Wheel support structure for a cart

A wheel support structure for a cart, such as a wheelbarrow. The structure includes two separate wheel axis each carrying a wheel. Each wheel axis is mounted on a holding arm, which is pivotable 180 degrees about a vertical frame portion, whereby the pair of wheels can be shifted between inner and outer positions. Upper and lower plate members, forming bearing flange members, are fastened to the vertical frame portion and to a vertical stud portion of the holding arm, respectively, and are selectively securable to each other in order to lock the associated wheel in the respective inner or outer position.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a wheel support structure for a cart, e.g. 
for a wheelbarrow, having a supporting frame, the wheel structure 
comprising two separate wheel axes each carrying a wheel, each wheel axis 
being mounted on a holding arm, which is pivotable about a substantially 
vertical frame portion for pivoting 180.degree. in a horizontal plane so 
as to enable selective positioning of each wheel in either an inner or an 
outer position relative to the longitudinal central plane of the cart. 
2. Description of the Related Art 
A similar wheel support structure is previously known from U.S. Pat. No. 
2,728,584. In the known structure, the pair of wheels are mounted in such 
a way that, in a first, inner position, the two wheels are located below 
the front end of the load container of the cart for use as a conventional 
wheelbarrow to be pushed in a forward direction and, in a second, outer 
position, the two wheels are located below the rear half of the load 
container for use as a cart to be pulled in the opposite, backward 
direction, wherein two handle rods are swung inwardly towards each other 
so as to form a combined pulling rod. When converting the wheelbarrow into 
a pulling cart or vice versa, a pair of nuts inside the load container 
have to be loosened, whereupon the wheelbarrow is turned upside down to 
enable swinging of the holding arms carrying the wheels into the other 
position. Thereupon, the nuts inside the load container must be tightened 
again. 
Another example of prior art is disclosed in the published Swedish patent 
application 7801158-2, wherein a wheel support structure corresponding to 
the opening paragraph is suggested (but not described in detail) at the 
end of the description. 
SUMMARY OF THE INVENTION 
On the basis of this prior art, the object of the present invention is to 
provide a wheel support structure, wherein a pair of wheels can be easily 
shifted between inner and outer positions, even if cart is loaded, and 
wherein each wheel is securely held in a well-defined inner or outer 
position upon shifting the wheel positions and locking the respective 
holding arm in a rigid position by means of a locking device. 
This object is accomplished by the features as set forth. Thus, each wheel 
can be easily swung into a respective inner or outer position while making 
rolling contact with the ground, whereby the cart does not necessarily 
have to be unloaded before shifting the wheel positions. The outer 
position of a wheel pair will provide a good lateral stability when 
rolling the cart, whereas shifting to the inner position makes it possible 
to roll the wheelbarrow over rather narrow bridges, planks or the like. 
Therefore, the cart is flexible and safe in use. Furthermore, by means of 
the extended plate members forming bearing flange surfaces and being 
selectively securable to each other and to the supporting frame at a rear 
location, each holding arm is securably lockable in the respective 
position, whereby oscillation of each wheel is avoided. 
In particular, the embodiment defined will give the further advantage that 
a pair of rear support members of the frame (conventionally serving to 
support the cart in a substantially horizontal rest position) can be 
replaced by a pair of rear wheels mounted in the same way as the first 
pair of wheels.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The wheelbarrow shown in FIGS. 1-4 comprises a load container 1 made of a 
suitable rigid and resistant material, e.g. a metallic plate material, and 
a frame, which supports the load container and is integral with a wheel 
support structure. 
The frame structure is preferably made of tubular members, e.g. of plated 
steel or aluminium, and comprises two longitudinal side members 2, 3 (see 
FIG. 3) which are extended rearwardly into slightly outwardly projecting 
rear portions 2a, 3a provided with handles 4, 5. The rear portions 2a, 3a 
are connected by a rear, transversal frame member 6 pernamently fastened 
e.g. by welding. 
The side members 2, 3 of the frame structure extend mutually in parallel at 
each side of the longitudinal central plane C (FIG. 3) of the wheelbarrow. 
The front ends of the side members 2, 3, located approximately at a 
distance of one third of the length of the load container, from the front 
end thereof, are integrally extended into a connecting frame member 
including upwardly and transversally outwardly curved side portions 2b and 
3b, respectively, and a transversal front portion 7, which is located at a 
lower level (in the horizontal rest position of FIG. 1) than the side 
portions 2b, 3b. It will be seen from FIG. 3 that the connecting front 
frame member 2b, 3b, 7 has a configuration substantially corresponding to 
the contour of the load container 1 below the front end portion 1b 
thereof, whereas the rear transversal frame element 6 is located 
substantially underneath the rear end portion 1a of the load container 
(compare also FIG. 1). Hereby, lifting hooks (not shown) can easily be 
hooked onto the respective front side portions 2b, 3b and the rear frame 
member 6 (or at the rearwardly extending portions 2a, 3a adjacent to the 
rear frame member 6) so as to conveniently lift the wheelbarrow safely in 
its frame. Moreover, the transversal front portion 7 serves as an abutment 
(as previously known per se) when forwardly tilting the wheelbarrow into 
the vertical rest position shown in FIG. 2. 
According to the invention, the wheelbarrow is provided with at least on 
pair of wheels 8, 9 mounted in a special wheel support structure, which is 
integral with the frame structure. In particular (see FIG. 4), each wheel 
8, 9 is mounted for free rotation on separate wheel axes 10 and 11, 
respectively, each of which is pivotable in a horizontal plane about a 
vertical pivot axis 12 and 13, respectively, so that each wheel 8, 9 can 
be shifted, by pivoting a respective holding arm forming an extension of 
each wheel axis, between an inner position 8, 9 (fully drawn) and an outer 
position 8', 9' (dash-dotted lines), these positions being located along a 
transverse imaginary line L which is perpendicular to the central 
longitudinal plane C of the wheelbarrow. In both positions 8, 9 and 8', 9' 
the pair of wheels will support the frame slightly in front of the center 
of gravity of the (loaded or empty) wheelbarrow. The outer positions 8', 
9' will give the wheelbarrow an excellent transversal stability, whereas 
the inner positions 8, 9 make it possible to roll the wheelbarrow on 
rather narrow bridges, planks or the like. Now, it is very easy to shift 
between the inner and outer positions of the pair of wheels by simply 
pivoting the holding arm with the respective wheel axis about the 
respective pivot axis 12, 13, even when the wheelbarrow is placed in its 
horizontal position (FIG. 1) and even when it is loaded. Moreover, the 
shifting is facilitated by the fact that the wheels make rolling contact 
with the ground during pivoting. 
The wheel support structure for supporting the wheel 8 (the support 
structure for the other wheel 9 being identical and thereof not shown in 
detail) is illustrated in larger scale in FIG. 5a, whereas a slightly 
modified embodiment thereof is shown in FIG. 5b. 
Referring to FIG. 5a, there is shown a tubular frame portion 14 fastened by 
welding to and projecting vertically downwards from the frame side member 
2 along the pivot axis 12. At the inside of the tubular frame portion 14, 
a tubular stud 15 is rotatably journalled so as to permit rotation thereof 
about the pivot axis 12. At its lower end, the stud 15 is fastened by 
welding to the above-mentioned, horizontally extending holding arm 16, 
which is likewise tubular and constitutes the wheel axis or shaft 10 at 
its outer, free end portion. The wheel 8 is provided with a hub 17, which 
is freely rotatable on the axis or shaft 10 between two lateral holding 
flanges 18 and 19 rigidly fastened to the shaft. 
In order to hold the vertical stud 15 in a fixed vertical position relative 
to the vertical frame portion 14, the stud 15 and the frame portion 14 are 
fastened by welding to horizontal plate members 20 and 21, respectively, 
forming bearing flange surfaces 20a, 21a in the region of the stud 15 and 
the frame portion 14. 
The embodiment of FIG. 5b differs from that of FIG. 5a only in that the 
vertical, tubular stud 15' is rotatably journalled at the outside of the 
vertical frame portion 14'. 
As illustrated in FIG. 1, the upper, horizontal plate member 20 is fastened 
to the vertical support portion 14 at its front end portion and extends 
longitudinally rearwardly to a similar, rear vertical frame portion 22, 
where it is likewise fastened by welding. Hereby, the upper horizontal 
plate member 20 (and the corresponding plate member 20' at the other side 
of the wheelbarrow, see FIG. 3) is securely and rigidly connected to the 
frame structure. The lower, horizontal plate member 21 (and 21' at the 
other side) is fastened to the stud 15 (see FIG. 5a) at its central 
portion and extends in opposite directions therefrom, so that either one 
of its free end portions 21f (forward), 21r (rear) can be positioned under 
and in line with the upper, rearwardly extending plate member 20. In 
either position, the lower, pivotable plate member 21 can be releasably 
secured to the upper, fixed plate member 20 by means of locking or 
fastening means 23, e.g. a pin through corresponding holes in the plates 
20, 21 and a wing nut for securing the pin in its locking position. In the 
secured position, the stud 15 will be held in an exact angular position 
relative to the frame portion 14, so that the holding arm 16 with the 
wheel axis is likewise exactly positioned along the transversal line L 
(FIG. 4). Hereby, the wheels will not oscillate when rolling on the 
ground. 
Two rear support members 24, each in the form of a plate element bent into 
a closed, triangular, elongated shape, are provided with vertical holding 
stud portions 25, each fitting into the respective rear vertical frame 
portion 22, and are secured to the upper, horizontal plate members 20, 20' 
by releasable locking or fastening means 23', e.g. identical to the means 
23. The rear support memebers 24 are dimensioned so as to hold the 
wheelbarrow in a substantially horizontal rest position. 
If desired, the rear support members 24 can be replaced by a pair of rear 
wheels 8a, 9a (illustrated by dash-dotted lines in FIGS. 1, 2 and 3), 
which are mounted in the same way as the front wheel 8, 9. Since the wheel 
diameter is greater than the distance between the front and rear frame 
portions 14, 22, one pair of wheels has to be placed in the inner position 
when the other pair is placed in the outer position, and vice versa. With 
such a wheel arrangement, preferably with the front wheels placed in the 
inner positions, the wheelbarrow can be pushed, without lifting in the 
handles 4, 5, on the ground where the supporting ground surface is wide 
enough, whereas the wheelbarrow can be rolled on the front wheels only, 
while lifting in the handles 4, 5, when passing over narrow passages, such 
as planks or the like. 
In order to achieve the desired simple shifting between the outer and inner 
wheel positions, while securing a rolling contact with the ground, it is 
essential that the respective wheel axis 10, 11 extends in a horizontal 
plane perpendicular to the respective pivot axis 12 or 13. Hereby, the 
wheel will follow a circular path with its axis directed towards the pivot 
axis when the holding arm is swung around the pivot axis. However, the 
holding arm may be inclined and/or curved as long as the wheel axis 
extends in such a horizontal plane perpendicular to the pivot axis. As 
another feasable alternative, the holding arm may be secured to a 
fork-like bracket carrying the respective wheel axis. However, the 
illustrated embodiment with a rectilinear, rather short holding arm 
constituting an extension of the wheel axis seems to be the most practical 
one. 
The wheel support structure described above may be modified within the 
scope of the appended claims, e.g. as regards the frame structure and the 
wheel holding arms. Also, the locking of the respective holding arm in 
each transversal position may be achieved by other means, e.g. by snap 
locking means, or fastening means without loose parts.