US3407904A - Hoist apparatus including current sensitive motor control means to hold a variably loaded cage chaired - Google Patents

Description

Oct. 29, 1968 w. G. A. TROLLOPE 3,407,904

' HOIST APPARATUS INCLUDING CURRENT SENSITIVE MOTOR CONTROL MEANS TO HOLD A VARIABLY LOADED CAGE CHAIRED Filed Nov. 24, 1964 2 Sheets-Sheet l DIRECTION OF MOTION OF CAGE U FIG.

INVENTOR;

WILLIAM G. A. TROL LOPE Oct. 29, 1968 w. G. A. TROLLOPE 3,407,904

HOIST APPARATUS INCLUDING CURRENT SENSITIVE MOTOR CONTROL MEANS TO HOLD A VARIABLY LOADED CAGE CHAIRED Filed Nov. 24, 1964 2 Sheets-Sheet 2 32 l2 DRUM 36 J\ CONSTANT VARIABLE EX CITATION TACKOMETER FIELD 48 MOTOR 4o GENERATOR To VARIABLE VOLTAGE 34 HOIST DRIVE MOTOR GENERATOR 528 U T ACTUAL CURRENT 54 RELAY C] 58 30 CURRENT LIMIT SETTING PRE-SET ACTUAL SPEED '7 4i REGULATOR DEVICE SPEED W 46 VARIABLE VOLTAGE DEVICE ADJUSTABLE FIG. 2

INVENTOR. WILLIAM G. A. TROLLOPE fimr United States Patent HOIST APPARATUS INCLUDING CURRENT SEN- SITIVE MOTOR CONTROL MEANS TO HOLD A VARIABLY LOADED CAGE CHAIRED William G. A. Trollope, Montreal, Quebec, Canada, as-

signor to Canadian Ingersoll-Rand (10., Ltd., Montreal,

Quebec, Canada, a corporation of Canada Filed Nov. 24, 1964, Ser. No. 413,588 6 Claims. (Cl. 187-29) This invention relates to hoists and more particularly to hoist control.

When vehicles, and in particular cars running on rails, are to be rolled into and out of a mine hoist cage, it is essential that the floor of the cage, or rails in the floor, should align fairly accurately with the corresponding opposite member at the shaft station. From the hoist control standpoint, there is no difficulty in getting the cage to stop at the proper position, since positioning accuracy in a modern hoist is good. However, as the car is rolled on or off the cage on to the station floor, it changes the load on the ropes on which the cage is suspended, which results in attendant change of the cage position due to the inherent elasticity of the cage ropes. Therefore as a mine car is rolled on or off the cage, the rails may be aligned for the first pair of the mine car wheels, but as the load on the cage ropes is changed by the unloading or loading of the mine car, the vertical position of the cage will change resulting in the interruption of the alignment of the rails. When the rails are not in proper alignment, the second and subsequent pairs of wheels of the mine car will be forced to negotiate a bump which be comes intolerable when a large number of cars are to be handled.

It is the general object of the present invention to avoid and overcome the foregoing and other difiiculties of and objections to prior art practices by the provision of a smoother operating hoist system.

This object, and those other objects of the invention which will be apparent from the following description taken in connection with the accompanying drawings, are attained by the provision of a hoist apparatus comprising a drum, at least one rope operatively associated with the drum for supporting a load, and a load carried by the rope. The drum is rotatable by electric drive means to vertically move the load onto a support; and means are responsive to the current drawn by the drum rotating means for controlling the tension on the rope when the load is on the support to prevent vertical movement of the load despite variations in the weight thereof.

For a better understanding of the present invention reference should he had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein: a

FIG. 1 is a diagrammatic view illustrating a hoist assembly;

Patented Oct. 29, 1968 FIG. 2 is a diagrammatic view of an electrical control system for the present invention.

Although the principles of the present invention are broadly applicable to hoists the present invention is particularly adapted for use in conjunction with friction hoists and hence it has been so illustrated and will be so described.

With specific reference to the form of the present invention illustrated in the drawings, and referring particularly to FIG. 1, a hoist apparatus is indicated generally by the reference numeral 10. The hoist apparatus 10 has a circular rotating means, such as a drum 12 and a rope 14, being operated by the drum 12 to support load. The cage side 16 of the rope 14 supports load such as a cage 18 and cars 28 While the counterweight side 20 of the rope 14 is connected to a weight 22 for stabilization. Hence, rotation of the drum 12 is operable to lower the cage 18 on to a set of sliding chairs 26 so that the top surface 19 of the cage floor 21 is in alignment with the station floor 24, in order to ensure that a car 28 in the cage 18 can be rolled smoothly in and out of the cage 18.

It will be understood that, even if the top surface 19 of the cage floor 21 is initially aligned with the station floor 24, the moving of a car 28 in or out of the cage ,18 will change the position of the cage 18 with respect to the position of the station floor 24 because the ropes 16 will change in length as the load changes. In order to keep the stop position of the cage 18 constant under varying load condition, means, such as an electrical con trol circuit, is provided as shown in FIG. 2.

Control circuit The hoist 10 can be powered in many different manners, for axample, by a variable voltage DC drive 32 as shown in FIG. 2. -In the variable voltage DC drive 32, the drum 12 is driven by a DC separately excited hoist motor 34. The hoist motor 34 usually has a constant excitation (field). The hoist motor 34 is powered by a motor-generator assembly 36, the generator 40 of which motorgenerator assembly 36 is also separately excited. The excitation of the generator 40, however, is variable and is utilized as the basis of the hoist control system. In the present illustration, the hoist 10 is manually controlled by means of a variable voltage device 46 which through a regulator 44, of the electronic or magnetic type, controls the field to the generator 40 thereby controlling the speed of the drum 12.

When the cage 18 is in motion, the hoist apparatus 10 is manually operated through a lever (not shown) connected to a standard variable voltage device 46 (FIG. 2). The motion of the operators lever varies the voltage through the regulator 44 which causes the regulator 44 to vary the generator excitation. This varies the electro motive force (hereinafter referred to as EMF) developed in the generator armature 41. The hoist motor 34 will in turn endeavor to move in such a direction and at such a speed that its back EMF will balance the generator EMF. Thus the movement of the variable voltage lever will control the direction and speed of motion of the hoist motor 34.

It will therefore be understood that, when the drum 12 is to be speeded up, the generator excitation is increased thus increasing the generator EMF. The motor EMF is now less than the generator EMF resulting in the generator 40 feeding power to the hoist motor 34 thus accelerating the hoist motor 34. Where the generator excitation is reduced it reduces the speed of the hoist motor 34 thus reducing the speed of the drum 12.

Modern refinements have been mainly concerned with improving the accuracy of control. Most of these devices use the negative feedback principle with the hoist motor I 34 being provided with a tachogenerator whose voltage output is accurately proportional to the speed of the drum 12. This voltage is fed to the regulator 44 where it is compared by the regulator 44 with the voltage fed into the regulator 44 by the variable voltage device 46. The difference between these two voltages is amplified by the regulator 44 and is applied to the generator 40 as a field of correct polarity. The generator 40 in turn corrects the speed of the hoist motor 34 so that the difference between the actual speed and the desired speed is reduced to a minimum.

To protect the direct current machines in the variable voltage DC drive 32 from excessive circulating current, a control circuit, such as a current limit circuit, is incorporated in the regulator 44. In the current limit circuit, a voltage proportional to the circulating current is obtained from a shunt 52 in the DC loop. This voltage is compared by the regulator 44 with a preset voltage fed into the regulator 44 by a relay 54. When the actual current exceeds the preset current, the generator field is changed in such a way as to reduce the excess current to a minimum. Thus it will be understood that the current limit circuit is only operative if the hoist assembly is trying to draw an excessive current as for example, if the drum 12 were stalled against its brakes.

Inasmuch as the hoist motor current is proportional to the torque output of the hoist apparatus 10, under constant speed conditions and the motor torque under constant speed conditions is proportional to the equivalent rope pull (as hereinafter defined) exerted on the hoist ropes 14, the current limit setting may be used to stabilize the hoist apparatus when the cage 18 is stalled against the chairs 26. The control circuit therefore will limit the torque that the hoist motor 34 will exert by the preset current set in the relay 54.

The driving torque that the hoist motor 34 will exert can be expressed as an equivalent rope pull which is the force transmitted by the drum 12 to the rope 14. In order to stabilize the cage 18 on the chairs 26, the equivalent rope pull is applied in the direction tending to force the cage 18 down on the chairs 26.

It will be understood by those skilled in the art that on a counterweighted friction hoist with tail rope 17 as shown in FIG. 1, the static tension in the ropes on the counterweight side is approximately constant at the drum 12 where the drum 12 is driving the cage 18 downward. The rope tension at the drum 12 at the cage side 16 will then be equal to the tension at the counterweight side 20 less the equivalent rope pull. Assuming the cage side tension to be T and the counterweight side tension to be T the relationship of the forces at the drum 12 can be expressed in equation form as follows:

T =T -equivalent rope pull T is equal to the combined weights of the counterweight 22 and the ropes on the counterweight side, and the equivalent rope pull can be set at a value leading to a safe value of T so that the cage side tension T can be chosen low enough to insure that the cage 18 will not rise off the chairs 26 when unloaded and yet not low enough to cause rope slip.

It will now be understood by those skilled in the art that with a preset equivalent rope pull, when the cage 18 is lowered on the chairs 26, the speed of the drum 12 will be controlled by the speed feedback circuit 58 from the tachogenerator 48 to the regulator 44. When the drum 12 is in motion the strength of the generator field is determined by the conditions in the speed feedback circuit. The drum 12 will be rotating at some desired speed and the current drawn by the motor 34 will not be high enough to be affected by preset current limit setting 30 in the current limit circuit.

When the cage 18 hits the chairs 26, the entire hoist apparatus will eventually stall. The actual speed of the drum 12 being near zero, will be way below the desired speed, which means that the hoist motor 34 will draw more current in an elfort to increase the speed of the cage 18. The hoist motor current will now reach the current limit setting so that when the hoist assembly 10 finally comes to absolute rest the torque of the hoist motor 34 will be controlled by the current limit setting 30 in the current limit circuit thereby fixing the equivalent rope pull and thus setting the tension T in the ropes at the hoist or the cage side 16. T is chosen low enough so that the cage 18 will not rise in the chairs 26 when the car 28 or outer pay load is removed, yet not low enough to cause the ratio T T to rise to a value high enough to cause the ropes 14 to slip relative to the drum 12. In practice, this means that the reaction between chairs 26 and cage 18 is greater than the weight of the car 28, or other pay load.

It will be recognized by those skilled in the art that the objects of the present invention have been achieved by providing a smoother operating hoist system, using a conveyance which can be rested on an unyielding base Without changing its vertical position with varying loads.

While in accordance with the patent statutes a preferred embodiment of the present invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

I claim:

1. A hoist apparatus comprising:

a drum;

at least one rope operatively associated with said drum to support a load;

a load carried by said rope;

electric means for rotating said drum to vertically move said load onto a support; and

means responsive to the current drawn by said rotating means for controlling the tension on said rope when said load is on a support to prevent vertical movement of said load despite variations in the weight of said load.

2. A hoist apparatus comprising:

a drum;

at least one rope operatively associated with said drum to support a load;

a load carried by said rope;

electric means for rotating said drum to vertically move said load onto a support; and

electric control means responsive to the current drawn by said rotating means for controlling the tension on said rope when said load is on a support to prevent vertical movement of said load despite variations in the weight of said load.

3. A hoist apparatus comprising:

a drum;

at least one rope operatively associated with said drum to support a load;

a load carried by said rope;

means including an electric power circuit for rotating said drum to vertically move said load onto a support; and

means operatively associated with said electric power circuit and responsive to the current drawn by said rotating means for controlling the tension on said rope when said load is on a support to prevent vertical movement of said load despite variations in the 'Weight of said load.

4. In combination with a loading level; a hoist apparatus comprising a load adapted to be vertically moved into alignment With said loading level; a rotatable drum, rope means associated with said drum and connected to said load such that rotation of said drum provides vertical movement of said load; electrical drive means for rotating said drum; chairing means cooperative with said load for supporting said load in alignment with said loading level; and electrical means for controlling said electrical drive means to cause said load, when supported by said References Cited chairing means, to be maintained on said chairing means despite variations in the weight of said load. UNITED STATES PATENTS 5. The combination of claim 4, further comprising said 2,628,336 2/ 1953 Jones 318144 controlling means being responsive to the current drawn 5 2 785 362 3/1957 Harding et a1 318 147 X by said drive means to control the tension on said rope 3297110 1/1967 B 187 29 means for preventing vertical movement of said chairing agnasco means.

6. The combination of claim 8, further comprising said ORIS F Prlmary 'Exammer' chairing means including a plurality of slidable hoist 10 LYNCH, Assistant Examinerchairs.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, D.C. 20231 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,407,904 October 29, 1968 William G. A. Trollope It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the drawings, Sheets 1 and 2, in Fig. l of the drawings the facing, vertical edges of the station floor 24 should be considered as spaced further apart to clear the floor 21 of the cage 18; in Fig. 2, the generator 40 should be considered as havj an armature 41 andTackOmeter 48 should be considered as the "Tachogenerator" of column 3, line 3 of the specification. Colun 2, line 37, "axample" should read example Column 5, line claim reference numeral "8" should read 4 Signed and sealed this 3rd day of March 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

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