HAND TOOL WITH IMPROVED DRIVE

The present invention relates to a hand tool, in particular a sanding machine, comprising a housing having accommodated therein a drive with drive shaft, a first bearing arranged eccentrically on the drive shaft, and a base plate connected to the first bearing, wherein coupling means are provided between the base plate and the housing to prevent a free rotation of the base plate around the shaft of the first bearing.

A hand-held sanding machine of the above stated type is known from EP-A-O 694 365. A second drive shaft is herein mounted on the eccentric bearing, and the base plate is mounted on the second drive shaft by means of a nut. Flexible legs extend between the base plate and the housing. The flexible legs are attached to the base plate. The flexible legs prevent a free rotation of the base plate around the (eccentric) shaft of the bearing. The base plate consists of a footplate to which a sheet of sandpaper can be attached. The footplate is of the orbital type and performs a regular orbital movement.

The footplate of the orbital type can be exchanged with a sanding shoe of the random orbital type. This sanding shoe is not provided with flexible legs which are in contact with the housing. The footplate is hereby free to rotate in a random orbit. A separate brake can optionally be provided when it is necessary to brake the sanding machine in the random orbit position so as to prevent damage to the workpiece for processing. Such braking means, as shown in DE 10142557, are subject to wear.

A machine resembling the above stated hand-held sanding

machine of EP 0 694 365 is known from EP 0 953 407 Al. Placed on the drive shaft is an eccentric (combined with the fan) , on which a bearing is mounted. The base plate is connected to the bearing. Flexible legs are further provided between the housing and the base plate. In this manner the base plate thus performs an orbital movement.

The base plate is otherwise mounted on a second drive shaft using a nut. The second drive shaft is nothing more than the eccentric shaft, around which the bearing is mounted and around which the base plate rotates. The footplate is mounted fixedly on the base plate. There is therefore no possibility of rotation between base plate and footplate during operation.

The object of the present invention is to provide a hand tool, in particular a sanding machine, with an improved drive. For this purpose the hand tool of the above stated type is characterized by a rotation shaft mounted on the base plate, and a first footplate which can be connected to the base plate for rotation around the rotation shaft. Because the rotation movement of the bearing is generated to the base plate by the coupling means, the base plate will begin to perform an orbital movement. Then connecting a footplate rotatably to the base plate will achieve that the footplate will begin to perform a random orbital movement. In this manner the sanding machine can be used as random orbital sanding machine.

Use is advantageously made of the modified drive so that one machine can also be utilized as orbital sanding machine. Provided for this purpose is a second footplate which can be connected to the base plate so as to be rotatable around the rotation shaft, and locking means are provided for locking possible rotation of the second footplate relative to the base plate. The second footplate performs the same movement

as the base plate in that the two are locked relative to each other in the direction of rotation.

The locking means are preferably arranged between base plate and footplate, and adapted to be inactive when the first footplate is connected to the base plate. The locking means preferably form part of the non-exchangeable part of the hand tool, and are only active when the second footplate is mounted on the hand tool.

As stated, the second footplate performs an orbital movement and can preferably be set in different, preferably six, rotation positions relative to the base plate by means of the locking means, which are adapted for this purpose. The footplate can hereby be set and handled with different sides in the direction of the sanding movement. A sheet of sandpaper attached to the footplate can hereby be used up evenly.

According to an embodiment the footplate can be connected to the base plate via an intermediate element. The intermediate element is mounted rotatably around the rotation shaft of the base plate, while the footplate can be mounted interchangeably on the intermediate element. The intermediate element remains connected to the non-exchangeable part of the hand tool. In addition, a circular movement is generated between the base plate and the intermediate element and is transmitted to the footplate in the case the hand tool is used as random orbital sanding machine.

The first bearing is further preferably mounted on an eccentric shaft part connected to the drive shaft. The shaft part can advantageously be integrated with the counterweight. This component can be embodied in simple and inexpensive manner as sintered part or casting. For the purpose of blocking a free rotation movement of the base plate around the base plate of the first bearing, the coupling means are

preferably further formed by flexible legs which extend between the base plate and the housing. The flexible legs ensure that the base plate does not co-rotate with the motor shaft while it is still mounted on an eccentric rotation shaft. The base plate performs an orbital movement.

The footplate further comprises a carrier plate and a foam layer which is carried by the carrier plate and which is provided with a fastening system enabling attachment of a sheet of sandpaper thereto. The fastening system is preferably formed by hooks of the hook-and-loop type of fastening means .

The first footplate is preferably a sanding shoe of the random orbital type, for instance with a round shape, while the second footplate is preferably a sanding shoe of the orbital type, for instance with a triangular shape.

In addition, the invention relates to an assembly of a hand tool and a first and a second footplate, wherein the footplates are exchangeable. A single machine is hereby obtained which can be employed for two different purposes. The invention will be elucidated with reference to the accompanying drawings. In the drawings:

Figure 1 shows a perspective view of a part of a hand tool in the random orbital mode according to a first preferred embodiment; Figure 2 shows a perspective partial view of the hand tool in the orbital mode according to the first preferred embodiment;

Figure 3 shows the configuration of figure 2 with exploded parts; Figures 4-6 show different cross-sections of the configuration of figure 2;

Figures 7-9 shows different cross-sections of the configuration of figure 1;

Figure 10 shows a part of the non-exchangeable part of the hand tool with two exchangeable footplates;

Figure 11 shows a perspective view of a part of a hand tool in the random orbital mode according to a second preferred embodiment;

Figure 12 shows a perspective partial view of the hand tool in the orbital mode according to the second preferred embodiment;

Figure 13 shows the configuration of figure 12 with exploded parts;

Figures 14 and 15 show different cross-sections of the configuration of figure 12;

Figures 16 and 17 show different cross-sections of the configuration of figure 11; and Figure 18 shows a part of the non-exchangeable part of the hand tool with two exchangeable footplates according to the second preferred embodiment of the invention.

Figure 1 shows a part of a sanding machine in random orbital mode. The same sanding machine in orbital mode is shown in figure 2. The same components are designated with the same reference numerals.

Sanding machine 1 (of which only a part is shown in figure 1) comprises a drive with drive shaft 2 and a bearing 3 arranged eccentrically relative to drive shaft 2. Bearing 3 is mounted on drive shaft 2 by means ^■ of an eccentric shaft 4 with counterweight 5. A base plate 6 is connected to bearing 3. Integrated with base plate 6 is a discharge channel 7 which can be coupled to a dust extraction system. Base plate 6 is provided with a rotation shaft 8 (see figure 3) around which an intermediate element 9 is rotatably mounted. A first footplate 10 (figure 1) or second footplate 11 (figure 2) is releasably connected to intermediate element 9. This preferably takes place by means of connecting means adapted

to effect the connection manually. No additional tools are hereby required for the purpose of removing and mounting the relevant footplate. Each footplate consists of a carrier plate 12, 13 respectively, and a foam layer 14, 15 respectively carried by carrier plate 12, 13, wherein foam layer 14, 15 is provided with a fastening system enabling attachment of a sheet of sandpaper 14a, 15a thereto.

The first footplate 10 is a sanding shoe of the random orbital type, in this case with a round shape. The second footplate 11 is a sanding foot of the orbital type, in this case with a triangular shape. As will be elucidated hereinbelow, first footplate 10 is freely rotatable relative to base plate 6 together with intermediate element 9, and this rotation option is also provided in the second footplate 11, but only to allow setting thereof in different discrete positions relative to base plate 6, while the rotation option of footplate 11 together with intermediate element 9 is prevented during operation by locking means.

Coupling means in the form of flexible legs 16 are further arranged between base plate 6 and the housing.

Reference numeral 17 designates a toothed wheel of a gear transmission situated between a motor (not shown) of sanding machine 1 and drive shaft 2. Finally, there are connected to drive shaft 2 two bearings 18, by means of which the assembly shown in figures 1 and 2 is mounted and positioned in a housing of the sanding machine.

Figure 3 shows the different components of the assembly of figure 2. Apart from carrier plate 13 and foam layer 15, the same elements are required for the purpose of forming the assembly according to figure 1. The base of the hand tool is identical, and only footplate 10, 11 has to be changed for the modes of the sanding machine shown in figures 1 and 2. Figure 3 shows the components already mentioned above as well

as the locking means, which can act between base plate 6 on the one hand and footplate 10, 11 on the other. The locking means consist of spring-loaded, protruding locking elements, such as balls 28 in the shown embodiment, which are connected to base plate 6 and which can engage in recesses 19 provided in footplate 11 (see figure 10) . It is also possible for recesses 19 to be arranged in base plate 6 and for balls 28 to be connected to footplate 11. When two balls 28 are applied, six recesses 19 are spread along the periphery, whereby footplate 11 can be locked in a rotation direction in six discrete rotation positions relative to base plate 6. By rotating footplate 11 the user can cause one of the three tips or sides of the sanding shoe to be set in forward sanding direction. During sanding however the balls 28 in recesses 19 ensure that footplate 11 does not rotate relative to base plate 6.

Between rotation shaft 8 of base plate 6 and intermediate element 9 is placed a slide bearing 20 which consists of two rings 21, 22 (see also figure 5) . A retaining ring 23 is further provided. This connects both slide bearing 20 and the locking means in the form of spring-loaded balls 28 to the non-exchangeable part of sanding machine 1. The element 24 designated with reference numeral 24, is provided only for the delta footplate 11 (see also figures 4, 5 and 10). It compensates the difference in weight between the (heavier) round footplate 10 and the delta footplate 11. Compensation element 24 has a protruding edge in which holes 32 are arranged for the purpose of dust extraction. Compensation element 24 drops into an internal hole 25 of base plate 6 and assists in centring and mutual engagement of the connecting means 26, 27 to be described hereinbelow. The round footplate 10 is provided for this purpose with a flanged edge 29 (see figures

7, 8 and 10) . Figure 3 further shows that intermediate ring 9 is provided with protruding connecting protrusions 26 which co-act with keyhole-shaped holes 27 arranged in footplate 10, 11. These connecting means 26, 27 bring about a releasable, bayonet-like connection between the exchangeable sanding shoe 10, 11 on the one hand and intermediate element 9 (or the other part of the sanding machine) on the other. This can also be clearly seen in figures 4, 7 and 10. Protrusions 26 can also be provided on footplate 10, 11, while keyhole- shaped holes 27 are then arranged in the intermediate ring. The advantage of this variant is that in the case of breakage the - vulnerable - protrusions 26 can be replaced in simple and inexpensive manner together with footplate 10, 11. It is otherwise possible to envisage numerous alternative bayonet constructions for the connecting means with which a footplate can be mounted on intermediate element 9.

The sections of figures 4-6 and 7-9 respectively show once again the configurations of figures 1 and 2. A comparison between figures 5 and 8 shows that the locking means are active when second sanding shoe 11 is coupled but not when first sanding shoe 10 is coupled. For this purpose sanding shoe 11 is provided with a protruding edge on which recesses 19 (see figure 10) are situated. Such a protruding edge whereby footplate 11 can come into contact with the locking means is not provided in first sanding foot 10. The locking means are not therefore active here. In the configuration shown in figures 7-9 sanding shoe 10 can therefore be rotated freely about rotation shaft 8 of base plate 6. In another embodiment (not shown) contact is indeed made with the locking means. In such a case the locking elements (for instance balls or pins) can for instance slide over a sliding surface of footplate 11 so that the locking means are

also inactive in this situation.

An alternative to the bayonet construction (26,27) described above with reference to the first embodiment is applied in a second preferred embodiment of the invention as shown in figures 11-18. The same reference numerals are used in these figures for components which are the same or almost the same. Since the construction and operation of the second embodiment moreover largely correspond with those of the first embodiment, a detailed description thereof is omitted. A drawback of vibrating constructions with exchangeable elements is that it has been found difficult in practice to embody such constructions such that they can last long enough in view of the conflicting requirements in tolerance. There must on the one hand not be too much play so as to ensure a good operation of the machine, while on the other hand play must be present in order to enable easy mounting of the footplates .

In a second preferred embodiment the connecting means for connecting intermediate element 69 to a respective footplate 40, 41 comprise a number of standing connecting protrusions 70 provided on the respective carrier plate 72,73. Two protrusions are preferably provided, although the application of a single protrusion or of more than two protrusions is also a possibility. In the embodiment shown in figure 18 the connecting protrusions 70 provided on carrier plate 72,73 of the respective footplates 41,40 are arranged on one side of the footplate. On the opposite side, footplate 40,41 is provided with a recess 43 with a shape substantially corresponding with the shape of a slide switch 52 provided on intermediate element 69. Further arranged in recess 43 is a fastening element 48, consisting of an upright wall 45 to which a lip is fixed.

Intermediate element 69 is in turn provided with a

number of apertures 42 at positions on intermediate element 69 corresponding with the positions of protrusions 70. Apertures 42 are formed such that standing protrusions 70 can engage therein. The above mentioned slide element 52 is arranged opposite the two apertures 42. Slide element 52 is provided with a loop-like element 50, the function of which will be elucidated below. Slide element 52 is herein arranged such that it can slide backward and forward (direction P) . The slide element or slide switch 52 is further arranged under spring force (using a compression spring 55, figures 14-17), this spring force ensuring that slide switch 52 is pushed forward. Two resilient legs 53 are further formed on slide element 52, these legs remaining hooked behind an elevation 54 after assembly. Slide element 52 is urged by the action of the spring to an extreme front position, also referred to as starting position, in which position legs 53 rest against elevation 54.

When the intermediate element is mounted on the footplate, connecting protrusions 70 are placed in the corresponding apertures 42, slide switch 52 is pushed rearward counter to the spring action so that the loop-like element 50 is positioned such that it can be slid over fastening element 48 of footplate 40, 41. Once slide switch 52 has been released, it is returned to the starting position by the action of spring 55. In this situation the loop-like element 50 hooks behind fastening element 48, thus creating a strong locking. Spring 55 and slide element 52 ensure that the play is pressed out of the construction so that the conflicting requirements of play for the purpose of assembly and tight fit during use can be satisfied.

A further difference from the first embodiment already described above is that, in the second embodiment, footplate 40, 41 is blocked in the rotation direction generated by the

machine in use, but is left free in the opposite direction, whereby the user is able to set one of the preferred positions. This is shown in more detail in figures 13-18.

Figures 13 and 18 show locking means which can act between base plate 6 on the one hand and footplate 40,41 on the other of sanding machine 31. The locking means consist of spring-loaded pins 68 which are connected to base plate 6 and can engage in recesses 79 provided in footplate 41. It is also possible for recesses 79 to be arranged in base plate 6 and for pins 68, or other protruding locking elements, to be connected to footplate 41. For two pins 68 six recesses 79 are distributed over the periphery, whereby footplate 41 can be locked in rotational direction in six discrete rotation positions relative to base plate 6. Compared to the above mentioned recesses 19 according to the first embodiment, recesses 79 have an elongate form. The depth of an elongate recess increases in one direction from a part 80 with a minimal depth, until a part 81 with a maximum depth is reached. This means that pins 68 under spring force can be placed in the locked position in a first direction in simple manner by rotating the footplate, in which position the pins 68 are positioned in the part with the greatest depth. Footplate 41 also remains locked in this position when machine 31 is set into operation. It is however also possible in this embodiment to unlock the footplate by rotation in a second, opposite direction, so that a different preferred position of the footplate can be set relatively easily.

In the second embodiment balls 28 are otherwise replaced by pins 68, which can protrude further outside the retaining ring. The pins can control the associated springs better than the balls, thereby simplifying assembly. The chance of balls bouncing out during assembly is hereby reduced, and assembly can be carried out with less caution. It is apparent that the

application of pins is not limited to the second embodiment, but that the first embodiment and other random embodiments can also be provided with such pins.

The exemplary embodiment shows that two types of sanders can be obtained with a simple drive, wherein only the footplate has to be exchanged in order to have the sander function in an orbital or random orbital mode.