Shaft seal with scraper

An annular scraper and a shaft seal including a scraper and a method for making the same. The seal and scraper are of bonded construction. The seal includes an outer shell such as a stainless steel capsule, a polytetrafluoroethylene sealing element, a brass scraper, and a bonded elastomeric ring behind the scraper to allow deflection and return of the scraper. The scraper is preferably a single member having a continuous, uniform scraping edge without any slits. A bushing can be included for guiding a reciprocating shaft (a cable or rod) in near perfect alignment. The process preferably includes the step of forming the scraping edge by pinching or piercing a brass member in the mold simultaneously with the steps of molding the elastomeric ring and bonding the elastomeric ring to the scraper. The process of making the seal includes the step of simultaneously forming the ring of polytetrafluoroethylene into a sealing element. The piercing step eliminates the need for a separate piercing step and provides improved concentricity of the annular scraping edge.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to annular scrapers and to shaft seals using 
scrapers and also to methods for making the same. 
2. Description of the Prior Art 
Scrapers and seals with scrapers are known, however, such prior devices 
using a brass scraper were of the assembled type mechanically held 
together, such as by a turned edge of a shell, as contrasted to the bonded 
construction of the present seal. Further, such prior art brass scrapers 
had slits (or splits) therein to attempt to afford some degree of 
flexibility, and they required a plurality of such brass scrapers to 
overlap the slits. However, such slits did afford a path for contaminants 
to enter the application and the overlapping was not completely successful 
in eliminating such paths. In addition, in control cables such as used on 
large bulldozers and other similar equipment there is a certain amount of 
cable deflection and previous scrapers could not handle this amount of 
deflection but would be permanently deformed allowing foreign contaminants 
to pass into the application. 
It is an object of the present invention to provide an improved scraper, 
seal and method for making the same which overcomes the problems in the 
prior art. It is a further object of the present invention to provide a 
scraper with a backup ring of resilient elastomeric material, which 
scraper can repeatedly resiliently accommodate the encountered amount of 
cable deflection and return to its original position without losing the 
scraping function. It is a still further object of the present invention 
to provide in combination with such a scraper a functional 
polytetrafluoroethylene sealing element with a sealing lip. It is another 
object of the invention to provide a scraper having a continuous, uniform 
scraping edge without the slits of the prior art. It is another object of 
this invention to provide a method for making a scraper, and a seal with a 
scraper, which eliminates a separate piercing step, which also provides 
improved concentricity of the scraping edge, which also provides a bonded 
construction, and which eliminates a leakage path around the outside of 
the scraper. It is still another object of this invention to provide a 
cable control type of seal with a scraper and a bushing which guides the 
shaft in near perfect alignment. 
SUMMARY OF THE INVENTION 
The present invention includes in one embodiment an annular shaft seal 
including a sealing element, a metal scraper, and a bonded resilient 
elastomeric ring. In a preferred embodiment the scraper has a continuous, 
uniform scraping edge. The sealing element is preferably a 
polytetrafluoroethylene sealing element mechanically held in place. A 
bushing can also be included by being press-fitted into an I.D. of a shell 
adjacent the sealing element and the scraper to provide true alignment of 
the shaft (the cable or rod, for example). The present invention also 
includes a method for making such a shaft seal in which the scraper is 
pierced during the molding step simultaneously with the molding of the 
elastomeric ring and the sealing element and bonding the ring to the 
scraper. Another embodiment of the invention is the combination of an 
annular scraper and an annular, resilient elastomeric back-up ring to 
provide flexibility for the scraper, and a method for making the same 
including piercing the scraper simultaneously with molding the elastomeric 
ring and bonding it to the scraper.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawing, FIG. 1 shows a typical prior art cable 
scraper 10, used, for example, in conjunction with a seal for a hydraulic 
valve and including a shell 12, a pair of brass washers 13 and 14 on 
either side of a rubber washer 15, a pair of frustoconical brass scrapers 
16 each having a plurality of slits 17 therein overlapped by the adjacent 
brass scraper, and a small, hard rubber ring 18 against which the distal 
end 20 of the shell is rolled over and crimped to hold the assembly 
together. Assembled seals of this type are not satisfactory in that, for 
example, in applications where they are used in bulldozers and similar 
large equipment in cold climates, the scrapers 10 allow ice, water, dirt 
and other contaminants into the assembly where such contaminants freeze 
rendering the equipment inoperative. Such contaminants enter through the 
slits 17 even when the scraper is properly against the shaft (not shown) 
and contaminants also enter when the scraper is deflected and deformed and 
fails to return to its original position against the shaft. 
FIG. 2 shows a seal 30 according to the present invention of bonded 
construction and comprising a shell 32 (preferably a stainless steel 
capsule) having a recess 34 in one end thereof, the single scraper 36 
preferably of brass, a polytetrafluoroethylene sealing element 38 and an 
annular resilient elastomeric back-up ring 40 preferably of nitrile bonded 
to both the shell 32 and the scraper 36. It is noted that the sealing 
element 38 has a functional sealing lip 42 for sealing purposes. The seal 
30 preferably also includes a bushing 44, such as a Garlock DU bearing, 
press-fitted into a cylindrical I.D. surface of the shell 32 adjacent the 
recess 34. The bushing 44 provides true alignment of the shaft (such as a 
cable or reciprocating rod extending through the seal 30). The bushing 44 
should have a length sufficient to minimize deflection of a cable as it 
passes through the scraper 36. 
The scraper 36 is preferably a single brass scraper having a continuous, 
uniform scraping edge 46. The term "continuous, uniform scraping edge" is 
defined herein to mean a continuous edge in contrast to the discontinuous 
scraping edges of the prior art brass scrapers (such as shown in FIG. 1) 
having a plurality of slits 17 therein to hopefully provide flexibility 
thereto. The elastomeric ring 40 is of sufficient size and resilient 
characteristics as to allow at least the normal amount of deflection of 
the scraper 36 to be repeatedly accommodated after which the scraper 
returns to its original position as shown in FIG. 2 without loss of the 
scraping function. The elastomeric ring 40 preferably has a hardness in 
the range of 40 to 80 IRHD. 
The polytetrafluoroethylene sealing element 38 is preferably held in place 
solely by mechanical locking between the shell 32 and the scraper 36, 
although other means can be used, if desired. The sealing element includes 
a sealing lip 42 which is formed after the molding process (described 
below with respect to FIGS. 3, 4 and 5) by a slight shrinkage of the 
polytetrafluoroethylene sealing element when it is removed from the mold. 
FIGS. 3, 4 and 5 show a molding process for producing the seal 30 shown in 
FIG. 2, including the steps of placing the shell 32 in a mold cavity 50 
defined by a core 52, a center ring 56, and an upper member 58. The upper 
member 58 is forced downwardly by a press during the molding process as 
will be well understood by those skilled in the art. After the shell 32 is 
placed in the cavity 50, a polytetrafluoroethylene ring 60 is placed in 
the recess 34, then a brass scraper member 62, preferably in the shape of 
a cup is placed upside-down on top of the polytetrafluoroethylene ring 60 
and the core 52, and then a blank prep form 64 of elastomeric material is 
placed on top of the brass scraper member 62. Upon closing the mold, the 
upper member 58 moves downwardly causing the blank prep form 64 to flow 
into the recess 34 forming the elastomeric ring 40 of FIG. 2, and also 
pushing the brass member 62 against the polytetrafluoroethylene ring 
causing the polytetrafluoroethylene ring to be formed into the sealing 
element 38 shown in FIG. 2. At the same time, the scraper 36 is pinched 
off or pierced between the mating I.D. surface of the upper member 58 and 
the O.D. surface of the core 52, thus producing the scraping edge 46 
thereof. Also at the same time, the elastomeric ring 40 is bonded to the 
shell 32 and to the scraper 36. After the completely bonded seal 30 is 
removed from the mold, the polytetrafluoroethylene sealing element 38 
cools and shrinks a small amount causing the formation of the sealing lip 
42 thereof. The left-over central portion 66 of the cup-shaped member 62 
is not a part of the finished seal 30. 
As discussed above, the resultant seal 30 of the present invention is a 
significant improvement over the prior art since the scraper 36 has no 
slits to allow contaminants to enter, the resilient back-up ring 40 allows 
repeated deflection and return of the scraper thus eliminating permanent 
deformation thereof and the consequent entering of contaminants into the 
application, the piercing step during molding provides a scraping edge 46 
of improved concentricity while eliminating a separate piercing step, and 
the bonded construction eliminates a leakage path around the outside of 
the scraper inside the shell. Further, the bushing 44 holds the shaft in 
near perfect alignment. 
While the present invention has been described with reference to FIG. 2 
showing the combination of a seal, scraper, and elastomeric ring, it is to 
be noted that the combination of the scraper 36 and back-up resilient ring 
40 can be used alone without the sealing element 38, if desired. In such 
case the scraper preferably has a continuous, uniform scraping edge 
without slits and the ring 40 is preferably bonded to the scraper 36. Such 
combination of the scraper 36 and ring 40 is preferably constructed by 
molding with the scraping edge 46 being pierced simultaneously with the 
ring 40 being molded and bonded to the scraper, as shown in FIG. 2. The 
sealing element 38 and the bushing 44 are not necessary to this 
deflectable scraper and method aspect of this invention. 
It is noted that the preferred material for the scraper material is brass, 
however, other materials and other metals can be used. The brass material 
is readily pierced by presently used molds and presses. The seal and 
scraper of this invention are useful with all shafts including 
"reciprocating shafts", which term is hereby defined for use in the 
present specification and claims as including control cables, rods, etc. 
The invention has been described in detail with particular reference to the 
preferred embodiments thereof, but it will be understood that variations 
and modifications can be effected within the spirit and scope of the 
invention as described hereinabove and as defined in the appended claims.