US1103891A - Time-element power-limiting device. - Google Patents

Description

A. PFAU.

TIME ELEMENT POWER LIMITING DEVICE. APPLICATION FILED M1144, 1913.

Patented July 14, 1914.

WITNESSES- ML'M Q/ INVENTEIR- EV Z WMA-ATT URN Ev.

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TIME-ELEMENT POWER-LIMITING DE VICE.

To all whom it may, concern I Be it known that I, ARNOLD PFAU, a citizen of the Republic of Switzerland, residing at Milwaukee, in the county of Milwaukee and State of \Visconsin, have invented a certain new and useful Improvement in Time- Element Power-Limiting Devices, of which the following is a specification.

This invention relates to improvements in the construction of devices for limiting the power furnished by a prime mover.

The object of the invention is to provide a device for limiting the power furnished by a. prime mover, which is simple in construc tion. and etlicient in operation.

The invention is applicable generally to governors for prime movers of any kind, being specifically illustrated in the accompanying drawing as applied to a governor for controlling the gate in the pipe line of a hydraulic turbine installation. The device is particularly applicable in the following cases: First, where the rate of flow. of the supply of water to the forebay is limited but where the forebay itself has considerable capacity and is capable of temporarily furnishingsufiicient water due to the storage capacity thereof to permit the power units connected with the foreloay to carry a temporary excessive overload. Second, where the normal water supply available is suiticicnt to furnish water under excessive overload conditions but where the electrical apparatus is capable of only momentarily carrying the undue overload without QXCQS' sive overheating. With the use of the present invention, automatic restoration of the system to a normal predetermined operating condition from a condition of excessive overload, is permitted without danger of destruction ofthe apparatus. The invention is particularly useful in cases of short circuits in the electrical power line supplied by the units, the excess power which with the present device may be furnished for a short period of time, in these cases usually being suflicient to burn out the short circuit on the line. thereby restoring the normal opcrating conditions. If. however, the excessive overload cannot be thus removed, the

generator is automatically protected against T 1E ST ARNOLD IPFAU, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO ALLIS-CI-LALMERS MANU- FACTURING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF 1131 111 4;-

Specification of Letters Patent. Application filed April 14, 1913. Serial No. 761,628.

rag OFFICE.

Patented July 14,

overheating by a limiting device which posit1vely prevents the generator from attemptmg to furnish more than its normal 'inaxi mum power after one effort to destroy the. cause of the overload has been made. The primary features of the inventioirdisclosed herein are claimed broadly in a co pending application Serial No. 755,54 filed March 17, 1913. A clear conception of an embodiment of the invention may be had by referring to the drawing accompanying and forming a part of this specification in which likeretercnce characters designate the same parts in the various views. Figure 1 is a diagrammatic disclosure of a power limiting device showing the ii arts in normal running position in full lines. and showing the floating lever and servo-motor controlling valve in a position corresponding to an excessive drop in speed of the prime mover, in dotted lines. Fig: 2 is a. diagrammatic disclosure of a power limiting device showing the main gate valve in full 25 open position, the servo-motor valve being returned to mid position, the secondary compensating means being under stress, and the actuating means of the power limiting device being likewise under stress. Fig. 3 is a diagrammatic disclosure of a power limiting device showing the main gate valve in full open position, the servo-motor valve in open position, and the springs of the secondary compensating and power limiting means in normal position. Fig. 4 is a diagrammatic disclosure of the power limiting device showing the main gate returned to its predetermined limiting position with theservomotor valve returned to mid position}. Thedevice disclosed in the drawing is illustrated as being applied to an indirect governor for a prime mover, not shown. The essential elements of the device are the main gate or valve 32; the. servo-motor 28);" .the servo-motor actuating valve 18; thegm v ernor or speed responsive means 1; the com pcnsating means comprising a spring casing, 42. a dash pot 39, piston 37, and connecting linkage: the bell crank 5O. 27, 49: the bell crank S), 51 52: the elastic connection he;

tween said bell cranks; 'and the dash pot 1 The main gate or valve 32 is located within and controls the pipe line leading to the prime mover, and is operable by means of a crank 31 which is connectedto the piston rod 30 of the piston 28 of the servo-motor 29. Pipes 20, 21, connect the piston chambers of the servo-motor 29 with the interior of the casing 17 of the servo-motor valve 18, the pressure inlet 19 to the casing being communicable past the valve 18 to either of the pipes 20, 21. During the time that one of the pipes 20, 21, is in communication with the pressure inlet pipe 19, the other of the pipes 20, 21, is in communication with exhaust. Fluid under pressure, preferably oil, is supplied through the inlet pipe 19 to the chambers of the servo-motor 29 to move the piston 28 in the desired direction, thereby positioning the valve 32.

The stem 4 of the servo-motor valve 18 has an adjustable collar 5 fixed thereto intermediate its ends, and another adjustable collar 6 secured to the upper end thereof. The sleeve 7 is slidable upon the valve stem 4 and is pivoted to one end of the floating lever 3. The compression spring 8 coacts with one of its ends against a surface of the collar 5 and with'its opposite end against a surface of 'thesleeve 7 this spring 8 tending at all times to force the collar6 in contact with the sleeve7. The floatin lever 3 has its mid portion connected to tie collar 2 of the speed responsive means 1. The'opposite free end of the floating lever 3 is connected to the upper end of the piston rod 33 of the piston 37. The piston 37 is provided with a small adjustable through port 38 and is reciprocable within the liquid. filled dash pct 39. The dash pot 39 is secured to 40' the uppcrcnd of the rod 40, the lower end of which connects with the end of the arm 49 of the bell crank-50, 27, 49. The bell crank 50,27, 49, is "pivoted to swing upon the stationary frame portion 26. The arm 27 of the bell crank 50, 27, 49, has its lower end connected with one end of the servomotor piston rod 30.

The secondary compensating means consists of a spring casing 42 carried by the connection 48, which has its lower extremity secured to the slide 41. The slide 41 is adjustably mounted upon the arm 49 of the bell crank 50, 27, 49. The lever 34 is pivoted or fulcrumed at the stationary frame portion and has its outer end pivotally connected to the piston rod 33. The spring rod 36, which is pivotally connected with the mid portion of the lever 34. is provided with uppcr and lower adjustable collars 47, 43, which are secured to the rod 36. The washers 46,. 44. are normally licld in contact with the collars 47, 43, rcs-zpectivcly, and with the cndsof the'casiiigsfi by means of a hclical compression means or spring 45.

The washers 46, 44, are loosely fitted around the spring rod 36 and are disengageable with the ends of the spring casing 42 by means of the collars 47, 43.

The power limiting device consists of a bell crank 9, 51, 52, which is pivoted to the stationary frame portion 10. The arm 51 of the bell crank 9, 51, 52, is connected with the arm 50 of the bell crank 50, 27, 49, by means of an elastic connection. The elastic connection consists of rods 11,24, which are telescopic relative to each other, and each of which has a collar 22, 23, secured thereto. The collar 23 of the rod 24 is adjustable along the length of the rod. The compression spring 25 is adjustable in initial compression and coacts between surfaces of the collars 22, 23. This spring25 tends at all times to maintain the length of the elastic connection constant for a predetermined setting of the collar 23. The arm 9 of the bell'crank 9, 51, 52, is so formed that it is capable of being swung into contact with. a lower surface of the collar 5 carried by the valve rod 4. The .iston rod 12'of the piston 15 is connected with the end of the arm of hell crank 9, 51, 52. The rod 12 carries the valve 14, and controls a large port formed directly through the piston 15, which permits free upward movement of the rod 12. The piston 15 is sliduble within the liquid filled dash pct 13 and is normally kept in contact with the valve 14 by the usual spring means, not shown. The upper and lower piston chambers of the dash pot 13 are connected by means of an adjustable by-pass 16 the size of which is variable in the usual manner, by means of a controlling valve. The initial compression of the spring 25 should be su'l'licient to permit the elastic power limiting connection to assume its wmal length regardless of the variations in the resistance o'lfcred to the movement of the bell crank 9. 51, 52, by the dash pot 13.

During the operation of the device and assuming the unit controlled by the regulating mechanism to be operating under normal running conditions, satisfying a load which is within and somewhat below the maximum power capacity, and that a sadden excessive overload is thrownnpon the prime mover. This evcessive overload immediately causes the speed rcsponsive means 1.to lower its collar 2, causing the floating inlet pipe 19 through the pipe 21 to the piston chamber at the right of the servo-mm tor piston 23.

The admission of fluid under pressure to the right hand piston chamber of the servomotor 29, causes the servo-motor piston 28 to move toward the'left and to place the valve 32 in full open position, as indicated in Fig. 2. The motion of the piston 29 toward the left acts throughthe piston rod to swing the bell crank 27, 49, 50, about its pivot on the stationary frame portion 26, thereby lowering the ends of the connections 40, 48, and raising the lower end of the rod 24. The lowering of the end of the connection or rod causes the dash pot 39, piston 37 and piston rod 33 to move downwardly and to lower the extreme right hand end of the floating lever 3. The lowering of the right hand end of the floating lever causes the lever to swing about the collar 2 as a fulcrum and to return the servo-motor actuating valve 18 to normal or closed position. The downward movement of the piston rod 33 causes the lever 34 to swing about its pivot on the stationary frame portion 35 and to force the spring rod 36 down, thus compressing the seconc ary compensator spring by an amount equal to the difference in the distance traveled by the spring rod 36 and the distance traveled by the connection 48. The upward movement of the bell crank arm and rod 24 compresses the power limiting spring 25 between the collars 23, 29, a certain amount beyond its initial compression, the degree of compression of the spring 25 depending upon the extent of movement of the arm 50 of the bell crank 27, 4-9, 50, and upon resistance offered by the dash pot 13 in restraining the movement of the bell crank 9, 51, 52.

Immediately after the mechanism has been positioned so as to place the springs 25, 45, under compression as indicated in Fig. 2, these springs become effective, the one in restoring the elastic power limiting connection to its normal length, and the other in bringing the washer 16 into coaetion with the upper end of the spring casing i2. During expansion of the spring 45 to restore coaction between the washer 4G and theupper end of the casing 42, the lever 34 is swung in an anti'clockwise direction, thus gradually raisingthe piston rod 33 and the piston 37. During raising of the piston 37, the fluid from the upper piston chamber of the dash pot 39 passes directly through the port 38 to the lower piston chamber thereof. Simultaneously with this by-passing of the fluid within the dash pot 39, the right hand end of the floating lever 3 is raised, while the collar 7 at the left hand end of the floating lever 3 is lowered and compresses the spring 8.

The power limiting spring 2:) expands simultaneously with the expansion of the secondary compensatimi spring 4-5. causing the rod 11 to swing the bell crank 9, 51, 52, about wise direction, it is brought gradually in contact with the collar 5 which is fixed to the valve rod 4 and which at the time of contact is being forced downward by the spring 8. The amount of initial compression and the expansive force of the spring 25 should be so adjusted and proportioned that the movement of the arm 9 in a clockwise direction is rapid enough to prevent opening of the valve 18 due to the compression of the spring 8, and will be continued until the valve 18 is carried in an upward direction beyond its normal mid position, so that fluid under pressure may be admitted directly through the pressure inlet pipe 19 and pipe 20 to the left hand piston chamber of the servo-motor 29. As the bell crank arm 9 is brought gradually in contact with and raises the collar 5 the spring 8 is further compressed between the collar 7 of the floating lever 3 and an upper surface of the collar 5. The clockwise rotation of the bell crank arm 52 causes the piston rod 12 and piston 15 to move downwardly within the dash pot 13, at the same time by-passing the fluid from the lower chamber of the dash pot 13 through the by-pass 16 into the upper chamber of the dash pot 13. After the springs 25, 45, have fully expanded, the mechanism assumes the position indicated in Fig. 3, providing the load on the prime mover is still above the normal set maximum.

Upon admission of fluid under pressure through the inlet pipe 19 and pipe 20 to the left hand piston chamber of the servo-motor 29, the servo-motor piston 28 is moved toward the right, causing the valve 32 to assume the position indicated in Fig. 4:. \Vith the valve 32 in this position the amount of fluid passing through the valve 32 is substantially equal in rate of flow to the constant rate of supply of fluid to the forebay from which the prime mover is supplied providing the invention is applied to an installation having limited supply. The motion of the piston 28 toward the right, simultaneously causes the bell crank 27, 49, 50, and the elements connected therewith to assume the position as indicated in Fig. 4. The ,positiori thus assumed is such that the servo-motor actuating valve 18 is in normal or closed position and cannot be opened by any further or subsequent decrease in speed of the prime mover since the collar 5 of the valve rod 4 is stopped from moving downwardly by the bell crank arm 9. The bell crank arm 9 is prevented from moving downwardly by the power limiting spring 25 which exerts an excess of upward pressure against the hell crank arm 51 through the rod 11. Any decrease in speed of the prime mover with the mechanism positioned as disclosed in Fig. 4, will cause the collar 2 to move the end of the floating lever 3 to which the collar 7 is connected downwardly and to further compress the spring 8 without affecting the position of the valve 18.

It will thus be seen that with the use of the present invention in an installation in which the forebay capacity is large, but in which the constant rate of water supply is limited, the power furnished to the prime mover can temporarily be raised beyond. a mover can temporarily be raised beyond a normal constant maximum andcan after lapse of a short time interval be brought back to the normal constant and held fixed at that point. The advantage ofthis arrangement is that if the excessive load is due to a short circuit on the electrical line to which the prime mover furnishes power, the excessive power which the prime mover is capable of temporarily furnishing may in most cases be suflicient to burn out the short circuit. By positively limiting the power after the surplus forebay capacity has been exhausted,

: or by preventing the furnishing of excess power after one attempt to destroy the cause of the excessive overload has been made, overheating and resulting possible destruction of the electrical apparatus is avoided.

By adapting the power limiting means to communicate the motion of the servo-motor 29 directly to the controlling means 18, the operation of the device is not affected "by failure in operation of the compensating devices or of the speed responsive means 1, with either of which the power limiting device might also be made cooperable. The application Serial No. 7 55,544, above referred to,-discloses a mechanism in which the power limiting device is made cooperable with the compensating means, such construction necessitating the use of a positive stop for limiting the downward movement of the collar of the speed responsive means. In the present invention the movable stop or arm 9 is directly cooperable with the controlling means 18 and is entirely independent of the movement of the speed responsive means 1. Vith this construction the collar 2 of the speed responsive means 1 is not brought. against a positive stop at any time but is free to move vertically at all times according to variations in the speed of the prime mover. By permitting freedom of movement of the collar 2, the friction and resulting wear produced by permitting the collar 2 to come in contact with a positive stop, is eliminated. It should be noted that the spring 8 is a very light spring, being of sul'iicient strength only to overcome the friction between the controlling means 18 and the casing 17.

It should be understood that it is not desired to be limited to the exact details of construction shown and described, forobvious modifications will occur to a person skilled in the art. I

It is claimed and desiredto secure by Letters Patent,

1. In an indirect governor for prime movers, a speed responsive means, a motor for actuating the mam valve of the prime mover, a means governed by sa1d speed responsive means for controlling said motor, and means independent of said speed responsive means and cooperable directly with said controlling means for finally returning-said valve toa predetermined limitingposition from a temporary position beyond."

2. In an indirect governorfor a prime mover, a speed responsive means, a motor for actuating the main valve of the prime mover, a means governed by, said speed responsive means for controlling said motor,

and means adapted to communicate the motion of said motor directly to said controlling means for finally returning said valve to a predetermined limiting posltion from a temporary position beyond.

3. In an indirect governor for a prime mover, a speed responsive means, a motor for actuating the mam valve of the prlme mover, a means governed by said speed re sponsive means or controlling said motor,

compensating means between said motor and said speed responsive means, and means independent of said compensating means for finally returning said valve to a predetermined limiting position from a temporary. position beyond.

mover, a controlling valve for said motor governed by said speed responsive means, and an elastic connection directly between said motor and said controlling valve for finally returning said main'valve to a predetermined limiting position from a temporary position beyond.

6. In an indirect governor for a prime mover, a speed responsive means, a motor for actuating the main valve of the prime mover, a means governed by said speed responsive means for controllingsaid motor,

compensating means between said 'motor and 125 said speed responsive means, and means independent of sa1d spee'd responsive means and of sa1d compensating means for finally I 4. In an indirect governor for a prime p beyond.

7. In an indirect governor for a prime mover, a speed responsive means, a main valve, means governed by said speed responsive means for controlling said valve, and a movable stop oooperable With said controlling means for finally returning said valve to a predetermined limiting position from a temporary position beyond, said speed responsive means being independent of and free to move as to said stop.

In testimony whereof, the signature of the inventor is aflixed hereto in the presence of two witnesses.

v ARNOLD PF AU. Wit esses:

. W. H. LIEBER,

G. F. DE WEIN.

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