IE52140B1 - Automatic storm protection control for wind energy system - Google Patents

Description

The present invention relates in general to wind energy plants, and more particularly, to storm protection of wind energy plants.

Changing the pitch, or angle, of air foil type propellers for speed regulation has long been in use for preventing over-speeding in normal winds and light storms. However, most of such governing devices, if they change the pitch sufficiently to prevent over-speeding In winds above 80 to 96 km/hr (50 to 60 miles per hour), when the blade angle to the wind is increased beyond a certain point in order to prevent any further Increase in speed, the outer portion of the propeller begins to act as a high speed centrifugal paddle” fan. Back pressures of 160 km/hr (100 miles per hour) or more are thus created against the back portions of the propeller and this back pressure in turn allows tremendous pressure buildup against the front side of the revolving propellers, often breaking them as well as subjecting the entire plant and tower to severe storm damage. - Winds exceeding 160 km/hr (100 miles per hour) are encountered at the tops of. towers and a successful wind energy system must be automatically controlled when such storms strike.

U.S. Patent No. 4068131 discloses a wind energy plant having the propeller axis offset from the vertical. U.S. Patent No. 4088420 discloses a wind electric pump in which the mast is offset from the centre of the gear assembly.

While the devices thus disclosed afford protection to the wind energy plant in storms wherein wind velocities do not exceed about 96 km/hr (60 miles per hour), and are thus adequate under most conditions, there are storms in which wind velocities exceed 96 km/hr, especially at the heights of the propellers of the wind energy power plants. As used herein, the term high winds, or the like, will refer to wind velocities with respect to the wind energy plant of about 96 km/hr and above. Even though such storms are rare in many areas, even the slimmest possibility of such a storm should be allowed for.

A drawback to presently known wind energy power plants Is that protection against high winds, that is, winds in excess of 96 km/hr is 2. either not possible nt all, or can be accorapl lulled only at conn I derail le expense. Accordingly, all known wind energy power plants either are not protected against high winds, or are protected inadequately, or are extremely expensive.

A device according to the present Invention reliably, yet inexpensively, protects a wind energy plant against high winds.

According to the invention a wind energy system comprises a variable pitch propeller assembly having a propeller arranged to rotate about a rotation axis, the propeller assembly being mounted upon a support means for pivotation about a pivot axis, the rotation axis of the propeller being offset from the pivot axis, a hypoid gear drive hy which rotation of the propeller is transmitted to a shaft rotatable about the pivot axis, a pitch control governor on the propeller assembly to change the pitch of blades of the propeller in response to wind velocity generated pressure against the blades, the propeller speed being independent of any electrical load on a generator driven by the propeller and being governor controlled until the blades are fully feathered, a tail assembly connected to the propeller assembly to assist in keeping the blades facing directly Into the wind until the blades are fully feathered, the connection between the tail and propeller assemblies including a pivot, the pivot control means to prevent pivotal movement between the propeller and tail assemblies until the blades are fully feathered and to allow limited pivotal movement between the propeller and tail assemblies after the blades are fully feathered, under the influence of wind pressure exerted on the propeller because of the combination of the hypoid gear drive propeller axis offset and the increased wind pressure created against the fully feathered blades, the pivot control means including a one-way damped snubber spring assembly to damp return movement of the propeller and tail assemblies after relative pivotal movement therebetween.

The device Includes means for folding the propeller axis and gear case assembly to one side when excessive wind pressure against the propellers develops in very high wind storms of 80 to 160 km/hr (50 to 100 miles per hour) or more. The device herein disclosed accordingly relies on a variable pitch governor to control propeller speed up to wind speeds 3. of about 80 km/hr and thus the wind plant continues to secure full power output even though the wind is considerably stronger than required to secure maximum power, which is usually and preferably realised at 40 to 56 km/hr (25 to 35 miles per hour). During the wind storms of higher velocity, in the 80 to 160 km/hr or above range, the damaging pressures explained above create a considerable pressure against the propeller and tower structure, often destroying or severely damaging known structures.

In the presently disclosed device, this wind pressure increase is used to swing the propeller axis around out of the wind. Under normal operation in winds up to 80 km/hr the variable pitch speed control prevents over-speeding and allows the production of full power, but above that wind velocity, the device of the present invention uses the air brake paddle effect of the propellers to create the required folding pressure without strain on the plant or tower structure. Thus, a wind energy plant according to the present invention will reliably deliver full output even in storms having very high and gusty winds.

The device includes a hinge means connecting the gear assembly to the tall section of the plant so that the gear assembly can pivot with respect to that tail section. A one-way damped snubber spring assembly that produces damping action only when the vane is returned to normal operating positions after folding out against the spring action, connects the gear assembly to the tail section. The snubber spring assembly permits relief of excessive wind pressure on the propellers above that required to produce full energy output from the plant alternator, or full mechanical power from a vertical drive shaft, as the case may be.

The back pressure that is applied by the wind to the propeller system will not fold the propeller system (together with the gear case assembly) until full power is first developed by the propeller, after which, Increased wind pressure applied to the propeller by excessive winds and/or storms will fold the operating plane of the propeller around to the side. This folding of the propeller reduces the contact area of the propeller blades with the wind to prevent any increased pressure against the propeller system, power mechanism and supporting tower. This storm safety control means is used with a means which prevents any excessive 140 propeller speed In strong winds by automatically changing the pitch, or angle of the propeller blades, to reduce their contact area with the wind when the speeds exceeds a preset rate. An automatic pitch change centrifugally operated speed governor can prevent speed increases above a preset rpm through wind speeds of 48 to 80 km/hr (30 to 50 miles per hour). However, If the propeller blades are turned at a sharp angle with their flat power face nearly parallel to the wind direction in stronger winds of 96 to 160 km/hr (60 to 100 miles per hour), each propeller blade acts as a centrifugal fan to restrict rotation, as the outer ends are travelling at linear speeds of about 160 km/hr or the like. Such retarding action creates an increased pressure from the wind, pushing back on the propeller huh and gear case. This increased wind pressure causes an offset propeller huh axis to swing around the vertical axis thereof (i.e·, the vertical pinion shaft in the tower), thus reducing the wind pressure against the propellers, giving positive, automatic and complete storm damage protection to the entire plant and tower. Full energy output Is maintained in all strong winds In storms with just enough wind pressure being applied to the propellers to maintain full power output while at the same time giving complete storm protection.

The one-way-damped snubber spring assembly action used in the device allows the plant to swing around quickly from sudden gusts of high winds as there is no snubber damping of the spring resistance to the folding action of the propellers. A slow return action, however, takes place when the propeller and gear case assembly start swinging back into the normal power position facing the wind. This one-way-damped snubber spring assembly action prevents any oscillating, or whipping, In turbulent or gusty winds often experienced In storms. The propeller can fold quickly out of the wind to prevent wind pressure damage hut must return back into the wind slowly, thus preventing any oscillation or swinging damage to the unit or extra strain on the tower.

The storm protection means disclosed herein allows positive variable pitch control which is necessary for proper regulation in normal wind speeds with the added protection of folding the unit out of the excessive wind pressure position during high wind storms. . 53140 IE Is noted that many wind plants, Including water pumping multi blade windmills, use wind pressure to fold them out of the wind for speed control. However, in the present device, because of and by the action of the offset hypold gear design employed, the propellers of the present device can he kept facing directly into the wind over the entire power producing range of wind speed up to 80 to 96 km/hr (50 to 60 miles per hour) and then, at that point, excess wind pressure can be used against the propellers, that is created solely by the paddle effect” resistance to any increase in speed of the propellers, for folding them sufficiently out of the wind to prevent storm damage to plant and tower.

Thus, it is not just a wind pressure folding method but a much improved system, as keeping the propellers facing directly into the wind delivers far more power output in gusty winds, instead of having the plant folding in and out of operating position constantly as a means of speed control. Variable pitch governor speed regulation gives maximum power during most of the wind periods throughout the year. The storm protection feature provides for the few hours per year when the winds may exceed the 80 to 96 km/hr during extremely high winds and storms. Such periods seldom occur each year, but the wind energy system must be protected against them.

The normal back pressure from the offset propeller axis is balanced by the counter torque of the hypoid gear drive design until maximum power is produced in wind velocities of 40 to 56 km/hr. Above that wind speed, up to a range of about 80 to 96 km/hr, the normal centrifugal action governor control regulates the speed through pitch change control, thus, the plant faces fully into the wind all the time except during the very few times when extreme winds occur.

Therefore, the device disclosed herein Is for a storm control that applies to a particular hypold gear drive, and is not applicable to all plants. Many wind operated devices have used just the wind pressure for their speed control, and there is nothing claimed herein on the mere folding of propellers around out of the wind per se. The invention described herein is embodied in a means having the advantage that a propeller drive wind energy system will produce considerably more energy if it faces directly Into the wind during the majority of operating hours per year instead of swinging back and forth in gusty winds that prevail most of the time, and such a wind energy system can only do this with a variable pitch propeller speed control that regulates the speed during most of the wind periods each year. This is achieved by the particular combination of variable pitch control and storm protection during the few hours of excessively high winds provided by the herein described invention wherein the propellers are folded to one side to relieve wind pressure In excessively high winds.

There is herein disclosed a means for protecting a wind energy plant against damage thereto caused in high winds. The plant includes a propeller assembly pivotally mounted on a wind energy plant support means by a hypoid gear drive means which offsets the pivot axis of the propeller assembly from the centre of the propeller asssembly. A variable pitch speed control governor Is provided on the propeller assembly for changing the pitch of propeller blades of the propeller assembly in response to wind velocity generated pressure against those blades. Pivot means are provided, pivotally connecting the propeller assembly to a tail assembly in a manner which permits the propeller assembly to pivot with respect to the tall assembly and the plant support means, under the influence of wind pressure exerted on the propeller assembly because of the combination of the hypoid gear drive propeller axis offset and the increased wind pressure created against the feathered blades in wind velocities above a range of about 80 to 96 km/hr, when the pitch angle of such blades is no longer changed by the action of the variable pitch speed control governor. Special pivot control means are connected to the propeller assembly for controlling pivotal movement thereof with respect to the tail section.

The present invention seeks to provide a wind energy system with protection against damage from high or gusty winds, which is reliable yet inexpensive to Instal, and which permits full power output from the plant under a wide range of wind velocities. 7. 214 0 How the invention may be carried into effect Is more fully hereinafter described with reference to the accompanying drawings, in which:Figure 1 is a side elevational view of a wind energy system 5 according to the present invention; Figure 2 is a view to an enlarged scale of part of Figure 1; Figure 3 is a sectional view on the line 3-3 of Figure 2; Figures 4 and 5 are plan views of the system In two positions illustrating the operation of the storm protection means; Figure 6 is an elevation of a plant shutdown system applicable to a system according to the present invention; Figure 7 is a side view on the lines 7-7 of Figure 6; Figure 8 is a partial elevation view of the system of Figure 6 in the actuated position; Figure 9 is a partial elevation view of another form of the plant shutdown system applicable to a system according to the present invention; Figure 10 Is a view on the lines 10-10 of Figure 9; and Figure 11 is a partial elevation view of the system of Figure 9 in the actuated position.

A wind energy plant W (Figure 1) embodying the present Invention Is mounted on suitable corner rails R and includes an alternator A, an alternator armature shaft AS and a drive shaft D connected to the shaft AS by a universel joint U. A gear assembly G is pivotally mounted on the plant by a mast pivot mount M, best shown in Figures 4 and 5, which includes a hypoid gear drive assembly h which offsets the centre of the gear assembly from the centre of the tower as fully described in U.S. Patent No. 4 088 420. A brake means H Is mounted on the plant for stopping the propeller should the need arise. It is here noted that the 8. 53140 pinion gh for the hypoid gear drive assembly shown in FIG. is located near the top of ring gear R for several reasons. The top located pinion is not submerged in oil in the gear oil sump. In cold weather, when the plant is starting to operate, friction drag of the pinion in cold oil would create a power loss and hinder startup of the propellers, especially in very cold weather. Furthermore, an oil seal is not needed with a top located pinion, nor is an oil tight sleeve around the pinion shaft needed with such a location.

The plant W includes a tilted propeller P and a tail section T Connected to the gear assembly. The plant further includes a governor g for controlling the pitch of the propeller blades which further includes yieldable means y and which is fully described in U. S. Patent Nos. 4,068,131 and 2,505,969. The tail section includes a pair of main braces B and B' and an intermediate br^ce B1' all of which are rearwardly converging to a rear tail vane V from the gear assembly G. The braces B and B' are interconnected by vertical struts S, and the intermediate brace B is connected at the rear end thereof to the tail vane and at the front end thereof to an arcuate cross brace C which is connected at the top thereof to main brace B and at the bottom thereof to main brace B'. The connection of the tail section to the gear section will be more fully discussed below. As afore25 discussed, propeller P is wind resistant by feathering and due to the offset nature of the mast pivot mount M, While this structure is effective in permitting full power output fqr usually encountered wind velocities, high winds, as may be encountered in severe storms, may damage even a plant including these structures.

Accordingly, the plant W further includes a storm 9 protection means 10 which includes a hinge means 14 connecting the plant gear assembly to the tail main braces. The hinge 14 includes a O-shaped carriage bracket 18 having a central portion 20 and end portions 22 and 24 with the central portion being attached, as by bolts 26, to the gear assembly G. Each main brace has a lug coupler 28 thereon and hinge pins 32 and 34 pivotally connect the carriage bracket to the main braces and ^hereby connect the gear assembly G to the tail section T. The gear assentoly, and hence the propeller P, are therefore pivotally connected to the tail section as can be seen in FIGS. 4 and 5 where the gear assembly has rotated about the hinge 14 from the FIG. 4 orientation with respect to the tail section into the FIG. 5 orientation with respect to the tail section.

A stop arm 40 is mounted on the main braces B and B’ to prevent the gear assembly from rotating beyond a predetermined position. Due to the tilted attitude of the propellers (see FIG. 1), these propellers will contact the plant frame if the gear assembly is permitted to rotate too far. Accordingly, orientation of the stop arm 40 is positioned to permit maximum rotation of the gear and propeller' assemblies without endangering the propellers due to contact with the remainder of the plant.

As indicated in FIGS. 2 and 5, the stop arm 40 is arcuate, and the gear assembly G includes an impact absorber 44 mounted thereon to contact the stop arm and thus cushion any impact between the gear assembly and the stop arm. Such impact cushioning means may be important in extremely high and gusty winds.

The storm protection means 10 further includes a one-way-damped snubber assembly 50 for regulating the pivotal movement of the gear assembly about the pivot axis defined by the hinge pins 32 and 34 and the carriage bracket 18. The snubber spring assembly includes a bracket 52 mounted on one of the vertical struts S, preferably, that strut ά nearest the gear assembly, and having a pair of spaced flanges 56 and 58 extending horizontally and being oriented in horizontal planes. The flanges are spaced parallel with each other and have aligned holes defined therethrouga for receiving a mounting bolt 60. The snubber spring assembly includes a spring loaded snubber 62 having a snubber spring 66 connected at one end to a rear eye bolt 68 which is anchored in the bracket 52 by the mounting bolt 60, and at the other end to a forward eye bolt 70. A one-way damping cylinder 74 surrounds the snubber spring to be coaxial therewith and serves to damp the return movement of the spring.

The forward eye bolt 70 is connected to an anchor bracket assembly 78 which is mounted on the gear assembly at a location remote from the hinge means 14 and with the mast pivot mount M interposed between the bracket assembly 78 and the hinge means 14. The anchor bracket 78 includes a base plate 82 extending essentially parallel with planar rear surface 84 of the gear assembly G, and spaced therefrom,and a bracket connecting arm 90 mounted, as by bol'ts 86, to the gear assembly G. The bracket connecting arm 90 is integrally attached to forward face 92 of the base plate 82 to be disposed at an angle therewith and to extend forwardly therefrom.

The base plate 82 is elongate and a stop pad 96, which is preferably rectangular and rubber, is mounted on rear face 98 of the base plate to extend vertically and is located to abut the cross brace C as indicated in FIG. 4 when the propeller rotational axis is aligned with the tail as shown in FIG. 4.

A mounting flange 100 is also mounted on the rear face 98 of the base plate 82 to extend rearwardly therefrom. The forward eye bolt 70 is pivotally attached to the mounting flange 100 by a pivot pin 102 thereby attaching the snubber assembly to the gear assembly on one side of the pivot axis defined by the mast mount M with the storm protection pivot axis defined by the hinge means 14 located on the other side of the pivot axis defined by the mast mount M.

The tension in the snubber spring 66 is adjusted so that the pivotal movement of the gear assembly G from the FIG. 4 orientation into the FIG. 5 orientation against the yielding portion of the snubber spring is controlled whereby even extremely high velocity apd gusty winds will not cause the gear assembly to slam into the stop arm 40 with impact sufficient to damage the gear assembly or other parts of the plant.

;The damping of the cylinder is adjusted so that the return motion of the gear assembly from the FIG. 5 orientation with respect to the tail to the FIG. 4 orientation with respect to the tail is closely controlled whereby the gear assembly will not be slammed into the cross brace C by the spring force of the snubber -spring · with sufficient force to damage any part of the plant W.

The snubber spring assembly 50 thus controls and regulates the pivotal motion of the gear assembly allowing free movement against spring resistance in the clockwise direction and strongly damped movement in the counterclockwise direction, about the hinge means 14 as viewed from the top and as shown in Figures4 and 5.

Because ot the snubber ‘.priny assembly '>(), even winds which move in very strong gusts are not likely to damage the plant W as both the wind caused pivoting and the snubber spring caused return movement of the qear assembly are closely controlled by the snubber spring assembly.

The wind energy plant W is therefore protected against damage due to normal winds by the offset pivotal axis defined by the mast mount M and against abnormally high winds, even gusts, by the snubber spring assembly 50.

It is noted that the snubber spring assembly 50 can use a snubber similar to snubbers used on storm doors, screen doors, and the like. The snubber spring assembly 50 differs from these devices only in the spring constants and damping constants used. Otherwise, the structure, function and operation of the snubber spring assembly spring and one-way-damping cylinder are similar to those snubbers.

Shown in FIG. 6 is a supplementary safety means 200 for protecting a wind energy plant against damage from ice formation on the propellers. As ice chunks on the propellers can cause extreme vibration, a plant can be severely damaged in a very short time, and in fact, this damage can even, in severe cases, destroy the plant.

The safety means 200 includes a caliper brake 202 mounted on the tower adjacent the drive shaft D on a tower 2£ cross-brace, or the like. A brake disc 206 is fixedly mounted on the drive shaft D and extends radially outward therefrom to surround that drive shaft in a concentric manner. The caliper brake 202 includes a housing 208 having a gap 210 defined therein. A plurality of upper and lower friction pads 212 and 214, respectively, are mounted in the housing to be movable toward and away from each other in a clamping movement. Suitable gearing, or the like (not shown), can be included in the caliper brake to effect such clamping movement of the friction pads. The brake disc 206 is interposed between the upper and lower friction pads to be frictionally contacted thereby upon clamping movement thereof. Thus, clamping movement of the friction pads 212 and 214 causes frictional engagement between those pads and the brake disc 206 to stop rotation of that disc, and hence to stop rotation of the drive shaft D and the propellers of the wind plant. Thus, using the caliper brake rotation of the propellers of the wind plant can be stopped An actuating handle 216 is pivotally mounted at proximal end 218 thereof to the housing 208 by a pivot pin 220, and is operably connected to the friction pads 212 and 214 via the internal mechanism of >t,he brake to cause those pads to execute the aforediscussed clamping·and unclamping movements upon pivotal movement of that handle.

The handle extends away from the housing 208 and includes a distal end 224 having a detaining hook 226 thereon and curving outwardly therefrom.

A mounting bracket 228 is fixedly attached to one of the legs R to be essentially 'horizontally disposed and to be located above the brake 202. A brake actuating cylinder 230 is pivotally mounted at one end thereof to the bracket 228 by a pivot pin 232, and depends downwardly therefrom toward the brake 202. The cylinder defines a chamber 236 in which fluid 240, such as oil, or the like, is contained. A piston 2M having a piston head 246 and a piston rod 248 is slidably mounted in the cylinder so the 14 53140 rod 248 extends outwardly of the cylinder toward the actuating handle 216. One end of the rod is fixed to the piston head, and the other end of the rod is pivotally attached to the actuating handle ?l(> by a 1 pivot pin 250 at a location between the d'istal and proximal ends of that actuating handle. The piston head sealingly engages the inner surface of the cylinder to divide that cylinder into an upper chamber 256 and a lower chamber 258, but the cylinder has fluid passage means for permitting ID movement of the fluid 240 from the upper chamber 256 to permit upward movement of the piston head within the cylinder. The fluid passage means can be bypass passages on the piston permitting fluid to move into the lower chamber 258 at a controlled rate as the piston moves up15 wardly, or reservoirs located externally of the cylinder along with fluid control means fluidly,connecting those reservoirs to the appropriate chambers of the cylinder. In any event, movement of the piston 244 axially of the cylinder 230 is controlled.

A spring 260 surrounds the piston rod within the cylinder 230, and yieldably urges the piston upwardly against the fluid in the upper chamber. The spring constant of spring 260 is selected so that, unless the piston rod 248 is constrained, that spring will cause the piston to move upwardly into the cylinder. In other words, the bias of the spring is not counterbalanced by the resistance of 53ft the fluid 240, and if the actuating-jiandle 216 is not constrained, the cylinder 230 will lift: the.handle .upwardly from the position shown therefor in FIG. 6 into the position shown therefor in FIG. 8. i (I The brake 202 is arranged so that upward movement of the actuating handle 216 results in clamping movement of the friction pads, thus stopping the rotation of the propellers in the manner disclosed above. In this manner, a plant stopping bias is always applied to the actuating handle 216 by the cylinder 230. This stopping bias is controlled by the fluid-spring combination, and thus will cause the propellers to stop in a closely controlled manner.

The rate with which the cylinder mechanism lifts the handle 216 is controlled so that frictional clamping pressure is applied to the disc brake at a rate which safely stops rotation of the propellers.

A handle retaining means 264 is associated with the safety means for preventing the actuating cylinder 230 from moving the handle 216 upwardly to actuate the brake 202. The retaining means 264 includes1 a roller 266 releasably placed on hook 226. The roller is connected to an actuating cable 2- ’ via a harness 270. The roller is rotatably retained in the harness by a pivot pin 272. The ZC actuating cable is attached to and wound about a drum 274 turnable by the hand crank H located near the bottom of the tower. The drum is mounted on the leg R by a suitable mounting bracket 276 and a brace 278. A tether chain C connects the harness 270 to the arm 216 for a purpose to be discussed below.

The handle retaining means 264 resists the upward bias of the actuating cylinder 230 to keep the bra?..- 202 in an unapplied configuration when the roller 266 is seated in the hook 226. The cable 280 is thus tensioned and maintained taut during operation of the plant. However, when the plant is to be shut down for some purpose, operating a crank H releases the tension on the cable 280, thereby permitting the cylinder 230 to lift the handle 216 and apply the brake 202.

It is seen that actuation of the brake handle !> 216 is controlled by the cylinder 230. Thus, if the cable 280 is quickly untensioned, that cable will simply go slack and continued application of the brake will be controlled by the cylinder 230. Thus, the rate of application of the brake 202 has an upper limit as determined by the cylinder 230. However, the lower limit of the brake application is controlled by the retaining means 264. Thus, the propellers can be stopped as slowly as desired, but can be stopped only as quickly as the cylinder will permit during manual operation. The upper limit of the rapidity with which the propeller rotation is stopped during manual operation is closely controlled as this limit can be critical to plant integrity and safety.

Ice formation on the propellers during a storm or the like may cause vibration of the plant 2() which may damage or destroy the plant. Thus, curing such conditions, it is safest to shut the plant down. An automatic shutdown means 300 is shown in PIG. 6 to include a mercury switch 302, or the like, mounted on the plant leg R and a solenoid 304 is connected thereto and mounted on Z5 the leg R adjacent the roller 266. As shown in FIG. 6, the mercury switch is mounted at a slight angle with respect to the horizontal. By selecting the angle of set, the trip-vibration level can be selected. The solenoid 304 has an actuating arm 308 with a flange 310 thereon. Suitable power means (not shown) such as a generator, or the like, which may be driven by the plant, is connected to the solenoid and switch via cables 312 and 314. The power system can also be self-contained, if so desired.

A contact flange 320 and a pair of pivot flanges !> 322 are mounted on the roller 266 to extend outwardly therefrom. The contact flange 320 is located to be contacted by the solenoid flange 310 upon actuation of that solenoid. Actuation of the solenoid by the mercury switch causes the arm 308 to extend outwardly thereby impacting the flange 320. This impact causes the roller to rotate in the clockwise direction in FIG. 6 causing the pivot flanges 322 to contact the outermost end of the hook 226. Continued rotation of the roller under influence of the solenoid actuator flange causes the roller to be unseated from the hook 266 as indicated by the arrow 330 in FIG. 6.

When the roller 266 rolls off, of the hook 226, the arm 216 is released from the retaining force of the handle retaining means 264, and the handle actuating cylinder 230 causes the handle to move upwardly thereby actuating the brake· 202 and stopping the rotation of the plant propellers in a controlled manner.

The mercury switch is set up to be sensitive to vibration of the plant, and to actuate the solenoid when plant vibration exceeds a certain level. Thus, plant vibration caused by ice formation on the propellers, or any other cause, will actuate the automatic shutdown means 300, and the propeller rotation will be stopped in a controlled manner, which control is effected by the control of the cylinder 230.

Thus, either automatic or manual plant shutdown is effected, and is carried out in a closely controlled manner so the propeller rotation can be stopped in a controlled manner no matter what the circumstances of the plant stoppage are.

The tether chain C prevents the loss of the roller 5 266 after the just-described emergency shutdown. After such a shutdown the roller can be replaced to reset the actuating means for future safety operation. The chain is connected to the outer end of the brake arm 216 to enable the operator, after the energency storm shutdown, to again place the plant back into operation position by simply cranking down more of the control cable on the winch. This action will pull down the brake arm 216 permitting the plant to start operating again. The plant will not have the safety feature when thus operating, but will place the plant back in service until such time as-the weather moderates permitting the operator to ascend the tower to replace the safety roller on the brake arm. Ice and storm conditions might prevent tower ascension for hours or days but could allow the plant to operate and produce valuable energy during the adverse weather. The propeller operating position for the safety means 200 is shown in FIGS. 6 and 7; whereas the safety means is shown in FIG. 8 in the vibration actuated position with the roller 266 unseated from the hook 226 by the mercury switch actuated solenoid 300.

Another form of the vibration actuated automatic shutdown means is shown in FIGS. 9-11, and is indicated by the reference numeral 200'. Shutdown means 200' is similar to shutdown means 200 except that the solenoidmercury switch of the shutdown means 200 is replaced by a releasable weight system 360 in the shutdown means 200*.

The releasable weight system 360 is most suitable for use with wind energy plants which do not generate electricity; whereas the mercury switch-solenoid system is most suitable •I for use with wind energy plants which do generate electricity I and can thus power the switch-solenoid system. However, the systems can be interchanged so long as suitable power sources are available for the switch-solenoid system.

The weight system 360 includes a mounting hook 364 affixed to the leg R by a fastener 366, or the like, and depending downwardly therefrom. A guide tube 370 is mounted on the leg R by bands 372 or the like, to be coaxial therewith. The guide tube 370 is hollow and has an axial internal bore 374 defined therein. A weighted piston 378 is movably received in the tube 370 and includes a shaft 380 haying a hook 382 located on the upper end thereof and an impact flange 384 located on the 'low^r end thereof.

The hook 364 ie slightly curved to be somewhat parabolic, whereas the hook 382 is sharply curved to be a segment of a circle and includes a thimble 388 on the outer end thereof. The hook 382 is supported on the hook 364 as shown in FIG. 9. A receiving ring 390 is located on the inside of the tube 370 near the bottom thereof.

Excessive vibration of the plant will jar the hook 382 off the hook 364, and the weight 378 will fall downwardly. The weight is guided by the tube 370, and the flange 384 impacts the flange 320 to unseat the roller 266 from the hook 226 to thereby release the handle 216 to be lifted from the FIG. 9 unbraking position into the FIG. 11 braking position in which the friction pads 212 and 214 clamp against the brake disc 206 to stop rotation of the drive shaft D in a controlled manner and hence stop the plant propellers in a controlled manner. The application of the brake 202 in both systems 200 and 200* is thus controlled by the cylinder 230 and is applied at a rate consonant with proper plant shutdown procedures.

The hook 382 is captured by the ring 390 to prevent the entire weight 378 from falling to the ground. The weight is reset by hand when the plant is to be restarted.

It is noted that in both systems, if there is a failure in the manual shutdown system, such as a break of the cable 280, or the like, the plant automatically shuts down at a controlled rate. Such a safety feature is thus added to the aforediscussed safety features. It is further noted that the hand crank H can have a ratchet-detent mechanism fer further controlling manual plant shutdown.

Claims (11)

1. A wind energy system comprising a variable pitch propeller assembly having a propeller arranged to rotate about a rotation axis, the propeller assembly being mounted upon a support means for pivotation about 5 a pivot axis, the rotation axis of the propeller being offset from the pivot axis, a hypoid gear drive by which rotation of the propeller is transmitted to a shaft rotatable about the pivot axis, a pitch control governor on the propeller assembly to change the pitch of blades of the propeller in response to wind velocity generated pressure against the 10 blades, the propeller speed being independent of any electrical load on a generator driven by the propeller and being governor controlled until the blades are fully feathered, a tail assembly connected to the propeller assembly to assist In keeping the blades facing directly Into the wind until the blades are fully feathered, the connection between the tail and 15 propeller assemblies including a pivot, and pivot control means to prevent pivotal movement between the propeller and tail assemblies until the blades are fully feathered and to allow limited pivotal movement between the propeller and tail assemblies after the blades are fully feathered, under the influence of wind pressure exerted on the propeller because of 20 the combination of the hypoid gear drive propeller axis offset and increased wind pressure created against the fully feathered blades, the pivot control means including a one-way-damped snubber spring assembly to damp return movement of the propeller and tail assemblies after relative pivotal movement therebetween. 25

2. A system according to claim 1, in which the snubber spring assembly includes a spring connected between the propeller and tail assemblies to prevent pivotal movement therebetween until the blades are feathered.

3. A system according to claim 2, in which the snubber spring assembly includes a cylinder surrounding the spring to damp return movement of the 30 propeller and tail assemblies.

4. A system according to claim 1, 2 or 3 Including stop means to prevent relative pivotal movement between the propeller and tail assemblies beyond a predetermined position.

5. Λ system according to claim 4, In which the stop means Includes a stop arm mounted on the tall assembly for engagement with the propeller assembly at the predetermined position.

6. A system according to claim 4 or 5, including impact absorber means 5 between the propeller and tail assemblies effective to absorb impact therebetween upon reaching the predetermined position.

7. A system according to any preceding claim, including impact absorber means between the propeller and tail assemblies effective to absorb impact therebetween upon reaching the unpivoted position on return 1q movement.

8. A system according to any preceding claims, in which the snubber spring assembly is connected between the propeller and tail assemblies, the connections of the tail assembly and of the snubber assembly to the propeller assembly lying on opposite sides of the rotation axis. 15

9. A wind energy system substantially as hereinbefore described and as shown In Figures 1 to 5 of the accompanying drawings.

10. A wind energy system substantially as described hereinbefore and as shown in Figures 1 to 8 of the accompanying drawings.

11. A wind energy system substantially as hereinbefore described and as 2Q shown in Figures 1 to 5 and 9 to 11 of the accompanying drawings.