US 3207005 A
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Description (OCR text may contain errors)
Sept. 21, 1965 H. M. GEYER MECHANICAL ACTUATOR SYSTEM 2 Sheets-Sheet 1 Filed June 17, 1963 INVENTOR HOWARD r1, GEYER M ms ATTORNEY Sept. 21, 1965 H. M. GEYER MECHANICAL ACTUATOR SYSTEM 2 Sheets-Sheet 2 Filed June 17, 1963 INVENTOR. HOWARD P1. GEYER MKEJLL H15 ATTORNEY United States Patent 3,207,005 MECHANICAL ACTUATOR SYSTEM Howard M. Geyer, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed June 17, 1963, Ser. No. 288,140 8 Claims. (Cl. 74-812) This invention pertains to mechanical actuators, and particularly to a mechanical actuator designed for handling high mass loads.
In my copending application, Serial No. 282,272, filed may 22, 1963, several electro-mechanical actuator systems for handling high mass loads are disclosed wherein a high efiiciency drive path is utilized for raising the load and a low efficiency drive path is used for lowering the load. The present invention relates to a simplified mechanical actuator of the same general type wherein the dead weight load is raised through an efficient spur gear train and lowered under free fall conditions through an inefficient worm gear train, and including means for locking the actuator system against movement due to the compressive load.
Accordingly, among my objects are the provision of a mechanical actuator for high mass loads including separate drives for manually raising the load and lowering the load under free fall conditions; the further provision of a mechanical actuator of the aforesaid type including a load proportional friction lock, or brake, for maintaining the actuator in an adjusted position; the further provision of a mechanical actuator of the aforesaid type including automatic means for releasing the brake when the load is raised and means for manually releasing the brake to lower the load under free fall conditions; and the still further provision of a mechanical actuator of the aforesaid type including a centrifugally actuated brake for controlling the rate of actuator movement under free fall conditions.
The aforementioned and other objects are accomplished in the present invention by utilizing a high efficiency spur gear train in the drive path for raising the high mass load, and a relattively low efliciency worm gear train in the drive path for lowering the high mass load. More specifically, the mechanical actuator includes a ball screw and nut assembly having a manual input from the spur gear drive path for raising the load, and a worm gear train coupled to the screw shaft and constituting the inefficient drive path for lowering the load under free fall conditions.
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 present invention is clearly shown.
In the drawings:
FIGURE 1 is a fragmentary, perspective view, partly in section and partly in elevation, of the high efficiency spur gear train constituting the drive path for raising the load.
FIGURE 2 is a fragmentary, perspective view, partly in section and partly in elevation, of the ball screw and nut together with the ineflicient worm gear train constituting the drive path for lowering the load.
With reference to FIGURE 1, the manual input of the mechanical actuator comprises a rod 10 having a longitudinally extending keyway 12, the rod extending through a diametrical hole in a hub 14 keyed to an input shaft 16. The position of the rod 10 may be adjusted by loosening the knob 18 and sliding the handle 10 diametrically relative to the hub 14. A spin or pump action handle 20 is pivotally connected at 22 to one end of the rod 10, and thus the hub 14 and the shaft 16 can be driven by either Patented Sept. 21, 1965 rotation of the rod 10 when the handle 20 is in the full line position, or a push or pull movement of the rod through the handle 20 when it is in the dotted line position.
The input shaft 16 is journalled by spaced ball bearing assemblies 24 and 26 in a suitable housing, not shown, and carries two cams 28 and 30 of opposite hands. The cams 28 and 30 are circumscribed by spur gears 32 and 34, respectively, with one-way clutch rollers 36 and 38 being situated therebetween. The cam 28 and the clutch roller 36 constitutes a one-way clutch which drives the spur gear 32 when the shaft 16 is rotated in the clockwise direction, and free wheels when the shaft 16 is rotated in the counterclockwise direction. Conversely, cam 30 of the roller 38 constitutes a one-way clutch which is engaged when the shaft 16 is rotated in the counterclockwise direction and is released, or free wheels, when the shaft 16 is rotated in the clockwise direction. In this manner, the manual input to the actuator for raising the load can be rotated in either direction without changing the movement of the output shaft.
The spur gear 32 meshes with an idler spur gear 40 which in turn meshes with a spur gear 42 attached to a shaft 44 journalled by spaced ball bearings 46 and 48. The spur gear 34 meshes with a spur gear 50 likewise attached to the shaft 44. A bevel gear 52 is connected with the shaft 44, the bevel gear 52 meshing with a second bevel gear 54 attached to a shaft 56 journalled by a ball bearing assembly 58. The shaft 56 constitutes the output shaft of the high efficiency drive for extending the actuator, or raising the load. As is apparent when the shaft 16 is manually rotated in the clockwise direction, the roller clutch 36 is engaged and the roller clutch 38 is disengaged. Accordingly, rotation will be imparted from the spur gear 32 through the idler gear 40 to the spur gear 42 so as to rotate the shaft 44 in the clockwise direction which will in turn rotate the output shaft 56 in the counterclockwise direction. Conversely, when the shaft 16 is manually rotated in the counterclockwise direction, the roller clutch 36 is released while the roller clutch 38 is engaged thereby driving the spur gear 34 in the counterclockwise direction so as to impart rotation to the gear 50 in the clockwise direction and hence rotate the output shaft 56 in the counterclockwise direction.
Referring to FIGURE 2, the output shaft 56 of high efiiciency manual input drive path has a second bevel gear 59 secured thereto which meshes with a bevel gear 60 drivingly connected with the screw shaft 62 of the conventional ball screw and nut assembly. The ball screw and nut assembly includes a nut, not shown, which is threadedly connected to the screw shaft 62 through a plurality of circulating balls, not shown, it being understood that the nut is connected to the load and restrained against rotation so as to reciprocate upon rotation of the screw shaft 62. A worm gear, or worm wheel, 64 is drivingly connected with the screw shaft 62, the worm wheel 64 meshing with a worm 66 constituting a reversible ineificient drive path for lowering the load, or retracting the actuator, under free fall conditions. The worm 66 may be formed integral with, or may be attached to, a shaft 68 extending transversely relative to the screw shaft 62. The worm shaft 68 is journalled by a ball bearing assembly 70, the inner race of which has a slip fit on the shaft, and the thrust loads are taken by a ball bearing assembly 72. A brake disc 74 is attached to the shaft 68, which brake disc is cngageable with the end surface of a stationary housing 76.
In addition, a centrifugal brake assembly 78 may, optionally, be keyed to the worm shaft 68, the centrifugal brake assembly including a pair of centrifugally responsive shoes 80 and 82 pivotally interconnected at 84 and biased inwardly about their pivot by a coil spring 86. It will be appreciated that during actuator retraction the worm shaft 68 will be rotated at a relatively high speed thereby causing the brake shoes 80 and 82 to pivot outwardly so as to engage the housing 76 and thus control the rate of actuator retraction under free fall conditions.
The worm 66 has a rack action relative to the worm wheel 64 due to the applied actuator load in the direction of arrow 88 which holds the brake disc 74 in engage ment with the housing 76 so is to lock the actuator against movement in the retract direction due to the compressive, or dead weight, load. In order to unlock, or release, the actuator brake, the other end of the worm shaft 68 has a release knob 90 coupled thereto through a thrust bearing 92. To release the look, a rotatable shaft 94 is provided having a cam, or eccentric, 96 engageable with the knob 90 and a handle 98 for rotatingthe shaft 94. When the shaft 94 is rotated the eccentric 96 will force the knob 90 and the worm shaft 68 in a direction opposite to that or arrow 88 so as to disengage the brake disc 74 from the housing 76.
Operation of the mechanical actuator in extending the actuator for raising the load can be achieved by rotating the rod in either direction, or by push-pull action, to rotation to the output shaft 56 and thus rotate the screw shaft 62 in the counterclockwise direction as seen in FIG- URE 2. counterclockwise rotation of the screw shaft will extend the actuator to raise the load, and through rack action between the worm wheel 64 and Worm 66 automatically release the lock by taking up the clearance between the shoulder 68a on the'worm shaft and the bearing 72 so that the worm spins free under no load. When the manual input is disconnected, the rack action between theworm wheel 64 and the worm 66 due to the compressive dead weight load'will cause the brake, or lock, to be engaged thus maintaining the actuator in its adjusted position. To retract the actuator and lower the load, the handle 98 is operated to release the brake through the knob 90 and the worm shaft 68 thus causing the screw shaft to rotate in the opposite direction under free fall conditions so as to impart rotation to the worm shaft, which constitutes the inefiicient drive path so as to dissipate the stored energy. As alluded hereinbeforc, the rate of actuator retraction can be controlled by utilizing the centrifugal brake construction 78.
While the embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.
What is claimed is as follows:
1. A mechanical actuator system for high mass loads including, a screw and nut actuator, gear train mechanism having dual drive paths operatively connected with said actuator, one of said drive paths including a high efficiency gear drive for extending said actuator and the other of said drive paths including a low efliciency reversible gear drive operable to permit retraction of said actuator by gravitational force, and manually releasable locking means in said low efficiency gear drive for preventing movement of said actuator under load.
2. The mechanical actuator system set forth in claim 1 wherein said high efficiency gear drive comprises a spur gear train.
3. The mechanical actuator system set forth in claim 2 wherein the input to said spur gear train comprises a manually rotatable shaft, a pair of oppositely acting oneway clutches connected to said input shaft, an output shaft coupled to said screw, and alternate spur gear drives connecting said one-way clutches and said output shaft whereby rotation of the input shaft in either direction will result in rotation of the output shaft in only one direction.
4. The mechanical actuator system set forth in claim 1 wherein said low elficiency reversible gear drive comprises a reversible worm and worm gear.
5. The mechanical actuator system set forth in claim 4 wherein the worm gear is connected to the screwand the worm is attached to a worm shaft extending transversely of the screw and capable of axial movement relative to the screw, and wherein said locking means comprises a friction brake disc secured to the Worm shaft separate drive paths including a high efficiency manual input for extending said actuator and raising a load connected thereto and a low efliciency reversible worm drive operable to permit retraction said actuator to lower said load under free fall conditions, and releasable locking means operatively connected with said reversible worm drive, said locking means being automatically released upon operation of the manual input and manually releasable to control actuator retraction.
8. The mechanical actuator system set forth in claim 7 wherein said worm drive includes a worm Wheel attached to said screw shaft, a worm meshing with said worm wheel and a worm shaft secured to said worm, said worm shaft being movable axially in opposite directions to engage and disengage said locking means.
References Cited by the Examiner UNITED STATES PATENTS 2,384,996 9/45 Hanson 748l2 X 2,670,826 3/ 54 Sussdorfi et a1. 748l2 X DON A. WAITE, Primary Examiner.