Machine element or mechanism – Mechanical movements – Rotary to or from reciprocating or oscillating
Patent
1992-07-28
1994-11-01
Herrmann, Allan D.
Machine element or mechanism
Mechanical movements
Rotary to or from reciprocating or oscillating
74 51, 1231974, 92140, F16H 2122
Patent
active
053599080
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a system for reversibly transforming rotary motion into self-guided rectilinear motion.
Rotary motion can be obtained from rectilinear motion in various known ways which are differently reversible. The connecting rod-crank mechanism and the cam-tappet mechanism are those which because of their simplicity and symmetricality have found practically unlimited use.
DESCRIPTION OF THE RELATED ART
One of the fields in which the application of these two mechanisms has found major use is the creation of pressure chambers of variable volume, this being the field common to both pumps (of the type comprising blades, axial pistons with an oblique head or plate or pistons controlled by eccentric tracks) and internal combustion engines. The mechanism which on account of its simplicity is most widespread and versatile is represented by piston sliding within a cylindrical chamber by the effect of the movement imposed on it by a connecting rod and crank. This mechanism is in fact used in nearly all internal combustion engines and in high pressure compressors and pumps.
In spite of this, this mechanism has serious conceptual limitations in terms of the necessary obliqueness assumed by the connecting rod during crank rotation. In this respect, this obliqueness creates very high transverse thrusts on the piston, causing it to rub damagingly against the internal cylinder walls. This results in considerable power losses due to friction, the need to lubricate the cylinder within which the piston slides, the need for long pistons (skirt) to reduce the specific transverse pressure, added weight to the piston in the form of the steel piston pin, which is necessarily long as it is diametrical, high quality materials, large engagement clearances detrimental to sealing, and the presence of elastic rings which by virtue of their theoretically impossible roundness result in an engagement with the chamber which is necessarily approximate. In the specific case of internal combustion engines the connecting rod-crank mechanism connected to each individual piston involves considerable over-dimensioning of the parts in relation to the drive torque. This is because the thrust generated on a piston by the explosion is used to implement the passive stages (intake, compression, exhaust) of the other cylinders, passing via the crankshaft. In the case of high pressure hydraulic pumps, all existing types derive conceptually from the use of surfaces (case) inclined to a relative advancement trajectory of a perpendicularly sliding tappet. These types therefore in all cases use a piston (or blade or tappet) which is stressed transversely by the relative operating contact with the rotating member (oblique disc, eccentric reference circumference within which for example radially sliding pistons rotate, etc) and reacts to said transverse forces by rubbing against the walls of the chamber or the like within which it slides to achieve pumping, this rubbing causing wear, power loss, efficiency reduction with time, and limitations on the maximum speed of rotation.
SUMMARY OF THE INVENTION
The object of the present invention is to obviate all the above-noted defects typical of a connecting rod-crank mechanism and of devices conceptually based on relative movement of an inclined plane or cams.
These and further objects will be seen to be attained on reading the ensuing description relating to a system for reversibly transforming rotary motion into self-guided rectilinear motion achieved by symmetrically coupling at least two connecting rod-crank mechanisms, which are mutually associated by the pivots of their connecting rod small ends and by the engagement of identical toothed wheels fixed symmetrically onto the two specific cranks. The ensuring detailed description illustrates the application of said system to variable volume chambers, particularly for liquid pumps, gas compressors, external combustion and internal combustion engines, hydraulic motors and compressed air motors, comprising pistons unde
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Herrmann Allan D.
Laub David W.
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