Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02348681 2001-05-24
Atty. Dkt.: 1039/3 -1-
REJ/Isg
Description
BELT SANDER WITH ORBITALLY TRANSLATED ABRASIVE BELT
Related Application
This application is related in part to Canadian
Patent File No. 2,298,961 entitled "Belt Sander with
Orbitally Translated Abrasive Belt" filed February 18,
2000, and now pending.
Technical Field
The present invention relates generally to machines for abrading
material and, more particularly, to an improved sanding machine for providing
an enhanced finish on work pieces.
Related Art
Motorized sanding machines have been used for many years to sand
the upper and lower surface of wooden work pieces that are conveyed along
a movable conveyor forming the worktable of the sanding machine. These
motorized sanding machines will typically utilize a wide sanding belt that is
entrained around vertically spaced rollers. A limitation to these sanding
machines is that they will often leave cross-grain scratch patterns in the
sanded
surface of the wooden work piece that results in an unattractive and perhaps
unacceptable finish in the work piece. A further problem relates to movement
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of the work piece induced by the rotational movement of the rotating sanding
belt of the sanding head. Mechanized hand sanders have been used in order
to provide an acceptable finish on wooden work pieces, but the sanding
operations are highly labor intensive and expensive.
Further, wide belt sanding machines with orbiting abrasive belts are well
known to those skilled in the art. Representative wide belt sanders are shown
in U.S. Patent No. 3,832,807 to Kaiser et al. and U.S. Patent No. 4,719,721 to
Stump. Generally, in this type of sanding apparatus, one or more (and
typically
two) individual sanding heads are utilized wherein each employs an endless
wide abrasive belt entrained over individual rollers or drums. At least one of
the rollers or drums is power driven to impart a high speed orbital motion to
the
abrasive belt. Generally, two individual sanding heads arranged in tandem are
provided wherein each is disposed vertically above a horizontal conveyor so as
to provide operative contact between the upper surface of work pieces being
fed through the machine and the surface of the abrasive belt. Further, the
first
sanding head is typically in the form of a contract drum for dimensioning at
the
drum stage and the second sanding head is in the form of a platen wherein the
finishing occurs at the platen station.
Another type of sanding machine is disclosed in U.S. Patent No.
4,742,650 to Sauder, Jr. et al. which provides a sanding machine for sanding
the surfaces or work pieces placed upon a conveyor that transports the work
pieces in a first direction wherein each of two sanding heads is oscillated at
twa
different frequencies relative to the work pieces on the conveyor. The first
oscillating frequency orbits the sanding heads in a circular motion overthe
work
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pieces on the conveyor, while the second oscillating frequency (which is
greater
than the first frequency) results in a vibration of the individual sanding
elements
engaging the work pieces. The double orbital motion sanding machine
disclosed in the patent includes a plurality of sander elements transversely
spaced above the conveyor, and the sander elements of first sanding head are
staggered with respect to the sander elements of the second sanding head.
This type of sanding apparatus, however, while useful for many purposes is not
as effective for sanding certain types of work pieces as the rotating endless
belt
sanding head-type of sanding machine.
Summary of the Invention
In accordance with the present invention, applicants provide a free
standing sander for abrading products that includes a sanding head having an
endless abrasive belt rotating around an upper roller and a lower roller. A
first
motor rotates at least of one of the upper and lower rollers of the sanding
head
so as to cause the abrasive belt to rotate endlessly around the upper and
lower
rollers. A conveyor is provided adjacent the lower roller of the sanding head
to convey the products towards the sanding head while the first motor rotates
the abrasive belt of the sanding head around the upper roller and the lower
roller. At least one rotatable eccentric shaft is rotatably mounted at one end
to
the upper roller and to the other end to the lower roller of the sanding head,
and a second motor is provided for rotating the at least one eccentric shaft
such that rotation of the least one eccentric shaft causes the sanding head to
move in a translational orbital movement.
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Further, in accordance with the present invention, applicants provide a
method of sanding products that includes placing a product on a conveyor belt
that moves the product through an abrading area. Next, the product is abraded
in the abrading area by a mechanism including a sanding head comprising an
endless abrasive belt rotating around an upper roller and a lower roller, a
first
motor for rotating at least one of the upper and lower rollers of the sanding
head where the rotation of the at least one roller causes the abrasive belt to
rotate endlessly around the upper and lower rollers, at least one rotatable
eccentric shaft rotatably mounted at one end to the upper roller and at the
other end to the lower roller of the sanding head, and a second motor for
rotating the at least one eccentric shaft such that rotation of the at least
one
eccentric shaft causes the sanding head to move in a translational orbital
movement.
Also, in accordance with the present invention, applicants provide a
second embodiment of the free-standing sander and method of sanding
products that utilizes an arcuate plate at the top thereof as a substitute for
the
top roller utilized in the prior embodiment of the inventive free-standing
sander
and method of sanding products.
It is therefore the object of the present invention to provide an improved
sanding machine of the type having a sanding head comprising an endless
rotating sanding belt entrained around an upper and lower roller that does not
leave cross-grain or otherwise unacceptable scratch patterns in the sanded
surface of the work piece.
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It is another object of the present invention to provide an improved
sanding apparatus of the type having a sanding head comprising an endless
rotating sanding belt wherein the sanding head is caused to move in a
translational orbital movement.
It is another object of the present invention to provide an improved
sanding machine of the type having a sanding head comprising an endless
rotating sanding belt that provides a homogeneous sanding pattern on the
surface of work pieces processed by the machine.
It is still another object of the present invention to provide an improved
sanding machine of the type having a sanding head comprising an endless
rotating sanding beltwherein both rotational movement and translational
orbital
movement are provided to the endless sanding belt in order to render
unnoticeable the scratches created by the sanding belt upon the work pieces.
It is still another object of the present invention to provide an improved
sanding machine of the type having a sanding head comprising an endless
rotating sanding belt that is particularly well adapted for cross-grain
sanding
of solid wood and veneers in such a way as to eliminate the pattern of
longitudinal scratches created by conventional sanding machines utilizing
sanding heads with rotating endless sanding be(ts.
It is still another object of the present invention to provide an improved
sanding machine of the type having a sanding head comprising an endless
rotating belt which combines a single orbital movement of the sanding head
with the conventional rotation of the endless sanding belt of the sanding
head.
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Some of the objects of the invention having been stated, other objects
will become evident as the description proceeds hereinafter, when taken in
connection with the drawings described below.
Brief Description of the Drawings
Figure 1 is a front perspective view of the sanding apparatus of the
present invention with parts broken away including parts from the support
frame for the sanding head and the bearings for the upper and lower rollers;
Figure 2 is a second front perspective view of the sanding apparatus of
the present invention with parts broken away including parts from the upper
and lower rollers and the support frame therebetween for better clarity of
understanding;
Figure 3 is a front perspective view of a second embodiment of the
sanding apparatus of the present invention with parts broken away for better
clarity of understanding; and
Figure 3A is a front perspective view of the arcuate plate sanding belt
tensioning mechanism shown in Figure 3 with parts broken away for better
clarity of understanding.
Best Mode for Carrying Out the Invention
With particular attention now directed to Figures 1 and 2 of the drawings,
the novel rotating belt sanding machine is generally designated 10. Sanding
machine 10 includes the sanding head generally designated 20 and the
conveyor generally designated 60. Sanding head 20 includes tension roller 22
and contact roller 24. Upper tension roller 22 ss supported by bearings 25A
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and 25B at each end thereof carried by supports 30A and 30B, and lower
contact roller 24 is supported by bearings 26A and 26B at each end thereof
carried by corresponding supports 28A and 28B at each end of contact roller
24. An endless sanding belt 32 is entrained around upper tension roller 22
and lower contact roller 24. Sanding head 20 is fixedly attached to vertically
moveable frame element 34 (only one side of four-sided frame element 34
surrounding sanding head 20 is shown in Figure 1) by sanding head support
element 36 which extends normally outwardly from two opposing sides of
frame element 34 and between tension roller 22 and contact roller 24. A pair
of spaced-apart and parallel eccentric shafts 38A and 38B are provided to
impart translational orbital movement to sanding head 20 in a manner to be
described hereinafter. Eccentric shaft 38A extends from contact roller support
28A at its lower end, to tension roller support 30A at its upper end, and
eccentric shaft 38B extends from contact roller support 28B at its lower end
to
tension roller support 30B (not shown) at its upper end. As can be seen with
reference to the drawings, eccentric shafts 38A and 38B when rotated will act
to provide translational orbital movement to sanding head 20.
With reference to Figure 2, it can be seen that two actuators 40A and
40B are provided in the top of sanding head support element 36 so as to urge
tension roller 22 upwardly or downwardly as required in order to properly
tension endless sanding belt 32 entrained around tension roller 22 and contact
roller 24. Two pneumatic actuators 42A, 42B are mounted on support 30B of
tension roller 22 to automatically center sanding belt 32 by turning the shaft
pin
22A. Electric motor 44 drives contact roller 24 by means of belt 46 and pulley
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48 mounted to the end shaft of contact roller 24. Second electric motor 50
serves to drive eccentric shafts 38A and 38B by means of pulley 50A mounted
to electric motor 50 which drives idle pulley 52B at the end of eccentric
shaft
38B by means of toothed belt 54. Idle pulley 52B in turn serves to drive idle
pulley 52A at the bottom end of eccentric shaft 38A by means of second
toothed belt 56 which extends between idle pulley 52B and idle pulley 52A.
Conveyor 60 comprises endless feed belt 62 for carrying work piece WP
beneath sanding head 20 to be acted upon by the combined rotation and
orbital movements of sanding belt 32. Feed belt 62 is entrained around driven
roller 64 and idle roller 66. Third electric motor 68 is provided to drive
driven
roller 64 through drive unit 70 which is a conventional gear transmission
mechanism.
Finally, with reference again to Figures 1 and 2 of the drawings, it can
be seen that four-sided frame element 34 to which sanding head 20 is affixed
by means of sanding head support element 36 extending between two
opposing sides thereof is provided with vertically adjustable movement by
means of lifting mechanisms 72A - 72D (72B - 72D not shown) provided at
each end of frame element 34. Lifting mechanisms 72A - 72D are most
suitabiyjack posts that act in response to motor aictuation (not shown)
through
a sprocket and chain mechanism (not shown) that is controlled, as desired, by
a suitable manual or suitable computer control mechanism (not shown).
Conveyor 60 is suitably mounted on support systems 74A- 74D (74C - 74D not
shown) which are most suitably fixed mounting blocks to hold conveyor 60
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stationary. Support systems 74A - 74D for conveyor 60 are supportably
mounted on machine base 76.
Finally, applicants contemplate that counterweights C can be provided
on idle pulleys 52A and 52B at the bottom end of eccentric shafts 38A and
38B, respectively, as required in order to suitably balance the eccentric
shafts.
1. Use of Novel Sanding Machine
A. Conventional Rotating Belt Sanding Machine
To fully appreciate the advancement of applicants' novel sanding
machine that provides simultaneous superimposed movements comprising
rotation of the sanding belt about the tension roller and contact roller and
translational orbital movement of the sanding belt, applicants note that
traditionally the surface sanding of flat panels is performed with
conventional
belt sanding machines by feeding a work piece into the sanding area by means
of a feed belt entrained around a motorized roller and an idle roller. A
vacuum
hold system can be utilized to apply vacuum to the feed table beneath the feed
belt to improve adhesion of a work piece to the feed belt. Normally, the feed
belt and support table therebeneath is set at a fixed level from the floor
such
that the rotating belt sanding head must vertically adjust in order to
accommodate different thicknesses of work pieces. However, it is also known
to utilize a fixed sanding head with a vertically adjustable feed belt and
support
table in order to accommodate work pieces of different thicknesses- The
sanding action performed by the sanding head on a work piece is obtained by
the sanding belt rotating around a contact roller (typically rubber or steel
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surface) and a tension roller that serves to maintain a proper tension to the
sanding belt between the two rollers.
The conventional sanding head is a contact roller (typically with a rubber
or steel surface). However, an alternative embodiment of the conventional
sanding machine is known that utilizes a pad/platen unit that is formed as a
one-piece construction for the entire working width of the unit or that is
segmented into various sections with electronic control of the intervention of
the various sections of the pad/platen unit.
Convention tension rollers are adapted to be raised or lowered for
applying the proper tension to the sanding belt as noted above, and when the
tension roller is lowered it will further allow for the substitution or the
replacement of the sanding belt as required during use of the sanding machine.
Moreover, it is well known for the tension roller to be provided with a
swinging
movement (in addition to the vertical movement) to maintain proper tracking of
the sanding belt on the sanding head during use of the sanding machine. Also,
although abrasive endless belts are well known in the sanding machine art, it
is also known for the sanding head to utilize other sanding media such as
rollers formed of steel, nylon or natural fiber brushes which are all well
known
in the industry for various abrasive/polishing and.uses.
B. Operation of Novel Sanding Machine
Applicants' novel sanding machine 10 combines a single orbital-
movement of sanding head 20 with the conventional rotation of sanding belt 32
about tension roller 22 and contact roller 24. In use, electric motor 50
rotates
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eccentric shafts 38A and 38B by means of belt 54 driving pulley 52B which in
turn motivates belt 56 so as to drive pulley 52A. The teeth on belts 54 and 56
serve to maintain a constant ratio of rotation of eccentric shafts 38A and 38B
by electric motor 50 and pulley 50A connected to the drive shaft thereof.
Eccentric shafts 38A and 38B are arranged in phase so that when the shafts
are turning the circular trajectories of each shaft 38A and 38B are in phase
and
the same radius of eccentricity of shafts 38A and 38B is achieved. Eccentric
shafts 38A and 38B impart the single translational orbital movement to lower
roller supports 28A and 28B and upper roller supports 30A and 30B which in
turn impart the single translational orbital movement to eccentric shafts 38A
and 38B and to tension roller 22 and contact roller 24.
Thus, sanding belt 32 is subject to two distinct contemporaneous
superimposed movements consisting of the rotation movement about rollers
22 and 24 as well as the single translational orbital movement imparted
thereto
by rotation of eccentric shafts 38A and 38B by electric motor 50.
Contemporaneously, electric motor 68 is motivating conveyor belt 62 about
driven roller 64 and idle roller 66 and electric motor 44 is imparting
rotational
movement to sanding belt 32 by imparting rotation to contact roller 24 through
belt 46 to pulley 48 connected to the shaft of contact roller 24. In order to
accommodate tensioning of sanding belt 32 by vertical adjustment of tension
roller 22, eccentric shafts 38A and 38B are splined on the top end (see Figure
2) to facilitate vertical movement of tension roller 22. To motivate tension
roller
22 upwardly and downwardly, two pneumatic actuators 40A and 40B are
provided in sanding head support element 36 positioned between tension roller
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22 and contact roller 24 and fixedly secured to frame element 34. As noted
hereinbefore, automatic centering of sanding belt is accomplished by turning
shaft pin 22A with pneumatic actuators 42A and 42B mounted on fixed support
30B for tension roller 22.
Thus, applicants' combination of rotational movement of sanding belt 32
and the simultaneous single translational orbital movement thereof provides an
unusually homogeneous sanding pattern on the surface of work piece WP that
can render almost unnoticeable the scratches created by sanding belt 32
during working of work piece WP. Although applicants have described the
present invention with particular reference to sanding of solid wood
orveneered
work pieces WP, applicants' inventive sanding machine is intended for other
applications including lacquered surfaces, plastic materials, marble, ceramic
tiles, stainless steel and copper sheet materials and other type of flat
surface
work piece materials.
H. Alternative Embodiment of Sanding Machine
Referring now to Figure 3 of the drawings, an alternative embodiment
of the novel rotating belt sanding machine is shown and generally designated
80. Sanding machine 80 is shown with like numerals for like parts that are
shown in the first embodiment of the sanding machine depicted in Figures 1
and 2 of the drawings. Sanding machine 80 is substantially identical to
sanding
machine 10 shown in Figures 1 and 2 of the drawings except for the
substitution of an arcuate plate P for upper roller 22 of sanding machine 10.
Arcuate plate P is mounted for vertical movement relative to cross support S
which is supported at ouposing ends thereof by tension roller supports 30A and
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30B. The use of arcuate plate P provides an alternative system for tensioning
endless sanding belt 32 which is entrained around the stationary arcuate plate
P and lower contact roller 24. Similarly to sanding machine 10, sanding
machine 80 has two actuators 81A, 81B which are each mounted to cross
support S at their lower end and arcuate plate P at their upper end so as to
urge arcuate plate P upwardly or downwardly as required in order to properly
tension endless sanding belt 32 entrained around arcuate plate P and contact
roller 24. Two pneumatic actuators 84A, 84B are mounted on tension roller
support S of arcuate plate P to automatically center sanding belt 32 by
oscillating the complete arcuate plate P supported in its center, the fulcrum
of
oscillation. The sanding belt 32 provides the signal of inversion of
oscillation
through a photocell (not shown) in a conventional manner that is well known to
one skilled in the art. (The centering system can be considered similar in
principle to the two pneumatic actuators 42A, 42B mounted on support 30B of
tension roller 22 in the first embodiment of the invention shown in Figures 1
and 2 of the drawings).
Otherthan the use of the modified tensioning system for sanding belt 32
as described hereinabove in lieu of tensioning roller 22 shown in the first
embodiment of the invention depicted in Figures 1 and 2 of the drawings, the
remaining functions and structural elements of sanding machine 100 are similar
to the first embodiment of the invention generally designated 10 in Figures 1
and 2 of the drawings.
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It will be understood that various details of the invention may be
changed without departing from the scope of the invention. Furthermore, the
foregoing description is for the purpose of illustration only, and not for the
purpose of limitation--the invention being defined by the claims.
