Abstract:
The present invention is concerned with a vacuum release suction device for regulating and controlling suction in an aspiration line, and which may be included in aspirators such as for example dentistry, surgery, or cosmetic tools. When operated, such tools generally generate noise which may become harmful to the tool user or for the patient on which the tool is used. More specifically, the suction device of the present invention includes a body having an inlet port and an outlet port defining a chamber in the body and a bypass inlet intersecting the chamber at an acute angle with respect to the longitudinal axis of the chamber, such that a main fluid stream is generated with minimized occurrences of flow separation, turbulence and therefore minimized generated aerodynamic noise.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to a suction device. More specifically, the present invention is concerned with a low noise vacuum release suction device and controllable aspirator using same.  
       BACKGROUND OF THE INVENTION  
       [0002]     Aspirators connecting a vacuum source to a nozzle having a hollow tip are widely used in a plurality of professional fields and, namely, in the medical field. In dentistry, for instance, aspirators are used by dentists or hygienists and dental assistants for aspirating saliva, blood, water and debris from the patient&#39;s mouth during a treatment or surgery. The aspirating tool and the user thereof have to deal with opposite concerns in such an application.  
         [0003]     Firstly, all liquid, solid particles and aerosols must be extracted in an effective manner, due to the health hazards they represent. The risks for the patient and the medical personnel tend to increase with the increasing use of high technology materials such as polymers and composites yielding toxic resin vapours and microscopic particles of silicium, quartz etc. when shaped with rotary instruments, cut, abraded or polished. These materials are often used for replacing silver amalgam fillings which, when deposited mechanically, produce toxic mercury vapours. Therefore, relatively strong suction and heavy airflow are desirable. However, contact of the aspirator tip aperture with the tongue or other delicate mouth tissues tends to block airflow, yielding a rapid negative pressure increase firmly grabbing the tissue against the aperture, and causing discomfort and risks of injury for the patient and stress both for the patient and the medical personnel. For that type of reasons, a vacuum release vent is now often provided on medical aspirators.  
         [0004]     The vacuum release vent is generally an auxiliary bypass orifice, smaller than the main suction port, provided along the aspirating line, which enables penetration of air into the suction line with some restriction when air intake is obstructed at the main port, thus preventing vacuum inrush and water hammer effects. An early design of such a vented aspirator is described in U.S. Pat. No. 3,516,160 issued to Leffler in June 1970, which introduces the Tip-A-Dilly™ aspirator  100  illustrated in  FIG. 4  of the appended drawings. The aspirator  100  includes a body  103  provided with two bypass orifices  101 ,  102  and terminated at its upstream end by a portion  105  provided with a main inlet bore  107  connected to a suction tip  106 , and at its downstream end by an outlet portion  104  for connection to a vacuum hose. In operation, when vacuum is applied at outlet  104 , a fluid stream  108 , typically containing air, body fluids and solid debris, is created in the main inlet  107 . At the same time, air from the surrounding atmosphere enters the body  103  through orifices  101 ,  102  and merges with the main stream  108  to exit the device at outlet  104  as mixed fluid stream  109 .  
         [0005]     Should the inlet of tip  106  be blocked by contact with body tissues for instance, the thereby modified ratio between the tip inlet effective cross-section and that of the bypass orifices  101 ,  102 , will automatically cause more air to be drawn through these orifices to prevent sudden increase of suction rate at the tip and firm grabbing of the tissues. However, air penetrating at high velocity through the small orifices in the inner chamber of the body  103  experiences turbulence due to rapid expansion at the inner side of the orifices and sharp edges at the interface between the inner chamber of the body  103  and the outlet portion  104 . Turbulence creates acoustic waves tuned by the resonant cavity provided by the inner chamber, thus generating a hissing noise.  
         [0006]     Other examples of such vented medical aspirators are described in U.S. Pat. No. 5,425,637 (Whitehouse et al.—June 1995), U.S. Pat. No. 5,509,802 (Whitehouse et al.—April 1996), U.S. Pat. No. 5,542,929 (Laabs et al.—August 1996) and U.S. Pat. No. 5,964,733 (Laabs et al.—October 1999).  
         [0007]     Noise in medical aspirators, particularly dental aspirators used extensively and repeatedly by dentistry personnel, is recognized as a very significant problem. Indeed, it is a source of fatigue, stress accumulation and it represents a real risk of hearing acuity degradation for medical personnel. This noise problem has been specifically addressed in U.S. Pat. No. 5,195,952 issued to Solnit et al. in March 1993 which introduces the Grab Free™.  
         [0008]     As illustrated in  FIG. 5 , the Grab Free™ is a device  100  which includes a plurality of tiny elongated bypass ports  111 ,  112  in the solid body  113 . The body  113  includes an outlet portion  114  and an inlet portion  115  with a lip  116  for insertion of a removable suction tip. The main fluid which flows from the suction tip enters the main inlet  117  which has a constant cross-section port up to the outlet of the device. Upon clogging of the main inlet, air is drawn through the bypass ports and merges smoothly with the main flow due to the acute angle of incidence. Therefore, fluid streams follow smooth paths and merge as combined flow  119  at the outlet of the device with minimal separation, turbulence and resonance, leading to a significantly reduced noise level. However, the concept of this device provides fixed vacuum compensation and does not allow the user to block one or more of bypass ports  111 ,  112  to control the aspiration rate at the tip. Also, the weight of the solid metal body  113  at the downstream end of the device  110  adds to that of the vacuum hose and connector to create a moment of rotation about the user&#39;s wrist, yielding physical fatigue and discomfort of the user, to compensate the lift of the aspiration tip.  
         [0009]     Suction control is indeed a desirable feature in aspirators used in dentistry as well as in many medical fields related to surgery, in lipectomy surgery or draining of wound fluids for instance. One may thereby avoid subjecting delicate tissues to too strong a suction force while properly performing aspiration of specific matters as needed. Therefore, some aspirator systems of the prior art justify and describe suction control or regulator devices of two types. In a first type, a venting port of relatively small effective area can selectively be either left open to provide a definite level of suction or blocked by a sleeve or a finger to momentarily increase suction, or vice versa. U.S. Pat. No. 4,534,542 (Russo—August 1985), U.S. Pat. No. 5,855,562 (Moore et al.—January 1999), U.S. Pat. No. 5,975,897 (Propp et al.—November 1999) and U.S. Pat. No. 6,045,516 (Phelan—April 2000), as well as Canadian patent No 2,042,523 (Nates—Oct. 1995) exemplify that first type of controlled vacuum aspirators.  
         [0010]     Fewer suction control devices of a second type are so designed to enable a user to continuously vary suction over a given range. Representative examples of aspirators implementing such suction control devices are described in U.S. Pat. No. 4,221,220 (Hansen—September 1980), U.S. Pat. No. 5,013,300 (Williams—May 1991), U.S. Pat. No. 5,730,727 (Russo—March 1998), U.S. Pat. No. 5,899,884 (Cover et al.—May 1999) and US patent application No 2002/0108614A1 filed by Schultz in April 2002.  
         [0011]     The published patent application by Schultz, which is illustrated in  FIG. 6 , teaches a hand-held medical component which is provided with a wide elongated port for regulating suction. Suction is provided from a device which comprises a body  123  with an inlet portion  125  and an outlet portion  124  for connection to a vacuum source. The device is further provided with a large opening and relatively large throat bypass inlet penetrating the body up to the inner chamber  122 . The large elongated opening of the bypass inlet  121  is so designed as to enable a user to control the suction rate at the inlet of suction tube  126  by selectively blocking a variable portion of said opening with a finger. Although such a feature is highly desirable in many applications, noise with such a device is still a major problem which prevents its extensive use in applications such as dentistry. Indeed, the main fluid stream  128  rapidly expands and separates when passing from the inlet  125  to the chamber  122  of much larger cross-sectional area. Similarly, the pressure compensating air flow penetrating the chamber from inlet  121 , experiences separation and turbulence due to the orthogonal incidence when merging into the main stream and to the sharp edges present at the interface. Therefore, the main and bypass flows could not merge to form an outlet fluid stream  129  without generating a highly noisy acoustic emission tuned according to the dimensions of chamber  122  and because of the resonant cavity yielding flow separation, turbulence, acoustic amplification and, consequently, intense irritating noise.  
         [0012]     With the exception of the Solnit Patent, all of the aforementioned patents have their bypass inlet extending straight through the outer wall of the aspirator body such that the incoming airflow substantially forms a right angle with respect to the fluid stream in the main bore of the device. Also, none of the auxiliary aperture shapes have been specifically designed in consideration of the aero-acoustic concerns for optimal merging of the bypass air flow from atmosphere with the main fluid stream, that is with minimal energy being dissipated and converted into sound waves, and minimal transfer of said sound waves to the surrounding work environment.  
         [0013]     Although the above examples show that some suction control bypass devices and controlled aspirating devices are contemplated in the prior art, these devices are nevertheless lacking important features necessary for them to provide adequate control of aspiration rate as required in medical applications for instance, while generating low level minimally annoying noise.  
         [0014]     It would therefore be a significant advance in the art of controlled suction aspirating devices to provide a low-noise suction control device and an aspirator using such a device, which can be advantageously controlled with a user&#39;s finger or sliding sleeve to provide a wide range of aspiration rates, while generating low and minimally annoying noise, according to preferred structures as contemplated in the present invention. It would also be desirable to provide an aspirator which enhances the physical comfort of a user through an ergonomic design providing weight balance and natural and adjustable tip angulations.  
       OBJECTS OF THE INVENTION  
       [0015]     An object of the present invention is therefore to provide a low-noise aspiration control port and an aspirator using same.  
       SUMMARY OF THE INVENTION  
       [0016]     More specifically, in accordance with the present invention, there is provided a suction device for an aspirator connectable to a vacuum source, the suction device including a body including an external surface, an inlet port located at a first end of the body, an outlet port located at a second end of the body, a chamber extending inside the body from the inlet port to the outlet port along a longitudinal axis, the chamber defining a flow direction from the inlet port to the outlet port, the suction device further including a bypass inlet diverging through the body from the external surface to the chamber generally along the flow direction.  
         [0017]     There is furthermore provided a suction device for an aspirator connectable to a vacuum source, the suction device including a body including an external surface, an inlet port located at a first end of the body, an outlet port located at a second end of the body, a chamber defined by a diverging portion from the inlet port to a junction position and a converging portion from the junction position to the outlet port, a bypass inlet extending through the body from the external surface in the vicinity of the inlet port to the chamber in the vicinity of the junction position.  
         [0018]     There is furthermore provided a suction device for an aspirator connectable to a vacuum source, the suction device including a body including an external surface, an inlet port provided in the vicinity of a first end of the body, an outlet port provided in the vicinity of a second end of the body, a chamber extending inside the body from the inlet port to the outlet port along a longitudinal axis, the chamber defining a flow direction from the inlet port to the outlet port, the suction device further including a bypass inlet extending through the body from an elongated aperture on the external surface to the chamber and at an acute angle with respect to the flow direction.  
         [0019]     There is furthermore provided a suction system for an aspirator connectable to a vacuum source including a suction device including a body including an external surface, an inlet port located at a first end of the body, an outlet port located at a second end of the body, a chamber extending inside the body from the inlet port to the outlet port along a longitudinal axis, the chamber defining a flow direction from the inlet port to the outlet port, the suction device further including a bypass inlet extending through the body at an acute angle with respect to the flow direction from an outer aperture on the external surface of the body to an inner aperture in the chamber, the suction system further including a control means operatively mounted over the outer aperture for blocking the bypass inlet, whereby upon operation of the vacuum source sealingly mounted to the outlet port, a first suction force is generated at the inlet port and a second suction force is generated at the bypass inlet, the first suction force being variable upon actuation of the control means.  
         [0020]     There is furthermore provided an aspirator connectable to a vacuum source for aspiring particles and or fluids including a suction device including a body including an external surface, an inlet port located at a first end of the body, an outlet port located at a second end of the body, a chamber extending in the body along a longitudinal axis from the inlet port to the outlet port, and a bypass inlet diverging through the body from the external surface to the chamber, whereby upon operation of the vacuum source sealingly mounted to the outlet port, a first suction flow is generated at the inlet port and a second suction flow is generated at the bypass inlet such that the first suction flow and the second suction flow combine in the chamber near the inner aperture.  
         [0021]     It is to be noted that the expression vacuum source is to be construed herein and in the appended claims as a system which is independently capable of generating a negative pressure inducing a suction flow or an aspiration line in the vicinity of the system, while in operation.  
         [0022]     Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0023]     In the appended drawings:  
         [0024]      FIG. 1  is a top view of the suction device according to an embodiment of the present invention;  
         [0025]      FIG. 2  is a cross sectional view taken along line  2 - 2  of  FIG. 1 ;  
         [0026]      FIG. 3  is a detail view of a bypass inlet taken from enclosure  3 - 3  of  FIG. 2 ;  
         [0027]      FIG. 4 , which is labeled “prior art”, is a longitudinal cross sectional view showing a first prior art suction device;  
         [0028]      FIG. 5 , which is labeled “prior art”, is a longitudinal cross sectional view showing a second prior art suction device;  
         [0029]      FIG. 6 , which is labeled “prior art”, is a longitudinal cross sectional view showing a third prior art suction device;  
         [0030]      FIG. 7  is a top view showing an outer aperture contour of the suction device of  FIG. 1 ;  
         [0031]      FIG. 8  is a table including the contour parameters of the outer aperture shown in  FIG. 7 ;  
         [0032]      FIG. 9  is a detail view of a lip contour taken from enclosure  9 - 9  of  FIG. 3 ;  
         [0033]      FIG. 10  is a table including the contour parameters of the lip of  FIG. 9 ;  
         [0034]      FIG. 11  is a top view of an aspirator equipped with a suction device according to the present invention;  
         [0035]      FIG. 12  is a cross sectional view taken along line  12 - 12  of  FIG. 11 ;  
         [0036]      FIG. 13  is an isometric exploded view of the aspirator of  FIG. 11 ;  
         [0037]      FIG. 14  is a partial isometric view of the suction device included in the aspirator of  FIG. 11 ;  
         [0038]      FIG. 15  is a partial isometric view of the tool adapter included in the aspirator shown of  FIG. 11 ; and  
         [0039]      FIG. 16  is a comparative chart representing the noise level generated by the suction device of the present invention and by three suction devices of the prior art. 
     
    
     DETAILED DESCRIPTION  
       [0040]     Generally stated, the present invention relates to a vacuum release or suction device  20 , as illustrated in  FIGS. 1, 2  and  3 , for controlling the suction rate in an aspiration line with minimal generated aerodynamic noise. The invention further relates to a hand-held aspirator of the type used for medical purposes, such as for aspirating body fluids from a patient, saliva, water, blood and debris from a patient&#39;s mouth during a dental treatment or surgery, for example. The contemplated aspirator may be controllable and is provided with a low noise suction device  20  of the present invention.  
         [0041]     Examples of prior art aspirators having suction capabilities are illustrated in FIGS.  4  to  6 .  
         [0042]     The device  20  according to an embodiment of the present invention will be described.  
         [0043]     The device  20  has a body  22  including a first end or main inlet portion  24  and a second end or main outlet portion  26 . The main inlet portion  24  has an inlet port  28  which is so configured as to be mounted to an aspirating tool and may comprise a ridge  30 , a groove (not shown) retaining a “O” ring seal member (not shown), or another positive coupling mechanism to attach tooling or extension tubing in a substantially fluid tight manner. The main outlet portion  26  has an outlet port  32  which is so configured as to be mounted to a vacuum source (not shown).  
         [0044]     The body  22  of the device further includes a chamber  34  which is provided between the inlet port  28  and the outlet port  32 ; and a bypass inlet  36  which generally extends through the body  22 , such that it connects or opens the chamber  34  to the atmosphere.  
         [0045]     The chamber  34  is made of two generally frusto-conical portions  38 ,  40 , such that the cross-sectional area of the chamber  34  gradually increases from the inlet port  28  to the vicinity of the bypass inlet  36  and then gradually decreases toward the outlet port  32 . This arrangement favors a smooth merge of a generally quasi laminar main flow  42  entering the inlet port  28  and a bypass flow  44  entering the bypass inlet  36  to constitute a combined outlet stream  45 .  
         [0046]     The first generally smooth and diverging frusto-conical portion  38  extends from the vicinity of inlet port  28  and generally up to the vicinity of the connection of the chamber  34  with the bypass inlet  36 , therefore providing a gradual increase of the cross-sectional area of the chamber  34 .  
         [0047]     This arrangement generally provides some velocity reduction of the main flow  42 , while minimizing the risks of sudden changes of flow direction and thus turbulence, particularly in the region of the bypass inlet  36  and to promote the merging of both flows  42 ,  44  in laminar or nearly laminar conditions.  
         [0048]     The second generally smooth and converging frusto-conical portion  40  extends from the vicinity of the connection of the chamber  34  with the bypass inlet  36  to the vicinity of the outlet port  32 .  
         [0049]     The ramping angle θi of the inlet frusto-conical portion  38  is advantageously selected between about 2 and about 7 degrees, with a preferred value of about 3.5 degrees with respect to chamber  34  longitudinal axis  46 , while the ramping angle θo of the outlet portion  40  is advantageously selected between about 3 and about 10 degrees, with a preferred value of about 7 degrees.  
         [0050]     As can be better seen from  FIG. 3 , the bypass inlet  36 , which extends through the body  22  of the device  20 , generally includes a lower ramp or surface  48 , an upper ramp or surface  50 , an outer aperture  52  and an inner aperture  54 . The bypass inlet  36  also includes a lip  56  near the outer aperture  52  and may adopt various configurations as it extends through the body  22 .  
         [0051]     One example illustrating an extending configuration for a bypass inlet  36  is shown in  FIGS. 1, 2 ,  3 ,  7  and  8 . This configuration is inspired from a profile known in the field of aeronautics as a “NACA inlet”, which has been specifically developed and optimized by the National Advisory Committee for Aeronautics, predecessor of the modern day NASA, to enable air flow to enter a body with minimal flow separation and turbulence. Reader may refer to NACA&#39;s research memorandum entitled “An Experimental Investigation of the Design Variables for NACA Submerged Duct Entrances” By Mossman et al. (Jan. 8, 1948) for a detailed teaching of the subject. This document is included herein by reference in its entirety.  
         [0052]     In this configuration, the outer aperture  52  of the bypass inlet  36  has a shape or contour which is generally flush with outside surface of the body  22  and the bypass inlet  36  is generally submerged in the body  22 . The contour of the outer aperture  52  is shown in  FIG. 7  and may be defined according to the table of coordinates provided in  FIG. 8 , for example.  
         [0053]     More specifically, as can be seen from  FIG. 7 , the outer aperture  52  generally includes a narrow end  58  of width W1 at its upstream end (nearer to the inlet portion  24  of the device  20 ) and a wide end  60  of width W2 forming the lip  56  at its opposite downstream end (nearer to the outlet portion  26  of the device  20 ). Ends  58  and  60  are generally connected by curvilinear lateral edges  62 ,  64  which are being defined in the Table of  FIG. 8 , given the width of the outer aperture  52  at given values of longitudinal position x. The edges  62 ,  64  can also be approximated by linear edges, forming a nearly triangular inlet. The overall length L of the outer aperture  52  is generally larger than width W2, which is larger than W1.  
         [0054]     W1 generally ranges from about 0 to about 20 millimeters, with a preferred value of about 0.8 millimeters, and W2 generally ranges from about 5 millimeters to about 25 millimeters with a preferred value of about 10 millimeters, and the length L generally ranges from about 10 millimeters to about 50 millimeters, with a preferred value of about 30 millimeters.  
         [0055]     Returning to  FIG. 3 , to direct the flow of air  44  from the bypass inlet  36  toward the outlet of chamber  34  with an acute incidence angle of about 3 to about 10 degrees, with a preferred value of about 7 degrees, the lower ramp  48  and the upper ramp  50  respectively form an angle αL and an angle αU ranging from about 3 degrees to about 10 degrees with respect to the longitudinal axis  46  of the chamber  34 , with a preferred value of about 7 degrees. Ramps  48 ,  50  may be substantially parallel (about same angle αL and αU), or may slightly diverge toward the inner aperture  54 . The lower ramp  48  and the upper ramp  50  of the bypass inlet  36  may be spaced by a distance ranging from about 1 to a bout 5 millimeters, with a preferred value of about 2.65 millimeters, as measured on a transversal axis (not shown) which is generally orthogonal to the longitudinal axis  46  of the chamber  34 .  
         [0056]     Further, the lip  56  is designed to provide a smooth transition from the external surface of the body  22  to the bypass inlet  36  in order to minimize airflow separation and resulting turbulence.  
         [0057]     A possible shape of the lip  56  is illustrated in  FIG. 9  and defined in the table of  FIG. 10 , wherein the values of the positions of the upper edge Yu and lower edge Yl are provided for given values of the longitudinal displacement x, as a function of d, which is the vertical distance between the upper and the lower ramps  48 ,  50  ( FIG. 3 ) and which is calculated as follows from equation (A): 
 
 d=L tg α/[ 1.481−0.75  tg α]   (A) 
        where α is the ramp angle (α=αL=αU) and L is the overall length of the outer aperture  52 , as illustrated in  FIG. 7 . A smooth transition at the entrance of lower ramp  48  is also contemplated to prevent flow separation, such that the radius of curvature r shown in  FIG. 3  should not be much smaller than about 5 millimeters.        
 
         [0059]     The design of the bypass inlet  52  is so configured as to provide minimum flow separation and turbulence as required to reduce the generated aero-acoustic noise. Turning back to  FIG. 2 , the vacuum source of the suction device  20  while in operation creates a negative pressure, i.e. suction, at the outlet port  32 , which in turn causes main flow  42  and bypass flow  44  to be drawn respectively from the main inlet port  28  and the bypass inlet  36  to merge at a junction position  54   a  near the inner aperture  54 , to constitute the combined outlet stream  45 . The bypass flow  44  is generally constituted from surrounding atmospheric air while main flow  42  may comprise a mixture of air, gases, liquids and solid matters to be extracted from a location using a suction tool to be connected to inlet portion  24 .  
         [0060]     The flows of fluid through main inlet port  28  and bypass inlet  36  are generally a function of the applied vacuum intensity and of the resistance to flow resulting from each inlet/bore characteristics. One of the characteristics determining flows of fluid is the effective cross-section and duct length of the inlet ports  28 ,  36 . Therefore, for given characteristics of the main inlet port  28  and suction tooling connected thereto, such as for example a rotary adapter and suction tip (not shown), modifying the effective area of the outer aperture  52  of the bypass inlet  36  modifies suction, i.e. flow and maximum pressure at the main inlet port  28 . The area of the outer aperture  52  is thus designed to define minimum desired values for the flow and pressure at the main inlet port  28 . In use, it is possible for a user to partly or totally block bypass inlet aperture  52 , with a finger, with part of a hand, or with any other blocking element to increase suction to a desired value as necessary at any time of an operation.  
         [0061]     A user may also merely block a portion of the relatively large bypass inlet aperture  52  with a finger or alternatively, using a sliding sleeve (not shown) to continuously control suction between a minimum and a maximum value. The optional use of a sleeve (not shown) may be useful to minimize direct contact of the user&#39;s gloved skin with the fluid and matters flowing through the device  20 , which could present risks of contamination or injury, although the current design of the preferred embodiment advantageously minimizes such contact.  
         [0062]     The device  20  which was described hereinabove may be used in a variety of applications, such as for example in a dentistry aspirator to extract debris along with water, saliva, blood and air from a patient&#39;s mouth. Such an embodiment is illustrated at  FIGS. 11 through 15 .  
         [0063]     The low-noise suction device or aspirator  70  includes a central portion  72  including a low-noise vacuum release or suction device  20  as described above. The main outlet portion  26  may include a female configuration which may be connected to a removable male adapter  74 . The male adapter  74  may be selected to be mounted to a variety of vacuum hoses, valves or other connection devices (not shown). Press-fit assembly or “O” rings  75   a  co-operating with grooves  75   b  may be contemplated to provide a substantially fluid tight connection.  
         [0064]     At the fore (upstream) end of the aspirator  70 , a tool adapter  76 , which is provided with an angular tool holding inlet portion  90 , is assembled over the main inlet portion  24  for rotation about the longitudinal axis of the aspirator  70 . An indexing mechanism, as shown in  FIGS. 14 and 15 , such as for example mating notches and ridges located on surfaces  80  and  82  of the aspirator  70  and tool adapter  76  respectively, are provided to positively set and maintain the angular position of the tool adapter  76  to a user selected comfortable position. A fluid tight rotary joint using “O” rings or ridges (not shown) on the main inlet portion  24  with or without mating grooves (not shown) inside the bore of the tool adapter  76  may alternatively be used, without any step indexing mechanism, in order to enable continuous full 360 degrees rotation of the tool adapter  76  about the aspirator  70  longitudinal axis. A hollow suction tip  84  comprising an inlet  86  and an outlet  88  is removably inserted in the inlet  90  of the angular tool holding portion  78 .  
         [0065]     From  FIG. 12 , it can be seen that the user may use one&#39;s thumb  92  to vary the effective area of the bypass inlet  36  to modify suction at the inlet  86  of suction tip  84 . In addition, part of the volume between the outer shell of the tool adapter  76  and its central bore is filled with a dense material such as for example a stainless steel bushing  94 , to increase the weight at the fore end of the aspirator  70 , thus improving balance and reducing stress and fatigue in the user&#39;s wrist by causing a displacement of the centre of gravity of the aspirator  70 .  
         [0066]     For dentistry applications, the angle φ of orientation of the tool holding portion  78  with respect to a longitudinal axis of the aspirator  70  is generally set between about 10 and about 45 degrees, with a preferred value of about 30 degrees. The tool adapter  76  may be further provided with a revolving means (not shown), for adjusting the angular orientation of the suction tip  84  about the longitudinal axis of the aspirator  70 .  
         [0067]     In such an application, a suction force ranging from about 35 to about 70 grams at tip inlet  86  is considered most desirable when the outer aperture  52  of the bypass inlet  36  is fully open, with a preferred value of about 70 grams. The maximum suction force generated by the aspirator  70  in the fully closed bypass inlet configuration is about 180 grams with about 250 millimeters Hg suction pressure applied to the aspirator  70 . This is achieved with a suction inlet cross-section of about 47 square millimeters at tip inlet  86  and a bypass cross-sectional area of about 27 square millimeters at inner aperture  54 . Accordingly, dimensions of the external bypass aperture  52  of an exemplary device are as follows: 
        10 millimeters&lt;L&lt;50 millimeters;     5 millimeters&lt;W2&lt;25 millimeters; and     0 millimeters&lt;W1&lt;20 millimeters.        
 
         [0071]     In an example, a prototype having the following dimensions was constructed, L=30 millimeters, W2=10 millimeters and W1=0.8 millimeters, leading to a calculated value of d=2.65 millimeters. To prevent flow separation, radius of curvature r at the entrance of the lower ramp  48  (see  FIG. 3 ) should be between about 2 millimeters and about 50 millimeters with a preferred value of about 7.5 millimeters.  
         [0072]      FIG. 16  provides a graphical comparison of the various levels of noise generated by the use of the three prior art aspirators which were shown in FIGS.  4  to  6  and by the prototype aspirator  70  including a suction device  20  of the present invention. As seen in this Figure, the total acoustic power emitted by the prototype, connected to a 250 millimeters Hg vacuum line through a US standard connection and with its bypass inlet  36  fully open, is about 5 db less than that of the Grab Free™ aspirator in the same condition, 12 db less than the Tip-A-Dilly™ aspirator in the same condition and 14 db less than the aspirator commercialized by the Siemens company with its European connection. The reader is reminded that a 5 db difference in acoustic power represents a reduction of more than 68% of the acoustic energy, and that a 10 db difference represents a 90% reduction of acoustic energy emission.  
         [0073]     In addition to these sonometric results, listening tests also revealed that the noise generated by the aspirator  70  prototype was considered by listeners to be far less irritating due to its different spectral distribution especially in the 1000 Hz to 6000 Hz range. This is mainly due to the much lower intensity at higher frequencies of the audio spectrum, while the higher levels recorded in the lower end result in an almost pleasant humming type of noise. It has to be noted that medical research shows that the human ear is most sensitive to frequencies comprised in the high and shrill 1000 Hz to 6000 Hz range.  
         [0074]     One can easily appreciate that the above described embodiments according to the present invention provide effective solutions for the reduction of noise in suction devices while providing the user with a wide range of suction control. Therefore, it can be seen that the low-noise vacuum release suction device and the controllable aspirator provided with such a suction device can be advantageously used in miscellaneous suction applications, and more particularly in dentistry, to reduce the stress experienced by the personnel due to noise.  
         [0075]     Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.