FIELD OF THE INVENTION:-
The present invention is related to an improved planet carrier adaptable to
Planetary Gear Box (PGB) for vertical spindle Bowl Mills.
BACKGROUND OF THE INVENTION:-
In a bowl mill raw coals are fed through a centre feed pipe. Coal falls at the
centre of the rotating Bowl. Bowl is lined with replaceable hard liners called bull
ring segments. Due to centrifugal force, the coal starts moving towards the bowl
periphery in a spiraling fashion. In the process, it reaches in between the
grinding roll and bull ring segments and gets crushed. The crushed coal is carried
out by the hot air under pressure to the classifier section for further
transportation to the boiler for firing. The drive of the Bowl is provided through a
Planetary Gear Box (PGB). This gear box transmits power from a motor running
at higher speed and the bowl rotating at lower RPM. Grinding takes place on
bowl at lower RPM.
Planet carriers are used to house and composed of three numbers of planet
gears. Planet gears are driven by a sun gear. Planet gears rotate on the
stationary ring gear. As planet gears rotate, Planet Carrier also rotates with
them. This leads to the rotation of Rotary Table which is fitted on the Planet
Carrier. On to the Rotary Table Bowl Hub is fastened with stud and nut
arrangement. On to Bowl Hub is mounted the Bowl. On to which grinding takes
place.
Planet Carriers are made from casting either nodular iron or weld-able carbon
steel castings. Figure 1 shows the Planet Carrier of prior art.
Problem with the prior art is that during final grinding of taper spindle, casting
defects like blow holes, sand inclusions get exposed. This forces us to remove
the component from the machine. Remove the defects either with weld gouging
or grinding or some such method till there are no traces of any defect. This has
to be ensured with Liquid die penetrant test. Then the component is preheated
to about 100°C based on the qualified welding procedure. Then the surface layer
is built up with welding electrode. Then again the taper machining is carried out.
After that the final grinding is carried out. This is a very time consuming and
costly rework.
Another disadvantage of the prior art is that there are three lobe shaped pillars
connecting the two flanges (Refer figure 1). If the contour of the lobe and its
location are not controlled during the casting process, it leads to fouling of planet
gear (Refer Figure 02). This becomes apparent only after the assembly of the
total gear box and during the no-load run test on the test bench. This leads to
the dismantling of the entire gear box and machining of the lobe. To machine
lobe it has to be loaded on to a horizontal boring machine. However loads
exerted during the horizontal boring operation tend to cause the fast wear of the
machine arm. This leads to frequent break down of the machine.
OBJECTS OF THE INVENTION:-
It is therefore, an object of the present invention to propose an improved planet
carrier adaptable to Planetary Gear Box (PGB) for vertical spindle bowl mills
which eliminates the disadvantages of existing state of art.
Another object of the present invention is to propose an improved planet carrier
adaptable to Planetary Gear Box (PGB) for vertical spindle bowl mills which
reduces the break-down hours.
A further object of the present invention is to propose an improved planet carrier
adaptable to Planetary Gear Box (PGB) for vertical spindle bowl mills which
increases the productivity of the bowl.
SUMMARY OF THE INVENTION:-
The present invention is provided with an improved Planet Carrier adaptable to
Planetary Gear Box (PGB) for vertical spindle bowl mills comprising an inverted
T shaped body having a round shaped top flange and an integral stem part
disposed perpendicularly on the top flange and the inverted T' shaped body
having 3 machined holes on the top flange disposed at 120° apart from one hole
to other hole and a round shaped bottom flange having 3 machined holes
disposed at 120° apart from one hole to other hole and the top flange and the
bottom flange are assembled by 3 cylindrical pillars by inserting in the holes of
top flange and the holes in the bottom flange and joined by welding and three
planet gears are assembled in between the top flange and the bottom flange and
disposed at 120° apart from one to other; characterized in that improved planet
carrier allows the planet gear to function freely without any foulness on the
peripheral body of the bowl.
BRIEF DESCRIPTION OF THE ACCOMPANYING PRAWINGS:-
Fig. 1 shows the planet carrier in casting condition.
Fig. 2 shows the arrangement of 3 planet gears around the sun gear. It deplete
the close gap between the lobe pillar and the planet gears. It also depicts
how it may lead to fouling of planet gears with the loaded pillars in case of
casting defect.
Fig. 3 shows the planet carrier with welded construction.
BRIEF DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION:-
As shown in Figure 3, the present invention is provided an inverted T shaped
body with a stem (3) and a top flange (2) which are made by integral forging.
Three holes (4) are machined on the top flange at 120° apart. Three cylindrical
pillars (8) are made forged steel and machined. A round shaped bottom flange
(5) is made of steel material and machined as per drawing. Three holes (6) are
machined on the bottom flange at 120° apart from one hole to other. Now the
three cylindrical pillars (8) are accommodated in between the 3 holes of top
flange and 3 holes of the bottom flange and fixed up by welding (9). Thereafter
placed three planet gears (7) in right position.
WE CLAIM:-
1. An improved Planet Carrier adaptable to Planetary Gear Box (PGB) for
vertical spindle bowl mills comprising:-
- an inverted T shaped body (1) having a round shaped top flange (2)
and an integral stem part (3) disposed perpendicularly on the top
flange (2);
- the inverted T shaped body having 3 machined holes (4) on top
flange disposed at 120° apart from one hole to other hole;
- a round shaped bottom flange (5) having 3 machined holes (6)
disposed at 120° apart from one hole to other hole;
- the top flange (2) and the bottom flange are assembled by 3
cylindrical pillars by inserting in the holes of top flange and the holes in
the bottom flange and joined by welding (9);
- three planet gears are assembled in between the top flange and the
bottom flange and disposed at 120° apart from one to other;
characterized in that improved Planet Carrier assembly allows the planet
gear to function freely without any foulness on the peripheral body.
2. The improved Planet Carrier as claimed in claim 1 wherein the upper
flange and stem are made by forging on the steel material.
3. The improved Planet Carrier as claimed in claim 1 wherein the cylindrical
pillars are made by machining on the steel materials.

The present invention is provided with an improved Planet Carrier adaptable to
Planetary Gear Box (PGB) for vertical spindle bowl mills comprising an inverted
'T' shaped body (1) having a round shaped top flange (2) and an integral stem
part (3) disposed perpendicularly on the top flange (2) and the inverted 'T'
shaped body having 3 machined holes (4) on the top flange disposed at 120°
apart from one hole to other hole and a round shaped bottom flange (5) having
3 machined holes (6) disposed at 120° apart from one hole to other hole and the
top flange (2) and the bottom flange are assembled by 3 cylindrical pillars by
inserting in the holes of top flange and the holes in the bottom flange and joined
by welding (9) and three planet gears are assembled in between the top flange
and the bottom flange and disposed at 120° apart from one to other;
characterized in that improved planet carrier allows the planet gear to function
freely without any foulness on the peripheral body.