Abstract:
A powered screed machine comprising means to drive a screed blade and means to power machine travel. The machine includes a pair of elongated modules disposed perpendicular to each other whereby a reciprocating weight within one of the modules causes forward and rearward movement of the machine and a reciprocating weight in the other module causes vibratory movement of the screed blade to groom the surface of freshly poured concrete.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is in the field of powered screeds used in the process of leveling, smoothing and creating an improved exposed surface on freshly poured concrete, cement, soil and like materials. Although the present invention is utilized in connection with many materials, the embodiment shown and described herein is directed to concrete. The word concrete includes a mixture of cement, sand, aggregate and water combined in a favorable ratio to create a product useful in the construction of floors, roads, driveways, sidewalks and the like. Concrete also embodies a mixture combined and mixed to a proper consistency and in a state of cure prior to set-up or hardening. 
     In the process of pouring concrete for floors, sidewalks, highways and the like, the exposed surface must be developed to a finished texture as required by the work specifications. This may vary from a rough nonslip surface to a slick polished finish. This is achieved by a process known as screeding. This process brings a tool into contact with the surface of the poured concrete, and by a reciprocating, dragging action causes the aggregate near and at the surface to settle thereby leaving cement and water exposed while, at the same time, leveling and smoothing the exposed surface material. 
     In one screeding system, common to the industry, an elongated wood beam or screed of sufficient length is manipulated in a side-to-side sawing motion along pairs of supporting rails temporarily set at the desired finished elevation of the surface being poured. This side-to-side motion is combined with pressure against the beam to force travel along the supporting rails. In this system, all power is applied manually by workmen positioned at opposite ends of the beam. 
     On larger areas, such as highway lanes and large floors, the typical process utilizes a screed provided with means to mechanically power both the sawing motion and travel along the guiding rails with travel being implemented by powered traction wheels. 
     A third system, in current use in the industry, includes a screed beam, power means to effect side-to-side sawing motion, a guide with a controlling handle and a frame on which all of the elements are mounted. This system commonly utilizes one operator in the fashion of a push-type lawnmower with the operator causing the machine to travel by applying a push or pull force to the machine handle. 
     BRIEF SUMMARY OF THE INVENTION 
     By this invention, a powered screed machine is provided which comprises power means fixed to a support frame together with a machine control system. The machine includes a screed weight module disposed parallel to the axis of the screed blade with a travel weight module disposed perpendicular thereto and being generally coaxially disposed with respect to the direction of travel of the machine. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a side elevational view showing the control elements of the powered screed machine according to this invention; 
         FIG. 2A  is a view similar to  FIG. 1 ; 
         FIG. 2B  is an elevational view taken generally from the right side of  FIG. 2A ; 
         FIG. 3  is a graphical representation showing the combination of reciprocatory movement in the direction of travel of the machine in combination with operation of the screed blade; 
         FIGS. 4A ,  4 B and  4 C show top, end and side views of the machine control elements, respectively; 
         FIG. 4D  is a sectional view taken along the line B-B in  FIG. 4A ; 
         FIG. 4E  is a sectional view taken along the line A-A in  FIG. 4A ; 
         FIGS. 5A and 5B  are similar to  FIGS. 2A and 2B , respectively, and show a modification of the invention; 
         FIG. 6A  is a side view of a portion of the machine control mechanism; 
         FIGS. 6B-6E  are sectional views taken along the line Y-Y in  FIG. 4E ; 
         FIGS. 7A-7E  are views similar to  FIGS. 6A-6E , respectively; 
         FIG. 8A  is an elevational of the machine with a portion thereof broken away; 
         FIGS. 8B-8F  are sectional views taken along the line X-X in  FIG. 4D  and  FIG. 8A ; 
         FIG. 9A  is a schematic top view of the machine; 
         FIG. 9B  is a side view of the machine control elements; 
         FIG. 9C  is a partial sectional view of the machine; and 
         FIGS. 9D and 9E  are sectional views taken along the line Y-Y in  FIG. 9C . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With particular reference to  FIG. 2B , the screed machine according to this invention includes power means  1 , screed-axis weight module  2 , travel-axis weight module  3 , support frame  4 , elongated screed blade  5  and handle frame  6 . The machine control system includes control cable housing  7 , control cable  8 , travel control arm  9  and control lever  10 . 
     During operation, the machine is held in an upright position by the operator with screed blade  5  disposed essentially normal to the surface being processed. With power means  1  operating, screed blade  5  is driven in a reciprocating left to right motion by means of screed-axis weight module  2 . Also, the machine is caused to reciprocate in a direction perpendicular to the screed reciprocating direction by means of travel-axis weight module  3 . Travel-axis weight module  3  is designed and constructed to selectively generate a force of variable intensity and in a reversible direction with respect to the machine direction of travel. The operator positions control handle  10  to effect travel forward and reverse along the surface being processed. 
     In  FIGS. 5A and 5B , an alternate embodiment of the machine is shown whereby power means  1  is located remotely on handle frame  6  and is supported by power means mount  11 . Power is transmitted to drive shaft  15  through flexible drive linkage  12 . 
     With reference to  FIGS. 8A-8F , screed-axis weight module  2  is provided with screed weight  21  which is driven by shaft  15  in combination with eccentric cam  22  wherein the axis of cam  22  is offset from the axis of shaft  15 . Weight  21  is supported and guided during travel by screed weight housing  23  and weight guide bushings  14 . Shaft  15  is rotated by power means  1 . The elongation of slot  24  perpendicular to the travel direction of weight  21  allows rotation of shaft  15  and eccentric cam  22  to effect movement of weight  21  only in the direction of the screed axis. As weight  21  is driven in a reciprocating motion by eccentric cam  22 , the inertial force produced by the reciprocation of weight  21  is applied through the combination of eccentric cam  22 , shaft  15 , shaft bearing  17  and support frame  4  to screed blade  5 . 
     Vibratory conveyors which move material in one direction operate on a principle well known in the art. The structural surface of the machine which contours the material being conveyed is moved in both the direction of material flow and in the opposite direction by means of a reciprocating weight connected to the supporting surface. Movement of conveyed material in the desired direction is effected by causing the reciprocating weight to be greater in magnitude in one direction than in the other. This is accomplished by applying a bias force to the weight in the form of a spring. As the weight is moved against the spring, its acceleration is decreased and energy thus expended is transferred to the compressed spring. As the motion reverses, stored energy in the spring is released thereby increasing the acceleration of the weight in the reverse direction. Therefore, during each cycle of reciprocation of the weight, the machine surface moves at a greater rate in one direction than the other, thereby moving the conveyed material in the desired direction. 
     With reference to  FIGS. 9A-9E , travel-axis weight module  3  is provided with travel weight  13  and elongated slot  24 . Eccentric cam  16  is mounted on and fixed to shaft  15  with the shaft being rotatably driven by power means  1 . Springs  18   c  and  18   d  are attached to spring frame  20  and to weight  13 . Elongation of slot  24  crosswise to the machine travel direction allows the rotation of shaft  15  and eccentric cam  16  to effect movement to weight  13  only along the axis of travel of weight  13 . Weight  13  is supported and guided by weight guide  19  and weight guide bushings  14 . If the combination of forces causes the machine to veer off line, weight  13  can be angled with respect to the direction of machine travel to counteract these forces and maintain the desired direction of travel of the machine. 
     As shown in  FIGS. 6A-6E , travel-axis weight  13  is attached to springs  18   a  and  18   b  with the opposite ends of the springs attached to spring frame  20 . The motion of travel of weight  13  causes the compression of spring  18   b  thereby resulting in storage of energy in spring  18   b . As shaft  15  and eccentric cam  16  continue to rotate energy stored in spring  18   b  is released to accelerate weight  13  to the left as it moves toward spring  18   a.    
     The continued rotation of shaft  15  and eccentric cam  16  causes the same force to be applied to spring  18   a  as was applied to spring  18   b  during the first 180 degrees of rotation. As shaft  15  and eccentric cam  16  rotate, there is a cyclic storage and release of energy in springs  18   a  and  18   b . During rotation of shaft  15  and eccentric cam  16 , spring frame  20  acts to maintain springs  18   a  and  18   b  in the same relative position from the central axis of the mechanism thereby causing the storage and release of energy to be equal and symmetrical with respect to the central axis. 
     With reference to  FIGS. 7A-7E , travel-axis weight module  3  is provided with spring frame  20  slidably mounted with respect to frame  4 , weight guide  19  and shaft  15 . The sliding motion of spring frame  20  is effected by the leverage force applied to arm  9  by control cable  8 . Arm  9  is pivotably mounted on pin  25  and pin  25  is fixed to frame  4 . Extension and retraction of control cable  8 , acting upon arm  9 , causes spring frame  20  to change its position relative to frame  4 , shaft  15 , eccentric cam  16 , weight  13  and springs  18   c  and  18   d . Specifically, spring frame  20  is caused to move closer to spring  18   c  by the retraction of control cable  8  acting on arm  9 . The location of spring frame  20  in this position causes spring  18   c  to have a shorter compressed length during all phases of the rotation cycle. This location of spring frame  20  also causes spring  18   d  to have a longer compressed length during the same phases of rotation cycle. The result of this difference in effective spring lengths is an imbalance of force on weight  13  and the accompanying imbalance of acceleration due to storage and release of spring energy during all phases of the rotation cycle. 
     During rotation of eccentric cam  16  from the position shown in  FIG. 7C  to that shown in  FIG. 7E , the energy stored in spring  18   c  is released and is combined with the force provided by eccentric cam  16  to enhance the acceleration of weight  13  as it moves toward spring  18   d . Since spring  18   d  has a longer compressed length, less energy is absorbed from weight  13  during this phase of rotation of cam  16 . 
     An imbalance of accelerating forces across weight  13  during movement from the position in  FIG. 7C  to the position in  FIG. 7E  results in travel-axis weight  13  being driven at a greater velocity during travel from spring  18   c  toward spring  18   d  than during travel from spring  18   d  toward spring  18   c . Hence, weight  13  applies a net force on frame  4 , through springs  18   c  and  18   d , spring frame  20 , eccentric cam  16  and shaft  15  that is greater in the direction from side B to side A than from side A to side B. This net force difference causes the machine to travel in a direction from side B toward side A. Reversing the direction of control handle  10  to cause control cable  8  to extend and reverse the position of arm  9  will move spring frame  20  in the opposite direction and thereby reverse the direction of machine travel in proportion to the extent of movement of control handle  10 .