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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a concrete screed apparatus and more particularly to a concrete screed apparatus which is preferably used by a pair of spaced-apart workers, wherein each of the workers have a concrete screed apparatus operatively secured to a leg of the worker so that the two workers may screed concrete. 
     2. Description of the Related Art 
     When concrete is being poured and finished, a pair of workers are normally positioned at the opposite ends of a screed board with the screed board being moved back and forth to level the concrete. Usually, the workers must perform the screeding operation while on their knees or in a kneeling position which is extremely tiresome and difficult. 
     SUMMARY OF THE INVENTION 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. 
     A concrete screed apparatus is disclosed for use by each of a pair of workers who are finishing concrete. Each of the concrete screed apparatuses comprises a first support adapted to be secured to the lower leg of the worker. An elongated second support, having inner and outer ends, is provided with the inner end of the second support being pivotally secured, about a horizontal axis, to the first support whereby the outer end of the second support may be vertically moved with respect to its inner end. The apparatus of this invention also includes a third support, having upper and lower ends, with the lower end of the third support being pivotally secured about a horizontal axis transverse to the longitudinal axis of the second support. The upper end of the third support has a hand gripping portion thereon which may be grasped by the worker. A fourth support is longitudinally movably mounted on the second support. Means is provided for selectively moving the fourth support along the length of the second support. A screed support is pivotally secured to the fourth support about a horizontal axis which is parallel to the longitudinal axis of the second support. An elongated screed or screed board is secured to the screed support whereby the longitudinal axis of the screed is transverse to the longitudinal axis of the second support. 
     In the preferred embodiment, the third support is length adjustable and includes a power cylinder for adjusting the length of the third support. In the preferred embodiment, the invention includes an electronic vibrator which operatively connected to the screed for vibrating the screed. In the preferred embodiment, the electronic vibrator is operatively secured to the fourth support. Further, the apparatus includes a solenoid actuated clamp for securing the screed to the screed support. 
     In the preferred embodiment, the inner end of the second support is vertically adjustably secured to the first support. Also, in the preferred embodiment, a laser beam apparatus is operatively secured to the first support which directs a horizontal laser beam from the first support towards the outer end of the second support. Preferably, a control mechanism is mounted on the first support for controlling the movement of the screed relative to the second support. In the preferred embodiment, a second concrete screed apparatus is operatively connected to the screed so that a pair of workers who are horizontally spaced apart may perform the concrete finishing operation. 
     Therefore, it is a principal object of the invention to provide an improved concrete screed apparatus. 
     It is a further object of the invention to provide a concrete screed apparatus which is utilized by a pair of horizontally spaced-apart workers. 
     A further object of the invention is to provide a concrete screed apparatus which includes a first support which is operatively secured to the lower leg of a worker and which has an elongated support pivotally secured thereto, about a horizontal axis, and which extends therefrom. 
     Still another object of the invention is to provide a concrete screed apparatus including means for raising and lowering the screed. 
     Another object of the invention is to provide a concrete screed apparatus which is vertically adjustably secured to a boot or the like in which the worker has his/her foot positioned. 
     Still another object of the invention is to provide a concrete screed apparatus which includes a vibrator, laser beam and means for moving the screed board back and forth relative to the workers. 
     These and other objects will be apparent to those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the present invention are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. 
         FIG. 1  is a perspective view illustrating a pair of workers utilizing a pair of the apparatuses of this invention; 
         FIG. 2  is a partial perspective view illustrating the support which is attached to the worker&#39;s lower leg and foot; 
         FIG. 3  is a side elevational view of the apparatus of this invention; 
         FIG. 4  is a perspective elevational view illustrating the length adjustable and hand held support; and 
         FIG. 5  is an exploded perspective view of a portion of the apparatus. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Embodiments are described more fully below with reference to the accompanying figures, which form a part hereof and show, by way of illustration, specific exemplary embodiments. These embodiments are disclosed in sufficient detail to enable those skilled in the art to practice the invention. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense in that the scope of the present invention is defined only by the appended claims. 
     In  FIG. 1 , the numeral  10  refers to concrete which has been poured and which is being screeded by a pair of workers  12  and  14  which are horizontally spaced-apart. Each of the workers  12  and  14  has a concrete screed apparatus  16  associated therewith for screeding the concrete  10 . 
     Apparatus  16  includes a first support  18  in the form of a boot or shoe into which the worker places his/her lower leg and foot. Preferably, a pair of straps  20  and  22  are utilized to securely position the worker&#39;s leg in the support  18 . 
     The numeral  24  refers to a control valve which is mounted on the support  18  for supplying air to various components of the invention. A vertically disposed support  26  is also secured to the support  18  and has a vertically disposed gear rack  28  associated with a channel  30  into which a vertically adjustable device  32  may be positioned in a vertically adjustable manner. The device  32  includes a flat bar  34  which is received by the channel  30  with the gear teeth  36  and  38  extending laterally therefrom which are selectively movable into contact with the gear rack  28  by means of the vertically movable actuator  40 . Bracket  42  is secured to the lower end of bar  34  and extends therefrom and has a hollow bushing or opening  44  formed in the outer end thereof. 
     The numeral  46  refers to an elongated second support having an inner end  48  and an outer end  50 . The support  46  is channel-shaped in cross section and has a pair of longitudinally extending grooves or channels  52  and  54  formed in the interior thereof. The inner end  48  of support  46  is pivotally secured to the bushing  44  by means of pin  56  which extends through the inner end of the support  46  and through the bushing  44 . The numeral  58  refers to an air motor having a drive shaft or power shaft  60  extending inwardly through the opening  62  formed in support  46  with the motor  58  being secured to the support  46  by any convenient means. A pulley  64  is mounted on the shaft  60  within support  46  for rotation therewith and has a drive belt or cable  66  extending therearound. A pulley  68  is also mounted in the interior of support  46  at the outer end of the support  46  and is rotatably mounted on the shaft  70  with the cable  66  extending around pulley  68 . 
     The free ends of cable  66  are secured to a support  72  which is longitudinally slidably mounted in the channels  52  and  54 . The numeral  74  refers to a support which is pivotally secured to the support  72  about an axis which is parallel to the longitudinal axis of support  46 . An air actuated vibrator  76  having a shaft  78  extending therefrom pivotally connects the support  74  to the support  72  as illustrated in  FIG. 5 . The numeral  80  refers to an air actuated clamp device which is secured to support  74  and which has a clamping member  82  extending therefrom which extends through opening  84  in support  74 . The numeral  86  refers to an elongated screed or screed board which is clamped into the support  74 . 
     The numeral  88  refers to an elongated telescopic support  88 , the lower end of which is pivotally secured to bracket  90  mounted on support  46  by means of pivot pin  92 . Support  88  preferably includes telescopic sections  94  and  96  which are telescopically moved with respect to one another by means of a power cylinder or electric actuator rod  98 . Support  88  includes a hand gripping portion  100  at its upper end. Controls  102  are provided in the hand gripping portion  100  for controlling the extension and retraction of the support  88  and various other functions of the components. 
     Preferably, a battery operated laser beam apparatus  104  is secured to the member  26  and directs a laser beam  106  horizontally therefrom to aid the workers in leveling the concrete being screeded. Preferably, the outer end of support  46  is closed by a cap  108 . Air for the various components is, provided by a remote unit  110 . 
     Thus it can be seen that a novel concrete screed apparatus has been provided which ideally suited for use by a pair of workers to screed fresh concrete to finish the same. The workers may move the screed apparatus by moving their legs and the outer ends of the supports  46  may be moved vertically through the use of the support  88 . The screed board  86  is easily moved towards and away from the workers by means of the motor  58 . The vibrator  76  vibrates the screed board  86  back and forth much like the workers must normally manually do. Therefore, it can be seen that a novel apparatus has been provided which relieves the workers from their back bending and laborious task of screeding concrete by hand. 
     Thus it can be seen that the invention accomplishes at least all of its stated objectives. 
     Although the invention has been described in language that is specific to certain structures and methodological steps, it is to be understood that the invention defined in the appended claims is not necessarily limited to the specific structures and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed invention. Since many embodiments of the invention can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

Summary:
A concrete screed apparatus is provided which may be used by a pair of workers, each of whom has the screed apparatus mounted to one of their legs or feet. The screed apparatus enables concrete to be easily screeded and properly finished without the workers doing the same on their knees or bending from the waist. The screed apparatus is adapted to move a screed board back and forth across the concrete to be finished which is also vibrated as it is being screeded.