Information
-
Patent Grant
-
6363874
-
Patent Number
6,363,874
-
Date Filed
Friday, March 31, 200024 years ago
-
Date Issued
Tuesday, April 2, 200222 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Morano; Joseph
- Wright; Andrew
Agents
- Fletcher, Yoder & Van Someren
-
CPC
-
US Classifications
Field of Search
US
- 060 222
- 114 151
- 440 40
- 440 42
-
International Classifications
-
Abstract
The present invention provides a propulsion system for a watercraft. The system includes a rotatable body adapted for fixed external mounting on a hull forward a transverse centerline of the watercraft. A prop is coupled to, and rotatable with, the rotatable body. The prop is coupled to a power transmission drive train, which is, in turn, coupled to a drive motor. The rotatable body is further coupled to an angular drive configured for orienting the prop to produce a thrust in a desired direction during operation.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to electric propulsion units for recreational watercraft. More specifically, the present invention relates to propulsion units which mount in a forward area of the watercraft.
2. Description of the Related Art
Recreational watercraft are typically used for a variety of activities such as fishing, cruising, water skiing, knee-boarding, tubing and like sports. To move the watercraft across the water, an adequate amount of thrust is necessary depending on the particular activity. The thrust may be provided by various types of propulsion systems, both engine-driven and electric-motor driven. Electrical and mechanical propulsion systems generally include outboard and inboard engine driven propeller systems.
Internal combustion engine drives are generally disposed at the rear of a watercraft at a transom, either outboard or inboard. Outboard motors are typically secured to the transom of a boat, while inboard motors have a propeller extending through the transom from an internal combustion engine disposed within a housing of the hull. Both outboard and inboard motors are particularly useful for high-speed and highly responsive navigation of the watercraft. Drawbacks of such drives, however, include their noise levels, exhaust emissions, relative complexity, size and weight.
Electric propulsion systems for pleasure craft are typically referred to as trolling motors or electric outboards. These systems include an electric motor which can be rotated at various speeds to drive a prop. The prop produces a thrust which is directed by proper orientation of the propulsion unit. In conventional trolling motors, for example, a control head may be manually oriented to navigate the boat in a desired direction, or a remote control assembly may be provided for rotating a support tube which holds the propulsion unit submerged during use. While certain relatively minor differences may exist, the term electric outboard is typically employed for the conventional trolling motor design, but with a horsepower range elevated with respect to the conventional trolling motor, such as in excess of 1 horsepower.
While the conventional trolling motor provides quiet and reliable navigation, extremely useful for certain activities such as fishing, there is considerable room for improvement. For example, conventional trolling motors are typically after-market, add-on units designed for mounting on the deck of a watercraft. Such units are typically supported by a mounting structure, a wide range of which may be obtained commercially. These structures allow for relatively straightforward deployment of the motor to position the propulsion unit below the waterline alongside the watercraft, and retraction of the unit for stowage on the deck. The entire motor and mount, however, generally remain securely fixed to the deck, both during use and when stowed. The resulting structure is somewhat cumbersome and occupies useful space on the deck, limiting access to the water in the area of the motor mount. Moreover, while much energy and creativity have been invested in Eboat designs, the aesthetics of the hull may be somewhat impaired by the trolling motor and mount positioned on the deck, typically adjacent to the bow. Furthermore, conventional trolling motors only provide thrust at a point around the perimeter of a watercraft, thereby allowing external forces such as wind to force the watercraft out of alignment with the desired direction of movement across the water.
SUMMARY OF THE INVENTION
The present invention provides a propulsion system for a watercraft to address these drawbacks. The system includes a rotatable thrust assembly, which is adapted for mounting on a hull, such as forward a transverse centerline of the watercraft. The system includes a prop or props coupled to, and rotatable with, the rotatable assembly. The prop is further coupled to a power transmission drive train, which is then drivingly coupled to a drive motor. The rotatable assembly is also coupled to an angular drive configured for orienting the prop to produce a thrust in a desired direction during operation.
In accordance with other aspects of the present invention, a propulsion system for a watercraft includes a recessional housing configured for mounting on a hull forward a transverse centerline of the watercraft. The system also includes a rotatable body, which is mounted in the recessional housing. The system further includes a prop coupled to, and rotatable with, the rotatable body. The prop is further coupled to a power transmission drive train, which is then drivingly coupled to a drive motor. The rotatable body is also coupled to an angular drive configured for orienting the prop to produce a thrust in a desired direction during operation.
The present techniques also offer a watercraft that includes a hull having a recessional housing forward a transverse centerline of the watercraft. A rotatable body is fixedly mounted in the recessional housing. A prop is coupled to, and rotatable with, the rotatable body. The prop is further coupled to a power transmission drive train, which is then drivingly coupled to a drive motor. The rotatable body is also coupled to an angular drive configured for orienting the prop to produce a thrust in a desired direction during operation.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
FIG. 1
is a top view of a watercraft illustrating an embodiment of the present invention disposed therein;
FIG. 2
bottom perspective view illustrating an embodiment of the invention having a propulsion assembly mounted in a recessional housing;
FIG. 3
illustrates a side view of the propulsion assembly disposed at a mounting area of the recessional housing;
FIG. 4
illustrates an exploded view of the propulsion assembly, exploded about the mounting area;
FIG. 5
is a cross-sectional top view of an embodiment of the invention, illustrating a rotatable thruster assembly disposed in a stationary housing;
FIG. 6
illustrates a cross-sectional top view of the stationary housing, and the rotatable thruster assembly oriented at 90° to produce a forward or reverse thrust;
FIG. 7
illustrates a cross-sectional top view of the stationary housing, and the rotatable thruster assembly oriented to produce a left or right thrust;
FIG. 8
illustrates cross-sectional top view of the stationary housing, and the rotatable thruster assembly oriented to produce thrust at an angle of 45°;
FIG. 9
illustrates a bottom perspective view of an alternate embodiment of the present invention, wherein the recessional housing is closed except for openings aligned with openings in the propulsion assembly;
FIG. 10
illustrates a cross-sectional view of an alternate embodiment of the present invention, wherein the rotatable thruster assembly has a flexible shaft assembly rather than the gearbox;
FIG. 11
illustrates a side view of an alternate embodiment of the present invention, wherein the rotatable thruster assembly is substantially disc-shaped and has a cylindrical conduit disposed therein; and
FIG. 12
illustrates a cross-sectional top view of the disc-shaped rotational thruster assembly.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Turning now to the drawings and referring first to
FIG. 1
, the present invention is configured for mounting in a watercraft
10
having a bow
12
, a stem
14
, a transom
16
at the stem
14
, a hull
18
. For navigational reference,
FIG. 1
indicates a forward
20
, a reverse
22
, a left
24
, and a right
26
direction, and a transverse centerline
28
, a longitudinal centerline
30
, and a 0° angle
32
, a 90° angle
34
, a 180° angle
36
, a 270° angle
38
, and a 360° angle
40
. The watercraft may also have a rear drive
42
, mounted either inboard or outboard as illustrated in FIG.
1
. The rear drive
42
, which may be a conventional outboard motor, for example, has a prop
44
for displacing water to propel the watercraft
10
. The invention provides a propulsion assembly
46
mounted to the hull
18
, such as in a position forward of the transverse centerline
28
, preferably along the longitudinal centerline
30
. The propulsion assembly
46
is controlled by a control system
48
, which may include instruments
50
disposed on a console
52
, and a foot pedal
54
for hands-free control of the propulsion assembly
46
. As will be appreciated by those skilled in the art, the foot pedal control input may be replaced or complemented by other input devices, including a joy stick, steering wheel, console switches, and so forth.
FIG. 2
illustrates a bottom perspective view of the watercraft
10
having the propulsion assembly
46
mounted in a recessional housing
56
, which is sealingly coupled to the hull
18
, typically forward of the transverse centerline
28
. The recessional housing
56
extends inwardly into the hull
18
, preferably to a mounting area
58
configured for the propulsion assembly
46
. A support
60
extends across the recessional housing
56
and over the propulsion assembly
46
in the illustrated embodiment. When provided, the support
60
is preferably streamlined with the hull
18
. However, the recessional housing
56
may be designed without a support
60
, or with an alternate orientation or design. Alternatively, the recessional housing
56
may be eliminated if the propulsion assembly
46
is properly supported and water drag is either insignificant or addressed by other means, such as a fin.
The recessional housing
56
may be manufactured separately from, or together with, the hull
18
. The recessional housing
56
is preferably manufactured from fiberglass, but may be made from metal such as aluminum, or a variety of other materials, such as moldable plastics, depending on the application. If manufactured separately from the hull
18
, the recessional housing
56
preferably has a reinforced area
62
extending around the recessional housing
56
to ensure a strong watertight mounting to the hull
18
. Furthermore, the recessional housing
56
preferably mounts along the longitudinal centerline
30
(see
FIG. 1
) to provide a more symmetric and balanced control of the watercraft
10
. However, if a plurality of propulsion assemblies
46
are mounted to the watercraft
10
, or if other considerations require, the propulsion assembly
46
may be mounted at other locations on the hull
18
.
The propulsion assembly
46
preferably includes a stationary housing
64
having a plurality of openings
66
disposed around the stationary housing
64
. The stationary housing
64
is coupled to the mounting area
58
by a support
67
, which supports the stationary housing
64
offset or spaced slightly from the mounting area
58
.
FIG. 3
illustrates a side view of an embodiment of the propulsion assembly
46
disposed at the mounting area
58
, wherein the hull
18
and the recessional housing
56
are illustrated as cross-sections along the longitudinal centerline
30
of the watercraft
10
(see FIG.
1
). As illustrated, the preferred embodiment of the present invention has the propulsion assembly
46
mounted symmetrically about the mounting area
58
. A part of the propulsion assembly
46
is mounted outboard, as indicated by reference numeral
68
, while part of the propulsion assembly
46
is mounted inboard, as indicated at numeral
70
. The stationary housing
64
is preferably sealingly fixed to the mounting area
58
.
1
n this embodiment, the propulsion assembly
46
includes a support and seal assembly
72
, which may include a first plate
74
, a seal
76
and a second plate
78
. The first plate
74
is disposed outboard
68
between the stationary housing
64
and the mounting area
58
. The seal
76
is preferably disposed inboard
70
at the mounting area
58
. The second plate
78
is disposed adjacent the seal
76
. In the embodiment of
FIG. 3
, the propulsion assembly
46
further includes an angular drive motor
80
and a primary drive motor
82
, which are mounted inboard opposite to the stationary housing
64
. The primary drive motor
82
and the angular drive motor
80
are preferably separate electric motors capable of forward or reverse operation. However, other power sources are possible, and reverse operation may be achieved through a separate gearbox. Wiring assemblies
84
and
86
are coupled to the angular drive motor
80
and the primary drive motor
82
, respectively. The wiring assemblies
84
and
86
are further coupled to the control system
48
(see FIG.
1
), which provides power to the propulsion assembly
46
and user control of its operation.
FIG. 4
illustrates an exploded view of the propulsion assembly
46
. As illustrated, the propulsion assembly
46
has a rotatable thruster assembly
88
, which rotatably fits into the stationary housing
64
. In operation, the rotatable thruster assembly
88
is rotated by a hollow drive shaft
90
extending from the angular drive motor
80
. The hollow drive shaft
90
rotatably fits through holes
92
,
94
,
96
and
98
of the second plate
78
, the seal
76
, the mounting area
58
and the first plate
74
, respectively. The hollow drive shaft
90
has a female joint
100
, which then fixedly couples to a male joint
102
of the rotatable thruster assembly
88
. The rotatable thruster assembly
88
provides a thrust, as indicated by arrow
104
, by propelling water through a thrust conduit
106
. A gearbox
108
is centrally disposed within the thrust conduit
106
, wherefrom props
110
and
112
are coupled to drive shafts
114
and
116
, respectively, on opposite sides of the gearbox
108
. The props
110
and
112
are axially aligned in this embodiment, but may be disposed out of alignment, depending on the particular configuration of the thrust conduit
106
. The props
110
and
112
also may be disposed on the same side of the gearbox
108
(i.e., coupled to the drive shaft
114
), or one of the props
110
and
112
may be eliminated entirely.
The thrust conduit
106
, as illustrated, is substantially straight and cylindrical in shape. However, the thrust conduit
106
may bend to an oblique angle depending on the desired angle of entry and exit of water. The thrust conduit
106
may also have a non-uniform cross-section for improved flow, or to accommodate the configuration of the internal components (i.e., the props
110
and
112
and the gearbox
108
).
In operation (FIGS.
6
-
8
), the props
110
and
112
displace incoming water, as indicated by arrow
118
, through the thrust conduit
106
. The props
110
and
112
are driven by the primary drive motor
82
, which has a drive shaft
120
drivingly coupled to the gearbox
108
. The drive shaft
120
is rotatably disposed through a support conduit
122
of the angular drive motor
80
, through holes
92
,
94
,
96
and
98
, and through a support conduit
124
of the rotatable thruster assembly
88
. In this embodiment, the drive shaft
120
is rigid. Alternatively, an embodiment of the drive shaft
120
may include a flexible shaft assembly. A geared end
126
of the drive shaft
120
engages the gearbox
108
. The gearbox
108
transmits torque from the drive shaft
120
to the props
110
and
112
. Where desired, the conduit may be positioned in a cross-direction (generally parallel to the craft transverse axis) for stowage, thereby reducing water intake and drag. Moreover, one or more covers (not shown) may be provided for capping one or more of the water passageways in this stowed position.
The stationary housing
64
is secured to the mounting area
58
via fasteners (see FIG.
4
), such as bolts
128
and nuts
130
. The bolts
128
are disposed through holes
132
,
134
,
136
,
138
and
140
, which extend through a flange
142
of the stationary housing
64
, the first plate
74
, the mounting area
58
, the seal
76
, and the second plate
78
, respectively. The bolts
128
are then secured by the nuts
130
. The angular drive motor
80
is secured to second plate
78
with bolts
144
, which extend through holes
146
on a flange
148
of the angular drive motor
80
. The bolts
144
then screw into threads
150
on the second plate
78
, for example. The primary drive motor
82
is coupled to the angular drive motor
80
via bolts
152
, which extend through holes
154
and engage threads
156
on the angular drive motor
80
.
FIG. 5
illustrates a cross-sectional top view of the rotatable thruster assembly
88
disposed in the stationary housing
64
. In this exemplary embodiment, the stationary housing
64
has a cylindrical cavity
158
, and the openings
66
extend through the stationary housing
64
in pairs diametrically opposite from one another. The openings
66
have cross-sections
160
substantially equivalent to a cross-section
162
of the thrust conduit
106
. The thrust conduit
106
rotates within the cylindrical cavity
158
, as the primary drive motor
82
turns the drive shaft
120
. As illustrated, the drive shaft
120
engages the gearbox
108
at bevel gears
164
and
166
, which in turn rotate the props
110
and
112
coupled to drive shafts
114
and
116
, respectively.
FIGS. 6-8
illustrate cross-sectional top views of the rotatable thruster assembly
88
disposed in the stationary housing
64
, wherein the rotatable thruster assembly
88
is oriented at 90° (
34
), 180° (
36
), and 45°, respectively.
FIG. 6
illustrates the rotatable thruster assembly
88
oriented to produce thrust in the forward
20
or the reverse
22
direction. To change the direction of the thrust, the thrust conduit
106
aligns with the openings
66
as disposed on the stationary housing
64
.
FIG. 7
illustrates the thrust conduit
106
oriented to produce thrust to the left
24
or to the right
26
. In
FIG. 8
, the thrust conduit
106
is oriented to produce thrust at an angle such as 45°.
FIG. 9
illustrates a bottom perspective view of an alternate embodiment of the propulsion system, wherein a recessional housing
168
is disposed in the hull
18
forward the transverse centerline
28
along the longitudinal centerline
30
(see FIG.
1
). The recessional housing
168
, in contrast to the recessional housing
56
, is completely closed except for a plurality of openings
170
aligned with the openings
66
on the stationary housing
64
. This provides an alternate way of protecting the propulsion assembly
46
and streamlining the hull
18
.
FIG. 10
illustrates a cross-sectional view of an alternate embodiment of the present invention, wherein the rotatable thruster assembly
88
has a flexible shaft assembly
172
rather than the gearbox
108
. The flexible shaft assembly
172
is disposed in a support tube
174
, which is sealingly fixed to the support conduit
124
and gradually bends 90° to a prop
176
. The flexible shaft assembly
172
is typically a pre-manufactured assembly having a stationary outer tube or sheath
178
and an inner shaft
180
. The support tube
174
also has sealed bearings
182
and
184
for the inner shaft
180
. The support conduit
124
has a drive bearing
186
, which is configured for the drive shaft
120
extending from the primary drive motor
82
.
FIGS. 11-12
illustrate an alternate embodiment, wherein a rotatable thruster assembly
188
replaces the rotatable thruster assembly
88
.
FIG. 11
illustrates a side view of the propulsion assembly
46
disposed at the mounting area
58
. In this alternate embodiment, the rotatable thruster assembly
188
has a disc-shaped body
190
with a thrust conduit
192
. Also, the rotatable thruster assembly
190
is preferably not fixed to the mounting area
58
, and there is no stationary housing
64
.
FIG. 12
illustrates section
12
—
12
of
FIG. 11
, which is a cross-sectional top view of the rotational thruster assembly
188
. As illustrated, the rotational thruster assembly
188
has essentially the same internal components as the rotational thruster assembly
88
. The gearbox
108
is centrally disposed within the thrust conduit
192
, and the props
110
and
112
are coupled to the drive shafts
114
and
116
, respectively, on opposite sides of the gearbox
108
. Although the stationary housing
64
is not required in this alternate embodiment, the stationary housing
64
may be desirable to improve stability and/or sealing to the mounting area
58
. Again, as noted above, the assembly may be rotated to a “no flow” or transverse stowed position to reduce drag.
While the invention may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims.
Claims
- 1. A propulsion system for a watercraft having a hull, the system comprising:a stationary housing disposed external to the hull, the stationary housing having a plurality of openings therethrough; a rotatable body disposed within the stationary housing; a prop coupled to the rotatable body and rotatable therewith; a power transmission drive train coupled to the prop; a drive motor coupled to the power transmission drive train; and an angular drive coupled to the rotatable body configured for orienting the prop to produce a thrust in a desired direction during operation by drawing in fluid through a first opening in the stationary housing and discharging the fluid through a second opening in the stationary housing.
- 2. The propulsion system of claim 1, wherein the rotatable body further comprises a primary conduit configured to house the prop, the primary conduit having an entrance and an exit.
- 3. The propulsion system of claim 2, wherein the primary conduit comprises a straight cylinder, and the entrance and the exit are disposed at ends thereof opposite one another.
- 4. The propulsion system of claim 2, wherein the primary conduit comprises a cross-section of uniform area along the primary conduit.
- 5. The propulsion system of claim 2, wherein the stationary housing comprises a plurality of pairs of openings disposed circumferentially around the stationary housing and configured for alignment with the entrance and the exit of the primary conduit as the rotatable body is rotated, through which the prop is configured to displace water during operation; anda control system coupled to the drive motor and the angular drive, wherein the drive motor is electric and the angular drive has an electric motor.
- 6. The propulsion system of claim 1, wherein the rotatable body is substantially disk-shaped.
- 7. The propulsion system of claim 1, wherein the plurality of openings extend between an external surface and an inner cavity in which the prop is disposed.
- 8. The propulsion system of claim 1, comprising a plurality of props drivingly coupled to the drive motor.
- 9. The propulsion system of claim 8, wherein the plurality of props are axially aligned with one another.
- 10. The propulsion system of claim 1, further comprising a gear box coupling the prop to the power transmission drive train.
- 11. The propulsion system of claim 10, wherein the prop is coupled to a shaft extending from the gear box.
- 12. The propulsion system of claim 1, wherein the power transmission drive train comprises a flexible shaft.
- 13. The propulsion system of claim 1, wherein the power transmission drive train is adapted for sealingly extending through the hull.
- 14. The propulsion system of claim 1, wherein the drive motor is electric.
- 15. The propulsion system of claim 1, wherein the drive motor is configured for mounting inboard of the hull.
- 16. The propulsion system of claim 1, wherein the drive motor is reversible.
- 17. The propulsion system of claim 1, wherein the angular drive is configured to rotate the rotatable body to an angle within an operable range relative to a transverse centerline.
- 18. The propulsion system of claim 17, wherein the operable range includes angles from 0° to 360° with respect to the taansverse centerline.
- 19. The propulsion system of claim 17, wherein the operable range includes angles from 0° to 180° with respect to the transverse centerline.
- 20. The propulsion system of claim 1, further comprising at least one steering member adapted to couple the angular drive to the rotatable body.
- 21. The propulsion system of claim 20, wherein the steering member comprises a hollow shaft adapted for disposal about the power transmission drive train.
- 22. The propulsion system of claim 1, further comprising a control system coupled to the drive motor and the angular drive.
- 23. The propulsion system of claim 22, further comprising a foot control coupled to the control system.
- 24. A propulsion system for a watercraft, the system comprising:a recessional housing configured for fixed external mounting on a hull forward a transverse centerline of the watercraft; a rotatable body rotatably mounted in the recessional housing, the rotatable body comprising a cylinder having an entrance and an exit disposed at opposite ends of the cylinder; a prop housed within the cylinder, coupled to the rotatable body and rotatable therewith; a power transmission drive train coupled to the prop; a drive motor coupled to the power transmission drive train; an angular drive coupled to the rotatable body configured for orienting the prop to produce a thrust in a desired direction during operation; and a stationary housing configured for fixed mounting in the recessional housing, the stationary housing having at least the prop disposed therein, and the stationary housing having at least one opening configured to permit the prop to displace water during operation.
- 25. The propulsion system of claim 24, wherein the rotatable body is substantially disk-shaped.
- 26. The propulsion system of claim 24, comprising a plurality of openings extending between an external surface and an inner cavity in which the prop is disposed.
- 27. The propulsion system of claim 24, comprising a plurality of props drivingly coupled to the drive motor.
- 28. The propulsion system of claim 24, wherein the power transmission drive train comprises a flexible shaft.
- 29. The propulsion system of claim 24, wherein the drive motor is electric.
- 30. The propulsion system of claim 24, wherein the angular drive is configured to rotate the rotatable body to an angle within an operable range relative to the transverse centerline.
- 31. The propulsion system of claim 30, herein the operable range includes angles from 0° to 180° with respect to the transverse centerline.
- 32. The propulsion system of claim 24, further comprising a hollow steering member disposed about the power transmission drive train, the hollow steering member coupling the angular drive to the rotatable body.
- 33. The propulsion system of claim 24, further comprising a control system coupled to the drive motor and the angular drive.
- 34. The propulsion system of claim 33, further comprising a foot control coupled to the control system.
- 35. A watercraft comprising:a hull having a recessional housing forward a transverse centerline of the watercraft; a stationary housing external to the hull and disposed within the recessional housing, the stationary housing having a plurality of openings for fluid flow therethrough; a rotatable body rotatably mounted within the stationary housing and the recessional housing; a prop coupled to the rotatable body and rotatable therewith; a power transmission drive train coupled to the prop; a drive motor coupled to the power transmission drive train; and an angular drive coupled to the rotatable body configured for orienting the prop to produce a thrust in a desired direction during operation.
- 36. The watercraft of claim 35, wherein the rotatable body further comprises a primary conduit configured to house the prop, the primary conduit having an entrance and an exit.
- 37. The watercraft of claim 35, wherein the rotatable body is substantially disk-shaped.
- 38. The watercraft of claim 35, comprising a plurality of openings extending between an external surface and an inner cavity in which the prop is disposed.
- 39. The watercraft of claim 35, wherein the power transmission drive train comprises a flexible shaft.
- 40. The watercraft of claim 35, wherein the drive motor is electric.
- 41. The watercraft of claim 35, wherein the angular drive is configured to rotate the rotatable body to an angle within an operable range relative to the transverse centerline.
- 42. The watercraft of claim 35, further comprising a hollow steering member disposed about the power transmission drive train, the hollow steering member coupling the angular drive to the rotatable body.
- 43. The watercraft of claim 35, further comprising a control system coupled to the drive motor and the angular drive.
- 44. The watercraft of claim 43, further comprising a foot control coupled to the control system.
US Referenced Citations (10)