U.S. patent application number 10/576128 was filed with the patent office on 2009-01-15 for flow medium-driven hand-held power tool.
Invention is credited to Cristian-Aurelian Coclici, Frank Fuchs.
Application Number | 20090017738 10/576128 |
Document ID | / |
Family ID | 35478795 |
Filed Date | 2009-01-15 |
United States Patent
Application |
20090017738 |
Kind Code |
A1 |
Fuchs; Frank ; et
al. |
January 15, 2009 |
Flow medium-driven hand-held power tool
Abstract
A hand-held power tool, having a housing (12) and a tool (70)
which is located on the housing in a way drivable to rotate and/or
oscillate and is drivable as intended by means of a flow of suction
air, especially with a vacuum cleaner, is made especially effective
in that a turbine (36) with a turbine wheel (38) serves as the
drive mechanism and is provided with means for calming the
inflowing and outflowing air, in particular with an upstream baffle
(74) and/or a downstream baffle, and the air flow approaching the
turbine wheel (38) is carried onward or deflected at an acute angle
to the vertical axis (40) of the turbine wheel (38), in particular
an angle of less than 50.degree..
Inventors: |
Fuchs; Frank; (Rutesheim,
DE) ; Coclici; Cristian-Aurelian; (Stittgart,
DE) |
Correspondence
Address: |
Striker, Striker & Stenby
103 East Neck Road
Huntington
NY
11743
US
|
Family ID: |
35478795 |
Appl. No.: |
10/576128 |
Filed: |
October 13, 2005 |
PCT Filed: |
October 13, 2005 |
PCT NO: |
PCT/EP2005/055230 |
371 Date: |
April 18, 2006 |
Current U.S.
Class: |
451/354 |
Current CPC
Class: |
B24B 55/102 20130101;
B24B 23/00 20130101 |
Class at
Publication: |
451/354 |
International
Class: |
B24B 23/00 20060101
B24B023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 2004 |
DE |
10 2004 058 581.4 |
Claims
1. A hand-held power tool, having a housing (12) and a tool (70),
which is located on the housing in a manner capable of being driven
in rotating and/or orbiting fashion and which can be operated as
intended by means of a flow of suction air, especially with a
vacuum cleaner, characterized a turbine (36) with a turbine wheel
(38) serves as the drive mechanism and is provided with means for
calming the inflowing and outflowing air, in particular with an
upstream baffle (74) and/or a downstream baffle, and the air flow
approaching the turbine wheel (38) is carried onward or deflected
at an acute angle to the vertical axis of the turbine wheel (38),
in particular an angle of less than 50.degree..
2. The hand-held power tool as defined by claim 1, characterized in
that the turbine wheel (38) is provided by a labyrinth seal (51),
which protects the turbine (36) against a pressure loss.
3. The hand-held power tool as defined by claim 1, characterized in
that the upstream baffle (74) serves as a bearing seat (76) for a
bearing (66) of the axial shaft (72).
4. The hand-held power tool as defined by claim 1, characterized in
that it has a downstream baffle (78), which together with
structures (80, 82) of the upstream baffle (74) forms a labyrinth
seal (84).
5. The hand-held power tool as defined by claim 1, characterized in
that the upstream baffle (74) is built into the structure of the
housing (12) in such a way that it reinforces the housing.
6. The hand-held power tool as defined by claim 1, characterized in
that the air for driving the turbine wheel (38) is made to pass
radially outward past it and is then extracted by suction radially
obliquely inward from the outer edge of the turbine wheel (38).
7. The hand-held power tool as defined by claim 1, characterized in
that the housing (12) has a radio switch, with which a counterpart
switch that switches the vacuum cleaner on and off is actuatable
and thus the hand-held power tool is simultaneously capable of
being switched on and off.
8. The hand-held power tool as defined by claim 1, characterized in
that it is designed as a surface sander, in particular as an
orbital sander.
Description
[0001] The invention is based on a flow-medium-driven hand-held
power tool as generically defined by the preamble to claim 1.
[0002] 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.
[0003] 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.
ADVANTAGES OF THE INVENTION
[0004] 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.
[0005] 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.
[0006] Because the drive mechanism comprises only lightweight
plastic parts, the hand-held power tool is especially light in
weight and handy.
[0007] 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.
[0008] 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.
[0009] 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.
DRAWING
[0010] The present invention is described in further detail below
in terms of an exemplary embodiment and the associated drawing.
[0011] Shown are:
[0012] FIG. 1, a longitudinal section through an orbital
sander;
[0013] FIG. 2, a longitudinal section through the turbine with the
upstream baffle for driving the orbital sander;
[0014] FIG. 3, a side view of the turbine with the compensation
mass;
[0015] FIG. 4, a side view of the turbine wheel of the turbine of
FIG. 2;
[0016] FIG. 5, a longitudinal section through the turbine wheel of
FIG. 4;
[0017] FIG. 6, a side view of the turbine of FIG. 2;
[0018] FIG. 7, a view of the turbine wheel from below;
[0019] FIG. 8, a top view of the upstream baffle;
[0020] FIG. 9, a side view of the turbine wheel with the axial
shaft inserted;
[0021] FIG. 10, a three-dimensional side view of the turbine wheel
obliquely from below; and
[0022] FIG. 11, a three-dimensional side view of the turbine wheel
obliquely from above.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
[0023] FIG. 1 shows a hand-held power tool 10, designed as an
orbital sander, looking toward a longitudinal housing shell 14
whose inside faces toward the observer. This shell, together with a
second, substantially symmetrical housing shell, not shown, forms a
bell-shaped housing 12 with a vertical axis 13. The housing is put
together from the two housing shells using screws, which pass from
the outside through the outer housing shell, not shown, and are
rotatable in screw domes 35 and as a result hold the two housing
shells together at a butt joint. On its top 20, the housing 12
changes over into a hollow-cylindrical handle 16, protruding
transversely from the vertical axis 13, that serves as a suction
air outlet 18. On its top 20, the housing 12 has an air flap 22,
which as needed opens or closes an opening 24 to the flow conduit
26 in the interior of the housing 12 for the sake of regulating the
entry of air. To that end, a region 86 of a conduit wall 28 close
to the opening 24 is perforated, so that the suction air can
communicate with the outside air in the hoselike flow conduit 26.
The conduit wall 28 is retained on the housing shells 14 by
load-bearing ribs 30. The load-bearing ribs 30 are joined to
reinforcing ribs 32 in the interior of the housing shell 14 and via
these ribs are joined to the outer housing wall or housing shell
14. As a result, the air conduit 26 or conduit wall 28 is
reinforced, and the housing 12 of lightweight construction is
stabilized in particular against vibration or resonance with the
suction air as it flows through.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] 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.
[0028] 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.
[0029] FIG. 2 shows a detail in longitudinal section through the
turbine wheel 38, with the upstream baffle 74 adjoining it axially
at the bottom and fixed in the housing 12, which is shown assembled
in FIG. 1. Here, a frustoconical convex load-bearing cone 48,
shaped somewhat like the body of a lemon squeezer, can be seen
which has a plurality of wheel blades 42 on its outside that are in
the form of flat plastic strips standing with their short side on
the load-bearing cone 48, and whose height increases gradually in
the direction toward the--virtual--tip of the cone. Via the wheel
blades 42, a conical cap 44, extending approximately parallel to
the load-bearing cone 48 or to the upper edges of the wheel blades
42, is guided. As a result, the flow conduit 49 of annular cross
section is formed between the load-bearing cone 48 and the conical
cap 44. This flow conduit is divided up by the wheel blades 42 into
a plurality of winding individual conduits, in which the suction
air for driving the turbine 36 can flow with especially low flow
resistance. The lower edge of the load-bearing cone 48 is inclined
relative to the cone axis by approximately 45.degree. and does not,
as in conventional radial turbines, extend at an angle of
approximately 90.degree. transversely to the cone axis. In an
especially favorable exemplary embodiment of the turbine 36, the
inflow angle of the blade is 40.degree., and the outflow angle is
30.degree.. An arrow 62 indicating motion shows that the air
flowing along the wheel blade 42 is deflected by 45.degree.,
measured relative to the axis 40; the deflection transversely to
the plane of the drawing is not yet taken into account.
[0030] 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.
[0031] 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.
[0032] 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.
[0033] 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.
[0034] 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.
[0035] The side view, shown in FIG. 3, of the turbine 36 of FIG. 2
shows the turbine housing 60 especially clearly as a detail; it is
retained in the housing 12 in a manner fixed against relative
rotation, and being locked or clamped to support ribs 30, it fits
tightly over the upstream baffle 74 and the turbine wheel 38 and in
particular forms the upper labyrinth seal 51 already described
above.
[0036] The side view shown in FIG. 4 of the turbine wheel 38 in the
form a detail shows the forward-extended front edges of the blades
42 at the bottom, and the longitudinal section in FIG. 5 of the
turbine wheel 38 of FIG. 4 again clearly shows the details
explained in conjunction with FIG. 2.
[0037] FIG. 6 shows a side view of the turbine wheel 38 with the
upstream baffle 74, in which the baffle blades 75 can be seen in
their oblique course on the curved support ring 77, retained on the
outside by the bracing ring 79.
[0038] FIG. 7 shows a view of the turbine wheel 38 from below, in
which the support ring 88, the inner support ribs 92 and outer
support ribs 90 are visible, and shows that the wall thickness of
these ribs becomes increasingly less, looking radially outward from
the inside--which has advantages in casting.
[0039] FIG. 8 shows a top view of the upstream baffle 74, looking
toward the inner support ring 77, the baffle blades 75 with an
inlet angle of 78.degree., and the outer bracing ring 79.
[0040] FIG. 9 shows a side view of the turbine wheel 38 with the
axial shaft 72 inserted, with the knurling 73 emphasized in the
drawing.
[0041] FIG. 10 shows a three-dimensional side view of the turbine
wheel 38 without the conical cap 44 obliquely from below; the
course of the blades 42 on the load-bearing cone 48 and the support
ring 88, the inner and outer support ribs 90, 92, and their
different wall thicknesses, can all be seen.
[0042] FIG. 11 shows a three-dimensional side view of the turbine
wheel 38 obliquely from above, without the conical cap 44; the
course of the blades 42 on the load-bearing cone 48 is especially
clearly visible.
[0043] 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.
[0044] 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.degree. to the axis of
rotation (see FIGS. 3 and 4). This oblique oncoming flow has the
advantage that the efficiency of the turbine 36 is increased
markedly, since the pressure loss inside the turbine 36 and inside
the upstream baffle 74 is minimized. The inflow angle of the blade
is 60.degree., and the outflow angle is 30.degree., to keep the
outflow losses as slight as possible. The angles for the inflow
region can vary between 0.degree. and 70.degree., and the angles in
the outlet region can vary between 10 and 60.degree.. The choice of
the angles depends both on the air quantity and on the expected
rpm. The upstream baffle 70 has the task of imposing the greatest
possible pilot spin on the air flow, and for this reason it has
baffle blades 75 with an outlet angle of 78.degree. (FIG. 8). To
minimize the air noises, the wheel blades 42 of the turbine wheel
38 are drawn somewhat forward at the load-bearing cone 48 and in
contrast to this the baffle blades 75 are drawn somewhat rearward
(FIGS. 4 and 6). Whistling noises between the wheel blades 42 and
baffle blades 75 are thus suppressed, since these blades sweep past
one another with a spacing of only 0.5 mm and become effectively
"lubricated". The slight spacing between the upstream baffle 74 and
the turbine 36 is necessary so that the turbine 36 will have an
ideal oncoming flow. An additional bracing ring 88 between the
bracing ribs 90 on the inside and on the underside of the
load-bearing cone 48 prevents a sharply fluctuating and
uncontrolled idling rpm of the turbine 36, which can assume very
high values (>20,000 rpm), since a fan effect caused by purely
radially located ribs can accordingly not occur. The bracing ring
88 and the bracing ribs 90 are made increasingly thin radially from
the inside outward, so that in injection molding, the material can
flow rapidly from the inside outward with little resistance and
fill all the voids in the injection mold.
[0045] 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
(FIGS. 1, 9, 10, 11). For reasons of space, the lower bearing 66 is
integrated directly with the upstream baffle 74 and makes a low
design of the hand-held power tool 10 possible.
[0046] An inventive quality is ascribed to the individual
characteristics recited above, since jointly they contribute to the
particular advantages of the embodiment.
* * * * *