Tool driving or impacting – Drive adjustable to completely change kind of drive
Reexamination Certificate
1999-09-13
2001-06-26
Smith, Scott A. (Department: 3721)
Tool driving or impacting
Drive adjustable to completely change kind of drive
C173S218000, C173S221000, C173S093500
Reexamination Certificate
active
06250399
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The invention relates generally to pneumatic tools. More specifically, this invention relates to a pneumatic tool with a reverse valve having an overdrive for variable torque and speed.
2. Related Art
Heretofore, various types of reverse valves have been used in pneumatic tools, e.g., impact wrenches and pulse tools. For example, U.S. Pat. No. 5,083,619 to Giardino et al., and assigned to
Chicago Pneumatic Tool Company
, discloses a plunger type reverse valve for reversing the direction of a rotor in an impact wrench. U.S. Pat. No. 3,714,994 to Zoerner et al., and assigned to
Gardner
-
Denver Company
, discloses rotary reverse valves. Furthermore, the related art includes overdrive reverse mechanisms for hydraulic motors, see, e.g., U.S. Pat. No. 3,586,466 issued to Erickson. All the patents referred to herein are hereby incorporated by reference.
One of the disadvantages of pneumatic tools is the ability to obtain variable torque and variable speed in the same tool in both forward and reverse directions. This is important in applications such as large structure construction, demolition or repair, e.g., bridges. For example, one problem in these applications which has long existed and has not been adequately addressed is providing enhanced torque and speed for removal of a lug nut subject to corrosion, dirt, or paint. Typically, a worker has two impact wrenches available, a small light weight impact wrench and a large heavy impact wrench. The small impact wrench is used for the majority of the lug nuts so a worker does not get tired and for ease of manipulation. The large impact wrench is for removal of difficult lug nuts. Such a large impact wrench is heavy and cumbersome to carry when only needed for hard to remove lug nuts. Furthermore, carrying two impact wrenches to be available for the occasional hard to remove lug nut, is time consuming and inefficient.
Heretofore, variable torque and speed hydraulic motors have been disclosed. However, hydraulics when used on hand-held tools has several disadvantages. For example, hydraulics retains heat generated by friction, etc. Another disadvantage is that hydraulic fluid must be contained in a sealed system. If the hydraulic system does not have adequate seals, hydraulic fluid will be lost from the system resulting in slick fluid leaking on the tool.
Another disadvantage in a hydraulic system, such as disclosed in U.S. Pat. No. 3,586,466, is that as torque is increased, speed decreases. This is because pressurizing a single chamber between the rotor and housing with a noncompressible fluid causes the rotor to rotate at a first speed and torque. However, by pressurizing two chambers, the rotor rotates at an increased torque and decreased speed since hydraulic fluid is not compressible, and does not expand to fill an area. In contrast, when air is subject to an increased area, it quickly expands to fill that area. Accordingly, pressurizing two chambers with air results in an increased torque and increased speed. A useful analogy is a balloon filled with air exploding when poked with a pin. This is because air in the balloon is compressed and moves quickly to neutralize the surrounding air pressure. In contrast, a balloon filled with water when poked does not explode, but slowly leaks. This is because the water is not compressed.
While the related art provides for pneumatic tools having reverse valves, and hydraulic motors having variable speed and torque, none provide a pneumatic tool having a reverse valve with variable speed and torque, i.e., overdrive. Such a device is needed to solve the long-felt problems in the power tool industry which have not been heretofore adequately addressed.
SUMMARY OF THE INVENTION
It is an advantage of this invention to overcome the above noted deficiencies. In order to do so, this invention provides a pneumatic tool including a housing; a rotor, rotatably mounted within the housing; an output shaft, operatively coupled to the rotor; pressure chambers, defined between the housing and the rotor; and a pneumatic reverse valve, operatively coupled to control the rotor, the pneumatic reverse valve having an overdrive providing increased torque and increased speed to the output shaft. Furthermore, the present invention provides for a reverse valve for a pneumatic tool having a housing; a rotor, rotatably mounted within the housing; and pressure chambers, defined between the housing and the rotor, the pneumatic reverse valve includes an overdrive for increased torque and increased speed.
One of the advantages of a pneumatic tool of this invention is the ability to obtain increased torque and increased speed in the same tool. This addresses the problems in applications such as large structure construction, demolition or repair, e.g., bridges.
A further advantage of this invention is that it does not have the problems of hydraulics. Pneumatic tools do not heat up like hydraulic motors, but are self cooling because as the air flows through the tool it expands and cools. Furthermore, pneumatic tools do not require a closed system like hydraulics having inherent sealing problems. Air enters a pneumatic tool through an inlet and exits into the atmosphere through an exhaust port. A pneumatic tool does not leak. Thus, a pneumatic tool does not require the complicated sealing structure of a hydraulic motor.
Another advantage of a pneumatic tool is that as torque is increased, speed is increased as well.
Another advantage of this invention is that the reverse valve allows control of motor direction and overdrive in both the forward and reverse directions.
A feature of the invention is that the reverse valve can be provided in a variety of forms. For instance, the reverse valve can be a plunger valve or, more preferably, a rotary reverse valve. Optionally, a plunger/rotary reverse valve combination may be used.
A rotary reverse valve of the present invention may include a rotatable planar element that includes at least three apertures therethrough. The openings of the rotatable planar element may direct flow of air through a variety of layout configurations which allow selective delivery of pressurized air to one or more ports. For example, the openings can be laid out in a T-shape, a y-shape, or a Y-shape with an extra opening between the upper openings (e.g., ø or peace sign shaped).
It is a further feature of a rotary reverse valve of the present invention that when the reverse valve takes the form of a rotatable planar element, the valve includes a rotatably positionable handle extending externally of the housing of the motor for positioning by the operator.
A pneumatic tool according to this invention includes pressure chambers defined between the housing and the rotor to provide an overdrive feature. Each of these chambers contains a first, forward-driving port for receiving pressurized air to drive the motor in a forward direction and a second, reverse-driving port to receive pressurized air to drive the motor in a reverse direction. As will be described herein, a further advantage of the present invention can be extended to a pneumatic tool with any number of pressure chambers surrounding the rotor.
The foregoing and other features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention.
REFERENCES:
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patent: 3093360 (1963-06-01), Krouse
patent: 3472323 (1969-10-01), Hall
patent: 3752241 (1973-08-01), Bent
patent: 3951217 (1976-04-01), Wallace et al.
patent: 4016940 (1977-04-01), Spring, Sr.
patent: 4708210 (1987-11-01), Rahm
patent: 4962787 (1990-10-01), Mayhew
patent: 5918686 (1999-07-01), Izumisawa
patent: 6047780 (2000-04-01), Lin
patent: 6082986 (2000-07-01), Seward et al.
Chicago Pneumatic Tool Company
Schmeiser Olsen & Watts
Smith Scott A.
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