A VALVE FOR A TANK AND ESPECIALLY FOR A FLOW CONTROL ARRANGEMENT HAVING A PLURALITY OF FLUID
STORAGE TANKS
BACKGROUND OF THE INVENTION
This invention relates generally to the field of flow control devices, and more particularly to a valve mechanism for a tank, and especially for a multiple tank arrangement having a flow control valve within each tank.
It is known to provide a plurality of fuel tanks on locomotive engines, with a fuel pump drawing fuel from each of the tanks simultaneously. In many applications, there is no flow control device used in the fuel line from the respective fuel tanks. In such an arrangement, when one of the tanks becomes empty, the fuel pump will draw air from that tank in lieu of fuel, thereby starving the engine of its necessary fuel supply. Once one tank becomes empty, cavitation in the fuel pump will prevent it from drawing the remaining fuel from the tanks that are not yet empty.
To overcome this problem, it is known to provide a flow control device such as an electronic solenoid valve within the fuel line from each respective tank. When a tank is nearly empty the respective fuel line solenoid valve may be closed prior to drawing air from that tank. However, such devices are complicated and relatively expensive, and have a probability of failure that is a function of the reliability of the separate fuel level measuring device and the electronic solenoid valve. Thus, there is a particular need for a fluid flow control arrangement for a plurality of fluid storage tanks that will permit a maximum amount of fuel to be drawn from the tanks and that is inexpensive to build and reliable to operate.
SUMMARY OF THE INVENTION
Thus there is a particular need for a fluid flow control arrangement having: a plurality of fluid storage tanks; a pump; a line connecting each of the tanks to the pump; an opening formed in each line within its respective tank for the passage of fluid from the tank into the line; a cam associated with each opening, each such cam being operable to be rotated from a first position remote from the respective opening
to allow unrestricted flow of fluid through the opening to a second position proximate the opening to restrict the flow of fluid through the opening.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of a multiple tank fuel system incorporating a fluid flow control valve arrangement.
Figure 2 is a top view of a valve.
Figure 3 is a cross-sectional view of the value of Figure 2.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 illustrates a fluid flow control arrangement having a plurality of fluid storage tanks 12, 14, 16 feeding a fluid such as diesel fuel, for example, to a pump 18. Pump 18 has an inlet line 20 connecting each of the tanks 12, 14, 16 to the pump 18. Pump 18 also has an outlet line 22 for providing the fluid, such as diesel fuel, for example, to an engine (not shown). A bypass line 24 is also provided at the outlet of the pump 18 in order to recycle fluid back to tanks 12, 14, 16 when the demand of the outlet line 22 is less than the pumping capacity of pump 18. Disposed in each of the tanks 12, 14, 16 is an opening in the respective ends of the inlet line 20, and an associated valve arrangement 26, 28, 30. During the operation of pump 18, fluid will pass from each of the tanks 12, 14, 16 into inlet line 20 for delivery to outlet line 22. When the fluid level in any of the tanks 12, 14, 16 reaches a predetermined low level, the respective valve 26, 28, 30 will operate to restrict the flow of fluid and air through a respective opening as pump 18 continues to draw fluid from the remaining tanks. Valve arrangement 26, 28, 30 includes both the fluid level sensing means and the fuel restriction means completely within the respective tanks 12, 14, 16 as discussed more completely with reference to Figures 2 and 3 below.
Figure 2 illustrates a top view of a valve 40 as may be used in any one or more of the valve arrangements 26, 28 30 of Figure 1. Figure 3 illustrates a cross-sectional view of valve 40 as viewed along Section A-A of Figure 2. As may be appreciated by viewing Figures 2 and 3 together, valve 40 includes a cam 42 operable to be rotated about shaft 44 by a float 46. Shaft 44 is attached by brackets 48 to a header 50.
Header 50 includes an interior chamber 52, which may be connected at an end 54 to a fuel line (not shown) such as inlet line 20 in Figure 1.
An opening 56 is also formed in header 50, connecting with chamber 52 to permit the flow of fluid contained within the tanks 12, 14, 16 into the chamber 52. As may be appreciated from Figure 3, which is viewed along a horizontal plane, as float 46 is rotated in the direction of Line B-B by changes in the fluid level within the respective tank 12, 14, 16, cam 42 is rotated from a first position remote from the opening 56 (not shown) to a second position (as illustrated) proximate the opening 56, thereby restricting the flow of fluid through the opening 56. Float 46 may be formed of any construction providing buoyancy in the fluid to be stored within the respective tank. In one embodiment, a stainless steel or other metal frame 58 is formed to encompass a buoyant insert 60. Insert 60 may be formed of rubber, wood, closed cell foam or plastic. A plurality of holes 62 may be formed in frame 58 in order to reduce the weight of the frame, thereby increasing the buoyancy of the float assembly 46. In some applications, such as in the fuel tank of a locomotive, it is important that the valve 40 be more likely to fail in an open position. For such applications, it may be desirable that the net buoyancy of the combination of the cam 42, shaft 44, and float 46 is positive in the fluid so that in the event of a mechanical failure of bracket 48, the cam 42 will be moved away from opening 56, thereby preserving the flow of fluid through opening 56.
As can be seen most clearly in Figure 3, float 46 has a cross-sectional area in the plane of the surface of the fluid that is greater along a lower cross-section than along an upper cross-section. This wedge shape provides a more stable float level when there are waves in the surface in the fluid within the tank. Because the cross- sectional area in the plane of the surface of the fluid gradually decreases from a lower cross-section to an upper cross-section, the incremental buoyancy created when a wave passes across the float 58 is less than it otherwise would be with a float having a more rectangular or symmetric cross-section. The wedge shape of float 46 also reduces the weight of the un-wetted portion of the float in relation to the wetted portion, thereby allowing the float to generate the necessary buoyancy force in a
reduced depth of fluid. This feature facilitates a design for valve assemblies 26, 28 30 that will permit the draining of the fluid to a lower level within tanks 12, 14, 16. As illustrated in Figure 3, with cam 62 in a position proximate to the opening 56, there remains a gap 64 between the sealing surface 66 of cam 42 and the sealing surface 68 of header 50. For an application of the fluid float control arrangement 10 in a locomotive, the diameter of generally circular opening 56 may be approximately one-half inch and the gap 64 no less than 0.003 inches. By insuring that the cam 42 is located no closer than 0.003 inches from the opening 56, there will continue to be a small flow of fluid through opening 56 even with the cam 42 in its closed position proximate the opening 56. The advantage of such an arrangement is that the fluid level in the respective tank will be drawn down to a level equal to the bottom of opening 56, thereby providing an additional quantity of fluid from the tank. Gap 64 should be maintained small enough so that the amount of air drawn through opening 56 with the cam in its closed position is small enough that it does not adversely affect the operation of pump 18 or any equipment located downstream of outlet pipe 22. To maintain gap 64 to a tight tolerance, it may be desirable to control the surface roughness of the sealing surfaces 66, 68 to no more than 200 micro inch and preferably to no more than about 63 micro inch.
It is known that a circular opening in a fuel supply line in a tank will generate a vortex within the fluid as the level of the fluid approaches the opening of the fuel line. Once such a vortex is formed, air will be introduced into the fuel line prior to the level of the fuel actually dropping to the level of the opening in the fuel line. Advantageously, the design of valve 40 precludes the formation of such a vortex by partially restricting the opening 56 as cam 42 moves from its open position remote from the opening 56 to its closed position proximate the opening 56. In particular, as the cam sealing surface 66 approaches the opening 56, it causes the flow area of the opening 56 to become non-circular, thereby preventing the formation of a vortex.
It is known that in multi-tank fluid systems having a valve on each respective tank suction line, that the amount of force needed to open a valve while the pump is operating may be large due to the suction force created by the pump. This problem may be overcome when using an electric solenoid valve by providing a solenoid
having sufficient force to overcome the pump suction force. Advantageously, the design of valve 40 avoids the need for such a large opening force by providing gap 64, thereby preventing the formation of a significant pressure differential across opening 56. The elimination of such suction forces is important to the proper operation of a mechanically driven float valve such as valve 40.
The combination of features of the fluid flow control arrangement and associated valve illustrated in Figures 1-3 is to provide a simple, inexpensive, reliable system that will allow a maximum amount of fluid to be drained from each of the plurality of tanks. While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalence may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appending claims.