CN1077833C - Motor-driven hand unit - Google Patents

Abstract

The invention relates to a motor-driven hand unit comprising a shaft (10) driven by a motor, which shaft is mounted by means of a bearing (13) in a recess (16) of a housing part (12) and carries a fan wheel (14) at an axial distance thereto. The bearing (13) is sealed on the axial side facing the fan wheel (14) in relation to said fan wheel (14) by means of an axial sealing element (30) rotating with the shaft (10), whereby said sealing element is embodied as a circular, rubber-elastic shaft seal, the flexible sealing lip (32) of which contacts the outside of the bottom part (17) of the housing (12) and seals the outlet (19) of same.

Description

Motor Driven Handheld Devices

The invention relates to a motor-driven handheld device.

Known this motor-driven hand-held device (DE-40 38 634 A1), in this device, the fan impeller axially is installed above the bearing of the shaft at a certain distance. For example, the handheld device is configured as a superfinishing device. When the motor is switched on and the shaft is thereby driven in rotation, the grinding dust generated during surface processing is sucked into a dust chamber by means of the rotating fan wheel through openings in the grinding plate and the sandpaper fastened thereto , and from this dust chamber through a discharge port into the connected container. Here, the bearing on the axial side facing the fan wheel is exposed directly to the dust in the dust chamber. As a result, the bearing becomes dusty relatively quickly, so that the bearing is difficult to access and the service life of the bearing is greatly reduced.

The purpose of the present invention is to provide a hand-held device driven by a motor, so that the bearing is well sealed relative to the dust chamber, preventing dust from entering the bearing, and preventing bearing lubricating grease from leaking, thereby improving the service life of the bearing.

According to the invention, a motor-driven hand-held device is proposed having a housing in which is housed an electric motor for driving a shaft which is mounted in the housing part by means of a bearing at an axial distance from the bearing The ground has a fan wheel, wherein the bearing is sealed against the fan wheel on the axial side facing the fan wheel by means of an axial sealing element that rotates coaxially.

The motor-driven hand-held device according to the invention has the advantage that the bearing is sealed from the dust chamber by the rotating axial sealing element, so that neither dust can get into the bearing, nor can bearing grease escape unintentionally from the bearing. This significantly increases the bearing service life.

A cost-effective, simple and well-tight axial sealing element can be obtained from a further advantageous embodiment of the invention. According to the invention, a good dust seal of the bearing can be achieved with a simple device, here, the elastic sealing lip balance tolerance, angular deviation, concentricity error and surface accuracy of the bottom surface, which also guarantees a permanent sealing contact . Due to the flexibility of the sealing lip, the surface of the housing part, in particular its bottom, on which the sealing lip abuts, is left untreated, for example without machining, without impairing the good sealing effect. Exactly, the surface does not have to be polished. Advantageously, the frictional effects can be reduced by adding grease to the contact area.

It is advantageous if the bottom surface which is in contact with the axial sealing element, in particular the flexible, at least one sealing lip, is not treated, for example machined, preferably greased. Furthermore, it is advantageous if the bearing, in particular the radial ball bearing, has on both sides contacting or non-contacting integrated seals in it, which seat in particular on the outer ring and axially relative to the inner ring. The end faces continue inward and extend at a distance therefrom. On the axial side of the bearing, especially the radial ball bearing, facing away from the axial sealing element, a washer that rotates with the shaft can be installed on the shaft, which is close to the end face of the inner ring and is at least very small. The small axial distance covers the sealing gasket in the bearing along the radial direction. It is also advantageous if the washer is formed from a sheet metal and if the washer and the inner ring of the bearing are secured axially on the shaft by means of a retaining ring. This produces a bearing seal on the opposite axial side in a simple and cost-effective manner, where less dust is generated in the hand-held device designed as a grinding device.

Furthermore, if the shaft has an eg eccentric bushing on the axial side of the fan wheel facing away from the axial sealing element, a grinding plate is rotatably mounted via a bearing on a corresponding sleeve-shaped inner ring, It is also beneficial. The bearing of the grinding plate can be formed as an open needle roller sleeve, which is axially sealed on the axial side facing the fan wheel by means of at least one sealing element, which is designed as a radial shaft sealing ring. It is also advantageous if two radial shaft sealing rings are mounted axially in series. At least one sealing element of the bearing can be designed as a sealing ring with a cross-section approximately corresponding to a flat U-shape with two protruding sealing lips. As a result, the bearing associated with the grinding plate is easily dust-tight on the axial side facing the dust chamber.

An exemplary embodiment of the invention is described in detail in the following description with the aid of the associated drawings. in:

Figure 1: Axial longitudinal section of the superfinishing device;

Figure 2: A partially enlarged schematic view of Figure 1.

1 and 2 show a motor-driven hand tool 1, in particular a grinding device, such as a superfinishing device, which has a housing 2, a motor 3 housed in an upper housing part 12, the motor A grinding plate 11 designed as an oscillating element is driven via a shaft 10 coaxial therewith. The shaft 10 is supported in the housing part 12 by means of a bearing 13 . In this hand tool, the housing 12 encloses a fan impeller 14 which is located in a dust chamber 15 enclosed by the housing part 12 and is mounted on the shaft 10 by means of a bushing 18 in a non-rotatable manner relative to the shaft 10 , so that it rotates about axis 10. The bearing 13 is located outside the dust chamber 15 and is accommodated in an approximately bowl-shaped receptacle 16 of the housing part 12 such that the bottom 17 of the receptacle 16 covers the bearing 13 on the side facing the fan wheel 14, here, The base 17 has a through hole 19 through which the shaft 10 fitted with the bushing 18 passes.

The bearing 13 is designed, for example, as a radial ball bearing, the outer ring 20 of which is fixed against rotation in the approximately bowl-shaped receptacle 16 and can be supported axially on the base 17 . The inner ring 21 is seated on the shaft 10 without relative rotation. The base 17 is dimensioned such that it extends radially approximately to the inner ring 21 . Bearing 13 , in particular a bearing designed as a radial ball bearing, is sealed against fan wheel 14 on the axial side facing fan wheel 14 by means of an axial sealing element 30 which is coaxial with shaft 10 and bushing 18 run. The sealing element 30 is formed by an annular, flexible and here in particular rubber-elastic shaft seal and has a sealing body 31 and a flexible sealing lip 32 which are integral with one another. The sealing lip 32 projects axially from the sealing body 31 approximately in the shape of an inverse frustum and is elastically displaceable relative to the sealing body 31 . The sealing element 30 is sleeved on the shaft 10 or the shaft sleeve 18 with a certain bias and elastically clamped and fixed. The radial dimensions of the sealing element 30 are chosen such that the sealing element 30 seals the through-opening 19 of the bottom 17 relative to the dust chamber 15 . The sealing element 30 rests elastically against the base 17 with its axial side facing the base 17 . The through hole 19 is thus hermetically closed without any possible voids. Due to the contact, the sealing element 30 , which rotates with the shaft 10 , rubs against the facing surface 22 of the bottom 17 . The sealing lip 32 protrudes in the direction of the bottom 17 and its surface 22 , where the sealing lip 32 rests against the surface 22 of the bottom 17 preferably with a low prestress. In this way, an at least low contact pressure of the sealing lip 32 is produced. Due to the displaceability of the sealing lip 32 , tolerances, concentricity errors, angular deviations or other similar errors, in particular of the base 17 , can be compensated. The sealing lip 32 plays a good sealing role in the axial direction, that is, the sealing of the bearing 13 relative to the dust chamber 15 . When the shaft 10 rotates, the sealing lip 32 is somewhat relieved by the centrifugal force, as a result of which the friction at the contact point with the base 17 and thus the wear of the sealing lip 32 can be reduced.

Housing part 12 preferably consists of light metal, here in particular die-cast aluminum. The surface 22 of the bottom 17 which is in contact with the flexible sealing lip 32 is untreated, for example unmachined, cast, rather this surface 22 does not have to be polished. It is advantageous if the surface 22 is greased, by which the friction in the region of the contact surface with the sealing lip 32 can be reduced.

The use of the axial sealing element 30 in the manner described achieves a good sealing of the bearing 13 from the dust chamber 15 and in a simple and cost-effective manner, especially when the axial sealing element 30 is already prevalent as a component of this type .

The bearing 13, in particular the radial ball bearing, has on both sides integrated seals 23 and 24, which are only schematically shown in FIG. It runs further inward toward the end face 25 or 26 and at a distance therefrom. On the shaft 10, on the axial side of the bearing 13 facing away from the axial sealing element 30, i.e. on the upper side of the figure, a washer 27, for example made of a thin plate, is mounted without relative rotation, which is coaxial with the shaft 10. Spin together. The washer 27 rests against the end face 26 of the inner ring 21 and covers the integrated sealing washer 24 radially with at least a small axial distance, so that between the rotating washer 27 and the non-rotating sealing washer 24 There is no friction. The use of non-ground shims for this type of sealing allows simple and low-cost assembly. Here, the end face 26 of the inner ring 21 protrudes somewhat axially beyond the built-in sealing washer 24, so that a narrow gap is created between the washer 27 and the sealing washer 24, which can be filled with a lubricant, such as lubricating grease , which is beneficial.

Mounted on the shaft 10 is a safety ring 28 , via which the spacer 27 and the inner ring 21 of the bearing 13 are secured axially on the shaft 10 via the spacer 27 . As the shaft 10 rotates, the spacer 27 acts as a retaining ring, which is sufficient to axially seal the bearing 13 on this side.

On the axial side of the fan wheel 14 facing away from the axial sealing element 30 , the shaft 10 has an eg eccentric bushing 40 on which the grinding plate 11 is rotatably supported by means of a bushing-shaped inner ring 41 via a bearing 42 superior. In the illustrated embodiment, the bearing 42 of the grinding plate 11 is formed by an open needle roller sleeve, which is axially sealed on the axial side facing the fan wheel 14 by means of at least one sealing element 43 which Between the grinding plate 11 and the sleeve-shaped inner ring 41 there is an interaction. The sealing element 43 is designed as a radial shaft sealing ring, here, in the exemplary embodiment shown, two identical radial shaft sealing rings are provided, which are mounted axially in series. In another embodiment not shown, at least one sealing element 43 is formed as a sealing ring with a substantially U-shaped cross-section and two protruding sealing lips, one of which is used as a sealing lip for sealing. function, the other sealing lip acts as a dust lip. By means of at least one sealing element 43 , the bearing 42 is sealed in a simple manner relative to the dust chamber 15 and to the dust generated therein at the point facing the fan wheel 14 .

Claims (12)

1. motor-driven hand-held device, has a housing, the motor that is used to drive an axle (10) is contained in the housing, this axle is installed in housing parts (12) lining and has a draught fan impeller (14) with bearing (13) the axial spacing ground that is separated by by means of a bearing (13), it is characterized in that bearing (13) is in axial seal element (30) sealing of rotating together by means of coaxial (10) with respect to draught fan impeller (14) towards the axial side of draught fan impeller (14).

2. according to the described hand-held device of claim 1, it is characterized in that axial seal element (30) is made of a shaft seal annular, flexible, caoutchouc elasticity.

3. according to claim 1 or 2 described hand-held devices, it is characterized in that, axial seal element (30) has a seal (31) and seal lip (32) that at least one is flexible, and seal lip has been alarmmed by seal (31) and can be moved with respect to the sealing body elasticity at an anti-truncated cone shape of axial side.

4. according to the described hand-held device of claim 1, it is characterized in that axial seal element (30) is nested with at axle (10) with prestressing force or is positioned on the axle sleeve (18) of the draught fan impeller (14) on the axle (10), and elasticity is fixed with clamping.

5. according to the described hand-held device of claim 1, it is characterized in that, housing parts (12) surrounds draught fan impeller (14) and surrounds a dust room (15), in the receiving member that roughly is bowl-type (16) lining of housing parts (12) and fixed like this, the basic loam cake in bottom (17) that makes receiving member (16) is on the bearing (13) of draught fan impeller (14) side in dust room (15) outside for bearing (13).

6. according to claim 1 or 5 described hand-held devices, it is characterized in that bearing (13) radially extends to the interior ring (21) of bearing (13) as the bottom (17) of radial ball bearing formation and housing parts (12).

7. according to claim 1 or 5 described hand-held devices, it is characterized in that axial seal element (30) makes the through hole (19) of bottom (17) with respect to dust room (15) axial seal.

8. according to the described hand-held device of claim 5, it is characterized in that axial seal element (30) flexibly leans against on the bottom (17) with its axial side towards bottom (17).

9. according to the described hand-held device of claim 3, it is characterized in that a flexible seal lip (32) of axial seal element (30) leans against on the bottom (17) with little prestressing force at least.

10. according to the described hand-held device of claim 1, it is characterized in that housing parts (12) is made of light metal.

11., it is characterized in that described hand-held device is a grinding attachment according to the described hand-held device of claim 1.

12., it is characterized in that housing parts (12) is made of die casting aluminium according to the described hand-held device of claim 1.