Contamination prevention device for ultra high speed dental type handpieces

A gas turbine operated handpiece instrument having a spin able front shaft mounted bur that is operated by pressurized gas or air. Two embodiments are disclosed. In one a flexible rubber like PVC one-way pinch valve is mounted on an exterior gas exhaust stack of the instrument's body housing. This embodiment allows for the internal lubrication of the turbine parts by compressing the valve sides towards each other and then spraying a lubricate into the housing through the opened valve. In another embodiment, a metallic one-way ball valve is mounted within an extension to the housing and this design is more suitable for dental bur offset instruments. In both designs, the turbine has impellers located within the hollow body of the instrument. The purpose of the one-way valves in both embodiments is to prevent contaminates from being sucked back into the housing as the gas turbine is being shut down during its complete operating range. A rear mounted hand operated plunger is connected to a plunger shaft to permit the ejection of the aligned bur's shaft when a bur change is desired.

BACKGROUND OF THE INVENTION 
Ultra high speed dental type handpiece instruments are conventionally 
configured in two major configurations. In one configuration the bur is 
aligned in a straight line with the dental instrument's handle. This 
configuration is used in dental laboratories for shaping anatomy and can 
also be used by wood carvers, glass engravers and other arts and craft 
users. It is not used in the oral cavity. 
In the second configuration, used by dentists within the oral cavity, 
called a contra angle handpiece, the cutting bur is angled sharply with 
respect to the handle. This angled mounting of the bur is necessary for 
the user to reach the top and bottom of a tooth structure. Other features 
the second configurations may have over those in the first configuration 
include fiber optics, and chip air and water lines to cool the tooth. 
The present invention discloses a new handpiece design which is similar to 
the first configuration, or laboratory style instrument, but differs by 
the way a turbine which is powered by the routing of input and exhaust 
gases. The inputted air is directly supplied to the front of the 
instrument near its bur head, rather than through or near the rear handle. 
In addition, the exhaust gas is not routed through the handle. By using a 
short length of PVC (polyvinyl chloride) tubing pinched closed at one end 
and mounted on the front end of the instrument near the bur, several 
advantages are achieved. 
One of the advantages is lubrication. In conventional designs lubrication 
is fed to the turbine by removing the input tubing from the handpiece and 
applying oil into the tubing resulting in most of the lubrication blowing 
out, without touching the internal bearings. In the present invention,. an 
aerosol lubricator, similar to WD40 .TM. is used by squeezing an exhaust 
port with the fingers to make the tubing round and then inserting the 
aerosol tip into the exhaust stack while pressing the plunger once. This 
applies a metered amount of lubrication directly into the turbine 
bearings, saturating them. Using a pinched end for the exhaust stack also 
has the added advantage of preventing dirt from entering the turbine 
housing should the handpiece be laid down in dirt. 
Still another advantage of using a pinched exhaust stack relates to an 
inherent problem in ultra high speed dental type instruments. As 
compressed gas.is used to power the instrument and there is positive air 
pressure existing in the instrument, there is no chance that dirt will 
enter the turbine housing. However, when the compressed gas supply is 
removed, the handpiece turbine continues to spin for several seconds as a 
result of momentum. During this time the spinning action becomes a vacuum 
pump and pulls contaminated air up the spindle, directly into the front 
bearing. For this reason dental handpieces need to be autoclaved to kill 
any biological matter that might have entered the turbine housing during 
its shut down operation. In the present invention, the pinched exhaust 
stack tubing causes the drive air pressure to decline slowly as it also 
closes the exhaust port to prevent the described vacuum pump phenomenon 
called "suck up". 
Details of the construction and operation of the present invention are 
described hereafter. 
DESCRIPTION OF THE PRIOR ART 
Air operated hand held dental instruments that are used to cut, grind, 
carve or engrave are known. For example, in the Murase invention (U.S. 
Pat. No. 5,340,312) an anti-contamination type elongated hand piece of a 
dental instrument is disclosed having an air turbine driven by compressed 
air. To prevent Karman's vortex street in the instrument, the inventor 
designed a unique rectilinear means formed by helical ridges or slots in 
the inner surface of air holes. 
The Rosenstatter patent (U.S. Pat. No. 5,476,380) discloses a dental 
handpiece with a selectively detachable tool holder that can be driven by 
either a mechanical structure or an air turbine. 
In U.S. Pat. No. 5,507,642 to Wohlgemuth a dental turbine drive with an 
arrangement to prevent suctioning of particles after deactivation of the 
drive air into the return air is disclosed. 
In the Lingenhole et al. reference (U.S. Pat. No. 5,676,542) the dental 
instrument described has a turbine driven straight, or angled, headpiece 
wherein roller bearing are sealed against contamination with a blocking 
ring. 
The present invention relates to a turbine operated hand held instrument 
with an air pressure regulator to maintain a constant back pressure to 
prevent contamination from entering the turbine housing all as more fully 
set forth in this specification. 
SUMMARY OF THE INVENTION 
This invention relates to a dental handpiece instrument having a spinable 
front bur that is operated by an air driven turbine within the instrument. 
A pressure regulator is used to prevent outside contamination from 
entering the instrument during all of its complete operating range. 
It is the primary object of the present invention to provide for an 
improved air turbine driven handpiece instrument having a pressure 
regulator to prevent contamination from entering the handpiece's housing. 
Another object is to provide for such a handpiece used in the dental art 
wherein the pressure regulator maintains a constant back pressure within 
the housing for the turbine. 
These and other objects and advantages of the present invention will become 
apparent to readers from a consideration of the ensuing description and 
the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a perspective view of the invention's preferred embodiment. The 
hollow, cylindrically shaped plastic housing or body member 1 has a gas 
inlet with a gas or air input tube 3 mounted on an extension with an 
internal passageway fixed to the body 1. At the body's front end, 
pressured gas, such as ambient air, is inputted to the interior of the 
hollow body at the inlet passageway or port 5. A rear plastic loop 7 
molded at its ends is mounted into the upper rear surface of the body 1 
and acts to retain the rear of tube member 3 in place on the body 1. 
A remote source of pressurized gas or air (not shown) is connected by 
tubing to the opened, rear end 9 to supply pressurized gas, ranging 
generally from 0 to up to 55 pounds per square inch (psi), to the hollow 
interior of the body 1. A reciprocable finger operated rear end plunger 11 
is associated with the rod 13, and the plunger extends from the external 
rear of the housing into the hollow interior of the body 1. At the front 
end of the body a spinable bur end 15 is mounted on the rotatable 
supporting rod 19. By pressing forward on the rear plunger end 11 the 
extension to rod 19, that is within the body 1, can be ejected when it is 
desired to replace the rod and its bur end 15 and then permit a new rod 
and bur end to be inserted in its place. 
On a body extension, with an internal passageway at the lower front side of 
the body 1, the outer valve 17 forms parts of the interior exhaust gas 
stack housing. The valve 17 is made of a flexible PVC material that is 
biased such that under normal conditions its internal gas passageway is 
pinched closed to the passage of gas through the valve to the outside of 
the housing. When sufficient internal gas pressure is developed, about 3 
to 5 psi, within the housing, however, a normally closed passageway within 
the valve opens to allow for the passage of gas from the housing to its 
exterior. 
Thus, depending on applied gas pressure, the pinch valve acts as a one-way 
check valve to either prevent the entry of external gas, and matter, into 
the housing or to allow gas and matter to exit from the housing 1. Within 
the confines of the housing or body 1 is a gas or air operated'turbine 
that is used to rotate the rod 19 and its front bur end 15. This rotation 
is powered by pressurized gas supplied via tube 3 to the turbine. The bur 
end rotates in unison with the turbine's impeller (see FIG. 2) and is 
mounted within the hollow body 1. As compressed gas is injected over these 
internal impeller blades of the turbine, the bur's shaft spins at speeds 
approaching 400,000 revolutions per minute (rpm). There is very little 
torque as the spinning of the bur shaft is based on the principle of high 
"angular velocity". Spent air exits from the turbine and the body 1 via a 
gas outlet in the body of the end of the passageway opening in the pinch 
valve exhaust stack 17. 
FIG. 2 is a reversed cross sectional view of the front portion of FIG. 1. 
In this view the PVC one-way pinch valve 17 for the lower gas exhaust 
stack is shown in a closed position. As pressurized gas enters the 
interior of hollow body 1 through the inlet gas opening 5 connected to 
tubing 3 (see arrow), the gas impinges upon the internal molded plastic 
turbine impeller 21 which rotates with the front bearing 23 and the front 
turbine spindle 25. There is a slight exterior side housing extension 
tubular member 27 with an external stepped diameter molded around the 
center input opening 5 into the body to permit the opened end of tubing 3 
to fit around the housing extension and to form a tight fit around the 
body gas inlet opening. On the lower front end of the body 1 there is 
another molded exit stack exhaust extension with an internal passageway 
opening 29. 
This outlet extension passageway communicates with the exterior passageway 
in the pinch one way check valve 17, shown in it closed and opened 
positions in FIGS. 3(a) and (b), respectively. To the front and rear of 
the turbine impellers 21, and mounted on the interior portion of shaft 19, 
are the two disk shaped bearing elements 23 and 31, respectively. These 
two shaft mounted bearing elements 23 and 31 rotate with the shaft 19 and 
its impeller 21 as pressurized gas (air) impinges upon the impeller's out 
blade surfaces to rotate the shaft. Several turbine retaining protrusions 
33, molded into the interior hollow surface of the body 1, prevent the 
turbine assembly elements 23 and 31 from moving to the front or rear of 
the body as the centrally mounted plunger shaft 35 moves in the body 1. 
The front end of plunger shaft 35 is shown in a straight line alignment 
with, but not touching, the center rear portion of impeller turbine 
assembly disk shaped element 31. Interior shaft guides and spring stop 37 
are formed with a center through hole molded into the interior of the body 
1 and acts to position the plunger's shaft 35 and insure the shaft's front 
end will point to the center of element 31. Centered on the rear end 
element 31 is front bur shaft 19. When the rear exterior plunger handle 11 
is pressed forward it forces the element 35 into engagement with the rear 
end of bur shaft 19, pushing out shaft 19 and cutting bur end 15. When 
this reciprocable action takes place, only the bur's center support shaft 
19 and bur end 15 are ejected while the other turbine assembly elements 
remain in place. 
FIG. 3(a) is a cross sectional view of the pinch valve valve 17 when in its 
normally closed position with the turbine not operating. The flexible PVC 
material making up the valve 17 is normally compressed such that the front 
end 41 of the internal slit like passageway 39 is normally closed. As gas 
pressure builds up within the body 1, the valve's internal passageway is 
spread apart and its front 41 is forced opened as shown in FIG. 3(b), 
permitting the free flow of gas from the body 1. If one desires to 
lubricate the internal turbine component members within housing body 1, 
the opening 41 may be forced opened from outside the body 1 by compressing 
the two sides of the normally closed slit passageway of valve 17 inwardly 
towards each other with one's fingers. While the valve is in this opened 
state, a user then sprays a lubricating aerosol oil within the body 1 
through the passageway openings 29 of the exhaust stack and its mounted 
valve as the pinch valve 17 remains in place on the housing. Thus, the 
normally closed pinch valve may be opened either by sufficient internal 
gas pressure or by applying an external compression pressure to its 
opposite sides outer surface. 
FIG. 4 is essentially the same as the FIG. 2 embodiment, except that a 
metallic one-way check ball valve 43 is used in place of the PVC pinch 
valve 17. The body, turbine and other parts are metallic to allow their 
use without melting in a heated autoclave. This one-way ball valve 43 
resides within the exit passageway 29 formed within a side housing 
extension 47 molded or cast into the exhaust air passage way of dental 
opatory handpieces. An inner reduced diameter passageway 45 in this 
extension 47 has a diameter less than that of the ball valve 43 and is 
used to retain the ball valve in place within the extension. Within the 
ball valve's retaining cavity 49 is a coil spring 51 that bears against 
the upper portion 53 of the ball valve 43. When pressurized air is 
exhausted, after impinging upon the impellers 21, if it has sufficient 
pressure, it can displace the ball valve 43 (see FIG. 5 (a)) from its 
normally spring biased seated position (see FIG. 5(b)). When displaced 
from its seated position by internal gas pressure working against the 
action of the bearing spring 51, there is a flow of gas around the 
displaced ball valve and out of the exit hole 29. The arrows indicate the 
direction of displacement of the ball valve 43. 
As previously mentioned, since compressed gas is used to power the 
instrument when there is a positive air pressure existing within the 
instrument there is no chance that air-carried-dirt will enter the turbine 
housing 1. Once, the compressed gas supply is removed, however, the 
handpiece turbine continues to spin for several seconds as a result of 
momentum. During this short time frame the spinning action becomes a 
vacuum pump and pulls contaminated external air into the outlet opening 
and up the spindle directly into the front bearing. To prevent this vacuum 
pump action from taking place, a one-way valve, whether the pinch valve of 
FIGS. 1-2 or the ball valve of FIGS. 4-5, is used. These valves prevents 
dirt and other undesired contaminants external of the housing from being 
sucked into the housing as the turbine is shut off. The flexible external 
pinch valve has the added benefit of allowing lubrication to be applied to 
the internal turbine workings and this embodiment would be more useful in 
straight line bur instruments used for shaping anatomy, polishing 
porcelain and metal, engraving and general carving purposes. The ball 
valve embodiment would find greater applicability if offset from the 
handle (about 60 degree) bur cutting dental instruments used in the oral 
cavity since it is made of metal and therefore more reliable and more able 
to stand the heat of an autoclave unit. The material used for the tubing 
in the pinch valve would more likely melt in the heat of the autoclave 
unit. 
Clearly, the basic principles used in the present invention need not be 
restricted to dental instruments. Any instrument having the elements as 
claimed are included within the scope of the subject matter covered. 
The plastic injection molding process can be used to make the body member 
1, its internal shaft and bearing retaining members, its external loop 7 
and the outlet molded two body side inlet and outlet extensions as a 
single molded unit. Injection molding is a plastic molding process whereby 
heat softened plastic material is forced under very high pressure into a 
metal cavity mold, usually aluminum or steel, which is relatively cool. 
The inside cavity of the mold is comprised of two or more halves, and is 
the same desired shape as the product to be formed (in this case the body 
1). High pressure hydraulics are used to keep the mold components together 
during the actual injection phase of the molding process. The injected 
plastic is allowed to cool and harden in the mold. The hydraulics holding 
the multiple component mold cavity together are released, the mold halves 
are separated and the solid formed plastic item is removed. Injection 
molding can be a highly automated process and is capable of producing 
extremely detailed parts at a very cost effective price. The process 
should be invaluable in producing this invention's handpiece cost 
effectively. 
Although the preferred embodiment of the present invention and the method 
of using the same has been described in the foregoing specification with 
considerable details, it is to be understood that modifications may be 
made to the invention which do not exceed the scope of the appended claims 
and modified forms of the present invention done by others skilled in the 
art to which the invention pertains will be considered infringements of 
this invention when those modified forms fall within the claimed scope of 
this invention.