Abstract:
A trailer includes a tongue, an upper frame, a lower frame coupled to the upper frame via a plurality of arms, and a lift assembly. The lift assembly includes 1) a hydraulic ram and 2) a hydraulic pump that is operatively connected to the hydraulic ram. The hydraulic ram raises the upper frame to a raised position when the hydraulic ram is retracted, and lowers the upper frame to a lowered position when the hydraulic ram is extended. The lift assembly is configured to be removably attachable to a trailer for retrofit operations, lift assembly replacement, or lift assembly reuse upon trailer sale or disposal. Also included is a method of raising and lowering a vehicle.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to trailers, and more particularly to trailers having hydraulic lift assemblies. 
     2. Description of the Related Art 
     Trailers are used to haul a variety of items, e.g., cars, all terrain vehicles, and boats. Boat trailers include both float trailers and cantilevered trailers. Float trailers do not actively move boats. Instead, boats are loaded on and unloaded from float trailers by backing the trailer down a boat ramp into enough water to float the boat onto and off the trailer. 
     Cantilevered trailers actively raise and lower boats with, e.g., a hydraulic lift system. Cantilevered trailers can raise and lower boats into and out of the water typically by a winch and pulley lift assembly or by a hydraulic lift assembly. A cantilevered trailer with winch and pulley lift assembly requires manual operation of the winch and pulley system to raise and lower the trailer, fatiguing an operator when multiple lifts are required. This problem particularly affects people, such as boat dealers, that raise and lower many boats a day. In addition, informed people find raising and lowering even a single boat difficult. In addition, trailers with winch and pulley systems take time to operate the winch. 
     Furthermore, winch and pulley systems are permanently mounted to the trailers, requiring the replacement of the entire trailer when a problem occurs with the winch and pulley system and, conversely, disposal of the winch and pulley system when the trailer is worn out. 
     Cantilevered trailers equipped with hydraulic lift assemblies are advantageous over those equipped with winch and pulley systems in that they are mechanized. A typical conventional trailer with hydraulic lift assembly has a hydraulic ram positioned between an upper and a lower frame of the trailer. Such positioning of the hydraulic ram has several drawbacks. For example, a hydraulic pump typically is located far from the hydraulic ram, requiring the use of long hydraulic hoses to connect the pump to the ram. Furthermore, when the hydraulic ram is positioned between the two frames of the trailer, the hydraulic ram is submerged when the trailer is backed down a ramp into water. Such submersion causes problems related to corrosion. 
     Thus, there is a need for a trailer that has a hydraulic lift assembly that avoids at least some of the problems noted above. In particular, the trailer should have a hydraulic ram that is kept out of the water during use. The trailer should have hydraulic conduits of a sufficiently short length such that they do not tangle with each other or other components of the trailer. Furthermore, there is a need for a hydraulic lift system that can be easily transferred from one trailer to another and/or that can be easily retrofitted onto an existing trailer. 
     SUMMARY OF THE INVENTION 
     The invention, which is defined by the claims set out at the end of this disclosure, is intended to solve at least some of the problems noted above. It is also applicable in applications other than boat hauling, in which there is a need to raise and lower vehicles and to haul vehicles. 
     In accordance with a first aspect of the invention, a trailer includes a tongue, an upper frame, a lower frame coupled to the upper frame via a plurality of arms and from which the tongue extends, and a lift assembly. The lift assembly includes 1) a hydraulic ram and 2) a hydraulic pump that is operatively connected to the hydraulic ram. The hydraulic ram raises the upper frame to a raised position when the hydraulic ram is retracted, and lowers the upper frame to a lowered position when the hydraulic ram is extended. 
     A lift assembly is provided that includes a ram stand, a hydraulic ram that is mounted on the ram stand, and a hydraulic pump that is operatively connected to the hydraulic ram. The lift assembly is configured to be attachable to a upper frame of a trailer. The hydraulic ram lifts the upper frame of the trailer to a raised position when the hydraulic ram is retracted, and lowers the upper frame to a lowered position when the hydraulic ram is extended. 
     Also provided is a method of raising and lowering a trailer. In the method, an upper frame of the trailer is raised by retracting a hydraulic ram that is connected to the upper frame. The upper frame of the trailer is lowered by extending the hydraulic ram. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a partial side view of a trailer made in accordance with a preferred embodiment of the invention, with the trailer in a raised position; 
     FIG. 2 a side elevation view of the trailer of FIG. 1, with the trailer in a lowered position; 
     FIG. 3 a side elevation view of the trailer of FIGS. 1 and 2 with a preferred embodiment of the invention, with the trailer in a raised position; 
     FIG. 4 is a sectional end view along line  4 — 4  of FIG. 1, showing a pontoon boat in phantom; 
     FIG. 5 a partial perspective view of the trailer of FIGS. 1 and 3, showing the lift assembly of the trailer with the trailer in a raised position; 
     FIG. 6 corresponds to FIG.  5  and shows the trailer in a lowered position; and 
     FIG. 7 an exploded view of the lift assembly and the trailer, showing the lift assembly detached from the trailer. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     1. Resume 
     Pursuant to the invention, a trailer is provided with a removable hydraulically powered lift assembly. The trailer includes an upper frame, a lower frame, a tongue, and the lift assembly. The lift assembly includes a hydraulic ram that raises the upper frame of the trailer to a raised position when the hydraulic ram is retracted and lowers the upper frame to a lowered position when the hydraulic ram is extended. Hence, the hydraulic ram pulls the upper frame of the trailer from the top rather than pushing the upper frame of the trailer from below as in traditional trailers with hydraulic lift assemblies. The lift assembly also includes a ram stand constructed so as to permit the lift assembly to be transferable to another trailer, retrofittable onto an existing trailer, and/or replaceable with, e.g., a standard winch. 
     2. A Preferred Embodiment of the Trailer 
     Referring first FIGS. 1-4, the trailer  20  described herein can be used to haul vehicles. The term “vehicles” as used herein includes, but is not limited to, boats, cars, trucks, all-terrain vehicles, snowmobiles, airplanes, or other vehicles. A preferred embodiment of the invention will be described in use to transport a boat. This example is not intended to limit the invention to trailers usable only with boats. 
     The trailer  20  includes an upper frame  22 , a lower frame  24 , a tongue  26 , and a lift assembly  28 . The trailer  20  also includes wheels  30 , which are supported on an axle  32 . In the illustrated embodiment, the trailer  20  includes four wheels  30  and two axles  32 , which are spaced apart such that the two axles  32  are located relatively close to each other. The axles  32  preferably are located about two-thirds of the way down the lower frame  24  from a front end of the trailer  20 . A vehicle, such as a pontoon boat, can be positioned on the upper frame  22  such that the vehicle can be hauled, launched into water, and retrieved from the water or deposited on land for storage or repair. 
     Each of the upper and lower frames  22  and  24  includes a series of longitudinal and lateral bars  34  and  36  that are welded or otherwise affixed to one another in a standard fashion. The upper frame  22  is connected to the lower frame  24  via pivot arms  37 , which are spaced about a periphery of the upper and lower frames  22  and  24 . The pivot arms  37  are attached at a bottom of the upper and lower frames  22  and  24  in a parallelogram linkage with pins  54 . Each pin  54  is received in a mount (not shown) that has a bushing (not shown) that supports the pin  54 . In a preferred embodiment, three sets of pivot arms  37  are employed behind the wheels  30  (although only two sets are shown in the drawings), and three sets of pivot arms  37  are used in front of the wheels  30 . The pivot arms  37  pivotably move the upper frame  22  backwardly over the lower frame  24  in a cantilevered manner as shown in FIGS. 2 and 3. A horizontal extension  38  extends from a front side of the upper frame  22 . The horizontal extension  38  includes an opening  40 . The upper frame  22  also includes a frame portion  42  of a clevis  44  at a front, top side of the upper frame  22 . 
     The tongue  26  extends outwardly from a center front of the lower frame  24 . The tongue  26  permits connection of the trailer  20  to a towing vehicle (not shown) via a hitch  27 . Other conventional components, such as chains (not shown) and electrical couplings (not shown) for powering, e.g., lights (not shown) on the trailer  20  can be carried on the tongue  26 . A conventional jack  45  can be used to support the tongue  26  on the ground in a horizontal position when the trailer  20  is removed from the towing vehicle. 
     Referring now to FIGS. 5 and 6, the lift assembly  28  includes a ram stand  46 , a hydraulic ram  48 , a hydraulic pump  50 , and a motor (not shown) are mounted. The ram stand  46  supports the ram  48  and overlies the pump  50 , the motor, and a power source  76 . When the hydraulic ram  48  is retracted, the pivot arms  37  are preferably generally perpendicular to the ground as is shown in FIG. 1 Conversely, when the ram  48  is extended, the pivot arms assume a more horizontal position as shown in FIG.  2 . 
     Referring to FIGS. 5-7, the ram stand  46  includes a diagonal brace  56 , first and second upright supports  58  and  60  that extend from and support the diagonal brace  56 . In a preferred embodiment, the first and second upright supports  58  and  60  are a short support  58  and a long support  60 , with the short support  58  positioned rearwardly from the tall support  60 . Additionally, the ram stand  46  preferably includes a horizontal brace  62  extend between and welded or otherwise affixed to short support  58  and long support  60 . 
     In addition, the ram stand  46  includes a front baseplate  64 , a middle baseplate  66 , and a rear base plate  68 . The front baseplate  64  is affixed to a bottom end of the long support  60 , the middle baseplate  66  is affixed to a bottom end of the short support  60 , and the rear baseplate  68  is affixed to the bottom of the diagonal brace  56 . Specifically, the lower end of the diagonal brace  56  is attached to the rear baseplate  68 , preferably at an angle of about 45 degrees from the tongue  26 . Each baseplate  64 ,  66 , and  68  includes two sets of openings  70  for receiving two U-bolts  72 . A U-bolt  72  is inserted into each set of openings  70  from an underside of the tongue  26  and secured therein with nuts (not shown) to clamp the baseplates  64 ,  66 , and  68  in place. 
     A tray  74  supports the power source  76  that supplies power to the motor. Preferably, the power source  76  is a 12-volt battery. The power source  76  can be secured to the tray  74  with a strap  78  that can be secured to a mount (not shown) on the tray  74 . The tray  74  includes two sets of openings (not shown) for receiving two U-bolts  80 , with four openings on the corners of the tray  74 . A U-bolt  80  is inserted into each of the two openings from an underside of the tongue  26  to clamp the tray  74  in place. The U-bolts  72  used in conjunction with baseplates  64 ,  66 , and  68  and the tray  74  allow for easy attachment and detachment of the lift assembly  28  from the rest of the trailer  20 , as is described in detail below and as is illustrated in FIG.  7 . 
     At its upper end, the diagonal brace  56  includes a first mount  82 , which preferably is a yoke  82  on which one end of the hydraulic ram  48  is mounted. Preferably, a bolt  84 , such as a ¾ inch hardened bolt, is used to secure the ram  48  to the first yoke  82 . The hydraulic ram is a bi-direction or two-stroke ram that includes a barrel  96  and a rod  98  disposed in the barrel  96 . A mount end  110  is pinned to the first yoke  82 . A rod end  104  is pinned on the upper frame  22 . The preferred size of the hydraulic ram  48  depends upon the weight of the vehicle being raised and lowered. For lifting most pontoon boats, the hydraulic ram  48  preferably has a diameter of between about 2 inches and about 2 ½ inches. Preferably, when the upper frame is in a lower position, the hydraulic ram  48  and the diagonal brace  56  form an acute included angle no greater than about 17° and more preferably, about 10°. This angle minimizes creation of bending moments in the diagonal brace  56  by transmitting substantially all or most of the ram force to the lower frame  24  through the diagonal brace  56 . Additionally, this minimizes bending moments in the upright supports  58  and  60 . 
     The diagonal brace  56  includes a second yoke  88  that is attached, such as by welding, at or near the intersection of the short support  58  and the horizontal brace  62 . The second yoke  88  is attached to a rear side of the diagonal brace  56 . In a preferred embodiment, the second yoke  88  includes two plates  90  with openings  92 . The second yoke  88  is configured and dimensioned to receive the horizontal extension  38  of the upper frame  22  when the upper frame  22  is lifted to a raised position. When the horizontal extension  38  is received in the second yoke  88 , a fastener such as a pin  94  can be inserted through the openings  92  in the second yoke  88  and the horizontal extension  38  to secure the upper frame  22  in a raised position for transport, as is shown in FIG.  5 . The pin  94  is removed when the upper frame is raised and lowered. 
     The hydraulic ram  48  raises the upper frame  22  to a raised position when the hydraulic ram  48  is retracted (FIG. 5) and lowers the upper frame  22  to a lowered position when the hydraulic ram  48  is extended (FIG.  6 ). Hence, the hydraulic ram  48  pulls the upper frame of the trailer  20  from the top rather than pushing the upper frame  22  of the trailer  20  from below as in traditional trailers with hydraulic lift assemblies. The upper frame  22  is lowered to launch a boat. Using a hydraulic ram  48 , as opposed to an electric motor, to lower boats advantageously extends the life of the battery  76 . 
     The hydraulic pump  50  preferably is mounted on the short upright support  58  of the ram stand  46 , such as with two bolts (not shown). Referring back to FIG. 1, the hydraulic pump  50  is a DC powered pump  50  that is powered by the motor. The hydraulic pump  50  has an internal flow control valve (not shown) that permits the hydraulic ram  48  to be extended and retracted by operation of a directional control switch  100 . A first conduit  102  couples the hydraulic pump  50  to the rod end  104  of the hydraulic ram  48 . The first conduit  102  preferably is about  18  inches long. A second conduit  108  couples the hydraulic pump  50  to the mount end  110  of the hydraulic ram  48 . The positioning of the first and second conduits  102  and  108  above or near the upper frame  22  and at a front end of the upper frame  22  advantageously locates them in a position where they are not submerged under water when the trailer  20  is used to launch or retrieve a boat. In addition, the length of the first and second conduits  102  and  108  assists in keeping them out of the water and preventing them from tangling with each other or with other components of the trailer  20 . 
     The directional control switch  100  controls the supply of electric power from the motor to a solenoid-actuated valve (not shown) that is internal to the hydraulic pump  50 . Activation of the directional control switch  100  changes direction of fluid flow to and from the hydraulic ram  48  to extend or retract the hydraulic ram  48 . The directional control switch  100  of a preferred embodiment includes an UP button and a DOWN button (not shown). Still referring back to FIG. 1, wires  109  operatively couple the motor to the direction control switch  100  and to a solenoid (not shown). Preferably, the wires  109  have a length of at least about  15  feet such that a user of the trailer  20  can use the direction control switch  100  and actuate the UP and DOWN buttons from a towing vehicle. 
     In a preferred embodiment, a control valve  111 , such as a flow restrictor  111  is included in the hydraulic system to regulate the flow of hydraulic fluid to the rod side  104  of the barrel. Preferably, the flow restrictor  111  is adjustable such that a user can select a desired flow regulation. The flow restrictor  111  limits the speed of the hydraulic ram  48  in the down cycle and is particularly useful when, for example, a heavy boat is being lowered on the trailer  20 . The weight of a heavy boat, e.g., a 4,000 pound boat, can undesirably push hydraulic fluid more rapidly than the hydraulic pump  50  itself to undesirably drive the hydraulic ram  48  down exclusively under the weight of the boat. The flow restrictor  111  prevents this from occurring and, thus, avoids problems associated with lowering a heavy boat. In addition, if desired, a control valve may be included in the hydraulic system to regulate flow of hydraulic fluid to the mount side  110  of the barrel  96 . In a preferred embodiment, a pressure relief valve (not shown) is included in the hydraulic system. Preferably, the pressure relief valve can be turned as high as 3,000 psi. 
     In a preferred embodiment, the lift assembly  28  is removable from the remainder of the trailer  20  by unfastening a bolt  112  of the clevis  44  and by unfastening the U-bolts  72  that secure the front, middle, and rear baseplates  64 ,  66 , and  68  of the ram stand  46  and the U-bolts  80  that secure the tray  74 , and by disconnecting the hydraulic system at the clevis  44 , as is described above. 
     The removability of lift assembly  28  from the remainder of the trailer  20 , permits, for example, a dealer to retain the lift assembly  28  after a trailer  20  or a boat and trailer  20  are sold. The buyer of the trailer  20  can substitute a traditional winch and pulley system for the lift assembly  28 . The dealer then can attach the lift assembly  28  to another trailer. 
     3. Operation of the Trailer and Lift Assembly 
     Typical use of the trailer  20  and lift assembly  28  will now be described. When the trailer  20  is in raised position, as is shown in FIGS. 1 and 5, the trailer  20  can be used to transport a boat (shown in phantom in FIG. 4) during, for example, transportation to and from water. To launch a boat from the trailer  20 , the trailer  20  is backed down a ramp towards the water. After the trailer  20  is sufficiently lowered into the water, the bolt is removed from the second yoke  88 , and the lift assembly  28  is engaged to lower the boat into the water. In particular, the DOWN button on the directional control switch  100  is depressed to extend the hydraulic ram  48 , which moves the upper frame  22  in a downward direction to lower the boat. The boat is then unsecured from the trailer  20  in a known fashion. FIG. 3 shows the trailer  20  in a partially lowered position, and FIG. 2 shows the trailer  20  in a fully lowered position. After the boat is launched, the trailer  20  can be removed from the water. 
     When retrieval of the boat is desired, the trailer  20  is lowered down the boat ramp preferably with the hydraulic ram  48  in an extended position and the upper frame  22  in a lowered position such as that shown in FIG.  2 . The boat is moved toward the upper frame  22  and is placed thereon. The UP button on the directional control switch  100  is depressed to retract the hydraulic ram  48 , which in turn lifts the upper frame  22  to a raised position (FIGS. 1 and 5) to raise the boat. The boat can be secured to the trailer  20  is a known fashion. The pin  94  is then inserted in the second yoke  88  to lock the frame  22  in its raised position, and the trailer  20  is removed from the water. 
     To remove the lift assembly  28  from the trailer  20 , the U-bolts  72  and  80  are released by removing the nuts thereon. The four U-bolts  72  and  80  are then removed from the front, middle, and rear bases  64 ,  66 , and  68  and from the tray  74  of the ram stand  46 . In addition, the bolt  112  holding the clevis  44  is released by removing the nut thereon and sliding the bolt  112  through the openings of the clevis  44 . The lift assembly  28  can then be removed from the trailer  20 , such as by lifting it. If desired, a traditional winch and pulley system then can be inserted at the frame portion  42  of the clevis  44 . Specifically, pulleys can be added to the frame portion  42  of the clevis  44  and a winch cable can be wrapped around the pulleys. 
     The lift assembly  28  can be transferred to another trailer by securing the U-bolts  72  and  80  around the tongue  26  of the new trailer and to the front, middle, and rear bases  64 ,  66 , and  66  and to the tray  74  of the ram stand  46 . Additionally, the frame portion  42  of the clevis  44  of the other trailer is attached to the rod end  104  of the hydraulic ram  48  of the lift assembly  28 . 
     The trailer  20  and lift assembly  28  are also beneficial to those in poor health, who may not want to use a manual winch and pulley system, and to boat owners that live inland or off-water and need to launch boats frequently. Additionally, boat dealers benefit from the invention because they oftentimes haul and launch boats 10 to 20 times a day. 
     Using the lift assembly  28 , a boat can be lifted in about 5 to 7 seconds, depending upon the weight of the boat and the setting of the flow control valve  111 . For example, a boat weighing 4040 pounds can be lifted in roughly 7 seconds. This compares very favorable to the time required to use a traditional winch and pulley system, which typically is on the order of 45 seconds to a minute. 
     In addition, the lift assembly  28  and the trailer  20  including the lift assembly  28  last longer than those with traditional hydraulic lift systems because the conduits  102  and  108  and hydraulic ram  48  typically are not submerged in water during use because of their positioning. Additionally, the desirable length of the conduits  102  and  108  minimizes or prevents tangling thereof. Furthermore, the length of wires  109  leading to the direction control switch advantageously to permit a user to control the extension and retraction of the hydraulic ram  48  from inside a towing vehicle.