Patent Application
20100201052
The present invention relates to a gas spring and particularly to an improvement to a gas spring used at a rear door or a seat back of a vehicle, for example.
Various proposals have been made for gas springs for use at a rear door or a seat back of a vehicle. Japan Patent Application Publication No. 2007-85377 (see, e.g., paragraphs 0005, 0006, 0008, 0009 and FIG. 7), for example, discloses a gas spring in which a dust seal is located in series with a rod guide at a head end portion of a cylinder body, in which a rod body moves in and out of the cylinder body.
The gas spring has a dust seal with a lip in sliding contact with an outer circumference of the rod body at the head end portion of the cylinder body which the rod body is moved into and out of. The dust seal is located in series with the rod guide with the rod body being similarly disposed in the head end portion of the cylinder body and penetrating through a shaft core portion.
In a gas spring of this type, the dust seal is formed of an elastic material. The rod guide is formed of a material more rigid than the dust seal, and as disclosed in the document, the dust seal and the rod guide are fixed inside the head end portion by folding an opening end portion of the cylinder body inward to form a seal.
Thus, in the gas spring disclosed in the Japanese application publication, concentricity of the rod body with the cylinder body is guaranteed by the rod guide when the rod body is moved inside the cylinder body and dust adhering to the outer circumference of the rod body is scraped off by a lip of the dust seal.
Technical Problem In the device described in the Japanese application publication, if the pressure of the gas sealed inside the device is proper there is no particular nonconformity. If, though, the sealed gas pressure is higher, there is a possibility that a slight nonconformity may occur.
That is, in most gas springs of this type, the thrust of the rod body projecting from inside the cylinder body is determined by the sealed gas pressure. Thus, at a given gas pressure, a larger diameter rod body with respect to the cylinder body will result in a larger thrust.
However, generally speaking, if the diameter of the rod body is large, its weight will also be large to a corresponding degree. A higher sealed gas pressure might thus be used so that a larger thrust can be obtained while decreasing the overall weight of the device by reducing the diameter of the rod body.
As a result, over time the rod guide inside the head end portion of the cylinder body may be pushed by the sealed gas pressure into the sealed end portion at the opening end portion of the cylinder body. This can impair the dust seal accordingly and there is a danger that a sealing margin of the lip, which is in sliding contact with the outer circumference of the rod body in the dust seal, may deviate from its intended configuration.
The present invention was made in view of such circumstances and is intended to provide an improved gas spring that can permanently maintain the sealing effectiveness of the lip in the dust seal without being affected by the pressure from the gas sealed inside the device, and to provide further improvements to the device's general properties.
A gas spring according to the present invention can be configured such that the rod body is linked with the cylinder body with a gas of a predetermined pressure is sealed inside the cylinder body and the rod body movable into and out of the cylinder body. The device can include a rod guide through which the rod body penetrates at a shaft core portion inside a head end portion where the rod body moves into and out of the cylinder body. A dust seal with a lip in sliding contact with an outer circumference of the rod body is located at a sealed end portion at an opening end portion of the cylinder body. An outer end of the rod guide can be placed in contact with the inside of the cylinder body, with the dust seal integrally incorporated at the outer end portion of the rod guide.
Since the outer end of the rod guide is brought into contact with the sealed end at the opening end portion of the cylinder body, even if the pressure of the gas sealed inside the cylinder body is high and the rod guide is thus pressed toward the sealed end portion, the dust seal is not compromised and the sealing of the dust seal lip is maintained over time as originally intended.
The present invention will be described based on presently preferred embodiments and in connection with the appended drawings, in which:
The gas spring according to the present invention may be used at a rear door or a seat back of a vehicle, for example, with one end connected to a so-called fixed side and the other end to a movable side forming elements of the vehicle.
A portion of a gas spring is illustrated in
A U-packing 5 and a retainer 6 are located inside the head end portion 1a of the cylinder body 1, in addition to the rod guide 3 and the dust seal 4.
The U-packing 5 has a back face at its left end in the figure. The back face abuts an inner end of the rod guide 3 so as to prevent leakage of gas sealed inside the cylinder body 1. The retainer 6 is fixed by roll-sealing the outer circumference of the cylinder body 1. The retainer 6 functions as a stopper that contacts a piston body (not shown) on the rod body 2 when the gas spring is operated and the rod body is extended to its maximum extent. The retainer 6 also defines an oil reservoir in which oil for lubrication is contained between it and the U-packing 5.
The rod guide 3 guarantees concentricity with respect to the cylinder body 1 as the rod body 2 moves into and out of the cylinder body 1. The rod body 2 penetrates the shaft core portion while providing a shaft length effective to maintain the concentricity.
The rod guide 3 has a predetermined mechanical strength and is made of a hard synthetic resin with an appropriate rigidity so as to contribute to reduction of the overall weight of the gas spring.
For its part the dust seal 4 has an annular lip 4a in sliding contact with the outer circumference of the rod body 2 so that when the rod body 2 is moved into the cylinder body 1, dust adhering to the outer circumference of the rod body 2 is scraped off by the lip 4a. The lip is formed of an elastic material so that it will not scratch the outer circumference of the rod body 2. Appropriate materials may include a synthetic resin material or a rubber material with appropriate elasticity, oil resistance, and weather resistance.
The above are characteristics of rod guides 3 and dust seals 4 even in conventional gas springs. In the gas spring of this invention, the rod guide 3 and the dust seal 4 are formed and have characteristic features as described below.
In the gas spring of this embodiment the dust seal 4 is integrally incorporated at an outer end portion 3a at the left end in the figure of the rod guide 3. The dust seal 4 projects from inside the cylinder body 1 along the rod body 2. In this embodiment, the rod guide 3 and the dust seal 4 are made as a single part (see
Also, when the dust seal 4 is incorporated into the rod guide 3, as compared with a conventional case where the dust seal 4 is arranged in series with the rod guide 3, the length required to arrange two components in series at the head end portion 1a of the cylinder body 1 is not required, thereby allowing a reduction in the axial length at the head end portion 1a.
The rod guide 3 in this embodiment integrally incorporates the dust seal 4. In order to dispose element in the head end portion 1a of the cylinder body 1, the opening end portion of the cylinder body 1 is sealed and fixed at the head end portion 1a with a sealed end portion 1b in contact with the outer end of the rod guide 3 (see
As a result, the rod guide 3 is carried by the sealed end portion lb in the opening end portion of the cylinder body 1 at the head end portion la of the cylinder body 1. Thus, even if the outer end of the rod guide 3 is strongly pressed against the sealed end portion 1b when sealing against a gas with a higher than normal pressure inside the cylinder body 1, the dust seal 4, which will be described later, will not be affected.
The dust seal 4 has its annular lip 4a in sliding contact with the outer circumference of the rod body 2, and in this way generally similar to the conventional dust seal as mentioned above. The dust seal 4 also includes an annular lip base portion 4b with the lip 4a on its inner circumference. The outer circumference of the lip base portion 4b is separated from the inner circumference of the sealed end portion 1b at the opening end portion of the cylinder body 1 with an appropriate gap S between them (see
In this embodiment, therefore, when the sealed end portion 1b at the opening end portion of the cylinder body 1 is brought into contact with the outer end of the rod guide 3 as shown in
In order to achieve this, the dust seal 4 in this embodiment has, as shown in
Since the base portion 4c is fitted in the recess portion 3b of the rod guide 3, the dust seal 4 is not deformed at the lip base portion 4b and the sealing performance of the lip 4a is compromised.
An outer diameter of the base portion 4c is smaller than the outer diameter of the rod guide 3, and thus, by allowing the dust seal 4 to move or “float” in its radial direction, the lip 4a can be better aligned against the surface of the rod body 2 so that their sliding performance can be improved.
In the alternative embodiment shown in
In the embodiment shown in
Also, and as shown in
As mentioned above, the dust seal 4 of these embodiments are fixed at a predetermined position and thus not affected by pressure from the gas sealed inside the cylinder body 1. The sealing pressure of the lip 4a against the outer circumference of the rod body 2 is thus neither increased nor decreased, and thus, the performance of the lip 4a can be maintained as intended.
In
If the base portion is in the form of an independent base portion 4c, the amount of material used to form the dust seal 4 can be reduced. If the base portion is an annular base portion 4d, the recess portion at the outer end portion 3a of the rod guide 3 is also annular, and forming it is thus made easier.
Obviously, other modifications and variations of the disclosed device are possible in the light of the above teachings. It is therefore to be understood that changes may be made in the particular embodiments described above which are within the full intended scope as defined in the appended claims.
While the present system and method has been disclosed according to the preferred embodiment, those of ordinary skill in the art will understand that other embodiments have also been enabled. Even though the foregoing discussion has focused on particular embodiments, it is understood that other configurations are contemplated. In particular, even though the expressions “in one embodiment” or “in another embodiment” are used herein, these phrases are meant to generally reference embodiment possibilities and are not intended to limit the system or methods disclosed herein to those particular embodiment configurations. These terms may reference the same or different embodiments, and are combinable into aggregate embodiments. The terms “a”, “an” and “the” may also mean “one or more”.
None of the description in this specification should be read as implying that any particular element, step or function is an essential element which must be included in the claim scope. The scope of the patented subject matter is defined by the allowed claims and their equivalents. Unless explicitly recited, other aspects of the instant disclosure as described in this specification do not limit the scope of the claims. Because many varying and different embodiments may be made within the scope of the novel concept(s) herein taught, and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
| Number | Date | Country | Kind |
|---|---|---|---|
| JP2007-262851 | Oct 2007 | JP | national |
This application is a continuation of International Application PCT/JP2008/068801, having an international filing date of Oct. 8, 2008,now pending, which claims priority to Japanese Patent Application No. 2007-262851, having a filing date of Oct. 9, 2007, now pending, and which are both hereby incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2008/068801 | Oct 2008 | US |
| Child | 12755416 | US |
