, without affecting the position of the operating lever. When the operator moves the lever back to center, the pilot valve moves to the right, and opens the pilot exhaust, which causes the motor pistons to move back to center, and therefore the main valve, and the elevator stops in its spward movement; and the reverse operation takes place in starting and stopping the elevator in its downward movement.

If we look at the upper part of each of the two drawings, we see that the pilot valve has a contracted passage and an enlarged passage for the supply, and a contracted passage and an enlarged passage for the exhaust. We also see an auxiliary piston valve, with a throttling plug on each end of its stem. We also find that the stem of this piston is so connected with the main valve stem that, when the main valve moves to the right, the throttling plugs move to the left, and vice versa. The effect of this is, as seen in figure 4, that, when the supply or exhaust of the pilot valve is open and the main valve moves to the right or to the left, the throttling plug closes the enlarged passage of the supply or the exhaust, so that the supply and exhaust passages to the motor cylinder are restricted on the return movements of the motor pistons. The result is that the return movements of the motor pistons and main valve are slow, while the outward movements are quick, and consequently the elevator starts quickly and stops slowly.

We are now prepared to determine the nature and scope of the Cole invention. At the time of his invention the plunger elevator art had already reached the practical or commercial stage. It had, fact, reached the stage of an advanced art. The Cole invention, therefore, does not mark the line between practical success and practical failure in plunger elevators, and hence his patent cannot be said to cover a broad pioneer invention. His patent is for a pilot valve

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which secures an automatic slow stop, while permitting at the same time a quick start. This at most is an improvement over prior pilot valves, which automatically insured a slow start and slow stop, or a quick start and quick stop, or which prevented a sudden start and sudden stop.

Cole started to make his pilot valve with the idea that in modern elevators of the plunger type it was very desirable to have an automatic quick starting and slow stopping elevator. His invention does not reside in the idea of quick starting and slow stopping, but in the means he devised for accomplishing this result. The patent correctly defines the invention when it declares:

"More particularly my invention consists of means attached to the valve mechanism which limits the rate of speed of closing the main valve in either direction without affecting the rate of speed of opening."

It is these means which constitute the real invention covered by the patent. This being true, the scope of the invention cannot be extended by the broad language which may be found in the specification, nor by the broad terms of the claims. A patentee cannot cover all means for accomplishing a certain result by a statement in the specification that his invention is not limited to the particular form of device described, nor by so framing the claims as to include all means for accomplishing the result. To hold that the Cole patent embraces all means for effecting a quick start and slow stop would be to hold that the patent covers a function or result. The monopoly to which Cole is entitled under his patent lies in the means by which he solved the problem of a quick start and a slow stop, namely, the auxiliary valve mechanism described in his patent, or what may be fairly considered the equivalent of that mechanism. The range of what will be regarded as equivalents depends upon the character of the invention, and, since the Cole patent is not for a mere improvement in details of construction, but represents a new and advanced step in the art, the court should apply the doctrine of equivalents as it is commonly applied in dealing with this class of patents by giving a fairly broad construction as to what will be considered equivalent means for accomplishing the same result.

The means attached to the valve mechanism by which Cole solved the problem of a quick start and slow stop are the enlarged passages of the pilot valve, the supplementary piston, the throttling plugs, and the connecting devices by which the throttling plugs are made to close the enlarged passages by the movements of the main valve. The essence of these means may be said to reside in so connecting the throttling plugs with the main valve that a part of the pilot valve passages will be closed by the movement of the main valve. On the question of infringement, the form of the pilot valve passages is not material, nor the form of the supplementary piston with the throttling plugs on each end, nor the form of connecting devices by which the main valve moves the throttling plugs to close in part the pilot valve passages; but what is material, since it is the very essence of the invention, is the closing of a portion of the pilot valve passages by the movement of the main valve. A pilot valve in which this