FIELD OF INVENTION

The current invention relates to a valve arrangement of a dental care unit according to the preamble of patent claim 1, especially in a context of a dental care unit arranged with several instrument places. BACKGROUND OF INVENTION

In the field of dental care various rotating and other hand instruments are used, which are powered by so called dental care units or other external sources. In addition to electricity, these instruments are also commonly powered by compressed air. Instruments as well as the objects that are being worked on with the instruments typically need to be cooled down, for which purpose it is known to use compressed air and/or water. Therefore, controlling of the dental care instruments typically also includes, in addition to actual control of operation of the dental care instruments, adjusting cooling of the instrument or the object being worked on.

A dental care unit typically includes a 'foot control, by which the pressure of both the instrument drive air and the so called cooling spray (air and water) is controlled either through valves arranged in the foot control or indirectly e.g. through an electric control system and magnetic valves.

As there typically is only one foot control and several instruments in a dental care unit, a valve arrangement is called for which enables controlling of several instruments. Among others, arrangements based on solenoid / plunger valves for individual flow channels have been used for this purpose, as well as solutions based on diaphragm valves controlled by pressure, and combinations of these.

It has been found that arrangements based on solenoid / plunger valves for individual flow channels do work well but when one valve is needed for each conduit the arrangement becomes relatively expensive, Diaphragm valve arrangements are considerably cheaper than solenoid / plunger valve arrangements. The diaphragm valves have been controlled for example by pressure, which is adjusted by valves arranged in connection with the foot control and instrument holders or by magnetic valves which are controlled by the control system of the dental care unit.

There are, however, certain problems related to diaphragm valves, especially when they are used for controlling water flow. For example, if one wishes to use only a small pressure in a water line to generate a small liquid flow, there is a risk that the pressure will in fact not be sufficient to open the diaphragm valve. On the other hand, upon closing a diaphragm valve it creates a pumping effect into the water line, which after ending use of the instrument and placing it on the instru- ment table of the dental care unit can result in - possibly a delayed - dripping of water from a tip of the instrument, on a patient, for example, The diaphragm valve arrangements have also typically been realised such that when the system is being switched off, the diaphragm valve will remains in an open position, which can result in an undesired and uncontrolled dripping of water as there is nothing stopping flow-out of the water still remaining in the system, for example on the floor of the treatment room after the end of a working day.

In some instances, thus, separate water valves operating on a technolo- gy other than diaphragm valve technology have been arranged in the conduits for instrument water. In the context of a dental care unit including several instrument places, however, such solutions are relatively expensive when three . valves may be needed for each instrument place, that is, for example a diaphragm valve for compressed air lines, anot- her valve for controlling operation of the diaphragm valve and a third valve for a waterline. On the other hand, in case there are metallic components in a water valve, water as such may over the time cause problems of its own for the operation of the valve. An arrangement has been presented in a patent publication US 5,201,899 in which a pressure controlled poppet valve is used for controlling water flow, the poppet valve being controlled by the air pressure prevailing directly behind the membrane and a piston. In this solution, flow of the water is blocked upon disappearance of the control pressure, which is a desirable feature in view of uncontrolled dripping of water from an instrument. On the other hand, as control pressure is needed for opening the water valve and as the diaphragm valves used for controlling the air pressure of the arrangement require disappearance of the control pressure in order to open, two control pressures op ^¬ posite to each other are needed in this arrangement. Sealings with such moving and sliding solutions are used in the arrangement which in order to function properly require tight manufacturing tolerances and are vulnerable to abrasion.

SUMMARY OF INVENTION

The object of the present invention and its preferable embodiments is to achieve a new solution for a valve arrangement for individual in ^¬ strument places of a dental care unit , The aim ' is a valve arrangement including an inexpensive diaphragm valve structure as one component and in which the structure of the valve arrangement and its control as a whole is realised by taking specifically into consideration, among ot- hers, the above-mentioned problems relating to dripping of water, and to sealings of the arrangement.

In the arrangement, compressed air delivery to an instrument can be controlled by an inexpensive diaphragm valve structure and, on the ot- her hand, e.g. a separate expensive solenoid valve dedicated solely for the purpose of water delivery is not needed for water delivery but water flow to an instrument and/or to an object to be worked on is. arranged with the help of a multiplexer valve structure comprising a permanent magnet valve structure, as defined in more detail in the Claims attached hereto. Controlling of operation of the diaphragm valve and the permanent magnet valve can be realised through exploiting a compressed air system of the dental care unit.

BRIEF DESCRIPTION OF FIGURES

Figure 1 shows a typical dental care unit, which comprises several instrument places for dental care instruments. Figure 2 shows multiplexer valve blocks according to the invention as a part of a pneumatic diagram of a dental care unit.

Figures 3a and 3b show a multiplexer valve block according to one embodiment of the invention in its two different operation modes.

DETAILED DESCRIPTION OF INVENTION

In the following, embodiments of the invention as shown in the attached figures will be described. A list of the components shown in the Figures as well as their reference numbers is to be found at the end of this description.

Figure 1 shows dental care instruments arranged to a typical dental ca- re unit. The dental care unit according to Figure 1 comprises a body part (2), a patient chair (3) and a console arm (4) extending from the body part (2) . At the end of the console arm (4) there is arranged an instrument console (6) on which hand pieces or. instruments (301), such as dentist's burrs and other hand instruments used in dental care, are placed. Hand pieces or instruments (301) are connected to the instrument console (6) via instrument tubes (7). The physical magnitudes required for using the instruments are delivered from the dental care unit via conduits going through the instrument tubes (7) and the console arm (4) . In one embodiments of the invention, one multiplexer valve block described in more detail in the following is arranged in connection with each of the instrument places in the instrument console (6) .

Figure 2 shows a pneumatic diagram, which describes an arrangement for realizing one preferable embodiment of the invention, and Figures 3a and 3b show a cross-section of a multiplexer valve block (200, 300) which can be used in the solution described in Figure 2, in its two different operating states. Figure 3a shows the valve block (300) in an operating state in which a conduit for pilot operating pressure (305.1) is not pressurized, and Figure 3b shows it ih a state in which the con- duit for pilot operating pressure (305.1) is pressurized.

Consequently, the term multiplexer valve block refers here to a distribution conduit arrangement of a dental care unit for individual instru- merits (or instrument places) and to a related valve arrangement. The typical basic functions of such an arrangement are i) opening and closing a flow connection between a distribution conduit for spray water (250, 350) of a hand piece / an instrument (201, 301) and a distribution conduit of the whole pneumatic arrangement for adjustable pressure of the spray water (50) ii) opening and closing a flow connec ^¬ tion between air conduits (220, 320, 230, 330) for a hand piece / an instrument (201, 301) and a distribution conduit of the whole pneumatic arrangement for air (20, 30), and iii) opening and closing a flow con- nection between a return conduit (240, 340) for air of a hand piece/ an instrument (201, 301) (for example return of drive air in case of a turbine and return of cooling air in case of a micro motor) and a return conduit (40) for air of the whole pneumatic arrangement. In order to achieve such functionalities, the arrangement of the attached Figu- res includes a selection valve of a magnetic valve type (202, 302) arranged in a water line (50, 250, 350), a diaphragm-operable selection valve (203, 303) for air lines and a plunger valve (204, 304) arranged to control its operating pressures. The arrangement further includes a conduit for pilot operating pressure (305.1), the pressure variations of which can be used for moving certain components of the valve arrangement, in a way to be described in more detail below.

The Figures show also a conduit for static pilot air pressure (10, 360) leading with respect to the instrument air conduits (220, 320, 230, 330, 240, 340) behind the diaphragm valve structure, a sound muffler conduit (209, 309) for the pilot air pressure as well as control / proportional valves (21, 31, 51) for instrument and pilot air (drive air) and water distribution of the whole pneumatic arrangement, and a sound muffler for the return air and an oil separator / collector (49) .

In the embodiment of Figures 3a and 3b, the valve block (300) comprises in addition to the above described elements also valve components (302. N, 303. N, 304 ,N) listed at the end of this description. Besides, in Figures 3a and 3b the reference number (305.1) refers to a conduit for pilot operating pressure (305.1), which can be arranged with for example a 3/2 functioning pilot valve (not shown in the Figure) through which pressure can be led in and out from that conduit. In this arrangement, there is no significant flow in this conduit (305.1). Figure 3a shows the valve arrangement in a dormant state, i.e. in a state in which an instrument is not in use or the air pressure and/or electricity is switched off. In this state, none of the conduits (320, 330, 340, 350) leading to a hand piece / an instrument (201, 301) is open, Instead, Figure 3b shows a state of the valve arrangement in which an instrument is being used.

Let' s consider first the operation of the valve arrangement according to figures 3a and 3b as regards to water flow, that is, regarding the distribution conduit (50) and further the conduit (350) leading to a hand piece / an instrument, According to Figure 3a, when the arrange ^¬ ment is in a non-activated state, a closing spring (302.8) forces a block plunger (302.7) of the magnet valve to a lower position, whereupon a seal (302.4) closes the connection from the water distribution conduit (50) to the conduit (350) leading to a hand piece / an instrument (210, 310). Further, a magnet plunger (302.6) (permanent magnet piston) of the magnetic valve arrangement is in this situation in an upper position as forced by a counter spring (302,5). This position is selected such that the effect of the field of the per- manent magnet (302.6) on the block plunger (302.7) is not strong enough so that it could pull the block plunger (302.7) to its upper position. When the magnet plunger (302.6) is moved in the way to be described below with the help of compressed air, it is possible to choose the counter spring (302.5) to be as strong as necessary to ensure that the for- ce it creates exceeds the tractive force between the magnet plunger (302.6) and the block plunger (302.7). (Compressed air is typically available in the dental care unit environment for creating sufficient force - as long as the diameter of the magnet plunger (302.6) is long enough. )

In a situation according to Figure 3b, that is for example when an instrument (201, 301) has been taken in use, pressure has been led to the pilot operating pressure conduit (305.1) and that pressure pushes the magnet plunger (302.6) down via a diaphragm (303.3). When the force of the closing spring (302.8) of the block plunger is dimensioned small enough, the magnet pulls the block plunger (302.7) to its upper position whereby also the seal (302,4) of the block plunger of the magnet valve moves and, hence, opens a connection between the water feed conduits (50) and (350) ,

When specifying the structure, the force of the magnet, the closing spring (302.8) of the work plunger and the dimensions of the structure naturally need to be so chosen that the magnetic field will overpower the counter spring in the operating position but not in the dormant position. On the other hand, concerning operation of the structure, it is even advantageous if the structure is not water-tight as regards to the block plunger (302.7) and the valve structure's body but instead, water can pass in-between them. In such a case, when the block plunger (302.7) moves there is practically no change in the water volume and no vacuum will be generated behind the block plunger (302.7) . Further, w- hen tightness of closure of the flow channel is based on a compressing seal pad, the operation principle of the structure is insensible to deformations of the seal.

Regarding control of air, on the other hand, an inverter valve (304) of the valve arrangement plays a noticeable role. In dormant state it keeps the pilot pressure conduit (360) for the diaphragm valves (i.e. of conduits (320, 330, 340) leading to a hand piece / an instrument) located behind the diaphragm valves of the conduits under the influence of the static control pressure conduit (10) of the arrangement and, thus, those diaphragm valves closed. But when the pilot operating pres- sure conduit (305.1) is pressurized, the inverter valve (304) releases the sealing pressure of the air conduit (360) of the diaphragm valve to the atmosphere, which enables opening of the diaphragm valves according to pressures prevailing in the conduits for adjustable pressures (20, 30, 40) .

When in a dormant state (Figure 3a) the plunger (304.7) of the inverter valve for pilot pressure is thus in the upper position as forced by the counter spring (304.8), whereby an O-ring (304.10) located above the plunger (304.7) squeezes against the upper edge of a chamber (304.9) of the inverter valve and connection from the conduit (360) for the pilot pressure for the diaphragm valves to the atmosphere via the sound muffler conduit for the pilot air pressure (309) is closed. Simultaneously, the connection between the distribution conduit (10) for static pressure and the conduit (360) for the pilot pressure for diaphragm valves is open, whereby the distribution pressure keeps the diaphragm valves closed. In a situation according to Figure 3b, i.e. for example when an instrument (201, 301) is taken to use, pressure is led into the pilot operating pressure conduit (305.1) which via a diaphragm (303,3) pushes the plunger (304.7) of the inverter valve down. Consequently, the seal of the plunger (304.6) of the inverter valve closes the feed conduit (10) and thus the the connection between the conduit (10) for the static distribution pressure and the conduit (360) for the pilot pressure for the diaphragm valve closes. At the same time, the above mentioned 0- ring (304 - 10) will no longer seal the connection from the chamber (304,9) of the inverter valve to the sound muffler conduit (309) for pilot air pressure but it will let the pressure prevailing in the conduit (360) for the pilot pressure of the diaphragm valves purge.

In the same way as in connection with water, compressed air is used in the construction also for moving the plunger (304,7) of the inverter valve for the pilot pressure, When the diameter of the plunger (304.7) of the inverter valve is arranged long enough, the counter spring (304.8) of the inverter valve for the pilot pressure can be specified to be strong enough to reliably hold the connection open between the conduit (10) for the static feed pressure ) and the conduit (360) for the pilot pressure for the diaphragm valves when the arrangement is in a non-activated state. If the conduit (305.1) for the pilot operating pressure of the valve arrangement is arranged to be pressurized for example as response to a hand piece / an instrument (201, 301) being picked up from an instrument table (6) of a dental care unit including several instrument places, it is then possible to lead water and/or air to the instrument in question - in the arrangement according to Figure 2, through proportional valves (21, 31, 51) , according to the amount the use of the instrument arranged to the instrument place in question requires .

One could think of even other structural details than those presented above to realize the above described functionality of the valve arrangement. However, in any case the arrangement essentially includes conduits (220, 320, 230, 330, 240, 340, 250, 350) for water and air leading to a hand piece / an instrument (201, 301), a diaphragm valve structure (203, 303) and means for controlling the diaphragm valve structure. In the arrangement, at least one of the conduits (220, 320, 230, 330, 240, 340, 250, 350) is arranged to- be closed by the diaphragm valve structure (203, 303) and said diaphragm valve structure (203, 303) is arranged to be a functional part of a multiplexer valve structure (300), which additionally includes at least a permanent magnet valve structure (202, 302) . The operation of the diaphragm valve struc- ture can be controlled through an inverter valve structure (204, 304) for pilot pressure which is included in the multiplexer valve structure (300). Movements of the permanent magnet (302.6) and of the plunger

(304.7) of the .. inverter valve structure (204 _/ 304) belonging to the magnet valve structure (202, 302) can be arranged to be realised through pressure variations in the pilot operating pressure conduit (305.1), and movements of the block plunger (302.7) of the magnet valve structure (202, 302) to follow the movements of the permanent magnet (302.6). Further, the permanent magnet valve structure (202, 302) may include a closing spring (3.02.8) of a block plunger arranged in functional connection with the. block plunger (302.7), ^' the power of the closing spring

(302.8) being so specified in relation to the tractive force that will be created between the magnet plunger (302.6) and the block plunger (302.7) that when the magnet plunger (302.6) is located at a first distance from the block plunger (302.7), the power of the closing spring (302.8) is stronger than said tractive force, and when, the magnet plunger (302.6) is located at a distance shorter than the first distance from the block plunger (302.7), the power of the closing spring (302,8) is smaller than said tractive force and said block plunger (302.7) will move due to the influence of said tractive force. The permanent magnet valve structure (202, 302) may be realised such, that in a non-active state said block plunger (302.7) closes at least one of said flow channels (220, 320, 230, 330, 240, 340, 250, 350), the block plunger (302.7)· then being in such a position with respect to the magnet plunger (302.6) in which the magnet plunger (302.6) cannot move it, and opens that at least one flow channel when being at a position in which the magnet plunger (302.6) has moved it. The magnet valve structure (202, 302) may be arranged to close and open at least one flow channel (250, 350) leading water to a hand piece / an instrument (201, 301) .

Also the plunger (304,7) of the inverter valve structure may be arran- ged to move through pressure variations of the conduit for pilot operating pressure (305.1), for example in a way in which both said permanent magnet valve structure (202, 302) and inverter valve structure (204, 304) are arranged to be in an activated state when the conduit for pilot operating pressure (305.1) is' pressurized and in a non- activated state when the conduit for pilot operating pressure (305,1) is not pressurized.

Further, the space in the valve arrangement in which said magnet plunger (302.6) and, on the other hand, said inverter valve structure (204, 304) are located is separated from a space arranged for the pilot operating pressure (305.1) by a flexible diaphragm structure (303.3), through which the power produced by the pilot air operating pressure is directed to the magnet plunger (302.6) of the magnet valve structure and to the plunger (304,7) of the inverter valve structure to move them.

As regards to conduits (220, 320, 230, 330, 240, 340, 250, 350) leading to a hand piece/ an instrument (201, 301) , at least one of the conduits can be a conduit for water (50, 250, 350), whereby specifically the above mentioned type permanent magnet valve (202, 302) is arranged in functional connection with it. The diaphragm valve structure (203, 303) , on the other, may be arranged to comprise at least two diaphragm valves each of which being arranged to close at least one air conduit (220, 320, 230, 330, 240, 340) .

One of the air conduits may be the spray air conduit (220, 320) of a hand piece / an instrument (201, 301), one a conduit for drive or cooling air (230, 330) of a hand piece / an instrument (201, 301) and one a return air conduit (240, 340) , whereby said diaphragm valve structure (203, 303) may comprise a diaphragm valve arranged in each of these conduits (220, 320, 230, 330, 240, 340) . The operation of the inverter valve structure (204, 304) in relation to said diaphragm valve structure (203, 303) may be arranged such that when the inverter valve structure is in a non-activated state, each valve of the diaphragm valve structure (203, 303) keeps its respective conduit (220, 320, 230, 330, 240, 340) closed.

One of the benefits of the above described arrangement is that flow of water to an instrument is always prevented when . the conduit for pilot operating pressure is not pressurized. Hence, none of the typical mal- function situations such as loss of pressure can cause undesired leaking of water.

On the other hand, there is no need to use sliding sealing surfaces in the construction which means that seals are not the most critical com- ponents of the structure as regards to manufacture and abrasion. Realising the sealings as described above offers a solution in which manufacturing tolerance of the structure may be quite broad and in which abrasion and deformation of the seals during their use will be compensated.

The arrangement is economically cost-effective, as inexpensive diaphragm valves may be used for leading compressed air to the instruments, and as both controlling operation of the diaphragm valve and leading water to the instrument may be realised via a valve structure, the function of which is based on the plunger valve principle which has proven to be well operative in other contexts.

The arrangement is directly applicable in both an electric and a traditional pneumatic control system.

REFERENCE NUMBERS USED IN THE FIGURES

1 Air pressure inlet (for example 5 bar)

5 Water pressure inlet (for example 3.5 bar)

10 Distribution conduit for static pressure (air)

20 Distribution conduit for adjustable pressure (air-instrument spray)

21 Control / proportional valve

30 Distribution conduit for adjustable pressure (drive air) 31 Control / proportional valve (drive air)

40 Conduit for return air

49 Sound muffler for return air and oil separator / collector,

50 Distribution conduit for adjustable pressure (water-instrument spray)

51 Control / proportional valve (water-instrument spray)

200, 300 Multiplexer valve block

201, 301 Hand piece / instrument, such as a micro motor, a turbine, a light curing device

202, 302 Selection valve of a type of magnetic valve (water-instrument spray)

203, 303 Selection valve with diaphragm as an operating member (spray, drive and return air)

204, 304 Pilot pressure inverter valve for diaphragm valve (air)

209, 309 Sound muffler conduit for pilot air pressure

220 _/ 320 Distribution conduit for hand piece / instrument (air- instrument spray)

230, 330 Distribution conduit for hand piece / instrument (turbine- drive air; micro motor-cooling air)

240, 340 Return conduit for hand piece / instrument (turbine-drive air; micro motor-cooling air)

250, 350 Distribution conduit for hand piece / instrument (water- instrument spray)

260, 360 Conduit for pilot air pressure for diaphragm valves

302.4 Seal of a block plunger of a magnet valve

302.5 Counter spring of a magnet plunger of a manget valve

302.6 Permanent magnet plunger of a magnet valve

302.7 Block plunger of a magnet valve

302.8 Closing spring of a block plunger of a magnet valve

303.3 Diaphragm of a diaphragm valve

304.7 Plunger of an inverter valve for pilot pressure

304.8 Counter spring of a plunger of an inverter valve for pilot pressure

305.1 Conduit for pilot pressure for operating the valve arrangement