GB2042081A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a pneumatic dental instrument a manually-operated stop-start and reversing valve 5 controls a rotary motor of e.g. the sliding-vane type, comprising a fixed eccentric cylinder 2 and a rotor 3, which has an output shaft 3' to which the shaft b of a tool e.g. a drill, can be attached. Air enters and leaves the rotor chamber within the cylinder by way of openings 8, 9 in the latter and longitudinal passages 6, 7 in the casing 10. <IMAGE>

Description

SPECIFICATION Hand-type dental instrument actuated by speed air motor This invention relates to hand-held, air powered dental instrument which can be gripped by dentist's hand for the treatment of patient's teech. More particularly, the present invention relates to an improved hand-held dental instrument provided therein with a lowspeed air motor for driving a dental tool such as a drill grinding tool or polishing tool, or any other dental tool of appropriate configuration.

Generally, any hand-held dental instrument must be as light as possible so that a dentist can operate it easily; it must produce minimum noise for the patient's comfort, and it should be capable of easy repair.

There are two types of hand held powered dental instruments, namely one powered by a low speed air motor (approx. 5,000-13,000 rpm), and another powered by an extremely high speed air motor (approx.

200,000-500,000 rpm). Conventional handheld dental instruments having a low-speed air motor, have various structural defects such that it has been difficult to achieve the high torque which is necessary for treating teeth.

To achieve the said high torque it has therefore been usual to employ high speed instruments having small air-turbine type motors. The obtained high-speed rotary power is transmitted to a deceleration device such as planetary gears to produce slow speed, high torque conditions as required for operating the dental tool. Accordingly, a conventional high speed instrument must be provided with a gearing device for deceleration, such gearing device being connected to a rotor of the air motor and a chucking or supporting device is connected to the gearing output for chucking or supporting the tool such as a tooth shaving tool. That is, according to the conventional arrangement, the rotor of the air motor and the chuck device are separated by a deceleration device.

The pressure of a gearing device housed in the grip, measures the size and weight of this grip, and thus, the convenience and comfort of handling the device is reduced. Further, since a gearing noise is produced during operation of the instrument the comfort of the patient is reduced. In addition, the gearing device is a source of malfunctioning and may require frequent repairs.

The invention, at least in its preferred form seeks to provide a handheld, air powered dental instrument which is adapted to produce a high torque at the low-speed rotation by means of an air motor, without requiring a deceleration device. That is, by providing a structure in which the rotor of the air motor is connected directly to a chuck device, the drawbacks of the conventional instruments can be eliminated.

An air-powered dental instrument actuated by a low-speed air motor comprising, in combination, a hand grip consisting of a casing containing an air motor and a chuck device for recording a dental tool such as a drill, a polishing tool or a grinding tool, said chuck being concentrically positioned with respect to the axis of rotation of a rotor of the motor; said casing defining first and second chambers; said first chamber including a plurality of air supply passages and exhaust passages defined by longitudinal projections provided around the inner surface of the casing the instrument including a cylinder contained eccentrically in the first chamber and provided with air inlets and outlets which communicate with said air passages, said rotor being contained rotatably within said cylinder; a valve member having therethrough air supply and exhaust passages communicating with said passages provided in the first chamber, said valve member being mounted into the second chamber; and air supply and exhaust hoses communicating with said air supply and exhaust passages respectively.

The dental tool, such as a shaving or polishing tool may be connected directly to the rotor by means of the chuck device, or by means of a transmission shaft contained in an angled hand which is connected to the chuck device.

The valve member is operatively mounted in the second chamber in the casing in a manner that it may be set into three stage positions, i.e. a normal stage position where the air supply and exhaust passages provided in the valve member, are connected to air supply and exhaust passages provided in the first chamber, respectively; a closed stage position where the passages are closed by the rear and surface of the casing; and a reverse stage position where the supply passage in the valve connects to the exhaust passage in the first chamber while the exhaust passage in the valve connects to the supply passage in the first chamber.

The normal stage position is for the operation of the instrument at a normal treatment, while the reverse stage position is used by a left-handed dentist or at a time when the tool is removed from the instrument.

The rotor provided in the cylinder preferably has, at its outer surface, radial grooves in which blades are slidably received. Further, the rotor has detour passages for introducing compressed air into the bottoms of the grooves when the blades are at their radially outermost positions.

For treating teeth by means of the instrument of the invention, the compressed air is forced into the air passage in the casing, then introduced through inlets into the cylinder and rotates the rotor by giving air pressure to the blades. With rotating the rotor, the air flows out from outlets provided in the cylinder into exhaust passages.

The rotor rotation is transmitted directly to the shaft of the tool, or through a shaft mounted in an angled hand to the tool so that the tool might rotate at the same speed as that of the rotor.

In the form of the invention as set forth, since air passages are provided around the inner surface of the casing by means of projections of different height, the air flows smoothly through the passages without being weakened by flow resistance. Further, as a cylinder of which the wall has a uniform thickness, can readily be positioned eccentrically from the casing within a row of projections projected from the casing, a more pre- cise working and positioning of the cylinder, can be effected than that of the conventional cylinder of which wall thickness is made not to be uniform so that the cylinder may be positioned eccentrically with relation to the casing. Accordingly, air loss is minimized resulting in improvement in rotary efficiency.

Thus, high rotary torque at low speed rotation, can be obtained from the rotor.

Therefore, it is not necessary to rotate the air motor at high speed and to decelerate the rotational speed, as is the case with the conventional arrangement. That is, since the low speed rotor power can be transmitted directly to the tool, the tool can rotate under conditions of high torque and at a speed in synchronism with that of the rotor and, thus, no gearing device for decelerating the speed is necessary.

The instrument of the invention can thus be light in weight and of short length, in comparison with the conventional instrument which is equipped with a deceleration device.

Since gearing is not used, the number of elements constituting the instrument is reduced.

Therefore, the production of the instrument becomes easier and there are no troubles with gearing. Further, unpleasant gearing noise is not produced.

In addition, since air detour passages also are provided for introducing additional air into ends of blade grooves the starting of the rotor is accelerated, resulting in further strengthening of the torque.

An embodiment of the invention will now be described in detail, and a modification thereof will be indicated, with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of a dental instrument according to the said embodiment of invention; Figure 2 is a longitudinal side view of the instrument of Fig. 1 showing the chuck device in released position; Figure 3 is a section along the line (III-III) of Fig. 2; Figure 4 is a section along the line IV-IV of Fig. 2; Figure 5 is a longitudinal side view of part of the instrument of Fig. 1 showing the chuck device in locked position; Figure 6 is a section along the line VI-VI of the Fig. 5; Figure 7 is a section along the line VII-VII of Fig. 5; Figure 8 is a section similar to that of Fig.

3, but indicates the rotor rotating in reverse direction; Figure 9 is a section similar to that of Fig.

4, but shows how the various passages connect for reverse rotation of the rotor; Figure 10 is a section similar to that of Fig.

4, but shows how the various passages are blocked preventing rotation of the rotor.

Figure ii is a side view of a dental instrument essentially the same as that of Figs. 1 to 10 except it includes the said modification of incorporating an angled hand.

In the drawings, Fig. 1 is a view showing a treatment tool B, consisting of a shaft b, and tool head b' such as a tooth shaving or polishing element, connected detachably to an air motor contained in a grip A.

Said grip A consists of a diecast cylindrical casing 10 of size easily grasped by the hand in the nature of holding a fountain pen, and contains the air motor. The air motor consists of a cylinder 2, a rotor 3 and a distributor plate 4 and a valve member 5, as will be seen in Fig. 2.

Said casing 10 has a smaller sized front portion 10' which is separated by a partition 11 from the main casing portion. The partition 1 1 is provided at its central portion with an opening for a rotor shaft 3'.

The casing 10 is provided with several longitudinal projections 1 3 on its surface so that it can be firmly gripped by the dentist.

The casing 10 defines therein a front chamber a and a rear chamber a', each of which takes up approximately half of the casing interior length. Said rear chamber a' is coentric with the casing 10, that is, the inside round surface of the casing forms the chamber a', as will be seen in Fig. 4, while a number of projections 14 each of which is of different length, project radially from the inside surface of the casing into the front chamber a and, thus, define a circular space 1 5 of the axis is eccentrical to the axis of casing 10 and in which cylinder 2 is located. Between the projections 14 are defined grooves of different depths and in normal separation the deeper grooves function as air supply passages 6 while shallow grooves function as exhaust passages 7.

As will be seen in Fig. 3, the inside of the front chamber a is provided at one side with a small projection 14'-which engages in a groove 1 6 of cylinder 2 as shown. Further, as will be seen in Fig. 4, a projection 14" is provided at the inside surface of the casing for fixing plates 4 contained in the rear chamber a' firmly to the casing 10.

Said cylinder 2 positioned in the round space 15, is provided with air openings 8 connecting to air passages 6 and with exhaust openings 9 connecting to exhaust passages 7, respectively. As mentioned above, as the groove 1 6 of the cylinder 2 engages with the projection 14' of the casing 2, the free rotation of the cylinder 2 is prevented.

The plate 4 is mounted into the end portion of the cylinder 2, and is fixed against rotation by the projection 14". The plate 4 has a central opening 1 7 which is coentrical with the casing 10 (Fig. 4).

In the cylinder 2, a rotor 3 is provided. The rotor 3 has projecting rotor shafts 3' at the front and 3" at the rear which pass through openings 1 2 partion 11 and 17, respectively, so as to lie concentric with the casing 10 (Fig.

2). The rotor is supported rotatably on bearings 18 and 19. The rotor is provided on its surface with radial grooves 20 in which blades 21 are slidably received. The blades 21 and rotor 3 act as a vane motor, and the blades move between positions of maximum and minimum projection as shown in Fig. 3 as the rotor rotates and shallow into the grooves 20, in accordance with the rotation of the rotor 3.

The plate 4 is pressed up to the end of projections 1 4 and to the rear surface of the cylinder 2 by a valve member 5, to trap the cylinder 2 and to close off the ends of the grooves. The plate 4 itself is fixed by the valve member 5 and the rotation thereof is prevented by the projection 14". The plate 4 is provided with passages 22 and 23 which communicate with air passages 6 and exhaust passages 7, respectively, and open at an inlet 22' and an outlet 23'. At the front of the plate 4, there are provided detour passages 24 and 24' which communicate the grooves 20 of the rotor 3, with passage 23.

The valve member 5 consists of a disc portion 5' mounted in the rear chamber a' and an end portion 5" of smaller size and extending from within the casing 10. As will be seen in Fig. 2, a cap 25 is mounted on the extending portion 5", in a manner enabling it to be screwed into the casing 1 0. A gasket 25' forms a seal between the end of cap 25 and disc portion 5'.

The extending portion 5' has a projection 26 by which a nut cap 27 is connected to member 5 so that the valve member 5 can be rotated. Further, the portion 5" is provided with an air passage 28 and an exhaust passage 29 which communicate with parts 28' and 29', respectively. The parts 28' and 29' are provided such that (i) when part 28' communicates with inlet 22', the other 29' communicates with the outlet 23' (normal stage position, Fig. 4); (ii) when the disc 5' is rotated and part 28' communicates with the outlet 23', the other 29' communicates with the inlet 22' (reverse stage position, Fig. 9) and (iii) at the intermediate position, the part 28' does not communicate with any of the openings 22', 23' (closed stage position, Fig.

10).

In order to simplify the precise positioning of the parts 28' 29', pins 30, 30', provided on the rear of plate 4 are so located as to engage with the ends of the part 29' as will be seen in Fig. 4 and Fig. 9, so that the normal or reverse stage position of the passages can be easily obtained. In this connection, an adjustment indication showing the normal, reverse or closed stage, is provided on the cap 27 and the cap 25. Said passages 28 and 29 are connected to an air hose 31 for introducing compressed air, and an exhaust hose 32, respectively.

With valve member 5 set for normal or forward operation, the compressed air is introduced into air passage 28 from an air hose 31, the air flows through part 28', inlet 22' passage 22, and passages 6, 6 from which it flows into cylinder 2, as will be seen in Fig. 2.

Within the cylinder 2, the air moves to rotate the blades 21, and the rotor 3 is rotated. The air passes out of outlets 9, 9 and flows back through exhaust passages 7, 7, passage 23, outlet 23', part 29', passage 29 and into the exhaust hose 32. The continuous supply of air rotates the rotor 3 and also the rotor shafts 3' and formed integrally with said rotor 3.

A part of the air in the exhaust passage 23 may flow, via the detour passage 24 and the detour passage 24', into the rotor grooves 20, 20 in the air supply passage side, so as to accelerate the outward movement of the blades 21.

When the valve member 5 is set to the reverse state (Fig. 9) by the turning of the cap 27, air supplied from the air hose 31 into the air supply passage 28, flows through the part 28', the outlet 23', the exhaust passage 23, passage 7, 7 and openings 9, 9, into the cylinder 2 so as to rotate the rotor 3 in the reverse direction. The exhaust air passes from the cylinder openings 8, 8, passages 6, 6, the passage 22, the inlet 22', the part 29', and the passage 29. Air may again pass into the grooves 20 stage, through the detour passage 24' so as to accelerate the outward movement of the blades 21.

To the grip A mentioned above, is connected a chuck device 40 which chucks or supports an instrument tool B. The rotor shaft 3', which projects from the casing part 10', is drilled at the end to define a cylindrical member 41 into which, in turn, a shaft of the tool B is inserted.

The rotor shaft 3' has a crosswisely piercing pin 43 at the position immediately adjacent the end of the cylindrical member 41. A slidable locking dog 44 is mounted on and a nut 45 is screwed over the member 41. On the nut 45 is slidably mounted a clamp dog 46. Onto the smaller casing 10' is screwed a cap 47 slidably supporting a clamp ring 48 which is fixed by a screw 49 to dog 44 and covers the rotor shaft 3', the locking dog 44, the nut 45 and so on.

The locking dog 44 has arms 52 and is urged forward by a spring 50. When the dog 44 moves backward the pin 43 engages between sleeve teeth 57 of dog 44 preventing dog 44 from rotating relative to the shaft 3'.

The inside of the front end 53 of the nut 45 is tapered as shown so as to conform to the end of the cylindrical member 41.

The clamp dog 46 has teeth 54' which are for engaging with teeth 54 of the nut 45, and arms 55 which can slide through slots 56 provided in an end cap 47A.

When the clamp ring 48 is pushed backward by hand, the clamp dog 46 and the locking dog 44 are pushed backwards and thus, the teeth 54' of the dog 46 engage with the teeth 54 of the nut 45 whilst the teeth 51 of the dog 44 engage with the pin 43.

Further, the arms 52 of the dog 44 engages with openings 56' of the cap 47. Accordingly, the rotation of shaft 3' and dog 44 relative to casing 10 is prevented (Figs. 5 thru 7).

In this condition, when the clamp ring 48 is rotated, the rotor shaft 3' is locked by the engagement of the lock dog 44, the pin 43 and the cap 47, and the cylinder nut 45 is screwed on the cylinder 41 of the locked rotor shaft 3', resulting in that the nut 45 moves backward. When the clamp nut 45 moves forward on the cylinder 41.

When the nut 45 moves backward, the bore of end 53 of tapered nut 45 is pressed over the cylinder 41 so that the shaft b is gripped by the cylinder 41. This is due to the contraction of the end of cylinder 41, which has slots 42 for this purpose. When the nut moves forward, the tapered bore end 53 is removed from the cylinder 41 and, thus the end of cylinder 41 can expand and the shaft b can be removed from the cylinder 41.

After the nut 45 has been so screwed, when the clamp ring 48 is released, the clamp dog 46 and the lock dog 44 return the original position without additional force, by the urging force of the spring 50.

In this way, by connecting the shaft b of the instrument member B directly to the rotor shaft 3' by means of the chuck device 40, the rotor power is transmitted directly to the shaft b.

Fig. 11 is a view showing how the instrument tool B' can be housed in a known angled hand V. The angled hand C contains a transmission shaft connected to the instrument, as described, so that the rotary power transmitted from the motor rotor can be transmitted to the instrument member shaft b. That is, the shaft b of the instrument member is inserted into the cylinder 41 of the rotor shaft 3' by means of the chuck device 40, as has been mentioned.

Claims (8)

1. An air powered dental instrument actuated by a low-speed air motor comprising, in combination, a hand grip consisting of a casing containing an air motor and a chuck device for recovering a dental tool such as a drill, a polishing tool or a grinding tool, said chuck being concentrically positioned with respect to the axis of rotation of a rotor of the motor; said casing defining first and second chamber; said first chamber including a plurality of air supply passages and exhaust passages defined by longitudinal projections provided around the inner surface of the casing, the instrument including a cylinder contained eccentrically in the first chamber and provided with air inlets and outlets which communicate with said air passages; said rotor being contained rotatably within said cylinder; a valve member having therethrough air supply and exhaust passages communicating with said passages provided in the first chamber, said valve member being mounted into the second chamber; and air supply and exhaust hoses communicating with said air supply and exhaust passages respectively.

2. An instrument according to claim 1, wherein the extent to which the longitudinal projections project inwardly from the inner suface of the casing varies so that the circular cylinder positioned within the row of the projections, is situated eccentric to the casing.

3. An instrument according to claim 1 or 2, wherein is manually manipulable for the fixing or release of a dental tool to ro said chuck.

4. An instrument according to claim 1, 2 or 3, wherein the chuck is such that the tool can be fixed thereto so that the shaft of the tool is concentric with the rotor axis.

5. An instrument according to claim 1, including an angled hand connected to the casing, the angled hand containing a transmission shaft which is connected to the rotor shaft and being for receipt of a dental tool.

6. An instrument according to any preceding claim, wherein the rotor has radial grooves in which blades are slidably received so that the air motor in fact acts as a vane motor and that detour passes are provided for introducing compressed air into the bottoms of the grooves when the blades at their radially outermost positions.

7. An instrument according to claim 1, wherein the valve member mounted into the second chamber, can be operated such that the air supply passages in the first chamber correspond to the exhaust passages in the valve member and the exhaust passages in the former chamber correspond to the supply passage in the valve, so that the rotor may be rotated in a reverse direction.

8. An air powered dental instrument substantially hereinbefore described with reference to the accompanying drawings.