[0001] The invention concerns an apparatus for finishing surfaces on workpieces by moving
these past rotating sanding or polishing elements which are caused to rotate about
their own longitudinal axis, while the elements are caused to perform a circular movement
over the workpiece being finished. Such an apparatus of the above-mentioned type is
often referred to as a carousel machine.
[0002] Carousel machines according to the prior art comprise an upstanding carousel element
at right angles to the face being finished. The carousel element mounts a sanding
head with a plurality of radially protruding sanding spindles with cylindrical sanding
elements, which in operation are caused to rotate about the longitudinal axis of the
spindles over the face being finished, while the sanding head is caused to rotate
about its axis. The workpieces are placed manually or automatically on a conveyor
moving them past the sanding head, during which passage the face of the workpiece
in question is finished.
[0003] To maintain a high production rate the workpieces are advanced on the conveyor with
a relatively high speed, e.g. 5-6 m/min or about 10 cm/sec. Typically, the sanding
elements on the spindles have a diameter of 25-30 cm and may be caused to rotate with
e.g. 1000 rpm. The carousel is rotated so that the sanding elements are moved in a
circular working region around the axis of rotation of the carousel. Sanding according
to the prior art proceeds unsymmetrically in several ways. If e.g. all the sanding
elements on the carousel rotate in the same direction, they will pass the surface
of the workpiece with a relatively great speed in the side where they rotate against
the feed direction of the workpiece, while they will pass in cumflow at the other
side and can therefore work relatively longer in the same region. A difference in
sanding effect of minimum 25% can often be observed between the cumflow side and the
counterflow side, which may e.g. mean that a lacquered door panel is sanded insufficiently
at one side, while the lacquer is sanded away at the other side.
[0004] To ensure that two successively positioned sanding elements overlap a workpiece so
that it does not have an unfinished rim area of varying width, the speed of rotation
of the carousel itself must be suitably high. Such a high speed of rotation is unfortunate
since the sanding elements will not have time to penetrate into the profiles of the
workpiece. This problem is solved according to the prior art by reducing the speed
- both the feed speed of the conveyor as well as the speed of the carousel, which
is of course an unacceptable solution.
[0005] Others try to solve the problem by providing the carousel element with more spindles
than six, e.g. eight or ten, whereby the unfinished rim area can be eliminated, but
for the necessary torque to be imparted to the spindles, the diameter of the hub of
the carousel element has to be increased significantly. This involves disuniform sanding
of in particular small workpieces, which gives the machine a large, passive area just
below the carousel element, and this area does not contribute to the finishing process.
[0006] Others (US 4 646 473) have tried to compensate for the unsymmetrical sanding occurring
in the cumflow side and the counterflow side, respectively, by turning the direction
of rotation of every other spindle. This entails that the areas in the sides of the
finished workpieces, i.e. to the right and to the left of the centerline of the machine,
are alternately worked with a sanding element in cumflow and one in counterflow so
that the finished face has a characteristic "washboard"-like structure.
[0007] The object of the invention is to provide an apparatus for surface finishing of workpieces,
which are given a high flow rate, the surface being treated symmetrically so that
the drawbacks of the prior art of disuniform sanding or polishing in the cumflow side
and the counterflow side are eliminated. Further, the diameter of the hub of the carousel
element should desirably be reduced so that the passive area below the carousel element
is diminished.
[0008] This object is achieved in that the apparatus is provided with two sanding heads
mounted successively so that they have substantially the same working area on a suitable
workpiece, said apparatus comprising means for rotating the first sanding head in
one direction and the second in an opposite direction.
[0009] The second head will hereby compensate for the unsymmetrical working or finishing
which the first head applies to the workpiece.
[0010] In addition to the opposite direction of rotation of the carousel elements, the spindles
may advantageously be mounted so that they rotate clockwise on one head and counterclockwise
on the other.
[0011] The two carousel elements may expediently be driven by a common drive, such as an
electric motor. Likewise, the rotation of the spindles on the two carousel elements
may be driven by a drive common to the two pairs of spindles.
[0012] Alternatively, a powerful electric motor can drive both the rotation of the spindles
and the rotation of the carousel elements.
[0013] The invention will be explained more fully by the following description of a preferred
embodiment with reference to the drawing, in which
fig. 1 is a side view of a preferred embodiment of an apparatus for finishing surfaces
according to the invention,
fig. 2 is an end view of the apparatus shown in fig. 1,
fig. 3 schematically shows a preferred embodiment of the power transfer configuration,
seen from above, for the apparatus shown in fig. 1,
fig. 4 is a side view of part of the configuration shown in fig. 3,
fig. 5 is a schematic side view of the rotatable parts in a sanding head,
fig. 6 shows schematically how the spindles are caused to rotate through engagement
with the crown wheel shown in fig. 5,
fig. 7 shows a preferred embodiment of the movement of thefinishing tool according
to the invention, and
fig. 8 shows schematically how the apparatus according to the invention can be built
so as to comprise four rotating sanding heads.
[0014] Figs. 1 and 2 show a preferred embodiment of the apparatus for surface finishing
of workpieces. The apparatus comprises a frame including a horizontally positioned,
rectangular base 10, four preferably vertical legs 12 which are secured in each of
the four corners of the base. The frame moreover comprises an upper, horizontal frame
member 14 which is attached to each of the four legs 12. The frame is moreover stiffened
with a plurality of cross braces; a pyramidal housing 16 extends downwardly from the
upper frame member 14 and terminates in an inner, horizontal frame 18 which carries
the actual carousel elements.
[0015] The frame moreover mounts a conveyor 50 adapted to move the workpieces to be finished
past the sanding heads; this conveyor 50 comprises a conveyor belt which is stretched
by two rollers 52, 54, said conveyor belt being driven by an electric motor 58 which
is secured to the base 10, and which has a wheel on its drive shaft, said wheel being
connected through a V-belt to a wheel 56 on one of the rollers of the conveyor. The
electric motor 58 is thus adapted to drive the conveyor through the belt drive, which
usually takes place by continuous operation.
[0016] The inner frame 18 carries two sanding heads 100 each of which, as appears from fig.
7, has four spindles with sanding elements 60. As shown, the sanding heads 100 are
adapted to rotate about a vertical axis, and the sanding elements 60 can then simultaneously
rotate about their own horizontal longitudinal axis. This will be explained more fully
below.
[0017] Fig. 3 shows the inner horizontal frame 18 which accommodates a plate 20 carrying
partly two electric motors 22, 24, two drive wheels 26, 28 and two carousel elements
30, 32. The electric motor 24, which rotates the carousel units, are shown from the
side in fig. 4. A plurality of details are omitted for clarity; it may e.g. be mentioned
that the electric motor 24 has a motor casing 40 which is attached to the frame of
course, but this is not shown in the drawing. The electric motor 24 has a drive shaft
41 which is journalled in two sets of roller bearings 42 for mechanical stability.
A gear wheel 43, which meshes with a corresponding gear wheel 63 on a shaft 61, is
secured on the drive shaft 41, said shaft 61 moreover carrying a drive wheel 64. The
shaft 61 is journalled in two sets of roller bearings 62. Further, the drive shaft
41 mounts a drive wheel 44 which, in operation of the electric motor 24, rotates in
a direction opposite to the drive wheel 64, which takes place because of the tooth
engagement between the gear wheels 43, 63.
[0018] The two carousel elements are moreover indicated in fig. 4 which shows the top of
a vertical shaft 81 on which a wheel 85 is secured. An additional wheel 84 is present
below this wheel 85, the additional wheel 84 being secured to a shaft section arranged
on the exterior of the shaft 81, as will be explained later in connection with fig.
5, so that the wheel 84 is movable with respect to the wheel 85. To the left on the
carousel element the wheel 84 is connected with the wheel 64 through a V-belt 70 shown
in fig. 3, while to the right on the carousel element the wheel 84 is connected with
the drive wheel 44 on the drive shaft 41 of the electric motor 24 through a V-belt
71. Similarly, the other wheels 85 on the carousel elements are connected with the
electric motor 22 through a V-belt 73 and a V-belt 72 connected with the wheel 26,
respectively.
[0019] Fig. 5 shows an example of a carousel element where the upper wheel 85 is fixed to
the shaft 81 in a manner known per se. The lower wheel 84 is secured to a shaft section
98 extending coaxially with the shaft 81, said shaft section 98 being connected with
a horizontal, plate-shaped member 97 which peripherally merges into an upwardly directed
bead and is rotatable with respect to the plate 20 about the vertical axis of the
carousel element. The rotatability is ensured through an annular ball bearing 95,
but the apparatus moreover comprises means for retaining the carousel in a vertical
direction, but this problem is well-known by persons skilled in the art and will therefore
not be described in more detail here. Thus, the sanding head is formed by the wheel
84, the plate-shaped member 97, the coaxially arranged shaft member 98 and also by
a guard member 92, which, as shown in fig. 6, may be square in horizontal section,
and a base plate 93 for guarding the gear wheels against dust. Further, a plurality
of bearing casings 95 are attached to the guard 92.
[0020] The upper wheel 85, which is secured to the shaft 81 as mentioned before, is connected
with the crown wheel 86 through a central shaft member. The central shaft member is
rotatable with respect to the coaxially arranged shaft member 98, said rotatability
being ensured through bearings 96 between the two shaft members. The crown wheel 86
is thus adapted to mesh with a plurality of conical gear wheels, so that rotation
is transferred to the spindle shafts 91 journalled in the bearing casing 95. Each
sanding head comprises four spindles in the preferred embodiment, so four conical
gear wheels 90 mesh with the crown wheel 86. The spindle shafts 90 are rotatably journalled
through roller bearings 94 mounted in the bearing casing 95. This embodiment ensures
that the sanding head (84, 92, 93, 95, 97, 98) is movable with respect to the plate
20, and that the shaft 81 driving the spindle shafts 91 is movable with respect to
the sanding head (84, 92, 93, 95, 97, 98).
[0021] Fig. 6 shows schematically how the spindle shafts 91 are mounted in engagement with
the crown wheel 86 through respective conical gear wheels 90. The sanding head is
shown to be square, but nothing prevents imparting a cylindrical shape to it.
[0022] It appears from fig. 7 how a workpiece is finished according to the invention, it
being moved past two rotating sanding heads which are rotated about their own vertical
axis of symmetry, the rotation of the two sanding heads being so arranged that the
sanding heads rotate in different directions. Further, as appears from fig. 7, the
spindles are so arranged in the preferred embodiment that all spindles on a sanding
head rotate in the same direction, and so that the sanding spindles of the two heads
rotate in mutually different directions. However, this is not necessary for the invention
to be worked.
[0023] Fig. 8 shows schematically that the machine can be constructed so as to comprise
more than two sanding heads; these may e.g. be arranged so that the direction of rotation
of successive sanding heads 200, 210 and 220, 230 are oppositely directed, but otherwise
operate according to the principles already mentioned. The working region of the two
pairs of sanding heads 200, 210 and 220, 230 may advantageously overlap along the
rim. The number of pairs of sanding heads is determined by the width of the workpiece
being finished.
[0024] The drive of the spindles does not have to be placed over the carousels, but may
e.g. take place in the actual sanding head where an electric motor will then be provided.
1. An apparatus for surface finishing faces on workpieces which are moved past, and comprising
sanding heads which may be caused to rotate about an axis which is preferably perpendicular
to the faces being finished, a plurality of sanding spindles protruding radially from
a sanding head, the axes of the spindles being substantially parallel with the faces
being finished, said spindles being so connected with respective sanding heads that
in addition to being caused to rotate about their own axis they can also be caused
to rotate about the axis of the sanding head, wherein two sanding heads are arranged
successively so that they have substantially the same working region on a passing
workpiece, said apparatus comprising means for rotating the first sanding head in
one direction and the second in an opposite direction.
2. An apparatus according to claim 1, wherein the apparatus moreover comprises means
adapted to rotate the spindles on the first sanding head in one direction, and means
for rotating the spindles on the second sanding head in an opposite direction.
3. An apparatus according to claim 1 or 2, wherein a conveyor is adapted to move workpieces
being finished past the successively positioned sanding heads.
4. An apparatus for surface finishing faces on workpieces which are moved through the
apparatus, comprising:
a frame;
two sanding heads secured to the frame and having axes of rotation which are substantially
perpendicular to the face being finished, said sanding heads being arranged so as
to have substantially the same working region on a passing workpiece;
a plurality of sanding spindles secured to respective sanding heads and arranged so
as to protrude radially therefrom and adapted to rotate about their own longitudinal
axis;
means for rotating the spindles about their longitudinal axis; and
means for rotating one sanding head in one direction and the other in an opposite
direction.
5. An apparatus according to claim 4, wherein the means for rotating the sanding spindles
about their longitudinal axis are moreover adapted to rotate the spindles on one sanding
head in one direction and the spindles on the other in another direction.
6. An apparatus according to claim 4, moreover comprising a conveyor adapted to automatically
move the workpieces past the sanding heads.
7. An apparatus for surface finishing workpieces which are moved through the apparatus,
comprising:
a frame;
several successively positioned sanding heads secured to the frame and having axes
of rotation which are substantially perpendicular to the face being finished, said
sanding heads being arranged so that several successively arranged sanding heads have
substantially the same working region on a passing workpiece;
a plurality of sanding spindles mounted on respective sanding heads and arranged so
as to protude radially therefrom and adapted to rotate about their own longitudinal
axis;
means for rotating the spindles about their own longitudinal axis; and
means for rotating a sanding head in one direction, and another sanding head having
substantially the same working region in an opposite direction.
8. An apparatus according to claim 7, wherein the means for rotating the sanding spindles
about their longitudinal axis are moreover adapted to rotate the spindles on one sanding
head in one direction and the spindles on the other in another direction.
9. An apparatus according to claim 7, further comprising a conveyor adapted to automatically
move the workpieces past the sanding heads.