PNEUMATIC ROTARY TOOL
A pneumatic tool includes a plastic grip. The grip includes an outer layer of soft material overmolded onto the plastic grip. The outer layer is of a one-piece construction and covers substantially an entirety of the grip. In a method of assembling a pneumatic rotary tool, a plurality of bolts are inserted through an end cover and a housing of the tool. The bolts are threaded into a clutch casing, wherein the bolts draw the end cover toward the housing and the housing toward the clutch casing so that the end caps and support sleeve of the air motor are compressed within the housing to fully seat the end caps onto the support sleeve so that the motor. The housing and the end cover cooperate to hold the air motor in proper alignment within the tool.
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This application is a continuation of U.S. application Ser. No. 10/182,167 filed Nov. 8, 2002, which is a U.S. National Application of International Application No. PCT/US01/02785 filed Jan. 26, 2001, which claims priority to the following: U.S. application Ser. No. 09/490,896 filed Jan. 27, 2000, issued Dec. 12, 2000 as U.S. Pat. No. 6,158,528 and filed as Reissue application Ser. No. 10/310,109 on Dec. 4, 2002, which reissued as U.S. Pat. No. Re. 39,009 on Mar. 14, 2006; U.S. Provisional Application No. 60/231,013 filed Sep. 8, 2000; U.S. Provisional Application No. 60/233,550 filed Sep. 19, 2000; and U.S. Provisional Application No. 60/239,754 filed Oct. 12, 2000, the entireties of each related application being herein incorporated by reference.
FIELD OF THE INVENTIONThe present invention generally relates to a pneumatic tool and a method of assembling a pneumatic rotary tool.
BACKGROUND OF THE INVENTIONThe invention is especially concerned with a powered tool that rotates an output shaft with a socket for turning a fastener element such as a bolt or nut. Tools of this type are frequently used in automotive repair and industrial applications. Conventionally, pneumatic rotary tools comprise a metallic outer housing with multiple metallic internal parts. These tools are strong and durable due to their metallic construction, although the all-metal construction makes them both somewhat heavy and costly. Pressurized air flowing through the tool powers tools of this type. As the air expands within the tool, it induces motion of an internal motor, powering the tool.
It is an aim of tool manufacturers to provide a pneumatic rotary tool that is as durable as an all-metal tool, but employs portions formed from lighter materials, such as plastic, where appropriate to reduce the weight and cost of the tool. One difficulty in the design of such a tool is the reduced rigidity of plastic as compared with a strong metal, such as steel. For instance, should a plastic tool fall against a hard surface, a metallic air motor inside the tool may shift and become misaligned, or canted, with respect to the housing and the output shaft, rendering the tool unusable. This problem has led tool manufacturers to create complex internal motor casings designed to inhibit the motor from canting in the housing. For example, U.S. Pat. No. 5,346,024 (Geiger et al.) discloses such a motor casing, described as a motor cylinder 15. This casing is cylindrical in shape, with one closed end that includes multiple parts, such as a back head 26 and bore 27, extending from the closed end. The cylinder, back head and bore are of unitary construction, making a closed end cylinder significantly more difficult to manufacture. Therefore, these casings are expensive to manufacture, which may mitigate the cost benefit of using lighter and less costly materials, such as plastic, for other parts. As such, a tool formed inexpensively from both lightweight material and metallic parts is desirable.
In addition, conventional rotary tools often incorporate mechanisms to regulate torque according to user input. One such tool uses back pressure within the air motor to regulate the torque output. As backpressure within the motor increases, the torque output of the motor decreases. Such a design is inefficient because it uses the maximum flow of pressurized air to power the tool, while operating below its maximum power. At lower torque settings, a large portion of air bypasses the motor for backpressuring the motor, adding no power to the tool. As such, a tool that can more efficiently regulate torque by using less pressurized air is needed. Moreover, a tool that can reduce backpressure in the motor will operate more efficiently, using less air for the same work.
Typically air motors incorporate a rotor having a plurality of vanes upon which the pressurized air can react, inducing rotation of the rotor. Pockets of pressurized air are received within compartments defined by adjacent vanes. Conventional rotary tools typically have a single exhaust port in the air motor for exhausting pressurized air from the motor. As each rotor compartment passes the exhaust port, much of the air within the compartment passes through the exhaust port and exits the motor. Any air remaining within the compartment after the compartment passes the exhaust port becomes trapped within the compartment. The volume of the compartment decreases as the compartment nears completion of a motor cycle, and the compartment must compress the air within the compartment for the rotor to continue to rotate. Compressing the air within the compartment (backpressure) reduces the rotational speed of the turning rotor. Backpressure reduces motor efficiency; thus, a pneumatic rotary tool that reduces backpressure losses within the air motor is desirable.
SUMMARY OF THE INVENTIONIn one aspect, a pneumatic rotary tool comprises a housing and a grip. The grip extends downwardly from the housing for allowing a user to grasp and hold the tool securely. The grip further comprises an outer layer of soft material formed to cushion and ease pressure on the user's hand and increase friction between the grip and the user. The outer layer is formed of a one-piece construction and covers substantially an entirety of the grip.
Other features will be in part apparent and in part pointed out hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
Corresponding reference characters indicate corresponding parts throughout the drawings.
DETAILED DESCRIPTION OF THE DRAWINGS Referring now to the drawings and specifically to
Referring now to
Additionally, an air exhaust 91 mounts on the lower portion of the grip 71, adjacent the air inlet 81 (
Turning to the interior workings of the tool 51,
The preferred molding process for forming the housing 53 around the air inlet cylinder 82 is a plastic injection molding process that is well known in the relevant art and described in further detail below.
The fitting 81a mounts the swivel connector 81b for pivoting of the swivel connector about the axis of the air inlet 81 via a snap ring 81c. Other mounting methods other that a snap ring 81c, such as a ball and detent, are also contemplated as within the scope of the present invention. An O-ring 81d seals between the fitting 81c and the swivel connector 81b to inhibit pressurized air entering the air inlet from escaping. The snap ring 81c and O-ring 81d do not inhibit the rotation of the swivel connector 81b on the fitting 81a. An upper end of the fitting 81a is threaded, as is the lower internal end of the air cylinder 82. The fitting 81a is threaded into the lower end of the inlet cylinder 82 until a flange 81e of the fitting abuts the lower end of the inlet cylinder. Another O-ring 81f seals between the fitting 81a and the inlet cylinder 82 so that air flows through the inlet cylinder to the working parts of the tool. A hex-shaped keyway 82d is designed to receive a hex-shaped key (a fragment of which is indicated at 82e) for rotating the fitting 81a within respect to the air inlet cylinder 82, thereby engaging the threads 82c and threading the fitting fully into the cylinder. The keyway 82d and key 82e may be formed in any number of matching shapes (e.g., star, square, pentagon, etc.) capable of transferring force from the key to the fitting 81a.
Moreover, the outer layer 73 of soft material, preferably formed from rubber, is overmolded onto the grip 71 after the plastic molding process. The preferred overmolding process forms the outer layer 73 directly on the grip 71, fusing the outer layer to the surface of the grip and providing a more secure gripping surface for the user. The overmolding process essentially requires the use of a mold slightly larger than the grip 71, such that the space between the grip and the mold can receive flowable rubber material, which forms the outer layer 73 of the grip, after the rubber cures. Because the rubber outer layer 73 fuses directly to the grip 71, the layer fits snugly over the grip and requires no further retention means. The snug fit helps the outer layer 73 stay seated against the grip 71 during tool 51 use, so that the user can firmly grip the tool without movement between the grip and the outer layer.
After the inlet 81, the air passes through a tilt valve 95, which can be opened by pulling the trigger 75 (
The pneumatic rotary tool 51 is of the variety of rotary tools known as an impact wrench. A Maurer Mechanism 131 (
Once the air passes through the rotation selector valve 83, the air travels through an air passage toward the air motor 119. The air passage may be configured with different passages as will now be described in greater detail. First, air passes through either the first or second passage 117,121 on its way to the air motor 119. Air directed through the first passage 117 passes through a torque selector 85 (
Turning to
Referring to
In the final position (
After passing through the first passage 117 and torque selector 85, the pressurized air enters the air motor 119 (
In the present invention, the end caps 179,181 engage and support the support and passaging sleeves 171,179 against canting with respect to the housing 53 under forces experienced by the tool 51 in use. Three distinct shoulder connections cooperate to rigidly connect the air motor 119, the Maurer is Mechanism casing 55 and the housing 53 (
The rotor 175 is rotatable within the passaging sleeve 173 (
As air travels through the air motor 119, the rotor 175 turns, causing the air cavities 237 to move through three stages: a power stage, an exhaust stage and a recovery stage (
At the end of the power stage, as the volume of the cavity 237 is increasing toward its maximum amount, the leading vane 177 passes a set of early stage exhaust ports 251 in the passaging sleeve 173 and support sleeve 171 (
As the rotor 175 rotates, the vanes 177 continually move radially inward and radially outward in their channels 235, conforming to the passaging sleeve 173 (
Returning to the exhaust air exiting the early stage exhaust port 251, the air then passes through a pair of orifices (not shown) in the housing 53 which lead to the air exhaust 91 in the grip 71 (
Operating in the reverse direction, the tool 51 works substantially the same, except that the air bypasses the torque selector 85. Air enters the tool 51 through the same air inlet 81. The rotation selector valve 83 diverts the air to the second passage 121 where the air travels upward through the tool 51 until it enters the exhaust manifold 255. The air then passes through the late-stage exhaust port 253 and enters the air motor 119 where it reacts on the opposite side of the vanes 177, thereby applying force to the rotor 175 in the opposite direction. The early-stage exhaust port 251 operates substantially the same as in the forward direction. The vane intake channel 261 and vane outlet channel 263 operate as before, except that they allow air to flow in opposite directions.
Typically, pneumatic rotary tools are almost entirely formed from a high strength metal such as steel. These tools are subjected to high stress and loading from proper use plus discrete impacts from being dropped or bumped. Although metal, such as steel, provides adequate strength, a significant drawback of an all-metal construction is the high weight and material cost. The design of the current invention eliminates these problems by forming the tool housing 53 from lightweight and inexpensive plastic. In addition, the design of the support sleeve 171 and the end caps 179,181 eliminates the need for machining expensive cup-like parts for the air motor. Such parts were a significant drawback of the prior art. The present invention employs a simple sleeve 171 and end cap 179,181 design that can withstand the impact loads of use with parts not requiring elaborate machining techniques as with the prior art. Moreover, the sleeve 171 and end cap 179,181 design is resistant to canting within the tool 51 because of the four bolts 135 and shoulder engagements between the parts.
The present invention is also directed to a method of assembling the pneumatic rotary tool 51 of the present invention. The tool 51 is designed for easy assembly according to the following method. The method described below is applicable to the tool 51 and its various parts as described above. The air motor 119 is assembled by engaging the rear external shoulder 201 of the first end cap 179 with an end of the support sleeve 171. The rotor 175 is then seated within the support sleeve 171 so that the splined shaft 215 extends outward through the first end cap 179. A plurality of vanes 177 are then inserted lengthwise into channels 235 of the rotor 175 for rotation with the rotor inside the sleeve 171. The second end cap 181 then engages the opposite end of the support sleeve 171 and the support shaft 213 for rotation of the rotor 175 within the sleeve, thereby completing construction of the air motor 119. The completed air motor 119 is then inserted into the housing 53.
The Maurer Mechanism 131 is then inserted into the Maurer Mechanism casing 55 so that the output shaft 57 of the Maurer Mechanism extends from the casing. The Maurer Mechanism casing 55 may then be engaged with the housing 53 for connection of the Maurer Mechanism 131 to the splined shaft 215 of the air motor 119. The Maurer Mechanism 131 will then rotate conjointly with the rotor 175 of the air motor 119. The end cover 59 then seats on the rear of the housing 53, thereby enclosing the air motor 119 within the tool housing.
To secure the Maurer Mechanism casing 55, housing 53 and end cover 59 together and ensure that the air motor 119 remains properly oriented within the housing, a plurality of bolts 135 are inserted through the end cover and housing. As described above, these bolts 135 thread into the Maurer Mechanism casing 55, drawing the end cover 59 toward the housing 53 and the housing toward the Maurer Mechanism casing. These bolts 135 compress the tool 51, including the end caps 179,181 and support sleeve 171 of the air motor 119 are compressed within the housing 53 to fully seat the end caps onto the support sleeve so that the motor, housing and end cover 59 cooperate to hold the air motor in proper alignment within the tool. The method described herein is preferred, although it is contemplated that the method steps may be reordered while remaining within the scope of the present invention.
The method preferably comprises another step where the housing 53 is formed by delivering flowable plastic to a mold to form the housing. The flowable plastic enters the mold and surrounds the air inlet 81 of the tool 51, creating the tool housing 53 with an air inlet cylinder having an interference fit within the housing. As discussed above, the inlet cylinder 81 allows source air to enter the tool 51 for use by the air motor 119. Other methods of forming a plastic housing 53 around an air inlet cylinder 81 are also contemplated as within the scope of the present invention. The method also preferably comprises a step of overmolding an outer layer 73 of soft material onto a portion of the housing 53 constituting a grip 71, after the step of molding the housing.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions, products, and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Claims
1. A pneumatic tool comprising:
- a housing; and
- a plastic grip extending downwardly from the housing for allowing a user to grasp and hold the tool securely,
- said grip further comprising an outer layer of soft material overmolded onto the plastic grip and formed to cushion and ease pressure on the user's hand and increase friction between the grip and the user, the outer layer being of a one-piece construction and covering substantially an entirety of the grip.
2. A pneumatic tool as set forth in claim 1 wherein the outer layer is formed from rubber.
3. A pneumatic tool as set forth in claim 1 wherein the outer layer is fused to the grip where the two are in contact with each other.
4. A pneumatic tool comprising:
- a housing;
- a plastic grip extending downwardly from the housing for allowing a user to grasp and hold the tool securely;
- an outer layer of material softer than the material of the plastic grip and overmolded onto the plastic grip, the outer layer being fused to the plastic grip for securing the outer layer to the plastic grip.
5. A pneumatic tool as set forth in claim 4 wherein the outer layer and the plastic grip are free of connecting structure other than the fusion of the outer layer to the plastic grip.
6. A method of assembling a pneumatic rotary tool comprising:
- bringing a first end cap into engagement with an end of a support sleeve;
- locating a rotor and a plurality of vanes within the support sleeve;
- bringing a second end cap into engagement with an opposite end of the support sleeve so that the first and second end caps, rotor and vanes cooperate to form an air motor;
- inserting the air motor into a housing;
- bringing a clutch casing encasing a clutch mechanism into engagement with the housing for engagement of the clutch mechanism with the air motor;
- seating a plastic end cover on the housing;
- inserting a plurality of bolts through the end cover and housing; and
- threading the bolts into the clutch casing, wherein the bolts draw the end cover toward the housing and the housing toward the clutch casing so that the end caps and support sleeve of the air motor are compressed within the housing to fully seat the end caps onto the support sleeve so that the motor, housing and end cover cooperate to hold the air motor in proper alignment within the tool.
7. A method as set forth in claim 6 further comprising molding the housing with flowable plastic over an inlet cylinder, wherein the flowable plastic surrounds and engages an exterior of the inlet cylinder for allowing source air to enter the tool.
Type: Application
Filed: Jan 17, 2007
Publication Date: Jul 5, 2007
Applicant: SP AIR KABUSHIKI KAISHA (Nagano)
Inventors: Osamu Izumisawa (Nagano), Kunihiro Yamamoto (Nagano)
Application Number: 11/624,003
International Classification: B21D 39/03 (20060101);