Hand-Held Power Tool Driven By A Flow Medium

Abstract

Disclosed is a hand-held power tool with a housing (12) and a tool (70)—a cutting tool, in particular—located thereon in a manner which allows it to be driven in a rotating and/or oscillating manner, it being possible to operate the tool (70) using a suction air flow, via a vacuum cleaner, in particular; the hand-held power tool is made particularly robust and safe against becoming clogged with chips by the fact that it is driven by a turbine (36) with a rotatable turbine wheel (38) and a stationary turbine housing (60); means ( ) are located between the turbine wheel (38) and the turbine housing (60) for carrying away dust and chips which accidentally enter this space.

Description

The present invention is directed to a hand-held power tool driven by a flow medium, according to the preamble of Claim 1.

U.S. Pat. No. 6,347,985 B1 makes known a hand-held power tool which is driven solely via the suction air flow of a vacuum cleaner. The core of the known hand-held power tool is a conventional Pelton turbine which uses the suction air from the vacuum cleaner to rotate the driven spindle and, therefore, to drive the tool. The efficiency and robustness of the known hand-held power tools with axial and Pelton turbines—also referred to as drag-type rotors—which provide mechanical power to a shaft solely via air impulses are not capable of meeting the high demands placed on the output and suction power of these hand-held power tools which can be operated using commercial vacuum cleaners. In particular, particles drawn in with the suction airstream can enter the narrow air gap between the turbine wheel and the turbine housing, which exists due to the design. Coarse particles are unable to escape. If they accumulate, they can jam the turbine and impair its performance.

ADVANTAGES OF THE INVENTION

The advantage of the present invention which has the features listed in Claim 1 is that a material-removing, hand-held power tool—designed as a sander or a milling machine, in particular—which does not include an electric motor is that it is driven by a turbine which can only be operated with suction air, e.g., from a vacuum cleaner, and which includes a rotatable turbine wheel and a stationary turbine housing. Means are located between the turbine wheel and the turbine housing to carry away particles such as dust and chips which accidentally enter this space. The present invention is highly efficient and robust for its intended use. As a result, a particularly high portion of flow energy from the intake and blast air can be converted to mechanical power. It is also ensured that sanding, milling, drilling, etc., operations which produce nearly no dust in the surroundings can be carried out, while dust particles forming during the sanding process are removed continually, thereby combining a high rate of material removal with highly effective suctioning away of grinding dust. In short, a particularly advantageous type of turbine is created, which is basically a cross between a classical direct-flow radial turbine and an axial turbine, and which is designed as a diagonal-flow radial turbine. It combines the advantage of minimal power loss with the advantage of increased energy yield from the airstream and therefore serves as a highly effective drive for air-moving power tools. The risk associated with the outgoing air which drives the turbine by flowing through it and which contains particles is offset by certain means. These means are located between the turbine wheel and the turbine housing and serve to carry away or allow the exit of wayward dust and chip particles which leave the main airstream and enter the spaces between the moving parts of the turbine, thereby threatening to impair their motion.

Given that the means are designed, at the least, as an opening which passes through the turbine housing close to the inflow point of the drive air, the particles can leave the turbine via a short path, without causing any noticeable blocking or braking effects. By providing openings in the side of the housing which have special shapes and locations, it is possible to direct coarse particles, in particular, radially—due to their direction of motion—out of the gap between the turbine wheel and the turbine housing before they can create a jam.

Given that the means described above are also formed via surface recesses and/or an increased surface roughness of the turbine wheel—adjacent to the opening of the turbine housing in particular—which serve to carry the particles along and create a preferably pulsing airstream toward the opening described—in order to blow the particles through this opening, continual particle removal is improved, and the risk of the turbine wheel becoming jammed with the turbine housing is reduced further.

Given that a stationary guide-blade row is located in front of the turbine wheel and serves as a bearing seat for a pivot bearing of the drive shaft of the turbine wheel, it performs the function of supporting the housing structure of the hand-held power tool, which allows the manufacturing costs of the hand-held power tool to be kept particularly low.

Given that the drive is composed only of lightweight plastic parts, the hand-held power tool is particularly lightweight and easy to handle.

Given that the hand-held power tool is provided with a wireless switch with which the vacuum cleaner can be turned on and off, convenient and easy operation of the hand-held power tool and the vacuum cleaner is made possible.

Given that the rotational speed of the hand-held power tool is regulated using an adjustable air flap, it is possible to adapt the machine speed to the particular working conditions in an easy, cost-effective manner using simple means.

Given that the housing of the hand-held power tool is composed of tubular parts which can be connected with each other using a flange, it is particularly dimensionally stable, robust, and lightweight.

DRAWING

The present invention is explained below in greater detail with reference to an exemplary embodiment and the drawing.

FIG. 1 shows a longitudinal cross section of a finishing sander

FIG. 2 shows a longitudinal cross section of the turbine with guide-blade row for driving the finishing sander

FIG. 3 is a side view of the turbine in FIG. 2

FIG. 4 is a sectional side view of the turbine, with turbine housing

FIG. 5 is a top view of the turbine wheel, with turbine housing

FIG. 6 is an oblique view of the turbine wheel, with turbine housing

FIG. 7 is a top view of the turbine housing

FIG. 8 is a top view of the turbine wheel

FIG. 9 is a side view of the chip outlet in the turbine housing

FIG. 10 is a top view of the chip outlet in the turbine housing

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

FIG. 1 shows a hand-held power tool 10 designed as a finishing sander, in a view of the interior of housing longitudinal shell 14. It forms—together with a second, not-shown, essentially symmetrical housing shell—a bell-shaped housing 12 with a normal axis 13. Housing 12 is joined by connecting the two housing shells using screws which pass through the outer, not-shown housing shell from the outside and can be screwed into screw mandrels 35, thereby holding the two housing shells together at a vertical joint. On its top side 20, housing 12 transitions into a hollow cylindrical handle 16 which projects transversely from normal axis 13 and serves as suction air outlet 18. An air flap 22 is mounted on top side 20 of housing 12, which opens or closes an opening 24 to flow channel 26 inside housing 12, to regulate the air intake as necessary. To this end, a region 86 of a channel wall 28 located close to opening 24 is perforated, so that the suction air can communicate with the outside air in tubular flow channel 26. Channel wall 28 is held on housing shells 14 via support ribs 30. Support ribs 30 are connected with reinforcement ribs 32 inside housing shell 14 and, via these, with the outer wall of the housing and housing shell 14. As a result, air channel 26 and channel wall 28 are reinforced, and, in particular, they are stabilized against vibrations and resonances with the suction air which flows through.

At the bottom, housing 12 terminates in a straight, circumferential lower edge 34, whose perpendicular projection downward forms a triangle with outwardly arched sides. A sanding disk 70 is located parallel with lower edge 34 and is connected with housing 12 in an elastically movable manner via elastic, oscillating body 75. Sanding disk 70 extends with its U-shaped base surface outwardly past the triangular, perpendicularly downwardly projected contour of lower edge 34 and has retaining means on its underside for accommodating a not-shown sanding pad. It can be driven in an orbital manner via a drive shaft 72 and an eccentric which is non-rotatably mounted on its end and is not described further, so that each point of the sanding disk and, therefore, every individual sanding grain of the sanding disk forms small circles, i.e., the typical sanding pattern created by an orbital sander.

Drive shaft 72 is driven in a rotating manner via a turbine wheel 38 of an air-drivable turbine 36, and is rotatably supported in housing 12 and in guide-blade row 74 via an upper and lower roller bearing 64, 66 and engages with its lower end in a third roller bearing 68 which is non-rotatably mounted via its outer ring in sanding disk 70. Between lower and third roller bearing 66, 68, drive shaft 72 is non-rotatably connected with a balancing mass 78 which serves to compensate imbalances, in order to cancel out oscillations of eccentrically moved sanding disk 70 far away from housing 12.

An upwardly projecting annular profile 80 is formed on the top side of balancing mass 78, which faces guide-blade row 74. It is enclosed by an annular groove 82 with slight clearance located in the closely adjacent underside of guide-blade row 74 and, together with annular profile 80, forms a lower, meander-like labyrinth seal 84. This prevents dust and chips from entering the gap or being moved to lower bearing 66 by the vacuum in the cavities in hand-held power tool 10, and between balancing mass 78 and guide-blade row 74 in particular. As such, the gap and lower bearing 66 are protected for a long period of time.

Drive shaft 72 is non-rotatably enclosed in the center by turbine wheel 38, thereby creating an inner, form-fit connection between the two parts via a knurl 73 in a defined circumferential region approximately in the center of drive shaft 72, in the recesses of which liquid plastic enters during the casting process, thereby creating the connection.

Turbine wheel 38 has a bell-shaped outer contour. A guide-blade row 74 with lattice blades 75—which is non-rotatably held and can be clamped between housing shells 14—abuts lower edge 34 axially downwardly. Lattice blades 75 are designed as plastic strips mounted on their narrow side, similar to wheel blades 42 of turbine wheel 38. Guide-blade row 74, which is designed as a short truncated cone, is at least partially enclosed on the outside by turbine housing 60—which is also non-rotatably supported in housing 12, at a distance equal to the height of lattice blades 75, thereby forming a lower continuation of annular flow channel 49 of turbine wheel 38, through which the suction air is drawn and directed. Via lattice blades 75, the suction air which flows in from the bottom to drive turbine wheel 38 in its direction of flow, and/or the suction air from flow channel 49 or wheel blades 42 of turbine wheel 38 is directed and its swirling is eliminated, thereby improving the efficiency of turbine 36 considerably, especially on the input side. Guide-blade row 74 forms—with a central recess 76 on its underside—a bearing seat for a bearing 66 of lower region of drive shaft 72, which fixes drive shaft 72 in position in housing 12 and guides it.

Turbine housing 60 encloses—with an annular groove 57 in its upper region—the outside of turbine wheel 38 and its annular sealing ridge 56 with a certain gap distance and forms an upper labyrinth seal 51 there. An opening 102 (FIG. 5) is located on each of two diametrically opposed sides in turbine housing 60 close to annular groove 57 so that wayward chips and dust particles which enter the region between the outside of turbine wheel 38 and turbine housing 60 can therefore exit as quickly as possible without braking or blocking turbine wheel 38. The unwelcome particles can be pushed out of these openings 102 via the mechanical transfer effect of turbine wheel 38 and via an airstream in addition to the suction airstream which drives the turbine, which is produced in the gap between turbine wheel 38 and turbine housing 60 via the design of the outer surface of turbine wheel 38 in the region of openings 102 when turbine wheel 38 rotates.

FIG. 2 shows a longitudinal cross section of turbine wheel 38 with guide-blade row 74—which terminates axially downwardly and is fixed in position in housing 12—as an isolated component, while it is shown installed in FIG. 1. A support cone 48 which is shaped like a truncated cone and is arched outwardly—similar to the cone of a juice squeezer—is shown, on which a large number of wheel blades 42 is mounted, which are shaped like flat plastic strips mounted in an upright position via their narrow sides on support cone 48, and the height of which increases gradually in the direction toward the—virtual—cone peak. A cover cone 44 which extends nearly in parallel with support cone 48 and the upper edges of wheel blades 42 is joined via wheel blades 42. As a result, a flow channel 48 with an annular cross section is formed between support cone 48 and cover cone 44. It is subdivided by wheel blades 42 into a large number of winding, individual channels, into which the suction air can flow with particularly low flow resistance to drive turbine 36. The lower edge of support cone 48 is tilted at an angle of approximately 45° to the cone axis and extends at an angle of approximately 90° transversely to the cone axis, unlike conventional radial turbines. With a particularly favorable exemplary embodiment of turbine 36, the inflow angle of the blades is 40°, and their outflow angle is 30°. As indicated by directional arrow 62, the air which flows along wheel blade 42 is redirected by 45° relative to axis 40. The redirection transverse to the plane of the drawing is not yet taken into account.

In the region of virtual cone peak 46, cover cone 44 abuts channel wall 28 of air channel 26 with minimal clearance; the suction air is guided aerodynamically through air channel 26 toward the vacuum source, i.e., toward the vacuum cleaner.

Support cone 48 or truncated cone of turbine wheel 38 is penetrated by a central hollow cylinder 54 which accommodates shaft 72. At the top, in the region of a virtual cone peak, hollow cylinder 54 forms a projecting, annular collar 52. Hollow cylinder 54 therefore attains a length such that drive shaft 72—with a defined axial extension and a defined region of its knurl 73—is positioned securely relative to the turbine wheel via this knurl 73 in the interior of hollow cylinder 54 and is enclosed by it, thereby resulting in reliable rotation between turbine wheel 38 and drive shaft 72.

Cover cone 44—which is designed as a truncated cone and with a concave arch which increases in the direction toward a virtual tip—includes an annular sealing ridge 56 in the lower one-third of its height, on its outside. It is provided for axial engagement in an enclosing annular groove 57 located on the inside of shell-like turbine housing 60 which faces turbine wheel 38 by extending over sealing ridge 56 as an upper labyrinth seal 51, and prevents pressure losses inside turbine 36, therefore increasing its efficiency considerably.

To operate hand-held power tool 10, air is suctioned at suction air outlet 18 and flows from the outside through suction holes 71 in sanding disk 70 and between the top side of sanding disk 70 and lower housing edge 34. The air drawn in from the outside enters annular channel 49 of guide-blade row 74 and travels further into the annular channel of turbine wheel 38.

If radial turbine wheel 38 and guide-blade row 74 come in contact with abrasive, dusty air, they can become worn and dust can deposit there, which can negatively affect the power and service life of the drive. To prevent this, the surfaces which come in contact with suction air are designed with slight, regular, golf ball-type recesses in particular, so they have low flow resistance and increased surface strength.

In the side view of turbine 36—from FIG. 2—shown in FIG. 3, one can see turbine housing 60 with one of the two openings 102. Turbine housing 60 shown in FIG. 1 is retained non-rotatably in housing 12 and is locked in position or clamped on support ribs 30 and extends past guide-blade row 74 and turbine wheel 38 closely or with clearance, and forms upper labyrinth seal 51 described above.

With a not-shown exemplary embodiment of the hand-held power tool—which is similar to the exemplary embodiments described above—a wireless switch is mounted on the housing, which communicates with a matching switch assigned to the vacuum cleaner, and which can be used to turn the vacuum cleaner and, therefore, the hand-held power tool, on and off in a convenient, cost-favorable manner.

Unlike a classical radial turbine, the air which flows through hand-held power tool 10 does not flow purely radially inwardly before it is redirected axially in turbine 36. Instead, it flows in the guide-blade row and in the radial turbine at an angle of 45° relative to normal axis 40 (see FIG. 2). The advantage of this oblique flow is that the efficiency of the turbine is increased markedly, since the loss of pressure inside turbine 36 and guide-blade row 74 is minimized. The inflow angle of the blades is 60°, and the outflow angle is 30°, in order to also keep the outflow losses as low as possible. The angles for the inflow region can vary between 0° and 70°, and the angles in the outflow region can vary between 10° and 60°. The angle is selected depending on the quantity of air and the rotational speed expected. The purpose of guide-blade row 74 is to provide the airstream with the greatest amount of pre-rotation possible. For this reason, it includes lattice blades 75 with an emergent angle of approximately 80°. A slight clearance is required between guide-blade row 74 and turbine 36, so that the airstream can contact turbine 36 in the most ideal manner possible. An additional support ring 88 between support ribs 90 on the underside of support cone 48 prevents a highly fluctuating and uncontrolled no-load speed of the turbine, which can be extreme (>20000 rpm), since a fan effect cannot occur when ribs are positioned purely radially. Support ring 88 and support ribs 90 are sized such that they become thinner in the radially outward direction, so that, during injection molding, the material can flow outwardly quickly and with low resistance and fill all cavities in the mold.

Additional collar 52 on inner ring of turbine wheel 38 is required so that drive shaft 72—which has been inserted and coated via injection molding—can be knurled in the center. For reasons of space, lower bearing 66 is integrated directly in guide-blade row 74 and makes it possible for hand-held power tool 10 to have a flat design.

A turbine 36 depicted spacially in FIG. 4 is composed of a turbine wheel 38 which is enclosed by a turbine housing 60 which encloses a guide-blade row 74 underneath turbine wheel 38.

Three particles—which are depicted as circles—e.g., grinding dust or chips 108—are shown between turbine housing 60—shown in a partially exposed view—and the outer surface of turbine wheel 38. In addition, oval indentations 103 are provided on the outer surface of turbine wheel 38, which can accelerate the ambient air and create a pulsing air flow, so that particles 108 wandering between turbine housing 60 and turbine wheel 38 are carried along and are preferably transported toward guide-blade row 74, so that they can join the main airstream flowing toward the external vacuum cleaner, which serves as drive means for operating turbine 36 and serves to remove the particles. As an alternative, particles 108 can be pushed and/or blown toward openings 102 (FIGS. 3, 5).

FIG. 5 shows a top view of turbine 36. Turbine wheel 38 is shown; it is enclosed in the upper region by turbine housing 60. Also shown in the figure are the two openings 102 which pass through turbine housing 60 on two diametrically opposed sides in the upper region and which serve to carry chips away, and, through openings 102, the adjacent outer side of turbine wheel 38.

FIG. 6 shows a spacial side view of turbine 36. The same details are depicted as in FIG. 5, but the design of keyhole-type opening 102 is illustrated more clearly. Turbine housing 60—which is designed as a stepped cylinder—extends downward in four steps and expands in the manner of a bell. An opening 102 which opens in the radial and axial directions passes through an uppermost, cylindrical step section on diametrically opposed sides; it extends into the next conical step section in the axially downward direction. Opening 102 is designed in the shape of a keyhole. It is 9 mm wide at the top, 3 mm wide at the bottom, and is approximately 15 mm tall. Its lower hole region 111 is offset to the left as shown in the drawing, eccentrically relative to upper region 112.

Leading edge 120 of opening 102 shown at the left in the figure extends—relative to normal axis 40—upwardly and toward the outside left, angled axially (see FIG. 9, angle α), and radially outwardly, opening at an angle. Leading edge 120 therefore offers the chips which are moving outwardly in the direction of rotation of turbine wheel 38 as indicated by rotational-direction arrow 130 a minimal rebounding surface; the chip-removal conditions are therefore favorable.

As shown in FIGS. 5 and 7, upper region 112 of opening 102 has a semicircular contour in the horizontal cover surface of stepped-cylindrical turbine housing 60, which is intersected by V-shaped, lower hole region 111 which extends downward toward the jacket surface. Semicircular, upper region 112 transitions into V-shaped edges 120, 121 of the abutting section—which narrows into the shape of a V—of lower hole region 111. A ramped knife edge 140 is formed in the transition of leading edge 120 into semicircular region 112, forming an angle β; this improves the outflow of chips, because the particles are then exposed to a minimal rebounding surface.

FIG. 7 shows a top view of turbine housing 60 with two diametrically opposed openings 102.

FIG. 8 shows turbine wheel 38 with guide-blade row 74 located underneath and onto which turbine housing 60 can be clipped axially.

FIG. 9 shows an enlarged view of one of the openings 102 in a side view according to FIG. 6. A directional arrow 160 indicates the outflow direction of particles 108. The unevenly V-shaped contour of opening 102 with upwardly angled edges is shown; a V is formed which has an acute angle at the bottom and transitions into a more obtuse V toward the top.

FIG. 10 shows an enlarged top view of one of the openings 102, in a vertical projection according to FIG. 5 or 7. Knife edge 140 is shown particularly clearly.

Chips 108 which enter the space between turbine wheel 38 and turbine housing 60 are guided by the angular geometry of opening 102 and its position in turbine housing 60 in the clockwise direction via turbine wheel 38 toward leading edge 120. From there, they are pushed or blown at an angle upwardly along leading edge 120 and, from there, radially outwardly into the interior of housing 12.

Chips which flow out of housing 12 and out of openings 102 can reach not-shown, downwardly guiding channels. Inspection flaps or openings can be provided in housing 12 in the region of openings 102, through which particularly tenacious accumulations of chips can be removed by hand from the outside.

Claims

1. A hand-held power tool with a housing (12) and a tool (70)—a cutting tool, in particular—located thereon in a rotatable manner, it being possible to operate the tool (70) using a suction air flow, via a vacuum cleaner, in particular,

wherein

a turbine (36) with a rotatable turbine wheel (38) and a stationary turbine housing (60) is used as the drive, and means (100) are located between the turbine wheel (38) and the turbine housing (60) for carrying away particles (108), such as dust and chips, which accidentally enter this space.

2. The hand-held power tool as recited in claim 1,

wherein

the means (100) are designed as at least one opening (102) which passes through the turbine housing (60).

3. The hand-held power tool as recited in claim 1, wherein

the means (100) are surface recesses (103) and/or raised surface roughness in the turbine wheel (38)—adjacent to the opening (102) of the turbine housing (60) in particular—for carrying the particles along and creating a preferably pulsing airstream toward the opening (102) to blow the particles outward through this opening (102).

4. The hand-held power tool as recited in claim 1,

wherein

the turbine (36) is provided with means for eliminating the swirling of the inflowing and outflowing air, in particular a guide-blade row (74)—and/or a rear guide grid; the airstream flowing onto the turbine wheel (38) is forwarded or redirected at an acute angle to the normal axis (40) of the turbine wheel (38), at an angle of 50° in particular.

5. The hand-held power tool as recited in claim 1,

wherein

the turbine wheel (38) is provided with a labyrinth seal (51) which protects the turbine (36) against loss of pressure.

6. The hand-held power tool as recited in claim 1,

wherein

the guide-blade row (74) serves as a bearing seat (76) for a bearing (66) of the drive shaft (72).

7. The hand-held power tool as recited in claim 1,

wherein

it includes a balancing mass (78) which, together with structures (80, 82) of the guide-blade row (74), forms a labyrinth seal (84).

8. The hand-held power tool as recited in claim 1,

wherein

the guide-blade row (74) is installed in the structure of the housing (12) such that it reinforces it.

9. The hand-held power tool as recited in claim 1,

wherein

the air for driving the turbine wheel (38) is directed from the outside onto the turbine (36) radially outwardly in the direction of rotation of the turbine (36), and, therefore, radially diagonally, and is subsequently drawn in temporarily axially by the outer edge of the turbine wheel (38).

10. The hand-held power tool as recited in claim 1,

wherein

it is designed as a surface grinding machine, a finishing sander in particular.

11. The hand-held power tool as recited in claim 1,

wherein

downwardly guiding channels are located next to the openings (102) between the turbine housing (60) and the housing (12) for removal of the chips which exit through the openings (102).

12. The hand-held power tool as recited in claim 1,

wherein

inspection flaps (15) for openings are located on the housing (12) near the openings (102), through which accumulated chips can be removed by hand from the outside.