Patent Grant
8182173
The present invention relates generally to screeds for leveling freshly-poured or “wet” concrete, and more particularly, to a portable vibratory screed having a laser-based grade indicator system. The preferred grade indicator system includes a remote indicator that facilitates an operator's ability to operate the screed while monitoring screed operation. The invention also relates to a screed whose handles and any other protruding components can be folded within the vertical and horizontal footprints of the screed for transport.
During a concrete pouring process, a material that includes aggregates, cement, and water is poured into an area that may be bounded by forms to contain the concrete material. As concrete is delivered into the pour area, a plurality of laborers, often called “puddlers,” using tools such as rakes, come-alongs, and/or shovels, distribute the concrete material to generally the desired elevation. Still other laborers, commonly equipped with a piece of lumber or other straight member referred to as a “strike-off,” move the strike-off across the concrete material. The process of manually striking-off the concrete material consolidates the material and forces the larger aggregate below the finished elevation. It also shapes the surfaces of the concrete to the desired slope or “grade.” The levelness of the finished surface is highly dependant on the skill of the personnel handling the strike-offs. Additionally, manually striking-off the concrete material is very labor-intensive and requires a great deal of skill and experience to ensure a flat and properly inclined finished surface.
The advent of the portable vibratory screed greatly reduced the labor associated with leveling of the concrete material. Portable vibratory screeds commonly include a vibration-inducing mechanism attached to a board or “blade” and one or more operator-manipulated handles that extends from the blade. The vibration mechanism typically comprises an “exciter” formed from one or more eccentric weights driven by a motor. Operation of the exciter consolidates the concrete material such that, as the blade is moved across the wet concrete, the vibrating blade forces the larger aggregate below the surface of the material and works a highly cementatious material with smaller aggregates, often called “cream,” to the finish surface of the material. Operator manipulation of the handle, as well as the rigidity of the blade, directly affects the flatness and inclination of the finished surface of the material. Accordingly, an operator's ability to control the pitch or tilt of the blade as well as the speed and direction of travel of the blade determines the flatness of the finished material.
The elevation of the finished material is commonly determined by the operator's visual inspection of the finish elevation in relation to the elevation references such as the forms. More recently, laser-based grade indication systems have been developed that provide precise position information that the operators can use as feedback to manipulate the screed. The typical laser system comprises a reference laser and a laser receiver. The laser is positioned on a tripod or similar support outside of the pour area and emits a laser beam in all directions at a known reference height. The laser receiver is mounted on a vertical post or mast supported on the screed blade at the reference height. The height of the receiver usually can be adjustable by adjusting the length of the mast but is fixed during any particular screeding operation. An indicator on the receiver indicates whether the receiver is level with, above, or below the desired reference plane or “grade” set by the laser transmitter. The operator relies on the grade information provided by the indicator as feedback to maintain the screed at the desired height and inclination.
In order to minimize interference from personnel and other obstructions in and around the pour area, some laser receivers are mounted on masts that extend over the operator's head. However, an operator cannot monitor operation of the working rear or leading edge of the screed blade while simultaneously viewing the receiver's indicator. He or she instead must repeatedly glance up and down so as alternately view the indicator and the leading edge of the screed. This constant glancing up and down can be very fatiguing to the operator. It also increases the chances of operator error.
In addition, the display provided by the typical commercial receiver's indicator is ill-suited for use on a concrete screed equipped a laser elevation/inclination indicator because its generic output only indicates whether the receiver is below or above a reference height. Some receivers do not provide any quantitative information about the magnitude of the offset. The operator therefore must use dead reckoning to determine the magnitude of screed manipulation that is required to obtain the proper height. Other systems attempt to provide an indication of the degree to which the screed is off-grade by flashing an out-of-grade indicator light at a frequency that progressively changes as the screed moves progressively further off-grade. These displays are not intuitive. They also require the operator to view the display for a relatively long period of time to process the information. That is, he or she must view the display sufficiently long to discern the frequency of the flashing display. The delay required for this processing time detracts from the operator's ability to react quickly to an out-of-grade condition and also distracts the operator from monitoring blade operation directly.
The need therefore has arisen to provide a portable vibratory wet concrete screed with a laser indicator whose receiver is relatively immune to interference from obstructions in the vicinity of the screed but whose indicator can be viewed by an operator while simultaneously monitoring operation of the screed blade.
The need also has arisen to provide a wet concrete screed with a laser elevation system that displays easily understandable qualitative and quantitative grade-based information.
Transporting wet concrete screeds having laser elevation systems and/or other portable vibratory wet concrete screeds can also prove a challenge. Screeds occupy “footprints” in both the horizontal and vertical planes defined by rectangular boxes the length, width, and height of which are defined by the maximum length, width, and height of the screed. Both the handles and the receiver masts of a wet concrete screed extend to a height of several feet well above the top of the exciter assembly, typically at least doubling the vertical footprint that would otherwise be occupied by the screed. In addition, the handles extend several feet behind the blade, typically at least tripling the horizontal footprint that would otherwise be occupied by the screed. While screeds have been provided with partially telescoping receiver masts and/or handles that fold approximately midway along their length to facilitate transport, the minimum vertical and horizontal footprints of these screeds are still typically at least double those of the blade and exciter combination. The only way to reduce the footprint of the screed to that of the blade and exciter assembly combination was to disassemble and remove the handles and receiver masts. Disassembling and removing those structures is a time-consuming process that risks loss of components. It also risks assembler error in reassembly.
The need therefore has arisen to provide a wet concrete screed in which the handle(s) and receiver masts (if present) can be folded flat onto the blade so as to reduce the vertical and horizontal footprints of the screed to essentially those provided by the screed and exciter combination.
In accordance with one aspect of the invention, a portable vibratory wet concrete screed includes a blade, an exciter that is selectively driven to induce vibrations in the blade, at least one operator-manipulated handle connected to the blade and extending upwardly and rearwardly from the blade, a laser receiver mounted on the screed at a height above an upper end of the handle, and an indicator that is operatively connected to the receiver. The indicator provides a visual indication of the screed height relative to a desired grade. It is located remote from the receiver at a location which, when viewed from the perspective of a person in the vicinity of a screed operator, is at least substantially in a focal area containing the working rear or trailing edge of the blade. The indicator preferably is located within 18″ and more preferably within 14″ of the rear edge of the blade.
In a preferred embodiment, the indicator includes a display that indicates a change of magnitude at which the screed is off-grade without changing a frequency of indicator flashing. More preferably, the display includes a plurality of lights that are illuminated in combinations that vary with the magnitude at which the screed is off-grade.
In accordance with another aspect of the invention, a portable vibratory screed includes a blade, an exciter that is selectively driven to induce vibrations in the blade, and at least one operator-manipulated handle that is connected to the blade and that extends upwardly and rearwardly. The handle is mounted on the blade so as to be foldable 1) from an upright, operative position in which the handle extends vertically and horizontally well beyond horizontal and vertical footprints occupied by a combination of the blade and the exciter; and 2) to a stowed position in which the handle is positioned at least substantially entirely within the horizontal and vertical footprints.
The screed of this aspect may be a wet concrete screed with a laser grade or elevation system, in which case it additionally includes a mast that supports a laser receiver that is mounted on the screed. The mast is foldable from an upright, operative position in which the mast extends well above the vertical footprint to a stowed position in which the mast is positioned at least substantially entirely within the horizontal and vertical footprints.
Folding may be facilitated by providing a mount assembly via which the handle and the receiver are mounted on the blade. The mount assembly preferably includes a base and a pedestal that is mounted on the base so as to rotate about a vertical axis. The handle and the receiver mast are each mounted on the pedestal so as to be pivotal about a horizontal axis.
Other aspects of the invention include a method of operating a wet concrete screed with laser screed elevation system having a remote indicator and a method of folding at least a handle of a wet concrete screed for screed transport or storage.
These and other aspects, advantages, and features of the invention will become apparent to those skilled in the art from the detailed description and the accompanying drawings. It should be understood, however, that the detailed description and accompanying drawings, while indicating preferred embodiments of the present invention, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the present invention without departing from the spirit thereof. It is hereby disclosed that the invention include all such modifications.
The drawings illustrate the best mode currently contemplated of practicing the present invention. In the drawings:
Still referring to
Portable vibratory screed 10 includes a board or blade 12 having a vibration mechanism or exciter 14 attached thereto. Blade 12 is generally b-shaped when seen in cross section in order to resist bending or twisting along its length. It is formed from extruded aluminum or other material such as magnesium and includes a bottom plate 20 extending the entire width of the blade 12 and a top, reinforced section 22 that extends over approximately the trailing or rear half of the bottom plate 20. (Terms such a “front”, “rear”, “leading”, “trailing,” etc. are used strictly for convenience and a frame of reference). The front portion of bottom plate 20 may be either planer, curved, or inclined. As best seen in
The exciter 14 may comprise any powered device that can be operated to induce vibrations in the blade. The illustrated exciter includes an engine 40 that is supported on a pedestal 42 mounted on top of the blade 12 near its rear wall 24. The engine 40 drives one or more eccentric masses (not visible) to impart vibrations to blade 12. The vibration of blade 12 consolidates and levels a material passed thereunder.
The operator's stations 108, 110 are mirror images of one another and located symmetrically of a centerline of the blade 12. They may be mounted at any desired positions along the length of the screed 10, such as at minimum vibrational nodes on the blade 12 as described in the '239 application. Right station 108 will be described, it being understood that the description applies equally to the left station 110.
Referring to
Referring to
While the receiver 54 provides usual information regarding grade, more user-friendly operation is provided by the remote indicator 56 due to its positioning. That is, the indicator 56 is provided at a location that permits the operator 104, as well as puddlers and other personnel located in the vicinity of the operator 104, to simultaneously focus on both the indicator 56 and the working rear edge 32 of the blade 12. Depending on each individual's height and posture, the eyes of these personnel typically are located 4 feet to 5½ feet behind and 5 feet to 6 feet above and behind the working edge of the blade 12. Their line of sight 90 (
It should be noted that placing the indicator 56 relatively close to the blade 12 not only permits the operator 104 to view the indicator 56 and the screed leading edge 32 simultaneously, but also reduces the imposition of vibrations on the indicator 56. In fact, at a maximum typical operating engine speed of 8000 RPM, the indicator 56 is subject to 7.9 G of vibrations. It would be subject to 26.6 G if it were mounted at the middle of the handle assembly 52.
Referring to
The indicator 56 is electronically connected to the receiver 54 so as to display grade-dependent information based on the signal transmitted to the receiver 54 by the laser transmitter 200. The electronic connection may be achieved through a cable, but a wireless connection is preferred because it is more robust than a cable-based system, whose cable is prone to breakage. Cables also obstruct the line of sight of personnel in the vicinity of the screed 10. The wireless signal may be transmitted by IF signal or IR signal. In the preferred embodiment, the signal takes the form of a Bluetooth® signal.
The nature of the display provided on the indicator 56 may be the same as or different from that on the receiver 54. In the preferred embodiment, the out-of-grade information displayed by both the receiver 54 and the indicator 56 is the same. In order to provide the user-friendly, intuitive, output, the display preferably indicates a change of magnitude at which the screed 10 is off-grade by a mechanism other than changing the frequency at which the lights flash. In a preferred embodiment, the sets of lights 132-140 are illuminated in combinations that vary with the magnitude at which the screed is off-grade. Turning now to
The lights preferably are illuminated at a constant flashing frequency rather than in a progressively changing flashing manner to provide an instantaneously discernable indication of screed height relative to the desired grade.
The exciter 14 and a blade 12, in combination, have “footprints” or rectangular horizontal and vertical areas that contain the exciter and blade. More specifically, referring to
Turning now to
Still referring to
Still referring to
A reduced diameter bottom end of the handle mounting tube 68 extends radially through a second section 226 of the first clamp assembly 214 and is rigidly affixed thereto by, e.g., welding or casting. The first and second horizontal clamp assemblies 214, 216 are conceptually the same as the vertical clamp assembly 184. A threaded shaft 230, having a knob 232 on the end, extends axially through a bore 234 in the second clamp section 226 of the clamp assembly 214 for selective mating with an internally threaded bore (not shown) in the first section 218. The clamp assembly 214 is locked by tightening the knob 232 and unlocked by loosening it. Mating teeth or lugs of the clamp sections 218, 226 are located relative to one another and to the mount assembly 50 as a whole such that the handle mounting tube 68 is capable of being locked in only two positions, namely, the position shown in
Similarly, a bottom end of receiver mast section 82 extends through a second section 240 of the second clamp assembly 216 and is rigidly affixed thereto by, e.g., welding or casting. A threaded shaft 242, having a knob 244 on the end, extends axially through a bore 246 in the second clamp section 240 for selectively mating with an internally threaded bore 248 in the first clamp section 220. The second clamp assembly 216 is locked by tightening the knob 244 and unlocked by loosening it. The mating teeth or lugs on the first and second clamp sections 220 and 240 are located relative to one another and to the mount assembly 50 as a whole such that the receiver mast 80 is capable of being locked into only two positions, namely, the position shown in
To ready the screed 10 for transport, the operator first loosens the knob 198 to unclamp the pedestal clamp assembly 184. He or she then grasps the handle 208 and rotates the pedestal 160 90° and retightens the knob 198. He or she then loosens the knob 232 of the handle clamp assembly 214, folds the handle 52 down, and retightens the knob 232. The process is then repeated with the receiver mast clamp assembly 216. All clamp components are permanently attached to other, larger components of the screed 10. The clamp assemblies need not and in fact cannot be disassembled when preparing the screed 10 for transport, so part losses are unlikely.
It should be noted that the folding mount assemblies of the type described above are also suitable for use with screeds lacking a laser receiver mast, in which case only the handle or handles would fold.
Referring again to
During this process, the laser transmitter 200 sends a 360 degree signal that is received by receivers 54. Each receiver generates a display, described above, that indicates whether the screed 10 is above, below, or level with the desired grade set by the transmitter 200. The same information is displayed on each indicator 56, which is continuously monitored by the associated operator 104 or 106 and used as feedback for manipulating the handle 52. Because the out-of-grade information is provided in an intuitive, instantaneous fashion rather than by flashing lights at a frequency that varies with the degree that the screed is out of grade, the operator 104 or 106 can process the displayed information essentially instantaneously. Puddlers and others in the pour area 102 can also rely on information provided by the indicator and/or the display on the receivers as feedback for their operations.
It is appreciated that many changes and modifications could be made to the invention without departing from the spirit thereof. Some of these changes, such as its applicability to riding concrete finishing trowels having other than two rotors and even to other self-propelled powered finishing trowels, are discussed above. Other changes will become apparent from the appended claims. It is intended that all such changes and/or modifications be incorporated in the appending claims.
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