Bearings – Linear bearing – Combined with seal or guard
Reexamination Certificate
2001-11-30
2003-06-03
Footland, Lenard A. (Department: 3682)
Bearings
Linear bearing
Combined with seal or guard
C384S484000, C074S424820
Reexamination Certificate
active
06572269
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a bearing apparatus comprising: a first member; a second member; rolling elements rotatably interposed between the first and second members to thereby effect relative movement therebetween; and a seal device for sealing at least a portion of a clearance defined between the first and second members.
Particularly, a first aspect of the present invention relates to a linear motion apparatus, which is one example of the bearing device, such as a linear guide apparatus and a ball screw apparatus, and more particularly to an improvement in a contact rubber seal device serving as a seal device.
A second aspect of the present invention relates to a water pump bearing, which is one example of the bearing apparatus and is suitable for use with a water-cooled automobile engine, and more particularly to a bearing having a seal device for preventing entry of water or moisture into a bearing supporting a rotary shaft of a water pump and preventing leakage of grease from the inside of the bearing.
A third aspect of the present invention relates to a rolling bearing, which is an example of the bearing apparatus, and more particularly to an improvement in a rubber seal device to be used in the bearing apparatus.
For instance, a linear guide apparatus to be used as a linear motion guide apparatus and a ball screw apparatus to be used as a linear motion drive apparatus have hitherto been known as typical ones of linear motion apparatus.
As shown in
FIG. 10
, the linear guide apparatus is equipped with a guide rail (functioning as interior member)
1
extending in its longitudinal direction; and a slider
2
(functioning as exterior member) sliding on the guide rail
1
so as to be movable in an axial direction while a predetermined clearance is provided between the slider
2
and the guide rail
1
.
A pair of rolling-element contact grooves
3
are formed on either side surface of the guide rail
1
so as to extend in the axial direction thereof. A pair of linear rolling-element contact grooves (not shown) opposing the rolling-element contact grooves
3
are formed in the interior surface of each wing
4
provided on either side of a slider main body
2
A of the slider
2
.
A plurality of steel balls (not shown) serving as rolling elements are rotatably provided between the rolling-element grooves
3
formed in the guide rail
1
and the counterpart grooves formed in the slider
2
, which mutually oppose. The slider
2
can travel along the guide rail
1
in the axial direction by means of rolling action of the steel balls. As the slider
2
travels, the steel balls interposed between the guide rail
1
and the slider
2
rotate and shift to the end of the slider main body
2
A of the slider
2
. In order to continuously move the slider
2
in the axial direction, an infinite number of steel balls must be circulated.
To this end, linear rolling-element channels (not shown) are formed so as to axially penetrate through each of the wings
4
of the slider main body
2
. An end cap
2
B serving as a rolling-element circulating component is provided at either longitudinal end of the slider main body
2
A. A rolling-element circulation R section having a semi-circular-shaped curve is formed in each end cap
2
B so as to establish mutual communication between the rolling-element grooves and the rolling-element passages, thus constituting an endless rolling-element circulation railway.
As shown in
FIG. 11
, a side seal member
5
(a contact seal having negative clearance with respect to the guide rail
1
) is attached to either end of the slider
2
for sealing an opening of a clearance defined between the guide rail
1
and the slider
2
. An underseal member
6
is affixed to the underside of the slider
2
.
Rubber material such as acrylonitrile butadiene (NBR) is commonly used for the seal members
5
,
6
and is formed integrally with reinforcing material, such as a steel plate. Particularly, when the seal member requires chemical resistance or heat resistance, fluoro rubber [such as FKM; vinylidenefluoride-hexafluoropropylene-based fluoro rubber or vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene-based fluoro rubber] is often used as rubber material. In the drawing, reference numeral
7
indicates a grease nipple.
Although not shown in the drawing, a ball screw apparatus, which is a linear motion apparatus, converts rotation of a screw shaft (or ball screw nut) into axial displacement of a ball screw nut (or screw shaft), through a plurality of balls (rolling elements) interposed between a helical screw groove formed in the outer circumferential surface of a screw shaft (inner member) and a helical screw groove formed in an inner circumferential surface of a ball screw nut (outer member). For example, a plastic seal member is attached as a contact seal device to either end of the ball screw nut, thereby preventing entry of extraneous matter into the ball screw nut from the outside or leakage to the outside of a lubricant from the inside of the ball screw nut.
The contact seal device is usually formed of resin material, such as polyacetal resin, into the shape of a ring. A thread to engage with the screw thread of the screw shaft is formed on an interior diameter section of the contact seal device, and a notch (discission) is formed in the contact seal device for radially cutting.
The notch is opened to open the ring widely, and the thus-opened contact seal device is fitted around the screw shaft. A lockscrew is screwed into a ball screw nut from an outer circumferential surface at the end thereof. The outer-diameter surface of the contact seal device is pressed inwardly, whereby the contact seal device is secured to the end of the ball screw nut.
However, the contact seal device employed in the related-art linear guide apparatus and that employed in the related-art ball screw apparatus involve the following problems.
First, a problem of the contact seal device employed in the linear guide apparatus will be described. The rotating speed of a main spindle of a machine tool employing a linear guide apparatus has recently been increased. In connection with a tool, a dramatic leap has been achieved in development of highly heat resistant material or a coating technique, in an attempt to increase the speed and efficiency of cutting work. In association with such a development, a synthetic cutting coolant of soluble type, which can be subjected to sewage processing by means of complete dissolution into water, has come to replace a related-art water-soluble cutting fluid of emulsion type, in order to make full use of all the capabilities of the cutting fluid. Namely, a cooling property for absorbing a large quantity of heat developing in the vicinity of a cutting point, permeability for reaching a cutting point momentarily, and lubricity at a high-temperature, high-pressure cutting point.
The major feature of the soluble-type synthetic cutting coolant lies in that a large number of various types of additive agents, such as amine, are added to the coolant in order to improve permeability. Hence, the coolant is highly permeable to rubber material, and the rubber material is susceptible to deformation, such as expansion or softening. Consequently, the rubber strength of a slide member (e.g., a rubber lip section) of the contact seal device belonging to the linear guide, which apparatus is used in an environment in which the apparatus is splashed with a soluble-type synthetic cutting coolant, becomes weak. Concurrently, a region of the seal member to be fastened becomes greater, and as a result abrasion of the seal member is accelerated. This results in a drop in sealing property of the seal member, which may deteriorate the life of the linear guide apparatus.
Particularly, when the rubber material of the seal member is made of FKM (i.e., vinylidenefluoride-hexafluoropropylene-based fluoro rubber or vinylidenefluoride-hexafluoropropylene-tetrafluoroethylene-based fluoro rubber), an amino-based additive is considered to induce
Aihara Nariaki
Uchiyama Takahiko
Yabe Toshikazu
Yokoyama Keisuke
Footland Lenard A.
NSK Ltd.
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