Non-contact shaft peripheral seal device

Abstract

Provided is a non-contact shaft peripheral seal device capable of suppressing or preventing breakage of a cylindrical seal member caused by axial movement of a porous member.　A non-contact shaft peripheral seal device 1 is attached to a casing 8 having a wall part through which a rotary shaft 2 penetrates, and forms a non-contact seal with an outer peripheral surface of the rotary shaft by pressurized gas supplied to an outer peripheral surface of the rotary shaft. The non-contact shaft peripheral seal device 1 includes: a connection plate 14 having an opening through which the rotary shaft can penetrate and connected to the casing in a state where the rotary shaft penetrates the opening; a cylindrical porous member 18 for supplying the pressurized gas to the outer peripheral surface of the rotary shaft at a position outside the connection plate; a cylindrical seal member 22 that is disposed radially outward of the outer peripheral surface of the rotary shaft so as to seal between one open end of the cylindrical porous member and the peripheral edge of the opening of the connection plate through which the rotating shaft extends, and that follows the movement of the porous member; and a tension adjustment member 32 that adjusts the tension of the seal member along the longitudinal direction of the rotary shaft so that the length of the seal member along the longitudinal direction of the rotary shaft is maintained within a predetermined range.

Description

Non-contact shaft seal device

[0001] The present invention relates to a non-contact shaft circumferential seal device, and more particularly to a non-contact shaft circumferential seal device that seals the outer periphery of a rotating shaft in a non-contact manner by supplying pressurized gas to the outer periphery of the rotating shaft.

[0002] A non-contact shaft circumferential seal device is known in which a pressurized fluid is supplied through a porous member arranged radially outward from the outer circumferential surface of a rotating shaft, thereby forming a fluid film between the outer circumferential surface of the rotating shaft and the porous member.

[0003] One known example of such a non-contact circumferential shaft seal device is one in which a porous member that supplies pressurized fluid is allowed to move within a certain range in the radial or axial direction relative to a stationary member such as a housing, and the space between such a movable porous member and the stationary housing is sealed by a cylindrical member (bellows) made of a flexible material (Patent Document 1).

[0004] Special Publication No. 2015-510091

[0005] However, since the non-contact shaft circumferential sealing device disclosed in Patent Document 1 is used in a location where the rotating shaft passes through a partition wall separating two regions where a pressure difference exists, the pressure difference between the two regions can cause the porous member to move in the axial direction.

[0006] If this movement is in the direction in which the porous member moves away from the housing, a large tension (tension in the tensile direction) acts on the cylindrical sealing member, which has one end attached to the stationary member (housing) and the other end attached to the porous member, causing the cylindrical sealing member (bellows) to stretch. If the amount of this stretching exceeds the allowable limit, the cylindrical sealing member may be damaged, such as torn.

[0007] On the other hand, if the movement direction is a direction in which the porous member approaches the housing, or if a higher pressure acts on the outer surface of the cylindrical sealing member than on the inner surface, a force (compressive stress) acts on the cylindrical sealing member to compress it in the axial direction, causing the cylindrical sealing member to bend radially inward, i.e., in the direction of the rotation axis. If the degree of this bending becomes too great, the cylindrical sealing member may come into contact with the rotation axis and be damaged.

[0008] The present invention has been made in consideration of these points, and aims to provide a non-contact circumferential axial sealing device that can suppress or prevent damage to a tubular sealing member caused by axial movement of a porous member.

[0009] According to another preferred aspect of the present invention, there is provided a non-contact shaft circumferential sealing device that is attached to a casing having a wall portion through which a rotating shaft passes, and that forms a non-contact fluid film between the outer peripheral surface of the rotating shaft and the rotating shaft using pressurized gas supplied to the outer peripheral surface of the rotating shaft, the non-contact shaft circumferential sealing device comprising: a connecting plate having an opening through which the rotating shaft can pass and connected to the casing with the rotating shaft passing through the opening; a cylindrical porous member that supplies pressurized gas to the outer peripheral surface of the rotating shaft at a position outside the connecting plate; a tubular sealing member that is arranged radially outward of the outer peripheral surface of the rotating shaft to seal between one open end of the cylindrical porous member and the periphery of the opening of the connecting plate through which the rotating shaft extends, and that follows the movement of the porous member; and a tension adjustment member that adjusts the tension of the sealing member along the longitudinal direction of the rotating shaft so that the length of the sealing member along the longitudinal direction of the rotating shaft is maintained within a predetermined range.

[0010] With this configuration, the tension adjustment member adjusts the tension of the sealing member along the longitudinal direction of the rotating shaft, and the length of the sealing member is maintained within a predetermined range, thereby preventing or suppressing situations such as the sealing member being stretched in the axial direction and torn, or bending radially inward and coming into contact with the rotating shaft and being damaged.

[0011] According to another preferred aspect of the present invention, the tension adjusting member is a coil spring arranged along the axis in the longitudinal direction of the rotating shaft.

[0012] According to this configuration, the expansion and contraction of the coil spring can be utilized to prevent or suppress the seal member from extending beyond an allowable range or bending radially inward.

[0013] According to another preferred aspect of the present invention, the coil spring is connected to the other open end of the porous member.

[0014] With this configuration, the coil spring is located on the outside of the aircraft, making it easy to access the coil spring for maintenance and the like.

[0015] According to another preferred aspect of the present invention, the device is provided with a cylindrical holder that holds the cylindrical porous member from the radially outer side and forms a fluid supply space between the cylindrical holder and the porous member, and the coil spring is connected to the porous member by having one end attached to one end of the holder.

[0016] According to this configuration, the coil spring is connected to a holder that is easy to process, which makes manufacturing and maintenance easier.

[0017] According to another preferred aspect of the present invention, the tubular seal member has a cylindrical body and flanges disposed on both ends of the cylindrical body and extending radially outward.

[0018] According to this configuration, the cylindrical seal member can be connected to the connecting plate or the holder using the flange, which facilitates the manufacturing process of the non-contact shaft circumferential seal device.

[0019] According to another preferred aspect of the present invention, one flange of the sealing member is clamped between the periphery of the opening of the connecting plate and a connecting plate side pressure plate, and the other flange of the sealing member is clamped between the other end of the holder and a holder side pressure plate.

[0020] With this configuration, the cylindrical sealing member can be attached to the non-contact shaft circumferential sealing device by the simple process of clamping one flange between the connecting plate and the connecting plate side pressure plate, and clamping the other flange between the casing holder and the holder side pressure plate, thereby facilitating the manufacture of the non-contact shaft circumferential sealing device.

[0021] According to another preferred aspect of the present invention, a plate is provided that is disposed along the rotation axis at a distance from the connecting plate with the porous member sandwiched therebetween, and the other end of the coil spring is connected to the plate.

[0022] According to this configuration, it is possible to connect the coil spring to the porous member with a simplified structure.

[0023] According to another preferred aspect of the present invention, the device comprises a rod-shaped member having a base end fixed to the connecting plate so as to extend from the connecting plate along the rotation axis, the rod-shaped member having a large diameter portion at its tip end against which the end of the coil spring can abut, and the coil spring is sheathed on the rod-shaped member with one end abutting the connecting plate and the other end abutting the large diameter portion.

[0024] With this configuration, it is possible to attach the coil spring close to the casing, thereby shortening the length of the non-contact shaft circumferential sealing device along the axis of the rotating shaft.As a result, the non-contact shaft circumferential sealing device can be attached to the casing even when there is not much space around the casing.

[0025] According to another preferred aspect of the present invention, the coil spring is a compression spring.

[0026] With this configuration, the compression spring, which serves as a tension adjusting member, suppresses excessive stretching of the tubular sealing member, thereby preventing or suppressing the tubular sealing member from being stretched and damaged due to movement of the porous body member.

[0027] According to another preferred aspect of the present invention, the coil spring is a tension spring.

[0028] With this configuration, the tension spring, which serves as the tension adjustment member, suppresses excessive bending (slackening) of the cylindrical sealing member, and the movement of the porous body member causes the cylindrical sealing member to be pressed in the axial direction and bend inward, preventing or suppressing damage due to contact with the rotating shaft.

[0029] According to another preferred aspect of the present invention, the porous member is made of a material selected from the group consisting of porous carbon, porous ceramics, and sintered metal.

[0030] In this way, in the present invention, the porous member for supplying pressurized gas can be made of a material selected from a plurality of types of porous materials.

[0031] According to another preferred aspect of the present invention, the coil spring is a compression spring interposed between the other end of the holder and the connecting plate, and the porous member is formed of a material selected from the group consisting of porous carbon, porous ceramics, and sintered metal.

[0032] With this configuration, the compression spring prevents the distance between both ends of the cylindrical sealing member from becoming shorter than a predetermined length, thereby preventing the cylindrical sealing member from bending inward, and as a result, preventing or suppressing the cylindrical sealing member from coming into contact with the rotating shaft and being damaged.

[0033] According to another aspect of the present invention, there is provided a non-contact shaft circumferential sealing device that is attached to a casing having a wall through which a rotating shaft passes, and that forms a contactless seal between the outer circumferential surface of the rotating shaft and the mounting plate and the rotating shaft by pressurized gas supplied to the outer circumferential surface of the rotating shaft, the non-contact shaft circumferential sealing device comprising: a mounting plate having an opening through which the rotating shaft can pass and connected to the casing with the rotating shaft passing through the opening; a cylindrical porous member that supplies pressurized gas to the outer circumferential surface of the rotating shaft at a position outside the mounting plate; a tubular sealing member that is arranged radially outward of the outer circumferential surface of the rotating shaft to seal between one open end of the cylindrical porous member and a circumferential edge of the opening in the mounting plate through which the rotating shaft extends, and that follows the movement of the porous member; and a tension adjusting member that adjusts the tension of the sealing member along the longitudinal direction of the rotating shaft so that the length of the sealing member along the longitudinal direction of the rotating shaft is maintained within a predetermined range, one end of the sealing member being sandwiched between the circumferential edge of the opening in the mounting plate and the wall of the casing, The other end of the seal member is sandwiched between the other end of the holder and a holder-side pressing plate.

[0034] According to another aspect of the present invention, there is provided a non-contact shaft circumferential seal device set comprising any of the above non-contact shaft circumferential seal devices and a sleeve that is fitted onto the rotating shaft so as to form the outer surface of the rotating shaft.

[0035] This configuration makes it easy to install the non-contact shaft seal into the device, and also simplifies the installation process. Furthermore, since there is no need to adjust the gap between the outer surface of the rotating shaft formed by the sleeve and the porous member, the performance of the non-contact shaft seal is guaranteed.

[0036] According to the present invention, it is possible to provide a non-contact circumferential axial seal device that can suppress or prevent damage to a tubular seal member caused by axial movement of a porous member.

[0037] FIG. 1 is a longitudinal sectional view taken along the rotation axis of a non-contact shaft circumferential sealing device according to a first embodiment of the present invention when attached to a screw feeder. FIG. 2 is a diagram showing the non-contact shaft circumferential sealing device according to the first embodiment attached to a rotating shaft having a modified sleeve. FIG. 3 is a longitudinal sectional view taken along the rotation axis of a non-contact shaft circumferential sealing device according to a second embodiment of the present invention when attached to a screw feeder. FIG. 4 is a longitudinal sectional view taken along the rotation axis of a non-contact shaft circumferential sealing device according to a third embodiment of the present invention when attached to a screw feeder. FIG. 5 is a longitudinal sectional view taken along the rotation axis of a non-contact shaft circumferential sealing device according to a fourth embodiment of the present invention when attached to a screw feeder. FIG. 6 is a longitudinal sectional view taken along the rotation axis of a non-contact shaft circumferential sealing device according to a fifth embodiment of the present invention when attached to a screw feeder.

[0038] The configuration of a non-contact shaft circumferential sealing device according to a first embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a longitudinal cross-sectional view of the non-contact shaft circumferential sealing device according to the first embodiment of the present invention, taken along the rotation axis, attached to a screw feeder.

[0039] The non-contact shaft circumferential sealing device of this embodiment is a non-contact shaft circumferential sealing device that seals the outer peripheral surface of a rotating shaft using pressurized gas supplied to the outer periphery of the rotating shaft, thereby forming a non-contact seal between the rotating shaft and a stationary member on the casing side through which the rotating shaft extends. The casing is assumed to be a container that contains a fluid such as gas, liquid, fluid, flowable powder, or granular material. The non-contact shaft circumferential sealing device of this embodiment is applied to, but is not limited to, a screw feeder, which is a device that supplies powder. Therefore, the casing through which the rotating shaft passes is the casing of a screw feeder with a screw disposed inside.

[0040] In the non-contact shaft circumferential seal device 1 of this embodiment, the rotating shaft 2 comprises a rotating shaft main body 6 that rotates the screw 4 inside the machine, and a hollow cylindrical sleeve 10 that is fitted to the machine-side portion of the rotating shaft main body 6 and forms the outer circumferential surface of the rotating shaft 2 where the rotating shaft 2 penetrates the casing 8. The sleeve 10 is made of a metal suitable for the usage conditions, such as stainless steel, chrome-plated or nickel-plated steel, and is configured so as not to rotate relative to the rotating shaft main body 6 due to frictional forces, etc.

[0041] The non-contact shaft circumferential sealing device 1 of this embodiment includes a connecting plate 14 having an opening 12 through which the rotating shaft 2 can pass. When the non-contact shaft circumferential sealing device is attached to an object device such as a screw feeder, the connecting plate 14 is connected and fixed to the casing 8 of the object device with connecting members such as screws 16, with the casing 10 of the rotating shaft 2 passing through the opening 12, as shown in FIG.

[0042] The non-contact shaft circumferential seal device 1 of this embodiment further includes a cylindrical porous member 18 that is disposed radially outward of the outer circumferential surface of the rotating shaft 2 (the outer circumferential surface of the sleeve 10) at an outer position (outside the machine) of the connecting plate 14 and supplies pressurized gas to the outer circumferential surface of the rotating shaft 2 (the outer circumferential surface of the sleeve 10). In this embodiment, the porous member 18 is made of porous carbon. However, the porous member 18 may be made of other porous materials, such as porous ceramics or porous sintered metal.

[0043] The inner diameter of the porous member 18 is set slightly larger than the outer diameter of the sleeve 10 so that when the porous member 18 is positioned radially outward of the sleeve 10, a gap of approximately 1 to 20 μm, preferably approximately 2 to 5 μm, is formed between the inner surface of the porous member 18 and the outer surface of the sleeve 10.

[0044] A cylindrical holder 20 is disposed at a radially outer position of the porous member 18, supporting the porous member 18 from the radially outer side. The holder 20 has approximately the same axial length as the porous member 18. The holder 20 is configured to be integral with the porous member 18 and to be movable in the axial and radial directions.

[0045] The holder 20 is also formed with a recess 20a extending around the entire circumferential direction on its inner circumferential surface at the center in the axial direction, and an air supply passage 20b that penetrates the holder 20 in the radial direction and whose tip side is in communication with the recess 20a. The open end of the recess 20a located on the inner circumferential side is covered with a porous member 18, and pressurized gas supplied to the recess 20a via the air supply passage 20b from a gas supply source (not shown) as indicated by arrow A is supplied to the entire outer circumferential surface of the porous member 18. In this embodiment, the supplied pressurized gas is pressurized air, but other pressurized gases such as argon or nitrogen can also be used depending on the usage mode.

[0046] The porous member 18 is fixed to the holder 20 by shrink fitting, adhesive, etc. The axial end face of the porous member 18 is sealed with epoxy resin or the like.

[0047] The pressurized gas supplied to the outer peripheral surface of the porous member 18 passes through the inside of the porous member 18, is ejected from the inner peripheral surface of the porous member 18, and is supplied to the outer peripheral surface of the sleeve 10, forming a layer of pressurized gas between the porous member 18 and the sleeve 10. This layer of pressurized gas forms a fluid film between the porous member 18 and the sleeve 10, and the sleeve 10 (rotating shaft 2) is supported by the non-contact shaft circumferential seal device 1 without contacting the porous member 18, which is a stationary member on the casing side.

[0048] The non-contact shaft circumferential seal device 1 further includes a cylindrical seal member 22. The seal member 22 has a cylindrical main body 22a and an inboard flange 22b and an outboard flange 22c that are disposed on both ends of the cylindrical main body and extend radially outward. The seal member 22 is disposed radially outward of the outer peripheral surface of the sleeve 10 (rotating shaft 2) so as to seal between the inboard open end of the cylindrical porous member 18 and the periphery of the opening 12 in the connecting plate 14 through which the sleeve 10 (rotating shaft 2) extends.

[0049] The cylindrical sealing member 22 is formed from an elastic material such as synthetic rubber, impermeable canvas, or the like, and seals the space inside the non-contact sealing device 1 between the inner surface of the porous member 18 and the outer surface of the sleeve 10 (rotating shaft 2) from the space outside the machine on the radially outer side.

[0050] The cylindrical sealing member 22 is fixed by sandwiching the flange 22b on the inside of the machine between the connecting plate 14 and a ring-shaped connecting plate side pressure plate 26 fixed to the connecting plate 14 by screws 24, and the flange 22c on the outside of the machine between the holder 20 and a ring-shaped holder side pressure plate 30 fixed to the holder 20 by screws 28.

[0051] Since the sealing member 22 is made of an elastic material, it deforms while maintaining a sealed state in response to the axial and circumferential movement of the porous member 18 and holder 20 that make up the non-contact shaft circumferential sealing device 1.

[0052] The non-contact shaft circumferential sealing device 1 further includes a tension adjusting member that adjusts the tension of the sealing member 22 along the longitudinal direction of the rotating shaft 2 so that the length of the sealing member 22 along the longitudinal direction of the rotating shaft 2 is maintained within a predetermined range.

[0053] In this embodiment, the tension adjusting member is a coil spring 32 arranged along the axis in the longitudinal direction of the rotating shaft 2. The coil spring 32 is a compression spring arranged between the axially outer end of the holder 20 and an annular plate 34 arranged spaced apart from the connecting plate 14 along the rotating shaft 2 with the porous member 18 sandwiched therebetween, with the coil spring 32 oriented to extend along the axial direction of the rotating shaft 2.

[0054] 1 shows only one coil spring 32, it is preferable that a plurality of coil springs 32 are arranged at equal angular intervals around the rotation axis 2. However, it is also possible to arrange the plurality of coil springs at unequal angular intervals. The annular plate 34 is fixed to the connecting plate 14 by a plurality of rods 36 (only one is shown in FIG. 1) at equal angular intervals around the rotation axis 2. It is also possible to arrange the plurality of rods 36 at unequal angular intervals.

[0055] The seal member 22 is biased by a coil spring 32, which is a compression spring, toward the casing 8 via the holder 20 so as to assume a desired position and shape, and is in a state in which a predetermined tension is applied.

[0056] With this configuration, even if pressure inside the aircraft acts on the holder 20 and porous member 18 with a force that, for example, moves them toward the outside of the aircraft, the coil spring 32 restricts the amount of movement of the holder 20 and porous member 18 toward the outside of the aircraft. As a result, the sealing member 22 connected to the porous member 18 is prevented from being stretched due to excessive tension being applied to it by the large movement of the porous member 18, and the sealing member 22 is prevented from being damaged.

[0057] The non-contact shaft circumferential sealing device 1 of this embodiment is preferably manufactured, transported, assembled, etc. as a set with the sleeve 10. For this reason, during transportation and assembly to a target device such as a screw feeder, the sleeve 10 is connected to the annular plate 34 by a set plate 38 with an L-shaped cross section and screws 40, 42. Once the assembly work to the screw feeder (target device), such as fixing the connecting plate 14 to the casing 8 and sheathing the sleeve 10 to the rotating shaft body 6, is completed, the set plate 38 and screws 40, 42 are removed, and the sleeve 10 becomes rotatable integrally with the rotating shaft body 6.

[0058] By transporting the sleeve 10 as a set fixed to the non-contact shaft sealing device 1 in this way, it becomes easier to align the porous member 18 with the sleeve 10 when assembling the non-contact shaft sealing device 1 to the target equipment. Furthermore, since there is no need to adjust the gap between the outer circumferential surface of the rotating shaft formed by the sleeve 10 and the porous member 18, the performance of the non-contact shaft sealing device 1 is guaranteed.

[0059] As shown in FIG. 2, a non-contact circumferential seal may be formed between the outer circumferential surface of a sleeve 44 fixed to a rotary shaft body 48 by a set screw 46.

[0060] Next, a non-contact shaft circumferential sealing device 50 according to a second embodiment of the present invention will be described with reference to Fig. 3. Fig. 3 is a view similar to Fig. 1, illustrating the configuration of the non-contact shaft circumferential sealing device 50 according to the second embodiment.

[0061] The configuration of the second non-contact shaft circumferential seal device 50 is the same as that of the non-contact shaft circumferential seal device 1 of the first embodiment. The difference between the first and second embodiments is that the non-contact shaft circumferential seal device 50 of the second embodiment does not form a non-contact shaft circumferential seal with a rotating shaft whose outer circumferential surface is formed by a sleeve, but forms a fluid film (non-contact shaft circumferential seal) with the outer circumferential surface of a rotating shaft 52 that is not covered by a sleeve.

[0062] Next, a non-contact shaft sealing device 70 according to a third embodiment of the present invention will be described with reference to Figure 4. The configuration of the portion forming the non-contact shaft sealing of the third non-contact shaft sealing device 70 is the same as that of the non-contact shaft sealing device 1 of the first embodiment. The non-contact shaft sealing device 70 of the third embodiment differs from the non-contact shaft sealing device 1 of the first embodiment in the arrangement of the coil spring, which is the tension adjusting member.

[0063] The non-contact shaft periphery sealing device 70 of the third embodiment includes a rod-shaped member 72 whose base end is fixed to the presser plate 26 on the connecting plate 14 side and which extends parallel to the rotation shaft, penetrating the presser plate 30 on the holder 20 side. A large diameter portion 74 is provided at the tip (outboard end) of this rod-shaped member. A coil spring 76, which is a compression spring, is fitted to the exterior of the rod-shaped member 72 so as to be positioned between the large diameter portion 74 and the presser plate 30 on the holder side.

[0064] With this configuration, even if a force acts to move the holder and porous member inward, the amount of movement of the holder 20 and porous member 18 inward is restricted by the coil spring 74, and as a result, the main body 22a of the seal member 22 connected to the porous member 18 and holder 20 is prevented from bending radially inward and coming into contact with the outer circumferential surface of the rotating shaft (sleeve), which would otherwise cause damage. Also, the axial length is shortened, making the device more compact.

[0065] Next, a non-contact shaft circumferential sealing device 80 according to a fourth embodiment of the present invention will be described with reference to Figure 5. The basic configuration of the fourth non-contact shaft circumferential sealing device 80 is the same as that of the non-contact shaft circumferential sealing device 70 according to the third embodiment. The difference between the non-contact shaft circumferential sealing device 80 according to the fourth embodiment and the non-contact shaft circumferential sealing device 70 according to the third embodiment is the location of the coil spring, which is a tension adjusting member.

[0066] As shown in Figure 5, in the non-contact shaft circumferential sealing device 70 of the fourth embodiment, a coil spring 82, which is a compression spring, is interposed between the pressure plate 26 on the connecting plate 14 side and the pressure plate 30 on the holder 20 side.

[0067] With this configuration, even if a force acts to move the holder and porous member toward the inside of the machine, the coil spring 82 restricts the amount of movement of the holder and porous member toward the inside of the machine, and as a result, the main body of the sealing member connected to the porous member is prevented from bending radially inward and coming into contact with the outer surface of the rotating shaft (sleeve), which would cause damage.

[0068] Next, a non-contact shaft circumferential sealing device 90 according to a fifth embodiment of the present invention will be described with reference to Fig. 6. Fig. 6 is a view similar to Fig. 1, illustrating the configuration of the non-contact shaft circumferential sealing device 90 according to the fifth embodiment.

[0069] The non-contact shaft circumferential sealing device 1 of the first embodiment differs from the non-contact shaft circumferential sealing device 90 of the fifth embodiment in the presence or absence of a connecting plate 14 .

[0070] The non-contact shaft circumferential sealing device 70 of the fifth embodiment does not have a connecting plate 14, and the casing side pressure plate (mounting plate) 26' that holds one end of the sealing member is integrated with the connecting plate 14 of the non-contact shaft circumferential sealing device 1 of the first embodiment.

[0071] 6, the inboard flange 22b of the cylindrical seal member 22 is sandwiched between the casing side retaining plate 26' and the casing 8. Furthermore, the casing side retaining plate 26' of the non-contact shaft circumferential seal 70 of this embodiment is fixed to the casing 8 by a rod 36 that is screwed into the casing 8.

[0072] Such a non-contact shaft circumferential seal 70 has an inexpensive and lightweight structure because the connecting plate is omitted.

[0073] The present invention is not limited to the above-described embodiment, and various changes and modifications are possible within the scope of the technical idea described in the claims.

[0074] In each of the above embodiments, a sealing member having a cylindrical main body and flanges on both ends of the main body is used as the sealing member, but a sealing member having another shape, such as a bellows shape, may also be used.

[0075] Furthermore, in the above embodiment, a coil spring is used as the tension adjusting member, but other types of springs such as leaf springs, and other elastic members may also be used.

[0076] 1: Non-contact shaft circumferential seal device 2: Rotating shaft 4: Screw 6: Rotating shaft body 8: Casing 10: Sleeve 12: Opening 14: Connecting plate 18: Porous member 20: Holder 20a: Recess 20b: Air supply passage 22: Sealing member 22a: Body 22b: Inner flange 22c: Outer flange 26: Connecting plate side pressure plate 30: Holder side pressure plate 32: Coil spring 34: Annular plate 36: Rod 38: Set plate

Claims

1. A non-contact shaft circumferential sealing device that is attached to a casing having a wall through which a rotating shaft penetrates and forms a non-contact seal with the outer peripheral surface of the rotating shaft by pressurized gas supplied to the outer peripheral surface of the rotating shaft, comprising: a connecting plate having an opening through which the rotating shaft can pass and connected to the casing with the rotating shaft passing through the opening; a cylindrical porous member that supplies pressurized gas to the outer peripheral surface of the rotating shaft at an outer position outside the connecting plate; a tubular sealing member that is arranged radially outward of the outer peripheral surface of the rotating shaft to seal between one open end of the cylindrical porous member and the periphery of the opening of the connecting plate through which the rotating shaft extends, and that follows the movement of the porous member; and a tension adjusting member that adjusts the tension of the sealing member along the longitudinal direction of the rotating shaft so that the length of the sealing member along the longitudinal direction of the rotating shaft is maintained within a predetermined range.

2. A non-contact shaft circumferential seal device as set forth in claim 1, wherein the tension adjustment member is a coil spring arranged along the axis in the longitudinal direction of the rotating shaft.

3. A non-contact shaft circumferential seal device according to claim 2, wherein the coil spring is connected to the other open end of the porous member.

4. A non-contact shaft circumferential seal device as described in claim 3, further comprising a cylindrical holder which holds the cylindrical porous member from the radially outward direction and forms a space for supplying fluid between the cylindrical holder and the porous member, and one end of the coil spring is attached to one end of the holder, thereby connecting the coil spring to the porous member.

5. A non-contact shaft circumferential seal device according to claim 4, wherein said tubular seal member has a cylindrical body and flanges disposed on both ends of said cylindrical body and extending radially outward.

6. A non-contact shaft circumferential seal device as described in claim 5, wherein one flange of the seal member is clamped between the peripheral edge of the opening of the connecting plate and a connecting plate side pressure plate, and the other flange of the seal member is clamped between the other end of the holder and a holder side pressure plate.

7. A non-contact shaft circumferential seal device according to claim 6, further comprising a plate disposed along the rotating shaft at a distance from the connecting plate with the porous member therebetween, the other end of the coil spring being connected to the plate.

8. A non-contact shaft circumferential seal device as described in claim 4, further comprising a rod-shaped member having a base end connected and fixed to said connecting plate so as to extend from said connecting plate along said rotating shaft, said rod-shaped member having a large diameter portion at its tip end against which an end of said coil spring can abut, said coil spring being sheathed on said rod-shaped member with one end abutting against said connecting plate and the other end abutting against said large diameter portion.

9. A non-contact shaft circumferential sealing device which is attached to a casing having a wall through which a rotating shaft penetrates and forms a non-contact seal with the outer circumferential surface of the rotating shaft by pressurized gas supplied to the outer circumferential surface of the rotating shaft, comprising: a mounting plate having an opening through which the rotating shaft can penetrate and connected to the casing with the rotating shaft penetrating the opening; a cylindrical porous member which supplies pressurized gas to the outer circumferential surface of the rotating shaft at an outer position outside the mounting plate; a tubular sealing member which is arranged radially outward of the outer circumferential surface of the rotating shaft to seal between one open end of the cylindrical porous member and the periphery of the opening of the mounting plate through which the rotating shaft extends, and which follows the movement of the porous member; and a tension adjusting member which adjusts the tension of the sealing member along the longitudinal direction of the rotating shaft so that the length of the sealing member along the longitudinal direction of the rotating shaft is maintained within a predetermined range, one end of the sealing member being sandwiched between the periphery of the opening of the mounting plate and the wall of the casing, a second end of the seal member being sandwiched between the second end of the holder and a holder-side pressing plate, 10. A non-contact shaft circumferential seal device set comprising the non-contact shaft circumferential seal device according to any one of claims 1 to 9 and a sleeve fitted onto a rotating shaft so as to form an outer peripheral surface of the rotating shaft.

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