This invention relates to a suction device to be used in dental care, comprising a suction source, a suction pipe to be joined to the suction source, a handle arranged at the end of the suction pipe and provided with a through suction hole and a solenoid valve arranged in the suction pipe between the suc¬ tion source and the handle to switch on the suction at the handle and to switch it off as well as a switch arranged in connection with the handle to guide the solenoid valve.

In dental care and surgery, various suction de¬ vices are used to remove from the mouth cavity of the patient mainly saliva, blood, water used for rinsing and cooling and filling material released in the mouth when grinding and drilling teeth and fillings and preparing fillings as well as grindings coming from the teeth. There are two main types of suction devices to be used in dental care. One of them has a relatively low suction effect, and a mostly bendable suction point joined to it is held in the mouth of the pa¬ tient during the whole treatment. The other type of suction devices has a considerably higher effect and such a suction device provided with a straight or slightly bent disposable or sterilizable suction point is arranged either by the dentist or the dental assistant in the mouth of the patient in a place de- sired each particular time during treatments re¬ quiring effective suction.

Especially in connection with suction devices of said other type, a suction motor generally posi¬ tioned outside the consulting room is used, which motor is switched on each time the sucker is used or

is on all the time, whereby the suction operation is controlled by guiding a valve joined to the suction pipe situated between the suction motor and the han¬ dle. This valve is usually a solenoid valve and it is guided either by means of a switch at the handle or a switch arranged in a rack of the suction device posi¬ tioned in a machine for dental treatment or in the vicinity thereof.

From U.S. Patent 4 215 476 is known a suction device, in which a solenoid valve switching on the suction at the handle is guided by means of a switch arranged at the handle. This switch to be used for guiding the solenoid valve is hand-operated and sit¬ uated at the handle relatively near to the suction point thereof. The use of this switch presupposes that the dental assistant or the dentist takes the handle in his hand in an exactly right position in order to have the switch easily available. Thus the switch makes the use of the handle somewhat more dif- ficult, but especially it complicates the structure of the handle. However, the greatest problem with such a handle is perhaps to keep it clean and to have it sterilized. It is actually not possible to clean reliably this kind of a handle provided with an outer switch, not to mention to sterilize it, which makes such a handle nearly unusable, because virus infec¬ tions of different kinds constitute a remarkable source of infections nowadays.

The object of the present invention is to set forth a suction device to be used in dental care, the handle of which device does not involve the problems mentioned above. This is achieved by means of a suc¬ tion device according to the invention, which device is characterized in that the switch is a switch re- sponsive to position, such as a mercury switch, ar-

ranged to guide the solenoid valve and to provide a switching-on of the suction at the handle when the end of the handle on the suction pipe side is situat¬ ed higher than the rest of the handle, substantially irrespective of the rotational position of the handle with respect to the longitudinal axis thereof.

The switch is most preferably arranged at a joining piece for the handle, to be joined to the end of the suction pipe. Alternatively, the switch can also be arranged in the handle itself. The switch is most preferably cast into the joining piece made of a plastic material or into the plastic material of the handle.

When using a mercury switch comprising an elon- gated switching tube, it is preferable that the switching tube is arranged substantially parallel with the axial direction of the handle.

By means of the above structural solutions, re¬ markable advantages are achieved with respect to the prior art. The use of a switch responsive to position for guiding a solenoid valve eliminates the need of a hand-operated switch. Thus the dental assistant or the dentist does not have to handle any switch, but he is able to control the suction merely by means of the position of the handle. When carrying out the switch according to the invention, the rotational position of the handle with respect to its longitudi¬ nal axis is not of significance to the operation either. In this way it is possible, if desired, to carry out the handle even as a fully symmetrical body of revolution, which body can thus be seized in ex¬ actly the same way in any rotational position thereof with respect to its longitudinal axis. When arranging the switch in the joining piece for the handle to be joined to the end of the suction pipe, the handle it-

self can be designed entirely in the manner desired, and particularly, it can be manufactured either dis¬ posable or of a sterilizable material. In this way, it is possible to entirely eliminate the sterilizing problems occurring in connection with the prior art handle. A substantial advantage is also created by that structural feature of the handle of the suction device according to the invention that it is now pos¬ sible to dimension the handle entirely as desired and thus make it ergonomically optimal. This has an in¬ fluence especially from that point of view that the handle can now be made relatively short, in which case, when holding it in hand like a pen, the tor- sional moment caused in the fingers of the holder by the suction pipe joined thereto is not near as big as it were if the handle were longer.

In the suction device according to the inven¬ tion, the switch arranged in connection with the han¬ dle can be cast directly into the joining piece joined to the end of the handle, or most preferably, of the suction pipe. In this way, it does not have any influence at all on the use of the handle or on the possibility of cleaning the surface of the handle or hardly on any other design thereof. In practice, the existence of the switch is observed only due to the fact that from the joining piece in question come out two conductors, which also can be mounted safely inside the suction hose without risking the safety of the patient. Consequently, these conductors have no influence on the outer structure of the handle either.

It is previously known from U.S. Patent Publi¬ cation 4 799 885 to apply a switch responsive to po¬ sition to the handle of a suction device. In the structure according to this patent, the switch does

not, however, guide a solenoid valve joined to the suction pipe, but a magnet coil, which tries to in¬ fluence a flap- or ball-like valve means arranged inside the handle. In this structure, placing the valve means in the handle has led to a very big, clumsy and heavy structure, which cannot be consid¬ ered usable for several reasons. Firstly, the device functions in only one rotational position with re¬ spect to its longitudinal axis. Even a slight devi- ation from this position endangers the function of the device. The function of the very switch respon¬ sive to position becomes indefinite, due to its loca¬ tion in an oblique position at a projection of the handle. However, the most substantial problems with the structure in question can be considered to be the dependence of the function of the very valve means on the rotational position of the handle with respect to the longitudinal axis thereof and especially on the fact that the magnetizing force shall be very big in order to be able to loosen for instance the ball-like valve means from the suction hole against the under¬ pressure produced by the suction device. Big forces like this make the use of the device more difficult, not to mention the danger which can be caused both to the user and especially to the patient to be treated by the obviously high operating voltage needed for the provision of these forces. In the same way, the supply line of this magnet makes, when joined to the projection of the handle, the use of the device more difficult and is subjected to damages.

The suction device of the invention is describ¬ ed in the following in greater detail referring to the enclosed drawing, in which

Figure 1 shows a cross-section of one exempli- fying embodiment of a handle- of a suction device ac-

cording to the invention and

Figure 2 shows an exemplifying circuit diagram of an electrical control system of the suction device of the invention. Figure 1 shows a partial cross-section of a handle 2 of a suction device of the invention and of structural elements joining it to the end of a suc¬ tion pipe 1. In this exemplifying embodiment of Fig¬ ure 1, the handle 2 itself is a body of revolution with a smooth outer surface and a through boring, to one end of which is joined a detachable suction point 8. This suction point can also be made in one piece with the handle 2. Such an embodiment is possible especially when the handle with the suction point is manufactured of a sterilizable material suitable for being sterilized in an autoclave, for instance. Such a handle can be made of metal or also of plastic. As appears from Figure 1, the handle 2 has no projec¬ tions, but it is a symmetric body of revolution with a smooth outer surface, easily sterilizable also by wiping.

The handle 2 is joined to the end of the suc¬ tion pipe 1 by means of a joining piece 5 by utiliz¬ ing bayonet joint solutions provided with gaskets, conventional in the field. On the other hand, the joining piece 5 is joined to the end of the suction pipe 1 by pushing the end of the pipe on a tubular portion 12 of the joining piece. The suction pipe 1 itself is shown in the figure with a folded structure to improve its flexibility. To secure the joint be¬ tween the joining piece 5 and the suction pipe 1, a sleeve-shaped protective casing 9 is further arranged thereon, which casing remains in place due to its shape and accurate dimensioning. The most substantial feature of the invention

consists of a switch 4 responsive to position and arranged inside the joining piece 5. In the structure described, this switch 4 responsive to position is a mercury switch cast into the plastic material of the joining piece 5. Only conductors 10 coming to the switch come out of the joining piece and these, too, on the inner surface of the joining piece 5. These conductors 10 can be led along a necessary length inside this suction pipe to a solenoid valve switch- ing on the suction at the handle or switching it off. The part of the suction pipe joined to the handle is mostly made of a flexible suction hose of the kind described, which is joined to a rigider suction pipe for instance in a rack of the handle. In connection with this joint, the conductors 10 can be led easily also outside the suction pipe and there to the sole¬ noid valve.

As appears from Figure 1, a switching tube 6 of the mercury switch 4 is a cylindrical elongated body, most conventionally manufactured of glass. Inside this glass tube is enclosed a drop 7 of a conductive liquid, such as mercury. On the inner surface of the glass tube there are also tags (not shown), which are short circuited by the mercury drop when it moves to the end of the tube in question. It is essential for the function of the handle according to the invention that the axial direction of the switching tube 6 is substantially parallel with the axial direction of the handle 2. Additionally, it is essential that the function of the switch is irrespective of the rota¬ tional position in which the handle is each time with respect to its longitudinal axis. In the case of the mercury switch, for example, this is achieved in such a way that the switching tube thereof consists of a body of revolution. The most natural shape of this

body of revolution is a cylinder. In the solution described, the mercury switch 4 is arranged to oper¬ ate in such a way that the mercury drop 7 short cir¬ cuits the tags when the end of the handle 2 on the suction pipe 1 side is higher than the rest of the handle. In this manner, it is easy to control the function of the suction device by means of the posi¬ tion of the handle. Not until the suction point 8 is leaned downwards when pushing it into the mouth of the patient, a switching-on of the suction takes place. When the handle is taken away from the mouth of the patient and its point rises to point upwards, the switch 4 switches off the suction at the handle. In this way the assistant or the dentist does not need to control the switching-on and switching-off of the suction by using manually a switch arm, which is of great significance already per se. It is also very essential that the operating time of the suction and the detrimental, relatively loud low-frequency sound caused thereby can be decreased to the minimum.

As can be seen from the structure of Figure 1, the part of the handle 2 above the gripping area of the handle becomes •very shor . This has the advantage that not nearly as big a torsional force is created to which the hand of the user of the handle is sub¬ jected as in case, if it were necessary to make the handle longer, as it is when mechanical hand-operated switches are applied.

In connection with Figure 1 an embodiment is described, in which the switch 4 responsive to posi¬ tion is located at the joining piece 5 to be joined to the end of the suction pipe 1. This switch could also be arranged inside the handle 2 in a quite cor¬ responding manner. In that case, all those advantages which above are mentioned to relate to the embodiment

of Figure 1 could not be achieved. Then the advantage is not achieved which is due to the fact that the embodiment of Figure 1 can be used together with han¬ dles of different kinds and also of different origin, if only the joining piece 5 is provided with suitable joining means for this handle. Consequently, the em¬ bodiment of Figure 1 is very suitable for being pro¬ vided also as an accessory for already existing sys¬ tems. Then it is only necessary to exchange the join- ing piece at the end of the suction pipe for the joining piece 5 of the invention and to switch the conductors coming out of it in a suitable manner, e.g. by means of the rack of the device, to the con¬ trol circuit of the solenoid valve. Figure 2 shows the electrical circuit a part of which is constituted by the switch 4 responsive to position. The circuit comprises a low-frequency, e.g. 24 V, power source supplying the coil of a solenoid valve 3. By means of this solenoid valve, the suction can be switched from the suction source (not shown) on or off the handle. The switch 4 responsive to po¬ sition is arranged in series with the coil of the solenoid valve 3 to control the switching of the cur¬ rent on this coil. Consequently, closing the switch 4 makes the solenoid 3 draw and open the suction to the handle. In the connection of Figure 2 is further in¬ dicated in broken lines a switch 11, which is arrang¬ ed in series with the switch 4. This can be for in¬ stance a micro-switch situated in the rack of the handle 2, which switch functions when the handle is arranged in place in the rack. It is understandable that also in parallel with the switch 4 can be ar¬ ranged a switch by means of which the function of the switch 4 can be bridged, and thus, the handle 2 be used .also when sucking from above downwards. There

is, however, a very little need of such a use.

The suction device according to the invention has above been described in connection with two exem¬ plifying embodiments only and it is understandable that even several structural changes can be made therein without, however, deviating from the scope of protection defined by the enclosed claims.