|
(11) | EP 2 687 328 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
|
|
|
|
|||||||||||||||||||||||
| (54) | Sanding machine for sanding wood panels or alike |
| (57) In a sanding machine, a wood panel (2) is fed underneath a sanding device (10) having
an abrasive belt (11) which is wound in a ring shape around a tensioning drum (13)
and a drive drum (12) defined by a cylindrical sleeve (21) fitted in a rotatory way
on a support shaft (16), which is moved from a lowered operating position to a lifted
rest position by an actuating device (24) connected to the support shaft (16) through
the interposition of a pneumatic shock absorber device (28); the supply pressure of
the pneumatic shock absorber device (28) being selectively controlled as a function
of a width of the panel (2).
|
[0002] In particular, the present invention relates to a sanding machine of the type comprising a conveyor belt, which has an upper transport branch defining a substantially horizontal support plane for at least one panel, and is adapted to feed the panel underneath a sanding device in turn comprising an upper tensioning drum, a lower drive drum and an abrasive belt which is wound in the shape of a ring around the tensioning drum and the drive drum for sanding an upper face of the panel.
[0003] Generally, the drive drum comprises a support shaft, which presents a first longitudinal axis, and is provided with two eccentric ends which are coaxial to each other and to a second longitudinal axis parallel to the first axis; and a cylindrical sleeve which extends around the support shaft coaxially to the first axis, and is coupled in a rotatory way to the support shaft for rotating, with respect to the support shaft, around the first axis itself.
[0004] The drive drum is moved by an actuating device around the second axis between a lowered operating position, in which the abrasive belt contacts the upper face of the panel, and a lifted rest position, in which the abrasive belt disengages the panel.
[0005] In order to allow the drive drum to move, in use, around the second axis as a function of a profile of said upper face, the sanding machine is provided with a shock absorber device comprising at least one pneumatic actuating cylinder interposed between the support shaft and the actuating device.
[0006] Since the actuating cylinder is supplied with constant pressure air, known sanding machines of the type described above have some drawbacks mainly due to the fact that the compression force exerted by the drive drum and, thus, by the abrasive belt on the upper face of the panel increases as the panel width, as measured parallel to said first and second axes, decreases. Accordingly, when the panel width is relatively reduced and the compression force exerted by the drive roll on the panel is higher that a given threshold value, the abrasive belt damages both the upper front corner and at least a part of the upper face of the panel itself.
[0007] It is an object of the present invention to provide a sanding machine for sanding wood panels and alike which is free from the above-described drawbacks and is easy and cost-effective to be implemented.
[0008] According to the present invention, there is provided a sanding machine for sanding wood panels and alike as claimed in the appended claims.
[0009] The present invention will now be described with reference to the accompanying drawings, which show a nonlimiting example thereof, in which:
figure 1 is a diagrammatic perspective view, with parts removed for clarity, of a preferred embodiment of the sanding machine of the present invention;
figure 2 is a diagrammatic side view, with sectional parts and parts removed for clarity, of the sanding machine in figure 1;
figure 3 is a diagrammatic side view, with parts removed for clarity, of a detail of the sanding machine in figures 1 and 2; and
figure 4 diagrammatically shows the operation of the detail in figure 3.
[0010] With reference to figure 1, reference numeral 1 indicates, as a whole, a sanding machine for sanding wood panels 2 and alike having a substantially parallelepiped shape.
[0011] The sanding machine 1 comprises a support frame 3 and an infeed device 4 in turn comprising a conveyor belt 5, which is wound in a ring shape around a pair of motor driven pulleys 6 mounted for rotating around respective longitudinal axes 7 parallel to each other and to a horizontal direction 8, presents an upper transport branch defining a horizontal support plane P for at least one panel 2, and is adapted to feed panels 2 in a horizontal direction 9 transverse to direction 8.
[0012] The sanding machine 1 further comprises a sanding unit 10 in turn comprising an abrasive belt 11 wound in a ring shape around a lower drive drum 12 and an upper tensioning drum 13 of the known type, which is mounted for rotating around a longitudinal axis 14 thereof parallel to axes 7, and is mobile, with respect to frame 3, in a vertical direction 15 orthogonal to directions 8 and 9 between a lowered rest position and a lifted operating position.
[0013] As shown in figure 2, drum 12 comprises a support shaft 16, which has a longitudinal axis 17 parallel to axes 7 and 14, and is provided with two eccentric ends 18, which are coaxial to each other and to a longitudinal axis 19 parallel to axis 17, and are coupled in a rotatory manner to frame 3 for allowing shaft 16 to rotate, with respect to frame 3, around axis 19. Shaft 16 further comprises a crank 20, which is fitted on one of ends 18 and extends radially outwards from end 18 itself.
[0014] Drum 12 further comprises a cylindrical sleeve 21 which extends around shaft 16 coaxially to axis 17, and is coupled in a rotatory manner to shaft 16 for rotating, with respect to shaft 16 and under the thrust of an actuating device 22 of the known type, around axis 17 itself.
[0015] Drum 12 is mobile around axis 19 between a lowered operating position, in which belt 11 contacts an upper face 13 of panel 2, and a lifted rest position, in which belt 11 disengages face 23 itself.
[0016] Drum 12 is moved and normally kept in its lowered operating position by gravity under the thrust of its own weight, and is moved from its lowered operating position to its lifted rest position by an actuating device 24 (figure 3) comprising a rocker arm 25 coupled in a rotatory manner to crank 20 for rotating, with respect to shaft 16, around axis 19.
[0017] Device 24 further comprises a first actuating cylinder 26 which is connected to frame 3 and has an output rod 27, which is connected to a first arm of rocker arm 25, and is mobile between a backward position (figure 3) and an extracted position (not shown); and a second actuating cylinder 28 which is fixed to a second arm of rocker arm 25 and has an output rod 29, which is provided with a free end adapted to arrange in contact with crank 20 and is mobile from and to a backward position (figure 3).
[0018] The operation of drum 12 and of device 24 will now be described with reference to figure 3 and starting from an instant when rod 27 is arranged in its extracted position, rod 29 is arranged in its backward position and drum 12 is arranged in its lifted rest position.
[0019] Following the displacement of rod 27 from its extracted position to its backward position, rocker arm 25 rotates around axis 19 in clockwise direction, crank 20 and drum 12 also rotate around axis 19 in clockwise direction by gravity under the thrust of the weight of drum 12, and drum 12 arranges in its lowered operating position in contact with the upper face 23 of panel 2, irrespective of the actual thickness of panel 2 itself.
[0020] When drum 12 is arranged in contact with panel 2, rod 29 is moved to an extracted position so as to exert on drum 12 a torque around axis 19 which is in any case lower than the torque with opposite sign exerted on drum 12 by the weight of drum 12 itself.
[0021] Accordingly, depending on the profile of face 23, drum 12 oscillates about axis 19 in clockwise direction under the thrust of its own weight when the thickness of panel 2 decreases and in counter clockwise direction under the thrust of panel 2 and of cylinder 28 when the thickness of panel 2 increases.
[0022] At the end of the process, rod 29 is moved back to its backward position and rod 27 is moved back to its extracted position so as to rotate rocker arm 25 in counter clockwise direction and allow rod 29 to move crank 20 in counter clockwise direction around axis 19 and drum 12 to its lifted rest position.
[0023] Device 24 further comprises a travel end member 30 which is mounted on rocker arm 25 on an opposing side of cylinder 28 with respect to crank 20, is mobile, with respect to rocker arm 25, from and towards cylinder 28 so as to selectively control the oscillation of drum 12 around axis 19, and is further mobile in a travel end position (not shown), in which member 30 locks crank 20 against rod 29 of cylinder 28 for preventing the oscillation thereof around axis 19.
[0024] According to a variant not shown, the travel end member 30 is eliminated and replaced with a thrust device acting on crank 20, for example a spring or a pneumatic actuating cylinder with fixed or adjustable stroke.
[0025] With regard to the above description, it should be pointed out that:
cylinder 28 defines a shock absorber device adapted to allow device 12 to oscillate around axis 19 as a function of the profile of the upper face 23 of panel 2 and, thus, the abrasive belt 11 to remove a constant amount of material from the whole face 23 itself; and
the thrust exerted by rod 29 on crank 20 is selectively controlled by a control unit 31 (figure 4) as a function of a width of panel 2 measured parallel to direction 8.
[0026] Unit 31 comprises a detecting device 32 adapted to detect the width of panel 2 in direction 8, a pressure regulator 33 arranged along a line 34 supplying air to cylinder 28, and an electronic control unit 35 adapted to selectively control the operation of regulator 33 as a function of a signal coming from device 32.
[0027] In use, the air supply pressure to cylinder 28 increases as the width of panel 2 decreases and it decreases as the width of panel 2 itself increases so as to always ensure a constant compression force of drum 12 on face 23 and a correct processing of face 23 itself.
[0028] In particular, device 32 comprises a plurality of mechanical contact members (not shown), which are distributed in direction 8, and are selectively moved from respective rest positions to respective operating positions under the thrust of panel 2. Of course, the control unit 35 receives in input and generates in output a signal proportional to the number of mechanical contact members (not shown) which are moved to their operating positions by panel 2.
1. A sanding machine for sanding wood panels (2) or alike comprising an infeed device
(4), which defines a support plane (P) for at least one panel (2), and is suited to
move forward the panel (2) in a first direction (9); a sanding device (10) mounted
above the support plane (P) and comprising, in turn, a drive drum (12), a tensioning
drum (13), and an abrasive belt (11), which is wound in a ring shape around said drive
and tensioning drums (12, 13), so as to sand an upper face (23) of the panel (2),
the drive drum (12) comprising a support shaft (16), which presents a first longitudinal
axis (17), is provided with a cylindrical sleeve (21) fitted in a rotatory way on
the support shaft (16) so as to rotate around the first axis (17), and is mounted
so as to rotate around a second axis (19), which is parallel to and distinct from
the first axis (17) itself; a first actuating device (22) for moving the cylindrical
sleeve (21) around the first axis (17); a second actuating device (24) for moving
the drive drum (12), with respect to the support plane (P), around the second axis
(19) from a lowered operating position to a lifted rest position; and at least one
pneumatic shock absorber device (28), which is interposed between the support shaft
(16) and the second actuating device (24), so as to allow, in use, the drive drum
(12) to move around the second axis (19) as a function of a profile of said upper
face (23); and characterised in that it comprises, furthermore, a detecting device (32) for detecting a width of the panel
(2) in a second direction (8), which is transverse to the first direction (9); and
a pressure regulator (33), which is suited to selectively control the feeding pressure
of the pneumatic shock absorber device (28) and, thus, the thrust exerted by the pneumatic
shock absorber device (28) on the drive drum (12) as a function of a signal coming
from the detecting device (32) and, thus, of the width of the panel (2).
2. A sanding machine according to claim 1, wherein said first and second axes (17, 19)
are arranged so as to allow the weight of the drive drum (12) to move the drive drum
(12) to its lowered operating position, and normally to keep it there.
3. A sanding machine according to claim 1 or 2, wherein the pressure regulator (33) is
selectively controlled so as to allow the pneumatic shock absorber device (28) to
exert on the drive drum (12) a torque around the second axis (19), which is in any
case lower than a torque with opposite sign, which is exerted on the drive drum (12)
by the weight of the drive drum (12) itself.
4. A sanding machine according to any of the previous claims, wherein the support shaft
(16) is provided with two eccentric ends (18), which are coaxial to each other and
to the second axis (19); the pneumatic shock absorber device (28) comprising an actuating
cylinder, which presents an output rod (29) acting on one of said eccentric ends (18).
5. A sanding machine according to claim 4, wherein the support shaft (16) comprises,
furthermore, a crank (20), which is coupled in an angularly fixed way to one of said
eccentric ends (18), and is arranged in contact with said output rod (29).
6. A sanding machine according to claim 4 or 5, wherein the pneumatic shock absorber
device (28) is mobile due to the thrust of the second actuating device (24), so as
to allow the output rod (29) to move the drive drum (12) from its lowered operating
position to its lifted rest position.
7. A sanding machine according to any of the previous claims, wherein the second actuating
device (24) comprises a crank mechanism (25) for moving the pneumatic shock absorber
device (28) around the second axis (19).
8. A sanding machine according to any of the previous claims, wherein the second actuating
device (24) comprises a rocker arm (25), which is mounted so as to rotate, with respect
to the support shaft (16), around the second axis (19), and presents a first arm,
to which the pneumatic shock absorber device (28) is fitted, and a further actuating
cylinder (26), which is connected to a support frame (3) of the drive drum (12), and
presents a further output rod (27), which is connected to a second arm of the rocker
arm (25), and is mobile between a backward position and a forward extracted position,
so as to move the rocker arm (25) around the second axis (19).
9. A sanding machine according to any of the previous claims, wherein the detecting device
(32) comprises a plurality of mechanical contact members, which are distributed in
the second direction (8), so as to selectively move from respective rest positions
to respective operating positions due to the thrust of the panel (2).
10. A sanding machine according to any of the claims from 1 to 8, wherein the detecting
device (32) comprises optical means for detecting the width of the panel.
11. A sanding machine according to any of the previous claims and comprising, furthermore,
an electronic control unit (35), which is suited to receive, as an input, a signal
coming from said detecting device (32) and to generate, as an output, a control signal
for controlling the operation of said pressure regulator (33).