Portable electric tool with balanced orbital movement

Abstract

 The portable electric tool comprises a driving shaft (50), an eccentric (24) rotated by the driving shaft (50), a turning support (23) for an operating element (22) mounted on said eccentric (24) and a counterweight (49) to balance the eccentric (24). The eccentric (24) and the counterweight (49) constitute a single piece which is mounted on an axial extension (21) of the driving shaft (50).

Description

[0001] The present invention relates to a portable electrical tool and particularly but not exclusively an orbital sanding machine with orbital movement of the operative element.

[0002] Known portable electric tools have a driving shaft, an eccentric rotated by the driving shaft and an annular support for the operative element which following rotation of the eccentric performs an orbital movement with a circular trajectory around the axis of the driving shaft.

[0003] With the operative element support is usually made integral a toothed ring which by engaging with a correspoding toothed ring integral with the fixed body of the tool and having a different number of teeth adds to the aforesaid orbital motion a rotation around the axis of the eccentric to permit the operative element to follow composite noncircular orbits which allow better machining of the surface engaged.

[0004] In said tool there is provided a balancing device for the eccentric masses which consists of a counterweight fixed to the rotating eccentric.

[0005] The object of the present invention is to accomplish a portable electric tool with orbital movement in which the arrangement of the eccentric and the associated counterweight is particularly simple and economical.

[0006] In accordance with the invention said object is achieved with a portable electric tool comprising a driving shaft, an eccentric made to rotate by the driving shaft, a turning support for an operative element mounted in a turning manner on said first eccentric, a toothed ring fixed to said turning support and engaging with a fixed coplanar toothed ring and a counterweight characterized in that the eccentric and the counterweight comprise a single piece mounted on an axial extension of the driving shaft.

[0007] An example of a practical accomplishment of the present invention is illustrated for greater clarity in the annexed drawings wherein:

FIG. 1 shows a longitudinal section of an orbital sanding machine accomplished in accordance with the present invention,

FIG. 2 shows a cross section of said sanding machine along line II-II of FIG. 1, and

FIG. 3 shows a chart representing the orbits followed by the mass to be balanced.

[0008] The orbital sanding machine illustrated in the drawings is structurally formed of a working head 10 from which extends at right angles a handle 12 including an exhaust duct 26 for the dust arising from the work.

[0009] The duct 26 terminates with a saw-toothed connector 28 for a flexible exhaust tube designed to convey the exhausted dust into a special collection container. Naturally to the connector 28 can also be directly applied a dust collection bag made of flexible material.

[0010] The working head 10 comprises an external body 11, within which is housed a mechanism for transmission of the motion of the armature shaft of the motor (not shown) to a plate 22 having suction holes 20 on which is applied a sheet of abrasive paper (not shown).

[0011] More precisely the plate 22 is fixed to a flanged annular support 23 born in a turning manner through bearings 40, 41 by an eccentric hub 24 fixed to an axial extension 21 of a driving shaft 50 made to rotate by the armature shaft of the motor through a bevel gear pair (not shown). With the annular support 23 is made integral a toothed ring 42 which is engaged with a coplanar toothed ring 43 having a larger number of teeth and which is fixed to the body 11 of the working head 10 (FIGS. 1 and 2).

[0012] A counterweight 49 extends laterally from the lower end of the eccentric 2 forming therewith a single piece mounted on the axial extension 21 of the driving shaft 50. The counterweight 49 is made in such a manner as to balance axially and transversally the weight of the eccentric 24 and the mass supported thereby.

[0013] During operation the armature shaft transmits through a bevel gear pair the motion of the driving shaft 21 an orbital movement which engagement with the toothed rings 42, 43 (FIG. 2) combines with a rotation around the axis of the eccentric 24 to originate a composite movement which follows the orbit with successive arcs indicated by the letter A in FIG. 3.

Claims

1. Portable electric tool comprising a driving shaft (50), an eccentric (24) made to rotate by the driving shaft (50), a turning support (23) for an operating element (22) mounted in a turning manner on said eccentric (24), a toothed ring (42) fixed to said turning support (23) and engaging with a fixed coplanar toothed ring (43) and a counterweight (49) characterized in that said eccentric (24) and said counterweight (49) constitute a single piece mounted on an axial extension (21) of the driving shaft (50).

2. Tool in accordance with claim 1 characterized in that said counterweight (49) extends laterally from the lower end of said eccentric (24).

3. Tool in accordance with claim 1 characterized in that said operating element (22) consists of the plate of an orbital sanding machine.

Drawing