Exhaust pipe with improved drain

A vertically-extending L-shaped exhaust pipe and method of manufacturing same are disclosed. The exhaust pipe includes a drain hole located at the bottom of the horizontal portion of the exhaust pipe for allowing liquids to drain from the pipe in order to avoid harming upstream exhaust system or engine components. An elliptically shaped guide is welded into an arcuate slot immediately upstream of the drain hole and is angled in the downstream direction so as to direct the flow of liquid toward the drain opening and away from upstream exhaust system components. The present invention is simple to manufacture, eliminates the need for a noisy flapper lid, and maintains the structural integrity of the exhaust pipe.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a moisture control system for an exhaust pipe for 
an internal combustion engine and, more particularly, relates to a 
vertically-extending exhaust pipe that includes a drain for the removal of 
rainwater and other fluids which, in the absence of a rain guard, would 
otherwise be directed to upstream exhaust system components or the engine. 
2. Discussion of the Related Art 
Many industrial and agricultural machines that are powered by an internal 
combustion engine have an exhaust system that terminates in a 
vertically-extending exhaust pipe exhausting gases from the engine to a 
position above the machine. These machines include farm tractors, some 
semi-tractors, and a variety of industrial machines such as towed portable 
generators. The typical vertically-extending exhaust pipe used in this 
type of machine is L-shaped so as to have a vertical portion and a 
horizontal portion meeting at an elbow. An inlet end of the horizontal 
portion is connected to an upstream component, such as a muffler, of the 
machine's exhaust system. An exhaust gas outlet is formed from an open 
upwardly-facing end of the vertical portion. During operation, exhaust 
gases generated by the engine pass through the exhaust system components 
and are emitted from the exhaust gas outlet. 
The upwardly-facing exhaust gas outlet of the typical vertically-extending 
exhaust pipe is exposed to the elements and, hence, is prone to invasion 
by moisture in the form of rainwater, snow, etc. when the engine is not 
operating. This moisture can degrade the operation of the exhaust system 
and lead to corrosion and early failure of the exhaust pipe and exhaust 
system components. In addition, when an engine having a 
vertically-extending exhaust pipe opening is started after being stored in 
a wet environment, the water that has accumulated in the exhaust pipe is 
ejected from the exhaust pipe by the outwardly flowing exhaust gases. This 
sooty mixture may soil or stain the operator or structures that are close 
to the exhaust pipe. Mechanisms therefore have been employed to keep 
rainwater and other moisture out of engine exhaust systems. 
The most common mechanism for inhibiting moisture flow into an exhaust pipe 
is the rain guard or flapper lid. The typical flapper lid is pivotally 
mounted on the upper end of the exhaust pipe, covers the upper opening of 
the exhaust pipe when the engine is not operating, and lifts under 
pressure of exhaust gases when the engine is operating. While such flapper 
lids are generally effective at keeping rainwater out of exhaust systems, 
they must be fairly lightweight and be loosely mounted on the upper end of 
the exhaust pipe in order to be lifted easily by the exhaust gases without 
creating excessive back pressure or becoming caked with soot. Such 
lightweight, loosely fitting metal flapper lids tend to rattle and "clank" 
a great deal during engine operation. Indeed, it has been discovered that 
the flapper lid is the noisiest component of an otherwise quiet machine 
such as a gasoline-powered portable generator. Moreover, these structures 
tend to be rather flimsy and often fail well before the exhaust pipe 
requires replacement. 
Various other solutions to the problem of exhaust pipe moisture flow have 
been proposed. For example, U.S. Pat. No. 2,468,961 to W. C. Curphy 
discloses a moisture-deflecting exhaust pipe attachment consisting of a 
tube bent so as to form a trap that attaches in a spaced relationship to 
the upper end of a vertically-extending exhaust pipe by a perforated 
connector ring. In operation, moisture entering the top of the bent tube 
flows along the tube walls and out of the attachment at the connector ring 
before reaching the exhaust pipe. Similarly, U.S. Pat. Nos. 2,887,032 and 
2,887,033 to P. H. Wachter, Jr., both disclose an attachment that is 
mounted onto the upper end of a vertically-extending exhaust pipe and that 
incorporates a trap and associated drain for preventing rain water from 
flowing into an engine exhaust system. Such separate attachments are 
needlessly complex, require fitting to the outlet end of the exhaust pipe, 
increase the effective height of the exhaust pipe, and may come loose if 
the fit is not correct. 
U.S. Pat. No. 4,450,934 to Max L. Davis discloses a complex trap 
arrangement disposed within a vertically-extending muffler canister. The 
trap arrangement includes a deflector plate that 1) channels downwardly 
flowing rainwater away from the muffler's inlet pipe and out through a 
drain hole and 2) permits upwardly-flowing exhaust gases to spiral 180 
degrees around the deflector plate and out of the muffler. While Davis' 
solution is integrated with an exhaust system component, lacks the 
additional fittings associated with other proposed solutions and does not 
significantly increase the height of the exhaust pipe, it is needlessly 
complex. 
Another, less elaborate solution to the problem of draining moisture from a 
vertically-extending exhaust pipe is to 1) cut a slot into a lower 
horizontal portion of the L-shaped exhaust pipe to form a drain and to 2) 
indent the bottom of the pipe upstream of the slot to form a channel. The 
channel generally directs rainwater toward the drain so that the rainwater 
will drain from the exhaust pipe before reaching other exhaust system 
components such as the muffler. Experience has shown, however, that these 
slots are only partially effective at preventing water from flowing into 
other exhaust system components. In addition, if the slots are large 
enough to provide even a generally effective drain, they seriously weaken 
the exhaust pipe structure to the point that the exhaust pipe corrodes and 
fails much sooner than it otherwise would. 
Thus, none of the solutions heretofore proposed for addressing the problem 
of draining moisture from a vertically-extending exhaust pipe provide a 
compact, simple, quiet, structurally sound, and effective mechanism for 
achieving the desired result. What is needed therefore is a 
vertically-extending exhaust pipe which includes a drain for diverting 
moisture from the engine exhaust system and which is simple, effective, 
quiet, and does not impair the structural integrity of the exhaust pipe. 
OBJECTS AND SUMMARY OF THE INVENTION 
It is therefore a principal object of the invention to provide a 
vertically-extending exhaust pipe that is capable of draining rainwater 
and other liquids which would otherwise accumulate in an engine's exhaust 
system and to do so without generating additional noise such as would 
result from the use of a flapper lid. 
Another object of the invention is to provide a vertically-extending 
exhaust pipe with a drain that meets the first principal object of the 
invention and, at the same time, that does not weaken the exhaust pipe to 
the point that the exhaust pipe corrodes and fails much sooner than it 
otherwise would. 
In accordance with a first aspect of the invention, these objects are 
achieved by providing an exhaust pipe that includes a 1) generally 
horizontal portion having a near end, a far end, and an exhaust gas inlet 
on its far end, and 2) a generally vertical portion having a near end, a 
far end, and an exhaust gas outlet on its far end. The vertical and 
horizontal portions join at their near ends at an elbow. A drain opening 
is formed in the bottom of the horizontal portion for allowing liquid to 
drain from the exhaust pipe, and a guide is positioned inside the exhaust 
pipe between the drain opening and the exhaust gas inlet for directing the 
flow of liquid toward the drain opening and away from the exhaust gas 
inlet. 
In accordance with another aspect of the invention, the guide of the 
exhaust pipe preferably is displaced at an acute angle with respect to the 
bottom of the generally horizontal portion and, more preferably, extends 
upwardly and inwardly away from the exhaust gas inlet. 
The guide of the exhaust gas pipe preferably is welded into place at the 
location of a slot in which it is seated to at least essentially 
completely seal the slot opening and to provide added structural integrity 
to the exhaust pipe in the vicinity of the drain hole. 
In order to maximize the effectiveness of the guide, the guide is placed at 
an angle of about 30.degree. with respect to the generally horizontal 
portion of the exhaust pipe, has a shape that conforms generally to the 
shape of the inner periphery of the exhaust pipe, and is positioned so as 
to overlie the drain opening. 
Yet another object of the invention is to provide a method of manufacturing 
an exhaust pipe having a drain for draining moisture from the exhaust 
pipe. 
In accordance with yet another aspect of the invention, this object is 
achieved by providing an exhaust pipe having 1) a generally horizontal 
portion having a near end and a far end and an exhaust gas inlet on the 
far end, and 2) a generally vertical portion having a near end and a far 
end and an exhaust gas outlet on the far end so that the near ends of the 
portions join at an elbow. Other steps include forming a drain opening in 
the exhaust pipe at the bottom of the horizontal portion for allowing 
liquid to drain from the exhaust pipe, cutting an arcuate slot into the 
base of the generally horizontal portion proximate to the drain opening, 
inserting a guide through the arcuate slot, fixing the guide in place, and 
welding the guide into the arcuate slot. 
Other objects, features, and advantages of the present invention will 
become apparent to those skilled in the art from the detailed description 
and the accompanying drawings. It should be understood, however, that the 
detailed description and accompanying drawings, while indicating preferred 
embodiments of the present invention, are given by way of illustration and 
not of limitation. Many changes and modifications may be made within the 
scope of the present invention without departing from the spirit thereof, 
and the invention includes all such modifications.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Pursuant to the invention, a generally L-shaped, vertically-extending 
exhaust pipe for use with an internal combustion engine includes a drain 
hole for permitting liquids, such as rainwater, that may enter the 
upwardly-facing exhaust gas outlet of the exhaust pipe to drain out of the 
exhaust pipe before reaching other exhaust system components such as a 
muffler. A guide for channeling liquid to the drain hole is fixed in the 
exhaust pipe immediately upstream of the drain hole. The guide is welded 
in place so as to at least substantially completely seal a slot in which 
the guide is seated. 
The inventive vertically-extending exhaust pipe is usable with virtually 
any machine having an internal combustion engine that employs or may be 
configured to employ a vertically-extending exhaust pipe. The invention is 
particularly useful with machines in which quiet operation is important. 
These machines include portable generator units, such as the portable 
generator 10 shown in FIG. 1. Portable generator 10 includes a chassis 12, 
wheels 14, an engine/generator housing 18, and an internal combustion 
engine (not shown) and a generator (also not shown) encased within the 
engine/generator housing 18. An exhaust system for the engine is also 
mounted within the engine/generator housing 18. The exhaust system 20 
includes an inlet pipe 21, a muffler 22, and the inventive exhaust pipe 26 
which is connected to an outlet pipe 23 of the muffler 22 via a collar 24. 
Collar 24 is shown as a flared section of exhaust pipe 26, but could also 
comprise a separate sleeve fitting. The exhaust pipe 26 directs exhaust 
gas upwardly from the generally horizontal outlet pipe 23 of the muffler 
22 and out to the atmosphere through a vent 28 in a roof 30 of the 
engine/generator housing 18. 
As can be seen most clearly in FIGS. 2-4, exhaust pipe 26 is a round pipe 
and is generally L-shaped so as to have 1) a generally horizontal portion 
32 with an exhaust gas inlet 34 on the far end, and 2) a generally 
vertical portion 36 with an upwardly-facing exhaust gas outlet 38 on the 
far end. The portions 32 and 36 join at an elbow 40 which is typically 
about 90 degrees. The portions 32 and 36 and elbow 40 preferably are 
formed from a single piece of bent pipe but conceivably could be formed 
from separate interconnected members. A drain hole 42 is bored into the 
bottom of the horizontal portion 32 of exhaust pipe 26 at or near the 
elbow 40. Drain hole 42 is preferably sized to be large enough to permit 
water to escape quickly from exhaust pipe 26 yet small enough not to 
significantly weaken the exhaust pipe 26. For example, for a typical 21/2" 
ID exhaust pipe, a drain hole with a diameter of less than 1", and 
preferably about 3/4", has been found to be optimal. A guide 44 is mounted 
within the horizontal portion 32 for directing the flow of moisture toward 
drain hole 42. Guide 44 is elliptically shaped so as to generally conform 
to the shape of the inner periphery of exhaust pipe 26 when the guide is 
fixed in place inside exhaust pipe 26. Guide 44 may, depending on the 
shape of the exhaust pipe 26 and on the location of the guide within the 
exhaust pipe and the orientation of the guide with respect to the exhaust 
pipe, also be ovaloid, circular, rectangular, or other shape so long as it 
generally conforms to the shape of the inner periphery of the exhaust 
pipe. As best seen in FIG. 6, guide 44 extends at an acute angle .alpha. 
(preferably about 30.degree.) with respect to the horizontal so as to 
extend over the drain hole 42 in order to direct moisture to drain hole 42 
without obstructing the flow of exhaust gases throughout the exhaust pipe 
26. In the case of a typical 21/2" ID exhaust pipe, guide 44 is preferably 
about 1.5" in length and is positioned about 2.5" from the exhaust gas 
inlet 34 of exhaust pipe 26. 
To fabricate the drain/guide assembly, an arcuate angled slot 46 is cut 
into the bottom of the horizontal portion 32 of exhaust pipe 26 
immediately upstream of drain hole 42 as seen in FIG. 2 to permit the 
insertion of a plate 48 from which the guide 44 is to be formed. Slot 46 
is angled, preferably at about 30.degree., away from the exhaust gas inlet 
end of the exhaust pipe 26 in order to guide insertion of plate 48 at the 
proper angle. The plate 48 is welded into slot 46, as shown in FIG. 3, so 
that slot 46 is at least substantially entirely sealed by the weld W and 
such that only the drain hole 42 remains. By at least substantially 
entirely eliminating the slot 46, the weld W improves the structural 
integrity of exhaust pipe 26 in the vicinity of drain hole 42. The plate 
48 is then cut or ground about an arc 50 so that the outer surface of the 
resulting guide 44 is essentially flush with the outer surface of the 
exhaust pipe 26. 
The operation of the novel exhaust pipe 26 of the present invention is 
simple and yet elegant. When rainwater, snow, or other moisture enters the 
upwardly-facing exhaust gas outlet 38 of exhaust pipe 26, it flows to the 
bottom of elbow 40 and is channeled by guide 44 to drain hole 42, where it 
flows out of exhaust pipe 26. Guide 44 prevents the flow of moisture past 
drain hole 42 and protects upstream exhaust system components from being 
damaged by the moisture. At the same time, guide 44 is easily welded into 
position to maintain the structural integrity of the exhaust pipe 26. 
Moreover, because its drain is formed integrally with it, the exhaust pipe 
26 is no longer higher than conventional vertically-extending exhaust 
pipes. Finally, when the engine is in operation, the inventive exhaust 
pipe 26 operates noiselessly and reliably--unlike exhaust pipes employing 
traditional flapper lids. 
The present invention provides a simple solution to the problem of draining 
moisture from a vertically-extending exhaust pipe without the use 
complicated, large traps or of a noisy flapper valve. It is easy to 
manufacture, and also maintains or improves the structural integrity of 
the exhaust pipe. 
Many changes and modifications could be made to the invention without 
departing from the spirit thereof. The scope of these and other changes 
will become apparent from a reading of the appended claims.