The present invention relates to dollies, or carts, adapted to transport large sheets of material across floors and the like.
It has long been a problem to move single large sheets of metal, glass, stone and ceramic about in manufacturing plants and in the field. As an example, a conference table may have a large stone or glass sheet top, for instance, a 5xc3x9710 foot rectanguloid or 6 foot diameter disk weighing 300 or more pounds. Typically, such a top rests on a detachable base, to facilitate transport. When such a large table top is be carried into an office building lobby, up an elevator, and through a finished office, care is needed to protect the top and things along the path. The same problems obtain when glaziers transport large sheets of glass any distance. As another example, in a fabrication shop, a sheet of steel or other material might need to be casually moved from one work station to another. Not only are such large sheet objects awkward to handle, but particularly in the field, it is important that the sheet be handled in a safe way which damages neither the sheet nor other things.
A common way to handle a large sheet is to have at least two or more workers manually carry the sheet. Other times, a conventional flat dolly is employed, even though the sheet tends to be unstable and prone to come off such a type unit. Lashing the sheet to the dolly is awkward and inconvenient.
Prior inventors have addressed the problem in various ways by designing special dollies. Many such dollies have xe2x80x9cAxe2x80x9d frames or other sloped structures mounted on their surface, to support the sheet. The angle at which the sheet is carried is fixed. The prior art dollies are often not suited for carrying round or oval sheets, as characterize many table tops. In general, the prior art A-frame type dollies are bulky and heavy; and, they are costly. They may be suited for certain factory settings. But, in the field it is inconvenient to transport such dollies due to their bulk and weight. The bottom line is that the dollies taught by the prior art tend to not be used because they are unsuitable for applications where a fragile environment, e.g., a finished office or living space, must be traversed.
Thus, there is a continuing need for a dolly which stably carries both rectangular and flat sheets, and which dolly is light, transportable, and economic to produce. And, experience shows that this may not be easy, because a large sheet mounted on a dolly can easily comprise an unstable combination.
An object of the invention is to provide means for transporting both large rectangular and large circular sheet objects. A further object of the invention is that such means be light in weight, convenient to use, easy to transport, and economic to fabricate.
In accordance with the invention, a sheet to be transported is placed edgewise on the base of a rectangular frame dolly base having four wheels, preferably swivel caster wheels. The frame of the dolly base is formed of two lengthwise running side beams and two opposing end members; and, it has a central rectangular opening. A sheet being transported leans against the vertical surfaces of a stanchion comprised of spindles and a horizontal top bar. The stanchion is mounted offset from the longitudinal centerplane of the base. As a rectangular sheet is being carried, it rests along a plane defined by the top surfaces of the front and rear members. When a circular sheet is transported it is cradled within the space between the front and rear members, and its lower edge is at an elevation less than said plane.
For stability during transport, the sheet center of gravity lies within the vertical projection of a no-contact zone, as preferably do the lower and upper parts of a sheet which contacts respectively the base and the stanchion. The no-contact zone is a region defined by the innermost portions of circles of rotation of swivel caster wheels where they touch the floor and swivel around their pivot axes. The inner surfaces of the stanchion which contacts the sheet lie along a vertical plane. That vertical plane is located within bounds of the no-contact zone, called Zone Z herein. Likewise, on the opposing side of the base, the inside of the frame hole of the base is also located within the no-contact zone vertical projection, to desirably position the bottoms of circular sheets placed on the dolly. More preferably, the stanchion and interior of the base frame are located within a sub-portion of the Zone Z, which is called Zone Y. Zone Y is defined by the innermost portions of the circles of rotation of the outer circumferences of the swivel wheels. In the preferred invention, the sheet lies against the stanchion at an angle with the horizontal of 75-90 degrees, preferably 75-85 degrees, most preferably 80-85 degrees.
Preferably, there a retention bar sticking up from the base surface at said opposing side, within the no-contact zone bounds, to position the bottom edge of a rectangular sheet. The retention bar serves the same purpose as the interior of the base frame does for circular sheets; and, when the retention bar extends across the opening of the base frame, it is substitutional for the inner edge of the base frame in determining where a circular sheet bottom will rest. The top surfaces of the end members comprises a resilient frictional material, e.g., rubber underlain by wood. Since the sheet weight is concentrated at two spaced apart points, local deformation of the resilient surface helps stop sideways slipping of the sheet. More preferably, the stanchion, frame hole and retention bar components of the dolly are analogously positioned with respect to a smaller zone, called the no-wheel zone, which lies within the no-contact zone. The no-wheel zone is defined by the innermost circumferential points of the wheels themselves, as compared to where they contact the floor.
In further accord with the invention a second horizontal bar, which is vertically adjustable, runs between the spindles of the stanchion. This provides an adjustable support which is particularly useful for small circular sheets. Preferably, the stanchion is removable from the base, by having the spindles mounted in sockets, or clamped to the base. Alternatively, the stanchion is hinged to the base, so it can be folded flat along the top surface. These features facilitate transport of the dolly to the point of use.
The dolly of the invention is useful for stably transporting a variety of shapes of sheets and economic to construct. The dolly configuration minimizes chance for damage to the sheet edges or by bending fracture during use. And even while providing these advantages, the dolly is light weight, adapted to easy transport, and economically made.
The foregoing and other objects, features and advantages of the invention will become more apparent from the following description of the best mode of the invention and accompanying drawings.