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Self-propelled concrete saw with forward motion speed control systemRelated Patent Categories: Mining Or In Situ Disintegration Of Hard Material, Automatic Control; Signaling Or Indicating, Of Hard Material Disintegrating Machines, Floor WorkingSelf-propelled concrete saw with forward motion speed control system description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070194617, Self-propelled concrete saw with forward motion speed control system. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of Invention [0002] The present invention relates to a saw for cutting concrete, asphalt, and other hard, flat surfaces and, more particularly, to a self-propelled concrete saw equipped with a forward motion speed control system. [0003] 2. Description of Related Art [0004] Large, horizontal slabs of concrete are frequently poured during the construction of buildings, bridges, roads, runways and the like. Once poured, such slabs must often be cut or scored using a concrete saw for various reasons such as, for example, to form expansion joints, to allow for foundation shifting, to create stress cracks along which the slab will split and/or to create high friction surfaces such as for bridge decks and airport runways. In most large-scale applications, a self-propelled concrete saw is used to cut or score the slab. Self-propelled concrete saws are also used to cut or score asphalt, stone and other hard surfaces. [0005] Most self-propelled concrete saws are equipped with a power plant (e.g., an internal combustion engine or electric motor) and a drive system that is configured to rotate a diamond impregnated saw blade during the cutting and/or scoring operation. The power plant is usually configured to produce maximum horsepower in a peak operational range, which is usually expressed in terms of a range of revolutions per minute ("RPM"). In this peak operational range, the power plant can generate maximum torque, and thus the work the saw blade can accomplish is also maximized. Internal combustion engines, in particular, are usually designed to provide maximum engine cooling in this peak operational range. [0006] Diamond impregnated saw blades are extremely durable, but they do wear out over time. Studies have shown that the service life of a diamond impregnated saw blade is maximized when the blade is rotated at a rate within a specified range of optimal angular velocities and when the torque loading on the blade is held within a specified range. Excessive angular velocities or torque loadings can result in premature wearing, while insufficient angular velocities or torque loadings can cause the cutting surfaces of the saw blade to become polished, which severely diminishes the cutting efficiency of the saw blade. [0007] Generally speaking, torque loading on a saw blade mounted on a self-propelled concrete saw is a function of the depth of cut, the rotational energy being transmitted to the saw blade by the power plant, and the forward motion speed of the concrete saw. The depth of the cut is usually application specific, and thus cannot be varied to optimize the speed of the cutting or scoring operation and/or the service life of the saw blade. The power plant is configured to operate in a peak range or band of optimal RPM's, and thus it is generally not advantageous to attempt to adjust the rotational speed of the power plant to optimize the speed of the cutting or scoring operation and/or the service life of the saw blade. [0008] In most conventional self-propelled concrete saws, the forward motion speed of the concrete saw is set at a constant predetermined speed, or is manually controlled by the operator of the concrete saw, who walks behind the saw making adjustments in response to perceived changes in the performance of the concrete saw. In either instance, an operator must manually select and control the forward motion speed of the self-propelled concrete saw in response to perceived torque loading on the saw blade in order to attempt to maintain the angular velocity of the blade and the torque loading on the blade within their optimal ranges. This requires a high level of operator skill and creates a risk that the operator will select a forward travel speed that will damage the blades. SUMMARY OF THE INVENTION [0009] The present invention provides a forward motion speed control system for a self-propelled concrete saw, a self-propelled concrete saw equipped with a forward motion speed control system and a method of controlling the forward motion speed of a concrete saw during a cutting or scoring operation. In one preferred embodiment of the invention, the forward motion speed control system senses and monitors the rotational speed of the saw blade and/or speed of a power plant transmitting rotational energy to a saw blade and adjusts the forward motion speed of the self-propelled concrete saw to maximize the forward motion speed of the self-propelled concrete saw while maintaining the rotational speed of the saw blade and/or the power plant in a peak operational range. [0010] The foregoing and other features of the invention are hereinafter more fully described and particularly pointed out in the claims, the following description setting forth in detail certain illustrative embodiments of the invention, these being indicative, however, of but a few of the various ways in which the principles of the present invention may be employed. BRIEF DESCRIPTION OF THE DRAWINGS [0011] FIG. 1 is a schematic side view of a self-propelled concrete saw according to the invention. [0012] FIG. 2 is a block diagram of a control system according to one embodiment of the invention. [0013] FIG. 3 is a flow chart illustrating a method of the invention for controlling the forward motion speed of a concrete saw during a cutting or scoring operation. DETAILED DESCRIPTION OF THE INVENTION [0014] With reference to FIG. 1, a self-propelled concrete saw 10 comprises a diamond impregnated saw blade 20, a power plant (illustrated as an internal combustion engine) 30 and an associated drive system for providing rotational energy to the saw blade 20, a frame 40 for supporting the power plant 30, and a set of front wheels 50 and rear wheels 60 connected to the frame. In the schematically illustrated self-propelled concrete saw 10, the rear wheels 60 are driven in a conventional manner using a prime mover 70, typically a hydraulic drive system such as that shown in U.S. Pat. No. 5,810,448 which is incorporated herein by reference in its entirety. The forward motion speed of the self-propelled concrete saw 10 during a cutting or scoring operation is controlled by a control system 80. It will be appreciated that power plant 30 may comprise any one of a variety of power sources other than an internal combustion motor, such as, for example, a diesel motor or an electric motor. [0015] In operation, the saw blade 20 preferably rotates in a direction that is the same as the rotation of the front wheels 50 as the self-propelled concrete saw 10 moves in a forward direction. The saw blade 20 thus naturally attempts to "climb out" of the cut as the cutting or scoring operation proceeds. This climbing out can be discernible as a decrease in the load on the saw blade 20, which will cause the RPM's of the internal combustion engine 30 to increase. [0016] It will be appreciated that the saw blade 20 can alternatively be rotated in a direction opposite that of the rotation of the front wheels 50 as the self-propelled concrete saw 10 moves in a forward direction. This is disadvantageous in some applications, however, as it can result in chipping of the surface of the concrete being cut or scored adjacent to the cut. [0017] As noted, the self-propelled concrete saw 10 schematically illustrated in FIG. 1 is equipped with a control system 80 in accordance with the invention. The control system 80 generates an output signal to the prime mover 70 to control the forward motion speed of the self-propelled concrete saw 10 in response to a first operational parameter that correlates to the rotational speed of the saw blade 20 during the cutting or scoring operation. [0018] The control system 80 includes a controller 90 and a memory device 100 for storing both data and software used in conjunction with the controller 90. The control system 80 further comprises a first sensor 110 that measures a first operational parameter of the self-propelled concrete saw 10, and then provides a first output signal representative of a rotational speed value for the saw blade 20 to the controller 90. Because the rotational speed (usually measured in terms of RPM's) of the power plant 30 providing rotational energy to saw blade 20 generally correlates to the rotational speed of the saw blade 20, the first sensor 110 is preferably an electronic load control module or a tachometer mounted on the internal combustion engine 30. Alternatively, the first sensor 110 can be a digital RPM sensor for measuring the actual rotational speed of the saw blade 20. [0019] Preferably, the controller 90 also receives input from a second sensor 120 that measures a second operational parameter of the self-propelled concrete saw 10 that correlates to the cutting depth of the saw blade 20. Data can also be provided to the controller 90 by a rotary transducer 130 mounted on one of the front wheels 50 of the self-propelled concrete saw. The output of the rotary transducer 130 can be used to determine the actual forward motion speed of the self-propelled concrete saw during the cutting or scoring operation. [0020] The controller 90 can also include a user input/output ("I/O") interface 140 combining an interface such as a display screen with user controls such as an alphanumeric keyboard or keypad that can be manipulated by the user. The I/O interface enables input of operational data for use by the controller 90. Continue reading about Self-propelled concrete saw with forward motion speed control system... 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