Sealing means for a thermostat

Abstract: A thermostat has a frame (4) having a valve seat (3), a rod (6) secured to the frame (4), a guide member (9) slidably mounted on the rod (6), and a valve secured (11) to the guide member (9). On the rod (6), a tubular sealing member (1) is slidably mounted. The sealing member (1) has a tubular body (7), a base portion (8), a closed head portion (2), and a plurality of annular grooves (19, 20) or annular projections (21, 22) formed in an inner wall of the body (7). The base portion (8) is secured to the guide member (9), and the head portion (2) is engaged with an end of the rod (6).

Description: BACKGROUND OF THE INVENTION The present invention relates to a sealing means for a thermostat mounted on a motor vehicle. 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. EP-A-0,249,451 discloses a wax-pellet thermostat having a sealing means in accordance with the preamble of Claim 1. 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. 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. These and other objects and features of the present invention will become more apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional view of a wax-pellet thermostat having a sealing means according to the present invention in a fully opened state; Fig. 2 is a sectional view of the thermostat in closed state; Figs. 3 to 6 are sectional views showing tubular sealing members of various types which are used in the sealing means of the present invention; Figs. 7 and 8 are sectional views showing a process for securing the sealing member to a guide member of the thermostat; Fig. 9 is a sectional view showing operation of the sealing member; and Fig. 10 is a sectional view of a metal mold unit for molding the sealing member. 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 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 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 sealing member 1 shown in Fig. 4 has a plurality of inner annular grooves 20 each of which has a 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 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 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 sealing member 1 is secured to the 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 sealing member 1 is automatically shaped into a bellows as shown in Fig. 9. Fig. 10 shows a metal mold unit for molding the 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, thereby improving the thermal efficiency of the engine. 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. 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 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.

Claims: A sealing means (1) for a thermostat having a frame (4) having a valve seat (3), a rod (6) secured to the frame (4), a guide member (9) slidably mounted on the rod, and a valve (11) secured to the guide member characterized by:- a tubular sealing member (1) made of rubber, the sealing member having a tubular body (7), a base portion (8), a closed head portion (2), and a plurality of annular portions (19) which are formed on the tubular body (7), the thickness of each annular portion being different from that of the tubular body; the tubular body (7) being slidably mounted on the rod (6), the base portion (8) being secured to the guide member (9) of the thermostat, and the head portion (2) being engaged with an end of the rod (6). The sealing means according to Claim 1 wherein each of said annular portions is an annular groove (19) formed in an inner wall of the tubular body (7). The sealing means according to Claim 1 wherein each of said annular portions is an annular projecting rib (20) formed on an inner wall of the tubular body (7). The sealing means according to Claim 1 wherein each of said annular portions is an annular projecting rib (22) formed on an outer periphery of the tubular body (7).

Inventors: KUZE YOSHIKAZU, KUZE, YOSHIKAZU
Applicants: KUZE YOSHIKAZU, KUZE, YOSHIKAZU
Application year: 1990
Main classification: F16J15
IPC codes: F16J3, G05D23, F16J15