Belleville spring loaded seal

Sealing structure (10,110) for a sealing a first joint member (11,111) to a second joint member (12,112) across a variable space therebetween. The sealing structure includes a frustoconical Belleville spring (17,117) and an annular support spring (18,118) defining an arcuate cross section having one end (19,119) connected to the Belleville spring, and an opposite end (20,120) sealingly mounted to the first joint member (11,111). A seal element (21,121) is fixed to the Belleville spring and has a lip portion (22,122) projecting into dynamic sealing engagement with the second joint member (12).

DESCRIPTION 
1. Technical Field 
This invention relates to joints having relatively movable members, and 
more particularly to means for sealing the joints between the relatively 
movable members. 
2. Background Art 
A large number of different seals have been developed for use in sealing a 
space between two members which may have relative movement toward and from 
each other. One joint in which such movement occurs and sealing of the 
space between the members is desirable is that found in the track 
structure of a track-type vehicle, such as a tractor or the like. Examples 
of improved seals for use in such track joints are illustrated in U.S. 
Pat. No. 3,614,113 of Duane L. Burke and U.S. Pat. No. 3,841,718 of Harold 
L. Reinsma, each of which patents is owned by the assignee hereof. 
More specifically, as shown in U.S. Pat. No. 3,614,113, a seal is provided 
including a resilient annular boot embracing the outer diameter of a pair 
of frustoconical Belleville springs. The springs are positioned back to 
back and the seal is positioned in an annular recess formed in one of the 
relatively movable joint members. The Belleville springs bias spaced 
portions of the boot into sealing engagement with confronting surfaces of 
the relatively movable joint members. 
In U.S. Pat. No. 3,841,718, a crescent seal ring is provided in the recess 
and a load ring is received within the crescent ring to load the crescent 
ring and urge the spaced portions thereof sealingly against the 
confronting surfaces of the relatively movable joint members. The seal 
ring is provided with a thin flexible hinge section so as to permit the 
deflection of the seal ring into sealing engagement with the confronting 
joint member surfaces to be effected primarily by the compression of the 
load ring. 
As discussed in the Reinsma U.S. Pat. No. 3,841,718, the structure thereof 
comprises an improvement over the seal structure of the earlier U.S. Pat. 
No. 3,390,922 of that patentee. In the earlier U.S. Pat. No. 3,390,922, 
the sealing force of the seal ring against the confronting surfaces of the 
joint members was derived substantially fully from the deflection of the 
thick seal ring itself and the load ring was of relatively soft material 
so as to act primarily as a filler or auxiliary static seal. 
DISCLOSURE OF INVENTION 
The present invention comprehends an improved joint seal received in the 
space between relatively movable first and second joint members including 
a frustoconical Belleville spring, an annular support spring defining an 
arcuate cross section having one end connected to an outer portion of the 
Belleville spring, and an opposite end sealingly mounted to the first 
member, and a seal element fixed to the Belleville spring and having a lip 
portion projecting into dynamic sealing engagement with the second member. 
In the illustrated embodiment, the spring constants of the Belleville and 
support springs are preselected to cumulatively cause the sealing force 
developed thereby in the seal element to continuously increase with an 
increase in deflection over the range of variable spacing between the 
joint members. 
In the illustrated embodiment, the spring constant of the support spring is 
substantially a constant over the range of variable spacing between the 
members. In the illustrated embodiment, the Belleville springs may pass 
over center in the range of variable spacing between the members. 
In the illustrated embodiment, the support springs are formed unitarily 
integrally with the Belleville springs. 
In the illustrated embodiment, the Belleville springs define a plurality of 
through openings and the seal elements extend through the openings so as 
to secure the seal elements to the Belleville springs. 
In the illustrated embodiment, the seal elements comprise a body of 
synthetic resin set in situ about the Belleville springs. 
Broadly, the invention comprehends the provision of a seal including a 
frustoconical Belleville spring having a plurality of through openings and 
a body of elastic synthetic resins set in situ on the spring and having a 
lip portion, a retaining portion, and a connecting portion extending 
through the openings to retain the lip portion fixedly secured to the 
spring. 
In the illustrated embodiments, the opposite end portion of the annular 
support springs is received in a recess in the first joint member and 
defines a static seal therebetween. 
In the illustrated embodiment, the opposite end portion of the support 
spring comprises a right circularly cylindrical portion. 
In one form the arcuate cross section of the support spring extends less 
than 90.degree. in its free state, and in another illustrated form, the 
arcuate cross section extends more than 90.degree.. 
In one form, the end portion of the support spring is received 
substantially fully within the recess, and in another form, is received 
only partially therein. 
Thus, the joint seal of the present invention is extremely simple and 
economical of construction while yet providing the highly desirable 
features discussed above.

BEST MODE FOR CARRYING OUT THE INVENTION 
In the illustrative embodiment of the invention as shown in FIGS. 1, 2, 4 
and 5 of the drawing, a sealing structure generally designated 10 is 
illustrated for use in sealing the space between the first joint member 11 
and a second joint member 12 which may have relative movement toward and 
from each other so as to have variable spacing therebetween. In the 
illustrated embodiment, member 11 comprises a portion of a first track 
link, member 12 comprises a bushing mounting a track pin 13 and receiving 
a portion of a second track line 14. Movement of members 11 and 12 toward 
each other may be limited by a thrust collar 15 formed integrally with 
link member 11, as shown in FIG. 1. 
First member 11 further defines a recess 16 opening toward second member 12 
and receiving the sealing structure 10, as best seen in FIG. 2. The 
sealing structure includes a frustoconical ring defining a Belleville 
spring 17, an annular support spring 18 defining an arcuate cross section 
and having one end 19 connected to an outer portion of the Belleville 
spring 17, and an opposite end 20 sealingly mounted to the first joint 
member 11. 
A seal element 21 is fixedly mounted to the Belleville spring 17 and 
includes a lip portion 22 projecting into dynamic sealing engagement with 
the second joint member 12, as shown in FIG. 2. 
Belleville spring 17 may be provided with one or more through openings 23. 
As shown in FIG. 4, the seal element comprises an annular element with one 
portion 23a of the opening defining a radially inner annular series and a 
second portion 23b of the openings defining a radially outer annular 
series offset of the inner series by one-half the spacing therebetween. 
As illustrated in FIG. 2, seal element 21 includes in addition to lip 
portion 22, a retaining portion 24, and connecting portions 25 extending 
through the Belleville spring openings 23. In the illustrated embodiment, 
the openings 23 are equiangularly spaced about the axis of the seal ring 
and thus the seal element 21 is uniformly supported throughout its annular 
extent on the Belleville spring. 
In the illustrated embodiment, seal element 21 is formed of a synthetic 
resin which may be molded in situ onto the Belleville spring. 
Illustratively, the seal element may be formed of polyurethane so as to 
provide excellent sealing characteristics. 
As further illustrated in FIG. 2, support spring end 20 may be received in 
a recess 26 in link member 11 opened toward the seal receiving recess 16. 
Spring end 20 may be suitably sealed in recess 26 to provide a positive 
static seal therewith. 
Referring now more specifically to FIGS. 2 and 5, it may be seen that the 
seal element lip portion 22 is urged sealingly against joint member 12 by 
the springy action of both the Belleville spring 17 and the support spring 
18. As shown by curve A in FIG. 5, the loading of the sealing lip follows 
a typical Belleville spring loading as the spacing between members 11 and 
12 decreases, i.e. effects a deflection of the Belleville spring. As shown 
in FIG. 5, the Belleville spring curve includes a reverse portion so that 
as the deflection increases from zero deflection, the load at first 
increases and then reaches a first peak followed by a decrease in the 
loading for a substantial further amount of deflection. The load then 
again increases with further deflection. 
Curve B of FIG. 5 illustrates the conventional load curve for an arcuate 
spring, such as arcuate spring 18. As shown, such a spring has a constant 
load-to-deflection characteristic. The combination of the two load 
characteristics results in curve C which, as shown in FIG. 5, provides a 
relatively high safety factor by bringing the load characteristics up to a 
substantially higher load range than that obtained by the use of a 
Belleville spring alone illustrated by Curve A, or an arcuate spring alone 
illustrated by Curve B. 
As shown in FIG. 5, the Belleville spring 17 is arranged to pass over 
center in the range of movement between the members 11 and 12 so as to 
obtain a greater range of load deflection. 
Support spring 18 includes an outturned arcuate portion 27 and an inturned 
arcuate portion 28. Referring now more specifically to the embodiment of 
FIG. 3, a modified form of sealing structure generally designated 110 is 
shown to comprise a sealing structure generally similar to sealing 
structure 10 but wherein the arcuate portion 118 of the support spring 
includes only an inturned portion 128, the end 120 extending from the 
outermost portion of the arcuate spring portion 118 into the recess 126. 
As shown in each of FIGS. 2 and 3, the spring end portions 20 and 120 
define right circularly cylindrical end portions received in corresponding 
right circularly cylindrical recesses 26 and 126, respectively. 
Sealing structure 110 further distinguishes from sealing structure 10 in 
that the support spring end 120 projects outwardly from the recess 126, 
whereas in sealing structure 10, the spring end portion 20 is received 
substantially fully within the recess 26. However, as seen in FIG. 3, link 
member 11 defines a radially inwardly facing surface 129 against which the 
spring end 120 facially abuts so as to radially outwardly support the 
spring end 120 outwardly of recess 126. 
As further illustrated in FIG. 3, the sealing element 121 may have a 
somewhat shortened axial extent as compared to that of the sealing element 
21 illustrated in FIG. 2. However, sealing structure 110 is generally 
similar to and functions generally similar to sealing structure 10 and 
provides a load curve generally similar to load curve C of FIG. 5 in 
combining the desirable spring characteristics of both the Belleville 
spring portion and the arcuate support spring portion of the sealing 
structure. 
In each of the illustrated embodiments, the support spring extends 
unitarily integrally from the Belleville spring. Thus, the joint spring 
structure may be formed as a single stamping from suitable spring sheet 
material. 
The forming of the seal element in situ about the Belleville spring in each 
of the embodiments permits the seal element to be secured to the 
Belleville spring not only by its mechanical hold thereon, but also by the 
adhesive-type bonding effected by setting of the synthetic resin in 
contact with the spring surfaces. 
Industrial Applicability 
The improved sealing structures 10 and 110 of the present invention provide 
an improved sealing of variably spaced joint members such as in the 
illustrated track joint disclosed above. The use of the coacting 
Belleville spring and arcuate support spring portions of the seal element 
support provides an improved deflection curve assuring positive sealing of 
the seal element lip portion with the confronting surface of the joint 
member 12 over the entire range of variable spacing between the joint 
members. 
The sealing structures provide all of the beneficial features of the 
Belleville-loaded seal structures while being relatively simple and 
economical of construction. As a result, the seal size may be relatively 
small while yet providing a positive dynamic seal between the seal element 
and the joint member 12. By virtue of the reduction in the overall size of 
the sealing structure, the recess 16 may be made relatively small so as to 
facilitate machining and minimize cost thereof. 
The static seal of the spring end 20 and 120 to the joint members 11 and 11 
may be effected by means of suitable sealant material 29 to further assure 
a positive static seal between the sealing structure and the joint member 
to which it is mounted. The static seal effectively prevents passage of 
dirt behind the seal which provides an improved sealing functioning in 
dirty environments, such as those in which joint structures such as the 
illustrative tractor track joint may be used. 
By forming the two springs integrally, a simple low cost spring support for 
the seal element is provided having the highly desirable loading 
characteristics discussed above providing improved long life, low 
maintenance functioning of the sealing structures. 
Other aspects, objects and advantages of this invention can be obtained 
from a study of the drawings, the disclosure and the appended claims. The 
foregoing disclosure of specific embodiments is illustrative of the broad 
inventive concepts comprehended by the invention.