Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
11;~035~
eACKGROUND OF l'HE INVENTI ON
This invention relates to fuel lines for use in fuel
injection systems to interconnect a fuel pump and an injection
nozzle.
Fuel injec~ion pumps employed in fuel injection
systems generate extremely high hydraulic pressures which may
range upwardly from several thousand pounds per square inch.
The pressures are generated in pulse form to direct fuel from
the pump through fuel lines to injection nozzles, typically
associated with engines or the like. Because of rapid cycling
and/or vibration associated with the power plant with which
the injection system may be used, there may be a tendency for
fittings to loosen and/or conduits to fracture under the
pressures involved.
In the case of either, fuel spillage will occur and
such spillage is particularly undesirable where the engine is
operating in an enclosed area and/or substantially unattended
thereby causing combustible vapors to form and/or permitting a
sizable accumulation of fuel to occur in an area where it is
unlikely to be discovered.
To avoid such difficulties, it has been suggested to
provide double walled fuel lines so that if the fuel carrying
conduit ruptures, lost fuel will be captured by an outer
conduit to prevent leakage. This approach eliminates leakage
due to fuel line rupture but does not prevent leakage due to
loosening of interengaging parts which are intended to be
sealed.Moreover, heretofore, this approach has been practiced
using rigid, precisely dimensioned, unbendable pipes or the
like, thereby making it extremely difficult to route fuel
lines from an injection pump to an injection nozzle.
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SUMMARY OF THE INVENTION
According to one feature of the present invention,
there is provided a double-walled fluid pressure line
comprising a first tube having opposed ends, axially
oppositely directed, radially outwardly facing sealing
surfaces on the ends of the first tube; a pair of washers one
on each end of the first tube disposed just axially inwardly
of the respective sealing surface; a pair of nuts one on each
end of the first tube and rotatable thereon, the nuts housing
respective ones of the washers and the sealing surfaces; a
second tube nominally concentrically disposed around the first
tube in spaced relation thereto to define an elongate annular
space, characterized in that at least one of the washers has a
greater radius than the corresponding sealing surface and an
axially extending passage extending therethrough; the axially
extending passage providing a path for fluid, leaking in use
from between the corresponding sealing surface and a
complementary surface of a part to which the corresponding end
of the first tube is coupled, from the leak to a port venting
the annular space.
Thus, any fuel leaking from the inner tube into the
outer tube is returned safely to the source
this minimizing the danger of fluid pressure build up
in the fuel line. Furthermore, if the leak is only
small the line can continue to function whilst
returning excess, leaking, fuel to the source.
The fuel source may comprise a reservoir or
tank alone or may include a fluid pump as well in
which case the outer tube may return fuel to the low
pressure side of the pump or to the reservoir or tank.
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Preferably, the supply line is bendable, the
inner tube being deformable into a required
configuration and the outer tube being resilient to
allow it to flex around bends in the inner tube to
maintain an open return path to the source.
Other features and advantages will become
apparent from the following specification taken in
connection with the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a schematic view of an engine plant;
Fig. 2 is an axial sectional view of one fuel
supply line;
Fig. 3 is an enlarged view of one end of the
fuel line; and
Fig. 4 is a sectional view illustrating a
typical relationship of the components of the
inventive fuel line when bent.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Fuel lines made according to the invention
are intended to be utilized, for example, with an
engine 10 supplied with fuel from a tank 12. The tank
12 has a conduit 14 extending to a conventional fuel
injection pump 16 which, in turn, provides fuel under
pressure and in pulse form in a desired sequence to a
plurality of fuel lines 18, to be described, which
convey the fuel to conventional fuel injection nozzles
20 associated with the engine 10. As will be seen,
the fuel lines 18 are double walled and are provided
with means which direct leaking fuel to a conduit 24
by which it may be returned to the tank 12 or,
alternatively, to the input of the injection pump 16,
or to an alarm 28.
0355
lhe fuel lines 18 are adapted to so return
leaked fuel if the fuel leakage occurs either due to
rupture or to leakage at the fittings.
With the foregoing in mind, one embodiment of a fuel
line made according to the invention will be described
in greater detail with reference to Figs. 2-4,
inclusive.
The fuel line includes a first, elongated,
metallic rigid tube 30 which has a wall thickness
sufficient to withstand the high pressures generated
by the pump 16. lhe precise wall thickness will
depend upon the inner diameter of the tube 30 which,
in turn, will be dependent upon the pressures
generated as well as fuel delivery requirements and
are well known in the art, forming no part of the
present invention. In the overwhelming majority of
cases,i such criteria will result in the tube 30,
while rigid, being bendable by conventional tube
bending equipment.
Each end of the tube 30 is provided with a
seallng surface 32 which, as illustrated, is
frusto-conical such that the two surfaces 32 are
opposed from each other and oppositely axially
directed. They also face radially outwardly. The
surfaces 32 are formed integrally on the tube 30 after
other components to be described are assembled
thereon. In the usual case, the surfaces 32 will be
formed by cold forming as swaging. Just axially
)355
inwardly of each of the surfaces 32 is a shoulder 34,
also cold formed, against which a sealing washer 36 is
abutted. The washers 36 will typically be formed of
steel or iron and will not deteriorate upon exposure
to petroleum products.
It will be observed from Fig. 3 that each
sealing washer 36 extends radially outwardly from the
radially outer extent 38 of each sealing surface 32
for purposes to be seen.
The respective ends of the tube 30 are
provided with nuts 40 and 41, each having an external
hex head configuration (not shown) for conventional
tightening purposes. The nut 40 has an interior
threaded surface 42 by which the same may be affixed
to a male fitting associated with either the pump 16
or nozzle 20, the male member being provided with a
sealing surface that will mate with the sealing
surface 32 at the associated end of the tube 30.
Oppositely of the threaded surface 42 is a
radially inwardly directed shoulder 44 for purposes to
be seen and intermediate the surface 42 and the
shoulder 44, the nut 40 receives and houses both the
associated washer 36 and the sealing surface 32.
The nut 41 is provided with a similar
threaded surface 46 for capturing a threaded male
member having a sealing surface designed to seal
against the sealing surface 32 at the associated end
11;~0355
of the tubing 30 as well as a radially inwardly directed
shoulder 48 which abuts the washer 36 at the associated
tubing end with the intermediate portion of the nut
hoùsing both the washer 36 and the sealing surface 32.
Axially inwardly of the shoulder 48 is an
enlarged diameter bore 50. The end of the nut 41 remote
from the internally threaded end 46 is of reduced
diameter, as shown at 52, and is received within an
enlarged diameter bore 54 within a fitting 56. A radially
outwardly opening, peripheral groove 58 in the nut 41
receives an annular seal 60 to establish a seal at the
interface between the fitting 56 and the nut 41.
The bore 54 extends to a reduced diameter bore 62
within the fitting 56. As illustrated, the tube 30
extends through both bores 62 and 50 and is of lesser
diameter than either. Two radially directed ports 64 are
provided with threads (not shown) and extend to the
reduced diameter bore 62. One of the ports 64 is adapted
to be connected to the conduit 24 of pump 16, or alarm 28,
while the other will typically be provided with a
removable plug for purposes to be seen.
The right-hand end of the fitting 56 is provided
with a threaded, reduced diameter section 66 which
receives the nut 68 of a conventional compression fitting.
A second, elongated, metal, rigid tube 70,
bendable with conventional tube bending equipment, has an
end 72 extending through the nut 68 and into the
11;~035S
reduced diamter bore 62. A conventional sealing sleeve 74
is disposed on the end 72 and within the nut 68 to
partially enter the bore 62 as well. Consequently, upon
tightening of the nut 68, the sleeve 74 sealingly engages
both the outer diameter of the second tube 70 and the
flared end 75 of the bore 62. The outer diameter of the
tube 70 is just slightly less than the diameters of the
bores 50 and 62. Thus, both the nut 41 and the fitting 56
may telescope onto the tube 70 to expose the ends of the
tube 30 to allow forming of the surfaces 32 and shoulders
34.
Moreover, the tube 70 is circular in cross
section as is the tube 30 and haæ an inner diameter
greater than the outer diameter of the tube 30 and is
nominally concentrically diæposed about the tube 30.
Because of the relationship of inner and outer diameters,
an elongated, annular space 76 exists between the tubes 30
and 70. The end of the tube 70 remote from the end 72 is
flared slightly as at 78 and is in abutment with the
sealing washer 36 associated with the nut 40.
As a consequence of the foregoing, it will be
appreciated that when the nuts 40 and 41 are secured to
male members in the fuel injection system and the nut 68
is tightened, the ends of the tube 70 will be sealed to
the tube 30 so that any rupture of the tube 30 will result
in leaking fuel being directed to the annular space 76 to
flow therethrough to the bore 62 and then via one of the
ports 64 to the conduit 24 and
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11~0355
activate the alarm 28. The presence of fuel in the
annular space 76 of any of tne lines may be visually
observed by removing the plugs (not shown) associated
with the other of the ports 64 to assist in
determining the leaky line.
In order to direct leaking fuel due to
looseness of interengaging sealing surfaces 32 to the
conduit 24, one or both of the washers 36 may be
provided with a small passage 80, as seen in Fig. 3.
The passage 80 extends generally axially through the
washer 36 to establish fluid communication between the
annular space 76 and a point radially outwardly of the
radially outwardmost extent 38 of the sealing surfaces
34. Thus, any leaking fuel traveling along the
surfaces 32 will ultimately reach the passage 80 to be
directed to the conduit 24.
In order to provide a fuel line that is
bendable on conventional tube bending equipment, the
tube 70 is provided with a relatively thin wall. In
most cases, the wall thickness will be on the order of
about l mm. or less and, in a highly preferred
embodiment, wherein the outer diameter of the tube 70
is slightly less than 0.4 inch, will be about 0.7 mm.
The tube 70 may be formed of steel or other similar
materials.
Fig. 4 illustrates a typical cross section
taken through the tubes 30 and 70 intermediate their
ends after being bent by tube bending equipment. The
surface 100 of the tube 70 engaged by the tool tends
to flatten and immediately adjacent thereto, the
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surface bulges as at 102 on opposite sides of the tube
70. The tube 30 is substantially nondistorted and is
engaged at opposite sides by the tube 70. However,
areas 10~ in the vicinity of the bulges 102 remain
open as part of the annular space 76 to allow the flow
of fuel to the conduit 24 in the manner previously
described.
Thus, it will be appreciated that a fuel line
made according to the invention ensures against fuel
spillage due to either rupture of the main fuel line
or leakage at sealed connections. It also provides
the significant advantage of being bendable with
conventional tube bending equipment without fear of
blocking the flow path to the return line, thereby
allowing easy installation without requiring precisely
fitted pipes of the like.
A highly significant feature of the invention
is the absence of interengaging structure extending
between the tubes 30 and 70 within the annular space
~O 76. If such structure were present, deformation such
as illustrated in Fig. 4 during bending of the fuel
line would not occur, but rather, the structure would
tend to collapse the first, thereby decreasing its
fuel carrying capacity and interfering with proper
operation of the injection system.
From the foregoing, it will be appreciated
then that the invention provides a highly useful
double walled fuel line for use with fuel injection
systems.
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