US3510107A

US3510107A - Multiple hoist synchronization system

Info

Publication number: US3510107A
Application number: US697085A
Authority: US
Inventors: Ridley Fidler
Original assignee: United Aircraft Corp
Current assignee: Raytheon Technologies Corp
Priority date: 1968-01-11
Filing date: 1968-01-11
Publication date: 1970-05-05
Anticipated expiration: 1987-05-05
Also published as: DE1815616B2; BR6905495D0; DE1815616A1; GB1247928A

Description

May 5, 1970 R. FIDLER 3,51

MULTIPLE HOIST SYNCHRONIZATION SYSTEM Filed Jan. 11, 1968 6 Sheets-Sheet 1 F/G/ /Z l@ M A m I I 6 40 52 i M g igi,

& Q XX INVENTOR RIDLEY FIDLER BY W AGENT y 1970 R. FIDLER 3,510,107

MULTIPLE HOIST SYNCHRONIZATION SYSTEM Filed Jan. 11, 1968 6 Sheets-Sheet 2 F /G. 3 a,

WW mu M J a? 1 x 54; 52

I4 0 :44 may i 444;

FIG. 5 I

May '5, 1970 R. FIDLER 3,510,107

MULTIPLE HOIST SYNCHRONIZATION SYSTEM Filed Jan. 11, 1968 6 Sheets-Sheet 3 W /M REAR May 5, 1970 R. FIDLER MULTIPLE HOIST SYNCHRONIZATION SYSTEM 6 Sheets-Sheet 5 Filed Jan. 11, 1968 FIG. 7

w 2 m a E T m United States Patent 3 510 107 MULTIPLE norsr SYNCIIRONIZATION SYSTEM Ridley Fidler, Milford, C0nn., assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed Jan. 11, 1968, Ser. No. 697,085 Int. Cl. B66d 1/48 U.S. Cl. 254173 27 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a hoist mechanism in which the speeds of a number of independently driven winch cables are synchronized in order to keep the suspended load in a fixed attitude while it is raised and lowered. Provisions are also made for individually operating the winches or operating the winches in pairs to shorten or extend the cables with respect to one another and change the attitude of the load.

This invention herein described was made in the course of or under a contract or subcontract thereunder with the Department of the Army.

BACKGROUND OF THE INVENTION This invention relates to a hoist mechanism in which the speeds of a number of independently driven winch cables are synchronized in order to keep a suspended load at a fixed attitude, such as a horizontal attitude, while the load is being raised or lowered.

It is often desirable in cargo-handling systems to employ a hoist mechanism which incorporates a number of winches for moving a bulk cargo load from one place to another. It is generally desirable that the winch cables operate at a uniform speed so that the attitude of the cargo is not changed while the winches are operating in unison. Variations in the cable speed may arise from a number of sources. For example, the different winches may be driven at the same speed but due to the differences in the amount of cable already wound upon the winch drum, the actual radius of one winch drum may be different from that of another and consequently the speed at which the cable is paid in or out may vary. In other instances, different winches or groups of winches may be operated from independent motors and since the motor speeds may vary due to different loads upon the cables, the cable speeds may also vary.

Hoist mechanisms in which a number of cables are driven independently by separated motors are often preferred since they will permit individual operation of the cables. For example, where a load must be suspended with the paid out cable lengths being unequal, the winches at sometime must be operated individually to achieve the desired paid out lengths. Systems with individually driven cables also permit the attitude of the cargo load to be changed while the load is suspended from the cables. In addition, in aircraft systems where Weight is a critical factor, it is desirable to employ separate winch motors for remotely positioned winches instead of heavy interconnecting power shafts which might pass through intervening passageways and structural components. In multiple winch systems where the load is only moved a short distance, differences in cable speeds may not prove critical. However, in a system such as the hoist arrangement for raising and lowering a cargo load from a hovering helicopter, a small difference in the speed of the winches may 3,510,107 Patented May 5, 1970 ice result in a substantial change in the attitude of the cargo load as it is raised or lowered from the hovering helicopter. A number of independently driven winches are often employed in such systems and some form of cable speed control is desirable to keep the cargo load in a level position while it is raised or lowered.

SUMMARY OF THE INVENTION This invention relates particularly to a hoist mechanism employing a number of independently driven winches in which the speeds of the cables are synchronized to keep the suspended load in a fixed attitude while it is being raised or lowered.

In particular, each winch is driven by a hydraulic motor in a system in which the hydraulic power is distributed in accordance with the power demanded by the motors to keep the winches operating at a constant speed in spite of differences in the loads on each winch and motor. The roportioning of hydraulic power is first made to different groups of winches and from different groups of winches to the various winches themselves. This proportioning is accomplished by hydraulic flow-dividing valves each of which include a torque motor operating a spool valve. The flow-dividing valves are in turn controlled by a feedback mechanism which includes a paidout cable length transducer for each cable to produce a feedback signal varying as a function of the paid-out length of the cable. The signals from the transducers are combined in an appropriate manner to proportion the proper amount of hydraulic power to the appropriate winches.

In particular, an electrical feedback signal representative of the paid-out cable length from one group of winches is compared with a feedback signal representative of the paid-out cable length from another group of winches. In one embodiment of the invention the representative cable length signal is the average of the paid-out lengths from the group and in another embodiment, the representative signal is the actual paid-out length of one of the winches in the group. A primary hydraulic flow-dividing valve is driven by the difference in the representative signals to proportion the hydraulic power between the group of winches. Within each group the flow is proportioned by secondary flow-dividing valves to the appropriate subgroups of winches in response to the difference in the representative paid-out cable lengths of the subgroups. At the lowest stages of distribution, the hydraulic flow-dividing valves distribute the hydraulic power between the winches themselves in response to the differences in the paid-out cable lengths of the winches. A high gain in the control system permits a small difference signal to operate the valves so that a fixed attitude will be maintained while the load is raised or lowered.

In still another embodiment of the invention, the requirement for a representative paid-out cable length signal is eliminated by providing only two hydraulic flow dividing valves which operate independently. The valves drive four winches which are positioned at the corners of a parallelogram. Each of the flow dividers operates one of the diagonal pairs of winches. In order to beep the individual winches, three-way valves are provided which connect the hydraulic motors directly with a hydraulic power source exclusive of the flow dividing valves.

Another feature of the invention is the provision for operating, or beeping, any of the winches individually or for operating selected pairs of the winches without interfering with the speed balancing system. This operation of the winches permits a change of attitude of the load while the load is suspended from the winches or permits an oddly shaped load to be picked up with the actual paid-out cable lengths of the several winches being unequal. Clutches are included between the paid-out cable length transducers in the feedback mechanism for each cable in order to prevent any unbalance of the biasing adjustment established by the feedback mechanisms for equalizing the speed of the winches. To prevent this adjustment from interfering with the beeping operation, the transducers are also deenergized when the clutches are disengaged.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a winch-supported cargo load under a crane-type helicopter in which the hoist speed synchronization apparatus may be employed.

FIG. 2 is a plan view of the crane-type helicopter showing the position of four hydraulically driven winches.

FIG. 3 is a detail drawing of one of the winches including a hydraulically driven motor and paid-out cable length potentiometer.

FIG. 4 is a diagram of the hydraulic system which drives the winch motors.

FIG. 5 is a schematic of the hydraulic flow-dividing valves in the hydraulic system of FIG. 4.

FIG. 6 is an electrical diagram of the control system which achieves speed synchronization of the four winch motors in FIG. 4.

FIG. 7 is an electrical diagram of a simplified control system which achieves speed synchronization of the four winches in FIG. 4.

FIG. 8 shows the hydraulic system which employs only two flow-dividing valves for a four-point hoist systern.

FIG. 9 is a simplified electrical diagram of the control system which achieves speed synchronization of the fourpoint hoist system in FIG. 8.

FIG. 10 depicts the load C.G. limitations imposed by the hoist system of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to FIGS. 1 and 2, a crane-type helicopter is seen having a fuselage 10, a motor 12 driving a rotor 14 through a transmission 16. A forward landing gear 18 is connected to cockpit 20 and since the helicopter is of the crane-type, it has an elongated

rear landing gear

22 and 24 projecting downwardly from laterally extending

struts

26 and 28. Suspended between the rear landing gear from the fuselage is a cargo load 30. The cargo load may be a pallet having a load fastened thereon, or a bulk container, or a passenger pod for transporting personnel.

Cargo load 30 is suspended from the fuselage 10 by means of

isolators

32, 34, 36 and 38 and winches 40, 42, 44 and 46. For a further description of the isolators and the pod positioning and supporting means, reference may be had to -U.S. Pats. Nos. 3,176,939 and 3,176,940. The winches employed in the present invention have been modified slightly from those described in the above-referenced patents; however, the isolators and the supporting lengths may be the same.

It will be noted that there are four winches for raising and lowering the cargo load from the fuselage 10 of the helicopter. In such an embodiment, it would be important that the winches operate at essentially the same speed so that when the helicopter is raising or lowering the cargo load while in a hovering condition, the altitude of the cargo would not change as the distance between the helicopter and the ground is traversed. It would also be important that provisions be included to individually operate the winches so that all loads can be drawn close to the fuselage at an altitude most suitable for high speed flight under the helicopter.

FIG. 3 shows a detail configuration of the winch which is the same for all four winches. The winch 40 has a housing which would be supported through the isolators in the helicopter embodiment. A winch cable 52 is wound upon the winch drum 54. The winch drum 54 has an external helical groove in which the paid-in portion of the cable is nested. The one end of the cable 52 is firmly attached to the drum and the other end of the cable 52 has an appropriate attaching device such as a hook (not shown) hanging pendantly over a scrub roller 56. The roller serves as a guide for the cable 52 as it is paid in or out from the drum 54. A hydraulic motor 58 is connected to the winch housing and since such motors generally operate at a high speed, a suitable gear reduction unit may be incorporated within the drum 54 to reduce the operating speed of the drum on the axis 60 and increase the driving torque. If desired, a self-actuated brake may be incorporated in the drive train between the hydraulic motor 58 and the drum 54 in order to lock the drum at a fixed position whenever the motor is not operating.

The hydraulic motor 58 is a conventional, reversible, fixed displacement hydraulic motor. In such motors, the rotational displacement of the motor is directly proportional to the quantity of fluid displaced by the motor and the direction of rotation is reversed when the direction of flow is reversed. If constant motor speeds are to be maintained, a larger load on a motor will require more hydraulic power than a small load. Conversely, a small load on the motor will require less hydraulic power. With motor rotation proportional to fluid displacement, motor speed remains proportional to fluid flow rate. At constant motor speed, therefore, the power must be varied by changing the pressure differential across the motor.

Mounted within a section of the housing 50 is a cable length potentiometer 62. The potentiometer 62 is connected to a gear 64 which is driven from a gear 66 connected to and rotating with the drum 54. The potentiometer is a conventional high precision linear transducer of the type shown in US. Pat. 3,331,047 which, when excited by DC voltage, produces an electrical signal varying in proportion to the length of cable paid in or out. A suitable potentiometer might have a ten-turn rotary wiper, a total resistance error of /2%, a linearity error of .03% and resolution error of .03%.

Interposed between the gear 64 and potentiometer 62 is a conventional magnetic particle clutch 68. The clutch 68 is engaged when an electrical signal is applied and disengaged when the electrical signal is removed. The potentiometer 62, therefore, will be connected to rotate with the drum 54 when the clutch 68 is engaged. The potentiometer will produce an electrical signal which varies linearly as the drum 54 rotates and cable is paid in or out. When the clutch is disengaged, the drum may rotate and pay cable in or out Without changing the signal generated by the potentiometer.

It will be noted that there is only a single layer of cable wound upon the drum. It may be desirable in certain embodiments of the invention to include several more layers of cable upon the drum. In such cases, the output signal of the potentiometer 62 driven from the drum 54 would deviate slightly from the actual paid-out cable length of the winch due to the fact that the effective radius of the drum 54 would change as the layers of cable were paid in or out. If a number of layers of cable are necessary, the accuracy of the system may be improved by attaching the potentiometer 62 to the roller 56 instead of the drum 54 so that a direct reading of the cable length paid in or out is obtained rather than a reading of the drum revolutions.

Reference to FIG. 4 will show the hydraulic system by which the four remotely positioned winches are powered. The

hydraulic motors

58, 70, 72 and 74 are connected respectively to the

winches

40, 42, 44 and 46. Hydraulic power in the form of pressurized hydraulic fluid is produced by the winch pump 78. The winch pump 78 normally delivers a constant flow of hydraulic fluid at a variable pressure but the rate of flow and direction of flow can be varied through an electrically actuated control valve 80. The pump 78 supplies hydraulic fluid to the

motors

58, 70, 72 and 74 through either

conduit

82 or 84 depending on the direction of flow established by the control valve 80. Since the

hydraulic motors

58, 70, 72 and 74 are the reversible fixed displacement type, the direction of operation of the motors, and therefore the winches, will be determined by the control valve 80.

Filters

86 and 88 are included in the

conduits

82 and 84. Check valves 90 surrounding the filter 86 and the check valves 92 surrounding the filter 88 ensure that the hydraulic flow will always pass in the same direction through the filters to avoid back-washing the filters when the direction of the hydraulic flow is reversed. A pressurereducing valve 94 is also included between the

conduits

82 and 84 to bypass excessive pressure from the high pressure side to the low pressure side of the hydraulic system. The check valves 96 connecting the pressure-reducing valve 94 between the

conduits

82 and 84 ensure that the valve 94 will experience a positive pressure differential in the proper direction for actuation of the valve. A shutoff valve 98 is included in conduit 84 to shut off the motors.

Interposed between the shutofl valve in conduit 84 and the

motors

58, 70, 72 and 74 are flow-dividing

valves

100, 102 and 104. It is important to note that the hydraulic valve 100 controls the flow in the two

conduits

106 and 108. The valve 102 in turn controls the flow through conduits 110 and 112 while the valve 104 controls the flow through

conduits

114 and 116. The total flow in conduits 110 and 112 passes through the valve 100 and conduit 106. The total flow through

conduits

114 and 116 passes through valve 100 and conduit 108. The distribution of the flows through these valves and conduits is controlled by the valves regardless of the direction of flow through the

motors

58, 70, 72 and 74 and the

conduits

82 and 84.

The hydraulic system between the winch pump and the motors is a closed hydraulic system and since there is no reservoir in this system it may be necessary from time to time to add additional hydraulic fluid lost through leakage. This is accomplished through a replenishing pump 118 which draws fluid from a reservoir 120. This pump may be any suitable pump and in the helicopter installation it can be a pump which supplies utility pressure for operating the landing gear and other auxiliary devices on the aircraft. In order to add fluid to the hydraulic system driving the winches, fluid is taken through a pressure reducer 122 which reduces the pressure to approximately 50 p.s.i. and directs the fluid either through check valve 124 in replenishing line 126 or check valve 128 in replenishing line 130 to the

conduits

82 or 84, respectively. The check valves are incorporated in

lines

126 and 130 so that the high pressure fluid from the winch pump 78 will not be lost through the replenishing system. When the pressure on the return side of the winch pump drops below the 50 p.s.i. pressure established by the pressure reducer 122, fluid will be added to the hydraulic system powering the winches. It will be noted that since the winch pump 78 will reverse the flow to the motors, either one of the

conduits

82 or 84 may serve as the return line to the pump 78, and consequently the two replenishing

lines

128 and 130 are necessary.

The replenishing pump 118 can also supply the control pressure for the control valve '80 which varies the flow delivered by the winch pump 78. In addition, the replenishing pump 118 can also supply fluid through a flow reducing orifice 132 and drain line 134 to the reservoir 120 for cooling the winch pump 78. A pressure reducer 136 between the high. pressure side of the replenishing pump 118 and the drain line 134 prevents excessively high pressures from damaging the winch pump. A filter 13 8 is also included to prevent contamination from affecting either the control valve or the orifice 132 and also prevents dirt from entering the hydraulic system for the winches.

The hydraulic flow-dividing

valves

100, 102 and 104 ensure that the hydraulic flaws through each of the

hydraulic motors

58, 70, 72 and 74 remain the same regardless of the power demanded by each of the motors. The valves are similar in construction to the conventional electro-hydraulic servo valves which have a torque motor operating a flapper valve to control a spool Valve. The flow-dividing valve is seen in greater detail in FIG. 5. In the upper portion of the valve, hydraulic control fluid from the replenishing pump 118 of FIG. 4 enters a port 140 and pases through a filter 142, through the orifices 144 and 146 and into control ducts 148 and 150, respectively. These control ducts direct the fluid through

nozzles

152 and 154 against a flapper 156 which is positioned in close relationship to each of the

nozzles

152 and 154. Fluid which passes through the

nozzles

152 and 154 is returned to the low pressure side of the replenishing pump 118 through conduit 176. The flapper 156 is caused to move closer to one nozzle or the other by a torque motor 158 which includes two electromagnetic coils 160 and 162 operating upon an armature 164 to which the flapper 156 is connected. When the flapper 156 moves closer to one of the nozzles, for example nozzle 152, the flow passing through that nozzle will decrease and consequently the pressure drop across the orifice 144 will decrease to increase the control pressure in duct 148. A corresponding decrease in the control pressure in duct 150 will occur because the flow will increase through the nozzle 154 and cause a corresponding increase in the pressure drop across orifice 146. The increase in the pressure in duct 148 and the decrease in the pressure in duct 150 will develop a pressure ditierential across the spool valve will restrict hydraulic flow for the winch motors passing between the

dual ports

168 and 170 and the single port 172. The summation of the flow through

ports

168 and 170 will equal the total flow through the port 172. This relationship remains true regardless of whether the flow enters the valve through single port 172 and is divided between

dual ports

168 and 170 or if the flow is in the reverse direction from

ports

168 and 170 to port 172. As the spool moves toward duct 150, it will close ofi the flow through the port 168. Essentially, the spool acts as a variable orifice for the

ports

168 and 170 which biases the hydraulic power converted by the winch motors to maintain constant speeds in spite of differences in the loads on the winches. In this regard, it will be noted that the spool shown in the schematic of FIG. 5 is slightly underlapped in that the lands of the spool 166 do not obstruct any portion of the

ducts

168 or 170 when the spool is in the normally centered position. Hydraulic flow will only be reduced in one of the

ports

168 or 170 when the spool moves away from its centered position. Those skilled in the art will recognize that the valve could be constructed with overlapping lands and ports so that a displacement of the spool from the normally centered position will not only reduce the flow through the one port but will also increase the flow through the other port. The disadvantage of the overlapped valve is that a greater power loss will occur when the valve is in its normally centered position due to the restrictions on each of the ports in the centered condition.

A feedback spring 174 connects the valve spool 166 to the flapper 156. The spring 174 ensures that the position of the spool 166 will vary in direct proportion to the position of the flapper valve between the

nozzles

152 and 154. The position of the flapper 156 when it is centrally located between the

nozzles

152 and 154 should correspond with a central position of the spool 166- on the two

ports

168 and 170 in which case the flow through each of these ports will be balanced. This balanced flow condition through the

ports

168 and 170 in turn corresponds approximately with balanced control currents through the electromagnetic coils 160 and 162 of the torque motor 158.

The control system by which the flow-dividing

valves

100, 102 and 104 are operated in response to the cable length potentiometers on the winches is shown in FIG. 6. The

winches

40, 42, 44 and 46 are shown in positions which correspond generally to the positions of the winches in FIG. 2. where the helicopter is viewed from above. The forward pair of

winches

40 and 42 are located to the left of FIG. 6 and the rear pair of

winches

44 and 46 are located on the right. The clutch 68 described in FIG. 3 connects the winch 40 to the cable length potentiometer 62. In a similar manner,

clutches

180, 182 and 184 connect the

winches

42, 44 and 46 to

potentiometers

186, 188 and 190, respectively. The potentiometers are transducers which have

wipers

192, 194, 196 and 198 varying the resistance of the potentiometers to develop voltages for controlling the flow-dividing

valves

100', 102 and 104. The excitation for the potentiometers is a 28 volt power source in the helicopter, and is transmitted through

switches

200, 202 and 204. The

conductors

206 and 208 lead from the separate contacts of switch 204 to opposite ends of the resistive elements in the potentiometers in order to reverse the excitation of the potentiometers. Switch 204 when in one position, therefore, will energize the one end of the potentiometers while the opposite end is floating. When the switch 204 is in the other position, the energized and floating ends are reversed. The reason for this reversible excitation will be explained in greater detail below.

The

wipers

192 and 194 of the

potentiometers

62 and 186 are operated respectively by the forward pair of

winches

40 and 42. The signals from the

potentiometers

62 and 186 are applied to a large, grounded input impedance in comparator 210 in order to obtain a phase sensitive difference signal representative of the difference in the voltages from the two

potentiometers

62 and 186. The plus and minus signs indicate that the positive value of the signal from the potentiometer 62 is compared with the negative value of the signal from potentiometer 186. Those skilled in the art will recognize that the input impedance to the comparator should be high compared with the total impedance of the potentiometer in order to maintain a linearity of the input signals with the position of the wiper. In an alternate embodiment, linearity could also be ensured by exciting the potentiometers with a 28 volt signal across the full resistor of the potentiometers rather than having one end of the potentiometers floating. The comparator 210 therefore produces a null signal when the values of the voltages from

potentiometers

62 and 186 are the same and this null signal is impressed upon the coils of flow-dividing valve 102 which proportions the flow between the hydraulic motors for the forward pair of

winches

40 and 42. If the signals from the

potentiometers

62 and 186 were not exactly equal, the comparator 210 would produce an unbalanced electrical signal representing the difference in the voltages derived from the

potentiometers

62 and 186 and bias the hydraulic power applied to the

winches

40 and 42 by moving the valve spool to increase or decrease the openings of the dual ports of the flow-dividing valves in accordance with the magnitude of the unbalanced signal.

The movement of the valve spool will generally open the port of the flow-dividing valve which is passing the smaller of the flow rates. This arises from the fact that the winch which is operating at the slower speed will cause the movement of the wiper connected thereto to fall behind the movement of the wiper on the opposite winch controlled by the same flow-dividing valve. As a result, the difference signal generated by the comparator 210 will increase and cause a further increase in the hy draulic power bias to the winch which is operating at the slower speed. An equilibrium condition will be established when the wipers move along the potentiometers at the same speed and at a fixed differential, as measured by the comparator 210'. The power bias to the winches will be stabilized and therefore the winches will continue to operate at the same speed. In this condition, the flow rates to the two winches will be the same regardless of the difference in the power demanded by the two

winches

40 and 42.

If the gain of the comparator 210 and the flow-dividing valve 102 is high, the fixed differential of the signals from the

wipers

192 and 194 at which the speeds of the

winches

40 and 42 are synchronized can be very small. This means that the control system of FIG. 6 will not only synchronize the speed of the winches but will synchronize the speed of the winches at an attitude of the load at which the paid-out cable lengths of the winches are practically equal as sensed by the potentiometers. For example, the suspended load can be held in a level attitude while it is raised or lowered from the helicopter. A very small difference in the paid-out cable lengths will produce a large error signal from the comparator 210* and cause the flowdividing valve to speed up the lagging winch until the small differential is essentially eliminated.

A brief consideration of this synchronizing operation will reveal that a reversal in the direction of operation of the winches will require a reversal in the direction of the hydraulic power bias when the deviations in the motions of the winches are measured by the

potentiometers

62 and 186. Consequently, the error signal produced by the comparator 210 must also be reversed in phase when the direction of operation of the winches is reversed. This is accomplished by reversing the excitation on the potentiometers through switch 204.

The proportioning of the hydraulic flow between the rear pair of

winches

44 and 46 is accomplished in a manner similar to the proportioning between the forward pair of winches. The

winches

44 and 46 operate the

potentiometers

188 and 190 having

wipers

196 and 198 which drive a comparator 212 and the flow-dividing valve 104. The switch 204 also reverses the energization of the

potentiometers

188 and 190 to reverse the phase of the error signal for the flow-dividing valve 104. Switch 204 is operated when the direction of operation of the winch motors is changed to raise or lower the cargo load.

The flow-dividing

valves

102 and 104 can level the load with respect to the lateral axis of the aircraft. In order to keep the cargo load level with respect to the longitudinal axis of the aircraft, a signal must be derived from the potentiometers to control the flow-dividing valve which proportions the flow between the fore and aft pairs of winches. This is accomplished by deriving representative paid-out cable length signals for the fore and aft cables from the averaging

networks

214 and 216 respectively. The averaging network 214 adds the signals from the

potentimeters

62 and 186 operatively associated with the forward pair of

winches

40 and 42. The signal derived from the averaging network 214 therefore is proportional to the average paid-out cable length of the forward pair of winches or the average distance between the cargo load and the one pair of winches. In the same manner, a signal proportional to the average paid-out cable length of the rear pair of

winches

44 and 46 is derived from the averaging network 216. These two signals are then fed to comparator 218 which produces a phase-sensitive difference signal for controlling the main flow-dividing valve 100 in the same manner that the

comparators

210 and 212 control the flow-dividing

valves

102 and 104. The flow-dividing valve 100, consequently, proportions the hydraulic power between the forward and rear pairs of winches in accordance with the difference in the averages of the paid-out cable lengths of the forward and rear pairs of winches. This proportioning of the hydraulic power can be thought of as the process for synchronizing the average speed of the forward pair of winches with the average speed of the rear pair of winches in accordance with the difference in the average distance between the cargo load and the forward pair of winches and the average distance between the cargo load and the rear pair of winches. This synchronization occurs in spite of dilferences in the power demanded by the winches to maintain equal speeds. Also, as with

comparators

210 and 212, a high gain of comparator 218 will operate the flow-dividing valve 100 in response to a small difference in the signals from averaging

networks

214 and 216. Such a gain will keep the cargo load substantially level with the longitudinal axis of the helicopter as the average speeds of the winches are synchronized. The phase of the error signal from the comparator 218 will also be reversed when the switch 204 reverses the energization of the transducers. This operation will be necessary whenever the direction of operation of the winches is reversed as mentioned above.

The operation of the flow dividing valves may be more clearly understood by an explanation of their functions. As shown in FIG. 5, the

ports

168 and 170 are always open when the valve is in its neutral position. In this condition, the pressure drops across the ports would be equal. If one of the winch motors must operate at a greater power level in order to maintain synchronous speed, the difference in the cable lengths of the winches developed by a ditference in speed will energize the proportioning of valve and cause the

ports

168 and 170 to open and close correspondingly and change the pressure drops across the ports until the proper power bias to the respective winch motors or pairs of winch motors is established. At this point the flows through the ports and the winch speeds will be the same. It will be noted that the flow-dividing values control the flow proportioning and the power distribution between the Winches regardless of the direction of fluid flow in the hydraulic circuit. Generally then, the ports of the flow divider valves are trimmed to pass balanced hydraulic power and biased by the cable angle transducers to provide balanced hydraulic flows.

Although two stages of hydraulic flow-dividing valves have been shown to distribute the flow between two groups of winches and between the winches of each group, it will be readily apparent that the two stages of flow-dividing valves could also be employed to proportion the hydraulic power between one group of winches and a third winch. Also if systems employ a number of groups of winches for raising the cargo load, additional flow-dividing valves could be added to divide the flow between the various groups in response to the differences in the averages of the paid-out cable lengths of each group. This apparatus, therefore, is not limited to a system having only four winches but can be employed in cargo-handling systems having a number of winches.

It is also an important feature of this invention that the winches may be operated individually or in selected pairs in order to change the attitude of the load while it is suspended from the winches or to extend or retract certain of the winch cables without operating the others. As discussed above, the potentiometers associated with each of the winch cables establish a power bias to the winches which will synchronize the speed of the winches in spite of variations in the load carried by each of the winches. It will be readily recognized that the individual operation of any of the winch cables would unbalance this power bias unless the potentiometers were disengaged from the cables during the individual operation, beeping, of the cables. It is for this reason that the electromagnetic clutches are incorporated between each of the winches and wipers of the potentiometers.

In order to operate the winches individually, switches 220, 222, 224 and 226 are included to deenergize the clutches respectively associated with the

wipers

192, 194, 196 and 198. In examining switch 220', which is typical of any one of these switches, it will be noted that when the switch is actuated electrical power derived through switch 228 and switch 230 will be removed from the clutch 68 to disengage wiper 192 from the winch 40. In addition, this electrical power will be applied as a 28 volt signal to both the comparator 210 and the averaging network 214 in order to introduce a maximum bias signal to flow-dividing

valves

102 and 100. This maximum bias signal in valve 102 will completely close the port of the valve 102 to the winch 44. Also, the maximum bias signal applied to the averaging network 214 and comparator 218 will completely close off the port of valve for the rear pair of

winches

44 and 46. Consequently, the only winch which will operate when hydraulic power is turned on will be winch 40.

It will be noted that the signals from the potentiometers may also interfere with the bias signal derived from switch 220 for beeping the winch 40. For this reason, a separate set of contacts associated with each of the

switches

220, 222, 224 and 226 will be broken at the time any one of these switches is actuated to deactivate relay 232 and deenergize all of the potentiometers. It will, therefore, be understood that operation of any one of the

switches

220', 222, 224 or 226 for beeping the winch motors will electrically deenergize all potentiometers, disengage the wipers from the winches and energize the flow-dividing valves to direct hydraulic fluid to the winch which is to be beeped. The direction in which the winches will operate during beeping will depend solely upon the winch pump which is controlled by the servo valve 80. It may be desirable to have several fixed flow rates to which this control valve can be set in order to establish a reduced flow from the winch pump when individual winches are beeped and prevent overspeeding of the hydraulic motors receiving the entire output of the winch pump.

It is another feature of this invention that the fore or aft pairs of winches can be operated independently. This is accomplished by the ganged

switches

230 and 234 operated by solenoid 236 and ganged

switches

238 and 240 operated by solenoid 242. When switch 244 is opened, solenoid 236 is deenergized and the clutches 68 and for

winches

40 and 42 are deenergized as well as all of the potentiometers. A beeping signal is applied to the comparator 210 and the averaging network 214. The application of the beeping signals to the comparator 210 will balance the power bias established by the flow-dividing valve 102. In addition, the signal produced by the averaging network 214 will bias the comparator 218 so that the aft pair of winches will be shut off and all hydraulic power will be directed to the forward pair of

winches

40 and 42. When solenoid 236 is deenergized, therefore, the forward pair of winches will be operated together and the rear pair of winches will remain stationary. Solenoid 242 together with the

switches

238 and 240 perform the identical function for the rear pair of winches so that when the switch 246 is opened and solenoid 242 is deenergized, only the rear pair of

winches

44 and 46 will be operated.

Switch 248 actuates solenoid 250 to apply power to the entire speed synchronization system. It may be desirable, for example, if a failure occurs in the speed synchronization system to deenergize the system by opening the switch 248 and deenergizing solenoid 250. In this case, the feedback springs in the flow-dividing valves tend to position the flappers and spools in their central position so that the ports through the valves are opened and the winches operate at approximately the same speed provided the cargo load has a center of gravity located substantially equidistant from the contact points of all of the winches.

A simplified embodiment of the electrical controls is seen in FIG. 7. In this embodiment the

comparators

210, 212 and 218, and the averaging

networks

214 and 216 have been eliminated. The resistive elements of the potentiometers are excited across their entire length from switch 204. In place of the comparators, the signals from the cable length potentiometers are fed directly to the coils of the torque motors in the flow dividers. Essentially, the signals comparison is made by the torque motor coils themselves. In order to eliminate the averaging networks and still acquire a representative paid-out cable length signal, potentiometer 260 has been added to one of the forward cable winches and potentiometer 262 has been added to one of the rear cable winches. These potentiometers are used to generate representative cable length signals for driving the primary flow dividing valve 100. In this case, the representative signal is equal to the cable length signal from only one of the winches. However, since speed synchronization between the forward pair or rear pair of winches is provided by the

flow divider valves

102 and 104, the cable length signal from one of the forward winches and one of the aft winches will be acceptable to synchronize the forward and aft winch speeds. It will be understood that these additional potentiometers would be connected to the winches through the

clutches

180 and 184 respectively (FIG. 1) as well as the

potentiometers

186 and 190.

The beeping system includes

individual switches

264, 266, 268 and 270 which actuate relays 272, 274, 276, and 278, respectively. The relays disconnect the potentiometers from

flow dividers

102 and 104 and apply a 28 volt signal directly to the one coil of the torque motors to fully bias the flow divider toward one of the Winch motors. In addition, the switches also actuate one of the

double relays

280 or 282 to fully bias the main flow divider valve 100 to the corresponding fore or aft pairs of winches. At the same time the double relay is actuated, the energization of the potentiometers is removed through ganged

switches

284 or 286. In this manner, any one of the winch motors can be operated individually. It will be readily understood that they can also be operated in pairs by gauging the

switches

264, 266, 268 and 270 or by inserting additional ganged switches in series with the above switches.

Still another embodiment of my invention is shown in FIGS. 8 and 9. In the simplified hydraulic schematic of FIG. 8, two

flow dividers

300 and 302 are employed to control the fiow rates between the four

winch motors

58, 70, 72 and 74 previously described with respect to FIG. 4. In this embodiment the flow divider 300 acts as a fiow proportioner for the diagonally paired

winch motors

58 and 74 while the flow divider 302 acts as a proportioner for the diagonally paired

motors

70 and 72. With the hydraulic power controlled to diagonally paired winches, the flow dividers operate independently but will move the load, within limitations defined below, at a synchronous speed. In order to simplify the hydraulic cut off for beeping the individual winches, three-

way valves

304, 306, 308 and 310 are interposed between the respective winch motors and the

flow dividing valves

300 and 302. These three-way valves have a passageway connecting the hydraulic motor with its respective flow dividing valve and a passageway which connects the motor to the hydraulic pump 78 through a bypass line 312 exclusive of the flow dividing valves. Each of the three-way valves can be actuated between two positions to correspondingly open and close the respective passages. When any one of the winches is to be operated by itself, the corresponding three-way valve will be actuated to its bypass position to connect the motor with bypass line 312 and the shutoff valve 98 will be closed to prevent any of the other winch motors from operating.

The control schematic for the diagonally paired winches is shown in FIG. 9 in simplified form. It will be understood that the same clutches incorporated with the potentiometers in FIG. 6 would be actuated during the beeping operation described above. It will be readily noticed that no representative paid out cable length signal is required with only two flow dividing valves connected as shown because each of the

valves

300 and 302 operate independent groups of winches. Because of this independence, limitations must be imposed on the location of the load center of gravity (C.G.) within the parallelogram defined by the cables 314, 316, 318 and 320 depicted in FIG. 10. The locus of points within which the C.G. of the load can lie is the shaded area between the lines connecting the mid-points of the sides of the parallelogram. This limitation is imposed by the facts that the power expended by each of the independent diagonal pairs must be equal and the speeds of the winches are controlled to be equal. This requires that each of the pairs of winches carries half of the load. This C.G. limitation in the helicopter installation is not unduly restrictive because the limitations of the aircraft itself generally define a C.G. location well within the boundaries established by the winch system.

Although the present hoist synchronization systems are shown in a cargo system for the helicopter, those skilled in the art will recognize that they may be advantageously employed in other multiple-winch hoisting systems where the winches have independent driving means.

It should be understood that the invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the spirit or scope of this novel concept as defined by the following claims.

I claim:

1. Apparatus for moving a cargo from one position to another comprising:

(a) a plurality of remotely positioned winches having cables adapted to connect to diiferent points on the cargo;

(b) controllable motor means connected to the winches for individually driving each of the winches;

(c) sensing means for determining the difference in the paid-out cable lengths of the winches; and

(d) control means connected to the controllable motor means for equalizing the speed of the cables in response to the sensing means.

2. Apparatus according to claim 1 wherein:

(a) the controllable motor means includes a hydraulic motor for each winch; and

(b) the control means connected to the controllable motor means includes a plurality of hydraulic flowdividing valves which distribute hydraulic flow to the motors to equalize the speed of the cables.

3. Apparatus according to claim 2 which includes:

(a) at least two pairs of winches;

(b) a first stage flow-dividing valve in the control means for separating hydraulic flow into a portion for the one pair and a portion for the other pair in response to the difference in representative paid-out cable lengths of each pair; and

(c) a second stage flow-dividing valve in the control means interposed between the first stage flow-dividing valve and the one pair of winches for receiving and distributing the portion of fiow for the one pair in response to the diiference in the paid-out cable lengths of the one pair.

4. Apparatus for raising and lowering a load at a fixed attitude comprising:

(a) two pairs of winches, each winch having a cable for raising or lowering the load;

(b) cable length sensing means operatively associated with the cables for producing signals varying as a function of the pair-out cable lengths;

(c) first control means for synchronizing the speed of the one pair of winches in response to the sensing means and cables of the one pair of winches;

(d) second control means for synchronizing the speed of the other pair of winches in response to the sensing means and cables of the other pair of winches; and

(e) third control means for receiving signals from the sensing means and synchronizing the speeds of the winches in the one pair with the speeds of the winches in the other pair.

5. Apparatus according to claim 4 and including:

(a) disengageable couplings between the sensing means and the cables of the one pair of winches; and

(b) means for disengaging the couplings without unbalancing the first, second, and third control means whereby the load can be moved by the one pair of winches without disturbing the speed synchronization established by the sensing means and the first, second, and third control means.

6. A speed synchronization control for two pairs of independently and hydraulically driven winches with cables, comprising:

(a) signal generating means connected with the cables for producing a first set of signals proportional to the paid-out cable length of each winch and a second set of signals proportional to a representative paidout cable length from each of the respective pairs of winches;

(b) a first hydraulic flow distribution valve having a fluid communication with each of the pairs of winches and controllable to vary the hydraulic flow through each pair, the valve being connected to the signal generating means and responsive to the second set of signals;

() a second hydraulic flow distribution value interposed in the fluid communication between the first valve and one pair of winches and controllable to vary the hydraulic flow through the winches of the one pair, the valve being connected to the signal generating means and responsive to the signals of the first set corresponding to the one pair of winches.

7. The speed synchronization control of claim 6 wherein the signal generating means produces signals in the second set proportional to the average paid-out cable length from each of the respective pairs.

8. The speed synchronization control of claim 6 wherein the signal generating means produces signals in the second set proportional to the paid-out cable length of one winch from each of the respective pairs.

9. A four-point hoisting mechanism comprising:

(a) two pairs of power-driven hoists mounted on a cargo support and adapted to be connected to a cargo load for raising and lowering the load;

(b) first means for producing signals proportional to the distances between the connected cargo load and each hoist of one pair;

(c) second means connected to the first means for proportioning power between the one pair of hoists in response to the difference in the signals from the first means;

(d), third means for producing signals proportional to the distances between the connected cargo load and each hoists of the other pair; and

(e) fourth means connected to the third means for proportioning power between the other pair of hoists in response to the diflerence in the signals from the third means.

10. The hoisting mechanism of claim 9 wherein: fifth means are operatively connected to the first, second, third and fourth means for proportioning the power between the second and fourth means in response to the first and third means.

11. The hoisting mechanism of claim 10 in which:

(a) the hoists are hydraulically driven; and

(b) the second, fourth and fifth means include valves which proportion hydraulic fluid flow between the hydraulically driven hoists.

12. A four-point hoist mechanism for a cargo carrier comprising:

(a) two pairs of hydraulically driven winches on the cargo carrier, each winch having a cable adapted to be connected to a load for raising and lowering the load from the carrier;

(b) a sensor operatively associated with the cable of each winch for producing a signal varying as a function of the paid-out cable length;

(c) first averaging means for receiving the signals produced by the sensors associated with one pair of winches and generating a signal representative of the average paid-out cable length of the one pair of winches;

(d) second averaging means for receiving the signals produced by the sensors associated with the other pair of winches and generating a signal representative of the average paid-out cable length of the other pair of winches;

(e) a hydraulic power source; and

(f) a first adjustable hydraulic flow-dividing valve connected between the hydraulic power source and each of the pairs of winches for proportioning the hydraulic power between the pairs of winches in response to the signals from the first and second averaging means.

13. Apparatus according to claim 12 wherein:

(a) a second controllable hydraulic flow-dividing valve is interposed between the first hydraulic flow-dividing valve and the one pair of winches and connected to the sensors associated with the cables of the one pair of winches, the valve dividing the hydraulic flow between the one pair of winches in response to the signals from the sensors.

14. Apparatus for synchronizing the speeds of two pairs of winch cables, each cable being independently operated by a hydraulically driven winch for lifting a load comprising:

(a) sensors operatively associated with each winch cable, each sensor developing a signal as a function of the paid-out cable length;

(b) first means responsive to the sensors associated with the one pair of winch cables for producing a first control signal as a function of the difference in the paid-out cable lengths of the one pair of cables;

(0) second means responsive to the sensors associated with the other pair of winch cables for producing a second control signal as a function of the difference of the pair-out cable lengths of the other pair of cables;

(d) a hydraulic power source for driving the winches;

(e) a first controllable hydraulic power distribution valve having a fluid communication with the hydraulic power source and connected to the winches operating the one pair of cables for distributing hydraulic power from the source between winches for the one pair, the valve also being connected to the first means and responsive to the first control signal, whereby the power distribution is controlled by the difference in the cable lengths of the one pair;

(f) a second controllable hydraulic power distribution valve having a fluid communication with the hydraulic power source and connected to the winches operating the other pair of cables for distributing hydraulic power from the source between winches for the other pair, the valve also being connected to the second means and responsive to the second control signal, whereby the power distribution is controlled by the difference in the cable lengths of the other pair.

15. Apparatus according to claim 14 wherein:

(a) the four winches are positioned at the corners of a parallelogram; and

(b) the winches for the respective pairs of cables lie on the diagonals.

16. Apparatus according to claim 14 further includmg:

(a) third means responsive to the sensors associated with each pair of winch cables for producing a third control signal as a function of the difference in representative paid'out cable lengths of each pair; (b) a third controllable hydraulic power dsitribution valve interposed between the hydraulic power source and the first and second hydraulic valves for distributing hydraulic power between the first and second valves, the third valve also being connected to the third means and responsive to the third control signal whereby the power distribution is controlled by the difference in the representative cable lengths.

17. Apparatus according to claim 14 wherein:

(a) each sensor is a transducer having a movable element associated with a cable for varying the sensor signal;

(b) disengageable clutches are interposed between the movable elements and the respective cables; and (c) means are provided for individually disengaging clutches whereby the speed synchronization signals established by the disengaged sensors are unaffected by movement of the respective cables.

18. Apparatus according to claim 17 wherein means are provided for disengaging pairs of the clutches interposed between the cables and sensors.

19. Apparatus according to claim 14 wherein:

(a) each hydraulically driven winch includes a reversible hydraulic motor to operate the winch; and

(b) the hydraulic source includes a reversible flow pump for changing the direction of operation of each motor and the driven winch.

20. Apparatus according to claim 19 wherein:

(a) each sensor is an electromechanical transducer developing an output signal from an excitation voltage in response to the paid-out cable length;

(b) the first means and the second means each employ a signal comparator producing a phase-sensitive difference signal from the output signals of the sensors;

() the first and second controllable hydraulic power distribution valves bias the hydraulic power between the winches as a iunction of the phase of the diiference signal from the comparators; and

(d) means are provided for reversing the excitation voltage on the transducers to permit the phase of the difference signal and the hydraulic power bias to the winches to be reversed when the direction of operation of the motors is reversed.

21. In a helicopter, a four-point hoist mechanism comprising:

(a) a first pair of winches mounted at a forward position of the helicopter, each winch being independently driven and having a cable for raising and lowering a load;

(b) a second pair of winches mounted at an aft position of the helicopter, each winch being independently driven and having a cable for raising and lowering the load;

(c) sensors operatively associated with the winches for producing signals varying as a function of the paidout cable lengths of the winches;

(d) first speed control means connected to the sensors for synchronizing the speeds of the Winches Within each pair in response to the signals from the sensors within the respective pairs; and

(e) second speed control means connected to the sensors for synchronizing the speed of the first pair of winches with the speed of the second pair of winches in response to sensor signals from 'both the forward and aft pairs of winches whereby the load can be raised and lowered from the helicopter at the synchronized speed of the winches.

22. Apparatus according to claim 21 wherein:

(a) fixed displacement hydraulic motors are respectively connected to each of the winches for independently driving each Winch;

(b) the second speed control means includes a first hydraulic flow-dividing valve which proportions hydraulic flow between the first pair and the second pair of winches; and

(c) the first speed control means includes:

(1) a second hydraulic flow-dividing valve interposed between the first hydraulic flow-dividing valve and the first pair of winches for dividing the proportioned hydraulic flow of the first valve between the hydraulic motors of the first pair of winches; and

(2) a third hydraulic flow-dividing valve interposed between the first hydraulic flow-dividing valve and the second pair of winches for dividing the proportioned hydraulic flow of the first valve between the hydraulic motors of the sec- 0nd pair of Winches.

23. Apparatus according to claim 22 wherein each bydraulic flow-dividing valve has two variable and coacting hydraulic flow ports trimmed to pass balanced hydraulic power and biased by the sensors to provide balanced hydraulic flows whereby the fixed displacement hydraulic motors drive the winches at a synchronous speed in spite of the dilferences in power required to drive the different winches.

24. Apparatus according to claim 23 wherein:

(a) each sensor is an electrically energized transducer having an adjustable element disengageably connected to the winch to vary the sensor signal with movement of the cable; and

(b) means are provided for simultaneously deenergizing all sensors, disengaging the adjustable element of a sensor operatively associated with a selected winch, and energizing the first and second speed control means to operate the selected winch individually without unbalancing the bias adjustment previously established by the sensors.

25. Apparatus according to claim 23 wherein:

(b) means are provided for simultaneously deenergizing all sensors, disengaging the adjustable elements of the sensors operatively associated with a selected pair of the winches, and energizing the first and second speed control means to operate the selected pair without unbalancing the bias adjustment previously established by the sensors.

26. A four-point hoist system comprising:

(a) two pairs of winches positioned at the corners of a parallelogram and diagonally opposite winches forming each of the pairs, each winch having a hydraulic motor and a cable for hoisting a load;

(b) transducers connected to each of the cables for generating signals proportioned to the length of cable paid out by the winches;

(c) a hydraulic fluid power source for driving the motors;

(d) a first hydraulic power proportioner connected in series with the source and the two motors for the one pair of winches for proportioning power from the source between the motors of the one pair, the proportioner also being connected to the transducers associated with the cables of the one pair of winches and responsive to the difference in the signals from the transducers; and v (e) a second hydraulic proportioner connected in series with the source and the two motors for the other pair of winches for proportioning power from the source between the motors of the other pair, the proportioner also being connected to the transducers associated with the cables of the other pair of winches and responsive to the difference in the signals from the transducers 27. Apparatus according to claim 26 further including three-way hydraulic valves interposed between each of the hydraulic motors and the respective propoitioners each valve having a closable series passage connecting 17 18 the respective proportioner and the motor and a ciosable FOREIGN PATENTS bypass passage communicating the motor with the source 742,094 9/1966 Canada exclusive of the proportioner.

HARVEY C. HORNSBY, Primary Examiner References Cited UNITED STATES PATENTS US. Cl. X.R.

2,957,582 10/1960 Lusk 254144 244137; 254*144, 184