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 10 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 2—2 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 16 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. 1 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 16 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 16 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.

3,629,596

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.