Motorized conversion system for pull-type golf carts

A power unit is provided for attachment to a non-motorized golf cart. The power unit converts the cart to a motorized golf cart of the type used to support and carry a golf bag. The power unit includes a motor, drive wheel assembly and battery support, all attached to a single leg which, in turn, is attachable to the frame of the golf cart by means of a releasable coupling which permits the leg to be oriented selectively, at different angles, relative to the golf cart frame. The releasable coupling also allows the leg to be folded against the frame when the cart is collapsed for transport and storage. A pair of relatively closely-spaced drive wheels, mounted on a unitary axle, supports the forward end of the cart and power unit. The drive wheels contact the ground and a reversible motor pushes or pulls the cart in the direction selected by the user. A control box is mounted on the handle of the golf cart to control the speed and direction of the motor. The power unit can be added to any conventional pull-type golf cart, converting it to a motorized cart.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to pull-type golf carts of the type used to 
carry a golf bag, together with clubs and related accessories. In 
particular, it relates to a motorized conversion system for making such 
pull-type golf carts self-propelled. 
Pull-type golf carts are lightweight, two-wheeled carriages for holding and 
supporting a golf bag. Such carts have a handle at the forward end which 
is grasped by the user and pulled in a trailing manner. Most of the weight 
of the golf bag and clubs is supported by the cart wheels, which are 
mounted on opposite sides of a bag-carrying frame. When the cart is 
stopped, it is tilted upwardly and the base of the frame supporting the 
golf bag is set on the ground behind the wheels, forming a three point 
stand. Most golf carts are made of tubular steel or aluminum frame 
members. Portable carts, intended for easy transport, usually include some 
type of mechanism for collapsing the wheels and handle against the bag 
support frame to allow the cart to fit in the trunk of a car. 
Several prior art systems have been developed for motorizing pull-type golf 
carts. Examples of systems which add a motor unit to a conventional golf 
cart are found in U.S. Pat. Nos. 3,719,247; 3,753,473; 3,941,198; 
4,105,084; and 4,615,406. Examples of systems developed as dedicated 
motorized carts (i.e., not intended to be pulled by hand) are found in 
U.S. Pat. Nos. Des. 300,577 and 4,974,693. 
One problem with the prior art systems for adding a motor to conventional 
pull-type golf carts is the complex and cumbersome procedures required to 
connect and disconnect the motorizing unit. For example, in U.S. Pat. No. 
3,719,247, the power unit is suspended between the cart wheels and 
separate drive shafts must be connected to each of the cart wheels. U.S. 
Pat. Nos. 3,753,473 and 3,941,198 include multiple points of attachment 
between the add-on power unit and the cart, complicating attachment and 
detachment procedures. Prior art conversion systems also tend to be 
excessively heavy, incorporating pivoting or steerable drive wheels, as in 
U.S. Pat. Nos. 3,941,198 and 4,615,406, which add weight and complexity. 
Furthermore, most prior art add-on motorizing units interfere with the 
collapsibility of the cart and must be removed before the cart can be 
collapsed for transport and storage. Dedicated motorized golf bag carts 
tend to be even heavier and more cumbersome to dismantle and transport 
than carts with add-on motorizing units. 
Since a golfer who owns a pull-type or motorized golf bag cart, and who 
plays at more than single golf course, will want to transport the cart 
from place to place, ease of transport is a important concern. It would be 
advantageous to have a power unit which can be quickly and easily added to 
a pull-type golf cart for motorizing the cart and which can also be 
collapsed against the cart for convenient transport. 
It would be particularly advantageous to have a power unit for motorizing a 
pull-type golf cart which did not have to be removed each time the cart 
was collapsed for transport. 
It would also be advantageous if such a power unit for motorizing a 
pull-type golf cart was relatively lightweight and simple to manufacture, 
install and use. 
Accordingly, the invention provides a power unit for attachment to a 
non-motorized golf cart of the type having a pair of cart wheels, a handle 
for moving and steering the cart, and a bag support frame for holding a 
golf bag. The power unit comprises a leg for attachment to the bag support 
frame of the cart, and a releasable coupling for securing the leg to the 
bag support frame in a selection of orientations relative to the bag 
support frame. An electric motor and drive wheel assembly is supported on 
the leg. The drive wheel assembly includes a rotatable axle driven by the 
motor, and a pair of drive wheels attached to the axle. A battery support 
is attached to the leg for supporting a battery to energize the motor. And 
a motor controller is connected electrically to the motor and connectable 
to a battery for controlling the motor. 
In its preferred form, the invention includes a single leg attached to the 
upper end of the golf cart frame, adjacent the point where the handle of 
the cart attaches to the frame. When the power unit is in its operable or 
"working" configuration (i.e., not collapsed), the leg extends downwardly 
at a large acute or perpendicular angle relative to the frame of the cart. 
The drive wheels mounted on the distil end of the leg, opposite the end 
attached to the golf cart frame, support the upper, front end of the cart 
and engage the ground to push or pull the cart along as the motor turns. 
The motor controller is affixed to the golf cart handle at a convenient 
location, providing selectable on/off, speed, and directional (i.e., 
forward/reverse) control. For transport, the releasable coupling between 
the leg and cart is loosened and the le is folded toward the frame into 
its collapsed configuration. In the collapsed configuration, the power 
unit is moved to a position against or adjacent the frame of the golf 
cart, in which the leg assumes a smaller acute or zero angle relative to 
the frame. In its collapsed configuration, the motor, wheels and other 
parts of the power unit are positioned close to the frame of the cart, 
with the power unit drive wheels nested between the cart wheels. The power 
unit need not be detached for transport, although the battery on the 
battery support is preferably removed. The unit does not appreciably 
interfere with the collapsibility of the cart wheels of a conventional, 
collapsible golf cart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a conventional pull-type, non-motorized golf cart 10 
is shown with the power unit 12 of the present invention added to the 
cart. The term golf cart, when used herein, refers to a bag-carrying cart, 
whether motorized or not, and not to other, larger types of golf carts 
designed to carry both persons and golf bags. Golf cart 10 includes a bag 
support frame 14 having a centrally-disposed, tubular central member 15 
which extends longitudinally parallel with a golf bag 16 supported on the 
cart. Central member 15 is angled upwardly in toward the front of cart 10, 
which is the direction of arrow 17 in FIG. 1 and to the left in FIG. 2. 
Frame 14 has a lower end 20, also called the first end 20, which is at the 
rear of the cart, where the frame and attached golf bag are near the 
ground. Attached to first end 20 of central member 15 is a bag support 
plate 22 against which the bottom 24 (see FIG. 2) of golf bag 16 rests. A 
curved bracket 28 serves as a strap holder for a lower strap 29 (see FIG. 
2) used to encircle the bottom of the golf bag to hold the bag on the 
cart. At the upper or forward end 30 of the central member 15 of frame 14, 
also called the second end, is a second bracket 32 for holding a strap 33 
which encircles the upper end of bag 16. 
A handle 40 for moving and steering the cart is attached to central member 
15 of frame 14 adjacent second end 30. On most collapsible carts, handle 
40 is attached to the frame by means of a resetable, releasable coupling 
42 which allows the handle to be pivoted relative to frame 14 and allows 
the handle to be set in selected orientations relative to cart frame 14. 
Coupling 42 includes a threaded set-screw or bolt with a wing-nut or knob 
43 which is tightened to draw together adjacent halves of the coupling to 
fix the relative orientations of the coupling elements which encircle the 
bolt. When the bolt is released by loosening knob 43, the handle can be 
moved between its extended position, shown in FIG. 1, and a collapsed 
position, wherein the handle is folded downwardly. 
Cart wheels 50 are attached to frame 14 by a pair of angled struts 52, also 
called wheel-support members. Struts 52 are attached to central member 15 
of frame 14 at a point on the frame, centrally disposed between the first 
and second ends 20, 30, respectively. An attaching yoke 54 clamped onto 
central member 15 connects wheel struts 52 to frame 14. The wheel struts 
52 include pivots 56 adjacent the clamping yoke 5 to allow the struts to 
pivot. A locking and releasing mechanism is incorporated into wheel-strut 
pivots 56, permitting the wheels 50 to be locked in either the extended, 
operable position, shown in FIG. 1, or the collapsed position, shown in 
FIG. 6. When the struts are in the operable position, the wheels 50 are 
spaced apart, away from frame 14, on opposite sides of central member 15. 
When the struts 52 are folded against frame 14, the wheels are drawn 
closer to central member 15, making the cart less bulky and allowing for 
easier transport and storage. Suitable detents or other devices (not 
shown) are customarily incorporated into the wheel strut pivot mechanisms 
56 to allow the wheels to be locked in either the extended or collapsed 
positions. On some carts, wheel struts 52 incorporate a parallel-bar 
linkage (not shown) to maintain the mutual parallel orientation of wheels 
52, when collapsed (as illustrated in FIG. 6). 
The foregoing has been a description of a conventional, prior art pull-type 
golf cart. What follows is a description of the add-on power unit of the 
present invention for converting cart 10 into a motorized golf cart in 
accordance with the present invention. Referring to FIGS. 1-3, the power 
unit 12 of the present invention is positioned below the central member 15 
of cart frame 14, forward of cart wheels 50. The power unit 12 includes a 
leg 60 for attachment to bag support frame 14. Leg 60 is a generally 
straight, unitary, tubular shaft which attaches to the central member 15 
of frame 14 by means of a releasable coupling 62. 
Coupling 62 is preferably a multidirectional hinge device which allows leg 
60 to be secured to the golf cart in a selectable orientation relative to 
the bag support frame. A preferred type of coupling which is suitable for 
this purpose is handle coupling 42, previously described, used to secure 
handle 40 to cart frame 14. Referring to FIGS. 2 and 3, coupling 62 is 
preferably a hinge joint having two adjacent, generally circular, 
projecting members 65, 68, which are rotatable relative to one another. 
One projecting member 65 is affixed to frame 14 on cart 10 and the other 
projecting member 68 is affixed to a first end 64 (the upper end) of leg 
60. Projecting member 65 is clamped onto central member 15 of frame 14, 
adjacent second end 30 and adjacent the attachment point for handle 40, by 
means of a tubular encircling clamp 69 of any conventional type. A pair of 
bolts 71 (one of which is shown in FIG. 2) may conveniently be employed to 
attach clamp 69 to central frame member 15. The adjacent circular 
projecting members 65, 68 of hinge coupling 62 are positioned 
side-by-side, with mutually-engaging, facing surfaces 70, 72, 
respectively. An opening extends through the center of both projecting 
members for receiving a bolt or other threaded fastener. Preferably a bolt 
73 is permanently mounted on projecting member 68. The shank of bolt 73 
extends through member 68 and its threaded end 75 projects outwardly from 
surface 72 of member 68. Alternatively, shank 75 can be a stud projecting 
from face 72 of member 65. A cooperating opening (not shown) is centrally 
disposed through projecting member 65. When projecting member 65 is 
positioned adjacent projecting member 68, the threaded end 75 of bolt 73 
is passed through the opening in projecting member 65. The threaded end 75 
of bolt 73 serves as a pivot axis around which the projecting members 65, 
68 are respectively turned to form a hinge joint. 
To clamp or squeeze members 65, 68 together, a wing nut or threaded knob 74 
is installed over the threaded end 75 of bolt 73 and tightened. When knob 
74 is tightened, the relative orientations of projecting members 65 and 68 
are fixed, as are the relative orientations of leg 60 and cart frame 14, 
to which the projecting members are attached. Facing surfaces 70, 72, on 
projecting members 65, 68 preferably incorporate texturing or ridges to 
inhibit rotational slippage between the two halves of the coupling, once 
knob 74 has been tightened on bolt 73. Leg 60 can be moved to any desired 
position or angular orientation with respect to cart frame 14 by loosening 
knob 74, repositioning leg 60 and retightening knob 74. If knob 74 is 
removed from bolt 73, the leg can be separated from the cart by separating 
the two halves of coupling 62. Releasable coupling 62 allows leg 60 to be 
secured to cart frame 14 in a selected orientation and allows the user to 
change the orientation as needed or desired. 
An electric motor and drive wheel assembly 80 is attached to and supported 
on leg 60, at or near the lower or second end 81 of the leg. Referring to 
FIGS. 2 and 3, the motor and drive wheel assembly 80 is a combination 
motor/worm gear/right-angle transmission, termed a motor assembly 83, 
which is generally manufactured and sold as a unit. The preferred motor 
used in assembly 83 is a 12-volt DC reversible motor. The output shaft of 
the motor (not shown) extends generally parallel to leg 60. A worm gear 
transmission 84 drives a transverse output shaft 86 extending outwardly 
from both sides of transmission housing 88. Output shaft 86 forms the axle 
on which a pair of drive wheels 90, 92 are mounted. The drive wheels are 
mounted to turn with shaft 86. One type of motor and transmission assembly 
suitable for use in the power unit of the present invention is a 
wheelchair-drive motor, modified for 12-volt operation. An example of such 
a motor assembly is a Model M-4100G-14, manufactured by Rae Corporation of 
McHenry, Ill. The preferred specifications for the motor assembly is as 
follows: maximum output speed (for axle 86)=132 r.p.m.; maximum 
torque=40-in.-lbs.; shaft diameter=1/2-inch; and voltage=12-volts D/C. 
Drive wheels 90, 92 are preferably 9-inch wheels of the same kind and size 
as cart wheels 50 on golf cart 10. The overall length of drive shaft axle 
86, from wheel 90 to wheel 92, is between 8- and 10-inches. 
A battery support 98 is attached to leg 60 for carrying a conventional 
rechargeable storage battery. Battery support 98 is in the form of a 
hinged support plate mounted above drive motor 82. Battery support plate 
98 is preferably attached to leg 60 by means of a hinge 100, which allows 
support plate 98 to be pivoted upwardly against leg 60 in the direction of 
arrow 102 (see FIG. 2) when the battery is removed. Support plate 98 
preferably includes upwardly-extending side walls 104 surrounding the 
bottom of the plate, producing a shallow pan enclosure which helps to 
retain a battery 106 on plate 98. Battery 106 is a conventional 12-volt 
rechargeable automotive or wheelchair-type battery and is preferably 
enclosed within a plastic housing 108. The housing is useful for covering 
and enclosing the battery terminals 110, 112 and helps contain any battery 
fluid which might escape from the battery during use. Preferably, either 
the battery or battery case is provided with a carrying handle 114 (shown 
in cross-section in FIG. 6) to facilitate lifting the battery off support 
plate 98 for transport, storage and recharging. 
Control circuitry and the wiring harness for the power unit of the present 
invention are illustrated schematically in FIGS. 4 and 5. Motor 82 
receives power from battery 106 through a motor controller 120, housed in 
a control box mounted on cart handle 40. The circuit diagram of FIG. 4 
illustrates schematically the internal elements of control box 120, 
including an on/off switch 122, speed controller 124 and forward/reverse 
switch 126. Speed controller 124 is shown as a variable resistance 
element, although it is within the scope of the present invention to use a 
different type of speed controller. One such alternative type of speed 
controller uses a D/C chopper, together with a pulse width modulator, to 
control motor speed by rapidly switching the motor on and off. In such a 
speed controller (termed a pulse-width-modulator or p.w.m.) the speed of 
the motor is increased or decreased by enlarging or reducing the 
percentage of time that power is supplied to the motor. Such p.w.m. 
controllers are well known in the art and have the advantage of using less 
power and producing greater motor torque at slow speeds than variable 
resistance controllers, although p.w.m. controllers are more expensive. 
The selection of the speed control device used at 124 in control box 120 
is a matter of design choice, within the scope of the present invention, 
and either a variable resistance or p.w.m. controller can be used to 
control the motor speed in the power unit. 
The exterior shape and configuration of control box 120 is shown in FIGS. 
1-2 and 5-6. Box 120 includes a speed control knob 130 for setting the 
speed of motor 82 by selectively adjusting controller 124 (in FIG. 5). 
On/off switch 122 is preferably a see-saw switch mounted on the side of 
control box 120. Forward/reverse switch 126 is preferably another see-saw 
switch used to select the direction of travel of motor 82. Some users of 
the power unit of the present invention may prefer to walk in front of the 
golf cart while others may prefer to follow the cart as it moves ahead of 
the user. Switch 126 allows the power unit to be operated in either 
direction. 
The rest of the wiring harness for power unit 12 is shown in FIG. 5, with 
the rest of the motorized cart removed for clarity. A four-lead wire 133 
extends from controller 120 along handle 40 to battery 106 and motor 82. A 
four-prong coupling plug 132 allows convenient separation of the handle 
end of cable 133 from the rest of the wiring harness. The connections 
contained in plug 132 are depicted schematically in FIG. 4. Connections 
are made to the positive and negative terminals on battery 106 using a 
pair of conventional jaw-type spring connector clips 134, 136 (see FIG. 
5). Two motor connection leads 137 extend to motor 82 (see FIGS. 4 and 5). 
Connector 132 provides a simple means of disconnecting the control box 120 
from the rest of the wiring harness, allowing the user to easily remove 
the cart handle from the cart. 
The power unit of the present invention can be conveniently collapsed 
against cart 10 for transport and storage. The power unit and cart are 
shown in their "working" or operating configurations in FIGS. 1 and 2. In 
the operating configuration, handle 40 is extended outwardly from frame 14 
and wheels 50 are spread apart from each other. The support leg 60 of 
power unit 12 is oriented at a large acute angle, or perpendicular, to 
control member 15 of cart frame 14. What is meant by a large acute angle 
is an angular displacement between leg 60 and central member 15 of the 
golf cart (indicated at 141 in FIG. 2) which is generally in the range of 
60.degree..90.degree.. On most conventional carts to which power unit 12 
is attached, that angular relationship tilts the cart forward enough to 
rest some of the weight of the cart on drive wheels 90, 92, providing an 
appropriate center of gravity for motorized operation of the cart. 
To collapse power unit 12 and cart 10, in the manner shown in FIG. 6, 
battery 106 is removed from the power unit, preferably together with 
battery case 108, using lift handle 114. The battery is removed after 
connector clips 134, 136 have been disconnected from battery terminals 
110, 112. Support plate 98 is then tilted upwardly against leg 60 in the 
direction of arrow 102 (see FIG. 2) to the position shown in FIG. 6. 
Releasable coupling 62 is then loosened by turning knob 74 and leg 60 is 
rotated against cart frame 14 until the leg is approximately parallel with 
central member 15 and angle 141 (FIG. 2) has been reduced to or near 
0.degree. or in the range of 20.degree. to 0.degree.. The wheels 90, 92 on 
the power unit are spaced closer together than wheels 50 on cart 10, even 
when the wheel struts 56 are moved to the collapsed configuration of FIG. 
6. That means the wheels of the power unit will nest between the wheels of 
the cart, when the cart is collapsed. After the cart wheels have been 
collapsed, handle 40 is pivoted downwardly over the power unit or, 
preferably, removed entirely from the cart, as shown in FIG. 6. Removal of 
the handle is accompanied by separation of the two halves of connector 132 
and the loosening and removal of knob 43. Without the battery, the cart 
and power unit are light enough to be lifted into the trunk of a car, even 
with a golf bag and clubs attached to the cart. The battery ca be 
conveniently recharged by any conventional means. 
The power unit, when mounted on a collapsible golf cart, provides a 
motorized cart for carrying a golf bag which is convenient to use and to 
transport. When the cart is in its "working" or operational configuration 
(i.e., not collapsed) the cart rests on four wheels, the two drive wheels 
in front and the two cart wheels in back. Drive wheels 90, 92 power the 
cart in either the forward or reverse direction, with the cart wheels 50 
supporting and stabilizing the cart as it moves over the ground. The 
motorized golf cart, resulting from a combination of power unit 12 and a 
conventional golf cart 10, greatly reduces the effort required by a golfer 
to transport his or her clubs, while permitting the golfer to gain 
enjoyment and exercise from walking. 
The power unit of the present invention can be added to virtually any kind 
of golf bag cart. Only two elements need to be attached to the cart. One 
is the releasable coupling device that supports the leg of the power unit, 
which must be attached to the frame of the cart. The second is the control 
box 120 which must be attached to the handle. The only wiring which must 
be added to the cart is the wire 133 extending from control box 120 to 
connector 132. The remainder of the wiring is supported on power unit 12. 
The power unit does not need to be removed from the cart for transport or 
storage. Should the user desire to temporarily remove the power unit and 
simply pull the golf cart, the two halves of the leg-support coupling 62 
can be separated, leaving in place the part 65 attached to the cart frame 
by bracket clamp 69. Control box 120 can be left on handle 40. Whenever 
the user desires to resume use of the power unit, it is simply reattached 
to bracket 69, the halves of the connector plug 132 are reattached, and 
the cart becomes a motorized cart. The entire installation process takes, 
at most, a few minutes. 
The use and operation of the power unit which provides the motorized golf 
cart of the present invention is simple and straightforward. It has been 
the preference of the inventor to operate the cart in a reverse direction, 
with the cart moving ahead and the user trailing behind grasping the 
handle to steer. The user simply switches on the on/off switch 122 
whenever he or she desires to move the cart ahead, adjusting speed control 
knob 130 as necessary. Steering is accomplished by guiding the cart with 
handle 40. The narrow spacing of drive wheels 90, 92 allows the user to 
easily redirect the cart by simply pushing it or urging it in the desired 
direction. To stop the cart, the user simply switches on/off switch 122 to 
the off position. 
The power unit of the present invention eliminates much of the complexity 
and weight of prior art motorizing units for golf carts. The entire drive 
train and power supply is mounted on a single leg, which can be easily 
attached and detached from the golf cart. Complex drive trains and pivot 
systems, which add weight, are eliminated. All parts of the power unit are 
preferably made of aluminum, to save weight and eliminate rust. That 
includes leg 60, battery support 98 and hinge 100, as well as releasable 
coupling 62 and the metal parts of wheels 90, 92. Only the motor assembly 
81 is not aluminum and it is enamel-coated to inhibit rust. 
The power unit, when added to a golf cart, is easy to assemble, transport 
and store. The power unit is collapsible with the cart. Except for removal 
of the battery (and detachment of the cart handle, which is optional) 
there is no need to dismantle or disconnect any part of the power unit for 
transport or storage. With the power unit attached to the golf cart, the 
cart becomes a four-wheeled cart which is stable on relatively level 
ground. Use of the motorized cart eliminates much of the carrying effort 
required for golf while permitting the user to exercise by walking with 
the cart. The power unit is safe and rugged and easily attachable to any 
conventional type of golf cart. In particular, the adjustability of the 
angle between leg 60 and cart frame 14 allows the power unit to be 
attached to virtually any size, type or configuration of golf cart because 
the power unit can be oriented to whatever position is necessary to 
support and move the cart. In that way, the power unit of the present 
invention represents a considerable advance in flexibility and 
adaptability over prior art golf cart motorizing devices.