US2729775A - Circuits for winch motors - Google Patents

Description

Jan. 3, 1956 F. N. WARE 2,729,775

CIRCUITS F'OR WINCH MOTORS Filed May 21, 1952 Pf6/ME M01/EE QUJQZOT.'

52 HMA/K W429i,

Unite CIRCUITS FR WINCH MTURS Frank N. Ware, Rogers City, Mich., assigner to United States Steel Corporation, a corporation of New .Hersey Application May 21, 1952, Serial No. 289,175

3 Claims. (Cl. S18-87) This invention relates to improved motor and generator circuits for operating a pair of Winches which are adapted to swing a boom horizontally.

The invention is particularly applicable to an unloading boom aboard a ship and is thus described, although obviously its use is not thus limited. An unloading boom commonly is swung horizontally by a pair of motor driven Winches and cables connected to its opposite sides. The port winch is operated as the heaving or take-up winch to swing the boom to port and the starboard winch to swing it to starboard, but in each instance it is necessary to snub the cable on the opposite side. The Winch on the side which is snubbed is referred to as the holdback or pay out winch, and it is usual to apply brakes to this winch for thus snubbing the cable.

An object of the present invention is to provide improved circuits which enable the motor of the holdback winch to operate automatically as a dynamic brake and which maintains a nearly constant holdback torque on this winch.

A further object is to provide improved circuits which enable a single variable voltage D. C. generator to drive either of the two winch motors, and the other motor to act as a constant torque dynamic brake.

A further object is to provide as a subcombination a motor which is adapted to act as a dynamic brake and which has improved means for maintaining a constant braking torque at varying speeds.

In accomplishing these and other objects of the invention, l have provided improved details of structure, a single form of which is shown in the accompanying drawing, in which:

Figure l is a diagrammatic top plan View of a ship equipped with an unloading boom and is illustrative of the structure with which the circuits of the present invention can be used; and

Figure 2 is a schematic wiring diagram of the circuits of the present invention.

Figure l shows somewhat diagrammatically a ship 10, the deck of which contains cargo hatches 12 and is equipped with an unloading boom 13. Normally this boom occupies a mid-position over the hatches, but it can swing outboard in either direction about a substantially vertical axis 14. The ship carries a port winch 15 and cable 16 for swinging the boom to port and a starboard winch 17 and cable i8 for swinging the boom to starboard. These cables are shown reeved for swinging the boom outboard to port; when it is desired to swing the boom outboard to starboard, the reeving is reversed. The ship has port and starboard control stations 19 and 20 which can be used alternatively for operating the boom. The ship can have a transfer switch 21 for cutting in either of the two control stations. It is to be understood that the ship has the usual means for raising and lowering the boom, and that the boom has the usual cargo engaging means, but since the invention does not concern these features, they are not shown.

Figure 2 shows a schematic wiring diagram of the ice improved circuits of the present invention. In this iigure all contacts are shown in the positions they occupy when the circuit is deenergized and the boom at rest. These circuits are powered by a variable voltage D. C. generator 255, which has output lines 26 and 27, and a D. C. exciter Z8, which has output lines 29 and 30. Preferably the generator and exciter are driven by a common prime mover 32. The port winch 15 is driven by a port winch D. C. motor 31 and the starboard winch 17 by a starboard winch D. C. motor 31a, both through suitable speed reduction gearing.

Generator 25 has a self-excited shunt field 33, a differential series iield .'54, and a separately excited field 35. The circuit to the self-excited shunt field 33 preferably contains resistors 36 and 37 and short-circuiting contacts for regulating the intensity of this lield. The separateiy excited field 3S is connected across the output lines 29 and 3i? from the exciter 2S and its circuit contains a plurality of resistors 39, itil, 41 and 42 and correspond ing short-circuiting contacts 39a, ila, 41a and 42a. The

voltage output of generator 25 can be varied by shorting out these different resistors, which thus afford a variable voltage control. By shorting them out successively as the generator starts to energize either of the winch motors, it is possible to maintain a nearly constant torque on the heaving winch despite the high inertia load of the boom, the list of the vessel, and variations in power requirements through the arc of boom travel.

The armatures of both the port and starboard winch motors 31 and Sia are connected in parallel across the generator output lines 26 and 27. The circuits thereto contain normally open contacts 4.3 and 43a respectively. The port winch motor has a separately excited iield 44 connected across the excited output lines 29 and 30 and the circuit thereto contains normally elo-sed contacts 45, a resistor do, and normally open shcrt-circuiting contacts i7 vior said resistor. Similarly the starboard winch motor has a separately excited iield li-a, contacts 45a, resistor ao and contacts 47o connected in the same fashion. Thus it is seen that generator 25 can energize either motor armature on closing of the normally open contacts 43 or i3d and that the exciter 28 energizes the separately 'excited field of this motor on closing of the short-circuiting contacts 47 or 47a, while the normally closed contacts l5 or 45a remain closed. Either motor which is thus energized drives its winch and swings the boom 13 in the corresponding direction. Movement of the boom rotates the other winch, and thus rotates its motor armature.

The motors have additional circuits which enable either of them to operate as a dynamic brake when its winch becomes the holdbacl; winch. In the port winch motor 31 this additional circuit includes a differential series field 48, a dynamic braking resistor 49, and normally closed contacts Sii, all connected in series across the motor armature. Normaliy open contacts 51 are connected between the separately excited 'held circuit and the armature circuit, and normally open contacts 52 between the output line Z9 of the exciter 28 and a center tap of the resistor 49. Similarly in the starboard winch motor 31a, this circuit includes a field 48a, a resistor 49a and contacts Stia, 51a and 52a all connected in the same fashion. When either motor is energized by the generator 2S, its normally closed contacts Si) or Sila open and its normally open contacts 51 or Sla and SZ or 52a remain open, whereby its dynamic braking circuit is inoperative.

ln the motor which acts as a dynamic brake the norn mally closed contacts 5d or 50a remain closed, the normally open contacts 51 or Sla and 52 or 52a close, the normally closed contacts 45 or 45a open, and the normally open contacts 43 or 43a and 47 or 47a remain open. This motor now acts as a generator which produces a current flow through the resistor 49 or 49a. Such current causes a holdback or counter torque eect on the winch, which torque normally would tend to increase in proportion to the motor speed. However, the circuit of the present invention maintains this holdback torque substantially consant irrespective of motor speed. This result is attained in part by the differential series field 48 or 48a in series with the resistor 49 or 49a. As the motor speed increases, the intensity of the differential field increases and is subtractive from the separately excited field 44 or 44a. This result is further attained by utilizing part of the ouput voltage of the dynamic brake motor to oppose the voltage which the exciter 28 applies to its separately excited field 44 or 44a. The separately excited eld of the dynamic brake motor is energized via contacts 52 or 52a, a portion of resistor 49 or 49a, contacts 50 or 50a, and contacts S1 or 51a. On the other side the energizing current must pass through resistor 46 or 46a. The polarity of the dynamic braking circuit is such that part of its voltage opposes and subtracts from the separately excited field voltage, which is of the opposite polarity. Thus, if line 29 is the positive and line 30 the negative of the exciter 28, the left side of the motor 31 or 31a would be the negative and the right side the positive (when the motor functions as a brake).

Reference may be rnade to the following sequence chart to furnish a clearer understanding of the positions of the contacts during various operations of my circuits. Contacts marked x" are closed; the others open.

Sequence chart for contacts associated with Dy. El. machines 31 and 31a in practice the various contacts are connected to a common actuator such as a master switch, which is duplicated at the two stations 19 and 2G. When this switch is actuated to close the contacts 43 and thus energize the armature cf the port winch motor 31, it also opens contacts Si. to disconnect the dynamic brake resistor of this motor and closes contacts 47 to short-circuit the resistor 46. At the same time it opens contacts 45a and closes contacts Sia and 52a of the starboard winch motor to set up this motor as a dynamic brake. Likewise when the master switch is actuated in the other direction to close the contacts 43a and thus energize the armature of the starboard winch motor, it also opens contacts Sila, closes contacts 47u, opens contacts 45, and closes contacts 51 and 52. The short-circuiting contacts 39a, 40a, 41a and 42a also conveniently can be controlled by the same master switch so that moving it farther in either direction automatically increases the voltage output of the generator 25 and accelerates whichever motor is being energized.

From the foregoing description it is seen that the present invention aiords a simple circuit arrangement which automatically enables the motor on the holdback winch to function as a dynamic brake and at the same time assures that the holdback torque remains constant throughout the speed range. The same circuits enable the drive motor to accelerate uniformly while the braking motor hold back its winch with a uniform torque.

While I have shown and described only a single embodiment of the invention, it is apparent that modifications may arise. Therefore, I do not Wish to be limited to the disclosure set forth but only by the scope of the appended claims.

l claim:

1. A D. C. motor adapted also to act as a dynamic brake comprising an armature, a separately excited field, a dynamic braking resistor connected across said armature, a diiierential series field and a set of contacts connected in series with said resistor, a connection between said resistor and said separately excited field enabling part of the voltage generated by said motor when acting as a dynamic brake to oppose the voltage in said separately excited field, and contacts in said last-named connection, said series field and said last-named connection being Cooperable to maintain the braking torque of said motor substantially constant at varying speeds.

2. in a drive which includes opposed Winches and cables adapted to pull in opposite directions, a pair of D.-C. motors each of which has an armature and a separately excited field winding, the armature of each motor being mechanically connected to a different winch for driving the latter, a common D.C. generator connected to energize the armature of either motor, and a common D.C. exciter connected to energize the field Winding of either motor, the combination with each motor, of a dynamic baking circuit and control connections for said braking circuit enabling either motor to act as a holdback while the other drives its respective winch, each braking circuit including a resistance, a field Winding differential with respect to the respective separately excited field winding and contacts connected in series across the respective motor armature, each control connection including contacts connected between the armature and the separately excited eld of the respective motor, contacts connected between said exciter and at least a portion of the respective resistance, and contacts connected between said exciter and the respective separately excited field, said first, second and third named contacts associated with either motor being adapted to open and said fourth named contacts associated therewith to close to enable that motor to drive its winch, the contacts associated with the other motor being adapted to assume opposite positions to enable this other motor to exert a holdback torque with current generated thereby both setting up a series field differential to the separately excited field and opposing the current from said exciter.

3. A combination as defined in claim 2 in which said holdback torque is substantially constant throughout the operating speed range.

References Cited in the tile of this patent UNITED STATES PATENTS 1,175,346 Dearborn Mar. 14, 1916 1,262,644 Strang Apr. 2, 1918 1,931,107 Dowell Oct. 17, 1933 2,147,662 Rosener Feb. 14, 1939 2,179,319 Binney et al. Nov. 7, 1939

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