BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to scaffolds and more particularly to a novel mobil collapsible scaffold. The invention relates also to a portable water tower embodying the scaffold.
2. Discussion of the Prior Art
In its broader aspects, the invention provides a scaffold which may be used to support any object in an elevated position above the ground and which is equipped with wheels to permit the scaffold to be transported from one location to another. A primary feature of the invention resides in the unique construction of the scaffold whereby the latter may be quickly and easily collapsed at one location for convenience of transportation and subsequently erected at another location. This collapsibility and portability of the scaffold is achieved with a scaffold structure which is relatively simple in construction, economical to fabricate, light weight, and compact.
The attached drawings illustrate one useful embodiment of the present supporting scaffold. This illustrated embodiment of the invention is a water tower of the general type used in the earth moving industry for servicing mobile water trucks. Thus, many earth working operations require periodic wetting of the soil. For example, dirt is frequently added to a land area to raise its surface level. An earth moving operation of this kind is commonly referred to in the trade as a "land fill." One of the major problems associated with such a land fill is maintaining the proper moisture content in the fill dirt to obtain the required degree of relative compaction of the dirt. If the fill dirt in its native state lacks the required moisture content, the land fill contractor is required to supplement the moisture by periodically wetting the dirt as the land fill operation proceeds. Such additional water is deployed over the area being filled by water trucks which are commonly referred to in the trade as "water pulls."
The storage capacity of a water pull is limited with the result that the pull must be refilled many times during the course of a typical land fill. This periodic refilling, or servicing, of the water pull creates a two-fold time loss involving the time required for the water pull to travel from its operating area to the water supply and back to the operating area, and the time required to actually refill of service the pull at the water supply. Moreover, many land fills are of such a magnitude as to require several water pulls. Servicing such a plurality of pulls introduces an additional time loss when it is necessary for the pulls to line up and wait their turn at the water supply or supplies.
These time losses are minimized by using several portable water towers placed at strategic locations around the fill. In this way, the time required for a water pull to travel from its operating area to a water tower and return is reduced and the tendency for the water pulls to line up at a water tower is minimized or eliminated. The use of a plurality of strategically located water towers at a land fill site, therefore, is highly desirable.
In order to be effective, water towers of the character described must satisfy certain requirements. The water towers, for example, must be highly portable so that they may be easily moved from one job to another. Accordingly, the dimensions and weight of the tower, when conditioned for transportation, must fall within the motor vehicle code specifications. The tower must be capable of being towed and landed by a relatively light truck. In addition, the tower should be capable of landing and being erected on a roughly cleared site, such as one which has been graded with a Caterpillar and blade, without auxiliary ditching or hand shoveling. Such landing and erection capabilities of the tower should exist on both level land and on mild slops. Finally, the tower must be capable of erection to a height such that its water tank is elevated a sufficient distance above the ground to position the down spout of the tank over the fill port of a water pull. Preferably, the tower should be capable of being erected by one man in a minimum of time. Water towers of the class described are disclosed in U.S. Pat. Nos. 3,315,929; 3,348,572 and 3,407,836.
One of the major problems associated with such water towers involves raising and lowering relative to one another the base frame of the tower and the ground wheels on which the tower is supported in transit. Thus, when a tower is erected at a job site, the wheels must be raised from and the base frame lowered into supporting contact with the ground. When towing the tower from one location to another, the frame must be raised from and the wheels lowered into supporting contact with the ground. The existing water towers, such as those disclosed in the earlier mentioned patents, utilize quite complex and costly means for this purpose. In many cases, separate means are required to raise and lower the frame and the wheels.
Another problem associated with water towers is stability and structural strength. Thus, such water towers are always subject to the danger of being struck by a truck. Quite often accidents of this type cause the tower to buckle and collapse.
SUMMARY OF THE INVENTION
The present invention provides an improved mobile collapsible scaffold which may be utilized in a water tower and which avoids the above and other disadvantages of the existing water towers. The scaffold or water tower has a base frame mounting a hinged collapsible framework including front and rear frame sections pivoted on the base frame and a top frame section extending between and pivoted to the upper ends of the front and rear sections. When the scaffold is utilized in a water tower, the top frame section supports a water tank, the frame structure is rotatable relative to the base frame between an erect position for use and a collapsed position for travel.
Located at opposite sides of the base frame are ground wheels on which the tower is supported in transit. According to a major feature of the invention these ground wheels are operatively connected to the collapsible framework of the tower in such a way that the wheels elevate from and the base frame lowers into supporting contact with the ground when the framework is raised to its erect position for use. When the framework is lowered to its collapsed position for travel, the base frame elevates from and the wheels lower into supporting contact with the ground.
Another important feature of the invention involves the structural strength of the scaffold or tower. According to this feature, the base frame and collapsible framework are provided with a very rugged construction which renders the tower substantially more immune to buckling or collapse in the event that the tower is struck by a truck.
The invention also possesses other novel features which contribute to those discussed above to provide a scaffold or water tower which is vastly superior to those currently available. Among these additional features, for example, are the use of bogey supported tandem wheels which improve the stability and load supporting capability of the tower. Also, the wheels may be adjusted to permit leveling of the tower on uneven terrain.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation of a water tower according to the invention showing the tower in its collapsed configuration;
FIG. 2 shows the tower in its erect position;
FIG. 3 is a section taken on line 3--3 in FIG. 2;
FIG. 4 is a section taken on line 4--4 in FIG. 2; and
FIG. 5 is a section taken on line 5--5 in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The mobile collapsible water tower 10 of the invention selected for illustration embodies a collapsible scaffold 12 according to the invention for supporting a water tank 14 with a rear spout 15. The scaffold 12 has an elongate base frame 16 with front and rear ends 18, 20. At the front end of the frame is a hitch 22 for connection to a towing vehicle (not shown). At the sides of the base frame 16, about midway between its ends, are wheels 23 on which the tower rolls when being towed. As will appear presently, the wheels 23 are elevated to lower the frame into supporting contact with the ground when the tower is elevated to its position of use. When the tower is lowered or collapsed for travel, the wheels are lowered to elevate the base frame out of contact with the ground to permit the tower to roll on the wheels.
At the upper side of frame 16 is a collapsible framework 24. This framework includes front and rear frame sections 26, 28, and a top frame section 30. Each front and rear frame section has parallel legs 32 joined by connecting cross members 34 and braces 36. The top frame section 30 has parallel end members 38 rigidly joined by connecting members 40 and braces 42. The lower ends of the end frame section legs 32 are attached, by pivots 44, to the longitudinal members 46 of the base frame 16. The upper ends of the legs are attached, by hinges or pivots 48, to the lower ends of the end members 38 of the top frame section 30.
The pivot axes of the framework pivots 44, 48 extend transversely of the base frame 16 in mutually parallel relation, such that the framework constitutes a hinged parallelogram structure. The framework is swingable in the fore and aft direction of the base frame between its collapsed position of travel shown in FIG. 1 and its erect position of use shown in FIG. 3. The end frame sections 26, 28 remain parallel to one another and the base frame 16 and top frame section 30 remain parallel to one another during movement of the frame between its erect and collapsed positions.
Water tank 14 is mounted on the top frame section 30 in parallel relation to this section. Accordingly, the tank remains parallel to the base frame 16 during raising and lowering of the framework 24. As shown in the drawings, the framework swings rearwardly of the base frame when raised and forwardly relative to the frame when lowered in a manner such that the rear end of the tank 14 projects beyond the rear end of the base frame in raised position and the entire length of the tank is situated between the ends of the frame in lowered position.
Framework 24 may be raised and lowered in various ways. The particular scaffold or water tower shown is equipped with framework elevating means 50 comprising essentially a block and tackle mechanism including blocks 52 on the rear frame section 26 and a braced upstanding post 54 on the rear end of the base frame 16 and a cable 56 having a number of runs extending between and around the pulleys of the blocks. One end of the cable is anchored. The other end of the cable is free and about a pulley 58 on the lower end of post 54 for connection to a vehicle. The framework is raised by driving the vehicle away from the tower and lowered by driving the vehicle toward the tower.
In the lowered or collapsed position of the framework 24, the front and rear end members 38 of the top frame section 30 rest on braced supports 60 rising from the front end and center of the base frame 16. Elevational movement of the framework is arrested, in its erect position, by abutment of the front and rear frame sections 26, 28 with braced upstanding stops 62 on the center and rear end of the base frame. The front and rear frame sections may be releasably secured to these stops in any convenient way to hold the framework erect.
One important feature of the invention resides in the rugged construction of the scaffold or tower, whereby the latter possesses a high degree of resistance to buckling or collapse in the event the tower is struck by a truck. This rugged construction is achieved by the sturdy braced construction of the front, rear, and top frame sections of the framework 24 and by the braced stops 62 which reinforce the front and rear frame sections when the framework is elevated.
As noted earlier, the ground wheels 23 raise and lower as the tower is raised and lowered. Another important feature of the invention involves the manner in which this is accomplished. According to this feature, the wheels are carried by wheel support members 64 comprising elongate frames extending longitudinally of the base frame 16 between and outboard of the front and rear frame sections 26, 28. The longitudinal axes of these frames parallel the base frame and top frame section 30. At their ends, the wheel support frames 64 are attached by pivots 66 to the frame sections 26, 28 at points between the frame section pivots 44, 48 and adjacent the lower pivots 44. The pivot axes of the wheel frame pivots 66 parallel the axes of pivots 44, 48 and are located in a plane parallel to the plane containing the axes of the upper pivots 44 and the plane containing the lower pivots 48.
Wheels 23 are arranged in sets at each side of the base frame 16. Each wheel set includes two pairs of wheels arranged in tandem and supported by a bogey 68, pivoted on the center of the respective wheel support frame 64. Bogies 68 and the pairs of tandem wheels straddle the side members of the base frame.
As shown in FIGS. 1 and 2, elevation of the framework 24 effectively elevates the wheel support frames 64, and hence the wheels 23, relative to the base frame 16, thereby lowering the frame into supporting contact with the ground. Lowering of the framework lowers the wheel support frames and wheels relative to the base frame to bring the wheels into supporting contact with the ground and raise the frame out of contact with the ground to condition the tower for movement by a towing vehicle. The framework may be locked in its collapsed position to prevent it from bouncing up and down in transit. It will be understood that the weight of the framework and water tank 14 and the mechanical advantage of the arrangement are such that lowering of the framework elevates the base frame out of contact with the ground, as stated.
If desired, the wheel bogies 68 may be made vertically adjustable relative to the wheel support frames 64 to permit leveling of the tower on uneven terrain.
In some cases, it may be desirable or essential to provide the scaffold with the ability to be towed from either end. To enable this towing capability, the illustrated scaffold or water tower is provided with a rear hitch tongue 70. This hitch tongue is selectively insertable into box channels 72, 74 rigidly fixed, one over the other, to the rear end of the tower frame. The tongue is releasably secured in either channel by a bolt (not shown) which may be inserted through any one of a number of sets of holes 76 in the tongue and channels to adjust the rearward extension of the tongue. When not in use, the tongue is secured in its fully retracted position of FIG. 2.