The present invention relates to portable, electrically driven equipment for mechanical machining and preferably equipment for driving dental tools.

Equipment of the above type is known, for example from DE-C2- 31 22 065 and DE-C2-31 22 062 which are hereby incorporated by reference into the present specification. The equipment comprises a housing which encases a power supply and a motor. A plug outlet is arranged at the bottom of the housing for charging the power supply, so that the power supply may be connected with and thus be charged from an external power supply, for example the mains via a transformer and a rectifier. The known equipment is limited to a relatively short and/or physically restricted use - with regard to power, effect or energy - owing to a limited electrical capacity or energy amount.

Equipment of the above type is also known from US-A-3,450,908, DE- B2-25 29 277, US-A- ,455,466, and US-A-3,548,134 which are also incorporated by reference into the present specification.

The object of the present invention is to provide equipment which overcomes a number of disadvantages in the known equipment.

The invention accordingly provides portable, electric equipment for dental use and comprising a tool part and one or more battery parts, which tool part, together with a battery part, when they are assembled, forms a manual apparatus for mechanical machining, and a recharging device for recharging one or more of the battery parts when separated from the tool part and received in the recharging device.

Thus, equipment is obtained in which one battery part may be used for driving the tool part while another corresponding battery part may be recharged in the recharging device so that mechanical machining operations may be carried out continuously.

In the preferred embodiment of the equipment according to the the equipment comprises one tool part, at least four

battery parts and a recharging device with four receiving parts for receiving four corresponding battery parts. This renders it possible generally always to have the required energy capacity available.

In the present invention it is advantageous that the tool part and the battery part of the equipment in an assembled condition are mutually rotatable and mutually separable,

- that the tool part comprises a housing, an electric motor which is mounted in the housing and has a shaft projecting from the housing, and which brings the shaft to rotate by supply of electrical energy, and at least one set of electric connecting means for supply of electrical energy to the motor,

- that the battery part comprises a housing, rechargeable battery means contained in the housing of the battery part, and at least one set of connecting means which are connected to respective poles of the battery means, and which are adapted to be connected to said set of connecting means of the tool part for establishing an electrical connection between the rechargeable battery means of the battery part and the electric motor of the tool part,

- that the tool part and the battery part in an assembled condition are adapted to establish electrical connection between the rechargeable battery means of the battery part and the electric motor of the tool part via the connecting means of the battery part and the connecting means of the tool part by mutual rotation from a neutral position, in which the electrical connection between the connecting means of the battery part and the connecting means of the tool part is interrupted, in a first direction into a first active position for transmission of electrical energy from the battery means to the electric motor in such a manner that the motor brings the shaft to rotate in a first rotational direction, - that the tool part and the battery part in an assembled condition are adapted to establish electrical connection between the rechargeable battery means of the battery part and the electric motor of the tool part via the connecting means of the battery part and the connecting means of the tool part by mutual rotation from said neutral position in a direction opposite to said first direction into a second active position for transmission of electrical energy from the batterv means to the electric motor in such a manner that

the motor brings the shaft to rotate in a direction opposite to said first rotational direction, and

- that the connecting means of the battery part are further adapted to establish connection to contact means on the recharging device for transmission of charging currect from the device to the rechargeable battery means, when the battery part is separated from the tool part and received in the recharging device.

Accordingly, a very simple and easily controlled reversal of the rotational direction of the motor is obtained, and it is also simple and easy to cut off the current to the motor in a well-defined neutral position between the two active positions.

It is further an advantageous feature of the present invention that the connecting means of the tool part and the connecting means of the battery part constitute two electric switches, of which the first one, when the tool part and the battery part are rotated in relation to each other to said first position, establishes a current path from the battery means in a first direction through the electric motor, of which the second one, when the tool part and the battery part are rotated in relation to each other to said second position, establishes a current path from the battery means in a second direction through the electric motor opposite to said first direction, and which, when the two parts of the housing are in said neutral position, interrupt the current paths from the battery means to the electric motor.

In a preferred embodiment of the equipment according to the invention the connecting means of the equipment comprise two terminals which are exposed on an outer surface of the housing of the battery part, and the connecting means of the tool part comprise two sets of contact terminals which are exposed on the tool part, and which are adapted to co-operate with said terminals.

In the portable electric equipment according to the invention, the housing of the battery part advantageously comprises a substantially straight, cylindrical, projecting insertion part or male part on which said terminals are exposed, and the housing of the tool part

comprises a receiving part or female part which is substantially complementary to the said insertion part and cooperates therewith, and in which said sets of contact terminals are exposed. Further, the terminals are exposed on a substantially plane surface of the substantially straight, cylindrical, projecting insertion part, and the sets of contact terminals are exposed on a substantially plane surface of the receiving part. This renders it possible to obtain a very small and compact structure where the housing may be shaped as a straight circular cylinder without projecting parts, which is suitable for hygienic and aesthetic reasons, and with regard to its use.

In the preferred embodiment the said terminals are arranged in a circular arc on said substantially plane surface of the insertion part, which circular arc has its centre positioned on the rotational axis of the insertion part. When the terminals and/or the contact terminals are spring-biased, a reliable energy transmission is obtained with long intervals between cleaning of the terminals, even under disadvantageous conditions. To avoid shortcircuiting between the terminals when cleaning is carried out with electrically conductive equipment, for example a steel brush or a file, a cam of a non-conductive material, for example plastic, projecting from the substantially plane surface of the insertion part may be provided, which cam preferably encloses at least part of at least one of the terminals.

To achieve a rapid and accurate assembly and fixation in the axial direction of the tool part and the battery part, these parts may suitably be adapted to be assembled by means of a bayonet joint. Such a joint may particularly suitably be combined with a fixation in a radial direction when the battery part is adapted to be rotatably retained in relation to the tool part by means of a spring-biased ball which is received in an axial bore in the housing of the tool part or of the battery-part, and which is adapted to co-operate with a channel, a groove or a track in the other housing.

In the preferred embodiment of the portable, electric equipment according to the -invention the equipment comprises two types of

battery parts with different power capacities and/or different requirements to the charging current, and the recharging device and the battery parts comprise co-operating coding means to permit recharging of one type of battery parts and to prevent recharging of another type of battery part in one type of receiving part in the recharging device. This renders it possible to use one and the same recharging device for two different battery parts without any risk of destroying the type of battery parts with the lower power capacity, and this also ensures that the type of battery parts with the higher power capacity may be recharged at the maximum charging current.

In a preferred embodiment of the equipment according to the invention this security is obtained by providing the first type of battery part with a first pin projecting from the substantially plane surface of the insertion part, and providing the second type of battery part with a second pin projecting from the opposite, substantially plane surface of the insertion part, and providing the tool part with two recesses corresponding to the first and second pins, respectively. The receiving parts of the recharging device and the receiving part of the tool part are thus substantially similar. They may therefore suitably be produced in the same manner, but providing the receiving part of the tool part with two recesses, while providing the receiving parts of the recharging device with one recess.

The invention also relates to a hand tool for mechanical machining, preferably for dental use, and comprising a tool part and a battery part of the above type. The invention further relates to a tool part of the above type, a battery part of the above type and a recharging device of the above type.

The invention also relates to an apparatus for driving dental tools, and comprising a housing, a coupling part arranged at a coupling end of the housing and comprising a cylindrical tubular part which projects from the housing and has an outer diameter of about 10 mm for connection to the dental tool, which coupling part has a plane, annular surface at the root of the tubular part, a motor mounted in the housing and a ratchet-shaped rotation transmission means which is coupled to the motor and projects from the housing into the tubular

part for transmission of rotation from the motor to the dental tool. Known equipment of the above kind can only be used in the Intra system prevailing in Europe, which restricts the possibilities of a geographical distribution of the equipment and simultaneously restricts the possibilities of a free choice between different types of tools in the market. The apparatus according to the invention eliminates this restriction in the prior art, as an annular groove is defined at the root of the tubular part in the coupling part of the apparatus according to the invention. The apparatus may suitably be formed in such a manner that the total length of the tubular part is a maximum of 28 mm, that the height of the tubular part over said plane, annular surface is a maximum of 25.5 mm, that the depth of the grooves is at least about 2 mm, at the most about 8 mm, and preferably about 5 mm, and that the outer diameter of the grooves is at least 14 mm and preferably about 15 mm, and preferably in such a manner that the distance from said annular surface to an edge of the ratchet-shaped rotation transmission means projecting farthest into the tubular part is a maximum of 11 mm and a minimum of 4 mm, and preferably less than 7.5 mm and more than 4.5 mm, and that the distance from the bottom of said groove to the edge of the ratchet- shaped rotation transmission means projecting farthest into the tubular part is a maximum of 19 mm and a minimum of 9 mm and preferably less than 13.5 mm and more than 11 mm. These structural measures render it possible for the apparatus to be used for dental tools of both the Intra type prevailing in Europe and the Mid-West type used in the U.S.A., and for the assembly between the apparatus and said dental tool to be carried out easily and without complications and with a reliable transmission of rotation. By forming the said annular surface with an outer diameter of between 20 and 28 mm and preferably of about 21 mm a hygienic and aesthetic transition of good applicability between the apparatus and dental tools of the Intra type, and good transition between the apparatus and a dental tool of the Mid-West type is obtained when the lower part of the cross-section of the groove is substantially congruent with the cross-section of a flange on a coupling part of such a tool.

The tubular part may suitably be slotted so that the tubular part may retain the dental tool securely by using the elastic effect of the

slot, and locking means may further be provided in the periphery of the upper part of the annular groove if an even better fixation of the tool is desired.

The coupling part may suitably be detachably mounted on the apparatus, whereby it may easily and simply be replaced by couplings for other tools, for example of the Star type and/or gears for changing the gear ratio between the motor and a tool.

The present invention further relates to an electric or electronic apparatus comprising a housing having a top side and a bottom side, with which the apparatus is arranged on a supporting surface, for example a floor, and comprising an electric switch on or in the housing and preferably projecting from it. The apparatus according to the invention is characterized in that the electric switch is a push button switch which is mounted on the bottom side of the housing of the apparatus and projects therefrom, that the apparatus comprises elastically deformable supporting means, for example one or more pads or feet of an elastically deformable material, preferably plastic, foam plastic or the like, which project from the bottom side, and that the supporting means are of such an elasticity that they may be deformed elastically by applying a pressure to the top side of the housing of the apparatus for actuation of the push button switch by bringing the push button switch into connection with said supporting surface.

Contrary to the known electric or electronic apparatus with electric switches , possibly electric push button switches mounted on the front or back plate of the housing or on a top plate of the housing, the push button switch is mounted in accordance with the invention projecting from the bottom side of the housing of the apparatus. This position and further the form of the elastically deformable supporting means characteristic of the invention achieve partly a mechanical protection of the push button switch when it is mounted projecting from the bottom side of the housing of the apparatus, partly a comfortable operation of the push button switch as pressure may be applied to the top side of the housing of the apparatus from above, for example by foot or by hand, according to the position of

the apparatus. The prerequisite for a correct actuation of the push button switch is thus merely that pressure is applied to the top side of the housing of the apparatus, which pressure must be sufficient for actuation of the push button switch and at the same time sufficient for elastic deformation of the supporting means. It is thus not necessary that a pressure be applied to the push button switch itself for actuation thereof. A well-known situation is thus that a dental drill has to be actuated simultaneously with the dentist holding the drill having all his attention directed to a critical positioning of the drill and possibly other instruments in a patient's mouth. Until now, the prerequisite for turning on or off the dental drill has been that the dentist In this situation would be able to actuate a push button switch mounted in a foot pedal. In the same situation, but with the structure of the electric or electronic apparatus characteristic of the invention an actuation of the switch of the dental drill mounted in the apparatus can be effected safely and reliably by the dentist merely stepping on the top side of the apparatus. As long as the pressure applied to the top side of the upper side of the housing is located within the supporting surface defined by the deformable supporting means and Is of a dimension which Is sufficient to overcome the actuation pressure of the push button switch and at the same time deform the elastically deformable supporting means, an actuation of the push button switch will be effected.

To ensure that even a pressure supplied to the periphery of the top side of the housing of the apparatus at the periphery of the top side will effect an actuation of the push button switch, It is preferred that the push button switch is mounted below the centre of mass of the apparatus or most often mounted centrally on the bottom side of the housing of the apparatus.

The supporting means characteristic of the invention may suitably form a closed ring encircling the push button switch and consequently enclosing it, or form an annular ribbon of an elastically deformable material projecting from the bottom side of the housing of the apparatus. This ribbon encircling the push button switch affords a further mechanical protection of the push button switch and further

protects the push button switch from dust and dirt which is collected by said ribbon. Therefore, this ribbon of an elastically deformable material will become dirty and unhygienic in time, for which reason it is preferred that the supporting means are mounted detachably on the bottom side of the housing of the apparatus, preferably by means of VELCRO-type locking means. To ensure that the push button switch is actuated even in the case where the apparatus is placed on a soft base, for example on a floor carpet or on the ground, it is preferred that a plate, for example a metal or plastic plate, is inserted in the supporting means and below the push button switch.

By providing the supporting means as detachable supporting means the apparatus according to the invention may alternatively be used as a conventional apparatus per se with the push button switch mounted in a front, side or back plate or a top plate of the housing of the apparatus when the apparatus is turned and arranged with the bottom side of the apparatus housing forming one of said sides. For this alternative use, the apparatus may suitably be adapted to be placed for example in a pocket or in a belt where the push button switch may be operated as a conventional push button switch, when the supporting means are removed from the bottom side. In the preferred embodiment of the apparatus according to the invention, this is a supply apparatus for supplying a dental drill. However, the apparatus according to the invention may be used for numerous other applications and contain any electric or electronic means and further be adapted to be connected to other equipment. Thus, the apparatus preferably comprises one or more electric connecting means, preferably of a locking type, for transmission of electrical current to or from the apparatus, and the apparatus may also comprise means for adjusting the power or voltage of the electrical current supplied or received. The apparatus according to the invention may generally advantageously be used as a foot switch for turning on and off a connected apparatus, for example a tool, and thus constitutes an alternative to the foot switches with built-in push button switches on the market at present. Alternatively, the apparatus may, for example, comprise a wireless sender or receiver for emission or reception of signals, the apparatus in this version advantageously

comprising RF (radio frequency), especially microwave, ultrasound or infrared transmission means.

The Invention will now be explained in detail with reference to the drawing, in which ' Fig. 1 is a perspective view of a first embodiment of a hand apparatus according to the invention with a dentist tool mounted thereon,

Fig. 2 shows a part of the embodiment shown in Fig. 1,

Fig. 3 shows another part of the embodiment shown In Figs. 1 and 2, Fig. 4 shows a detail in the joint between the two said parts,

Fig. 5 is a cross-sectional view of the embodiment shown in Figs. 2 and 3, with cross-sections in several planes,

Fig. 6 schematically shows the function of the apparatus of Figs. 1-

5, Fig. 7 is a detailed view of an embodiment of the apparatus according to the invention and shown in Fig. 6,

Fig. 8 shows a recharging device according to the invention,

Fig. 9 shows a recharging device according to the Invention with a battery part mounted therein, Figs. 10 to 12 show embodiments of a coupling between the apparatus shown in Fig. 1 and three different types of dental tools, Intra system, Mid-West system and Star system, respectively, and

Fig. 13 shows an embodiment of an apparatus according to the invention.

Fig. 1 shows an apparatus according to the invention and comprising a housing having two parts 11 and 12 which are mutually rotatable. The two parts 11 and 12 may easily be separated by overcoming a small retaining force. The housing further comprises a coupling part 13 on which a dental tool 14 is mounted.

Fig. 2 shows one part 11 defining a circular cylindrical chamber which may receive three electrical battery elements 15 which are received in a battery holder 10 which may be retained by means of an external thread In a corresponding internal thread in the part 11. The battery holder 10 and thus the housing part 11 have an insertion part 16. This part 16 comprises three electrical terminals of which

two terminals 17 - in Fig. 2 the two upper ones - have one polarity and may possibly be integrally formed, and of which one terminal 18 - in Fig. 2 the bottom terminal - has the opposite polarity.

Fig. 3 shows the parts 12, 13 and 14. The part 12 has a receiving part 20 for co-operation with the insertion part 16 shown in Fig. 2, in which receiving part four contact terminals 21 with connecting wires 22 to a motor 23 mounted in the part 13 are embedded. The part 12 is retained in the coupling part 13 by means of a threaded joint.

The motor 23 which comprises a ratchet-shaped rotation transmission means 24 for transmitting rotation from the motor to the dental tool 14 is screwed on to the coupling part 13 by means of two screws 25. The coupling part 13 further comprises a cylindrical tubular part 26 projecting from the housing, for coupling of the dental tool 14.

The connection between the part 10 retained in the part 11 and the part 12 is shown schematically in Fig. 4. It appears from Fig. 4 that the insertion part 16 of the part 10 comprises four spring-biased balls 27 which are adapted to be received in a groove 28 in the receiving part 20 for fixation of the two parts 10 and 12 in the axial direction. The part 12 further defines three axial grooves 30 in which a spring-biased ball 29 mounted on the insertion part 16 may be received so that the parts 10 and 12 may be fixed or retained in desired relative rotational positions corresponding to a neutral position and two different active positions.

A projecting pin 31 is further provided on a cam 19 of the insertion part 16, which pin is adapted to guide the insertion part 16 in relation to the receiving part 20 by engagement in a guide groove 33 in the receiving part 12.

From Fig. 5 it appears that the terminals 17, 18 establish a connection with two of 'the four contact terminals 21 when the parts 11 and 12 are connected and when these parts or the part 10 and the part 12 are mutually rotated. The contact terminals are spring- biased by springs 32, which ensures, together with the engagement of

the ball 29 in one of the grooves 30, that good electrical contact is obtained between the terminals 17, 18 and the contact terminals 21.

The contact principle is schematically illustrated in Fig. 6, and it appears clearly from the Figure how the current to the motor 23 may be interrupted and reversed.

Fig. 7 shows a special embodiment of the cam 19, on which projections 35 have been formed between the terminals 17 and 18 in such a manner that the risk of short-circuiting the terminals is minimized.

Fig. 8 shows an embodiment of a recharging device according to the invention. The recharging device or the recharger 70 comprises a housing 71 on the upper side 72 of which a number of recharging cells are formed. In three of these recharging cells, three battery parts 73, 74 and 75 are shown. Two of the battery parts 73 and 74 are adapted to receive a relatively high charging current while the third battery part 75 is adapted to receive a relatively lower charging current. The design of a recharging cell is also illustrated in the Figure. Such a recharging cell Is designated by reference numeral 77, and it appears that the recharging cell 77 comprises a receiving part 78 which substantially corresponds to the receiving part for the part 12 shown in Figs. 2 and 3 and being designated by numeral 20. Thus, the receiving part comprises a guide groove 79 (corresponding to the guide groove 33) and a groove 80 (corresponding to the groove 28) for receiving the four spring-biased balls 27 on the insertion part 16 of the part 10 for fixation of such a part in the receiving part 78. The recharger further comprises on one side 82 thereof a switch 83 and a control light 84. The recharger may be supplied with a suitable charging current from an DC source, such as a car battery or a solar battery, but in the embodiment shown the recharger may be connected to the mains via a wire 85 and a plug 86. The recharger shown thus comprises transformer means and rectifiers to obtain the desired charging currents. The apparatus shown may further comprise an electronic circuit for controlling for example the charging time or for controlling a rapid charging function.

Fig. 9 shows part of a receiving part 49 for a recharger according to the invention, in which recharger a battery part is mounted having an insertion part comprising a cam 19. This is to illustrate how battery elements are safeguarded against the supply of too high a charging current when one and the same recharger is used for recharging battery elements of different capacities contained in otherwise compatible housings. In the recharger a V-shaped notch 64 is formed in which two sets of charging terminals 65 and 66 are provided, from which charging currents of different powers are supplied. The charging current provided by the terminals 66 is thus higher than the charging current supplied from the terminals 65. A battery part containing rechargeable batteries which can only tolerate the low charging current supplied from the terminals 65 thus has a pin 36 which projects from the cam 19 and prevents the terminals 17 and 18 from being brought into contact with the charging terminals 66 which supply the high charging current. Conversely, a battery part containing rechargeable batteries adapted for a higher charging current will be provided with a projecting pin 36' ensuring that the terminals of such a battery part can only obtain a fixed active position in the recharger when the terminals are brought into connection with the charging terminals 66.

Figs. 10 and 11 show a special embodiment of the coupling part 13 which has a tubular part 26. For abutment of the bottom side of a dental tool 14 of the Intra type (shown in Fig. 10) a plane, annular surface 42 is formed at the upper side of the coupling part. The tubular part 26 has slots 38 at its upper end so that the tubular part may securely retain the dental tool by exploiting the spring action of the slotting. At the root of the tubular part 26 is formed an annular groove 41 which, in cross-sectional view, is congruent with a flange 44 of a dental tool 39 of the Mid West type (shown in

Fig. 11). The ratchet-shaped rotation transmission means 24 (shown in Fig. 3) may thus transmit rotation to both said types of dental tools .

The coupling part 13 is preferably detachable and may thus for example be replaced by a coupling part of the type shown in Fig. 12 comprising a coupling 45 so that the apparatus may be used for

transmission of rotation for a dental tool 40 of the Star type. This coupling 45 has a shaft means 46 for transmission of rotation from the ratchet-shaped rotation transmission means 24 to a toothed shaft part on the Star tool 40. A bearing part 47 is mounted around the shaft means 46, and the coupling 45 may be fastened to the coupling part 13 by means of a threaded joint 48.

The coupling part 13 may also be replaced by a coupling part comprising a gear part for changing the gear ratio between the motor 23 and a tool.

Fig. 13 shows an apparatus with a dental tool 14 mounted thereon. The apparatus is connected to a power supply contained In a housing 50 via a wire 61 and two plugs 62 and 63, of which the plug 62 is adapted to cooperate with a socket 59 In the housing 50 for transmission of current from the power supply contained in the housing 50 to the motor of the apparatus. The housing 50 of the power supply has a top side 51 and a bottom side 52 from which an electrical push button switch projects. A pad 56 of an elastically deformable material, for example foam rubber, may be fastened to the bottom side 52 of the housing 50 by means of VELCRO-type locking means. A metal plate 58 is laid Into the pad 56, which plate abuts the switch 53 when the pad is fastened to the bottom side 52 of the housing. The housing 50 also comprises a socket 60 of a standardized and locking type for transmission of current from an external supply source, such as a charging apparatus, to the source of current or supply comprised In the housing 50 and preferably constituted by rechargeable batteries, such as Ni-Cd-batteries.

On the bottom side the apparatus may further be provided with switches for, for example, adjustment up and down of the speed of the dental tool.

The design of the power supply 50 may also be used for other apparatuses.