WO1996019157A1

WO1996019157A1 - Device for a vacuum powered combinated discharge and suction system

Info

Publication number: WO1996019157A1
Application number: PCT/SE1995/001524
Authority: WO
Inventors: Olle Olsson
Original assignee: Olle Olsson
Priority date: 1994-12-20
Filing date: 1995-12-18
Publication date: 1996-06-27
Also published as: SE9404417L; AU4320896A; SE502740C2; SE9404417D0

Abstract

The object of the invention is to provide a vacuum powered emptying system for drainage tanks at dentist's chairs and the like, having a suitable vacuum level for spot extraction devices at the same time as the emptying of the drainage tanks can be performed in a simple way in spite of the pumping head to the drainage piping being higher than said suitable vacuum level, the entire system being closed inside the public surgery area and all inlet and outlet openings being located outside the surgery premises. This object has been fulfilled, according to the invention, by the maximum fluid volume in each drainage tank (1) and the dimensions of the adherent vertical discharge pipe (5) being adapted to one another and to the vacuum level hv of the vacuum pump (9), which equals the highest suitable vacuum level in the spot extraction devices (2), in such a way that during emptying, the tank content will form a fluid column in the discharge pipe (5) of a height h, said height being so much smaller than the height hv that air will be sucked through said fluid column at such a velocity that the drainage fluid will be disintegrated and transported up to the drainage piping (7) at the height H.

Description

Device for a vacuum powered combinated discharge and suction system

Technical area

The present invention relates to a device for vacuu - powered, combined drainage and spot extraction systems for e.g. dentist's chairs and similar applications in accordance with the preamble of the accompanying patent claims.

When arranging e.g. dental surgeries in existing build¬ ings, which is frequently the case, the necessary drain¬ age at the dentist's chair, from saliva extractor and rinsing fountain, have hitherto commonly been arranged in a conventional manner by means of floor drains in the immediate vicinity of the chair. This generally requires the mounting of new drainage piping into the floor struc¬ ture, as the chair must generally be placed in the centre of a room that normally did not have a floor drain before. This fact used to be a limitation when arranging new dental surgeries, as new drainage piping cannot be fitted between the ceiling of the apartment below and the existing floor of the dental surgery-to-be, without permits from authorities, the landlord and the tenant below. Primarily, far-reaching encroachment in the apart- ment below is often necessary, leading to major distur¬ bances for the tenant living there. Secondly, there is always a certain risk of sewage leaks from such piping, and as the sewage from the dentist's chair may contain mercury as well as bacteria from the oral cavities of the patients, it is not regarded as at all suitable to arrange such piping within other inhabited areas of the building. In practice, this has lead to the fact that establishment of new dental surgeries has been limited to locations above basements and other auxiliary premises, where it has been easier to obtain permits, and more seldom above apartments and similar premises.

Background of the invention

Recently, there have been attempts at solving this prob¬ lem by internal pumping systems for the drainage from the dentist's chairs, systems that may be located altogether within the apartment intended for hosting the dental surgery. A small drainage tank is then located at floor level, in a so called "media box" close to the dentist's chair, and this tank is connected to the rinsing fountain by means of drainage pipes inside the so called "media column" which supplies electrical power, water, etc. to the chair equipment. For reasons of space, this tank has a relatively small volume, about one to two litres, and thus has to be emptied relatively frequently. The empty¬ ing is commonly performed by means of vacuum.

A dentist's chair usually stands, as mentioned above, in the centre of the floor of a room, and the dentist and the dental nurse must be able to move freely around substantially all sides of the chair. For this reason, the discharge pipe is preferably drawn vertically from the media box towards the ceiling, where continuing piping, without being in the way, subsequently connects the discharge pipe to a vacuum pump which may be placed in a separate pump room and be serving all the chairs of a larger dental surgery, without causing disturbing pump and motor noise in the surgery room. In order to efficiently bring along all solid particles during emptying, the drainage tank is most commonly designed with a sloping bottom and with the discharge pipe connected at the lowest point thereof. In order to further enhance fluid circulation during discharge, so as to carry away the major part of the solid particles through the discharge pipe, the replenishing air pipe, which has to be arranged so that air can quickly replace the fluid volume in the tank during the emptying process, is also connected at the bottom of the tank.

In the pump room, there may be a separator upstream of the vacuum pump to catch the solid, often environmentally dangerous, particles like amalgam, etc. coming with the drainage water. The latter then flows down into a collec¬ tion tank, from where it can be emptied into an existing floor sink by gravity. The exhaust air from the vacuum pump is discharged to the exterior through a suitable filter.

For systems with several chairs and accompanying drainage tanks to be emptied, the system is supplemented by a number of valves and a preferably computerised control system that opens and closes valves in the pipes leading to the individual tanks, emptying them one at a time at predetermined intervals, the lengths of which are set so as normally not to overfill the tanks.

The same vacuum pump is simultaneously used to provide the necessary vacuum in the saliva extractors. These extractors are therefore arranged so as to be always in connection with said vacuum pump, independently of the functional position of the valves controlling the empty¬ ing sequence of the various tanks. When the saliva extractor is to be used and is lifted from its hook, a valve opens and connects the saliva extractor directly to the vacuum pump.

However, these hitherto known vacuum based drainage systems have a number of disadvantages.

One major disadvantage has been the contradiction exist¬ ing between the comfort demands set by the saliva extractor and the pumping head requirements for the emptying system in order to allow locating the drainage piping invisibly above an inner ceiling in this type of premises.

According to comprehensive tests within the trade, the vacuum level in a saliva extractor should be about 1,5 m Aq (meters of water column), and not above 2,0 m Aq, for two reasons. One reason is simply the risk of the saliva extractor clinging to the oral mucous membranes and damaging these when being removed, the other is that too high a vacuum causes a disturbing noise level.

On the other hand there are statutory demands on rooms of this type to have a minimum ceiling height of 2,4 m. Thus, in order to suck the drainage fluid in the conven- tional way in a fluid column up to this height, a vacuum in the order of 2,4 m Aq or more, is needed, if the ceil¬ ing-mounted pipes are to be mounted invisibly above an inner ceiling.

In a conventional system of the prior art, one can then select to use two vacuum pumps having different vacuum settings, or possibly a control system lowering the vacuum level to the saliva extractors. Both these conceivable solutions entail higher cost and an increased risk of technical problems. The alternative would be to locate the highest level of the pipes at 2 m or somewhat lower, which would cause standing height problems for tall people and would be very unattractive from an aesthetical viewpoint.

.Another technical problem is how the drainage tanks are supplied with replenishing air, when their fluid level rapidly decreases during discharge. If the replenishing air is supplied via the rinsing fountain drain hole, this would create a noise each time the tank is emptied. Up to now, replenishing air pipes have been drawn up to end above the inner ceiling, which has muffled the sound but not eliminated it completely. An alternative would be to draw all said air pipes individually to the machinery or pump room or to the building exterior, but that would entail unnecessarily high costs.

A third technical problem is to ventilate the drainage tanks as they are successively filled when rinsing the patient's mouth, etc. As previously mentioned, it is important that the discharge replenishing air pipe is connected at the bottom of the tank to enhance fluid circulation during discharge. Consequently, this pipe cannot ventilate the tank volume above the fluid surface, but with such a design, the air pressure inside the tank would rise, as would the fluid level in the replenishing air pipe and in the line from the rinsing fountain. In order to utilise the tank volume optimally, this problem has hitherto been resolved by means of a small, separate venting hole in the top of the tank. This will work well as long as the tank is never overfilled but is emptied before that, but there is a leakage risk, e.g. if the discharge control system would malfunction. The object of the present invention is therefore to provide a vacuum powered emptying system for drainage tanks at dentist's chairs and the like, in which the above disadvantages have been eliminated in a simple way and where the entire system is enclosed inside the public surgery rooms and has openings for entering and exiting air in the open air and an outlet for the drained sewage water only inside a separately arranged, ventilated machinery room.

Said object is achieved according to the invention by a device for vacuum-powered, combined drainage of drainage tanks and simultaneous provision of vacuum for spot extraction systems by dentist's chairs and similar appli- cations, the characteristics of which are stated in the accompanying patent claims.

Description of a preferred embodiment

The invention will be described below in the form of a preferred embodiment example, with reference to the accompanying drawings, wherein:

Fig. 1 shows, schematically, the main parts of a vacuum-powered, combined drainage and spot extraction system according to the invention, but does not, for the sake of clarity, show all component parts and functions, but only those being directly associated with the present invention,

Fig. 2 shows in more detail, how the tank and the piping system may in principle be arranged by a dentist's chair, and a section, not according to scale, through a drainage fluid tank and its discharge pipe, which schematically shows the relation between room height, suitable vacuum in m Aq and the same fluid volume, inside the tank and being sucked up into the discharge pipe respectively, according to the invention, and

Fig. 3 shows, in two side views, how on the one hand the collected drainage water amount in the tank rests in said tank immediately before being emptied, and how it on the other is sucked up into the discharge pipe at the beginning of the discharge phase. The figure also shows an alter¬ native embodiment of the invention having an ejector in the discharge pipe to increase the pumping head power. This figure is also not on scale but only schematical.

As shown in Fig. 1, a system for vacuum-powered, combined drainage and spot extraction systems for e.g. dentist's chairs and similar applications, arranged according to the invention, comprises the following main parts:

At the (not shown) dentist's chairs, in this embodiment example three chairs, there is provided respectively; one tank 1 for drainage fluid at the floor level, one saliva extractor 2 of a known kind, and a conventional mouth rinsing fountain 3. From the rinsing fountain 3 to the tank 1 there is a pipe 4, which, seen from the tank, is an inlet pipe for the drainage fluid. In this pipe there is a remote controlled shut-off valve 13, normally being held open by the not in detail described control system, but which is closed during emptying of the tank 1 to eliminate suction noise from the fountain 3. From the tank 1 at each dentist's chair there is a substantially vertical drainage pipe 5 leading up to a ceiling-mounted piping system 7, and in each drainage pipe there is a shut-off valve 12, normally being held closed by the not in detail described control system, but which is opened for emptying of that specific tank. The piping system 7 connects to a vacuum pump 9, located in a separate machinery room 26 in order to achieve sound¬ proofing of the surgery rooms. Between the piping system 7 and the vacuum pump 9 there is provided a not in more detail described separation system 8, preferably compris¬ ing several tanks, separators, filters and valves, all in order to clean the drainage fluid from amalgam and other solid particles before the water is led out into the normal drainage system by way of a floor sink 18. The used air from the vacuum pump passes via a filter 10 into the open air through an exhaust pipe 17. Each tank is provided with a level gauge 23, which, if the pre¬ programmed control system has not previously ordered emptying of the tank, will do so at a certain predeter¬ mined maximum volume in the tank. See below for further information on the significance of this volume.

The saliva extractors 2 at each chair are in practice commonly provided with shut-off valves, which are auto¬ matically opened when the extractor is lifted off its suspension hook. It is however an important principle of the device according to the present invention, that the saliva extractors are always to be ready for use and supplied with a suitable vacuum, independently of any discharge process at any drainage tank 1, that might be running simultaneously. In order to facilitate under¬ standing of the device according to the invention, we have therefore selected in this example to show each saliva extractor as being used, i.e. in constant connec- tion, via the piping system 7, with the vacuum pump 9, and we have therefore omitted these automatic shut-off valves, the existence of which must have no significance for the invention as such, but they are only there to save energy and reduce unnecessary noise.

The vacuum pump 9 is arranged always to provide a controlled vacuum of a level h_v suitable for the saliva extractors in accordance with the above description, i.e. about 1,5 - 2,0 m Aq. The vertical distance between the tank 1 bottom and the piping system 7 level at the ceil¬ ing is H, whereby H is larger than h_v. This means that the vacuum pump cannot suck a homogenous fluid column from the tank bottom level to the piping system level and that the tank 1 in an arrangement according to the known art would not be emptied.

In the device according to the invention, however, the fluid volume inside the tank 1, when the tank mounted level gauge 23 at the latest orders the tank to be emptied via the not in detail described control system, is so adapted to the diameter of the discharge pipe 5, that the entire volume in the drainage tank 1 will form a fluid column in the discharge pipe 5, with a height h which is so much smaller than said suitable work vacuum h_v, that this work vacuum will suck air through said fluid column, when the discharge pipe 5 is connected to the piping system 7 and the vacuum pump 9 via the valve 12. In Figs. 2 and 3, the maximum fluid volume in the tank 1 before it is emptied is shown as a single-hatched area, and the same volume sucked up into the respective discharge pipe 5 is shown as a cross-hatched area. Figs. 3a and 3b show the static position before emptying, whereas Fig. 3c shows discharge in progress. The capacity of the vacuum pump is furthermore adapted so that the air will flow through the drainage fluid in the discharge pipe 5 at such a speed that the fluid will successively disintegrate and follow the air flow up to ceiling level and on through the piping system 7 to the separation apparatus 8, even if the room ceiling height results in a piping system 7 height H which considerably exceeds the height of the water column corresponding to the highest suitable vacuum level h_v in the saliva extractors.

The chosen capacity of the vacuum pump 9 and the shape of the bottom of the tank 1, as well as the location in the tank of the ends of primarily the discharge pipe 5 but also the air inlet pipe 11 for the replenishing air that is rapidly sucked into the tank during discharge, also contribute to agitating the fluid in the tank 1 during discharge, making it sweep away a substantial part of the solid amalgam particles etc. that has aggregated on the tank floor. These particles will follow the fluid and the air bubbles up through the piping system and along to the separation apparatus 8. Any remaining particles will subsequently be brought along by the strong air flow arising after the discharge pipe 5 has been completely emptied of drainage fluid.

By the device according to the present invention, all air inlet pipes 11 are connected to a ceiling-mounted piping system 15 and terminating in an intake 16 in the open air outside the surgery, in order to reduce the intake noise and to prevent even small amounts of contaminated air to be returned to the premises. As the not in detail described control system empties one tank 1 at a time, it would be possible, as the other rinsing fountains 3 must be available for use also during the time that one tank is emptied, for drainage fluid from another tank l than the one being emptied, to rise backwards into its respec¬ tive replenishing air line 11 due to the vacuum occurring in the piping 15 when a tank 1 under discharge is rapidly being replenished with air. In order not to have to size the piping 15 so large that this back suction does not become a problem, which would lead to high cost, every air replenishing pipe 11 is equipped with a shut-off valve, in the preferred embodiment example in the form of a check valve 14, which closes automatically if the flow direction is reversed and prevents any reverse flow in the pipes 11.

The ventilation of the top region of the tank 1 while fluid is flowing in from the fountain 3 also takes place within the closed replenishing air system via an air line 24 connected to the air inlet pipe 11. For safety reasons, this connection preferably lies at a higher level than the upper edge of the rinsing fountain 3, see Fig. 2.

Fig. 3 also shows a variant of the device according to the invention, where a small connection pipe with an adjustable restriction is arranged between the replenish- ing air inlet pipe 11 and the discharge pipe 5, just below that fluid level which will be the highest continu¬ ous one inside said pipe when discharging commences. When the valve 12 has opened and the vacuum pump starts to suck air through the pipe 11, a smaller portion will pass through the restricted pipe 25 and create a high speed air jet at the end of the pipe 25 inside the pipe 5, which will create a certain ejector effect which increases the disintegration of the fluid and contributes to the flow. The valves 13 and 14 required for control of the emptying sequence in these systems are commonly relatively large and are servo controlled electro-pneumatically by the not in detail described control system, by means of smaller so called solenoid valves 19, which are normally mounted at the ceiling together with the piping system 7, and which are supplied with compressed air from a compressed air source 20. When these valves 19 switch, their exhaust air will cause a certain noise which may be disturbing. This has been eliminated in the device according to the present invention, as the device comprises a ceiling- mounted closed replenishing air system 15. The exhaust lines 21 and 22 from the valves 19 are connected to this piping system and thereby the disturbing noise is elimi- nated together with any oil mist that might discolour the ceiling plates after a long period of service.

The invention is not limited by the embodiment examples described above and depicted in the drawings, but may be varied within the scope of the accompanying patent claims. The device may for example of course be utilised also for other combined drainage and spot extraction systems than those for dentist's chairs. The number of connected drainage tanks 1 and spot extractors 2 may of course be varied freely. In the same manner, the size of the tanks 1 may be varied arbitrarily, provided that other parameters necessary for the function of the device according to the principles of the invention, e.g. the size of the discharge pipe, the flow rate capacity and the pre-set vacuum level of the vacuum pump and the distance in height between the bottom of the tank and the ceiling level piping, can be adapted to such variations. The shut-off valves in the pipes 11, which in the described embodiment example are designed as check valves 14, may of course be replaced by shut-off valves of the same type as those located in the discharge pipes and be controlled to closing and opening by the not in detail described control system that controls the other shut-off valves, to achieve the same effect. Also, the air inlet pipes may be equipped with filters if wanted. The machin¬ ery room may preferably be put under sub-atmospheric pressure in order to prevent all remnants of mercury vapour from reaching the surgery rooms, etc.

Claims

Patent Claims:

1. Device for vacuum-powered sequential emptying of one or several drainage fluid tanks and simultaneous supply of vacuum to spot extraction devices, e.g. emptying of drainage tanks (1) for rinsing fountains (3) at the same time as supplying vacuum to saliva extractors (2) and the like for e.g. dentist's chairs, a small drainage tank (1) being provided at room floor level and each tank being connected to a drainage fluid inlet, e.g. a mouth rinsing fountain (3) , by means of an inlet pipe (4) , as well as to a piping and valve system (7, 12) at the room ceiling level by means of a substantially vertical discharge pipe (5) , said piping and valve system connecting said sepa- rate drainage pipes (5) from one or several drainage tanks (1) , together with the vacuum lines from one or several spot extraction devices (2) , to a common vacuum pump (9) , which may be placed in a separate machinery room (26) , said pump being arranged to provide at all times a work vacuum suitable for the spot extraction devices (2) , independently of the functional position of the valves (12, 13) simultaneously controlling the emptying sequence of the different tanks (1) , said tank or tanks also being connected to an air inlet pipe (11) at the lower end of the tank (1) necessary for allowing replenishing air to rapidly replace the fluid volume in the tank when being emptied, the system being, in case of several fluid tanks (1) to be emptied, equipped in a not in detail described but known way, with a number of control valves (12, 13) and a preferably computerised control system, opening and closing said valves in the pipes to the individual tanks (1) in a certain sequence and emptying them one at a time at predetermined intervals, adapted in time so that overfilling of the tanks will normally be avoided, c h a r a c t e r i s e d i n that the maximum allowed fluid volume in each drainage tank (1) and the dimensions of said substantially vertical discharge pipe (5) are adapted to one another, to the height H of the horizontal ceiling-mounted piping system (7) above the drainage tank

(I) and to the pre-set vacuum level h_v of the vacuum pump (9) , which equals the height of the water column corre¬ sponding to the highest suitable vacuum level in said spot extraction devices (2) , in such a way that when the emptying of a tank is started, the total maximum fluid volume in the drainage tank (1) , when sucked up into the discharge pipe (5) , will form a fluid column having a height h, said height being so much smaller than the height h_v that said work vacuum h_v will suck air through said fluid column at such a flow rate that the drainage fluid will be transported up to the ceiling level on the height H above the drainage tank, and on through the piping system (7) to the separation apparatus (8) , by being disintegrated due to the velocity of the air flow and being transported along with it, even if the room ceiling height H substantially exceeds the height h_v, and in that the flow capacity of the vacuum pump (9) is adapted to the discharge pipe (5) dimensions in such a way that the air flow velocity in the empty pipe (5) will subsequently become high enough to bring along amalgam residues and any other remaining solid particles on the tank (1) bottom up through the piping system (7) and away to the separation apparatus (8) .

2. Device according to claim 1, c h a r a c t e r i s e d i n that the air inlet pipes

(II) for replenishing air to the drainage tanks (1) during emptying are connected to a common, closed piping system (15) fetching its air outside the surgery premises, and in that each of these air inlet pipes (11) is provided with a shut-off valve (14) which, when a tank

(I) is emptied, prevents reverse flow of drainage fluid through said air inlet pipe from any other tank (1) .

3. Device according to any one of claims 1 or 2, c h a r a c t e r i s e d i n that the air inlet pipe

(II) is connected to the bottom of the drainage tank (l) and in that the venting of the top end of the tank (1) is made to the air inlet pipe (11) via a separate venting line (24), connecting the highest point of the tank (1) to said pipe (11) .

4. Device according to any one of claims 1, 2 or 3, c h a r a c t e r i s e d i n that the exhaust lines (21, 22) from the pneumatic solenoid valves (19) of the control system are connected to said closed replenishing air piping system (15) .

5. Device according to any one of claims 1 to 4, c h a r a c t e r i s e d i n that the air inlet pipe

(11) is connected to the discharge pipe (5) by means of a connection line (25) , with a small cross-section area and an adjustable restrictor, the end of said line being located in the centre of the cross section of the pipe (5) , just below the level h of the sucked-up fluid column when the discharge process is beginning, and being aimed in the flow direction in order to achieve an ejector effect contributing to the fluid transport through said discharge pipe (5) .