Labyrinth seal with contaminant purging passageway for bearing housings

An improved seal assembly for a bearing housing is provided and includes piston rights which do not contact the rotating shaft, and a grease supply passageway connected to a labyrinth, and a grease purging passageway exiting axially through the seal assembly.

FIELD OF THE INVENTION 
The present invention relates to seals for bearing housings and in 
particular to seals for use in high contamination environments. 
BACKGROUND OF THE INVENTION 
Seals for bearing assemblies are necessary in machines such as pumps, 
turbines, agitators and the like to seal bearings contained in housing. 
The bearings in the housing support shafts which normally protrude from 
both ends of the bearing housing. 
The bearings require lubrication and an absence of contaminants to properly 
operate. At the point where the shaft protrudes from the bearing housing 
seals are necessary. Due to the rotation of the shaft and the stationary 
housing it is also necessary to use seals which minimize frictional losses 
and heat generation. 
In high contaminant environments effective sealing is especially important. 
Labyrinth seals are well-known in these types of applications wherein 
different members of the seal assembly interconnect to form a tortuous 
labyrinth making it especially difficult for contaminants to penetrate the 
seal and affect the bearings. 
One type of seal is sometimes called a "Taconite Seal" which is a premium 
seal used for contaminated environments, ie. mining or heavy equipment 
operations where excessive dust and dirt particles are present. Taconite 
seals typically have a labyrinth and a number of additional sealing 
elements. Often these sealing elements include lip seals or v-ring seals 
which contact the surface of the shaft during rotation. In some cases 
these seals actually rotate with the shaft inducing friction, heat and 
ultimately seal failure. Most types of labyrinth seals include means to 
purge grease through the seal by applying grease into the labyrinth under 
pressure. 
SUMMARY OF THE INVENTION 
The present invention is directed to an improved structure and a better 
method of lubricating the interconnecting sealing elements and to purging 
grease from the labyrinth defined therebetween. 
Specifically, it is an object of the invention to provide a seal for a 
bearing housing for use in high contaminant environments. 
It is a further object of the invention to provide a seal for a bearing 
housing which can be configured to fit any standard SAF style pillow block 
(bearing housing). 
It is a further object of the invention to provide a seal for a bearing 
housing that utilizes grease-purgeable labyrinth providing grease purging 
through the piston rings and through a second, axial grease escape 
passageway. 
It is further object of the invention to provide such a seal for a bearing 
housing which includes a minimum of contact-type sealing element such as 
o-rings and piston rings. 
Thus there is provided an improved seal assembly for a bearing housing for 
use in high contaminant environments including a generally fixed annular 
member and a rotatable annular member interconnected to form a labyrinth 
therebetween. The labyrinth is sealed using non-interfering piston rings 
which contact with the generally fixed member as opposed to the rotating 
member. Purging of contaminant from the labyrinth is achieved by applying 
grease through a supply channel to two distinct points in the labyrinth; 
one point being between the piston rings and the second point being 
between the piston rings and the atmosphere, thereby achieving superior 
purging.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The seal assembly of the present invention is a Taconite-type seal. 
Referring to the figures the seal has two main parts; a first annular 
member termed an adapter ring 20, and a second annular member termed in 
flinger ring 18. These two rings interconnect and a labyrinth 34 is formed 
between them. The labyrinth makes it difficult for flying debris 36, dirt 
or other particles to penetrate the seal and enter the interior of the 
housing 12 and contaminate the bearings 14. (A pillow block style housing 
is shown in the drawings however a variety of bearing housing types could 
be adapted to.) The labyrinth is typically filled with grease 38 which 
enters through a top mounted grease fitting 16. The other main elements of 
the seal include o-ring 21 mounted adjacent the shaft 10, a larger o-ring 
22 mounted at the interconnection with the pillow block housing 12 and two 
laminar piston rings 24 located between the adapter and flinger rings. 
In operation, the flinger ring would normally rotate with the shaft 
(sometimes being secured thereto with a set screw 28, through a set screw 
opening 27) while the adapter ring remains stationary. The labyrinth is 
routinely cleaned by "purging" lubricant, typically grease, through the 
labyrinth. This is accomplished by inserting more grease into the 
lubricant or grease fitting. The grease enters the seal assembly through 
grease fitting 16 and then enters a second passageway termed the grease 
feed channel 17. This passage continues downwardly and connects with the 
labyrinth intermediate the piston rings. This second passageway also has a 
horizontal component termed the axial purge hole 30 which connects with 
the labyrinth between the rings and the atmosphere. Grease entering the 
fitting travels downwards between the two piston rings and also outwardly 
through the axial purge hole 30 and then exits the labyrinth. This way any 
particulate matter located in the beginning stage of the labyrinth is 
removed. This dual purging of the labyrinth provides superior removal of 
contaminant. 
Most other taconite seals involve lip seals or v-rings which contact the 
shaft when it is rotating, and/or the seal actually rotate with the shaft. 
None of the sealing elements in the present seal assembly actually contact 
the shaft. This reduces wear substantially and prolongs seal and shaft 
life. Contact is eliminated by using only two laminar (piston) rings which 
both remain stationary. They do so by having their interference with the 
adapter 20 and not the flinger 18. This piston ring arrangement also 
allows a "grease dam" 26 to be formed between the rings. 
Greater misalignment capabilities are also possible than with other prior 
art techniques that utilize contact seals. Generally, any misalignment in 
the shaft cause extreme wear on the contact seals thereby increasing the 
likelihood of contamination to the bearing and ultimately bearing failure. 
In the present invention greater misalignment capabilities are achieved by 
building in clearance in the labyrinth and in particular in the seating 
arrangement of the piston rings. 
Again referring to the labyrinth in FIG. 5, clear gaps between the rings 24 
and the flinger 18 can be seen. This degree of clearance permits a maximum 
shaft misalignment of approximately 1/2 a degree which is exceptional for 
this type of seal. 
The grease delivery system combined with the axial purge hole 30 are also 
new. Instead of requiring grease to be purged through the rings as in some 
prior art devices, purging occurs through a specific passageway. 
It will be appreciated that the above description related to the preferred 
embodiments by way of example only. Many variations on the invention will 
be obvious to those knowledgeable in the field, and such obvious 
variations are within the scope of the invention as described and claimed, 
whether or not expressly described.