Lubrication – Slide-bearing lubrication
Reexamination Certificate
2001-05-29
2003-07-22
Kim, Chong H. (Department: 3682)
Lubrication
Slide-bearing lubrication
C074S089440, C384S013000, C384S381000
Reexamination Certificate
active
06595327
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to a linear motion unit having a runner that is arranged so as to be movable back and forth on a rod along the rod's axis, and also having at least one lubricating device which at least partially surrounds the rod and which includes at least one lubricating element that stands in lubricating contact with the rod and at least one lubricant reservoir that is immovably joined to the runner.
2. The Prior Art
Such a linear motion unit is known, for example from EP 0,874,172 A1. In this linear motion unit embodied as a roller spindle drive, two lubricating devices are arranged on the axial ends of the runner assembly and axially contiguous thereto. Each lubricating device is composed of a lubricating element of a polymer foam that contains lubricant and that is in lubricating engagement with the threaded spindle. In addition, each lubricating device has a lubricant reservoir that is axially adjacent to the lubricating element and is connected to the lubricating element by a passage, so that more lubricant can be supplied to the lubricating element from the lubricant reservoir in the event of excessive consumption of lubricant.
A major disadvantage of this known linear motion unit is the small active lubricating length of its lubricating elements, which results in a high contact pressure of the lubricating elements and correspondingly severe wear of the polymer foam material. In addition, all dirt wiped from the surface of the rod is deposited in the pores of the polymer foam material, a clogging it. This can impede the dispensing of lubricant and can also lead to hardening of the polymer foam material, both of which impair adequate lubricating contact of the lubricating elements with the surface of the rod.
In addition, linear motion units are known from DE 198 33 228 A1 and U.S. Pat. No. 5,749,266, which disclose lubricating devices comprised of lubricating elements made of polymer foam that contains lubricant. Furthermore, DE 197 54 454 A1 discloses a linear motion unit in which the lubricating device has an external lubricant reservoir. For the sake of completeness, reference is also made to DE 299 19 250 U1 regarding the state of the art.
SUMMARY OF THE INVENTION
In contrast to the prior art devices, the object of the invention is to provide a linear motion unit of the aforementioned type which permits the use of lubricating elements with large active lubricating length while preserving compact construction of the overall linear motion unit.
This object is attained in accordance with the invention through a linear motion unit of the class in which the lubricant reservoir is arranged radially outside the lubricating element with respect to the axis of the rod. In comparison with the known lubricating device from the class-defining EP 0,874,172 A1, the lubricating element can thus have a significantly greater extension in the direction of the rod axis with the same axial length of the lubricating device and the same supply volume of the lubricant reservoir, so that the aforementioned disadvantages thereof can be avoided in a simple manner in accordance with the invention. Consequently, in the most favorable case, the entire axial extent of the lubricating device can be used to lubricate the surface of the rod. The lubricating element should advantageously have an active lubricating length of at least 15 mm, preferably at least 25 mm.
The radially concentric arrangement of lubricating element and lubricant reservoir can be provided in a simple manner in the case of a lubricating device having only a lubricating function in that the lubricating device has a base body on whose inner circumferential surface is arranged at least one lubricating element, and whose outer circumferential surface forms, at least in part, an inner boundary wall of the lubricant reservoir. In accordance with the invention, the lubricating device need not fully enclose the rod. Rather, it can still perform its function if it merely extends around the rod in a U-shaped or horseshoe manner. With regard to sealing of the lubricating device toward the outside, it is preferred for purposes of simplifying the constructive design for the base body to be designed in a sleeve shape.
To provide the outer boundary wall of the lubricant reservoir, it is possible in accordance with another embodiment of the invention to provide a preferably sleeve-shaped cover body whose inner circumferential surface encloses the outer circumferential surface of the base body at a distance over at least part of its length. Alternatively, it is also possible for the outer boundary wall of the lubricant reservoir to be formed by the inner circumferential surface of a recess in the runner or a part connected thereto. In the latter case, the receiving volume of the lubricant reservoir can be increased by sectional enlargement of this recess.
Simple and cost-effective manufacture results when the base body and, if applicable, the cover body are manufactured as injection-molded parts, preferably of plastic.
To facilitate the resupply of lubricant from the lubricant reservoir to the lubricating element, it is proposed that at least one radial connecting opening may be provided in the base body through which the lubricant contained in the lubricant reservoir can reach the at least one lubricating element. As is described below in greater detail, the throughput of lubricant can be influenced by the size and shape of the connecting opening and/or by elements arranged in this opening.
A variety of embodiments are also conceivable with respect to the interior design of the base body of the lubricating device.
In one embodiment, the inner circumferential surface of the base body can have at least one helical groove in which a correspondingly helical lubricating element is accommodated. If the linear motion unit is a roller spindle drive and if the threaded spindle of the roller spindle drive has a plurality of spindle grooves, i.e. if the threaded spindle is multiple-threaded, then it is advantageous for the lubricating device to also have a number of helical lubricating elements that corresponds to the number of threads and each of which lubricates one of the spindle grooves. If the intention is to lubricate not just the spindle grooves of the threaded spindle, but also the rest of the outer circumferential surface of the threaded spindle, then additional lubricating elements can be provided on the inner circumferential surface of the base body for this purpose. It is advantageous for each of the thread grooves to be in lubricant exchange contact with the lubricant reservoir via its own connecting opening.
In another embodiment, at least one axially-extending groove in which a lubricating strip is accommodated can be formed in the inner circumferential surface of the base body. Such a lubricating strip can, of course, touch only the outer circumferential surface of the rod and thus wet it with lubricant. However, if the spindle grooves of a rod embodied as a threaded spindle are also to be supplied with lubricant, then the lubricating strip can further possess a plurality of projections, each of which engages a corresponding spindle groove. If lubrication of the remaining outer circumferential surface of the threaded spindle is to be avoided, this can be accomplished by appropriately long wetting of the projections which engage the spindle grooves. By this means, the connecting sections of the lubricating strip located between two adjacent projections can be spaced apart from the outer circumferential surface of the threaded spindle.
It is advantageous for the lubricating element to extend over essentially the entire length of the groove. However, if sufficient axial space is available, a wiping element can be arranged in the groove ahead of and/or behind the lubricating element viewed in the direction of the groove's extension, such wiping element's purpose being primarily to wipe from the surface of the rod dirt particles that enter the lubricating region and to
Kim Chong H.
Rexroth Star GmbH
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