The invention is based on a flow-medium-driven hand-held power tool as generically defined by the preamble to claim 1.
From U.S. Pat. No. 6,347,985 B1, a hand-held power tool is known that is driven solely by way of the suction air flow of a vacuum cleaner. The key element in the known hand-held power tool is a conventional Pelton turbine, which uses the suction air of the vacuum cleaner for rotating the power takeoff spindle and thus for driving the tool.
The efficiency of the known hand-held power tools, with axial and Pelton turbines, also known as resistance rotors, which output a mechanical power to a shaft solely on the basis of the air pulse, are only limitedly capable of meeting stringent requirements in terms of the working performance and suction extraction power of these hand-held power tools that are capable of being operated with commercially available vacuum cleaners.
The invention having the characteristics of claim 1 has the advantage that the hand-held power tool, designed without its own electric motor and operated as a sander with only the suction air of a vacuum cleaner, has such high efficiency for its intended purposes that an especially large amount of flow energy from the suction air or blown air can be converted into mechanical power, and virtually dust-free sanding, drilling or the like, with continuous removal of the dust particles produced in the sanding process, is assured, thus combining a high degree of chip removal with highly effective suction extraction of the sanding dust; in short, an especially advantageous variety of turbine—a kind of hybrid between a classical radial turbine with a flow through it and an axial turbine—is created, which is designed as a radial turbine that has a diagonal flow through it. It combines the advantage of low pressure loss with that of increased energy yield from the air flow and therefore forms a highly effective drive mechanism for electric tools that have an air flow through them.
Because there is a fixed upstream baffle, located in front of the turbine wheel and acting as a bearing seat for a rotary bearing of the axial shaft of the turbine wheel, it takes on a load-bearing function of the housing structure of the hand-held power tool, and thus the production costs for the hand-held power tool can be kept especially low.
Because the drive mechanism comprises only lightweight plastic parts, the hand-held power tool is especially light in weight and handy.
Because the hand-held power tool is provided with a radio switch, with which the vacuum cleaner can be switched on and off, convenient, simple operation of the hand-held power tool and of the vacuum cleaner is possible.
Because the speed governing for the hand-held power tool is done by means of a variably adjustable air flap, adapting the rpm of the power tool to the working conditions at the time can be done easily and inexpensively.
Because the housing of the hand-held power tool comprises tubular parts, which can be connected to one another via flanges, it is especially dimensionally rigid and sturdy despite its own low weight.
The present invention is described in further detail below in terms of an exemplary embodiment and the associated drawing.
Shown are:
At the bottom, the housing 12 ends in a straight, encompassing lower edge 34, which in its vertical projection downward forms a triangle with convex sides. Located parallel to the lower edge 34 is a sanding disk 70, which is elastically movably joined to the housing 12 via elastic oscillating bodies 75. The sanding disk 70, with its outline of an iron for clothing, protrudes on the outside past the triangular contour of the lower edge 34 projected vertically downward, and on its underside it has retention means for receiving a sanding sheet, not shown. It can be driven orbitally via an axial shaft 72 and an eccentric, not identified by reference numeral, seated on its end in a manner fixed against relative rotation, so that every point of the sanding disk and thus each individual grain on the sanding sheet describes small circles, which is the typical sanding pattern of an orbital sander.
The axial shaft 72 is slaved in rotating fashion via a turbine wheel 38 of an air-drivable turbine 36 and is rotatably supported in the housing 12 and in the upstream baffle 74 via one upper and one lower roller bearing 64, 66, and with its lower end it engages a third roller bearing 68, which is seated with its outer ring in a manner fixed against relative rotation in the sanding disk 70. Between the lower roller bearing 66 and the third roller bearing 68, the axial shaft 72 is joined in a manner fixed against relative rotation to a compensation mass 78, which serves as an imbalance compensator, to keep vibration of the eccentrically moved sanding disk 70 away from the housing 12.
The compensation mass 78, on its upper side toward the upstream baffle 74, has an upward-protruding annular profile 80. This profile is embraced at the top by an annular groove 82 with a slight spacing, this groove being located in the closely adjacent underside of the upstream baffle 74 and together with the annular profile 80 jointly forming a lower, meandering labyrinth seal 84. This seal prevents dust and chips from being moved in the gap or to the lower bearing 66 as a result of the underpressure in the hollow chambers in the interior of the hand-held power tool 10, and in particular between the compensation mass 78 and the upstream baffle 74, so that the lower bearing remains unimpaired for a long time.
The axial shaft 72 is embraced centrally by the turbine wheel 38 in a manner fixed against relative rotation, and an intimate form-locking connection is made between the two parts, by means of knurling 73 in a defined circumferential region, approximately in the middle of the axial shaft 72, into the indentations of which the plastic, which is liquid in the casting process, enters and thus brings about the connection.
The turbine wheel 38 has a bell-shaped outer contour, and the lower edge 34 is adjoined axially downward by an upstream baffle 74 with baffle blades 75 that is held in the housing 12 in a manner fixed against relative rotation or can be clamped between the housing shells 14. The baffle blades 75, like the wheel blades 42 of the turbine wheel 38, are designed as plastic strips standing on their short sides. The upstream baffle 74, designed as a short truncated cone, is embraced on the outside at least partially by the turbine housing 60, likewise placed in the housing 12 in a manner fixed against relative rotation, at the spacing of the height of the baffle blades 75, so that a lower extension of the annular flow conduit 49 of the turbine wheel 38 is thus formed, through which the suction air is drawn or conducted. Via the baffle blades 75, the suction air flowing in from below is steered, for driving the turbine wheel 38, in the flow direction of the turbine wheel, or in the flow direction of the flow conduit 49 or of the wheel blades 42 of the turbine wheel 38, and is calmed, so that as a result the efficiency of the turbine 36, especially on the inlet side, is improved considerably. The upstream baffle 74, with a central recess 76 on its underside, forms a bearing seat for a bearing 66 of the lower region of the axial shaft 72, which bearing fixes the axial shaft in the housing 12 and guides it.
At the top, in the region of the virtual tip 46 of the cone, the conical cap 44, with minimal spacing, borders on the conduit wall 28 of the air conduit 26, through which the suction air is guided in a streamlined way to the underpressure source or to the vacuum cleaner.
The load-bearing cone 48 or truncated cone of the turbine wheel 38 is penetrated by a central hollow cylinder 54 for receiving the axial bolt 72. Toward the top, in the region of a virtual tip of the cone, the hollow cylinder forms a protruding annular collar 52. As a result, the hollow cylinder 54 attains a length such that the axial shaft 72, given a defined axial oversize and given a defined region of its knurling 73, is positioned relative to the turbine wheel in a way that is secured with this knurling 73 in the interior of the hollow cylinder 54 and is embraced by that cylinder, so that a secure rotary fixation is achieved between the turbine wheel 38 and the axial shaft 72.
The frustoconical conical cap 44, with increasingly concave curvature in the direction of the virtual tip 46, has an annular sealing bead 56 on its outside, a third of the way up. This bead is intended for axial engagement with an annular groove 57, located toward the turbine wheel 38 inside the shell-like turbine housing 60, that fits over the sealing bead 56 and thereby functions as an upper labyrinth seal 51 and prevents pressure losses in the interior of the turbine 36 and thus enhances the turbine efficiency considerably.
For operating the hand-held power tool 10, air is extracted by suction at the suction air outlet 18 and flows through suction extraction openings 71 in the sanding disk 70 and in from the outside between the top of the sanding disk 70 and the lower edge 34 of the housing. The air aspirated from outside gets into the annular conduit 49 of the upstream baffle 74 and onward into that of the turbine wheel 38.
The contact of the radial turbine wheel 38 and of the upstream baffle 74 with abrasive air containing dust can lead there to a grinding down and dust deposition effect, which can impair the performance of the drive mechanism and its service life. To counteract this, the surfaces touched by suction air are structured, in particular by means of small, typically golf-ball-like dimples, such that they have low flow resistance with increased surface strength.
The side view, shown in
The side view shown in
In an exemplary embodiment of the hand-held power tool, not shown, its housing—in a way similar to the exemplary embodiments above—has a radio switch, which communicates with a counterpart switch associated with the vacuum cleaner, and with which turning the vacuum cleaner and thus the hand-held power tool on and off is achieved conveniently and inexpensively.
The air that flows through the hand-held power tool 10 does not, as in a classical radial turbine, flow purely radially inward before it is deflected axially again in the turbine 36, but instead, both in the upstream baffle and in the turbine 36, it flows at an angle of approximately 40° to the axis of rotation (see
The additional collar 52 on the inner ring of the turbine wheel 38 is necessary so that the axial shaft 72 put in place or spray-coated can be knurled in the middle. With knurled shafts, care must be taken in their manufacture to assure that they remain as symmetrical as possible, so that they cannot be inserted wrong (
An inventive quality is ascribed to the individual characteristics recited above, since jointly they contribute to the particular advantages of the embodiment.
Number | Date | Country | Kind |
---|---|---|---|
10 2004 058 581.4 | Dec 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2005/055230 | 10/13/2005 | WO | 00 | 4/18/2006 |