LEVADIZED DOOR HYDRAULIC CLOSURE CYLINDER DESCRIPTION OF THE INVENTION This invention pertains to the technique of methods and apparatus related to drawbridges, and more specifically, to methods and apparatus related to the opening and closing of drawbridges. It is well known in the art to attach drawbridges to vehicle trailers or other forms of vehicle loading containers to assist with the loading and unloading of vehicles. In general, drawbridges include a platform or deck and an adjustment system used to move the platform. To load cargo from one surface of the ground to the vehicle platform, the cover is placed in a lowered position where it is generally parallel with the ground surface. The loading can then be easily placed on the cargo receiving surface of the cover. The cover is then raised to a raised position generally parallel with the vehicle platform. The cargo can then be moved from the cargo receiving surface and loaded into the vehicle. To unload the loading of the vehicle, stages are carried out in reverse. Various types and styles of drawbridges are known in the art. Some non-limiting examples include conventional drawbridges, drawbridges
deployable or folding, drawbridges type rail, and drawbridges for special purposes. FIGURE 1 shows a known rail-type drawbridge system and provides a list of the main components. FIGURE 2 illustrates the basic operation of the drawbridge system. Note that the rail-like drawbridge platform or cover 19 not only rises and falls with a lifting cylinder 16, but also opens and closes with a locking cylinder 17. A more detailed view of the closing cylinder 17 is shown in FIGURE 3 and a hydraulic scheme of the drawbridge system is shown in FIGURE 4. One or more torsion springs 38, one visible in FIGURE 1, are used in a known way to help open the cover 19. Although the drawbridge system shown in FIGS. 1-4 works well for its intended purpose, such drawbridge systems have disadvantages. A disadvantage refers to the fact that the force required to open the cover usually varies. The required strength of roof opening varies for various reasons. The most common of these reasons are: (a) damage to the deck / platform, (b) corrosion at the deck hinge; (c) atmospheric temperatures; and, (d) the position of the vehicle, and thus the drawbridge system, on a slope, such as when the vehicle is parked at
the side of a hill. As noted in the above, known drawbridge systems use a torsion spring to help open the cover. However, the use of such a spring does not allow adjustment of varied opening forces (except that the spring could be replaced with another spring having different characteristics - this would be expensive, time consuming and impractical). Another disadvantage is the noise. Specifically, conventional wire springs typically have a higher initial opening torque amount and the torque is reduced to zero at an angle anterior to the opening range of the cover opening. This allows the inert gravity forces to continue opening the cover after the torque of the applied wire spring is zero. The hydraulic fluid resistance is typically designed to be relatively low so as not to prevent the opening of the cover. This typically causes a relatively rapid opening of the cover, which can cause a relatively high noise. Such high noise can be a detriment to the operation of the drawbridge assembly - especially in areas with strict noise reduction standards and regulations, such as hospitals and residential areas. The present invention provides methods and apparatus for easily varying the opening force of the
drawbridge system and thus overcomes the above difficulties and others, while providing better and more advantageous general results. According to one embodiment of this invention, a drawbridge system can include a cylinder assembly used to open the cover of a drawbridge. The cylinder assembly may have a portion of hydraulic fluid on one side of a piston and a portion of air (or other gas) on the other side of the piston. The cover is closed using hydraulic pressure on the hydraulic fluid portion to move the piston in one direction. The opening of the cover is aided by using gas pressure in the gas portion to move the piston in another direction. According to another embodiment of this invention, energy, in the form of compressed gas, which will be used to open the cover can be stored inside the cylinder or in an auxiliary device connected to the gas portion of the cylinder. According to another embodiment of this invention, a gas system may include a regulator which is used to preset the gas pressure within the gas system. According to yet another embodiment of this invention, a hydraulic system may include a flow control valve that is used to control the flow rate of the hydraulic fluid.
An advantage of this invention is that the force required to open a drawbridge cover can be easily adjusted to meet the required operating conditions. Another advantage of this invention is that the drawbridge cover can be opened in a controlled and relatively slow manner. Another advantage of this invention is that the drawbridge cover can be opened in a more silent manner. Another advantage of this invention is that the opening force of the drawbridge cover can be adjusted to compensate for wear on the cover. Yet another advantage of this invention is that the costs of the drawbridge assembly can be reduced. Yet another advantage of this invention, according to one embodiment, is that the leakage hydraulic fluid flow rate, if the hydraulic line is cut, can be controlled. Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains, from a reading and understanding of the following detailed specification. BRIEF DESCRIPTION OF THE DRAWINGS The invention can take physical form in certain
parts and arrangement of parts, of which the modalities in this specification will be described in detail and illustrated in the accompanying drawings that are part of it and in which: FIGURE 1 is a perspective view in plan of a drawbridge type rail of the prior art. FIGURE 2 illustrates the operation of the drawbridge system shown in FIGURE 1. FIGURE 3 is a close-up side view of the lock cylinder shown in FIGURE 1. FIGURE 4 is a hydraulic diagram of a hydraulic system that can used with the drawbridge system shown in FIGURE 1. FIGURE 5 is a perspective view of a cylinder assembly according to an embodiment of this invention. FIGURE 6 is a side view, shown partially in section, of the cylinder assembly shown in FIGURE 5. FIGURE 7 is a side view, at an angle different from that shown in FIGURE 6, of the cylinder assembly shown in FIGURE 6. 5, but that also includes a hydraulic line. FIGURE 8 is an end view of the cylinder assembly shown in FIGURE 5.
FIGURE 9 is a hydraulic schematic of a hydraulic system that can be used with an embodiment of this invention. FIGURE 10 is a view of the cylinder assembly shown in FIGURE 7 but with an aggregate flow control valve. With reference now to the drawings, wherein the presentations are for purposes of illustrating the embodiments of the invention only and not for purposes of limiting the same.FIGURES 5-8 show a cylinder assembly 100 that can be used in place of the closing cylinder 17 and the torsion spring 38 described above with respect to the drawbridge system shown in FIGURES 1-4. The general operation of a drawbridge system using the inventive cylinder assembly 100 is as described above, except as described in the following. With continued reference to FIGS. 5-8, the main components of the cylinder assembly 100 are the following: 100 cylinder assembly 101 packing gland 102 connecting rod assembly 103 piston 104 drum assembly
105 O-ring 106 O-ring 107 Rod seal 108 Spare ring 109 Piston seal 110 Connecting rod seal 111 Wear ring 112 Retaining ring 113 Plug plug 114 Lock nut 115 Tank valve, 1/8 npt, w / cap 116 gas discharge valve, established, in one embodiment, at 42,184-40,005 kg / cm2 (500-569 psi). With reference still to FIGS. 5-8, the assembly
100 of cylinder includes a piston 103 connected to an assembly
102 of connecting rod. The piston 103 is placed inside an assembly
104 drum, as shown. The cylinder assembly 100 has a portion 117 of hydraulic fluid on one side of the piston 103 and a portion 118 of air (or other gas) on the other side of the piston 103. The cover is closed using hydraulic pressure in the fluid portion 117 Hydraulic to move the piston 103 in the direction Al. The opening of the cover is aided by using the gas pressure 118 to move the piston 103 in the direction A2. As a result, a spring is not required. Energy, in the form of compressed gas, which is
used to open the cover can be stored inside the cylinder 100 or in an auxiliary device connected to the gas portion 118 of the cylinder 100. The auxiliary storage can include a pneumatic or pneumatic over hydraulic accumulator. As the cover is closed with hydraulic pressure, the gas pressure within the gas portion 118 and / or the auxiliary device increases. When the hydraulic pressure is released from the hydraulic fluid portion 117 of the cylinder 100, the gas pressure within the gas portion 118 is sufficient to drive the piston in the A2 direction and consequently open the cover. With continued reference to FIGS. 5-8, the gas pressure is retained in the gas portion 118 of the cylinder 100 by the piston 102, the piston seal 109, the cylinder walls, the end closure of the cylinder and by a plurality of types of air / gas valves. The valve is placed inside a valve stem or directly in the cylinder. The valve stem may be, but is not limited to, a "tire valve" type shank or a metallic line. A pressure relief valve 116 can be connected to the gas portion 118 of the cylinder 100 to prevent over-pressurization. In one embodiment, the gas portion 118 is pressurized to a desired pressure, the "set pressure", when the cover is in the open position - in which case the piston 103 will move
completely in the A2 direction. An operator can vary the set pressure to adapt to a variety of operating conditions of opening resistance of the cover; some of which were observed in the previous. Referring now to FIGS. 1-8, using the cylinder assembly 100 of this invention allows greater control of the opening of the cover 19 compared to other energy storage methods. It is believed that this improvement is due to the operation of at least three mechanisms. The first is that the pneumatic torque is applied at a lower magnitude. The second mechanism is that the lowest torque is applied over the total opening rotation margin of the cover. The third mechanism is that the hydraulic fluid flow resistance is set higher in the case of convention. This reduces the inert gravity forces that open the cover. It is believed that the combination of these three mechanisms allows the cover to open in a slower, more controlled and quieter way. With continued reference to FIGURES 1-8, this invention allows easy adjustment of the opening force of the cover by simply adjusting the gas pressure in the gas portion 118 of the cylinder 100. The gas pressure can be set, for example , at any pressure between 0 and 8.437 kilograms per square centimeter (kg / cm2) (0 and 120
Pounds per square inch (PSIG)). This pressure range is easily available from a variety of commercial sources and engine compressors. The invention is not limited to the listed operating conditions. The particular device used to adjust the gas pressure can be any selected with good engineering judgment such as, for example, a gas pressure regulator. Referring now to FIGS. 9-10, in another embodiment, a flow control valve 120 is added to the hydraulic fluid portion 117 of the cylinder assembly 100, as shown. The flow control valve 120 provides several advantages. An advantage is revealed in the situation where the hydraulic line 122, which provides hydraulic fluid to the cylinder assembly 100, is "cut" or opened. To understand this advantage, with reference to FIGURES 3, 4 and 6, a case is first considered where the hydraulic line 122 is cut (or otherwise opened) without the use of a flow control valve. In this case, the hydraulic pressure supplied to the hydraulic fluid portion 117 of the cylinder assembly 100 may fall and the gas pressure in the gas portion 118 may cause the piston 103 to move in the direction A2. Note that the speed of movement in the A2 direction, as well as the leakage hydraulic fluid flow rate can only be limited by
the pressure in the gas portion 118 and the size of the opening in the hydraulic line 122. If the opening in the hydraulic line 122 is relatively large, there is the possibility of a relatively rapid flow rate of leaking hydraulic fluid, which, for example, could "spray" a person who may be near the drawbridge. Now, with reference again to FIGS. 9-10, consider the case where the hydraulic line 122 is cut (or otherwise opened) with the use of a flow control valve 120. In this case, the hydraulic pressure supplied to the hydraulic fluid portion 117 of the cylinder assembly 100 may fall again and the gas pressure in the gas portion 118 may again cause the piston 103 to move in the direction A2. Note, however, that the speed of movement in the direction A2, as well as the proportion of leaking hydraulic fluid flow, are now limited by the flow control valve 120. In this way, no matter how large the opening in the hydraulic line 122 may be, the flow rate of the leaking hydraulic fluid will be limited and in the same way the "spray" that can be experienced by a person who may be near will also be limited. of the drawbridge. The particular flow control valve 120 used can be of any type selected with good judgment of
engineering. In one embodiment, the flow control valve 120 is positioned very close to or on the cylinder assembly 100, as shown. Referring still to FIGS. 9-10, other advantages of the flow control valve 120 include controlling the opening and closing ratios and reducing the noise during operation. 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 long as they fall within the scope of the appended claims or the equivalents thereof. Having thus described the invention, it is now claimed: