Abstract:
A self-adjusting seal for sealing a joint. The joint includes a support member, a mis-alignable component, and a changeable gap between the support member and the mis-alignable component. The seal includes a first part having a generally annular configuration formed of a resiliently crushable material and defining a planar outer seal face to statically seal to the support member and a first seal part opening extending therethrough. A second seal part axially adjoins the first part. The second seal part has a generally annular configuration formed of a rigid material and a second seal part opening extending therethrough in axial alignment with the first seal part opening. The first and second seal part openings define a non-rotation feature to prevent rotation of the seal on the support member, the second seal part defining a planer inner seal face configured to dynamically and sealingly interface with the mis-alignable component.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to seals and, more particularly, to debris seals for joints such as pinned joints. 
       BACKGROUND 
       [0002]    The operation of machinery in dusty environments can present challenges. One such challenge is protection of machine bearings from effects of dust and debris. Off-highway trucks, for example, are especially susceptible to bearing contamination due to the presence of high concentrations of dirt, water, and other contaminants in the working environment of the trucks. 
         [0003]    One bearing type that is susceptible to contamination is the bearing arrangement located in the pinned joints attaching struts and similar components to the truck frame. One reason for this vulnerability is that the strut connects to the frame with an open structure that permits movement of the strut in the joint. One such structure includes a spherical-type bearing. 
         [0004]    Spherical-type bearings or joints are commonly used in suspension systems to couple a shock or strut to a part of the machine, such as a control arm, in a fashion that allows the shock or strut to pivot or rotate around one or more axes relative to the control arm. In order to function properly over their service life, spherical bearings may be lubricated and efforts are made to minimize the amount of debris that enters the bearing and collects on internal surfaces, particularly those internal bearing surfaces that rub against one another as the bearing operates. Some spherical bearings types do not require lubrication. In those bearing types, preventing debris from coming into contact with internal bearing and joint surfaces becomes even more important because there is no fluid to contain and remove the debris. 
         [0005]    To maintain the operational state of the bearing and minimize the amount of debris that enters the bearing, various attempts have been made in the past to seal the bearing. Some past solutions include bearing seals that entail seating a relatively small lip seal in the outer race of the bearing so that the seal rides on the ball or inner race as the bearing operates. However, in order to seat within the outer race, the lip seal must be relatively small, which tends to reduce the effectiveness of the seal. Moreover, such seals tend to fall off the edge of the ball or inner race and become crushed when the pin of the bearing moves into a maximum rotational position. 
         [0006]    Other past solutions provide a type of flexible covering or boot over the entire bearing. Although such a covering may reduce the amount of debris that enters the bearing, it generally does effectively retain the lubrication within the internal structures of the bearing. Moreover, such a covering may not be appropriate for certain applications and may make visual inspections, repair, and routine maintenance of the bearing more difficult. In addition, in order to properly seal the bearing, such coverings or boots are often assembled tightly around one or more parts of the bearing and/or the components coupled to the bearing. If the different components to which the boot is coupled move relative to one another, particularly if they rotate relative to one another, the tight fit of the boot against each component causes different portions of the boot to move relative to one another, which may cause the boot to twist or wrap up and become damaged. 
         [0007]    In pinned joints with spherical-type bearings, the strut can move in the joint along the pitch direction, where the strut pivots in a plane normal to the axis of the pin. The strut may also move in the yaw and roll directions in addition to pitch. The misalignment of parts produced by movement in the yaw and roll directions, in particular, requires the provision of a changeable gap between the strut and the support structure to which it is attached. It can be difficult to prevent contamination from entering through the gap, into the joint, and into a bearing supporting the strut on the frame. 
         [0008]    It will be appreciated that this background description has been created by the inventors to aid the reader, and is not to be taken as an indication that any of the indicated problems were themselves appreciated in the art. While the described principles can, in some respects and embodiments, alleviate the problems inherent in other systems, it will be appreciated that the scope of the protected innovation is defined by the attached claims, and not by the ability of any disclosed feature to solve any specific problem noted herein. 
       SUMMARY 
       [0009]    In an embodiment, the present disclosure describes a self-adjusting seal for sealing a joint. The joint includes a support member, a mis-alignable component, and a changeable gap between the support member and the mis-alignable component. The seal includes a first part having a generally annular configuration formed of a resiliently crushable material and defining a planar outer seal face to statically seal to the support member and a first seal part opening extending therethrough. A second seal part axially adjoins the first part. The second seal part has a generally annular configuration formed of a rigid material and a second seal part opening extending therethrough in axial alignment with the first seal part opening. The first and second seal part openings define a non-rotation feature to prevent rotation of the seal on the support member, the second seal part defining a planer inner seal face configured to dynamically and sealingly interface with the mis-alignable component. 
         [0010]    Another aspect of the disclosure provides a joint for a machine, including a support structure formed on the machine. The support structure includes a boss. A pin has a longitudinal axis and is disposed on the support structure. A spherical bearing assembly is disposed about the pin. A mis-alignable component is movably disposed on the spherical bearing, the mis-alignable component defining at least one changeable gap with the support structure and a self-adjusting seal is mounted on the support structure and about the boss to seal the changeable gap. The seal includes a first part having a generally annular configuration formed of a resiliently crushable material and defining a planar outer seal face to statically seal to the support member and a first seal part opening extending therethrough. A second seal part axially adjoins the first part. The second seal part has a generally annular configuration formed of a rigid material and a second seal part opening extending therethrough in axial alignment with the first seal part opening. The first and second seal part openings define a non-rotation feature to prevent rotation of the seal on the support member, the second seal part defining a planer inner seal face configured to dynamically and sealingly interface with the mis-alignable component. 
         [0011]    Other aspects of the disclosure provide wherein the first seal part may be formed of open cell polyurethane. The second seal part may be formed of a metal material. The inner seal face of the second seal part may include a low-friction material. The low-friction material may be PTFE. The second seal part may include an inner layer of rigid material and an outer layer of PTFE axially adjoining the inner layer. The second seal part may be formed of a composite material. The composite material may be fiber reinforced plastic. The PTFE may be one of a layer of low-friction material and embedded in the composite material. The non-rotation feature may include a rounded portion and a rectangular portion extending radially from the rounded portion. The first and second seal parts each may include an outer periphery and a flat formed on the outer periphery, wherein the flat of the first seal part is aligned with the flat of the second seal part. The self-adjusting seal may be disposed between the support structure and the mis-alignable component in a compressed state to permit the seal to expand to fill the changeable gap when the changeable gap widens. The self-adjusting seal may be axially compressed about 5 percent to about 20 percent. 
         [0012]    Further and alternative aspects and features of the disclosed principles will be appreciated from the following detailed description and the accompanying drawings. As will be appreciated, the principles related to seals for a pinned joint as disclosed herein are capable of being carried out in other and different embodiments, and capable of modification in various respects. Accordingly, it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and do not restrict the scope of the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a portion of a perspective view of an exemplary machine including a pinned joint with a strut attached to a support structure of a machine frame. 
           [0014]      FIG. 2A  is a perspective view of a first embodiment of a seal for the pinned joint of  FIG. 1 . 
           [0015]      FIG. 2B  is a cross section view of the seal of  FIG. 2A . 
           [0016]      FIG. 3A  is a perspective view of a second embodiment of a seal for the pinned joint of  FIG. 1 . 
           [0017]      FIG. 3B  is a cross section view of the seal of  FIG. 3A . 
           [0018]      FIG. 4  is a perspective view of a seal disposed on a support structure of the machine frame. 
           [0019]      FIG. 5  is a cross section view of the pinned joint of  FIG. 1  and the seal of  FIG. 2  with the strut aligned with the pin of the joint. 
           [0020]      FIG. 6  is a bottom view of the pinned joint of  FIG. 1  and the seal of  FIG. 2  wherein the strut is misaligned with the pin of the joint illustrating the conformance of the seal to the misalignment. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]      FIG. 1  is a portion of an exemplary machine  20  including a pinned joint  22  with a strut  24 , or a similar device, attached to a support structure  26  of the machine. The support structure  26  may be formed on the machine frame (not shown) or a part  28  of the machine. In the illustrated embodiment, the part  28  of the machine illustrated herein houses the running gear portions of the machine, but the sealing arrangements shown herein have additional applications in different portions of the machine, or in different machines. 
         [0022]    The machine  20  may be any machine, such as a truck, that includes a strut  24 , or the like, connected at one end to the support structure  26  and at the other end to the frame (not shown) of the machine. The strut  24  is a dynamic component, i.e., a component that is movable during operation relative to the support structure  26 . 
         [0023]    The joint  22  includes the support structure  26 , which may be a clevis-shaped joint with double ears, and an attached strut  24 , which may also be any mis-alignable, dynamic component. The strut  24  may be a conventional strut or a shock absorber. While a strut is shown to provide context to the structure of the joint  22  and the components associated with the joint, it will be understood that any mis-alignable part could be substituted therefor, such as a control arm, a suspension component, a steering mechanism component, a stabilizer, a bar, and the like. 
         [0024]    A pair of seals  34 , according to embodiments of the disclosure, is provided in the joint  22 . Each seal of the pair of seals is disposed respectively on opposite sides of the strut  24  to seal between the support structure  26  and strut  24 . The joint  22  is shown with the lower part  30  of the strut  24  connected to the support structure  26 . It will be understood that the upper part of the strut  24  (not shown) may be attached to the machine  20  in a similar fashion. The strut  24  is held in the support structure  26  by a pin  32 . The pin  32  has a pin axis “A” that extends along a longitudinal dimension of the pin  32 . 
         [0025]    The construction of the joint permits motion between the strut  24  and the support structure  26 . Specifically, the strut  24  is pivotally mounted on a spherical bearing (see  FIG. 5 ), which is disposed about pin  32  to permit the strut to rotate about axis A. The rotation axis of the spherical bearing around the pin axis A is denoted as the “X” axis. An axis along a longitudinal dimension of the strut is denoted as the “B” axis, as shown in  FIG. 1 . The motion about the X axis may be considered a pitch motion, which is in a plane normal to the X axis. The strut  24  may also twist about or deviate from the strut axis “B” to produce either a roll motion about the B axis or a yaw motion out of the pitch motion plane. When the strut  24  rotates about or deviates from the B axis, the axis of the bore (not shown) of the lower part  30  of the strut  24  becomes misaligned with the axis A of the pin  32 . The misalignment causes a difference in the alignment and gap between the strut lower part  30  and the support structure  26  of the joint  22 . The seal  34  adapts or self-adjusts to the misalignment to reject the entry of contamination in the misaligned state. 
         [0026]      FIG. 2  shows a first embodiment of a seal  34  that accommodates the misalignment of the strut lower part  30  and the support structure  26  of the joint  22 , to maintain a sealing engagement between the strut lower part and the support structure. The seal  34  includes two main parts: a first seal part  36 , which is elastomeric, compressible and generally annularly-shaped, and a second seal part  38 , which is attached to the first seal part. The second seal part  38  is less compressible than the first seal part  36  and is similar in shape to the first seal part. The first seal part  36  operates statically, i.e., the first seal part  36  presents a non-dynamic interface. The second seal part  38  is designed to operate dynamically, which is meant herein to indicate an operating condition of the seal part in which the second seal part  38  presents a dynamic interface that permits relative movement of a part in contact with the second seal part  38 . 
         [0027]    The first seal part  36  of the seal  34  is generally annular and includes a first seal part opening  40  formed axially therethrough that has a non-rotation feature  42 . The non-rotation feature  42  may have a keyhole configuration with a rounded portion  44 , one side of which forms a rectangular extension  46  of the rounded portion. 
         [0028]    The first seal part  36  is formed of a resiliently crushable material. The resiliently crushable material may be a compressible elastomeric material, which may be open-cell foam or semi-open cell foam material. One example of a suitable compressible elastomeric material is polyurethane having a density of about 300 to 650 kg/m 3 . 
         [0029]    The outer face  48  of the first seal part  36  is flat or planar and may include a counterbore  50  that has a shape similar to the non-rotation feature  42 , but with a greater diameter. The outer periphery  52  of the first seal part  36  may include a flat  54 , which cooperates with the non-rotation feature  42  to orient the seal  34  by cooperative engagement with corresponding structures (see  FIG. 4 ) on the support structure  26 . 
         [0030]    The second seal part  38  of the seal  34  is formed of a harder material that is relatively less flexible and less compressible than the material that makes up the first seal part  36 . For example, the second seal part  38  may be formed of a metal such as steel, or like materials, or a composite material such as fiberglass, glass filled nylon, carbon reinforced plastic, and the like. The second seal part  38  includes an inner face  56  that is flat or planar and is at least partially made from low friction materials, includes low-friction coatings, or is shaped with a smooth surface finish to provide relatively low friction properties. One embodiment of an inner face  56  with low friction properties can be provided by forming a layer or coating of a low friction material, such as PTFE, on the inner face, or providing the second seal part  38  with an effective amount of embedded PTFE. Embedding the PTFE can be provided in a cloth matrix added to the composite version, such as a layer of scrim. Any suitable low friction substance is contemplated. 
         [0031]    The shape of the second seal part  38  is similar to the first seal part  36  in that it is generally annular with a generally rounded periphery  58  that has a common extent or boundary with the outer periphery  52  of the first seal part. The second seal part  38  has a second seal part central opening  60  in the shape of a keyhole similar to that of the non-rotation feature  42  of the first seal part  36 . The second seal part  38  forms a central opening  60 , which may have a greater diameter than the corresponding non-rotation feature  42  of the first seal part. In an installed configuration, each seal  34  is oriented such that the outer face  48  of the first seal part is adjacent to the support structure, and the inner face  56  of the second seal part  38  is adjacent the strut  24 . 
         [0032]    In operation, the first seal part  36  of the seal  34  compresses when a pressure increase on the part that results from the strut  24  becomes misaligned relative to the support structure  26 , especially in areas having a relatively smaller gap, i.e., in areas that become pinched, which includes areas on the top left and bottom right in the orientation of structures shown in  FIG. 6 . Conversely, the seal  34  expands in response to a reduction in pressure from the strut in areas of a larger gap, or areas that are pulled apart, as also shown in  FIG. 6 . The second seal part  38  of the seal  34  tends to stay aligned and in contact with the strut  24  regardless of alignment of the strut and the changeable gap and permits the strut to pivot about pin  32  easily due to the low friction provided between these components, as described above. 
         [0033]    During operation, the seal  34  can compress and expand when it is installed in a pre-compressed state. For example, the seal  34  can be installed when the seal is compressed or pre-crushed by nine (9) or more millimeters (mm). The pre-compression of the elastomeric or elastic seal material permits the seal material to elastically expand and accommodate a change in the space between the strut  24  and the support structure  26  by about 7 millimeters. In other words, the seal  34  can be compressed about 30-40 percent (%) installed, so it can elastically adapt to changes in the alignment of the strut  24  in the support structure  26 . 
         [0034]      FIGS. 3A and 3B  provide a seal  134  similar to the seal  34  described in  2 A and  2 B, but with a dual layer, second seal part  138  added to the seal. In particular, the seal  134  includes two main parts: a first seal part  136 , which is elastomeric, compressible, and generally annular, and a second seal part  138 , which is attached to the first seal part. The second seal part  138  is less compressible and is similar in shape to the first seal part  136 . 
         [0035]    The first seal part  136  of the seal  134  is generally annular and includes a first seal part opening  140  formed therethrough that has a non-rotation feature  142 . The non-rotation feature  142  may have a keyhole configuration with a rounded portion  144 , one side of which is a rectangular extension  146  of the rounded portion, but other shapes can be used. 
         [0036]    The first seal part  136  is formed of a compressible elastomeric material, which may be open-cell foam or semi-open cell foam material. One example of a suitable compressible elastomeric material is polyurethane having a density of about 300 to 650 kg/m 3 . 
         [0037]    The outer face  148  of the first seal part  136  may include a counterbore  150  that has a shape similar to the non-rotation feature  142 , and a greater diameter than the corresponding internal opening. The outer periphery  152  of the first seal part  136  may include a flat  154  that cooperates with the non-rotation feature  142  to orient the seal  134  by cooperative engagement with corresponding structures (see  FIG. 4 ) on the support structure  126 . 
         [0038]    The second seal part  138  of the seal  134  is formed of two layers of material. The inner layer  162  is made or formed from a harder material that is less flexible than the first seal part  136 . For example, the inner layer or support portion  162  of the second seal part  138  may be formed of a metal such as steel, or like materials, or a composite material such as fiberglass, glass filled nylon, carbon reinforced plastic, and the like. The outer layer  164  of the second seal part  38  includes an inner face  156  that may be formed of, or at least include a portion or a coating formed using a low friction material. One embodiment of inner face  156  includes a low friction material, such as PTFE. Any suitable low friction substance is contemplated. 
         [0039]    The shape of the second seal part  138  is similar to the shape of the first seal part  136  in that it is generally annular with a generally rounded periphery  158  that has a common extent or boundary with the outer periphery  152  of the first seal part  136 . The second seal part  138  has a second seal part central opening  160  that is formed in the shape of a keyhole that corresponds to the shape of the non-rotation feature  142  of the first seal part  136 . The second seal part central opening  160  may be of a greater diameter than the non-rotation feature  142  of the first seal part. In an installed configuration, each seal  134  is oriented such that the outer face  148  of the first seal part is adjacent the support structure and the inner face  156  of the second seal part  138  is adjacent the strut  24 . 
         [0040]      FIG. 4  shows part of the support structure  26 , i.e., one ear of a clevis type structure, with a seal  34  in position. Specifically, the support structure  26  includes a boss  66  attached to the support structure. The boss  66  includes a bore  68  formed therethrough. The bore  68  is sized and oriented to receive the pin  32  (see  FIG. 1  and  FIG. 5 ). The boss  66  includes a lug  70 . The lug  70  can be configured to limit the maximum misalignment of the strut  24 . 
         [0041]    The seal  34  fits around the boss  66  and lug  70  with the rounded portion  44  of the first seal part opening  40  positioned around the boss and the non-rotation feature  42  positioned over the lug  70 . The first seal part  36  of the seal  34  is positioned adjacent the support structure  26  and the second seal part  38  of the seal is positioned such that it may be brought into contact with a strut  24 . It will be understood that the thickness of the seal  34  can be greater than the thickness of the boss  66  and, therefore, stands proud of the boss by a predefined distance or height. The structure of the support structure  26  illustrated herein requires a corresponding, matching second ear of a clevis type structure provided with a corresponding seal  34  to provide the sealing of the entire joint  22  (see  FIG. 5 ). 
         [0042]      FIG. 5  shows the joint  22 , with the seals  34 , strut  24 , support structure  26 , and associated elements in cross section. The joint  22  includes a spherical bearing assembly  72  disposed within the lower part  30  of the strut  24 , and is mounted about the pin  32  to moveably support the strut and retain the same in a centered position within, and also in engaged relation with, the support structure  26 . The spherical bearing assembly  72  includes a convex portion  74  disposed on the pin  32 , and a concave portion  76  movably disposed about the convex portion and adjacent the strut lower part  30 . 
         [0043]    Seals  34  are sealingly interposed between the support structure  26  and the strut lower part  30 . The seals  34  are kept in abutting, sealing contact with the spherical bearing assembly  72 . The first seal part  36  of each seal  34  is adjacent a support structure  26  to provide the static interface therebetween. The second seal part  38  of each seal  34  is adjacent the strut  24  to provide a dynamic interface therebetween. 
         [0044]    Both the strut lower part  30  and pin  32  share the same axis A in  FIG. 5 . The seals  34  can react to misalignment of the strut  24  in the joint  22  when the axis of the strut becomes misaligned with the axis of the pin  32 . While the pin  32  is held captive in the support structure  26 , the strut  24  can move relative to the pin  32 . One example of misalignment is illustrated in  FIG. 6 . 
         [0045]    In  FIG. 6 , the axis of the pin (not shown), which is also the axis of the pinned joint  22 , is represented by line AP. The axis of the strut  24  lower end  30  is represented by line AS. In the condition shown, the axis AS is misaligned with the axis AP, to illustrate one exemplary operating condition. In this operating condition, Therefore, the seals  34 A,  34 B have a changed configuration to accommodate and maintain a sealing engagement between the strut  24  lower end  30  and the support structure  26 , such that they continue to discourage the entry of contaminants into the interior of the joint  22  despite the misalignment of the strut  24 . In particular, the strut  24  lower part  30  is twisted (in the figure) in the counterclockwise direction. Accordingly, the top (in the figure) of seal  34 A is relatively more compressed and the bottom of seal  34 A is relatively less compressed compared to an aligned state of the strut  24  in the joint  22 . In addition, the top (in the figure) of seal  34 B is relatively less compressed and the bottom of seal  34 B is relatively more compressed compared to an aligned state of the strut  24  in the joint  22 . 
       INDUSTRIAL APPLICABILITY 
       [0046]    The present disclosure is applicable to many machines, for example, off-highway trucks, which are commonly used in construction sites, mines and quarries. Typically, such machines employ a set of struts or shock absorbers attached to a joint including a support structure on the machine. The joint is designed to permit some movement of the strut. The seals disclosed herein are adaptable to seal the joint and protect interior elements of the joint, such as non-lubricated bearings, from contaminants. 
         [0047]    Although the disclosed embodiments have been described with reference to a machine with struts, the disclosed embodiments are applicable to any machine having a mis-alignable component attached thereto and the need to exclude debris from a bearing or bushing that supports the mis-alignable component. 
         [0048]    It will be appreciated that the foregoing description provides examples of the disclosed devices. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated. 
         [0049]    Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. 
         [0050]    Accordingly, this disclosure includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.