Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Patent
1988-11-21
1990-10-30
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
123197AC, F16H 2130, F16H 2120, F02B 7532
Patent
active
049660438
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a crank drive as known e.g. in piston motors. Such crank drives comprise a crank shaft and a connecting rod which is linked eccentrically to the crank shaft by means of a connecting rod bearing.
SUMMARY OF THE INVENTION
The invention provides an improvement in the characteristics of a crank drive with regard to the dependence of the travel of the piston relative to the angle of rotation. The improvement is provided by arranging the connecting rod bearing eccentrically on a rotatably mounted planetary wheel. The planetary wheel is in engagement with a sun wheel by non-slip turning surfaces on each wheel. The wheels are advantageously forced against each other. The sun wheel is mounted to the casing. The ratio of the sun wheel diameter to the planetary wheel diameter is substantially equal to 1:1, in at least one embodiment, and substantially equal to 2:1 in other embodiments.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects obtained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a side view of the first embodiment;
FIG. 2 is a section along the line II--II in FIG. 1;
FIG. 2a is a mirror image of FIG. 2.
FIG. 3 is a graph of the function of the crank drive according to FIG. 1 and FIG. 2, with crank angle values on the abscissa vs. acceleration on the ordinate;
FIG. 4 is a side view of a second embodiment;
FIG. 5 is a side view of a third embodiment;
FIG. 6 is a section along the line VI--VI in FIG. 5; and
FIG. 7 is a schematic side view of a fourth embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the embodiment according to FIG. 1 and FIG. 2 a disc 4 acting as a crank 3 and having external teeth 5 is rotatably mounted in a casing 1 on a cylindrical journal 2. A sun wheel 8 having the shape of a toothed wheel 7 is rigidly and coaxially connected to the journal 2. The journal 2 can be rotated and arrested within limits with regard to the casing 1. A planetary wheel 13 having the shape of a toothed wheel 12 and having externally teeth is mounted rotatably to the crank disc 4. The planetary wheel is mounted eccentrically and parallel to the axis 11 of the journal 2. The teeth 9 of the sun wheel 8 and the teeth 14 of the planetary wheel mesh with one another.
In the present embodiment the geometrical radius r of the planetary wheel 13 is half the size of the geometrical radius R of the sun wheel 8.
The planetary wheel 13 has a paraxial pin 18 being eccentric with an eccentricity X with regard to the axis 17 of the planetary wheel 13. The connecting rod bearing 19 of a connecting rod 20 is rotatable on the pin 18.
The external teeth 5 mesh with a pinion 23 of a paraxial shaft 24. When the crank drive is used in a piston motor, the shaft 24 can be the driven shaft.
The section shown in FIG. 2 is mirrored at the center plane 25 (FIG. 2a), so that two crank discs 4 are rotatable around the axis 11 and mesh with the pinions 23 belonging to the crank disks on the shaft 24. The crank discs 4 carry a planetary wheel 13 each. These planetary wheels 13 are rigidly connected with each other by the pin 18 and they mesh with one sun wheel 7 each. For better visibility, however, the parts arranged symmetrically to the center plane 25 have been omitted in FIG. 2.
During operation, the pin 18 and with it the connecting rod bearing 19 move on an approximately elliptical orbit around the journal 2. By choosing the eccentricity X of the pin 18 on the planetary wheel 13 relative to the distance Z between the axes 11 and 17, the characteristics of the crank drive can be changed significantly with regard to a conventional crank drive equivalent to the value X/Z=0.
FIG. 3 shows diagrammatically,
REFERENCES:
patent: 1118285 (1914-11-01), Johnson
patent: 1210861 (1917-01-01), Sitney
patent: 1408439 (1922-03-01), Buckminster
patent: 2369747 (1945-02-01), Munn
patent: 4073196 (1978-02-01), Dell
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