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United States Patent Application 20170029216
Kind Code A1
Jackson; Daniel W. ;   et al. February 2, 2017

All-Steel Reciprocating Floor Slat System


A roll-formed steel slat for use in a reciprocating floor slat conveyor system. The roll-formed steel slat is formed in a manner so as to have an upper, load-carrying surface, and a pair of downwardly depending side legs. Each side leg terminates in a foot. One foot is vertically offset from the other to provide a "hold-down" function that prevents the slat from vertically rising as the slat reciprocates back-and-forth.

Inventors: Jackson; Daniel W.; (Madras, OR) ; Foster; Randall Mark; (Madras, OR) ; Keeley; Nathan; (Madras, OR) ; Matthews; Victor; (Madras, OR) ; Delamarter; Scott; (Madras, OR)
Name City State Country Type

Keith Manufacturing Co.



Assignee: Keith Manufacturing Co.

Family ID: 1000002254617
Appl. No.: 15/224196
Filed: July 29, 2016

Related U.S. Patent Documents

Application NumberFiling DatePatent Number
62198596Jul 29, 2015

Current U.S. Class: 1/1
Current CPC Class: B65G 25/065 20130101
International Class: B65G 25/06 20060101 B65G025/06


1. A roll formed steel slat for use in a reciprocating floor slat conveyor system, comprising a slat formed from a strip of steel, the slat being formed to have at least an upper load carrying surface and a pair of side legs, with one side leg on each lateral side of the upper load carrying surface, and with the side legs depending downwardly and inwardly relative to the upper load carrying surface, and further, with each side leg terminating in a laterally inwardly directed foot portion, and with the foot portion of one side leg being vertically offset relative to the foot portion of the other side leg.


[0001] The present disclosure relates to reciprocating floor slat conveyor systems.


[0002] Reciprocating floor slat conveyor systems are well-known. These systems are often built into the floors of truck trailers that haul materials in bulk.

[0003] The typical reciprocating floor slat conveyor system consists of multiple, bearing mounted, parallel floor slats that are driven back-and-forth in a reciprocating action. The action or motion of the floor slats are typically driven in "stages" as follows: First, in the case of truck trailers, all of the slats are moved in one direction, at the same time. This stage moves the load on the floor a short distance toward the exit end of the trailer. Then, a lesser number of slats are retracted, or returned, in the opposite direction (typically, in stages of one-third of the slats at a time). Because of the fewer number of moving slats involved in the return stage, the greater total friction between the load and the larger number of nonmoving slats allows the moving slats in the return stage to slide underneath the load, without moving the load backward.

[0004] Returning one-third of the slats at a time, in three separate return stages, brings all of the slats to the original start position, with the load staying in place during the return stages. Once all of the slats return, then the sequence repeats itself, with all of the slats moving, once again, toward the exit end of the trailer. This, in turn, also moves the load another short distance toward and out from the exit end of the trailer. Repetitive cycling of the slats in stages in the manner just described causes the load to be inched out from the trailer.

[0005] There is a specialized market for conveyors like the above. These systems have become a substitute for and have replaced hydraulic dump lifts for certain kinds of applications. From the standpoint of historical development, these kinds of conveyors may have been initially developed to haul bulk silage for cattle feed and similar kinds of bulk materials. Since then, they have been adapted for many other uses, such as the garbage hauling markets; and certain kinds of specialized designs have been developed that allow trucks with these conveyors to haul rock, gravel, or asphalt.

[0006] As a consequence of different market needs, many different kinds of floor slat configurations have been designed over the years to adapt reciprocating floor slat conveyors to different hauling scenarios. The floor slats themselves are usually made from aluminum, for reasons relating to weight (i.e., light weight systems are desirable for truck trailers), and due to manufacturing and installation considerations. Long lengths are required for a typical floor slat (generally corresponding to the length of a trailer). Aluminum slats can be mass produced by extrusion.

[0007] For reasons relating to the abrasive wear caused by certain kinds of loads, there has been a need to develop a successful steel floor slat system in lieu of aluminum slats. Steel slats have been used in the past in combination with aluminum slat parts. For example, spaced-apart, inverted "V"-shaped reciprocating slats have been made of steel and used in combination with spaced-apart "fixed" slats made of aluminum. This system has been used to haul certain kinds of heavy bulk material that create loading impacts and abrasive wear on the moving slats--large rock would be an example. In this design, the "moving" steel slats provide better wear characteristics for the load-carrying surfaces. They are spaced from each other a certain distance and ride on bearings that are supported by the underlying "fixed" aluminum slats. This design, as a whole, creates peaks and valleys from one side of the trailer to the other side, which is a function of the "V" shape.

[0008] The use of steel in the "V" configuration is a better design relative to all-aluminum systems for certain kinds of specialized hauling applications. However, although the design works well for certain hauling applications, it does not provide a conveyor floor surface that can be driven on with a forklift. This is a drawback that limits the use of trailers that have this type of floor configuration. In other words, the trailer tends to be used "one way" and is empty on the return.

[0009] Truck haulers would like a "steel" floor slat system that can handle the specialized loads carried by a "V"-shaped steel slat system, but one that also provides a flat conveyor floor surface, from side-to-side, so that a forklift can be driven onto the trailer's floor when empty. This would allow the same trailer to be used to haul heavy bulk materials in one direction, but after unloading, the trailer can be loaded by a forklift in a conventional way with palletized loads, if desired. This is more utilitarian and allows the trailer to be used to generate revenue on the back-haul, rather than come back empty.

[0010] For the above reason, and others discussed below, there has been a long felt need for an "all steel" reciprocating floor system that can provide multiple uses. Because of the difficulty of manufacturing a suitable steel slat system, as of yet, the reciprocating floor slat industry has been unable to create a commercially viable "all-steel" floor slat design that can provide a flat, driveable surface inside the trailer.

[0011] The foregoing and other features will be better understood upon review of the drawings and description that follows.


[0012] The several embodiments described and illustrated in this specification include a roll-formed slat that may provide a load-carrying surface, or in the alternative, may have an additional strip of hardened steel attached above the roll-formed slat that provides the load bearing surface. Regardless, the roll-formed steel slat is intended to be used in a reciprocating floor slat conveyor system.

[0013] The roll-formed slat is formed from a strip of steel via a roll-forming process. The slat is formed to have at least an upper load-carrying surface, or upper surface portion, as well as a pair of side legs, one on each side of the upper load-carrying surface. Each side leg depends downwardly and laterally inwardly relative to the upper load-carrying surface. Each side leg also terminates in the shape or form of a laterally inwardly directed foot portion.

[0014] The foot portion of one side leg is vertically offset relative to the foot portion of the other side leg, in order to create a "hold-down" function relative to supporting bearings. The supporting bearings provide slidable support surfaces for back-and-forth reciprocating movement of the slat.

[0015] The purpose of the "hold-down" function is to allow the slat to capture a bearing edge in a manner so that the floor slat cannot rise substantially while the slat reciprocates. The purpose of the "hold-down" function is to impede bulk materials, making up the load (which is a typical use of reciprocating conveyors), from working downward and between different reciprocating slats. One foot portion might provide a "hold-down" function while the other foot portion (which can be vertically offset below the other one) may provide a supporting function, although design variables may dictate different arrangements.

[0016] The above summary is not intended to limit the claiming of different embodiments described herein.


[0017] In the drawings, like reference numerals and letters refer to like parts throughout the various views, and wherein:

[0018] FIG. 1 is a cross-section of an all-steel floor slat system;

[0019] FIG. 2 is a view similar to FIG. 1, but shows a different embodiment;

[0020] FIG. 3 is a view similar to FIGS. 1 and 2, but without showing any detail on the specific construction of slat bearings;

[0021] FIG. 4 illustrates a series of different slat constructions for an all-steel conveyor;

[0022] FIG. 5 is an enlarged view of one of the slat constructions in FIG. 4;

[0023] FIG. 6 is a view like FIG. 5, but shows a lateral slat seal on one side of the slat;

[0024] FIG. 7 is a view similar to FIGS. 5 and 6, but shows the slat on a bearing;

[0025] FIG. 8 is a view similar to FIG. 6, but shows two slats side-by-side;

[0026] FIG. 9 is similar to FIG. 8, but shows the slats with bearings;

[0027] FIG. 10 is an enlarged sectional view of another one of the slat configurations shown in FIG. 4;

[0028] FIG. 11 is similar to FIG. 10, but shows the FIG. 10 slat with a lateral seal;

[0029] FIG. 12 is similar to FIGS. 10 and 11, but shows the slat on a bearing; and

[0030] FIG. 13 is a view similar to FIG. 12, but shows two slats together, mounted side-by-side.


[0031] Referring to the drawings, and first to FIG. 1, shown generally at 10 is an improved "all-steel" floor slat system. The system 10 shown in FIG. 1 (and other figures) consists of a series of floor slats, indicated generally at 14 (further described below), that are positioned side-by-side from one side (typically a trailer wall) of the conveyor to the other side.

[0032] Referring to FIG. 3, for example, arrow 10 illustrates the general location of the conveyor system relative to one wall 12, labeled as "steel wall." The wall 12 could be a side-wall of a trailer or some other equivalent configuration. Trailer widths are typically about 96 inches, although the width can be a variable.

[0033] Returning to FIG. 1, each individual slat configuration 14 shown in the Figure consists of a flat or top slat portion that is made of a flat strip of steel (indicated generally by arrow 15); and a lower slat portion, also made of a strip of steel (indicated generally by arrow 16). Unlike the top slat portion 15, the lower slat portion 16 is roll-formed into the desired cross-sectional shape, as shown. Roll-forming is important to the design and is further discussed below.

[0034] The top slat portion 15 (or "top slat") provides the load bearing surface. It can be made from a strip of hardened steel, such as steel that is marketed under Hardox.TM. or Domex.TM. trademarks. As just mentioned, the top slat 15 is not roll-formed and, as can be seen in FIGS. 1-3, all of the top slats 15 collectively create a flat, load-bearing surface across the side-to-side width of the conveyor system. This configuration allows the system to carry heavy bulk materials such as glass. Once empty, a forklift can be driven onto it, to load pallets on the floor, if desired.

[0035] Each top slat 15 is suitably connected to the lower slat portion 16. The connection between the two slat portions 15, 16 can be made in many different ways, i.e., by spot welding, rivets, bolts, or other fasteners. An adhesive connection may also be possible. The point is: the top slat 15 provides a hardened steel surface that is connected to the lower slat portion 16 by any viable means that can make the needed structural connection.

[0036] The lower slat portion 16 is also made of steel, but it is a "milder" form of steel that can be roll-formed. "Mild" steel is a known term of art.

[0037] FIG. 1 illustrates one version of the lower slat portion 16. There, the lower slat portion 16 has an upper horizontal surface 18 that is in contact with the lower horizontal surface 20 of the top slat 15 (see left-hand slat 14 in FIG. 1). The interface between these two surfaces 18, 20, is the point where the two slat portions 15, 16 are connected, as described above. The lower slat portion 16 also has downwardly and inwardly depending legs 22, 24, one on each side, that extend down to inwardly directed, lateral "feet" 26, 28 (see central slat 14 in FIG. 2).

[0038] The lower slat portion 16 is made from a single strip of mild steel that is dimensioned to be bent into the configuration shown in FIG. 1 (other configurations are discussed below). During the roll-forming process, the lower slat portion 16 is bent at 30, 32, 34, 36 into the shape shown in FIG. 1 (see the right-hand side of the Figure).

[0039] The slat configuration(s) 14 (i.e., the combination of portions 15 and 16) reciprocate back and forth on a bearing (indicated generally by arrow 46) with the inside surface 48 of the lower slat portion 16 riding on the top horizontal surface 50 of the bearing (see right-hand slat 14 in FIG. 2). The bearing 46 is made of conventional plastic materials of the kind that are used in reciprocating floor conveyor systems. The bearing 46 is typically designed to be load-supporting. However, for the all-steel system described here, the bearing also needs to provide a "hold-down" function and prevent "lift" of the slat 14 relative to others. This is further described below.

[0040] In the embodiment in FIG. 1, the lower slat portion 16 is roll-formed so that one of the slat feet 26 will be vertically offset (higher) relative to the other one 28 (see central slat 14 in the Figure). In FIG. 1, the left-hand slat foot 26 is shown in sliding contact with a lower lateral edge 44 of the bearing 46. The lateral edge 44 of the bearing 46 "holds down" the lower slat portion 16 and thereby prevents it from lifting upwardly, as the combination of top slat 15 and lower slat portion 16 reciprocate on the bearing 46.

[0041] It is to be appreciated that it is desired to have bearing edge 44 in close sliding contact with slat foot 26, with no gap or "slop" between the two surfaces. It is likely that the shape or angles of these surfaces will be made so that there is resistance to any upward movement when these components are installed. Moreover, it may be preferred to design bearing 46 so that is causes positive hold-down forces on each slat 14. In other words, "positive" hold-down" means that the slat and bearing combination are assembled to minimize upward movement of the slat as it reciprocates.

[0042] On the other lateral side of the lower slat portion 16, the foot 28 rests on a lower bearing flange 52. As can be seen, in this specific embodiment, there is no hold-down function because of a gap 54 (see general arrow 54 vis-a-vis the right-hand slat configuration 14 in FIG. 1) between the foot 28 and a horizontal surface 56 on the other lateral side of bearing 46. In this example, the offset allows the lower foot 28 to rest upon the bearing in a supporting relationship, rather than a "hold-down" relationship. The advantage is that the right-hand foot can be used to shift weight support from the bearing to underlying support structure (not shown).

[0043] It is to be appreciated, at this point, that the "all-steel" nature of the design disclosed here provides certain advantages over aluminum slats. One advantage is that roll-forming allows the lower slat portions 16 to have a uniform wall thickness (indicated generally by arrows 38 in FIGS. 1, 2, and 5-13) following the edge-to-edge contours of the lower slat portion 16 (i.e., from edge 40 of one slat foot 26 to the edge 42 of the other slat foot 28).

[0044] Steel also has a lower coefficient of friction, which means it should be easier to drive a steel slat back and forth on a bearing surface relative to a similar part that is made from aluminum. This provides efficiencies in that less power may be required to drive a bearing-mounted "all-steel" slat.

[0045] Steel slats also have a better degree of wear when one steel surface is sliding against another. With respect to this point, and referring now to the right-hand side of FIG. 2, each top slat portion 15 has an outer lateral edge 58 that extends over a gap 60, between slat configurations 14, and rides on the outer edge 62 of the upper surface 18 of the lower slat portion 16 (see left-hand side of FIG. 2).

[0046] Referring now to the right-hand side of FIG. 2, the interface (general arrow 64) of items 58, 62 creates an area of sliding contact that might not be practical using aluminum, for reasons relating to wear. The load on the top slat portion 15 normally presses edge 58 down onto surface 62 with the pressure of the load causing a sliding/sealing action between adjacent lateral slat configurations. Although the precise dimensions have not yet been determined, it is believed it is best to have as little overlap between surfaces 58 and 62 as possible. In other words, it is desirable to minimize the sliding contact surface in the region indicated by arrow 64.

[0047] FIG. 2 illustrates an alternative embodiment where the feet 26, 28 of the lower slat portion 16 are not offset relative to each other. In other words, the horizontal bearing surfaces 44, 56 both provide a "hold-down" function on opposite lateral sides of the bearing.

[0048] Before moving on to the other slat configurations illustrated in the drawings, it is worthwhile to discuss the roll-forming tooling needed to create the slats. Roll-forming enables slat profiles to be made out of steel, in the forms illustrated in FIGS. 1-13, and in particular, in various forms like the ones illustrated in FIG. 4.

[0049] FIG. 5 is particularly unique because it illustrates an alternative, "one strip" slat configuration 65 that may stand alone (i.e., without the "hard" top slats 15 previously described). In other words, FIG. 5 illustrates an "all steel" floor slat that is roll-formed from a single strip of steel, with top surface 67 carrying the load. In this specific configuration, one side leg 22 can be roll-formed to have the folded side edge or side configuration that is indicated generally at 66. The folded edge provides a rounded or blunted side edge 68 for sliding or near-sliding contact with an adjacent slat 72 (see FIG. 8).

[0050] Referring again to FIG. 5, roll-forming also enables a circular recess 70 to be bent length-wise into the slat's side 22. The recess 70 would extend laterally along the length of the slat 65. The recess 70 is shaped to receive a lateral seal 74 that closes the gap 76 (see FIG. 8) between slats. An advantage to roll-forming is that the vertical position of the recess 70 is easy to adjust relative to the vertical height of side leg 22.

[0051] Using roll-forming, the configuration illustrated in the various Figs. can be made from relatively thin strips of mild steel (i.e., 16 or 18 gauge). The inner edges 78, 80 of the lateral feet 26, 28 may also be suitable for folding, in the manner illustrated in FIGS. 5-9. This may allow the lateral feet 26, 28 to function better with the type of bearing illustrated in the figures for performing either the hold-down or supporting functions described above. For example, folding the edges 78, 80, as shown, may be an improved way to attach the slat to the bearing 46. In other words, and while it is not illustrated in FIGS. 1 and 2, specifically, the folded edges 78,80, may be a better way of avoiding steel-to-plastic wear in the embodiments shown in FIGS. 1 and 2, where the feet slide back and forth against the underside of the bearing.

[0052] The slats illustrated in FIGS. 5-13 are different from the embodiments of FIGS. 1-3 in that the slat embodiments in FIGS. 5-13 do not require the "hold-down" effect or function described above. However, it is to be appreciated that the type of bends and folds illustrated in FIGS. 5-13 could be applied to the lower slat portions 16 in FIGS. 1-3. The point is: roll-forming allows uniformly thin strips of steel to be shaped in different ways for reciprocating slats in a floor conveyor.

[0053] With respect to the steel recess 70 described above, in particular, aluminum slats have been made with integrated seal recesses that are similar in shape and function. However, the aluminum slats are extruded and have required non-uniform material thickness in certain areas of the slat. This is believed to be an issue in the region of the recess. With roll-formed steel slats, wall thickness remains the same through the various bends that are created during the roll-forming process.

[0054] Roll-forming also enables slat profiles to be made out of steel in various cross-sectional configurations, as illustrated at 82, 84, 86, 88, 90 in the lower half of FIG. 4. Although steel weighs more than aluminum, the roll-forming process enables the wall thickness to be much less than thicknesses required by aluminum (e.g., the 16 and 18 gauge steel thicknesses discussed above), thereby reducing the total weight of the steel while still taking advantage of the better strength and wear qualities of steel versus aluminum.

[0055] Typically, roll-forming is a continuous bending operation that involves passing a long strip of steel through sets of rollers in a continuous line, with different sets incrementally making part of a bend, until the final cross-sectional shape is achieved. This allows for optimizing strip thickness while creating the variety of cross-sectional profiles disclosed here, although different profiles require a dedicated set of roll tools to create the desired final shape.

[0056] The design of the rolls may start with what is called a "flower pattern" that defines a sequence of sections of the final cross-section, each section corresponding to roll sets for making the desired bend. It is not believed that anyone in the reciprocating floor conveyor industry has conceived of the idea of using roll sets and roll-forming as a method of manufacturing an all-steel floor slat system.

[0057] FIGS. 10-13 illustrate yet another slat configuration that corresponds to the slat configuration illustrated at 92 in FIG. 4. The primary difference between configuration 92 and 65 is that the folded edge 68 (initially described relative to slat 65 in FIG. 5) is blunted, as shown at 94.

[0058] The foregoing description is not intended to limit the scope of patent coverage. The scope of patent coverage is to be limited only by the patent claims allowed by the customs of local law, the interpretation of which is to be made in accordance with the doctrines of patent claim interpretation for the applicable jurisdiction.

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