Abstract:
The invention relates to a rolling boot ( 26 ) and to a rolling boot assembly including such a rolling boot and two attaching parts. The rolling boot ( 26 ) comprises a first axially flexible portion ( 38 ) having a first radially outer collar ( 27 ), a second axially flexible portion ( 39 ) having a second radially outer collar ( 28 ), and an approximately cylindrical connecting portion ( 40 ) which adjoins the two portions ( 38, 39 ) on the radial inside. The rolling boot assembly is provided with a first attaching part ( 24 ) comprising a fixing portion ( 34 ) which opens towards the second portion and which, from the outside, continuously approaches the first portion ( 38 ) of the rolling boot ( 26 ) in the direction of the first collar ( 27 ), as well with a second attaching part ( 25 ) comprising a fixing portion ( 37 ) which opens towards the first portion ( 38 ) and which approaches the second portion ( 39 ) in the direction of the second collar ( 28 ).

Description:
TECHNICAL FIELD  
         [0001]    The invention relates to a rolling boot and to a rolling boot assembly for sealing a plunging unit with a long plunge or for sealing a plunging joint.  
         BACKGROUND OF THE INVENTION  
         [0002]    U.S. Pat. No. 6,306,045 discloses a plunging unit which comprises a universal joint with an outer part, an inner part and means for transmitting torque between the outer part and inner part, as well as a journal firmly connected to the inner part and an axially displaceable shaft connected in a rotationally fast way relative to the journal by means of rolling contact members.  
           [0003]    For sealing purposes, a convoluted boot is provided which comprises a first collar at the joint end, a second collar at the shaft end and a wall which connects the two collars and comprises folds. The first collar of the convoluted boot is secured by a first attaching part to the outer part of the universal joint, and the second collar of the convoluted boot is secured to the sleeve of the plunging assembly. The convoluted boot prevents dirt from entering the joint and plunging space, and prevents lubricant from leaving the joint and plunging space.  
           [0004]    U.S. Pat. No. 6,426,033 discloses a rolling boot made of a thermoplastic elastomer for sealing a universal joint. The rolling boot comprises a first collar with a larger diameter to be secured to an outer joint part of the universal joint and a second collar with a smaller diameter to be secured to a shaft firmly connected to the inner part of the universal joint, as well as a wall in the shape of half a torus for connecting the collars. The rolling boot is produced from a thermoplastic elastomer by injection molding or blow molding.  
           [0005]    Using convoluted boots made of a thermoplastic material for sealing the above-mentioned plunging units or plunging joints, especially when such units or joints are used in propeller shafts, is problematical in that the high rotational speeds lead to failure of the convoluted boot. Rolling boots, on the other hand, made of rubber are able to withstand the high rotational speeds, but they are not suitable for compensating for long plunging distances.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention provides a rolling boot and a rolling boot assembly for sealing a plunging unit or a plunging joint with a long plunge. The rolling boot/rolling boot assembly is very wear-resistant, even at high rotational speeds.  
           [0007]    In one embodiment, a rolling boot with a first axially flexible portion comprising a first radially outer collar, a second axially flexible portion comprising a second radially outer collar, and an approximately cylindrical connecting portion which adjoins the two portions on the radial inside of the two portions is provided. One advantage of this embodiment is that the rolling boot, by means of the two axially flexible portions, is able to compensate for axial displacements of the attaching parts to be attached to the two collars. Because rolling boots are made of a resilient rubber, they are wear-resistant, even at high rotational speeds. As a result, even if the plunging unit or the plunging joint is in operation for a long period of time, the rolling boot ensures that the lubricant cannot escape from the sealed space and that dirt cannot enter the space.  
           [0008]    According to a further embodiment of the invention, the connecting portion is provided with a portion. In this way, it is ensured that at high rotational speeds of the plunging unit or of the plunging joint, such as occurs in, propeller shafts, the rolling boot in the region of the connecting portion is held radially inward and does not bulge outward. The reinforcing portion can be substantially centered between the two collars, as a result of which the rolling boot acquires a greater degree of stability when rotating. In another embodiment, the reinforced portion is provided in the form of an external sleeve or internal sleeve. Alternatively, the reinforced portion can also be integrated into the wall of the connecting portion, for instance by vulcanising in a fiber or fabric sleeve. Ribs or naps can also be formed on the inside of the sleeve to protect the sleeve against chafing.  
           [0009]    According to another embodiment, the connecting portion is axially displaceable relative to a journal positioned therein. This is advantageous in that, when the collars are axially displaced relative to one another, the connecting portion of the rolling boot is able to move freely and thus is able to assume the position with the least amount of stress. Alternatively, the connecting portion can also be axially secured by the reinforcing portion on a journal positioned in the connecting portion. In this way, the connecting portion is held in an axially defined position, which can be advantageous, especially in plunging units with a shorter plunge.  
           [0010]    According to a further embodiment of the invention, the first portion and the second portion of the rolling boot are axially open towards one another in an annular-shell-shaped way. In this way, it is ensured that the wall of the entire rolling boot is curved in one sense only, while at the same time permitting the two collars to be axially displaceable relative to one another.  
           [0011]    According to an even further embodiment of the invention, the diameter of the first collar is greater than the diameter of the second collar, and the second collar can be inserted into the first portion. With a given length of a plunging unit or plunging joint to be attached, there is thus achieved a maximum axial plunging capacity of the rolling boot. In an advantageous embodiment, the smallest radius of curvature of the first portion in a longitudinal section is greater than the smallest radius of curvature of the second portion in a longitudinal section.  
           [0012]    The present invention also provides a rolling boot assembly having a rolling boot with a first axially flexible portion comprising a first radially outer collar, a second axially flexible portion comprising a second radially outer collar and an approximately cylindrical connecting portion which adjoins the two portions on the radial inside of the two portions. The assembly also includes two attaching parts, wherein a first attaching part comprises a structural portion which is open towards the second portion of the rolling boot, which, from the outside, tangentially approaches the first portion of the rolling boot in the direction towards the first collar, and which serves to receive the first portion of the rolling boot. The structural portion can be cylindrical.  
           [0013]    The advantage of this rolling boot assembly with two attaching parts is that the rolling boot can simply be attached to two opposed attaching parts of a plunging unit. The first and the second attaching parts can be formed out of plate metal. By means of a cylindrical or conically widening structural portion of the first attaching part, the first portion of the rolling boot can be provided with stability and guidance, as a result of which the rolling boot is prevented from bulging out when rotating. The first collar of the rolling boot can be provided in the form of a bead which engages a correspondingly designed crimping of the first attaching part. In this way, the rolling boot is securely connected to the first attaching part across the entire circumference.  
           [0014]    In one embodiment, the second attaching part comprises a structural portion which is open towards the first portion of the rolling boot and which, from the outside, tangentially approaches the second portion of the rolling boot and serves to receive the second portion of the rolling boot. The structural portion can be cylindrical. In this way, in the plunged condition of the plunging unit, the second portion of the rolling boot is securely held in a defined position without coming into contact with the opposed first portion of the rolling boot. When the rolling boot assembly is extended, the second portion of the rolling boot is rolled out along an inner journal. The second collar of the rolling boot can be provided in the form of a bead which engages a correspondingly designed crimping at the attaching part end which is closer to the first portion. In this way, the rolling boot is securely connected to the second attaching part across the entire circumference.  
           [0015]    According to a further embodiment of the invention, the greatest outer diameter at the open structural portion of the second attaching part is smaller than the smallest inner diameter at the open structural portion of the first attaching part and, when the attaching parts are articulated relative to one another up to a maximum operating angle, there still exists a radial gap between the first attaching part and the second attaching part in the region where they are closest to each other. In this way, even in the plunged condition of the plunging unit, and even if the two attaching parts at least partially axially overlap, the joint to be attached can be articulated without the two attaching parts contacting one another or becoming damaged. Because of the overlap of the two attaching parts, the length of a journal positioned in the rolling boot can be reduced to a minimum, which has a positive effect on the critical shaft speed.  
           [0016]    A further advantageous assembly comprises at least one plunging assembly including a sleeve with outer grooves, a journal with inner grooves and balls guided in pairs of outer grooves and inner grooves, as well as a rolling boot assembly according to any one of the above embodiments, wherein the second attaching part is connected to the sleeve of the plunging assembly and wherein the first attaching part is at least indirectly connected to the journal.  
           [0017]    An advantage of the assembly is that the rolling boot is able to compensate for axial plunging paths even directly between the sleeve and the journal, and even at high rotational speeds the assembly features good wear properties.  
           [0018]    A still further advantageous assembly comprises at least one constant velocity joint including an outer part having outer tracks, an inner part having inner tracks and being connected to a journal, and torque transmitting balls or rollers, as well as a rolling boot assembly according to any one of the above embodiments, wherein the first attaching part is connected to the outer part of the constant velocity joint and wherein the second attaching part is at least indirectly connected to the journal.  
           [0019]    This embodiment permits the rolling boot to compensate for axial displacement paths even directly between the outer part of the joint and the journal, with the rolling boot comprising advantageous wear properties even at high rotational speeds.  
           [0020]    According to a further embodiment of the invention, the journal of the plunging assembly is directly connected to the inner part of the constant velocity joint. The constant velocity joint can be provided in the form of a fixed ball joint. The convoluted boot extends over the space between the outer part of the joint and the sleeve of the plunging assembly.  
           [0021]    Other advantages and features of the invention will also become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention.  
         [0023]    In the drawings:  
         [0024]    [0024]FIG. 1 is a longitudinal section through a plunging assembly with a rolling boot assembly.  
         [0025]    [0025]FIG. 2 shows an axially shortened plunging assembly according to FIG. 1:  
         [0026]    (A) with an aligned universal joint  
         [0027]    (B) with an articulated universal joint.  
         [0028]    [0028]FIG. 3 shows an axially extended plunging assembly according to FIG. 1:  
         [0029]    (A) with an aligned universal joint  
         [0030]    (B) with an articulated universal joint. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    FIGS.  1  to  3  will be described jointly below. They show a plunging assembly  1  which forms part of a CV-jointed driveshaft for the driveline of a motor vehicle. The plunging assembly  1  is connected to a constant velocity joint  2  provided in the form of a fixed joint. Other types of constant velocity joints could also be used. The plunging assembly  1  comprises a journal  3 , a sleeve  4  and torque transmitting balls  15  which are held in a cage  16 .  
         [0032]    The journal  3  is a hollow journal and at its end facing away from the constant velocity joint  2 , it comprises inner grooves  11  which extend parallel to the longitudinal axis X. A radial thickening  13  is formed on the end of the inner grooves  11  facing the joint. In the inner grooves  11  there is an axially displaceable held cage unit  14  which, per inner groove, comprises a plurality of balls  15  arranged one behind the other in an annular cage  16  holding the balls  15 .  
         [0033]    The sleeve  4  comprises outer grooves  12  which are circumferentially distributed at the joint end; they extend parallel to the longitudinal axis X and are arranged opposite the inner grooves  11  of the journal  3 . Each pair of radially opposed grooves  11 ,  12  is engaged by a plurality of balls  15  which transmit torque between the sleeve  4  and the journal  3 . The rolling path of the cage unit  14  relative to the journal  3  is delimited at the joint end by the radial thickening  13  of the journal  3 , and at the shaft end by a radial recess  17  of the sleeve  4  which serves as a stop for the cage  16  and the balls  15  respectively. The sleeve  4  is closed by a cover  21  which prevents lubricant from running from the space of the cage unit  14  into the interior of the adjoining shaft attaching piece  18 . To permit the equalization of pressure between the chamber formed by the plunging unit  1  and the interior of the shaft to be attached during the sliding-in and sliding out movement of the plunging assembly  1 , the cover  21  is provided with a central pressure equalizing aperture  22 .  
         [0034]    The constant velocity joint  2  comprises an outer part  5 , an inner part  6 , balls  7  which engage suitable outer tracks  45  of the outer part  5  and radially opposed inner tracks  46  of the inner part  6  for torque transmitting purposes, as well as a cage  8  for holding the balls  7  in the homokinetic central plane. The constant velocity joint  2  is provided in the form of a fixed joint with counter tracks. The pairs of ball tracks  45 ,  46  open across the circumference alternately in axially opposed directions, with only one of the pairs being shown in a sectional view. The inner part  6  comprises a bore  9  with longitudinal splines into which the journal  3  is inserted in a rotationally fast way. The journal  3  and the inner part  6  are axially connected to one another by a securing ring  10 . Other mechanisms for connecting the journal  3  and inner part  6  are also contemplated.  
         [0035]    To prevent any lubricant from escaping from the joint and plunging space and to prevent dirt from entering the space, there is provided an inventive sealing assembly which comprises a first attaching part  24  adapted to be connected to the outer part  5  of the constant velocity joint  2 , a second attaching part  25  adapted to be connected to the sleeve  4  of the plunging unit  1 , as well as a rolling boot  26  sealingly connecting the two attaching parts  24 ,  25 . The two attaching parts  24 ,  25  are less resilient than the boot material and can be produced, for example, by deformation from plate metal. At the joint end, the rolling boot  26  comprises a first collar  27 , a second collar  28  at the sleeve end and a boot wall connecting the two collars. The two collars  27 ,  28  are provided in the form of beads which are engaged by correspondingly designed crimpings  29 ,  30  of the respective attaching parts  24 ,  25 .  
         [0036]    The first attaching part  24  comprises a cylindrical collar portion  32  which centeringly embraces the outer part  5  of the constant velocity joint  2  and which is followed by a radially inwardly extending flange portion  33  which is in surface contact with the end face of the outer part  5  and is held by fasteners such as bolts  19 . The disc-shaped flange portion  33  changes into a cylindrical fixing portion  34  which is provided with the inwardly directed crimping  29  engaged by the bead-shaped first collar  27  of the rolling boot  26 .  
         [0037]    The second attaching part  25  comprises a sleeve-shaped clamping portion  35  which is designed according to the outer contour of the sleeve  4  and is secured on the radial outside of the sleeve. Part of the inwardly directed cover  36  can be clamped in underneath the sleeve-shaped clamping portion  35 . Further, along towards the constant velocity joint  2 , the second attaching part  25  finally changes into a cylindrical fixing portion  37  whose outer diameter approximately corresponds to the outer diameter of the sleeve  4 . At the end of the second attaching part  25 , which end faces the constant velocity joint  2 , there is provided the inwardly directed crimping  30  which is engaged by the bead-shaped second collar  28  of the rolling boot  26 .  
         [0038]    The first collar  27  of the rolling boot  26  is followed by a first wall portion  38  in the shape of half a torus which, if viewed in a longitudinal section, comprises a greater radius of curvature and which, substantially, serves to compensate for angular movements of the constant velocity joint  2 . The second collar  28  is followed by a second wall portion  39  in the shape of half a torus which, if viewed in a longitudinal section, comprises a smaller radius of curvature than the first one and which, substantially, serves to compensate for plunging movements of the shaft  4  relative to the journal  3  and which, depending on the plunging condition of the plunging assembly  1 , is positioned closer to, or further away from, the first collar  27 . The wall portions  38 ,  39 , by means of their convex outer faces, point in axially opposed directions relative to the joint  2  and the plunging unit  1 . Between the wall portions  38 ,  39 , there is positioned a central wall portion  40  which is cylindrical, which extends coaxially relative to the thickening  13  and rests closely thereagainst. On the radial outside of the central wall portion  40  there is provided a reinforcing portion in the form of a sleeve or ring  41  which prevents the rolling boot  26  from bulging out when the assembly rotates at a high speed. The central wall portion  40  can, with radial play, be axially displaceable relative to the thickening  13  or it can be clamped to the thickening  13  by means of the reinforcing ring  41 . The reinforcing portion  41  can also be integrated into the wall of the connecting portion  40 , and can rest against the radial inside of the central wall portion  40 . The inside of the connecting portion can also include rib or map-like reinforcements, which provide protection against chaffing.  
         [0039]    Between the cylindrical fixing portion  37  of the second attaching part  25  and the journal  3 , there is formed an annular chamber which serves to accommodate the second wall portion  39  of the rolling boot  26  when the plunging unit  1  is in the plunged condition. As can be seen in FIG. 2, the rolling boot  26 , in the completely plunged condition of the plunging unit  1 , touches in osculation the inner face of the cylindrical portion  37 , starting from the second collar  28  held at the end of the second attaching part  25 , then extends in the shape of half a torus and, thereafter, extends with a radial gap coaxially relative to the journal  3 . The gap ensures that the rolling boot  26  is axially movable relative to the journal  3 . The inner diameter of the fixing portion  34  of the first attaching part  24  is greater than the outer diameter of the fixing portion  37  of the second attaching part  25 , so that the latter, in the completely plunged condition, while at least partially overlapping, is able to enter the first attaching part  24 . In this way, it is ensured that, with a given length of the rolling boot  26 , the axial plunging capacity is considerable. The first wall portion  38  of the rolling boot  26 , which wall portion is at the joint end, touches in osculation the inner face of the cylindrical fixing portion  34 , starting from the first collar  27 , and then extends in the shape of half a torus relative to the central wall portion  40 .  
         [0040]    In the articulated position of the constant velocity joint  2 , with the plunging assembly  1  simultaneously having reached its maximum plunge, as shown in FIG. 2 b,  the first attaching part  24  has radially inwardly approached the second attaching part  25  on one side. In the example shown, the two attaching parts  24 ,  25  are out of contact with one another up to an angle of 11° as enclosed between the outer part  5  and the inner part  6 , and only contact one another at larger articulation angles of the constant velocity joint  2 .  
         [0041]    When the journal  3  is moved out of the sleeve  4 , the second wall portion  39  unrolls out of the chamber formed by the second attaching part  25  and positions itself annularly around the journal  3 . The central wall portion  40  is pulled by the reinforcing ring  41  towards the joint  2 , as a result of which the radius of curvature of the first wall portion  38  increases. When the journal  3  is fully extracted out of the sleeve  4 , as shown in FIG. 3A, the cage  16 , at the shaft end, is in contact with a securing ring  20  and, at the joint end, with the radially inwardly pulled cover  36  underneath the second attaching part  25 , as a result of which the journal  3  is prevented from being extracted any further. The second wall portion  39  at the shaft end is nearly completely extracted from the chamber formed by the second attaching part  25  and annularly rests against and around the journal  3 . The central wall portion  40  is positioned centrally over the thickening  13  of the journal  3 .  
         [0042]    In the articulated position of the constant velocity joint  2 , with the plunging assembly according to FIG. 3B being in the fully extended position, the second attaching part  25  no longer prevents the annular movement of the first attaching part  24  with the outer joint part  5  relative to the journal  3 . This position thus permits a greater articulation angle than previously, so that the maximum joint articulation angle of approximately 15° is achieved, which is shown here.  
         [0043]    While the invention has been described in connection with one or more embodiments, it should be understood that the invention is not limited to those embodiments. Thus, the invention covers all alternatives, modifications, and equivalents as may be included in the spirit and scope of the appended claims.