Abstract:
A collapsible, portable hoist that can be assembled and operated by a single individual, for lifting and conveying heavy objects onto and off of trucks, especially pickup trucks. When not in use, the hoist collapses down to a flat storage configuration that rests on, and is secured to, the truck&#39;s cargo walls without any portion extending beyond the truck. In order to deploy the hoist, one rotates its support frame up from the stowed position and then suspends from it the rail along which a trolley or other implement used to convey the object will travel. When the hoist is fully deployed, the trolley rail is mounted high above the bed, permitting tall objects to be manipulated. The hoist is constructed so as to be readily removable from the truck.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to hoisting devices. More particularly, this invention relates to a collapsible and portable hoisting device for lifting heavy loads. More particularly still, this invention relates to such a hoisting device configured to be stowed on a small truck, such as a pickup truck, in such a manner that it is available for ready deployment and use in moving a heavy object either onto or off of the truck. 
   2. Description of Prior Art 
   Hoisting devices are used to lift and convey objects weighing several hundred to several thousand pounds without the need to use power equipment such as forklifts or mobile cranes. Numerous such devices are used in industrial settings, where they are often used to load and unload trucks. Industrial-sized hoists for such purposes are typically very large and usually permanently installed at hoisting stations dedicated to the requirements of a particular type of truck. They do not provide any help for the occasional need to hoist a heavy object, or even, for the need of the many individuals and businesses that deliver and pick up heavy objects repeatedly at locations not equipped with any type of hoisting or lifting mechanism. For example, individuals and businesses with pickup trucks have periodic need to transport such things as bricks, lumber, logs, large stones, trees with root balls, mechanical systems and office supplies. These and other items routinely need to be delivered to various construction sites and other locations, but not to the extent that would justify the expense of installing a permanent hoisting mechanism at any one of these sites. Thus, and especially for the intermediately heavy loads—those that are very heavy but still capable of being lifted by one or two workers, such as a packet of roofing tiles or bricks for a fireplace the burden of loading and off-loading frequently falls on the arms and backs of the workers. Lifting and conveying of heavy objects by hand is considered to be the single largest source of on-the-job injury in occupations involving manual labor. 
   Ideally, a hoisting device for handling loads up to one to two thousand pounds would be installed on all the trucks that might be engaged in the type of pickup and delivery described above. Such a device must be capable of being stowed when not in use and readily erectable when needed. Furthermore, it is desirable that the device be such that it can be assembled, operated and disassembled by a single person within a reasonable time interval, say, less than an hour. 
   Several attempts have been made to provide a portable hoist for use with a pickup truck. For example, Johnson (U.S. Pat. No. 5,862,926) discloses a pickup-truck-loading hoist that can be disassembled for stowing when not needed. When deployed, it consists of a front frame and a rear frame that support a trolley rail running between the frames and extending out behind the rear frame, that is, out beyond the end of a truck bed. Unfortunately, the Johnson hoist disassembles into a large number of individual pieces for which there is no systematic mechanism for securely storing them in or on the truck. This means that the loose pieces must either be carried in the bed of the truck, or removed from the truck, pending the next need for the hoist. There are obvious disadvantages with each option. Moreover, there are other disadvantages with the Johnson hoist. When the pickup&#39;s bed is fully loaded, it appears to be difficult to disassemble and store the hoist. Also, deployment of the hoist requires that the pickup&#39;s tailgate be removed, the rear frame of the Johnson hoist needing to rest on the trailer hitch. Finally, the nature of the rear frame of the Johnson hoist serves as a serious bottleneck in the degree to which it restricts the size of a load that can be handled by the hoist and transported by the truck, because of the relatively small clearance that it permits between the carrying member and the bed of the truck on which it is installed. In addition, when deployed, the section of the rail extending beyond the back of the truck is not directly supported; it is cantilevered. Thus, the load that a rail of given bearing strength can support is less that it would be if it were supported closer to its end point. For lifting heavier loads, a heavier rail and/or additional frames and braces are required. The use of additional frames or braces, however, results in greater effort to assemble/disassemble the hoist. Or a heavier rail may be safely installed only by the efforts of two or more people, which is a disadvantage. 
   Sunderland (U.S. Pat. No. 4,930,970) also discloses a portable hoist for use with a pickup truck. The hoist of Sunderland consists principally of a vertical front post and a vertical rear frame that, when the hoist is assembled, support a trolley rail that extends rearward from the back of the truck bed. For disassembly, the post, frame and rail can be collapsed into the truck bed. This presents the same disadvantage as Johnson in that storing the hoist in the truck bed reduces the primary advantage of having a vehicle with a truck bed in the first place-valuable cargo space in the bed is occupied by the hoist. 
   The Sunderland hoist has other disadvantages. For example, if a load takes up the width of the bed, the hoist cannot rotate down into the bed for travel. In addition, when deployed, the section of the rail extending beyond the back of the truck is not directly supported. Thus, the load that a rail of given bearing strength can support is less than it would be if supported closer to its end point. For lifting heavier loads, a heavier rail and/or additional frames and braces are required. The use of additional frames or braces, however, results in greater effort to assemble/disassemble the hoist. Or a heavier rail may be safely installed only by the efforts of two or more people, which is a disadvantage. Lastly, the outrigger support system disclosed by Sunderland requires that the truck on which the system is to be installed undergo substantial modification. Use of the outriggers is desirable when loading/unloading heavy loads, to relieve stress on the truck&#39;s suspension system, but adding them in the Sunderland system is an added inconvenience. 
   What is needed, therefore, is a collapsible hoist mountable on a truck and easily deployed, operated and stowed by a single person. What is further needed is such a hoist that is capable of lifting an object that is initially several feet beyond the end of the truck and depositing it in the truck&#39;s cargo bed, where the object is equal in weight to the load-bearing capacity of the truck. What is yet further needed is such a hoist that occupies minimal space on the cargo bed when the hoist is deployed and minimal space when it is stowed. Finally, what is needed is such a hoist that is easily mounted on and detached from its host truck without the need to modify the truck&#39;s frame. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a hoist that is mountable on a small truck and is easily deployed, operated, and stowed by a single person. It is a further object to provide such a hoist that is capable of lifting a load having a weight up to the load-bearing capacity of the host truck, and of lifting and transporting such a load onto the truck cargo bed from a point several feet beyond the end of the truck and, when the host truck is a pickup truck, several feet beyond the lowered tailgate of the pickup truck. It is a further object to provide such a hoist that occupies a very small amount of bed space when collapsed and stowed in a pickup truck. Finally, it is an object to provide such a hoist that is easily mounted on and detached from a truck without the truck having to be substantially modified. 
   The basic idea of the invention is a two-yoke trolley rail support frame wherein the two yokes, a front yoke and a rear yoke, are initially stored together atop a truck&#39;s sidewalls, then rotated up from a reinforced bearing assembly, alternately referred to as the mounting frame. (In the Preferred Embodiment the bearing assembly is located near the rear of the sidewalls.) This bearing assembly is reinforced because the sidewalls of a pickup truck are not, by themselves, capable of supporting a hoist or the loads that would be handled by that hoist. While the Preferred Embodiment makes use of the following two methods of reinforcing the bearing assemblies, it is to be understood that other methods may be used as well to ensure that the weight of the load and support frame are not borne by the sidewalk and end wall, but rather are placed on an entity that can support it, thus shifting the burden away from the weak sidewalls and end wall. Method  1  makes use of a sidewall brace that attaches to the side of the bearing assembly nearest the truck&#39;s longitudinal centerline. The top of this sidewall brace attaches to the bearing assembly by bolting or other suitable means. The bottom of this sidewall brace bears on the cargo bed of the truck and may be bolted to the cargo bed or attached by some other means to the cargo bed. Optionally, the bottom of these sidewall braces maybe attached, with specialized fittings, to the truck&#39;s frame below that cargo bed. Method  2  of reinforcing the bearing assembly utilizes downriggers that attach to each side of the bearing assembly outboard of the cargo bed and pivot down to bear on the ground when necessary and pivot up to a stowed position when necessary. It should be understood that the front yoke may be substituted by a post, a bipod, a tripod or any other suitable means to support the forward end of the trolley rail. 
   Summarizing, the collapsible hoist of the present invention includes (1) a mounting frame that is designed to be placed atop the cargo walls which line three sides of the cargo bed, (2) a support frame designed to be pivotally affixed to the mounting frame. (3) a trolley rail (“rail”) that depends from the support frame when the hoist system is fully deployed, and (4) various ancillary components to permit the first three elements to link together and to be effectuated. The rail provides a support and guide for the load-lifting and conveying mechanism, the rail&#39;s length determining the distance over which the load can be conveyed. For most embodiments of the invention, the rail consists of two I-beam segments, which, when deployed, are coupled together to make a track equal in length to the sum of their two individual lengths. In this manner, a maximum travel distance for the object being moved can be achieved while ensuring that the hoist can be stowed without extending beyond the back or out the sides of the truck. The mounting frame is secured atop the truck&#39;s sidewalls, in most embodiments, by additional coupling to the truck&#39;s longitudinal rails, as described below. It also includes outrigger-type support members for transferring some of the load&#39;s weight to the ground during loading and off-loading operations. In most embodiments these outriggers extend largely downward when in use, rather than angling away from the truck, and hence are “downriggers”. The support frame includes, in major part, yokes from which the rail is suspended when the hoist is fully deployed. Each of the yokes has a crossbar that will extend horizontally across the width of the truck bed when mounted on the truck, regardless of whether they are deployed. Each yoke crossbar extends between, and links together, two yoke legs. The leg ends opposite the crossbar are coupled pivotally to the mounting frame, generally to a reinforced yoke-bearing assembly constituting part of the mounting frame and located near the rear of the truck. Some embodiments could use yokes with telescoping, or otherwise extensible, legs to gain additional vertical clearance or lateral reach for certain needs. 
   The manner in which the support frame is attached to the mounting frame permits especially rapid deployment (and stowing) of the hoist. This means that it can be quickly swung about the pivot point(s) (bearings) into its operating configuration and then, after being used to move a heavy object, swung back down into its stowed position. Overall, the time required to set up the hoist and make it ready to lift a one-ton object, has been measured to be approximately 20 minutes, starting with the hoist in a completely stowed configuration. 
   Another feature of the invention going to meet the objectives stated above is the option of using a rail made up of two segments, each of which is equal in length to the length of the truck&#39;s bed. This permits a maximal travel of the load being conveyed by the hoist and yet permits the hoist to be stowed completely on board the host truck with no elements extending beyond the cargo bed. This is not to rule out embodiments that use a single unitary beam as the trolley rail or, for that matter, collapsible rails made of more than two segments. 
   Another important element of the present invention is its dual approach to maximizing the vertical clearance available between the trolley rail and the bed of the truck. Two elements contribute to this great clearance. First, the mounting frame (which is really the base of the hoist system) is designed to be placed atop the sidewalls of the truck&#39;s cargo compartment. That, by itself, provides one to two feet additional clearance over that provided by most, if not all, of the prior-art hoists associated with pickup trucks. The additional clearance provided by basing the hoist atop the cargo walls more than justifies the additional support thereby necessitated for the cargo walls. 
   To provide yet further clearance consistent with a support frame limited in size by the requirement that it be completely stowable within the confines of the host truck, the support frame is shaped so that the trolley rail can be placed nearly as high as the support frame itself, even though it is to be suspended from the support frame. This is done by cutting away much of the rail at that point where it couples to the support frame. Again, the supplemental strengthening of the rail in that region necessitated by this approach is more than justified in most applications by the increased clearance thereby provided. Truly tall, as well as heavy, objects can thus be hoisted and conveyed onto the pickup truck with the present invention. However, it should be borne in mind that for some applications of the present invention, it may be possible or even desirable to use an embodiment of the invention that does not entail cutting a notch in the rail. 
   In the Preferred Embodiment hoist, the supplemental support for the cargo walls includes coupling of the hoist mounting frame to the longitudinal frame rails of the truck, without, however, the need to make any holes in the truck&#39;s frame or to weld anything to that frame. Other embodiments may simply add a weight-distributing plate to the bottom of the sidewall-support braces, where the plate is then supported by the truck&#39;s cargo-bed. Yet other embodiments may make use of holes made in the truck&#39;s frame or may weld to the truck&#39;s frame. 
   When collapsed, the hoist separates into substantially flat elements that are securely stowable atop the host truck&#39;s cargo walls. It is to be emphasized that the collapsed hoist takes up a very small portion of the bed itself when stowed. More particularly, both the front and rear yokes fold down toward the front of the truck, both coming to rest atop that portion of the mounting frame that resides atop the three cargo walls. In the Preferred Embodiment, after the yokes are stowed, each segment of the trolley rail is then secured along the side cargo walls (sidewalls) atop the yoke&#39;s legs. 
   As stated, the support frame (the two yokes) is pivotally attached to the mounting frame generally at a position near the back of the truck when the hoist is mounted on a truck. More particularly, the yokes of the support frame are attached to the mounting frame by means of yoke bearings. For embodiments with two yokes and two yoke bearings, there will be a right yoke bearing atop the right sidewall near its rear end and, directly across from it, a left yoke bearing atop the left sidewall. Both yokes are coupled to the same portion of the mounting frame and share a common pivot axle on each yoke bearing. Thus, the right legs of both yokes attach to the right bearing assembly portion of the mounting frame and the left leg to the left bearing assembly portion of the mounting frame, but in such a way that the two yokes can pivot independently of one another on the common pivot axles. For simplicity, the Summary discussion will from this point out, treat the hoist as having two yokes and two yoke bearing assemblies. Other embodiments may have mounting frames that provide the respective yokes with bearings independent of each other; hence, for example, the front yoke would have right and left bearing assemblies and the rear yoke would have right and left bearing assemblies, for a total of four bearing assemblies in the mounting frame. 
   As a heavy object is being lifted off the ground in order to be conveyed onto the truck, or as an object already on the truck is conveyed rearward as part of the off-loading process, the rear end of the truck will tend to sink down as the truck&#39;s rear suspension takes on more weight. It is essential for efficient operation of the hoist system that this sinking down be minimized. It is also essential to alleviate some of the stress from the truck&#39;s rear suspension so as to not cause harm to that rear suspension. In addition, otherwise, even without the cantilevered rail bending under the weight of the load, the initially horizontal rail becomes a rail that runs “uphill” as one goes from the rear of the truck to the front. Pulling a one-ton load “uphill”, even with the most smoothly operating beam trolley, is not something to be desired by the single operator doing the work. Thus, the downriggers play an important role, as they limit the degree to which the rear end of the truck can be forced down. It is generally a good rule of practice to deploy the downriggers at the start of the loading/unloading process, after having positioned the truck so that its hoist can reach the load. And it is generally a good rule of practice to stow the downriggers just prior to driving the truck away after completing the loading/unloading process. 
   In some embodiments of the invention, the downriggers are pivotally attachable to the top of the rear portion of the sidewalls or to the mounting frame, in such a manner that they can be deployed downward into load-bearing position as needed and otherwise remain folded up out of the way along the outside of the sidewall. In the Preferred Embodiment, the downriggers are pivotally attached to the reinforced yoke bearing assemblies and share their pivot axles with the yokes. In the Preferred Embodiment, they are constructed and placed in such manner that when initially deployed, they do not reach the ground. However, as the rear end of the truck is pressed down during the loading process, the downriggers lower and engage the ground and, from that point, support the balance of the load. Once the object is loaded on the truck, and the truck is ready to be driven away, it is necessary to retract the downriggers, transferring the entire load to the truck&#39;s suspension for the first time. To achieve one of the purposes of the present invention, it is necessary that a single operator be able to quickly retract the downriggers, and, in particular, to avoid the necessity of a separate intermediate step, such as shifting the truck&#39;s weight to a jack so as to be able to release the compression forces on the downrigger so that it can be swung up for stowing. There are a number of ways to achieve this through the design of the downrigger. For example, a lever mechanism may be built in to allow for a gradual retraction(shortening) of the downrigger and hence reduction of the force being supported by it, thereby smoothly and gradually shifting the load to the truck&#39;s suspension. Other embodiments may use other types of outriggers, downriggers or temporary supports. 
   It can be seen that a similar situation prevails when an object is being offloaded from the truck. Initially, the object will be sitting on the bed of the truck and the truck&#39;s suspension will be bearing the entire weight. However, in general, the load may be far enough forward that the weight is somewhat distributed between the front and rear axles, so that the truck&#39;s rear end may not lowered to the point where the truck displays a severe pitch. When the load is lifted by the hoist prior to subsequent conveyance rearward, nothing changes. However, as the load is moved rearward, significant pitch will occur unless the downriggers have been deployed. There is no problem retracting the downriggers when this off-loading is complete, since at the end of the unloading process, the weight will have been deposited on the ground or elsewhere and will no longer be loading down the rear end of the truck. 
   In most embodiments of the hoist, the rail segments are stored on top of everything else on the truck&#39;s sidewalls. When starting to assemble the hoist, one first removes the rail segments and temporarily lays them aside. Next, assuming that the yoke that is stowed directly beneath the rail segments is the rear yoke, that yoke is lifted up by its crossbar and swung around on the pivot axles (bearings) until its legs extend to the rear making an angle with the vertical approximately equal to its operating angle, which, in most embodiments, will be approximately 45 degrees. At that point, the rear yoke is temporarily fixed in place so that it holds that angle. This can be done by any of a variety of means, including—as an example and not as a means of suggesting a limit of the possibilities—the provision of yoke anchor detents that mate with complementary features in the yoke&#39;s legs. As another, simpler, example, one can simply attach a cord of a strategic length to the rear yoke. It is to be emphasized that the techniques proposed for deploying and stowing the hoist are guided by the invention&#39;s requirement that these actions must be reasonably performable by a single individual, working alone. In any event, once the rear yoke is temporarily fixed in place, the front yoke may be rotated up by lifting its crossbar, which, like that of the rear yoke, is stowed atop the front wall of the cargo area. When the front yoke has been rotated to the point where it is oriented at about 45 degrees from the vertical toward the front of the truck, it is linked to the rear yoke in such a way that the maximum angle that can exist between the front and rear yokes is fixed; this angle will be approximately 90 degrees. In the Preferred Embodiment, a cord of strategic length, between the mounting frame and the front yoke legs, holds the front yoke at its deployed position of approximately 45 degrees forward of vertical. And another cord of strategic length, between the front yoke legs and the rear yoke legs, holds the rear yoke at its deployed position of approximately 45 degrees rearward of vertical. When this is the case, the act of lifting the rear yoke will eventually serve to lift the front yoke as well because once the rear yoke is approximately vertical, the yoke linking mechanism will pull the front yoke along. When both yokes are pulled up to their deployed position, their respective crossbars will be at heights such that, when the trolley rail is attached to the yokes, the trolley rail will be approximately horizontal. 
   Before installing the trolley rail, and with the yokes still temporarily in place, a front yoke brace, initially stored on the front wall, or some other location, is connected between a centered front wall brace and the front yoke&#39;s crossbar. This front yoke brace serves to keep the front yoke at the proper orientation regardless of whether the temporary link between the front yoke and rear yoke is taut. Further, it provides support to the front yoke and hence, for the forward end of the trolley rail, for those occasions in which the load suspended from the trolley rail is located at a position far forward in the bed and is thus largely supported by the front yoke. 
   Once the front and rear yokes are rotated into position and the front yoke brace is fastened, the trolley rail is prepared to be suspended from the yokes. In most embodiments, this involves first joining the two trolley rail segments together. Since the device conveying the load laterally, which in the Preferred Embodiment is a standard beam trolley, is to run along the entire trolley rail, it is essential that the means used to join the two segments not provide any impediment at all to the passage of that conveying device. The bolting flange that is affixed to each segment to facilitate joinder must be designed with that in mind. Once assembled, the trolley rail is ready to be lifted to its deployed position. 
   The point on the trolley rail where the rear attachment takes place can be designed to be near the rear extremity of the trolley rail, or at a location further forward on the trolley rail, leaving the distal end of the trolley rail cantilevered rearward from the crossbar of the rear yoke. Of course, the further out distally that the trolley rail can be supported, the less strain is introduced in the end of the trolley rail for a given trolley rail strength and given load. This allows the hoist to lift heavier loads for a given trolley rail, or conversely permits a lighter trolley rail to be used with a given load. Providing support for the trolley rail this far out toward the end of the trolley rail also permits heavy loads to be lifter several feet further out from the end of the host truck, thus eliminating the need to remove the tailgate to facilitate loading. Conversely, for given materials and dimension constraints, the further rearward the trolley rail can be extended, the farther from the truck that a load can be manipulated. 
   Within the scope of the invention, there is a wide range of embodiments where the particular choice being selected shall be based on need and the interconnection between travel length, vertical clearance and trolley rail strain. For example, vertical clearance is increased by configuring the hoist so that the yokes are closer to vertical during operation. Typical of the trade-offs involved in improving a particular operating feature, however, is that additional clearance is obtained at the cost of reducing the load-conveying distance. On the other hand, if a greater degree of cantilever can be tolerated, the trolley rail can be left the same length as was used with the 45 degree yoke-deployment angle. This will be limited by the degree of trolley rail strain under load that can be tolerated. To a certain extent, greater cantilever stress can be compensated for by using a heavier gauge of metal for the trolley rail, but at the cost of heavier assemblage, and so on. 
   The trolley rail is designed to receive a slidable or rollable support, such as a beam trolley or internal slide, that can be easily moved along the trolley rail while supporting a heavy object. The most straightforward approach, given that the trolley rail will generally be an I-beam, is to mount a beam trolley so that its wheels can roll along the trolley rail&#39;s lower flange. It is a good practice with this approach to provide a stop at each end of the trolley rail so as to restrain the trolley from running off the end of the trolley rail. Also, when this trolley rail is made up of two or more separate I-beam segments, the bolting flanges by which the segments are joined need to be tapered in such a way that the vicinity of the lower flange near the point of joinder has nothing in it to impede the trolley wheels. 
   The most physically demanding part of assembling the hoist would normally be the act of the lone operator needing to lift the trolley rail up into position at the underside of the two yoke crossbars. The trolley rail, when assembled, weighs approximately 100 lbs when made of steel. Adding to the operator&#39;s burden is the necessity to install fasteners through the trolley rail to join it to the two yokes. Although it could be lifted by the operator&#39;s muscles alone, the difficulty of these two acts (lifting the trolley rail and installing the fasteners) argues strongly for a mechanical lifting aid. To accomplish this, the Preferred Embodiment makes use of a plate bracket which is attached to the top of the rear yoke crossbar. This plate bracket performs three functions. Two of these functions will be explained later, but first, it is used as a temporary lifting point to mechanically hoist the trolley rail up into position so that it can be firmly attached to the rear yoke crossbar. (Though the plate bracket is used as a temporary lifting point, it remains in place throughout the loading/unloading process due to its need to perform its other functions.) The plate bracket is generally triangular in shape and near its upper corner is a hole to which a pair of mating lifting eyes is temporarily installed so that there is an eye on the right side of the plate bracket and there is an eye on the left side of the bracket. The two hooks of a ratchet cable puller hoist are attached to these eyes with the cable of the ratchet cable puller hoist looped under the assembled trolley rail which is lying loosely on the truck bed parallel with the long axis of the truck. Now the ratchet cable puller hoist is operated to lift the rear end of the trolley rail up off the truck bed so that the rear of the trolley rail is approximately half the distance between the truck bed and the rear yoke crossbar. Now, the operator manually lifts the front end of the trolley rail up and holds it in alignment with its mating hole at the front yoke crossbar and he then installs a bolt or some other suitable fastener. Manual lifting of the front end of the trolley rail is made relatively easy because the ratchet cable puller hoist is supporting most of the weight of the trolley rail during this process. Now, the operator, remaining on the truck bed (or standing on a short step ladder placed near the lowered tailgate) resumes operating the ratchet cable puller hoist until the notch in the trolley rail engages the rear yoke crossbar and the bolt holes in the trolley rail align with the bolt holes in the plate bracket; then bolts are installed and tightened. This not only serves to support the rear of the trolley rail, but it also uses the plate bracket to reinforce the trolley rail to compensate for the fact that a large notch has been cut out of the trolley rail. This is the second of the three functions of the plate bracket mentioned earlier. Now the operator removes the ratchet cable puller hoist and temporary mating eyes and sets them aside. Now, in the Preferred Embodiment, two support struts are connected to the top bolt hole (which was previously used for the mating eyes) in the plate bracket with one strut positioned forward of the plate bracket to bolt to a flange near the bolting flanges of the trolley rail and the other strut is positioned rearward of the plate bracket to bolt to a flange toward the rear end of the trolley rail. This rearward strut serves to reduce cantilever stresses on the trolley rail; hence it allows the use of a lighter gauge trolley rail than would otherwise be necessitated and would be necessitated in the prior art. So it can be seen that the third function of the plate bracket is to provide support for these two support struts. 
   The present invention contemplates various hoist sizes and strengths, so as to provide portable hoisting capacity corresponding to the truck style and its gross weight rating. For example, the hoist of the invention is adaptable for use with flatbed utility trucks. For mounting on a flatbed truck, the mounting frame, the support frame and other components would be fastenable to the edge of the bed. The length and height of the assembled trolley rail would also be adjusted to take maximum advantage of the constraints provided by the truck, recognizing that the lengths of the segments to be assembled into the trolley rail may be limited by the length of the truck bed. Within these constraints, however, it is possible to choose a shorter or longer trolley rail length, depending on the uses envisioned for the hoist. For example, for use in lifting lighter, harder-to-reach loads, it may be desirable to adjust the deployed yoke angle so that the deployed trolley rail is relatively close to the bed, but is longer and thus extends farther out beyond the back of the bed. Conversely, it may be desirable to have a higher, shorter rail for handling tall objects that lend themselves to positioning just beyond the end of the truck. 
   In most applications, the hoist of the present invention will be removably attached to the truck by bolts, clamps, straps and/or other easily removable fasteners. Because the hoist, although designed to have minimal weight, does weigh several hundred pounds, this capacity to easily remove much of the hoist system from the truck during periods of non-use is an advantage of the present invention. 
   Other objects and advantages of the present invention will be made apparent by the following description of the drawings and the detailed description of the Preferred Embodiment of the invention. While a Preferred Embodiment is disclosed, this is not intended to be limiting, rather, the general principles set forth herein are considered to be merely illustrative of the scope of the present invention and it is to be further understood that numerous changes may be made without straying from the scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of the Preferred Embodiment of the hoist according to the invention, assembled, deployed and starting to lift a load situated behind the host truck, a pickup truck. 
       FIG. 2  is a perspective view of the hoist of  FIG. 1 , collapsed and stowed atop the cargo-bed walls of the host truck. 
       FIG. 3  is an exploded perspective view of the components of the Preferred Embodiment of the hoist. 
       FIG. 4  is a rear view of the assembled, deployed hoist shown in  FIG. 1 . 
       FIG. 5A  is a top view of the deployed hoist of  FIG. 1 . 
       FIG. 5B  is a perspective view of one of the yoke bearing assemblies of the Preferred Embodiment. 
       FIG. 5C  is an end-on (orthographic) view of the yoke anchor of  FIG. 5B , viewed from the front. 
       FIG. 6A  is a side view of the assembled trolley rail of the Preferred Embodiment. 
       FIG. 6B  shows an end-on (orthographic) view of the shape of the connecting flange on each trolley trail segment at the end that is to be joined to the other segment in the Preferred Embodiment. 
       FIG. 6C  shows how the beam trolley can roll past the joinder point of the two trolley rail segments. 
       FIG. 7  is a side view of the plate bracket. 
       FIG. 8  is a front view of the plate bracket with the temporary lifting eyes attached. 
       FIG. 9  is a side view of one of the downriggers in its stowed position, including the fixture that secures the downriggers bottom point to a downrigger stowage flange on the mounting frame. 
       FIG. 10  illustrates how the free end of one of the downriggers is removably attached to a downrigger stowage flange while the downrigger is stowed. 
       FIG. 11  is a side view of one of the downriggers with the extension-retractor lever partially lowered so as to cause the retraction of the extension, disengaging the downrigger from the ground. 
       FIG. 12A  is a side view of the attachment of the sidewall brace to the frame rail of the pick-up truck. 
       FIG. 12B  is an end-on view of the sidewall brace attachment shown in  FIG. 12A . 
       FIG. 13  is a side view of the front wall brace as attached to the frame of the pick-up truck. 
       FIG. 14A  is a front view of the rear yoke. 
       FIG. 14B  is a front view of the front yoke. 
       FIG. 14C  is a rear view of the front yoke. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  and  FIG. 2  depict the deployed and stowed configurations, respectively, of the Preferred Embodiment hoist  100  of the invention, mounted on a conventional pick-up truck  20 . The truck  20  on which the hoist  100  is mounted has a bed  8  bordered by sidewalls  26 , a front wall  32 , and a tailgate  70 . The hoist  100  includes a mounting frame  23  and a support frame  40 . The support frame  40  is made up principally of a front yoke  47 , a rear yoke  50  and a front yoke brace  65 . 
     FIG. 1  shows the hoist  100  engaged in starting to lift a load  121 , which will be conveyed using a beam trolley  119  along a trolley rail  68 . The load  121  is being lifted by the chain hoist  9 , which is being supported by the beam trolley  119 , which bears on the lower flange of the trolley rail  68 . Downriggers  146  are shown attached to that part of the mounting frame  23  that is located near the rear of the sidewalls  26 . The downriggers  146  are seen to not quite reach the ground. As more of the load  121  is borne by the trolley rail  68 , the rear end of the truck  20  will be forced lower on its suspension, so that the downriggers  146  contact the ground and take over the support of the load  121 . One purpose of this action of the downriggers  146  is to prevent the truck from settling down into a position that causes the trolley rail  68  to deviate significantly from the horizontal. The goal is to move the load suspended from the rail  68  by hand, or by a mechanical device such as a ratchet cable puller hoist, to a position where it is over the point in the bed  8  that it will occupy during transport. 
   As shown in  FIG. 11 , each of the downriggers  146  incorporates a downrigger extension  152  made up of three pivotally-connected sections and an extension-retractor lever  155 , where the extension  152  retracts within a sleeve  149  when said extension-retractor lever  155  is pulled out so as to form a greater angle with respect to said sleeve  149 . When one of the downriggers  146  is in its fully extended position on an unloaded truck, the extension  152  terminates a few inches above the ground. As the load  121  starts to be lifted by the deployed hoist  100 , the rear end of the truck  20  lowers on its suspension until the extension  152  touches the ground, or touches one or more pads laid on the ground to distribute the load, after which all additional loading is borne by the outriggers  146 . After the load is aboard the truck, the lever  155  associated with each of the downriggers  146  is unfastened from its securing point. The lever  155  connects with a middle piece of extension  152  through a side opening in the sleeve  149 . As lever  155  is lowered, the external portion of the extension  152  gradually moves up (retracts) into the sleeve  149 , thereby slowly transferring the load onto the truck&#39;s suspension, which results in a lowering of the truck as that suspension compresses. Each of the downriggers  146  is then pivoted about its associated bearing assembly  126  and attached to the mounting frame  23  for stowage during travel. 
     FIG. 2  shows the hoist  100  collapsed and stowed atop the sidewalls  26  and the front wall  32 , so that nearly the entire area of the bed  8  is left unencumbered and available for other purposes. 
     FIG. 3  is an exploded view of the hoist  100 , as configured when stowed. The deployed mounting frame  23  is shown  FIG. 4  with its two sidewall braces  35  and front wall brace  38  extending downward approximately vertically. It should be understood that, although just two sidewall braces  35  are shown in the Preferred Embodiment, additional braces may be installed, depending on the bearing requirements of the embodiment. In the Preferred Embodiment, the sidewall braces  35  are positioned toward the rear of the bed  8 . As shown in  FIG. 3 ,  FIG. 4 , and partially in  FIG. 2 , affixed at a position adjacent to each of the sidewall braces  35  is a yoke reinforced bearing assembly  126 , shown in detail in  FIG. 5B  and  FIG. 5C . The yoke reinforced bearing assembly  126  and its mate on the apposite side of the bed  8  serve as the mounting frame attachment points for the front yoke  47 , the rear yoke  50  and the downriggers  146 . The yoke reinforced bearing assembly  126  includes a pivot axle  162 , shown in  FIG. 5C , about which the downriggers  146  pivot downward while being deployed and upward while being stowed, and about which the rear yoke  50  and the front yoke  47  separately pivot upward while being deployed and downward when being stowed. 
   The mounting frame  23  is directly affixed to the sidewalls  26  and front wall  32 , as partially seen in  FIG. 1 , with bolts being used for this purpose in the Preferred Embodiment. As shown in  FIG. 5B , each of the sidewall braces  35  is rigidly bolted at its upper end to the bearing assembly  126 . The bearing assembly  126  is welded to the mounting frame  23  thereby forming a welded seam  24 . The mounting frame  23  in the Preferred Embodiment is made of angle iron. As shown in  FIG. 12A  and  FIG. 12B , each of the sidewall braces  35  is welded on its lower end to a base plate  36  so that the base plate  36  is an integral part of the sidewall brace  35 . Each base plate  36  is connected with bolts through the truck bed  8  and, in the Preferred Embodiment, through a piece of angle iron bed reinforcement  45  that bears up against the bottom of truck bed  8 . This angle iron bed reinforcement  45  is a single piece that runs transversely under the truck bed in such a manner that each end of it is situated directly beneath a sidewall brace  35 . The angle iron bed reinforcement  45  is in turn supported by means of a threaded rod  160  that connects to pre-existing holes in the truck&#39;s longitudinal frame rails  44 . Similarly, as shown in  FIG. 13 , the front wall brace  38  abuts the front wall  32 , where it is bolted to the mounting frame  23  and its base rests on the truck bed  8 . A threaded rod  161  connects the front wall brace  38  to the truck&#39;s frame below by means of a transverse frame rail bracket  350  coupled to a transverse frame rail  351 . 
   By looking at  FIG. 1 , it can readily be seen that lifting a one ton load  121  would cause extreme moment forces about the yoke bearings  126  which would result in approximately a one ton upward force at the yoke brace  65 . By linking the forward wall brace  38  to the truck&#39;s frame below, the hoist system is able to tolerate those moment forces. 
   With reference again to  FIG. 1 , it can be seen that the support frame  40  is made up of three components, a front yoke  47 , a rear yoke  50 , and a front yoke brace  65 . From  FIG. 1 ,  FIG. 3  and  FIG. 6A , it can be seen that the trolley rail  68  includes a front rail segment  104  and a rear rail segment  107 , and, when the hoist  100  is completely deployed, it is coupled to a plate bracket  77 , a front support strut  131  and a rear support strut  134 . In the Preferred Embodiment, the rear rail segment  107  has a deep triangular section removed from it at the point where it is connected to the rear crossbar  71 . This enables the trolley rail  68  to be positioned even higher than it would be otherwise, consistent with the goal to maximize the vertical clearance while remaining within the constraints imposed on the hoist. These constraints include in particular the fact that in the Preferred Embodiment, the height of the support frame  40  is limited by the length of the bed  8  of the host truck  20 . Other embodiments could use yokes with telescoping legs or otherwise extensible legs to increase vertical clearance or lateral conveyance distances. Because the greater vertical clearance is obtained in the Preferred Embodiment at the cost of weakening the rear rail segment  107  by the cut-out, additional strengthening is provided to the trolley rail by the front support strut  131  and the rear support strut  134 . Additional strengthening is also provided by the way in which the plate bracket  77  is used in coupling rail segment  107  to the rear crossbar  71 . 
   The operator begins to deploy the hoist  100  by detaching the downriggers  146  from their stowed position alongside the mounting frame  23 . The downriggers  146  are allowed to pivot at the bearing assemblies  126 , downward so that their lower end is now several inches off the ground; usually it is a good practice to place plywood or metal pads below them to distribute the weight over soft ground. With the downriggers  146  now deployed, the operator removes and temporarily sets aside the front rail segment  104  and the rear rail segment  107 , both of which are stowed atop the rear yoke  50  which is supported by the mounting frame  23  which in turn is supported by the sidewalls  26  reinforced by the sidewall braces  35  and the front wall  32  reinforced by the front wall brace  38 . Next, the rear yoke  50 , the next element down, is rotated by lifting the rear yoke crossbar  71  upward until the rear yoke  50  extends to the rear of the truck  20  at an angle of approximately 45 degrees beyond vertical. In the Preferred Embodiment, the hoist is stowed with an inter-yoke cord  129  (shown in  FIG. 1 , but not in  FIG. 3 ) of a specific length, connecting the rear yoke  50  to the front yoke  47 , such that as the rear yoke  50  is pulled into position as stated, the front yoke  47  is pulled along into its proper support position, which leaves it approximately 45 degrees toward the front of the truck  20 . In other words, the inter-yoke cord  129  is chosen and placed so that when the front yoke  47  and the rearyoke  50  are maximally separated, the angle between them will be approximately 90 degrees. Similarly, there isa front yoke cord  130  (shown in  FIG. 1 ) which limits the travel of the front yoke  47 . Hence the two yokes  47  and  50  are temporarily held in their approximate deployed position freeing the operator to install the remaining components necessary to deploy the hoist. The next component to be installed is the yoke brace  65  ( FIG. 4  and  FIG. 5A ) which links the front yoke crossbar  56  to the front wall brace  38 . In the Preferred Embodiment, the yoke brace  65  is bolted at both connection points. 
     FIG. 7  shows details of the plate bracket  77  that can be seen in context in  FIG. 1 .  FIG. 1  shows the plate bracket  77  affixed at the point where the deployed rear rail segment  107  is connected to the rear yoke  50 . The plate bracket  77 , plays an important role in augmenting the strength of the trolley rail  68  at the point where the rear rail segment  107  has a cut-out  122  ( FIG. 6A ). The plate bracket  77  has a generally triangular top section  80  and a notched bottom section  83 . It also has three rail bolt holes  86 , two in the top section  80  and one in the bottom section  83 . In addition, the top section  80  has a top bolt hole  89  which is used for two different purposes at different times. Top bolt hole  89  is first used to install the temporary lifting eyes  128 . Then, when the temporary lifting eyes  128  are no longer needed, they will be removed and the top bolt hole  89  will be used for attaching the front support strut  131  and the rear support strut  134 . The bottom section  83  is partially triangular in shape with plate bracket notch  123  cut out of one side. This plate bracket notch  123  is shaped to mate with the rear yoke crossbar  71  As shown in  FIG. 14A , the rear yoke crossbar  71  is made of channel iron in the Preferred Embodiment, though it could be made of a number of alternative cross-sections. The plate bracket notch  123  in the bottom section  83  of plate bracket  77  is shaped so that the rear yoke crossbar  71  fits snugly into it and is held in place by a stud  74  on the rear crossbar  71 , as shown in  FIG. 14A , that mates with notch bolt hole  78  in the plate bracket  77 . 
     FIG. 6A ,  FIG. 6B , and  FIG. 6C  depict how a front rail segment  104  bolts together with a rear rail segment  107 , to form the trolley rail  68 . Both the rail segments are I-beams, consisting of top and bottom flanges separated by a web  114 . Both rail segments terminate at one end in a segment-connecting bolting flange  113 , at the end that is to be joined to the other segment. The segment-connecting bolting flange  113  extends at a constant width, from a point several inches above the top flange down to approximately the midpoint of the web  114  and tapers in width so that by the time it has reached the bottom flange of the rail segment, it is no wider than the web  114  is thick. Absence of the segment-connecting bolting flange  113  along the bottom of the interface between rear rail segment  107  and front rail segment  104  allows a beam trolley  119  to roll along trolley rail  68  without interference at that interface. In the Preferred Embodiment, the trolley rail segments are steel I-beams with a ten-inch web, two-and-three-quarter-inch flanges and eighth-inch thick steel. The bolting flange  113  is made of one-half inch by four inch flat bar. 
   The assembled trolley rail  68  can now be laid loosely in the bed  8  of truck  20  parallel to the truck&#39;s longitudinal centerline, or if there is cargo on the bed that needs to be unloaded, the trolley rail  68  can be laid atop the cargo if possible or it can be laid along side the cargo if necessary. Now the temporary lifting eyes  128  are installed in the plate bracket  77  using the top bolt hole  89 , as shown in  FIG. 7  and  FIG. 8 . Now the two hooks of a ratchet cable puller hoist are attached to the two temporary lifting eyes  128  with the cable of the ratchet cable puller hoist looped under the assembled trolley rail  68  approximately near the cut-out section  122  of the rear rail segment  107 . Now the ratchet cable puller hoist is operated to lift the rear end of the trolley rail  68  up off the truck bed (or cargo) so that the rear of the trolley rail  68  is approximately half the distance between the truck bed  8  and the rear yoke crossbar  71 . Now the operator moves to the front end of trolley rail  68  and manually lifts the front end of the trolley rail  68  up and holds the rail front bolt hole  110  in alignment with the front yoke crossbar clevis  59  ( FIG. 14C ) and then a bolt is installed. The trolley rail  68  will now pivot on this bolt as the ratchet cable puller hoist is operated again to raise the rear end of the trolley rail  68  up to where the cut-out section  122  of the rear rail segment  107  mates with the rear yoke crossbar  71  and the plate bracket  77 . With the plate bracket bolt holes  86  ( FIG. 7 ) aligned with trolley rail bolt holes  125  ( FIG. 6A ) one bolt is now installed to temporarily hold the trolley rail  68  in its deployed position. Now the ratchet cable puller hoist can be removed and set aside and the temporary lifting eyes  128  are removed and set aside. Now the remaining two bolts are installed in bolt holes  125  ( FIG.6A ) and the front support strut  131  and rear support strut  134  are installed. Both support struts share the top bolt hole  89  on the plate bracket  77  ( FIG. 7 ) as their upper attachment point and their lower attachment points are the two strut flanges  135  ( FIG. 6A .) The purpose of front support strut  131  and rear support strut  134  is to strengthen the rear rail segment  107  against bending under the stress of the load. This completes the assembly of the support frame  40 . This is the Preferred Embodiment of the deployment method for the Preferred Embodiment hoist. 
   As shown in  FIG. 6C , the beam trolley  119  is now slid onto the lower flange of the trolley rail  68  and a rear stop  109  is bolted to the rear end of the of the trolley rail  68  to prevent the beam trolley  119  from inadvertently rolling off the lower flange of trolley rail  68 . The beam trolley  119  is prevented from rolling off the forward end of trolley rail  68  by the front stop  108  ( FIG. 6A ), which is permanently attached to trolley rail  68 . 
   A chain hoist  9  or other lifting mechanism is now hung from beam trolley  119  and its lower hook attached to load  121 ; then it is operated to lift the load off the ground to a height so that the bottom of the load will clear the truck bed  8 . As the load is lifted off the ground the truck&#39;s  20  suspension will compress or lower until the deployed downriggers  146  contact the ground (or a pad on the ground). This will likely cause the truck  20  and trolley rail  68  to tilt slightly so that now the suspended load  121  will need to pulled up a slight incline in order to be positioned over truck bed  8 . 
   For particularly heavy loads, the Preferred Embodiment method calls for a ratchet cable puller hoist to be attached at one end to either the load  121  or to the beam trolley  119  and at the other end to the front frame brace  65  or any other suitable attachment point. The load  121  is then pulled into the cargo area using the mechanical advantage of the ratchet cable puller hoist and lowered by means of the chain hoist  9  to the bed  8  at a desired location. 
   With the load  121  now resting the cargo bed  8 , the operator now needs to make a decision. He needs to give consideration to the following issues. First, the weight of the deployed hoist  100  puts more strain on the truck&#39;s  20  rear suspension than a disassembled and stowed hoist  100 . Therefore, if the weight of load  121  is at or near the weight bearing capacity of truck  20 , it is recommended that hoist  100  be disassembled and stowed before retracting downriggers  146 . But if the weight of hoist  100  plus the weight of load  121  are considerably less than the recommended weight capacity of truck  20 , then the operator may choose to retract and stow downriggers  146  while leaving hoist  100  in the assembled/deployed configuration. He must not do this, however, if there is a chance that the assembled/deployed hoist  100  may be a hazard to safe operation of truck  20 . If safe operation of truck  20  is in question, hoist  100  must be disassembled and stowed prior to moving truck  20 . 
   For off-loading a heavy object, a ratchet cable puller is anchored to a dedicated eye  158  that is an integral part of rear stop  109  ( FIG. 6A ), and is used to pull a suspended load rearward to facilitate offloading. 
   It should be understood that the Preferred Embodiment set out here is merely illustrative of the present invention. Numerous variations in design and use of the present invention will be obvious to one skilled in the art, in view of the following claims, without straying from the scope and field of the invention as disclosed herein above.