Sanding machine

A sanding machine for sanding the surfaces of work pieces placed upon a conveyor operable to transport the work pieces along a first direction is disclosed wherein each of two sanding heads is oscillated at two different frequencies relative to the work pieces on the conveyor. The first oscillating frequency orbits the sanding heads in a circular motion over the work 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. Each sanding head includes a plurality of sander elements transversely spaced above the conveyor, the sander elements of the first sanding head being staggered with respect to the sander elements of the second sanding head. The orbiting sub-frames mounting the respective sets of sander elements are driven by crank mechanisms cantilevered by one end thereof being affixed to the main frame, while the opposing end is engageable with a movable support hingedly connected to the main frame to facilitate a removal of the sanding belts forming a part of each sander element.

BACKGROUND OF THE INVENTION 
This invention relates generally to machines constructed for abrading 
material and, more particularly, to an improved sanding machine for 
placing a finished surface on wooden work pieces. 
Mechanized sanding machines have been provided to sand the upper and or 
lower surface of wooden work pieces being conveyed along a movable 
conveyor forming the work table of the sanding machine. These machines, 
such as found in U.S. Pat. No. 3,832,807, will typically utilize a wide 
sanding belt entrained around vertically spaced rollers. Such machines 
will often leave cross grain scratch patterns in the sanded surface of the 
wooden work piece, resulting in an unattractive and unacceptable finish in 
the work piece. A further problem relates to a movement of the work piece 
induced by the rotational movement of the sanding head. 
Mechanized hand sanders, such as shown in U.S. Pat. No. 4,478,010, can 
provide an acceptable finish on the wooden work piece; however, such 
sanding operations are highly labor intensive and, therefore, expensive. 
It would be desirable to provide a mechanized sanding machine operable to 
sand the upper surface of wooden work pieces placed upon a conveyor that 
would emulate the sanding operation of a mechanized hand sander. 
SUMMARY OF THE INVENTION 
It is an object of this invention to overcome the aforementioned 
disadvantages of the prior by providing a sanding machine having sanding 
heads operable to oscillate at two different frequencies relative to the 
work piece being conveyed on a conveyor. 
It is another object of this invention to provide a sanding machine having 
first and second oscillating mechanisms to emulate the sanding operation 
of a mechanized hand sander. 
It is an advantage of this invention that a fine finish can be placed upon 
a wooden work piece by mechanized sanding machine without the necessity of 
utilizing hand labor. 
It is another advantage of this invention that a fine finish can be placed 
upon a wooden work piece by a mechanized machine utilizing a coarser 
sandpaper than previously known in the art to provide a similar finish. 
It is still another object of this invention to provide a sanding head 
comprising a plurality of spaced apart sander elements having individual 
sanding belts rotatably mounted thereon to engage the work pieces on the 
movable conveyor positioned immediately therebeneath. 
It is a feature of this invention that the amplitude of the orbiting motion 
induced into the sanding heads by the first oscillating mechanism is 
greater than the distance between the individual sander elements. 
It is another feature of this invention that the first oscillating 
mechanism is partially supported by a removable support member hingedly 
connected to the main frame. 
It is another advantage of this invention that the movable support member 
facilitates the removal and replacement of individual sanding belts on the 
sander elements. 
It is still another feature of this invention that the spacing of the 
sander elements on the first sanding head of the sanding machine is 
staggered with respect to the spacing, of the sander elements on the 
second sanding head. 
It is yet another object of this invention to vibrate the individual 
sanding belts during the sanding operation of the sanding machine. 
It is yet another feature of this invention that a dampening mechanism is 
engaged with the individual sanding belts to reduce the noise caused by 
the vibration in the belts above the work piece being sanded. 
It is yet another object of this invention to minimize the time of contact 
of the sanding paper with the workpiece. 
It is still another feature of this invention that the timing of the 
vibratory motion of the individual sanding elements is timed so that 
adjacent sanding elements oppose each other to effect a removal of 
material from the work piece instead of an overall movement of the 
workpiece. 
It is yet a further advantage of this invention that a satisfactory finish 
can be placed on a wooden work piece with only one pass through a 
mechanized sanding machine. 
It is yet another feature of this invention that the conveyor is vertically 
adjustable relative to the sanding heads to accomodate work pieces having 
different thicknesses. 
It is yet a further object of this invention to provide a mechanized 
sanding machine, which is durable in construction, inexpensive of 
manufacture, carefree of maintenance, facile in assemblage, and simple and 
effective in use. 
These and other objects, features and advantages are accomplished according 
to the instant invention by providing a sanding machine for sanding the 
surfaces of work pieces placed 20. upon a conveyor operable to transport 
the work pieces along a first direction wherein each of two sanding heads 
is oscillated at two different frequencies relative to the work pieces on 
the conveyor. The first oscillating frequency orbits the sanding heads in 
a circular motion over the work 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. Each sanding head includes a plurality of sander elements 
transversely spaced above the conveyor, the sander elements of the first 
sanding head being staggered with respect to the sander elements of the 
second sanding head. The orbiting sub-frames mounting the respective sets 
of sander elements are driven by crank mechanisms cantilevered by one end 
thereof being affixed to the main frame, while the opposing end is 
engageable with a movable support hingedly connected to the main frame to 
facilitate a removal of the sanding belts forming a part of each sander 
element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and, particularly, to FIGS. 1-4, a mechanized 
sanding machine 10 incorporating the principles of the instant invention 
can be seen. Any left and right references are used as a matter of 
convenience and are determined by standing at the front or input side of 
the machine, i.e., the view of FIG. 2, such that the conveyor 15 will 
transport work pieces placed thereon into the machine 10. 
The sanding machine 10 includes a stationary main frame 12 having a series 
of generally vertically extending angle members forming legs 13 which 
support the sander 10 above the floor F. The frame 12 supports above the 
floor F a generally horizontal work table 15 in the form of conveyor 16 
which is driven by an electric motor 17 and operable to transport work 
pieces W, representatively shown in FIGS. 3 and 4, through the machine 10 
for a sanding operation. The conveyor 16 is provided with screw type 
height adjusting members 18 which can be actuated by the wheel 19 to raise 
and lower the conveyor 16 relative to the sanding heads 20,22 in a 
conventional manner to accommodate work pieces with different thicknesses. 
The sanding machine is preferably constructed as a double headed machine 
having a first sanding head 20 positioned forwardly of a second sanding 
head 22, as seen from the perspective of the work pieces W being fed 
through the machine 10 by the conveyor 16. Each of the sanding heads 20,22 
is similarly constructed, except for the number and particular arrangement 
of the sander elements which, as best seen in FIG. 4, are arranged in a 
staggered relationship as will be described in greater detail below. 
Accordingly, the description of the construction of the first sanding head 
20 will be construed as being applicable to both the sanding heads 20,22. 
The sanding head 20 includes a sub-frame 24 connectable to a crank 
mechanism 25 to affect a reciprocable movement of the sanding head 20 in a 
circular pattern including a component extending transversely of the 
conveyor belt 16. The crank mechanism 25 is preferably constructed with a 
pair of gearboxes 26,27 disposed along the left and right sides, 
respectively, of the machine 10 and connected by a shaft 28. The shaft 28 
is driven by an electric motor 29 and belt drive 31 interconnecting the 
motor 29 and a sheave 32 on the shaft 28. Extending generally vertically 
out of each respective gearbox 26,27 is a driven shaft 34 to which crank 
shafts 35 are eccentrically connected such that a rotation of the driven 
shaft 34 creates an orbiting of the crank shafts 35. The sub-frame 24 is 
comprised of an upper member 36 and a spaced apart lower member 38 
interconnecting corresponding transversely spaced crank shafts 35 to form 
a sub-frame assembly operable to orbit in a circular motion relative to 
the main frame 12 upon a driving rotation of the connecting shaft 28. A 
series of counter weights 39 mounted on the crank shafts 35 counterbalance 
the offset mass of the sanding heads 20,22 being orbited by the crank 
mechanism 25. 
The sanding head 20 further includes a plurality of transversely spaced 
sander elements 40 mounted on the sub-frame 24 for reciprocation 
therewith. As best seen in FIGS. 1-5, each sander element 40 includes an 
endless sanding belt 42 entrained around an upper roller 43 and a pair of 
fore-and-aft spaced lower rollers 44. A conventional pneumatic belt 
tensioning mechanism 45 is provided adjacent the upper roller 43 to 
maintain proper tension within the sanding belt 42. Each upper roller 43 
is mounted on a transverse drive shaft 47 rotatably supported by brackets 
46 connected to the upper sub-frame member 36. The drive shaft 47 is 
drivingly coupled to an electric motor 48 to effect a rotation of the 
sanding belts 42. 
As best seen in FIGS. 5-8, the lower sub-frame member 38 rotatably mounts a 
vibratory drive shaft 51 having a double timing pulley sheave assembly 52 
mounted on the upper portion thereof. The shaft 51 terminates below the 
lower sub-frame member 38 in an eccentrically mounted bearing 54 on which 
a sanding pad 55 is affixed. The sanding pad 55 includes a rectangular 
formed shoe 56 having upstanding ears 57 positioned at each respective 
corner thereof. Corresponding transversely spaced pairs of ears 57 support 
the rotatable mounting of the respective pair of lower rollers 44 to 
rotatably support the sanding belt 42 on either fore-and-aft side of the 
sanding pad 55. A counterweight 59 counterbalances the offset mass of the 
sanding pad 55 with respect to the axis of rotation of the vibrating drive 
shaft 51 to balance the driving rotation of the shaft 51. The sanding pad 
55 is also provided with a sponge rubber portion 58 affixed to the lower 
side of the formed shoe 56 to form a cushion between the shoe 56 an the 
rotating sanding belt 42 and to transfer the vibration induced by the 
eccentrically mounted shoe 56 to the sanding belt 42 to improve the 
sanding action on the work piece. A stationary sealed dust cover 53 is 
connected to the bottom frame member 38 and terminates adjacent the shoe 
56 to prevent the introduction of dust to the bearing 54 and to prevent 
the rotation of the shoe 56, while permitting the vibratory motion of the 
shoe 56. 
While the crank mechanism 25 eccentrically mounting the sub-frame 24 for 
reciprocal movement thereof relative to the main frame 12 forms a first 
oscillating mechanism 60 for moving the sanding heads 20,22 relative to 
any work piece W being sanded on the work table 15, the eccentrically 
mounted sanding pad 55 on the vibrator drive shaft 51 forms a second 
oscillating mechanism 62 to move the sanding pads 55 relative to the work 
piece W independently of the oscillation induced by the first oscillating 
mechanism 60. The first oscillating frequency is a relatively low 
frequency of approximately 120 revolutions per minute with an amplitude 
approximately 2 inches, whereas the second oscillating frequency, i.e., 
the jitterbug vibration of the individual sanding belts 42, is 
significantly higher at about 7,000 revolutions per minute with an 
amplitude of about 0.1 inch. 
The individual vibrator drive shafts 51 are driven from an electric motor 
64 stationarily mounted on the main frame 12 so as to reduce the mass 
being reciprocated on the sub-frame 24 and to avoid undue stresses on the 
electric motor 64. Because the sub-frame 24 and the sander elements 40 
mounted thereon are being reciprocated by the first oscillating mechanism 
60 relative to the electric motor 64, a special drive coupling 65 
interconnects a jackshaft 66 rotatably mounted in the lower subframe 
member 38 adjacent the electric motor 64. An example of a drive coupling 
65 that will accommodate the reciprocal movement of the jackshaft 66 
relative to the stationary electric motor 64 is the Schmidt Model L200 
offset coupling. A drive pulley 68 mounted on the jackshaft 66 is 
drivingly coupled to the adjacent double pulley assembly 52 by a drive 
belt 69. The rotational power is transferred between adjacent double 
sheave assemblies 52 by additional drive belts 69 entrained between 
corresponding portions of adjacent double sheave assemblies 52. The 
oscillating action of the shoe 56 is depicted schematically in FIG. 8 in a 
sequential manner from quadrant to quadrant, the respective positions of 
the corners of the shoe 56 and roller 43 mounted thereon depicting the 
limits of the oscillatory motion induced by the eccentricity of the shoe 
56 mounted on the drive shaft 51. To reduce the vibrations emanating from 
the long spans of the sanding belts 42 stretching from the lower rollers 
44 to the upper roller 43 on each sander element 40, a dampening mechanism 
49 is provided adjacent each lower subframe member 38 to engage the 
sanding belt 42, which is best seen in FIGS. 1, 3 and 5. The dampening of 
the belts 42 reduces the operational noise of the machine 10 and increases 
belt life. 
Referring again to FIGS. 1-4, the main frame 12 is also provided with 
stationary upper and lower frame members 71,72. These frame members 71,72 
are affixed at the right side thereof to the legs 13 of the main frame 12 
and extend toward the left side of the machine 10 in a cantilevered 
fashion. The respective gearboxes 26,27 are mounted between these 
horizontal frame members 71,72 to stationarily mount the gearboxes on the 
main frame 12. The left side of the main frame 12 is provided with a frame 
extension 74 on which a movable frame support 75 is hingedly secured. The 
frame support 75 is formed to snugly receive the left gearbox 26 between 
upper and lower members 76,77. The frame support 75 is engageable with a 
clamping mechanism 78 secured by an overcenter latch 79 to rigidly secure 
the frame support 75 into engagement with the left gearbox 26. In this 
manner, the horizontal frame members 71,72 and the crank mechanism 25 can 
be supported by the left side of the main frame 12. However, when it is 
desirable to remove the sanding belts 42 from the respective sander 
elements 40 on the sanding heads 20,22, the movable frame support 75 can 
be unlatched and swung about its hinge axis on the frame extension 74 to 
permit access to the sanding heads 20,22 for removal and replacement of 
the sanding belts 42 while the frame members 71,72 and crank mechanism 25 
extends in a cantilevered manner from the right side of the main frame 12. 
In operation, the operator places work pieces W on the upper surface of the 
conveyor 16 to be transported into engagement with the first sanding head 
20. Optional hold-down rollers 80 may extend transversely of the conveyor 
belt 16 on fore-and-aft sides of each of the sanding heads 20,22, as best 
seen in FIGS. 3 and 4, and can be utilized to hold the work piece W 
against the conveyor belt 16 while the sanding heads 20,22 engage the 
upper surface of the work piece W for a sanding operation thereof. It has 
been found, however, that by phasing adjacent eccentrically mounted 
sanding pads 55 at 180.degree. with respect to the oscillations 
therebetween while rotating all drive shafts 51 in the same direction, the 
hold-down rollers would not be necessary so long as the work piece W 
contacted at least two of the individual sander elements 40 while engaged 
with the respective sanding heads 20,22, i.e., the countervibrating 
sanding pads 55 will hold the work piece on the conveyor 16 without 
causing a shifting thereof while sanding its surface. Accordingly, 
maintenance of the phase differential between adjacent second oscillating 
mechanisms 62 would require the use of timing belts 69, such as 
representatively shown in FIGS. 5 and 6, extending between adjacent double 
timing pulley assemblies 52, thereby maintaining the offset phase 
relationships therebetween. 
The first sanding head 20 is orbited by the first oscillatory mechanism 60 
to move the sander elements 40 over the upper surface of the work piece W 
with a circular motion while the second oscillating mechanism 62 vibrates 
the sanding belts 42 in a significantly higher frequency than that induced 
by the first oscillating mechanism 60. To assist in an understanding of 
the operation of the first oscillating mechanism 60, reference can be had 
to the schematic view of FIG. 9 wherein the motion of the subframe 24 and 
a representative sander element 40 relative to the main frame 12 can be 
seen in phantom. In this manner, the sanding machine 10 imitates the hand 
sanding operation utilizing a vibratory hand sander. The work piece W 
passes from the first sanding head 20 to the second sanding head 22 where 
a second sanding operation is completed. As best seen in FIG. 4, the 
sander elements 40 on the second sanding head 22 are staggered with 
respect to the location of the sander elements 40 on the first sanding 
head 20, such that the sander elements 40 on the second sanding head 22 
are aligned with the spaces between the respective sander elements 40 on 
the first sanding head 20. Accordingly, the second sanding head 22 
provides a uniform sanding treatment to the work piece W and places a fine 
finish on the upper surface of the work piece W with only one pass through 
the machine 10. The sanding machine 10 can also be provided with a 
conventional dust collection mechanism (not shown) to extract dust from 
the sanding belts 42 and from within the machine 10 and transport the dust 
to a location remote from the sanding machine. To facilitate the removal 
of dust from the belts, an air bar 81, representatively depicted in FIG. 
1, is positioned to blow dust off the sanding belts 42 to increase their 
operative life. 
When replacement of the sanding belts 42 is deemed necessary, the operation 
of the sander 10 is shut down by cutting power to the individual electric 
motors 17,29,48 and 64. The movable frame support 75 can be unlatched and 
rotated about its hinge axis to expose the respective sanding head 20,22. 
A relaxing of the pneumatic tensioning mechanism 45, as shown in phantom 
in FIG. 5, removes the tension from the sanding belts 42 and permits the 
individual belts 42 to be removed from the respective sanding heads 20,22 
through the left side of the machine passing through the opening formed by 
the removed support member 75. Following replacement of the sanding belts 
42, the tensioning mechanism 45 can be reactivated, the movable frame 
support 75 reclamped and latched into supportive engagement with the left 
gearbox 26 and the machine 10 returned to a sanding operation. 
Alternative embodiments of the above-described sanding machine would 
include the inversion of one or more sanding heads to sand the bottom side 
of work pieces run through the machine. Proper arrangement of individual 
upright and inverted sanding heads could provide a sanding machine to sand 
both the upper and lower surfaces of a work piece with only one pass 
through the machine. A further alternative embodiment can be seen in FIG. 
10. The sanding head 20 is turned diagonally to the line of travel of the 
work piece on the conveyor 16. The angular relationship of the sanding 
head 20 to the frame 12 is such that adjacent individual sanding elements 
40 overlap from the perspective of the work piece on the conveyor 16 so 
that no gap between the sanding elements 40 is presented to the work 
piece. This specific configuration would eliminate the need to have double 
sanding heads. As noted above, an inverted oblique sanding head 20 could 
also be provided to sand the lower side of the work piece. Operationally, 
the obliquely mounted sanding head 20 would function as described above. 
It will be understood that changes in the details, materials, steps and 
arrangement of parts which have been described and illustrated to explain 
the nature of the invention will occur to and may be made by those skilled 
in the art upon a reading of this disclosure within the principles and 
scope of the invention. The foregoing description illustrates the 
preferred embodiment of the invention; however, concepts, as based upon 
the description, may be employed in other embodiments without departing 
from the scope of the invention. Accordingly, the following claims are 
intended to protect the invention broadly, as well as in the specific form 
shown.