Abstract:
The light-weight live-floor module has a floor surface, parallel cables laid on the floor surface, a length of conveyor belt laid on the cables, a movable bulkhead and a winch system for moving the belt, the cables and the bulkhead back and forth in unison, such as a shuttle. The belt has just enough length to cover the return axis and the floor surface on which goods are transported, thereby reducing any unnecessary weight in the live floor structure. The cables and the belt are wrapped over different axes for eliminating relative movement between the cables and the belt. One axis is set higher than the floor surface for easily breaking static friction under the belt. In a method for breaking static friction between a conveyor belt and a floor surface, a first segment of the belt is jolted upwardly while tension is applied in the belt.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 61/282,065 filed Dec. 10, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to the field of live-bottom trailers, and more particularly it pertains to live-bottom trailers using a conveyor belt that is movable along the floor of the trailer, and cables mounted under the conveyor belt to reduce friction between the conveyor belt and the floor of the trailer. 
       BACKGROUND OF THE INVENTION 
       [0003]    The live-bottom trailers that are of interest herein are used in road construction to haul sand, gravel, rocks, broken pavement and new asphalt. Live-bottom trailers having conveyor belts movable along the floors thereof also include agricultural trailers used for hauling potatoes and other vegetable or grains from a harvester. Known live-floor trailers also include highway transport trailers that are used for transporting dry freight in boxes and on pallets. 
         [0004]    Common live-bottom trailers have a conveyor-type rubber belt sliding over the floor of the trailer for moving the content of the trailer toward the rear door of the trailer and for speeding up the unloading of the trailer. The same conveyor belt is also used for more easily loading the trailer. These highway trailers and semi-trailers can carry several tons of material. 
         [0005]    Examples of these live-bottom trailers found in the prior art are described in the following documents:
   U.S. Pat. No. 3,498,482 issued to M. Lewis on Mar. 3, 1970;   U.S. Pat. No. 3,593,864 issued to W. H. Moser on Jul. 20, 1971;   U.S. Pat. No. 3,704,798 issued to H. L. Carpenture, Jr. et al. on Dec. 5, 1972;   U.S. Pat. No. 3,722,717 issued to L. K. Stryczek on Mar. 27, 1973;   U.S. Pat. No. 3,888,366 issued to E. D. Prahst on Jun. 10, 1975;   U.S. Pat. No. 3,953,170 issued to J. O. Webb on Apr. 27, 1976;   U.S. Pat. No. 3,998,343 issued to V. E. Fors on Dec. 21, 1976;   U.S. Pat. No. 4,162,735 issued to M. Lewis on Jul. 31, 1979;   U.S. Pat. No. 4,431,360 issued to M. Maeno in Feb. 14, 1984;   U.S. Pat. No. 4,518,303 issued to W. H. Moser on May 21, 1985;   U.S. Pat. No. 4,664,583 issued to J. N. Gust on May 12, 1987;   U.S. Pat. No. 4,747,747 issued to S. M. Fusco et al. on May 31, 1988;   U.S. Pat. No. 4,842,471 issued to G. L. Hodgetts on Jun. 27, 1989;   U.S. Pat. No. 6,837,668 issued to D. J. B. Brown on Jan. 4, 2005;   U.S. Pat. No. 7,147,423 issued to R. Golden et al. on Dec. 12, 2006.   
 
         [0021]    In another type of live-bottom trailers, the load inside the trailer is moved on steel cables that are laid along the floor of the trailer. In these applications, a conveyor belt is not used. The cables are pulled along the floor of the trailers by winches or hydraulic cylinders, for carrying the load over the floor surface. Because the total surface of the cables that is in contact with the floor of the trailer is smaller than the footprint of the load to be moved, and because there is a lesser coefficient of friction provided by the cables, the force required to overcome friction is considerably reduced. 
         [0022]    Examples of trailers in the prior art, having parallel cables laid on the floor thereof are listed below:
   U.S. Pat. No. 3,272,358 issued to F. Thompson on Sep. 13, 1966;   U.S. Pat. No. 4,082,196 issued to D. W. Lutz et al. on Apr. 4, 1978;   U.S. Pat. No. 4,111,318 issued to D. E. Lutz on Sep. 5, 1978;   U.S. Pat. No. 4,113,122 issued to D. E. Lutz on Sep. 12, 1978;   WO 87/01996 filed by Luigi Pellegrino, published on Apr. 9, 1987;   U.S. Pat. No. 5,171,122 issued to L. Pellegrino on Dec. 15, 1992.   
 
         [0029]    A number of prior art documents also disclose movable bulkhead arrangements for pushing the content of a trailer all at once toward the rear door of the trailer. These documents are listed herein below for illustrating progress made in the art:
   U.S. Pat. No. 2,606,677 issued to A. E. Snedeger on Aug. 12, 1952;   CA Patent 1,031,735 issued to H. D. Rezac on May 23, 1978;   U.S. Pat. No. 5,143,508 issued to D. E. Lutz et al. on Sep. 1, 1992;   U.S. Pat. No. 5,314,290 issued to D. E. Lutz et al. on May 24, 1994.   
 
         [0034]    The various concepts described in the prior art have a common advantage of emptying a trailer in a more efficient manner. Although the advantages of a conveyor belt; a series of parallel cables moving on the bottom surface of a trailer, and a movable bulkhead are easy to appreciate, a combination of the three elements wherein the cables are used to move both the conveyor belt and the bulkhead, has not been seen in the prior art. This deficiency in the art may be explained by the challenges that this combination represents to designers and builders of these trailers. 
         [0035]    One of the challenges encountered in the design and construction of a live-bottom trailer with floor cables mounted under a conveyor belt is a relative movement between the conveyor belt and the floor cables. This relative movement could causes the gouging of grooves in the bottom surface of the belt and can destroy the belt in a relatively short time. 
         [0036]    Another challenge is a total weight of the combination. Truck owners are oftentimes paid by the ton of material transported. The weight of accessories mounted inside a trailer takes away available space and available cargo weight for that trailer. Therefore the advantages of a live-floor mechanism must have sufficient value to offset the losses in revenue from a reduction of cargo weight for that trailer. 
         [0037]    It is believed that this weight restriction factor, primarily, has been a major impediment in the past for designing and building a live-bottom trailer having a conveyor belt; parallel cables mounted under the belt and a bulkhead that is movable with the belt and cables. 
       SUMMARY OF THE INVENTION 
       [0038]    In the present invention, however, there is provided a light-weight live-floor module that has a floor surface, parallel cables laid on the floor surface, a length of conveyor belt laid on the cables, a movable bulkhead and mounting arrangements that provide an outstanding weight-efficiency ratio. As a result, the tension required to move a load on the belt is provided in great proportion by the cables and in a lesser extent by the belt. 
         [0039]    In the following description of several aspects of the present invention, the scope of the invention should not be limited to a narrow interpretation of the elements described and to the exact parts illustrated in the drawings. Therefore, generic terminology is used herein where ever it is possible without reducing the clarity of the description. The expression “goods-carrying sheet” is used to designate a conveyor belt made of thick rubber with one or more plies; a conveyor belt made of interlinked metal links or mesh, or a belt made of fabric, fibreglass, nylon, webbing, canvas or similar flexible material. Similarly the word “pullers” should be understood as encompassing cables, ropes, strings, flat straps, chains, or other pulling elements having sufficient tensile strength to perform as expected. Also, the expression “return axis” is used to designate a roller, a pulley, a wheel or a static bumper on which a belt or a cable changes direction. 
         [0040]    The expression “light-weight” is used herein because the load carried and pulled on the live-floor module is shared by both the conveyor belt, and to a greater extend, by the cable system. Because the tension in the belt is greatly reduced, the conveyor belt can be much lighter than in other conventional live-bottom trailers. Also the expression “live-floor module” is used herein because its applications are not limited to trailers. The present live-floor module can be used as a base on which a highway transport trailer is built. Similarly, the live-floor module can be used as a base for building straight-frame box trucks, gravel-type semi-trailers, or it can be used as a stand-alone conveyor on docks of warehouses for example for handling material in and out of transport trailers. The live-floor module described herein can also be scaled down for installation in cube vans and pickup trucks. 
         [0041]    In one aspect of the present invention, there is provided a live floor comprising a sheet return axis mounted to an extremity thereof and a goods-carrying sheet having first and second ends. The goods-carrying sheet is wrapped over the sheet return axis, with the first end extending above a plane of the live floor and the second end extending below the aforesaid plane. There is also provided a mechanism connected to the first and second ends for moving the goods-carrying sheet about the sheet return axis for loading and unloading goods on the goods-carrying sheet. 
         [0042]    The goods-carrying sheet has just enough length to cover the sheet return axis and the floor surface on which goods are transported, thereby reducing any unnecessary weight in the live floor structure. As it will be understood, the total length of the goods-carrying sheet is a same dimension or substantially a same dimension as the length of the live-floor module itself. Also the goods-carrying sheet in the live-floor module according to the present invention is made of a thinner and a lighter material than a same arrangement on a live-floor system of the prior art. 
         [0043]    In another aspect of the present invention, there is provided a live-floor module comprising first and second spaced-apart return axes mounted side-by-side on an extremity thereof. A series of parallel pullers are laid on a surface of the live-floor module; and a goods-carrying sheet is laid on the parallel pullers. The pullers are affixed at their ends to extremities of the goods-carrying sheet. The pullers are wrapped over the first return axis and the goods-carrying sheet is wrapped over the second return axis. This arrangement is advantageous for eliminating relative movement between the goods-carrying sheet and the parallel pullers when the goods-carrying sheet and the parallel pullers move around the extremity of the live-floor module. 
         [0044]    In yet another aspect of the present invention, there is provided a live-floor module comprising a floor surface; a roller mounted on an extremity of the floor surface; a series of parallel pullers laid on the floor surface, and a goods-carrying sheet laid on the parallel pullers. The pullers are affixed at their ends to extremities of the goods-carrying sheet. The pullers and the goods-carrying sheet are wrapped over the roller and the roller is mounted higher than the floor surface. When tension is applied to the pullers and to the goods-carrying sheet, the goods-carrying sheet is forced upwardly near the roller to break static friction between the goods-carrying sheet and the floor surface near the roller. 
         [0045]    Yet in a further aspect of the present invention, there is provided a method for breaking static friction between a goods-carrying sheet and a floor surface. This method comprises the steps of jolting a first segment of the goods-carrying sheet upwardly, and simultaneously applying a tension in the goods-carrying sheet. Because the goods-carrying sheet and the pullers have some elasticity, the jolting movement mentioned above and the simultaneous tension in the goods-carrying sheet, set a longitudinal vibration that is propagated along the goods-carrying sheet to break static friction along the goods-carrying sheet and the floor surface. 
         [0046]    The upward jolt breaks the static friction under the first segment of the goods-carrying sheet. The longitudinal tension between the first segment of the goods-carrying sheet and the floor surface is suddenly released. This tension is applied to a next segment which also causes static friction to break under that second segment, and so on until the entire goods-carrying sheet is set in motion. This phenomenon works equally well with goods-carrying sheets loaded with gravel or dry freight. Because of this initial upward jolt in the first segment of the goods-carrying sheet, the breaking of the static friction is effected in a peeling-like action with less force and less work than in the live-floors of the prior art. 
         [0047]    This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0048]    One embodiment of a light-weight live-floor module is illustrated in the attached drawings. In these drawings the same numerals are used to identify the same elements. In the drawings; 
           [0049]      FIG. 1  illustrates a partial side, top and rear-end perspective view of the live-floor module according to the preferred embodiment of the present invention; 
           [0050]      FIG. 2  is a partial side, top and front-end perspective view of the basic structure of the live-floor module according to the preferred embodiment of the present invention; 
           [0051]      FIG. 3  is a top view of the winch system for pulling the cables and draw bar assemblies along the preferred live-floor module; 
           [0052]      FIG. 4  is a partial longitudinal cross-section view of the basic structure of the preferred live-floor module, as seen substantially along line  4 - 4  in  FIG. 2 ; 
           [0053]      FIG. 5  is a partial transverse cross-section view of the live-floor module, as seen substantially along line  5 - 5  in  FIG. 1 ; 
           [0054]      FIG. 6  is a cross-section view through the discharge end of the live-floor module as seen along line- 6 - 6  in  FIG. 1 ; 
           [0055]      FIG. 7  is a graph illustrating the forces affecting the movement of the conveyor belt in the preferred live-floor module; 
           [0056]      FIGS. 8 ,  9 , and  10 , are illustrations of other types of pullers that can be used under the conveyor belt in replacement of the floor cables in the preferred live-floor module. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0057]    While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will be described in details herein one specific embodiment of a light-weight live-floor module for use in trailers and warehouses. It should be understood that the present disclosure is to be considered as one example of the principles of the invention and is not intended to limit the invention to the embodiment illustrated and described. 
         [0058]    Referring firstly to  FIG. 1 , the preferred light-weight live-floor module  20  has a base  22 , two side walls  24 ,  26 , and a movable bulkhead  28 . A live-floor system, generally designated as label  30  is incorporated into the base  22 . In use, a load (not shown) is placed on the live-floor system  30  between the side walls  24 ,  26  and the bulkhead  28 . A winch system  32  is mounted at the front end of the base  22  and it is used for moving the bulkhead  28  and the live floor toward the discharge end of the trailer and back. 
         [0059]    In the illustration of  FIG. 1 , the bulkhead  28  is shown in an intermediate position along its trajectory. It should be understood that the bulkhead  28  can be retracted close to the winch system  32  such that the cargo space available between the side walls  24 ,  26  is a large as possible. In use, the bulkhead  28  is movable to the discharge end of the live-floor module  20  and back such as a shuttle. 
         [0060]    It will be appreciated that the live-floor module  20  illustrated in the drawings can be equipped with an undercarriage of a semi-trailer or a transport trailer for example for hauling gravel or packaged freight. The live floor module  20  can also be mounted on a stationary support frame for use in a warehouse. 
         [0061]    Referring now to  FIGS. 1-6 , additional structural details of the preferred live-floor system  30  will be explained. 
         [0062]    The preferred live-floor system  30  comprises a plurality of spaced-apart parallel floor cables  34  that are attached at their ends to an upper draw bar  36  and to a lower draw bar  38  respectively. The attachment of the floor cables  34  to the draw bars  36 ,  38  is preferably done using crimped-on clevis and turnbuckle (not shown), but can also be done using other clamps and tighteners known in the field of cable ferrules and hardware. 
         [0063]    The floor cables  34  are drawn tight between the draw bars  36 ,  38  and over respective return sheaves  40  at the discharge end of the base  22 . 
         [0064]    A length of conveyor belt  50  is drawn tight over the floor cables  34 . The length of conveyor belt  50  is attached at its ends to the upper draw bar  36  and to the lower draw bar  38 , respectively. The conveyor belt  50  is stretched over a return roller  52  at the discharge end of the base  22 . The length of conveyor belt  50  is also movable back and forth with the bulkhead  28  such as a shuttle. 
         [0065]    The floor cables  34  are supported directly over a hard floor surface  54 , such as hardwood or most commonly, metal plates. The conveyor belt  50  is supported in a large portion by the floor cables  34 . Preferably, the hard floor surface  54  has rails  56  encased therein under each floor cable  34 . These rails  56  are made of a low friction material such as Teflon™. These rails  56  will be described again later when making reference to  FIGS. 8-10 . 
         [0066]    It will be appreciated that when a load of dry goods on pallets is carried on the live-floor module  20 , that load is supported entirely by the floor cables  34 . When a load of gravel or other similar aggregate material is supported on the conveyor belt  50 , the conveyor belt flexes and therefore, the belt is supported partly by the floor cables  34  and partly by the hard floor surface  54 . 
         [0067]    Referring now to  FIGS. 2 ,  3  and  4 , the winch system  32  of the live-floor module  20  and other structural details will be explained. 
         [0068]    Firstly, the bulkhead  28  is attached to the upper draw bar  36 . The upper portion of the bulkhead  28  has two saddle members  60  that are movably mounted over upper longitudinal rails  62  on the side walls  24 ,  26 , respectively. These saddle members  60  are fastened to a pair of guide cables  64 ,  66  by crimp-type connectors  68  for example. Each one of the guide cables  64 ,  66  extends around a respective one of the walls  24 ,  26 , on sheaves  70  at each corner of the walls. The guide cables  64 ,  66  form closed loops and are also fastened by crimp-type connectors  68  or otherwise to the lower draw bar  38  for movement with the lower draw bar  38 . 
         [0069]    A displacement of the lower draw bar  38  entrains a similar movement of the saddle members  60  and the bulkhead  28  in the opposite direction. Because the bulkhead  28  is driven by the upper draw bar  36  at its lower end and it is driven by the guide cables  64 ,  66  at its top end, excessive strength in its structure is not required. The bulkhead  28  needs only to be made of relatively small structural members such that its weight is relatively light as compared to conventional bulkheads in trailers of the prior art. Also, the bulkhead  28  needs not to be guided in T-slots or otherwise in the base  22  of the live-floor system  30 . Its attachments to the upper draw bar  36  and to the upper rails  62  are sufficient to fulfill its purpose. 
         [0070]    The base  22  of the live-floor system  20  is made of structural steel and has a passage “P” extending horizontally along its length. The return portion of the conveyor belt  50  and floor cables  34  extend along this passage “P”, as can be seen in  FIGS. 4 and 6 . 
         [0071]    The base  22  has upper cross members  80  extending across the upper portion thereof, and lower cross members  82  extending across the lower portion thereof. The base  22  has a gap between the upper cross members  80  and the lower cross members  82 . This gap defines the passage “P”. Other framing members are included in the base  22  to strengthen the base  22  against bending, twisting and skewing. These additional framing members have not been illustrated herein because they do not represent the focus of the present invention. 
         [0072]    Because of the passage “P” and the mounting of the conveyor belt  50  and the lower draw bar  38  along this passage “P”, the preferred live-floor module  20  is compact in thickness. The preferred live-floor module  20  is thereby usable as a modular floor for trucks. It is usable as an add-on floor that can be strapped onto a sub-floor and taken out when needed, or it can be used as a stand alone unit on a loading dock of a warehouse for example. It will also be appreciated that the preferred live-floor module  20  can be used without the bulkhead  28 , or without the side walls  24 ,  26 , or without both the bulkhead and side walls to handle dry goods on pallets for example. 
         [0073]    The winch system  32  is illustrated in greater details in  FIG. 3 . The winch system  32  is also built for strength and light weight. The winch system  32  has two pulley systems mounted in tandem and each giving a mechanical advantage. 
         [0074]    A first pulley system comprises a first pulley  92  mounted to the upper draw bar  36  and a second pulley  94  mounted to the lower draw bar  38 . A first winch cable  96  has an end segment  98  tied to a shock absorber  100  that is mounted to a cross member  102  on the base  22 . A second segment  104  which is continuous with the end segment  98  extends around the first pulley  92 , and to the winch drum  90 . It is wrapped several turns  106  around the winch drum  90 . A third segment  108  continuous with the second segment  104  extends from the turns  106  on the winch drum  90  to the second pulley  94  mounted on the lower draw bar  38 . A fourth segment  110  continuous with the third segment  108  extends around the second pulley  94  and through to the cross member  102  to a second shock absorber  112  that is mounted to the cross member  102 . 
         [0075]    The second pulley system is a mirror image of the first one, and therefore, it is illustrated using the same labels as in the first pulley system but with a prime symbol on each label. 
         [0076]    Because there are two pulley systems mounted in tandem and each is giving a mechanical advantage, the components of the winch system  32  are smaller and lighter in weight than other winch system where a single cable arrangement would have been used. 
         [0077]    Referring now to  FIGS. 6 and 7 , two important aspects of the preferred live-floor module  20  will be explained. Firstly, the discharge end of the live-floor module  20  has a series of cable return pulleys  40  mounted along a same axis, and a belt return roll  52  that is mounted on a different axis than the series of cable return pulleys  40 . The series of pulleys  40  and the roll  52  are also referred to herein in a broader sense as return axes. 
         [0078]    The reason for this mounting using separate roll and pulley axes is to avoid damaging the underside of the belt by a relative movement and associated friction between the floor cables  34  and the underside of the conveyor belt  50 . It will be appreciated that such damage would occur if a same axis would have been used. 
         [0079]    Secondly, the upper segments of the cable-return pulleys  40  are set slightly higher than the floor surface  54  of the live-floor system  30 . The cable-return pulleys  40  are set higher by a dimension “H” as illustrated in  FIG. 6 . A dimension “H” of about one half inch is sufficient for the intended purpose. 
         [0080]    When tension is applied all at once in the floor cables  34  by the winch system  32  and by the lower draw bar  38 , these floor cables  34  straighten up in a snap and cause a first segment “S 1 ” of the conveyor belt  50  to be jolted upward. This sudden upward jolt has the effect of breaking static friction between the conveyor belt  50  and the floor surface  54  along at least the length of belt segment “S 1 ”. The segments “S 1 ”; “S 2 ”; “S 3 ”; etc, as illustrated in the drawings are not drawn to scale, and are used simply to facilitate the description of a phenomenon that occurs in the live-floor module  20  in use. 
         [0081]    It is important to indicate again that the conveyor belt  50  is under the same tension as in the floor cables  34  because of common attachments of the floor cables  34  and the conveyor belt  50  to the upper and lower draw bars  36 ,  38 . It is also important to understand that both the conveyor belt  50  and the floor cables  34  have a substantial yield strength and elasticity. The presence of the cables  34  ensures that both the cables  34  and the conveyor belt  50  are not stretched beyond their respective elastic limit or yield strength, when an unloading phase of the live-floor module  20  is initiated. 
         [0082]    In order to facilitate the following explanation, the horizontal tension in the conveyor belt  50  and in the floor cables  34  is represented by the bar-code-like symbols  120  in  FIG. 7 . The upward jolt given to the first segment “S 1 ” of the conveyor belt  50  by the floor cables  34  is represented by the curve  122  in  FIG. 7 . 
         [0083]    When the conveyor belt  50  is loaded with gravel for example, the upward jolt  122  given to the conveyor belt  50 . by  the floor cables  34  is quickly dampened as illustrated in  FIG. 7 . However, this upward jolt  122  and associated tension  120  in the floor cables  34  and in the conveyor belt  50  cause static friction under at least the first segment “S 1 ” to be broken. Because kinetic friction is less than static friction, a large portion of the tension  120  in the conveyor belt  50  and in the floor cables  34  is then suddenly released from segment “S 1 ” and applied to a next segment “S 2 ”. 
         [0084]    The upward jolt  122  applied against the first segment “S 1 ” is generated in a snap and the static friction under the first segment “S 1 ” is also broken in a snap. The release of the static friction under the first segment “S 1 ” generates a horizontal shock wave along the conveyor belt  50  that progressively moves as a flash along the conveyor belt  50 . 
         [0085]    Although the upward jolt  122  is quickly dampened by a load of aggregate material, the resulting horizontal shock wave  120  is only reduced by a difference between static and kinetic friction. As a result, static friction under the conveyor belt  50  is broken in a peeling motion without using great force in the conveyor belt  50 . The conveyor belt  50  used in the preferred live-floor module  20  is thinner and lighter in weight than the conveyor belts in other live-floor modules not having floor cables thereunder. 
         [0086]    Because the weight of a live-floor module is greatly affected by the thickness of the conveyor belt, a reduction in the belt thickness has a large effect on the total weight of the entire live-floor module. Because of the relatively low stress requirement in the conveyor belt  50 , because of the lighter winch  32  and the light-framed bulkhead  28 , it is estimated that a reduction in weight of 5,000-6,000 lbs., is achievable with the preferred live-floor module  20  as compared to live-floors of the prior art. 
         [0087]    Another aspect of the preferred light-weight live-floor module  20  is explained in  FIGS. 8 ,  9  and  10 . Although the preferred live-floor module  20  has floor cables  34  that can be interpreted as being circular braided steel cables, it can be appreciated that equivalents pullers can be used to obtain similar advantages as the floor cables  34 . Some of these equivalent pullers are flat straps  126  made of metal or plastic material, as shown in  FIG. 9  or power-transmission chains  128  as shown in  FIG. 10 . 
         [0088]    Other equivalents for other components are also possible and therefore, the components, dimensions mentioned herein and the accompanying illustrations should not be considered as limitation in the present invention.