US 2387713 A
Description (OCR text may contain errors)
Oct. 30, 1945. 2. c. BRADFORD ACTUATOR Filed June 27, 1944 2 Sheets-Sheet l INVENTOR BY M5 ATTORNEYS 2:125:- c. 599mm Oct. 30, 1945. 2. c. BRADFORD 2,387,713
ACTUATOR Filed June 27, 1944 2 Sheets-Sheet 2 INVENTOR G4-- 25/255 6. BQHDFOIQD a M5 5/3, it 9244',
63 ATTORNEYS Patented Oct. 30, 1945 ACTUATOR Zerbe 0. Bradford, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application June 27, 1944, Serial No. 542,406
This invention relates to an improved actuator driven by an electric motor for raising and lower ng a load.
It is among the objects of the present invention to provide an electrically driven load raising and lowering actuator which operates in either direction at a predetermined speed regardless of the influence of weight to increase its speed as the actuator is being operated to lower the weight.
A further object of the present invention is to provide a motor actuated load raising and lowering device having a braking member adapted to hold the device immovable while the motor is inoperative and having also a centrifugal brake adapted to retard the operation of the device when under the influence of the load being lowered, the speed of the device tending to exceed that at which the motor is rotating it.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred embodiment of the invention is clearly shown.
In the drawings:
Fig. 1 is a fragmentary view of one form of installation of the present device showing the device attached to the landing gear of an airplane for purposes of retracting and lowering said landing gear. In this figure the wheels are in the lowered position.
Fig. 2 is a view similar to Fig. 1, however, showing the landing gear wheel in its retracted position.
Fig. 3 is a longitudinal view partly in section and partly in elevation of the actuating device.
Fig. 4 is a transverse section with certain parts in elevation, the view being taken along the line 4-4 of Fig. 3.
Fig. 5 is a diagrammatic view showing the electrical devices and their electrical connections as used in the installation.
The actuator comprises a motor frame or housing 20 in which the motor armature 2| is supported by a ball bearing 22 at the one end of the armature shaft 23, the ball bearing being retained within a recess provided in a partition member 24 to the housing 20. The armature shaft 23 has a cup-shaped driving disc 25 keyed thereto so as to rotate therewith, said driving cup being provided with an outwardly extending annular flange 26, the peripheral edge of which lies adjacent the innerwall of the motor frame or housing 20. An electromagnet winding 21 is supported within the housing 20 and surrounds the driving cup 25.
A gear housing 3|! is recessed to receive and support the one end of the motor housing 20. This housing 30 has a partition 3| centrally recessed to receive and carry the ball bearing 32. This ball bearing 32 provides a journal in which the end 33 of a stub shaft is supported, the opposite end of said stub shaft, designated by the numeral 34, being concentric with the end 33 thereof and being rotatably supported in a ball bearing 35. The end of the stub shaft portion 33 extending beyond the ball bearing 32 is formed to provide key-ways for receiving inwardly extending keys formed on the inner surface of the hub portion of the electromagnet armature disc 36, which disc normally rests upon and frictionally engages a brake ring 31 secured to the partition 3| in the housing 30. When in this normal position, that is, when resting upon the brake ring 31, the armature disc 36 lies horizontally with and is spaced from the annular flange 26 of the driving cup 25 secured to the rotating armature shaft 23 of the motor. A retainer cup extends into a recess formed in the stub shaft portion 33, said retainer cup having an outwardly extending flange 38 resting upon the upper surface of the armature disc 36. A headed screw 39 is secured in the stub shaft centrally of the recessed portion 33 thereof, said screw having'a spring 40 surrounding it, the one end of said spring abutting against the under surface of the head .of screw 39, the opposite end of the spring seating upon an inwardly extending flange provided on the retainer cup 38. This spring yieldably urges the armature disc 36 normally to engage the braking ring 31 inasmuch as the said armature disc is slidably keyed to the stub shaft portion 33.
A tubular screw shaft having a helical groove 5| formed in its outer surface for substantially its entire length, is threadedly received by an annular gear 60 and is securely fastened to said gear by pins-52. The screw shaft 50 has a nut 53 thereon, the inner annular wall of which is provided with a helical groove 54 coinciding in size and pitch with the helical groove 5| formed on the screw shaft. Helical grooves 5| and 54 of the screw shaft and nut 50 and 53 respectively, coincide to form an annular helical passage in which a plurality of balls 55 are provided which act as threads mechanically to connect the screw shaft with the nut. Ducts 56 in the nut provide return passages for the ball tubes. This is a standard construction similar to that completely illustrated and described in the copending appliation. 0i Calvin J. Werner, Serial No. 468,475,
filed Dec. 10, 1942. This nut 50 has a trunnion member 51 adapted to receive a lever supporting the rod raised and lowered by the actuating device. An accordion plaited seal 58 has its one end secured to a collar 59 attached to the trunnion E1, the opposite end of said seal being secured to a ring 6| interiorly threaded so as to be received by the threaded lower end of the gear housing 30. A similar accordion plaited sealing sleeve 62 has its one end secured to collar 59, the other end being secured to a fixture 63 attached to a member 64 which is secured to the lower end of the screw shaft 50.
The upper end of the screw shaft 50 is recessed to form a seat for the ball bearing 35 in which the lower end 34 of the stub shaft is journalled. Two ball bearings I and II are provided in the gear housing 30, said ball bearings rotatably supporting the gear $0. This gear 60 is recessed at its upper end to provide internal gear teeth 12. Two ball bearings I and IS in the housing 36 rotatably support the annular ring gear I? having an internal ring gear 78 at its lower end and an external ring gear is adjacent its upper end.
A portion of the stub shaft directly above the portion 30 journalled in bearing 35 and concentric with the screw shaft 50 is designated by the numeral 80 and is eccentric to the stub shaft portions 34 and 33. Two ball bearings BI and 82 are supported by this eccentric portion 80 of the stub shaft, said ball bearings supporting a single member 83 providing two epicycloid gears, the numeral 80 designating the lowermost epicycloid gear, the teeth of which mesh with the teeth 72 of the gear 60, while the numeral 85 designates the other epicycloid gear, the teeth of which mesh with the interior gear teeth I8 of the ring gear l'I. Another portion of the stub shaft which is designated by the numeral 90 being above the eccentric portiontll of the upper end 33 of said stub shaft forms a counterbalance and also a means in which the centrifugal brake shoe Si is pivotally supported. This pivotal brake shoe as illustrated in Fig. 4 is carried by a pin 92 secured in the counterbalance portion 90 of the stub shaft. A spring 93 urges a plunger 90 into engagement with one end of the centrifugal braking weight 9| normally urging it away from the ad jacent inner annular wall of the portion of the ring gear TI having the outer gear teeth I9.
Housing 30 has a'tangential tubular extension 95 in which a shaft 96 is rotatably supported by bearings 91. Shaft 96 has a worm pinion 33 which meshes with the teeth IS in the annular gear 'I'I. Any suitable manual means for actuating the shaft 96 may be attached thereto. The shaft 96 with its worm pinion 98 meshing with the teeth I9 of ring gear TI performs two functions, (1) the function of holding the ring gear 11 against rotation when the electric motor actuates the screw shaft 50, and (2) as a means for manually rotating the ring gear TI to effect man- I ual rotation of the screw shaft 50 when for any reason the electric motor is inoperative.
The Figs. 1- and 2 show one application of use for the improved actuator of the present invention. The gear housing 30 is secured to the forked end of a lever I00 which may be pivoted to the fuselage IOI of an airplane as at I02.
As has previously been described, the nut 53 operatively connects with the screw shaft 50 so that rotation thereof will cause the nut to move longitudinally in either direction on said shaft,
provides a trunnion 51 to which the one end of the lever I03 is pivotally attached, the opposite end of said lever being pivotally secured to a pin I 04 on the structure IOI of the airplane. The one end of another lever I05 is pivotally secured to the trunnion 51, the opposite end being hinged to the shock absorbing lever I06 by the pin I0'I. The one end of the shock absorbing lever I06 is hingedly secured to the pin I08 on the fuselage IOI, the opposite end of said lever I06 providing the spindle I09 upon which the landing wheel IIO of the airplane is mounted. The diagrammatic Fig. 5 illustrates the electrical'device applied to the installation as described in Figs. 1 and 2. The numeral I20 designates a limit switch closed to complete its circuit when the landing gear moves from its nested position toward its extended position as shown in Fig. l and opened to break its circuit when the landing gear is moved to its nested position as shown in Fig. 2. The numeral I2I indicates a similar switch opened to break its circuit when the landing gear is in its fully extended position as shown in Fig. l and closed to complete its circuit when the landing gear is moved from its extended position toward its retracted position as shown in Fig. 2. In its retracted position as shown in Fig. 2 the landing gear engages any suitable locking mechanism designated by the numeral I22 which securely holds the landing gear in this retracted position and takes all the load thereof from the trunnion 5'! on the nut. To lower the landing gear from its retracted position to its extended position the operator must first actuate the mechanism represented by the numeral I22 to release the landing gear and permit its downward movement from the nested into its extended position. Inasmuch as this locking mechanism may be of any suitable standard construction, no detailed showing thereof has been made, the mechanism merely being represented in the Figs. 1 and 2.
The electric motor referred to as a whole by the numeral 200 is the prime mover of the present device. The source of power for operating this electric motor is shown to be a storage battery I30. One side of the battery is grounded, the other side is connected to the movable contact arm I 3! of a selector switch having two stationary terminals 32 and I33 with which the movable contact ISI may be engaged to complete operating circuits. Two contactors I35 and I36 are provided automatically to control the motor circuit after the operator has actuated the selector switch contact I3I into the proper position to effect motor operation.
Assuming that the actuator is in the'up or retracted position, in which position the nut is shown in the Fig. 3 and in which position the device is shown in Fig. 2 and assuming that the operator wishes to extend his landing gear for purposes of landing the plane, he will actuate the selector switch contact I3I clockwise so that it will engage the contact I33. Now current from the battery flows through the selector switch contact I3I to terminal I33 of said switch thence through the closed limit switch I2 I through the magnet winding I31 of the contactor I38 back to the battery via ground connections. Current flowing through the magnet winding I 31 will move the actuator I36 so that the bridging member I30 thereof connects stationary contacts I39 and I00 and the bridging member I iI thereof connects the stationary contacts I42 and I03. With the contactor I36 closed, current from the battery may now flow from the junction point I04 across terminals Ill and I via the bridge I" thence to the Junction point I" through the field winding I" of the motor 200 to the Junction point I" thence across contacts I42 and I" via the bridging member III to the junction point I" at which point there will be a division of the current flow. a portion flowing across the armature of the motor 200 back to the battery via ground connections, the other portion or the current flow flowing through the electromagnet winding 27 and thus back to the battery via. the ground connections. Completion of these circuit: causes the electric motor 200 to operate and at the same time energizes the electromagnetic clutch winding 21 so that the armature disc 28 of the electromagnet clutch will be attracted and move out of engagement with the braking member 21 and into Operative engagement with the motor driven ring 25 thereby to connect the rotating motor with the screw shaft 50 through the reduction gearing aforedescribed. The screw shaft 50 is now rotated in a direction causing the nut 82 thereon to move outwardlyalongthe screw shaft away from the gear housing 30 toward the end member 64 on said screw shaft. Asa result the levers I05, I03 and I06 are moved to lower the landing wheel IIO toward its extended position as shown in Fig. 1. It will be seen that as the wheel moves from the positionas shown in Fig. 2, which is the full nested position, toward the position as shown in Fig. l, which is the fully extended position, the enormous weight of the landing gear is applied upon the nut 53 and it will have a tendency to cause said nut to exert a turning effort upon the screw shaft 50 causing it and the speed reduction gearing and motor to be rotated'at an excessive speed which might in time or under certain circumstances be dangerous. To avoid this, applicant has provided a centrifugal braking weight 9| in the stub shaft of the speed reducing gearing which, when the rotating speed of the shaft predeterminately exceeds the speed at which it is bein driven by the electric motor 200 to lower the load, will move outwardly in response to centrifugal force, said weight frictionally engaging the inner surface of the annular gear 11 thereby braking the rotational speed of the reducing gear, retarding it and holding it below the danger limit. As soon as the landing gear reaches its fully extended position, the switch I2I through which the operating circuit of the motor is completed will be opened, thereby breaking the motor circuit and discontinuing its operation. During this time the limit switch I20 has been permitted to close, however its closing has no effect on circuits as long as the movable contact I3l of the selector switch is in neutral or even in engagement with the contact I33 of said switch.
When the operator desires to retract his wheels for flying purposes, the selector switch contact III is actuated to engage the stationary terminal I32. Switch I20 being closed as lon as the landing gear is in extended position and being opened only when said landing gear has reached its fully retracted position, will now permit current to flow from the battery I30, selector switch contact I3I and its terminal I32 across switch I20 through the electromagnet winding I51 of the contactor I35 and back to the battery via ground connections. Energization of the winding I51 will cause the bridging element I58 to bridge contacts I59 and I60 and also the bridging member IGI to bridge contacts I62 and I03. Now current from the battery flowing to the junction point I may cross from contact I60 to contact II! via'the bridging member I58, then pass to the junction point I41 thence through the motor field winding 6 (in a direction opposite however to the flow when contactor I36 is effective) to the junction point I" thence from contact I02 to contact I02 via the bridging member I" to the junction point I" where the same division of current flow takes place, one through the armature of the motor 200, the other through the electromagnet winding 21 thence back to the battery via ground connections. Now the motor operatesin the opposite direction and the electromagnet winding 21 being energized will cause the motor again to be connected with the screw shaft 50, rotating it however in the opposite direction so that now the nut 53 thereon will be caused to move upwardly from the end member 04 toward the housing 30. As this occurs the landing gear wheel IIO will be lifted through its lever connections with the nut trunnion 51 and be moved into its nested position as shown in Fig. 2 where it will be held and maintained within the locking member I22 and where again switch I20 is opened and switch I2I is again closed. During this operation the centrifugal device is unnecessary, and therefore it has been designed so that the braking weight 9| thereof may move outwardly only in response to rotation of the speed reducing gearing in a direction to operate the screw shaft 50 so that it will lower the nut 53.
If at any time the electric motor 200 is rendered inoperative for any cause the operator actuates the manual mechanism attachable to the shaft 86 so that the shaft 96 will be rotated manually. Manual operation of the shaft 96 causes the worm pinion 98 to rotate the annular gear 11 and, due to the fact that the eccentric stub shaft is held against rotation by the engagement of the armature disc 36 with the braking ring 31 under the influence of the spring 40, this rotation of the annular gear 11 will rotate the epicycloid gear 03 about the eccentric portiton of the shaft,
causing said epicycloid gears to in turn effect a rotative effort upon the annular gear 12 which is secured to the screw shaft 50 and consequently by the manual operation f the worm pinion 98, the screw shaft 50 may be rotated independently of the electric motor.
From the aforegoing it has been shown that applicant has provided a motor actuated load raising and lowering device which is equipped with a braking member adapted to hold the device immovable while the motor is inoperative and thereby retain the load thereon in its position, said device having also a centrifugal brake designed and constructed to retard the operation of the device when, under the influence of the load being lowered thereby, the speed of the device tends to exceed that safe limit at which the motor is rotating.
While the embodiment of the resent invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.
What is claimed is as follows:
1. In a device of the character described, the combination with a screw shaft; a load supporting, travelling nut on said shaft; an electric motor for rotating aid shaft in one direction to lift the load and in the opposite direction to lower the load; speed reducing gearing comprising two ring gears, the first held against rotation, the
second attached to the screw shaft and an epicyclic gear meshing with both ring gears; a stub shaft driven by the electric motor and having an eccentric portion upon which the epicyclic gear is rotatably supported; and a spring loaded weight pivotally carried by the stub shaft, said weight being operative to bethrown into frictional engagement with the first ring gear at a predetermined speed of the stub shaft, thereby providing a centrifugal brake for limiting the rotational speed of the screw shaft in the load lowering direction.
2. In a device of the character described the combination with a screw shaft; a load supporting, travelling nut on said shaft; an electric motor for rotating said shaft in one direction to lift the load and in the opposite direction to lower the load; speed reducing gearing for connecting the electric motor with the screw shaft, said gearing comprising two ring gears, one of which is normally held against rotation the second being attached to the screw shaft, a stub shaft driven by the motor and an epicyclic gear on the stub shaft and operatively engaging both ring gears; and a weight pivotaily carried by the stub shaft said weight being operative to be thrown into frictional, braking engagement with the said one ring gear under the influence of the load on the downwardly moving nut, when the speed of said stub shaft redeterminately exceeds the speed at which the electric motor drives it in this one direction.-
3. In a device of the character described the combination with a screw shaft; a traveling nut on said screw shaft, adapted to carry a load; a reversible electric motor; speed reducing gearing comprising a stub shaft driven by the electric motor, an epicyclicpgear on the stub shaft and two ring gears meshing with said epicyclic gear, one normally held stationary the other secured to the screw shaft; means for connecting the stub shaft of the speed reducing gearing with the motor; and means for limiting the speed of the screw shaft when it is being rotated to move the nut to lower its load, said means comprising a centrifugal weight supported by the rotatlnz stub shaft of the speed reducing gearing and adapted to be thrust into braking engagement with the stationary ringgear of the speed reducing gearing in response to rotation of the screw; shaft in one direction at a predetermined SD88 4. In a device of the character described the combination with a screw shaft; a traveling load supporting nut threadedly carried by the screw shaft; speed reducing gearing comprising an picyclic gear mounted on a stub shaft driven by the motor and meshing with two separate ring gears one of which is normally held against rotation the other being operatively connected to said screw shaft; a reversible electric motor; a brake member; an electromagnet clutch having a movable armature slidably keyed to the stub shaft of the speed reducing gearing and yieidably urged into normal gripping engagement with the brake member to hold the speed reducing gearing and the screw shaft attached thereto, against rotation, said electromagnet having a winding adapted to be energized when the electric motor is energized to run in either direction for moving the armature from the brake member, into operative engagement with the electric motor; and a centrifugal weight supported by the stub shaft of the speed reducing gearing said weight being operative frictionally to engage the nonrotatable ring gear for limiting the rotational speed of the screw shaft as it is being operated by the electric motor to move the nut for lowering the load. ,7
ZERBE C. BRADFORD.