US2036798A - Hydraulic operator - Google Patents

Description

T. W. DRIESCH HYDRAULIC OPERATOR Filed June l2, 1934 PatentedA Apr. 7, 1936 HYDRAULIC OPERATOR Theodore W. Drlesch, Schenectady, N., Y., assignor to General Electric Company, a corporation of New York Application June 12, 1934, Serial No. 730,238

3 Claims.

This invention relates to hydraulic operating mechanism, more particularly to hydraulic operating vmechanism in which an electric motor driven impeller pump immersedin a fluid container is utilized to produce a differential in fluid pressure on opposite sides of a piston to effect movement thereof, and it has for an object the provision of a simple, reliable and improved device of this character.

More specilcially this invention relates to hydraulic operating mechanism in` which the electric motor is mounted above the surface of the fluid and the impeller pump is rotated by means of a shaft connecting the motor and the impeller, and a more specific object of the invention is the provision of means for preventing the introduction of air into the impeller due to rotation of theshaft. An additional object is the provision of means for cushioning the end of the return stroke of the piston, thereby to eliminate .undesirable shocks and stresses.

is an improvement of the hydraulic operating mechanism disclosed in U. S. Patent No. 1,993,-` 613 to Walter O. Lum, lled December 19, 1929 and assigned to the assignee of the present invention.

In carrying this invention into effect in one form thereof a piston is movably mounted in a fluid container, and the impeller is located within the fluid container beneath the surface of the uid. The pump impeller drive shaft extends above the surface of the liquid to an electric driving motor and a cover pipe is provided which surrounds the impeller shaft and extends from a point at or near the surface of the fluid to a point a substantial distance beneath the surface.

The pump housing is provided with intake and exhaust passages which communicate respectively with fluid on opposite sides of the piston, and means actuated by the piston, near the extremity of its return stroke, are provided for gradually throttling the exhaust passage and thereby decreasing the rate of the return flow of fluid so as to cushion the termination of the piston stroke.

For a better and more complete understanding of the inventiomreference should now be had to the following specificationv 'and' to the accompanying drawing in which Fig.l 1 is an elevation partly in section and with parts broken away, and Fig. 2 is a broken view in elevation partlyr in section illustrating an operating condition of the cushioning means.

Referring now to the drawing, a cylindrical This invention iiuid container I is provided with a cover plate y II upon which an electric driving motor I2 is vertically mounted. The cover plate II is constructed to provide an integral supporting platform I3 beneath the top of the container II). 5

The cylindrical casing I0 is filled with a suitable fluid medium, such for example as oil, to a point substantially level with the platform I3. A piston I4 is arranged within the cylindrical casing III for vertical movement, which is transmitted to an external load by means of a pair of connecting rods I5. The lower ends of these "connecting rods I5 are secured by suitable fastening means I6 to the piston I4 whilst the up.- per ends of these connecting rods extend through the cover plate II and are secured to a crosshead I'I which is adapted to be connected to a suitable load. At the bottom of the container is an impeller pumpillustrated as comprising a housing I8 within which an impeller I9 is ro- 20 tatably mounted. The housing I8 is provided with suitable centrally disposed intake passages 2U together with a plurality of exhaust ports 2i arranged clrcularly in the housing I8. 'Due to the section taken in Fig. lof the drawing, only a single exhaust port 2| is clearly visible. v

As shown, the housing member I8 is -secured by a suitable fastening means to the 'lojwe'r' extremity of a tubular member 22 theupper extremity of which is suitably secured to the supporting platform I3. Openings 23 are provided in the wall of the tubular member 22, thus providing communication from the space above the piston I4 to the intake passages 20 of the pump. It will also be clear that the walls of the tubu 35 lar member 22 serve as a partition means between the intake passages 20 and exhaust ports 2I and thus restrict the discharge of the pump to the space beneath the piston.

A vertical drive shaft 24 is rotatably mounted 40 in a bearing 25 in platform I3 and in a. bearing 26 which is centrally mounted in the pump housing I8. This drive shaft 24 is connected to the motor shaft 2l by suitable coupling means 28 so that rotation of the motor effects rotation of the pump impeller I9. In order to prevent the formation of a Vortex in the fluid with theI resultant introduction-of air into the pump impeller due to rotation of the shaft 24, a cover pipe 29 is provided which surrounds the drive 50 shaft 24 and extends from a point at or near the surface of the fluid to a point a substantial distance beneath the surface. The inside diameter of the cover pipe 29 is slightly greater than the outside diameter of the shaft 24 so as 55 to provide a slight clearance and thus prevent actual contact. At its upper extremity, 4the cover pipe 29 is provided with a flange 33 which,

constructed, means havebeen//pro'vided for cushioning the return stroke of the piston upon deenergization of the pump driving motonfor the purpose of preventing/the swiftly descending pisv ton from striking its stop with a heavy hammer blow and setting up undesirable shocks and stresses in the mechanism. These means have left something to be desired with respect to controlling or varying the cushioning action during the descent of the piston. In order to cushion the return stroke of the piston and to eliminate these undesirable shocks and stresses,. a baiiiei plate 3| is provided for controlling the return flow of the fluid from beneath the piston through the pump to the space above the piston. As shown, this baille plate is in the form of a attened ring surrounding the central intake of the pump housing and covering the circular row of exhaust ports 2|. When the pump is at rest,

the baille plate 3| is seated snugly against the pump housing so as to cover up the exhaust ports and cut oif communication between the! pump chamber and the space beneath the piston. Holes are provided in the baille plate through which studs 32 project and screw into the housing I3. Sufdcient clearance is allowed between the head of the stud and the bame plate to allow the latter to rise on these studs and uncover the exhaust ports when a fluid pressure is established by rotation of the pumplimpeller.

Aligned holes are provided in the piston I4 and in the baille plate 3| through which projects an adjusting rod 33. The upper extremity of this rod extends through the tank cover plate and is provided with suitable thumb adjusting and lock nuts 34. A helical spring 35. surrounds the rod 33 and is arranged between the piston I4 and the baille plate 3|. A similar spring 36 is arranged between the lock nuts 31 at the lower extremity of the rod and the lower surface of the baille plate 3|. When the mechanism is in the deenergized condition in which it is illustrated in Fig. 1, the weight of the piston I4 compresses the spring 35, and this compressional force in turn compresses the spring 33.

With the above understanding of the elements and their organization in the completed device, the operation of the device itself will readily .be understood from the following description:

Energization of the motor by connection with a source of electric power produces rotation of the drive shaft 2l and pump impeller I3. Fluid is directed into the intake passages 23 of the pump impeller by means of the tubular member 22. This fluid is drawn into the centrally disposed intake passages 33 and 33 in the impeller chamber. The impeller forces the fluid in a radial direction through the exhaust passages 2| as a result of which, a fluid pressure is produced against the lower surface of the baiiiel plate 3| of sufficient magnitude \to cause the bameplatetoriseortilton thestuds32 and uncover the exhaust ports. Fluid is thus discharged from the impeller pump tcthe space beneath the piston i4 thus producing a pressure differential across the piston, i. e., a difference inffluld pressure .onopposite sides ofthe piston: This causes the piston to move in an upward transmitted through the connecting rods I3 to the external load to which the cross-head |1 is connected.

As heretofore constructed without a cover pipe surrounding the drive shaft 23, a vortexin the fluid was formed by rotation of the shaft at high speed. The apex of this vortex followed downwardly along the shaft until it reacheda point at which air was admitted into the intake of the impeller pump. This proved to be very undesirable because the presence of air gradually'reduced the fluid pressure and increased the time required for lifting the load. The provision of the cover pipe 23 surrounding the drive shaft. and extending from a point at or near the surface of the liquid to a point several inches beneath the surface effectively prevents the -formation of a vortex (which always begins to form at the surface) and prevents any air being drawn into the pump impeller. As a result, a maximum fluid pressure differential is produced and this increased pressure decreases the time required for lifting the load. In other words, the maximum lifting capacity of the device is substantially increased.

As the piston risesin the cylindrical container the compression on the springs 35 and 33 is gradually released until the piston I4 finally moves out of contact with the spring 35 entirely. At this time, the spring 35 is fully released but the spring 36 is still under suflicient compression to maintain the baille plate 3| in its open position even though the fluid pressure against the lower surface of the baiiie plate should disappear.

As long as the motor |2 is maintained energized, driving the pump impeller I3, the diiferential fluid pressure across the piston I3 is maintained. When the piston reaches the end of 'its upper stroke this pressure is still maintained and is not increased due to the fact that the pump is not a positive displacement pump.

Deenergizatioii of the motor I2 stops the pump and the dierential fluid pressure across the piston I3 disappears; as a result the piston descends under the attraction of gravity :forcing the fluid back through the discharge opening in the pump housing and thence out through the intake opening and the tubular member 22 to the space above the piston. During this time, they baille plate 3| is maintained in its raised position by means of the spring 33 as clearly illustrated in Fig. 2 of the drawing. This allows unrestricted return ow of fluid and the descent of the piston continues at a rapid rate until the piston strikes the upper extremity of the released spring 35. AsY the piston engages the spring 35, the latter is gradually compressed and; gradually overcomes the pressure of the spring 33 therebyforcing baille plate 3| slowly toward its seat. .This gradually reduces the return flow of the fluid from the space beneath the piston to the space above the piston. Since the iiow of fluid controls the speed at which the piston returns, it is clear'that the piston must slow down. Continued descent of the piston continues to force the baille plate downwardly thereby throttling 'the passageway and the returniiowofuiduntilthebameplateisnnally seated against the pump housing and completely coverstheexhaustporte. Thisseatingofthe baille plate occurs at the instant the reachestheendofitsreturnstroke.

load and amount of travel. Thus, blows and stresses due to rapid descent of the piston are entirely eliminated. Y 4

Although in accordance with the provision of the patent` statutes, this invention is described as embodied in concrete form, it will be understood that the elementsand arrangements shown and described are merely illustrative and that the invention is not n'limited thereto since alterations and modifications will readily suggest themselves to persons skilled in the art without departingirom the spirit of this invention or from thescope of the annexed claims. lWhat I claim as new and desire to secure by Letters Patent of the United States is:

1. An hydraulicl operating mechanism comprising a liquid container, a piston movably mounted therein, an impeller pump immersed in said liquid and provided with an intake communicating with the liquid on one side of said piston and with an exhaustcommunicating with the opposite side of said piston, an' electric motor for driving said pump thereby to effect transfer 'of liquid from'one side of said piston to the opposite side thereof and produce a differential in the liquid pressure len -opposite sides of said piston to eiect movement thereof, a plate member covering said exhaust and arranged to uncover said exhaust when said impeller is energized and means actuated by the return stroke of said piston for gradually moving Jsaid member to close said exhaust gradually at the end of said return stroke thereby gradually tothrottle the return ow of vsaid iiuid and to cushion the return stroke of said'piston. 1

2. An hydraulic operating mechanism comprising. a fluid container, a piston movably` said intake and from the iuid on the opposite side of said piston to said exhaust, an electric motor for-driving said pump to produce a differential in the iluid pressure on opposite sides of said piston thereby .to produce a working stroke of said piston, a bae plate seated to cover said exhaust and responsive to energize.- tion of said pump to uncover said exhaust. and spring means connected to said plate and arranged to be engaged by said piston near the end ofthe return stroke thereof for gradually seating said plate and throttling said exhaust thereby to cushion the termination of said return stroke.

3. An hydraulic operating mechanism comxprising a ,uid container, a piston( movably mounted therein, a pump immersed in the uid comprising a, housing provided with a centrally disposed intake port and a plurality of exhaust ports arranged in a circle surrounding said in- I'take port and' having an impeller rotatably mounted in said housing, partition means comprising a tubular member affording eommunica'y tion from the duid on one side of said piston to said intake and from said exhaust tojthe fluid on the opposite sideof said piston, a drive shaft extending into said iluid and connected'v to said impeller, an electric motor 'connected to drive said shaft to produce a diderential in the fluid pressure on opposite sides of said piston to eifect a working stroke thereof, a ring shaped baille plate seated to cover saidexhaust ports and responsive to energization of said y pump for uncovering said ports, a rod projecting through said piston and baille plate, spring meanson said rod engaging said baille plate arranged to be engaged bysaid piston on the relturn stroke thereof for gradually seating said baille plate and throttling the return flow of fluid when said pump is deenergized, and a cover on said shaitfor preventing the introduction air into said pump due to rotation of said shaft.

` mononnw. DRJEscH. Y

Images