Fluidic control assembly for dental tools

A fluidic control assembly for controlling the supply of drive air and/or water to a tool such as a dental handpiece in response to its presence or absence in a hanger in which it is removably stored. The assembly comprises a primary fluidic control and a secondary control, with the primary fluidic control having a control valve which directs the flow of drive air from a source of supply through a primary chamber to a main outlet coupled to the handpiece. The control valve extends into a secondary chamber having means for operating the control valve in response to a predetermined pressure level in the secondary chamber. The secondary chamber communicates with the secondary control, which is integrated in the hanger for sensing the presence or absence of the tool in the hanger. The secondary control causes a build-up of pressure in the secondary chamber when the tool is absent from the hanger and causes the pressure in the secondary chamber to drop below the predetermined level when the tool is present.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a fluidic control assembly for controlling the 
delivery of air and/or water to dental equipment and, more particularly, 
to a fluidic control assembly for a dental tool such as a handpiece. 
2. Description of the Prior Art 
Conventional dental drills are operated at relatively high speeds by an air 
turbine driven from a source of air at a regulated pressure. High speed 
dental drills usually also have provision for discharging water as a 
stream, or jet in direct proximity to the drill. Likewise air may be 
delivered either with or without the drill itself being turned on. Water 
and air are supplied to the drill from separate water and air supply 
source in the dental office. 
It is typical for the supply of air and/or water to be operated from a foot 
switch under the control of the dentist. In addition to the foot switch, a 
control assembly is used to automatically control the supply of drive air 
to the dental drill and to discharge a stream of water into the oral 
cavity. The control assembly is generally designed to operate in response 
to the removal of the tool or handpiece from its cradle. Prior art control 
assemblies are designed to use pneumatic valves in combination With 
electrical and/or hydraulic controls to form a complex and expensive 
control unit, which is difficult to install and generally requires a 
substantial amount of expertise to repair and maintain. 
A more recent control arrangement developed by applicant uses a modular 
fluidic block design as shown and described in U.S. Pat. No. 4,459,106. 
Although the fluidic block forms a compact control unit, it is 
operationally dependent upon the accuracy in alignment between a source of 
compressed air and a sensing chamber for detecting the presence or absence 
of the handpiece in its hanger. A laminar flow of air must bridge an air 
gap and strike a diaphragm in the sensing chamber When the tool is removed 
from the hanger. The tool otherwise fills the air gap, blocking the air 
flow. Accordingly, the accuracy in alignment between the source of 
compressed air and the sensing chamber is critical to the operation of the 
control unit and requires each unit to be factory tailored and tested. 
Moreover, the operation between the control unit, the handpiece, and the 
valve diaphragm in the sensing chamber are so mechanically interrelated 
that specialized personnel are necessary to undertake the installation of 
the control unit in the dental office. In addition, the control unit is 
part of the hanger assembly and cannot be separated for repair. 
Accordingly all repair must be done directly in the dental office or the 
entire assembly, including the handpiece and hanger, must be removed from 
the dental office. 
A substantial need has developed for a more simplified control unit, and 
preferably of miniature size which requires no special training to 
install, is easy to maintain, and may be physically independent of the 
hanger assembly so that the control unit can be repaired simply by 
replacement with a substitute unit While the inoperative unit is returned 
to the factory. 
SUMMARY OF THE INVENTION 
it is the principal object of the present invention to provide a miniature 
size fluidic control assembly in the form of a cassette for controlling 
the supply of air and water to a dental tool which is inexpensive to 
manufacture, easy to install and requires no maintenance. 
it is a further object of the present invention to provide an inexpensive 
control assembly for controlling the supply of air and water to a dental 
tool which incorporates a primary fluidic control unit for providing drive 
air and/or water to the dental tool and a secondary control responsive to 
the presence and/or withdrawal of the dental tool from its hanger to 
actuate the primary unit. 
it is an even further object of the present invention to provide a fluidic 
control assembly for supplying air and/or water to a dental tool which 
includes a manual bypass in said secondary control for permitting a tool 
to be removed from its hanger for replacement of a dental burr without 
causing drive air and/or water to be supplied. 
These and other objects are attained in accordance with the fluidic control 
assembly of the present invention which includes: 
a primary fluidic control unit for supplying 
drive air and/or water to a dental tool adapted to be removably stored in a 
hanger and a secondary pneumatic control for causing the primary control 
to either supply or interrupt drive air to such dental tool in response to 
the presence or absence of the dental tool from its hanger; wherein the 
primary fluidic control unit is formed from a modular body comprising: 
a control chamber having a main inlet and a main outlet; 
means for introducing drive air through said main inlet and into said 
control; 
a control valve for directing drive air from said chamber into said main 
outlet when said valve is open; 
a secondary chamber; 
means for bleeding air from said control chamber into said secondary 
chamber; 
means in said secondary chamber for opening said control valve When the 
pressure in said secondary chamber builds up to above a predetermined 
level; 
means for discharging air from said secondary chamber to maintain the 
pressure therein below said predetermined level; and 
means for coupling said secondary chamber to said secondary control wherein 
said secondary control includes means for blocking the discharge of air 
from said secondary chamber in response to the absence of said dental tool 
from the hanger.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows an overall block diagram of a dental handpiece control system 
incorporating the fluidic control assembly (10) of the present invention. 
For multiple handpiece operation, a separate fluidic control assembly (10) 
is required for each dental handpiece, although the source of compressed 
air and water may be common to all handpiece controls. Each handpiece 
control in a multiple handpiece operation may also operate from a common 
foot switch (12). 
A source of compressed air (14) and a source of water (16) is typically 
available in all dental offices. The source of compressed air (14) is 
regulated by a pressure regulator (17) and is then fed through a valve (V) 
and a flow restrictor (18) into an air supply line which feeds into the 
primary fluidic control unit (20). The flow restrictor (18) is added as an 
option to provide manually adjustable pressure regulation before delivery 
to the handpiece. An adjustable pinch valve may be used for the flow 
restrictor (18). The valve (V) is conventional and operated by the foot 
switch (12). The regulated compressed air through valve (V) is also fed 
through an air-operated switch (19) in line (21). The air-operated switch 
(19) may be manually operated or responsive to the foot switch (14) to 
provide an additional air signal to the control unit (20). Water is 
supplied to the unit (20) from the water supply (16) under the control of 
an on/off switch (22). The delivery of air and/or water is controlled by 
the operation of the primary fluidic control (20) in combination with a 
secondary control (25). 
The fluidic control assembly (10) of the present invention comprises the 
primary fluidic control unit (20) and the secondary control (25). The 
secondary control (25) preferably forms an integral part of the instrument 
hanger (26). The instrument hanger (26) represents a conventional cradle 
for accommodating a dental tool or handpiece (H), such as a dental drill. 
The primary fluidic control unit (20) is of modular design and preferably 
in the form of a miniature-sized cassette which is readily located an 
mounted in any desired location in the dental office. The control unit 
(20) may be separated from the secondary control (25) and from the 
instrument hanger and handpiece. The air and water supply lines (27) and 
(28) are the only connections from the primary fluidic control unit (20) 
to the handpiece (H). 
The preferred construction of the primary fluidic control unit (20) is 
shown in FIGS. 2A and 2B. The control unit (20) has a body (30) composed 
of any desired material, preferably of elastomeric plastic. A plurality of 
cavities (31), (32) and (33) are molded into the body (30). It is 
preferred to mold a substantial number of cavities in forming the body 
(30) so as to minimize the requirement for machining. The exposed cavities 
are then sealed using a cover plate (29), as is shown in FIG. 2B. The 
cover plate (29) may have a transparent section (23) forming a window to 
observe the flow of water through the body (30). 
A drilled channel (34) is formed between the cavities (31), (32) and (33), 
and a plurality of openings (35) and (36) are machined through the body 
(30) into the open areas (31) and (33), respectively. A threaded fitting 
(37) is threadably inserted into the opening (36). The fitting (37) 
includes an open passageway (38) and two barbed connections (39) and (40) 
extending from the open passageway (38). The primary fluidic control unit 
(20) is coupled to the secondary control (25) of FIG. 3 through conduits 
(41) and (42), respectively. Another threaded fitting (43) is threadably 
inserted into the opening (35). The threaded fitting (43) has a central 
passageway (44) and a barbed inlet fitting (45), with a central opening 
(46) forming the main inlet for drive air into the fluidic control unit 
(20) from the air supply line (8) in FIG. 1. 
A channel 50) is formed in the body (30) connecting the area (32) to a 
barbed outlet fitting 52) for supplying drive air into the tubing (27) 
under the operation of a main control valve (62). Tubing (27) is connected 
to the dental handpiece (H). The main control valve (62) includes a drive 
piston (63) connected between an upper piston head (64) and a lower piston 
head 65 . The drive piston (63) extends between cavities (31) and (33), 
with the upper piston head (64) located in cavity 31 and the lower piston 
head 65) located in cavity 33. The upper piston head (64) has a conical 
surface (66) for engaging the valve seat (67) to close the control valve 
(62) when the upper piston head (64) is forced downwardly. The control 
valve (62) is opened when the lower piston head (65) is urged upwardly, 
lifting the head (64) off the valve seat (67) to provide ingress to air 
flow from cavity (31) to area (32) via the channel (34). 
A flexible diaphragm (68) is connected to the lower piston head (65) to 
divide the cavity (33) into sections for forming a separate upper area 
(69). The lower piston head (65) has a conical surface (70) for engaging a 
valve seat (71) when the drive piston (63) is urged upwardly to open the 
main control valve (62). The flexible diaphragm (68) contacts a ledge (72) 
When the control valve (62) is fully open. In this position the upper 
section (69) is isolated from the cavity (33). An elongated passageway 
(73) in the body (30) connects the upper section (69) to the atmosphere to 
provide fast relief for exhausting pressure from the cassette and to 
maintain separation between the outlet flow of drive air and the flow of 
bleed air into area (33). 
The drive piston (63) has an orifice (74) extending longitudinally through 
the piston (63) to provide direct access between cavity (31) and cavity 
(33). The orifice (74) is a restricted opening of small diameter which 
permits drive air to bleed through the control valve (62) into cavity (33) 
at a slow rate. The static pressure in cavity (33) builds up until the 
control valve (62) is opened. The build up of static pressure is under the 
control of the secondary control (25) of FIG. 3, as will be explained in 
greater detail in connection with the description of the operation of the 
fluidic control unit (20). 
A channel (54) is machined in the body (30) for connecting cavity (32) to a 
hollow inlet fitting (55) to which the air signal line (21) of FIG. 1 is 
connected. A valve member (53) is interposed in channel (54) to control 
the flow of water from the inlet conduit (16) to the water supply line 
(28). The water supply line (28) is connected to the handpiece (H). The 
valve member (53) has an upper head (76) and a lower head (77). The lower 
head (77), in conjunction with an "O" ring (78) are urged against a wall 
surface (79) when drive air is present in channel (50) to open channel 
(54) permitting air to flow from the air supply line (21) through valve 
(53) in response to actuation of the air-operated switch (19) in FIG. 1. 
The air flow through valve (53) is directed into a one-way check valve 
(80) located in cavity (81). The check valve (80) has a stem (82) and is 
axially movable within the cavity (81). A two-way valve (83) extends 
between cavity (81) and cavity (84). The two-way valve (83) has a head 
(85) in cavity (84) and a head (86) in cavity (81). A hollow fitting (87) 
with a barbed inlet (88) is connected to the supply of water in the dental 
office through the inlet tubing (16) for providing water into cavity (84). 
When the two-way valve (83) is open, water flows from cavity (84) through a 
channel (89) into the supply tubing (28) leading to the dental handpiece 
(H). The supply tubing 28 is connected to a barbed inlet (90) in a hollow 
fitting (91) threaded into the channel (89). The water pressure in cavity 
(84) will normally force the head (85) of the two-Way valve (83) to its 
closed position with the "O" ring (92) engaging the wall surface (93). The 
two-way valve (83) is forced to open When the stem (82) of the check valve 
(80) is urged against the head (86) to break the seal formed by the "O" 
ring (92). The amount of water fed through the tubing (28) is controlled 
by a pinch valve (95) represented by an adjustable screw threaded into the 
body (30) and having one end (96) adapted to contact the supply tube (28) 
within a channel (97) formed in the body (30). 
The body (30) of the control unit (20) also includes a channel (99) in 
Which chip air is directed from the chip air supply line (7) of FIG. 1 
through a one-way check valve (101). The chip air is fed through the 
hollow fitting (102) and barbed inlet (103) into the supply line (105) 
leading to a separate chip air dispenser (not shown). Supplementary air 
from the air supply (8) may also be fed into the supply line (105) alone 
or in combination with the supply of chip air. The supplementary air is 
supplied through the main control valve (62) when it is open. The drive 
air from the air supply (8) passes through the open control valve (62) and 
through a check valve (106) into a channel (107) communicating with 
channel (99) under the control of a manual air coolant adjustment assembly 
(108). The air coolant adjustment assembly (108) includes a manually 
adjustable fitting (109) which has a threaded outer body (110) that is 
threaded into a female threaded interior opening (111). An elongated 
piston (112) extends from the body (110) through the channel (107) into 
the channel (99). The piston (112) has a head (104) at one end with an "O" 
ring (113) disposed under the head (104). The "O" ring (113) is positioned 
above a ledge (114). The piston (112) has a male thread (116) at its 
opposite end which is thread into the body (110). By turning a knurled 
knob (115) extending from the fitting (109), the piston (112) is forced to 
turn, moving either upwardly or downwardly in the channel (107). When the 
"O" ring (113) engages the ledge (114), no supplementary air will flow 
into the channel (99). The amount of supplementary air is regulated by 
adjustment of knob (115). An air gauge (not shown) may be connected to a 
barbed fitting (116) to read the air pressure of the air supply through 
the check valve (106). 
The secondary control (25), as shown in FIG. 3, is formed as an integral 
part of the handpiece hanger (120). The hanger (120) is adapted to be 
mounted in a stationary position affixed to a support (121) which fits 
into a conventional hanger bracket not shown) in the dental office. The 
handpiece (H), shown in phantom lines, rests in the cavity (122) of the 
hanger (120). In the at-rest position, the handpiece (H) presses against 
the secondary control valve (130) which lies in a channel (131) formed in 
the hanger (120). The forward end (132) of the control valve (130) is 
movable laterally over a relatively small distance. The control valve 
(130) has a head (133) at its opposite end with an "O " ring (134) mounted 
thereabout. A hollow fitting (135) with a barbed inlet (136) is threadably 
inserted into the cavity (137). The tubular conduit (42) is connected to 
the barbed inlet (136) for coupling the cavity (137) in hanger (120) to 
the cavity (33) in the control unit (20). 
A rotary valve assembly (140) is also connected to the hanger (120) to 
enable a dental burr to be changed in the dental drill without operation 
of the drill. The rotary valve assembly (140) has a tubular body (141) 
which is rotatably mounted over a fitting (142) threaded into the hanger 
(120). A valve (143) is connected to the fitting (142). The valve (143) 
has a central opening (144) and a cross drilling (145). The tube (41) is 
mounted over an inlet (146) to provide direct access between the cavity 
(33) in the control unit (20) and the opening (144). The tubular body 
(141) of the rotary valve assembly (140) has an aperture (148) which is 
manually alignable with the cross drilling (145) upon rotation of the body 
(141). in the aligned or open position, the rotary valve assembly, (140) 
permits removal of a burr without operation of the dental turbine. In the 
closed position, with the opening (148) out of alignment with cross 
drilling (145), the secondary control (25) determines if air and Water is 
supplied to the handpiece (H). 
OPERATION OF THE FLUIDIC CONTROL 
With the handpiece (H) at rest in the hanger (120), the secondary control 
valve (132) is physically shifted to its open position with the head (133) 
and "O38 ring (134) displaced from the ledge (137). In this position, air 
is permitted to escape into the atmosphere through the cavity (122). The 
discharged flow of air is so low, however, that it cannot be heard. The 
air escapes from around the forward end (132) of the control valve (130). 
The escape of air from the secondary control valve (132) prevents any 
build-up of pressure in cavity (33) of the control unit (20). Accordingly, 
the drive air flowing into chamber (31) from the air supply line (8) will 
keep the main control valve (62) closed. Upon removal of the dental 
handpiece (H) from the hanger (120), the air flow through conduit (42) 
will force the secondary control valve (130) to close. Assuming the rotary 
valve assembly (140) is in the closed position, with the valve (143) out 
of alignment with aperture (148), a back pressure Will develop in cavity 
(33) increasing the static pressure until a predetermined pressure is 
reached, sufficient to open the main control valve (62) by forcing the 
diaphragm member (68) upwards. This occurs relatively rapidly, opening the 
main supply of drive air from cavity (31) through the open control valve 
(62), through channel (50) and into the air supply line (27) to operate 
the drill. 
If a supply of water to the drill is also desired, the air switch (19) is 
activated under the operation of the foot control or manually to provide a 
supply of air through line (21). This depresses the valve member 53), 
which allows drive air from cavity (32) to enter check valve (80), moving 
it axially into contact with the head (86) of the two-way valve (83) 
which, in turn, opens valve (83) to permit water to pass from supply line 
(16) into the supply conduit 28). The flow of water is controlled by the 
flow control pinch valve (95) under the manual operation of knob (150). 
If the handpiece (H) is momentarily returned to the hanger (120), drive air 
immediately ceases to flow as a result of closing the main control valve 
(62) by releasing the static pressure in cavity (33). A burr can be 
changed in the dental drill without the supply of drive air to the drill 
by unlocking the rotary valve assembly (140). This permits air to escape 
from the aperture (148) and prevents any build-up of pressure in cavity 
(33). 
Although only one handpiece control unit (20) is shown for a single 
handpiece (H), if multiple handpieces are to be controlled, a 
corresponding multiple number of control units (20) are necessary. The 
multiple control units (20) may be arranged in tandem using the said 
source of air and water, as shown in FIG. 1.