Air damper used in glove box of automobile

Abstract: An air damper suitably used in the glove box of an automobile comprises a cylinder (1) having a first open end (13) and a second end (3), a guide cap (6) covering the first open end, and a piston (2) movable in the cylinder. A compression coil spring (7) is inserted in the cylinder between the piston and the guide cap. The coil spring forces the piston toward the second end of the cylinder in the free state. The piston has a hook piece (11), which is threaded with a spring. At least one end of the spring is taken out of the cylinder via the guide cap, and connected to the glove box. The guide cap has a stopper means projecting inside the coil spring and toward the piston. If the glove box is opened and the string is pulled out of the cylinder, the piston moves toward the guide cap. The piston then strikes the stopper means of the guide cap before the coil spring is fully compressed.

Description: The present invention generally relates to an air damper, and more specifically, to an improved structure of a cylindrical air damper installed in, for example, the glove box of an automobile. A conventional cylindrical air damper fixed to the glove box of an automobile is disclosed in, for example, Japanese Utility Model Registration No. 2557064. This type of air damper is used to dampen the abrupt opening motion of the glove box, or to prevent unpleasant noise due to sudden opening. The air damper allows the glove box to open slowly about the pivoting axis against the gravitational force. The conventional air damper comprises a cylinder with openings at both ends, and a piston moving in the cylinder. A string is coupled with the piston, and it extends out of the cylinder from the remote end. A valve is attached to the base or the close end to control the quantity of the air passing through the cylinder. A guide cap is attached to the remote end of the cylinder to guide the string. A compression coil spring is inserted between the guide cap and the piston. The air damper is fixed to, for example, the instrument panel, which is the back wall of the glove box. The string extending from the guide cap of the cylinder is coupled to the glove box. When the glove box is unlocked to start opening, the string is pulled out of the cylinder, and the piston coupled to the spring moves inside the cylinder, while compressing the coil spring. Consequently, the air flows into the cylinder via the valve, which give the damper effect to the cylinder. With this arrangement, the glove box slowly open toward the opening position. When the glove box is pushed toward the close position, the piston is pushed back toward the valve by the restoring force of the compression coil spring, pulling the string back inside the cylinder. At this time, the valve is open to let the air stored in the cylinder escape, and accordingly, the piston moves back to the home position smoothly. The full-open position of the glove box using an air damper has to be regulated. In general, a guide groove is formed in the instrument panel itself or the cover sheet furnished to an appropriate place on the instrument panel, as disclosed in Japanese Utility Model No. 2587728. A stopper pin is provided to the side face of the glove box in such a manner that the stopper pin moves along the guide groove as the glove box is opened or closed. If the glove box slowly opens by its own weight, the stopper pin moves in the groove, and comes to the end of the groove. The abutment between the stopper pin and the end of the groove regulates the full-open position of the glove box. However, providing a separate component for regulating the full-open position of the glove box causes the entire structure of the glove box to become complicated, while limiting the storage capacity of the box. It may be proposed that the air damper itself is used to regulate the full-open position of the glove box, making use of the maximum compressed position of the spring. Using the air damper as the open position regulation means, however, causes other problems. The compression coil spring is weakened due to excessive load of the glove box, brittle portions of the air damper may be broken, and the full-open position fluctuates because of the spring force. These problems have prevented the air damper from being used as the open position regulation means as it is. EP-A-1 114 945 was cited under Article 54(3) EPC for novelty purposes only during examination of this application. The citation discloses an air damper comprising: a cylinder having first and second ends with a guide cap covering the first end. A piston is moveable in the cylinder and a compression coil spring inserted in the cylinder between the piston and the guide cap biases the piston toward the second end. A string is coupled with the piston and extends out of the cylinder via the guide cap. The piston is coupled to a shaft which limits movement of the piston towards the first end to stop the spring from being fully compressed. EP-A-0 562 284 discloses an air damper according to the preamble of claim 1 hereinafter. Therefore, it is desirable to overcome the problems in the prior art techniques and to provide an improved structure of an air damper which may be used in the glove box of an automobile. The improved air damper is capable of functioning as a means for regulating the full-open position of the glove box, without causing the compression coil spring of the air damper to be damaged or deteriorated. The present invention provides an air damper comprising: a cylinder having a first open end and a second end; a guide cap covering the first open end; a piston movable in the cylinder; a compression coil spring inserted in the cylinder between the piston and the guide cap and for forcing the piston toward the second end of the cylinder; and a string coupled with the piston and extending out of the cylinder via the guide cap; characterized in that the guide cap comprises a stopper means projecting into the cylinder, wherein the piston strikes the stopper means of the guide cap before the compression coil spring is fully compressed when the string is pulled by an external force. The piston may further comprise a hook piece that is threaded with the string and at least one end of the string extends out of the cylinder. In the embodiment of the invention described in detail hereinafter, the stopper means is located inside the compression coil spring. This arrangement allows the air damper to be kept compact, without requiring an extra space for accommodating the coil spring. The piston in the embodiment has a hook piece facing the guide cap. The hook piece is threaded with the string in such a manner that at least one end of the string is taken out of the cylinder via the guide cap. In other words, the string is doubled at the hook piece and movable through the hook piece. The one end of the string is coupled with the side edge of the glove box. If the glove box is opened, the string is pulled out of the cylinder, which causes the piston to move toward the guide cap. Since the guide cap comprises a stopper means, the piston strikes the stopper means before the compression coil spring is fully compressed. This arrangement can prevent the coil spring from being deteriorated due to excessive load by the weight of the glove box. Simultaneously, the stopper means reliably defines the full-open position of the glove box, because the glove box is retained in a stable manner at a position determined by the length of the stopper means. In order that the present invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Fig. 1 is an exploded perspective view of an air damper according to the embodiment of the invention; Fig. 2 is a cross-sectional view of the piston used in the air damper shown in Fig. 1; Fig. 3 is a cross-sectional view of the guide cap used in the air damper shown in Fig. 1; Fig. 4 is a cross-sectional view of the air damper assembled into a single unit; and Fig. 5 illustrates in a cross-sectional view the air damper when the glove box is at the full-open position, with the piston in contact with the abutment wall of the guide cap. Fig. 1 illustrates an example of the air damper according to the embodiment of the invention in an exploded view. The air damper comprises a cylinder 1 having a first open end 13 (Fig. 4) and a second open end 3, and a piston 2 accommodated in the cylinder so as to be movable along the axis of the cylinder 1. The first opening 13 functions as a leading port, and the second opening 3 functions as an air hole 3. A string 8 is coupled to the piston 2 in order to transfer a damper effect generated by the motion of the piston to the glove box (not shown). The string 8 may be a lace, a code, a belt, or the like. A guide cap 6 is provided to the leading port to guide the string 8 out of the cylinder 1. An end cap 5 is provided to the air hole 3 with an air valve 4 between them. The air damper also has a compression coil spring 7, which is inserted in the cylinder 1 between the piston 2 and the guide cap 6. In the free state, the spring 7 forces the piston 2 toward the end cap 5. The cylinder 1 has an L-shaped hook 9 on its outer face near the leading port in order to hook one end 8a of the string 8. The piston 2 has O-rings 10 around the outer face, and a hook piece 11 threaded with the string 8. The string 8 is doubled at the hook piece 11 in a movable manner, and extends in the axial direction in the cylinder 1. As has been mentioned above, one end 8a of the string 8 is hooked at the L-shaped hook 9, and the other end 8b is coupled to a side edge of the glove box (not shown). In this example, the ends 8a and 8b are looped. Fig. 2 illustrated in a cross-sectional view the piston 2, to which a string 8 (illustrated by a ghost line) is coupled. The O-rings 10 are fit into the threads formed in the outer face of the piston 2. The hook piece 11 has a swelling wall, which functions as a reel to allow the string 8 to be pulled in both directions. The piston 2 has an orifice 2a at the bottom face. Fig. 3 illustrates in a cross-sectional view the guide cap 6 provided to the leading port of the cylinder 1. As is illustrated in Figs. 1 and 3, the guide cap 6 has a pair of stopper plates 14A, between which a partition 15 is inserted. The guide cap 6 has a hole 12 for receiving one end 8a of the string 8, and a guide hole 13 for allowing the other end 8b of the string 8 to be pulled out of the cylinder 1. Both ends 8a and 8b of the string 8 doubled at the hook piece 11 are separated by the partition 15 and inserted in the holes 12 and 13, respectively. The stopper plates 14A extend inside the compression coil spring 7 toward the hook piece 11 of the piston 2. This arrangement eliminates necessity for an extra space, and prevents the cylinder 1 from becoming large. When assembling the air damper shown in Figs. 1 through 3, the string 8 is threaded in the hook piece 11 of the piston 2, and pulled in double inside the compression coil spring 7. Then, the piston 2 and the compression coil spring 7 are inserted into the cylinder 1 from the leading port. The hole 12 of the guide cap 6 is threaded with one end 8a of the string 8, while the guide hole 13 of the guide cap 6 is threaded with the other end 8b of the string 8, before the guide cap 6 is fixed to the cylinder 1. The guide cap 6 is then attached to the cylinder 1, and one end 8a of the string 8 is hooked at the L-shaped hook 9. In this manner, the air damper is assembled into a single unit, as shown in Fig. 4. The stopper plates 14A of the guide cap 6 project into the cylinder 1 inside the compression coil spring 7. When installing the air damper in the glove box of an automobile, the cylinder 1 of the air damper is secured to the instrument panel (not shown) or the cover (not shown) attached to an appropriate place on the instrument panel. Then, the looped end 8b of the string 8 extending from the guide cap 8 is pulled out of the cylinder 1, and coupled to the side edge of the globe box. In the preferred embodiment, the string 8 is doubled in the cylinder, and therefore, the amount of pull of the string 8 is twice as much as the displacement of the piston 2. If the glove box is unlocked, the glove box pivots about its axis and starts opening under the gravitational force. As the glove box opens, the string 8 is pulled out of the cylinder 1, and the piston 2 moves toward the guide cap 6, while compressing the compression coil spring 7. The air compressed in the cylinder starts flowing through the orifice 2a of the piston 2, and the flow resistance of the air flowing through the orifice 2a generates a damper effect, which prevents the glove box from abruptly opening. As a result, the gentle opening of the glove box is guaranteed. Then, the hook piece 11 of the piston 2 hits the tips of the stopper plates 14A projecting from the guide cap 6 before the compression coil spring 7 is completely compressed, as illustrated in Fig. 5. The stopper plates 14A prevent the piston 2 from further advancing toward the guide cap 6. In other words, the full-open position of the glove box is defined in a stable manner by the abutment between the piston 2 and the stopper plates 14A without causing undesirable fluctuation in the full-open position. This arrangement does not require an additional separate means for regulating the full-open position. Because the compression coil spring 7 is not fully compressed even if the glove box is held at the full-open position, the spring force will not be weakened. In addition, the air damper is protected from being damaged or broken due to the full compression of the coil spring. If returning the glove box to the close position, the piston 2 is pushed back toward the end cap 5 by the restoring force of the compression coil spring 7, accompanying the string 8. During the return motion of the piston 2, the valve 4 is opened, and the air stored between the piston 2 and the end cap 4 is escaped via the valve 4 into the atmosphere so as to guarantee the smooth return of the piston 2. As has been described, the air damper of the embodiment guarantees gentle opening of the glove box, and at the same time, it functions as a means for regulating the full-open position of the glove box. In addition, the full-open position of the glove box can be easily adjusted simply by changing the length of the stopper plates. Because the stopper plates prevent the compression coil spring from being fully compressed under the excessive amount of load, the air damper works in a reliable manner without being damaged or broken due to deterioration of the coil spring. Although the present invention has been described by reference to an example, the invention will not be limited to the example. It should be appreciated that there are many modifications and substitutions without departing from the scope of the invention, which are defined by the appended claims.

Claims: An air damper comprising: a cylinder (1) having a first open end (13) and a second end (3); a guide cap (6) covering the first open end; a piston (2) movable in the cylinder; a compression coil spring (7) inserted in the cylinder between the piston and the guide cap and for forcing the piston toward the second end of the cylinder; and a string (8) coupled with the piston and extending out of the cylinder via the guide cap; characterized in that the guide cap comprises a stopper means (14) progecting into the cylinder, wherein the piston strikes the stopper means of the guide cap before the compression coil spring is fully compressed when the string is pulled by an external force. A air damper as claimed in claim 1, wherein the piston (2) has a hook piece (11) that is threaded with the string (8) and at least one end of the string extends out of the cylinder (1).

Inventors: OOKAWARA TOSHIHIKO, OOKAWARA, TOSHIHIKO, Ookawara, Toshihiko, Piolax Inc.
Applicants: PIOLAX INC, PIOLAX INC.
Application year: 2001
Main classification: B60R7
IPC codes: F16F9, B60R7