Abstract:
A leveling system for freshly poured concrete is provided comprising a hand screed and a hand float. The system includes a laser beam leveling system consisting of a laser transmitter mounted on the hand screed and a laser beam receiver target mounted on the hand float. The hand screed further includes an inclinometer mounted on top of the hand screed for maintaining the angle of the screed when the screed is used on sloped surfaces. Bubble levelers positioned on top of the hand screed and the hand float are used to maintain the hand screed and the hand float in a level position.

Description:
FIELD OF THE INVENTION 
   The present invention relates to concrete construction, including concrete finishing, handling and leveling. More specifically, the present invention relates to tools for leveling fresh concrete after it has been poured. 
   BACKGROUND OF THE INVENTION 
   In the concrete industry, “screeding-boards” are common tools used to level concrete that has been freshly poured. For the purposes of this specification and the claims contained herein, the term “plastic concrete” shall refer to freshly-poured concrete that has not yet set up and hardened. 
   The types of screeds used in leveling plastic concrete vary from a 2×4 plank of wood, which is manually pushed or pulled through the concrete to a mechanical screed, which is gas and occasionally electrically powered. Often, the type of screed used depends upon the size and complexity of the surface area to be leveled. Conventional manual and power screeds have their distinct problems. 
   Power screeds are commonly used only for larger spaces and lack the versatility required to screed concrete in smaller spaces, such as doorframes, concrete pedestals, or floors with pipes and/or trenches. Mechanical screeds are often too expensive and bulky for the average individual to use (such as in a home-renovation project). 
   Manual screeds continue to be used in the majority of concrete projects. Manual screeds are necessarily used for small surface areas, slopes and around difficult spaces such as drains and columns. However, manual screeds are labourious to use and difficult to maneuver through the concrete. Manual screeds are also problematic due to difficulties in consistently and accurately maintaining the screed level throughout the screeding process. 
   The conventional method of guiding manual screeds is relatively inaccurate. Manual screed operators usually use string lines and, in large commercial projects, perhaps a laser leveling system to create reference guides in the plastic concrete and then attempt to move the screed blade on the guides to produce a flat and level floor. The laser leveling system usually comprises a reference laser and a laser receiver mounted on a post. Once the receiver is leveled relative to the reference laser, the foot of the post is at the desired concrete height. The post is then used to establish guide pins in the plastic concrete indicating the desired concrete height. The concrete is screeded using these guides. 
   Various attempts have been made to increase the accuracy of portable screeds by attaching a component of the laser leveling system directly to the portable screed. These are discussed below. 
   U.S. Pat. No. 4,752,156 provides a portable screed comprising: a stationary laser projector, which is separate from the screed, and a laser receiver, which is adjustably mounted on to the screed itself. The receiver can be vertically adjusted to receive the signal at different heights. The screed also contains a sight-level included on the screed for leveling of the entire screed. However, this reference fails to teach the use of an inclinometer for screeding sloped surfaces at different angles because the laser transmitter is stationary. 
   U.S. Pat. No. 5,288,166 involves a laser-operated automatic grade control system, having a laser projector and a laser receiver, which automatically detects elevation relative to the laser and adjusts the height of the finishing tool via an adjustable hydraulic cylinder. However, the system taught by this reference is too large to be used on sloped surfaces. 
   U.S. Pat. No. 6,758,631 provides a portable screed guidance system. Mounted on the screed are inclination measuring device(s) and leveling device components(s) (e.g. laser sensor) for measuring height relative to a stationary reference laser signal positioned in the worksite. This device is not suitable for use in leveling plastic concrete in confined spaces. 
   U.S. Pat. No. 6,089,787 Allen et al. provides a mechanical vibrating portable screed having laser sensors positioned on the screed. The screed derives elevation information from a remote laser, in response to which the gradient may be adjusted automatically or by the screed operator. This screed is bulky and does not provide a means for screeding on slopes of varying degrees or in small areas. 
   Plastic concrete can be screeded through the use of concrete elevation pins placed throughout the surface where concrete is to be poured. Screeding off elevation pins can be problematic in that costly time can be lost in correctly placing and re-adjusting the pins. Moreover, conventional laser systems provide only horizontal measurements and are not useful where screeding sloped concrete surfaces is required. 
   There is a need for a concrete-leveling system that can be used in small spaces and that is easy to control and comfortable to maneuver. The use of traditional hand screeds, having no handles or handles of rectangular shape, results in hand and finger injury, in missed work due to injury and in poor workmanship due to fatigue from using the traditional screed board. 
   It is, therefore, desirable to have a concrete-leveling system that overcomes the shortcomings of the prior art and the problems discussed above. 
   SUMMARY OF THE INVENTION 
   The present invention is a system for leveling freshly poured concrete while it is in a plastic or malleable state. The system comprises a hand screed that is used in combination with a hand float that acts as a reference point for the hand screed. A reference level signal transmitter on one of the hand screed and the hand float whereas a reference level signal receiver is mounted on the other of the hand screed and the hand float. For the purposes of this specification and the claims that follow, the term “hand float” shall mean to include any device that can act as a reference point for the hand screed and can include a hand trowel or a shortened or smaller version of the hand screed. 
   In a representative embodiment of the present invention, the transmitter is a laser mounted on the hand screed that produces a visible light beam. The transmitter may be built into the hand screed, such that the light beam projects from one end of the hand screed, or it may be mounted on top of the hand screed with a turret that allows the transmitter to rotate about an axis that is perpendicular to the horizontal axis of the hand screed. A thumbscrew on the turret allows the user to set the azimuth of the transmitter to be adjusted to a preset angle. 
   In a representative embodiment, the receiver is a set of cross hairs mounted on the hand float. In its basic form, a concrete installer places the hand float at a location in work site where it acts as a reference point. The installer then screeds the plastic concrete with the hand screed, maneuvering the hand screed so that the light beam from the transmitter lines up with the cross hairs on the hand float. In alternate embodiments of the present invention, both the hand screed and hand float have bubble levels mounted on them to aid the installer in placing both the hand float and hand screed in a level position. Furthermore, the hand screed may also comprise an inclinometer that is a device that adjusts the angle of a bubble level on the inclinometer that allows an installer to work the hand screed on a desired angle for sloped concrete surfaces. 
   It is an object of the present invention to provide a plastic concrete-leveling system for guiding the screed operator in manually directing the hand screed while screeding concrete. 
   It is another object of the present invention to provide a means for indicating the level of the screed relative to the signal receiver located on the hand float. 
   It is another object of the present invention to provide a level measuring system wherein the signal transmitter and inclinometer are mounted on the hand screed and the reference level signal receiver is mounted on the hand float. 
   It is another object of the present invention to provide a hand float with a reference level signal receiver that acts as a level guide marker for a hand screed. 
   It is another object of the present invention to provide a means of using a laser beam leveling system consisting of a laser beam transmitter and an inclinometer, both mounted on a hand screed, and a laser beam receiver, mounted on a hand float, to guide the screed operator in manually directing the hand screed while screeding on either a horizontal or sloped concrete surface. 
   It is another object of the present invention to provide a hand screed with attached bubble levelers to provide greater convenience and accuracy to the screed operator in measuring the level of the screed. 
   It is another object of the present invention to provide a hand float with attached bubble levelers for use in leveling the hand float when the hand float, with attached level signal receiver, is being used as a portable screed level guide marker. 
   Broadly stated, one aspect of the present invention is a plastic concrete leveling system, comprising: a hand screed having a longitudinal axis extending therethrough; a hand float; a reference level signal transmitter operatively attached to one of said hand screed and said hand float; and a reference level signal receiver operatively attached to the other of said hand screed and said hand float. 
   Broadly stated, another aspect of the invention is a hand screed for use with a plastic concrete leveling system having a reference level signal receiver, comprising: a generally horizontal handle defining a longitudinal axis extending therethrough, said handle having top and bottom surfaces; a screed plate operatively attached to said bottom surface; and a reference level signal transmitter operatively attached to said handle whereby said transmitter is capable of producing a reference level signal. 
   Broadly stated, yet another aspect of the present invention is a hand float for use with a plastic concrete leveling system having a reference level signal transmitter, comprising: a substantially flat float board having top and bottom surfaces; a handle operatively attached to said top surface; and a reference level signal receiver operatively attached to said hand float whereby said receiver is capable of receiving a reference level signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an elevational side view of the hand screed of a representative embodiment of the present invention with the laser mounted at one end of the hand screed. 
       FIG. 2  is a top plan view of the hand screed of a representative embodiment of the present invention with the laser of  FIG. 1  removed. 
       FIG. 3  is a magnified elevational side view of the laser transmitter mounted on the hand screed of a representative embodiment of the present invention. 
       FIG. 4  is a perspective view of the hand screed of an alternate embodiment of the present invention. 
       FIG. 5  is a magnified perspective view of the hand screed of an alternate embodiment of the present invention. 
       FIG. 6A  is an elevational side view of the degree plate and turret of a representative embodiment of the present invention. 
       FIG. 6B  is a top plan view of the laser and turret of a representative embodiment of the present invention. 
       FIG. 6C  is a top plan view of the degree plate of a representative embodiment of the present invention. 
       FIG. 7A  is an elevational side view of the laser mounted on the hand screed of a representative embodiment of the present invention. 
       FIG. 7B  is a perspective view of an alternate embodiment of the present invention depicting a moveable laser mounting clamp. 
       FIG. 7C  is a side elevational view of the laser mounting clamp of  FIG. 7B . 
       FIG. 8  is a perspective view of the hand float of a representative embodiment of the present invention. 
       FIG. 9  is an elevational side view of the hand screed and the hand float of a representative embodiment of the present invention in operation on a horizontal surface. 
       FIG. 10  is a perspective view of the hand screed and the hand float of a representative embodiment of the present invention in operation on a sloped surface. 
       FIG. 11A  is an elevational side view of the inclinometer of a representative embodiment of the present invention set to a preset angle. 
       FIG. 11B  is a perspective view of the inclinometer of a representative embodiment of the present invention in its retracted position. 
       FIG. 12  is a perspective view of a first alternate hand grip attachment for the hand screed of a representative embodiment of the present invention. 
       FIG. 13  is a perspective view of a second alternate hand grip attachment for the hand screed of a representative embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   The present invention is illustrated in the attached  FIGS. 1 through 13 . Referring to  FIGS. 1 ,  2  and  3 , hand screed component  1  consists of handle  3 , screed plate  5 , inclinometer  19 , laser  23  and turret  25 . Laser  23  is a visible light laser that is readily available in the construction industry, as well known by those skilled in the art. Mounted on top of handle  3  are bubble levels  9  that are rigidly positioned, one lengthwise and two widthwise, on the upper surface of handle  3  for easy visibility and to ensure accurate and convenient leveling of hand screed  1 . Located on top of handle  3  are watertight compartments  17  and  21  to store inclinometer  19  and laser  23  when hand screed  1  is not in use. Also located on top of handle  3  is mounting pad  27  which comprises mounting hole  33  and pin holes  29  for mounting turret  25  on hand screed  1 . 
   Referring to  FIGS. 4 and 5 , an alternate embodiment of hand screed  1  is shown. In this embodiment, laser  23  is mounted within handle  3  at one end. Aperture  35  located on the end of handle  3  allows light from laser  23  to emit from hand screed  1 . In both of the embodiments described above, handle  3  comprises groove  7  that runs lengthwise along the bottom of handle  3 . Groove  7  is adapted for slidably engaging screed plate  5 . Screed plate  5  has an inverted T-shape comprising ridge  8  for sliding into groove  7 . The bottom of screed plate  5  has a flat surface for resting upon the concrete and for smoothing the concrete when hand screed  1  is drawn across the surface of the concrete. Screed plate  5  is, preferably, made from a composite plastic suitable for screeding plastic concrete, as well known to those skilled in the art. 
   Handle  3  is grasped by an operator to pull hand screed  1  over the plastic concrete. As hand screed  1  is manually drawn through the plastic concrete, it strikes off and levels the surface, to yield an area of uniform flatness and gradient. 
   Referring to  FIGS. 1 ,  2  and  3 , laser  23  is removably positioned in turret  25  that, in turn, is removably mounted on mounting pad  27 . Referring to  FIGS. 6A , B, C and  FIG. 7A , turret  25  comprises member  36  that snugly fits into hole  33  located on mounting pad  27 . Turret  25  further comprises thumbscrew  38  and azimuth plate  31  for setting the azimuth angle of laser  23  relative to hand screed  1  when laser  23  is mounted on top of mounting pad  27 . Azimuth plate  31  is mounted on mounting pad  27  and held in position via pins  40  that fit into pinholes  29 . 
   Referring to  FIGS. 7B and 7C , an alternate mounting system for laser  23  is shown. In this embodiment, laser  23  (not shown) is operatively attached to turret plate  70  that is secured to fixed plate  64  by threading bolt  72  into threaded hole  68 . Plate  64  further comprises key  66  that slides into keyway  62  disposed on clamp mounting plate  60 . Clamp mounting plate  60  is affixed on top of sliding clamp  56  that is adapted to slide along top rail  4  of handle  3 . Tightening thumbscrew  58  secures clamp  56  to handle  3 . With this arrangement, clamp  56  can be positioned at any location along handle  3  that is the most efficient and practical for the installer. 
   Referring to  FIGS. 8 and 9 , hand screed  1  can be guided on a horizontal surface using laser  23  and cross hair target  37  located on hand float  39 . Hand float  39  comprises float board  41  and handle  42  mounted thereon. At least two bubble levelers  9  are rigidly attached to handle  42  that allow the hand float  39  to be leveled side-to-side and front-to-back. Preferably, bubble levelers  9  are embedded in handle  42 . Laser receiver  37  is, preferably, rigidly attached to or embedded on at least one side of handle  42 . 
   Bubble levelers  9  on the hand float  39  in combination with the laser system allow hand float  39  to serve as a portable and stable level guide post. Target  37  has embedded cross hairs to assist the line of sight alignment of the light beam between laser  23  and target  37 . 
   Before commencing screeding, hand screed  1  is placed on the plastic concrete. Hand float  39  is placed in a desired reference location. Target  37  is adjusted to receive the light beam from laser  23  such that the elevation of hand screed  1  can be manually adjusted while the plastic concrete is screeded via line of sight alignment of laser  23  and target  37 , without requiring constant interruption to manually determine the level of the concrete surface. 
   Referring to  FIGS. 10 ,  11 A and  11 B, handle  3  further supports inclinometer  19  releasably mounted thereon. In one embodiment, inclinometer  19  may be an electronic inclinometer. In another embodiment, inclinometer  19  comprises members  47  and  49 . Bubble level  9  is imbedded lengthwise in member  47 . Member  49  has gradient markings to indicate units of inclination such as degrees. Thumbscrew  51  threadably attaches member  47  to member  49  and can be adjustably positioned along the central hole that spans the length of member  49 . Thumbscrews  51  can be tightened to temporarily lock inclinometer  19  at a given angle. Members  47  and  49  attach to pivot joints  53 . In one embodiment, pivot joints  53  are removably attached to the upper surface of handle  3  by magnet  54  so that inclinometer  19  can be stored in compartment  17  when hand screed  1  is not in use. 
   The angle of inclinometer  19  can be adjusted for use of hand screed  1  on a sloped surface such that when hand screed  1  is positioned on a slope, inclinometer  19  can be used to measure the degree of the slope relative to horizontal. Inclinometer  19  is used for maintaining the angle of hand screed  1 . So long as the degree of the slope relative to horizontal remains constant while screeding, the angle of the concrete slope will be uniform. Use of inclinometer  19  in combination with laser  23  and target  37  allows the operator screeding on an incline to ensure that the slope is of uniform angle and of uniform elevation at that angle. 
   In one embodiment, hand screed  1 , laser  23  and inclinometer  19  are made of lightweight materials such that an operator may physically raise and lower hand screed  1  while working the concrete in order to maintain alignment of laser  23  with target  37 . 
   In an alternative embodiment, handle  3  may comprise hand support  13  having grip  12  which may be oval or round in shape as shown in  FIG. 12 . Grip  12  is either fixed or swivel about its center. Hand support  13  is either permanently mounted on hand screed  1  or slides onto handle  3  from one end to a desired location and secured with thumbscrew clamp  15 . 
   In a further alternative embodiment shown in  FIG. 13 , hand support  13  comprises pistol grip  14  whose ergonomic shape makes operating hand screed  1  more comfortable for an operator. Pistol grip  14  is rotatably attached to the top of hand support  13 . As with the previous embodiment described, hand support  13  is either permanently mounted on hand screed  1  or slides onto handle  3  from one end to a desired location and secured with thumbscrew clamp  15 . 
   Although a few preferred embodiments have been shown and described, those skilled in the art will appreciate that various changes and modifications might be made without departing from the scope of the invention. The terms and expressions used in the preceding specification have been used herein as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding equivalents of the features shown and described or portions thereof, it being recognized that the scope of the invention is defined and limited only by the claims that follow.