S. L. Bapat of Department of Mechanical Engineering has invented
a compact drive mechanism for a
Reciprocating machines are generally
power consuming type or
power generating type.
Drive to the above machines is
given through a drive mechanism
comprising crank shaft and connecting
rod arrangement(s) connected
to piston(s) reciprocating in
During reciprocating motion of the
piston in the cylinder, the connecting
rod exerts a force component
perpendicular to the piston because
of which the piston rubs more
against the corresponding side of
the cylinder causing uneven and
non-uniform wear and tear to both
the piston and cylinder. This may lead to leakage of the working fluid
and malfunctioning of the machine.
In order to rectify the problem reconditioning/replacement of the
piston and/or cylinder liner may be required.
Balancing of side force is done by attaching balancing weights to the
crank to reduce the vibrations. However, in a single
cylinder drive mechanism it is not possible to balance the side force
completely and hence some vibrations are
unavoidable. Wear and tear to the gudgeon pin and crank pin are unavoidable,
calling for the periodic replacement.
Breakage of the above pins may also occur at times.
The compact drive mechanism consists of two horizontal circular discs
parallel to each other, both having a coinciding
circumferential groove of same size and shape. One of these discs
is stationary while the other (driving disc) is rotated
using a prime mover. A vertical (driven) disc with external surface
matching the curvature of the grooves is placed in
between the two horizontal plates. It rotates in the grooves about
the central axis of the mechanism and also about its
own horizontal axis, which ends up in a planetary motion. This vertical
disc has equally spaced circular holes, with same
pitch circle diameter through it.
Similarly, the horizontal stationary disc has same number of holes
to hold tubes acting as cylinders. Two circular rods are
coupled to each other at right angle to obtain a L-shaped member.
The horizontal limbs of such L-shaped members are
inserted through holes in the vertical disc and the guide sleeve
where they rotate and reciprocate and act as load bearing
limbs. The vertical limbs act as pistons and reciprocate (and simultaneously
rotate) in the respective cylinders mounted
on horizontal stationary disc. One rotation of the vertical disc
is equivalent to two strokes (one upward and one downward)
of each piston. Thus, the rotary motion is converted to reciprocating
one using this compact drive mechanism.
The drive mechanism enables it to have large stroke to diameter
ratio. Moreover, the orientation of the drive mechanism
has no effect on the performance of the application for which
it is used. The line contact between the mating members
ensures least frictional loss. The number of piston-cylinder
combinations and angular phase difference between
them can be adjusted within the geometrical constraints.
invention aims to provide a compact drive mechanism of a reciprocating
machine which is efficient in performance
and allows the piston to reciprocate in the cylinder linearly
thereby eliminating side thrust.
Indian patent application no. 480/MUM/2000 Patent grant no. 200858
Inventors: S L Bapat