Note: Descriptions are shown in the official language in which they were submitted.
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TOOL ASSEMBLY WITH A MULTI-DIMENSIONALLY
Resiliently mounted TOOL
The present invention relates to a tool assembly with a multi-dimensionally
resiliently mounted tool provided with an elongated blade for machining a
workpiece by guiding the tool along a workpiece contour to be machined.
Such a tool assembly is known, for example, from DE 299 03 312, EP 99
926 268 or US 09/512,365. Specific reference is made to the above named
published prior art. The tool assembly disclosed in these publications
concerns a tool that is movable on several planes. The tool is designed as a
deburring cutter for deburring resilient or soft workpieces, especially those
of plastic or rubber. The deburring cutter is rotatingly resiliently mounted
about its longitudinal axis in the tool assembly. The longitudinal axis of the
deburring cutter is arranged at a distance from the longitudinal axis of the
tool assembly. In addition, the deburring cutter is rotationally resiliently
mounted about the longitudinal axis of the took assembly.
The tool assembly known in prior art has proven very successful in practical
applications, in particular in the deburring of moulded articles immediately
after mould release. Moulded articles of plastic or rubber are subjected to
cooling after mould release. To shorten the turnaround time, deburring of
moulded articles is started immediately after mould release. Cooling of the
workpiece results in an intensive shrinking of the workpiece during the
deburring process. The shrinking dimensions of the workpiece can be
compensated without problem with the tool assembly known in prior art
because the tool is multi-dimensionally resiliently mounted.
The objective of the present invention is to design and further develop a tool
assembly of the type mentioned above to further improve the machining of
workpieces made of resilient materials.
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The invention achieves this objective, starting out from the tool assembly of
the type mentioned above, by creating a tool assembly which includes
oscillation means allowing the tool to move back and forth in a direction
that is substantially parallel to the length of the blade.
With the tool assembly according to the invention, even workpieces made
of a resilient material such as fabric or leather can be machined without
problem. The tool assembly can be used for the quick and accurate removal
of residual pieces of fabric or leather from shoes or clothing.
The back and forth movements of the tool across the guiding direction of
the tool and parallel to the length of the blade clearly improve the cutting
accuracy of the tool, and in particular, they also clearly reduce the pressure
required in pilot direction. This means that even workpieces of resilient
materials, which produce very little or no back pressure, can be machined
without problem. The tool can be guided much more quickly and accurately
along the workpiece contour to be machined.
In accordance with an advantageous further development of the present
invention, it is suggested that the oscillation means move the tool into a
linear lifting movement which runs substantially parallel to the length of the
blade.
The cutting pressure can be further reduced in accordance with another
advantageous further development of the present invention, in which the
oscillation means additionally move the tool into a pendulum movement that
runs substantially parallel to the pilot direction of the tool.
Another reduction of the cutting pressure can be achieved by means of
another advantageous further development of the present invention, where
the oscillation means enable the tool to perform a lifting movement and in
addition a pendulum movement whose direction is substantially parallel to
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the pilot direction of the tool. Thus, the tool performs a lifting / pendulum
movement.
According to a preferred embodiment of the present invention, it is
suggested that the tool be designed as a deburring cutter for deburring the
workpiece along the contour.
Preferably, the lifting or lifting / pendulum movement has a frequency of
more than 10 Hertz. Thus, the tool performs at least 10 full back and forth
movements per second. Preferably, the lifting movement or lifting /
pendulum movement has a frequency of about 100 Hertz.
The lifting movement or lifting / pendulum movement is particularly easy to
produce if the oscillation means are designed as an electric oscillator which
causes the lifting movement or the lifting / pendulum movement of the tool.
Preferably, the tool is fastened to the tool assembly by a tool receptacle.
The oscillating means are linked to the tool receptacle. The tool receptacle
is
mounted in the tool assembly in such a way that an activation of the
oscillation means caused the lifting movement or lifting / pendulum
movement of the tool assembly with the tool.
According to an alternative embodiment, it is suggested to design the
oscillation means as a hydraulically or pneumatically operated valve
arrangement which causes the lifting movement or lifting / pendulum
movement of the tool. By means of a hydraulic or pneumatic valve
arrangement, it is also possible to achieve relatively great lifts and high
mechanical frequencies.
In accordance with one preferred embodiment of the present invention, it is
suggested that the valve arrangement be provided with a cylinder with a
differential pressure piston which can be connected to the tool, for example
via the tool receptacle, whereby pressure chambers charged with different
pressures are formed in the cylinder on both sides of the plunger. The back
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and forth movement of the differential pressure plunger in the cylinder is
caused when the pressure applied in the pressure chambers is alternatively
increased and decreased. The movement of the differential pressure plunger
is transferred to the tool which performs a lifting movement or a / pendulum
movement as the result. The cylinder is arranged in the tool assembly. The
variable pressures for charging the pressure chambers of the cylinder can
also be produced in the tool assembly by suitable means, or they can be
supplied to the cylinder from outside the tool assembly.
Advantageously, the valve arrangement is provided with two 5 / 2-way
valves connected back to back, whereby the variable pressures are applied
at the outputs of one of the two 5 / 2-way valves for charging the pressure
chambers of the cylinder. Each output of the two 5 / 2-way valves is
connected to actuating connections of the other 5 / 2-way valve. In this
manner, a flip flop function can be achieved hydraulically or pneumatically.
Preferably, each of the actuator connections on one of the two 5 / 2-way
valves is provided with an adjustable throttle for adjusting the frequency or
maximum deflection of the lifting movement or lifting / pendulum
movement. With the adjustable throttles, the tool assembly can be optimally
adapted to workpieces made of different materials.
Finally, it is suggested that the oscillation means are provided with an
eccentric cam rotatably mounted in the tool assembly, in which the tool is
eccentrically mounted, whereby the tool is resiliently mounted in the tool
assembly at a distance from the eccentric mounting. When the oscillation
means are of such design, they allow the tool in a particularly simple
manner to perform a lifting / pendulum movement.
In accordance with another advantageous further development of the
present invention, it is suggested that at least one force and torque sensor
be provided between the tool and the guidance means of the tool assembly
for guiding the tool along the workpiece contour. The force and torque
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sensors can measure forces and torques which act between the tool and the
guidance means, while the tool is guided along the workpiece contour to be
machined. Depending on the kind of workpiece to be machined, the forces
and torques should be within a range that can be preset. If they are too
high, this could be a sign that the bearing pressure of the tool on the
workpiece is too high. If the forces and/or torques are too low, this could be
a sign that the pressure of the tool on the workpiece is too low or that the
tool is not even touching the workpiece at all. With the help of the force
and torque sensors, the bearing pressure of the tool on the workpiece can
be exactly monitored or perhaps even adjusted during machining.
The tool assembly according to this further development is also preferably
provided with oscillation means to cause a lifting movement or lifting /
pendulum movement. However, the tool assembly with at least one force
and torque sensor has the above mentioned advantages even without the
characteristics described in Claim 1. Protection under the present patent is
therefore also to extend to tool assemblies of the latter kind, which are
lacking the characteristics described in the generic part of Claim 1.
In accordance with a preferred embodiment of the present invention, it is
suggested to provide means to calculate drive signals for the guidance
means of the tool assembly which depend on output signals of at least one
force and torque sensor. The guidance means are designed, for example, as
a handling device, in particular as an industrial robot, in which case the
tool
assembly is fastened to the end effector of the robot arm. The means of
calculating drive signals are part of a drive for the robot. The output
signals
of the force and torque sensors are taken into account when the drive
signals are calculated as part of a control or regulating system. In this
manner, the tool can be guided with a constant bearing pressure along a
workpiece contour to be machined.
Further characteristics, applications and advantages of the invention become
apparent in the following description of embodiments of the invention
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shown in the drawings. All described or shown characteristics constitute the
subject of the invention separately as well as in any combination, regardless
of how they are summarized in the claims or references thereto and
regardless of their formulation in the description or their presentation in
the
drawings, in which
Figure 1 shows a preferred embodiment of the tool assembly according
to the invention;
Figure 2 shows a valve arrangement for the tool assembly shown in Fig.
1, in a first position;
Figure 3 shows the valve arrangement shown in Fig. 2, in a second
position;
Figure 4 shows the course of a lifting movement of a tool of the tool
assembly shown in Fig. 1, and
Figure 5 shows a tool assembly according to the invention, with a force
and torque sensor.
In Fig. 1, an entire tool assembly according to the invention is referred to
as
number 1. Tool assembly 1 comprises a multi-dimensionally resiliently
mounted tool 2. Tool 2 is rotatably mounted in a tool receptacle 3 about a
longitudinal axis 4 of tool 2. The rotational movement of tool 2 about the
longitudinal axis 4 is indicated by arrow 5. Tool 2 is arranged eccentrically
in tool assembly 3, i.e. at a distance from a longitudinal axis 6 of tool
receptacle 3. Tool receptacle 3 is rotatable about longitudinal axis 6
together with tool 2. This rotational movement is indicated by double arrow
7. Such a tool assembly with a multi-dimensionally resiliently mounted tool
is known, for example, from DE 299 03 312, EP 99 926 268 or US
09/512,365. Specific reference is made to the above named published prior
art. In addition, the tool can also be movable in other directions or about
other rotational axes.
Tool 2 comprises an elongated blade 8 for machining a workpiece. For this
purpose, tool 2 is guided in the direction of arrow 9 along a workpiece
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contour to be machined. For that purpose, tool 2 is guided in the direction
of arrow 9 along a workpiece contour to be machined. Tool 2 is designed as
a debarring cutter for debarring the workpiece along the contour. Any
handling device can be used to guide tool 2, including an industrial robot, in
which case tool assembly 1 would be fastened to an end effector 10 of a
robot arm.
According to the invention, tool assembly 1 is provided with oscillation
means 1 1 to enable tool 2 to perform a back and forth lifting movement 12,
at least during machining of the workpiece, in a direction that is
substantially parallel to the length of blade 8. In addition, the oscillation
means 1 1 can also enable tool 2 to perform a back and forth pendulum
movement 13 in a direction that is substantially parallel to pilot direction 9
of tool 2, so that the overall result is a lifting / pendulum movement.
Through lifting movement 12 and lifting / pendulum movement 12, 13, the
pressure that must be applied to tool 2 in pilot direction 9 for the machining
of the workpiece can be clearly reduced. Thus, it is possible for the first
time to cut/machine workpieces made of very flexible materials such as
fabric or leather. The oscillation means 1 1 are connected to tool 2 via
coupling elements 14, a tool holder 15 and tool receptacle 3. The oscillation
means are firmly connected to a housing 16 of tool assembly 1. The tool
holder 15 is fully floating in housing 16. As an alternative, it is also
conceivable to design the oscillation means 1 1 in such a way that they act
immediately upon tool holder 15, tool receptacle 3 or tool 2.
It is conceivable that the oscillation means 1 1 could be operated
electrically.
This could be achieved, for example, with an electromagnet, whose
armature is mechanically connected to tool 2 and which is charged with a
voltage of cyclically alternating polarity.
However, an especially high lifts and a high mechanical frequency of lifting
movement 12 or lifting / pendulum movement 12, 13 can be achieved if the
oscillation means 11 are activated pneumatically or hydraulically. Figures 2
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and 3 show a valve arrangement (referred to as number 17) with oscillation
means 1 1 that can be pneumatically activated. This valve arrangement 17
comprises a pneumatic cylinder 18 with a differential pressure plunger 19
that is connected to tool 2. On both sides of plunger 19 in cylinder 18,
pressure chambers 20, 21 are formed to which different pressures p1 and
p2 can be applied. If pressure p2 is greater than pressure p1, plunger 19
moves to the left in the direction of an arrow 22 (see Fig. 2). If pressure p1
is greater than pressure p2, plunger 19 moves to the right in the direction of
arrow 23 (see Fig. 3). By alternately increasing and decreasing pressures p1
and p2, piston 19 and thus also tool 2 can be enabled to perform a back
and forth lifting movement 12.
The cyclically changing pressures p1 and p2 are produced by two 5 / 2-way
valves 24 and 25 connected back to back. To explain the function of valve
arrangement 17, reference is made to the position of the 5 / 2-way valves
24 and 25 in the position shown in Fig. 2. A constant pressure p3 is applied
to inputs P of the 5 / 2-way valves, which is led to exits B. Output B of
second 5 / 2-way valve 25 is connected to a left-hand actuating connection
26 of first 5 / 2-way valve 25. A right-hand actuating connection 27 of first
5 / 2-way valve 24 is connected to an output A of second 5 / 2-way valve
25 and ends in a first air outlet connection R1 of second 5 / 2-way valve
25, First 5 / 2-way valve 24 is therefore pushed to the right by the
pressures applied to actuating connections 26 and 27 (see Fig. 2).
Outlet B of the first 5 / 2-way valve 24 is connected to a second actuating
connection 29 of second 5 / 2-way valve 25. A first actuating connection
28 of second 5 / 2-way valve 25 is connected to an output A of first 5 / 2-
way valve 24 and ends in air outlet connection R1. The pressures applied to
actuating connections 28 and 29 of second 5 / 2-way valve 25 cause valve
25 to perform an actuating movement toward the left into the position
shown in Fig. 3. Now, constant pressure p3 is applied to output A of
second 5 / 2-way valve 25 and is led to second actuating connection 27 of
first 5 / 2-way valve 24. The first actuating connection 26 of first 5 / 2-way
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valve 24 is connected to air outlet connection R2 via output B of second 5 /
2-way valve 25. This also causes the first 5 / 2-way valve 24 to move left
from the position shown in Fig. 2 to the position shown in Fig. 3.
In turn, the position of first 5 / 2-way valve 24 shown in Fig. 3 has the
effect that a higher pressure is applied to first actuating connection of
second 5 / 2-way valve 25 than to the second actuating connection 29, so
that the second 5 / 2-way valve 25 is moved from the position shown in
Fig. 3 back to the right into the position shown in Fig. 2. Thus, the two 5 /
2-way valves 24 and 25 are connected back to back in such a way that
they perform a constant back and forth movement when constant pressure
p3 is applied. In the position of first 5 / 2-way valve 24 shown in Fig. 2,
pressure p2 is greater than pressure p1. However, in the position of first 5 /
2-way valve 24 shown in Fig. 3, pressure p1 is greater than pressure p2.
This means that valve arrangement 17 can enable tool 2 to perform a
constant lifting movement. Fig. 4 shows the path of lift h over time t. It is
clearly distinguishable that lift h follows a saw-tooth type of path. Angle a,
which determines the steepness of the lift and thus also the frequency of
the lifting movement, can be varied with an adjustable throttle 30 which is
connected to the first actuating connection 26 of first 5 / 2-way valve 24.
Furthermore, the maximum deflection hmaX of the lifting movement can be
varied with a second adjustable throttle 31 which is connected to the
second actuating connection 27 of first 5 / 2-way valve 24.
Fig. 5 shows another preferred embodiment of tool assembly 1 according to
the invention. In this embodiment, a force and torque sensor 33 is arranged
between tool 2 and the industrial robot or, to be more precise, between tool
assembly 15 and end effector 10 of the robot arm. The forces and torques
acting upon tool 2 during the machining process are transferred to force and
torque sensor 33 via tool receptacle 3, tool holder 15 and the force and
torque transfer means 32. The output signals of the force and torque sensor
are taken into account by a control system of the industrial robot when the
control signals for the adjusting elements of the robot are calculated so that
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tool 2 is pushed against the workpiece at a constant bearing pressure during
the machining process. The bearing pressure can be controlled and/or
regulated by the control system of the industrial robot. The embodiment of
tool assembly 1 shown in Fig. 5 may also be provided with oscillation
means 1 1 which enable tool 2 to perform a lifting movement 12 or a lifting /
pendulum movement 13.
