Pressure actuated drain valve for marine drive

A pressure actuated drain valve for automatically draining the cooling water from a marine drive engine when the engine is stopped. The drain valve includes a spring-loaded diaphragm which moves to a closed position when the engine water pump is operating to close an outlet from the engine cavities to be drained. The diaphragm automatically moves to its open position when the engine water pump is off to open the outlet to allow cooling water to drain from the engine cavities.

BACKGROUND OF THE INVENTION 
The present invention relates to marine drives, and more particularly to a 
valve for automatically draining the cooling water from a marine engine 
when the engine is stopped. 
Various types of drain valves are typically used in a marine environment. 
For example, drain valves referred to as "self-bailers" or automatic bilge 
valves for attachment to the bottom of a boat which operate on the suction 
principle are well known. Such bailers typically include an exhaust 
aperture which, in use, is directed toward the rear or stern of the boat. 
Water collecting in the boat is discharged through the exhaust aperture by 
means of suction created by movement of the boat through the water. 
Examples of such devices may be found in the following U.S. patents: No. 
271,060 to Graham; No. 2,655,121 to Cuneo; No. 2,884,888 to Pugol; No. 
2,959,144 to Youtie; No. 2,966,875 to Irey; No. 3,011,468 to O'Gara; No. 
3,067,714 to Allmand; and No. 3,875,888 to Bier. 
Drain valves, however, have not been up to this point commonly used with 
recreational marine drive engines which utilize seawater for cooling. In 
standard arrangements, cooling water drainage is accomplished by allowing 
gravity to cause the cooling water to flow out of the engine through an 
orifice in the engine housing which is always open. Nevertheless, in 
several prior known marine drive engines, namely, the "MerCruiser", 60, 
80, and 90 engines sold by the assignee of the present invention, there 
was used a floating plastic ball for opening and closing a drain circuit. 
These plastic balls floated upward within a ported cavity to close the 
drain circuit when cooling water was pumped to the engine. In turn, when 
the water pump stopped, gravity caused the cavity containing the ball to 
drain thus uncovering the drain circuit and draining cooling water from 
the engine. 
Such floating ball drain valves have several inherent disadvantages due to 
their principle of operation. Most noticeably, the forces which made the 
ball float were relatively small making the valve's operation erratic when 
the environment departed from a new, clean condition. Since the ball 
chamber was directly in the flow path of the cooling water it could "see" 
any debris ingested by the pump, and, because of the chamber's shape, the 
debris could be accummulated in the chamber to the extent that the ball's 
desired motion was either impeded or prevented. The result was to produce 
either overheating or loss of drainage depending upon the ball's position 
at the time of debris accummulation. A loss of drainage also could result 
in accelerated corrosion if the engine is being used in salt water. 
SUMMARY OF THE INVENTION 
A pressure actuated drain valve for a marine drive engine which 
automatically drains cooling water from the engine when the engine is 
stopped. 
The drain valve includes a spring loaded flexible sealing member in the 
form of a diaphragm which is normally biased in its open position and 
movable to a closed position in response to fluid pressure in the cooling 
circuit when the engine water pump is operating. In its open position, 
cooling water is allowed via gravity to flow out of the engine cavities 
through an outlet in the engine housing. In its closed position, the 
diaphragm covers the outlet to prevent cooling water drainage so long as 
the water pump is operating. Preferably, the diaphragm is substantially in 
the form of a truncated cone and seats against correspondingly shaped 
walls in a valve chamber, and includes a small diameter opening positioned 
over the outlet which permits minimal drainage to occur even while the 
pump is operating to insure proper sealing action. 
The drain valve of the present invention overcomes the disadvantages of 
prior "floating ball" arrangements since it is pressure actuated allowing 
for higher forces to be used during operation which results in a more 
dependable operation, particularly in dirty environments. Additionally, 
the actuation and sealing forces of the present device are significantly 
greater than the "floating ball" design due to the greater difference in 
seating area of a diaphragm versus a floating ball. Further, the present 
device does not have its sealing element in the primary flow path making 
the accummulation of debris less likely. Finally, the movable sealing 
element of the present device is also less sensitive to debris 
accummulation than a floating ball. 
The present invention thus provides a pressure actuated drain valve for a 
marine drive engine which will automatically and reliably drain the 
cooling water from the engine cooling circuit when the engine is stopped. 
In addition to the above noted advantages, the present device improves 
corrosion resistance and simplifies winterization of the engine thus 
increasing engine life and reducing owner expenses.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings, FIG. 1 illustrates a marine propulsion 
system, generally designated by the numeral 1, having a water cooled, six 
cylinder, internal combustion engine 2 drivingly connected through a boat 
transom 3 to stern gear drive 4 having gear drive housing 5 for rotating 
propeller 6. Fuel supply is provided by a fuel pump (not shown) drawing 
fuel from a remote tank (not shown) and delivering the fuel to carburetor 
7 for combustion within engine 2. It should be noted that although the 
present invention is shown as being utilized with V-6 engine 2, it may be 
utilized with various other forms of marine drive systems incorporating an 
engine water cooling system which draws cooling water from an external 
seawater location, namely, the lake, sea or ocean in which the boat is 
being utilized. 
Referring now to FIG. 2, there is illustrated in schematic form a flow 
diagram of the water flow in the cooling system or circuit for engine 2 
shown in FIG. 1. More particularly, upon start up of engine 2, pump 8 
draws water through a pair of lower seawater inlets 9 and forces it 
through a main passage 10 to exhaust manifold cover 11. Since engine 2 is 
a V-6 design, water passes through port side cylinder block 12 and then 
through port side cylinder head 13, and finally through thermostat 14 into 
water discharge line 15. Likewise, cooling water from manifold cover 11 
also passes through starboard side cylinder block 16, and then through 
starboard side cylinder head 17 and finally through starboard thermostat 
18 into discharge line 15 where it returns to the lake, sea or ocean. 
Cooling water from cylinder head 13 also passes into line 19 and cooling 
water from cylinder head 17 also passes into line 20 and then through a 
water pressure relief valve 21 of the poppet valve type into line 22 which 
in turn communicates with water discharge line 15. 
In order to drain the cooling system or circuit for engine 2, drain 
passages 23, 24 and 25 are provided. Drain passage 23 communicates from 
the port side cylinder block 12 to one side of a drain valve 26, and drain 
passage 24 communicates between exhaust manifold cover 11 and the other 
side of drain valve 26. Drain passage 25 in turn communicates between the 
starboard side cylinder block 16 and drain passage 24. As shown, a pilot 
pressure line 27 also communicates between main passage 10 and drain valve 
26, and an outlet 28 communicates from valve 26 through gear drive housing 
5 to a location externally of gear drive 4 so that upon drainage, water 
flows back into the lake, sea or ocean. 
Referring now to FIGS. 3-5, there is shown a preferred embodiment of drain 
valve 26. As illustrated, drain valve 26 includes a flexible sealing 
element in the form of a truncated cone shaped rubber diaphragm 29, and a 
spring 30 for biasing diaphragm 29 in its open position, as shown in FIG. 
4. As shown best in FIG. 5, diaphragm 29 includes a substantially flat 
disc-shaped or circular web portion 33 having a cylindrically shaped wall 
portion 31 extending from the periphery of web portion 33. Wall portion 31 
is inclined outwardly with respect to web 33 at an angle, as illustrated, 
of about 30.degree., and web 33 includes an opening 34 located centrally 
therein over outlet 28 having a diameter of approximately 0.06 inches. 
Opening 34 allows for cooling water to leak past diaphragm 29 even when 
diaphragm 29 is in its closed position, as shown in FIG. 3, so as to 
provide an adequate sealing function and to allow drainage of passage 27. 
Spring 30 is composed of a pair of S-shaped spring members 35, 36, which 
include lower legs 37, 38 attached to legs 31, 32 respectively of 
diaphragm 29, upper legs 39, 40 and S-shaped central portions 41, 42 which 
provide the spring force therefor. Members 35, 36 may be made of any 
corrosion resistant material such as stainless steel having sufficient 
resiliency to act as a spring for diaphragm 29. 
As shown best in FIGS. 3 and 4, upper legs 39, 40 of spring members 35, 36 
are sandwiched between a pair of housing members 43, 44 for securely 
mounting diaphragm 29 in its proper location within a chamber 45 defined 
thereby. Chamber 45 includes a pair of opposite inclined walls 46, 47 
which communicate with drain passages 23, 24 respectively, and a lower 
flat wall 48 which communicates with outlet 28. Walls 46 and 47 are 
inclined outwardly with respect to wall 48 to form a correspondingly 
shaped seat for diaphragm 29 which allows for adequate sealing of passages 
23-25 in its closed position, as shown in FIG. 3. Drain passages 23-25 as 
well as outlet 28 communicate with one side of diaphragm 29 while main 
passage 10 and pilot pressure line 27 communicate with the opposite side 
of diaphragm 29. 
In operation, when pump 8 is operational, fluid pressure in main passage 10 
is communicated via line 27 to one side of diaphragm 29 causing diaphragm 
29 to seal passages 23-25 and outlet 28. Due to the dimensions of line 27, 
approximately 0.5 psig is available above diaphragm 29 to actuate the 
sealing function of diaphragm 29. On the other hand, when pump 8 is shut 
off, diaphragm 29 moves to its open position via the force of spring 30 to 
allow drainage of cooling water from passages 23-25 through outlet 28. 
Various modes of carrying out the invention are contemplated as being 
within the scope of the following claims particularly pointing and 
distinctly claiming the subject matter which is regarded as the invention.