US 3629596 A
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I United States Patent Inventor James Mllner Wills 56] References Cited A l No $332" UNlTED STATES PATENTS mire Dec. 29, 1970 2,362,l5l 11 1944 Ostenberg 290/1 Patented Dec. 21,1971 3,l02,205 8/1963 Combs 290/1 Assignee Gmlfil Ekcmc p- Primary Examiner-G. R. Simmons Altorneys-Raymond H. Quist, Henry W. Kaufmann, Frank L.
Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: The structure of a free piston engine is in- FREE PISTON GiENERATOR tegrated with a magnetic circuit. The magnetic circuit has al- 3 2 temate magnetic flux paths with common central legs having US. Cl 290/1, generating coils thereon. A portion of the reciprocating piston 123/46 completes first one flux path and then the other. Permanent Int. Cl t. 02p 9/04 magnets are included in the circuit arranged so that the Field of Search I 290/1; direction of magnetic flux in the central leg reverses' as the 12 /46 piston reciprocates, thereby generating an alternating current.
"5B 64 7o 56 ea so \72 34 36 f 32 [8 4 l2- 50 -ss l PATENTEU UECZI I971 SHEET 1 [1F 2 INVENTOR.
JAMES M. WILLS ATTORNEY.
PATENTED 05021 IQTI 3.629.596
SHEET 2 [IF 2 INVENT JAMES MW 3 BYWWW I ATTORNEY.
FREE PISTON GENERATOR BACKGROUND OF THE INVENTION This invention relates generally to prime-mover-generating plants, and more particularly, to a free piston generator.
Gasoline engines are effective as prime movers for generators at ratings of 1,000 watts or above, but below that size they become temperamental and unreliable. Below the 1,000 -watt range and down to the range where primary batteries become practical, say watts, there is a need for an economical and reliable prime mover generator. Free piston engines have previously been disclosed, but have been used primarily as air compressors or hot gas generators.
SUMMARY OF THE INVENTION In a preferred form of the invention, a cylinder having combustion chambers at each end encloses a reciprocating shuttle having a piston at each end. The cylinder is enlarged in the center to form bounce chambers at each end, and the shuttle also is enlarged to form scavenge pistons at each end. A combustible mixture is carbureted alternately to each bounce chamber, and is forced by the respective scavenge piston through a passage in the shuttle to the combustion chamber at the opposite end of the cylinder. The combustible mixture forces out the exhaust gases from the previous cycle and is ignited by compression, then driving the shuttle.
A magnetic circuit extends from the enlarged center portion of the cylinder including a plurality of radially extending, centrally located legs, and annular disks at each end. Axially extending members connect the central legs with the disks on either side. The enlarged portion of the shuttle completes a first magnetic circuit including one annular disk and the central legs in one shuttle end position, and a second magnetic circuit including the other annular disk and the central legs in the opposite shuttle end position. Permanent magnet(s) are included in the magnetic circuit arranged so the direction of magnet is flux in the central legs alternates as the shuttle reciprocates. Coils are wound on the central legs so that an alternating current is induced by the changing magnetic flux.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic in cross section of a free piston generator in accordance with the invention; and
FIG. 2 is a schematic cross section along the line 22 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, cylinder 10 has combustion chambers 12 and 14 at each end. Shuttle 16 has pistons 18 and 20 at opposite ends, and reciprocates within cylinder 10. Bounce chambers 22 and 24 are provided in an enlarged central portion of cylinder 10.
As shuttle 16 moves to the left, a combustible mixture is carbureted through check valve 26 into bounce chamber 24. The combustion mixture introduced into combustion chamber 12 during the previous cycle is compressed by the left movement of piston 18 until it ignites, forcing shuttle 16 to the right. The enlarged central portion of shuttle 16 forms scavenge pistons 28 and 30. As scavenge piston 30 moves to the right, the combustible mixture contained in bounce chamber 24 is forced into shuttle passage 32. When exit 34 of shuttle passage 32 becomes aligned with intake port 36, the combustible mixture is admitted to combustion chamber 12 and forces the burned gases out exhaust port 38.
During movement of shuttle 16 to the right, a combustible mixture is carbureted to bounce chamber 22 through check valve 40. This mixture is forced into shuttle passage 42 when shuttle 16 is forced to the left by combustion in chamber 14, and then into combustion chamber 14 when intake port 44 is aligned with exit 46 of passage 42. The incoming combustible mixture forces the burned gases out exhaust port 48, and recharges combustion chamber 14 for the next cycle. Thus each movement of shuttle I6 to the left charges the right combustion chamber, and causes compression ignition of the mixture in the left combustion chamber. The reverse happens when the shuttle moves to the right.
Since there is no piston rod extending outside cylinder 10 in the embodiment of the free piston engine of this invention, an alternate means for starting the engine must be employed. Intake valve 50 is provided to admit a compressed gas such as air to combustion chamber 12 overcoming the tension spring associated with valve 50, thereby driving shuttle 16 to the right. In a similar manner, intake valve 52 is used to admit compressed gas to combustion chamber 14 to drive shuttle 16 to the left. By utilizing compressed gas to move shuttle 16 toand-fro, combustible mixtures are introduced to the combustion chambers and ignition produced.
In accordance with the invention, a magnetic circuit is associated with the free piston engine thus far described. Referring to FIGS. 1 and 2 in which the same identifying numbers are used to identify the same parts, near the ends of the enlarged portion of cylinder 10 annular disks 54 and 56 are provided. Radially extending from the enlarged portion of cylinder 10, and at the center thereof, are a plurality of bars 58 each having a coil 60. Forming connections between bars 58 and disks 54 and 56 are members 62. At least the annular portions 64, 66, and 68 are of a magnetic material, whereas the annular portions 70 and 72 between the magnetic portions 64, 66, and 68 are of diamagnetic material.
Considering just the upper portion of FIG. I for the moment, it can be seen that a first magnetic circuit comprising annular portion 64, disk 54, member 62, bar 58, and annular portion 66 has been described. This circuit is completed by the enlarged portion of shuttle 16 in the position illustrated.
A second magnetic circuit comprising annular portion 68, disk 56, member 62, bar 58, and annular portion 66 is also provided. This magnetic circuit is incomplete when shuttle I6 is in the left position.
Coil 60 is mounted on bar 58, an element common to both magnetic circuits. If magnetic flux is caused to change in bar 58, a current is generated in coil 60 in accordance with wellknown principles. This change of magnetic flux is produced by having the direction of magnetic flux in the first and second magnetic circuits opposite as far as the common element, bar 58, is concerned. Magnetic flux is produced in this invention by incorporating one or more permanent magnet elements in the magnetic circuits. Members 62 may be permanent magnets having their north poles at the left and their south poles at the right, for example. Under this arrangement, a coercive force exists tending to produce a counterclockwise magnetic flux in both the first and second magnetic circuits. In the position of shuttle 16 illustrated, however, a complete magnetic path including the enlarged portion of shuttle 16 exists only in the first magnetic circuit. Thus the magnetic flux in bar 58 is upwardly directed.
When shuttle 16 moves to the right, the first magnetic circuit is broken, and the second magnetic circuit is completed. Now the magnetic flux in bar 58 is downwardly directed. Thus as shuttle l6 reciprocates, the magnetic flux in bar 58 changes between upwardly and downwardly. The changing magnetic flux in bar 58 induces an alternating current in coil 60. Obviously each of the bars 58 shown in FIG. 2 and their associated coils will have the changing flux and alternating currents described.
The permanent magnets required may be other than members 62. Disks 54 and 56 may constitute the permanent magnets, with the periphery of disk 54 being the north pole, and its central portion the south pole. Disk 56 would have its north pole in the central portion, and its south pole at the periphery.
Finally, the enlarged portion of shuttle 16 may be the permanent magnet with the north pole at the left end and the south pole at the right end. Of course, the poles of the magnets may all be versed from those described.
Coils 60 may be connected in parallel as shown, or in series if desired, and are connected to output terminals 74.
While a particular embodiment of a free piston generator has been shown and described, it will be obvious that changes and modifications can be made without departing from the spirit of the invention and the scope of the appended claims.
said passage means connecting each of said bounce chambers with the combustion chamber at the opposite end of said cylinder is in said shuttle.
I claim: 5 3. A free piston generator comprising: 1. A free piston generator comprising: a cylinder having a combustion chamber at each end; a cylinder having a combustion chamber at each end; said cylinder having an enlarged central portion forming a said cylinder having an enlarged central portion forming a bounce chamber at each end;
bounce chamber at each end; a shuttle comprising a double-ended piston designed to a shuttle comprising a double-ended piston designed to reciprocate within said cylinder;
reciprocate within said cylinder; said shuttle having an enlarged center portion constituting a said shuttle having an enlarged center portion constituting a double-ended scavenge piston;
double-ended scavenge piston; means for introducing a combustible mixture alternately to means for introducing a combustible mixture alternately to each of said bounce chambers;
each of said bounce chambers; passage means connecting each of said bounce chambers passage means connecting each of said bounce chambers with the combustion chamber at the opposite end of said with the combustion chamber at the opposite end of said ylin cylinder; a magnetic circuit comprising a magnetic circuit comprising a. alternate paths including a first annular disk adjacent to a. alternate paths including a first leg adjacent to one end one end of Said enlarged central portion of said of said enlarged central portion of said cylinder, cylinder, b. a second leg adja ent t th the nd f id enlarged b. a second annular disk adjacent to the other end of said central portion of said cylinder, enlarged central portion of said cylinder, c. acentral leg, c. a plurality of radially extending legs adjacent to the d. each of aid l extending di ll f id l d center of said enlarged central portion of said cylinder, central portion of said cylinder, d. axially extending members closing said magnetic cire. axially extending members closing said magnetic circuit between said first annular disk and the outer ends cuit between said fir t l g d id nt l l d id of said radially extending legs, and between said second second leg and said central leg at the outer end of said annular disk and the outer ends of said radially extendfirst, second, and central legs, and 8 8 and i f. said enlarged portion of said shuttle completing one alenlarged portion of 4 f f f g one temate path of said magnetic circuit when it is at one imam i of 531d magnetic w i at one end of said enlarged portion of said cylinder, and end of F enlarged Porno of sad h q and completing the other alternate path when it is at the completmg Path "f' at the other end of said enlarged portion of said cylinder; 35 Said enlargFd of Sa'd cyhnderi I a coil surrounding said central leg of said magnetic circuit; cons ""9"" of Sam 'adlany extend'ng legs of and magnetic circuit; and at least one element of said magnetic circuit constituting a at east one element of said magnetic Circuit COnFtitUtmg a permanent magnet so arranged that as said shuttle Permanent i f amfnged that F F Shume reciprocates within said cylinder the direction of mag- 40 recfpmcatfis wfthm 831d cylmde' the d'rcct'on of W netic flux in said central leg alternates and an alternating P 9 lesaltemates and an alternating current is induced in said coiL current IS induced in said c0115. 2. A free piston generator in accordance with claim 1