TREPAN A MOLETTES A ETANCHEITE AMELIOREE

ROLLER CUTTER WITH IMPROVED SEALING

Abrégé français

L'invention concerne un trépan à molettes (14) conçu pour être utilisé au niveau d'une tête de forage pour le forage rotatif d'un front de formations de sol et de roche, ledit trépan à molettes ayant un axe central (CL) et comportant un moyeu (24) doté de rangées d'éléments de broyage (29), au moins un élément de broyage ayant son axe longitudinal à un angle par rapport à une normale à l'axe central (CL), ledit moyeu pouvant tourner par rapport à un arbre (33) ayant des ergots d'arbre (34, 35), le trépan à molettes étant doté d'au moins un élément de rétention de joint (38) agencé à une extrémité axiale du moyeu afin de maintenir des moyens d'étanchéité (37) en position, le moyeu comprenant au moins un creux circonférentiel (44) positionné axialement vers l'intérieur par rapport à une collerette dépassant radialement vers l'intérieur (43) dans le moyeu.

Abrégé anglais

A roller cutter (14) intended to be used at a drill head for rotary boring of the front of earth and rock formations, said roller cutter having a centre line (CL) and being provided with a hub (24) provided with rows of crushing members (29), at least one crushing member having its longitudinal axis at an angle relative to a normal to the centre line (CL), said hub being rotatable in relation to a shaft (33) having shaft spigots (34, 35), the roller cutter being provided with at least one seal retainer (38) arranged at an axial end of the hub in order to hold sealing means (37) in position, wherein the hub comprises at least one circumferential recess (44) positioned axially inward relative to a radially inward projecting flange (43) in the hub.

Revendications

5
Claims
1. A roller cutter (14) intended to be used at a drill head for rotary boring
of the
front of earth and rock formations, said roller cutter having a centre line
(CL)
and being provided with a hub (24) provided with rows of crushing members
(29), at least one crushing member having its longitudinal axis at an angle
relative to a normal to the centre line (CL), said hub being rotatable in
relation
to a shaft (33) having shaft spigots (34, 35), the roller cutter being
provided
with at least one seal retainer (38) arranged at an axial end of the hub in
order
to hold sealing means (37) in position, characterized in that the hub
comprises at least one circumferential recess (44) positioned axially inward
relative to a radially inward projecting flange (43) in the hub.
2. The roller cutter according to claim 1, characterized in that one side
surface of the flange constitutes a boundary of the recess.
3. The roller cutter according to claim 1 or 2, characterized in that the seal
retainer has a maximum axial extension (X) and the flange and the recess are
positioned radially outward from said seal retainer and are axially entirely
contained within said axial extension.
4. The roller cutter according to claim 1, 2 or 3, characterized in that the
recess holds an O-ring (45) in position.
5. The roller cutter according to any of the preceding claims, characterized
in that at least one seal retainer comprises a radially outward directed
projecting part (41) at a position forming a seal retainer's axial and radial
outermost end.
6. The roller cutter according to claim 5, characterized in that the
projecting
part is a ring.
7. The roller cutter according to claim 6, characterized in that the ring is
metallurgically bonded to the seal retainer.

6
8. The roller cutter according to any of the preceding claims, characterized
in that the hub comprises at least one circumferential indent (42) radially
outward from and adjacent to the projecting part on the seal retainer.
9. The roller cutter according to any of the preceding claims, characterized
in that at least one seal retainer has a groove (46) at its axially outermost
end.

Description

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1
Roller cutter with improved sealing
Technical Field and Background
The present invention relates to a roller cutter for a drill head for rotary
boring of a front of earth and rock formations according to the preamble of
the
independent claim.
A roller cutter comprising an improved sealing is addressed in U.S. Pat.
No. 5,984,024. It shows sealing means held in position by a seal retainer. The
roller
cutter also comprises relief holes having conical plugs which are removed in
order to
refill the roller cutter with lubricant, such as grease or oil. However, with
this solution
dirt frequently reaches the sealing means and knocks the 0-rings of the seal
out of
position, thus decreasing its sealing efficiency.
Another roller cutter with improved sealing is addressed in U.S. Pat. No.
7,278,500. It shows sealing means protected by a cover in order to prevent
dirt from
reaching the interior of the roller cutter. However, with this solution it is
problematic to
refill the roller cutter with lubricant.
Summary
One object of the present invention is to provide a roller cutter with
improved sealing compared to existing roller cutters.
According to a one aspect, there is provided a roller cutter, having a
centre line comprising: a hub provided with rows of crushing members, at least
one
crushing member having its longitudinal axis at an angle relative to a normal
to the
centre line, said hub being rotatable in relation to a shaft having shaft
spigots, the
roller cutter being provided with at least one seal retainer arranged at an
axial end of
the hub in order to hold sealing means in position, wherein the hub comprises
at
least one circumferential recess positioned axially inward relative to a
radially inward
projecting flange in the hub.
Brief Description of the Drawings
In the detailed description of the present invention reference will be
made to the accompanying drawings, wherein,
Fig. 1 schematically shows an axial cross-section through a raise-boring
head having roller cutters according to the invention.

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Fig. 2 schematically shows a roller cutter according to the present
invention as well as a saddle in side view.
Fig. 3A schematically shows the roller cutter according to the present
invention in a partial cross-section.
Fig. 3B schematically shows an enlarged section according to Fig. 3A.
Detailed Description
The features and advantages of the present invention are well
understood by reading the following detailed description in conjunction with
the
drawings in which like numerals indicate similar elements and in which:
FIG. 1 illustrates how a pilot hole 11, which in a known way is pre-drilled
between an upper and a lower, not shown, level in a mine is reamed by means of
a
drill head designated 10. The drill head 10 is connected to a drive stem 12 by
means
of which the drill head is rotated and is pressed against a ring-shaped
surface 13 that
surrounds the pilot hole 11. The surface 13, thus, defines the face of the
earth
formation.
The invention relates to earth boring in general, but is primarily intended
for raise boring. At raise boring, a distance is drilled between the lower and
the upper
level in a mine, and then the pilot hole is reamed by means of a drill head
having a
large diameter.
The drill head 10 comprises a body 16 and a plurality of rollers or cutters
14, which are rotatably mounted on the body in fasteners or saddles 15. Each
roller
cutter comprises circumferential rows of buttons or crushing members of
cemented
carbide in a known way. The saddles 15 are mounted on the body 16. The drive
stem
12 is connected to the body 16. The body 16 has a mounting surface 17 on which
the
saddles 15 are carried.
FIG. 2 illustrates how the saddle 15 comprises a bottom surface 18,
which is intended to be connected, for instance by screwing or welding, to the
mounting surface 17. Furthermore, the saddle 15 comprises two legs 19, 20,
between which the roller cutter is mounted. The legs 19, 20 are, at the ends
thereof
facing away from the bottom surface 18 formed with arms 21. The arms 21 have
different lengths from the bottom surface 18. Fastening devices in the form of
threaded bolts 22 and nuts 23 are intended to hold the roller cutter 14 and
the saddle
15 together.

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FIG. 3A illustrates the roller cutter having a shaft 33 with a longitudinal
centre line CL. Directions in the following description refer to this centre
line. Axially
outward refers to a direction towards the arms 21, and radially outward means
a
direction away from the centre line. The ends of the shaft 33 each has a shaft
spigot
34, 35, which is intended to abut against a support surface (not shown) in the
arms
21 of the saddle 15.
A hub 24 is rotatably mounted on the shaft 33 via bearing members 26.
The bearing members 26 are received in circumferential grooves in the hub 24.
The
hub 24 is locked axially in relation to the shaft 33 by means of a lock member
28,
preferably in the form of balls, which co-operate with circumferential grooves
in both
the shaft 33 and the hub 24.
The roller cutter 14 has inserts or crushing members 29 mounted in rows
at an envelope surface of the hub 24. At least one of the crushing members 29
has
its longitudinal centre line CL1 at an angle relative to a normal to the
centre line CL of
the roller cutter 14.
FIG. 3B illustrates that between the axial ends of the hub 24 and the
shaft 33 the cutter 14 is at at least one end, preferably both, provided with
seal
retainers 38. The seal retainer 38 has a maximum axial extension X. The seal
retainer 38 supports sealing means 37 that prevents the lubricant, such as
grease or
oil, from leaking out from the interior of the cutter 14. In one embodiment
the sealing
means 37 is of the type mechanical face seal, also called duo-cone seal. It
comprises
two 0-rings 37A and 37B, made of a resilient material, and two seal rings 37C
and
37D, often made of cast iron. The most radially outward surfaces of the seal
rings,
37C and 37D, have a concave shape in order to axially fix the 0-rings, 37A and
37B,
in position.
The seal retainers 38 are equipped with relief holes 39 having plugs 40
mounted in said holes to prevent lubricant from leaking out through said holes
39.
The plugs 40 may be conical and are removed when the roller cutter 14 needs
refilling of lubricant. With this method air escapes the interior of the
roller cutter 14,
thus making the refilling of lubricant easier.
The seal retainer 38 has a radially outward projecting part 41 at its axially
and radially most outward part. Adjacent to, and radially outward from the
projecting
part 41 is a circumferential indent 42 in the hub 24. The indent 42 and the
projecting
part 41 form a labyrinth which further decreases the risk of dirt reaching the
interior of

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the roller cutter 14. There may be a radial space, of about 1.4 to 2 mm,
between the
hub 24 and the seal retainer 38 in order to separate the hub 24 from the seal
retainer
38 even at loads of up to 30 metric tonnes. For the same reason, there may be
a
radial and axial space, of about 1.4 to 2 mm, between the hub 24 and the
projecting
part 41.
In one embodiment, the projecting part 41 is in the form of a ring
attached to the seal retainer 38. This ring 41 can be metallurgically bonded
to the
seal retainer 38, preferably by welding.
Axially inward from the indent 42, there is a radially inward projecting
flange 43 in the hub 24. The flange 43 has substantially parallel side
surfaces and an
end surface substantially parallel to the centre line CL. Further axially
inward from the
flange 43, there is a circumferential recess 44 in the hub 24 in order to hold
an 0-ring
45 in position. One side surface of the flange 43 constitutes a boundary of
the recess
44. The flange 43 and the recess 44 are positioned radially outward from the
seal
retainer 38 and are axially entirely contained within the seal retainer's 38
axial
extension X.
There is a groove 46 at the axially outermost end of the seal retainer 38,
in order to facilitate attachment of the ring 41.
A snap ring 47 is used in conjunction with a lock ring (not shown) to lock
the seal retainer 38 in position on the shaft 33.
Another 0-ring 48, made of a resilient material, prevents leakage
between seal retainer 38 and shaft 33.
If dirt enters the area between hub 24 and seal retainer 38 then a force
will be transmitted through the dirt to the seal retainer 38 which may lead to
the seal
retainer 38 starting to rotate. A dowel pin 49 fixes the seal retainer 38
statically in
position thus hindering it from rotational movement.
The 0-rings, 37A, 37B, 45 and 48, are all made of a resilient material.
Examples of such materials are silicone, Viton and nitrile rubber. The
material
chosen depends on the load and temperature the 0-ring is supposed to be
exposed
to.
The present invention is not limited to the above described
embodiments. Different alternatives, modifications and equivalents might be
used.
The above mentioned embodiments should therefore, not be considered limiting
to
the scope of the invention, which is defined by the patent claims.

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