Patent Grant
7044682
1. Field of the Invention
This invention relates generally to concrete finishing machines, and, more particularly, to apparatus for controllably adjusting the pitch of the trowel blades of such machines.
2. Background Information
Concrete finishing machines have been used for many years to level and finish large concrete pads. Such machines typically include a rotatable trowel blade assembly having a plurality (e.g., three or four) of generally planar trowel blades mounted on trowel arms projecting radially outwardly from a common hub, all of which are rotated by a gasoline-powered engine. The trowel blades rest directly on the concrete surface to be finished and support the machine's entire weight.
Concrete finishing machines typically further include means for controllably pivoting the trowel blades about their respective radial axes, to change their pitch relative to the concrete surface to be finished. Changing the blades' pitch correspondingly changes the proportion of blade surface contacting the concrete surface, such that the machine's weight is supported by a larger or smaller area of the surface.
In use, the machine makes several passes over the concrete surface as the concrete hardens, with the blade pitch being specially selected for each pass. In the initial pass, when the concrete is still very wet and plastic, the blade pitch is usually adjusted to be substantially parallel with the concrete surface, thereby lying flat upon it and spreading the machine's weight over a maximum surface area. In subsequent passes, as the concrete hardens and becomes less plastic, the blade pitch is progressively increased, with the pitch used in the final pass sometimes being as much as about 30 degrees.
Improvements in recent concrete formulations have made some concrete slabs include pockets or areas of varying plasticity. In such situations, it is necessary to rapidly adjust the trowel blade pitch in order to produce the desired finish. It is also necessary to adjust the trowel blade pitch when the machine is being moved to an adjacent area where the concrete is at a different stage of hardness. In this situation, which frequently occurs when very large concrete pads are being formed, the blade pitch must be adjusted very rapidly.
In the past, the pitch of the trowel blades was typically adjusted using a thrust collar that pushed downwardly on fingers projecting upwardly from the rear sides of the respective trowel arms. Typically, such a downward force on the thrust collar is provided by a yoke or fork that is pivotally secured to the machine's frame and connected to an actuator means adjacent the device's handlebars. By operating the actuator means, the pitch yoke is manipulated thereby applying (or removing) a force on the thrust collar. Examples of such a yoke and thrust collar pitch control can be seen in U.S. Pat. Nos. 3,412,657 (Colizza et al.), U.S. Pat. No. 3,791,754 (Zochil), U.S. Pat. No. 4,232,980 (Tertinek et al.), U.S. Pat. No. 4,577,993 (Allen et al.), U.S. Pat. No. 4,673,311 (Whiteman, Jr.), and U.S. Pat. No. 5,405,216 (Allen et al.).
A disadvantage to this use of yoke (or fork) is the fact that the thrust collar is depressed (or lifted) at two points, namely by its contact with the ends of the two arms of the yoke. Having pressure applied at two points can lead to slight tilting of the thrust collar and thereby resulting in wear between the thrust collar and the drive shaft and/or the thrust collar wear bushing inserted between the drive shaft and the thrust collar. What is needed is a method of moving a thrust collar that eliminates this wear caused be the application of pressure by a yoke.
A second disadvantage with a yoke and thrust collar system is the necessity to use cables, chains and other means of moving the yoke. In order to conceal and protect these means, they typically extend from the handlebars to pitch controller via the inside of the handle. Because of this, such a handle is limited in minimum diameter and is unable to be foldable. What is needed is the ability to fold the handle.
A third disadvantage to the prior art yoke and thrust collar system is the fact that the user must physically supply the force necessary to move the thrust collar into engagement with the fingers of the arms of the blades. Various mechanical means are shown in the prior art which help reduce the amount of force required, but the fact remains that the user is still required to physically depress or lift the thrust collar. What is needed is a pitch controller that does not require the user to physically manipulate the thrust collar.
A fourth disadvantage to many renditions of the old yoke system is the convenience of the user. The trailing edge of each trowel blade, which contacts the concrete surface on which the machine rests, is spaced from the blade's pivot axis. Any change in blade pitch therefore transfers the machine's weight by raising or lowering the machine on the surface. Since the machine is generally quite heavy, usually weighing several hundred pounds, the screw handle used for blade pitch adjustment must have threads with a very small pitch to permit the operator to rotate it conveniently. Consequently, the blade pitch adjustment can be made only very slowly. This has been proven to be unsatisfactory in many situations. Some concrete finishing machines have overcome the slow pitch adjustment afforded by the screw handle described above by replacing the screw handle with a long lever attached to the machine's framework. Although this configuration permits a rapid adjustment of the blade pitch, it is not generally convenient to use. This is because the lever requires large movements for lever advantage and because the lever is not conveniently located on the machine handle itself and thus requires the operator to control the machine using merely one hand and unsteady footing. What is needed is a means of changing pitch which requires less digital manipulation than the prior art methods.
It should be appreciated from the foregoing that there is a significant need for a concrete finishing machine having a trowel blade adjustment apparatus that can be used by the operator to mechanically adjust the trowel blade pitch, yet is simple in construction and convenient to use. The present invention fulfills this need.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
The present invention is an improved pitch controller. Such a pitch controller particularly configured for use with a concrete finishing trowel. The preferred embodiment utilizes the existing mechanical rotation of the drive shaft and/or attached rotors to serve as the source of the force required to raise and lower the weight of the trowel while the pitch of the blades is adjusted. Thus, the present invention includes any means of using the rotation of the drive shaft and/or attached rotors to adjust the pitch of the blades. For instance, using the drive shaft's rotation to maneuver a thrust collar away from the trowel transmission and into engagement with the blade pitch mechanism of the trowel, thereby increasing or decreasing the pitch of the attached blades.
In one embodiment, the present invention comprises an improved concrete finishing trowel or machine. This trowel having a drive means (i.e., engine, motor, turbine, etc.) having extending therefrom a drive shaft. This drive shaft connecting with and configured to rotate a rotatable blade assembly. This rotatable blade assembly adapted to finish a concrete surface. This rotatable blade assembly having a generally vertical axis of rotation and a plurality of radially spaced apart concrete finishing blades extending outwardly from said vertical axis for frictionally contacting the concrete surface. These blades each defining a longitudinal axis generally perpendicular to the vertical axis.
The trowel further having a pitch controller for varying the pitch of the blades by rotating them about their longitudinal axis. This pitch controller utilizing the rotation of the drive shaft to rotate the blades. This pitch controller comprising a thrust collar, a nut, and a bearing. The thrust collar comprising a plate configured to bear downwardly on the rotatable blade assembly thereby varying the pitch of the blades by rotating them about their longitudinal axis. The said thrust collar further comprising a hollow shaft able to receive the drive shaft therethrough, this hollow shaft having an exterior surface which is threaded.
The pitch controller's nut being configured for threading onto the exterior surface of the thrust collar. This nut having an upper surface for supporting a bearing. This bearing configured to support the lower surface of the drive means or other component of the body of the trowel.
Finally, the pitch controller comprises a clutch for selectively engaging and disengaging the pitch controller. In use, the nut can be threaded in a first direction on the thrust collar and towards the thrust collar plate. Likewise, the nut can be threaded in an opposite, second direction on the thrust collar and away from the thrust collar plate. Travel in the first direction resulting in a reduction in the degree of downward bearing upon the rotatable blade assembly by the thrust collar plate thereby resulting in a decrease in pitch. Travel in the second direction resulting in an increase in the degree of downward bearing upon the rotatable blade assembly by the thrust collar plate thereby resulting in an increase in pitch.
In this preferred embodiment, the drive means drives the drive shaft thereby rotationally driving the thrust collar and the rotatable blade assembly. The clutch is configured to stop the nut while the drive means is driving, thereby resulting in travel in the second direction and moving the thrust collar away from the nut. Likewise, the clutch is configured to transmit the rotation of the thrust collar to achieve travel in the second direction thereby drawing the thrust collar nearer the nut. This is particularly seen where the diameter of the thrust collar is greater than the nut, whereby rotation of the thrust collar results in expedited rotation of the nut.
Still other objects and advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description wherein I have shown and described only the preferred embodiment of the invention, simply by way of illustration of the best mode contemplated by carrying out my invention. As will be realized, the invention is capable of modification in various obvious respects all without departing from the invention. Accordingly, the drawings and description of the preferred embodiment are to be regarded as illustrative in nature, and not as restrictive.
While the invention is susceptible of various modifications and alternative constructions, certain illustrated embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but, on the contrary, the invention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention as defined in the claims.
Referring initially to
The blades 88 are configured to rest directly on a wet, semi-plastic concrete surface 19 to be finished and these blades 88 support the machine's 80 entire weight. The blades 88 are all pivotable about their respective radial axes to typically change their pitch relative to the concrete surface 19 over a range typically extending from substantially 0 degrees to about 30 degrees. This pivoting changes the area of the blade surface contacting the concrete and thus changes the pressure applied to the concrete. The pivoting also correspondingly raises or lowers the machine on the surface.
Referring now to
The thrust collar 22, preferably lined with an oil-impregnated thrust collar bushing 97 (shown in
Referring now to
Optionally, as shown in
The nut 30 is provided having a geared rim 34 and a threaded inner surface 36 able to receive therein the threading of the thrust collar's threaded neck 28. This nut 30 is able to travel along the threaded neck 28 of the thrust collar 22. The upper surface 32 of the nut 30 is configured to support a bearing 48 which in turn supports the bottom 98 of the transmission case 96, the drive means lower surface or another portion of the concrete finishing trowel.
In use, the drive shaft 84 turns the spider 86 and the thrust collar 22. The nut 30, being threaded onto the thrust collar 22, rotates with the thrust collar 22 by default. As shown in
As the thrust collar 22 unscrews downwards from the nut, the underside 24 of the thrust collar plate bears downwardly on the blade pitch mechanism 89 of the trowel blades, namely upon the fingers 92. This downward force upon the fingers 92 causes the arms 90 to rotate about their respective radial axes and thus increases the pitch of the blades 88. When the desired degree of pitch is obtained, the user would manipulate the control handle to cause the gear 54 to release the nut 30, thereby moving the clutch 50 into its neutral position.
As shown in
At any desired point, the user could disengage this gear 54 by moving the clutch 50 into “neutral” thereby stopping the screwing back in. This process allowing for an infinite adjustment in the reduction of the pitch. Allowing for the total screwing back in of the thrust collar would preferably result in generally zero degree of pitch.
Referring back to
Referring now to
In the embodiment shown, the interconnector 72 is connected to a clutch 50 for selectively engaging and disengaging the pitch controller 10. In the preferred embodiment, the clutch 50 has three modes, namely “increase pitch,” “maintain pitch” and “decrease pitch.”
When the clutch 50 is, via said control handle 70 and said interconnected interconnector 72, in the “increase pitch” mode, the pitch controller is engaged to increase pitch. In the preferred embodiment, when in this mode, the clutch 50 engages a pawl 52 which stops the rotation of the nut 30. Stopping the rotation of the nut, as discussed above, causes the thrust collar 22 to unscrew out of the nut 30 thereby resulting in the thrust collar 22 depression of the fingers 92 of the blade pitch mechanism 89 resulting in the rotation of the trowel blades about their radial axis, increasing pitch. This action is particularly shown in
When the clutch is, via said control handle 70 and said interconnected interconnector 72, in the neutral (“maintain pitch”) mode, the pitch controller is left in its current degree of pitch. In the preferred embodiment, in such a mode, the nut 30 remains in a fixed location upon the treads of the thrust collar, rotating at the exact same rate as the thrust collar, maintaining the position of the trust collar and thus the current degree of pitch.
When the clutch 50 is, via said control handle 70 and said interconnected interconnector 72, in the “decrease pitch” mode, the pitch controller 10 is engaged to decrease pitch. In the preferred embodiment, when in this mode, the clutch 50 engages a gear 54 which engages both the geared rim 23 of the thrust collar and the geared rim 34 of the nut. This dual gear 54 geared to cause the nut 30 to rotate at a rate greater than the rotation of the thrust collar 22, thereby screwing the thrust collar 22 back into the nut 30. This results in the thrust collar 22 exerting less pressure downwards on the fingers 92 of the blade pitch mechanism 89, thereby resulting in a reduction in the rotation of the trowel blades about their radial axis, decreasing pitch.
In another embodiment, the present invention could utilize rubber rollers and coated surfaces to achieve the same effect as the utilization of clutch gear or cog and the geared edge of the nut and the geared edge of the thrust collar.
Another embodiment of the present invention comprises a thrust collar having a neck having a threaded outer surface.
Another embodiment of the present invention comprises a thrust collar having a generally perpendicular pin extending therefrom for contacting the spider (rotatable blade assembly).
Because the prior art devices required engagement and disengagement mechanisms which at least partially transit through a hollow handle, the present invention comprises, in another embodiment, a power trowel having a folding handle, with or without the invented pitch controller.
While there is shown and described the present preferred embodiment of the invention, it is to be distinctly understood that this invention is not limited thereto but may be variously embodied to practice within the scope of the following claims. From the foregoing description, it will be apparent that various changes may be made without departing from the spirit and scope of the invention as defined by the following claims.
This application claims priority from U.S. application Ser. No. 60/437,480, filed Dec. 31, 2002, having the same inventors, the disclosure of which is incorporated herein by reference.
| Number | Name | Date | Kind |
|---|---|---|---|
| 2869441 | Barnes | Jan 1959 | A |
| 2888863 | Eisenbeis | Jun 1959 | A |
| 3000378 | Thieme et al. | Nov 1961 | A |
| 3412657 | Colizza et al. | Nov 1968 | A |
| 3791754 | Zochil | Feb 1974 | A |
| 4198178 | Carlstrom et al. | Apr 1980 | A |
| 4232980 | Tertinek et al. | Nov 1980 | A |
| 4320986 | Morrison | Mar 1982 | A |
| 4577993 | Allen et al. | Mar 1986 | A |
| 4673311 | Whiteman, Jr. | Jun 1987 | A |
| 4784519 | Artzberger | Nov 1988 | A |
| 4859114 | Artzberger | Aug 1989 | A |
| 5096330 | Artzberger | Mar 1992 | A |
| 5108220 | Allen et al. | Apr 1992 | A |
| 5405216 | Allen et al. | Apr 1995 | A |
| 5632570 | Balling | May 1997 | A |
| 5816739 | Allen | Oct 1998 | A |
| 5993109 | Motl et al. | Nov 1999 | A |
| 6048130 | Allen et al. | Apr 2000 | A |
| 6368016 | Smith et al. | Apr 2002 | B1 |
| 20040165952 | Glenn et al. | Aug 2004 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20040165952 A1 | Aug 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| 60437480 | Dec 2002 | US |
