Abstract:
A lubricating element for rolling element tracks, particularly linear motion systems, has a body composed of a lubricant-storing material, which includes an application section capable of being brought in contact with a rolling element bearing surface to supply lubricant; the body has an elongated shape in a first storage region adjacent to the application section, and a lubricant flow through the first storage region triggered via the dispensing of lubricant at the application section is essentially oriented in the longitudinal direction of the first storage region.

Description:
CROSS-REFERENCE TO A RELATED APPLICATION 
       [0001]    The invention described and claimed hereinbelow is also described in German Patent Application DE 10 2006 033 850.2 filed on Jul. 21, 2006. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d). 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to a lubricating element for rolling element tracks, particularly linear systems, with a body made of a lubricant-storing material, which includes an application section capable of being brought in contact with a rolling element bearing surface to supply lubricant. 
         [0003]    Linear systems in the sense of the present application are rolling element screw drives (e.g., ball spindle drives), rolling element ring bushings (e.g., ball ring bushings), and rolling element-supported profiled rail guides, which are often also referred to as linear guides. An aspect shared by all of these linear systems is that a nut element or carriage element is supported such that it is movable along a linear guide element, and a longitudinal displacement of the nut element or carriage element takes place by rolling elements (balls or rollers) rolling between tracks formed on the nut element or carriage element and the guide element. The rolling bodies move along a closed path in a rolling element circuit with a load channel formed between facing bearing surfaces on the linear guide element and on the nut element or carriage element, and a return channel that connects the two ends of the load channel and is typically guided by the nut element or carriage element. 
         [0004]    To ensure that the rolling of the rolling elements is satisfactory, the tracks of linear systems of this type must be lubricated with a lubricant (typically a lubricating oil), mainly in the region of the load channel. To enable compensation of lubricant losses that unavoidably occur during operation of a system of this type, it is desired that lubricant be supplied continually during the entire operating period, the lubricant supply ideally remaining consistent for the entire duration of operation and being chosen such that its level exactly compensates the lubricant losses. 
         [0005]    Publication U.S. Pat. No. 5,492,413 discloses a sealing plate for a carriage of a profiled rail guide that is supported such that it is movable along a guide rail. The sealing plate is mounted on both axial ends of the carriage and is bonded with a layer made of a lubricant-saturated, foamed material, which performs the lubricating function. The inner edge of this foamed material layer forms a lubricant delivery lip resting on the guide rail, which is supplied with lubricant from the surrounding regions of the foamed material layer. 
         [0006]    Publication EP 0 B74 172 B2 also discloses a sealing plate for a profiled rail guide with an integrated lubricating device, which is installed on the axial ends of a carriage. With this multi-component lubricating device, an element, e.g., a perforated plate, which limits the flow path of the lubricant from the first layer to the second layer, is located between a first, lubricant-storing layer, which is not in contact with the guide rail, and a second, lubricant-supplying layer, the inner edge of which bears against the guide rail. As a result, the rate at which lubricant is supplied is limited in a manner such that it remains as stable as possible, independently of the stored quantity of lubricant, which decreases the longer the linear guide operates. 
         [0007]    A further system—designed as a single piece—for lubricating rolling element tracks of a profiled rail guide is made known in JP 5-71143 U. With this system, lubricant-saturated foamed material inserts are inserted in a receiving space of a sealing unit installed on the axial ends of the carriage. The insides of the foamed material inserts are in contact with the rolling element bearing surfaces of the guide rail. 
       SUMMARY OF THE INVENTION 
       [0008]    The object of the present invention is to provide a lubricating element for rolling element tracks, which has the simplest design possible and makes it possible to adjust the lubricant supply rate in a satisfactory manner, even over longer periods of time. 
         [0009]    This object is attained according to the present invention in that, in the case of a lubricating element for rolling element tracks, particularly linear systems, with a body composed of a lubricant-storing material, which includes an application section capable of being brought in contact with a rolling body bearing surface to supply lubricant, the body has an elongated shape in a first storage region adjacent to the application section, and a lubricant flow through the first storage region triggered via the dispensing of lubricant at the application section is essentially oriented in the longitudinal direction of the first storage region. 
         [0010]    A “lubricant-storing material” is understood to mean a material that can be saturated with a lubricant (i.e., a liquid with suitable viscosity) and that is capable of storing a certain quantity of this lubricant. When the term “effective porosity” is used to describe the portion of the volume formed by cavities or pores in a material of a specified total volume of the material, this means that a lubricant-storing material has an effective porosity greater than zero. The effective porosity can be a constant, but it is often the case that the effective porosity depends on the quantity of a stored lubricant, because the pores can expand as the quantity of stored lubricant increases. 
         [0011]    The “elongated shape of the body”—according to the present invention—in the first storage region means that a preferred direction exists in the first storage region, i.e., its longitudinal direction, in which the total extension of the first storage region is clearly greater than in all directions orthogonal to the preferred direction. With elongated bodies of this type, the square root of the cross-sectional area measured orthogonally to the preferred direction is therefore clearly smaller than the total extension of the body in the preferred direction. Expressed graphically, it could therefore be said that, in the first storage region, the body has a cord-like shape or, specifically with regard for its ability to be saturated with lubricant—a wick-like shape. 
         [0012]    In the state in which the lubricating element is installed in the linear system for operation, an application section—located on the body—of the lubricating element bears against a rolling body bearing surface, so that, when there is relative motion between the nut element or carriage element and the guide element, the application section glides along the rolling element bearing surface and supplies a certain quantity of lubricant to the rolling element bearing surface while this gliding motion takes place. When the lubricating element is assigned, e.g., to the carriage element or the nut element, the application section glides along the rolling element bearing surface formed on the guide element. The quantity of lubricant dispensed is replenished from the first storage region adjacent to the application section. During operation, this results in a lubricant flow through the first storage region toward the application section. This lubricant flow is essentially driven by a concentration gradient of stored lubricant that arises from the application section through the first storage region. In addition, depending on the installation position, further effects can also play a role, e.g., shear force effects when the device is installed in a nearly vertical position. 
         [0013]    If one assumes that, when a lubricating element is used in a linear system, the first storage region is saturated essentially evenly with lubricant, then the first storage region becomes increasingly depleted of lubricant as operation continues, and this depletion progresses from the regions adjacent to the application section outwardly in the longitudinal direction of the first storage region. Associated therewith is an evenly declining rate of supply of lubricant at the application section, which is due to the fact that the concentration gradient of lubricant that arises in the first storage region becomes increasingly flat as the first storage region continues to empty. A basic aim is to attain a rate of lubricant supply that is as constant over time as possible, so this decrease in the rate of lubricant supply is basically undesired. It has been shown, however, that with a lubricating element of the type according to the present invention, the decline in the rate of lubricant supply can be adjusted and controlled relatively well in a first storage region with an elongated shape. This makes it possible to remain within a range between a maximum desired rate of lubricant supply (when the first storage region is saturated evenly) and a minimum desired rate of lubricant supply (when the first storage region has been emptied nearly entirely), for any application. By choosing a cross-sectional area of the body in the first storage region that is sufficiently large, it is also possible to keep the difference between the maximum rate of lubricant supply and the minimum rate of lubricant supply within reasonable limits, even over longer operating periods. 
         [0014]    Typically, a single first storage region adjacent to the application section is sufficient. Designs for the lubricating element are also feasible, however, with which several first storage regions abut the application section and extend outwardly from there in the form of several “cords” or “wicks”. 
         [0015]    The application section can be located in an end-face end region of the first storage region. During operation of the linear motion system, a lubricant flow through the first storage region oriented essentially in one direction therefore results, the lubricant flow being oriented toward the end-face end region, and the starting point of which is continually displaced toward the diametrically opposed, end-face end regions of the first storage region. 
         [0016]    The body can be formed, e.g., of an open-cell foamed material. Ester-based PUR foamed materials have proven to be a suitable foamed material, for example. Foamed materials of this type can be foamed and then pressed to form panels having a desired pore size. Panels have proven suitable, e.g., with a relative density after pressing of between 60 and 250 kg/m 3 , particularly approximately 200 kg/m 3 . Foamed materials of this type are available under the trade names Inducon, Normont, and Cellofoam. In the past, it has been shown that these foamed materials are suitable in terms of their wear resistance and chemical resistance, and in terms of their lubricant absorption capacity. 
         [0017]    The body can be cut out of a foamed material panel, e.g., using water-jet cutting, and is relatively easy to manufacture in this manner. 
         [0018]    It is not required to use a separate application section. Instead, the application section can be formed as a single piece with the first storage region, which is favorable in terms of manufacturing. For example, the body can include at least one indentation in the first storage region. The application section is formed between the indentation and one or more lateral surfaces of the body, or the body can include several indentations in the first storage region. The application section is formed between the indentations and, possibly, lateral surfaces of the body. Roughly speaking, it could be said that a cut-out end of the first storage region forms the application section. The size, i.e., the cross section in particular, of the application section can thereby be adapted to the particular rolling element bearing surface. 
         [0019]    In addition, the region between the indentation and the lateral surface, or the region between indentations, which is provided to form the application section, is capable of being folded over, thereby forming a right angle with the adjacent surface of the body. The application section is then positioned transversely to the longitudinal direction of the first storage region, at least in the installed state of the lubricating element. The angle between the direction of extension of the application section and the longitudinal direction of the first storage region is preferably essentially 90°. This method of creating the application section requires that the material of which the body is composed have a certain formability and/or elasticity. Since this material must still have porosity, so it is capable of storing lubricant (a foamed material is typically used), it can be assumed that practically any feasible material will allow the region provided for the application section to be folded over. To name an example of this design of the application section, the body can include—on an end face in the first storage region—at least one slot, which extends essentially in the longitudinal direction of the first storage region, and one of the two subregions produced as a result can be folded over on the end face, so that this subregion projects laterally, and its longitudinal direction extends at a right angle, e.g., essentially orthogonally, to the longitudinal direction of the upper storage region. 
         [0020]    The cross section of the application section can be smaller than the cross section of the body in the first storage region. The “cross section of the application section” basically refers to the size of the surface of the applicator, which includes the regions of the applicator in contact with the track or at least with the bearing surfaces of the rolling elements formed in the track. This cross section is typically chosen depending on the dimensions of the particular track, i.e., ultimately the dimensions of the rolling elements, such that the application section can bear essentially at least against the actual rolling element bearing surfaces. When balls are used as the rolling elements, for example, the rolling element tracks can have a gothic track profile, with two diametrically opposed ball surfaces forming the ball bearing surfaces. When the application section is rectangular in design, so that its corners bear against the ball bearing raceways of the gothic track profile, the corners are pressed together elastically, so that they bear against the bearing surfaces over a broader width. The applicator need not bear against the base of the track, however. In practical applications, embodiments have proven effective with which the cross section of the applicator is only half as large or one-fourth as large as the cross section of the body in the first storage region. 
         [0021]    The cross section of the applicator has negligible influence on the rate of lubricant supply, since the length of the applicator is negligibly small compared with the length in the longitudinal direction of the first storage region. As a result, a concentration gradient that is sufficiently great is always formed across the application section. 
         [0022]    For example, the body in the first storage region can have a rectangular cross section. In this case, it can be cut out of a panel-type material particularly easily. Other cross sections, particularly round or oval cross sections, are also feasible, of course. 
         [0023]    To accommodate a first storage region with a long length in the longitudinal direction in the most compact space possible, it can be provided that the body in the first storage region is wound into the shape of a spiral or a ring. This system is particularly favorable when the linear system includes a cylindrical guide element, e.g., a spindle of a rolling element screw drive or a cylinder guide of a ring bushing. In the case of a rolling element screw drive, the spiral wound storage region can be wound around the guide element. An application section bent at a right angle relative to the longitudinal direction (=circumferential direction of the spiral turns) of the first storage region is in contact with the outer surface of the guide element in which the rolling element tracks are formed. 
         [0024]    With a lubricating element with a body spiral-wound in the first storage region, to prevent lubricant from being transported between spiral turns and transversely to the winding direction, it can be provided that the individual spiral turns have clearance between each other. Lubricant can therefore only be transported longitudinally to the winding direction of the spiral turns. As an alternative or in addition thereto, it can be provided that a lubricant-impermeable intermediate layer, e.g., composed of plastic, is located between individual spiral turns. Any type of essentially lubricant-impermeable plastic material can be chosen for the intermediate layer. For example, rubber rings inserted between the individual spiral turns have proven to be suitable. 
         [0025]    In a suitable embodiment, the body in the first storage region can be enclosed by a jacket composed essentially of lubricant-impermeable material, e.g., plastic, and the body-jacket combination is wound in the shape of a spiral or a ring. Even when the individual spiral turns bear against each other, the jacket prevents lubricant from being transported between the individual turns, thereby enabling lubricant in the first storage region to be transported essentially only in the longitudinal direction of the first storage region, i.e., in the direction of the turns. The jacket can be a tube, for example, that is pulled over the body in the first storage region, after it is cut out of a panel-type material. As an alternative, it can be provided that the body in the first storage region is wrapped with a strip of composed essentially of lubricant-impermeable material, e.g., plastic, and the body-jacket combination is wound in the shape of a spiral or a ring. With this variant, the often difficult step of sliding a tube composed of lubricant-impermeable material over the body in the first storage region can be eliminated. The same lubricant seal can be attained, instead, by wrapping the body with the strip, preferably in a spiral manner, with the individual layers of the strip overlapping partially. 
         [0026]    One of the simplest methods for ensuring that lubricant is not transported transversely to the winding direction of the spiral turns with a spiral-wound first storage region with individual spiral turns bearing against each other is to cut the body out of a panel of open-cell foamed material; the top and underside of the panel is closed-cell in design, and the body in the first storage region is wound such that the closed-cell lateral surfaces touch each other. The closed-cell lateral surfaces form a largely impenetrable barrier for the lubricant, so that lubricant is also transported here essentially in the longitudinal direction of the first storage region (i.e., in the winding direction of the spiral turns). 
         [0027]    If desired, the embodiments of the lubricating element body described above can be used for the entire body rather than only in the first storage region. 
         [0028]    It is favorable when the body includes a second storage region adjacent to the elongated, first storage region. The second storage region does not need to have an elongated shape similar to that of the first storage region. Instead, the cross section of the second storage region—as measured orthogonally to the longitudinal direction of the first storage region—can be larger, by any extent, than the corresponding cross section of the first storage region. Provided the application section is located on one of the end faces of the first storage region, it is possible, e.g., that the second storage region abuts the end face of the first storage region diametrically opposed to the application section. The function of the second storage region is as follows: 
         [0029]    When a linear system is operated, lubricant is transported primarily from the first storage region toward the application section. As a result, the first storage region becomes increasingly depleted of lubricant as operation continues. After a sufficiently long period of operation, this would result in the first storage region become fully depleted of lubricant. In this situation, the lubricating element would have to be replaced or resaturated with lubricant. When a second storage region abuts the first storage region, however, which has a preferably considerably greater volume available for storing lubricant than does the first storage region, shutdown periods in which the linear system is at a standstill for a relatively long period of time can be used to automatically refill the lubricant supply stored in the first storage region. Provided that the lubricant concentration in the second storage region is greater than in the first storage region—which would typically be the case after a certain period of operation, because only the quantity of lubricant stored in the first storage region has decreased—when the carriage or the nut of the linear system is at a standstill, lubricant flows from the first storage region into the second storage region, thereby refilling the first storage region. 
         [0030]    When the linear system is started up once more, the rate of lubricant supply via the application section is therefore clearly higher than it was at the end of the most recent shutdown period. In fact, it approaches the new state when the shutdown period is sufficiently long. Even very brief shutdown periods can be utilized in this manner as standstill phases of the carriage and the nut. 
         [0031]    The first storage region therefore performs the function of an intermediate storage element, which is refilled during shutdown periods with lubricant supplied from the second storage region. As a result, the rate of lubricant supply can always be held between a predetermined maximum value when the first storage region is completely full and a minimum value—which is close to the predetermined maximum value—when the first storage region has been nearly entirely depleted of lubricant, and this for the entire service life of a linear system in this manner, lifetime lubrication of linear systems can be realized in a very simple manner. 
         [0032]    The first and second storage regions can be designed as single pieces, e.g., they can be cut from the same panel of foamed material. 
         [0033]    With linear systems with a cylindrical guide element, e.g., rolling element screw drives or ring bushings, it is favorable when the second storage region is annular in design, thereby enabling the spindle or guide cylinder to be passed through it. The annular shape can be realized very easily by bending or winding a suitably cut-out foamed material panel, and it results in a compact design of the lubricating element and a lubricating unit which includes the lubricating element. 
         [0034]    Preferably, it is provided that the inventive lubricating element is integrated in a lubricating unit for tracks of rolling elements of a linear system, particularly in a rolling element screw drive or a ball screw drive, of a profiled rail guide or a ring bushing. The linear system includes a nut element or carriage element that is movably guided via rolling elements along a linear guide element. The lubricating unit is installed on an axial end of the nut element or carriage element. With a nut element or carriage element provided with a lubricating unit on both axial ends, lubrication of the rolling element tracks can take place even in the load channel in any direction of motion before the rolling elements guided in their endless circuit come in contact with the bearing surface. This results in extremely efficient lubrication that requires a very small amount of lubricant. 
         [0035]    The inventive lubricating element is suited most particularly for use in cases in which the linear system is a rolling element screw drive, particularly a ball screw drive, including a spindle as the guide element, and a nut element enclosing the spindle, as the movable element; at least one nut groove with two end regions—the nut groove extending around the axis in the manner of a helix and guiding rolling elements—is formed in the inner circumferential surface of the nut element, the nut groove definining—together with the outer circumferential surface of the spindle—a helical rolling element screw path extending between the two end regions; the rolling element screw path is appended by a rolling element return path extending between the two end regions to form a closed rolling element recirculating path, which is filled with an endless row of rolling elements—ready to roll at all times—lying in the nut groove and on a helical trajectory of the outer circumferential surface; a rolling element deflection for transferring the rolling elements between the rolling element screw path and the rolling element return path or between the rolling element return path and the rolling element screw path is located on the nut element in each of the end regions. 
         [0036]    In this case, it is favorable when the lubricating unit is mountable on the nut element such that any rotary position between the lubricating unit and the nut element can be set, preferably steplessly. This makes it possible to adjust the axial position of the application section to a certain thread pitch by rotating the lubricating unit and the nut element relative to each other accordingly. With the lubricating unit, an annular receiving space for the lubricating element can be formed, e.g., in a cylindrical lubricating element housing, in fact, such that an inner wall of the lubricating element housing encloses the linear guide element, e.g., the spindle of a rolling body screw drive or the cylinder guide of a ring bushing. An opening can be formed in the inner wall of the receiving wall, through which the application section of the lubricating element is guided in order to contact the rolling body bearing surface. With a rolling element screw drive, e.g., the application section guided through the opening comes in contact with a spiral running groove for the rolling elements formed in the outer surface of the spindle. 
         [0037]    To attain the greatest flexibility possible with a rolling element screw drive in particular, it can also be provided that an application nose is insertable in the inner wall of the lubricating element housing, in which the opening for the application section is formed. This application nose can be slidable into the inner wall, e.g., in the axial direction. By providing various positionings of the axial position of the opening for various application noses, the same lubricating element housing can be used for different thread pitches on the spindle. It is also possible to attain a correct orientation of the application nose or the application section relative to the thread turns even when the application nose or the application section is fixed in position in the radial direction when the lubricating unit is mounted on the nut element or bush element such that it can be adjusted in various rotary positions relative to the nut element or such element. When holes with different-sized cross sections are also provided in the application nose, the same lubricating unit—its housing, in particular—can also be used for several ball diameters. This results in an extraordinarily great deal of flexibility. 
         [0038]    Finally, it can be provided that the receiving space is closed by a cover. The cover can also perform further functions, e.g., it can seal off the carriage or protect the nut from contamination, in particular. It is also feasible that the application nose is not fixed in position rigidly by the cover, but rather with a small amount of play in the axial direction, thereby allowing the opening to adjust automatically relative to the thread pitch. 
         [0039]    The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]      FIG. 1  shows a perspective exploded view of a first embodiment of an inventive lubricating unit with the inventive lubricating element, which is designed to be installed on the axial end of a nut element of a rolling element screw drive, 
           [0041]      FIG. 2  shows the lubricating unit in  FIG. 1 , in the assembled state, 
           [0042]      FIG. 3  shows a cross-sectional view through the lubricating unit shown in  FIGS. 1 and 2  in a state in which it is installed on the axial end of a nut element of a ball screw drive. 
           [0043]      FIG. 4  shows the embodiment—depicted in FIG.  1 —of an inventive lubricating element with an annularly bent, first storage region and an adjacent, annularly bent, second storage region, in a perspective view, 
           [0044]      FIG. 5  shows a cut-out, foamed material panel, which is used to form the lubricating element shown in  FIG. 4 , 
           [0045]      FIG. 6  shows a further embodiment of an inventive lubricating element that essentially corresponds to the embodiment shown in  FIG. 4 , with the exception that the application section has a larger cross-sectional area, 
           [0046]      FIG. 7  shows a cut-out, foamed material panel, which is used to form the lubricating element shown in  FIG. 6 , 
           [0047]      FIG. 8  shows a further embodiment of an inventive lubricating element, which has been wound in the shape of a spiral, 
           [0048]      FIG. 9  shows a further embodiment of an inventive lubricating element, which is wound in the shape of a spiral, with a spiral-shaped, plastic element located between the individual spiral turns, and 
           [0049]      FIG. 10  shows a further embodiment of an inventive lubricating element that essentially corresponds to the embodiment shown in  FIGS. 4 through 7 , with the exception that a plastic ring is located between the circular ring turns of the first and second storage region, in order to separate the two. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0050]      FIG. 1  shows a perspective exploded view of a lubricating unit for a rolling element screw drive; it is labeled in general with numeral  10  and includes an inventive lubricating element  12 . Lubricating unit  10  is designed to be installed on the axial end of a nut of the rolling element screw drive. Lubricating unit  10  includes a main body  14 , in which an annular receiving space  16  is formed. Lubricating element  12  is inserted into receiving space  16 . Receiving space  16  is closed with a cover  18 , which is set in place after lubricating element  12  is installed on main body  14 . A seal is also located in cover  18 , which bears against the upper surface of the spindle of the rolling element screw drive and ensures that no foreign subjects enter the intermediate space between the nut element and the spindle surface. The seal therefore serves to hermetically seal the rolling element running channel formed between the nut element and the spindle. Projecting edge  20  formed on the front side of cover  18  includes several recesses  20   a,  into which an assigned projection of the seal (not shown in  FIG. 1 ) can engage. This allows the seal to be fixed in place relative to the cover and prevented from rotating in the circumferential direction. To adapt to different thread pitches, one of the recesses  20   a  in which the seal is inserted is assigned to a predetermined thread pitch, thereby ensuring that the seal can engage with the helical running element bearing surface. 
         [0051]    Lubricating element  12  shown in  FIG. 1  is designed essentially annular in shape overall, with a first storage region  22 , which extends in an annular manner and has the shape of a strand with a relatively small cross section, and with a second storage region  24 , which also extends in an annular manner in wide regions and is located concentrically with first storage region  22 . Second storage region  24  adjoins first storage region  22  as a single piece in a transition section  26  located between first storage region  22  and second storage region  24  in the axial direction. First storage region  22  and second storage region  24  are separated from each other by an annular gap  28  located outside of transition section  26 . 
         [0052]    The annular contour of first storage region  22  and second storage region  24  is not entirely closed, but rather has an essentially axially-extending opening gap  30 ,  32 . 
         [0053]    An application section  34  projecting toward the inside of the ring abuts the free end of first storage region  22 . Application section  34  is cut as a single piece out of the material forming first storage region  22  and is folded over toward the ring axis. In the state of being installed for operation, free end  35  of application section  34  bears against the rolling element track designed in the shape of a spiral in the outer surface of the spindle. Lubricating element  12  is then saturated with lubricant, which is gradually dispensed onto the rolling element track via application section  34 . 
         [0054]    Lubricating unit  10  includes a separate application nose  36 , which is insertable in the axial direction into inner circumferential wall  38  of lubricating element main body  14 . An opening  40  is formed in application nose  36 , through which—when lubricating element  12  is installed—application section  34  projecting inwardly from first storage region  22  is guided, so that its free end  36  bears against the rolling element track. 
         [0055]    Various lubricating elements  12  can be inserted in receiving space  16 , provided they have its essentially annular shape with the outer diameter and inner diameter in the region between the outer surface and inner surface of annular receiving area  16 . Lubricating element inserts  12  are saturated with a lubricant, e.g., oil, before or immediately after they are inserted into receiving space  12 . 
         [0056]    On its front end bearing against the nut of the rolling element screw drive, main body  14  includes latch hooks  42  that extend in the axial direction and are distributed concentrically around its inner surface. In the embodiment shown, lubricating unit  10  is mounted on the nut of the rolling element screw drive using latch hooks  42 , a clamping ring  44  designed as a segmented split washer, and a lock nut  46 . To this end, latch hooks  42  are brought in engagement with a circumferential groove ( 56 , see  FIG. 3 ) formed in the inner surface of the nut of the rolling element screw drive. Circumferential groove  56  normally serves to accommodate the seal designed to protect the nut against penetration by foreign substances from the outside, the seal now being located in cover  18  when lubricating unit  10  is installed. To ensure better retention of lubricating unit  10  in circumferential groove  56 , latch hooks  42  do not engage in circumferential groove  56  directly, but rather via auxiliary clamping ring  44 . Clamping ring  44  includes a projection  48  extending in the circumferential direction on its inner circumferential edge, which extends much further inward than the very shallow depth of annular groove  56 . This makes it possible to use larger latch hooks  42 , with correspondingly greater stability. Lock nut  46  serves to ultimately fix lubricating unit  10  in position axially on the nut. Lock nut  46  engages in a thread cut into the outer circumference of main body  14  of lubricating unit  10  and, after latch hooks  42  engage with projection  48 , lock nut  46  is tightened and brought to bear against a front side of the nut. 
         [0057]    To illustrate the interrelationships described above,  FIG. 2  shows lubricating unit  10  in  FIG. 1  in the assembled state, but still as a separate component and not installed on the nut of a ball screw drive. 
         [0058]    The cross-sectional view in  FIG. 3  shows how lubricating unit  10  is installed on nut body  54  of a ball screw drive composed of a nut  50  and a spindle  52 . Auxiliary clamping ring  44  is inserted in circumferential groove  56  formed in the inner surface of nut body  54  and bears tightly against its base under the effect of its preload. Latch hooks  42  also bear against projection  48  of the clamping ring—which projects radially inwardly and extends in the circumferential direction—and secures lubricating unit  10  from moving in the axial direction away from nut main body  54 . The distance between the inner—in the radial direction—surface of latch hooks  42  and the outer—in the radial direction—surface of spindle  52  is chosen to be so small that the latch hooks cannot become disengaged from projecting section  48  of auxiliary clamping ring  44  when spindle  52  is inserted. The nut unit composed of nut  50  and lubricating unit  10  must therefore be removed from spindle  52  before lubricating unit  10  can be removed. Since latch hooks  42 —when engaged with auxiliary clamping ring  44 —also have a certain amount of preload in the radially outward direction, an external force that presses latch hooks  42  inward is required to disengage  15  clamping rings  42  from auxiliary clamping ring  44 . Lubricating unit  10  is ultimately fixed in position on nut main body  54  in the axial direction by tightening lock nut  46  relative to nut main body  54 . 
         [0059]    In  FIG. 3  it is shown that application section  34  extending inwardly in the radial direction away from the first storage region engages in rolling element running groove  58  formed in a spiral shape in the outer surface of spindle  52 , so that its free end is in contact with the base of the rolling element running groove. The elasticity of application section  34  made of a foamed material ensures that, during operation of the ball screw drive, the free end of application section  34  is always in contact with the rolling body bearing surface and can provide it with lubricant. 
         [0060]      FIG. 4  shows lubricating element  12 —which was shown in FIG.  2 —separately, and in an enlarged view. In addition to the explanations provided with reference to  FIG. 2 , above,  FIG. 4  clearly shows the single-piece design of lubricating element  12  with first storage region  22 —which is shaped like a strand, designed as a cord or wick, and bent in an annular shape—abutting a second storage region  24 —designed as a flat ring—in the axial direction of the annulus via a transition section  26 . Neither first storage region  22  nor second storage region  24  are closed to form a complete ring. Instead, they each include a gap  30  and  32 , which extends in the axial direction. Application section  34 , which projects radially inwardly, abuts the end—that is diametrically opposed to transition section  26 —of first storage region  22 , which forms an annular strand. Application section  34  is formed by cutting out and bending a front side—located on the inner edge—of the material of which the first storage region is composed. Annular first storage region  22  has an essentially square cross section. When the lubricating element operates (i.e., when lubricant is supplied to the rolling element bearing surface via end face  35 —which bears against the rolling element bearing surface—of application section  34 ), the lubricant flows through the first storage region essentially in the circumferential direction of the annulus, i.e., perpendicularly to its square cross-sectional area. Second storage region  24  is also annular in shape, although its cross section has the shape of an elongated rectangle. 
         [0061]      FIG. 5  shows a foamed material panel  70 , which is used to form lubricating element  12  shown in  FIG. 4 . Foamed material panel  70  was originally cut out in a rectangular shape, with a longitudinal side and a narrow side, which is clearly shorter by comparison. Starting on a narrow side, an elongated indentation is formed parallel to the longitudinal side, which extends nearly to the diametrically opposed end face of the panel. This indentation forms recess  28  extending in the axial direction between the narrow strip forming first storage region  22  with a nearly rectangular cross section and the wider strip forming second storage region  24 , the cross section of which has the shape of an elongated rectangle. On the end face of the narrow rectangular strip, which forms first storage region  22 , the material is cut once inwardly parallel to the flat side of the rectangle, and it is cut a second time perpendicularly to the flat side of the rectangle; the latter incision extends through only half of the thickness of the material. These two cut surfaces form two regions with a nearly square cross section on the end face; one was cut off completely, and the other eventually forms application section  34 . 
         [0062]    An open-cell foamed material is used to manufacture lubricating element  12 . To create the open-cell foamed material, a plastic is foamed and pressed to form panels with the desired pore size, e.g., approximately 200 kg/m 3 . The foamed material inserts which form lubricating element  12  are cut from these panels using water-jet cutting. The inserts are saturated with a lubricant, e.g., a lubricating oil, then they are inserted in receiving space  16  of lubricating unit  10  shown in  FIG. 1 . Instead of a purely open-cell foamed material, a foamed material can be used, e.g., with which the open-cell foamed material is closed-cell in design on the top and bottom flat sides. This has the advantage that the lubricant cannot leak out of the closed-cell edge regions, thereby ensuring that the lubricant can essentially only flow parallel to the flat sides. Plastic foamed materials manufactured via foaming, gelation and subsequent vulcanization of the foam are top selections as the material for lubricating element  12 . The thickness of the foamed material panels manufactured using this method can be between 1.0 and 15.0 mm. Ester-based polyurethane foams have proven to be suitable, for example. They are available under the trade names Inducon, Normont and Cellofoam, for instance. 
         [0063]      FIGS. 6 and 7  show views of a further embodiment of an inventive lubricating element  112 , which correspond to the views in  FIGS. 4 and 5 . With the lubricating element shown in  FIGS. 4 and 5 , components that correspond to the components of lubricating element  12  depicted in the previous figures are labeled with the same reference numerals plus  100 . To prevent unnecessary repetitions, only the differences in the embodiment shown in  FIGS. 6 and 7  compared with the embodiment described above will be described in greater detail, and reference is made to the description of the previous figures for explanation of the remaining aspects. 
         [0064]    In the embodiment shown in  FIG. 6 , application section  134  is formed merely by creating at least one slot or indentation extending essentially parallel to the flat side of foamed material panel  170 . Then the radially inward subsection can be folded toward the inside. The cross-sectional area of application section  134  is therefore half as large as that of first storage region  122 , in contrast to the embodiment shown in the previous figures, with which the application section has essentially one-fourth the cross-sectional area of the first storage region. The remaining design of lubricating element  122  shown in  FIGS. 6 and 7  is identical to the lubricating element depicted in the previous figures. 
         [0065]    A further embodiment of an inventive lubricating element  212  in the form of a strand of foamed material—wound in the shape of a spiral—is shown in  FIG. 8 . With this embodiment as well, the components that are identical to or that have the same function as the components described with reference to the embodiments depicted in the previous figures are labeled with the same reference numerals plus  200  as compared with the embodiment shown in  FIGS. 4 and 5 . Identical aspects of the embodiment depicted in  FIG. 8  will not be described, either. Instead, reference is made to the description of the previous embodiments. 
         [0066]    Lubricating element  212  depicted in  FIG. 8  includes only a first storage region  222  with an adjacent application section  234 . It does not include a second storage region. Instead, first storage region  222  is formed out of a very long, strand-shaped piece of foamed material, which is wound in the shape of a spiral such that a lubricating element  212  with an overall essentially annular shape results, which can also be inserted in receiving space  16  of lubricating unit  10 , similar to the storage elements described previously. The individual windings of the strand-shaped and spiral-wound first storage region  222  abut each other. To prevent lubricant from flowing transversely to the longitudinal direction of first storage region  222 , i.e., transversely to the circumferential direction of lubricating element  212  via a “short circuit” of the lubricant flow between turns, lubricating element  212  can be made of a panel-shaped, open-cell plastic foam, in the case of which two diametrically opposed longitudinal side surfaces are closed-cell in design, thereby ensuring that lubricant cannot be transported through these lateral surfaces. Lubricating element  212  is then wound in first storage region  222  such that two of the closed-cell lateral surfaces abut each other. 
         [0067]    With lubricating element  312  shown in FIG.  9 —which, similar to lubricating element  212  shown in  FIG. 8 , also includes only one spiral-wound and essentially strand-shaped first storage region  322  with an adjacent application section  334 —a spiral-wound layer  360  composed of a panel-shaped, lubricant-impermeable material (e.g., plastic) is located between the individual spiral turns of first storage region  322 , in order to prevent a “short circuit” between the turns. Due to intermediate layer  360 , the individual spiral turns of first storage region  322  have clearance between each other, and they are insulated from each other in terms of transport of lubricant transversely to the circumferential direction of the spiral turns. 
         [0068]    With regard for the remaining aspects, the embodiment shown in  FIG. 9  corresponds to the embodiment depicted in  FIG. 8 . Further aspects will therefore not be described and, instead, reference is made to the description of the embodiment shown in  FIG. 8  and the embodiments depicted in the previous figures. It should be pointed out that components in  FIG. 9  that are identical to components described with reference to the previous embodiments are provided with the same reference numerals plus  300  as compared with the embodiment depicted in  FIGS. 4 and 5 . 
         [0069]    It should be pointed out that, in the embodiments with a spiral-wound first storage region, a short circuit between turns can also be prevented by inserting the strand-shaped first storage region in a tube composed of plastic foil, then winding the foamed material-tube combination in the shape of a spiral, or by wrapping the strand-shaped first storage region with a strip of plastic foil and then winding the foamed material-strip combination in the shape of a spiral. 
         [0070]    In all of the embodiments, the spiral-wound lubricating element can be adapted to the size of receiving space  16  in main body  14  of lubricating unit  10  by selectively choosing the width of the strand-shaped first storage region and the number of turns. The desired maximum and minimum rate of lubricant supply can also be influenced in this manner. The cross section of the application section is generally always chosen such that it results in the best possible contact with the track surface. 
         [0071]    Finally,  FIG. 10  shows a further variant of an inventive lubricating element  412 , which is very similar to lubricating element  12  depicted in  FIGS. 4 and 5 . Components that are identical to components described previously with reference to the embodiment depicted in  FIGS. 4 and 5  are labeled with the same reference numerals plus  400 . In the cases in which the function of these components is identical, they will not be described, and reference is made instead to the description of  FIGS. 4 and 6 . 
         [0072]    With lubricating element  412  shown in  FIG. 10 , a plastic ring  462  open on one side is inserted in gap  428 , which is formed axially between the narrow, annular first storage region  422  with a nearly square cross section and the wide, annular second storage region  424 . Plastic ring  462  maintains clearance between first storage region  422  and second storage region  424 , thereby preventing the first storage region from coming in contact with the second storage region anywhere except for connection section  426 . In this manner as well, lubricant from second storage region  424  is also prevented from being transported into first storage region  422  while avoiding connection section  426 . In this manner, it is ensured that the lubricant must always flow through first storage region  422  along its entire longitudinal extension, i.e., in the circumferential direction of the ring, before it reaches application section  434 . 
         [0073]    For all of the embodiments shown, suitable lubricants have been found to be lubricating oils with a viscosity between 70 and 90 mm 2 /sec. at 100° C., and 900 to 1000 mm 2 /sec. at 40° C., e.g., the lubricating oil sold under the trade name Mobil SHC600 series 639, which has a viscosity of 79.5 mm 2 /sec. at 100° C., and 933 mm 2 /sec. at 40° C. 
         [0074]    It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above. 
         [0075]    While the invention has been illustrated and described as embodied in a lubricating element and lubricating unit, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention. 
         [0076]    Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.