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Patents Find prior art Discuss this patent View PDF Download PDF Publication number US4474531 A Publication type Grant Application number US 06/453,763 Publication date Oct 2, 1984 Filing date Dec 27, 1982 Priority date Dec 27, 1982 Fee status Lapsed Inventors Herbert G. Weiss Original Assignee U.S. Windpower, Inc. Export Citation BiBTeX, EndNote, RefMan Patent Citations (9), Referenced by (10), Classifications (10),Legal Events (6) External Links: USPT
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    Patents  Find prior art Discuss this patent View PDF Download PDF Publication number US4474531 A Publication type Grant Application number US 06/453,763 Publication date Oct 2, 1984 Filing date Dec 27, 1982 Priority date Dec 27, 1982 Fee status Lapsed Inventors Herbert G. Weiss   Original Assignee U.S. Windpower, Inc.     Export Citation BiBTeX, EndNote, RefMan  Patent Citations (9), Referenced by (10), Classifications (10),Legal   Events (6)  External Links:  USPTO, USPTO Assignment, Espacenet  Windmill with direction-controlled feathering US 4474531 A   ABSTRACT   A windmill employs a separate wind vane pivotably mounted on the chassis of the windmill. An internal sensor detects feather the windmill blades whenever the angle exceeds a predetermined maximum. IMAGES (1)   CLAIMS (1) What is claimed as new and desired to be secured by Letters Patent is: 1. A windmill comprising: a. a tower; b. a chassis mounted on said tower for pivoting with respect thereto in response to wind direction; c. a turbine, including a turbine shaft and blades extending outward from said shaft, mounted on said chassis for rotatichassis normally to pivot into an orientation in which the axis of said shaft is approximately parallel to the wind directioaxes thereof between active positions, in which said blades experience a relatively high force from wind whose directioa minimum when the axis of said shaft is approximately parallel to the wind direction, both when the front end of said cperpedicular to the axis of said shaft so that centrifugal force tends to counteract the bending force applied by the wind d. a wind vane mounted on said chassis for rotation with respect to said chassis in a plane substantially parallel to the shaft; and e. a pitch-control mechanism for monitoring the angle between the directions of said wind vane and said turbine shaft said blades present minimum wind resistance when the front of said chassis faces away from the wind. DESCRIPTION  BACKGROUND OF THE INVENTION The present invention is directed to windmills and, in particular, to means for controlling turbine-blade pitch. Cost and efficiency considerations dictate that windmill parts should be as light in weight as possible. On the other hantherefore, windmills have been designed to minimize the stress experienced by the structure in response to expected One way to reduce blade stress is to incline the blades slightly forward along the axis of rotation, i.e. in the wind directibend the blades in the forward direction. This expedient, however, depends on a proper orientation of the windmill with which the axis of rotation is aligned with the wind direction.  Although the windmill turbine is free to rotate to align itself with the wind, I have found that windmill turbines do not alwtherefore result. Under such stress, blades may be damaged at their roots, or their tips may be bent back (downwind) It is an object of the present invention to reduce the likelihood that sudden wind shifts will enable the wind to apply a foSUMMARY OF THE INVENTION The foregoing and related objects are achieved in a windmill mounted on a support structure so that it can pivot to facethe shaft. The turbine is mounted to rotate with respect to the chassis about the shaft axis, and the chassis and the tur shaft is approximately parallel to the wind direction and a front end of the chassis faces into the wind. The blades can band a feathered position, in which the wind force experienced by the blades is substantially at a minimum.   According to the present invention, the windmill further includes a wind vane mounted on the chassis to rotate with resangle of the wind with respect to the axis of the turbine shaft. A pitch-control mechanism monitors the angle between texceeds a predetermined maximum. Such an arrangement is particularly beneficial in a windmill whose blades are inclined rearward from a plane perpendicBRIEF DESCRIPTION OF THE DRAWINGS These and further features and advantages of the present invention are described in connection with the accompanyinFIG. 1 is a simplified perspective view of a windmill embodying the present invention; and FIG. 2 is a block diagram of a control system employed in an exemplary embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 depicts a windmill 10 mounted on a tower 11 that supports the windmill above the ground. A windmill chassis 12direction is indicated by an arrow 16.  A wind turbine 18 includes a number of blades 20 that are mounted on a turbine shaft 22 rotatably mounted in the winddirection from the shaft 22 but are inclined slightly rearward--i.e., in the ordinarily downwind direction--from the normal downwind direction, and the centrifugal force of the resultant spinning includes an upwind component, when the bladegenerally from the bow, though; wind whose velocity is in a direction opposite that indicated by the arrow 16 applies a f The windmill chassis 12 includes windmill equipment of the type illustrated, for example, in U.S. patent application Ser. powered by the spinning turbine. There might also be apparatus for receiving instructions from a remote location. The interior equipment also includes a pitch controller for controlling the pitch of the blades 20. When the windmill is tuthe wind causes no appreciable spinning and its force on the blades 20 is at a minimum. In accordance with the present invention, a wind vane 24 is pivotably mounted at 26 on the windmill chassis 12 so as tsince the windmill must include a considerable amount of equipment and thus has a relatively high moment of inertia aindicate wind direction. Consequently, during changes in wind direction, the orientation of the wind vane 24 is a better iwind vane 24 to indicate the angle between the wind and the direction in which the windmill is pointing. When that angle is below a predetermined maximum, say 45°, the windmill operates in its conventional manner. When the turbine 18 and thus minimize the wind force experienced by the windmill. One of the ways to control blade pitch in response to the relative position of the wind vane 24 is depicted in FIG. 2, whimentioned Chertok et al. application, which is hereby incorporated by reference.  An angle sensor 26 in FIG. 2 transmits signals containing information regarding the orientation of the wind vane 24 witpurposes and can range from simple limit switches to synchros or other types of angle-sensing devices. In the Chertok et al. windmill, blade pitch is controlled by an actuating rod that extends coaxially within the turbine shaf   actuating rod, and the actuating rod threadedly engages an actuating nut that can be rotated with respect to the turbinthe nut. The blade pitch then remains the same so long as the actuating nut spins at the same rate as the shaft does. In order to maintain a given pitch, therefore, a clutch, represented in FIG. 2 by block 28, acts between the turbine shaft must rotate in a direction opposite that of the shaft rotation so that the threaded engagement will cause the rod to advain FIG. 2 by block 30, that can rotate the actuating nut at a rate higher than that of the turbine shaft in the same directioa direction opposite to that of the shaft until the desired pitch is achieved. When the desired pitch is achieved, the clutc A pitch change to increase power can be achieved by releasing clutch 28 and driving the nut in the same direction as, The Chertok et al. arrangement also includes a brake, represented in FIG. 2 by block 32, that can be operated to stop fail safe: power is normally applied to it, keeping it in its released state, but if there is a power failure, the clutch 28 is reThe clutch 28, the servomotor 30, and the brake 32 are all controlled by a microprocessor 34 that typically monitors thethese commands, it controls the pitch of the blades 20 in accordance with stored routines. In order to carry out the teachings of the present invention, the microprocessor 34 can also be programmed to respondbrake 32 to feather the turbine 18 when the angle between the windmill and the wind is greater than a predetermined desired for greater angles to be tolerated when the wind speed is relatively low. In the alternative, the angle sensor 26 can be employed merely to remove power from the control system and thus autof the pitch-control system. In operation, the internal controls, not shown in the drawings, may receive a command from a remote location to begin adjustment of the blade pitch from the feather pitch position, which is the normal pitch when the windmill is not in operasensor 26 will prevent adjustment of the blade pitch to its start-up value. This result is only temporary, though, becausevelocity increases, the chassis 12 of the windmill will align with the wind, the angle sensor 26 will permit the start-up pit As the wind velocity increases, the force on the turbine blades 20 increases, but the speed of rotation also increases, tIt is possible, however, for the wind to shift too quickly for the windmill to slew around fast enough in response. In this sthe centrifugal force to add to, rather than subtract from, the bending force of the wind. Since the design of the blades can be excessive if they are not feathered immediately. Since the wind vane 24 immediately senses the change in winapply the brake 32, and the turbine blades 20 are thus feathered. Alternatively, the servomotor 30 can be used to feathexcessive strains are avoided. Eventually, the chassis 12 of the windmill will realign itself with the wind, and the angle sensor 26 will sense this realignmotor 30 to adjust the blades to the desired pitch, which will then be maintained by the clutch 28. It is apparent that the present invention decreases the likelihood of excessive stress caused by misalignment between PATENT CITATIONS   Cited Patent Filing date Publication date Applicant US2360791 * Mar 22, 1941 Oct 17, 1944 Morgan Smith S Co Wind t
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