High-speed Ground Transportation System

Abstract

A high-speed ground transportation system comprising a tube through which a vehicle is adapted for propulsion from a first station to a second station, the tube having an entrance valve adjacent the first station and an exit valve adjacent the second station adapted, when closed, to block off an evacuated section of the tube from valve-to-valve. Each valve comprises a toroidal cylinder and a gate constituted by a piston movable between a closed position blocking the tube, in which the piston extends out of an open end of the cylinder, and an open position clearing the tube, in which the piston is withdrawn into the cylinder. The gate of the entrance valve is actuated by vacuum derived from the tube; the gate of the exit valve is automatically opened and is closed by action of atmospheric air.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of our copending U.S. Pat. application Ser. No. 710,582 filed Mar. 5, 1968, now abandoned, entitled High-Speed Ground Transportation System.

Description

BACKGROUND OF THE INVENTION

The invention is in the field of high-speed ground transportation systems particularly of the type shown in U.S. Pat. No. 3,438,337 of Lawrence K. Edwards, issued Apr. 15, 1969, entitled High-Speed Ground Transportation System. In that patent is shown a system comprising a duct or tube through which a vehicle is adapted for propulsion as a free piston. Valves are provided adjacent the ends of the tube, with stations constituted by airlocks open to the atmosphere outward of the valves. The section of the tube between the valves is preevacuated. With the vehicle in a first station, on opening the respective valve acting as an entrance valve, atmospheric air pressure on the rear of the vehicle propels it into said section of the tube. After the vehicle has passed the entrance valve, the latter is closed to trap a slug of air between the entrance valve and the rear of the vehicle. This trapped slug of air expands to apply propulsion force to the rear of the vehicle, with attenuation of the air behind the vehicle to restore vacuum in the tube, and with compression of air ahead of the vehicle. The valve at the other end of said section of the tube, acting as an exit valve, opens when the pressure ahead of the vehicle reaches a predetermined value and the vehicle passes therethrough and stops in the second station, the exit valve then closing. A problem attendant upon such a system is that of providing suitable entrance and exit valves, and this invention is directed to the solution of this problem.

SUMMARY OF THE INVENTION

Among the several objects of this invention may be noted the provision of a valve construction suitable for use either as an entrance valve or exit valve in a system such as above described, or in similar systems; the provision of such a valve construction which, as regards its use as an entrance valve, is operated by vacuum derived from the evacuated tube, no separate power source for valve operation being required; the provision of such a valve construction which, as regards its use as an exit valve, opens automatically, no control action being required; the provision of a valve construction such as described which, while not requiring extensive machining of parts and therefore being economical to construct, is adapted effectively to maintain vacuum in the tube; and the provision of such a valve construction adapted to be readily opened in the event of an emergency.

In general, a valve of this invention, located adjacent a station, comprises a toroidal cylinder on the outside of the tube having its toroidal axis transverse to the tube. As used herein, "toroidal cylinder" refers to a toroidal cavity or void adapted to accommodate a piston, which will be described. "Toroid" is used in the classical sense, i.e., it need not be circular in cross section; however, in this context the toroidal cylinder and the toroidal piston of one embodiment of the invention are segments of toroids rather than complete ones. This cylinder has one end open to the tube on that side of said axis toward the station. A gate constituted by a piston is rotatable about said axis between a closed position extending out of said open end of the cylinder into the tube and blocking the tube, and an open position within the cylinder clear of the tube. Control means is provided for effecting opening of the gate enabling use of the valve as an entrance valve. In its use as an exit valve, the gate of the valve is adapted automatically to open via pressure of air built up between the front of the approaching vehicle and the gate. Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1E are diagrammatic views showing the operation of a section of a high-speed ground transportation system equipped with valves of this invention at its entrance and exit ends;

FIG. 2 is a longitudinal section of a valve of this invention, the gate of the valve being shown in its closed position blocking the tube;

FIG. 3 is a transverse section on line 3--3 of FIG. 2;

FIG. 4 is a view similar to FIG. 2 showing the valve in its open position clear of the tube;

FIG. 5 is a transverse section on line 5--5 of FIG. 4;

FIG. 6 is a transverse section on line 6--6 of FIG. 2;

FIG. 7 is a perspective of the gate per se of the valve;

FIG. 8 is a longitudinal section of a modified version of the valve;

FIG. 9 is a transverse section on line 9--9 of FIG. 8;

FIG. 10 is a vertical section on line 10--10 of FIG. 9;

FIG. 11 is a longitudinal section showing another modification;

FIG. 12 is a transverse section on line 12--12 of FIG. 11;

FIG. 13 is a side elevation of another modification of the valve;

FIG. 14 is an end view of FIG. 13;

FIG. 15 is a diagrammatic sectional view showing the FIG. 13 modification;

FIG. 16 is a view similar to FIG. 15 showing the use of the FIG. 13 valve as an entrance valve; and

FIG. 17 is a view similar to FIG. 15 showing the use of the FIG. 13 valve as an exit valve.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, there is indicated at 1 in FIGS. 1A-1E a duct or tube, typically a subterranean tube, in which a vehicle 3 is adapted for propulsion as a free piston by differential pressure between the front and rear of the vehicle. The tube 1 is shown as extending from a station S1 to a station S2 along the route of a transportation system. Entrance of the vehicle from station S1 to the tube is via an entrance valve A at the entrance end of the tube. Exit of the vehicle from the tube to station S2 is via an exit valve B at the exit end of the tube.

Valves A and B, when closed, block off a section 1a of the tube from valve-to-valve between stations S1 and S2. Provision is made for evacuating this section of the tube down to low pressure (of the order of 1 p.s.i., for example) as by means of suitable evacuating pump equipment. Each station S1 and S2 is in communication with the earth's atmosphere and hence at atmospheric pressure. FIG. 1A shows both valves A and B closed, and the vehicle 3 in the station S1 about to start a trip from station S1 to station S2. Section 1a of the tube between the valves has been evacuated down to low pressure, e.g., of the order of 1 p.s.i. The trip is initiated by opening valve A, resulting in atmospheric pressure, acting on the rearward end of the vehicle, propelling it past valve A into the tube section 1a (see FIG. 1B). After the rearward end of the vehicle has passed by valve A and a predetermined amount of air (at atmospheric pressure) has been allowed to enter the tube behind the vehicle, valve A is closed (see FIG. 1C). This traps a slug of air in the tube between valve A and the rearward end of the vehicle, and expansion of this slug of air causes the vehicle to accelerate until it reaches a point where the pressure ahead of the vehicle is approximately equal to the pressure behind the vehicle. The vehicle then begins to decelerate, compressing air between the forward end of the vehicle and valve B, with attenuation of air behind the vehicle. As the vehicle approaches valve B, pressure in the tube ahead of the vehicle increases to the point where it causes valve B to open, and the vehicle comes to a stop in station S2, valve B closing behind it.

This invention is particularly concerned with a valve construction and operating system therefor suitable for each of the entrance and exit valves A and B. It will be understood that valves A and B may be identical, and simply installed in reversed positions at the station S1 and S2 ends of the tube 1. Referring to FIGS. 2-7, showing the valve A at station S1, there is indicated at 5 a valve housing located at the top of the tube 1. This housing is formed to provide a toroidal cylinder generally designated 7 on the outside of the tube. This cylinder has a span of about 100.degree. to 180.degree.. It extends lengthwise with respect to the tube, that is, the toroidal axis of the cylinder extends horizontally crosswise of the tube above the tube. The toroidal cylinder 7 has a relatively long section 7a of relatively large bore and a relatively short section 7b of smaller bore. The small-bore section 7b is on the side of the toroidal axis toward the station S1, and opens into the tube 1 as indicated at 7c. A shaft 9 is journaled in the valve housing 5 on the toroidal axis of cylinder 7. Keyed on this shaft is a gate 11 constituted by a differential rotary toroidal piston which is adapted to swing about the axis of shaft 9 between the closed position in which it is illustrated in FIGS. 2 and 3 extending out of the open end of the cylinder 7 into the tube 1 blocking the tube 1 and an open position within the cylinder wholly withdrawn and clear of the tube (see FIGS. 4 and 5). The differential rotary piston 11 has a relatively long section 11a having a diameter corresponding to that of the bore of cylinder section 7b, and a relatively short section 11b at its upper end having a diameter corresponding to that of the bore of cylinder section 7a. As shown, the piston 11 may be of hollow construction to decrease its weight. A counterweight 13 for the piston is keyed on shaft 9 outside cylinder 7. The center of gravity of counterweight and piston combination is indicated at G, and it will be observed that this overcenters as the piston swings between its closed and open position.

The lower end face of the toroidal piston 11 (i.e., the lower end of its smaller-diameter section 11a) is designated 15. The upper end face of the toroidal piston 11 (i.e., the upper end of its larger-diameter section 11b) is designated 17. The face of the step between the larger-diameter section 11b and the smaller-diameter section of the piston is designated 19. The valve housing has an auxiliary chamber 21 which is in communication with the cylinder 7 at the juncture of the cylinder sections 7a and 7b, the arrangement being such that face 19 of the piston (which faces in the direction toward the open end 7c of the cylinder) is subject to pressure in chamber 21.

The cross-sectional diameter of section 11a of the piston 11 is somewhat larger than the internal diameter of the tube 1, and, when the piston is in its closed position of FIGS. 2 and 3, the margin of its lower end face 15 seals against an annular shoulder or seat 23 in an enlarged section 25 of the tube. This section 25 is shaped with a curvature such that the piston must swing through a predetermined finite angle Y, which may be about 15.degree., for example, before there is communication of air between the tube and the station.

The valve housing 5 is formed with a port 27 for communication from cylinder section 7a to the atmosphere. This port is located intermediate the ends of cylinder 7, nearer to its closed end 7d than its open end 7c, and has a check valve 29 therein which is adapted to open in the direction for flow from the cylinder section 7a to the atmosphere. Housing 5 is also formed with a vacuum manifold 31 in communication with the evacuated tube 1 on the vacuum side of the valve A via a check valve 33 which is adapted to open in the direction for flow of air from the manifold 31 into the tube. Manifold 31 is adapted for communication with the port 27 via a pilot valve 35, and for communication with chamber 21 via a pilot valve 37. The latter is a two-way valve, adapted in a first position to block communication between manifold 31 and chamber 21 while establishing communication between the earth's atmosphere and chamber 21 via an atmospheric air inlet port 38, and in a second position to block port 38 while establishing communication between manifold 31 and chamber 21. The valve housing is also formed with a bleed passage 39 for supplying air at atmospheric pressure from a chamber 41 in communication with the earth's atmosphere to the closed end 7d of cylinder section 7a.

The pressure in tube 1 acting on the lower end face 15 of the toroidal gate or piston 11 is designated P1. The pressure in cylinder section 7a acting on the upper end face 17 of the piston 11 is designated P2. The pressure in chamber 21 acting on the face 19 of the piston 11 is designated P3. The pressure in manifold 31 is designated P4. The pressure in the tube at the end of the station is designated P5.

Valve B at station S2 is identical to valve A, being installed in reversed position in respect to valve A, as will appear from FIGS. 1A-1E.

Operation is as follows:

Considering conditions prior to a trip of the vehicle from station S1 to station S2, the vehicle will be poised at rest in station S1. Valves A and B are closed (i.e., their pistons or gates 11 are closed). Section 1a of the tube 1 between valves A and B will have been evacuated down to low pressure, e.g., of the order of 1 p.s.i. Pilot valve 35 of the operating system for each of valves A and B is closed. Pilot valve 37 of the operating system for each of valves A and B is set as shown in FIG. 2 for admission of air at atmospheric pressure to chamber 21 while blocking passage 31 from chamber 21. As to each of valves A and B, pressures P1-P5 are then as follows: ---------------------------------------------------------------------------

Valve A Valve B __________________________________________________________________________ P1 Vacuum Vacuum P2 Atmospheric Atmospheric P3 Atmospheric Atmospheric P4 Vacuum Vacuum P5 Atmospheric Atmospheric __________________________________________________________________________

The trip in initiated by opening valve A. This is accomplished by opening pilot valve 35 of valve A, dropping P2 to vacuum. With P1 and P2 vacuum, the P3 atmospheric pressure acting on the pressure face 19 of the piston 11 swings the piston 11 open. As the piston moves past port 27, residual air in cylinder section 7a is trapped and compressed, along with air entering cylinder section 7a via the bleed 39. Thus, pressure P2 rises and slows the piston. Ultimately, pressure P2 exceeds atmospheric pressure, and air is forced out through the bleed 39 back to the atmosphere and the piston is brought to a soft cushioned stop at the position shown in dotted lines in FIG. 4. After the piston stops, air at atmospheric pressure enters cylinder section 7a through the bleed 39 and slowly moves the piston back to a position as shown in solid lines in FIG. 4 wherein the port 27 is partially opened, and the bleed is balanced by flow of air (via pilot valve 35, which is open) into manifold 31.

On opening of the piston or gate 11 of valve A, the vehicle 3 is propelled into section 1a of the tube 1 via atmospheric pressure acting on the rear of the vehicle. After the vehicle has passed valve A, the pilot valve 35 of valve A is closed. A predetermined amount of atmospheric air is allowed to enter section 1a of the tube 1 from the station S1 behind the vehicle, and then the piston or gate 11 of valve A is closed. This is accomplished by setting pilot valve 37 in position for communication between chamber 21 and manifold 31, and for blocking the atmospheric air inlet port 38. At this time, pressures P1 and P5 are atmospheric. Pressure P2 is atmospheric since pilot valve 35 has been closed, and the bleed 39 has supplied atmospheric air to the portion of cylinder section 7a below port 27 (i.e., to the left of face 17 in FIG. 4). Thus, a force equal to atmospheric pressure times the area of pressure face 19 of the piston, i.e., the amount by which the area of face 17 exceeds the effective area of face 15, acts to close the piston. As the piston closes, the air in cylinder section 7a expands, meaning that pressure P2 decreases. Pressure P1 also decreases due to throttling of air rushing into the tube 1 behind the vehicle. The chambers in the valve and its passages are dimensioned so that the forces on the piston cause it to slowly and softly seat against the shoulder 23 at the S1 end of section 1a of the tube. Pressure P2 in cylinder section 7a returns to atmospheric pressure while pressure P1 continues to decrease, insuring that the piston face 15 seats firmly against the shoulder 23. Pilot valve 37 is then returned to its initial FIG. 2 position for admission of air at atmospheric pressure to chamber 21 while blocking manifold 31 from chamber 21.

When the piston or gate 11 of valve A is closed, expansion of the slug of air trapped in the tube 1 between the rear of the vehicle and this gate supplies an accelerating force on the rear of the vehicle, and the vehicle continues to accelerate until it reaches the point where the pressure ahead of the vehicle is approximately equal to the pressure behind the vehicle. The vehicle then begins to decelerate, compressing residual air in the tube 1 ahead of the vehicle (with attenuation of air behind the vehicle). Thus, as the vehicle approaches valve B, it compresses air between the forward end of the vehicle and the end face 15 of the piston or gate 11 of valve B, meaning that pressure P1 acting on end face 15 of valve B rises. This may be envisioned by referring to FIG. 2 and considering that it shows valve B (instead of valve A) and station S2 (instead of station S1) and that the vehicle is approaching the end face 15 of the piston from the left.

As pressure P1 acting on the end face 15 of piston 11 of valve B rises, pressures P2, P3 and P5 are atmospheric. Pressure P1 ultimately rises above atmospheric pressure, and a force equal to pressure P1 minus 1 atmosphere times the area of the end face 15 of piston 11 of valve B acts to swing the latter open. The piston travels through angle Y before communication is established between the tube section 1a and the station S2. Thus, it travels through this angle before pressure P1 is reduced to atmospheric pressure. As the piston 11 of valve B travels through this angle, the center of gravity G of the counterweight and piston combination overcenters (i.e., passes over the axis of rotation of the piston), and the resulting gravity bias on the piston in conjunction with its inertia insure that the piston opens fully. Pressure P2 remains at atmospheric pressure due to venting via the check valve 29 until the piston passes the port 27 and, when this occurs, air is trapped in cylinder section 7a, causing P2 to rise, slowing the motion of the piston and bringing it to a soft cushioned stop.

With the piston or gate 11 of valve B open, the vehicle passes through the valve and proceeds into the station B. As the rearward end of the vehicle passes the valve B, P1 and P5 drop to vacuum. With P2 and P3 at atmospheric pressure, the piston 11 of valve B starts to close. As it closes, air in cylinder section 7a is expanded and its pressure P2 decreases. As P2 decreases to near vacuum, face 19 of piston 11 acts against atmospheric pressure P3 in chamber 21 to slow the motion of the piston, so that the closing motion is soft. Air then bleeds into cylinder section 7a via the bleed port 39 to raise P2 to atmospheric pressure to insure that the piston seats firmly against shoulder 23.

With valve B closed, entry of air into station S2 behind the vehicle is limited to leakage from atmosphere around the piston 11. Hence, as the train proceeds into the station, pressure P5 remains low and the effect is to continue to decelerate the vehicle until it stops in station S2 (FIG. 1E).

In case of an emergency, it may be necessary to flood the tube with air by opening one or the other or both of valves A and B. This can be readily accomplished by opening the pilot valve 35 of the desired valve or valves. With the pilot valve 37 in the position shown in FIG. 2 so that pressure P3 in chamber 21 is atmospheric, the piston 11 opens quickly on opening valve 35 (which effects dropping P2 to vacuum).

FIGS. 8-10 illustrate a modification of the above-described construction for valves A and B, which operates on the same basic principles, but which utilizes an auxiliary piston for driving the gate instead of utilizing a single differential piston as the gate. As shown therein, the valve comprises a main toroidal cylinder 47 extending lengthwise of the tube 1 at the top of the tube, i.e., the toroidal axis of the cylinder extends horizontally transversely of the tube above the tube. The toroidal bore of this cylinder is of uniform diameter throughout its extent, and opens at 47c into the tube on that side of the toroidal axis toward the station. A shaft 49 is journaled on the toroidal axis of cylinder 47. Keyed on this shaft is a gate 51 constituted by a toroidal piston adapted to swing about the axis of the shaft between a closed position extending out of the open end 47c of the cylinder into the tube blocking the tube and an open position within the cylinder clear of the tube. This gate or piston 51 is of uniform diameter throughout its extent, corresponding to the bore of cylinder 47, and may be of hollow construction as illustrated to reduce its weight. The lower end face of piston 51 is designated 53 and its upper end face is designated 55. When the piston is in its closed position, its lower end face 53 seals against shoulder 23 around the tube, as above.

Cylinder 47 has a port 27a (corresponding to port 27) provided with a check valve 29a (corresponding to check valve 29), and a vacuum manifold 31a (corresponding to manifold 31) provided with a check valve 33a (corresponding to check valve 33). Manifold 31a is adapted for communication with port 27a via a pilot valve 35a (corresponding to pilot valve 35). A bleed 39a (corresponding to bleed 39) is provided for supplying air at atmospheric pressure from a chamber 41a (corresponding to chamber 41) to the closed end of cylinder 47.

An auxiliary toroidal cylinder 57 is located alongside the tube 1 and main cylinder 47 in coaxial relation to the latter. The shaft 49 extends from the main cylinder over to the auxiliary cylinder and has a toroidal auxiliary piston 59 keyed thereon working in the auxiliary cylinder. The ends of this auxiliary piston are designated 59a and 59b. The auxiliary cylinder has a chamber 61 at one end (corresponding to chamber 21) and a pilot valve 37a (corresponding to pilot valve 37). The other end of the auxiliary cylinder is interconnected with the main cylinder as indicated at 63. The auxiliary piston serves as a counterweight for the main piston 51, and the center of gravity of the combination of the two pistons is indicated at G. It will be observed that this overcenters as the main piston 51 swings between its closed and open positions.

The sum of the area of the upper end face 55 of the main piston 51 and the area of the lower end face 59a of the auxiliary piston is equal to the area of the upper face 17 of piston 11; the area of the lower end face 53 of the main piston 51 and the area of the upper end face 59b of the auxiliary piston 59 are respectively equal to the area of the lower end face 15 of piston 11 and area of the upper end face 19 of piston 11. Accordingly, the operation of the valve is basically the same as that of the valve A or B described above. Thus, as to the entrance valve function of the valve shown in FIGS. 8-10, on opening pilot valve 35a, dropping P2 to vacuum, P3 acting on face 59b of the auxiliary piston 59 swings the auxiliary piston counterclockwise as viewed in FIG. 10 to swing the piston or gate 51 open, and valve 35a is then closed. On setting pilot valve 37a in position for communication between chamber 61 and vacuum manifold 31a, the auxiliary piston is swung in clockwise direction as viewed in FIG. 10 to swing the piston or gate 51 closed. As to the exit valve function of the valve shown in FIGS. 8-10, rise in P1 on approach of the vehicle swings the piston or gate 51 open.

FIGS. 11 and 12 show another modification of the valve construction of FIGS. 2-7 wherein the bore of the toroidal cylinder is generally of uniform diameter throughout its length. The cylinder is here designated 7e to distinguish it from cylinder 7. The toroidal piston, designated 11c to distinguish it from piston 11, has a cross-sectional diameter somewhat less than that of the bore in cylinder 7e, and is provided at its upper end with a sealing ring 11d, forming an enlargement corresponding to 11b, and providing a pressure face 19a corresponding to face 19. This sealing ring, accommodated in an annular groove 71 in the piston, is in sliding sealing engagement with the bore of the cylinder. The effect of the smaller cylinder bore 7b of the construction shown in FIGS. 2-7 is provided by a sealing ring 73 mounted in the cylinder below chamber 21, with which the piston is in sliding sealing engagement. Two counterweights 13 are shown in FIG. 12 for the piston. Otherwise the construction corresponds to that shown in FIGS. 2-7, and the operation is the same.

FIGS. 13-17 illustrate a further modification of the valve similar to the modification in FIGS. 8-10 but having a special gate construction. As shown, this further modification has a main toroidal cylinder or chamber 77 (similar to 47) which curves upward away from tube 1 and which is open at its lower end indicated at 77c to the tube on that side of the toroidal axis toward the station S. The short section of the tube 1 on the station side of the valve is referred to as the airlock AL. A shaft 79 (like shaft 49) is journaled on the toroidal axis of the chamber 77. The latter is of circular cross section and its toroidal axis is transverse to and slightly above the tube. The upper end of the chamber 77 is closed as indicated at 77d, with this closure being of inwardly directed frustoconical form.

The gate of the modification shown in FIGS. 13-17 is designated in its entirety by the reference numeral 80. It is constituted by two conical members 81 and 83 mounted with their axes generally at right angles on a frame 85 which extends radially outward from shaft 79. These two conical members are preferably formed as hollow conical shells, 81 being the lower and 83 the upper of the two. Member 81, which may be referred to as the cap, has its apex secured to the frame 85 adjacent the outer end of the latter as indicated at 87 and extends on the bottom side of the frame with its conical axis at a 45.degree. angle to the frame. Member 83, which may be referred to as the driver, has its apex secured to the frame 85 adjacent the outer end of the frame as indicated at 89 and extends on the top side of the frame with its conical axis at a 45.degree. angle to the frame. The gate 80 is swingable on the axis of shaft 79 between the closed position shown in solid lines in FIG. 15 and the open position shown in dotted lines in FIG. 15. In the closed position, frame 85 is generally at an angle of 45.degree. below horizontal, and the rim 81a of the cap 81 is in sealing engagement with the shoulder 23 around the tube 1. In the open position, wherein the gate is swung upward, both conical members 81 and 83 are retracted into the chamber 77 clear of the tube 1, the driver (i.e., the upper conical member) nesting over the conical upper end closure 77d of chamber 77. The driver 83 is preferably slightly larger than the lower conical member and has a slightly greater moment arm about shaft 79 than the cap 81. Its rim 83a fits in chamber 77 with a small clearance C therebetween.

An auxiliary cylinder or chamber 89 is located alongside the tube 1 and the main cylinder or chamber 77 in coaxial relation to the latter. This auxiliary chamber 89 is a partial toroid, preferably of rectangular cross section, having a lower end 89a which is open to the atmosphere and an upper end 89b which is closed. The shaft 79 extends from the main chamber into the auxiliary chamber. An impeller 91 in the form of a vane extends radially outward from the shaft 79 in chamber 89 and has a relatively tight sliding fit in chamber 89 to serve as a piston therein. It is also so weighted and so located on the shaft 79 as to constitute a counterweight for the gate 80, preferably establishing the center of mass of the entire gate/impeller assembly (which assembly may be referred to as the rotor R) adjacent to or on the axis of rotation of this assembly (i.e., the axis of shaft 79).

The position of the rotor R is controlled by controlling the pressures in the main chamber 77 and the auxiliary chamber 89. For this purpose, the auxiliary chamber 89 has a vacuum vent 92 having a pilot valve 93 therein extending from a point near its upper end to a vacuum manifold 95. It also has a relatively large atmospheric vent 97 having a pilot valve 99 therein and a relatively small atmospheric vent 101 having a pilot valve 103 therein at its upper end. These pilot valves are linked together in suitable manner such that the two atmospheric vents 97 and 101 are open when the vacuum vent 92 is closed and vice versa.

The main chamber 77 has an atmospheric outlet 105 at the top with a check valve 107 therein that allows for flow of air out of chamber 77 to the atmosphere while checking against flow back into the chamber; a relatively large air inlet 109 having a check valve 111 and a pilot valve 113; and a relatively small air inlet 115 with a pilot valve 117 therein. A passage 119 interconnects the tube 1 on the side of gate 80 away from the station and chamber 77 adjacent its upper end. This passage has a pilot valve 121 therein. Air inlet 109 is connected to passage 119. At 123 is indicated a bias port which extends from about the midpoint of the outer side of chamber 77 to the vacuum manifold 95 and which has a pilot valve 125 and baffles 127 therein.

The relative angular location and size of the vacuum vent 119 and atmospheric outlet 105 of the main chamber 77 and the vacuum vent 92 and atmospheric vents 97 and 101 of the auxiliary chamber shown in the drawings are illustrative only. The operation of the FIG. 13 valve depends on the proper location and sizing of each of these items (one example of which is shown in FIG. 15). They can be installed at different lateral locations so that any angular location is possible for any of these items.

The operation of the valve shown in FIGS. 13-15 is described below in conjunction with a trip of a train from station S1 to station S2 to FIG. 1A. The description uses the nomenclature and valve numbers from FIG. 15. For convenience and clarity, FIGS. 16 and 17 show the entrance valve A and exit valve B, respectively, each oriented to correspond to FIG. 1A. Further, FIG. 16 shows only those features necessary for the valve to operate as an entrance valve and FIG. 17 shows only the features required for the valve to operate as an exit valve; the pilot valves or check valves associated with the various features not shown are always closed for the situation illustrated.

ENTRANCE VALVE OPENING (FIG. 16)

Before the trip begins, the train is stationary in station S1, valves A and B are closed, and the tube has been evacuated (FIG. 1A). The condition of the pilot valves of entrance valve A and various pressures within this valve are as follows: ---------------------------------------------------------------------------

Pilot Valve Condition Chamber Pressure* __________________________________________________________________________ 93 closed Main** 77 A 99 and 103 open Auxiliary*** 89 A 113 closed Tube 1 V 117 closed Airlock AL A 121 closed 125 closed __________________________________________________________________________

The forward end of the train is in the airlock so that flow of atmospheric air from the station S1 into the airlock is prevented.

The trip is initiated by opening entrance valve A. This is accomplished by opening the pilot valve 121 of valve A. The pressure in the main chamber 77 rapidly decreases as air flows out through the vacuum vent 119 into the tube 1. As the pressure nears tube pressure, the rotor R begins to move because the torque caused by the pressure difference across the driver 83 exceeds that caused by the pressure difference across the cap 81. This happens somewhat before the pressure reaches tube pressure, since the driver 83 has a slightly larger area and moment arm than the cap 81. As the main chamber 77 drops to tube pressure, the rotor R rapidly accelerates until the valve has opened sufficiently for the atmospheric air in the airlock AL to escape into the tube 1. The acceleration is somewhat impeded by expansion of the air in the auxiliary chamber 89 until the impeller 91 passes the large atmospheric vent 97, after which there is essentially no pressure difference on the impeller. After the air has escaped from the airlock AL, the rotor R coasts with virtually no acceleration or deceleration until the driver 83 begins to cross the vacuum 119 of the main chamber 77. As the driver crosses the vent, the flow of air out of the chamber 77 is progressively cut off and the thin air is compressed, causing a braking torque which brings the rotor R to a soft stop shortly after the driver has fully passed the vent 119. The clearance C around the driver 83 provides sufficient damping to eliminate any tendency to bounce. It seems desirable to locate the center of mass of the rotor R such that the force of gravity will provide a small torque that insures that the rotor continues to move slowly until the driver rests against the conical closure 77d of the main chamber 77.

With entrance valve A open, the train proceeds into the tube 1, as indicated in FIG. 1B, and pilot valve 121 of entrance valve A is closed.

ENTRANCE VALVE CLOSING (FIG. 16)

When the rear end of the train has passed entrance valve A, the condition of the pilot valves of entrance valve A and various pressures within the valve are as follows: ---------------------------------------------------------------------------

Pilot Valve Condition Chamber Pressure __________________________________________________________________________ 93 closed Main 77 A 99 and 103 open Auxiliary 89 A 113 closed Tube 1 A 117 closed Airlock AL A 121 closed 125 closed __________________________________________________________________________

The gate assembly 80 is clear of the tube 1 with the driver 83 resting against the conical closure 77d of the main chamber 77.

Entrance valve A is readied for closing by opening pilot valve 113, thus opening the large inlet 109. The valve does not move, however, because no pressure differential exists. When the train has proceeded a predetermined distance into the tube, entrance valve A is closed on command. This is accomplished by a single operation that closes pilot valves 99 and 103 and opens pilot valve 93. The air in the auxiliary chamber 89 is quickly exhausted via the vacuum vent 92 and atmospheric pressure acting on the impeller 91 drives the valve A closed. Pressure in the main chamber 77 remains essentially equal to tube pressure because of the large inlet 109. As the impeller 91 crosses the vacuum vent 92, it begins to compress the thin air in the auxiliary chamber 89. When the pressure exceeds atmospheric, it slows the rotor R and brings it to soft stop just before the cap 81 engages the seat 23. Damping is provided by a fixed leakage past the impeller 91. This occurs even though a pressure drop develops across the cap 81 as it impinges upon the flow. This pressure drop causes the cap 81 to seat firmly as the compressed air in the auxiliary chamber 89 leaks past the impeller 91. Once entrance valve A is closed, pilot valves 93 and 113 are closed and pilot valves 99 and 103 are reopened thus returning the entrance valve to the conditions that prevailed before the trip began.

The train continues on its trip to station B as shown in FIG. 1C.

During entrance valve operations, only pilot valves 93, 99, 103, 113 and 121 were used and the check valve 107 did not open. If the valve were never to be used as an exit valve, pilot valves 117 and 125, check valve 105, and their associated ducting (FIG. 15) would not be needed as indicated on FIG. 16. System considerations, however, may make it desirable for all valves to be alike so that the trains can be operated in reverse if necessary.

EXIT VALVE OPENING (FIG. 17)

As the train approaches station B, the condition of the pilot valves of exit valve B and various pressures within the valve are as follows: ---------------------------------------------------------------------------

Pilot Valve Condition Chamber Pressure __________________________________________________________________________ 93 closed Main 77 4 99 and 103 open Auxiliary 89 A 113 closed Tube 1 less than A 117 closed Airlock AL A 121 closed 125 open __________________________________________________________________________

With pilot valve 125 open, there is a continuous flow of air from the airlock AL, past the driver 83 which has a small amount of clearance C around it, into the main chamber 77, and out through the bias port 123 to the vacuum manifold 95. The bias port is sized so that this flow results in a predetermined pressure (P) in the main chamber 77 that is somewhat less than atmospheric. The bias port may contain baffles as indicated at 127 so that the pressure drop from the main chamber 77 to the vacuum manifold occurs in several steps, thereby avoiding a potential source of noise.

As the train approaches exit valve B, it is rapidly compressing the air ahead in the tube 1. When the tube pressure reaches a pressure somewhat less than the bias pressure P in the main chamber 77, the exit valve begins to open. This occurs before the pressure reaches P because the area and moment arm of the driver 83 are slightly larger than those of the cap 81. The rotor R accelerates rapidly as the tube pressure continues to rise. The air in the auxiliary chamber 89 expands until the large atmospheric vent 99 is passed by the impeller 91, but the resisting force on the impeller is small compared to that pushing the cap 81.

As the gate assembly 80 moves into the main chamber 77, the pressure in the main chamber 77 rapidly rises to atmospheric since the bias port 123 does not have sufficient capacity to hold the bias. When the pressure reaches atmospheric, air exhausts through the atmospheric outlet 105 as well as the bias port 123 thus maintaining approximately atmospheric pressure in the main chamber 77 until the driver 83 crosses the bias port 123 and atmospheric outlet 105. As it crosses the atmospheric outlet 105, flow is progressively cut off and the driver 83 compresses the air bringing the rotor R to a soft stop. Again, bounce is prevented by the damping effect of the clearance C around the driver 83. The rotor R comes to rest with the driver 83 against the conical closure 77d of the main chamber 77 and the train proceeds through the exit valve B as shown in FIG. 1D.

EXIT VALVE CLOSING (FIG. 17)

Once the train has passed through exit valve B into station B, the valve must be closed to preserve the vacuum in the tube 1. The air that was trapped behind the train when the entrance valve A closed has been expanded to near vacuum. The train has nearly stopped and its rear end is in the airlock AL blocking flow of air from the station S2 into the tube 1. The condition of the pilot valves of exit valve B and various pressures within the valve are as follows: ---------------------------------------------------------------------------

Pilot Valve Condition Chamber Pressure __________________________________________________________________________ 93 closed Main 77 V 99 and 103 open Auxiliary 89 A 113 closed Tube 1 V 117 closed Airlock AL V 121 closed 125 closed __________________________________________________________________________

As soon as the rear end of the train has passed through the exit valve, pilot valve 117 is opened and air enters the main chamber 77 through the small inlet 115. With vacuum operating on the other surfaces of the gate assembly 80, the rotor R accelerates until it reaches a speed that is limited by the flow rate through the small inlet 115. The rotor R continues at this speed until the exit valve is nearly closed. When the impeller 91 crosses the atmospheric vent 99, it begins compressing the air trapped in the auxiliary chamber 89 which brakes the rotor R and brings it to a stop with the cap 81 seated. Leakage past the impeller 91 and flow of air through the small atmospheric vent 103 allows the compressed air to escape so that the cap 81 remains seated with no bounce.

The train comes to a stop in station B as shown in FIG. 1E and the pilot valve 117 of exit valve B is closed so that the valve is ready to be biased for the approach of the next train.

When the valve is used only as an exit valve, pilot valves 93, 99, 103, 113 and 121 are not used, as indicated in FIG. 17.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

What is claimed is:

1. In a high-speed ground transportation system having an evacuated tube adapted for propulsion of a vehicle therethrough, a station for the vehicle in communication with the earth's atmosphere, and a valve for the tube adjacent the station, said valve comprising a toroidal cylinder on the outside of the tube having its toroidal axis transverse to the tube, said cylinder having one end open to the tube on that side of said axis toward the station, and a gate constituted by a piston rotatable about said axis between a closed position extending out of said open end of the cylinder into the tube and blocking the tube and an open position within the cylinder clear of the tube.

2. In a high-speed ground transportation system as set forth in claim 1, said cylinder having a port in communication with the atmosphere, and a check valve for said port adapted to open in the direction for flow of air from the cylinder to the atmosphere.

3. In a high-speed ground transportation system as set forth in claim 2, said port being located intermediate the ends of the cylinder and being blocked by the piston as it rotates past said port, and said cylinder having a bleed at its other end in communication with the atmosphere for bleeding atmospheric air into said other end of the cylinder.

4. In a high-speed ground transportation system as set forth in claim 3, means for drawing a vacuum in the cylinder via said port.

5. In a high-speed ground transportation system as set forth in claim 4, said means for drawing a vacuum in the cylinder comprising an interconnection between said port and a source of vacuum, and a pilot valve in said interconnection.

6. In a high-speed ground transportation system as set forth in claim 5, said source of vacuum being said tube.

7. In a high-speed ground transportation system as set forth in claim 5, said interconnection including a check valve therein adapted to open in the direction for flow of air from the cylinder to said source of vacuum.

8. In a high-speed ground transportation system as set forth in claim 5, said piston being a differential piston having an enlarged section adjacent its end toward said other end of the cylinder providing a pressure face facing toward said open end of the cylinder, and means for selectively applying atmospheric air or vacuum to said pressure face.

9. In a high-speed ground transportation system as set forth in claim 8, said means for selectively applying atmospheric air or vacuum to said pressure face comprising a chamber in communication with the cylinder, and a pilot valve having a connection to the atmosphere and a connection to said source of vacuum and adapted in a first position to establish communication from the atmosphere to said chamber and in a second position to establish communication between said chamber and said source of vacuum.

10. In a high-speed ground transportation system as set forth in claim 5, said piston being connected to an auxiliary toroidal piston rotatable in an auxiliary toroidal cylinder, said auxiliary cylinder having one end interconnected with said first-mentioned cylinder, and means for selectively applying atmospheric air or vacuum to the other end of said auxiliary cylinder.

11. In a high-speed ground transportation system as set forth in claim 10, said means for selectively applying atmospheric air or vacuum to said auxiliary cylinder comprising a chamber in communication with said auxiliary cylinder, and a pilot valve having a connection to the atmosphere and a connection to said source of vacuum and adapted in a first position to establish communication from the atmosphere to said chamber and in a second position to establish communication between said chamber and said source of vacuum.

12. In a high-speed ground transportation system as set forth in claim 1, said tube having an enlarged section providing an annular seat therearound engageable by the end of the piston in the tube in the closed position of the piston.

13. In a high-speed ground transportation system as set forth in claim 12, overcentering biasing means for the piston acting to bias it in closing direction when the piston is in closed position and to bias it in opening direction after the piston has swung open a predetermined amount.

14. In a high-speed ground transportation system as set forth in claim 12, said enlarged section of the tube being shaped so that the piston, in swinging open away from said seat, swings through a finite angle before communication of air is established between the tube and the station.

15. In a high-speed ground transportation system as set forth in claim 14, means for counterbalancing the piston with the center of gravity of the piston and said counterbalancing means located to overcenter as the piston swings between closed and open positions so that the piston is biased in closing direction when in its closed position and in opening direction after it has swung open through said finite angle.

16. In a high-speed ground transportation system as set forth in claim 1, said piston being of hollow toroidal form.

17. In a high-speed ground transportation system as set forth in claim 1, said piston comprising a first member constituting a driver and a second member constituting a cap.

18. In a high-speed ground transportation system as set forth in claim 17, said driver and said cap each comprising a conical shell and arranged with their apices adjacent one another and their axes generally at right angles to one another.

19. In a high-speed ground transportation system as set forth in claim 17, said piston being connected to an auxiliary piston rotatable in an auxiliary toroidal cylinder, the first-mentioned cylinder being closed at its other end, a passage having a pilot valve therein interconnecting the tube and the first-mentioned cylinder adjacent its said closed end, an air inlet interconnecting said passage and the closed end of the first-mentioned cylinder having a check valve and a pilot valve therein, said auxiliary cylinder being open at one end and closed at the other and having a vacuum vent adjacent its closed end having a pilot valve therein, and relatively large atmospheric vent adjacent its closed end and small atmospheric vent at its closed end each having a pilot valve therein.

20. In a high-speed ground transportation system as set forth in claim 17, said piston being connected to an auxiliary piston rotatable in an auxiliary toroidal cylinder open at one end and closed at the other, said first-mentioned cylinder being closed at its other end and having an atmospheric outlet with a check valve therein adjacent its closed end, an air inlet with a pilot valve therein at its closed end and a bias port intermediate its ends connected to vacuum and having a pilot valve therein, said auxiliary cylinder having a relatively large atmospheric vent adjacent its closed end and a relatively small atmospheric vent at its closed end each having a pilot valve therein.

21. In a high-speed ground transportation system as set forth in claim 17, said piston being connected to an auxiliary piston rotatable in an auxiliary toroidal cylinder open at one end and closed at the other, the first-mentioned cylinder being closed at its other end, a passage having a pilot valve therein interconnecting the tube and the first-mentioned cylinder adjacent its said closed end, an air inlet interconnecting said passage and the closed end of the first-mentioned cylinder having a check valve and a pilot valve therein, said auxiliary cylinder having a vacuum vent adjacent its closed end having a pilot valve therein, and relatively large atmospheric vent adjacent its closed end and small atmospheric rent at its closed end each having a pilot valve therein, said first-mentioned cylinder having an atmospheric outlet with a check valve therein adjacent its closed end, an air inlet with a pilot valve therein at its closed end and a bias port intermediate its ends connected to vacuum and having a pilot valve therein.