U.S. patent application number 13/918346 was filed with the patent office on 2013-12-19 for fastener-driving device and controlling method.
The applicant listed for this patent is Hilti Aktiengesellschaft. Invention is credited to Chafic Abu Antoun, Peter Bruggmueller.
Application Number | 20130336809 13/918346 |
Document ID | / |
Family ID | 48670411 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130336809 |
Kind Code |
A1 |
Antoun; Chafic Abu ; et
al. |
December 19, 2013 |
FASTENER-DRIVING DEVICE AND CONTROLLING METHOD
Abstract
The driving device 1, in accordance with the invention, has a
ram 3, which, driven by compressed air, drives in the fastener 2. A
pump device 5 produces the compressed air. The pump device 5 has a
pump cylinder 23, a pump piston 22, and an annular magnet
arrangement 28, 46 around the pump cylinder 23. The pump piston 22
can move in the pump cylinder 23, along an axis 11. An axial
closure 25 of the pump cylinder 23 closes off, with the pump piston
22, a pump volume 27 within the pump cylinder 23. The annular
magnet arrangement 28, 46 has a magnetic coil 28, which encloses
the pump cylinder 23 and which overlaps, along the axis 11, at
least in part, with the magnetizable closure 25 and, in part, with
the magnetizable pump piston 22.
Inventors: |
Antoun; Chafic Abu; (Buchs,
CH) ; Bruggmueller; Peter; (Bludesch, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hilti Aktiengesellschaft |
Schaan |
|
LI |
|
|
Family ID: |
48670411 |
Appl. No.: |
13/918346 |
Filed: |
June 14, 2013 |
Current U.S.
Class: |
417/53 ;
417/212 |
Current CPC
Class: |
B25C 1/04 20130101; F04B
19/00 20130101; B25C 1/06 20130101 |
Class at
Publication: |
417/53 ;
417/212 |
International
Class: |
F04B 19/00 20060101
F04B019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 19, 2012 |
DE |
10 2012 210 347.3 |
Claims
1. A driving device to drive in fasteners, comprising a compressed
air driven ram, and a pump device producing the compressed air,
wherein the pump device comprises a pump cylinder having a pump
volume, a magnetizable pump piston that moves in the pump cylinder
along an axis, a magnetizable axial closure, which, with the pump
piston, closes off the pump volume within the pump cylinder, and an
annular magnet arrangement with a magnetic coil, wherein the magnet
arrangement encloses the pump cylinder and the magnet arrangement
overlaps, along the axis, at least in part, the magnetizable
closure and, at least in part, the magnetizable pump piston.
2. The driving device according to claim 1, wherein the closure and
the pump piston each comprise a soft magnetic material.
3. The driving device according to claim 1, wherein the closure
overlaps, along the axis, at least 10% of the magnetic
arrangement.
4. The driving device according to claim 1, wherein the pump piston
overlaps, along the axis, at least 10% of the magnetic
arrangement.
5. The driving device according to claim 1, further comprising a
pressure chamber, which provides intermediate storage for the
compressed air produced by the pump device.
6. The driving device according to claim 5, wherein the pressure
chamber has a volume dimensioned to hold an air quantity for one
driving operation to fewer than five driving operations.
7. The driving device according to claim 5, wherein an air quantity
held by the pump volume is less than the air quantity provided for
the driving operation.
8. The driving device according to claim 1, wherein the ram is
rigidly connected with a driving piston and the driving piston is
arranged to be capable of closing off a work volume within a hollow
guide cylinder, and the compressed air can be fed into the work
volume.
9. A control method for a driving device, the method comprising:
producing compressed air by feeding a current pulse into a magnetic
coil, producing a magnetic field that moves a magnetizable pump
piston within the magnetic coil in a pump cylinder; and
accelerating a ram with the compressed air, such that the ram
drives a fastener in a driving direction.
10. The control method according to claim 9, comprising loading a
pressure chamber with compressed air, actuating an operating
element by a user, and accelerating the ram with the compressed air
from the pressure chamber.
11. The control method according to claim 10, wherein loading of
the pressure chamber comprises energizing the magnetic coil with a
sequence of current pulses, for multiple back and forth movement of
the pump piston.
12. The control method according to claim 11, wherein an amplitude
and/or a duration of the current pulses increase within a
sequence.
13. The driving device according to claim 2, wherein the closure
overlaps, along the axis, at least 10% of the magnetic
arrangement.
14. The driving device according to claim 2, wherein the pump
piston overlaps, along the axis, at least 10% of the magnetic
arrangement.
15. The driving device according to claim 3, wherein the pump
piston overlaps, along the axis, at least 10% of the magnetic
arrangement.
16. The driving device according to claim 2, further comprising a
pressure chamber, which provides intermediate storage for the
compressed air produced by the pump device.
17. The driving device according to claim 3, further comprising a
pressure chamber, which provides intermediate storage for the
compressed air produced by the pump device.
18. The driving device according to claim 4, further comprising a
pressure chamber, which provides intermediate storage for the
compressed air produced by the pump device.
19. The driving device according to claim 6, wherein an air
quantity held by the pump volume is less than an air quantity
provided by the driving operation.
20. The driving device according to claim 2, wherein the ram is
rigidly connected with a driving piston and the driving piston is
arranged to be capable of closing off a work volume within a hollow
guide cylinder, and the compressed air can be fed into the work
volume.
Description
BACKGROUND OF THE INVENTION
[0001] The invention under consideration concerns a driving device
for the driving of fasteners, such as nails, rivets, pins, braces,
clamps, or other, preferably, pin-like fastening elements.
Furthermore, the invention concerns a controlling method for a
driving device.
BRIEF SUMMARY OF THE INVENTION
[0002] The driving device, in accordance with the invention, has a
ram, which drives in the fastener, driven by compressed air. A pump
device produces the compressed air. The pump device has a pump
cylinder, a pump piston, and an annular magnet arrangement around
the pump cylinder. The pump piston can move in the pump cylinder,
along an axis. An axial closure of the pump cylinder closes off,
with the pump piston, a pump volume within the pump cylinder. The
annular magnet arrangement has a magnetic coil, which encloses the
pump cylinder and which, along the axis, overlaps, at least in
part, with the magnetizable closure, and in part, with the
magnetizable pump piston.
[0003] The pump cylinder, with its half side closed by the closure,
forms, together with the pump piston, a linear piston stroke pump.
The drive of the piston stroke pump is carried out by the magnetic
coil, which can draw the magnetizable pump piston into the center
of the magnetic coil and thereby can compress the air in the pump
volume.
[0004] The arrangement of the closure within the magnet
arrangement, preferably, within the magnetic coil, has proved to be
efficient for the compression of the air. The necessary force for
the compression of the air rises more or less inversely to the
diminishing distance between the pump piston and the closure. As a
result of the arrangement of the magnetizable closure within the
magnet arrangement, the force exerted by the magnetic coil on the
pump piston is also increased more or less inversely to the
distance between the closure and the pump piston. The energy can be
transferred optimally by the magnetic coil onto the volume work of
the pump volume via the entire movement of the pump piston.
[0005] The closure and the pump piston are preferably formed from a
soft magnetic material. As soon as the magnetic coil is not
energized, the closure and the pump piston are largely unpolarized
and are depolarized by the surrounding stray fields. Without the
magnetic coil, the closure and the pump piston are not attracted to
each other.
[0006] One development provides for the closure to overlap with at
least 10% of the magnet arrangement, preferably, the magnetic coil,
along the axis. The pump piston preferably overlaps, in each
position, for at least 10% with the magnet arrangement, preferably,
the magnetic coil, along the axis.
[0007] One development provides for a pressure chamber to have
intermediate storage for the compressed air produced by the pump
device. The pump device does not drive the ram directly. A volume
of the pressure chamber is dimensioned to hold an air quantity for
one driving operation or for fewer than five driving operations. An
air quantity held by the pump volume is advantageously less than
the air quantity provided for one driving operation. The pump
piston requires several strokes, until an air quantity needed for
the driving operation is made available.
[0008] One development provides for the ram to be rigidly connected
with a driving piston, the driving piston to close off a working
volume within a hollow guide cylinder, and for it to be possible to
feed the compressed air into the working volume. The compressed
air, which is produced by the pump device and held, in the interim,
in the pressure chamber, accelerates the driving piston in the
guide cylinder. The ram is carried along by the driving piston and
drives in the nail or another fastening means.
[0009] A controlling method for the driving device has the
following steps: generation of the compressed air, in that a
current pulse is fed into a magnetic coil, and the magnetic field
produced moves a magnetizable pump piston within the magnetic coil
in a pump cylinder, and acceleration of a ram with the compressed
air onto a fastener arranged in the driving direction. The driving
device converts electrical energy into a magnetic field, into a
compression of air, and subsequently, into the kinetic energy of
the ram. The conversion of the energy from the magnetic field into
compression is particularly efficient using the pump piston,
conducted within the magnetic coil.
[0010] A development provides fir a pressure chamber to be loaded
with the compressed air and, as a response to an actuation of an
operating element by the user, for the ram to be accelerated with
the compressed air from the pressure chamber. The loading of the
pressure chamber is carried out by energizing the magnetic coil
with a sequence of current pulses for the multiple back and forth
movement of the pump piston. One single stroke to make available
the air quantity for the driving operation has the obvious
advantage that the additional pressure chamber and an intermediate
storage of the compressed air are omitted. The driving device is
lighter and has fewer loss channels. The multiple stroke has
nevertheless proved to be more efficient, since the pump device
works in an especially efficient manner, in particular with a short
stroke, and thus the disadvantages of the additional pressure
chamber are more than compensated for.
[0011] An amplitude and/or a duration of the current pulses can
increase within one sequence. The pump device does more volume
work, in particular by attaining a higher pressure, with increasing
air quantity in the pressure chamber per stroke, so as to further
load the pressure chamber.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0012] The following description explains the invention with the
aid of the exemplary embodiments and figures. The figures show the
following:
[0013] FIG. 1, a driving device
[0014] FIG. 2, a pump device of the driving device
[0015] FIG. 3, a succession of switching sequences
[0016] FIG. 4, a section of the driving device
[0017] The same or functionally similar elements are shown with the
same reference symbols in the figures, unless otherwise
indicated.
DETAILED DESCRIPTION OF THE INVENTION
[0018] FIG. 1 shows an exemplary driving device 1 for nails 2 or
similar pin-like fastening elements. The driving device 1 has a
compressed air-driven ram 3, which drives the nail 2 into a
workpiece. The compressed air for one driving operation is kept in
the pressure chamber 4. A pump device 5 in the driving device 1
loads the pressure chamber 4 with an air quantity sufficient for
the driving operation and to the needed pressure level.
[0019] The components of the driving device 1 that are essential
for the functionality are located within a housing 6, in
particular, the ram 3, the pressure chamber 4, and the pump device
5. The user can conduct the driving device 1 with a handle 7 and
can hold it while driving the nails 2. The handle 7 is not
detachably connected with a housing 6 of the driving device 1, but
it is rigidly connected or with dampening elements. The driving
device 1 is primarily supplied with electrical energy, for example,
by means of a battery packet 8, which can be affixed, in a
nondetachable or preferably in a detachable manner, to the handle 7
or the housing 6, by the user. A triggering switch 9 is on or near
the handle 7; it triggers a driving operation upon actuation by the
user. Preferably, in addition to the actuation of the triggering
switch 9, there is also the release of a safety mechanism, for
example, by pressing the driving device to a wall.
[0020] The ram 3 has an impact head 10, which is adapted, in its
form, to the nails 2 used. The impact head 10 has typically,
approximately, the same diameter as a head of the nails 2. The
impact head 10 is conducted along a work axis 11 within a nail
guide 12. The nail 2 is placed, for the driving operation, into an
essentially tubular nail holder 12. The placing of the nail can be
done manually by the user, semiautomatically or automatically, by a
feeder. The impact head 10 strikes the nail 2 within the nail guide
12 and drives the nail 2 in the driving direction 13, along the
work axis 11 from the nail guide 12, perhaps into a workpiece.
[0021] On its back end, turned away from the nail, the ram 3 is
provided with a driving piston 14. The driving piston 14 preferably
has an essentially larger diameter than the impact head 10, so as
to drive the ram 3 efficiently with the compressed air.
[0022] The driving piston 14 is inserted into a guide cylinder 15,
closed on half its side. The driving piston 14 lies, all-round, on
the inner jacket surface 16 of the guide cylinder 15,
pressure-tight, and is conducted by the jacket surface along the
work axis 11. An end of the guide cylinder 15, turned away from the
nail 2, is closed by a bottom 17. The driving piston 14 thus closes
off a pneumatic work volume 18 in the driving direction 13 within
the guide cylinder 15.
[0023] The pressure chamber 4 is connected with the work volume 18
via a controllable supply line 19. The supplying through the supply
line 19 is preferably carried out via an opening in the bottom 17.
The supply line 19 comprises a switchable valve 20, which is opened
as a response to an actuation of the triggering switch 9.
[0024] The pressure chamber 4 has a sufficient volume, so as to
store an air quantity for preferably precisely one driving
operation. The volume is, for example, in the range of 100 cm.sup.3
to 300 cm.sup.3. With a fully loaded pressure chamber 4 for one
driving operation, the pressure is between 7 bar and 10 bar. The
pressure chamber 4 is surrounded with a thermally insulating jacket
21, which, for example, a wall of the pressure chamber 4 lines on
the inside or is placed on the outside surface. The jacket 21 is,
for example, made of a plastic, preferably, of a foamed
plastic.
[0025] The pump device 5 (FIG. 2) fills the pressure chamber 4 with
air, until the air quantity needed for the driving operation and/or
the pressure needed for the driving operation are attained. The
pump device 5 has a linearly moved pump piston 22. In the
embodiment shown, the pump piston 22 is conducted along the work
axis 11; the pump piston 22, however, can also be conducted along
another axis 11. The pump piston 22 moves within a hollow pump
cylinder 23. The cross section of the pump piston 22 and the inside
cross section of the pump cylinder 23 fit exactly, so as to
guarantee a pressure-tight closure. Sealing rings on the pump
piston 22 can reconcile tolerances in production. Opposite a front
surface 24 of the pump piston 22, the pump cylinder 23 is closed by
a stationary closure 25. The front surface 24 of the pump piston 22
and the front surface 26 of the closure 25, facing it, enclose air
in a pump volume 27.
[0026] The pump piston 22 is moved by a magnetic coil 28 along the
axis 11. The magnetic coil 28 is located around the pump cylinder
23; preferably, the magnetic coil 28 is coaxial to the axis 11 of
the pump cylinder 23. The drive is based on reluctance forces which
act on the pump piston 22. The pump piston 22 is made of a
magnetic, preferably, ferromagnetic material. The magnetic field
produced by the magnetic coil 28 in the pump cylinder 23 pulls the
pump piston 22 into the pump cylinder 23.
[0027] The pump piston 22 is made of a soft magnetic material,
whose coercive field strength is less than 1000 A/m. A weak
external magnetic field can already change or cancel an existing
polarization in the pump piston 22. The magnetic polarization
impressed by the magnetic coil 28 therefore essentially remains
contained in the pump piston 22 only for the duration of the field
applied by the magnetic coil 28. The pump piston 22 is, for
example, made of ferromagnetic steel, preferably, a soft-annealed
steel.
[0028] The closure 25 is made of a soft magnetic material, for
example, the same material as the pump piston 22. The magnetic
field produced by the magnetic coil 28 is introduced by the closure
25 into the pump cylinder 23. The magnetic field fins between the
front surface 24 of the pump piston 22 and the front surface 26 of
the closure 25, parallel to the axis 11. The closure 25 projects
along the axis 11 into the magnetic coil 28. A front end section 29
of the magnetic coil 28 thus overlaps with the closure 25. The
front end section 29 assumes at least 10% of the magnetic coil 28.
A length 30 of the front end section 29 preferably is between 10%
and 30% of the length 31 of the magnetic coil 28. The pump piston
22 never comes out completely from the magnetic coil 28. In the
basic position of the pump piston 22--that is, in its position
moved out the furthest from the pump cylinder 23--the pump piston
22 overlaps with a back end section 32 of the magnetic coil 28. The
back end section 32 has a length 33 of at least 10% of the length
31 of the magnetic coil 28, preferably, up to 20% of the length 31
of the magnetic coil 28. The pump volume 27 is completely within
the magnetic coil 28, with a length 34 of at most 80% of the
magnetic coil 28.
[0029] The pump volume 27 is clearly smaller than the volume of the
pressure chamber 4. For example, the pump volume 27 contains less
than 20%, preferably, between 5% and 10% of the air quantity needed
for a driving operation. The efficiency of the pump device 5 rises
greatly, in a nonlinear manner, with increasing approximation of
the pump piston 22 to the closure 25. The efficiency of the total
system of the driving device 1 is increased by the small pump
volume 27, instead of a pump volume in the order of magnitude of
the pressure chamber 4, in spite of the additional expense of
making available the pressure chamber 4 and the losses resulting
from the pressure chamber 4.
[0030] The pump device 5 is controlled by a control device 35. The
control device 35 loads the pressure chamber 4 upon the start of
the operation or after a driving operation. The loading is carried
out by a sequence 36 of current pulses 37, which are fed into the
magnetic coil 28 (FIG. 3). With each of the current pulses 37, the
pump piston 22 is drawn from its basic position into the magnetic
coil 28 and compresses the air in the pump volume 27. A large part
of the compressed air flows into the pressure chamber 4. A spring
39 and/or an additional magnetic coil 40 can draw out the pump
piston 22 from the pump cylinder 23 into the basic position. The
pump volume 27 is ventilated before the next current pulse 37. For
example, the pump piston 22 releases a ventilating channel 41, as
soon as the pump piston 22 is moved back to the basic position.
Preferably, the ventilating channel 41 is opened, as soon as the
pump piston 22 begins its backward movement. A position sensor can
determine whether the pump piston 22 has reached the basic
position.
[0031] The sequence 36 preferably comprises at least 5 current
pulses 37, preferably, at most 30 current pulses 37. The pressure
chamber 4 is completely pumped by the pump device 5, corresponding
to 5 to 30 strokes. The introduction of energy of the current
pulses 37 increases during the sequence 36; preferably, the
duration 42 of the current pulses 37 is increased; alternatively or
additionally, the amplitude 43 of the current pulses 37 can be
increased. The duration 42 and the current strength/amplitude 43
can be definitively prespecified. The current pulses 37 are
coordinated in such a way that the pump piston 22 is drawn from its
basic position to the closure 25, preferably without touching the
closure 25 at the end. The force exerted by the magnetic coil 40 on
the pump piston 22 rises with the selected buildup during its
movement to the closure 25. The characteristic curve of this
increase is similar to the characteristic curve of the increase of
the counterforce being built up by the compressed air. The current
strength 43 can be maintained constant during a current pulse
37.
[0032] The closure 25 is provided with an outlet valve 44, for
example, a nonreturn valve. The outlet valve 44 preferably opens as
soon as the pressure in the pump volume 27 exceeds the pressure in
the pressure chamber 4. The pump device 5 increases the pressure
within the pump volume only slightly above the pressure in the
pressure chamber 4, so as to shift the air quantity from the pump
volume 27 into the pressure chamber 4. The thermal losses appearing
during the compression can be kept small in this way. The outlet
valve 44 closes as soon as the pump piston 22 moves back to the
basic position.
[0033] The user can actuate the triggering switch 9, so as to
trigger the driving operation. The control device 35 preferably
first tests whether the pressure chamber 4 is loaded. If the
pressure chamber 4 is not loaded, for example, after a long
inactivity of the driving device 1, the control device 35 loads the
pressure chamber 4. The pressure chamber 4 is loaded with the
complete sequence 36 of the current pulses 37. The control device
35 shortens the sequence 36, if the pressure chamber 4 is partially
loaded. For example, the control device 35 determines, by means of
a pressure sensor, the pressure in the pressure chamber 4. For each
pressure, a notation is made in a control table as to how many of
the first current pulses 37 of the sequence 36 are to be
skipped--that is, with which of the current pulses 37 of the
sequence 36, one is to begin. If the pressure chamber 4 is loaded,
the control device 35 opens the controllable valve 20. The air
quantity under pressure in the pressure chamber 4 accelerates, by
means of the driving piston 14, the ram 3. After the driving
operation, the driving piston 14 is retrieved--for example, by
means of a pump, a spring, a motor, the user--and the switchable
valve 20 is closed. The work volume 18 is preferably ventilated for
the retrieval of the driving piston 14. The control device 35 loads
the pressure chamber 4 by means of the sequence 36 of current
pulses 37.
[0034] The magnetic coil 28 is preferably surrounded by a magnet
yoke 46. The magnet yoke 46 covers, with a ring 47 in each case,
the two front sides 48 of the magnetic coil 28. The magnet yoke 46
extends, in a radial direction, to the pump piston 22 or the
closure 25. Ribs 49 of the magnet yoke 46, running parallel to the
axis 11, connect the two rings 47. The magnet yoke 46 is, for
example, formed from individual plates of a ferromagnetic
steel.
[0035] The pump piston 22 has a shell-like structure consisting of
an outer shell 50 and a core 51. The radially outermost shell 50 is
made of a ferromagnetic material. The magnetic field is conducted
within the outer shell 50. A wall thickness of the outer shell 50
is in the range between 5% and 25% of the diameter of the pump
piston 22. A core 51 of the pump piston 22 can be hollow or it can
be filled with a nonmetal material, for example, plastic. The front
surface 26 is preferably a plate of steel, so that it is not
deformed during the compression. Alternatively, the pump piston 22
can be a massive cylinder made of a ferromagnetic material, for
example, steel.
[0036] FIG. 4 shows a development of the guide cylinder 15 for the
driving piston 14 and the pressure chamber 4. The pressure chamber
4 is permanently open to the work volume 18 in the guide cylinder
15. The driving piston 14 forms the switchable valve 20 and
prevents the air in the pressure chamber 4 from flowing out, until
a driving operation is triggered. A blocking mechanism 52, for
example, a ratchet element, holds the driving piston 14 in its
basic position. The blocking mechanism 52 can be released by the
control device 35, whereupon the driving piston 14, acted on by
pressure, is accelerated in the driving direction 13.
* * * * *