Patent Publication Number: US-2022219270-A1

Title: Grid-type workpiece carrier

Description:
The invention relates to a grid-type workpiece carrier having grid elements that intersect one another and have notches engaging in one another so that they form a grid. 
     Workpiece carriers are used to prepare and retain one or more workpieces in order to process them in a fabrication station. As examples, the processing may comprise hardening, cleaning, transport, heat treatment or sintering. One simple embodiment of a workpiece carrier is a substantially rectangular plate having supports and/or retainers for one or more workpieces. 
     A grid-type workpiece carrier, as shown in DE 10 2009 037 293 A1 for example, is stable, material-saving and weight-saving, and permits access to the workpiece from several sides. Such a grid-type workpiece carrier may be made from plank-like carbon or ceramic grid elements that engage in one another. 
     The stated task is to provide an alternative grid-type workpiece carrier. 
     The task is accomplished by a workpiece carrier having the features of claim  1 . 
     The grid-type workpiece carrier comprises a multiplicity of plank-like first grid elements disposed in parallel and having notches, and a multiplicity of plank-like second grid elements disposed transversely thereto and having notches. The notches of the first and second grid elements have the form of slits, for example, and engage in one another in such a way that the first and second grid elements intersecting one another form a grid. A mechanically secure fixation of the first grid elements takes place only at some of the second grid elements disposed transversely to them. These second grid elements, on which the first grid elements are mechanically securely fixed, are located on opposite sides of the grid in a peripheral region of the grid. 
     In other words: The second grid elements beyond the peripheral region do not have to be joined mechanically securely to the first grid elements, but instead are retained in their place by the first grid elements engaging from above and below. The second grid elements beyond the peripheral region have, both on the upper side and on the underside of the grid, notches in which the intersecting first grid elements engage and thus retain the second grid elements in their position. 
     In such a grid, the first grid elements may be disposed in longitudinal (long) direction and the second grid elements in transverse (cross) direction or vice versa relative to them. 
     The workpiece carrier may be used for various fabrication steps, such as hardening, cleaning and transport. 
     Advantageously, the second grid elements on which the first grid elements are fixed mechanically securely are the outer grid elements on opposite sides of the grid. This permits a simple fixation on the readily accessible outer sides of the grid. 
     In one embodiment, the first and second grid elements are metals, which permits their simple fabrication as well as the formation of a stable grid and welding as the fixation technique. Steel, which permits the use of the workpiece carrier at up to 1200 degrees Celsius, for example, may be considered as the metal. 
     Furthermore, due to the use of this material, the workpiece carrier is resistant to emulsions and oils. Since steel can be easily machined, the workpiece carrier can be adapted in simple manner to various workpieces. A workpiece carrier adapted to the needs may be made in simple manner from prefabricated grid elements. 
     The mechanically secure fixation is a fixation of points of intersection of grid elements engaging in one another together with use of a fixation means, which extends beyond the mere engagement of the grid elements in one another. In one embodiment, the mechanically secure fixation is a substance-to-substance bond; for example, the mechanically secure fixation may be a welded joint, especially a spot-welded joint, or an adhesive bond. These fixation systems are stable and easy to make. In one embodiment, a substance-to-substance bond is used as the mechanically secure fixation only of one part of the first grid elements. 
     At least one part of the first and of the second grid elements has, on a side turned toward their grid upper side, workpiece support areas, which retain the workpiece or workpieces. 
     The workpiece support areas may be designed as raised or recessed portions on the grid upper side of the first or second grid elements, in order thereby to permit the supporting of the workpiece in a suitable position. 
     In one embodiment, the notches are disposed in comb-like manner either in the first or in the second grid elements. “Comb-like” means that all notches are disposed either on the upper side of the grid element or on the underside of the grid element. The upper side of the grid element is turned toward the grid upper side. The underside of the grid element is turned toward the grid underside. It is to be noted that, in the case of comb-like first grid elements, both first grid elements having their notches on the upper side and first grid elements having their notches on the underside are possible. The second grid elements then have notches both on upper side and underside. The reverse is the case for comb-like second grid elements. 
     In one embodiment, the second grid elements beyond the peripheral region are joined interlockingly without play to the first grid elements. This permits a good fit and a joint that possibly is additionally interlocking. Alternatively, the second grid elements beyond the peripheral region are joined interlockingly with play with the first grid elements, so that mechanical or thermal stress may be absorbed. 
     Further advantageous embodiments will become apparent from the dependent claims. 
    
    
     
       The invention will be explained in more detail in the following on the basis of exemplary embodiments in the drawings. 
         FIG. 1A  schematically shows an exemplary embodiment of a grid-type workpiece carrier in a plan view. 
         FIGS. 1B, 1C, 1D  show exemplary embodiments of plank-like grid elements of the workpiece carrier illustrated in  FIG. 1A  in a side view. 
         FIG. 2  shows a further exemplary embodiment of a grid-type workpiece carrier. 
         FIG. 3  shows a further exemplary embodiment of a grid-type workpiece carrier. 
     
    
    
     In the figures, like or functionally like-acting component parts are denoted with the same reference symbols. 
       FIG. 1A  schematically shows an exemplary embodiment of a grid-type workpiece carrier in a plan view. 
     The workpiece carrier comprises a multiplicity of longitudinally disposed plank-like grid elements LE, LR as well as, disposed transversely relative to them, a multiplicity of plank-like grid elements QR, QM. The longitudinally and transversely disposed grid elements QR, QM, LE, LR intersecting one another form a grid. 
       FIGS. 1B, 1C, 1D  show the plank-like grid elements QR, QM, LE, LR illustrated in  FIG. 1A  in the side view. The plank-like grid elements QR, QM, LE, LR are strap-shaped or strip-shaped. They are indeed cuboid, but have very small width in comparison with height and length. Their height is smaller than their length. The grid elements QR, QM, LE, LR are metal, preferably of steel. 
     The grid comprises several plank-like grid elements LE, LR disposed parallel to one another in longitudinal direction. Perpendicular to them, several grid elements QR, QM disposed in transverse direction extend in a manner disposed in parallel. The outer longitudinally disposed grid elements LR are in a peripheral region that includes these two grid elements LR. Asymmetrically disposed grid elements are also conceivable. 
     The longitudinally and transversely disposed grid elements QR, QM, LE have notches A 1 , A 2 , which engage in one another at points of intersection KP of the grid elements QR, QM, LE. The grid elements QR, QM, LE, LR in this exemplary embodiment have a rectangular basic shape, such that the contour of the side view deviates from the rectangular shape only at the notches A 1 , A 2 . 
     The outer transversely disposed grid elements QR have only notches A 1  on an upper side of the grid, and so they have a comb-like contour line in the side view. The grid elements QM disposed transversely between them have notches A 2  only on an underside of the grid. The outer notches A 2  of the longitudinally disposed grid elements LE, LR are disposed on the underside and the notches Al situated between them are disposed on the upper side. 
     The notches A 1 , A 2  of the longitudinally disposed grid elements LE, LR are disposed in a manner corresponding to the transversely disposed grid elements QR, QM, and so, at the points of intersection KP of the grid, a notch A 1  on the upper side of a grid element QR, LE, LR engages in a notch A 2  on the underside of the intersecting grid element QM, LE, LR and vice versa. The width of the notch A 1 , A 2  corresponds substantially to the width of the embraced grid element QR, QM, LE, LR. The sum of the heights of two notches A 1 , A 2  engaging in one another corresponds substantially to the height of the grid elements QM, QR, LE. Although longitudinally and transversely disposed grid elements QM, QR, LE, LR engage in one another substantially interlockingly, the joints may nevertheless have play. This is a fabrication-related and use-related freedom of movement, in which the grid elements QM, QR, LE, LR are allowed to move relative to one another during or after assembly. Play at the points of intersection KP is able to absorb thermal or mechanical stress that acts on the grid. 
     For fixation of the grid, the transversely disposed grid elements QR, QM are mechanically securely fixed on the outer longitudinally disposed grid elements LR in the peripheral region. The fixation joint SP is advantageously a substance-to-substance bond, for example, a welded joint, or an adhesive bond. A joint in the form of spot welds is compatible with a simple manufacture and a robust, secure joint. 
     A mechanically secure joint exists only between the transversely disposed grid elements QR, QM and the outer longitudinally disposed grid elements LR in the peripheral region. The grid elements LR, QM, QR fixed mechanically securely in such a manner have a ladder-like structure. The grid elements LE disposed longitudinally beyond the peripheral region are joined by interlocking with the transversely disposed grid elements QR, QM, which engage in the notches A 1 , A 2  on the upper side and underside of the grid elements LE. Because of the engagements on upper side and underside of the grid elements LE, a joint in addition to this is not necessary to retain the grid elements LE beyond the peripheral region in their position. 
     It is to be noted that, in the case of longitudinally and transversely disposed grid elements QR, QM, LM engaging in one another without play, the interlocking joint at the points of intersection KP beyond the peripheral region may be additionally accompanied by a frictional connection. 
     In one alternative exemplary embodiment, the fixation of the transversely disposed grid elements QR, QM may take place at more than or other than the longitudinally disposed outer grid elements LR. The boundary region would then be correspondingly broader. 
     The mechanically secure fixation only on longitudinally disposed grid elements LR in the peripheral region permits the formation of a stable grid with reduced complexity. Furthermore, the exclusive fixation in the peripheral region has the advantage that, in case of mechanical or thermal stress, a relative motion on the basis of the play at the points of intersection KP of the longitudinally and transversely disposed plank-like grid elements LE, QM, QR is possible, which prevents a deformation of the entire grid during its use as workpiece carrier in the fabrication. 
       FIG. 2  shows a further exemplary embodiment of a grid-type workpiece carrier. It has a multiplicity of longitudinally disposed plank-like grid elements LR, LE 1 , LE 2 . Furthermore, four transversely disposed grid elements QR, QM are provided. The longitudinally and transversely disposed grid elements LR, LE 1 , LE 2 , QR, QM intersect and thus form a grid. 
     In the peripheral region, two longitudinally disposed grid elements LR having rectangular basic shape are provided respectively on opposite sides. First longitudinally disposed grid elements LE 1  and second longitudinally disposed grid elements LE 2  are provided in the region between them. The first longitudinally disposed grid elements LE 1  have workpiece support regions WA 1 . The workpiece support region WA 1  is designed as an elongated recess on the upper side and it extends between two adjacent transversely disposed grid elements QR, QM. The second longitudinally disposed grid elements LE 2  have, between adjacent transversely disposed grid elements QR, QM, a multiplicity of semicircular recessed portions on the upper side, which likewise function as workpiece support regions WA 2 . 
     A first followed by a second grid element LE 1 , LE 2  is disposed longitudinally adjacent to the longitudinally disposed grid elements LR in the left peripheral region. The grid elements LE 1 , LE 2  longitudinally disposed between them are disposed in groups, each comprising three grid elements LE 2 , LE 1 , LE 2 . A group comprises a sequence of a second, a first and a second grid element LE 2 , LE 1 , LE 2 . The distance between the groups is larger than the distance between the individual grid elements LE 2 , LE 1 , LE 2  of the group. The arrangement and shape of the workpiece support regions WA 1 , W 2  together with the grouping permits a workpiece support and secure retention for several workpieces. 
     The longitudinally disposed grid elements LR, LE 1 , LE 2  have outer slit-like notches on the underside and two slit-like notches between them on the upper side. The notches engage in corresponding notches of the transversely disposed grid elements QR, QM. 
     The transversely disposed outer grid elements QR and the transversely disposed grid elements QM between them differ in their shape only in that the outer grid elements QR project somewhat further beyond the outer longitudinally disposed grid elements LR. The outer transversely disposed grid elements QR have slit-like recesses only on the upper side. The transversely disposed grid elements QM situated between them have slit-like notches only on the underside. Between the notches for the groups of longitudinally disposed grid elements LE 1 , LE 2 , recessed portions AU are provided on the upper side of the transversely disposed grid elements QR, QM. Mechanically secure fixations SP are provided between the transversely disposed grid elements QR, QM and the outer longitudinally disposed grid elements LR. In an alternative embodiment, mechanically secure joints SP may also be provided on alternative or further longitudinally disposed grid elements LR in the peripheral region. In this exemplary embodiment, the joints SP are spot welds. 
       FIG. 3  shows a further exemplary embodiment of a grid-type workpiece carrier having a multiplicity of longitudinally disposed grid elements LR 1 , LR 2 , LE 1 , LE 2  and intersecting transversely disposed grid elements QR 1 , QR 2 , QM 1 , QM 2 , which form a grid. 
     In the peripheral region, two longitudinally disposed plank-like grid elements LR 1 , LR 2  are provided respectively on opposite sides. Respectively two transversely disposed plank-like grid elements QR 1 , QR 2  are provided at the periphery. The outer transversely disposed grid elements QR 1  have notches only on the upper side. The transversely disposed, peripheral grid elements QR 2  adjacent to them have notches only on the underside. This is also the case for the transversely extending grid elements QM 1  and QM 2  disposed between them. 
     The longitudinally disposed grid elements LR 1 , LR 2 , LE 1 , LE 2  are respectively provided on the outside with one notch disposed above and between these with notches disposed below. 
     Both the two adjacent outer transversely disposed grid elements QR 1 , QR 2  and the two adjacent outer longitudinally disposed grid elements LR 1 , LR 2  are fastened at corner points of the grid with fixation elements FE in such a way that respectively the two outer intersecting grid elements QR 1 , QR 2 , LR 1 , LR 2  are joined to one another. Such a fixation element FE may be disposed as a screw or rivet in a corner quadrant of the grid. Alternatively, a welded joint may be provided. 
     The transversely disposed grid elements QM 1 , QM 2  between the two adjacent outer transversely disposed grid elements QR 1 , QR 2  are mechanically securely fixed, for example by spot welds SP, on the outer longitudinally disposed grid elements LR 1  in the peripheral region. Alternatively, other joints, preferably substance-to-substance bonds are conceivable. The fixation may alternatively take place at other or further longitudinally disposed grid elements LR 2  in the peripheral region. 
     Although the longitudinally disposed grid elements LE 1 , LE 2  beyond the peripheral region are not fixed mechanically securely to the transversely disposed grid elements QR 1 , QR 2 , they are retained in the grid, whether with or without play, by virtue of their interlocking joints. The interlocking joint is achieved by the interaction of the transversely extending grid elements QR 2 , which engage from above and are adjacent to the outer transversely disposed grid elements QR 1 , and the other transversely disposed grid elements QR 1 , QM 1 , QM 2 , which engage from below. 
     Beyond the peripheral region, the grid elements QM 1 , QM 2 , LE 1 , LE 2  in the region of intersection of the notches engaging in one another are lowered, so that workpiece support regions WA 3 , WA 4  are formed by upwardly projecting rectangular raised portions between them. The width of the raised portions differs for longitudinally and transversely extending raised portions. 
     A further embodiment of workpiece support regions WA 5  is shown in the lower left grid region. Sleeve-like retainers, into which the workpiece or a workpiece retainer (not illustrated in FIG.  3 ), which may be forked, for example, may be inserted, are introduced into the lowered portions of the points of intersection of the grid elements LE 1 , QM 2 . 
     It is to be noted that the designations “longitudinally” and “transversely” used above are derived from the orientation of the diagram in  FIGS. 1A, 2 and 3 . In an alternative representation, the grid element may be rotated by 90 degrees, so that “longitudinally” and “transversely” would be interchanged. More generally, and in an alternative phrasing, “longitudinally” corresponds to a first direction and “transversely” to a direction perpendicular or almost perpendicular to it. 
     The features indicated in the forgoing and those indicated in the claims as well as those that can be inferred from the figures can be advantageously combined and implemented both individually and in various combinations. The invention is not restricted to the described exemplary embodiments but instead may be modified in quite a few ways within the scope of the abilities of persons skilled in the art.