Seal for a rolling bearing

A seal for a rolling bearing has two annular sheet metal members and a resilient sealing element. The two annular members have adjacent axially extending portions which are radially spaced apart to provide an annular axially extending gap. The sealing element is fixed to one annular member, bridges the gap and is in rubbing contact with the other annular member.

BACKGROUND OF THE INVENTION 
(1) Field of the invention 
The invention concerns a seal for a rolling bearing. In particular the seal 
has applications for bearings in a roller for a conveyor belt. 
Conveyor belts are used in a variety of industries many of which present 
environments hostile to bearings; for example, the coal mining industry. 
In such an industry there is a lot of dust which must be prevented from 
reaching the bearing and damaging it. Consequently a seal is provided 
outboard of the bearing in order to protect it. 
(2) Description of the prior art 
Published U.K. Patent Specification No. 990354 (Hans Ziller) concerns a 
seal for roller and ball bearings. The seals disclosed in this prior art 
publication comprise two sheet metal rings and a flexible oil resistant 
sealing ring, and their construction is such that the metal rings overlap 
each other radially and provide a complicated path for any foreign 
particles entering the seal. However this has the disadvantage that the 
possibility of any foreign particle becoming trapped and causing the seal 
to jam is increased. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide a seal for a rolling bearing which 
is easy to assemble and relatively cheap to manufacture. 
The seal has two sheet metal annular members, which are radially spaced 
apart and form an annular axially extending gap, and a resilient ring 
bridging the gap. When used for a bearing on a roller for a belt conveyor, 
the annular gap is raised away from the roller and any buildup of 
material, for example, dust, on the roller. The resilient ring is on the 
inside of the seal, that is adjacent to the bearing, and is arranged to 
prevent loss of lubricant from the bearing and not to allow foreign 
particles to get wedged in the gap and cause the seal to jam. 
The adjacent portions of the two metal annular members defining the annular 
axially extending gap are preferably flush so that dust and the like is 
not allowed to build-up and material is allowed to drop straight down. 
By off-setting the two metal annular members, the resilient ring which is 
attached to one of the metal members, is urged into resilient rubbing 
engagement with the other of the metal members. 
With many conveyor belt installations, the rollers are arranged to form a 
shallow U-shape, with two adjacent rollers lying horizontally and an 
inclined roller at each end. The invention provides an end shield for the 
seal to prevent material accumulating on the seal of an inclined roller.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
Referring to FIG. 1 the conveyor roller shown comprises a shaft or spindle 
10, a tube 11 extending co-axially along and around the spindle and an end 
cap 12 mounted one at each end of the tube. Each end cap 12 is formed from 
two separately made parts and comprises a sleeve 13 radially spaced from 
the spindle 10 and an annular flange 14 extending radially outwardly from 
the sleeve and being fixed, by for example welding, at its radially outer 
periphery to the tube 11. The sleeves 13 of the two end caps extend from 
their respective flanges 14 axially inwardly of the tube 11 and towards 
each other. 
A rolling bearing 15, in the embodiment shows a ball bearing comprising an 
outer race ring 16, an inner race ring 17 and a single annular row of 
balls 18, is secured between the spindle 10 and the sleeve 13 of the end 
cap 12 and mounts the tube 11 for rotation about the spindle. 
The sleeve 13 of the end cap 12 provides two annular recesses 19 and 20 in 
its bore locating two seals 21 and 22 respectively one each side of the 
rolling bearing 15. Seal 21 is a sheet metal ring snapped into recess 19 
on the axially inner side of the bearing 15 and forms a narrow annular 
sealing gap 23 between its radially inner periphery and the surface of the 
spindle 10. 
Seal 22 comprises two sheet metal annular members 24 and 25, annular member 
24 surrounding annular member 25, and a sealing element 26. Each annular 
member 24, 25 comprises an annular disc 27, 28 respectively, a first or 
radially outer annular portion 29, 30 respectively extending axially from 
the outer periphery of the disc and a second or radially inner annular 
portion 31, 32 respectively extending axially in the opposite direction to 
the first annular portion from the inner periphery of the disc. The first 
annular portions 29 and 30 of the members 24 and 25 respectively extends 
in opposite axial directions. First or radially outer annular portion 29 
of member 24 is convex in a section plane including the axis and is 
located in annular recess 20 of end cap 12. Second or radially inner 
annular portion 32 of member 25 is tubular and is a push-fit onto spindle 
10. 
The first or radially outer annular portion 30 of radially inner member 25 
is spaced radially inwardly from and is adjacent to the second or radially 
inner annular portion 31 of radially outer member 24 and together portions 
30 and 31 define an axially extending annular gap 33 between them with 
their free ends level with each other. The two annular discs 27 and 28 are 
axially offset and the sealing element 26, which comprises a ring of 
resiliently deformable material such as rubber or a plastics, is attached 
to disc 28 on the side opposite to the level free ends extends across and 
bridges the said annular gap 33 and is in rubbing contact with member 24. 
Sealing ring 26 is flat in its relaxed state and, by being attached to 
member 25 having the axially shorter of the two portions 30 and 31 
defining the said annular gap 33, it is in firm contact with member 24. 
When mounting seal 22, inner member 25 with sealing ring 26 is first 
pushed onto spindle 10 and then outer member 24 is snapped into position 
in the recess 20 of end cap 12. 
The rolling bearing 15 is packed with grease and seals 21 and 22 prevent 
loss of grease from the bearing and entry of foreign particles which might 
damage the bearing. Seal 22 is particularly useful in dusty conditions 
such as on a conveyor roller used in a coal mine because it removes the 
sealing gap from the spindle 10 and allows a certain amount of dust to 
build up on the spindle before it reaches the said annular gap 33. Dust 
particles which do enter the said annular gap 33 are prevented passing, by 
sealing element 26 into the grease and bearing 16. 
The conveyor roller shown in FIG. 2 is very similar to that shown in FIG. 1 
in comprising a spindle 40, an end cap 41, a rolling bearing 42 and a seal 
43. End cap 41 is made in one piece and has a sleeve 44 which provides an 
annular recess 45 in its bore for seal 43. Seal 43 comprises two sheet 
metal annular member 46 and 47, member 46 surrounding member 47, and a 
sealing element 48. Member 46 has a radially inner axially extending 
annular portion 49 and member 47 has a radially outer axially extending 
annular portion 50, and the two portions 49 and 50 together define an 
axially extending annular gap 51 between them. Since portion 49 is axially 
shorter than portion 50 with their free ends level, sealing element 48 is 
attached to member 46, extends across and bridges the annular gap 51 and 
is in rubbing contact with member 47. The feature that the annular sheet 
metal member to which is attached the sealing element is axially located 
in a recess is preferred because that member is mounted first and allows 
the other member to be mounted and adjusted to fit in the same operation. 
The part of the conveyor roller shown in FIG. 3 comprises a spindle 60, an 
end cap 61, a rolling bearing 62, a seal 63 and a shield 64. The end cap 
61 is made in one piece and has a sleeve 65 having no recesses to locate 
seal 63. Seal 63 comprises two sheet metal annular members 66 and 67, 
member 66 surrounding member 67, and a sealing element 68 attached to 
member 66. Outer member 66 is a push-fit in the bore of the sleeve 65. The 
two members 66 and 67 provide two axially extending annular portions 69 
and 70 respectively defining an annular axially extending gap 71. 
The shield 64 is mounted on the spindle 60 on the opposite side of the 
axially outermost seal, that is seal 63, to the bearing 62 and has an 
annular flange 72 extending radially outwardly past the two portions 69 
and 70 of the seal 63 defining the axially extending annular gap 71. Such 
a shield 64 may prove useful when using a roller having such a seal 63 in 
dusty conditions since dust particles will initially build-up on the 
spindle 60 on the axially outer side of the flange 72. Care has to be 
exercised however in case dust particles are trapped between the seal 63 
and shield 64 and are allowed to build-up and reach annular gap 71. The 
shield 64 is usually made from a heavier gauge of sheet metal than the 
components 69, 70 of seal 63 and gives the seal 63 protection against 
damage from impinging material. 
Although the seal 22, 43, 63 has been described in connection to a conveyor 
roller it can equally be used to seal a rolling bearing mounted on a shaft 
in some other form of housing. Instead of having a sealing element 
comprising a flat ring 26, 48, 68 which is strained to achieve a firm 
rubbing contact by the annular discs of the two members being axially 
offset, a sealing element may be formed having a flat annular portion and 
a conically extending portion. Then the annular discs of the two members 
can be located on the same plane lying normal to the axis with the sealing 
element distorted to a flat shape for firm rubbing contact. 
Although the seal 22, 43, 63, described and shown has two annular members 
which are in axial section basically an S or Z shape, the S or Z shape can 
be more pronounced so that the annular disc extends conically. Also other 
basic shapes are possible, for example a C or U shape, with the radially 
outer and inner annular portions of each member extending in the axial 
direction and being joined together by an annular disc. Instead of using a 
rubber or plastics ring as the sealing element 26, 48, 68 nylon flock may 
be attached to the annular axially extending surface of one of the two 
annular axially extending portions defining the said annular gap 33, 51, 
71 which surface is radially opposed to the other of the two portions. The 
nylon flock will extend radially and be in rubbing contact with the said 
other of the two portions defining the gap and prevent the entry of dust 
particles. 
All the components of the seal can be made of plastics as well as same 
being made of sheet metal.