Baby stroller conversion assembly

An assembly for converting a three-wheeled baby stroller to a two-wheeled bicycle trailer configuration. The conversion assembly includes an upper frame attachment attached to the upper stroller frame. Left and right support members are connected to a forward portion of the upper frame attachment and extend downward and each have at a lower end thereof an axle extension assembly. This assembly is positioned between the end of the stroller rear axle and the stroller rear wheel to extend the rear wheel base of the stroller to provide increased stability. A tow arm assembly extends from a forward end of the upper frame attachment and at a forward end thereof carries a hitch which clamps to the seatpost of a bicycle. An elongated baseplate is positioned at the forward end of the stroller lower frame and securely clamped thereto. Left and right side suspension members are attached at an upper end to the tow-arm assembly and at a lower end to the baseplate and support the front end of the stroller frame when the front wheel thereof is removed. The baseplate further serves as a carrier for the removed front wheel. The base plate has a connector positioned forward of the stroller connectors which receive the lower ends of the stroller upper frame tubes. With the lower ends of the stroller upper frame tubes moved forward into the baseplate connector, the center of gravity of the stroller seat is moved forward and is lowered to provide increased stability. The left and right side suspension members also serve to transmit lifting forces produced on the rear wheels of the stroller to the seatpost of the bicycle so that the weight of the rider on the bicycle counters the lifting force to inhibit tipping and rolling.

TECHNICAL FIELD 
The present invention relates to three-wheeled baby strollers, and more 
particularly, to an assembly for converting the three-wheeled baby 
stroller to a two-wheeled bicycle trailer. 
BACKGROUND OF THE INVENTION 
All-terrain, three-wheeled baby strollers have been designed to be pushed 
by parents while jogging, fast walking or even just slow walking in grassy 
parks and on rough roads and sidewalks. Such strollers use large wheels to 
accommodate the rough terrain. While such strollers allow parents to take 
infants along when jogging and walking, there are times when parents wish 
to ride their bicycles for exercise or fun. While bicycle seats are 
available so that an infant can ride along, some find it more convenient 
and safer to use a trailer which is towed by the bicycle. Such trailers 
use large wheels to accommodate rough terrain, as do all terrain, 
three-wheeled strollers, but usually utilize only two large rear wheels. 
For those parents who already have a three-wheeled stroller or do not wish 
to purchase both a three-wheeled stroller and a bicycle trailer, it would 
be desirable to provide a conversion assembly to simply convert a 
three-wheeled baby stroller to a two-wheeled bicycle trailer. Such a 
conversion assembly should be easy and quick to attach to the 
three-wheeled stroller to convert it to a two-wheeled bicycle trailer, and 
easy and quick to remove to reconvert the bicycle trailer to a stroller. 
Such a conversion assembly would eliminate the need and expense to 
purchase a separate bicycle trailer. The bicycle trailer that results from 
use of the conversion assembly should be stable and safe for the infant 
occupant. 
It can be appreciated that a substantial need exists for a baby stroller 
conversion assembly for use to convert an all terrain, three-wheeled baby 
stroller to a two-wheeled bicycle trailer. The present invention provides 
such a conversion assembly. 
SUMMARY OF THE INVENTION 
The present invention resides in a conversion assembly for use with a baby 
stroller having a forward wheel, left and right rearward wheels rotatably 
mounted on left and right stub axles, and a rear axle having left and 
right ends with corresponding left and right end openings to removably 
receive a corresponding one of the left and right stub axles therein. The 
stroller has a downwardly sloping upper frame supporting a baby seat. The 
upper frame has a lower end and an upper end. A handle is connected to the 
upper frame toward the upper end thereof. 
The stroller further includes a base frame with a forward end and a 
rearward end. The forward wheel is removably attached to the base frame 
toward the forward end thereof. The base frame has a connector at a 
position toward the forward wheel to releasably attach the lower end of 
the upper frame to the base frame. 
The stroller has an upwardly extending frame with an upper end pivotally 
connected to the upper frame at a position between the handle and the 
lower end of the upper frame. The upwardly extending frame is rotatable 
relative to the base frame to permit the lower end of the upper frame to 
selectively move forward with the forward wheel removed. The conversion 
assembly of the present invention is usable to couple the baby stroller in 
the configuration of a two-wheeled bicycle trailer to a bicycle having a 
frame supporting a bicycle seat. 
The conversion assembly includes an upper frame attachment having a 
rearward upper frame attachment portion pivotally connected to the upper 
frame of the baby stroller at a position toward the handle. The upper 
frame attachment also includes a forward attachment portion. The 
conversion assembly also includes left and right support members, each 
having an upper end portion pivotally connected to the forward attachment 
portion and a lower end portion having an axle extension assembly. The 
axle extension assemblies each have an inner stub axle removably 
positionable in a corresponding one of the left and right end openings of 
the rear axle when the rearward wheel stub axle is removed therefrom. Each 
axle assembly also includes an outer opening to removably receive a 
corresponding one of the left and right rearward wheel stub axles therein. 
The conversion assembly has a tow-arm having a rearward end portion 
connected to the forward attachment portion. The tow-arm also has a 
forward tow-arm end portion positionable toward the bicycle seat. 
The conversion assembly has a base frame attachment having a releasable 
connector securable to the base frame toward the forward end thereof. The 
base frame attachment also includes an upper frame connector positioned 
forward of the connector of the base frame to releasably attach the lower 
end of the upper frame to the base frame attachment. The conversion 
assembly has a suspension member with an upper end portion connected to 
the tow-arm and a lower end portion connected to the base frame 
attachment. A hitch is attached to the forward tow-arm end portion to 
couple the tow-arm to the bicycle frame at a position toward the bicycle 
seat. 
The conversion assembly is useful with a baby stroller upper frame having 
left and right upper frame members. The upper frame attachment includes 
left and right attachment members with each having a rearward end portion 
pivotally connected to a corresponding one of the left and right upper 
frame members. The left and right attachment members also have a forward 
end portion. The upper frame attachment further includes a forward 
attachment member extending between the forward end portions of the left 
and right attachment members. The upper end portions of the left and right 
support members are pivotally connected to a corresponding one of the left 
and right attachment members toward the forward attachment member. 
The tow-arm includes laterally spaced-apart left and right tow-arm members. 
Each of the tow-arm members has a rearward end portion connected to the 
forward attachment portion at spaced-apart locations. The tow-arm members 
also include a forward end portion. The forward end portions of the left 
and right tow-arm members are connected together, and the hitch is 
connected to both of the forward end portions of the left and right 
tow-arm members. 
The suspension member includes laterally spaced-apart left and right 
suspension members. Each of the suspension members has an upper end 
portion connected to a corresponding one of the left and right tow-arm 
members at a spaced-apart distance. The lower end portions of the left and 
right suspension members are connected to the base frame attachment with a 
distance therebetween less than the spaced-apart distance of the upper end 
portions. This provides the left and right suspension members with a 
V-shaped arrangement when viewed from the direction of the rear axle. 
In the preferred embodiment, the base frame attachment is a plate. The 
plate has an aperture for receiving a threaded axle and nut of the forward 
wheel to allow the forward wheel to be clamped to the plate for carrying 
when removed from the stroller for two-wheeled bicycle trailer operation. 
A canopy is supported by the upper frame attachment and defines an 
enclosure having the baby seat therewithin.

DETAILED DESCRIPTION OF THE INVENTION 
As shown in the drawings for purposes of illustration, the present 
invention is embodied in a conversion assembly 10, shown in FIG. 1, for 
converting an all-terrain baby stroller 12, shown in FIG. 3, into a 
bicycle trailer, shown in FIG. 2, attached to a bicycle 13 for towing. The 
baby stroller 12, as best illustrated in FIG. 3, has a foldable frame 14 
and a transversely extending rear axle assembly 16 designed to permit 
folding of the frame and selective removal of the two rear wheels 18 
rotatably mounted to the rear axle assembly. The forward end of the frame 
14 has a single front wheel 20 rotatably mounted thereto. The frame 14 
includes left and right side horizontal base frame tubes 22 extending 
rearwardly from the front wheel 20 in parallel configuration to the rear 
axle assembly 16. 
The frame 14 also includes left and right, downwardly sloping upper frame 
tubes 24 which extend from a handle 26 used to push the stroller 12 in 
converging configuration to the horizontal base frame tubes 22 at a 
position near the rearwardmost extent of the front wheel 20. A footrest 
23, shown in phantom line in FIG. 3, is affixed to both of the upper frame 
tubes 24 and rigidly holds the forward portions of the upper frame tubes 
in a fixed spaced-apart relation. 
As best shown in FIG. 4, a lower terminal end 24a of each upper frame tube 
24 is releasably coupled to the horizontal base frame tubes 22 by a frame 
connector 28 affixed to both of the horizontal base frame tubes. The frame 
connector 28 has left and right tube receiver portions 30 through which 
the horizontal base frame tubes 22 extend. The frame connector 28 is fixed 
in place on the horizontal base frame tubes 22 at a position near the 
rearwardmost extent of the front wheel 20 using rivets 32. A bridge 
portion 34 of the frame connector 28 spans between the left and right tube 
receiver portions 30 to rigidly hold the two horizontal base frame tubes 
22 in a fixed spaced-apart relation and also provide a platform to which a 
front wheel caliper brake (not shown) is attached therebelow by a bolt 36. 
The frame connector 28 has left and right connector portions 38, each 
positioned above a forward end portion of a corresponding one of the left 
and right tube receiver portions 30. Each connector portion 38 has a slot 
40 therein sized to removably receive a tongue portion 42 of a fitting 44 
fixedly attached to the lower terminal end 24a of a corresponding one of 
the upper frame tubes 24. The tongue portion 42 is sized to fit snugly 
within a corresponding one of the connector slots 40. An aperture 46 is 
formed in each connector portion 38 and a corresponding aperture 48 is 
formed in each tongue portion 42 of the fittings 44 so that the apertures 
46 and 48 will be in alignment when the tongue portion is inserted within 
the corresponding connector portion. The apertures 46 and 48 are sized to 
receive a removable lock pin 50 with a detent ball 52 snugly therein to 
securely hold the tongue portion 42 within the corresponding connector 
portion 38, and thereby rigidly attach the upper frame tubes 24 to the 
horizontal base frame tubes 22. When desired for folding of the frame 12 
for compact transport or storage, the two lock pins 50 are removed and the 
tongue portions 42 pulled out of the connector slots 40 for detachment of 
the lower terminal end 24a of the upper frame tubes 24 from the horizontal 
base frame tubes 22. 
The frame 14 further includes left and right upright support tubes 54 
extending between the rear axle assembly 16 and the upper frame tubes 24 
at a position below and forward of the handle 26. The upright support 
tubes 54 are pivotally connected to the upper frame tubes 24 by left and 
right pivot joints 56, and fixedly connected to the axle assembly 16 by 
couplers, as will be described below to permit folding of the stroller 12 
when the tongue portion 42 of the fittings 44 are released to free the 
lower terminal ends 24a of the upper frame tubes 24 from the horizontal 
base frame tubes 22. 
As shown in FIGS. 5A and 5B, the rear axle assembly 16 uses a non-rotating 
tubular rear axle 58. Each of the horizontal base frame tubes 22 is 
coupled to the rear axle 58 by a first coupler 60 with a tubular connector 
portion 62 rotatably receiving the rear axle 58 therethrough to permit 
rotation of the horizontal base frame tubes relative to the rear axle upon 
folding of the frame 14 for storage or transport, or as will be described 
below, for attachment of conversion assembly 10 to the stroller 12. The 
first coupler 60 also has a frame tube receiver portion 64 within which a 
corresponding one of the left or right horizontal base frame tubes 22 is 
inserted and fixed in place using rivets 66. A gusset 68 is fixedly 
attached to both the tubular connector portion 62 and the frame tube 
receiver portion 64 of each first coupler 60 to rigidly hold them 
together. 
Each of the upright support tubes 54 is coupled to the rear axle 58 by a 
second coupler 70 with a tubular connector portion 72 receiving the rear 
axle 58 therein. The tubular connector portion 72 and the rear axle 58 are 
fixedly attached together by rivets 74. The rear axle 58 has left and 
right end portions 58a that project outward beyond the outer end of each 
of the tubular connector portions 72. The second coupler 70 also has a 
frame tube receiver portion 76 within which a corresponding one of the 
left or right upright support tubes 54 is inserted and fixed in place 
using rivets 78. A gusset 80 is fixedly attached to both the tubular 
connector portion 72 and the frame tube receiver portion 76 of each second 
coupler 70 to rigidly hold them together. As a result, the upright support 
tubes 54 and the rear axle 58 are fixed together and rotate as a unit when 
the frame 14 is folded. With this arrangement, the first coupler 60, which 
holds one of the horizontal base frame tubes 22, and the second coupler 
70, which holds one of the upright support tubes 54, can be freely rotated 
relative to each other by a sufficient amount to allow the folding of the 
upright support tubes downward relative to the horizontal base frame tubes 
for folding of the stroller 12 or attachment of the conversion assembly 
10. 
As best seen in FIGS. 6A and 6B, the rear axle 58 includes an outer metal 
tube 82 and a thicker walled inner metal tube 84 snugly positioned 
coaxially within the outer axle tube 82. The outer and inner axle tubes 82 
and 84 are fixedly connected together by the rivets 74 which also serve to 
fixedly attach the tubular connector portion 72 to the rear axle 58 
described above. The inner axle tube 84 is open at both its left and right 
ends, and has a uniform interior diameter along its full length. 
Referring again to FIGS. 5A and 5B, and to FIG. 7, the rear axle assembly 
16 further includes left and right spindles or stub axles 86 having a 
circular cross-section. Each of the rear wheels 18 of the stroller 12 is 
rotatably mounted on an outer end portion 88 of a corresponding one of the 
stub axles 86 using conventional bearings. The rear wheel 18 is rotatably 
retained between a retainer head portion 86a of the stub axle 86 at an 
outer end thereof and a retainer clip (not shown) positioned in a retainer 
clip groove 90 located between the outer end portion 88 and an inward end 
portion 92 of the stub axle 86. The inward end portion 92 of each stub 
axle 86 is sized to be inserted into and snugly retained within the 
corresponding left or right end of the inner axle tube 84. In the 
illustrated embodiment, the inward end portion 92 of both the left and 
right stub axles 86 have the same diameter round cross-section so that the 
user can conveniently interchange the left and right rear wheels and their 
stub axles on the left and right ends of the inner axle tube 84. 
An inward end 94 of the inward end portion 92 of each of the left and right 
stub axles 86 has a circumferential bevel to form a tapered end to 
facilitate insertion into the corresponding left or right open end of the 
inner axle tube 84 for attachment of the rear wheels 18 to the tubular 
rear axle 58. The inward end portion 92 of the stub axles 86 are sized to 
slide easily within the inner axle tube 84 once the user partially inserts 
them into the left and right open ends thereof using only a slight inward 
force applied by the hand of the user. Similarly, the inward end portion 
92 of the stub axles 86 easily slide out of the left and right ends of the 
inner axle tube 84 when it is desired that the rear wheels 18 be removed 
for storage or transport with or without folding of the stroller 12, or 
for attachment of the conversion assembly 10. 
The inward end portion 92 of the left and right stub axles 86 are retained 
within the corresponding left and right ends of the inner axle tube 84 by 
left and right user-actuated, releasable lock mechanisms. Each of the 
releasable lock mechanisms includes a circumferential groove 96 formed on 
the inward end portion 92 of the stub axle 86 and a movable pin 98 which 
extends through an aperture 100 extending fully through forward-facing 
wall portions of the tubular connector portion 72 of the second coupler 70 
and the outer and inner axle tubes 82 and 84 of the rear axle 58. The 
aperture 100 extends into the interior of the inner axle tube 82 at the 
location aligned with the stub axle groove 96 when the inward end portion 
92 of the stub axle 86 is fully inserted into the end of the inner axle 
tube. The pin 98 has sufficient length when in an engagement position 
shown in FIG. 6A to project within the stub axle groove 96 and thereby 
prevent axial withdrawal of the stub axle 86 from within the inner axle 
tube 84. 
The pin 98 is held in the engagement position by a flat strip spring 102. 
The spring 102 has a forward leg portion 104 fixedly attached to 
forward-facing wall portion of the frame tube receiver portion 76 of the 
second coupler 70 by a first pair of the rivets 78 and carrying the pin 
98. In the illustrated embodiment, the pin 98 is formed integral with the 
spring forward leg portion 104. The spring 102 also has a rearward leg 
portion 106 fixedly attached to a rearward-facing wall portion of the 
frame tube receiver portion 76 of the second couple 70 by a second pair of 
the rivets 78. The forward and rearward leg portions 104 and 106 of the 
spring 102 are connected together by a lower portion 108 which extends 
below the tubular connector portion 72 of the second coupler 70. The 
spring 102 is shaped and affixed to the frame tube receiver portion 76 of 
the second coupler 70 so that the forward leg portion 104 lays flat 
against the forward-facing wall portion of the frame tube receiver portion 
76 and the rearward leg portion 106 is bowed away from the rearward-facing 
wall portion as shown in FIG. 6A. This biases the pin 98 into the 
engagement position within aperture 100, but the rearward leg portion 106 
is bowed sufficiently to permit sufficient forward movement of the forward 
leg portion 104 to move the pin 98 forward to the disengagement position 
shown in FIG. 6B whereat the pin does not interfere with the insertion or 
withdrawal of the inward end portion 92 of the stub axle 86 into or from 
the inner axle tube 84. 
When inserting the inward end portion 92 of the stub axle 86 in the end of 
the inner axle tube 84 to attach one of the rear wheels 18 to the frame 
14, the pin 98 will be first engaged by the tapered inward end 94 of the 
stub axle and pushed forward into the disengagement position to permit 
passage thereby of the inward end portion of the stub axle. When the 
inward end portion 92 of the stub axle 86 is fully inserted into the inner 
axle tube 84, the stub axle groove 96 is in alignment with the pin 98 and 
the spring 102 will automatically move the pin into the engagement 
position within the stub axle groove, thereby locking and holding the stub 
axle in position during use of the stroller 12. 
The stub axle 86 is removed when it is desired to remove the rear wheel 18 
from the frame 14 by the user simply pressing forward on the rearward leg 
portion 106 of the spring 102 to move the forward leg portion 104 and the 
attached pin 98 forward into the disengagement position shown in FIG. 6B 
whereat the pin is withdrawn from the stub axle groove 96. Then, the 
inward end portion 92 of the stub axle is easily removed from the inner 
axle tube 84 by the user pulling the stub axle clear of the inner axle 
tube. As such, the rear wheels 18 can be quickly and easily removed and 
reattached to the frame 14 without tools. 
The inward end portion 92 of the stub axle 86 has a circular cross-section 
and the stub axle groove 96 extends around the full circumference thereof 
so that the pin 98 will engage the groove regardless of the rotational 
orientation of the stub axle. Thus, the user can insert the inward end 
portion 92 of the stub axle 86 into the end of the inner axle tube 84 
without regard for the rotational orientation of the stub axle and always 
achieve a secure locking of the stub axle within the inner axle tube. 
An inward tubular stop 110 is positioned on the outer axle tube 82 of the 
rear axle 58 inward of the tubular connector portion 62 of each of the 
first couplers 60 and is fixedly attached to the rear axle by rivets 112. 
The inner tubular stop 110 and the corresponding tubular connector portion 
72 of the second coupler 70 on the left and right ends of the rear axle 58 
rotatably retain the first couplers 60 therebetween on the rear axle. 
The conversion assembly 10 of the present invention is shown fully 
assembled in FIG. 1, but not attached to the stroller 12. The conversion 
assembly 10 includes an upper frame attachment 114 having upwardly arching 
left and right attachment members 116 and 118, respectively. As shown in 
FIGS. 2, 9, 10A and 10B, a rearward end portion or end of each of the left 
and right attachment members 116 and 118 (forming a rearward attachment 
portion of the upper frame attachment 114) is pivotally connected for 
movement in a substantially vertical plane to a corresponding one of the 
left and right upper frame tubes 24 by left and right pivot connectors 
120. Each of the pivot connectors 120 is securely clamped to one of the 
upper frame tubes at a position just forward of the handle 26. While the 
left and right pivot connectors 120 allow the left and right attachment 
members 116 and 118 to pivot relative to the upper frame tubes 24 of the 
stroller, they are clamped securely enough thereto to not move along the 
upper frame tubes during use of the conversion assembly 10. The pivot 
connectors 120 are, however, flexible enough to be spread apart and 
removed from the left and right upper frame tubes 24 when desired. The 
pivot connectors 120 each use a manually operable wing nut 121 which 
allows the user to selectively inhibit or allow the rotation of the upper 
frame attachment 114 relative to the upper frame tubes 24, as needed to 
change the stroller between the three-wheeled stroller configuration of 
FIG. 10A and the two-wheeled bicycle trailer configuration of FIG. 10B. 
A forward attachment member 122 forming a part of the upper frame 
attachment 114 extends between and is fixedly attached to forward end 
portions or ends of the left and right attachment members 116 and 118. In 
the illustrated embodiment, the left and right attachment members 116 and 
118 and the forward attachment member 122 of the upper frame attachment 
114 form a forward attachment portion and are integrally formed from a 
continuous substantially rigid tube. 
The conversion assembly 10 further includes left and right side support 
members 124 and 126, respectively. An upper end portion or end of each of 
the left and right side support members 124 and 126 is pivotally connected 
for movement in a substantially vertical plane to a corresponding one of 
the left and right attachment members 116 and 118 along a forward end 
portion thereof rearward of the forward attachment member 122 by left and 
right pivot connectors 128. While the left and right pivot connectors 128 
allow the left and right side support members 124 and 126 to pivot 
relative to the left and right attachment members 116 and 118 to 
facilitate changing the stroller between the three-wheeled stroller and 
two-wheeled bicycle trailer configurations, they are clamped securely to 
the left and right attachment members and secured in place by rivets 129 
to prevent movement along the left and right attachment members during use 
of the conversion assembly 10. The upper ends of the left and right side 
support members 124 and 126 are removably coupled to the left and right 
pivot connectors 128 by removable lock pins 128a to facilitate folding of 
the conversion assembly 10 when removed from the stroller 12, and also to 
facilitate assembly and disassembly of the conversion assembly. 
A lower end portion or end of each of the left and right side support 
members 124 and 126 has an axle extension assembly 130 fixedly attached 
thereto. The axle extension assembly 130 is best shown in FIG. 8 for the 
right side support member 126. The axle extension assembly 130 includes a 
coupler 132 having a side support member receiver portion 134 within which 
a corresponding one of the left or right side support members 124 or 126 
is inserted and fixed in place using rivets 136. The coupler 132 also has 
an axle extension receiver portion 138 which receives an inner end portion 
of a tubular axle extension 140 therein. The axle extension receiver 
portion 138 and the axle extension 140 are fixedly attached together by 
rivets 142. The axle extension 140 includes a single wall metal tube 
segment having the same outer diameter as the outer axle tube 82 and the 
same inner diameter as the inner axle tube 84 of the rear axle 58. A 
gusset plate 143 is fixedly attached to both the side support member 
receiver portion 134 and the axle extension receiver portion 138 to 
rigidly hold them together. 
The axle extension 140 extends inward from an outer end of the axle 
extension receiver portion 138 only partially into the axle extension 
receiver portion so that the inner end thereof forms a recess 138a to 
receive the end portion 58a of the rear axle 58 snugly therein for 
increased stability. A spindle or stub axle 144 having a circular 
cross-section is fixedly retained in the opening of the inner end portion 
of the axle extension 140 and has an inward end portion 146 projecting 
inward therefrom. The inward end portion 146 is substantially identical to 
the inward end portion 92 of the stub axles 86 and is sized to be 
removably inserted into and snugly and rotatably retained within the 
corresponding left or right end of the inner axle tube 84 of the stroller 
rear axle 58. An inward end 148 of the inward end portion 146 of the stub 
axle 144 has a circumferential bevel to form a tapered end to facilitate 
insertion into the corresponding left or right open end of the inner axle 
tube 84. As with the stub axle 86, the stub axle 144 of the axle extension 
assembly 130 also includes a circumferential groove 150 extending around 
the full circumference of the stub axle. The groove 150 is positioned on 
the stub axle 144 so as to be in alignment with the pin 98 carried by the 
spring 102 of the stroller 12 such that when the stub axle 144 is fully 
inserted into the end of the inner axle tube 84 of the stroller rear axle 
58, the pin 98 will project into the groove 150 and will prevent axial 
withdrawal of the stub axle 144 from within the inner axle tube 84, in the 
same manner as described above for the stub axle 86 which carries the rear 
wheel 18. As with the stub axle 86, the stub axle 144 of the axle 
extension assembly 130 can be quickly and easily removed when desired by 
the user simply pressing forward on the rearward leg portion 106 of the 
spring 102 to move the pin 98 forward into the disengagement position (as 
shown in FIG. 6B for the stub axle 86). With this arrangement, the left 
and right side support members 124 and 126 are free to rotate relative to 
the rear axle 58 and the stroller upright support tubes 54 to facilitate 
changing the stroller between the three-wheeled stroller and the 
two-wheeled bicycle trailer configurations. 
The axle extension 140 extends outward beyond an outer end of the axle 
extension receiver portion 138 and has an opening sized to receive therein 
the inward end portion 92 of one of the stub axles 86 on which the rear 
wheels 18 are mounted. The axle extension assembly 130 uses the same 
user-actuated releasable lock mechanism as used with the stroller second 
coupler 70. This includes a movable pin 152 which extends through an 
aperture 154 extending through a forward facing wall portion of the side 
support member receiver portion 134 and the wall of the tube segment of 
the axle extension 140. The aperture 154 extends into the interior of the 
axle extension 140 at a location aligned with the stub axle groove 96 when 
the inward end portion 92 of the stub axle 86 is fully inserted into the 
end opening of the axle extension 140. The pin 152 has sufficient length 
when in an engagement position to project within the stub axle groove 96 
and thereby prevent axial withdrawal of the stub axle 86 from within the 
axle extension 140. The pin 152 is held in the engagement position by a 
flat spring 156 having the same design as the spring 102 described above 
for the releasable lock mechanism of the stroller 12. The spring 156 has a 
forward leg portion fixedly attached to the forward facing wall portion of 
the side support member receiver portion 134 of the coupler 132 by the 
rivets 136. The forward leg portion carries the pin 152. 
By using the axle extension assemblies 130 of the left and right side 
support members 124 and 126, the distance between the rear wheels 18 of 
the stroller 12 is widened for use in the two-wheeled bicycle trailer 
configuration and the increased wheel base provides for increased 
stability to reduce the likelihood of the stroller 12 tipping and rolling 
over when used in the bicycle trailer configuration and towed by the 
bicycle 13 at higher speeds greater than typically encountered when used 
in the three-wheeled stroller configuration. 
It is noted that the attachment of the axle extension assemblies 130 to the 
stroller rear axle 58 also provides a secure attachment of the left and 
right side support members 124 and 126 to the rear axle 58 of the stroller 
12. The left and right side support members 124 and 126 hold the left and 
right attachment members 116 and 118 securely in position and prevent them 
from pivoting upward or downward during use of the stroller 12 in the 
bicycle trailer configuration. Further, as will be described below, when 
the stroller 12 is towed behind the bicycle 13 a towing force is 
transmitted through the upper frame attachment 114 to the upper frame 
tubes 24 of the stroller 12. A portion of the towing force is also 
transmitted from the upper frame attachment 114 through the left and right 
side support members 124 and 126 to the left and right ends of the rear 
axle 58. In such fashion, the towing force applied by the bicycle 13 to 
the conversion assembly 10 is distributed to both the left and right upper 
frame tubes 24 and the left and right ends of the rear axle 58. This 
applies a balanced and distributed pulling force to the stroller 12 
without applying too much force or an unbalanced force to any one 
component of the stroller. Further, the towing force is applied at points 
toward the rear of the stroller, not by pulling on the forward ends of the 
horizontal base frame tubes 22. 
It is noted that the upper frame attachment 114 also serves to support a 
canopy 158, as best seen in FIGS. 2 and 11. The canopy 158 has a roof 
portion 159 extending between and attached to the left and right 
attachment members 116 and 118. The canopy 158 also has a front portion 
and left and right side portions, each with a clear plastic window 160 
forming a portion thereof to provide visibility for an infant being 
carried in a fabric seat 162 (see FIGS. 10A and 10B) supported by the 
upper frame tubes 24. The window 160 also provides the parents with a view 
of the infant in the seat 162 enclosed within the canopy. The canopy 158 
provides an enclosure to protect the infant in the seat 162 from any water 
or other matter that may fall from the sky or be kicked rearward by the 
rear tire of the bicycle 13, and from wind. The lower edges of the canopy 
158 are tied together under the stroller seat 162. It is noted that while 
the upper frame attachment 114 and the left and right side support members 
124 and 126 are attached to the stroller 12 to convert it to the bicycle 
trailer configuration, they may remain on the stroller with the canopy 
158, as shown in FIG. 11, to provide protection for the infant in the seat 
162 even when the stroller 12 is being used in the three-wheeled stroller 
configuration. 
It is also noted that the upper frame attachment 114 and the left and right 
side support members 126 and 124 also serve as a roll-bar cage to protect 
the infant within the seat 162 in the event that the stroller 12 should 
tip and roll over when being towed as a bicycle trailer behind the bicycle 
13. While in a normal use such rolling over of the stroller when 
configured as a two-wheeled bicycle trailer should not occur, particularly 
with the use of the axle extension assemblies 130, in the event of an 
accident produced by impact or excessively high operating speeds, the 
infant is provided with an extra margin of protection by the provision of 
the roll-bar cage. 
The conversion assembly 10 further includes a tow-arm or tow-arm assembly 
164 having left and right tow-arm members 166 and 168, respectively. As 
shown in FIGS. 1, 2, 9, 10A and 10B, a rearward end portion or end of each 
of the left and right tow-arm members 166 and 168 is connected to the 
forward attachment member 122 of the upper frame attachment 114 by left 
and right connectors 170. The left and right connectors 170 are clamped 
securely enough to the forward attachment member 122 to not move along the 
forward attachment member during use of the conversion assembly 10. The 
left and right tow-arm members 166 and 168 are removably coupled to the 
forward attachment member 122 by removable lock pins 170a to facilitate 
connection and disconnection of the tow-arm assembly 164 for use of the 
stroller 10 in the two-wheeled bicycle trailer configuration shown in FIG. 
2 with the tow-arm assembly attached, and for use in the three-wheeled 
stroller configuration shown in FIG. 11 without the tow-arm assembly 
attached. 
A forward end portion or end of each of the left and right tow-arm members 
166 and 168 is fixedly attached to a hitch arm 172. The hitch arm 172 has 
a forward end flexibly attached to a conventional hitch 174 which can be 
removably clamped to a seat post 176 of the bicycle 13 just below a seat 
177 thereof using a knob 178 threadably received on a threaded member 180. 
Manual rotation of the knob 178 securely but releasably clamps left and 
right clamp members 182a and 182b, respectively, about the seat post 176. 
The full towing force applied to the stroller 12 when converted to the 
two-wheeled bicycle trailer configuration is transmitted through the 
tow-arm assembly 164 to the forward attachment member 122 of the upper 
frame attachment 114. As described above, this force is then transmitted 
through the left and right attachment members 116 and 118 to the left and 
right upper frame 24, with a portion thereof transmitted from the upper 
frame attachment 114 through the left and right side support members 124 
and 126 to the left and right ends of the rear axle 58. 
As described above, when the stroller 12 is used in the three-wheeled 
stroller configuration in FIGS. 3 and 10A, the lower terminal ends 24a of 
the upper frame tubes 24 are releasably coupled to the horizontal base 
frame tubes 22 by the frame connector 28. This is accomplished by the 
tongue portions 42 of the fittings 44 fixedly attached to the upper frame 
tubes being received in the connector portions 38. When in this position, 
the frame 14 of the stroller 12 is configured as shown in FIG. 10A. It is 
noted that FIG. 10A shows attachment of the upper frame attachment 114 and 
the left and right side support members 124 and 126 which allows the 
stroller to be used in the three-wheeled stroller configuration with the 
canopy 158 attached as shown in FIG. 11. In this configuration, the 
approximate center of gravity of the infant in the seat 162 is located at 
a point 184 shown in FIG. 10A which is almost directly above the rear axle 
58 of the stroller 12. While the overall center of gravity of the stroller 
12 with the infant in the seat 162 is somewhat forward of the rear axle 
58, the front wheel 20 of the stroller can be easily lifted off of the 
ground for turning or going over an obstacle by the user pressing downward 
on the handle 26. 
When the stroller 12 is in the two-wheeled bicycle trailer configuration, 
it is desirable that the overall center of gravity of the stroller be 
moved forward and lowered to produce greater stability of the stroller 
when being towed at high speeds in the bicycle trailer configuration. To 
accomplish this, the conversion assembly 10 includes an elongated base 
frame attachment or baseplate 186 which is positionable between the left 
and right connector portions 38 of the frame connector 28 as shown in FIG. 
9. With the front wheel 20 removed, the baseplate 186 is positioned over 
the bridge portion 34 of the frame connector 28 in longitudinal alignment 
with the horizontal base frame tubes 22. The baseplate 186 has an aperture 
188 positioned to coincide with the bolt 36 which holds the front wheel 
caliper brake of the stroller in place. The aperture 188 is sized to allow 
the bolt 36 to project freely through the aperture. A rearward end of the 
baseplate 186 has a downwardly projecting first stop or lip 190, which as 
best shown in FIG. 10B is positioned at a rearward end of the bridge 
portion 34 of the frame connector 28. The baseplate 186 also includes a 
downwardly projecting second stop or lip 191 positioned forward of the 
first lip and a forward end of the bridge portion 34 of the frame 
connector. The lips 190 and 191 help to properly locate the baseplate on 
the bridge portion 34 and also helps prevent the baseplate from sliding 
forward or rearward relative to the horizontal base frame tubes 22 of the 
stroller 12 when used in the bicycle trailer configuration. 
The baseplate 186 has a releasable connector or clamp 192 positioned 
therebelow which clamps the baseplate to both of the base frame tubes 22. 
The clamp 192 includes an upper clamp member 192a fixedly attached to the 
underside of the baseplate and a lower clamp member 192b. A threaded wing 
nut 193 (see FIG. 10B) is positioned below the lower clamp member 192b and 
is threadably received on a threaded member which is fixedly attached to a 
manually rotatable knob 194 positioned above the baseplate and extends 
downward through the baseplate through an aperture in the baseplate. To 
attach the baseplate 186 to the horizontal base frame tubes 22, the knob 
194 is turned while holding the wing nut 193 against rotation to spread 
the upper and lower clamp members 192a and 192b apart and then the 
baseplate is positioned between the connector portions 38 of the frame 
connector 28 with the upper clamp member 192a above the horizontal base 
frame tubes 22 and the lower clamp member 192b below them. The knob 194 is 
then turned to pull the lower clamp member 192b toward the upper clamp 
member 192a and securely clamp the baseplate 186 to the horizontal base 
frame tubes 22 of the stroller 12. As noted, when properly positioned the 
aperture 188 will have the bolt 36 located therewithin and the downwardly 
projecting lip 190 will be at the rearward end of the bridge portion 34 of 
the frame connector 28. The baseplate 186 is a rigid metal plate with 
sufficient strength that it will not bend significantly under the loads 
encountered while using the stroller 12 in the two-wheeled bicycle trailer 
configuration. 
As best illustrated in FIGS. 1 and 9, an elongated upper frame connector 
196, having a U-shaped cross section, is fixedly attached to a front end 
portion of the baseplate 186. The connector 196 is formed by an upper 
plate 196a and a lower plate 196b which are spaced apart by a sufficient 
distance to snugly receive the tongue portions 42 of the fittings 44 
attached to the lower terminal ends 24a of the upper frame tubes 24 
therewithin. The upper and lower plates 196a and 196b are fixedly attached 
together at a forward end thereof by a forward end wall 196c. The upper 
plate 196a has a pair of spaced apart apertures 198 positioned so that 
when the tongue portions 42 of the fittings 44 are positioned within the 
space between the upper and lower plates 196a and 196b the apertures 198 
will be aligned with the apertures 48 of the tongue portions. The 
apertures 48 and 198 are sized to receive removable lock pins 200 to 
securely hold the tongue portions 42 in place within the connector 196 
during use of the stroller 12 in the two-wheeled bicycle trailer 
configuration, as shown in FIGS. 2, 9 and 10B. 
As illustrated in FIG. 10B, when the tongue portions 42 of the fittings 44 
attached to the upper frame tubes 24 are positioned within the connector 
196, the approximate center of gravity of the infant in the seat 162 
indicated by the point 184 is moved forward from its location shown in 
FIG. 10A for the three-wheeled stroller configuration. This is because the 
connector 196 attached to the baseplate 186 is positioned at a forward end 
of the baseplate significantly forward of the connector portions 38 of the 
frame connector 28. When the baseplate 186 is clamped to the horizontal 
base frame tubes 22 using the clamp 192, the lock pins 50 (see FIG. 4) are 
removed and the tongue portions 42 are removed from the slots 40 of the 
connector portions 38. As shown in FIG. 10B, the upper frame tubes 24 are 
rotated about the pivot joints 56 and the lower ends thereof are moved 
forward. When in this position, the tongue portions 42 are then inserted 
into the connector 196 and the lock pins 200 inserted into the apertures 
198 and through the apertures 48 of the tongue portions 42 to secure the 
tongue portions therein. In doing so, the seat 162 and hence the 
approximate center of gravity indicated by point 184 is moved forward 
relative to the rear wheels 18, and also lowered. As shown in FIG. 10A, 
the approximate center of gravity shown as point 184 is at a distance 
d.sub.1 above the ground level when in the three-wheeled stroller 
configuration. When in the two-wheeled bicycle trailer configuration shown 
in FIG. 10B, the approximate center of gravity indicated by point 184 is 
at the height d.sub.2 above the ground level, with the distance d.sub.2 
being significantly less than the distance d.sub.1. As such, not only does 
the approximate center of gravity move significantly forward of the rear 
axle 58, but it is also lowered to provide significantly increased 
stability of operation at the higher speeds which are encountered when 
pulling the stroller 12 in the two-wheeled bicycle trailer configuration 
with the bicycle 13. This provides increased safety to the infant riding 
in the seat 162 from accidental tilting and rolling over. 
It is noted that when the upper frame tubes 24 are moved as described above 
from the three-wheeled stroller configuration shown in FIG. 10A to the 
two-wheeled bicycle trailer configuration shown in FIG. 10B, not only do 
the upper frame tubes 24 rotate relative to the upright support tubes 54 
about the pivot joints 56, but if the upper frame attachment 114 and the 
left and right side support members 124 and 126 are already attached to 
the frame 14 of the stroller 12, as shown in FIG. 10A, it is necessary for 
them to also rotate relative to the frame and to each other. This is 
allowed by the upper frame attachment 114 being pivotally coupled to the 
left and right upper frame tubes 24 by the pivot connectors 120 and to the 
left and right side support members 124 and 126 by the pivot connectors 
128. With such pivotal connection of the components, the stroller 12 can 
be easily and quickly converted between the three-wheeled stroller 
configuration and the two-wheeled bicycle trailer configuration using the 
conversion assembly 10. 
Since when in the two-wheeled bicycle trailer configuration the front wheel 
20 of the stroller 12 is removed, it is necessary to support the forward 
end of the horizontal base frame tubes 22 to prevent them from rotating 
downward and contacting in the ground. To accomplish this, the conversion 
assembly 10 includes left and right side suspension members 202 and 204, 
respectively. An upper end portion or end of each of the left and right 
side suspension members 202 and 204 is pivotally connected for movement in 
a left or right laterally inclined plane to a corresponding one of the 
left and right tow-arm members 166 and 168 of the tow-arm assembly 164 
along a mid portion thereof by left and right pivot connectors 206. While 
the left and right pivot connectors 206 allow the left and right side 
suspension members 202 and 204 to pivot relative to the left and right 
tow-arm members 166 and 168, they are clamped securely to the left and 
right tow-arm members and secured in place by rivets 208 to prevent 
movement along the left and right tow-arm members during use of the 
conversion assembly 10. 
A lower end portion or end of each of the left and right side suspension 
members 202 and 204 is pivotally connected for movement in the left or 
right laterally inclined plane to a forward end of the baseplate 186 just 
rearward of the connector 196 by a hinge pin 210. The hinge pin 210 
extends between tabs 212 fixedly attached to the baseplate 186. The lower 
ends of the left and right side suspension members 202 and 204 are 
connected to the baseplate 186 by the pivot pin 210 and the tabs 212 with 
a closer spacing therebetween than the upper ends of the left and right 
side suspension members where connected to the left and right tow-arm 
members 166 and 168. This provides the suspension members when viewed from 
the front or rear with a V-shaped configuration. The pivotal connection of 
the upper and lower ends of the left and right side suspension members to 
the left and right tow-arm members and the baseplate is provided to allow 
folding for compact storage of the conversion assembly 10 when removed 
from the stroller. During use in the bicycle trailer configuration no 
pivotal movement is intended at these pivotal connections. 
When the hitch 174 is clamped to the seat post 176 of the bicycle 13, the 
left and right side support members 124 and 126 which extend between the 
upper frame attachment 114 and the rear axle 58 hold the upper frame 
attachment 114 in position and prevent it from dropping downward. Since 
the horizontal base frame tubes 22 are pivotally connected to the rear 
axle 58 through the first couplers 60 and are rotatable relative to the 
rear axle, without support the horizontal base frame tubes 22 of the 
stroller are free to rotate downward under the weight of the stroller and 
the weight of the infant being carried in the seat 162. The left and right 
side suspension members 202 and 204 provide the needed support by 
extending between the left and right tow-arm members 166 and 168 and the 
baseplate 186, which is clamped to the horizontal base frame tubes 22. 
They serve to hold the forward end of the stroller up to prevent it from 
rotating downward into contact with the ground. The length of the left and 
right suspension members 202 and 204 is selected to hold the horizontal 
base frame tubes 22 of the stroller in a position generally parallel to 
the ground when in the two-wheeled bicycle trailer configuration of FIG. 
10B at about the same height as does the front wheel 20 when in the 
three-wheeled stroller configuration of FIG. 10A. The left and right side 
suspension members 202 and 204 are connected to the left and right tow-am 
members 166 and 168 so as to have a slight forward upward slant. The left 
and right side support members 124 and 126, the left and right tow-arm 
members 166 and 168, the hitch arm 172, and the left and right side 
suspension members 202 and 204 are manufactured from substantially rigid 
tubes. 
When the front wheel 20 of the stroller 12 is removed for use in the 
two-wheeled bicycle trailer configuration, it is desirable to have a place 
to carry the front wheel along in case it is desired to change the 
stroller back to the three-wheeled stroller configuration. With the 
conversion assembly 10, the removed front wheel can be positioned in a 
horizontal attitude above the baseplate 186 and supported by the baseplate 
below the upper frame tubes 24 and rearward of the connecting member 196 
as shown in FIG. 10B. In this position the removed front wheel 20 is 
sufficiently below the seat 162 so that it does not interfere with use of 
the stroller in the bicycle trailer configuration. To secure the removed 
front wheel 20 in position on the baseplate 186, the baseplate has an 
elongated slot 212 having an enlarged rearward end opening portion 214. 
The slot 212 is located rearward of the clamp 192 and forward of the 
second lip 191 at a position to be forward of the bridge portion 34 of the 
frame connector 28. Thus, the slot 212 is readily accessible from above 
and below the baseplate 186. 
The enlarged portion 214 of the slot 212 is sized to allow the axle and 
wheel nut threaded thereon of the removed front wheel 20 to freely move 
therethrough when the removed front wheel is initially placed on the 
baseplate 186. With the axle of the removed front wheel 20 extending 
through the enlarged portion 214 and the wheel nut threaded thereon 
positioned below the baseplate 186, the removed front wheel is moved 
forward to position the axle of the front wheel in the forward narrow 
portion of the slot 212. The wheel nut is larger than the width of the 
slot and can be tightened from below the baseplate 186 to clamp the 
removed front wheel 20 securely to the baseplate while being carried 
during use of the stroller in the two-wheeled bicycle trailer 
configuration. 
The conversion assembly 10 when attached to the stroller 12 in the 
two-wheeled bicycle trailer configuration of FIG. 10B provides an 
extremely stable and roll resistant bicycle trailer. In the past, prior 
art three-wheeled strollers that were converted to two-wheeled bicycle 
trailers had an unacceptable tendency to tip and roll over during usage. 
This typically occurred when one rear wheel of the trailer hit a curb or 
rock so as to quickly and severely lift only the one side of the bicycle 
trailer. It also sometimes occurred when the bicycle pulling the bicycle 
trailer attempted a high speed curve or sharp corner turn and the force 
picked up the inside wheel of the stroller when in the bicycle trailer 
configuration. One significant benefit of the conversion assembly 10 of 
the present invention is that its construction reduces the chances for 
tipping and rolling of the stroller when in the bicycle trailer 
configuration. In part, this is accomplished because of the axle extension 
assemblies 130 that provide a wider rear wheel base, and the movement of 
the center of gravity of the infant in the seat 162 significantly forward 
of the rear axle 58 and lower than when the stroller 12 is used as a 
three-wheeled stroller. Increasing the rear wheel base produces a higher 
rotational inertia. 
Further, by connecting the tow-arm assembly 164 to the seat post 176 of the 
bicycle 13 just under the seat 177 and extending it rearward to engage an 
upper portion of the upper frame tubes 24 at two spaced apart locations 
toward the rear of the stroller, the towing forces are transmitted from a 
high point on the bicycle to a high point on the stroller, both of which 
are significantly higher than the approximate center of gravity indicated 
by point 184 of the infant in the seat 162 and of the general center of 
gravity of the stroller with the infant in the seat. With this 
arrangement, the stroller 12 when in the two-wheeled bicycle trailer 
configuration tends to have a line of towing extending from just under the 
seat 177 of the bicycle 13 to the handle 26 of the stroller. Further, the 
axis of rotation of the stroller produced by the forces which tend to tip 
and roll the stroller extends from just under the seat 177 to the ground 
contact point of the rear wheel 18 of the stroller opposite the rear wheel 
being lifted to produce the tipping and rolling. This axis of rotation is 
much higher, relative to the center of gravity, than prior art bicycle 
trailers converted from three-wheeled strollers. As such, gravity acts as 
a restoring force through a greater angular displacement during tipping 
and rolling than with such prior art bicycle trailers. Hence, the use of 
the conversion assembly 10 of the present invention produces a bicycle 
trailer which is safer and less inclined to tip and roll. 
To further inhibit tipping and rolling, the left and right side suspension 
members 202 and 204 are designed to apply a downward force to the stroller 
to counter any upward force on one of the rear wheels that tends to tip 
and roll the stroller. Any such upward force is transmitted through the 
stroller frame 14 to the left and right side suspension members 202 and 
204 to the tow-arm assembly 164 that is clamped at its forward end to the 
seat post 176 of the bicycle 13 and tends to lift the bicycle and the 
adult rider thereon. However, this upward force is countered with the 
significant downward force produced by the weight of the adult rider and 
the bicycle, which tends to offset the upward force and significantly 
inhibit tipping and rolling of the stroller. The same result occurs to the 
extent the lifting force is transmitted through the left or right side 
support members 124 and 126. 
The left and right side suspension members 202 and 204 further act to 
inhibit tipping and rolling when the bicycle 13 is ridden through a 
high-speed curve. To illustrate this, consider the bicycle 13 turning to 
the left and naturally leaning to the left. The tendency for the stroller 
12 in such a situation is for the inside or left rear wheel 18 to lift 
upward, particularly if it hits a bump, and roll about the outside or 
right rear wheel. However, since the bicycle 13 is being leaned to the 
left side in such a left hand turn, part of the weight of the leaning 
adult bicycle rider and the leaning bicycle tends to be offloaded from the 
rear wheel of the bicycle and transferred back to the stroller through the 
left and right tow-arm members 166 and 168 and the left and right side 
suspension members 202 and 204 to the rear wheels of the stroller. This 
tends to further inhibit tipping and rolling of the stroller when turning. 
As previously noted, with the conversion assembly 10 of the present 
invention, even should the stroller tip and roll over, the upper frame 
attachment 114 and the left and right side support members 124 and 126 
form a roll cage to protect the infant in the seat 162. When the stroller 
12 is in the two-wheeled bicycle trailer configuration of FIG. 10B, the 
tow-arm assembly 164 and the left and right side suspension members 202 
and 204 also tend to add protective structure to protect the infant in the 
seat 162 during a roll. 
It will be appreciated that, although a specific embodiment of the 
invention has been described herein for purposes of illustration, various 
modifications may be made without departing from the spirit and scope of 
the invention. Accordingly, the invention is not limited except as by the 
appended claims.