Sealing means for a thermostat

A thermostat has a frame having a valve seat, a rod secured to the frame, a guide member slidably mounted on the rod, and a valve secured to the guide member. On the rod, atubular sealing member is slidably mounted. The sealing member has a tubular body, a base portion, a closed head portion, and a plurality of annular grooves or annular projections formed in an inner wall of the body. The base portion is secured to the guide member, and the head portion is engaged with an end of the rod.

CROSS-REFERENCE TO RELATED APPLICATION 
This invention is disclosed in part in my co-pending application entitled 
Tubular Member For Sealing a Reciprocating Rod, Ser. No. 07/608,380, filed 
on Nov. 2, 1990. 
BACKGROUND OF THE INVENTION 
The present invention relates to a sealing means for a thermostat mounted 
on a motor vehicle, and more particularly to a tubular sealing member 
which can be automatically deformed in the form of a bellows when the 
tubular member is contracted. 
The wax-pellet thermostat is used in a cooling system of the motor vehicle. 
When coolant temperature in the cooling system rises above a predetermined 
temperature, a valve in the thermostat opens to pass the coolant to a 
radiator, thereby lowering the temperature of the coolant. The valve is 
closed when the temperature drops. Consequently, a guide member mounting 
the valve reciprocates along a rod. In order to seal a sliding portion of 
the guide member, a dynamic seal such as a packing is provided. However, a 
conventional seal is liable to be deteriorated because of severe 
circumstances. More particularly, the coolant includes fine molding sands, 
fine particles of rusted iron, oil and other particles which form a sludge 
with antifreeze mixture. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a sealing means having 
high durability. 
Another object of the present invention is to provide a sealing means 
having a high sealing effect. A further object of the present invention is 
to provide a sealing means having a long stroke with a small size. 
According to the present invention, there is provided a sealing means for a 
thermostat having a frame having a valve seat, a rod secured to the frame, 
a guide member slidably mounted on the rod, and a valve secured to the 
guide member. The sealing means comprises a tubular sealing member made of 
rubber, the sealing member having a tubular body, a base portion, a closed 
head portion, and a plurality of annular portions, the thickness of each 
annular portion being different from that of the tubular body, the tubular 
body being slidably mounted on the rod, the base portion being secured to 
the guide member of the thermostat, and the head portion being engaged 
with an end of the rod. 
In an aspect of the invention, each of the annular portions is an annular 
groove formed in an inner wall of the tubular body. 
In another aspect of the invention, each of the annular portions is an 
annular projecting rib formed on an inner wall or an outer periphery of 
the tubular body. The thinner portions of the tubular body are expanded to 
automatically form a bellows when the tubular sealing member is 
contracted. The tubular sealing member is extended to a straight tubular 
form. Thus the tubular member covers the entire sliding portion to protect 
it. 
Since the tubular member is made into a straight tubular form, a very small 
tubular member can be easily manufactured by molding at a low cost. 
These and other objects and features of the present invention will become 
more apparent from the following description with reference to the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIGS. 1 and 2, the wax-pellet thermostat of the present 
invention has a thermostat frame comprising a first frame 4 and a second 
frame 16 secured to the first frame 4. The first frame 4 has a valve seat 
3. The thermostat comprises a steel rod 6, a tubular sealing member 1 of 
rubber which is slidably mounted on the steel rod 6 and secured to the 
first frame 4 at a top portion 5, a guide member 9 slidably engaged with 
the rod 6, a primary valve 11 secured to the guide member 9, a heat 
conductive cylinder 14 secured to the guide member 9, a rubber diaphragm 
15 secured to the guide member 9, and wax pellets 13 provided in the 
cylinder 14. A return coil spring 17 disposed surrounding the cylinder 14 
is provided between the primary valve 11 and the bottom of the second 
frame 16. A snap ring 12 is engaged with the guide member 9 for securing 
the primary valve 11 to the guide member 9. 
FIG. 2 shows the valve in the closed state. When the temperature of the 
coolant rises in excess of a predetermined temperature, the wax pellets 13 
expand. This forces the diaphragm 15 against the steel rod 6. As the wax 
pellets 13 squeeze the diaphragm 15 around the rod 6, the wax pellets 13 
overcome the coil spring 17 and the guide member 9 moves downward, thereby 
opening the primary valve 11 as shown in FIG. 1. 
When the thermostat cools, the wax pellets 13 contract. Then, the coil 
spring 17 returns the valve 11 to the closed position as shown in FIG. 2. 
The tubular sealing member 1 is compressed into a bellows. 
Referring to FIGS. 3 to 6 showing various types of the tubular sealing 
member 1 to which the present invention is applied, each of the tubular 
sealing members 1 is adapted to automatically form a bellows when 
compressed. 
The tubular sealing member 1 comprises a tubular body 7 as shown in FIG. 3. 
The tubular body 7 has a base portion 8, a head portion 2 having a closed 
head and a plurality of annular grooves 19 circumferentially formed in an 
inner wall thereof. The annular groove 19 is formed to have a curvature in 
section having a large radius R. 
The tubular sealing member 1 shown in FIG. 4 has a plurality of inner 
annular grooves 20 each of which has sectional curvature having a small 
radius r. 
The sealing member 1 shown in FIG. 5 has a plurality of annular projecting 
ribs 21 circumferentially formed on the inner wall of the tubular body 7. 
The sealing member 1 shown in FIG. 6 has a plurality of annular projecting 
ribs 22 formed on the outer periphery of the tubular body 7. 
Referring to FIGS. 7 and 8, the tubular sealing member 1 is slidably 
mounted on the steel rod 6 at the tubular body 7 thereof. The inside of 
the closed head portion 2 of the tubular sealing member 1 is engaged with 
the top end of the steel rod 6 and the base portion 8 having a skirt 
portion is mounted in a seal pocket 10 provided on the guide member 9. An 
outer periphery 18 of the seal pocket 10 is bent at a predetermined 
hydraulic pressure so that the tubular sealing member 1 is secured to the 
guide guide member 9 with a sealing effect. 
When the guide member 9 moves upward along the steel rod 6 by the force of 
the spring 17, the tubular sealing member 1 is automatically shaped into a 
bellows as shown in FIG. 9. 
FIG. 10 shows a metal mold unit for molding the tubular sealing member 1. A 
female mold 23 is mounted on a male mold 24, thereby forming a cavity 
there-between. Melted rubber is poured from an inlet 25 into the cavity. 
From the foregoing, it will be understood that the present invention 
provides a thermostat in which a tubular sealing member is mounted on the 
steel rod of the thermostat for sealing the steel rod. The sealing member 
prevents the guide member from introducing the coolant and foreign 
materials through the sliding portion between the steel rod and the guide 
member. Thus, overcool and overheat of the engine do not occur caused by 
the coolant entering the thermostat, thereby improving the thermal 
efficiency of the engine and hence reducing harmful exhaust gases. 
Furthermore engine trouble caused by overheating does not occur. 
The tubular sealing member is compressed from the straight tubular form to 
the bellows, so that a large stroke can be obtained with a member having a 
small length. Thus the thermostat can be small in size. 
Since the sealing member becomes a bellows when compressed, sealing effect 
between the steel rod and the guide member is improved. 
The applicant conducted the following durability experiment and had the 
good result. 
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Reciprocating stroke 
10 mm 
Spring load 11.5 kg 
Cycle time 6 seconds 
(On time: 3 seconds, -Off time: 3 seconds) 
Life 310.000 cycles 
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While the invention has been described in conjunction with preferred 
specific embodiment thereof, it will be understood that this description 
is intended to illustrate and not limit the scope of the invention, which 
is defined by the following claims.