EP1714739A1

EP1714739A1 - Hand guided sanding tool

Info

Publication number: EP1714739A1
Application number: EP05252431A
Authority: EP
Inventors: Gianni Borinato; Shisong Zhang
Original assignee: Positec Power Tools Suzhou Co Ltd
Current assignee: Positec Power Tools Suzhou Co Ltd
Priority date: 2005-04-19
Filing date: 2005-04-19
Publication date: 2006-10-25

Abstract

A dual function powered oscillating sanding tool includes a first rotary drive shaft (6) rotatable about a first axis (4), a second rotary drive shaft (12) rotatable about a second axis (10) which is located radially eccentrically relative to the first axis (4) and a housing (2, 20) containing the first rotary drive shaft (6) and the second rotary drive shaft (12). A sanding platen (21) and a sanding shoe (22) may be selectively mounted on the second rotary drive shaft (12). An elastic restraining element (31) is resiliently mounted between the sanding shoe (22) and the housing (2, 20) so as to restrain the sanding shoe (22) in a regular orbit for fine sanding

Description

The present invention relates to a sanding tool capable of selectively performing regular orbital sanding or random orbital sanding.
In a conventional random orbital sander, an oscillating disc is driven by a rotary drive element and can rotate with respect to the rotary drive shaft to perform a coarse sanding operation. In a conventional regular orbital sander, an oscillating disc is driven by a rotary drive element and can perform a fine sanding operation. US-A-6132300 discloses a dual function sander with a connection means including a plurality of rigid elements and a plurality of flexible columns which are axially interengageable. Oscillating plates may be selectively mounted on the sander by the connection means to perform orbital sanding or random orbital sanding. However, the connection means is complex to manufacture, the flexible columns are easily invalidated and high quality materials are required. The connection means are exposed to torsional forces imparted by frictional torque between the bearing and the drive shaft.
The present invention seeks to improve the operability and longevity of a dual function sanding tool by selectively restraining a rotary sanding element in a radial plane. More particularly, the present invention relates to a sanding tool with restraining elements resiliently mounted in the radial plane between the restrainable rotary sanding element and the skirt of the housing.
Viewed from a first aspect the present invention provides a sanding tool comprising:

a first rotary drive shaft rotational about a first axis;
a second rotary drive shaft rotational about a second axis which is eccentric to the first axis;
a housing containing the first rotary drive shaft and the second rotary drive shaft and terminating at its basal end in a skirt bounding a mouth;
a bearing mounted on the first rotary drive shaft and supporting the second rotary drive shaft so as to impart to the second rotary drive shaft in use a tendency to rotate about the second axis;
a restrainable rotary sanding element selectively fastened to the foot of the second rotary drive shaft beyond the mouth; and
one or more elastic restraining elements resiliently mounted between the restrainable rotary sanding element and the skirt which in use apply a restoring torque to the second rotary drive shaft which resists the tendency of the second rotary drive shaft to rotate about the second axis so as to restrain the restrainable rotary sanding element in a regular orbit for fine sanding.

By confining the one or more elastic restraining elements to the radial plane defined by the restrainable rotary sanding element and the skirt, certain disadvantages of conventional sanding tools may be overcome.
Typically the housing comprises an upper housing part and a lower housing part. The upper housing part generally houses the motor. The lower housing part generally houses the first rotary drive shaft and the second rotary drive shaft. The bearing may support the second rotary drive shaft in a fan (eg a cooling fan and/or an exhaust fan). The first rotary drive shaft may be supported at an upper end by an upper bearing. The skirt is a distinguishable edge of the lower housing of any suitable shape.
Preferably the housing (eg the lower housing part) comprises a substantially bell-shaped body terminating at its basal end in a substantially truncated square skirt bounding the mouth.
The or each elastic restraining element may be fixed to one of the restrainable rotary sanding element and the skirt and biased against the other of the restrainable rotary sanding element and the skirt. The or each elastic restraining element may be fixed to the restrainable rotary sanding element and the skirt.
In a preferred embodiment, a first pair of internal platforms diametrically opposed relative to the second axis extend from the inner face of the skirt and a second pair of internal platforms diametrically opposed relative to the second axis extend from the inner face of the skirt. Particularly preferably a third pair of internal platforms diametrically opposed relative to the second axis extend from the inner face of the skirt and a fourth pair of internal platforms diametrically opposed relative to the second axis extend from the inner face of the skirt.
Each of the first, second, third and fourth pair of internal platforms may be any suitable shape. Each of the first, second, third and fourth pair of internal platforms may be parallel to the skirt. The first, second, third and fourth pair of internal platforms may be mutually disposed in a substantially rectangular (eg square) configuration.
Preferably the housing terminates at its basal end in a substantially truncated square skirt bounding the mouth and each internal platform extends from the truncated portion of the truncated square skirt partially along and substantially parallel to the non-truncated portion of the truncated square skirt.
Preferably the inner face of the or each internal platform defines an engagement surface for engaging an elastic restraining element and the engagement surface of the or each pair of diametrically opposed internal platforms is substantially parallel.
Preferably the one or more elastic restraining elements are a plurality of elastic restraining elements, preferably a plurality of pairs of elastic restraining elements, particularly preferably a plurality of pairs of elastic restraining elements diametrically opposed relative to the second axis, especially preferably two pairs of elastic restraining elements diametrically opposed relative to the second axis.
Preferably the or each elastic restraining element is adapted to undergo restrained oscillatory displacement (eg wobble) along the skirt (eg along the engagement surface).
Preferably the elastic restraining element is substantially orthogonal to the engagement surface.
Preferably the or each elastic restraining element comprises:

a spring resiliently mounted between the restrainable rotary sanding element and the skirt, preferably between the restrainable rotary sanding element and
an internal platform.

Preferably the elastic restraining elements comprise:

two pairs of springs diametrically opposed relative to the second axis.

Preferably the or each spring is fixed at a first end to a portion (eg an upstanding portion) of the restrainable rotary sanding element and is supported within a sleeve mounted on the upper surface of the restrainable rotary sanding element, wherein a second end of the or each spring opposite to the first end is connected to a contact member which is resiliently urged into contact with the skirt. Particularly preferably the contact member is a rolling member (eg a ball).
Typically the or each spring is fixed at or near to the perimeter of the restrainable rotary sanding element
Preferably the or each spring is fixed at a first end to a portion (or portions) of the restrainable rotary sanding element and a second end opposite to the first end is in contact with adjacent internal platforms. The spring may be an elongate folded spring. The first end may be fixed to a portion (or portions) of the restrainable rotary sanding element by convention fastening members (eg screws). The first end may be a substantially horizontal folded end portion. The second end may be a substantially vertical folded end portion.
Preferably the restrainable rotary sanding element has a plurality of columns extending from its upper surface, each column houses a supporting spring and the supporting spring supports a supporting member to support the housing. Particularly preferably the supporting member is a rolling supporting member (eg a supporting ball).
Preferably the restrainable rotary sanding element is selectively replaceable with a non-restrainable rotary sanding element free to rotate about the second axis to perform a random orbit for coarse sanding.
The restrainable rotary sanding element may be a sanding shoe. The non-restrainable rotary sanding element may be a sanding platen. The restrainable rotary sanding element may be fastened to the foot of the second rotary drive shaft using any conventional fastener. A sanding sheet is typically fixed to the restrainable rotary sanding element or the non-restrainable rotary sanding element in a conventional manner.
In a preferred embodiment, the restrainable rotary sanding element and the housing have no axially interengageable (eg mating) portions.
Viewed from a further aspect the present invention provides a sanding tool device comprising:

a first rotary drive shaft rotational about a first axis;
a second rotary drive shaft rotational about a second axis which is eccentric to the first axis;
a housing containing the first rotary drive shaft and the second rotary drive shaft and terminating at its basal end in a skirt bounding a mouth;
a bearing mounted on the first rotary drive shaft and supporting the second rotary drive shaft so as to impart to the second rotary drive shaft in use a tendency to rotate about the second axis,

Viewed from a yet further aspect the present invention provides a restrainable rotary sanding element selectively fastenable to the foot of a second rotary drive shaft of a sanding tool device as defined hereinbefore,
wherein the restrainable rotary sanding element is adapted so that between the restrainable rotary sanding element and the skirt are resiliently mountable one or more elastic restraining elements which in use apply a restoring torque to the second rotary drive shaft to resist the tendency of the second rotary drive shaft to rotate about the second axis so as to restrain the restrainable rotary sanding element in a regular orbit for fine sanding.
The present invention will now be described in a non-limitative sense with reference to the accompanying Figures in which:

Figure 1 shows a sectional view of a first embodiment of the sanding tool of the invention fitted with a sanding shoe;
Figure 2 shows a sectional view along the line A-A in Figure 1;
Figure 3 shows a sectional view of a second embodiment of the sanding tool of the invention fitted with a sanding shoe;
Figure 4 shows a sectional view along the line B-B in Figure 3;
Figure 5 shows an embodiment of the sanding tool device of the invention fitted with a sanding platen; and
Figure 6 shows a sectional view along the line C-C in Figure 5.

With reference to Figures 1 to 6, the sanding tool of the present invention includes generally a lower housing part 20, an upper housing part 2 and a motor (not shown) housed in the upper housing part 2. The lower housing part 20 is a substantially bell-shaped body which terminates at its basal end in a substantially truncated square skirt 20a bounding a mouth. The lower housing part 20 contains a first rotary drive shaft 6 and a second rotary drive shaft 12.
The first rotary drive shaft 6 is supported at an upper end by a first bearing 8 and is driven by the motor rotationally about a first axis 4. The second rotary drive shaft 12 is supported by a second bearing 14 in a motor fan 7 which is mounted on the first rotary drive shaft 6 within the lower housing portion 20. The motor fan 7 draws in air through the mouth of the lower housing portion 20. The second rotary drive shaft 12 is rotational about a second axis 10 which is radially eccentric to the first axis 4.
A first pair of internal platforms 30a,a' diametrically opposed relative to the second axis 10 and a second pair of internal platforms 30b,b' diametrically opposed relative to the second axis 10 extend from the inner face of the truncated square skirt 20a. In particular, each internal platform 30a,a',b,b' extends from the truncated portion of the truncated square skirt 20a partially along and substantially parallel to the non-truncated portion of the truncated square skirt 20a. The inner face of each internal platform 30a,a',b,b' defines an engagement surface and the engagement surfaces of each pair of diametrically opposed internal platforms 30a,a' and 30b,b' are parallel.
In the first embodiment (Figures 1 and 2), a sanding shoe 22 is fastened to the foot of the second rotary drive shaft 12 by means of a pressing plate 16 and a locking screw 18. A sanding sheet 24 with a plurality of holes is fixed to the basal face of the sanding shoe 22 in a conventional manner. Elastic restraining elements 31a,a',b,b' mounted on the perimeter of the upper surface of the sanding shoe 22 are substantially orthogonal to and engage the respective engagement surfaces of the internal platforms 30a,a',b,b'. As described below, this engagement is capable of preventing the sanding shoe 22 from rotating about the second axis 10 so as to restrain the sanding shoe 22 in a regular orbit about the first axis 4 for fine sanding.
Each elastic restraining element 31 comprises a base 32 mounted on the upper surface of the sanding shoe 22 by a screw and a sleeve 36 set in the base 32. Contained in the sleeve 36 are a spring 38 fixed to the sanding shoe 22 and a ball 34 biased outwardly by the spring 38 into contact with the engagement surface.
When the first rotary drive shaft 6 is driven by the motor, the sanding shoe 22 rotates with respect to the first axis 4. A frictional force is generated between the second bearing 14 and the second rotary drive shaft 12 which gives the sanding shoe 22 a tendency to rotate about the second axis 10. However the frictional torque applied to the sanding shoe 22 in this manner is counterbalanced by an opposing torque applied by the elastic restraining elements 31a,a',b,b' to the sanding shoe 22 about the second axis 10. The elastic force of the elastic restraining elements 31a,a',b,b' acting against the engagement surfaces generates the opposing torque. In practice, the elastic restraining elements 31a,a',b,b' wobble against the respective engagement surfaces as they continuously equilibrate in response to the frictional torque.
The sanding shoe 22 has four columns 25 extending from its upper surface. Each column 25 houses a supporting spring 28 and the supporting spring 28 supports a supporting ball 26. Through the biasing action of the supporting spring 28, the supporting ball 26 serves to support the lower housing part 20.
In the second embodiment (Figures 3 and 4), a sanding shoe 22 is fastened to the foot of the second rotary drive shaft 12 by means of a pressing plate 16 and a locking screw 18. A sanding sheet 24 with a plurality of holes is fixed to the basal face of the sanding shoe 22 in a conventional manner. A first pair of internal platforms 30a,a' diametrically opposed relative to the second axis 10, a second pair of internal platforms 30b,b' diametrically opposed relative to the second axis 10, a third pair of internal platforms 30c,c' diametrically opposed relative to the second axis 10 and a fourth pair of internal platforms 30d,d' diametrically opposed relative to the second axis 10 extend from the inner face of the truncated square skirt 20a. The first and second pair of internal platforms 30a,a',b,b' are as hereinbefore defined and the third and fourth pair of internal platforms 30c,c',d,d' are identical to the first and second pair of internal platforms 30a,a',b,b'.
Elastic restraining elements 31a,a',b,b' mounted on the perimeter of the upper surface of the sanding shoe 22 engage the engagement surface. As described below, this engagement is capable of preventing the sanding shoe 22 from rotating about the second axis 10 so as to restrain the sanding shoe 22 in a regular orbit for fine sanding.
In the second embodiment, each elastic restraining element 31a,a',b,b' comprises a long spring 50 composed of folded elastic material. The springs 50 include a horizontal folding edge 40 fastened to the upper surface of the sanding shoe 22 at each end by a screw and a vertical folding edge 39 biased against adjacent internal platforms (eg 30a and 30b'). The frictional torque generated by the second bearing 14 and the second rotary drive shaft 12 is counterbalanced by the restoring torque applied by the elastic restraining elements 31 a,a',b,b' to the sanding shoe 22 about the second axis 10 so as to restrain the sanding shoe 22 in a regular orbit for fine sanding.
Figures 5 and Figure 6 illustrate an embodiment of the sanding tool device of the invention with a sanding platen 21 fastened to the foot of the second rotary drive shaft 12. The sanding platen 21 is a regular circular shape. The sanding platen 21 is free to rotate in an unrestrained manner about the second axis 10 to perform a random orbit for coarse sanding.
By allowing the sanding tool device to be selectively equipped with the sanding platen 21 and the sanding shoe 22, the elastic restraining element 31 helps to achieve a dual function with a simple structure at low cost. Because the distance between the elastic restraining element 31 and the housing 20 is small, the sanding tool exhibits little torsion. Thus the elastic restraining element 31 is less prone to invalidation and has a longer life.

Claims

A sanding tool comprising:
a first rotary drive shaft (6) rotational about a first axis (4);

a second rotary drive shaft (12) rotational about a second axis (10) which is eccentric to the first axis (4);

a housing (2, 20) containing the first rotary drive shaft (6) and the second rotary drive shaft (12) and terminating at its basal end in a skirt (20a) bounding a mouth;

a bearing (14) mounted on the first rotary drive shaft (6) and supporting the second rotary drive shaft (12) so as to impart to the second rotary drive shaft (12) in use a tendency to rotate about the second axis (10);

a restrainable rotary sanding element (22) selectively fastened to the foot of the second rotary drive shaft (12) beyond the mouth; and

one or more elastic restraining elements (31a,a',b,b') resiliently mounted between the restrainable rotary sanding element (22) and the skirt (20a) which in use apply a restoring torque to the second rotary drive shaft (12) which resists the tendency of the second rotary drive shaft (12) to rotate about the second axis (10) so as to restrain the restrainable rotary sanding element (22) in a regular orbit for fine sanding.
A sanding tool as claimed in claim 1 wherein the housing (2, 20) comprises a substantially bell-shaped body terminating at its basal end in a substantially truncated square skirt (20a) bounding the mouth.
A sanding tool as claimed in claim 1 or 2 wherein a first pair of internal platforms (30a,a') diametrically opposed relative to the second axis (10) extend from the inner face of the skirt (20a) and a second pair of internal platforms (30b,b') diametrically opposed relative to the second axis (10) extend from the inner face of the skirt (20a).
A sanding tool as claimed in claim 3 wherein a third pair of internal platforms (30c,c') diametrically opposed relative to the second axis (10) extend from the inner face of the skirt (20a) and a fourth pair of internal platforms (30d,d') diametrically opposed relative to the second axis (10) extend from the inner face of the skirt (20a).
A sanding tool as claimed in claim 3 or 4 wherein the housing (20) terminates at its basal end in a substantially truncated square skirt (20a) bounding the mouth and each internal platform (30a,a',b,b',c,c',d,d') extends from the truncated portion of the truncated square skirt (20a) partially along and substantially parallel to the non-truncated portion of the truncated square skirt (20a).
A sanding tool as claimed in claim 3, 4, or 5 wherein the inner face of the or each internal platform (30a,a',b,b',c,c',d,d') defines an engagement surface for engaging an elastic restraining element (31a,a',b,b') and the engagement surface of the or each pair of diametrically opposed internal platforms (30a,a',b,b',c,c',d,d') is substantially parallel.
A sanding tool as claimed in any preceding claim wherein the one or more elastic restraining elements (31a,a',b,b') are a plurality of elastic restraining elements (31a,a',b,b'), preferably a plurality of pairs of elastic restraining elements (31a,a',b,b'), particularly preferably a plurality of pairs of elastic restraining elements (31a,a',b,b') diametrically opposed relative to the second axis (10), especially preferably two pairs of elastic restraining elements (31a,a',b,b') diametrically opposed relative to the second axis (10).
A sanding tool as claimed in claim 7 wherein the or each elastic restraining element (31 a,a',b,b') is adapted to undergo restrained oscillatory displacement along the skirt (20a).
A sanding tool as claimed in claim 6 wherein the elastic restraining element (31a,a',b,b') is substantially orthogonal to the engagement surface.
A sanding tool as claimed in claim 9 wherein the or each elastic restraining element (31a,a',b,b') is adapted to undergo restrained oscillatory displacement along the engagement surface.
A sanding tool as claimed in any preceding claim wherein the or each elastic restraining element (31a,a',b,b') comprises:
a spring (38, 50) resiliently mounted between the restrainable rotary sanding element (22) and the skirt (20a),
A sanding tool as claimed in claim 11 wherein the spring (38, 50) is resiliently mounted between the restrainable rotary sanding element (22) and an internal platform (30a,a',b,b',c,c',d,d').
A sanding tool as claimed in claim 12 wherein the elastic restraining elements (31a,a',b,b') comprise:
two pairs of springs (38, 50) diametrically opposed relative to the second axis (10).
A sanding tool as claimed in claim 12 or 13 wherein the or each spring (38) is fixed at a first end to a portion of the restrainable rotary sanding element (22) and is supported within a sleeve (36) mounted on the upper surface of the restrainable rotary sanding element (22), wherein a second end of the or each spring (38) opposite to the first end is connected to a contact member (34) which is resiliently urged into contact with the skirt (20a).
A sanding tool as claimed in claim 14 wherein the contact member is a rolling member (34).
A sanding tool as claimed in claim 15 wherein the or each spring (50) is fixed at or near to the perimeter of the restrainable rotary sanding element (22).
A sanding tool as claimed in claim 12 or 13 wherein the or each spring (50) is fixed at a first end to a portion or portions of the restrainable rotary sanding element (22) and a second end opposite to the first end is in contact with adjacent internal platforms (30a,a',b,b',c,c',d,d').
A sanding tool as claimed in any preceding claim wherein the restrainable rotary sanding element (22) has a plurality of columns (25) extending from its upper surface, each column (25) houses a supporting spring (28) and the supporting spring (28) supports a supporting member (26) to support the housing (2, 20).
A sanding tool as claimed in claim 18 wherein the supporting member is a rolling supporting member (26).
A sanding tool as claimed in any preceding claim wherein the restrainable rotary sanding element (22) is selectively replaceable with a non-restrainable rotary sanding element (21) free to rotate about the second axis (10) to perform a random orbit for coarse sanding.
A sanding tool as claimed in any preceding claim wherein the one or more elastic restraining elements (31a,a',b,b') are fixed to one of the restrainable rotary sanding element and the skirt.
A sanding tool device comprising:
a first rotary drive shaft (6) rotational about a first axis (4);

a second rotary drive shaft (12) rotational about a second axis (10) which is eccentric to the first axis (4);

a housing (2, 20) containing the first rotary drive shaft (6) and the second rotary drive shaft (12) and terminating at its basal end in a skirt (20a) bounding a mouth;

a bearing (14) mounted on the first rotary drive shaft (6) and supporting the second rotary drive shaft (12) so as to impart to the second rotary drive shaft (12) in use a tendency to rotate about the second axis (10),
wherein a restrainable rotary sanding element (22) is selectively fastenable to the foot of the second rotary drive shaft (12) beyond the mouth and the skirt (20a) is adapted so that between the restrainable rotary sanding element (22) and the skirt (20a) are resiliently mountable one or more elastic restraining elements (31a,a',b,b') which in use apply a restoring torque to the second rotary drive shaft (12) to resist the tendency of the second rotary drive shaft (12) to rotate about the second axis (10) so as to restrain the restrainable rotary sanding element (22) in a regular orbit for fine sanding.
A restrainable rotary sanding element (22) selectively fastenable to the foot of a second rotary drive shaft (12) of a sanding tool device as claimed in claim 21, wherein the restrainable rotary sanding element (22) is adapted so that between the restrainable rotary sanding element (22) and the skirt (20a) are resiliently mountable one or more elastic restraining elements (31a,a',b,b') which in use apply a restoring torque to the second rotary drive shaft (12) to resist the tendency of the second rotary drive shaft (12) to rotate about the second axis (10) so as to restrain the restrainable rotary sanding element (22) in a regular orbit for fine sanding.