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You are an expert at summarizing long articles. Proceed to summarize the following text: 
RELATED APPLICATIONS 
     This application is a continuation of PCT/EP2013/076980, filed Dec. 17, 2013, which claims priority to DE 10 2012 224 340.2, filed Dec. 21, 2012, both of which are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     The invention relates to a mast arm for a concrete distributor mast, comprising an elongated box profile support composed, in at least some sections, of a lower wall, an upper wall, and two lateral walls that connect the walls, and comprising at least one partition sheet metal element arranged in a hollow cross section of the rectangular-shaped closed box profile support. The invention further relates to a method for the production of one such mast arm. 
     DE 196 44 410 A1 discloses a concrete distributor mast as a support for a concrete delivery pipe with several mast arms connected for articulation and having a closed box-shaped profile. It is thereby proposed that the mast arms have a box profile, and that at least one mast arm contains a reinforcing partition wall which runs transversely through the interior chamber. There is nothing further about the fixing or assembly of the sheet metal partition wall from this printed specification. 
     SUMMARY 
     This disclosure further improves the products and methods known from the prior art and provides a stress-resistant construction of a mast arm which can be produced simply and with precision, particularly for a concrete distributor mast. 
     This disclosure stems from the idea of preventing the notch effect through transverse welding joints. It is accordingly proposed according to this disclosure that the partition sheet metal element is welded to the box profile support by way of longitudinal welding joints which run along the box profile support in the direction of its longitudinal axis. A technically favorable welding process can thereby be ensured and the stiffening action of a sheet metal partition plate utilized without welding joints which run transversely to the stress direction of the arm acting on the arm like notches. Even with reduced sheet metal thicknesses the load capacity or bearing strength and the torsional rigidity of the arm can thus also be clearly increased. 
     An advantageous design proposes that the longitudinal welding joints run in the connection area between the upper and lower walls and the lateral walls in the direction of the longitudinal axis so that joining them together becomes easier. 
     The longitudinally aligned bonded welding joint can be simplified in that the partition sheet metal element is formed from a flat partition sheet metal plate with welding lugs protruding at the edges, and that the longitudinal welding joints are each attached to a welding lug. 
     In order to provide a fixed connection it is advantageous if the welding lugs are each welded to an edge section of the partition sheet metal plate, preferably on both sides. 
     A further improvement can be achieved in that the partition sheet metal plate preferably has corner parts which engage by diagonal stays into the corner regions of the box profile support, and that a welding lug is arranged on each corner part. 
     Also from a structural point of view it is an advantage if the preferably T-shaped designed welding lugs have a connecting web which protrudes on both sides over the partition sheet metal plate for the purpose of welding with the box profile support, and if the welding lugs have a base surface which bears with a flat surface area against the upper and lower walls or the lateral walls. 
     A design which is particularly advantageous from the technical production point of view is one in which the upper and lower walls or the lateral walls are provided with cutouts for introducing the longitudinal welding joints as a fill layer. The fill layer thereby fills up the relevant cutout at least in some areas. 
     It is also favorable if each upper and lower wall and one lateral wall are welded to one another in a connecting area by a cap joint which covers the longitudinal welding joint. The cap joint thereby stands in direct or material-bonding contact with the longitudinal welding joint. The longitudinal welding joints can thereby coincide with the support welding joints which are normally present in any case and which connect the upper and lower walls and the lateral walls. 
     It is advantageous particularly for a space-saving and at the same time highly stable arm structure if the box profile support is bent in at least one crank portion, and if the crank portion is reinforced by a partition sheet metal element. 
     This disclosure also provides a distributor mast with several mast arms connected to one another for articulation for holding a concrete delivery pipe wherein at least one mast arm is reinforced with a partition sheet metal element according to this disclosure. The partition sheet metal element is welded to the box profile support by way of longitudinal welding joints which run along the box profile support. 
     A further advantageous measure consists in prefabricating the partition sheet metal element from a flat partition sheet metal plate and welding lugs attached along the edges thereof, and then fixing it in the box profile support in the connecting region between the walls and lateral walls by way of a longitudinal welding joint at the welding lugs. 
     It is also advantageous from the technical production point of view if the upper and lower walls or the lateral walls are provided with cutouts, and if a longitudinal welding joint is introduced as a fill joint in each of the cutouts. The longitudinal welding joints can thereby be covered by a cap joint for connecting a lateral wall to one of the upper and lower walls. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned aspects of exemplary embodiments will become more apparent and will be better understood by reference to the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  shows a mast arm for a concrete distributor mast with a built-in partition sheet metal plate in a transparent perspective illustration; 
         FIG. 2  is an enlarged sectional view of a partition sheet metal plate portion of the mast arm of  FIG. 1 ; 
         FIG. 3  is a perspective partial view of the partition sheet metal plate portion when attaching the upper wall; 
         FIG. 4  is a cross sectional view of a section of the mast arm in the region of a built-in partition sheet metal plate. 
     
    
    
     DESCRIPTION 
     The embodiments described below are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the following description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of this disclosure. 
     In this disclosure, terms such as “vertical,” “parallel,” “horizontal,” “right angle,” “rectangular” and the like are used to describe the orientation, position or general shape of structural elements disclosed herein. As would be readily recognized by one of ordinary skill, it shall be understood for purposes of this disclosure and claims that these terms are not used to connote exact mathematical orientations or geometries, unless explicitly stated, but are instead used as terms of approximation. With this understanding, the term “vertical,” for example, certainly includes a structure that is positioned exactly 90 degrees from horizontal, but should generally be understood as meaning positioned up and down rather than side to side. Other terms used herein to connote orientation, position or shape should be similarly interpreted. Further, it should be understood that various structural terms used throughout this disclosure and claims should not receive a singular interpretation unless it is made explicit herein. 
     The mast arm  10  illustrated in  FIG. 1  can be connected with articulation via articulated ends  12 ,  14  to further mast arms as an articulated mast for guiding a concrete delivery pipe, wherein laterally angled arm regions  16  (also referred to herein as “crank portions”) enable the arm packet to be folded in in a space-saving manner. The mast arm  10  has a box profile support  18  which is elongated along a longitudinal axis and which is comprised of an upper belt  20 , a lower belt  22 , and two lateral walls  24 ,  26  forming a rectangular cross section. Partition sheet metal elements  28  are arranged in the angled regions  16  for reinforcement in the hollow cross section of the box profile support  18  which is illustrated in transparent form. 
     As can best be seen from  FIG. 2  each partition sheet metal element  28  consists of a basic-shaped rectangular flat partition plate  30 , and four welding lugs  32  protruding at the edges in the corner regions. 
     In order to save weight the partition sheet metal plate  30  is provided with recesses  34  wherein the corner parts  36  which are provided with welding lugs  32  remain connected by way of diagonal stays  38  so that parallelogram displacements of the box profile support  18  are prevented. 
     The T-shaped welding lugs  32  are fixedly connected at their base arm to an edge section of the sheet metal plate  30  by way of a peripheral welding joint  40 . The connecting web  42  of the welding lugs  32  protruding each side crosswise at the partition plate  30  enables welding with the box profile support  18  via a longitudinal welding joint  44  which runs in the direction of the support longitudinal axis, as will be explained in further detail below. The longitudinal welding joints  44  are thereby each located in the connection region between a wall  20 ,  22  and a lateral wall  24 ,  26 . In the installed position the welding lugs  32  lie with their free base surface  45  flat against the walls  20 ,  22 . 
     The production and assembly of the box profile support  18  will be explained below with reference to  FIGS. 3 and 4 . The partition sheet metal elements  28  are prefabricated separately in that the partition plate  30  is cut out from a flat iron material and then the welding lugs  32  are welded on. In a further method step the walls  20 ,  22  are provided on the edges with cutouts  46  for introducing the longitudinal welding joints  44 . With the end production of the box profile support  18  first the lower wall  22  and the two lateral walls  24 ,  26  are welded to one another and to the positioned partition sheet metal elements  28 , wherein the partition sheet metal elements  28  can also ensure an improved dimensional stability during assembly. The upper wall  20  is then placed and fixed in the direction of the arrow  48 . 
     The respective longitudinal welding joint  44  is introduced from outside as a fill joint into the belt cutout  46  in the region of the welding lugs  32  ( FIG. 4 ). The welding connection of the lateral walls  24 ,  26  to the upper belt  20  is then carried out via connecting joints  50  (also referred to herein as “cap joints”—see ¶ [0012]) which run in the edge region along a marginal overhang of the lateral walls  24 ,  26  above the upper belt  20 , and cover the longitudinal welding joints  44  in the region of the cutouts  46 . It is evident that the welding joints  44 ,  50  are also attached correspondingly on the lower belt  22 . Thus for assembly no welding work is necessary inside the box profile support  18 . Furthermore notch effects as a result of transverse welding joints are avoided. 
     While exemplary embodiments have been disclosed hereinabove, the present invention is not limited to the disclosed embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of this disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Summary:
A mast arm for a concrete distributor mast comprises an elongated box profile support composed, in at least some sections, of a lower belt, an upper belt, and two lateral walls that connect the belts, and comprising at least one partition sheet metal element arranged in a hollow cross-section of the box profile support, the partition sheet metal element being welded to the box profile support along longitudinal welding joints running along the box profile support.