FIELD OF INVENTION
The present invention relates to a sealing arrangement in the twin output shafts of drive gearbox of bar mill. More particularly, the invention relates to sealing arrangement in case of pressurized lubrication system.
BACKGROUND OF THE INVENTION
In the case of a drive arrangement for a bar mill vertical and horizontal stands, comprising a drive motor, drive gearbox, spindle, coupling and rolling stand with work rolls. The main drive gearbox of vertical stand is a parallel shaft with single input and two vertically offset output shafts directed downward with 3 stage reduction (fig. 1 & 2) and pressurized lubrication system. The first stage being a spiral bevel gear set, while the other stages are helical gears.
The primary system to protect and extend the life of gearbox is the sealing system. Common sealing devices for gearbox include: compression packing's, labyrinth seals, mechanical face seals, and radial lip seals. For decades radial lip seals have been the most common form of sealing for gearboxes. In the case of pressurized lubrication system, the sealing device has to play vital role and failing which profuse oil leakage results especially from the twin output shafts of the gearbox. This is having very high fire hazard as the red hot bar is being passed underneath the drive gearbox of vertical stand.
An innovative sealing technology (fig. 3 & 4) is incorporated on the twin output shafts of the drive gearbox for providing effective sealing to the pressurized lubrication system. This innovative sealing technology incorporated in the drive gearboxes of both vertical as well as horizontal stands of bar mill. Out of four numbers of vertical shafts, first two shafts are having blind end covers and hence no leakage.

OBJECT OF THE INVENTION
Therefore it is an object of the invention to propose a sealing arrangement in the Twin output shafts of drive gearbox of bar mill which is capable of complete arresting of oil leakage in twin output shafts.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - Shows a schematic arrangement of the gear train of vertical stand.
Fig. 2 - Shows the drive gear box with two vertical shafts.
Fig. 3 - Shows the sealing arrangement on Twin output shaft according to the invention.
Fig. 4 - Shows the plan view of the twin output shafts.
Fig. 5 - Shows a photographic view of the twin output shaft with common sealing elements according to prior art.
Fig. 6 - Shows a photographic view of twin output shaft with sealing arrangement according to the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
Common sealing devices can provide a consistent, reliable sealing system for most applications. However there are drawbacks with vertical shaft gearbox with pressurized lubrication system as there is no control of oil flow through the bearing. In turn this produces the profuse oil leakage from the vertical shaft. For this reason an innovative sealing technology is incorporated in the twin output shafts of the drive gearbox of bar mill.

The new sealing arrangement is developed from combination of oil throw (2) which acts as main sealing element, double radial lip seals (9) with grease lubrication in tandem as back up sealing element and oil flow isolator/restrictor (4) for controlled oil flow for bearing and a free flow oil drainage system. It incorporates the concept of a tortuous path for fluid sealing with concepts of centrifugal price, pressure differential and drain back design. The sealing arrangement has an oil collector with large drain back system (1). The tortuous path means a twisted path. The new sealing arrangement incorporates a unitized single piece design consisting of a rotor and a stator. The rotor (oil throw) is mated to the shaft by means of an o-ring, while the stator (oil collector cum end cover and oil isolator/restrictor) is mated to the housing bore by means of double radial lip seals (9). The rotor consists of rotating oil throw (2), sleeve (3) and o-ring (13) assembled with the rotating output shaft, while the stator consists of oil collector (1), oil flow restrictor (4), double radial lip seals (9), seal retainer (5), seal separator (6), spacer (12) and o-rings (10) and is assembled to the stationary housing. The stator and rotor feature creates pressure difference in tortuous path and ensures minimum passage oil to escape through oil flow restrictor (4). The rotation of twin output shaft (S1 and S2) along with oil throw (2) ensures the oil to flew away from leakage prone twin output shaft (S1 and S2) and collected in oil collector (1).
The oil flow restrictor (4) stops oil from flowing near the sealing area which creates a primary blockage / control of oil flow to the sealing area. Oil throw (2) directs away the residual oil flow from oil flow restrictor (4) by rotor centrifugal action towards the large drain holes of the oil collector cum end cover (1). The oil collector cum end cover (1) has large drain holes for quick return of oil by gravity back to sump which prevents oil flooding at seals and thus improves seal-ability. The new sealing arrangement has also the seal retainer (5), seal separator (6), sleeve (3), spacer (12), o-rings (10, 13) and hexagonal socket head screw (7, 8) for seal retainer (5) and end cover (1) or oil collector. About 25-30 cc of grease is injected through grease nipple (11) in every 30 days.

WE CLAIM
1. Sealing arrangement in the twin output shafts of drive gearbox of bar mill comprising;
arranging a rotor and a stator disposing an oil throw (2) as main sealing element; arranging double radial lip seals (9) as back up sealing element; arranging oil flow isolator/restrictor (4) to control oil flow; arranging free flow oil drainage system (1); characterized in that,
the rotor (oil throw) is mated to the shaft by means of o-ring while the stator (oil collector cum end cover and oil restrictor) is mated to the housing bore by means of double radial lip seals when the feature of stator and rotor creates pressure difference in twisted path and ensures minimum passage oil to escape through oil flow restrictor (4) wherein the rotation of twin output shaft S1, S2 along with oil throw (2) ensures the oil to flow away from leakage prone twin output shaft (S1S2) and is collected in oil collector (1) when oil flow restrictor (4) stops oil from flowing near the sealing area to create a primary blockage/control of oil flow to the sealing area wherein the oil throw (2) directs away the residual oil flow from oil flow restrictor (4) by rotor centrifugal action towards the large drain holes of the oil collector cum end cover (1) when the oil collector cum end cover (1) with large drain holes quickly returns the oil by gravity back to sump to prevent oil flooding at seals and thus improving seal-ability.
2. Sealing arrangement as claimed in claim 1, wherein the rotor comprises a rotating oil throw (2), sleeve (3) and o-ring (13) assembled with the rotating output shaft.
3. Sealing arrangement as claimed in claim 1, wherein the stator comprises oil collector (1), oil flow restrictor (4), double radial lip seals (9), seal retainer (5), seal separator (6), spacer (12) and o-rings (10) and is assembled to the stationary housing.

ABSTRACT

The sealing arrangement in the twin output shafts of drive gearbox of bar mill consists of disposing in the said arrangement an oil throw (2) as main sealing element, double radial lip seals (9) as back up sealing element an oil flow restrictor (4) to control oil flow and a free flow oil drainage system (1) when the feature of rotor oil throw and stator (oil collector cum end cover) disposed in the arrangement creates pressure difference in twisted path for fluid sealing and ensures passage oil to escape through oil flow restrictor (4). The rotation of twin output shaft (S1, S2) along with oil throw (2) ensures the oil to flow away from leakage prone twin output shaft (S1, S2) and is collected in oil collector (1). Oil flow restrictor stops oil from flowing near the sealing area when oil throw (2) directs away the residual oil flow from oil flow restrictor (4) by rotor centrifugal action towards the large drain holes of the oil collector (1) which quickly returns the oil by gravity back to sump to prevent oil flooding at seals and thus improving seal-ability.