Note: Descriptions are shown in the official language in which they were submitted.
i ~ - -I ~- . n . I
CA 02236356 2005-O1-25
PNEUMATIC TOOL WITH A REVERSE VALVE
HAVING AN OVERDRIVE
BACKGROUND OF THE INVENTION
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.
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. Patent 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. Patent No. 3,719,994 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. Patent No.
3,586,466 issued to Erickson.
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
1
CA 02236356 1998-04-29
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. patent 3,586,966, is that as torque is
increased, speed decreases. This is because pressurizing a
2
CA 02236356 1998-04-29
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
3
CA 02236356 1998-04-29
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
4
CA 02236356 1998-04-29
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
IS 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., lY 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
5
CA 02236356 1998-04-29
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.
BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiments of this invention will be
described in detail, with reference to the following figures,
wherein like designations denote like elements, and wherein:
Fig. 1 shows an isometric view of pneumatic hand tool
including a rotary reverse and overdrive selection valve in
accordance with an embodiment of the present invention;
Fig. 2 shows a rear view of the interior of a valve housing
including the valve in accordance with the first embodiment of
6
CA 02236356 1998-04-29
the present invention;
Fig. 3 shows a cross-sectional view of the valve housing
along line 3-3 of Fig. 2 in accordance with the present
invention;
Fig. 4 shows a cross-sectional view of the valve housing
along line 4-9 of Fig. 2 in accordance with the present
invention;
Fig. 5 shows an isometric view of the valve in accordance
with the first embodiment of the present invention;
Fig. 6 shows an isometric view of the valve in accordance
with a second embodiment of the present invention;
Fig. 7 shows an isometric view of the valve in accordance
with a third embodiment of the present invention;
Fig. 8 shows an isometric view of the valve in accordance
IS with a fourth embodiment of the present invention;
Fig. 9 shows a rear view of a motor chamber in accordance
with an embodiment of the present invention;
Fig. 10 shows a rear view of a motor chamber in accordance
with an alternative embodiment of the present invention;
Fig. 11 shows a front view of an inner housing of the motor
in accordance with the present invention;
Fig. 12 shows a side view of the inner housing of the motor
in accordance with the present invention; and
7
CA 02236356 1998-04-29
Fig. 13 shows a rear view of the inner housing of the motor
in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention is disclosed for use with pneumatic
S tools, such as an impact wrench, nut runner, or pulse tool. It
should be noted, however, that a reverse and overdrive selection
valve in accordance with the present invention can be used on a
variety of pneumatic tools having various reverse valve
configurations such as a plunger valve having an axis parallel to
the output shaft (shown in U.S. patent 5,083,619), plunger valves
having an axis perpendicular to the output shaft (not shown) and
combination plunger/rotary reverse valves (not shown).
Furthermore, the present invention is disclosed, illustratively,
for use with a rotary reverse valve. However, it should be noted
that the present invention may find applicability in any reverse
valve on a pneumatic tool.
Fig. 1 shows an isometric view of a pneumatically driven
hand tool including a first embodiment of a rotary reverse and
overdrive selection valve 20 in accordance with the present
invention. The valve 20 is shown positioned in a valve housing
12 attached to the rear of a pneumatic tool 10 including an
output shaft 60.
In order to select a drive option with the valve 20 shown in
8
CA 02236356 1998-04-29
Fig. 1, the operator turns the valve handle 22 to a selected
position. In the particular embodiment shown, the operator may
choose between a forward position, a reverse position, a forward
overdrive position and a reverse overdrive position. The drive
option positions are illustrated to the operator by an arrow
provided on the valve handle 22 which points to markings on the
valve housing 12. For this particular embodiment of valve, "F"
and "R" indicate forward and reverse, respectively, and
"FX2" and "RX2" indicate forward and reverse overdrive,
respectively.
So that operation of the reverse and overdrive selection
valve can be better understood, the internal operation of the
pneumatic motor will now be described. In Fig. 2, a rear view of
the interior of the valve housing 12 including the reverse and
overdrive selection valve 20 in accordance with a first
embodiment of the present invention is shown. Figs. 3 and 4,
show cross sectional views of the air driven tool including the
valve housing 12, taken from the perspective of lines 3-3 and 4-4
of Fig. 2, respectively.
Referring to Figs. 3 and 4, the pneumatic tool 10 has a
motor housing 9 and valve housing 12. The motor housing 9
includes a rotor chamber 51 for rotatably supporting a rotor 50.
The rotor 50 is in turn operatively coupled to the output shaft
60 of the tool. At the rear of the motor housing 9, an inner
9
CA 02236356 1998-04-29
housing 30 is connected so as to limit the openings into the
motor housing 9. The valve housing 12 is sealingly attached by
bolts (not shown) to the rear of the motor housing 9 to provide
pressurized air via opening 14, shown in Fig. 4.
As exemplified by comparing Figs. 9 and 10, the number of
pressure chambers 19 provided to drive the rotor 50 may be
changed to accommodate different sized rotors, higher or lower
speeds, higher or lower torque, etc. For simplicity, however,
the present invention will be primarily described hereafter in
terms of a two chambered housing. To form the chambers 19, as
shown in Fig. 9, the interior periphery of the motor housing 9 is
provided with alternating circumferentially spaced concavities 15
and cylindrical surface portions 16. When the rotor 50 is placed
within the motor housing 9, pressure chambers 19A, 19B are
defined between the rotor 50 and concavities 15. Otherwise, the
rotor 50 is seated in the cylindrical surface portions 16 for
rotation.
The rotor 50 is driven by pressurized air entering through
one or more of ports 35-38 formed in the motor housing 9. The
pressurized air entering through ports 35-38 rotates the rotor by
moving a plurality of vanes 54 seated in radially extending slots
52 in the rotor 50. It should be understood that although eight
vanes 54 are shown, more or fewer vanes may be used. The vanes
are biased outwardly by pressurized air delivered to the
CA 02236356 1998-04-29
innermost part of the slots 52 and by centrifugal force. The
outer ends of vanes 54 are held in contact with the inner
periphery of the motor housing 9 regardless of whether the vanes
59 are within the cylindrical portions 16 or pressure chambers
19A-B. To allow escape of the pressurized air to the atmosphere,
a plurality of exhaust ports 13 are provided surrounding the
rotor chamber 51. The exhaust ports extend into the valve housing
12 as shown at 13A.
Returning to the motor, each pressure chamber 19A, 19B
includes two ports: a first port 35, 37 and a second port 36, 38.
The first and second ports of each chamber are located at
opposite ends of the chamber. To direct pressurized air to the
ports 35-38, an inner housing 30, as detailed in Figs. 11-13, is
provided at the rear of the rotor chamber 51. The inner housing
30 includes a plurality of openings 31-34 which allow pressurized
air to pass from the valve housing 12 into ports 35-38.
Inner housing 30 also is provided with a bearing 72, having
balls 73, to support the axle of the rotor 50 (not shown).
Furthermore, inner housing 30 is provided with a circular lip 39,
shown in detail in Figs. 12 and 13, which extends rearwardly into
the valve housing 12 to rotatably direct the valve 20 as will be
described below.
In operation, first ports 35, 37 of chambers 19A, 19B,
either alone or in combination, drive the rotor in a first
11
CA 02236356 1998-04-29
direction (e. g., a forward clockwise direction as shown in Fig.
8) when pressurized air is directed therethrough from inner
housing openings 31 and/or 33, respectively. Similarly, second
ports 36, 38 drive the rotor in a second direction, either alone
or in combination, (e.g., a reverse counterclockwise direction as
shown in Fig. 8) when pressurized air is directed therethrough
from inner housing openings 32 and/or 39, respectively. When two
ports are receiving pressurized air, the tool will be in an
overdrive state.
In accordance with the present invention, as shown in Figs:
1-7, a reverse and overdrive selection valve 20 is provided to
determine which inner housing openings 31-34 and, hence, which
pressure chamber ports 35-38 receive pressurized air from valve
housing 12. As shown in Figs. 5-7, the valve for a two chambered
motor can take a variety of forms without departing from the
scope of the present invention.
In general, the valve 20 includes a rotatable planar element
18 including apertured raised areas 21 and a handle extension 29.
As shown in Figs. 2-9, the valve 20 rotatably sits in a valve
housing manifold 70 of the valve housing 12. A seal 100 seals
the planar element 18 inside the valve housing manifold 70 and a
seal 110 seals the handle extension 29 inside a handle bore 74 on
the rear of the valve housing 12. With the valve housing
manifold 70 sealed by the seals 100, 110, the valve housing can
12
CA 02236356 1998-04-29
receive pressurized air via opening 14 to be directed to the
rotor 50 via the inner housing 30 and valve 20. So that an
operator can adjust the valve, the handle extension 29, on a face
external of the valve housing, includes the before mentioned
handle 22 for turning of the valve.
To direct pressurized air from the valve housing manifold
70, the valve 20 is rotatably supported around the circular lip
39 of the inner housing 30. Each apertured raised area 21 on the
valve 20 includes one aperture 25-27 that extends through the
planar element 18 and raised area 21. By rotation of the valve
20, the apertures 25-27 are alignable with inner housing openings
31-39 to selectively deliver pressurized air through inner
housing openings 31-34 to selective ports 35-38. To accommodate
driving the motor with pressurized air through only one port, at
least one aperture 27 is positioned such that the valve may be
located to align that aperture with one of the ports 35-38.
Furthermore, to accommodate the overdrive feature through
delivery of pressurized air through two ports, at least two
apertures 25, 26 are provided on opposite sides and equidistant
from the axis of the valve. For instance, as shown in Fig. 3, in
the reverse overdrive position, valve apertures 25, 26 are
aligned with inner housing apertures 32, 34, respectively, to
deliver pressurized air to second ports 36, 38.
As illustrated by Figs. 5-7, positioning of the raised
13
CA 02236356 1998-04-29
aperture areas 21 and, hence, apertures 25-27; 125-127; and 225-
227 can be varied. Varying the positioning of the apertures
allows changing the position of the handle 22 of the valve. For
instance, as shown in Fig. l, the valve 20 of Fig. 5 allows for a
certain location of the valve by laying the raised aperture areas
21 in a general y-shape. In fig. 6, the valve 120 includes four
apertures 125-128 laid out in a general Y-shape with the fourth
aperture laid out equidistant between upper branches of the Y-
shape (i.e., ~ or peace sign lay out). In fig. 7, the valve 220
includes three apertures 225-227 laid out in a general T-shape.
The number of apertures in the valve and, therefore, the
number of positions the valve is capable of achieving are
determined by the number of chambers in the motor. In the two
chamber motor illustrated, the valve 20, shown in Fig. 5, is
IS capable of positioning in at least four positions, for example: a
first position in which valve aperture 27 is in pneumatic
communication with inner housing opening 31 to drive the motor in
the forward direction via first port 35; a second position in
which valve aperture 27 is in pneumatic communication with inner
housing opening 34 to drive the motor in a reverse direction via
second port 38; a third position in which valve apertures 25 and
26 are in pneumatic communication with inner housing apertures
32, 34 to drive the motor in a reverse overdrive direction via
second ports 36, 38; and a fourth position in which valve
14
CA 02236356 1998-04-29
apertures 25 and 26 are in pneumatic communication with inner
housing apertures 31, 33 to drive the motor in a forward
overdrive direction via first ports 35, 37.
Figures 8 and 10 illustrate that the motor in accordance
with the present invention may include more than two chambers -
each chamber including a first and second port. As is clear from
Fig. 10, all of the first ports and all of the second ports are
equidistant around the rotor chamber (all first ports are
separated by 120 degrees and all second ports are separated by
120 degrees).
As shown in Fig. 8, the rotary valve for use with a three
chambered motor includes three sets of apertures: (1) 327; (2)
325, 326; and (3) 328-330. The set of apertures 328-330 are
positioned equidistant (separated by 120 degrees) so that all
chambers, for either a forward or reverse direction, can receive
pressurized air when the valve is positioned in the proper
location (full overdrive). Additionally, the apertures 325, 326
are positioned 120 degrees from each other around the valve so
that two chambers, for either a forward or reverse direction, can
receive pressurized air (intermediate overdrive). The third
aperture 327 is positioned so that one chamber can receive
pressurized air.
Each set of apertures 327; 325, 326; and 328-330 are
positioned so as not to interfere with operation of another set
CA 02236356 1998-04-29
of apertures. In other words, while the apertures of a given set
are selected to provide pressurized air to one, two or three of
the ports, the apertures not within the given set are positioned
so that they do not provide pressurized air to any of the other
ports.
Accordingly, in this alternate embodiment, the valve is
capable of being positioned in at least six positions: a first
position allowing flow to the first port of any one of the
pressure chambers; a second position allowing flow to the second
port of any one of the pressure chambers; a third position
allowing flow to the first port of any two of the pressure
chambers; a fourth position allowing flow to the second port of
any two of the pressure chambers; a fifth position allowing flow
to the first port of all of the pressure chambers; and a sixth
position allowing flow to the second port of all of the pressure
chambers.
While this invention has been described in conjunction with
the specific embodiments outlined above, it is evident that many
alternatives, modifications and variations will be apparent to
those skilled in the art. Accordingly, the preferred embodiments
of the invention as set forth above are intended to be
illustrative, not limiting. Various changes may be made without
departing from the spirit and scope of the invention as defined
in the following claims. For instance, the device should not be
16
CA 02236356 1998-04-29
limited to use with just air since other gases are contemplated
to be applicable.
17
