APPARATUS FOR PROVIDING PRESSURIZED LIQUID TO A DEVICE, HIGH SPEED FLOOD COOLED MOTOR/GENERATOR THEREFOR

Abstract: An apparatus for providing pressurized liquid for operating a hydraulically operated device of an airplane comprises a pump for pumping liquid, a high speed flood cooled permanent magnetic motor for driving the pump, a drive connecting the motor to the pump for driving the pump with the motor, and a control for operating the motor as a variable speed motor. The pump, motor, drive and control are incorporated in one unit. Fluid passages in the unit circulate liquid being pumped by the drive through the pump case, control and motor for cooling. The motor includes stator and a rotor with an airgap therebetween having a thickness of at least 0.1 inch for reducing hydraulic friction losses in the motor without increasing motor size considerably.

Description: APPARATUS FOR PROVIDING PRESSURIZED LIQUID TO A DEVICE, HIGH SPEED FLOOD COOLED MOTOR/GENERATOR THEREFOR Field of the Invention The present invention relates to an improved apparatus for providing pressurized liquid to a device such as a hydraulically operated actuator of an 4. airplane, and to a high speed flood cooled dynamoelectric machine which can be used in the apparatus. Background and Summary of the Invention Larger size airplanes need a large quantity of pressurized hydraulic liquid to operate various actuators and other devices therein. However, there is no space for one large size pump to carry a large quantity of the hydraulic liquid. There are other problems like leakage associated with one source of a large quantity of pressurized hydraulic liquid. Conventionally, induction motors are used to drive hydraulic pumps for providing the pressurized hydraulic liquid to operate the various actuators and other devices on large airplanes. These motors are fluid cooled by liquid being pumped by the pumps. To achieve good performance of electric motors such as induction or switched reluctance and synchronous, the airgap separation between stator and rotor of the motor has to be relatively small, less than 0.1 inch, and typically .03- .04 inch, for an induction motor having a rating of between 60 and 180 KVA, for example. Otherwise, the size of the motor will be increased considerably which, from the standpoint of size and weight, is undesirable, especially in an airplane. A small airgap in these induction motors gives rise to large fluid losses at higher motor speeds. Normally, in fluid cooled dynamoelectric machines, heat is removed from an end portion of stator and rotor windings. This gives rise to high temperature of the windings in a center portion of an iron core thereof. And thus, the motor/generator cannot operate at high current density, which increases the size of the motor considerably. Another problem with conventional induction motors used to drive hydraulic pumps in apparatus for providing pressurized hydraulic liquid for operating various actuators and other devices in an airplane, is that the windings of these motors are impregnated with varnish to reduce vibration, and provide rigidity. However, varnish fills the spaces in the windings and thus no liquid can flow through the windings. In the past, motor-pump units for airplanes also required the use of grease- packed bearings and/or rotary shaft seals. Both of these have relatively short life at higher speeds. There is a need for an improved apparatus for providing a large volume of pressurized liquid to a device such as a hydraulically operated actuator of an airplane, which avoids the aforementioned disadvantages of the known systems used to operate these actuators and other devices. An object of the present invention is to provide an improved apparatus for supplying a large volume of pressurized liquid to a device such as a hydraulically operated actuator of an airplane which avoids the aforementioned disadvantages and drawbacks of the known systems therefor. A further object of the invention is to provide an improved high speed flood cooled dynamoelectric machine useful in this apparatus. These and other objects of the invention are attained by the improved apparatus of the invention for providing a large volume of pressurized liquid to a device. The apparatus comprises a pump for pumping a liquid, a high speed flood cooled permanent magnet motor for driving the pump, a gear drive connecting the motor to the pump for driving the pump with the motor, and a control for operating the motor as a variable speed motor. The pump, motor, drive and inverter-control are incorporated in one unit. This reduces the total weight of the system, eliminates the need for rotating seals and allows the same pumped liquid to be circulated through the fluid passages of the apparatus for cooling the inverter- control and motor thus increasing reliability. A permanent magnet dynamoelectric machine is used for better efficiency, and lower weight. The motor includes a stator and a rotor with an airgap therebetween. The liquid for cooling is circulated through this airgap for cooling the motor after the coolant has flowed through the control and motor stator windings where it is warmed. This reduces the viscosity of the liquid and thereby windage losses of the subsequently cooled motor. According to another feature of the invention, the permanent magnet motor is provided with an unusually large airgap, a single airgap larger than 0.1 inch. This reduces hydraulic friction losses in the machine without increasing machine size considerably. The motor is flood cooled by the liquid being pumped to reduce the size of the motor and provide lubrication to the bearings. Stator windings of the motor are not impregnated to allow the liquid to flow through slots in the armature of the stator which allows the liquid to remove heat directly from the windings. Thus, the motor can operate at relatively high current densities. The rotor of the motor is sealed so that the liquid circulated through the airgap does not react with the permanent magnets of the rotor or enter the rotor and cause balancing problems. According to a further feature of the disclosed embodiment of the invention, the rotor of the apparatus comprises a hollow rotor shaft formed of at least two pieces connected to one another including a first piece formed of a magnetic material and a second piece connected to the first piece and formed of a non¬ magnetic material, to reduce the weight of and magnetic leakage from the rotor. Supports are also provided on both sides of end turns of the stator windings in the motor to reduce vibration of the stator windings. These supports increase reliability of the winding and force the liquid coolant to flow through the stator slots. The pump in the disclosed embodiment of the apparatus includes a centrifugal impeller and an axial piston pump, and gear pump, which are rotatably driven by the motor of the apparatus. Due to the large displacement required of the axial piston pump, it is limited to relatively low speeds, as compared with the motor of the apparatus. Directly coupling the motor to such a pump will result in a significantly larger motor design due to the mismatch in optimum speeds. Therefore, a gear reduction on the order of 2:1 is incorporated to minimize the overall size and weight of the apparatus. An additional feature of the gear set is to provide all of the interval cooling flow for the apparatus by acting as a positive displacement spur gear pump. The apparatus in the disclosed, preferred embodiment further includes means for operating the pump as a motor for driving the dynamoelectric machine of the apparatus as an electrical generator as a back up electrical supply for the airplane, for example. Because the axial piston pump is an overcenter design, it can maintain the same sense of direction of rotation while operating as a hydraulic motor driving the dynamoelectric machine as a generator. An additional feature of the apparatus of the invention is that the motor diameter to length is optimized for minimum weight and hydraulic friction losses. In particular, the length to diameter ratio of the dynamoelectric machine in the disclosed embodiment is on the order of 2: 1 which results in the motor having minimum weight and hydraulic friction losses. These and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the disclosed, preferred embodiment of the invention taken with the accompanying drawings which illustrate a preferred embodiment in accordance with the present invention. Brief Desπriptinn of Drawings Fig. 1 is a schematic diagram of an apparatus according to the invention for providing pressurized liquid to a device, the flow path of the liquid through the apparatus being depicted; Fig . 2 is a cross sectional view of the apparatus of Fig. 3 taken along the section line 11-11 through the motor of the apparatus; Fig. 3 is a cross sectional view of the apparatus of Fig. 1 taken along a longitudinal central axis of the pump and motor of the apparatus; Figs. 4 and 5 are each an enlarged views of sections of the apparatus of Fig. 2 taken along the lines IV-IV and V-V, respectively, showing a portion of a partition through which insulated electrical leads extend, and which also conveys cooling liquid into the stator of the motor; Fig. 6. is an enlarged cross sectional view of the apparatus of Figs. 1 and 3 taken along the section line VI-VI in Fig. 3 showing the liquid passage for coolant; Fig. 7 is a cross sectional view taken along the line VII-VII in Fig. 3; Fig. 8 is an enlarged view of a slot in the stator armature with stator windings schematically shown therein as depicted within the circle of Fig. 7; Fig. 9 is a cross sectional view taken along the line IX-IX in Fig. 3; Fig. 10 is a cross sectional view of the apparatus of Fig. 3 taken along the line X-X illustrating the meshing gears of the drive between the motor and the pump within the apparatus, the drawing also shows the inlet and discharge as well as the sealing features surrounding the gear set; Fig. 1 1 is a cross sectional view of the apparatus of Fig. 3 taken along the line XI-XI; and Fig. 12 is a sectional line taken along the line XII-XII in Fig. 3 illustrating the housing about the axial piston pump, the pump itself not being shown in the drawing. Detailed Description nf Disclosed Embodiment Referring now to the drawings, an apparatus 1 according to the invention for providing pressurized liquid to a hydraulically operated actuator or other device of an airplane, for example, is shown schematically in Fig. 1 . The apparatus 1 comprises a centrifugal pump 71 to supply charge to an axial piston pump 2 and a gear pump 4. The axial piston pump 2 is for supplying high pressure liquid, typically oil. The gear pump 4 reduces the motor speed to drive the pumps and supply coolant to the motor and inverter. The apparatus 1 further includes a control 5 for operating the motor 3 as a variable speed motor. A centrifugal boost impeller 6 is located upstream of the axial piston pump 2 in the apparatus. The pump 2, motor 3, drive 4 and control 5 are incorporated in one unit. Fluid passages 7 are provided in the apparatus for circulating a portion of the liquid being pumped by the pump through the drive 4, control 5 and motor 3 for cooling these components and lubricating bearings therein. The apparatus 1 includes no dynamic, rotating seals or grease-packed bearings. The apparatus 1 is shown in further detail in Fig. 3 of the drawings. The motor 3 of the apparatus 1 is a brushless DC motor adapted to be driven at variable speeds by electrical power from the control 5. Control 5 comprises liquid-cooled power electronics including an inverter and a controller for operating the motor 3 as a variable speed motor. A fluid passage 8, shown schematically in Fig. 3, conveys liquid coolant through the control 5 from an inlet 9 to an outlet 10. The control 5 is connected to the housing 1 1 of the motor 3 by suitable fasteners with the liquid coolant exiting outlet 10 being directed into an annular chamber 12 of the motor 3 adjacent the right end of the stator 13 of the motor by way of passage 14 in the motor housing 1 1 communicating between annular chamber 1 2 and the outlet 10 of control 5. The dynamoelectric machine 3, which normally operates as a motor for driving the axial piston pump 2 as well as the centrifugal boost impeller 6 by way of gear pump 4, can also be operated as a generator to provide a backup electrical power supply on the airplane if needed . In such case, the axial piston pump 2 is employed as a motor driven by high pressure hydraulic liquid supplied to the main discharge outlet 1 6 of the apparatus 1 . A wobbler plate control 1 7 for adjusting the pump 2 for operation as a hydraulic motor to drive the rotor 1 8 of machine 3 is depicted in Fig. 1 1 . The motor 3 is a high speed permanent magnet motor adapted to be flood cooled by the hydraulic liquid circulating through the motor from the control 5. The liquid coolant exits the motor through an outlet 19 in motor 3. The flow path of the liquid coolant through the motor is shown by the arrows in Figs. 1 and 3. Cooling the drive 4 and control 5 before the motor 3 advantageously warms the hydraulic liquid to lower its viscosity and thereby reduces the windage losses of the motor. The motor housing 1 1 surrounds the stator 1 3 and rotor 1 8 of the motor. The stator and rotor are separated by an unusually large airgap, preferably a single airgap larger than 0.1 in. through which the liquid coolant is circulated after passing through the stator 1 3. The liquid flow through the stator and the airgap are in opposite directions along the axis A-A of the apparatus, see Fig. 3. The stator 13 of the motor 3 within housing 1 1 includes an armature 21 having slots 22 therein through which stator windings 23 extend. End turns 24 of the stator windings extend from opposite ends of the armature as depicted in Fig. 3. A cylindrical rotor receiving opening 25 extends through the stator along the axis A-A. The end turns 24 of the stator windings are supported on both sides, by supports 26 and 27 at the right end of the motor 3 as shown in Fig. 3, and by support 28 at the left end of the stator. The stator windings 23 in the slots 22, while insulated, are not impregnated with varnish which allows the liquid coolant to flow through the slots 22 as part of the fluid passages in the motor 3 of the apparatus 1 whereby the liquid coolant can remove heat losses directly from the stator windings and the motor can operate at relatively high current densities. The supports 26, 27 and 28 on both sides of the end turns 24 reduce vibration and increase the reliability of the stator windings and force the liquid coolant to flow through the stator slots 22. The supports 26, 27 and 28 are clamped in position in recesses 29 and 30 of the motor housing 1 1 about the end turns 24 at respective ends of the stator windings 23 by means of respective end plates 31 and 32 secured to the motor housing 1 1 by threaded fasteners 33. An insulation material 34 is located about the supports between the end plates 31 and 32 and the housing 1 1 , and the supports, to prevent electric sparking to housing. The insulation material 34 has a high dielectric strength and chemical resistance to the liquid coolant such as Skydrol liquid, for example. One suitable material for insulation 34 is known by the tradename Ryton. The liquid coolant from the annular chamber 12 passes through tubes 36-40 along with electrical leads 41 from the stator windings of the motor. The electrical leads are also connected to the terminals 42, 43 and 44 which extend through an area insulated with respect to the housing 1 1 of the motor. External connectors 45, 46 and 47 are electrically connected with respective terminals 42, 43 and 44 for power distribution to the stator windings from the control 5. One end of the tubes 36-40 extend through apertures 48 in the end wall 32. Liquid coolant conveyed to the stator windings through the tubes flows through the slots 22 about the stator windings because the windings are not impregnated with varnish. The radially inward surface of the annular stator is formed by thin metal sleeve 49 connected to the armature 21 and defining the cylindrical rotor receiving opening 25. The rotor 18 of the motor includes a plurality of permanent magnets 50, see Figs. 3, 6 and 7. The magnets 50 are supported on a hollow rotor shaft 51 formed of two pieces, 52 and 53. The respective ends of the rotor are rotatably supported in bearings 54 carried in annular recesses in the end plates 31 and 32 with the rotor extending through the rotor receiving opening 25 of the stator. The outer surface of the rotor is formed by a metal sleeve 55 which is spaced from the radially inner surface of the stator by the aforementioned unusually large airgap, 56 see Figs. 3, 6 and 7. As noted above the fluid passages in the apparatus 1 for circulating the liquid coolant include the airgap 56 through which the liquid coolant is circulated. The large airgap reduces hydraulic friction losses in the motor 3 without increasing motor size considerably. The metal sleeve 55 and an end plate 57 of the rotor are welded to the rotor shaft to seal the rotor against ingress of the liquid coolant flowing through the airgap 56. In this way, the permanent magnets 50 of the rotor do not react with the liquid coolant and the rotor is not unbalanced by the liquid. The sleeve piece 52 of the rotor shaft 51 is formed of a magnetic material while the end piece 53 of rotor shaft 51 , which is welded to the sleeve piece 52, is formed of a non¬ magnetic material to reduce magnetic flux leakage and bearing currents. The use of the hollow rotor shaft 51 permits the weight of the apparatus to be reduced. The length to diameter ratio of the motor 3 is preferably on the order of 2: 1 for minimizing the machine weight and the hydraulic friction losses. The power rating of the motor 2 is preferably 60 KVA- 185 KVA. In the disclosed embodiment both the inverter of the control 5 and the motor 3 have a power rating of 80 KVA. The use of a permanent magnet motor 3, rather than an other motor for driving the pump 2 results in better efficiency, lower weight and easy control for variable speed operation. The brushless permanent magnet machine generates a large torque while tolerating a large airgap. The diameter of the motor can also be minimized while reducing hydraulic friction losses through the use of an unusually large airgap through which the liquid coolant is circulated . The flow rate of the liquid coolant through the flood cooled motor 2 in the disclosed embodiment may be up to 10 gpm for example. The circulating liquid also provides lubrication to the bearings in the apparatus. As indicated above, the incorporation of the motor, pump, and the inverter and controller of the control 5 in one unit reduces the total weight of the system as compared with conventional arrangements and eliminates the need for rotating seals, allowing the same pumped liquid to cool the motor, inverter and controller and thus increase reliability. In operation of the apparatus 1 , hydraulic liquid for powering a hydraulic actuator 59 of an airplane, shown schematically in Fig. 3, is taken in an inlet 58 of pump housing 60. The liquid interacts with the centrifugal boost impeller 60 which increases the pressure of the incoming hydraulic liquid and directs it radially outwardly of the impeller to annular chamber 61 from where a portion of the pressure boosted hydraulic liquid is conveyed by parallel passages 62 and 69 to the cavity containing the intermeshing gear drive 4 and the axial piston pump 2, respectively. The gears 64 and 65 provide both the drive between the axial piston pump 2 and motor 3 as well as lubrication and cooling oil thru passage 7 to the control 5 and motor 3 as well as the case 63. A pressure relief valve, shown schematically at 67 in Fig. 1 , regulates the pressure therein of the flow of coolant liquid to the control 5 and motor 3 downstream. Most of the incoming hydraulic liquid exiting the impeller 6 is received in a plenum 68 in communication with an intake 69 of axial piston pump 2. The pump 2 is pressure compensated and takes in the incoming hydraulic liquid and to the actuator 59 or other devices of the airplane. The pressurized liquid exits the pump 2 by way of pump outlet 70 and pump housing outlet 19. Typical operating conditions for the apparatus 1 include driving the rotor 18 of the motor 3 at a high speed such as 1 2,000 rpm. The drive 4 is a power transmission speed reduction which reduces the speed from the motor to the piston pump 2. The reduction of the gear set in the disclosed embodiment is on the order of 2: 1. Hydraulic liquid at the inlet 58 of the pump housing is at a relatively low system pressure of 50 psi, for example. The boost impeller 6 raises the pressure of the hydraulic liquid to 150 psi, for example. The pump 2 discharges liquid into a system pressure of 3000 psi, for example. The gear drive 4 urges the hydraulic liquid through the passages of the apparatus 1 for progressively cooling and lubricating the case 63, control 5 and motor 3 before the coolant exits the outlet 19 of motor 3. As a result of the features of the invention, the motor 3 can be operated at a relatively high current density such that the efficiency of the motor 3 and apparatus 1 is 80 to 90%. Having thus described the preferred embodiment of the invention, it should be understood that numerous structural modifications and adaptations may be made without departing from the spirit of the invention.

Claims: CLAIMS We claim: 1. An apparatus for providing pressurized liquid to a device, said apparatus comprising a pump for pumping of liquid, a high speed flood cooled permanent magnet motor for driving said pump, a drive connecting said motor to said pump for driving said pump with said motor and also pumping cooling liquid for said apparatus, and control means for operating said motor as a variable speed motor, wherein said pump, motor, drive and control means are incorporated in one unit, fluid passages being provided for circulating liquid being pumped by said pump through said drive, said control means and said motor for cooling. 2. The apparatus according to claim 1 , wherein said drive also functions as a positive displacement pump providing lubrication and cooling flow to said pump, control and motor. 3. The apparatus according to claim 1 , wherein said motor includes a stator and a rotor with an airgap between said stator and said rotor and wherein said fluid passages circulate said liquid for cooling to said motor and through said airgap between said stator and said rotor of said motor after said liquid has flowed through said control means thereby reducing the viscosity of said liquid for cooling said motor and a windage losses of said motor. 4. The apparatus according to claim 3, wherein said motor has a power rating of between 60 KVA and 180 KVA and said airgap has a thickness of at least 0.1 inch for reducing hydraulic friction losses in the motor without increasing motor size considerably. 5. The apparatus according to claim 3, wherein said rotor is sealed so that said liquid circulated through said airgap does not react with permanent magnets of said rotor or enter said rotor and cause balancing problems. 6. The apparatus according to claim 3, wherein said rotor further comprises a hollow rotor shaft formed of at least two pieces connected to one another including a first piece formed of a magnetic material and a second piece connected to said first piece and formed of a non-magnetic material to reduce the weight of and magnetic leakage from said rotor. 7. The apparatus according to claim 3, wherein said stator includes an armature having a rotor receiving opening and stator windings including end turns extending from opposite ends of the armature, said rotor including permanent magnets and being journalled within said motor so as to extend within said rotor receiving opening of said stator with said rotor being separated from said stator by said airgap. 8. The apparatus according to claim 7, wherein said stator windings extend through slots in said armature, said stator windings in said slots not being impregnated to allow said liquid coolant to flow through said slots as part of said fluid passages in said motor whereby the liquid coolant can remove heat directly from said stator windings and the motor can operate at relatively high current densities. 9. The apparatus according to claim 8, wherein said fluid passages circulate said liquid coolant through said slots from a first axial end of said armature to a second axial end thereof and circulate said liquid in an opposite direction through said airgap of said motor. 10. The apparatus according to claim 8, further comprising supports provided on both sides of said end turns of said stator windings to reduce vibration of said stator windings and force said liquid coolant to flow through said stator slots. 1 1 . The apparatus according to claim 1 , wherein said rotor, said drive and said pump are rotatably connected with one another in said apparatus without using a rotating seal or grease-packed bearings therein. 12. The apparatus according to claim 1 , further comprising means for operating said pump as a motor with pressurized liquid for operating said permanent magnet motor as an electrical generator. 13. The apparatus according to claim 1 , wherein the length to diameter ratio of said motor in on the order of 2: 1 for minimizing the motor weight and the hydraulic friction losses thereof. 14. In an airplane comprising at least one hydraulically operated device and an apparatus for providing pressurized hydraulic liquid for operating said device, the improvement comprising said apparatus including a pump for pumping a liquid, a high speed flood cooled permanent magnet motor for driving said pump, a drive connecting said motor to said pump for driving said pump with said motor and a control means for operating said motor as a variable speed motor, wherein said pump, motor, drive and control means are incorporated in one unit, fluid passages being provided for circulating liquid being pumped by said pump through said drive, said control means and said motor for cooling, and wherein said motor includes a stator and a rotor with an airgap therebetween, having a thickness of at least 0.1 inch as one of said passages through which said liquid for cooling is circulated. 15. A high speed flood cooled dynamoelectric machine comprising: a housing; a stator within said housing including an armature having a rotor receiving opening and stator windings including end turns extending from opposite ends of the armature; a rotor including permanent magnets, said rotor being journalled within said housing so as to extend within said rotor receiving opening of said stator with said rotor being separated from said stator by an airgap of at least 0.1 inch; and fluid passages in said machine for circulating a liquid coolant through said dynamoelectric machine for cooling said machine, said fluid passages including said airgap through which said liquid coolant is circulated whereby hydraulic friction losses in said motor can be reduced without increasing machine size considerably. 16. The machine according to claim 1 5, wherein said rotor is sealed so that said liquid coolant in said airgap does not react with said permanent magnets or enter said rotor and cause balancing problems. 17. The machine according to claim 1 5, wherein said rotor further comprises a hollow rotor shaft formed of at least two pieces connected to one another including a first piece formed of a magnetic material and a second piece connected to said first piece and formed of a non-magnetic material to reduce the weight of and magnetic leakage from said rotor. 18. The machine according to claim 1 5, wherein said stator windings extend through slots in said armature, said stator windings in said slots not being impregnated to allow said liquid coolant to flow through said slots as part of said fluid passages in said machine whereby the liquid coolant can remove heat directly from said stator windings and the machine can operate at relatively high current densities. 19. The machine according to claim 18, wherein said fluid passages circulate said liquid coolant through said slots from a first axial end of said stator to a second, opposite axial end thereof and circulate said liquid coolant in an opposite direction through said airgap of said machine. 20. The machine according to claim 18, wherein supports are provided on both sides of said end turns of said stator windings to reduce vibration of said stator windings and force said liquid coolant to flow through said stator slots. 21. The machine according to claim 15, further comprising control means integral with said machine for operating said machine as a variable speed motor, said fluid passages circulating said liquid coolant in said machine through said control means prior to circulating the liquid coolant through said airgap whereby the liquid coolant is warmed and has a lower viscosity when circulated through said airgap for minimizing windage losses of said machine. 22. The machine according to claim 15, wherein said machine is a DC permanent magnet motor, and further including a pump adapted to be rotatably driven by said motor for pumping a liquid, said pump being integral with said motor, a drive rotatably connecting said rotor of said machine and said pump for driving said pump, and wherein said fluid passages circulate some of said liquid being pumped by said pump through said motor as said liquid coolant for flood cooling said motor. 23. The machine according to claim 22, wherein said rotor, said drive and said pump are rotatably connected with one another without using a rotating seal therein. 24. The machine according to claim 22, wherein said pump includes a centrifugal impeller and an axial piston pump which are adapted to be rotatably driven by said motor. 25. The machine according to claim 22, further comprising means for operating said pump as a motor with pressurized liquid for operating said dynamoelectric machine as an electrical generator. 26. The machine according to claim 15, wherein the length to diameter ratio of said machine is on the order of 2:1 for minimizing the machine weight and the hydraulic friction losses thereof.

Inventors: BANSAL MADAN L, DURTSCHI WILLIAM, THOMSON SCOTT, BANSAL, MADAN, L., DURTSCHI, WILLIAM, THOMSON, SCOTT
Applicants: SUNDSTRAND CORP, SUNDSTRAND CORPORATION
Application year: 1997
Main classification: F04B53
IPC codes: F04B17, F04B23, F04B53, F04C11, F04C15, F04D13, F04D15, H02K3, H02K5, H02K7, H02K9, H02K11