JPS6147540B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a sudden stop device for an air bearing type handpiece, and in particular to a leak-free exhaust passage for discharging air used up for rotational driving of an air turbine to the atmosphere. This invention relates to a sudden stop device for a medical air bearing type handpiece equipped with a shutoff valve or a flow rate adjustment valve.

(Prior art) As a conventional sudden stop device for an air bearing type handpiece, Japanese Patent Publication No. 46-31519 and Utility Model Application Publication No. 1987-
This was disclosed in Publication No. 124413. The former uses two three-way solenoid valves 21, 22 and an opening delay relay 38 to control a switch 37, as shown in FIG. The supply of air from the compressed air source to the passage 17 is started, a braking force is applied to the turbine, and after the turbine is stopped, the residual pressure is passed through the air supply passage 16 which is shut off by the three-way solenoid valve 21 which is opened to the atmosphere by the relay 38. is removed. On the other hand, the latter is an improvement on the former to stop the rotation of the turbine in the shortest possible time by reducing fluctuations in the delay operation due to deterioration of the delay relay and changes in the environment such as temperature and humidity. As shown in Figure 3, air timer 3 is used instead of the delay relay.
15, release the foot switch 320 to start stopping, and switch the four-way solenoid valve 302 to connect the compressed air source 301 to the exhaust passage 316 of the hand piece 300.
The air supply passage 31 is communicated with the turbine to apply braking force to the turbine.
6 to the atmosphere, and after a predetermined period of time has elapsed, the pilot valve 310a is moved as shown in the figure to open the exhaust passage 31.
The supply of compressed air to 7 is cut off. Therefore, compressed air is injected from the rear of the turbine and compressed air is supplied to the bearing mechanism even during braking.
There will be no inconvenience such as the bearing mechanism becoming under negative pressure and dust etc. being sucked in. However, these prior art techniques have the following drawbacks.

(Problem to be Solved by the Invention) In other words, in both of these two prior arts, compressed air for braking is supplied from the exhaust passage during braking, and is discharged to the outside air from the air supply passage, so the supply pressure The pressure in the bearing air supply hole also drops due to the drop in air pressure, and the gap in the thrust direction of the bearing is not formed properly, causing metal contact, and compressed air is supplied from the exhaust passage, resulting in a drop in the pressure in the bearing air supply hole. The disadvantage is that the voids in the metal are eccentric in one direction, causing metal contact and accelerating wear. The air gap in the radial direction regulates the rotational axis of the turbine and is as small as 5 to 15 microns. Moreover, the size of the air gap is determined by the shape of the air supply hole and the shape of the bearing, and the tolerance is small (for example, the inner diameter of the air supply hole If the diameter is 0.18φ and the gap in the radial direction is 10.5μ, high-speed rotation of 500,000 rpm is possible.) Even wear of 1 to 2μ will significantly reduce bearing performance, resulting in a decrease in rotational speed the next time it is used. , which induces the bad phenomenon of increased noise.

(Means for Solving the Problem) The sudden stop device for an air bearing type handpiece of the present invention comprises: an air bearing that supports a rotating shaft that supports a cutting tool; a turbine provided integrally with this rotating shaft; In an air bearing handpiece, the air bearing type handpiece includes an air supply passage that supplies compressed air to a bearing and a turbine, and an exhaust passage that exhausts air used up to drive the rotation of the turbine. It has a switching valve for opening and closing an air passage to release residual pressure, and a timer circuit for controlling the switching valve, and the exhaust passage is an exhaust passage without air bleed, and the exhaust passage is opened and closed. The present invention is characterized by providing an on-off valve or a flow rate regulating valve for the purpose of the present invention, and a control means for controlling these switching valves, on-off valves, or flow rate regulating valve. A new and improved air bearing that supplies air to maintain radial bearing function and closes the exhaust passage to stop air flow in the thrust gap, creating negative bearing stiffness and causing sudden stops due to friction. The purpose of the present invention is to provide a sudden stop device for a type handpiece.

(Function) Compressed air supplied from the air supply passage continues to be supplied to the air bearing even after the exhaust passage is shut off by closing the exhaust passage opening/closing valve or flow rate adjustment valve to stop the rotation of the turbine after using the handpiece. , to form an air flow within the radial bearing gap to ensure the radial bearing function. The opening/closing valve or the flow rate regulating valve provided in the exhaust passage can be opened and closed as detailed in the specification and drawings of the patent application “Air Turbine Handpiece Control Device” filed on the same day by the applicant. By adjusting the rotation speed of the air turbine, the rotation of the air turbine with excellent torque retention is controlled.At the same time, in order to stop the turbine suddenly, the flow of exhaust gas is stopped by completely closing the turbine. It functions to prevent pressure drop and to prevent outside air from flowing back into the bearing and preventing minute foreign matter from entering. It also stops the flow of air in the air gap in the thrust direction of the air bearing, creating negative bearing stiffness in the thrust bearing. The tightening friction brings the turbine to a sudden stop. This thrust direction air gap is generally 40μ to 70μ
Even if it expands to about 10μ due to wear, there will be no major change in performance.

(Example) Hereinafter, an example of the sudden stop device for an air bearing type handpiece of the present invention will be described with reference to the drawings.

FIG. 1a is a longitudinal sectional view of the head of an air bearing type dental air turbine handpiece suitable for use in an embodiment of the present invention, and FIG. FIG. 1c is an explanatory diagram of a preferred first embodiment of the sudden stop device, FIG. 1c is an explanatory diagram of the second embodiment, and FIG. 1d is an explanatory diagram of the third embodiment.

In FIG. 1a, an air bearing type dental air turbine handpiece 100 is provided integrally with a rotating shaft 112 that supports a cutting tool, and is rotatably mounted in a head housing 111 via a pair of upper and lower bearings 113, 114. Supported air turbine 115
, an air supply passage 116 that supplies compressed air to the air turbine 115 , and an air supply passage 116 that supplies compressed air to the air turbine 115 .
It has an exhaust passage 117 with no leakage bleed air for discharging the air used for the rotational drive to the atmosphere. Both bearings 113 and 114 are configured in an annular shape,
Further, O-rings 118 installed on the upper and lower sides of the bearing air grooves 113' and 114' of each bearing section are connected to the bearings 113 and 114 and the head housing 111'.
Maintains an airtight relationship with Therefore, the bearing air grooves 113' and 114' are also maintained airtight. Each bearing 113, 114 is formed with a plurality of air supply holes 119 extending in the radial direction, the inner ends of which open into the inner surfaces of the bearings 113, 114, that is, the bearing surfaces, and the outer ends of which open through ring-shaped surface passages 119'. ,
It communicates with bearing air grooves 113' and 114'.
Furthermore, air supply branch pipes 121, 122, 123 are provided on the handpiece body side of the head housing 111.
and an exhaust pipe line 124 are formed, each branch air supply line communicating with the air supply passage 116, and the exhaust passage connecting the inner surface of the exhaust passage 117, through which the passage 116 passes, and the outer surface of the passage 116. It communicates with the space between. The branch line 123 opens through a nozzle 123' facing the surface of the turbine blade.
Therefore, when air is injected from nozzle 123', turbine 115 rotates. Exhaust passage 124
is open facing the back side of the turbine blade. Therefore, the air used to rotate the turbine 115 is discharged from the exhaust pipe 124 through the exhaust passage 117 to the outside. On the other hand, since the air supply pipe 121 communicates with the upper bearing air groove 113' and the air supply pipe 122 communicates with the lower bearing air groove 114', the air sent to the pipes 121 and 122 is The outer peripheral surface of the shaft 112 and each bearing 1 pass through the air supply hole 119.
13 and 114, that is, the gaps a and b between the bearing surfaces. The sent air causes the shaft 112 to float away from the bearing surface, and also to create a gap c between the upper surface of the turbine 115 and the lower surface of the upper bearing 113, which handles the load in the radial direction of the shaft 112. The gap d between the lower surface of the turbine 115 and the upper surface of the lower bearing 114 is the gap a,
b, and also communicates with the exhaust pipe line 124. Therefore, the air sent to the gaps a and b is subsequently sent to the gaps c and d, whereby the turbine 115 is spaced apart in the thrust direction and floats, and copes with the load in the thrust direction.

On the other hand, FIG. 1b shows a first embodiment of the sudden stop device of the present invention. Air supplied from a compressed air source 141 passes through a filter (not shown) and a pressure reducing valve 143, and then enters a 3-port 2 port as a pilot valve.
It passes through the position switching valve 144 and further passes through the air supply passage 116, is supplied to the handpiece 100, and is guided to the bearings 113, 114 and the turbine 115 via the air supply branch pipes 121, 122, 123 as described above. . The exhaust gas used to drive the rotation of the turbine 115 passes from the exhaust pipe line 124 through the exhaust passage 117,
It passes through a pilot on-off valve 145, a variable throttle valve 146 and a servo valve 147 arranged in parallel, and is discharged to the atmosphere. The exhaust passage 117 leading to the servo valve 147 has a structure that is highly airtight and has no air bleed. Rotation speed control is turned on when you step on it.
ON-OFF switch 1 that turns OFF when released.
48 and a servo motor control circuit 149, the foot controller 150 is controlled according to the amount of depression. The amount of depression is converted into, for example, a pulse electric signal in a servo motor control circuit 149, which adjusts the opening degree of a servo valve 147 equipped with a pulse motor that obtains the amount of shaft rotation in proportion to the number of input pulses. Stopping of the air turbine 115 is started by removing your foot from the foot controller 150. First, the ON-OFF switch 148 is turned OFF, and the timer circuit 160 and the pilot valve 144 are turned OFF.
The supply of electric power to the 3-port 2-position switching valve 151, which serves as a main control valve for controlling the supply of compressed air to the 3-port 2-position switching valve 151, is stopped, and the supply of compressed air is immediately cut off by the spring force. Accordingly, the control air pressure to the opening/closing valve 145 of the exhaust passage 117 is also depressurized and moved to the closed position by the spring force, thereby blocking the exhaust passage 117 as described in the (action) column. As a result, the rotation of the air turbine 115 is suddenly stopped. From the moment you take your foot off the float controller 150 until the turbine 115 suddenly stops, compressed air continues to be supplied to the handpiece 100 via the pilot valve 144 controlled by the timer circuit 160.
bearings 113 and 11 until bearings 5 completely stop rotating.
4 maintains the radial bearing function. The timer circuit 160 connects the main control valve 151 to the on-off valve 14.
5 to the control air pipe 161 to the pilot valve 14
Branch pipe 16 that branches in parallel and connects to 4 and communicates with it.
It is composed of a check valve 162 provided at the branch pipe 1', a variable throttle valve 163 and an air tank 164 provided at the other branch pipe 161", and the ON-OFF switch 14 is turned on when the handpiece 100 is in operation.
8 is in the ON state, the air tank 164 is filled with compressed air from the compressed air source 141.
The pilot valve 144 is held open even during the braking period when the ON-OFF switch 148 is OFF. However, braking started and the ON-OFF switch 148
When the main control valve 151 is turned off, the main control valve 151 moves to the atmosphere release state as described above, and the compressed air in the air tank 164 is discharged to the atmosphere via the throttle valve 163, and the pilot valve 144 is activated by spring force. The air supply pipe 116, which had been moved to the atmosphere and then closed,
The residual pressure inside the hand piece 100 and the exhaust pipe 117 is released to the atmosphere. This prevents the handpiece 100 from inadvertently operating due to residual pressure.

On the other hand, the second embodiment shown in FIG. This is done by closing the 3-port 2-position switching valve 172 in the air supply passage 116 that mainly controls starting
As in the first embodiment, after the stop time has elapsed by an appropriate timer circuit, the air conditioner is moved to the atmosphere release state and the residual pressure is released. In addition, the third embodiment shown in FIG. 100
The rotation speed and stop of the motor are controlled.

(Effects of the Invention) As described above, according to the sudden stop device for an air bearing type handpiece of the present invention, the on-off valves 145, 171 or the flow rate adjustment valve 1 provided in the exhaust passage 117
By completely blocking the exhaust passage 117 by the air bearing 73, negative rigidity is created on the thrust surface of the bearing, and the turbine 115 is suddenly stopped, and the air supply is continued until the sudden stop. ,114
Because it retains the radial bearing function of
The rotational performance and load performance of the handpieces 100, 100c are not impaired, and the housing 111
Since the internal pressure is kept high, it is possible to prevent the backflow of outside air and the intrusion of foreign matter into the bearing portion at the same time, greatly improving the durability of the air bearing type handpieces 100, 100c. Furthermore, safety is greatly improved by immediately stopping the rotation of the tool due to its elliptical nature after the treatment. Furthermore, by providing the switching valves 144, 172 in the air supply passage 116 and releasing the residual pressure after the rotation of the turbine 115 is stopped, it is possible to prevent the handpieces 100, 100c from inadvertently operating due to the residual pressure. Safety will be further improved.

[Brief explanation of the drawing]

FIG. 1a is a longitudinal sectional view of the head of an air bearing type dental air turbine handpiece suitable for use in an embodiment of the present invention, and FIG. An explanatory diagram of a preferred first embodiment of the sudden stop device, FIG. 1c is an explanatory diagram of the second embodiment, FIG. 1d is an explanatory diagram of the third embodiment, and FIG. 2 is a conventional dental FIG. 3 is an electric/pneumatic control circuit diagram of a conventional dental air bearing turbine. (Explanation of symbols) 100, 100c...Air bearing handpiece, 112...Rotating shaft, 113, 114
...Air bearing, 115...Air turbine, 116...
Air supply passage, 117...Exhaust passage, 145, 171...
Opening/closing valve, 173...Flow rate adjustment valve, 144, 172...
Switching valve, 160...timer circuit.

Claims (1)

[Scope of Claims] 1. An air bearing that pivotally supports a rotating shaft that supports a cutting tool, a turbine that is provided integrally with the rotating shaft, an air supply passage that supplies compressed air to the air bearing and the turbine, and An air bearing type handpiece comprising an exhaust passage for discharging air used up for rotational driving of a turbine, wherein the air supply passage includes a switching valve for opening and closing the air supply passage to release residual pressure; and a timer circuit for controlling a switching valve, and the exhaust passage is an exhaust passage without air bleed, and is provided with an on-off valve or a flow rate adjustment valve for opening and closing the exhaust passage. Sudden stop device for bearing type handpiece. 2 The air supply passage is provided with a 3-port 2-position switching valve that opens and closes the air supply passage, and the air supply passage is
An on-off valve or a flow rate adjustment valve for opening and closing the air supply passage is provided, and the air supply passage is kept open for a predetermined period of time from the start of stopping until the rotation of the turbine stops, and after the elapse of the predetermined period, the switching valve is opened. A control circuit is provided to close the opening/closing valve or the flow rate regulating valve so as to close the opening/closing valve or the flow rate regulating valve so as to close the exhaust passage and to shut off the exhaust passage at the same time as the stop starts. Stop device.