Spindle drive unit

Details Spindle drive unit Spindle drive unit

1998-09-08

2001-03-13

Bucci, David A. (Department: 3682)

Machine element or mechanism

Mechanical movements

Reciprocating or oscillating to or from alternating rotary

C074S459500

Reexamination Certificate

active

06199440

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a spindle drive unit comprising a spindle having a spindle axis and an external circumferential surface, a nut embracing said spindle and being in threaded engagement with said spindle and at least one wiper assembly comprising at least one wiper member in wiping engagement with said external circumferential surface of said spindle, said wiper assembly being removably fastened to said nut in an axial end portion thereof.
2. Description of the Prior Art
A spindle drive unit like this is known from the DE 28 22 560 A1. In this known solution the wiper assembly comprises a sealing ring attached to the internal circumference of a sleeve. The sealing ring sealingly abuts on the back of an external thread of the spindle. The sealing ring is permanently riveted to the sleeve. The wiper assembly consisting of the sealing ring and the sleeve may be fixed to the nut when the nut is mounted on the spindle. For this purpose an axially projecting tubular socket is welded on the nut. The sleeve of the wiper assembly supporting the sealing ring is pushed on said tubular socket. Then the wiper assembly is manually adjusted in the axial direction with respect to the tubular socket until the sealing ring is optimally positioned on the back of the external thread of the spindle. After adjusting the wiper assembly, it is axially and circumferentially fixed to the tubular socket by means of pins and a clamp strap.
For this known solution an adaptation of the nut is necessary to be able to mount the wiper assembly. The nut has to be subjected to a welding process to attach the tubular socket to it. If a conventional nut, which can be obtained as a component of mass production, is to be used, it is often completely impossible to weld a tubular socket from the outside on the nut. Often the material of the nut or the components connected therewith do not allow welding of a tubular socket, for example due to high sensitivity to heat, great danger of deformation or poor welding properties. This especially applies to precision spindle drive units, which are used in machine tools or measuring devices. Moreover, welding is a comparatively extensive and difficult process as the tubular socket has to be positioned exactly in the radial direction in order to guarantee uniform abutment relations of the sealing ring at the back of the spindle thread across the entire circumference. Even in conventional nuts often no suitable place for welding the tubular socket is found for reasons of design or space. Finally, the tubular socket is no longer removable from the nut after welding so that the nut is assigned to a certain purpose of application and can no longer be used for other applications in which a wiper assembly axially attached from the outside is under certain circumstances not necessary anymore. In this case the welded tubular socket would be disturbing and require unnecessary space.
From U.S. Pat. No. 3,643,521 there is known a further spindle drive unit having a spindle and a nut being in threaded engagement with the spindle. In a mounted state of the nut a sealing ring can be attached to the nut from axially outside. The sealing ring engages with a threaded groove in the external circumferential surface of the spindle and is screwed on the spindle from one end of the spindle. A plurality of axially oriented peg receiving holes are provided in an axial end face of the nut distributed along the circumference. Similar peg receiving holes are also provided in the sealing ring. If the sealing ring, when mounted on, is turned into its desired axial position relative to the nut, the peg receiving holes in the sealing ring and the nut are aligned and then equipped with pegs which keep the sealing ring to the nut without being able to be turned. By means of a pretensioning member supported on the nut the sealing ring is axially biased away from the nut against the turn of the spindle thread.
Even in the solution according to DT 20 01 558 a conventional and commercially available nut cannot readily be used to attach the sealing ring. It is rather that the nut has to be purposefully machined to create the preconditons for mounting the sealing ring. For the peg receiving holes have to be drilled which causes an additional expenditure of work. Moreover the mounting of the sealing ring is extraordinarily laborious since the sealing ring has to be held against the action of the pretensioning member relative to the nut to be able to insert the individual pegs into the peg receiving holes which have been brought in alignment.
SUMMARY OF THE INVENTION
It is an object of the present invention to enable simple mounting of a wiper assembly on a nut in a spindle drive unit, largely avoiding special measures of adaptation at the nut.
To achieve this object the present invention provides a spindle drive unit, comprising a spindle having a spindle axis and an external circumferential surface, a nut embracing said spindle and being in threaded engagement with said spindle and at least one wiper assembly comprising at least one wiper member in wiping engagement with said external circumferential surface of said spindle, said wiper assembly being removably fastened to said nut in an axial end portion thereof, wherein said wiper assembly, for its fastening to the nut, is removably connectable with an adapter in a rotationally fixed manner, said adapter being removably connectable with said nut in an axially and rotationally fixed manner.
The adapter free of wiping tasks forms an interface member between the nut and the wiper assembly. The adapter is a component physically distinct from the nut and the wiper assembly—or a constructional unit. Said component or constructional unit may on the one hand be optimally adapted to the fastening possiblities of the nut, preferably of a conventional nut. This means that the adapter can be designed in such a way that it may be fixed to the nut without specially machining the nut, for example providing a welded tubular socket or bores. Thus, the nut can also be used for applications in which the wiper assembly and the adapter are not desired or not necessary. On the other hand, the adapter may be optimally adapted to the fastening possiblities present at the wiper assembly. For it has to be considered that in designing the wiper assembly first of all its wiping funciton is of importance. Therefore in fixing the wiper assembly it always has to be considered that its wiping function is optimally guaranteed. The adapter solves the obvious conflict of goals between a simple, however operatively secure fixing of the wiper assembly with at the same time an optimally ensured wiping function and the desired intactness of the nut so that a commercially available nut can be used requiring no subsequent treatment.
With respect to mounting it is favourable when at least the wiper member may be mounted on and dismounted from said nut in a mounting state of said nut in which said nut is mounted on said spindle. Then the spindle does not have to be dismounted from its spindle bearings in order to be able to fix the wiper member to the nut with interposition of the adapter. It is advisable that said adapter, in said mounting state of said nut, may also be mounted on or dismounted from said nut.
The mounting of the spindle drive unit is further simplified when at least a part of said wiper assembly including the wiper member and said adapter may be premounted to form a constructional unit and may be attached to said nut in the form of said constructional unit. In this case it is again favourable when the premounted constructional unit which comprises said wiper member and said adapter may be mounted on and dismounted from said nut in a mounting state of said nut in which said nut is mounted on said spindle.
A laborious axial positioning of the adapter relative to the nut is avoided when first cooperating axial abutment means are provided on said adapter and on said nut, respectively, and define an axial position of said adapter rel

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