Fluid Power System For A Self-contained Unloading Unit

Abstract

A precharged, closed circuit, fluid power system for a material handling unit which permits controlled gravitational unloading of heavy objects such as heavy concrete pipes from the bed of a truck. The system comprises extensible cylinders, fluid pump, reservoir and control apparatus.

Description

BACKGROUND OF THE INVENTION

The present invention pertains to fluid power systems for material or article handling apparatus, which apparatus includes a vertically swinging load support arm means and also cooperating guide rails for supporting and guiding the object being lowered by the arm means.

Unloaders of the general type with which the invention finds particular utility are shown in the U.S. Pat. No. 2,776,762, issued Jan. 8, 1957, and entitled "Vehicle Unloading Apparatus," and the present invention is an improvement over the hydraulic system and return spring arrangement shown in that patent.

SUMMARY OF THE INVENTION

The present invention provides an improved fluid power operating mechanism and control for self-contained apparatus for gravitationally unloading objects from the edge of a vehicle or the like.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being made to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the unit and showing it in disassembled relationship to the unloading vehicle, the latter of which is shown only fragmentarily;

FIG. 2 is a side elevational view of the unit shown in FIG. 1, showing the unloading arms in a moved position, and the unit attached to the platform, and with the support legs in the transport position;

FIG. 2a is an exploded, perspective view of the detachable mounting brackets for fastening the unloader to the truck body;

FIG. 3 is an elevational view, similar to FIG. 2, with certain parts shown as being broken away or in section with the support legs in the ground engaging position, and showing the pivotal arms in various positions relative to the guide rails;

FIG. 4 is a plan view of the device shown in FIG. 3;

FIG. 5 is a sectional view taken generally along line 5--5 in FIG. 2, of the connection between the frame, the support leg, and the pivotal arm, certain parts being shown as broken away and in section for the sake of clarity;

FIG. 6 is a hydraulic circuit diagram according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The apparatus A can be used to unload objects from a stationary platform or from the platform of a vehicle and such a vehicle platform P has been shown only in a fragmentary manner. The platform includes an upper, flat surface 1, a rear, generally vertical surface 2 in which an opening 3 is formed by oppositely facing steel channel members 4 and 5. The rear surface 2 also has a pair of lugs 6 extending rearwardly therefrom which comprise part of a detachable connecting means for the apparatus.

FRAME

The unloading apparatus includes a frame F which can be inserted into and removed from the opening 3 and which can be locked in position on the vehicle. This frame F includes two laterally spaced, oppositely facing C-shaped channel members 10 and 11 which are rigidly fixed together at one end by a large tubular member 12. A vertically disposed steel plate 14 is rigidly secured to the other end of members 10 and 11, as by welding.

The frame also includes vertically disposed, tubular support members, such as an outer support member 19 and an inner support member 20 secured as by welding to the rear side of the plate 14, and such a pair of support members is secured at each end of the plate 14.

TELESCOPING LEGS

A ground engaging leg 21 is telescopingly mounted within the outer support member 19 to provide an adjustable height for the unit. The leg 21 is formed from a C-shape channel member and has a guide plate 22 welded across its upper end between its parallel sides. The leg 21 has a detachable pad 23 at its lower end which is detachably fixed thereto by the bolt means 23a which extends through a hole in the lower portion of the leg and through an alignable hole in the pad member. A bearing plate 24 is welded to the interior of the lower end of the support member 19 and when the leg is in a downwardly extended, supporting position, as shown in FIG. 5, the guide plate of the leg abuts against the bearing plate of the support member. The retractable leg is held in this extended position by the removable pin means 25 which extends through the support member and through the leg.

To assemble the leg in the tubular support member, the detachable pad 23 is not attached to the leg and the leg is then inserted into the tubular member from the upper end thereof. Then the pad 23 is attached to the lower end of the leg.

PIVOTAL ARM MEANS

Arm means 30 are pivotally mounted at one end to the frame for swinging between an upper position and a lower discharging position. More specifically, the arm means includes a pair of arms 31 and 32 which are pivotally attached, respectively, on pins 31a and 32a which extend through the support members 19 and 20, and through the arms 31 and 32. The arm means have a free end which as shown in FIG. 1 is located above the unloading platform when in the object receiving position. These free ends can then be swung downwardly in an arcuate movement and to a discharge position as shown by the lowest broken line position in FIG. 3. Thus, as the arms swing in a downwardly direction, the object O rolls off the platform and is carried by the arm means to a lower position.

The present invention finds particular utility in unloading large and heavy objects such as concrete pipe, which pipe is also relatively fragile in nature. It is therefore necessary to be able to smoothly and rather gently lower these large objects without any bumping or shock.

GUIDE MEANS

For the purpose of insuring smooth and gentle handling of the objects, guide rail means have been provided for cooperation with the arm means as the latter lowers the object. More specifically, the guide rail means includes a pair of guide rails 41 and 42 which are detachably connected at one end to the inner support member 20 and extend rearwardly and downwardly from their point of attachment.

The guide rail means are connected to the inner support member 20 in such a manner that they can be easily moved between the unloading position shown in FIG. 3 and an upper storage position as shown in FIG. 2. In other words, a quickly detachable connection is provided between the frame and guide rails and this connection includes a slot 40 (FIG. 3) in the inner support member 20 and a hook 44 (FIG. 3) fixed at the end of the rails and which engage the slot. When the guide rails are in the upper position as shown in FIG. 2, the unit can be readily stored without the guide rails being lost or misplaced.

As shown in FIG. 3, as the object is being lowered by the arm means, the object is also being supported and guided by the guide rails. Thus, the object does not drop abruptly or move erratically in the lowering direction. Instead, the object is under control at all times due to the combined action of the arm means and the guide rail means. This is true even during the lower movement of the object, that is at the final stages of unloading when the arm means are in their lower position.

ATTACHING MEANS

The entire unit can be quickly and easily attached to and detached from the platform as follows. The platform has an angle iron 43 rigidly fixed thereto and at each side thereof and a rearwardly extending tang 44 is welded to the angle iron. A brace 45 is pivotally mounted to the rear side of the outer support member 19 and this brace 45 has a bracket 46 pivoted to its other end. This bracket in turn is bifurcated and has an aperture 47 extending through the bifurcated portion, which aperture 47 is alignable with an aperture 48 in tang 44. Thus, a bolt means 49 can be inserted through the aligned aperture when the brace 45 is in the position shown in FIG. 3, thereby attaching the apparatus rigidly to the truck frame. If additional locking means is required, a pair of slots 49a (FIG. 1) may be formed in the steel plate 14 of the apparatus so as to receive the pair of alignable lugs 6 extending rearwardly from the vehicle frame. Removable pins 49c (FIG. 2) are then inserted into the lugs after the lugs have been engaged in the slots of plate 14.

FLUID POWER SYSTEM

Actuating means are provided for raising the arm means and this actuating means is carried directly and entirely on the frame F. The arm actuating means includes a pair of extensible cylinder means 50 and 51, each including a cylinder 53 and piston rod unit 54 slideable therein. Fluid pressure is admitted to the rod end of the cylinder means 50, 51, to power operate the means in the retracting direction, to thereby raise the arm means 30. These cylinder means may be attached at one of their ends to a tubular pressure tank 12 and the other of their ends are attached to the cross brace 55 rigidly fixed between arms 31 and 32.

The cylinder means is used to raise the arm means, the weight of the object being unloaded is sufficient to cause the arm means to lower. In other words, the unloading takes place by gravitation.

Tank 12 is of tubular or cylindrical shape and extends between members 10 and 11 and is welded thereto. The tank has a partition 56 across its length which divides the tank into a pressure chamber 63 and an atmospheric chamber 64. Fluid level equalizer valve 65 is located between the chambers 63 and 64 and will be referred to later. Valve 65 is normally closed.

The fluid reservoir, atmospheric pressure chamber 64 has a filler and breather cap 62 which is vented to atmosphere. The pressure chamber 63 of the tank also has a precharge and pressure release valve 66 and a mid-stroke fluid level plug 69, for purposes that will appear.

As shown in FIG. 6, the tank 12 is connected to the head end of the cylinder means by conduits 56. A two-way, normally closed, fluid flow valve V is also connected to the tank 12 by means of conduit 57, the valve V is connected via conduit 58 to an adjustable, flow restricting or regulating valve 59 which restricts or regulates the rate of descent of the pivoted arm means 30. The valve 59 is connected, via a fluid connection in the form of a conduit 60, to the rod ends of the cylinder means 50, 51. This regulating valve 59 restricts the flow of fluid therethrough to accommodate different weights of pipes or other objects being unloaded. The weight of the pipe on the arms causes the cylinder means to extend and causes pressure to build up in the tank 12. The valve 59 can be adjusted as to its flow regulating characteristics. When the arm means 30 are being raised by contraction of the cylinder means, fluid can flow freely through valve 59.

As shown in FIG. 1, the two-way, fluid flow valve V is mounted on the frame F of the apparatus at any suitable location and its operating lever 61 is located at a convenient, out of the way location at the side of the unit as shown in FIG. 1. Valve V can be actuated manually by lever 61 or by other means, such as for example, electrically actuated solenoid valve, not shown, but of conventional design.

Chamber 63 is sealed and is precharged with fluid, for example dry nitrogen or other gas which tends to keep the moisture out of the system. In an emergency, compressed air could be supplied from the vehicle air brake system or the like in order to precharge chamber 63.

While relative pressures will be used to illustrate the invention, it should be remembered that these pressures can be varied in accordance with the specific requirements. In any event, the precharged pressure could be in the neighborhood of 80 p.s.i. and the maximum pressure developed in the system, when the arm means 30 is fully lowered due to the weight of the objects, may be as high as 385 p.s.i. These values are based, of course, on the estimates of the required force which is necessary to raise and hold the arms. The pressure can be adjusted by the volume relationship of the chamber 63 and the actuating cylinders.

Assume it is desired to unload the pipe. The control valve V would be shifted (to the left as viewed in FIG. 6) to permit fluid to flow at a controlled rate from the rod end of the cylinder means via conduit 60 and into the precharged, pressure chamber 63, thereby building up the pressure in that chamber. When the arms have been forced to their lowest position, the pressure in chamber 63 will be at the maximum, say for example, at 385 p.s.i. As the arms are then raised, fluid flows from the head end of the cylinder means via conduit 56 to the atmospheric chamber 64.

The precharged or minimum pressure required in the system would be such as to hold the arms in the "up" position, but at the same time would permit them to begin lowering when the pipe to be unloaded enters the V-shaped space between the arm means 30 and the guide rails 41, 42.

The final pressure developed, of say 385 p.s.i. would necessarily be sufficiently high to return the arms from the lower-most position, where a very poor mechanical advantage is initially present. However, as the arms begin their upward ascent, the mechanical advantage of the hydraulic cylinder means improves, and the pressure in the chamber 63 drops back to the precharge value.

Thus, a closed fluid system is controlled by the spring centered, two-way control valve V. The pressure in the pressure chamber of the tank will vary from the precharged pressure to the final pressure developed by the weight of the pipe causing the cylinder means to extend and forcing the fluid from the cylinders into the storage tank, building up the pressure therein.

In the event that fluid in the pressure chamber 63 is lost in any manner, such as past the piston seals to the fluid chamber 64, it can be transferred from chamber 64 back to chamber 63 by first exhausting the remaining pressure in the chamber 63 by opening valve 66, opening the fluid level plug 69 in the chamber 63, and then opening the fluid level equalizing valve 65 between the two chambers 63 and 64 of the tank. This balancing of the fluid level in the two chambers should be done with the cylinder means 50, 51 at their mid-stroke. When the fluid from chamber 64 reaches the fluid level plug hole 69, the valve 65 is closed, the plug of valve 69 replaced and the chamber 63 recharged with pressure fluid via valve 66.

Claims

I claim:

1. In a self contained unloading unit having pivoted arm means for unloading objects by swinging from an upper position to a lower discharge position,

a precharged, closed circuit fluid power system for controlling gravitational lowering of said arm means and objects and for returning said arm means to said upper position, said system including, a fluid tank having a prechargable pressure chamber and also having an atmospheric chamber, a fluid level equalizing valve located between said chambers, and a precharge valve connected to said pressure chamber to permit precharging pressurization thereof, extensible fluid cylinder means mounted on said unit and connected to said arm means, said cylinder means having a fluid connection at one end with said atmospheric chamber and having at its other end a second fluid connection with said pressure chamber, a fluid flow control valve in said second fluid connection and a flow restricting regulating valve in said second fluid connection for restricting fluid flow from said other end of said cylinder means to said pressure chamber when said arm means are being lowered by the weight of objects thereon.

2. A unit as set forth in claim 1 further characterized in that said cylinder means comprises a cylinder having a head end and a rod end, and a piston and piston rod slideable in said cylinder, and said one end of said cylinder means is the head end thereof, said cylinder means being arranged so that extension thereof acts to lower said arm means.

3. A unit as defined in claim 1 further characterized in that said flow restricting regulating valve permits free fluid flow from said pressure chamber to said other end of said cylinder means so as not to impede movement of said arm means in the upward swinging direction due to pressure fluid from said pressure chamber passing through said flow control valve to said other end of said cylinder means.

4. A self-contained unloading unit comprising, pivoted arm means mounted on said unit for unloading objects by swinging from an upper position to a lower discharge position;

a precharged fluid power system on said unit and for controlling gravitational lowering of said arm means and objects thereon and for returning said arm means to said upper position, said system including, a fluid tank having a prechargable pressure chamber and also having an atmospheric chamber, a fluid level equalizing valve between said chambers a precharge valve in communication with said pressure chamber, extensible fluid cylinder means mounted on said unit and connected to said arm means, said cylinder means having a fluid connection at one end with said atmospheric chamber and having at its other end a second fluid connection with said pressure chamber, a fluid flow control valve in said second fluid connection and shiftable between closed and open positions, and a flow restricting regulating valve in said second fluid connection and located between said flow control valve and said other end of said cylinder means for restricting fluid flow from said other end of said cylinder means to said pressure chamber when said arm means are being lowered by the weight of objects thereon and said flow control valve is open.