Abstract:
A segmented concrete screed for screeding concrete on a concrete casting bed includes a plurality of individual screed units each of which may be raised and lowered independently of the others such that screeding operations may selectively bypass obstructions in the concrete to be screeded.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   None 
   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   This invention relates to concrete casting machines which cast concrete panels. Previously, hollow core concrete panels have been formed by many methods, including single and multiple pass casting using moving beds and with stationary beds. The hollow cores are made by using slipform extruders that leave core material in place over which concrete is formed. Once cured, the panels are cut to length and lifted and tilted to remove the core material which may be reused. 
   Some hollow core panels have been made with an insulating layer across the entire surface, as shown in U.S. Pat. No. 4,628,653, the disclosure of which is incorporated herein by reference. Basically, a hollow core panel is cast and interlocking sheets of insulation are laid down before a final pour of concrete. This uniform layer of insulation increases the R-value of the finished wall panels and floor plank. 
   Recently, the assignee of this invention has developed a machine and process that uses foam billets to provide insulation and to eliminate the need for using slipform extruders and core material. The invention is described in published U.S. patent application US 20030115822A1 which was published on Jun. 26, 2003, the disclosure of which is incorporated herein by reference. A further benefit of this invention is that it allows casting concrete panels with openings therethrough, such as for windows. A pass through opening during casting means that current screed apparatus of casting machines will not function properly. 
   The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. § 1.56(a) exists. 
   BRIEF SUMMARY OF THE INVENTION 
   The invention provides a modified concrete screed for machines for casting concrete panels which is adjustable so the screeding operation may bypass zones on the bed when desired. 
   The inventive segmented screed of the invention basically modifies any standard concrete casting apparatus as shown in U.S. Pat. Nos. 3,217,375; 3,523,343; 4,004,874; 4,289,293 and 4,457,682, the disclosures of which are incorporated herein by reference. Such casting machines have a casting bed that is either stationary or is driven along rails. The casting bed has a bottom pallet and side forms. Normally, a screed is positioned above the cast concrete between the side forms such that it may screed the poured top surface of the concrete. In this invention, the screed is modified such that it includes a plurality of segments, each of which may be raised or lowered independently of the others such that screeding may be bypassed at any desired location. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of the invention is hereafter described with specific reference being made to the drawings in which: 
       FIG. 1  is a perspective view of the segmented screed of the invention; 
       FIG. 2  is a side elevational view of the segmented screed showing a segment lowered against concrete; and 
       FIG. 3  is a front elevational view of the screed with segments down. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Casting machines which employ the segmented screed have a casting bed  10  that is either stationary or is driven along rails. The casting bed  10  has a bottom pallet  14  and side forms  16 ,  18 . The concrete panel  20  being formed is shown in  FIG. 1  and has an upper surface  22  which requires screeding. The concrete panel  20  shown includes one or more defined openings  28  and would typically include a plurality of foam billets as shown and described in published U.S. patent application U.S. 20030115822A1. That method allows concrete panels to be cast without the need to tilt the finished panels to remove core material from longitudinal voids. This allows the use of forms  26  which define a pass through opening  28 . Unfortunately, the top of the forms  26  will interfere with prior art screeds. 
   Screed  30  of the invention, like existing screeds, is suspended above the bed  10  and is movable relative to the bed by the bed moving or by its being driven along the length of the bed. Screed  30  includes a framework  32  to which a plurality of screed units  34  are slidably attached via bolts  36  which allow the screed units  34  to be moved vertically relative to the framework  32 . The screed units  34  each have a lower screed plate  38  which when combined with the other screed units provides the screeding of the concrete. 
   Lower screed plate  23  as shown in the drawings has a leading edge which hits the concrete and a flat bottom surface which smoothes the concrete. 
   Each screed unit includes a hydraulic mechanism  40  including a hydraulic cylinder  42 , piston  44  and attachment point  46  to the screed unit  34  as best shown in  FIG. 2 . Conventional controls for the hydraulic mechanisms  40  allow control of the vertical position of each screed unit  34  such that all may descend down to the surface  22  of the concrete to screed the concrete. Alternatively, as shown in  FIGS. 1 and 3  several of the screed units  34  may be lifted free of the concrete surface  22  just before and obstruction such as the top of the form  26  only to descend thereafter to resume screeding of the entire top surface  22 . 
   The screed  30  has been shown with a system that raises and lowers the individual screed units  34  using hydraulics. Pneumatic or any electronic control as by motors may be utilized instead. 
   While this invention may be embodied in many different forms, there are shown in the drawings and described in detail herein specific preferred embodiments of the invention. The present disclosure is an exemplification of the principles of the invention and is not intended to limit the invention to the particular embodiments illustrated. 
   The above disclosure is intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in this art. All these alternatives and variations are intended to be included within the scope of the claims where the term “comprising” means “including, but not limited to”. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the claims. 
   This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.