Abstract:
A system for recirculating sealing liquid back into the liquid seal portion of a Stirling engine is disclosed. The system uses two pumping devices alternatively coupled to an accumulation reservoir to receive escaped liquid and to return it to the liquid seal. As sealing liquid accumulates, it is selectively pumped into one pumping device, while the other is discharging previously accumulated liquid. The system is then switched so that the operation of the two pumping devices is reversed.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a system for recirculating sealing liquid that has leaked from a liquid seal portion of a Stirling engine back into the liquid seal portion. 
     Stirling engines have received increasing attention in recent years owing to their high torque characteristics, clean exhaust gases, low noise, low fuel expense, low maintenance, and high durability when compared with a conventional gasoline engine. Furthermore, the thermal efficiency of a Stirling engine is equal or superior to that of the internal combustion engine because in a Stirling engine hydrogen or helium is used as the working fluid instead of air, and hence the temperature efficiency of the thermal heat exchangers is greatly improved. 
     However, since hydrogen or helium as the working fluid has a relatively small molecular structure, it is difficult to properly seal a Stirling engine. Stirling engines have accordingly exhibited high leakage rates in the sealing area between the cylinder wall and the piston rod. Conventional &#34;roll sox&#34; seals have been reasonably effective but their durability is low due to the choice of materials used therein. 
     Recently, multiple seal rings have been used to form a compound seal with a block seal portion and a liquid seal portion positioned therebelow in order to enhance durability. 
     However, the problem of leakage of the sealing liquid used in the liquid seal portion has remained, and research to solve this problem has not defined a suitable mechanism therefor. Hence, the problem of leakage remains and an effective engine must take such leakage into account. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of this invention to provide a recirculation system for handling sealing liquid that leaks out of the liquid seal portion of the compound seal. 
     Briefly, and in accordance with the present invention, a pair of pumping devices are provided each having a cylinder and piston which divides each cylinder into two chambers. One of the chambers of each of the pumping devices is provided with a spring, and working gas leaking from the block seal portion is introduced thereinto, while the second chamber of each of the pumping devices selectively communicates with a liquid tank into which sealing liquid that has leaked is accumulated. The liquid seal portion communication is established with an electromagnetic valve actuated by a signal from the second chamber; hence sealing liquid that has leaked is introduced into one of the second chambers while sealing liquid contained in the other of the second chambers is returned into the liquid seal portion. 
     It is an object of this invention to provide a system that recirculates sealing liquid back into the liquid seal portion of a compound seal for a Stirling Engine. 
     It is another object of this invention to provide a devices that is more efficient than prior art device and improves the commercial utility of a Stirling engine. 
     These and other objects of this invention will become apparent from the description of the drawings and the preferred embodiment which follow. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings; 
     FIG. 1 is a schematic view showing a system for recirculating sealing liquid that has leaked back into the liquid seal portion for use in a Stirling engine according to the present invention; and 
     FIG. 2 shows an electrical circuit to actuate an electromagnetic valve according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the drawings, and initially to FIG. 1, reference numeral 2 designates a block seal portion for preventing leakage of the working fluid, typically hydrogen or helium numeral 3 a liquid seal portion disposed below the block seal portion 2, and 31, 32 seal elements for sealing the sealing liquid. The sealing liquid is a common type of oil or other well known sealing oil. Reference numerals 4 and 5 denote a first and a second piston type pumping devices, respectively. 
     The first and the second pumping devices 4 and 5 are provided with pistons 61, 61&#39; respectively in cylinders 6, 6&#39; to divide the same into two chambers, A, B and A&#39;, B&#39;, respectively. The chambers A, A&#39; are provided with springs 7, 7&#39;, respectively and working fluid is introduced in the chambers through a pipe 8. The chambers B, B&#39; are adapted to receive and discharge sealing liquid that has leaked from the liquid seal portion 3. As shown in FIG. 1, the sealing liquid escaping from the liquid seal portion 3 is accumulated in a tank 10 through a pipe 9, and the accumulated liquid is introduced into the chambers B, B&#39; by the energization of an electromagnetic valve 15 by actuation of contacts 14, 14&#39; provided in the chambers B, B&#39; through a pipe 40 and a pipe 41. For purposes of clarity, the electrical contacts to the valve are shown in FIG. 2. Liquid may be introduced into chamber B, B&#39; on an alternative basis or by selective switching of the valve 15. 
     The pipe 12 is adapted to introduce leaked sealing liquid from the tank 10 to either the chamber B or B&#39; by a pump 11 through valve 15 to lines 40 or 41. The pipe 13 is adapted to discharge the same from either the chambers B or B&#39; to the liquid seal portion 3. 
     FIG. 2 shows an electric circuit used to actuate the contacts 14, 14&#39; and the electromagnetic valve 15 shown in FIG. 1. The valve is schematically shown in FIG. 1. Essentially it performs two coupling functions. In a first position input line 12 is coupled to line 41 and discharge line 13 is coupled to line 40. This is shown in FIG. 1. In a second coupling the valve would shift to perform the cross coupling as diagramatically shown where input line 12 would be coupled to line 40 and output 13 coupled to line 41. Such valves are well known in the art and are readily available on a commercial basis. One of electrodes 50 of the electromagnetic valve 15 is electrically coupled to the first and the second pumping devices 4, 5. In the first and the second pumping devices 4 and 5, at least one of the seal rings 62, 62&#39;, respectively, is a metallic, electrically conductive seal ring, so that the piston forms part of the electrode. The contacts 14, 14&#39; are insulated from the chambers B, B&#39; by insulators 16, 16&#39;, respectively to block the electrical conduction between the contacts and the cylinders 6, 6&#39;. The contacts 14, 14&#39; are connected to the electromagnetic valve 15 through a keep relay 17 coupled to electrode 52. The reference numeral 18 designates an electric source for the relay. 
     In operation, sealing liquid that has leaked is supplied into the chamber B&#39; of the second pumping means 5 by the pump 11 as shown in FIG. 1. Simultaneously, pre-introduced leaked liquid into the chamber B of the first pumping means 4 is discharged into the liquid seal portion 3 by the biasing force of the spring 7 and the leaked working gas pressure in the chamber A. When the leaked sealing liquid in the chamber B is completely discharged, that is, when the piston 6 reaches the bottom dead center, the contact 14 is actuated to actuate the electromagnetic valve 15 by the keep relay 17. The valve position shifts as shown schematically in FIG. 1. Thus, the pipe 12 is connected to line 40 to introduce the subsequent liquid that has leaked into the chamber B and the pipe 13 is connected to a line 41 to discharge the liquid from the chamber B&#39;. 
     When the leaked liquid is completely discharged from the chamber B&#39; namely, when the piston 61&#39; reaches bottom dead center, the contact 14&#39; is actuated to switch the electromagnetic valve to the original state as shown in FIG. 1. These operations are repeatedly carried out so as to continuously return leaked sealing liquid into the liquid seal portion 3. 
     Alternatively, proximity switches can be used as the electrical contacts. Further, it is preferable to provide a circuit to terminate action of pump 11 when the leaked liquid has filled either the first or second pumping devices. In that regard, a bypass circuit 42 is provided to recirculate the liquid back into the reservoir 10 when the leaked liquid has filled with either first or second pumping means. 
     It is apparent that other modifications are possible without departing from the essential scope of this invention.