Expansible chamber devices – With toothed gear – spline or thread rigid with working member
Patent
1987-04-10
1990-04-10
Garrett, Robert E.
Expansible chamber devices
With toothed gear, spline or thread rigid with working member
74435, 74131, 74 50, F01B 900
Patent
active
049150197
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to the transformation of a reciprocal movement obtained from a piston by the thrust of a fluid, into a rotary movement recoverable on a shaft or reciprocally.
Such transformation is traditionally obtained by a link-crank assembly with the drawbacks inherent in this system. In fact, the analysis of the force exerted on the link reveals a horizontal component, absorbing energy. In addition, for a constant rotational speed of the shaft, that of the piston follows a sinusoidal function, whence a reduced mean linear speed.
In use in thermal engines, the link-crank assembly makes it necessary to use different expedients such as ignition and exhaust advance, movement of the piston in accordance with a rigid mathematical law.
The present invention proposes overcoming these drawbacks and provides a device for transforming a reciprocal movement into a rotary movement which, while being of great mechanical simplicity, allows optimum efficiency to be obtained without requiring the use of ignition and exhaust advance of the thermal engines.
SUMMARY OF THE INVENTION
The device of the invention includes essentially two racks connected to the piston of the engine and which drive alternately a toothed sector carried by the drive shaft, two cams being also carried by the drive shaft and serving as guides for four rollers fixed to the mobile rack-piston assembly.
Advantageously, the second and last but one teeth of each of the racks are partially truncated, as well as the end teeth of this toothed sector cooperating with the racks.
The profile of the cam is designed so as to provide ignition only at the end of compression and so as to have a variation of the volume of the chamber, so of the pressure of the ideal mixture, during the whole combustion time.
Furthermore, a better exhaust and filling are obtained during the time when the piston is stopped at the end of its stroke, corresponding to a zone of the cam concentric with the axis of rotation of the output shaft.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of the invention, one embodiment thereof will be described hereafter with reference to the accompanying schematic drawings in which:
FIG. 1 shows a device having two racks cooperating with a toothed sector;
FIG. 2 shows a front and vertical sectional view of one of the cams fixed on the output shaft; and
FIG. 3 shows one embodiment with two opposed pistons.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In FIG. 1 there is shown the device of the invention formed of two racks 1, 2 integrally secured to pistons (not shown in this Figure) and moving as a single block for meshing alternately with a toothed sector 3 fixed on the output shaft. In the example chosen, racks 1, 2 have 9 teeth and the toothed sector 3 integrally secured to the output shaft has 8 teeth, for a pinion of the same modulus having 20 teeth. The second and last but one teeth of each rack 1, 2 as well as the end teeth of the toothed sector 3 are truncated, as shown in FIG. 1. This Figure shows the toothed sector 3 in an intermediate position, separated from racks 1, 2.
To provide drive continuity two cams 4, one of which is shown in FIG. 2, are fixed on the output shaft for taking over. A groove 5 formed in cam 4 guides a roller fixed to the piston-rack assembly. Groove 5 is broken down into five zones:
zone of angle .alpha., corresponding to the simultaneous drive of the ouput shaft by cam and rack at a distance V,
zone of angle .beta., corresponding to a deceleration of the rack-piston assembly,
zone of angle .gamma., stopping of this assembly,
zone of angle .delta., acceleration of the assembly,
zone of angle .OMEGA., simultaneous drive by cam and rack at speed -V.
During the end of travel strokes, the possibility of modifying the path of the groove of the cams allows the speed of movement of the mobile assembly, and so the variation of the volume of the combustion chamber to be controlled at will, depending on the fuel used.
During the rack drive the linear speed of the piston is
REFERENCES:
patent: 1346139 (1920-07-01), Smith
patent: 2513514 (1950-07-01), Poage
Denion Thomas
Drucker William A.
Garrett Robert E.
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