Pipe joints or couplings – Packed – Gasket retainer
Reexamination Certificate
2002-05-09
2003-11-04
Nicholson, Eric K. (Department: 3679)
Pipe joints or couplings
Packed
Gasket retainer
C285S347000, C285S353000
Reexamination Certificate
active
06641179
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to fittings and, in particular, to fittings for mobile air conditioning systems.
BACKGROUND OF THE INVENTION
Mobile air conditioning systems provide summertime comfort to millions of automobile drivers and passengers on the road. The air conditioning system typically circulates a refrigerant, applying work in a well-known thermodynamic cycle to remove heat from the refrigerant prior to circulating it into the passenger compartment of the vehicle. Circulating the refrigerant in and out of the vehicle and through the refrigeration system components requires many fittings that interconnect the components, typically through hoses and tubes. In a mobile air conditioning system, the fittings must be sufficiently robust to withstand the rigors present in the engine compartment of a moving vehicle, without loosening or otherwise enabling the refrigerant to leak from the system. The fittings must also be removable to permit the system to be appropriately maintained. Due to the dynamic, thermal, and chemical environment within the engine compartment, regular maintenance of the mobile air conditioning system is essential.
Many of the fittings used in mobile air conditioning systems, particularly those used in Class 8 trucks, comply with a standard published by the Standards Committee of the International Mobile Air Conditioning Association, Inc., the standard known in the industry as the IMACA 305 Standard. For purposes of the present disclosure, the term “IMACA 305 Standard” means the standard described in “IMACA Component Standard 305 Fittings and Tubing Details for Mobile Air Conditioning Systems,” copyrighted 1997 by International Mobile Air Conditioning Association, Inc. The MACA 305 Standard defines a physical standard covering details for threaded connections and tube end forms for flare and O-ring type connections, as well as hose insert details for barb style fittings for mobile air conditioning systems.
FIG. 1
illustrates an exploded view of a typical fitting assembly
50
complying with the IMACA 305 Standard. The fitting assembly
50
includes a tubular male fitting member
52
that sealingly engages a female fitting member
72
. The male fitting member
52
(see IMACA 305,
FIG. 7A
, Option
1
) includes a tubular proximal portion
54
, a tubular distal or pilot portion
56
, and a circumferential bead
58
disposed between the proximal portion
54
and the pilot portion
56
. A swivel nut
60
slidably engages the proximal portion
54
and is restrained from sliding off the distal end of the pilot portion
56
by the circumferential bead
58
. The swivel nut
60
comprises a conventional hexagonal portion
62
with a threaded orifice having an inside diameter greater than the diameter of the circumferential bead
58
, so that the threaded portion can slide over the circumferential bead
58
and a smaller diameter neck portion
64
that engages the circumferential bead
58
when the fitting assembly
50
is properly assembled.
The female fitting
72
shown in
FIG. 1
(two-piece construction shown; a rigid, one-piece construction is also acceptable per IMACA 305 Section 5) includes a tubular proximal portion
74
, a tubular intermediate portion
75
having an inside diameter selected to slidably receive the male fitting pilot portion
56
, and a tubular distal portion
76
having an inside diameter that is larger than the intermediate portion
75
to accommodate an O-ring
51
between the pilot portion
56
and the distal portion
76
. A swivel nut
80
having outer threads
83
adapted to engage the male fitting swivel nut
60
, is slidably disposed on the proximal portion
74
and retained from sliding over the distal end of the female fitting
72
by the intermediate portion
75
and/or the distal portion
76
. The swivel nut
80
includes a conventional hexagonal portion
82
to facilitate installation and disengagement of the fitting assembly
50
. The O-ring
51
is provided between-the male fitting
52
and the female fitting
72
to substantially seal the connection when the fitting assembly
50
is properly assembled.
FIG. 2
presents a partially cut-away view of the assembled fitting assembly
50
. It will now be appreciated that fitting assembly
50
is releasably engaged by inserting the pilot portion
56
of the male fitting
52
into the distal portion
76
of the female fitting
72
and into the intermediate portion
75
. The IMACA 305 Standard defines the pilot portion's
56
outside diameter as nominally 0.001 inch smaller than the nominal inside diameter of the intermediate portion
75
. The male fitting
52
is inserted into the female fitting
72
until the circumferential bead
58
abuts against the distal portion
76
of the female fitting
72
. The O-ring
51
in the assembled fitting
50
is compressed between the pilot portion
56
and the female fitting
72
distal portion
76
. The swivel nuts
60
,
80
are engaged to bring and hold the male and female fittings
52
,
72
tightly together.
The O-ring
51
provides a seal between the female fitting
72
and the male fitting
52
to prevent the leakage of refrigerant from the connection. The region between the male fitting
52
and female fitting
72
that receives the O-ring
51
, is frequently referred to as the O-ring “gland” and is detailed in isolation in FIG.
3
. The gland
65
is shown with the O-ring
51
in phantom. It is now clear that the distal portion
76
of the female fitting
72
is larger in diameter than the intermediate portion
75
in order to accommodate the O-ring
51
. To achieve an optimal and reliable sealed connection, the O-ring
51
must be compressed in the gland
65
a suitable amount such that a seal is produced against both the inner surface of the distal portion
76
and the outer surface of the pilot portion
56
.
It is also noted that the fitting depicted in FIGS.
1
—
3
is defined in various sizes in the IMACA 305 Standard and with various pilot portion
56
lengths, the two-dimensional size of the gland region shown in
FIG. 3
is generally the same for all of the defined connection sizes. In particular, the width of the O-ring aperture between the female fitting distal portion
76
and the male fitting pilot portion
56
, denoted as W in
FIG. 3
, is nominally 0.135 inch (per IMACA
305
,
FIG. 5B
, Table
5
B), and the corresponding depth, denoted as D in
FIG. 3
, is nominally 0.0445 inch (derived from dimension in IMACA 305,
FIG. 5B
, Table
5
B) (the distal portion
76
is nominally flared 5°, denoted as angle A in
FIG. 3
, so the depth varies slightly across the width).
Although the illustrated fitting assembly
50
utilizes a two-piece female fitting
72
(including the swivel nut
80
), many straightforward alternative configurations;are utilized in the industry—including, for example, an alternative assembly described in the IMACA 305 Standard wherein a one-piece rigid female fitting is utilized with the interior of the nut portion of the female fitting having substantially the same geometry as the interior of the tubular portion of the female fitting
72
shown in
FIG. 1.
, Similarly, although
FIGS. 1 and 2
show an embodiment wherein the pilot portion
56
is smaller in diameter than the proximal portion
54
, other configurations are possible, including, for example, configurations described in the IMACA 305 Standard wherein the pilot portion is larger in diameter than the proximal portion.
Although
FIGS. 1 and 2
show the fitting assembly
50
in a horizontal orientation, in many applications the female fitting
72
is oriented vertically or at an angle of inclination, with the distal portion
76
facing upwardly. The vertically oriented fitting assembly
50
is assembled by bringing the male fitting
52
downwardly to engage the female fitting
72
. In connecting the fitting assembly, the O-ring
51
is typically first lubricated with an appropriate lubricant and then slid over the pilot portion
56
of the male fitting
52
until it is adjacent the circumferential bead
58
. The mal
Decoteau Ronald Allen
Wierlo Steven Jay
Christensen O'Connor Johnson & Kindness PLLC
Nicholson Eric K.
Paccar Inc
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