AU2017213341B2

AU2017213341B2 - Air tool

Info

Publication number: AU2017213341B2
Application number: AU2017213341A
Authority: AU
Inventors: Taishin Imai; Keiichi Murakami
Original assignee: Nitto Kohki Co Ltd
Current assignee: Nitto Kohki Co Ltd
Priority date: 2016-01-25
Filing date: 2017-01-25
Publication date: 2019-05-09
Anticipated expiration: 2037-01-25
Also published as: AU2017213341A1; TWI617391B; JPWO2017130994A1; JP6494805B2; GB2566582B; KR102061479B1; KR20180095906A; CN108495735B; CN108495735A; GB2566582A; TW201738032A; DE112017000484T5; GB201810989D0; WO2017130994A1

Abstract

[Problem] To provide a pneumatic tool in which an expansion chamber is formed without requiring an increase in the external size of a housing. [Solution] In this pneumatic tool, a housing has: a cylindrical motor housing section 30A that has a motor-accommodating part 30a and an output shaft-accommodating part 30b which is connected contiguously to an end of the motor-accommodating part 30a, and which accommodates an annular bearing 22 and a motor output shaft extending out of the annular bearing; a tool shaft housing part 30B; and a curved corner housing part 30C that connects the motor housing part 30A and the tool shaft housing part 30B. The output shaft accommodating part 30b has an expansion chamber 36 which is connected to an exhaust connection hole 34 extending radially outward of the annular bearing 22, and which extends in the circumferential direction and the longitudinal axis direction. The expansion chamber 36 is configured to have an inner volume large enough to allow for expansion of exhaust air that passes through the exhaust connection hole 34 and comes into the expansion chamber 36.

Description

AIR TOOL

TECHNICAL FIELD [0001] The present invention relates to air tools having an air motor and, more particularly, to an air tool having an expansion chamber of large cubic capacity provided in the flow path of exhaust from an air motor at a position close to the air motor, thereby increasing the air motor operating efficiency.

BACKGROUND [0002] An air grinder, which is an air tool, generally has a structure in which a tool driving shaft is drivably connected to a rotational drive output shaft of an air motor through a bevel gear unit, and a rotary abrasive disc is attached to the distal end of the tool driving shaft.

[0003] For such an air grinder, it is necessary, in order to increase the air motor operating efficiency, to reduce the pressure at the exhaust side of the air motor as much as possible to thereby increase the differential pressure between the air supply-side pressure and the air discharge-side pressure across the air motor. In an air grinder for example, an expansion chamber is provided in an exhaust passage to allow expansion of air discharged from an air motor, thereby reducing the exhaust-side pressure.

[0004] Further, in the above-described air grinders, exhaust from the air motor is blown onto the peripheral wall of a part that accommodates the bevel gear unit, thereby suppressing the lubricant scattered from the rotating bevel gear from adhering to the peripheral wall, and also allowing the lubricant adhering to the peripheral wall to be removed therefrom and to adhere to the bevel gear again, and thus making an attempt to achieve efficient lubrication.

[0005] The above-described attempt to increase the air motor operating efficiency, i.e. the provision of an expansion chamber, is likely to cause an increase in the external size of the housing of the air motor. When the external size increases, the above-described air grinder or other hand-held air tool may suffer from the following problems: it becomes difficult for the worker to grip the air tool; it becomes difficult to visually

- 1 2017213341 11 Apr 2019 recognize a working region which is at the distal end of the air tool; and it becomes difficult to work in narrow spaces, e.g. comer areas.

[0006] To increase the lubrication efficiency by supplying exhaust into the bevel gear unit chamber, it may be conceivable to blow exhaust from the air motor directly onto the bevel gear to thereby allow lubricant particles entrained in the exhaust to adhere to the bevel gear. In this regard, however, the exhaust supplied into the bevel gear unit chamber is high-pressure and high-speed gas. Therefore, even if the exhaust is blown onto the bevel gear, no substantial adhesion of lubricant to the bevel gear can be expected.

[0007] An advantage of the present disclosure is that it provides an expansion chamber in an exhaust passage of an air motor without causing an increase in external size of an air tool, and another advantage of the present disclosure is that it provides an air tool configured to enable a bevel gear unit to be lubricated even more efficiently by introducing reduced-pressure exhaust into a bevel gear chamber.

SUMMARY [0008] According to a first aspect, there is provided an air tool comprising an air motor having a rotor driven to rotate about a first longitudinal axis, a cylindrical rotor casing rotatably accommodating the rotor, and a motor output shaft extending from one end of the rotor along the first longitudinal axis, a tool driving shaft extending along a second longitudinal axis at a predetermined angle to the first longitudinal axis; an annular bearing unit closing an end of the rotor casing at the one end of the rotor and rotatably supporting the motor output shaft, a bevel gear unit having a first bevel gear provided at an end of the motor output shaft and a second bevel gear provided at an end of the tool driving shaft to mesh with the first bevel gear, thereby drivably connecting the motor output shaft and the tool driving shaft, and a housing accommodating the air motor, the annular bearing unit, the bevel gear unit, and the tool driving shaft. The housing has the following: a cylindrical motor housing section extending in the direction of the first longitudinal axis, the motor housing section having a motor

-2 2017213341 11 Apr 2019 accommodating section accommodating the air motor and an output shaft accommodating section contiguously connected to an end of the motor accommodating section to accommodate the annular bearing unit and a portion of the motor output shaft that extends from the annular bearing unit; a cylindrical tool shaft housing section accommodating the tool driving shaft; and a corner housing section bent to connect an end of the motor housing section and the tool shaft housing section. The motor accommodating section has an exhaust receiving portion provided radially outside the rotor casing, the exhaust receiving portion extending in both a circumferential direction and the direction of the first longitudinal axis to receive exhaust discharged from the rotor casing. The output shaft accommodating section has an exhaust communication hole extending radially outside the annular bearing unit in the direction of the first longitudinal axis to communicate with the exhaust receiving portion. The output shaft accommodating section further has an expansion chamber extending in both the circumferential direction and the direction of the first longitudinal axis to communicate with the exhaust communication hole. The expansion chamber has a curved crosssectional area larger than that of the exhaust communication hole so as to have a cubic capacity allowing expansion of exhaust entering the expansion chamber through the exhaust communication hole. At least one of the corner housing section and the output shaft accommodating section has an exhaust outlet extending from the expansion chamber to communicate with the outside of the housing.

[0009] In this air tool, the expansion chamber is provided in the output shaft accommodating section. The portion of the output shaft accommodating section in which the expansion chamber is provided is a portion that accommodates a portion of the output shaft that extends from the annular bearing unit, and a portion of the housing that surrounds the periphery of the output shaft has a thick wall. The expansion chamber is provided in the thick-walled portion so as to extend in both the circumferential and axial directions, thereby forming a large cubic capacity for receiving exhaust. Therefore, there is substantially no need to increase the external

-3 2017213341 11 Apr 2019 size of the housing. Exhaust that enters the expansion chamber formed in this way is greatly reduced in pressure therein. Accordingly, it is possible to reduce the pressure at the exhaust side of the air motor and hence possible to increase the pressure difference between the exhaust side and the intake side of the air motor, thereby making it possible to increase the air motor operating efficiency.

[0010] Specifically, the arrangement may be as follows. The expansion chamber is spaced from the annular bearing unit in the direction of the first longitudinal axis, and the exhaust communication hole has two communication hole portions extending in the direction of the first longitudinal axis between the annular bearing unit and the expansion chamber. The two communication hole portions are circumferentially spaced from each other.

[0011] Further, the expansion chamber may extend in the circumferential direction over an angle range of from 150° to 180° about the motor output shaft.

[0012] The air tool may further include an exhaust blow hole extending from the expansion chamber and opened on a wall surface of a chamber accommodating the bevel gear unit to blow exhaust onto the gear unit.

[0013] In the above case, it is preferable that the exhaust blow hole be directed to blow exhaust onto tooth surfaces of the first bevel gear that face in the direction of rotation of the first bevel gear when rotating.

[0014] Embodiments of the air tool according to the present invention will be explained below on the basis of the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS [0015] Fig. 1 is a longitudinal sectional view of an air grinder as one embodiment of the present invention.

Fig. 2 is a sectional plan view of the air grinder taken along a longitudinal axis A of a rotor in Fig. 1.

Fig. 3 is a sectional view taken along the line III-ΠΙ in Fig. 1, showing the configurations of an expansion chamber and exhaust communication holes, together

-42017213341 11 Apr 2019 with the relationship therebetween, in which illustration of a tool driving shaft and so forth is omitted, and in which a first bevel gear is shown by the outline.

Fig. 4 is a rear view of a housing of the air grinder in Fig. 1 when the air grinder is viewed from the rear side thereof.

Fig. 5 is an illustration showing one form of blowing exhaust onto the bevel gear.

DESCRIPTION OF EMBODIMENTS [0016] As shown in the accompanying drawings, an air grinder 10 as an air tool according to the present invention has a basic structure comprising an air motor 18, a tool driving shaft 20, an annular bearing unit 22, a bevel gear unit 28, and a housing 30. The air motor 18 has a rotor 12 driven to rotate about a first longitudinal axis A, a cylindrical rotor casing 14 rotatably accommodating the rotor 12, and a motor output shaft 16 extending from one end (left end as seen in the figures) of the rotor 12 along the first longitudinal axis A. The tool driving shaft 20 extends along a second longitudinal axis B substantially perpendicular to the first longitudinal axis A, and an abrasive disc D is attached to the lower end thereof. The annular bearing unit 22 closes the left end of the rotor casing 14 and rotatably supports the motor output shaft

16. The bevel gear unit 28 has a first bevel gear 24 provided at the left end of the motor output shaft 16 and a second bevel gear 26 provided at the upper end of the tool driving shaft 20 to mesh with the first bevel gear 24, thereby drivably connecting the motor output shaft 16 and the tool driving shaft 20. The housing 30 accommodates the air motor 18, the annular bearing unit 22, the bevel gear unit 28, and the tool driving shaft 20. In the illustrated example, the air motor 18 is a vane air motor. Reference sign 18a denotes vanes accommodated in respective radially extending grooves formed on the rotor 12. As the rotor 12 rotates, the vanes 18a slide against the inner peripheral surface of the rotor casing 14 while being displaced in the radial direction. Reference sign 14a denotes exhaust ports provided interspersedly over substantially half around the rotor casing 14. Compressed air which has driven the rotor 12 is

-5 2017213341 11 Apr 2019 discharged to the outside of the rotor casing 14 through the exhaust ports 14a.

[0017] The housing 30 has a cylindrical motor housing section 30A, a cylindrical tool shaft housing section 30B, and a comer housing section 30C. The motor housing section 30A has a motor accommodating section 30a extending in the direction of the first longitudinal axis A to accommodate the air motor 18 and further has an output shaft accommodating section 30b contiguously connected to the left end of the motor accommodating section 30a to accommodate the annular bearing unit 22 and a portion of the motor output shaft 16 that extends leftward from the annular bearing unit 22.

The tool shaft housing section 30B accommodates the tool driving shaft 20. The comer housing section 30C is bent to connect the left end of the motor housing section 30A and the upper end of the tool shaft housing section 30B.

[0018] The motor accommodating section 30a has an exhaust receiving portion 32 provided radially outside the rotor casing 14. The exhaust receiving portion 32 extends in the circumferential direction over 360° and also extends in the direction of the first longitudinal axis A (along substantially the entire length of the rotor 12) to receive exhaust from the exhaust ports 14a.

[0019] The output shaft accommodating section 30b has an exhaust communication hole 34 extending radially outside the annular bearing unit 22 in the direction of the first longitudinal axis A to communicate with the exhaust receiving portion 32. The output shaft accommodating section 30b further has an expansion chamber 36 provided at a position spaced forward from the annular bearing unit 22 and communicated with the exhaust communication hole 34. In the illustrated example, the exhaust communication hole 34 comprises a first communication hole portion 34a (e.g. three first communication hole portions 34a circumferentially spaced from each other) extending in the direction of the first longitudinal axis A through a support projection 30e of the housing 30 that is configured to engage the outer peripheral surface of the rotor casing 14. The exhaust communication hole 34 further comprises a second communication hole portion 34b extending annularly radially outside the annular

-62017213341 11 Apr 2019 bearing unit 22 to communicate with the communication hole portion 34a, and a third communication hole portion 34c extending from the second communication hole portion 34b to communicate with the expansion chamber 36. In the illustrated example, as shown in Fig. 3, the expansion chamber 36 is provided to curve in the circumferential direction over substantially 180°, and two arcuate third communication hole portions 34c are formed to communicate with the circumferential opposite ends, respectively, of the expansion chamber 36. The expansion chamber 36 has a crosssectional area larger than any of the first to third communication hole portions 34a to 34c so as to have a cubic capacity allowing expansion of exhaust entering the expansion chamber 36 through the exhaust communication holes 34. It is preferable that the expansion chamber 36 should extend over from substantially 150° to substantially 180° in accordance with the circumferential spacing angle between the two exhaust communication holes 34. In this embodiment, the expansion chamber 36 extends over an angle range of substantially 180° so that the circumferential opposite end portions of the expansion chamber 36 overlap the exhaust communication holes 34 as seen in Fig. 3. [0020] At least one of the output shaft accommodating section 30b and the corner housing section 30C (both of them in the illustrated example) is provided with an exhaust outlet 38 or 40 communicated with the expansion chamber 36 and communicating with the outside of the housing 30. In the present invention, the expansion chamber 36 is provided in the output shaft accommodating section 30b by using a portion thereof around the motor output shaft 16 extending from the annular bearing unit 22, which portion is thicker in wall thickness than a portion of the output shaft accommodating section 30b around the annular bearing unit 22, thereby allowing exhaust from the air motor 18 to expand while avoiding an increase in circumferential size of the housing 30, and thus discharging the expanded exhaust to the outside from the exhaust outlets 38 and 40. In the illustrated example, the exhaust outlets 38 and 40 are provided in a side surface of the comer housing section 30C, as shown in Fig. 4, and communicated with the outside through a single large opening 42 configured to allow a

-7 2017213341 11 Apr 2019 sound absorbing material or the like (not shown) to be installed therein.

[0021] Fig. 5 shows one example of the arrangement of an exhaust blow hole 44 extending from the expansion chamber 36 and opened on the wall surface of a chamber 28a accommodating the bevel gear unit to blow exhaust expanded in the expansion chamber 36 onto the first bevel gear 24. The exhaust blow hole 44 is configured to blow exhaust entraining lubricant particles from the air motor onto the first bevel gear 24, thereby allowing the lubricant to adhere to the first bevel gear 24. In this regard, it is preferable to direct the exhaust blow hole 44 toward the tooth surfaces facing in the direction of rotation, as shown in the figure. The reason for this is to enable efficient lubrication by making the lubricant adhere to the surfaces that engage the second bevel gear. In the present invention, exhaust that has been reduced in pressure and speed in the expansion chamber 36 is blown onto the first bevel gear 24, and this enables oil to efficiently adhere to the tooth surfaces of the first bevel gear 24. The reason why exhaust is blown onto the first bevel gear 24 is that the first bevel gear 24 heats up more easily than the second bevel gear 26 because the first bevel gear 24 is made smaller in diameter (smaller in the number of teeth) than the second bevel gear 26 to transmit rotation from the first bevel gear 24 to the second bevel gear 26 after the speed thereof has been reduced. In Fig. 5, a hole 19 opened in a lower left-hand portion is for fitting a spindle lock when the abrasive disc is to be replaced to lock the gear so that the tool driving shaft 20 having the abrasive disc attached thereto will not rotate.

[0022] Although one embodiment of the air tool according to the present invention has been explained above, the present invention is not limited thereto. For example, the air tool is not limited to the air grinder, but the present invention is applicable to other air tools, e.g. an air sander, and an air screwdriver.

[0023] Throughout the specification and the claims that follow, unless the context requires otherwise, the words “comprise” and “include” and variations such as “comprising” and “including” will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of

-82017213341 11 Apr 2019 integers.

[0024] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge.

[0025] It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that the invention is not limited to the embodiment or embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the scope of the invention as set forth and defined by the following claims.

List of Reference Signs:

[0026] Air grinder 10;

Rotor 12;

Rotor casing 14;

Exhaust port 14a;

Motor output shaft 16;

Air motor 18;

Hole 19;

Tool driving shaft 20;

Annular bearing unit 22;

First bevel gear 24;

Second bevel gear 26;

Bevel gear unit 28;

Chamber 28a;

Housing 30;

Motor housing section 30A;

Motor accommodating section 30a;

-92017213341 11 Apr 2019

Output shaft accommodating section 30b; Support projection 30e;

Tool shaft housing section 30B;

Comer housing section 30C;

Exhaust receiving portion 32;

Exhaust communication hole 34;

First communication hole portion 34a; Second communication hole portion 34b; Third communication hole portion 34c; Expansion chamber 36;

Exhaust outlet 38, 40;

Opening 42;

Exhaust blow hole 44

Claims

1. An air tool comprising:

an air motor having a rotor driven to rotate about a first longitudinal axis, a cylindrical rotor casing rotatably accommodating the rotor, and a motor output shaft extending from one end of the rotor along the first longitudinal axis;

a tool driving shaft extending along a second longitudinal axis at a predetermined angle to the first longitudinal axis;

an annular bearing unit closing an end of the rotor casing at the one end of the rotor and rotatably supporting the motor output shaft;

a bevel gear unit having a first bevel gear provided at an end of the motor output shaft and a second bevel gear provided at an end of the tool driving shaft to mesh with the first bevel gear, thereby drivably connecting the motor output shaft and the tool driving shaft; and a housing accommodating the air motor, the annular bearing unit, the bevel gear unit, and the tool driving shaft;

the housing having:

a cylindrical motor housing section extending in a direction of the first longitudinal axis, the motor housing section having a motor accommodating section accommodating the air motor and an output shaft accommodating section contiguously connected to an end of the motor accommodating section to accommodate the annular bearing unit and a portion of the motor output shaft that extends from the annular bearing unit;

a cylindrical tool shaft housing section accommodating the tool driving shaft; and a corner housing section bent to connect an end of the motor housing section and the tool shaft housing section;

the motor accommodating section having an exhaust receiving portion provided radially outside the rotor casing, the exhaust receiving portion extending in both a circumferential direction and the direction of the first longitudinal axis to receive

- 11 exhaust discharged from the rotor casing;

the output shaft accommodating section having an exhaust communication hole extending radially outside the annular bearing unit in the direction of the first longitudinal axis to communicate with the exhaust receiving portion, and an expansion chamber extending in both the circumferential direction and the direction of the first longitudinal axis to communicate with the exhaust communication hole, the expansion chamber having a curved cross-sectional area larger than that of the exhaust communication hole so as to have a cubic capacity allowing expansion of exhaust entering the expansion chamber through the exhaust communication hole;

at least one of the comer housing section and the output shaft accommodating section having an exhaust outlet extending from the expansion chamber to communicate with an outside of the housing.

2. The air tool of claim 1, wherein the expansion chamber is spaced from the annular bearing unit in the direction of the first longitudinal axis, the exhaust communication hole having two communication hole portions extending in the direction of the first longitudinal axis between the annular bearing unit and the expansion chamber, the two communication hole portions being circumferentially spaced from each other.

3. The air tool of claim 1 or 2, wherein the expansion chamber extends in the circumferential direction over an angle range of from 150° to 180° about the motor output shaft.

4. The air tool of any one of claims 1 to 3, further comprising:

an exhaust blow hole extending from the expansion chamber and opened on a wall surface of a chamber accommodating the bevel gear unit to blow exhaust onto the gear unit.

5. The air tool of claim 4, wherein the exhaust blow hole is directed to blow exhaust onto tooth surfaces of the first bevel gear that face in a direction of rotation of the first bevel gear when rotating.