Machine element or mechanism – Elements – Pitmans and connecting rods
Reexamination Certificate
1999-08-26
2001-08-28
Green, Mary Ann (Department: 3682)
Machine element or mechanism
Elements
Pitmans and connecting rods
C092S240000, C092S191000, C092S109000
Reexamination Certificate
active
06279421
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to rocking piston and diaphragm compressors as well as vacuum pumps. More specifically, the present invention relates to an improved connecting rod assembly for use in rocking piston compressors, diaphragm compressors and vacuum pumps that has reduced length variations thereby providing a more consistent compression ratio and reduced variations in compressor or pump performance.
BACKGROUND OF THE INVENTION
Rocking piston compressors, diaphragm compressors and vacuum pumps all use the reciprocating motion of a connecting rod to produce increased pressures within a control volume, such as a cylinder. The amount of stroke of the connecting rod determines the compression ratio for the fixed control volume. Therefore, variations in the length of the connecting rod assembly translate to variations in the compression ratio and ultimately variations in compression or vacuum pump performance. These performance variations may include changes in flow, amperage draw, maximum pressure output or vacuum levels.
A typical design for a connecting rod assembly includes a connecting rod, a diaphragm or cup and a retainer to hold the diaphragm or cup on the connecting rod. An example of a typical currently-available connecting rod assembly for a diaphragm compressor is illustrated in
FIGS. 1-3A
. A connecting rod assembly for a rocking compressor or a vacuum pump is shown in FIG.
3
B. Specifically, a connecting rod assembly is shown at
10
a
which includes a connecting rod
11
a,
a diaphragm
12
a
and a retainer plate
13
a.
The retainer plate
13
a
sandwiches the diaphragm
12
a
between the retainer plate
13
a
and a disk portion
14
a
of the connecting rod
11
a.
Because the connecting rod assembly
10
a
must be serviceable with common hand tools, threaded fasteners, such as screws
15
a
are used to secure the retainer plate
13
a
to the disk portion
14
a
of the connecting rod
11
a
. The connecting rod
11
a
includes a crank end
16
a
that is connected to the disk portion
14
a
by way of a middle section
17
a.
The problem associated with the diaphragm rod assembly
10
a
is best illustrated in
FIGS. 3A and 3B
. Specifically, the overall length of the assembly
10
a
is dependent upon three separate parts: the overall length or height of the connecting rod
11
a,
the thickness of the diaphragm
12
a
(see
FIG. 3A
) or cup seal
12
b
(see
FIG. 3B
) as well as the thickness of the retainer
13
a
or
13
b
. As a result, a rod assembly having an intended length or height of 5⅛″ may have a height variability range exceed 0.02″. The specific variability range for the assemblies
10
a
and
10
b
illustrated in
FIGS. 1-3B
is 0.023″. This variability range is significant in that it is found that in excess of 50% of the possible variability of the compression ratio is caused by the height variability of the rod assembly.
Yet another factor that compounds this problem is that the diaphragm
12
a
or cup seal
12
must be serviceable using common hand tools readily available to the unskilled equipment operator. Further, serviceability is important in that the retainer plate and diaphragm must be easily removed for replacement of the diaphragm. One problem associated with currently-available connection rod assemblies is that the overall height or length of the assembly changes when the diaphragm is changed. Specifically, referring back to
FIGS. 1-3B
and, specifically to
FIGS. 3A and 3B
, it will be noted that the thickness of the diaphragm
12
a
or cup seal
12
b
can affect the overall height of the assembly if the diaphragm
12
a
or cup seal
12
b
prevents the retainer
13
a
,
13
b
from engaging the disk portion
14
a
,
14
b
of the connecting rod
11
a,
11
b.
Therefore, there is a need for an improved connecting rod assembly wherein the assembled height variability is reduced as much as possible. Further, there is a need for an improved connecting rod assembly which is quickly and easily serviced and wherein the changing of the diaphragm or cup seal does not affect the overall height of the assembly. Still further, there is a need for an improved connecting rod assembly that can serve as al replacement for existing connecting rod assemblies and existing rocking piston compressors, diaphragm compressors and vacuum pumps.
SUMMARY OF THE INVENTION
The present invention satisfies the aforenoted need by providing a connecting rod assembly that comprises a connecting rod comprising a crank end connected to a diaphragm or cup end with a middle section disposed therebetween. The diaphragm end comprises a disk portion for supporting an annular diaphragm or cup seal. The disk portion is disposed between the middle section and a distal end section. The diaphragm or cup seal is sandwiched between the disk portion of the connecting rod and an annular retainer. The distal end section of the connecting rod extends through both the annular diaphragm and the annular retainer.
In an embodiment, the distal end section of the connecting rod has an outer face and the crank end of the connecting rod has a lowermost point. The assembly therefore has an overall length defined by a distance between the lowermost point of the crank end of the connecting rod and the outer face of the distal end section of the connecting rod.
In an embodiment, the retainer is attached to the disk portion with at least one threaded fastener.
In an embodiment, the retainer is attached to the disk portion with at least one screw.
In an embodiment, the retainer comprises a lower annular section that engages the disk portion of the diaphragm or cup end of the connecting rod and an upper annular section that extends radially outwardly beyond the lower annular section. As a result, an annular recess is provided underneath the upper annular section for accommodating an inner portion of the annular diaphragm and sandwiching the inner portion of the annular diaphragm between the upper annular section of the retainer and the disk portion of the diaphragm or cup end of the connecting rod.
In an embodiment, the retainer is attached to the disk portion with at least one screw that extends through the lower annular portion of the retainer.
In an embodiment, the present invention provides a method for reducing variations in a compression ratio of a compressor or a vacuum pump. The method comprises the steps of providing a connecting rod assembly as described above for purposes of replacing an existing connecting rod assembly with an overall height that is dependent upon the height of the connecting rod as well as the thicknesses of the retainer and/or the diaphragm.
It is therefore an advantage of the present invention to provide an improved connecting rod assembly with reduced height variability.
Yet another advantage of the present invention is that to provide an improved connecting rod assembly that may be conveniently used as a substitute for existing prior art connecting rod assemblies.
Yet another advantage of the present invention is that it provides an improved connecting rod assembly whose overall height is dependent only upon the height or length of the connecting rod and not dependent upon the thicknesses of either the retainer or the diaphragm.
Still another advantage of the present invention is that it provides an improved means for reducing the variations in the compression ratio of a compressor or a vacuum pump.
Another advantage of the present invention is that it provides a means for reducing the variations in flowrate, amperage draw, maximum pressure or vacuum levels in compressors and vacuum pumps.
Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
REFERENCES:
patent: 4924759 (1990-05-01), Plummer
patent: 4993925 (1991-02-01), Becker et al.
patent: 5064359 (1991-11-01), Plummer
patent: 5092224 (1992-03-01), Rozek
patent: 5213025 (1993-05-01), Rozek
patent: 5231917 (1993-08-01)
Faulkner Edward
Morgan George
Barnes & Thornburg
Gast Manufacturing, Inc.
Green Mary Ann
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