[0001] Rotary drums for sanding belts have been used in the past but, for the most part,
they are made up of several parts and require assembly which adds to production costs.
Also, a major drawback of drums previously made for this purpose is the relatively
short operating life re- quring replacement and adding to the overall cost of sanding
operations. Because of these drawbacks a need has arisen for an improved drum for
sanding belts wherein the drum is of simple and rugged construction, has a long operating
life and can be produced at minimal cost.
[0002] One prior art arrangement is shown in US-A-22 21 173. This reference shows a drum
for a sanding belt in which a drum body has a central web having a central pin receiving
hole, a circular outer periphery and a pair of flanges integral with the web at the
outer periphery thereof and projecting laterally from opposed sides of the outer periphery.
[0003] The drum shown in this reference is of sponge rubber material and is therefore relatively
soft. It is provided with a smooth outer surface either by so casting the rubber or
by cementing a peripheral band to the sponge body. In either case this need for a
special outer surface complicates the construction of the drum. Furthermore, in addition
to a central driving pin, the drum is provided with a central driving hub through
which the pin passes. This again complicates the manufacture of the drum because the
hub portion requires assembly to the body of the drum.
[0004] In order to secure the abrasive band to the drum body the drum body is made fractionally
larger than the band so that it has to be compressed to allow mounting of the abrasive
band. In operation the abrasive band is held both by the precompression in the sponge
rubber material and also by the effects of centrifugal force acting on the yieldable
core of the drum.
[0005] A further drum for a sanding belt is shown in GB-A-992 300. Here the body of the
drum is made of foamed plastic material and is provided with special abrasive strips
at its surface which coact with the inner surface of the abrasive band to retain the
same on the drum. The body of this drum is, in similar fashion to the drum of US-A-22
21 173 of relatively thick-walled construction and has at most only vestigal flanges.
Again a special driving hub is provided which leads to unnecessary complications when
manufacturing the drum.
[0006] Accordingly the object of the present invention is to provide an improved drum for
sanding belts which is of simple and rugged construction, has a long operating life,
can be produced at minimal cost and which nevertheless ensures that the abrasive band
remains in position on the drum during use.
[0007] In order to satisfy this object there is provided, in accordance with the present
invention, a drum for a sanding belt in which a drum body has a central web having
a central pin-receiving hole, a circular outer periphery, and a pair of flanges integral
with the web and projecting laterally from opposed sides of said outer periphery,
characterised in that said web has a boss integral therewith and surrounding said
central pin receiving hole; in that the drum body is formed from a natural rubber
having a hardness in the range of 45-65 Durometer; and in that the web and flanges
are of thin wall construction with the radially inner surfaces of the flanges diverging
conically away from the web at an angle whereby to permit the flanges to be sufficiently
flexible so as to bow radially outwardly due to centrifugal force as the web expands
radially outwardly upon rotation of the drum.
[0008] Thus it will be seen that the drum body is of a one-piece construction which therefore
greatly simplifies manufacture. Furthermore, the web portion of the drum has an integral
boss with a central pin receiving hole which ensures that the drive for the drum can
be readily transmitted to the drum without having to make the web unduly thick. The
use of a natural rubber having a hardness in the range 45-65 Duro- meters for the
drum body enables the use of a relatively thin-walled construction which facilitates
manufacture and also retention of the abrasive band on the drum. The conically diverging
flanges not only simplify the manufacturing process but also assist in the outward
bowing of the flanges under centrifugal force which contributes to reliable retention
of the abrasive band thus ensuring that the band does not move circumferentially around
the drum or axially of the drum when the drum and belt are rotated.
[0009] In one embodiment the drum has a pair of annular ribs at the outer side extremities
of the two flanges. A sanding belt having a pair of axially spaced inner peripheral
shoulders on the inner surface of the belt is used with this type of drum so that
the ribs engage the shoulders when the belt is on the drum to prevent axial movement
of the belt on the drum.
[0010] Embodiments of the invention will now be described by way of example only with reference
to the accompanying drawings which show:
Fig. 1 is a perspective view of one embodiment of the sanding drum of the present
invention;
Fig. 2 is a vertical section through the drum and illustrating the way in which it
is mounted on the chuck of a hand drill;
Fig. 3 is an enlarged fragmentary, cross sectional view of the drum, showing a second
embodiment of the drum for use with a sanding belt having abrasive on both the inner
and outer surfaces thereof;
Fig. 4 is a view of the sanding belt used with the drum of Fig.3;
Fig. 5 is a view similar to Fig. 3 but showing the drum of Figs. 1 and 2; and
Fig. 6 is a view similar to Fig. 4 but showing a sanding belt of the type used with
the drum of Figs. 1, 2 and 5.
[0011] A first embodiment of the sanding belt drum of this invention is broadly denoted
by the numeral 10 and is shown in Figs. 1, 2 and 5. Drum 10 is formed from a resilient
material and comprises a circular, flexible, imperforate central web 12 and a pair
of flexible outer peripheral flanges 14 integral with web 12 so that drum 10 is of
a one-piece construction. The web and flanges are preferably formed simultaneously
in a molding process. The web is of a thin wall construction and, as shown in Figs.
2 and 5, is provided with a pair of bosses 16 at the center thereof for support purposes.
The bosses project laterally from opposite sides of the web. While Fig. 5 shows the
sides of the web parallel with each other, they could be tapered from the center outwardly
with the thinnest part near the outer periphery of the web to provide additional support.
[0012] A pin 18 extends through the boss and the web as shown in Fig. 2. Thus, a chuck 20
on a hand drill or the like can grip the pin for rotating drum 10 about the central
axis of web 12.
[0013] Flanges 14 have cylindrical outer surfaces and project laterally in opposed directions
from the outer periphery of web 12 as shown in Figs. 2 and 5. The flanges have respective
integral ribs 22 at their outer extremities. These ribs are formed with the flanges
in a molding process. The flanges have a thin wall construction and, because they
are resilient, they are essentially flexible so as to flex radially outwardly when
subjected to centrifugal force. Similarly, web 12, being of a thin wall construction,
and formed from a resilient material can expand or stretch radially outwardly under
centrifugal force as drum 10 is rotated at high speed, such as 2200 rpm or the like.
This assures a positive frictional engagement between the web and the flanges and
the inner surface of a sanding belt mounted on the drum for rotation.
[0014] For additional holding capabilities, ribs 22 are provided for use with a sanding
belt 24 (Fig. 6) which comprises a band 26 provided with annular shoulders 28 on the
inner surface thereof at locations spaced inwardly from the opposed sides thereof.
These shoulders can be formed by securing a band to the inner surface of band 26 with
the inner band having an axial length less than that of band 26.
[0015] Shoulders 28 abut ribs 22 in the manner shown in Fig. 5 when band 26 is mounted on
flange 14. Thus, a tendency for the belt to move axially of the drum is countered
in two ways, first by the frictional engagement between the flange and the inner surface
of band 26 and, secondly, by the stop feature provided by the engagement of ribs 22
with shoulders 28.
[0016] Drum 10 has the following typical dimensions: Maximum diameter of about 3.80 inches,
web thickness of about .25 inch, total axial length of flanges 14 of about 1.40 inches,
and angle a (Fig. 3) of about 5°. The radially inner surfaces of the flanges thus
diverge conically away from the web at the angle a. The material of drum 10 is typically
55 Durometer natural rubber but can have a hardness in the range of 45-65 Durometer.
[0017] In use, pin 18 is secured in the conventional manner to chuck 20 and sanding belt
24 is then placed on the drum and seated on the flanges 14 in the manner shown in
Fig. 5. Then the hand drill associated with chuck 20 is actuated to rotate drum 10
and thereby permit the sanding of a surface by the outer surface of band 26 which
is provided with an abrasive in the usual manner. During the sanding operation, web
12 will expand radially outwardly and flanges 14 will flex outwardly yet web 12 will
generally maintain its disc-like shape since it is rotating in its own plane. There
will be no circumferential movement of band 26 relative to flanges 14 during rotation
of drum 10 because of the frictional engagement of web 12 and flanges 14 and the inner
surface of band 26. Moreover, this frictional engagement plus the stop action afforded
by ribs 22 will prevent any substantial axial movement of band 26 relative to flanges
14.
[0018] Fig. 3 illustrates another embodiment of drum 10, namely drum 10a. This drum is substantially
the same in all respects as drum 10 except that drum 10a has no ribs 22. Instead,
drum 10a has a completely cylindrical outer surface and is adapted for use with a
sanding band 24a which may have abrasive on both its inner and outer surfaces. Abrasive
need not be on the inner surface and, if used, it need not cover the entire inner
surface as shown in Fig. 4. If used, however, the abrasive on the inner surface provides
greater friction between the drum 10 and the sanding belt. Without the abrasive on
the inner surface, there will be sufficient friction between the flange of drum 10a
and the inner surface of sanding belt 24a because of the expansion or stretching of
the central web of drum 1 Oa and the flexing of outer peripheral flanges due to centrifugal
force, thereby causing the web and flanges to be pressed with greater force against
the inner surface of the sanding belt to achieve an increased frictional force.
[0019] Although the foregoing invention has been described in some detail by way of illustration
and example for purposes of clarity of understanding, it will be obvious that certain
changes and modifications may be practiced within the scope of the appended claims.
1. A drum (10) for a sanding belt (24; 24a) in which a drum body has a central web
(12) having a central pin-receiving hole, a circular outer periphery, and a pair of
flanges (14) integral with the web and projecting laterally from opposed sides of
said outer periphery, characterised in that said web (12) has a boss (16) integral
therewith and surrounding said central pin receiving hole; in that the drum body is
formed from a natural rubber having a hardness in the range of 45-65 Durometer; and
in that the web (12) and flanges (14) are of thin wall construction with the radially
inner surfaces of the flanges diverging conically away from the web at an angle (a)
whereby to permit the flanges (14) to be sufficiently flexible so as to bow radially
outwardly due to centrifugal force as the web (12) expands radially outwardly upon
rotation of the drum (10).
2. A drum as set forth in claim 1 and characterised in that each flange (14) has a
projection (22) on the outer side extremity thereof for engaging a respective shoulder
(28) on the inner surface of a sanding belt.
3. A drum as set forth in claim 2 and characterised in that the projection (22) on
each flange (14) comprises an annular rib.
4. A drum as set forth in any preceding claim and characterised in that said drum
has a maximum diameter of about 9.65 cm, in that the thickness of said web is about
0.64 cm, in that the total axial length of said flanges (14) is about 3.56 cm and
in that said angle (a) is about 5°.
1. Tambour (10) pour une bande de ponçage (24; 24a), dans lequel un corps de tambour
comporte un voile central (12) présentant un trou central de réception d'une broche,
un bord périphérique circulaire extérieur, et deux ailes (14) réalisées d'une seule
pièce avec le voile et faisant saillie latéralement des côtés opposés dudit bord périphérique
extérieur, caractérisé en ce que ledit voile (12) est réalisé d'une seule pièce avec
un bossage (16) qui entoure ledit trou central de réception d'une broche; en ce que
le corps du tambour est réalisé en un caoutchouc naturel ayant une dureté dans la
gamme de 45-65 au duromètre; et en ce que le voile (12) et les ailes (14) sont d'une
réalisation à paroi mince, les surfaces radialement intérieures des ailes divergeant
conique- ment à partir du voile sous un angle (a) afin de permettre aux ailes (14)
d'être suffisamment flexibles pour s'incurver radialement vers l'extérieur sous l'effet
de la force centrifuge lorsque le voile (12) se dilate radialement vers l'extérieur
lors de la rotation du tambour (10).
2. Tambour selon la revendication 1 et caractérisé en ce que chaque aile (14) comporte,
sur son extrémité latérale extérieure, une saillie (22) destinée à engager un épaulement
correspondant (28) de la surface intérieure d'une bande de ponçage.
3. Tambour selon la revendication 2 et caractérisé en ce que la saillie (22) de chaque
aile (14) comprend une nervure annulaire.
4. Tambour selon l'une quelconque des revendications précédentes et caractérisé en
ce que ledit tambour présente un diamètre maximal d'environ 9,65 cm, en ce que l'épaisseur
dudit voile est d'environ 0,64 cm, en ce que la longueur axiale totale desdites ailes
(14) est d'environ 3,56 cm et en ce que ledit angle (a) est d'environ 5°.
1. Eine Trommel (10) für ein Schleifband (24; 24a), wobei ein Trommelkörper eine Zentralscheibe
(12) mit einer zentralen Stiftaufnahmeöffnung, einem kreisförmigen Außenumfang und
zwei mit der Scheibe integrale und seitlich von entgegengesetzten Seiten des Außenumfangs
abstehende Flansche (14) besitzt, dadurch gekennzeichnet, daß die Scheibe (12) einen
damit integralen und die zentrale Stiftaufnahmeöffnung umgebenden Nabenwulst (16)
besitzt, daß der Trommelkörper aus einem Naturgummi mit einer Härte im Bereich von
45 bis 65 Durometer gebildet ist und daß die Scheibe (12) und die Flansche (14) dünnwandig
aufgebaut sind, wobei die radial innenliegenden Flächen der Flansche kegelförmig von
der Scheibe mit einem Winkel (a) auseinanderlaufen, so daß die Flansche (14) so ausreichend
flexibel sein können, daß sie sich bei einer Drehung der Trommel (10) infolge der
Zentrifugalkraft radial nach außen biegen, während die Scheibe (12) sich radial nach
außen dehnt.
2. Eine Trommel nach Anspruch 1, dadurch gekennzeichnet, daß jeder Flansch (14) mit
einem Vorsprung (22) an der äußeren Seitenkante versehen ist zur Anlage an eine jeweilige
Schulter (28) an der Innenfläche eines Schleifbandes.
3. Eine Trommel nach Anspruch 2, dadurch gekennzeichnet, daß der Vorsprung (22) an
dem jeweiligen Flansch (14) eine Ringrippe bildet.
4. Eine Trommel nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß
die Trommel einen maximalen Durchmesser von ca. 9,65 cm besitzt, daß die Stärke der
Scheibe ca. 0,64 cm beträgt, daß die gesamte Axiallänge der Flansche (14) ca. 3,56
cm beträgt und daß der Winkel (a) etwa 5° beträgt.