Pumping feature on wear sleeve for unitized seal

A fluid seal assembly with a primary seal element and a wear sleeve element. The primary seal includes a casing and a seal element that contacts a sealing surface on the wear sleeve. The wear sleeve has a cylindrical portion that overlies a portion of the sealed mechanism, and the cylindrical portion has a surface pattern thereon formed by metal cold flow, preferably by drawing and ironing. The surface pattern includes at least one hydrodynamic pumping element having a contoured portion that is radially offset from the remainder of the cylindrical portion of the sleeve.

The present invention relates generally to fluid seals, usually oil seals, 
and more particularly, to novel hydrodynamic oil seals and methods for 
producing them. 
By "hydrodynamic" is meant an oil seal which, when one of the sealed parts 
is rotated to the other, develops a positive pumping pressure serving to 
return liquid phase oil accumulating on a surface wetted by the oil back 
into the sealed cavity. This phenomenon of oil being "pumped" or forced 
between the seal band formed by contact between a portion of the 
elastomeric seal body and the surface against which it is working is 
referred to as "hydrodynamic" because the pumping action occurs only upon 
relative movement of the parts. This is distinguished from a static seal 
which depends in part on interference or a snug fit between associated 
parts. In the seal industry, a seal between parts which are never intended 
to move relative to each other is usually referred to as a static or 
secondary seal, while a seal between parts which move relative to each 
other is referred to as a dynamic or primary seal. 
By way of background, hydrodynamic seals have been known for many years. 
Most hydrodynamic seals operate by the type of pumping action referred to 
above, wherein vanes, ribs or the like are formed on a part of the 
elastomeric seal lip body on or near the primary seal band area. While 
some seals have been proposed wherein auxiliary formations of one sort or 
another, including the ribs or vanes just referred to, are formed 
literally along the primary seal area, this type of seal does not usually 
deliver good static or "at-rest" performance. Therefore, the most common 
hydrodynamic seals are those wherein the primary seal band, formed by the 
convergence of frustoconical surfaces, lies snugly along the surface of a 
shaft or other part to be sealed, and the ribs or vanes are formed on one 
(or conceivably both) of the frustoconical surfaces- Seals of this type 
include those shown in U.S. Pat. Nos. 3,640,542, 3,790,180 and 3,807,743, 
for example. 
Other forms of hydrodynamic seals include those wherein the frustoconical 
air or exterior side of the seal includes other formations such as pads or 
sinuous ribs approaching and departing periodically from the seal band or 
a point of contact between the seal lip and its companion sealed surface. 
Still other forms of hydrodynamic seal include those wherein sinuosity in 
the lip itself is effective to create a pumping action which arises by 
reason of the difference in angular inclinations between the air and oil 
sides of the seal. These seals include those disclosed in U.S. Pat. No. 
3,927,600, for example, which patent is owned by the assignee hereof. 
Those seals referred to above and shown in the various patents enumerated 
operate on the principle of a pumping action created by the relative 
motion between the pumping formation and the oil lying on a smooth 
surface. In these kinds of seals, where there is little, if any, oil over 
and above that creating a thin film of lubricant between the two sealed 
parts, there is not sufficient additional oil for pumping to occur. A 
thin, strongly adherent lubricating film then usually remains in place 
which is effective to lubricate the parts. When there is excess oil, it is 
pumped back into the cavity from which it leaked. 
While the rib, vane or like kinds of seals just described are by far the 
most common kinds of hydrodynamic seals, proposals have also been made 
regarding a reversal of parts, i.e., forming grooves or the like in the 
shaft itself and leaving the seal lip free from pumping ribs, vanes or 
other formations. Such proposals are not believed to have achieved 
measurable success, whether the pumping formations are formed as 
depressions or grooves within the shaft or as projections extending 
outwardly from the shaft surface. Most of such proposed constructions are 
not generally thought to be practical, for various reasons. 
For example, forming grooves in an expensive, precisely machined shaft 
surface, particularly one that has been finished ground and/or hardened, 
is very expensive and time consuming relative to forming the pumping 
elements on the other mating part, that is, the elastomeric seal body, a 
part which is made by molding. 
In addition, imparting radially extending formations into a shaft would 
call for multi-piece molds or mold with movable parts, or for 
post-manufacturing operations of various kinds. 
However, certain advantages can be gained with the use of the contoured 
shaft concept, assuming that the difficulties therewith can be overcome. 
In this connection, the present invention provides a seal assembly with 
the pumping elements advantageously located on a part fixed to the shaft 
surface rather than on the elastomeric seal body itself. These advantages 
include the potential for better performance during the initial or 
"bedding in" phase of operation, reduced variation of pumping 
effectiveness during seal life, and the ability to control rib or vane 
formation and surface finish in the same operation. 
In this respect, any hydrodynamic seal works best when the surface finish 
of the shaft with which it is associated can be carefully controlled. It 
is now known in the seal industry that whereas a sealed metal surface 
having excessive roughness in its finish will cause rapid seal wear and 
thus be the subject of questionable performance in use, a surface finish 
which is too smooth may surprisingly not possess the ability to seal well, 
either. Some surface finishes are so smooth that the number of aspirates 
or surface projections is insufficient to engage and retain a film of oil. 
Thus, the thin film of oil necessary to lubrication cannot be retained on 
the surface. Such excessively smooth surface finishes may also create an 
adverse static leakage or capillary action situation which results from a 
combination of cohesive forces in the oil film and the wetting action on 
the shaft or seal. 
Because of the foregoing difficulties, successful seals have not been 
proposed or able to be produced on a large scale which were able to 
incorporate pumping grooves, slots or like formations on the metal part of 
the shaft seal unit. 
However, according to the present invention, it has now been made possible 
to produce such a seal by forming grooves, slots, or other desirable 
formations on the skirt portion of an oil seal wear sleeve. According to 
the invention, therefore, a two-element seal is preferably provided. One 
element includes a casing and an elastomeric seal body and the other 
element includes a wear sleeve with one surface of its skirt portion 
adapted to be received in snug, liquid-tight static seal relation to an 
associated shaft. According to the invention, "drawing and ironing" 
metal-forming techniques are used to provide slots, grooves, vanes or 
other hydrodynamic formations in the exposed surface of the wear sleeve 
skirt, usually its outside diameter or ("o.d.") without compromising the 
surface finish necessary to a good secondary seal between the other skirt 
surface, usually its inside diameter ("i.d.") and the outside diameter of 
the shaft. In other words, one surface of the wear sleeve skirt has 
hydrodynamic formations, while the other surface does not. 
If the seal lip acts inwardly, the seal element is pressed in the 
counterbore and the wear sleeve fits over the shaft OD. If the seal is an 
outwardly acting seal, however, for example, the sleeve is pressed into 
the counterbore and its primary sealing surface will face in; the seal 
element having the lip is pressed over the shaft OD and the seal lips acts 
outwardly against the sleeve. Seals of the present invention are effective 
in both applications. 
In view of the failure of the prior art to provide a successful seal 
assembly having an oil seal element and a wear sleeve element which 
includes a wear sleeve skirt incorporating hydrodynamic pumping elements 
formed by a drawing and ironing process, it is an object of the present 
invention to provide such a novel seal assembly and one or more methods of 
making it. 
Another object is to provide an improved oil seal assembly which includes a 
wear sleeve component having pumping formations such as slots or vanes 
extending inwardly or ribs extending outwardly from the seal-facing 
surface of the sleeve skirt for cooperative action with a portion of the 
elastomeric seal lip forming the other portion of the seal assembly, with 
the sleeve also having an opposite skirt surface free of slots, ribs or 
raised formations to insure a good static seal. 
Yet another object of the invention is to provide a wear sleeve which is 
readily receivable over a portion of an existing shaft and which will 
create a hydrodynamic effect when the wear sleeve skirt is mated with a 
conventional oil seal having an elastomeric lip portion, and the parts are 
rotated relative to each other. 
A still further object of the invention is to provide a method of forming a 
wear sleeve so as to incorporate a pattern of plural hydrodynamic elements 
on at least one of its skirt or axial flange surfaces. 
A further object of the invention is to provide a method of providing a 
pumping action in a conventional fluid seal by associating such a seal 
with a wear sleeve having hydrodynamic elements formed in the skirt or 
axial flange of the wear sleeve. 
Another object of the invention is to provide the capability of achieving 
varying degrees of hydrodynamic pumping action or performance using the 
same elastomeric seal, such capability being provided by associating the 
seal with a sleeve having different hydrodynamic patterns on its active 
surface. 
Yet another object of the invention is to provide an apparatus and method 
for creating hydrodynamic formations in the skirt portions of wear sleeve 
elements. 
A still further object of the invention is to provide a method of forming 
hydrodynamic formations in wear sleeves which includes disposing a wear 
sleeve forming blank in a drawing and forming die, and securing said blank 
against axial movement while passing a drawing punch through the die 
opening so as to iron the skirt thus formed and impress a hydrodynamic 
surface pattern on the wear sleeve skirt, the reverse image of such 
pattern having been imparted to a facing surface of the forming die. 
Yet another object is to provide a drawing and forming punch and die 
arrangement for producing patterned wear sleeves, with the die set 
including forming die with a generally cylindrical, patterned inside 
surface, and a drawing punch with its outer or working surface spaced 
apart from the patterned surface by a distance less than the thickness of 
the blank of material from which wear sleeve is to be formed, and whereby 
upon relative movement of punch and the die, the skirt will be drawn to an 
extended length and a reduced thickness, while hydrodynamic formations 
will be formed by cold metal flow in the portion of the wear sleeve skirt 
facing the patterned surface of the forming die. 
An additional object of the invention is to provide a hydrodynamic seal 
incorporating a wear sleeve with hydrodynamic formations therein, with the 
wear sleeve being effective to provide hydrodynamic performance in seals 
using materials which previously rendered achieving a hydrodynamic 
capability difficult or impossible. 
A still further object of the invention is to provide a wear sleeve unit 
having extremely small but effective grooves, slots, or ribs capable of 
imparting a hydrodynamic action to a seal wherein the seal lip is made 
from a relatively non-elastomeric material such as a sheet of a TFE 
material. 
A still further object of the invention is to provide a seal unit wherein 
the hydrodynamic formations are formed by cold flow in a material which is 
more wear-resistant than is the associated material used to form the seal 
lip. 
The foregoing and other objects and advantages of the invention are 
achieved in practice by providing a wear sleeve having hydrodynamic 
pumping elements formed therein by a drawing and ironing method and 
apparatus. The invention also achieves its objects by providing an oil 
seal assembly including a seal unit comprising a casing and a sealing 
element that includes a seal band portion, with the seal band thus formed 
acting to contact the skirt portion of a shaft-covering wear sleeve 
element, with the skirt including at least one pumping formation ironed 
into its surface, whereby relative rotation of the parts creates a pumping 
action within the film of oil separating the wear sleeve skirt and seal 
band surfaces, respectively. 
The manner in which the foregoing and other objects and advantages of the 
invention are achieved in practice will become more clearly apparent when 
reference is made to the following detailed description of the preferred 
embodiments of the invention set forth by way of example, and shown in the 
accompanying drawings, wherein like reference numbers indicate 
corresponding parts throughout.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
While the present invention may be embodied in different forms and types of 
seal assemblies, a description of certain presently preferred forms of 
seal will be given. In these units, the seal assembly is a two-element 
unit, including a primary seal element and a wear sleeve element, and the 
hydrodynamic elements are formed in a portion of the outer diameter of the 
wear sleeve skirt. In some examples, the primary seal unit is of a 
conventional elastomeric construction, and in others, the primary seal is 
made from a resinous film. The hydrodynamic or pumping element or other 
elements may be of any suitable form, and may be "male" or "female", i.e., 
embossed or debossed. 
It is within the scope of the invention to have certain of the parts 
reversed in orientation, that is, to have the seal rotate and the wear 
sleeve remain fixed. The patterns may consist of sunken or debossed 
grooves, slots or the like, or may comprise raised formations such as 
ribs, for example. The patterns of individual elements, may vary widely 
according to the choice of the user. Likewise, the preferred materials 
from which the wear sleeve skirt is made is a drawing grade of steel; 
however, other ferrous and non-ferrous materials may be used in 
appropriate applications. 
The drawings illustrate certain forms of seal that embody the present 
invention and show illustrative, preferred methods of making the products. 
Thus, referring to FIG. 1, there is shown an oil seal assembly generally 
designated 20 and shown to include a primary seal unit generally 
designated 22 and a wear sleeve unit generally designated 24. In use, as 
shown in FIG. 2, the seal unit 22 is intended to be inserted within a 
counterbore 26 in a machine member 28. The machine member may include a 
principal bore 29 serving to locate a bearing assembly generally 
designated 30 which journals a rotary shaft 32 by engagement between a 
bearing race 33 and the outside diameter surface 34 of the shaft 32. 
The above-described parts define at least in part a sealed region 36 lying 
to the right of the seal assembly 20 as shown in FIG. 2, and it is this 
area 36 wherein the oil or other fluid sought to be retained is confined. 
To the left as shown in FIG. 2 is an exterior region 37; dirt, grit and 
the like from this area is not intended to enter the sealed region and the 
oil from the sealed region 36 is not intended to leak into the outside 
area or atmosphere 37. 
Referring again to the details of the mechanism, the primary seal unit 22 
includes a suitably formed rigid casing generally designated 38 and 
usually made from metal. The primary seal casing 38 includes an axially 
extending mounting flange 40 and a radially extending, lip body bonding 
flange 42, an inner margin of which has bonded thereto an elastomeric seal 
body 44. A pair of frustoconical surfaces, namely, an "air" side surface 
46 and an "oil" side surface 48 meet along a generally circular locus to 
form a seal band 50. As is conventional in current seal products, a 
bonding tab 52 lies at one end of the seal body 44 for attachment to the 
inner margin of the radial casing flange 42. 
An excluder lip 54 is shown to be formed as a part of the body 44; such a 
lip 54 is preferred in many instances, but is not strictly necessary to 
the practice of the invention. The elastomeric seal body 44 also includes 
a spring groove 56 for confining a garter spring 58 adapted to provide or 
enhance a radial compressive load to be applied by the seal band 50 to the 
outer diameter shaft surface 34 to provide the "primary" seal, i.e., the 
seal between parts that move relative to each other. 
Referring now to the other component, namely, the wear sleeve unit 24, this 
unit 24 is shown in FIG. 2 to include a radially extending excluder flange 
60 of a given thickness. According to the invention, the wear sleeve 24 
also includes an axially extending, shaft-engaging skirt portion 62 of 
reduced thickness relative to the thickness of the flange 60. The outer 
diameter surface 64 (FIG. 4) of the wear sleeve 24 includes, as is best 
shown in FIGS. 3-5, a plurality of individual hydrodynamic groove elements 
66, arranged in an array or pattern such as that shown at 67 in FIG. 3. 
The elements 66 of the formation are extremely small, narrow slots, grooves 
or the like, as will be described. The inside diameter surface 68 of the 
skirt portion 60 is completely cylindrical and desirably includes no 
discontinuities or formations of any kind, either impressed within or 
extending outwardly from the i.d. surface 68 of the skirt 62. As is shown 
in FIG. 4, the i.d. surface 68 of the skirt 62 may optimally include a 
rubber sleeve unit 70 bonded thereto, and the sleeve may include plural, 
spaced apart mounting ribs 72 for snug, liquid-tight engagement with the 
outer diameter surface 34 of the shaft 32. Wear sleeves including this 
feature are commonly referred to as "rubber i.d." sleeves (or seals). If 
the skirt 62 has a metal i.d. only, such surface 62 fits snugly over the 
surface 34 of its shaft 32. 
Referring again to FIGS. 3 and 4, it will be noted that the wear sleeve 
unit 24 is also shown to include an inner end face surface 74 which may be 
engaged by or closely spaced apart from a snubber 75 (FIG. 2) on the 
primary seal unit 22. Such a snubber may act as an auxiliary excluder unit 
or may merely serve to position the parts upon initial assembly. 
Referring now to FIG. 5, two arrows show a thickness designated "T.sub.s " 
showing the thickness of the sleeve and in addition, there are spaced 
apart dimensional arrows schematically, and not to scale, showing the 
depth "D.sub.f " of the hydrodynamic formations impressed thereon. In a 
typical application, the thickness "T.sub.s " of the wear sleeve may be 
from about 0.020" to 0.040" or more in thickness, while the depth of the 
formation "D" is very small in relation to such height. In one preferred 
form of the invention, the depth of this formation or element is only 
about 0.0005", i.e., one-half of 1/1000th of an inch. Preferably, the 
formation for most applications is between about 0.0005" and 0,001". In 
other cases, this dimension may be even smaller; it may be as large as 
0.003" or more, for example, depending on different aspects of the 
situation including the type of sealed medium, the remainder of the 
surface finish on the shaft, the operating temperature and the material 
from which the seal body is made. 
Referring now to FIG. 6, there is shown a drawing and forming die assembly 
generally designated 76 and shown to include a forming die generally 
designated 78, a holddown ring generally designated 80, a forming die 
support ring generally designated 82, and a drawing punch generally 
designated 84. When it is desired to make sleeves embodying the invention, 
a blank generally designated "B" for forming a wear sleeve 24, is disposed 
within the assembly 76. The wear sleeve forming blank "B" is shown as in 
FIGS. 6 and 6A to include a center opening generally designated 86, 
defined by an inner, skirt-forming margin 88. The outer diameter of the 
blank is defined by a flange-forming margin 90. 
Referring again to FIG. 6, it is shown that the forming die 78 of the die 
and punch assembly includes a die body 92, with an upper, work support 
surface 94 and a lower mounting surface 96 as well as an inwardly directed 
surface 98 for forming the outside diameter of the wear sleeve skirt 62. 
The surface 98 includes a patterned area 100 lying generally centrally of 
the inside cylindrical surface 98 as a whole. The patterned area is shown 
and described in detail elsewhere herein. A tapered shoulder 102 is shown 
to define the lower edge of the surface 98. 
Referring now to FIGS. 7-9, construction and operation of the drawing punch 
84 are shown. This part is essentially a cylindrical rod with an outer 
diameter surface 104 that is preferably very smooth; the punch 84 also 
includes a lower bevel or taper 85 for initial engagement of the edge of 
the inner blank margin 88. 
Referring now to the drawing and forming operation of the invention, as 
shown in FIGS. 6-9, the operation is relatively straightforward and 
analogous to the so-called "drawing and ironing" type of metal forming 
possible with suitable tooling. 
In particular, and referring to FIG. 6, assuming it is desired to create a 
patterned wear sleeve having plural hydrodynamic elements thereon 
according to the invention, a blank "B" such as that shown in FIG. 6A is 
positioned intermediate the holddown ring 80 and the upper surface 94 of 
the drawing and forming die body 92. With the ring precisely centered by 
means (not shown) known to those skilled in the art, a forming press is 
actuated so as to move the die set just described in the desired sequence. 
First, the holddown ring 80 is advanced under high force until it "bottoms 
out", firmly clamping the outside margin 90 of the blank "B" between 
itself and the forming die upper surface 94. Thereupon, the drawing and 
forming punch 84 is advanced downwardly as shown in FIGS. 7 and 8. 
Initially, contact is made as shown in FIG. 8 where the leading or beveled 
edge 85 of the forming punch 84 contacts an upwardly directed surface of 
the skirt-forming portion 88 of the blank "B". At this point, initial 
deformation of the being-formed skirt takes place. As shown in FIG. 8, 
this initially deflects the skirt both axially downwardly and radially 
outwardly and into snug relation with the inside surface 98 of the drawing 
and forming die body 92. As the punch is advanced while precisely aligned, 
the skirt 62 is finally formed as shown in FIG. 9. The skirt-forming area 
88 of the blank "B" is drawn into a cylindrical shape with the o.d. and 
i.d. wear sleeve surfaces 64, 68, being fully dimensioned and formed upon 
completion of the punch stroke. 
Referring now to dimension changes during wear sleeve formation, FIGS. 13A 
and 13B, show that, in the prior art, the thickness of the skirt "T.sub.s 
" in FIG. 13B would be substantially equal to the thickness of the flange 
"T.sub.f ", which in turn would be the same as the thickness "T.sub.b " of 
the blank "B" from which the wear sleeve is formed. Hence, according to 
prior art skirt-forming techniques, when a blank of thickness "Tb" is 
formed into a so-called "L-cup" (referring to its shape in cross-section) 
a wear sleeve results which has the same or similar thickness in its 
radial portion as in its axial flange. The skirt length "L" in FIG. 13B is 
able to be calculated by known methods and, depending on the size of the 
center opening and the length of draw, will have a characteristic length. 
In FIG. 13A, this length is listed as "L@ T.sub.b " meaning that the 
length will be a certain length, provided that the thickness of the 
being-formed skirt section remains substantially the same as the thickness 
of the material from which the blank is made. 
Referring now to FIG. 14A, the drawing and forming action used to make a 
skirt according to the present invention is shown. Here, a thickness 
"T.sub.b ", is shown for a blank "B." Typically, this might be 0.032" for 
example. When a forming operation according to the present invention is 
completed, the thickness of the radial flange of the wear sleeve "T.sub.f 
" as shown in 14B will be substantially equal to the initial thickness 
"T.sub.b " of the blank itself. However, when the skirt shown in FIG. 14B 
is formed according to the present invention, then the skirt portion 62 
will have a measurably reduced thickness "T.sub.r ", and an elongated 
length "L@T.sub.r. Customarily, in a preferred form of the present 
invention, the flange is elongated some 15% to 18% with respect to the 
dimension it would have without thickness reduction. The thickness of the 
flange is usually reduced by about 20%, by way of example, during this 
operation. The finished skirt might then typically have a thickness 
T.sub.r of 0.025-0,028, for example. 
The drawing and ironing operation thus described is achieved by providing a 
suitable working clearance between the drawing punch o.d. surface 104 
(FIGS. 7-9) and the i.d. surface 98 of the drawing and forming die. By way 
of example, in a typical prior art wear sleeve forming operation, given a 
shaft diameter of just less than 2.00", and assuming that the i.d. of the 
wear sleeve were to be fit metal-to-metal on the shaft o.d., then the 
drawing punch might have an o.d. of 2,000 and, assuming a metal thickness 
of 0,032", then the i.d. of the forming die might be 2.060". This would 
thus create a total working clearance (on diameters) of 0.060 between the 
punch and the die. With such a diametral clearance, the actual clearance 
at any one point would be one-half that amount or 0.030". This would thus 
create a reduction of approximately only 0.001" to 0.002" at each point on 
the part surface, i.e., a thickness reduction of approximately 3% or less. 
The elongation of the skirt would likewise be minimal, being accounted for 
by the thickness changes in the part as made. 
In the practice of the present invention, the interference relative to the 
metal might be increased from a line-to-line dimension or 0.001", as just 
described, to perhaps 0.004" to 0.007 for an initial 0,032" wall 
thickness. This would then result in a substantial thickness reduction and 
a concomitant skirt elongation, of the order of 15% to 25% elongation, for 
example. 
Referring now to an important feature of the invention, this thickness 
reduction is responsible for creating the forces used to cause the cold 
flow of metal used to impart the desired pattern on the wear sleeve 
surface. The surface contour of the wear sleeve is characteristic of, and 
is imparted to by, the surface finish on the i.d. of the wall section 100 
of the forming die 92. Here, as shown in FIGS. 7-11, for example, where 
there are individual vanes, ribs 103 or other embossed areas on the tool, 
the reverse "image" of these areas will be faithfully reproduced and 
appear as grooves or slots on the o.d. or seal-facing surface of the wear 
sleeve. In other words, as the metal is confined by extreme pressure 
between the o.d. of the punch surface 104 and the i.d. of the die wall 98, 
it is in effect able to undergo cold flow into a virtually exact, 
complementary replication of the surface with which it is in contact. 
Referring now to other modifications of the form of wall ironing apparatus 
and method just described, and to the description of the product, it will 
be understood that a large variety of wear sleeves may be made in the 
manner described. 
Referring to one aspect of the invention, it is noted that the wear sleeve 
24 has been described as including a radial flange 60. In most seal 
applications, there is a benefit to having such a radial flange. The 
reasons for such flange include its use as a mating surface for a snubber 
or an auxiliary excluder lip. Such a flange can be used in assembling seal 
the two components such that the parts have a desired axial clearance. In 
addition, such a flange provides a holddown area for the blank when the 
skirt is being drawn as described herein. However, the presence of such a 
flange is not absolutely necessary in the finished product, and hence, it 
might be removed from the final product if this were considered desirable 
for some reason. Likewise, the flange could effectively be retained but be 
reformed into another configuration for one or more purposes known to 
those skilled in the art. 
According to the method just described, and one which is by far the most 
common, the radial flange extends outwardly and the skirt portion has an 
outwardly facing or o.d. surface which engages the seal band on the 
elastomer component of the seal assembly. However, so-called radially 
outwardly acting seals are also known, and were such a seal to be made, 
the orientation of the parts would be reversed. 
In other words, during manufacture, the flange might be directed inwardly 
and the blank would be initially supported on a mandrel. A mandrel would 
be thus be the stationery die element and have its outer diameter surface 
patterned so as to create a counterpart pattern in the finished product. 
In such an instance, the movable element in the dieset would be a draw 
ring that would be moved Over the mandrel to form the skirt of the wear 
sleeve. In this way the radially outwardly facing surface of the skirt 
would be plain but its inwardly directed surface would be patterned. As 
long as the stationery element of the die set contains the patterned 
surface, and the relative movement of the die parts is such as to wipe the 
skirt-forming metal over and into contact with the patterned surface with 
sufficient force to cause the requisite cold flow, the objects of the 
inventive method can be achieved. 
In the embodiments described, the finished wear sleeve product has had a 
debossed, grooved, or slotted surface. This is caused by raised formations 
such as the ribs 103 on the forming die wall. If the forming die of the 
type shown in FIGS. 7-9 and 11 were made so as to have reverse image 
formation such as slots or grooves therein, then the wear sleeve would 
bear a male or outwardly extending pattern on its surface. It is 
considered within the ambit of the invention, therefore, to make wear 
sleeves that are slotted or grooved on the one hand, or, in an alternate 
embodiment, to have outwardly extending ribs or vanes formed thereon. The 
intended application and other factors are used to determine which form of 
invention is preferred for a particular application. 
FIG. 16 illustrates an alternative form of wear sleeve generally designated 
24a. The sleeve 24a has OD and ID surfaces 64a, 68a defining therebetween 
a wear sleeve skirt 62a extending axially from the inner margin of the 
sleeve radial flange 60a. 
In FIG. 16, the thickness of the skirt T.sub.s is shown. The skirt 
thickness is illustrated by the dimension T.sub.s, and the height of the 
ribs or vanes 66a extending upwardly therefrom are shown to be formations 
having a height H.sub.f. As in the other examples, the ribs or vanes 66a 
protrude only very slightly above the remainder of the OD wear surface 
64a, typically in an amount of about 0.0005 inches, although such ribs may 
be made somewhat higher in an appropriate application. FIG. 16 is 
accordingly diagrammatic in character and not to scale, it being 
understood that the skirt thickness T.sub.s might typically be from 0.0020 
up to as much as 0.0062 or more, for example. In any case, the height of 
the formations is just sufficient to obtain the desired pumping action and 
still low enough to maintain a good static seal. 
Referring now to the exact hydrodynamic pattern, a relatively "steep" helix 
is shown in the embodiment of FIGS. 1-14. This type of formation has been 
shown for ease of illustration. However, at least in some instances, it is 
preferred to have the formations comprised of only one or two elements, 
arranged in a very shallow pitch. 
FIG. 17 shows a wear sleeve generally designated 24b that embodies such a 
pattern. Here, the radial flange 60b is conventional and the outer 
diameter 64b of the skirt is likewise conventional. However, one or more 
very shallowly angled grooves or indentations 66b are provided and are 
shown to be of a very shallow pitch. In the example intended to be 
illustrated, although the drawing is not to scale, the pitch of the helix 
is 32 threads or grooves per inch, and each of the grooves has a depth of 
0.0005 to 0.001 inches below the remainder of the outer surface 64b. In 
the instance just illustrated, i.e., one wherein the pitch is about 
0.030-0.033 inches per groove, the actual seal band, depending upon its 
state of wear, may span only one or two grooves. 
A very shallow or gradual pitch angle, such as that referred to above and 
schematically illustrated in FIG. 17 tends to create a more effective 
static seal and to have a somewhat diminished, although still effective 
pumping action. Selection of the pitch angle can be made depending upon 
the width of the seal band, and should account for the possibility that 
there may be some very slight misalignment or cocking of the seal within 
the bore. The angle of the helix should be at least somewhat in excess of 
any angle which might occur from a very slightly misaligned seal. 
Referring now to FIG. 15, another version of the novel seal is illustrated. 
Here, a shaft 32c positions a rubber mounting section 70c for a wear 
sleeve generally designated 24c. The wear sleeve here is identical to its 
counterpart 24 in FIGS. 1-3, for example, in that it includes a radial 
flange 60c, an axial flange or a skirt 62c having the grooves 66c similar 
or identical to those described in connection with the other embodiments 
of the invention. Likewise, other portions of the seal, including the seal 
casing 38c having the axial and radial flanges 40c, 42c are provided. 
However, in the example illustrated in FIG. 15, a molded elastomer section 
111 is shown to position a seal element 113 made from a contoured sheet of 
a non-elastomeric material such as a sheet of polymeric 
tetrafluoroethylene (TFE) filled with glass fibers and graphite. The TFE 
element 113 includes a contoured margin 115 having a radially inwardly 
facing surface 117 adapted to make contact with the outer surface 64c of 
the wear sleeve. A radially outer section of the TFE element 113 includes 
a contoured, snubber-forming annular rib 119 overlying an enlarged annular 
elastomeric rib 121. According to this form of the invention, the section 
119 of the TFE face engages the axially inwardly directed end face surface 
74c of the radial flange 60c. 
The embodiment of 15 is intended to illustrate that the seal element used 
to contact the wear sleeve need not be made from a molded lip or trimmed 
lip elastomer, but may be made from non-elastomeric materials, or from 
other materials known to be effective for fluid seals. A TFE seal element 
113 has been illustrated in the embodiment of FIG. 15 to show that, 
providing the pumping elements on the wear sleeve has additional 
advantages. For example, it has proved difficult to impart hydrodynamic 
formations, including those of a very gradual pitch, to TFE seal elements. 
In the past, the sheets of TFE from which a seal element is cut were often 
required to contain embossed or debossed sections with raised or depressed 
hydrodynamic formations, imparted by coining, for example. Since seals 
made from TFE sheets or wafers are relatively incapable of supplying a 
resilient radial compressive load to the seal area, their ability to seal 
under a wide range of conditions may be compromised. Using the 
hydrodynamic wear sleeve of the present invention, advantage can be taken 
of the good static seal provided by such units and this may be combined 
with the hydrodynamic capabilities made available by using the extremely 
shallow, narrowly angled grooves. 
Referring now to another matter, while the manner of making blanks from 
which the novel wear sleeves of the present invention are formed is not in 
itself considered novel, it is possible to make such wear sleeves in a 
rapid, effective manner. 
FIG. 12 illustrates one manner in which a plurality of blanks "B" can be 
arranged for machine feeding from a coil. After an initial blanking and 
piercing operation is performed, a coil of continuous sheet material 
remains. This comprises a plurality of individual blanks B1, B2, B3, etc., 
each having a connecting tab 97 attaching it to a continuous strip 99 used 
in indexing and feeding operations incident to use of the die set 76. The 
tabs 97 are arranged in pairs, as is known to those skilled in the art. A 
die set such as that shown in FIGS. 6-9 may be sequentially fed with an 
array "A" of blanks B1, B2, etc. with each of the tabs 97 being sheared 
from the remainder of the blank B as a part of the intermittent drawing 
and forming operation. 
The invention is intended to comprehend forming of a wide variety of 
patterns, including those which have previously been proposed and/or used 
on the elastomeric part of hydrodynamic oil seals. Specifically, these 
include variable depth grooves or ribs, vanes arranged in a series of V 
configurations so as to provide bidirectional pumping, or sinuous patterns 
for the same purpose. In addition, the formation of triangles, or 
elliptical, oval, or circular sections, may also prove advantageous, 
depending on the application, including the sealed mechanism, the 
lubricant, and the temperatures expected to be encountered. 
In addition to the advantages discussed above, the present invention can 
provide a great deal of adaptability and low cost in use. The wear sleeve, 
as pointed out, may be made with or without a rubber mounting surface. 
Auxiliary hydrodynamic formations may also be placed on the elastomeric 
portion of the seal if desired, although this is usually not necessary or 
even desirable. 
Providing the exceptionally minute dimensional contours can in many cases 
render the seal assembly very attractive where the elastomer or similar 
portion of the seal is relatively hard. In this connection, while the seal 
lip may be made from a conventional elastomeric material, it is becoming 
increasingly common to either make the primary seal lip from a 
fluorocarbon material, a fluoroelastomer, or similar material that does 
not deform readily and rapidly. Thus, the invention is also useful where 
the primary seal lip is not made from a soft elastomer and hence is not 
flexible, but is made from a harder elastomer or an altogether 
non-elastomeric material. Composite lips, i.e., those made from an 
elastomer having a fluorocarbon layer bonded thereto are also 
advantageously used with the invention. 
As pointed out, the invention can be very useful in reducing the stock of 
part numbers required to be made or invented for a variety of 
applications. A primary seal unit can be manufactured and used 
satisfactorily without a wear sleeve, with an ordinary wear sleeve, or 
with a wear sleeve made according to the invention. As long as the seal 
itself is satisfactory, it may be used with wear sleeves of the kind just 
described, or with those having more or less contouring in the 
hydrodynamic formations. This effectively enables the existing seals to be 
"tailored" to difficult applications with only a change in a drawing die 
being required to achieve a different level of hydrodynamic pumping. 
It will thus be seen that the present invention provides a novel apparatus 
method and product having a number of advantages and characteristics, 
including those pointed out herein and others which are inherent in the 
invention. The preferred embodiments of the invention having been 
described by way of example, it is anticipated that variations and 
modifications of the described forms of methods and apparatus will occur 
to those skilled in the art. It is anticipated that such modifications and 
changes may be made without departing from the spirit of the invention or 
the scope of the claims appended hereto.