Patent Application
20100254763
1. Field of the Invention
The invention relates generally to concrete finishing trowels and, more particularly, to riding concrete finishing trowels having power steering systems.
2. Description of the Related Art
A variety of machines are available for smoothing net and partially cured concrete. These machines range from simple hand trowels, to walk-behind trowels, to self-propelled riding trowels. Regardless of the mode of operation of such trowels, the powered trowels generally include one or more rotors that rotate relative to the concrete surface. Riding finishing trowels can generally finish large sections of concrete more rapidly and efficiently than manually pushed or guided hand-held or walk behind finishing trowels.
Riding concrete finishing trowels typically include a frame having a cage that generally encloses two, and sometimes three or more, rotor assemblies. Each rotor assembly includes a driven vertical shaft and a plurality of trowel blades mounted on and extending radially outwardly from the bottom end of the driven shaft. The driven shafts of the rotor assemblies are driven by one or more engines mounted on the frame and typically linked to the driven shafts by gearboxes of the respective rotor assemblies.
The weight of the finishing trowel, including the operator, is transmitted frictionally to the concrete surface by the rotating blades, thereby smoothing the concrete surface. The pitch of individual blades can be altered relative to the driven shafts via operation of a lever and/or linkage system during use of the machine. Such a construction allows the operator to adjust blade pitch during operation of the power trowel. As commonly understood, blade pitch adjustment alters the pressure applied to the surface being finished by the machine by altering the contact surface area of the blades.
The rotor assemblies of riding trowels also can be tilted relative to the vertical axis of the driven shaft for steering purposes. By tilting the rotor assemblies, the operator can utilize the frictional forces imposed on the blades by the concrete surface to propel and steer the vehicle. Generally, the vehicle will travel in a direction perpendicular to the direction of tilt of the rotor assembly. Specifically, tilting the rotor assembly from side-to-side and fore-and-aft steers the vehicle in the forward/reverse and the left/right directions, respectively. It is also commonly understood that, in the case of a riding trowel having two rotor assemblies, the driven shafts of both rotor assemblies should be tiltable side-to-side for forward/reverse steering control, whereas only the driven shaft of one of the rotor assemblies needs to be tilted fore-and-aft for left/right steering control.
Many riding trowels are equipped with steering assemblies that are manually operated. Such systems are disclosed in applicant's co-pending patent application publication no. 2009/0028642 filed on Jan. 29, 2009 and titled “Concrete Trowel Steering System” as well as U.S. Pat. No. 4,046,484 to Holz and U.S. Pat. No. 5,108,220 to Allen et al. Such assemblies typically include two steering control handles mounted adjacent the operator's seat and accessible by the operator's left and right hands, respectively. Each lever is coupled, via a mechanical linkage assembly, to a pivotable gearbox of an associated rotor assembly. The operator steers the vehicle by tilting the levers fore-and-aft and side-to-side, thereby tilting the gearboxes side-to-side and fore-and-aft, respectively.
Manually operated steering control assemblies of the type disclosed in the Holz and Allen et al. patents are relatively difficult to operate because they require the imposition of a significant physical force by the operator both to move the handles to a particular position and to retain them in that position. Although the system disclosed in Patent Application Publication No. 2009/0028642 reduces the physical demands on the operator, such mechanical physical control of riding trowels can become fatiguing over the course of prolonged operation. To address these problems, trowels have been designed that are steered by powered actuators. For instance, applicant's prior U.S. Pat. No. 6,368,016 discloses a trowel that that is steered using electrically powered actuators to tilt the gearboxes. Still other power trowel steering systems are disclosed in U.S. Pat. Nos. 5,890,833, 6,053,660, and 6,592,290 to Allen and U.S. Pat. No. 5,816,740 to Multiquip. Each of the patents discloses a trowel that is steered by hydraulic actuators. Riding power steered finishing machines typically have one or more joysticks that are positioned proximate an operator seat. The joysticks generate instructions that are communicated to electronic or hydraulic actuators whose operation tilts the respective gearboxes to effect the steering operation. The actuators usually are energized proportionally to the direction and extent of joystick movement. Regardless of whether of the particular operating modality, for each joystick position, the actuator will tilt the gearbox a predetermined magnitude. Progressive changes in joystick tilting will commonly result in progressive changes in gearbox tilting. Because the operator input forces are very small, operator fatigue is significantly reduced during operation when compared to operation of traditional, mechanically steered machines.
Regardless if the steering system is electrical, mechanical, hydraulic, or a combination thereof, the response characteristics of the actuators of a riding power steered trowel are typically preset. These values commonly define the sensitivity and responsiveness of the steering system of the trowel to manipulations of the joystick. Typically, these values are factory preset. They set the extent of gearbox tilting for each of a full range of joystick positions. One system, proposed by the assignee and disclosed in European Application No. EP 1,586,723, additionally permits the response characteristics of an electrically steered trowel to be programmed in the field using a personal data assistant (PDA). Programming the trowel's controller requires intricate knowledge of electronic controls and of how to calibrate those controls. As a result, control calibration, adjustment, and/or fault detection functions are commonly performed by very well-trained personnel. Such configurations yield power steering equipped riding finishing trowels whose steering operation is generally fixed or preset after the fluid system is configured or after the controller is programmed. That is, the gearbox is tilted the same, predetermined amount for each joystick position under all operating conditions.
However, operator preference, as well as concrete and weather conditions, can affect the desired responsiveness of the steering system. Most notably, operators prefer a steering that can be “feathered” or have high resolution when maneuvering along the perimeter of a work area or around obstructions in the work area. Hence, they would prefer to operate the joysticks through a relatively large stroke with a relatively small response to maximize steerability. Conversely, when the machine is being operated over long straight stretches in the center of an unobstructed work area, they would prefer that the steering system respond more for given joystick stroke in order to maximize responsiveness. With respect to concrete conditions, the riding trowel becomes more responsive to steering inputs as the surface of the concrete cures. With respect to weather conditions, overcast, shaded, or otherwise protected concrete surfaces generally take longer to cure and are less susceptible to the drying effects of wind and sun, thereby effecting steering performance of the power trowel used for finishing such surfaces. In short, it is desirable for a variety of reasons to be able to adjust the response characteristics of a steering system of a trowel on the fly, i.e., while operating the trowel. Heretofore available power-steered riding trowels did not have this capability.
Accordingly, there is a need for a ride-on concrete finishing trowel having a power steering system that can be switched between two or more preset steering modes in which each steering mode incorporates a distinct steering association.
A steering system according to one aspect of the invention includes a steering system that can be quickly and conveniently switched between two or more preset steering modes.
Another aspect of the invention is to provide a power concrete finishing trowel that meets the first principal aspect, that is cost-effective to implement, and that is generally simple to operate.
One or more of these aspects are achieved by a power steering system for a power trowel that includes one or more manually manipulated steering command signal generators, such as joysticks. Actuators, configured to tilt at least a portion of the rotor assemblies to steer the trowel, receive instructions from the signal generators via a controller. The controller stores at least two sets or families of response characteristics, each of which is associated with a respective preset steering mode. A selector can be manipulated by the operator to select one of the steering modes. The selector may comprise a switch that can be actuated by the operator while steering the trowel. Such a configuration allows the operator to select a set of steering responses that best suits prevailing operating conditions and/or his or her preferences.
Another aspect of the invention resides in a method of controlling operation of a power steered riding rotary trowel that includes selecting between at least two preset steering modes. The selection preferably can be made by a seated operator while the trowel is traveling.
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.
Preferred exemplary embodiments of the invention are illustrated in the accompanying drawings in which like reference numerals represent like parts throughout, and in which:
Still referring to
Referring to
The pitch of the blades 62 relative to the plane of operation of each of the right and left rotor assemblies 24 and 26 can be individually adjusted by a dedicated blade pitch adjustment assembly 70. Each blade pitch adjustment assembly 70 includes a generally vertical post 72 and a crank 74 which is mounted on top of the post 72. Each crank 74 can be rotated by an operator positioned in seat 34 to vary the pitch of the trowel blades 62. In the typical arrangement, a thrust collar 76 cooperates with a yoke 78 that is movable to force the thrust collar 76 into a position pivoting trowel blades 62 about an axis that extends in a perpendicular direction relative to the axis of the driven shaft 60. The pitch of blades 62 is often varied as the material being finished sets and becomes more resistant to being worked by the blades.
Both rotor assemblies 24 and 26, as well as other powered components of the finishing trowel 20, are driven by a power source such as internal combustion engine 42 mounted under operator's seat 34 as seen in
As is typical of riding concrete finishing trowels of this type, trowel 20 is steered by tilting a portion or all of each of the rotor assemblies 24 and 26 so that the rotation of the blades 62 generates horizontal forces that propel machine 20. The steering direction is generally perpendicular to the direction of rotor assembly tilt. Hence, side-to-side and fore-and-aft rotor assembly tilting cause machine 20 to move forward/reverse and left/right, respectively. The most expeditious way to effect the tilting required for steering control is by tilting the entire rotor assemblies 24 and 26, including the respective gearboxes 58. The discussion that follows therefore will describe a preferred embodiment in which the entire gearboxes 58 tilt, it being understood that the invention is equally applicable to systems in which other components or only portions of the rotor assemblies 24 and 26 are tilted for steering control.
More specifically, the machine 20 is steered to move forward by tilting the gearboxes 58 laterally relative to the intended direction of travel to increase the pressure on the inner blades of each rotor assembly 24, 26. Conversely, trowel 20 is propelled in a backward or reverse direction by tilting the gearboxes 58 laterally to increase the pressure on the outer blades of each rotor assembly 24, 26. Crab or side-to-side steering requires tilting of only one gearbox, with forward tilting of right rotor assembly 24 increasing the pressure on the front blades of the rotor assembly 24 to steer the machine 20 to the right. Similarly, rearward tilting of rotor assembly 24 increases the pressure on the back blades of the rotor assembly 24 thereby steering machine 20 to the left.
Steering system 22 tilts the gearboxes 58 of the right and left rotor assemblies 24, 26 in response to operator manipulation of joysticks 28, 30. As shown schematically in
The steering system 22 could be electrically powered, in which case the actuators 104, 106, 108 are electrically powered actuators such as electric screw jack actuators as described in Applicant's prior U.S. Pat. No. 6,368,016, the subject matter of which is hereby incorporated by reference in its entirety. However, the steering system of the illustrated embodiment is hydraulically powered, and the actuators 104, 106, and 108 are hydraulic actuators in the form of double-acting hydraulic cylinders. Fluid flow to and from the hydraulic cylinders is controlled by a valve manifold 102 the individual valves of which are controlled electrically using signals from the controller 100. The hydraulic steering system 22 also includes an unpressurized reservoir 110 that is in fluid communication with a pump 112 and a fluid return 114. Pump 112 draws fluid from the reservoir 110 and delivers pressurized hydraulic fluid to manifold 102 via a filter 113. Instructions, received from controller 100 in response to manipulation of joysticks 28, 30, are used to control valves in the manifold 102 to control fluid flow to and from the double acting hydraulic cylinders forming the actuators 104, 106, 108 to effectuate the desired tilting movement of the respective rotor assembly 24, 26.
The manifold 102 of the presently preferred embodiment includes a plurality of electronically actuated pressure metering valves that can be controlled to vary the pressure on each side of each steering cylinder 104, 106, and 108 between 0 and a maximum of, e.g., 1,000 psi. Six valves are provided in this embodiment. Each has a control or inlet/outlet port coupled to the associated cylinder port, an inlet port coupled to the pump 112, and an outlet port coupled to the reservoir 110. Each valve is responsive to signals from the controller 100 to maintain a pressure in the controlled hydraulic cylinder port that is determined to achieve the commanded response for a given joystick position for a selected steering mode. A proportional pressure reducing valve that acts as an inherently hydraulic closed loop pressure metering unit to achieve a desired pressure at its controlled port is preferred. The “hydraulic closed loop” functionality emulates the electronic closed loop control with a load sensor in an electrically steered trowel. Suitable valves are commercially available, e.g., from Thomas Magnete USA, specifically the PPCD 06 series.
Although steering system 22 is shown as what is commonly understood as an electric over hydraulic or electro-hydraulic system, it should be appreciated from the above discussion that controller 100 could be otherwise connected to electric actuators 104, 106, 108 so as to provide a fully electronic steering system. It is further envisioned that those power trowels having mechanical steering linkages could be adapted for power steering operations via integration of an electric or hydraulic actuator between the respective gearbox and the corresponding steering handle. Such a configuration would also allow replacement of the mechanical steering handle with an electronic joystick.
Still referring to
Referring to the flowchart of
The procedure 138 proceeds from Start in Block 140 to Block 142, where controller 100 reads the steering mode that is derived from the detected position of the steering mode selector 31. Having received the selected steering mode 142, the position or displacement signals that serve as the steering command signals are received from each of the joysticks 28, 30 and read at Block 144. The procedure 138 then proceeds to Block 146, where the controller 100 consults the pre-stored map and reads the steering association data reflecting the desired response associated with the prevailing joystick signal positions in the selected mode. It then generates appropriate actuator control signals and transmits them to the valves of manifold 102 in Block 148. Each of the valves responds to these signals by metering the pressure in the associated hydraulic cylinder port to a level determined to achieve the desired tilting force applied to the gearboxes 58 by the actuators 104, 106, 108. The procedure 138 then proceeds to End in block 150. Understandably, rather than associating joystick translation to a respective tilting force, it is appreciated that joystick translation could alternatively be associated with other information such as actuator stroke and/or rotor tilting. In addition, other values and/or other open loop or closed loop control schemes could be used to control the actuators.
As mentioned above, each steering mode associates a given range of movement of a joystick 28, 30 with different responses in actuators 104, 106, 108. Said in another way, in each steering mode, steering system 22 provides a different actuator response curve for the same range of joystick translation. Sample response curves 160, 162, and 164 in
Referring to
Curve 162 plots the response of the valves for the actuators 106 and 108 in response to fore and aft movement of the joysticks 28 and 30 for forward/reverse propulsion and turning in the second mode. Curve 164 plots the response of the valves for the actuator 104 in response to side-to-side movement of the joystick 28 for side to side steering in the second mode. Both curves 162 and 164 are preferably non-linear, reflecting lower sensitivity and resulting higher steering resolution at smaller joystick strokes and higher sensitivity and resulting lower steering resolution at higher strokes. As the “droops” in the shape of curve 162 and 164 increase, the pressure response of the associated valves decreases through most of the range of joystick movement when compared to the linear response curve 160, converging back to full pressure at full joystick movement, if necessary. (The reduced average magnitude and slope of curve 164 reflects the fact that, due to the geometry and dynamics of trowel operation, the forces and associated hydraulic cylinder pressure required for side-to-side steering are less than those required for fore and aft steering). This mode might be desired by an operator desiring “fine” steering, such as when steering the machine along the edge of a work area or maneuvering around a post or other obstruction. The first steering mode reflected by the linear response of curve 160, on the other hand, might be desired when operating along long passes with relatively little steering and/or when working in sluggish conditions such as initial panning on wet concrete.
The modes illustrated graphically by
Hence, the inventive system provides a power steered riding finishing machine whose steering performance can be changed between a number of different preset steering modes by a seated operator while the trowel is traveling. Each mode may itself be separately adjustable at the factory or in the field by suitably programming the controller. The power steering system allows the finishing trowel to be individually configured as a function of the conditions and operator preferences associated with any given finishing project.
Although the best mode contemplated by the inventors of carrying out the present invention is disclosed above, practice of the present invention is not limited thereto. It will be manifest that various additions, modifications and rearrangements of the features of the present invention may be made without deviating from the spirit and scope of the underlying inventive concept. The scope of still other changes to the described embodiments that fall within the present invention but that are not specifically discussed above will become apparent from the appended claims and other attachments.
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.
