FOLDING SUPPORT ARM FOR A LIFTING DOOR ASSEMBLY DESCRIPTION OF THE INVENTION This invention pertains to the technique of methods and apparatus with respect to drawbridges and more specifically to methods and apparatus with respect to folding a drawbridge platform in and out of a storage condition. It is well known in the art to attach drawbridges to vehicle trailers or other forms of vehicle loading supports to assist with loading and unloading vehicles. In general, drawbridges include a platform or deck and some motorized system, often including a hydraulic system, used to move the platform. To load the cargo from a floor surface to the base of the vehicle, the platform is placed in a lowered position where it is generally parallel with the floor surface. The cargo can then be easily placed on the platform. The platform then rises to a raised position, generally parallel with the base of the vehicle. The loading can then easily be loaded into the vehicle. To unload the vehicle's cargo, the inverse stages are adopted. Various types and styles of drawbridges are known in the art. Some of the drawbridges,
sometimes referred to, drawbridges that turn in one direction or are folded, fold or collapse in a stowed or stored condition. Frequently this storage condition is placed below the vehicle's cargo support. When it is desirable to use the drawbridge, it can be deployed outside the storage condition. U.S. Patent No. 3,369,679 to Robinson, which is incorporated herein by reference, is entitled "ESTIBABLE ELEVATOR APPARATUS" and describes a known example of a collapsible drawbridge. Robinson provides: a lifting device that includes: (1) a mounting frame for use to install the lifting device under the base of a truck; (2) a parallel arm joint supported on the mounting frame; (3) a cover or platform carried by the arm joint; (4) an actuator operating between the mounting frame and the parallel arm joint for use in raising the joint and cover; and (5) an articulation spring acting between the sections of the joint to assist in the folding and unfolding of the cover. The Robinson lifting device works well for its intended purpose. It has the disadvantage, however, of exposing the articulation spring to damage and corrosion. The use of an articulation spring is also known
exposed similar to that used by Robinson but where the articulation spring has almost unlimited spring adjustment possibilities, within the given limits. Although this design has the advantage of a wide range of spring adjustment, it also provides the possibility of error of adjustment. The present invention provides methods and apparatus for better protecting the articulation spring from exposure. Methods and apparatus are also provided with respect to a new simple articulation spring adjustment. This invention, in this way, overcomes the above and other difficulties while providing better and more advantageous complete results. According to one embodiment of this invention, a drawbridge assembly can include: a frame member; a mounting assembly for use to mount the drawbridge assembly in a vehicle; a platform assembly that includes a platform; and, an elevator assembly for use to move the platform between a folded position, a lowered position, and an elevated position. The lift assembly may have a hinge assembly that includes: (a) at least a first lift arm having a first end operatively connected to the frame member and a second end operatively connected to the platform; and, (b) at least one
first support arm having a first end operatively connected to the frame member and a second end operatively connected to the platform. The support arm may include: (1) a first member; (2) a second member having a channel that receives at least a portion of the first member for relative sliding movement; and (3) a tension spring operatively connected to the first and second members to provide a deflection force to assist in the folding of the platform. The tension spring may be located at least partially within the channel. According to another embodiment of this invention, a method can include the steps of: Providing an elevator assembly that includes: a frame member; a mounting assembly for use to mount the lifting assembly in a vehicle; a platform assembly that includes a platform; and, an elevator assembly for use to move the platform between a folded position, a lowered position and a raised position. The lift assembly can have a hinge assembly that includes: (a) at least a first lift arm having a first end operatively connected to the first frame member and a second end operatively connected to the platform; and (b) at least a first support arm comprising: a first member; a
second member who has a channel; and a tension spring; joining a first end of the tension spring to the first member; sliding the first member and the tension spring within the channel in a first direction; joining a second end of the tension spring to the second member; sliding the second member within the channel in a second direction; attaching a sliding limiter to the first support arm to limit the sliding movement of the first member with respect to the second member; and joining a first end of the first support arm to the frame member and a second end to the platform. An advantage of this invention is that the articulation spring is protected from damaging the forces and exposing the corrosive elements. Another advantage of this invention is that the articulation spring can be easily adjusted to eliminate the adjustment error of the user. This will greatly increase the probability that the spring force conforms to the proper specification as established by the manufacturer. Still other benefits and advantages of the invention will become apparent to those skilled in the art to which a reading and understanding of the
following detailed specification. BRIEF DESCRIPTION OF THE DRAWINGS The invention can take physical forms in certain parts and arrangement of parts, modalities of which will be described in detail in this specification and are illustrated in the accompanying drawings that form a part thereof and in which: FIGURE 1 is a perspective side view of an elevator shown in the folded position. FIGURE 2 is a perspective side view of a portion of a vehicle that can receive an elevator according to this invention. FIGURE 3 is a perspective side view of an elevator shown in FIGURE 1, but shown in the lowered position. Figure 4 is a perspective view of the elevator shown in FIGURE 1, shown in high condition. FIGURE 5 is a side perspective view similar to that shown in FIGURE 4 although from a different angle. FIGURE 6 is a view of the side perspective assembly of a support arm according to an embodiment of this invention. With reference now to the drawings where the
Projections are for purposes of illustrating the embodiments of the invention only and not for purposes of limiting the same, FIGURE 1 shows an elevator assembly 100 that includes an articulation assembly 200 according to this invention. While the elevator assembly 100 shown is of the style known as one-way turning or folding, it is noted that this invention can be used with any style of drawbridge, type and size, when applied with reliable engineering judgment. The lift assembly 100 can be mounted to a vehicle 10, as shown in FIGURE 2, having a loading support 12 with a vehicle base 14. The vehicle 10 may also have a threshold 16 on an outer edge of the load carrier 12 and the conventional vehicle frame members (not shown) to which the lift assembly 100 may be attached to the vehicle 10 in any conventional manner. Any type and style of vehicle will work well with this invention when applied with a reliable engineering judgment. Referring now to FIGURES 1-5, the lift assembly 100 may include a mounting assembly 110, a platform assembly 130 that includes a platform or cover 132, an elevator assembly 150 and a base extension 170. The mounting assembly 110 may include one or more mounting tubes 112 and one or more mounting plates 114 as well as other components shown but not referenced. He
Mounting assembly 110 is used to mount the lift assembly 100 to the vehicle frame in any conventional manner and will not be described in detail in this way. The base extension 170 has a first side 172 that can be spliced to the vehicle 10, such as along the threshold 16 and a second side 174 that can be spliced to the first end 134 of the platform 132, as shown. The base extension 170 may also have a surface 176 of traffic that can be used to receive traffic for loading and unloading the cargo. A portion of each clamp member 160, 160, which will be described later, may extend through a corresponding opening 180, 180 defined in the base extension 170, as shown in FIGURES 4 and 5. With continuous reference to the FIGURES 1-5, the elevator assembly 150 is used to move the platform 132 between a folded, closed or stored position (shown in FIGURE 1), a low position (shown in FIGURE 3) and an elevated position (shown in FIG. FIGURES 4 and 5). The elevator assembly 150 may include a control system (not shown) and a hydraulic system (not shown) used to operate one or more cylinders 152 (two visible in FIGURES 3 and 5) to move the platform 132. The basic operation The control and hydraulic systems are well known and will not be described in detail. The elevator assembly 150
it may also include the previously observed articulation assembly 200 that supports the platform 132 during use, movement and when in its storage position. The articulation assembly 200 may include a pair of lift arms 153, 153 and a pair of support arms 154, 154. Preferably, the lifting arms 153, 153 remain parallel to each other through all movements of the joint assembly 200. It is similarly preferred that the support arms 154, 154 remain parallel to each other through all movements of the joint assembly 200. Each lift arm 153, as best seen in FIGURE 3, can be operably linked to the first end 155 in a drawbridge frame member (such as a mounting tube 112 as shown) and operably linked to a second end 157 a the platform 132. Each support arm 154, as best seen in FIGURES 1 and 3, can also be operably joined to the first end 156 in a drawbridge frame member (such as the mounting tube 112 as shown) and operably linked to the second end 158 to the platform 132. While the particular types of connections between each lift arm 153 and each support arm 154 and the frame and platform member 132 may vary according to need, in the embodiments shown, each Union includes pivotal movement to allow range of motion
desired for platform 132. According to another embodiment, clamp members 160, 160 previously observed, are fixedly joined (such as by welding) to opposite sides of platform 132, as shown. A pivot pin 162 allows each second end 157, 158 to pivot with respect to each clamp member 160. Referring now to FIGS. 1 and 3-6, each support arm 154 may include an expansion mechanism 159, such as a telescopic arrangement, which allows the length of the support arm 154 to be adjusted during movement of the platform 132. In one embodiment, each support arm 154 includes a first member 154a that at one end 158 is attached to the platform 132, as discussed above, and the other end 161 is slidably or telescopically received within a second member 154b. The second member 154b may have one end 156 that attaches to the mounting tube 112, as discussed above, and another end 163 that defines a channel 165 that receives the first member 154a. In a more specific embodiment, the channel 165 can extend substantially to the full length of the second member 154b. A tension spring 190 can be operatively connected between the first and second members 154a, 154b to provide a biasing force to assist in the folding and unfolding of the drawbridge assembly 100 by diverting the first and second members 154a, 154b
towards the other. To protect the tension spring 190 from the forces of damage and to expose it to the corrosive elements, it can be placed within the channel 165. While the particular design of the channel 165 can be any selection with reliable engineering judgment, to increase the protection of the spring 190 of tension, the channel 165 can surround or substantially surround the tension spring 190. For the embodiment shown, this tension spring 190 is achieved by defining the channel 165 with four walls. Other forms and methods of the channel to encircle the channel are within the specification of this document. Referring now to FIGURE 6, each support arm 154 may be assembled as follows. A first end 191 of the tension spring 190 is connected to the end 161 of the first member 154a. While this connection can be made in any selected form with reliable engineering judgment, for the embodiments shown, a spring-binding loop 192 is placed between a pair of tie-down clamps 2a, 2b, extending from the end 161 of the first member 154a. A connecting pin 193 is then inserted through the holes formed in the joining clamps 2a, 2b and through the spring connection loop 192. The connecting pin 193 is then secured to the connecting clamps 2a, 2b so that the spring connecting loop 192 remains attached to the connecting pin 193. While this
Assurance can be made in any form chosen with the reliable engineering judgment, by the embodiment showing a pair of platelets 3a, 3b that join outside the surfaces of the joining clamps 2a, 2b. A securing member, such as a screw 4a, then extends through a hole in at least one plate 3a and is received within a screw opening at one end of the connecting pin 193. To increase the stability of the connection, a second securing member, such as a second screw 4b, may extend through a hole in the plate 3b and be received into a threaded opening at the other end of the connecting pin 193. To prevent the plates 3a, 3b from pivoting around the screws 4a, 4b, a second hole can be provided in each plate 3a, 3b to receive the screws 5a, 5b which are then secured to the clamps 2a, 2b as shown. In one embodiment, shown, the screws 4a, 4b, 5a, 5b are inserted with respect to the outer surfaces of the plates 3a, 3b. In this form, the outer surfaces of the plates 3a, 3b remain relatively reliable and form sliding surfaces that are received on an internal surface of the channel 165 when the first member 154a moves telescopically with respect to the second member 154b. With continued reference to FIGURE 6, once the first end 191 of the tension spring 190 is connected to the
First member 154a, a second end 194 of tension spring 190 is connected to second member 154b. While this connection can be made in any selected form with reliable engineering judgment, for the embodiment shown, the first member 154a slides within the channel 165 in the Al direction until a spring-binding loop 195 is in alignment with a hole 196 formed in the second member 154b. A connecting pin 197 is then inserted through the hole 196 and through the spring union loop 195. The connecting pin 197 is then secured to the second member 154b so that the spring connecting loop 195 remains attached to the connecting pin 197. While this assurance can be made in any selected form with reliable engineering judgment, for the embodiment, showing the distal end of the connection pin 197 and threaded and extends through another hole (not visible) formed on the opposite side of the second member 154b and are referred to by a nut 198. This one-stage spring adjustment is easy to achieve eliminating the adjustment error of the user. This ensures that the deflection force of the tension spring 190 will be the force required by the manufacturer's specification. Still referring to FIGURE 6, first member 154a then slides into channel 165 in direction A2 until a portion of a notch 189 formed in the first
member 154a is aligned with a first opening 187a formed in the second member 154b. A slip limiter 199, used to limit the sliding movement of the first member 154a with respect to the second member 154b, is then attached to the support arm 154. While this joining can be done in any selected form with reliable engineering judgment, for the embodiment shown the slide limiter 199 includes a rod 185 that is inserted through the first opening 187a, through the notch 189 and then extends through a second opening 187b aligned with the first opening 187a although formed on the opposite side of the second member 154b. The sliding limiter 199 can be secured in place by a securing member, such as a screw 6a which is secured to the second member 154b as shown. The sliding limiter 199 limits the sliding movement of the first member 154a in the Al direction when a first end surface 189a of the notch 189 contacts the rod 185. Similarly, the sliding limiter 199 limits the sliding movement of the first member 154a in direction A2 when a second end surface 189b of the indentation 189 contacts the rod 185. The length of the indentation 189 can then be established to determine the range of movement of the first member 154a with respect to the
second member 154b. The multiple modalities have been described, in the above. It will be apparent to those skilled in the art that prior methods and apparatus may incorporate changes and modifications without departing from the general scope of this invention. It is intended to include all modifications and alterations as far as it is within the scope of the appended claims or the equivalents thereof. In an alternate embodiment, for example, the first member 154a that at one end 158 is attached to the platform 132, may contain the channel 165 while the second member 154b that at one end 156 is attached to the assembly 110 may slide or telescopically received within the first member 154a. Having described the invention in this way, now it is claimed: