JP7281368B2 - Sealing device and sealing structure - Google Patents

Description

The present invention relates to sealing devices and sealing structures.

Conventionally, sealing devices are used to seal a gap between relatively rotating inner and outer members in a variety of applications. Seals have a limited life and are replaced periodically.

Patent Literature 1 discloses a device for monitoring deterioration of the sealing function of a sealing device, that is, leakage of a liquid to be sealed. With such a device, the sealing device can be replaced before the end of the life of the sealing device. Seals used in dusty environments, for example, have a shorter life than those used in clean environments, but the use of such technology allows timely replacement of individual seals. can.

Japanese Patent Application Laid-Open No. 2004-308905

It would be desirable to be able to more accurately detect leakage of the sealed liquid. Also, it is desirable that the provision of equipment for monitoring leakage of the sealed liquid is not troublesome.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a sealing device and a sealing structure that can more accurately detect leakage of a liquid to be sealed and reduce the labor required to deploy equipment.

A sealing device according to an aspect of the present invention is a sealing device that is disposed between an inner member and an outer member that rotate relative to each other and seals a gap between the inner member and the outer member, The inner member is at least partially formed from a conductive material. The sealing device includes an attachment portion attached to the outer member, an annular lip disposed radially inward of the attachment portion and extending toward the inner member, and an annular lip disposed between the lip and the inner member. an elastic ring made of an elastic material to which the inner member is interference fit; at least two electrodes arranged on the inner peripheral surface of the elastic ring; and electrical conduction between the electrodes arranged on the elastic ring. It has a measuring device for measuring the condition and a radio transmitter arranged on the elastic ring for repeatedly or continuously transmitting a signal indicative of the measurement result of the measuring device.

In this aspect, the state of electrical conduction between the at least two electrodes arranged on the inner peripheral surface of the elastic ring interposed between the lip and the inner member reflects the state of sealing between the elastic ring and the inner member. do. For example, if the liquid to be sealed does not enter between the elastic ring and the inner member, the electrodes contact the inner member, which is partially formed of a conductive material, and the resistance or impedance between the electrodes is low and the flow between the electrodes is low. The current is large, and when the liquid to be sealed enters between the elastic ring and the inner member (there is leakage of the liquid to be sealed), the resistance or impedance between the electrodes is high and the current flowing between the electrodes is small. Therefore, by measuring the electrical conduction state between the electrodes, it is possible to accurately detect whether or not there is leakage of the liquid to be sealed. The meter measures electrical conductivity between the electrodes, and the wireless transmitter transmits a signal indicative of the measurement results of the meter. An external receiving device receives a signal indicative of the measurement result of the measuring device, and by analyzing the measurement result it is possible to recognize whether there is a leakage of the liquid to be sealed. Since the transmitter is a radio transmitter arranged in an elastic ring, there is no need for cable deployment.

It is a cross-sectional view of a sealing structure according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1 showing a cross-section of an elastic ring and a rotating shaft in a normal state of the sealing structure; FIG. 3 is a partially broken enlarged perspective view of an elastic ring and its surroundings in a normal state; FIG. 4 is an enlarged perspective view with a part broken away of an elastic ring and its surroundings in an abnormal state; 7 is a graph showing an example of measurement results of a measuring device with a sealed structure according to the embodiment; FIG. 5 is a cross-sectional view showing a cross section of an elastic ring and a rotating shaft of a sealing structure according to a modified example of the embodiment of the present invention during normal operation; FIG. 7 is a graph showing an example of the measurement result of the measuring instrument having the sealed structure according to the modified example of FIG. 6. FIG. FIG. 8 is a cross-sectional view of a sealing structure according to another modification of the embodiment of the invention;

Various embodiments of the present invention will now be described with reference to the accompanying drawings. The drawings are not necessarily drawn to scale and some features may be exaggerated or omitted.

As shown in FIG. 1 , the sealing structure according to the embodiment of the present invention has a cylindrical rotary shaft (inner member) 2 and a housing (outer member) 4 for the rotary shaft 2 . Most of the rotating shaft 2 is made of an electrically conductive material, such as steel. The housing 4 has a cylindrical shaft hole 4A in which the rotating shaft 2 is arranged. While the housing 4 is stationary, the rotary shaft 2 rotates around the central axis Ax.

A sealing device 1 , which is a packing, is arranged in the gap between the rotating shaft 2 and the housing 4 .

The sealing device 1 is annular, but only its upper part is shown in the figure. In the figure, the right side is the liquid side where the sealed liquid (for example, oil) is arranged, and the left side is the air side. The sealing device 1 seals the gap between the rotary shaft 2 and the housing 4, suppresses leakage of liquid from the liquid side to the air side, and suppresses the entry of water and dust from the air side to the liquid side.

The sealing device 1 is a composite structure having a resilient ring 12 and a rigid ring 14 . The elastic ring 12 is made of an elastic material such as an elastomer. Rigid ring 14 is made of a rigid material, such as metal, and reinforces elastic ring 12 . In this embodiment, rigid ring 14 has a generally L-shaped cross-sectional shape. In this embodiment, almost the entire rigid ring 14 is embedded in the elastic ring 12 and is in close contact with the elastic ring 12 .

The sealing device 1 has an outer cylindrical portion 16 , an inner cylindrical portion 17 and a connecting ring portion 18 .

The outer cylindrical portion (attachment portion) 16 is composed of the elastic ring 12 and the rigid ring 14 and is attached to the shaft hole 4A of the housing 4. As shown in FIG. Although the mounting method is not limited, for example, the outer cylindrical portion 16 is fitted into the shaft hole 4A of the housing 4 by an interference fit (that is, press-fitted).

The connecting ring portion 18 connects the outer cylindrical portion 16 and the inner cylindrical portion 17 arranged radially inside the outer cylindrical portion 16 . The connecting ring portion 18 is also composed of the elastic ring 12 and the rigid ring 14 .

The inner cylindrical portion 17 is composed only of the elastic ring 12 and surrounds the rotating shaft 2 . The inner cylindrical portion 17 has a main lip (seal lip) 20 and a dust lip 21 . The main lip 20 is an annular protrusion that protrudes radially inward, and the tip of the main lip 20 slidably contacts the outer peripheral surface of the rotating shaft 2 . The main lip 20 mainly serves to seal the liquid to be sealed.

The dust lip 21 is an annular projection having a truncated cone shape extending radially inward and toward the atmosphere side. The tip of the dust lip 21 slidably contacts the outer peripheral surface of the rotating shaft 2 . The dust lip 21 mainly serves to prevent water and dust from entering from the air side to the liquid side.

A dust lip 22 extends from the connecting portion between the inner cylindrical portion 17 and the connecting ring portion 18 . The dust lip 22 is an annular projection having a truncated cone shape extending radially inward and toward the atmosphere side. The dust lip 22 extends toward the rotating shaft 2 , and an elastic ring 40 to be described later is interposed between the tip of the dust lip 22 and the rotating shaft 2 . The dust lip 22 also mainly plays a role in suppressing the intrusion of water and dust from the atmosphere side to the liquid side. Since the main lip 20 and the dust lip 21 are located on the liquid side of the dust lip 22, the liquid to be sealed does not normally exist in the vicinity of the dust lip 22, or the amount of liquid to be sealed is very small.

In the drawing, the rotating shaft 2 is shown in phantom lines, but the lips 20, 21, and 22 are shown deformed by receiving reaction force from the rotating shaft 2. As shown in FIG. Lips 20, 21, 22 are made of an elastic material.

Although not essential, a garter spring 24 is wrapped around the outer circumference of the inner cylindrical portion 17 . The garter spring 24 compresses the inner cylindrical portion 17 radially inward and presses the main lip 20 against the rotating shaft 2 .

An elastic ring 40 made of an elastic material such as an elastomer is arranged between the tip of the dust lip 22 arranged closest to the atmosphere among the lips 20 , 21 , 22 and the rotating shaft 2 . The rotating shaft 2 is tightly fitted to the elastic ring 40 . Therefore, the elastic ring 40 normally rotates together with the rotating shaft 2 .

As shown in FIGS. 1 and 2 , two electrodes 42 are arranged (for example, embedded) in the inner peripheral surface of the elastic ring 40 , and the electrodes 42 are brought into contact with the outer peripheral surface of the rotating shaft 2 . In FIG. 2, hatching of the elastic ring 40 is omitted. As shown in FIG. 2, the two electrodes 42 are arranged in the circumferential direction of the elastic ring 40 at intervals. Since the elastic ring 40 normally rotates together with the rotating shaft 2, the relative angular positions of the two electrodes 42 with respect to the rotating shaft 2 remain unchanged.

As shown in FIG. 2, electrodes 42 are powered by a battery 44 . As long as the electrodes 42 are in contact with the portion of the rotating shaft 2 made of conductive material, current from the battery 44 continues to flow through the circuit comprising the two electrodes 42 and the rotating shaft 2 .

Electrode 42 may be formed from a hard conductive material, such as copper. Preferably, however, the electrodes 42 are formed from an elastomer containing a powder of conductive material. Since the electrode 42 is made of a material similar to that of the rest of the inner peripheral surface of the elastic ring 40, the pressure acting between the elastic ring 40 and the dust lip 22 is substantially uniform in the circumferential direction. In any case, the inner surface of the electrode 42 smoothly connects to the inner peripheral surface of the elastic ring 40 .

A measuring device 46 for measuring the electrical conductivity between the electrodes 42 is arranged on the elastic ring 40 . In this embodiment, the measuring device 46 is an ammeter, but could also be an ohmmeter or an impedance meter.

A radio transmitter 48 for transmitting a signal indicating the measurement result of the measuring device 46 is also arranged on the elastic ring 40 . The wireless transmitter 48 may be an IC tag using the principle of RFID, or may be another type of wireless transmitter. Wireless transmitter 48 repeatedly (eg, periodically) or continuously transmits a signal indicative of the measurement results of meter 46 . The signal indicating the measurement result of the measuring device 46 may be in human or machine recognizable form.

In this embodiment, the measuring device 46 and the wireless transmitter 48 are embedded in the elastic ring 40, but the measuring device 46 and/or the wireless transmitter 48 are not in contact with the dust lip 22 on the elastic ring 40, e.g. It may be arranged and fixed to the end surface of 40 .

On the other hand, the outer peripheral surface of the rotating shaft 2 has a conductive region made of a conductive material and a non-conductive region made of a non-conductive material. A region inside the outer peripheral surface of the rotating shaft 2 is made of a conductive material. Specifically, a non-conductive piece 50, which is a thin plate made of a non-conductive material, is embedded in a part of the outer peripheral surface of the rotary shaft 2 which is entirely made of a conductive material. Non-conducting segments 50 correspond to non-conducting areas. Other portions of the outer peripheral surface of the rotating shaft 2 correspond to conductive regions. In this embodiment, two non-conducting segments 50 are provided.

The non-conductive piece 50 is made of a hard resin material with a low coefficient of friction, such as polyetheretherketone (PEEK), polyphenylene sulfide (PPS), polytetrafluoroethylene (PTFE). The outer peripheral surface of the non-conductive piece 50 is flush with the rest of the rotating shaft 2 .

In the above configuration, if the two electrodes 42 arranged on the inner peripheral surface of the elastic ring 40 are in contact with the conductive region of the rotating shaft 2, the resistance or impedance between the electrodes 42 is low, and the resistance between the electrodes 42 is low. The current flowing through is large. On the other hand, if one or both of the two electrodes 42 are in contact with the non-conductive area (non-conductive segment 50) of the rotating shaft 2, the resistance or impedance between the electrodes 42 is high and the current flowing between the electrodes 42 is small.

In this embodiment, in a normal state where the liquid to be sealed does not enter between the elastic ring 40 and the rotating shaft 2, the two electrodes 42 of the sealing device 1 are positioned on the outer peripheral surface of the rotating shaft 2, as shown in FIG. It is brought into contact with the conductive area (the area other than the non-conductive strip 50).

Since the rotating shaft 2 is tightly fitted to the elastic ring 40, the elastic ring 40 normally rotates together with the rotating shaft 2 together with the electrode 42, as shown in the enlarged view of FIG. A frictional force _F1 between the elastic ring 40 and the rotating shaft 2 can be expressed by the following formula.

F ₁ = μ ₁ N ₁ = 2πμ ₁ T
Here, μ ₁ is the coefficient of friction between the elastic ring 40 and the rotating shaft 2 and N ₁ is the binding force of the elastic ring 40 to the rotating shaft 2 . T is the tension of the elastic ring 40;

The tip of the dust lip 22 is pressed against the outer peripheral surface of the elastic ring 40 . A frictional force _F2 between the elastic ring 40 and the dust lip 22 can be expressed by the following equation.

F ₂ = μ ₂ N ₂
where μ ₂ is the coefficient of friction between the elastic ring 40 and the dust lip 22 and N ₂ is the binding force of the dust lip 22 to the elastic ring 40 .

As shown in FIG. 3, under normal conditions, that is, when the liquid to be sealed does not enter between the elastic ring 40 and the rotary shaft 2, F ₂ <F ₁ . In this state, the elastic ring 40 rotates at an angular velocity R ₂ equal to the angular velocity R ₁ of the rotating shaft 2 . That is, the relative angular position of the elastic ring 40 and the rotating shaft 2 remains unchanged, and the current from the battery 44 continues to flow through the circuit comprising the two electrodes 42 and the rotating shaft 2, as shown in FIG. A constant current value is measured. The resistance or impedance between electrodes 42 is low and the current flowing between electrodes 42 is high.

On the other hand, as shown in FIG. 4, when the liquid to be sealed (for example, oil) enters between the inner peripheral surface of the elastic ring 40 and the outer peripheral surface of the rotating shaft 2 (there is leakage of the liquid to be sealed), F ₂ > becomes _F1 . In FIG. 4, the arrow OF indicates the flow of the sealed liquid. In this state, the elastic ring 40 rotates at an angular velocity R ₂ smaller than the angular velocity R ₁ of the rotating shaft 2 . That is, the relative angular position between the elastic ring 40 and the rotating shaft 2 changes, and the electrode 42 contacts the conductive area of the outer peripheral surface of the rotating shaft 2 or the non-conductive segment 50 . Therefore, as shown in FIG. 5, the current flowing between the electrodes 42 periodically increases and decreases. Here, the amount of the liquid to be sealed that enters between the elastic ring 40 and the rotating shaft 2 is very small. is assumed to contact the minute protrusions on the outer peripheral surface of the rotating shaft 2 .

By analyzing the measurement result of the measuring device 46 for measuring the electrical conduction state between the elastic ring 40 between the dust lip 22 and the rotating shaft 2 and the rotating shaft 2, it is detected whether there is leakage of the liquid to be sealed. Is possible.

When an extremely large amount of liquid to be sealed enters between the inner peripheral surface of the elastic ring 40 and the outer peripheral surface of the rotating shaft 2, the current flowing between the electrodes 42 is interrupted if the liquid to be sealed is insulative. , if the liquid to be sealed is conductive, the current flowing between the electrodes 42 will be a substantially constant low value. However, since the current flowing between the electrodes 42 increases or decreases before that, leakage of the sealed liquid can be detected early.

A measuring device 46 measures the state of electrical conduction between the electrodes 42 and a wireless transmitter 48 transmits a signal indicative of the measurement results of the measuring device 46 . An external receiving device (not shown) receives the signal indicating the measurement result of the measuring device 46, and by analyzing the measurement result, it is possible to recognize the sealing state between the elastic ring 40 and the rotating shaft 2. . Transmitter 48 is a wireless transmitter located on elastic ring 40, thus eliminating the need for cable deployment.

FIG. 6 is a cross-sectional view taken along the line II-II of FIG. 1, similar to FIG. 2, but shows cross-sections of the elastic ring and the rotating shaft of the sealing structure according to the modified example in a normal state. In this modification, in a normal state in which the liquid to be sealed does not enter between the elastic ring 40 and the rotating shaft 2, the two electrodes 42 of the sealing device 1 are positioned on the outer peripheral surface of the rotating shaft 2, as shown in FIG. A non-conducting region (non-conducting strip 50) is contacted.

In this modification, in the normal state, the relative angular position between the elastic ring 40 and the rotating shaft 2 remains unchanged, the resistance or impedance between the electrodes 42 is high, and the current flowing between the electrodes 42, as shown in FIG. is small (eg zero). On the other hand, when the liquid to be sealed enters between the elastic ring 40 and the rotating shaft 2 (when the liquid to be sealed leaks), the relative angular position between the elastic ring 40 and the rotating shaft 2 changes, and the electrode 42 As shown in FIG. 7, the electric current flowing between the electrodes 42 periodically increases or decreases by contacting the conductive area or the non-conductive area on the outer peripheral surface of the rotating shaft 2 . Here, the amount of the liquid to be sealed that enters between the elastic ring 40 and the rotating shaft 2 is very small. is assumed to contact the minute protrusions on the outer peripheral surface of the rotating shaft 2 .

By analyzing the measurement result of the measuring device 46 for measuring the electrical conduction state between the elastic ring 40 between the dust lip 22 and the rotating shaft 2 and the rotating shaft 2, it is detected whether there is leakage of the liquid to be sealed. Is possible.

When an extremely large amount of liquid to be sealed enters between the inner peripheral surface of the elastic ring 40 and the outer peripheral surface of the rotating shaft 2, the current flowing between the electrodes 42 is interrupted if the liquid to be sealed is insulative. , if the liquid to be sealed is conductive, the current flowing between the electrodes 42 will be a substantially constant low value. However, since the current flowing between the electrodes 42 increases or decreases before that, leakage of the sealed liquid can be detected early.

FIG. 8 is a cross-sectional view of a sealing structure according to another modification. In this modification, the dust lip 22 is not provided, and an elastic ring 40 is arranged between the air-side inclined surface of the main lip 20 and the rotating shaft 2 . The rotating shaft 2 is tightly fitted to the elastic ring 40 . Two electrodes 42 are arranged on the elastic ring 40 , and the two electrodes 42 are arranged in the circumferential direction of the elastic ring 40 . Also in this case, as in the above-described embodiment and modification, the electrical conduction state between the elastic ring 40 and the rotating shaft 2 is measured by the measuring device 46 to detect the leakage of the sealed liquid from the main lip 20. can be recognized accurately.

1, the elastic ring 40 is arranged between the tip of the dust lip 22 and the rotating shaft 2, and the elastic ring 40 is arranged between the inclined surface of the main lip 20 on the atmosphere side and the rotating shaft 2. may An elastic ring 40 may be arranged between the tip of the dust lip 21 and the rotating shaft 2 . In either case, two electrodes 42 may be arranged on the elastic ring 40 , and the two electrodes 42 may be arranged in the circumferential direction of the elastic ring 40 .

Although the invention has been illustrated and described with reference to preferred embodiments thereof, it will be appreciated by those skilled in the art that changes in form and detail can be made without departing from the scope of the invention as set forth in the claims. One thing will be understood. Such changes, alterations and modifications are intended to fall within the scope of the present invention.

For example, in the above embodiment, the housing (outer member) 4 is stationary while the rotating shaft (inner member) 2 rotates about the central axis Ax. However, the present invention is also applicable to constructions in which the inner member is stationary and the outer member rotates. Moreover, the present invention can also be applied to a structure in which the inner member and the outer member rotate and the inner member and the outer member rotate relative to each other.

The sealing device 1 according to the embodiment is a single sealing member, but the basic structure of the sealing device is not limited to the embodiment, and the present invention can be applied to a sealing device in which a plurality of sealing members are combined. be. Also, the shape of the lip that presses the elastic ring against the inner member is not limited to the embodiment.

In an embodiment, two non-conducting segments 50 are provided and the angular spacing between the two non-conducting segments 50 is equal to the angular spacing between the two electrodes 42 . However, the number of non-conductive segments 50 may be one, three or more.

In the embodiment, the number of electrodes 42 arranged on the elastic ring 40 is two, but the number of electrodes may be three or more.

The above embodiments and variations may be combined unless inconsistent.

Aspects of the invention are also described in the following numbered clauses.

Clause 1. A sealing device disposed between relatively rotating inner and outer members for sealing a gap between said inner and outer members, said inner member being at least partially made of an electrically conductive material. formed,
a mounting portion attached to the outer member;
an annular lip disposed radially inward of the mounting portion and extending toward the inner member;
a resilient ring of resilient material interposed between the lip and the inner member to which the inner member is an interference fit;
at least two electrodes disposed on the inner peripheral surface of the elastic ring;
a measuring device disposed on the elastic ring for measuring electrical conductivity between the electrodes;
A sealing device, characterized in that it comprises a radio transmitter arranged on said elastic ring for repeatedly or continuously transmitting a signal indicative of the measurement result of said measuring device.

Clause 2. a sealing device according to clause 1;
the inner member;
having the outer member;
an outer peripheral surface of the inner member having a conductive region made of a conductive material and a non-conductive region made of a non-conductive material, the conductive region and the non-conductive region being arranged in a circumferential direction of the inner member;
A sealing structure, wherein the inner region of the outer peripheral surface of the inner member is made of a conductive material.

According to this clause, if at least two electrodes arranged on the inner peripheral surface of the elastic ring are in contact with the conductive region of the inner member, the resistance or impedance between the electrodes is low and the current flowing between the electrodes is big. If one or both of the at least two electrodes are in contact with the non-conductive region of the inner member, the resistance or impedance between the electrodes is high and the current flowing between the electrodes is small. If no liquid to be sealed enters between the elastic ring and the inner member, the relative angular position of the elastic ring and the inner member remains unchanged and the current flowing between the electrodes is constant. On the other hand, when the liquid to be sealed enters between the elastic ring and the inner member (when the liquid to be sealed leaks), the relative angular position of the elastic ring and the inner member changes, and the current flowing between the electrodes is Increase or decrease (eg periodically). Therefore, by analyzing the measurement result of the measuring device, it is possible to detect whether or not there is leakage of the liquid to be sealed.

Article 3. The at least two electrodes of the sealing device are in contact with the conductive regions on the outer peripheral surface of the inner member in a normal state in which the liquid to be sealed does not enter between the elastic ring and the inner member. The sealed structure according to clause 2.

According to this provision, under normal conditions, the relative angular position of the elastic ring and the inner member remains unchanged, the resistance or impedance between the electrodes is low, and the current flowing between the electrodes is large. When the liquid to be sealed enters between the elastic ring and the inner member (when the liquid to be sealed leaks), the relative angular position between the elastic ring and the inner member changes, and the electrodes are connected to the conductive surfaces of the outer peripheral surface of the inner member. Contacting an area or contacting a non-conducting area causes the current to flow between the electrodes to increase or decrease (eg, periodically).

Article 4. One or both of the at least two electrodes of the sealing device are brought into contact with a non-conductive region on the outer peripheral surface of the inner member in a normal state in which no liquid to be sealed enters between the elastic ring and the inner member. A sealing structure according to clause 2, characterized in that

According to this provision, under normal conditions, the relative angular position between the elastic ring and the inner member remains unchanged, the resistance or impedance between the electrodes is high, and the current flowing between the electrodes is small. When the liquid to be sealed enters between the elastic ring and the inner member (when the liquid to be sealed leaks), the relative angular position between the elastic ring and the inner member changes, and the electrodes are connected to the conductive surfaces of the outer peripheral surface of the inner member. Contacting an area or contacting a non-conducting area causes the current to flow between the electrodes to increase or decrease (eg, periodically).

1 sealing device 2 rotating shaft (inner member)
4 housing (outer member)
16 Outer cylindrical part (mounting part)
20 Main lip Main lip (seal lip)
21, 22 Dust lip 40 Elastic ring 42 Electrode 44 Battery 46 Measuring device 48 Radio transmitter 50 Non-conductive strip (non-conductive area)

Claims (2)

A sealing device disposed between relatively rotating inner and outer members for sealing a gap between said inner and outer members, said inner member being at least partially made of an electrically conductive material. formed,
a mounting portion attached to the outer member;
an annular lip disposed radially inward of the mounting portion and extending toward the inner member;
a resilient ring of resilient material interposed between the lip and the inner member to which the inner member is an interference fit;
at least two electrodes disposed on the inner peripheral surface of the elastic ring;
a measuring device disposed on the elastic ring for measuring electrical conductivity between the electrodes;
A sealing device, characterized in that it comprises a radio transmitter arranged on said elastic ring for repeatedly or continuously transmitting a signal indicative of the measurement result of said measuring device. A sealing device according to claim 1;
the inner member;
having the outer member;
an outer peripheral surface of the inner member having a conductive region made of a conductive material and a non-conductive region made of a non-conductive material, the conductive region and the non-conductive region being arranged in a circumferential direction of the inner member;
A sealing structure, wherein the inner region of the outer peripheral surface of the inner member is made of a conductive material.

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