GB1561227A

GB1561227A - Dental handpiece

Info

Publication number: GB1561227A
Application number: GB633977A
Authority: GB
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1976-02-16
Filing date: 1977-02-15
Publication date: 1980-02-13
Also published as: FR2340716B1; CH613109A5; IT1084908B; BR7700826A; ATA930976A; AT350174B; FR2340716A1; DE2606062A1; JPS5299692A

Abstract

It has a drive part (1) which can be connected via a connection armature (2) to a supply pipe (3) and in which a drive motor is arranged. A grip part (5) can be coupled to the drive part (1) and can be turned relative to the latter, which grip part has at its free end a head part (6) with a tool (7). In order to transfer a coolant from the supply pipe (3) to the head part (6) of the handpiece, corresponding coolant conduit sections (30, 24) are present in the said handpiece parts. An intermediate piece (4) can additionally be introduced between drive part (1) and grip part (5), which intermediate piece (4) can be coupled to one of the two handpiece parts (1, 5) in such a way that it cannot be turned and it can be coupled to the other handpiece part in such a way that it can be turned, and it has a further conduit section (11) for the coolant, and coupling members (10, 29) which, in the coupled state, engage in matching counter-members (9, 26) of the drive part (1) or the connection armature (2) on the one hand and of the grip part (5) on the other hand and connect the coolant conduit sections (30, 28, 27) of drive part (1) or connection armature (2) and grip part (5) to one another. The invention is proposed in particular for dental handpieces with a miniature motorized drive in the handpiece. <IMAGE>

Description

(54) A DENTAL HANDPIECE (71) We, SIEMENS AKTIENGESELLSCHAFT, a German company, of Berlin and Munich, Germany.

do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a dental handpiece.

Known handpieces comprise:- a drive section, which is attachable to a supply hose via a connector with a drive motor being disposed in the housing of the drive section; a grip section, which may be coupled to the drive section and may be rotated relative to the drive section; a head section with a working instrument at its free end; and coolant line sections for at least one coolant, running from the supply hose to the head section of the handpiece. In the known handpieces of this type the coolants (air and/or water) required for cooling the treatment site are conveyed to the head section of the handpiece via flexible hose lines which run externally along the handpiece.

The hose lines generally have a certain surplus length which enables the grip section (known as "hand and angle pieces") to rotate relative to the drive section without overstretching the hose lines. This type of arrangement with an exposed routing of the coolant line does have certain drawbacks; in particular, the exposed hose is in the way when the handpiece is manipulated.

Incorporating the coolant lines in the handpiece has already been suggested, i.e.

disposing them inside the handpiece at least within the region where the drive section is coupled to a grip section, in such a manner that the coolant line sections are joined together when the grip section is mounted on the drive section. Rotatability of the grip section relative to the drive section was produced by the arrangement of suitably sealed annular channels.

The last-mentioned suggestion of incorporating the coolant lines in the various sections of the handpiece however requires not only grip sections of a new design but also new drive sections and connectors.

According to one aspect of the present invention, there is provided a dental handpiece in assembled or dismantled form and comprising:- a drive section which has a housing in which is disposed a drive motor; a grip section which is or can be coupled at one end to the drive section and is adapted to be rotated relative thereto; a head section attached or attachable to the other end of the grip section; and an intermediate member located or locatable between and/or around the drive and grip sections, which intermediate member is or is adapted to be coupled rotatably or non-rotatably to one of the drive and grip sections and is or is adapted to be coupled rotatably to the other, the intermediate member including coupling members engaging or engageable with (when the intermediate member is located between and/or around the drive and grip sections) at least one matching counter member of the drive section on one side of the intermediate member and at least one matching counter member of the grip section on the other side of the intermediate member, which coupling and counter members form part of at least one coolant line extending the lengths of the drive and grip sections to the head section.

According to another aspect of the present invention, there is provided a dental handpiece in assembled or dismantled form and comprising:- a connector; a drive section which is attachable in use to a supply hose via the connector, and which has a housing in which is disposed a drive motor; a grip section which is or can be coupled at one end to the drive section and is adapted to be rotated relative thereto; a head section attached or attachable to the other end of the grip section; and an intermediate member located or locatable between and/or around the drive and grip sections, which intermediate member is or is adapted to be coupled rotatably or non-rotatably to one of the drive and grip sections and is or is adapted to be coupled rotatably to the other, the intermediate member including coupling members engaging or engageable with (when the intermediate member is located between and/or around the drive and grip sections) at least one matching counter member of the drive section or the connector on one side of the intermediate member and at least one matching counter member of the grip section on the other side of the intermediate member, which coupling and counter members form part of at least one coolant line extending the lengths of the drive and grip sections to the head section.

Conveniently, the intermediate member is in the form of a sleeve which is or may be coupled to the drive and grip sections, the intermediate member enclosing that end region of the grip section which faces the drive section.

In such a case, conveniently, when the intermediate member is coupled to the drive and grip sections, the drive section abuts the grip section.

Also in that case, preferably when the intermediate member is coupled to the drive section, the intermediate member overlaps at least part of the housing of the drive section.

In one embodiment of the handpiece according to the present invention that part of at least one coolant line extending substantially the length of the intermediate member is in the form of a guide duct communicating with a coupling member in the form of a plug, which plus is connectible with a counter member in the form of a bore located in the connector (when present) or in the drive section.

In this case, conveniently that part of the coolant line between the guide duct and the plug is flexible.

Also conveniently, the bore opens radially.

In one possible arrangement, at least part of the guide duct is disposed in that part of the intermediate member which can overlap the housing.

Conveniently, in this case, the guide duct is in the form of a bore, running essentially paraxially in the overlapping part of the intermediate member.

Alternatively, the overlapping part of the intermediate member is provided with a paraxial groove for accommodating part of the coolant line.

In one particular embodiment of the handpiece according to the present invention, the overlapping part of the intermediate member, when coupled to the drive section, encloses the drive section eccentrically.

In an alternative embodiment of the present invention, part of at least one coolant line is disposed within the limits of the drive section in a paraxially extending cavity of the drive section, the or each coolant line part terminating in a counter member intended to be connected to one of the coupling members of the intermediate member.

In practice, generally disposed in the connector (when present) or in the drive section is a supply socket for a coolant which socket opens radially, in which socket a plug connected to a further coolant line extending over the length of the drive section may be inserted.

Conveniently, the or each coolant line part is disposed in a space between the housing and the motor.

Alternatively the or each coolant line part is disposed in a paraxial groove on the inner or outer face of the housing.

Conveniently, the motor is an electric motor having a stator and a rotor, and the or each coolant line part is disposed in a paraxial groove in an external part of the stator.

Preferably the or each coolant line part is formed by a small tube disposed in said cavity or in the said paraxial groove.

In such a case, the or each small tube is a component part of the connector (when present) or of the intermediate member and, when the connector and drive section are connected together or the intermediate member and the drive section are connected together, the or each small tube extends through the said cavity or the said paraxial groove in the drive section.

In a further embodiment of the handpiece according to the present invention, the or each coolant line part within the drive section terminates, in the region of that face of the drive section facing the grip section, in a counter memberin the form of a bore or a projection, the matching coupling member of the intermediate member being a projec- - tion or bore, respectively.

In use, the head section is provided with a working instrument.

Preferably, the intermediate member is non-rotatably mountable with respect to the drive section.

Preferably part of the intermediate member is provided with at least one annular channel for allowing supply of coolant during relative rotation between the drive section and the grip section.

Thus the present invention-relates to a modification of the dental handpiece of the type stated previously, in which, without having to make any alterations, or any significant alternations, to the drive section, it is possible to couple grip sections with incorporated line routing to drive sections, which were previously only suitable for coupling to grip sections with exposed coolant line routing. The alterations which might have to be made should be such that drive sections already on the market can be adapted without major technical difficulties or expense; thus the drive sections with the advantages of incorporated coolant routing may be used as required.The prerequisite is that the practitioner is able to continue to use the earlier grip sections; the reason for this, particularly, is that for certain types of work no coolant is needed at all at the head section of the handpiece; for these types of work he can then use the grip sections of the old design which are provided for exposed coolant line routing. To do this he need merely remove the coolant hose from the connection piece at the head section.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a side view of one embodiment of a dental handpiece according to one aspect of the present invention complete with an attached supply hose; Figure 2 is an axial section through an intermediate member constituting part of the embodiment shown in Figure 1; Figure 3 shows, partly as a side view and partly as an axial section, a portion of another embodiment of the present invention; Figure 4 is a cross-section taken along the line IV - IV in Figure 3, of the intermediate member and a conduit disposed therein; Figure 5 is a cross-section through an embodiment which is a modification of the embodiment shown in Figure 4;; Figure 6 is an axial section through a drive section and associated connector of one embodiment of another aspect of the present invention; Figure 7 shows, partly as a side view and partly as an axial section, a portion of the drive section shown in Figure 6 with the intermediate member and part of the grip section in the uncoupled state; Figure 8 shows a cross-section through an arrangement in which two conduits are located in an outwardly facing recess in the housing of the motor within the drive section; and Figure 9 shows a cross-section through an arrangement in which two conduits are disposed in a recess within the stator of a motor within the drive section.

Figure 1 shows a dental handpiece which includes a drive section 1 in which a drive motor (driven by electricity or air, but not shown) is disposed in a generally cylindrical housing. Coupled to the rearward end of the drive section 1 is a connector in the form of a connection fitting 2 fitted to a supply hose 3, and coupled to the forward end of the drive section l is an intermediate member 4 and a grip section 5. At the forward end of the grip section 5 is an angular head section 6 on which a working instrument 7 (e.g. a drill) is rotatably mounted, the instrument 7 being driven by the drive motor disposed in the interior of the drive section 1, via suitably designed drive shafts (not shown in Figure 1).The intermediate member 4 disposed between the grip section 5 and the drive section 1 may be removed easily both from the drive section 1 and from the grip section 5. The grip section 5, furthermore, is freely rotatable relative to the drive section 1 and, when connected to the drive section 1, it may be secured against axial displacement by means of a coupling device, (not shown in Figure 1). The supply hose 3 contains the necessary supply lines for the drive and also for at least one coolant (air and/or water) for the instrument 7. In the coupled state the connection fitting 2, the drive section 1 and the grip section 5 further contain lengths of coolant line joined together for conveying the coolant(s) to the head section 6 of the handpiece.That part of the coolant line which terminates in the region of instrument 7 and runs along the head section 6 is visible from the exterior and is denoted by the reference number 8 in Figure 1. A supply socket 9 is provided in the connection fitting 2, as is shown in more detail in Figure 3. Into the socket 9 may be inserted a plug 10, connected by means of a conduit in the form of a flexible hose 11 to the intermediate member 4.

Figure 2 shows details of the intermediate member 4. It comprises a body in the form of a sleeve, the internal diameter of which corresponds to the external diameter of the rear end of the grip secton 5.

At the rear end, indicated by the reference numeral 14, of the intermediate member 4 the internal diameter is increased to define an annular recess 12 with a face 13 between the two parts of different internal diameter. In that part of the member 4 with smaller internal diameter is an annular groove 15 communicating with a guide conduit 16 having a radial portion leading to a paraxial portion terminating in a connection nipple 17 on which the flexible hose 11 is secured. The diameter of the recess 12 corresponds to the external diameter of the drive section 1. The forward end of the drive section 1 is located in the recess 12 and abuts face 13, with the end part 14 embracing the forward end of the drive section 1. The annular groove 15 is sealed outwardly by O-rings disposed on both sides but not specifically designated in Figure 2.One object of the intermediate member 4 is to connect that part of the coolant line along the drive section 1 (i.e. the hose 11) to that part of the coolant line disposed in the grip section 5 (i.e. to that part corresponding to the duct 27 shown in the different embodiment illustrated in Figure 3). Thus, relative to the coolant line routing, the intermediate member 4 lies between the drive section 1 and the grip section 5.

Figure 3 shows another embodiment of the arrangement of the intermediate member coupled to the drive section 1 and the grip section 5. In contrast to the embodiment described with reference to Figures 1 and 2, the intermediate member here denoted 20 extends over a substantial part of the housing 21 of the drive section 1. As is evident from Figure 4, which shows the intermediate member 20 in cross-section along the line IV - IV in Figure 3, that part 22 embracing the housing 21 is provided with a longitudinally extending bulge 23 in one region of the circumference, in which a guide duct 24 is disposed. The guide duct 24 is provided with a radially disposed part at its forward end terminating in an annular groove 25 provided in the intermediate member 20 and communicating with a bore 26 in which that part 27 of the coolant duct in the grip section 5 terminates.Here too, there are O-rings, not designated specifically, at the coupling point, to seal off the medium to be guided in the coolant line parts. A flexible hose 28 is connected to the guide duct 24 and is connected to a plug 29 corresponding to the plug 10 in Figure 2, via which the attachment of a supply line 30 to the guide duct 24 is achieved. A screw ring 31 is arranged on the connection fitting 2, by means of which the drive section 1 is attached to the connection fitting 2.

The guide duct 24 may be in the form of a paraxial bore in the part 22 or, as shown in Figure 4, may be constituted by a small tube in an appropriately provided bore. An alternative embodiment is that in which the part 22, which acts as a sleeve, of the intermediate member 20 enclosing the housing 21 of the drive section 1 is deformed to provide, between the housing 21 and the intermediate member 20, a longitudinallyextending groove into which are fixed one or, if several media are to be conveyed to the headpiece (as in the case of Figure 7), several conduits for conveying the coolant.

Figure 5 shows in cross-section an arrangement of this type, in which part 32 of the intermediate piece 20 enclosing the housing 21 defines a groove 33. A construction in which the sleeve of the intermediate member is disposed eccentrically to the housing is also advantageous. Sufficient room is thereby created at a point on the periphery for disposing a supply conduit without significantly increasing the diameter of the drive section.

As an alternative to the flexible hose 28 in Figure 3 or 11 in Figure 1 which is connected to the supply line 30 (in Figure 3) via the plug 29 or 10, a small metal tube (e.g. of brass) may be provided which, because of the choice of material, has a certain elasticity. Thus the plug 29 can be withdrawn from the supply socket 9 and hence from the supply line 30 with little difficulty due to the spring-like action of the tube. When the plug 29 is plugged into the socket 9, however, it remains in engagement with the connection fitting 2 because of the springlike action of the tube holding it in place, and at the same time it thus prevents the intermediate member 20 or 4 from becoming axially displaced with respect to the drive section 1.

The part 22 of the intermediate member 20 which, as shown in Figue 3, encloses the housing 21, does not have to extend over the entire periphery. On the contrary, it is possible to provide a cover for the coolant line only, which is constructed in the shape of a bulge and runs paraxially along the handpiece. However, a design which encloses the entire motor housing does make it possible to sterilize all the parts touched by the user of the handpiece without having to sterilize the motor itself, an operation which is very problematic both with an air motor and an electric motor, and which can only be done at a correspondingly high cost. The sleeve-shaped part 22 of the intermediate member 20 which encloses the housing 21 may advantageously be so designed that it extends as far as the screw sleeve 31, as indicated by broken lines in Figure 3.

The construction of the embodiments described above make it possible to couple up drive sections of the earlier design with hand and angle pieces without having to make alterations to the drive section.

In the embodiments which are described below, however, slight alterations to the drive section are necessary, but these alterations do not call for any great technical expertise, nor do they involve much expence. Instead, they have the advantage over the constructions described hitherto that the external diameter of the drive section is not changed and that there are no parts of lines protruding from the housing of the drive section.

Figure 6 shows a further embodiment of a connector, part of the supply hose, and a drive section, in which embodiment two media are conveyed from the supply hose to the head section (not shown) of the handpiece. The connector or connection fitting 35 is provided with supply lines 36 and 37 for air and water respectively. The two lines lead radially towards the periphery of the connection fitting 35, similar to the manner shown in Figure 3, but only one line reaches the periphery and forms an extraction point like the sole extraction point 34, which can be closed off by a dummy plug 38.

When a grip section with exposed coolant line(s) is being used, a suitably designed plug is inserted into the extraction point 34, in order to convey the medium to the head section. Provided paraxially within the connection fitting 35 are two coolant line parts 39 and 40, which communicate with the supply lines 36 and 37 respectively. The line parts 39, 40 communicate with two line parts 39a, 40a which run outside the stator 41 and inside the housing 42 of the drive section 43.

Both line parts 39a and 40a end in coupling members 44, 45 of different lengths which project from a leading face 46, of the drive section 43. Projecting from the leading face 46 is a hollow shaft 47 which surrounds the drive shaft 48 of the electric motor 49, on to which hollow shaft 47 is pushed the grip section (as shown in Figure 7).

A screw sleeve 50 is provided for connecting the connection fitting 35 to the drive section 43. The line parts 39, 39a and 40, 40a are each single-piece pipe lines rigidly held in the connection fitting 35. Within the limits of the housing 42 of the drive section 43, the line parts 39a and 40a run in the aforementioned air space between the stator 41 and the housing 42, which air space is normally present for the passage of compressed air to cool the motor 49 or the motor housing 42.

In an alternative arrangement (not shown), the line parts 39 and 40 may be fixed on the housing 42 of the drive section 43 or on the intermediate piece 51 (shown in Figure 7) such that the line parts 39 or 40 engage corresponding bores on the connection fitting (not shown in Figure 7) when the drive section 43 and connection fitting 35 are coupled together, O-rings being present in this case too, to seal off the line connections.

Figure 7 shows in the uncoupled state the drive shaft end of the drive section 43, a matching intermediate member 51 and the trailing end region of a matching grip section 52. The intermediate member 51 comprises an annular body provided with two bores 53, 54, running parallel to the axis but of differing length within the member 51, which open into two annular channels, 55, 56 respectively. When the intermediate member 51 and the grip section 52 are coupled together, the channels 55, 56 are sealed on either side by O-rings (not designated specifically). Similar to the intermediate member 4 in Figure 2, the intermediate member 51 is provided with a recess 57 with a diameter corresponding to the external diameter of the housing 42 of the drive section 43.The internal diameter of the intermediate member 51, apart from in the region of the recess 57, in turn corresponds to the external diameter of the grip section 52; in the coupled state, therefore, the grip section 52 fits over the shaft 47 of the drive section 43, the trailing end face of the grip section 52 butting against the face 46 of the drive section 43. The rearward face of the recess 57 of the intermediate member 51 similarly butts against the peripheral region of the face 46 of the drive section 43.

Two radial bores 58 and 59 are provided in the grip section 52, and communicate with coolant line parts 60, 61 respectively running parallel to the longitudinal axis of the grip section 52, which parts lead to a head section of the handpiece (not shown in Figure 7, but similar to the head section 6 of Figure 1) and there terminate in a nozzle directed towards the instrument (numbered 7 in Figure 1). Also provided is a drive shaft 62, which, when the grip section 52 is coupled with the drive section 43, engages the driving shaft 48 in Figure 6, to transfer the drive motion of the motor 49 to the instrument 7 disposed in the head section 6.

The coolant line sections 39a, 40a may be composed either of separate tubes )as in Figure 6) or of bores. The coupling members 44, 45 may be present in both cases, either on the drive section (as shown) or on the intermediate member. Arranging the coupling members on the intermediate member has the advantage that it is directly possible to couple on existing grip sections; for instance, the rear face of the grip section may directly abut the front face of the drive section without obstruction by the coupling members.

An alternative arrangement (not shown) is also possible, in which the line parts 39, 39a. 40 and 40a are formed as a component part of the intermediate member 51. In such a case, within the housing 42 of the drive section, these line parts lead through air spaces in the motor and open directly into appropriate bores provided in the connection fitting 35.

Figures 8 and 9 show in a cross-sectional representation two possible embodiments for routing the coolant lines along the drive section. In Figure 8, two coolant line parts 63 are disposed in an outwardly facing groove 65 formed in the housing 64 and running along the drive section, whereas in Figure 9 the line parts 66 are disposed in a groove 69 provided in the stator 67 and are fully enclosed by the housing 68 of the drive section. A further embodiment (not shown) is that in which the housing is provided with an internal groove, such that the air space between the stator and the housing, which air space is generally present, is further enlarged to accommodate the line parts satisfactorily.

The term "connection fitting" or "connector" used in this specification refers to the component which connects the drive section and the supply hose. In the simplest case, as shown in the drawings, this may be a fitting mounted securely on the hose, to which the drive section is attached by means of a screw sleeve or ring. In the case where there is means for controlling the flow of the medium to be conveyed to the head section of the handpiece, the means may be a control valve, as described in British Patent Application 1 424 715 for example. A control valve of this type may itself either be incorporated in the hose fitting or be a separate part attachable to the hose fitting.

An advantage of the present invention is that, because of the intermediate piece, a drive section which is connected with a grip section in which the coolant line runs externally, that is a grip section with an, exposed coolant line, can instead be connected to a grip section with incorporated line routing. A further advantage arises from the fact that, in the event of failure of the coolant line routing, the drive motor does not necessarily break down as well or have to be renewed with the coolant lines.

WHAT WE CLAIM IS: 1. A dental handpiece in assembled or dismantled form and comprising:- a drive section which has a housing in which is disposed a drive motor; a grip section which is or can be coupled at one end to the drive section and is adapted to be rotated relative thereto; a head section attached or attachable to the other end of the grip section; and an intermediate member located or locatable between and/or around the drive and grip sections, which intermediate member is or is adapted to be coupled rotatably or non-rotatably to one of the drive and grip sections and is or is adapted to be coupled rotatably to the other, the intermediate member including coupling members engaging or engageable with (when the intermediate member is located between and/or around the drive and grip sections) at least one matching counter member of the drive section on one side of the intermediate member and at least one matching counter member of the grip section on the other side of the intermediate member, which coupling and counter members form part of at least one coolant line extending the lengths of the drive and grip sections to the head section.

2. A dental handpiece in assembled or dismantled form and comprising:- a connector; a drive section which is attachable in use to a supply hose via the connector, and which has a housing in which is disposed a drive motor; a grip section which is or can be coupled at one end to the drive section and is adapted to be rotated relative thereto; a head section attached or attachable to the other end of the grip section; and an intermediate member located or locatable between and/or around the drive and grip sections, which intermediate member is or is adapted to be coupled rotatably or nonrotatably to one of the drive and grip sections and is or is adapted to be coupled rotatably to the other, the intermediate member including coupling members engaging or engageable with (when the intermediate member is located between and/or around the drive and grip sections) at least one matching counter member of the drive section or the connector on one side of the intermediate member at at least one matching counter member of the grip section on the other side of the intermediate member, which coupling and counter members form part of at least one coolant line extending the lengths of the drive and grip sections to the head section.

3. A handpiece according to claim 1 or 2, wherein the intermediate member is in the form of a sleeve which is or may be coupled to the drive and grip sections, the intermediate member enclosing that end region of the grip section which faces the drive section.

4. A handpiece according to claim 3, wherein, when the intermediate member is coupled to the drive and grip sections, the drive section abuts the grip section.

5. A handpiece according to claim 3 or 4, wherein, when the intermediate member is coupled to the drive section, the intermediate member overlaps at least part of the housing of the drive section.

6. A handpiece according to any one of claims 1 to 5, wherein that part of at least one coolant line extending the length of the intermediate member is in the form of a guide duct communicating with a coupling member in the form of a plug, which plug is connectible with a counter member in the form of a bore located either in the drive section or, when the present claim is appendant to claim 2, in the connector.

7. A handpiece according to claim 6, wherein that part of the coolant line between the guide duct and the plug is flexible.

8. A handpiece according to claim 6 or 7, wherein the bore opens radially.

9. A handpiece according to claim 6, 7 or 8, when appendant to claim 5, wherein at least part of the guide duct is disposed in that part of the intermediate member which can overlap the housing.

10. A handpiece according to claim 9, wherein the guide duct is in the form of a bore, running essentially paraxially in the overlapping part of the intermediate member.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. air space is generally present, is further enlarged to accommodate the line parts satisfactorily. The term "connection fitting" or "connector" used in this specification refers to the component which connects the drive section and the supply hose. In the simplest case, as shown in the drawings, this may be a fitting mounted securely on the hose, to which the drive section is attached by means of a screw sleeve or ring. In the case where there is means for controlling the flow of the medium to be conveyed to the head section of the handpiece, the means may be a control valve, as described in British Patent Application 1 424 715 for example. A control valve of this type may itself either be incorporated in the hose fitting or be a separate part attachable to the hose fitting. An advantage of the present invention is that, because of the intermediate piece, a drive section which is connected with a grip section in which the coolant line runs externally, that is a grip section with an, exposed coolant line, can instead be connected to a grip section with incorporated line routing. A further advantage arises from the fact that, in the event of failure of the coolant line routing, the drive motor does not necessarily break down as well or have to be renewed with the coolant lines. WHAT WE CLAIM IS:

1. A dental handpiece in assembled or dismantled form and comprising:- a drive section which has a housing in which is disposed a drive motor; a grip section which is or can be coupled at one end to the drive section and is adapted to be rotated relative thereto; a head section attached or attachable to the other end of the grip section; and an intermediate member located or locatable between and/or around the drive and grip sections, which intermediate member is or is adapted to be coupled rotatably or non-rotatably to one of the drive and grip sections and is or is adapted to be coupled rotatably to the other, the intermediate member including coupling members engaging or engageable with (when the intermediate member is located between and/or around the drive and grip sections) at least one matching counter member of the drive section on one side of the intermediate member and at least one matching counter member of the grip section on the other side of the intermediate member, which coupling and counter members form part of at least one coolant line extending the lengths of the drive and grip sections to the head section.

8. A handpiece according to claim 6 or 7, wherein the bore opens radially.

11. A handpiece according to claim 9,

wherein the overlapping part of the intermediate member is provided with a paraxial groove for accommodating part of the coolant line.

12. A handpiece according to claim 10, wherein the overlapping part of the intermediate member, when coupled to the drive section, encloses the drive section eccentrically.

13. A handpiece according to any one of claims 1 to 5, wherein part of at least one coolant line is disposed within the limits of the drive section in a paraxially extending cavity of the drive section, the or each coolant line part terminating in a counter member intended to be connected to one of the coupling members of the intermediate member,

14. A handpiece according to claim 13, wherein disposed either in the drive section, or, when the present claim is appendant to claim 2, in the connector is a supply socket for a coolant which socket opens radially, in which socket a plug connected to a further coolant line extending over the length of the drive section may be inserted.

15. A handpiece according to claim 13, wherein the or each coolant line part is disposed in a space between the housing and the motor.

16. A handpiece according to claim 13, wherein the or each coolant line part is disposed in a paraxial groove on the inner or outer face of the housing.

17. A handpiece according to claim 13, wherein the motor is an electric motor having a stator and a rotor, and the or each coolant line part is disposed in a paraxial groove in an external part of the stator.

18. A handpiece according to any one of claims 13, 15 16 and 17, wherein the or each coolant line part is formed by a small tube disposed in said cavity or in said paraxial groove.

19. A handpiece according to claim 18, wherein the or each small tube is a component part of either the intermediate member or, when the present claim is appendant to claim 2, the connector; and, when the connector and drive section are connected together or the intermediate member and the drive section are connected together, the or each small tube extends through ths said cavity or the said paraxial groove in the drive section.

20. A handpiece according to one of claims 13 to 19 wherein the or each coolant line part within the drive section terminates in the region of that face of the drive section facing the grip section, in a counter member in the form of a bore or a projection, the matching coupling member of the intermediate member being a projection or bore, respectively.

21. A handpiece according to any preceding claim, wherein the head section is provided with a working instrument.

22. A handpiece according to any preceding claim, wherein the intermediate member is non-rotatably mountable with respect to the drive section.

23. A handpiece according to any preceding claim, wherein part of the intermediate member is provided with at least one annular channel for allowing supply of coolant during relative rotation between the drive section and the grip section.

24. A dental handpiece substantially as hereinbefore described with reference to, or as illustrated in, Figures 1 and 2, or Figure 3, or Figure 3 as modified by Figure 4 or 5, or Figures 6 and 7, or Figures 6 and 7 as modified by Figure 8 or 9.