Patent Publication Number: US-2023138015-A1

Title: Shaft Seal, in Particular Radial Shaft Seal

Description:
BACKGROUND OF THE INVENTION 
     The invention concerns a shaft seal, in particular a radial shaft seal, with a seal element that comprises a seal section that under elastic deformation contacts the outer side of a mounting sleeve, and with a grease ring located on the mounting sleeve. 
     The invention concerns a method for installation of this shaft seal, in particular radial shaft seal. 
     Shaft seals are subjected to a seal-tightness test by means of an air leakage test after installation. It is determined thereby whether the required sealing action is ensured. Sometimes, the seal elements are not air-tight so that an air leakage test, despite correct installation, would cause an error message. For this reason, a grease is employed that is applied onto the seal section of the seal element before the shaft seal is pulled onto a mounting sleeve. The grease seals the region between the seal section and the shaft even when the seal element itself is not comprised of an air-tight material. At the customer, the shaft seal is pulled off the mounting sleeve onto the shaft. Since the seal grease is already located on the seal section, a new distribution of the applied grease at the seal section occurs when pushing the shaft seal onto the shaft. Due to this double distribution of the applied grease, there are again and again unfavorable distributions of the applied grease which has the result that such shaft seals, despite correct installation, are indicated as errors because they do not pass the air leakage test. 
     Therefore, it is the object of the invention to design the shaft seal in such a way that a reliable testing in respect to air passage is ensured. 
     SUMMARY OF THE INVENTION 
     This object is solved according to the invention in that the grease ring is applied axially adjacent to the free end of the seal section on the mounting sleeve. 
     This object is further solved by a method for installation of the disclosed shaft seal in which the shaft seal is pulled off the mounting sleeve and pushed onto the shaft, wherein the grease ring is applied axially adjacent to the free end of the seal section of the seal element onto the mounting sleeve, and wherein the grease ring and the seal section are pushed by a mounting tool onto the shaft and the seal section on the shaft is pushed in such a way onto the grease ring that the grease of the grease ring is distributed between the seal section and the shaft. 
     In the shaft seal according to the invention, the grease ring is not applied onto the seal section but axially adjacent to the free end of the seal section on the mounting sleeve. When therefore the shaft seal is pushed onto the mounting sleeve, there is no distribution of the grease yet that is applied only once the shaft seal has been pulled onto the mounting sleeve. Only once the shaft seal upon installation in an apparatus is pushed off the mounting sleeve onto the shaft, the seal section of the shaft seal moves onto the grease ring so that, upon displacement of the shaft seal on the shaft into the installation position, the grease is uniformly distributed below the seal section. In this way, in a simple manner it is achieved that the region between the seal section and the shaft is sealed properly by the grease and the subsequent air leakage test is passed even when at least the seal section itself is not air-tight. 
     Not only greases are to be understood as greases but also other media such as oils, resins or the like. Only for reasons of simplification, greases or grease rings is used herein. 
     The grease ring is applied in a preferred manner in such a way onto the mounting sleeve that it contacts the end face of the seal section. In this way, it is ensured that, upon displacement of the shaft seal on the shaft, the grease is distributed reliably and uniformly below the seal section. 
     For a reliable air leakage test, it is advantageous when the grease ring extends about the circumference of the mounting sleeve, i.e., forms a closed ring. Then, by displacement of the shaft seal on the shaft, the grease is uniformly distributed about the circumference of the shaft below the seal section. 
     The grease ring is positioned in a preferred embodiment in a radial plane of the mounting sleeve. This also contributes to the grease being uniformly distributed about the circumference during the displacement process of the shaft seal on the shaft. 
     In the method according to the invention, after pushing the shaft seal onto the mounting sleeve, the grease ring is applied axially adjacent to the free end of the seal section. For installation of the shaft seal, subsequently the shaft seal is pushed by means of a mounting tool off the mounting sleeve and onto the shaft. In doing so, the grease ring which is located axially adjacent to the free end of the seal section is first pushed onto the shaft prior to the seal section subsequently reaching the shaft. In this context, the seal section is pushed across the grease ring, which is already present on the shaft, so that, upon subsequent displacement of the shaft seal into the installation position, the grease is distributed uniformly between the seal section and the shaft. It is thus ensured that the subsequent air leakage test will be passed. 
     So that the seal section can reliably move onto the grease ring, the seal section in a preferred embodiment is elastically expanded when passing from the mounting sleeve onto the shaft. Since the grease ring in the push-on direction is located in front of the seal section of the shaft seal, in this manner the seal section is moved reliably onto the grease ring already present on the shaft so that the grease is uniformly distributed upon further displacement of the shaft seal. 
     The subject matter of the application results not only from the subject matter of the individual claims but also from all specifications and features disclosed in the drawings and the description. They are claimed as important to the invention, even if they are not subject matter of the claims, inasmuch as individually or in combination they are novel in relation to the prior art. 
     Further features of the invention result from the additional claims, the description, and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be explained in more detail with the aid of an embodiment illustrated in the drawings. 
         FIG.  1    shows in axial half section a shaft seal according to the invention and support unit. 
         FIG.  2    shows a first step for installation of the shaft seal in an apparatus. 
         FIG.  3    shows a second step for installation of the shaft seal in an apparatus. 
         FIG.  4    shows a third step for installation of the shaft seal in an apparatus. 
         FIG.  5    shows a fourth step for installation of the shaft seal in an apparatus. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The shaft seal described in the following is advantageously a radial shaft seal that is installed in an apparatus  1  ( FIG.  5   ). It has an installation opening  2  in which the shaft seal is seated. 
     The shaft seal has a carrier  3  which in axial section is L-shaped and comprises a cylindrical wall  4  that passes at a right angle into a radially inwardly extending bottom  5 . It has a central opening  6  in which or through which a shaft  7  is extending. 
     The outer side  8  of the bottom  5  is surrounded at least partially by an envelope  9  that is comprised of elastomeric material and attached in a suitable manner to the carrier  3 . 
     The envelope  9  in the region of the bottom  5  is advantageously embodied such that it extends across the rim of the opening  6  to the inner side  10  of the bottom  5 . 
     The envelope  9  at the outer side passes advantageously into a cover  11  that covers the wall  4  of the carrier  3  at least across a portion of its axial width. In the installation position illustrated in  FIG.  5   , the cover  11  forms the static sealing action of the shaft seal. Advantageously, the side of the cover  11  which is facing the wall of the installation opening  2  is provided with a corrugated profiling  12  that, when pressing the shaft seal into the installation opening  2 , is elastically deformed and ensures a proper static sealing action in this way. 
     Advantageously, the cover  11  also covers the free end face  13  of the wall  4  at least partially. The region  14  of the envelope  9  that covers the wall  5  at the inner side  10  has an outer side  15  at which the seal element  16  is fastened. In the embodiment, it is an annular seal disk that is comprised advantageously of PTFE and is elastically deformed in the radial inner region in the illustrated installation position. The seal element  16  has the radially extending fastening section  17  which is fastened at the outer side  15  of the region  14  of the envelope  9 . 
     The fastening section  17  of the seal element  16  is position preferably in a radial plane of the shaft seal and passes, steadily curved, into a seal section  18  that is elastically deformed in the installation position, surrounds the shaft  7 , and is contacting the shaft  7  under a radial force. The seal section  18  can be provided at its side facing the shaft  7  with a return conveying structure  19 . 
     The shaft seal is received prior to its installation in a support unit  20  ( FIG.  1   ). It is comprised of a mounting sleeve  21  and a protection cap  22 . The mounting sleeve  21  has a cylindrical wall  23  which at one end passes into a radially outwardly oriented annular flange  24  and at the other end passes into a radial bottom  25 . 
     The annular flange  24  extends to the level of the bottom  5  of the carrier  3  of the shaft seal which is axially contacting the annular flange  24 . 
     The bottom  25  of the mounting sleeve  21  is provided at its end face which is facing away from the annular flange  24  with a central recess  26 . Its rim  27  is advantageously embodied so as to widen conically. 
     The cylindrical outer side  28  of the wall  23  is expanded in the region of the bottom  27  in regard to the diameter. Advantageously, the cylindrical outer side  28  passes by a cone section  29  into a cylindrical section  30  that has a greater diameter than the outer side  28 . 
     The seal element  16  is positioned with its seal section  18  under radial pretension on the cylindrical outer side  28  of the mounting sleeve  21 . 
     The protection cap  22  has a conical wall  31  which contacts with its free end  32  the fastening section  17  of the seal element  16 . The wall  31  surrounds at a distance the wall  23  of the mounting sleeve  21 . 
     The conical wall  31  of the protection cap  22  passes into a radially extending bottom  33  which is provided at its side facing away from the mounting sleeve  21  with a circumferentially extending projection  34 . The bottom  33  of the protection cap  22  is designed in an exemplary fashion such that its inner side  35  facing the mounting sleeve  21  is positioned at the level of the end face  36  of the bottom  25  of the mounting sleeve  21 . 
     The mounting sleeve  21  and the protection cap  22  delimit an annular receiving space  37  in which the seal section  18  as well as most of the fastening section  17  of the seal element  16  are accommodated in a protective way. The remainder of the shaft seal projects past the mounting sleeve  21  and the protection cap  22 . 
     When the shaft seal is to be installed, a seal-tightness test by means of an air leakage test is performed. In this context, it is tested whether the shaft seal seals properly. For the leakage test, a grease  38  is used that, after pulling the shaft seal onto the mounting sleeve  21 , is applied immediately in front of the free end of the seal section  18  onto the outer side  28  of the wall  23 . The grease  38  is applied in front of the seal section  18  in an annular shape onto the outer wall side  28  ( FIG.  1   ). The grease  38  is located on the cylindrical outer wall section  28  and advantageously at a minimal distance away from the cone section  29 . During transport of the shaft seal, the protection cap  23  protects the grease  38  located on the mounting sleeve  21 . 
     For installation of the shaft seal in the apparatus  1 , first the protection cap  22  is removed that is gripped at the annular projection  34  by a corresponding mounting tool and can be easily axially removed ( FIG.  2   ). Now the grease ring  38  with the seal section  18  of the seal element  16  is exposed. 
     The grease  38  must reach the area below the seal section  18  when the air leakage test is performed. This is achieved in the subsequently disclosed manner upon removing the mounting sleeve  21  from the shaft seal. 
     By means of a mounting tool  39 , the installation of the shaft seal in the apparatus  1  is carried out. With the mounting tool  39 , the shaft seal is moved with the mounting sleeve  21  axially against the shaft  7  ( FIG.  3   ). The mounting tool  39  engages the part of the envelope  9  projecting past the mounting sleeve  21 . With the mounting tool  39 , the shaft seal with the mounting sleeve  21  is contacted at the end face of the shaft  7  that engages with its free end the recess  26 . 
     Upon further displacement with the mounting tool  39 , the shaft seal is pulled off the mounting sleeve  21  and axially pressed into the installation opening  2  of the apparatus  1 . The seal section  18  and the grease  38  positioned in front of it are moved across the cone section  29  of the mounting sleeve  21  so that the seal section  18  is radially expanded. The outer diameter of the cylindrical wall section  30  of the mounting sleeve  21  is larger than the outer diameter of the shaft  7  so that the seal section  18  reaches properly the shaft  7  ( FIG.  4   ). The grease  38  is pushed in this context by the seal section  18  past the cone section  29  and the cylindrical wall section  30  onto the shaft  7 . 
     As soon as the seal section  18  rests completely on the shaft  7 , the mounting sleeve  21  can be removed. With the mounting tool  39 , the shaft seal is pushed farther into the installation opening  2  of the apparatus  1  into its installation position. During this displacement process, the seal section  18  moves onto the grease ring  38  so that the latter is distributed below the seal section  18  ( FIG.  5   ). This distribution process is favored in that the outer diameter of the wall section  30  of the mounting sleeve  21  is greater than the outer diameter of the shaft  7 . This has the result that during the assembly process first the grease ring  38  reaches the shaft  7  while the seal section  18  is still located on the cylindrical wall section  30  of the mounting sleeve  21  ( FIG.  4   ). 
     Upon displacement of the seal section  18  by the mounting tool  39 , the seal section  18  moves onto of the grease ring  38  which has the result that the grease  38  is distributed uniformly between the shaft  7  and the seal section  18  when the seal section  18  is displaced on the shaft  7  into its installation position. 
     The grease  38  seals the region between the seal section  18  and the shaft  7  reliably so that the subsequent air leakage test is passed reliably. 
     Moreover, the grease  38  has the advantage that pressing the shaft seal into the installation opening  2  of the apparatus  1  and the running-in process of the seal section  18  are facilitated. 
     The described method is particularly advantageous when the seal element  16  is formed by a PTFE disk. It is not air-tight in the new state so that in case of an air leakage test, despite proper installation, an error message would be produced because the air would pass through between the seal section  18  and the shaft  7 . Due to the described method, the grease  38  uniformly moves below the seal section  18  so that the region between the seal section  18  and the shaft  7  is properly sealed against air passage during the air leakage test. 
     The described configuration and assembly can be used, of course, also for seal elements that are comprised of other materials, for example, of the rubber-type material. 
     As grease  38 , the greases are conceivable which are conventionally used in such air leakage tests, for example, greases with rheopex or thixotropic properties. In principle, in addition to greases, also other suitable media are conceivable, for example, oils, resins or the like. These other media can also have rheopex or thixotropic properties. 
     In the illustrated embodiment, the radial shaft seal is provided additionally with a dust lip  40  which however is not mandatory. It is advantageously formed as one piece together with the envelope  9  and surrounds the shaft  7  at a minimal radial distance. The dust lip  40  is engaged across during transport of the shaft seal by the radial flange  24  of the mounting sleeve  21  and is thus protected ( FIG.  1   ).