Bearings – Linear bearing – Combined with seal or guard
Reexamination Certificate
1999-08-10
2001-07-10
Hannon, Thomas R. (Department: 3682)
Bearings
Linear bearing
Combined with seal or guard
C384S045000
Reexamination Certificate
active
06257765
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a linear guide apparatus, and more particularly relates to a sealing device for a linear guide apparatus which lubricant can be stably fed to the rolling elements over a long period of time.
Further, the present invention relates to a linear guide apparatus, and more particularly relates to a linear guide apparatus, to the lip portion of the sealing device of which lubricant can be automatically fed, so that the life of the sealing device can be prolonged.
A first conventional example will be described as follows. An example of the conventional linear guide apparatus, which is commonly used, is shown in FIG.
37
. This conventional linear guide apparatus includes: a guide rail
1
extending in the axial direction, on the outer surface of which a rolling element rolling groove
3
is formed; and a slider
2
incorporated to the guide rail
1
in such a manner that the slider
2
strides the guide rail
1
. The slider
2
is composed of a slider body
2
A and end caps
2
B attached to both ends of the slider body
2
A. On inner side surfaces of both wing portions
4
of the slider body
2
A, there are provided rolling element rolling grooves (not shown in the drawing) which are opposed to the rolling element rolling groove
3
formed on the guide rail
1
. Also, in the slider body
2
A, there are provided rolling element returning paths (not shown) which penetrate thick portions of the wing portions of the slider body
2
A. On the other hands, the end caps
2
B have curved paths (not shown) which communicate the rolling element rolling grooves of the slider body
2
A with the rolling element returning paths formed in parallel to the rolling element rolling grooves. In this way, a circulation circuit of the rolling elements is formed by the rolling element rolling grooves, the rolling element returning paths and the curved paths formed on both sides. For example, a large number of rolling elements composed of steel balls are charged into the circulation circuit in which the rolling elements are circulated.
The slider
2
incorporated to the guide rail
1
is smoothly moved along the guide rail
1
when the rolling elements are rolling in both rolling element grooves which are opposed to each other. While the rolling elements are rolling in this way, they circulate endlessly in the rolling element circulation passages formed in the slider.
As a sealing device to seal an opening between the slider
2
and the guide rail
1
for the purpose of dust protection, as shown in
FIG. 38
, there are provided side seals
5
on both ends (end faces of the end caps
2
B), and also there is provided an under seal
6
on the lower surface of the slider
2
. Conventionally, these seals are made of rubber such as NBR (acrylonitrile butadiene rubber). In this connection, reference numeral
7
in
FIG. 37
is a grease nipple.
A second conventional example of the linear guide apparatus is disclosed in Unexamined Japanese Patent Publication No. Hei. 6-346919 previously proposed by the present applicant. A third conventional example of the linear guide apparatus is disclosed in Unexamined Japanese Patent Publication No. Hei. 7-35146 previously proposed by the present applicant.
The second conventional example will be described as follows. Between the outer surface of the guide rail and the inner surface of the slider moving along the guide rail, there is provided a seal device having a seal lip portion made of rubber or synthetic resin containing lubricant. The seal lip portion comes into contact with an outer surface of the guide rail and seals a gap formed between the inner surface of the slider and the outer surface of the guide rail. Since the seal lip portion of the seal device is made of rubber or synthetic resin containing lubricant so that the seal lip portion has a self-lubricating property, the lubricant contained in the seal gradually oozes out and is automatically fed to a frictional surface of the seal portion. Therefore, the abrasion of the seal lip portion can be suppressed.
The third conventional example will be described as follows. At least a portion of the layer made of rubber or synthetic resin and a portion of the layer made of rubber or synthetic resin containing lubricant are overlapped and integrally joined. At least, on the layer of rubber or synthetic resin containing lubricant, there is formed a seal lip portion which comes into contact with an outer surface of the guide rail so as to seal a gap formed between the inner surface of the slider and the outer surface of the guide rail. Since the seal lip portion also has a self-lubricating property in this third conventional example, lubricant contained in the seal itself gradually oozes out and is fed to a frictional surface of the seal, so that the abrasion of the lip portion can be suppressed. Since the layers are overlapped as described above in the third conventional example, it is possible to provide the following advantages. When the number and thickness of the overlapped layers are appropriately determined, the mechanical strength of the seal lip portion can be arbitrarily set in accordance with the use of the linear guide apparatus.
As shown in
FIGS. 52
to
53
B, the sealing device of the second conventional example is described as follows. Lubricant is made to ooze from a surface of the guide rail
1
by the action of contact resistance of the seal
5
. Accordingly, there is provided no relief
73
as shown in
FIG. 53A
in the contact portion
71
shown in
FIG. 53B
where the seal
5
comes into contact with the guide rail
1
, but an area of the portion where the seal
5
comes into contact with the guide rail
1
is increased. Further, there is formed a recessed groove
72
in the contact portion
71
where the seal
5
comes into contact with the guide rail
1
, so that the portion
71
is divided into two portions. Then the thus divided portions are contacted with the guide rail
1
by two steps. Therefore, the intrusion of foreign objects can be prevented by the contact of two steps better than the contact of one step. Further, lubricant can be held by the recessed groove
72
, so that the sliding property of the seal
5
can be enhanced.
However, the above conventional linear guide apparatus has the following disadvantages.
As the slider
2
runs along the guide rail
1
, a quantity of grease previously charged inside the slider
2
is decreased. Therefore, the lubrication between the lip portion of the side seal
5
and the guide rail
1
becomes poor, and also the lubrication between the lip portion of the under seal
6
and the guide rail
1
becomes poor. Due to the poor lubrication, the lip portions gradually wears away. Due to the progress of abrasion, the sealing property is deteriorated, and foreign objects such as cutting chips enter the inside of the slider
2
, which shortens the life of the linear guide apparatus in some cases.
When the slider
2
runs and the rolling elements roll, grease can be fed to the rolling element rolling groove
3
of the guide rail
1
via the rolling elements. Accordingly, the abrasion is relatively small in a portion of the lip which comes into contact with the rolling element rolling groove
3
. On the other hand, the abrasion tends to increase in a portion of the lip which comes into contact with an upper surface of the rail to which no grease is fed because of poor lubrication. Due to the foregoing, the lip portion wears away and damaged. In this way, the life of the linear guide apparatus is shortened.
From this point of view, when the above second example and the third one are adopted, the abrasion of the seal lip portion can be suppressed since the seal lip portion has a self-lubricating property. However, even in the above conventional examples, the following problems may be encountered. A quantity of lubricant oozing from rubber or synthetic resin containing lubricant is not sufficient to lubricate the balls and rollers which guide the movement of the slider of the linear guide apparatus, that is, i
Igarashi Yutaka
Kato Soichiro
Tsukada Toru
Ueki Fumio
Yabe Toshikazu
Hannon Thomas R.
NSK Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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