Improved oscillating hand tool

Abstract: A dual function powered oscillating hand tool comprises (i) a drive unit (5) having an electric motor and a drive shaft (7); (ii) a bearing (15) mounted on the drive shaft (7) and located radially eccentrically relative to the drive shaft (7); (iii) a second drive shaft (14) mounted on the eccentric bearing (15) and (iv) means (13) for mounting a sanding head (20,21) on the second drive shaft (14). The sanding head (20,21) may comprise a sanding platen (21) for random orbit sanding or a sanding shoe (20) for orbital sanding and the tool further comprises means selectively engageable to restrict the random orbit of the sanding shoe (20) to a regular orbit.

Description: The present invention relates to a powered oscillating hand tool comprising a drive unit having an electric motor with a drive shaft to which a sander head can be attached. In general, known sanders can be described as either random orbit sanders or orbital sanders. In random orbit sanders, a circular platen is driven by a drive system which comprises an eccentric bearing so that the platen can spin independently of the motor, and the platen describes a random orbit. Such sanders are in general used for the removal of relatively large quantities of material. Alternatively, the sander may be of the orbital type, with a shaped shoe, the drive system of which comprises an eccentric which is restrained so that the sander shoe cannot spin independently of the motor and it therefore describes a regular orbit. The shoes of such sanders are available in a range of shapes and such sanders are in general used for the removal of relatively small quantities of material, for example for detailed work or for finishing. By choice of a suitably shaped shoe, it is possible to access areas which are inaccessible with a random orbit sander. The fixed eccentric drive system of the orbital sander is cheaper and simpler to manufacture than the eccentric bearing of the random orbit sander. Known sanders have been either of the random orbit type or the orbital type, which has meant that when the user wished to have the ability to perform both coarse and detailed sanding operations, it has been necessary for him to purchase two separate units, one of each type, or to purchase only one unit and suffer the disadvantages thereof. A sander according to the preamble of claim 1 is disclosed in DE-A-4118392. According to this document, a sander body has attached thereto an accessory member which can be selectively attached to the platen of a random orbit sander and thereby convert the unit to an orbital sander by restraining the free rotation of the platen about its axis. It is an object of the present invention to provide a sander in which the above disadvantages are reduced or substantially obviated. The present invention therefore provides a dual-function powered oscillating hand tool according to claim 1. The invention will now be further described with reference to the accompanying drawings in which Figure 1 is a side view, partially in section, of the drive unit of a first embodiment of a hand tool according to the present invention, shown without an operating head; Figure 2 is a side view of the lower part of the drive unit of Figure 1 when fitted with an orbital sander shoe; Figure 3 is a side view of the lower part of the drive unit of Figure 1 when fitted with a random orbit sander platen; Figure 4 is a side view, partially in section, of the drive unit of an alternative embodiment of a hand tool according to the present invention, shown without an operating head; Figure 5 is a side view of the lower part of the drive unit of Figure 4 when fitted with an orbital sander shoe, and Figure 6 is a side view of the lower part of the drive unit of Figure 4 when fitted with a random orbit sander platen. Figure 1 shows a drive unit (5) including an electric motor (not shown) located in upper housing (6) and driving shaft (7). A fan (8) mounted on shaft (7) is arranged to draw air in from mouth (9) of lower housing (10) and direct it through extractor duct (11) to exhaust outlet (12). A nut (13) is used to secure operating heads (see Figures 2 and 3) to shaft (14) which is housed in the fan (8) by bearing (15) which is eccentrically located radially in respect to shaft (7). Two pairs of hollow, tapering, flexible columns (16) made of rubber are arranged around the mouth (9) of the lower housing (10). Each flexible column (16) has a more flexible cranked leg (17) projecting from the column (16) a short distance from the tip (18) so that in the unstressed position the end (19) of the leg (17) projects beyond the tip (18) of the column (16). Drive unit (5) can alternatively be fitted with an (oscillating) orbital sander shoe (20), (Figure 2) or with a random orbit sander platen (21) (Figure 3). As seen in Figure 2, shoe (20) which is supported by tips (18) of the flexible columns (16), is driven by the electric motor through shafts (7,14). The cranked legs (17) in this case are deflected from the flexible columns (16) to lie level with the upper surface of the shoe (20). A perforated sandpaper sheet (not shown) may be attached to the outer face (22) of the shoe (20), for example by the use of hook-and-loop fabric such as that sold as VELCRO (RTM) glued to face (22). Holes (23) passing through the shoe (20) facilitate the removal of dust etc, from the sanding face through the shoe (20) to exhaust outlet (12) via the duct (11). An extractor hose (not shown) may be attached to the exhaust outlet (12). As seen in Figure 3, platen (21) is driven by the electric motor by means of shafts (7,14). Again, a perforated sandpaper sheet (not shown) may be attached to the outer face (24) of the platen (21), for example by the use of hook-and-loop fabric glued to the face (24). Holes (25) passing through the platen (21) again facilitate removal of dust etc, through the platen (21) to exhaust outlet (12). In this case, tips (18) of the flexible columns (16) are held away from the platen (21) so that the ends (19) of the cranked legs (17) contact the platen (21). In operation, ends (19) of legs (17) drag against the rotating platen (21) to exert a braking effect. The invention thus provides a powered oscillating power tool which can easily be fitted with an orbital sander head or with an efficiently braked random orbit sander head without requiring adjustment to the drive. In an alternative embodiment shown in Figures 4 to 6 of the accompanying drawings, like components are similarly numbered as in Figures 1 to 3. In this embodiment, as can be seen from Figure 4, four upstanding spigots (72) are provided on the underside of the floor (74) of the motor housing. These spigots (72) are suitably made of a thermoplastic material and are preferably integrally moulded with the floor (74) of the motor housing. Drive unit (5) can alternatively be fitted with an orbital sander shoe (76), (Figure 5) or with a random orbit sander platen (78), (Figure 6). As can be seen from Figure 5, four legs (80) are provided on the backing plate of the shoe (76). As the shoe (76) is mounted on the shaft (14), each of the legs (80) engages a corresponding spigot (72). The legs (80) are shaped for engagement with the spigots (72) and may be made of any flexible material, e.g. rubber or a synthetic plastics material, and may be welded, screwed, bonded, integrally moulded with or fastened by any appropriate means to the shoe (76). As can be seen from Figure 6, the shoe (76) may be removed and replaced by a random orbit sander platen (78). If it is wished to provide braking for the sander in the random orbit mode, then a separate brake must be provided in a manner known per se. In operation, in the orbital mode, each of the legs (80) engages in a corresponding spigot (72) and the motion of the shoe is restricted to a conventional regular orbit. In the random orbit mode, the platen is free to rotate in a random orbit. In the embodiment shown in Figures 4 to 6, the legs are attached to the shoe, and engage in spigots in the drive unit. It is, however, within the scope of the invention for the legs to be attached to the drive unit and engage with spigots on the backing plate of the shoe. With this variation, it is possible for the legs to provide a braking effect in random orbit mode, thus obviating the need for a separate brake component. While the powered oscillating hand tool according to the invention is particularly adapted for use with sanding heads such as random orbit sanding platens and orbital sanding shoes, it is of course within the scope of the invention to provide a tool to which further alternative oscillating heads can be attached.

Claims: A dual-function powered oscillating hand tool comprising: a drive unit (5) having a housing (6,10) and a first drive shaft (7); a bearing (15) mounted on the first drive shaft (7) and located radially eccentrically relative thereto; a second drive shaft (14) mounted on the eccentric bearing (15) and rotatable about the axis thereof, wherein the housing (6,10) has an opening (9) for the first (7) and second (14) drive shafts, first and second platens interchangeably mountable on the second drive shaft (14), one of which first and second platens co-operates with coupling means for coupling with the drive unit (5) to prevent free rotation of said one platen about the bearing (15) axis, the other of said first and second platens being arranged, when mounted on the second drive shaft, with free rotation with respect to the bearing (15) axis, and characterized in that the coupling means consist of a plurality of rigid components (72) and a plurality of flexible columns (16, 80) , each column of the plurality co-operable with a rigid component (72), one of which flexible columns (16, 80) or rigid components (72) being fixed on said one platen and the other of which flexible columns (16, 80) or rigid components (72) being fixed on the housing (6,10) and that the flexible columns are arranged about the opening (9); wherein only when said one platen prevented from free rotation is mounted, the flexible columns and the rigid components are in engagement whereas said other platen lacks any such coupling means and wherein fitting of a platen to the drive unit (5) requires no adaptation to the drive unit other than direct substitution of the one platen for the other platen, or vice versa. A dual-function powered oscillating hand tool according to claim 1 characterised in that each flexible column (16, 80) of the plurality co-operates with the corresponding rigid component (72) by insertion of said each column into a rigid location point defined by each rigid component. A dual-function oscillating hand-tool according to claim 1 characterised in that each flexible column (80) of the plurality is hollow and the corresponding rigid component (72) includes a boss which engages the hollow column (80). A dual-function powered oscillating hand-tool according to any one of the preceding claims characterised by further including a brake (17) which is operative when one of said first and second platens is arranged for free rotation with respect to the bearing (15) axis. A dual-function powered oscillating hand-tool according to claim 4 characterised in that the columns of the plurality (80) are located on the drive unit (5) and are a component of the brake (17).

Inventors: MARTIN MICHAEL, MARTIN, MICHAEL
Applicants: BLACK & DECKER INC, BLACK & DECKER INC.
Application year: 1995
Main classification: B24B23
IPC codes: B24B23