Patent Description:
Belt tensioners are utilized to ensure the associated belt, such as a belt in an automotive vehicle, is placed and maintained in the desired state of tension. Such belt tensioners can in some cases be exposed to environmental factors and outside contaminants, such as dust, dirt, fluids, etc. However, many existing belt tensioners do not provide sufficient protection from such environmental factors and outside contaminants.

Examples of known belt tensioners are disclosed in documents <CIT>, <CIT> or <CIT> The document <CIT> discloses a tensioning system comprising a spring case having a pivot tube and an outer cylindrical portion;an arm pivotally coupled to the spring case to pivot relative to the spring case, the arm having a pulley portion and a body portion, wherein the body portion has a radially outer flange and a radially inner flange, the radially inner flange being seated within the spring case;a bushing positioned between the radially inner flange of the arm and the spring case; and an annular lip seal having a body portion with a flexible flange extending therefrom and a gap between the body portion and the flexible flange.

The aforementioned aims are reached by a tensioning device as claimed in the appended set of claims.

<FIG> is a front view of a belt system, generally designed <NUM>, shown in association with a belt tensioner <NUM>. The belt system <NUM> includes an endless power transmitting element <NUM>, such as a belt, chain or the like, which passes around a variety of pulleys, gears, guides. The power transmitting element <NUM> thereby drives a plurality of driven accessories, and/or is driven by one or more of the components. The power transmitting element <NUM> can, in one case, take the form of a timing belt/chain, a drive belt/chain, a transmission belt/chain or the like for use in an automotive vehicle. The tensioner <NUM> engages the power transmitting element <NUM> to apply the desired force to the power transmitting element <NUM> and to induce the desired tension.

With reference to <FIG> and <FIG>, the tensioner <NUM> includes an arm <NUM> movably coupled to a spring case or base <NUM>. The tensioner <NUM> further includes a belt engagement surface <NUM> positioned at one end of the arm <NUM>, and a biasing mechanism or energy storing device <NUM> positioned between and operatively engaging the arm <NUM> and spring case <NUM>. In one embodiment, the belt engagement surface <NUM> takes the form of a generally cylindrical roller <NUM> rotatably coupled to the arm <NUM> via a bearing <NUM>, as shown in <FIG>, such that the roller <NUM> can rotate as the belt <NUM> rolls past the tensioner <NUM>. Alternately the belt engagement surface <NUM> can take the form of a smooth, but non-rotatable, component with high-lubricity, or a toothed sprocket (for use with a chain), etc. The belt engagement surface <NUM> is aligned with, and/or rotatable about, an axis <NUM>.

The arm <NUM> is pivotally coupled to the spring case <NUM>, and the spring case <NUM> is configured to be fixedly and non-rotatably coupled to an anchor body <NUM>, such as an engine, engine block, engine cover, frame, etc. In one embodiment the tensioner <NUM>/spring case <NUM> is coupled to the anchor body <NUM> by a threaded fastener <NUM>, such as a bolt, extending through a central opening <NUM> of a pivot tube <NUM> of the tensioner <NUM> and into the anchor body <NUM>. The bolt <NUM> thereby defines, or is aligned with, an axis <NUM> about which the arm <NUM> is pivotable. The axis <NUM> is thus, in the illustrated embodiment, radially offset from the axis <NUM> of the belt engagement surface <NUM>. The tensioner <NUM> could also be configured in and/or mounted in various other configurations and manners, such as in a tab/ear mounting configuration.

The biasing mechanism <NUM> can take the form of a spring, such as a helical coil spring in the illustrated embodiment. The biasing mechanism <NUM> urges the arm <NUM>/roller <NUM> into contact with the belt <NUM> with the desired amount of force, and allows the arm <NUM> to pivot about the axis <NUM> (i.e. in the directions of the arrow <NUM> shown in <FIG>) to accommodate varying forces applied to the arm <NUM>/roller <NUM> by the belt <NUM>. A bushing <NUM> is positioned between the arm <NUM> and the spring case <NUM>, and a spring cap <NUM>, or cover, is located at one axial end of the spring <NUM> to cover and protect the spring <NUM>.

In the embodiment of <FIG>, the arm <NUM> includes a pulley portion 18a carrying the roller <NUM> and a body portion 18b positioned adjacent to the spring case <NUM>. The body portion 18b of the arm <NUM> includes a generally flat, center annular portion <NUM>, a radially outer flange <NUM>, and a radially inner flange <NUM> positioned between the center portion <NUM> and the outer flange <NUM> in the radial direction. The arm <NUM> also includes a connecting portion <NUM> positioned between the outer <NUM> and inner <NUM> flanges. The spring <NUM> is positioned adjacent to and radially inside the radially inner flange <NUM>, and above and adjacent to the center portion <NUM>.

The spring case <NUM> includes an inner cylindrical portion <NUM>, an outer cylindrical portion <NUM> and a generally flat body portion <NUM> positioned between the inner cylindrical portion <NUM> and the outer cylindrical portion <NUM> in the radial direction. The outer cylindrical portion <NUM> includes an end flange <NUM> extending radially outwardly from an upper end thereof. The outer cylindrical portion <NUM> and the end flange <NUM> of the spring case <NUM> are positioned between the outer flange <NUM> and the inner flange <NUM> of the arm <NUM> in a radial direction thereof. In this manner various portions of the arm <NUM> and spring case <NUM> nest, or overlap, in the axial and/or radial directions.

The spring cap <NUM> is positioned at the upper, central end of the tensioner <NUM>. The spring cap <NUM> includes an inner tube portion <NUM> which is positioned between the pivot tube <NUM> and the spring <NUM> such that the spring <NUM> is positioned between the inner tube portion <NUM>/spring cap <NUM> and the radially inner flange <NUM> of the arm <NUM> in the radial direction.

One end of the spring <NUM> is fixedly coupled to the arm <NUM> (e.g. in one case to the radially inner flange <NUM>, or connecting portion <NUM>, or center portion <NUM> of the arm <NUM>), and the other end of the spring <NUM> is fixedly coupled to the spring cap <NUM> (e.g. in one case to the inner tube portion <NUM> of the spring cap <NUM>). The spring cap <NUM> is, in turn, fixedly coupled to the spring case <NUM> via the pivot tube <NUM>. In this manner, when the arm <NUM> is pivoted (i.e. in the direction of arrows <NUM> of <FIG>), the spring <NUM> is wound or unwound, depending upon the direction of pivoting, to provide the desired biasing force to the arm <NUM>.

In the embodiment of <FIG>, the bushing <NUM> is positioned between the arm <NUM> and the spring case <NUM>. In the illustrated embodiment the bushing <NUM> includes a cylindrical portion <NUM> at one end thereof, a flange portion <NUM> at the other end thereof, and a generally conical portion <NUM> positioned between the flange portion <NUM> and the cylindrical portion <NUM>. The cylindrical portion, or pivot bushing <NUM>, helps to provide proper radial alignment between the arm <NUM> and spring case <NUM>, and is positioned between the outer cylindrical portion <NUM> of the spring case <NUM> and the radially inner flange <NUM> of the arm <NUM>. The flange portion of the bushing, or spring bushing <NUM>, helps to provide proper axial alignment between the arm <NUM> and the spring case <NUM>, and is positioned between the end flange <NUM> of the spring case <NUM> and the connecting portion <NUM> of the arm <NUM>.

Finally, the conical portion of the bushing, or the damper bushing <NUM>, provides damping characteristics to the tensioner <NUM>, and can provide radial and/or axial positioning between the arm <NUM> and spring case <NUM>, and is positioned between the outer cylindrical portion <NUM> of the spring case <NUM> and the radially inner flange <NUM> of the arm <NUM>. The bushing <NUM> can be made from a wide variety of materials, but is made of plastic or polymer materials in one case. Further details relating to tensioners, which can utilize the seals disclosed herein, can be found in <CIT>, <CIT>, <CIT>, and <CIT>.

In some cases environmental factors and outside contaminants, such as dust, dirt, fluids, etc. can penetrate the tensioner <NUM> and cause the bushing <NUM>, or other components, to wear. Wearing of the bushing <NUM> or other components can adversely effect the performance of the tensioner <NUM>. Therefore, in the embodiment of <FIG> a seal system <NUM> is provided to reduce the penetration of contaminants to the bushing or other components.

The illustrated seal system <NUM> includes a V-ring seal <NUM>, or lip seal, having a body portion <NUM> and an integral, flexible flange <NUM>. A gap <NUM> is positioned between the flange <NUM> and the body portion <NUM>, and the flange <NUM> is relatively thin, and therefore deflectable, relative to the body portion <NUM>. In the illustrated embodiment, the seal <NUM> is positioned on the radially outer surface of the outer cylindrical portion <NUM>, and below the end flange <NUM> of the spring case <NUM>.

The seal system <NUM> further includes a seal plate <NUM> that is coupled to the outer flange <NUM> of the arm <NUM>, extending radially inwardly therefrom. The seal plate <NUM> can be secured to the outer flange <NUM>/arm <NUM> by staking, but could also be secured by various means, such as welding, adhesives, brazing, etc. Alternatively, the seal plate <NUM> can be formed as a unitary one-piece body with the arm <NUM>/outer flange <NUM>.

The upper surface <NUM> of the seal plate <NUM> defines a seal counterface which sealingly engages the flange <NUM> of the seal <NUM>. In particular, the seal <NUM> and seal plate <NUM> are arranged such that the seal <NUM>/flange <NUM> is placed into compression in the axial direction when the tensioner <NUM> is assembled/mounted to ensure proper sealing and allow for wear in the tensioner <NUM>. The seal <NUM> may also be stretched/placed in tension in the radial direction by stretching the seal <NUM> to a greater diameter than the seal <NUM> assumes when it is not mounted to the tensioner <NUM>. The seal <NUM> can be made of a wide variety of materials, such as rubber, synthetic rubber, a butyl material, a trial nitrile, etc. Moreover, the seal <NUM> can take a variety of configurations besides the V-ring seal shown herein, such as O-rings, X-rings and U-rings. The seal <NUM> may be relatively compressible but have the ability to accommodate relatively high tolerances and wear. In particular, it may be desired for the seal <NUM> to be compressible to allow some travel/movement, but not provide much resistance to such travel/movement. The V-ring seal provides a relatively high amount of travel (to allow for wear and tolerance) without much compressive force, thereby reducing temporary damping and damping variation from seal contact. However, other shapes can be utilized.

As the flange portion <NUM> of the bushing <NUM> wears, the axial position of the arm <NUM> relative to the spring case <NUM> can be shifted (typically, the arm <NUM> and spring case <NUM> on either side of the flange portion <NUM> move closer together in the axial direction). This shift in position causes the seal plate <NUM> to move axially away from the seal <NUM>. In this case the seal <NUM>/flange <NUM> simply expands in the axial direction, increasing its gland size, following the seal plate <NUM> and maintaining a proper seal. On the other hand, if the seal plate <NUM> were to move toward the seal <NUM> (for example, due to uneven wear of the bushing <NUM> causing canting or skewing of the arm <NUM> relative to the spring plate <NUM>), the seal <NUM>/flange <NUM> will be compressed, decreasing its gland size, and again maintaining a proper seal.

Therefore, the seal assembly <NUM> can accommodate a shift in axial position between the seal plate <NUM> and seal <NUM> in either axial direction. In this manner wearing of the bushing <NUM>, and axial shifts in position between the arm <NUM> and spring case <NUM>, are easily accommodated.

The seal assembly <NUM> can also accommodate wear in the cylindrical portion <NUM> of the bushing <NUM>. In particular, such wear may cause the seal <NUM> to move radially inwardly or outwardly relative to the seal plate <NUM>. In this case, however, the flange <NUM>/seal <NUM> simply slides radially inwardly across the seal plate <NUM>/counterface <NUM> to accommodate such a shift in position. The seal assembly <NUM> may have or provide radial clearance for the seal <NUM> on either side of the seal plate <NUM> to allow the seal <NUM>/flange <NUM> to slide radially across the seal plate <NUM>, while maintaining the seal. However, it should be noted that such radial movement of the seal <NUM> across the seal plate <NUM> is designed to accommodate wear, and is not necessarily designed to accommodate off-center or eccentric movement of the arm <NUM> relative to the spring case <NUM>.

Wear of the conical portion <NUM> of the bushing <NUM> may cause the seal <NUM> to shift both axially and radially relative to the seal plate <NUM>. As described above, however, the compressible/movable nature of the seal <NUM> enables the seal assembly <NUM> to accommodate such wear/movement. As also noted above, the bushing <NUM> or parts thereof may wear unevenly over time, which can cause the arm <NUM> to pitch, or form an angle, relative to the spring case <NUM>. The flexible, dynamic nature of the seal assembly <NUM> therefore allows the seal assembly <NUM> to accommodate such pitching or offset of the arm <NUM>.

The seal assembly <NUM> thereby maintains a seal around the bushing <NUM> to prevent contaminants, such as dust, dirt, fluids and other environmental factors from reaching the bushing <NUM>, helping to ensure proper operation of the tensioner <NUM> and extending the life of the tensioner. The illustrated seal assembly <NUM> is also positioned radially outside the spring <NUM>, isolating the spring <NUM> from the outside environment. The seal assembly <NUM> thus helps to protect the spring <NUM>, extend its useful life, and ensuring proper operation of the tensioner <NUM>.

In the illustrated embodiment, the seal <NUM>/seal assembly <NUM> is concentrically/coaxially mounted relative to the bolt <NUM>/axis <NUM>. This arrangement helps to ensure that, under normal operating conditions, the seal <NUM> does not move in the radial direction relative to the seal counterface <NUM> whenever the arm <NUM> is pivoted relative to the spring case <NUM>. In particular, repeated radial movement of the seal <NUM> relative to the seal counterface <NUM> could create a sweeping action that could lead to the introduction of contaminants inside the seal assembly <NUM>, which could cause wear in the bushing <NUM> or other components, and could also cause wear in the seal <NUM> itself.

<FIG> illustrates the seal <NUM> in a particular arrangement in which the flange <NUM> of the seal <NUM> is positioned on the bottom side of the seal <NUM>, engaging the seal plate <NUM>. However, this configuration can be reversed such that the body <NUM> of the seal <NUM> is positioned adjacent to the seal plate <NUM>, and the flange <NUM> of the seal <NUM> is positioned at the top, engaging the end flange <NUM> of the spring case <NUM>. In this reversed configuration the seal assembly <NUM> can still accommodate axial and radial movement between the arm <NUM> and spring case <NUM> in all directions. Moreover, the seal <NUM> can be turned on its side in either direction thereof, such that the flange <NUM> faces either the outer cylindrical portion <NUM> of the spring case <NUM> or the radially outer flange <NUM> of the arm <NUM>, while still maintaining a proper seal and accommodating relative axial and radial movements between the arm <NUM> and spring case <NUM>. Thus, the seal <NUM> can be rotated <NUM>°, <NUM>°, or <NUM>° from its position shown in <FIG>.

<FIG> illustrates an alternate embodiment having a seal assembly <NUM>' similar to that of <FIG> and described above. The tensioner <NUM> of <FIG> is somewhat similar to that of <FIG>, but utilizes a pivot tube <NUM> formed as one piece with the spring case <NUM>, and the spring <NUM> is an expansion spring which unwinds as the tensioner <NUM> moves from its free arm to its nominal position. Moreover, the spring cap <NUM> has an inner tube portion <NUM> with a shorter axial length than that in the embodiment of <FIG>.

In the embodiment of <FIG> the seal <NUM> is positioned above (instead of below) the end flange <NUM> of the spring case <NUM>, and engages the underside of the connecting portion <NUM> of the arm <NUM>. In this manner, the underside of the connecting portion <NUM> acts as the seal counterface <NUM> that the seal <NUM> flexibly and sealingly engages, providing the same benefits as described above in the embodiment of the <FIG>. Moreover, the seal <NUM>, in this embodiment, is rotated <NUM>° from the position of the seal <NUM> shown in the embodiment of <FIG> such that the flange <NUM> is positioned on the top side of the seal <NUM>. The seal <NUM> in <FIG> (as well as the other embodiments described below and shown in <FIG> and <FIG>) can also be arranged in the various other configurations and orientations, and take the form of the various seals and utilize the same materials described above in the context of <FIG>.

Since the seal <NUM>, in the embodiment of <FIG>, is positioned on top of the end flange <NUM>, instead of the below the end flange <NUM> (as in the embodiment of <FIG>), the seal <NUM> will be compressed (instead of expand) when the arm <NUM> and spring case <NUM> move closer together (e.g. when the flange portion <NUM> of the bushing <NUM> wears). In this case, however, the seal <NUM>/flange <NUM> is simply compressed and retains the desired seal.

The embodiment of <FIG> also utilizes a supplemental, or secondary seal <NUM>. In this embodiment, the secondary seal is a V-ring seal <NUM> having a body portion <NUM>, flange <NUM> and gap <NUM>. The secondary seal <NUM> is sealingly positioned between the spring cap <NUM> and the arm <NUM>, in a groove <NUM> on the underside of the spring cap <NUM>. In the illustrated embodiment, the secondary seal <NUM> is positioned adjacent to the head of the fastener <NUM> (e.g., in one case, closer to the head of the fastener <NUM> than to the distal end). The secondary seal <NUM> of <FIG> can also be located in any of the four rotational positions described above for the primary seal.

The secondary seal <NUM> can have the same dynamic seal characteristics as the primary seal <NUM> described above. For example, as the spring bushing <NUM>, or flange portion <NUM> of the bushing <NUM>, wears, the axial gap between the arm <NUM> and spring case <NUM> may be reduced, thereby causing the arm <NUM> to move away from the spring cap <NUM>, and the secondary seal <NUM> expands (i.e. its gland area increases). Thus, it can be seen that the primary <NUM> and secondary <NUM> seals, in the embodiment of <FIG>, operate in tandem such that as one seal <NUM>/<NUM> expands, the other is compressed. However, it is also possible that the primary seal <NUM> can utilize the configuration/orientation shown in <FIG>, in which case the primary <NUM> and secondary <NUM> seals would expand/compress in the same manner.

The secondary seal <NUM> blocks external contaminants from reaching the bushing <NUM> through any gap between the spring cap <NUM> and the arm <NUM>. Thus the primary seal <NUM> prevents contaminants from reaching a first (upper) exposed end of the bushing <NUM>, and the secondary seal <NUM> prevents contaminants from reaching a second (lower) exposed end of the bushing <NUM>. The secondary seal <NUM> of <FIG> can also be utilized in the tensioner of <FIG>, or in the other designs disclosed herein.

<FIG> illustrates another tensioner <NUM> which is somewhat similar in operation and principle to those of <FIG> and <FIG>, but utilizes a lower-offset design. Moreover, rather than having portions of the arm <NUM> and spring case <NUM> nest or overlap significantly in the axial direction, the arm <NUM> and spring case <NUM> meet in a planar face-to-face contact area separated by a spring bushing or flange bushing <NUM>. The inner flange <NUM> of the arm <NUM> is positioned radially inside the spring <NUM>, adjacent to the pivot tube <NUM>. The tensioner <NUM> of <FIG> further includes a pivot bushing <NUM> between the arm <NUM> and the pivot tube <NUM>, and a damper bushing <NUM> positioned at an axial top surface thereof. A deflected arm plate, or cover <NUM>, is positioned on top of the damper bushing <NUM> to maintain the damper bushing <NUM> in place. In this embodiment, then, rather than having a single bushing <NUM> with three separate portions to provide three separate functions, three separate bushing <NUM>, <NUM>, <NUM> are provided, each bushing <NUM>, <NUM>, <NUM> providing a separate function.

The embodiment of <FIG> uses a seal system <NUM>" which is similar in appearance and function to the seal system <NUM>' disclosed in <FIG>. In particular, the seal <NUM> is positioned such that the body <NUM> is positioned adjacent to (and above) the end flange <NUM> of the spring case <NUM>, and the flange <NUM> of the seal <NUM> engages the arm <NUM>. However, in the embodiment of <FIG> the seal system <NUM>" is positioned at roughly/generally the axial midpoint of the tensioner <NUM> and positioned adjacent to the spring bushing <NUM> to fluidly isolate the spring bushing <NUM> and prevent contaminants from contacting the spring bushing <NUM>.

The embodiment of <FIG> also utilizes a secondary seal <NUM>', somewhat similar to the secondary seal <NUM> of <FIG>. However, the secondary seal <NUM>' of <FIG> is positioned between the arm <NUM> and the deflected arm plate <NUM>. Moreover, the secondary seal <NUM>' in <FIG> is shown rotated <NUM>° from the position of secondary seal <NUM> of <FIG>. However, the secondary seal <NUM>' of <FIG> can be located in either position. The secondary seal <NUM>' fluidly isolates and protects the damper bushing <NUM> from contaminants.

In the embodiment of <FIG>, when the spring bushing <NUM> wears, the primary seal <NUM> will be further compressed (i.e. its gland area will decrease). When the damper bushing <NUM> wears, the secondary seal <NUM>' will also be further compressed (i.e. its gland area will decrease).

<FIG> illustrates another tensioner <NUM> with a moderate offset and utilizing a flat spring <NUM>, instead of a spring with a round cross section as in <FIG>. In this embodiment the pivot tube <NUM> is formed as one piece with the spring case <NUM>. The tensioner of <FIG> <NUM> includes a bushing component <NUM> including both a cylindrical portion <NUM>, positioned between the arm <NUM> and the pivot tube <NUM>/spring case <NUM>, and a damper portion <NUM>, positioned between the deflected arm plate <NUM> and the arm <NUM>. The tensioner <NUM> also includes a flange portion bushing <NUM> positioned between the face-to-face contact area of the arm <NUM> and the spring case <NUM>, somewhat similar to the bushing <NUM> in the embodiment of <FIG>.

In this embodiment, the seal <NUM>‴ is positioned at a radially inner position between the arm <NUM> and spring case <NUM>, radially inside a seal stop <NUM> that is integral with the spring case <NUM>. In this particular embodiment, the flat spring <NUM> includes an anchor hook which is positioned externally of the spring case <NUM>, thereby making sealing of the spring case <NUM>/tenioner <NUM> difficult. Accordingly, in this case, the seal <NUM>‴ is positioned radially inwardly of the spring <NUM>, adjacent to the bushing <NUM>, and sealingly positioned between the arm <NUM> and spring case <NUM> to seal the bushing <NUM>.

The secondary seal <NUM>' is positioned between the arm <NUM> and the deflected arm plate <NUM>, similar to the secondary seal <NUM>' in the embodiment of <FIG>. However, in the embodiment of <FIG>, the secondary seal <NUM>' is positioned in a generally closed cavity and therefore can be located in any of the four radial positions referenced above. Thus, the primary <NUM>‴ and secondary <NUM>' seals of <FIG> seal the cylindrical portion <NUM> and damper bushing portions <NUM> to ensure proper operation of the tensioner <NUM>.

As can be seen, the various seals disclosed herein help to prevent contaminants from reaching various internal components of the tensioner, including in various cases the bushings or parts thereof, the spring, or other parts. Reducing the introduction of contaminants thereby helps to provide longer life and proper operation to the tensioner, which in turn extends the life and ensure proper operation of the belt system <NUM>.

Claim 1:
A tensioning system (<NUM>) comprising:
a spring case (<NUM>) having a pivot tube (<NUM>) and an outer cylindrical portion (<NUM>);
an arm (<NUM>) pivotally coupled to the spring case (<NUM>) to pivot relative to the spring case (<NUM>), the arm (<NUM>) having a pulley portion (18a) and a body portion (18b), wherein the body portion (18b) has a radially outer flange (<NUM>) and a radially inner flange (<NUM>), the radially inner flange (<NUM>) beaing seated within the spring case (<NUM>);
a spring (<NUM>) seated within the radially inner flange (<NUM>) of the arm (<NUM>) and operatively coupled to the arm (<NUM>) to bias the arm (<NUM>) relative to the spring case (<NUM>);
a bushing (<NUM>) positioned between the radially inner flange (<NUM>) of the arm (<NUM>) and the spring case (<NUM>); and
an annular lip seal (<NUM>) having a body portion (<NUM>) with a flexible flange (<NUM>) extending therefrom and a gap (<NUM>) between the body portion (<NUM>) and the flexible flange (<NUM>), wherein the annular lip seal (<NUM>) is seated below or above an end flange (<NUM>) of the spring case (<NUM>) and is positioned on a portion of a radially outer surface of the outer cylindrical portion (<NUM>) of the spring case (<NUM>) and is sealingly engaged between the radially outer flange (<NUM>) of the arm (<NUM>) and said radially outer surface of the spring case (<NUM>) and a connecting portion (<NUM>) of the arm (<NUM>) or a seal plate (<NUM>) coupled to the outer flange (<NUM>) of the arm (<NUM>), wherein the annular lip seal (<NUM>) is in compression in the axial direction in the assembled state and is optionally in radial tension;
wherein the annular lip seal is configured to expand or compress to maintain a seal between the arm (<NUM>) and the spring case (<NUM>) and to block external contaminants from reaching the bushing as wear of the bushing (<NUM>) occurs.