U.S. patent application number 12/872233 was filed with the patent office on 2012-03-01 for wide belt sander.
Invention is credited to Wen-Chi CHANG.
Application Number | 20120052777 12/872233 |
Document ID | / |
Family ID | 45697882 |
Filed Date | 2012-03-01 |
United States Patent
Application |
20120052777 |
Kind Code |
A1 |
CHANG; Wen-Chi |
March 1, 2012 |
WIDE BELT SANDER
Abstract
A wide belt sander has a base, a driving axle, a driven axle
bracket, a driven axle, a belt and an automatic adjustment device.
The driving axle has a central axis. The driven axle bracket is
pivotally mounted on the base along a longitudinal axis
perpendicular to the central axis of the driving axle. The driven
axle is rotatably mounted on the driven axle bracket along a
rotating axis parallel with the central axis of the driving axle.
The automatic adjustment device drives the driven axle bracket to
swing relative to the base along the longitudinal axis in a simple
harmonic motion and has two pushed elements and a cam. The pushed
elements are mounted separately on the driven axle bracket. The cam
is mounted between and alternatively pushing the pushed elements to
swing the driven axle bracket relative to the base.
Inventors: |
CHANG; Wen-Chi; (Shengang
Hsiang, TW) |
Family ID: |
45697882 |
Appl. No.: |
12/872233 |
Filed: |
August 31, 2010 |
Current U.S.
Class: |
451/355 |
Current CPC
Class: |
B24B 21/10 20130101;
B24B 21/20 20130101 |
Class at
Publication: |
451/355 |
International
Class: |
B24B 23/00 20060101
B24B023/00 |
Claims
1. A wide belt sander comprising: a base; a driving axle rotatably
mounted on the base and having a central axis; a driven axle
bracket pivotally mounted on the base along a longitudinal axis
perpendicular to the central axis of the driving axle; a driven
axle rotatably mounted on the driven axle bracket along a rotating
axis parallel with the central axis of the driving axle; a belt
endlessly mounted around the driving and driven axles; and an
automatic adjustment device mounted between the base and the driven
axle bracket to drive the driven axle bracket to swing relative to
the base along the longitudinal axis in a simple harmonic motion
and comprising two pushed elements mounted separately on the driven
axle bracket; and a cam rotatably mounted on the base and mounted
between and alternatively pushing the pushed elements to swing the
driven axle bracket relative to the base.
2. The wide belt sander as claimed in claim 1 further comprising an
electrical adjustment device mounted on the base to pivot the
driven axle bracket relative to the base to adjust a period of the
simple harmonic motion of the automatic adjustment device.
3. The wide belt sander as claimed in claim 2, wherein the
automatic adjustment device comprises a gear box adjustably mounted
on the base 10; a driving shaft rotatably mounted on and extending
into the gear box; a driven shaft rotatably mounted on and
extending out from the gear box and on which the cam is mounted;
and a gear device mounted in the gear box, mounted between the
driving shaft and the driven shaft and comprising a worm rod
co-axially mounted on the driving shaft; and a worm gear securely
mounted on the driven shaft and engaging the worm rod.
4. The wide belt sander as claimed in claim 3, wherein the pushed
elements are rotatably mounted on a bottom of the driven axle
bracket at an interval and have a center line defined between
centers of the pushed elements; and the cam has a rotating center
where is mounted around the driven shaft and located at the center
line between the pushed elements.
5. The wide belt sander as claimed in claim 4, wherein each pushed
element is a bearing having a central hole defined through the
pushed element; and two securing bolts mounted respectively through
the central holes of the pushed elements and mounted securely on
the bottom of the driven axle bracket.
6. The wide belt sander as claimed in claim 5, wherein the base has
a channel defined along a direction perpendicular to the central
axis of the driving axle; and two threaded holes defined in the
base adjacent to the channel; and the gear box is mounted
adjustably in the channel in the base and has a bottom; two ribs
formed on the bottom and slidably held in the channel in the base;
a wing mounted on and laterally protruding from the bottom of the
gear box and having two elongated holes defined through the wing
and aligning respectively with the threaded holes in the base; and
two bolts mounted respectively through the elongated holes and
screwed respectively into the threaded holes in the base.
7. The wide belt sander as claimed in claim 6, wherein the base
further comprises a holding bracket to which the driven axle
bracket is pivotally connected and the gear box is adjustably
mounted and having an axle hole defined in a top of the holding
bracket; the driven axle bracket has a central shaft formed on and
protruding downward from the driven axle bracket and rotatably and
slidably extending into the axle hole in the holding bracket; and a
pneumatic cylinder is mounted between the holding bracket and the
driven axle bracket and has a first end provided with a universal
jointer and connected to the holding bracket with the universal
jointer; and a second end connected co-axially to the central shaft
on the driven axle bracket to provide a supporting effect to the
driven axle bracket.
8. The wide belt sander as claimed in claim 7, wherein the
electrical adjustment device comprises two contacting switches
mounted on the base respectively at two sides of the belt; two
electromagnetic switches electrically connected respectively to the
contacting switches and mounted on the base respectively at two
sides of the driven axle bracket; and two springs each having two
ends connected respectively one of the electromagnetic switches and
the driven axle bracket, wherein the springs are connected
respectively to the two sides of the driven axle bracket to provide
pulling forces in opposite directions to the driven axle
bracket.
9. The wide belt sander as claimed in claim 8, wherein each
contacting switch has a contacting arm protruding from the
contacting switch selectively abutting with the belt and having a
ceramic sleeve mounted around the contacting arm.
10. The wide belt sander as claimed in claim 9 further comprising a
limiting device mounted between the driven axle bracket and the
holding bracket to limit the swinging range of the driven axle
bracket and comprising a limiting bracket mounted on the bottom of
the driven axel bracket, being inversed U-shaped and having two
ears respectively formed on and protruding from two ends of the
limiting bracket; two limiting bolts mounted respectively on the
ears of the limiting bracket and protruding toward each other; and
a base bracket mounted securely on the top of the bolding bracket
and having a top extending into the limiting bracket to a position
between the limiting bolts.
11. The wide belt sander as claimed in claim 2, wherein the
electrical adjustment device comprises two contacting switches
mounted on the base respectively at two sides of the belt; two
electromagnetic switches electrically connected respectively to the
contacting switches and mounted on the base respectively at two
sides of the driven axle bracket; and two springs each having two
ends connected respectively one of the electromagnetic switches and
the driven axle bracket, wherein the springs are connected
respectively to the two sides of the driven axle bracket to provide
pulling forces in opposite directions to the driven axle
bracket.
12. The wide belt sander as claimed in claim 11, wherein each
contacting switch has a contacting arm protruding from the
contacting switch, selectively abutting with the belt and having a
ceramic sleeve mounted around the contacting arm.
13. The wide belt sander as claimed in claim 1, wherein the
automatic adjustment device comprises a gear box adjustably mounted
on the base; a driving shaft rotatably mounted on and extending
into the gear box; a driven shaft rotatably mounted on and
extending out from the gear box and to which the cam is attached;
and a gear device mounted in the gear box, mounted between the
driving shaft and the driven shaft and comprising a worm rod
co-axially mounted on the driving shaft; and a worm gear securely
mounted on the driven shaft and engaging the worm rod.
14. The wide belt sander as claimed in claim 13, wherein the pushed
elements are rotatably mounted on a bottom of the driven axle
bracket at an interval and have a center line defined between
centers of the pushed elements; and the cam has a rotating center
where is mounted around the driven shaft and located at the center
line between the pushed elements.
15. The wide belt sander as claimed in claim 14, wherein each
pushed element is a bearing having a central hole defined through
the pushed element; and two securing bolts mounted respectively
through the central holes of the pushed elements and mounted
securely to the bottom of the driven axle bracket.
16. The wide belt sander as claimed in claim 13, wherein the base
has a channel defined along a direction perpendicular to the
central axis of the driving axle; and two threaded holes defined in
the base adjacent to the channel; and the gear box is mounted
adjustably in the channel of the base and has a bottom; two ribs
formed on the bottom and slidably held in the channel in the base;
a wing mounted on and laterally protruding from the bottom of the
gear box and having two elongated holes defined through the wing
and aligning respectively with the threaded holes in the base; and
two bolts mounted respectively through the elongated holes and
screwed respectively into the threaded holes in the base.
17. The wide belt sander as claimed in claim 1, wherein the base
further comprises a holding bracket to which the driven axle
bracket is pivotally connected and the gear box is adjustably
mounted and having an axle hole defined in a top of the holding
bracket; the driven axle bracket has a central shaft formed on and
protruding downward from the driven axle bracket and rotatably and
slidably extending into the axle hole in the holding bracket; and a
pneumatic cylinder is mounted between the holding bracket and the
driven axle bracket and has a first end provided with a universal
jointer and connected to the holding bracket with the universal
jointer; and a second end connected co-axially to the central shaft
on the driven axle bracket to provide a supporting effect to the
driven axle bracket.
18. The wide belt sander as claimed in claim 17 further comprising
a limiting device mounted between the driven axle bracket and the
holding bracket to limit the swinging range of the driven axle
bracket and comprising a limiting bracket mounted on the bottom of
the driven axel bracket, being inversed U-shaped and having two
ears respectively formed on and protruding from two ends of the
limiting bracket; two limiting bolts mounted respectively on the
ears of the limiting bracket and protruding toward each other; and
a base bracket mounted securely on the top of the bolding bracket
and having a top extending into the limiting bracket to a position
between the limiting bolts.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a sander, and more
particularly to a wide belt sander having adjustment devices to
make a belt moving smoothly and keep deviations from occurring.
[0003] 2. Description of Related Art
[0004] To polish surfaces of an article, a sander is always used
and substantially comprises a base, two axles and a belt. The axles
are rotatably mounted on the base and are arranged in parallel, and
the belt is endlessly mounted around the axles and is driven to
polish an article. To keep the belt from deviating during the
polishing process, an adjustment device is always arranged on the
conventional sander. For example, Taiwan Patent No. 1279285,
entitled to "Wide Belt Sander With A Reciprocal Adjustment Device"
discloses an adjustment device having two cams mounted respectively
at two sides of a pushed element that is secured on a driven axle
bracket. When the rotation of the cams, the pushed element is
alternatively pushed by the cams to make the driven axle bracket to
swing in a simple harmonic motion. Accordingly, the travel track of
the running belt can be automatically and actively adjusted to
prevent deviation of the belt from occurring.
[0005] However, the conventional adjustment device has the
following drawbacks.
[0006] 1. The cams have to be rotated simultaneously but in
reverse, a specific gear box is necessary. The gear box of the
conventional adjustment device has to be designed or manufactured
specifically, so the cost for manufacturing is high.
[0007] 2. The belt of the conventional sander still deviates due to
uneven force applied to the running belt during the polishing
process even when the conventional adjustment device is
arranged.
[0008] To overcome the shortcomings, the present invention tends to
provide a wide belt sander to mitigate or obviate the
aforementioned problems.
SUMMARY OF THE INVENTION
[0009] The main objective of the invention is to provide a wide
belt sander having an adjustment device to make a belt moving
smoothly and keep deviations from occurring.
[0010] The wide belt sander in accordance with the present
invention has a base, a driving axle, a driven axle bracket, a
driven axle, a belt and an automatic adjustment device. The driving
axle is rotatably mounted on the base and has a central axis. The
driven axle bracket is pivotally mounted on the base along a
longitudinal axis perpendicular to the central axis of the driving
axle. The driven axle is rotatably mounted on the driven axle
bracket along a rotating axis parallel with the central axis of the
driving axle. The belt is endlessly mounted around the driving and
driven axles. The automatic adjustment device is mounted between
the base and the driven axle bracket to drive the driven axle
bracket to swing relative to the base along the longitudinal axis
in a simple harmonic motion and has two pushed elements and a cam.
The pushed elements are mounted separately on the driven axle
bracket. The cam is rotatably mounted on the base and is mounted
between and alternatively pushing the pushed elements to swing the
driven axle bracket relative to the base.
[0011] Other objects, advantages and novel features of the
invention will become more apparent from the following detailed
description when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of a wide belt sander in
accordance with the present invention;
[0013] FIG. 2 is a partially exploded perspective view of the wide
belt sander in
[0014] FIG. 1;
[0015] FIG. 3 is an enlarged perspective view of a contacting
switch of the wide belt sander in FIG. 1;
[0016] FIG. 4 is an enlarged front view of the wide belt sander in
FIG. 1;
[0017] FIG. 5 is an enlarged top view in partial section of the
gear box of the wide belt sander in FIG. 1;
[0018] FIG. 6 is an enlarged operational side view in partial
section of the gear box in FIG. 5;
[0019] FIG. 7 is an enlarged operational top view of the automatic
adjustment device of the wide belt sander in FIG. 1 showing that
the cam is at the 0.degree. position;
[0020] FIG. 8 is an enlarged operational top view of the automatic
adjustment device in FIG. 7 showing that the cam is at the
90.degree. position;
[0021] FIG. 9 is an enlarged operational top view of the automatic
adjustment device in FIG. 7 showing that the cam is at the
180.degree. position;
[0022] FIG. 10 is an enlarged operational top view of the automatic
adjustment device in FIG. 7 showing that the cam is at the
270.degree. position;
[0023] FIG. 11 is an enlarged perspective view of the electrical
adjustment device of the wide belt sander in FIG. 1; and
[0024] FIG. 12 is an enlarged operational end view in partial
section of the wide belt sander in FIG. 1.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0025] With reference to FIGS. 1, 2 and 4, a wide belt sander in
accordance with the present invention comprises a base 10, a
driving axle 20, a driven axle bracket 30, a driven axle 40, a belt
50, an automatic adjustment device and an electrical adjustment
device.
[0026] The base 10 comprises a bottom frame, a column 12, a slider
13, a motor 14, a holding bracket 15 and an axle frame 150. A
second belt 11 may be endlessly mounted on the bottom frame in a
horizontal direction to provide a further polishing effect. The
column 12 is upwardly mounted on the bottom frame. The slider 13 is
slidably mounted on the column 12 with a threaded rod that is
mounted rotatably on the column 12. A dove-tail engagement is
mounted between the slider 13 and the column 12 to allow the slider
13 slidable relative to the column 12 smoothly. The motor 14 is
mounted on the slider 13. The holding bracket 15 is securely
mounted on the slider 13 above over the bottom frame and has a top,
an axle hole 151, a channel 152 and two threaded holes. The axle
hole 151 is defined in the top at the middle of the holding bracket
151. The channel 152 is defined in the top near one end of the
holding bracket 15. The threaded holes are defined in the top of
the holding bracket 15 near the channel 152. The axle frame 150 is
securely attached to the holding bracket 15 at one end opposite to
the slider 13.
[0027] The driving axle 20 is rotatably mounted between the slider
13 and the axle frame 150 below the holding bracket 15 and has a
central axis. The driving axle 20 is connected to and driven by the
motor 14. In addition, the channel 152 in the top of the holding
bracket 15 is defined along a direction perpendicular to the
central axis of the driving axle 20.
[0028] The driven axle bracket 30 is pivotally mounted on the base
10 along a longitudinal axis perpendicular to the central axis of
the driving axle 20. The driven axle bracket 30 has a central shaft
31 formed on and protruding downward from the bottom of the driven
axle bracket 30 and rotatably and slidably extending into the axle
hole 151 in the holding bracket 15.
[0029] In addition, a pneumatic cylinder 60 is mounted between the
holding bracket 15 and the driven axle bracket 30. The pneumatic
cylinder 60 has a first end connected to the driven axle bracket 30
and a second end connected to the holding bracket 15 with a
universal jointer. The cylinder 60 can provide a supporting effect
to the driven axle bracket 30 to keep the driven axle bracket 30
away from the driving axle 20 at a desired distance.
[0030] The driven axle 40 is rotatably mounted on the driven axle
bracket 30 along a rotating axis parallel with the central axis of
the driving axle 20. The belt 50 is endlessly mounted around the
driving and driven axles 20,40.
[0031] Additionally, an axle adjusting device is mounted between
the base 10 and the driven axle bracket 30 to change a distance
between the driving and driven axles 20,40. The axle adjusting
device comprises a handlebar 61 and a pushing plate 64. The
handlebar 61 is pivotally mounted on the holding bracket 15 with a
pivot 62 and has a guiding channel defined through the handlebar 61
at one end of the handlebar 61. The pushing plate 64 is pivotally
mounted on the holding bracket 15, is pivotally and slidably
connected to the guiding channel in the handlebar 61 with a sliding
pivot 63 and is connected to the central shaft 31. When the
handlebar 61 is pulled upward, the driven axle bracket 30 is moved
toward the driving axle 20 with the transmission of the pushing
plate 64 and compresses the cylinder 60. Accordingly, the distance
between the driving and driven axles 20,40 can be shortened, and to
replace a worn belt 50 with a new one is convenient.
[0032] When the handlebar 61 is released, the driven axle bracket
30 can be pushed upward to the original position where the belt 50
is at a tightened condition for polishing with the recoil force
provided by the pneumatic cylinder 60.
[0033] With reference to FIGS. 1, 2 and 4 to 6, the automatic
adjustment device is mounted between the base 10 and the driven
axle bracket 30 to drive the driven axle bracket 30 to swing
relative to the base 10 along the longitudinal axis in a simple
harmonic motion. The automatic adjustment device comprises a gear
box 70, a cam 71, two pushed elements 72,73 and a driving assembly.
The gear box 70 is adjustably mounted on the holding bracket 15 of
the base 10. The gear box 70 has a bottom and two ribs 701 formed
on the bottom of the gear box 70 and slidably held in the channel
152 in the holding bracket 15. A wing 702 is mounted on and
laterally extends from the bottom of the gear box 70 and has two
elongated holes 703 defined through the wing 702 and aligning
respectively with the threaded holes in the holding bracket 15.
With two bolts 704 extending through the elongated holes 703 in the
wing 702 and screwed into the corresponding threaded holes in the
holding bracket 15, the gear box 70 is securely mounted on the
holding bracket 15. With releasing the bolts 704, the gear box 70
can be moved along the channel 152 in the holding bracket 15 to
adjust the position of the gear box 70 relative to the holding
bracket 15.
[0034] The gear box 70 comprises a driving shaft 705, a driven
shaft 708 and a gear device. The driving shaft 705 is rotatably
mounted on and extends into a side of the gear box 70. The driven
shaft 708 is rotatably mounted on and extends out from the top of
the gear box 82. The gear device is mounted in the gear box 70 and
is mounted between the driving shaft 705 and the driven shafts 708.
The gear device comprises a worm rod 709 and a worm gear 709'. The
worm rod 709 is co-axially mounted on the driving shaft 705. The
worm gear 709' is securely mounted on the driven shaft 708 and
engages the worm rod 709. Accordingly, the driven shaft 708 can be
rotated with the driving shaft 705 at a reduced speed.
[0035] The cam 71 is mounted securely on and driven by the driven
shaft 708. Preferably, the cam 71 is mounted on a middle position
of the top of the gear box 70.
[0036] The pushed elements 72,73 are mounted on the bottom of the
driven axle bracket 30 at an interval. The pushed elements 72,73
have a center line defined between centers of the pushed elements
72,73. The cam 71 is mounted between the pushed elements 72,73 and
alternatively pushes the pushed elements 72,73 to swing the driven
axle bracket 30 relative to the base 10 as shown in FIGS. 7 to 10.
The cam 71 has a rotating center where is mounted around the driven
shaft 708 and located at a middle point of the center line between
the pushed elements 72,73. Thus, the cam 71 has an equal distance
to each pushed element 72,73. Preferably, each pushed element 72,73
is a bearing having a central hole 720,730 defined through the
pushed element 72,73. Two securing bolts 721,731 are mounted
respectively through the central holes 720,730 of the pushed
elements 72,73 and mounted securely to the bottom of the driven
axle bracket 30 to mount the pushed elements 72,73 on the driven
axle bracket 30.
[0037] The driving assembly is mounted on the base 10 to drive the
cam 71 to rotate and comprises a driving pulley, a driven pulley
706 and a driving belt 707. The driving pulley is co-axially
connected to and rotated with the driving axle 20. The driven
pulley 706 is co-axially connected to the driving shaft 705. The
driving belt 707 is mounted around the driving pulley and the
driven pulley 706. When the driving axle 20 is rotated by the motor
14, the cam 71 will also rotate with the transmission of the
driving assembly, the driving shaft 705, the gear device in the
gear box 70 and the driven shaft 708.
[0038] Additionally, an indicating board 80 is securely mounted
between the holding bracket 15 and the driven axle bracket 30 and
has multiple mounting holes 801, an upper indication channel 81 and
a lower indication channel 82. The mounting holes 801 are defined
through the indicating board 80. Multiple bolts 802 are mounted
respectively through the mounting holes 801 and screwed into the
threaded holes 803 defined in the holding bracket 15 and the driven
axle bracket 30 to secure the indicating board 80 on the holding
bracket 15 and the driven axle bracket 30. The upper indication
channel 81 and the lower indication channel 82 are laterally
defined through the indicating board 80 and are parallel with each
other. Each indication channel 81,82 has an index mark 83 formed on
an edge of the channel 81,82. An upper pointer 84 is mounted on the
driven axle bracket 30 at the middle point of the center line
between the pushed elements 72,73 and extends into the upper
indication channel 81 in the indicating board 80. A lower pointer
85 is securely mounted on the gear box 70 at a position aligning
with the cam 71 and extends into the lower indication channel 82 in
the indicating board 80. With the arrangement of the pointers 84,85
and the indication channels 81,82, the positions of the driven axle
bracket 30 and the gear box 70 are identified. When the driving and
driven axles 20,40 are completely parallel with each other, the
pointers 84,85 correspond respectively to zero points of the index
marks 83.
[0039] With reference to FIGS. 1 to 3, 7 and 11, the electrical
adjustment device is mounted on the holding bracket 15 of the base
10 to pivot the driven axle bracket 30 relative to the base 10 so
as to adjust a period of the simple harmonic motion of the
automatic adjustment device. The electrical adjustment device
comprises two contacting switches 91,92, two electromagnetic
switches 94,95, a holding frame 93, a connecting frame 96 and two
springs 941,951. The contacting switches 91,92 are mounted on the
top of the holding bracket 15 of the base 10 respectively at two
sides of the belt 50. Each contacting switch 91,92 has a contacting
arm 911 protruding from the contacting switch 91,92, selectively
abutting with an edge of the belt 50 and having a ceramic sleeve
912 mounted around the contacting arm 911. The ceramic sleeve 912
can keep the contacting arms 911 from being damaged or worn off by
the running belt 50.
[0040] The holding frame 93 is mounted securely on the top at one
end of the holding bracket 15. The electromagnetic switches 94,95
are electrically connected respectively to the contacting switches
91,92 and are mounted on two ends of the holding frame 93
respectively at two sides of the driven axle bracket 30. The
electromagnetic switches 94,95 have a timing function to switch the
electromagnetic switches 94,95 off automatically after a
predetermined time, for example 5 seconds.
[0041] The connecting frame 96 is mounted securely on one end of
the driven axle bracket 30 and has a bottom having two sides and
two ends and two connecting ears 962. The connecting ears 962 are
respectively formed on and protrude from the two ends and the two
sides of the bottom of the connecting frame 96.
[0042] The springs 941,951 are connected respectively to the
electromagnetic switches 94,95 and the driven axle bracket 30. Each
spring 941,951 has two ends connected respectively a corresponding
one of the electromagnetic switches 94,95 and one of the connecting
ears 962 on the connecting frame 96. Accordingly, the springs
941,951 are connected respectively to the two sides of the driven
axle bracket 30 via the connecting frame 96 to provide pulling
forces in opposite directions to the driven axle bracket 30.
[0043] Before the wide belt sander is in used, the positions of the
driven axle bracket 30 and the cam 71 of the automatic adjustment
device must be zeroized. With reference to FIGS. 9 and 10, to
zeroize the position of the driven axle bracket 30, the driving
belt 707 is detached from the driving and driving pulleys 706 and
the motor 14 is switched on to rotate the driving axle 20. At this
time, the cam 71 is kept at a 0.degree. or 180.degree. position as
shown in FIGS. 7 and 9. With the rotation of the driving axle 20,
the driven axle 40 will be rotated with the transmission of the
belt 50 but the cam 71 keeps stationary. Because the driven axle
bracket 30 is pivotally mounted on the holding bracket 15 with the
central shaft 31, the angular position of the driven axle bracket
30 is adjusted manually relative to the holding bracket 15 to make
the belt 50 running in a desired travel track. After moving the
indicating board 80 to make the zero point of the index mark 83 on
the upper indication channel 81 aligning with the upper pointer 84,
the bolts 802 are screwed completely into the threaded holes 803 in
the holding bracket 15 and the driven axle bracket 30 to securely
the indicating board 80 on the driven axle bracket 30 at the
zeroized point.
[0044] Then, the bolts 704 for securing the gear box 70 are
released, and the position of the gear box 70 is adjusted along the
channel 152 to make the lower pointer 85 aligning with the zero
point of the index mark 83 on the lower indication channel 82. At
this position, the cam 71 is at the middle of the center line of
the pushed elements 72,73. Accordingly, the driven axle bracket 30
and the cam 71 are zeroized, and the driving belt 707 is mounted
around the driving and driven pulleys 706.
[0045] Consequently, the cam 71 can be rotated with the
transmission of the driving assembly, the driving shaft 705, the
gear device and the driven shaft 708 while the driving axle 20 is
rotating. Accordingly, with reference to FIGS. 6 to 8, the pushed
element 72,73 will be alternatively pushed by the cam 71 to make
the driven axle bracket 30 to swing relative to the central shaft
31 in a simple harmonic motion. With the swinging of the driven
axle bracket 30, the travel track of the running belt 50 can be
automatically and actively adjusted, such that the movement of the
running belt 50 is stable and smooth. Within one rotation of the
cam 71, the driven axle bracket 30 can be adjusted twice and this
means that two adjustment frequencies are provided. The movement
travel of the running belt 50 is smooth, and the belt 50 can be
kept from being worn off at a single edge. The useful life of the
belt 50 can be prolonged and the belt 50 is durable.
[0046] If the sander is applied with an uneven force to cause the
deviation of the belt 50, the belt 50 will abut against the
contacting arm 911 of one of the contacting switches 91,92. Thus,
the pushed contacting switch 91,92 will send a signal to activate
the corresponding electromagnetic switch 94,95 to pull the
corresponding spring 941,951 with a pulling force of 0.8 to 1.5 Kg.
Consequently, the pulled spring 941,951 will pull the driven axle
bracket 30 to swing via the connecting frame 96, and the period of
the simple harmonic motion of the automatic adjustment device can
be changed. Accordingly, the belt 50 can move backward the desired
travel track. After the predetermined time set up in the
electromagnetic switch 94,95, for example 5 seconds, the
electromagnetic switch 94,95 is switched off and the driven axle
bracket 30 can be pivoted to an original position with the recoil
forces provided by the springs 941,951. Therefore, another
adjustment effect is provided, such that double adjustment
functions can be provided by the automatic adjustment device and
the electrical adjustment device.
[0047] With reference to FIGS. 2 and 12, a limiting device is
mounted between the driven axle bracket 30 and the holding bracket
15 to limit the swinging range of the driven axle bracket 30. The
limiting device comprises a limiting bracket 97, two limiting bolts
972 and a base bracket 974. The limiting bracket 97 is mounted on
the bottom of the driven axel bracket 30, is inversed U-shaped and
has two ears respectively formed on and protruding from two ends of
the limiting bracket 97. The limiting bolts 972 are mounted
respectively on the ears of the limiting bracket 97 and protrude
toward each other. The base bracket 974 is mounted securely on the
top of the bolding bracket 15 and has a top extending into the
limiting bracket 97 to a position between the limiting bolts
972.
[0048] Accordingly, when the driven axle bracket 30 is swung by the
automatic adjustment device or the electrical adjustment device,
the swinging range of the driven axle bracket 30 can be limited by
the abutment of the base bracket 974 with one of the limiting bolts
972.
[0049] With the aforementioned description, the wide belt sander
has the following advantages.
[0050] 1. With a single cam 71 arrangement, the gear device in the
gear box 70 has not to be specifically designed and manufactured.
The gear box 70 can be a standardized product, such that the cost
for manufacturing the wide belt sander can be reduced.
[0051] 2. To assemble a single cam 71 onto the gear box 70 is easy
and convenient, and the zeroizing process of the cam 71 is also
easy.
[0052] 3. The wide belt sander in accordance with the present
invention has two adjustment means, such that the travel of the
belt 50 can be well controlled on a desired track. The useful life
of the wide belt sander can be prolonged and is durable.
[0053] Even though numerous characteristics and advantages of the
present invention have been set forth in the foregoing description,
together with details of the structure and function of the
invention, the disclosure is illustrative only, and changes may be
made in detail, especially in matters of shape, size, and
arrangement of parts within the principles of the invention to the
full extent indicated by the broad general meaning of the terms in
which the appended claims are expressed.
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