Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to sanding devices and in
particular to a pad assembly for a rotary disc sander of the
~acuum type.
In my copending application, serial number 240,516
filed on November 26, 1975 I have described several embodiments
of a vacuum sanding device of the double-acting type. The
present invention is directed specifically to a pad assembly
for a rotary vacuum operated disc sander but the means for
driving the disc and the vacuum creating means for the disc
assembly may be the same as that in application 240,516.
Rotary sanding devices revolve at fairly high speeds
and are used in grinding operations and heavy duty forms of
work such as automobile bodies etc. Due to the nature of the
work and the varied materials to be sanded or ground, it has
until this time been dificult to obtain an efficient rotary
sanding assembly having an attached vacuum arrangement. This
is mainly due to the fact that the ground particles clog up
small passages in the disc, particularly when the pad is
flexed under pressure.
The present invention overcomes the deficiencies of the
prior art by providing a vacuum rotary sander with a flexible
pad body that is secured to a rigid head member which in turn
is connectable to a pneumatic rotating device as described in
application 240,516. Additionally, the rigid head may be
enclosed by a vacuum housing such as that shown in application
240,516 whereby the particles ground by the pad assembly are
quickly and efficiently carried away from the unit. A plurality
of apertures in the head communicate with other apertures in
the lower surface of the pad by way of internal channels in the
pad body and these channels are angled toward the direction of
rotation of the pad so that there is a leading action to the
vacuum function applied to the apertures when the pad is being
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rotated. Apertures in the lower portion of the pad coincide
with apertures in an abrasive disc which is removably ~ecured
to the assembly and, in a preferable form, the apertures in the
lower part of the pad are elongated in the direction opposite
to that of rotation so as to allow some slippage of the abrasive
disc relative to the pad assembly without losing alignment of
the apertures in either member.
According to one broad aspect therefor, the present
invention relates to a pad assembly for a vacuum rotary sander,
said assembly comprising a) a circular upper pad portion
of firm but resilient material and having a plurality of
evenly spaced apertures concentrically arranged therein and
positioned approximately midway between the centre of said
upper pad portion and the circumferential edge thereof, b)
and an elongated channel extending from each said aperture
angularly outwardly in the direction of rotation of the assembly,
each ~aid channel being open along its bottom edge, c) a lower
pad portion of relatively soft flexible material and having an
inner and outer row of evenly spaced concentrically arranged
apertures therein, said lower pad portion being bonded to said
upper pad portion so that the inner row of apertures on the
lower pad portion coincide with the apertures in the upper
pad portion to form a plurality of inner vacuum holes and
wherein the outer row of apertures on the lower pad portion
coincide with outer terminal ends of the channels in the upper
pad portion, the material of the lower pad intermediate the
inner and outer rows of apertures therein forming a flexible
bottom wall for said channels, d) said upper pad portion having
an inwardly and upwardly tapering circumferential sidewall with
a groove adjacent the upper end thereof, said pad assembly
being adapted to receive a sanding disc on the lower surface
thereof with apertures therein coinciding with those in the
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the lower pad assembly, and retained thereon by a flexible
backing held in the ~idewall groove by elastic retaining means,
and e) a circular rigid head member secured concentrically
to the top of the upper pad portion and adapted for connection
to rotative and vacuum means, said rigid member having a
plurality of apertures therein somewhat larger than, and
coinciding with the apertures in the upper pad portion.
In accordance with another aspect, the present
invention relates to a vacuum sanding assembly having a
circular pad and abrasive disc attachable thereto, the pad and
disc having corresponding apertures therein for suction of sanded
material into said assembly, a device for positioning and loading
the abrasive disc onto the pad comprising a circular, planar
member having a central upstanding primary pin thereon adapted
to centre central apertures in the abrasive disc and pad, an
upstand side wall tapering inwardly on its outer surface and
having an O-ring retaining lip at its upper end, and at least a
pair of spaced secondary pins secured to and upstandinq from
the planar surface and corresponding to a selected pair of
coincident apertures in the abrasive disc and pad.
The invention is illustrated by way of example in the
accompanying drawings wherein: i
Figure 1 is a partially sectioned, fragmented top view
of the several elements of the pad assembly;
Figure 2 is another fragmented top view with the
elements in assembled condition;
Figure 3 is a fragmented sectional view taken along the
line 3-3 of Figure 2; and
Figure 4 is a partially sectioned view of the pad
assembly in operation.
Referring to Figures 1 and 2, a pad assembly 10 has
circular lower and upper pad portions 11 and 12 and a circular
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head member 14. In Figure l, the lower pad portion is shown
as a single sheet of relatively soft, flexible material such
as rubber and having a plurality of inner apertures 16 and
outer apertures 18 in the surface thereof. The direction of
rotation of the assembly is shown by arrow R. The inner row
of apertures 16 is positioned approximately midway between
the center aperture 20 in the lower pad portion 11 and the
outer terminal edge thereof with the outer row of apertures 18
being positioned more or less adjacent to the outer
circumferential edqe of the assembly. The inner row of
apertures are circumferentially, evenly spaced with respect
to one another as are the apertures 18 of the outer row and
while the apertures 16 and 18 may be circular, I prefer that
they be elongated as shown.
In Figure 1 the upper pad portion 12 is provided with
channels 20 which interconnect the apertures 16 and 18 when
the upper pad portion 12 is placed on top of the lower pad
portion 11 and bonded thereto as shown in Figure 1. In the
upper portion of Figure 1, the position that the channels 20
will assume are shown in pecked line and in the central part
of Figure 1 which is a top view of the upper pad portion 12,
the elongated channels 20 are shown providing a communication
between the inner and outer rows of apertures 16 and 18
respectively. The inner terminal ends 22 and outer terminal
end~ 24 of the channels 20 coincide with the inner and outer
apertures 16 and 18 respectively when the upper pad portion 12
overlays the lower pad portion 11.
The upper pad portion is manufactured from resilient
material that is quite firm with respect to the material of the
lower pad portion.
The head member 14 is of rigid material and is shown
in the fragmented portion of Figure 1. Head 14 has apertures
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26 which, when head 14 is bonded to the upper surface of
upper pad portion 12, coincide with the inner terminal ends
22 of the channels 20 and the inner row of apertures 16 in
the lower pad portion as shown for example in Figure 2.
Preferably, apertures 26 in head 14 are slightly larger than
the apertures which they overlay and also, they are preferably
elongated as shown in Figure 1. The head 14 is also provided
with a central, threaded sleeve 28 for connection to suitable
rotating means.
Referring to Figure 2, the fragmentary top view of the
assembly 10 shows the path of communication between the outer
row aperture 18, channel 20, inner row aperture 16 and aperture
26 in the head 14. It will also be evident that because of
the elongation of the inner and outer rows of apertures in a
d$rection away from that of rotation R, the outer row of
apertures 18 has a "leading" portion 30 and a trailing portion
32 and inner row aperture also has a leading portion 34 and a
trailing portion 36.
The reason for providing leading and trailing portions
to the above apertures is that when an abrasive disc having
apertures therein coincident with those in the pad assembly,
it is applied to the lower surface of the pad assembly and held
thereon by a flexible skirt and elastic retaining means, there
is sometimes slippage between the surface of the abrasive disc
and the supporting pad assembly due to the amount of torque
applied to the abrasive disc by the surface being ground
resulting from a lot of pressure being exerted on the disc by
the operator. It will be appreciated that because of the
elongation of the apertures and the leading and trailing
portions thereof, the abrasive disc can slip rearwardly a
substantial amount though the apertures therein will still be
in communication with the trailing ends 32 and 36 of the outer
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apertures 18 and inner apertures 36.
It will also be noted from Figure 1 and Figure 2 that
the outer apertures 18 are circumferentially offset from the
inner apertures 16 and that the channels 20 interconnecting
those apertures are angularly directed towards the direction
of rotation R of the pad assembly and this angulation provides
an improved grit gathering result when the pad is rotated at
high speed.
Refering to Figure 3, the upper pad portion 12 can be
manufactured from a single disc member although I prefer to
make it from two di~cs, an upper disc 12a and a lower disc 12b.
Upper disc 12a of quite firm but resilient material and a lower
disc 12b of softer, more flexible material. In either case, the
upper pad portion 12 has an aperture 13 therein coincident
with aperture 26 in the head 14 and with aperture 16 in the
lower pad assembly 11. It will be seen from Figure 3 that
the construction of the upper pad portion 12 provides the
channel 20 with upper and end walls and that the material 21
between the inner and outer rows of apertures 16 and 18 in the
lower pad assembly provides the channel 20 with a flexible,
bottom wall. In cross-section therefore channel 20 has two
inlets, 18 and 16 and a large exhaust outlet, 13 and 26.
The abrasive disc 38 is provided with a flexible backing
40 adhesively secured thereto and which incorporates a flexible
peripheral skirt 42 which is folded into a groove 44 in the
sidewall of the lower pad assembly 12 and retained therein by
the indicated taper to that sidewall as well as by a resilient
0-ring or other suitable retaining means as shown in Figure 4.
The abrasive disc 38 is provided w~th an inner row of
apertures 46 and an outer row of apertures 48 and it will be
evident from Figure 3 that when the disc is mounted onto the
lower face of the pad, inner apertures 46 are coincident with
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apertures 16 in the lower pad assembly 11 as well as apertures
13 in the upper assembly and 26 in the head 14 while the outer
row of apertures 48 in the disc are coincident with apertures
18 in the lower pad assembly 11.
The present invention also provides for a loading
means 50 for quickly and accurately positioning and applying
the abrasive disc 38 to the lower face of the pad assembly. The
loader 50 has a circular planar platform or surface 52 provided
with a central pin 54 which aligns central aperture 56 in the
abrasive disc and a central aperture 58 in the pad assembly 10.
At least two and preferably three additional pins 60 are
provided on the surface of the loader 50 and these pins are
positioned so as to be coincident with the inner row of
apertures 46 in the abrasive disc and apertures 16 in the lower
pad assembly. Additionally, the pins 60 are long or high enough
to enter the aperture 13 in the upper ends of the upper pad
portion 12 and as aperture 13 does not have a trailing portion,
the abrasive disc 38 will be so positioned that its apertures
46 and 48 will be aligned with t*e leading portions 30 and 34
of the outer apertures 18 and inner apertures 16 respectively.
The outer periphery of the loader 50 has an upstanding
wall 62, the outer surface of which tapers inwardly as shown
at 64 and is provided with a lip 66 for retaining an elasticized
O-ring 68 or the like. It will be appreciated from Figure 3
that the abrasive disc is first placed downwardly onto the
floor or surface 52 of the loader 50 with the apertures being
positioned over their respective pins and then the pad assembly
is lowered down onto the pins as well. The O-ring 68 can then
be moved upwardly and will automatically pull the flexible
skirt 42 upwaraly along the tapered sidewall of the pad assembly
and will come to rest in the groove 44 as shown in Figure 4.
Alternatively, a telescoping form of loader may be
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utilized as shown in my Canadian patent 772,369 of November 28,
1967. Such a telescoping loader would of course have to
utilize the pin assembly disclosed herein.
Refering now to Figure 4, the pad assembly is shown in
operation grinding the surface of a workpiece 70. Due to the
relatively firm material of the upper pad portion 12, a
substantial pressure may be applied to the outer peripheral
area of the pad assembly and as most rotary sanding is done
with this form of pressure on the peripheral area of the pad,
the flexible lower wall in the channel 20 ensures that the
maximum amount of surface of the lower pad 11 is in contact
with the surface of the work 70.
It will be evident from Figure 4 that by virtue of the
position and size of the apertures and channels, that the
grit 72 flows smoothly through the channel 20 and out through
the exit apertures 26 into the vacuum housing H shown in pecked
line.
While the invention has been described in connection
with a specific embodiment thereof and in the specific use,
various modifications thereof will occur to those skilled in the
art without departing from the spirit and scope of the
invention as set forth in the attached claims. The terminology
and expressions which have been employed in this disclosure are
used as terms of description and not of limitation and there is
no intention in the use of such terminology and expressions to
exclude any equivalents of the features shown and described
or portions thereof but it is recognized that various
modifications are possible within the scope of the invention
claimed.
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SUPPLEMENTA~Y DISCL~SURE
The invention is further illustrated in Figures
5 ~nd ~ wherein
Figure 5 is a perspective view of a further
embodiment of the lower pad assembly 12; and
Figure 6 is a cross-sectional view similar to
Figure 3 illustrating the additional embodiment of Figure 5.
Referring to the drawings, an additional soft pad
73 ~ormed of sponge material or the like is inserted between
the lower pad 12b and the abrasive disc 38. As shown in Figure
5, sponge pad 73 is provided with inner and outer rows of
apertures to register with those in the pad member 12b.
Sponge pad 73 is normally used in situations where a softer
sanding application is required, the resiliency of the sponge
pad providing more "giveH to the abrasive disc when the operator
is for example sanding an area of multiple contours. In the
past, sometimes the sponge pads 73 slipped away from the lower
pad 12b after prolonged use. In accordance with the embodiment
of Figures 5 and 6, the lower pad assembly 12b is provided on
its bottom surface with a plurality of small protuberances or
pxojections 74 which, when the sponge pad 73 is placed against
the lower pad assembly 12b, provides additional grip between
the two faces of the members in question. While Figure 5
illustrates only a small number of projections 74 on the lower
surface of pad 12b, it will be appreciated that these projections
can be applied in any density required and normally would cover
the whole surface of pad 12b.
It will be appreciated that the projections 74
dig into the upper or juxtaposed surface of the sponge pad 73
particularly on the peripheral area that is against the surface
being sanded and there is an actual clutch action provided
between the two gripped surfaces. It will further be appreciated
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that even i~ the face o~ the sponge pad pulls away slightly
fro~ the face-of the pad 12b, it will not rotationally slip
because of the fact that the sponge pad is riding on top of the
projections 74
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