US1998103A - Electrohydraulic motor - Google Patents

Description

April 16, 1935.

F. H. SMITH ELEGTROHYDRAULIC MOTOR Original Filed Dec. 3l, 1930 4 Sheets-Sheet 1 foe/VEY April 16, 1935. F. H. SMITH ELECTROHYDRAULIC MOTOR Original Filed Deo. 5l, 1930 4 Sheets-Sheet 2 "5.1:: :HEL

April 16, 1935. F. H. SMITH ELECTROHYDRAULIC MOTOR Original Filed Deo. 31, 1930 4 Sheets-Sheet 3 llllllllllllli IIIIIIIIII April 16, 1935. F. H. SMITH 1,998,103

ELECTROHYDRAULIC MOTOR Original Filed Dec. 3l, 1930 4 Sheets-Sheet 4 IHIIHIIIII Patented Apr. 16, 1935 UNITED Vs'm'rlazs PATENT OFFICE ELECTROHYDRAULIC MOTOR Frank H. Smith, Summit, N. J., assigner to Elevator Supplies Company, Incorporated, Hoboken, N. J., a corporation of New Jersey Original application December 31, 1930, Serial No.

505,934. Divided and this application Ovember 19, 1931, Serial No. 576,101

9 Claims. (Cl. 60-52) exible manner, for example to supply energy for operating parts on moving objects such as elevator cars, and provides improvements there- This application is a division of my application Serial No. 505,934, led December 3l, 1930.

The invention provides electro-hydraulic means to operate elevator doors or gates, for example in such manner that there is obtained a strong and adequate force for operating the elevator doors, almost instant action at the maximum force, almost instantaneous reversing movements oi the doors at any stage of movement thereof, resilient and flexible movement of the doors and connected parts, diierent speeds of opening and closing, limitation of the driving force acting on the doors when the doors Strike a person or obstruction, automatic checking and stopping of the doors at the end parts of their movements.' holding or locking of the doors in their open and closed positions, and relief of the doors from the driving force of the electro-hydraulic device in their open and closed positions, even though the electric motor continues to run.

The invention further provides an electro-hydraulic motor comprising an impeller driven in one direction by the electric motor, together with means for obtaining reversing movements of the hydraulic element.

The invention further provides an electro-hydraulic motor combined with means for checking or cushioning its action at the end parts of its action, whereby to eiect a cushioning or gradual stopping of the parts operated by the motor and prevent shocks and noise of the parts in coming to a stop at the end position or positions. lt further provides means for effecting adjustment of the cushioning or checking action, whereby such checking action may be varied as desired.

' The invention further provides a compact and simple form of reversing electro-hydraulic motor. in which the construction is such that the motor is not liable to get out of order, which is capable of being fitted into restricted spaces, in which the valve mechanism is closely assocated with the impeller and its housing, and in which in fact the impeller housing may have the additional function of a valve. It further provides a reversing electro-hydraulic motor which acts almost instantly with its full force,

which does not build up an undue or dangerous force when the part or parts operated thereby meet an obstruction, and in which the electric motor and the impeller driven thereby may continue to run without binding or strain when the part operated by the motor meets an obstruction, or when the electric motor continues to run after the valve has been moved to a cut-olf position.

Several embodiments of the invention are illustrated in the accompanying drawings, wherein:

Figure 1 is a vertical sectional view of one embodiment of the electro-hydraulic motor,

shown as operatively connected to a sliding door such as used on subway cars, the section being on line I-I, Fig. 2.

Fig. 2 is a top plan view of the parts shown in Fig. l.

Fig. 3 is a horizontal sectional view on the line IIL-III, Fig. l.

Fig. 4 is an enlarged horizontal sectional view of the pump shown in the lower part of Fig. l, and showing the valve in position cutting the pump oi from the hydraulic motor.

Fig. 5 is a view similar to Fig. 4 showing the valve in position for driving the piston of the hydraulic motor, shown in Fig. 1, to the left.

Fig. 6 is a view in elevation of parts of the mechanism for operating the valve which controls the low of liquid from the pump to the hydraulic cylinders.

Figs. '7 and 8 are respectively a horizontal sectional view and a vertical sectional view of another embodiment of the pump and valve shown in Figs. l-6 inclusive; the housing of the impeller combining the function of a valve in Figs. 1-6 and in Figs. 7 and 8 the valve and impeller housing are separate.

Figs. 9 and l0 are views similar to Figs 7 and 8 and illustrating a third embodiment of pump in which the pressure of the liquid is stepped up by the driving action of a series of impellers, the section in Fig. 10 being on line X-X, Fig. 9.

One embodiment of the electro-hydraulic motor is illustrated in Figs. 1 to 6, inclusive. The motor is shown as applied to the simple operation of opening and closing a sliding door D. Numeral i 0 designates the electro-hydraulic motor as a whole. Numeral l2 designates an electric-motor of suitable construction being preferably a constant speed motor. Numeral I4 designates a pump driven by the electric motor I2, and numeral I6 designates a double-acting hydraulic cylinder, said cylinder comprising the portions I9 and and the double-acting piston 22 comprising the portions 23 and 24, hereinafter more fully explained. Ports 21 and 28 lead from the pump to each side of the piston 22, to serve for conveying uid under pressure to one side or other of the double-acting piston 22, and also conveniently to serve as passages through which the fluid on one side of the piston may be vented when fluid is being supplied to the opposite side.

In order to provide compactness of construction and to obtain other advantages, the pump I4 is conveniently located about midway of the cylinder I6, and conveniently slightly below its axis, and the electric motor I2 is conveniently located over the pump I4.

The pump I4 comprises a wheel or impeller within a suitable housing 32. The impeller or wheel 30 is preferably keyed upon a Shaft 34 which is driven directly by the motor I2. A reservoir for fluid is conveniently provided by a space 36 between the two cylinder portions I 9 and 20 of the double-acting cylinder I6, the portions I9 and 20 being spaced to provide this reservoir. The reservoir 36 is conveniently of about the same width as the diameter of the cylinder. The wheel 30 as here shown is of the balanced double impeller type, and passages 38, 39, through the impeller housing 32 lead to the intake of the upper and lower portions of the wheel, Fig. l, the passages 38 being directly in communication with the reservoir 36, and the passages 39 being in communication therewith through the channels 4I around the impeller housing. See Figs. 4 and 5. 'I'he pump I4 has a peripheral chamber 40 into which the impeller 30 forces liquid when driven.

Power is preferably taken from the piston 22 at a point intermediate the double-acting cylinder. The power is conveniently taken from a shaft 44 running across the upper part of the reservoir, at a level which is conveniently above the level of the oil in the device, whereby to eliminate the necessity for packing around moving parts passing through the cylinder, the cylinder, reservoir and pump housing being conveniently formed in one piece, as shown. The ends of the cylinder I6 are covered by caps 45, 46. As above stated, the shaft 44 passes throughthe housing above the oil level, and no other moving part passes through the housing below this point. Inspection holes I2EL with removable cover plates may be provided in the upper part of the casing for observation of the operation of the parts and the oil level.

As before stated, the double-acting piston 22 is conveniently separated into two parts 23, 24, which are connected through the reservoir 36 by means of a thrust-rod 50. Means are provided for connecting the piston 22 in driving relation with rock-shaft 44. To this end, thrust-rod 50 is conveniently provided with a rack 52 adapted to mesh with a gear segment 54 fixed upon the aforesaid shaft 44. For the purpose of symmetry, the thrust-rod 50 is conveniently formed as a divided or rectangular frame, and the rack 52 is conveniently formed on the two long sides thereof, and the segmental gear 54 duplicated, as showing in 54, to engage with the rack portion 52 on the thrust-rod or frame 50. The frame construction of the thrust-rod further permits of the impeller shaft 34`passing downwardly to the impeller through the axis of the double-acting cylinder I6. The shaft 44 on which the segmental gears 54, 54 are mounted, and which transmits the power of the hydraulic piston 22, is conveniently cored in its middle, as indicated at 58, to

permit of the impeller shaft 34 passing through the same, and of the said shaft 44 rocking without hitting the shaft 34.

As heretofore stated, the electric motor I2 is preferably a motor of the type which is energized to run in one direction, and consequently the impeller 30 of the pump also runs in one direction. Means are provided for having the one-way driven impeller act to effect movement of the piston 22 in reverse directions, whereby to effect rocking movement of the shaft 44, and consequently a back and forth movement to the part connected to the motor, as for example to effect the opening and closing movements of a door. This means conveniently comprises a valve for connecting the pressure chamber 40 of the pump I4 to one or other of the cylinder portions I9, 20. In the construction illustrated in Figs. l, 4 and 5, the impeller housing 32 is preferably given the function of a valve. To this end the impeller housing 32 is conveniently rotatably fitted in the pump housing I4, so as to be capable of being oscillated therein as hereinafter described. 'I'he impeller housing is provided at the two sides thereof with outlet openings 60, 6I, in communication with chamber 40 and placed so that one registers with one or other of the passages 21, 28, when the other is out of register with said passages, or vice versa. For example, as shown in Fig. 5, the outlet passage 6I registers with the passage 28 leading to the cylinder portion 20, while at the same time the outlet passage 60 is cut olf from the passage 21 leading to the opposite cylinder portion I9. Furthermore, the angular relation of the outlets 60, 6I is preferably such that the impeller housing containing these passages 60, 6I may be turned to a position wherein the outlet ports 60, 6I are out off from both passages 21, 28 leading to the cylinder ends. This position is shown in Fig. 4, wherein it will be seen that the outlet passages 60, 6I are out of register with both passages 21, 28.

Means 65 are provided for moving the valve controlling the flow of liquid to the cylinder ends I9 and 28. 'I'he valve (in this case the impeller housing 32) is conveniently provided with a gear or segment 61 fixed to a neck 68 thereof concentric with the axis of the shaft 34. This gear 61 meshes with a gear segment 69 carried by a shaft 10, extending upwardly through the reservoir and upwardly through the cylinder housing or casing, preferably at a point above the liquid level therein, as shown. A lever or arm 12 is conveniently fixed to the upper exterior end of the shaft 10, as shown, and the shaft 10, and consequently the valve (impeller housing 32) moved back and forth by moving the arm 12 back and forth. The arm 12 is conveniently moved by an electric engine 15 (or other suitable means) through suitable linkage, as shown at 11. Engine 15 is here shown as a pair of solenoids 15a, 15b provided with movable cores 80, 8I. The cores 80, 8l are connected to a rocking beam 83, which is in turn connected to the link 11. When one or the other of the solenoids is energized to attract its armature 80, 8|, the valve 32 (impeller housing) is shifted from a position to admit fluid to one end I9, 2U or the other of the hydraulic cylinder, as hereinafter more fully explained in the description of operation.

Means are preferably provided for automatically checking the piston 22 at the ends of its stroke, and thereby cushioning the end portions of the movement of the part moved thereby, as

for example the opening and closing movements of the door shown The cushioning is conveniently effected through the valve 32, and to this end connections may be provided between the shaft IlY and the said valve 32. These operating means or connections conveniently comprise a pair of cams 90, 9| fixed upon the rock shaft 44, and means for transmitting the motion from each of these cams to the gear 61. These means conveniently comprise a pair of rock shafts 93, 94, having arms 95, 96 thereon so positioned as to be struck and moved at proper times by the said cams 90, 9|. The rock shafts 93, 94 are preferably arranged to pass through the cylinder casing above the liquid level therein, and are provided at their inner ends with worm gears 91, 98 which mesh with worms |08, IDI xed upon vertical shafts |03 and 10 having gear segments |84 and 69 at their lower ends in mesh with the gear 61 fixed to the Valve 32 (the shaft 10 and gear segment 69 also serving for conveying motion imparted to the rock arm 12 to the valve 32 through gear 61, as heretofore explained). When rock-shaft 93, gears 91, |88, shaft |03 and segment E04 are actuated, the segment 69, shaft 1I), gears @8,1m and rock-shaft 94 move reversely.

The cams 9|! and 9| are preferably fixed upon the end of the shaft @d by means of a clamping nut |01. Loosening of this nut permits of shifting of the angular position of one or both oi the said cams 90, 9| and thereby permits of adjustment or timing of the checking or cushioning action through the operation of the parts just described. The cams 90, 9| are set to make contact with arms 93, 98 as one or other of the pistons 23, 26 approaches its end of the cylinder. Contact with one or other of the arms 95, 96 causes it to turn the valve 32 to the position shown in Fig. 4, wherein the passage leading from the cylinder end which is being vented is closed, and consequently the movement of the piston 22 (and the part operated thereby) checked or cushioned. The cams 98, 9| and the parts associated therewith may be so contrived and set as to give considerable range and variety to the checking or cushioning action.

in the construction where the impeller housing 32 also serves as a valve, the friction of the liquid driven by the impeller normally tends to rotate the housing and may even rotate the housing if left free to turn. In the arrangement shown in Figs. l-6 the direction of rotation of the impeller 38 and direction in which the friction of the liquid set in rotation thereby, acts is counterclockwise, and as shown by the arrows, Figs. 2 and 5. Moreover, the force required to move the housing 32 in one direction will be greater than that required to move it in the opposite direction. Suitable means may be provided to counteract the turning action on housing 32 of the fluid driven by the impeller. This means may for example be a spring H2 attached to rocking beam 83 and acting thereon in a direction opposite to the pull of the housing 32 transmitted thereto through segment 69, shaft 18, arm 12 and link 11. The spring. l l2 will aid the solenoid 15a in pulling to shift the valve (housing 32) and will counteract the pull of the friction of the liquid on housing 32 when the solenoid 15b pulls the valve (housing 32) to shift it in the opposite direction, thereby equalizing the force required to move the valve in either direction. The force of the spring H2 may be adjusted by suitable means I I2, here shown as a bracket adjustably held on its support by binding screws.

It will be observed that spring |2 acts normally in a direction to aid the opening solenoid 15a. This arrangement has a further advantage, both in the construction where the friction of the liquid in the pump exerts a turning action on the valve, and where it does not. When neither solenoid 15a or 1.",b is energized, the tendency of the spring I I2 is to move the valve to the opening position, i. e. the position bringing about the opening of the door. In elevator practice it is of great importance to quickly reverse a closing` movement of a door to avoid accidents, and the normal tendency of spring I I2 is to move the valve to door opening position and thus favor speed of operation in reversing the parts to door opening operation. When liquid flows under pressure through either the port 8| (or Sla, Blb) and passage 28 or port 60 (or 60a, 60h) and passage 21, the force of the stream will prevent movement of the valve under the action of either the spring II2 or the frictional drag onithe valve (in that formv where the valve is subject to such drag), but the tendency of spring II2 to move the valve to door opening -position persists, and furthermore in the present described arrangement, the spring will move the valve to door-opening posi-Y tion when the flow through the valve ceases and neither solenoid is energized. That is, after the door is closed and the closing solenoid de-energized, the spring I i2 will move, the valve to dooropening position, so that even in case of failure of the solenoids, the valve will be in position for door-opening.

Means may be provided for opening or closing the door at different speeds. For example, it may be desired to open the door at a speed faster than the speed of closing. The means may be various; it is however very conveniently combined with the valve 32 and its operating means. For example, abutments 85, 86 (Fig. l) may be provided in the paths of cores 80, 8| of engine 15. By setting one of the abutments so that the core abutting the same cannot move as far as the other core, one of the ports 30, 8| will not open one of channels 21, 28 as widely as the other. For example, if abutment 86 be set so as to allow core 3| less movement than core 80. the port 68 will only partially open, and the closing movement of piston 22, and consequently the closing movement of the door D will be slower than the opening movement. Furthermore, by adjusting both abutments 85, 8E the speed of opening and closing may be made faster or slower as the ports 5U, 8| are more or less widely opened, as well as the diierential movement heretofore described. Another very simple way of securing a difference in speed in opening and closing would be to vary the size of the ports 88, 6|.

Operation Assume the door shown in Fig. 1 to be in closed position, and it be desired to open it. The valve 32 will be in the position shown in Fig. 4. The electric motor l2 will ordinarily be previously started (running in one direction). A push button or other suitable device will then be operated to cause the electric engine 15 to shift the valve 32 from the position shown in Fig. 4 to the position shown in Fig. 5. This will bring the irnpeller outlet 8| into registration with passage '28, and the compressed fluid from the impeller will push the piston 22 in a direction to move to the left, as viewed in Fig. l. The piston will drive the thrust bar 50 so as to cause the rack 52 thereon to drive the gear segment, 54 connected to the shaft 44 in a clockwise direction, thereby causing the arm d to swing upwardly and to the right, bringing the door with it to its open position. As the door approaches the end of its opening movement its action is preferably checked or cushioned through the means heretofore described, that is the cam 90 in this instance strikes the rock arm 96, and through the connections 94, 98, 10, 69 and gear 61 moves the valve 32 to the position shown in Fig. 4, wherein both outlets 60, 6| from the impeller housing are cut off from the passages 21, 28. The movement of the door is thereby checked, and furthermore it is virtually locked in open position, inasmuch as the end 20 of the cylinder lately receiving compressed fluid is cut off from the supply of fluid driven by the impeller 30, through the closing action of the valve 32, and the end I9 of the cylinder lately venting fluid is also closed from further venting by the action of the valve 32 in cutting off the passage 21 from the reservoir 36, the valve being provided with solid portions |09 which cover and close the passages 21, 28 in the position of the valve shown in Fig. 4, so that flow to and from both ends of the cylinder I6 is cut off in the position of the valve shown in Fig. 4.

After the door is open, the impeller may continue to turn in its housing without binding, as the liquid wili slip or circulate and allow the motor to turn with about the same (or less) resistance as it does when driving the piston 22. The electric motor I2 is'preferably a constant speed motor, so as to deliver a substantially constant torque, and not increase its torque or driving force when resistance is encountered to the movement of the piston 22, as would be the case if the door met an obstruction in either its opening or closing movement. This is a safety feature which prevents serious injury being done to anyone caught between the iamb and the door in clos- 111g.

As the piston end 24 is being driven by fluid from the impeller, the opposite end I9 of the cylinder is being vented through the passage 21, the oil passing upwardly and downwardly in the passage 4| in the valve, and being drawn in through the impeller intake passages 38, 39, there being free access at the same time for` the oil to rise in the reservoir 36, and thereby avoid the cylinder end |9 being vented against any pressure other than that necessary to overcome the resistance in the passages, which is slight.

To close the door, the operation of the device is very similar to its operation in opening the door. The valve parts will be again in position shown in Fig. 4. The solenoid 15b will be operated to rock the rocking beam 83 to move the connections to shift the valve so as to bring the impeller outlet passage 60 into registration with the passage 21 leading to the end I9 of the cylinder. The impeller will thereupon drive oil through the outlet passage 60, passage 21 and into cylinder I9 against the piston end 23. This will drive the piston t the right, producing a counter-clockwise rotation of gear segment 54 and shaft 44 carried thereby. Arm d connected to shaft 44 will move downwardly and to the left, sliding the door to closing position. As the door approaches closing position, the cam 9| will come into contact with rock arm 95, which rock arm will rotate the shaft |03 and through segment |04 rotate or shift the valve 32 again to the position shown in Fig. 4, wherein both passages 21 and 28 are cut off from the impeller. This completes a description of one cycle of operation of the device.

Referring to Figs. 7 and 8, illustrating another embodiment of the pump I4, the valve is formed separate from the impeller housing 32. The valve is designated by numeral I|4 and is advantageously in the form of a'sleeve between the impeller housing 32 and the motor casing. A spider-bracket I |6 having a driving flt against the motor casing and set screws ||8 bearing against neck 68 serve to prevent turning of the impeller housing 32. Ports 6|)n and 6|, 6|b are provided in valve II4. A gear |20 is provided on valve 4 and meshes with gear segments 69 and |04 on shafts 10 and |03 through which turning movements are imparted to valve I I4. Blocks |22 of slightly greater width than the ports 60s, 6|, 6|b are placed in the middle of passages 21 and 28 dividing these passages into branches 21B, 21b and 28, 28h.

In the position shown in Figs. 7 and 8 the valve ||4 places impeller outlet 60 in communication with passage 21 through branch 21b admitting fluid under pressure from the pump I4 through port ||la to cylinder portion I9 (Fig. 1) thereby driving piston 22 to the right. Fluid from cylinder portion 20 is vented to reservoir 36 through passage 28, branch 28h, port 6|b, and passage 4|. At the end of the stroke of piston 22, cam 9| and arm 95 rocks shaft 93 causing worm gears 91, |00 to turn shaft |03 and segment |04 thereon so as to turn valve ||4 through its gear |20 to a position where port 609' is masked by block |22, and ports 6 Ia and 6 |b are masked by the walls of the motor housing, thereby cutting off both passages 21, 28 from the pump I4 and reservoir 36. When the solenoid 15b is energized to reverse the movement of piston 22, armature 8| pulls through link 11, arm 12, shaft and segment 69 to turn valve I4 to bring port 6| into register with discharge passage 6| and branch 28a and passage 28, whereby iiuid under pressure flows to cylinder portion 20, driving piston 22 to the left. At the same time port 60* in valve ||4 is brought into register with branch 21S, passage 21 and passage 4|, whereby fluid is vented from cylinder portion I9 to reservoir 36. I

Referring to Figs. 9 and 10, the shaft 34 has fixed thereon two impellers 30, 30, The impeller housing 32 and valve ||4 may be constructed as in Figs. 7 and 8, the impeller housing being stationary. The peripheral chamber 40 is connected by intake passages 38, 39EL leading to the intake on both sides of impeller 30a. By the arrangement described fluid is acted on serially by the two impellers 30 and 30a and its pressure increased. Discharge from impeller 30 is into a peripheral chamber 4|)a and from thence through outlet passages 60 and 6 I Fluid vented from passages 21, 28 at proper times passes to reservoir 36 through passages 4|. The operation of valve I4 is the same as described in reference to Figs. 7 and 8.

The checking, starting and stopping are accomplished resiliently and fiexibly, shock being very greatly minimized, with consequent longer useful life of the mechanism and greater reliability. Furthermore, a very considerable effort is employed in modern practice for operating doors (the door operating engine having an applied force equal to about 200 pounds for example) in order to obtain the desired speed, and by the present means a push or effort of such magnitude in a door operating engine may be obtained with a small electric motor turning at relatively high speed, as contrasted with a large electric motor, where electrical means are used for operating doors through mechanical connections. Furthermore, the electro-hydraulic motor can be reversed with greater facility and speed than electrical means such as referred to. This is a safety factor of major importance in elevator practice. The construction is furthermore greatly simplied, the functions of moving, checking, cushioning, stopping and locking the door being performed by one unit, Whereas heretofore such simplicity could not be obtained in electrical operators, and could only be approached in pneumatic systems with their greater limitations as regards conveying compressed air to the moving car, expensive compressor equipment, and supervision required to keep in good Working condition. Such parts as clutches and brakes are eliminated, for example. The limitation of the driving force by the use of a constant speed electric motor and the slip of the impeller in the liquid, when the door meets an obstruction is a further important safety feature of the invention.

rlhe invention may receive other embodiments than those herein specifically illustrated and described.

What is claimed iszl. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a pump comprising a rotary impeller for supplying liquid under pressure for driving said motor, an electric motor driving said impeller in one direction, and means for reversing the flow of liquid to said hydraulic motor while the electric motor is running, so that the direction of action of said hydraulic motor may be reversed and its reverse movement begun under the full driving force of the electric motor; said pump further comprising a rotatable housing having the function of a valve and forming a part of said means for reversing the flow of liquid to said hydraulic motor; said reversing means further comprisinga motordevice and means for controlling said motordevice to effect reverse movements of said housing-valve; and means for counteracting the frictional drag on said housing of the liquid set in motion by said impeller, whereby the effort of said motor-device in reversing said housing valve is equalized.

2. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a pump comprising a rotary impeller for supplying liquid under pressure for driving said motor, an electric motor driving said impeller in one direction, and means for reversing the flow of liquid to said hydraulic motor while the electric motor is ,running, so that the direction of action of said hydraulic motor may be reversed and its reverse movement begun under the full driving force o f the electric motor, said reversing means including an impeller-housing provided with ports communicating with said double-acting. hydraulic motor, and valve means thereon for controlling the said ports in said impeller housing.

3. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a pump comprising a rotary impeller for supplying liqid under pressure for driving said motor, an electric motor driving said impeller in one direction, and means for reversing the flow of liquid to said hydraulic motor while the electric motor is running, so that the direction oi action of said hydraulic motor may be reversed and its reverse movement begun under the full driving force of the electric motor, and means for automatically cutting off the flow to said hydraulic motor at the end part of its movement to automatically stop the same; said cutting-off means comprising cams operated by said piston.

4. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a double-acting reciprocating piston therein, a pump comprising a rotary impeller for supplying liquid under pressure for driving said double-acting piston, an electric-motor driving said impeller, a rock-shaft for applying the force developed upon said piston, driving connections to said rock shaft from a part of said double acting piston intermediate its ends, and means for automatically cutting off the flow to said hydraulic motor at the end part of its movement to stop the same, said latter means comprising cams on said rock-shaft.

5. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a double-acting y reciprocating piston therein, a pump comprising a rotary impeller for supplying liquid under pressure for driving said double-acting piston, an electric-motor driving said impeller, a rock-shaft for applying the force developed upon said piston, and driving connections from a part of said double-acting piston intermediate its ends to said rock shaft, means for reversing the flow of liquid to said hydraulic motor for driving the same in opposite directions, and means for automatically cutting off the flow to said hydraulic motor at the end part of its movement to stop the same.

6. An electro-hydraulic motor according to claim 5, wherein said cut-off means comprises cams on said rock-shaft, arms in the path of said cams and means connecting said arms and said reversing means for operating the latter.

7. An electro-hydraulic motor according to claim 5, wherein said cut-oil' means comprises cams on said rock-shaft, arms in the paths of said cams, and means connecting said arms and said valve for operating the latter, said lastnamed means comprising shafts passing through the motor housing above the liquid level.

8. An electro-hydraulic motor according to claim 5, said means for reversing the ow of said liquid comprising' a motor-device, and a valve operated thereby, said motor permitting independent movement of said valve, said cut-off means comprising parts for moving said valve independently of said motor-device.

9. An electro-hydraulic motor, comprising a double-acting hydraulic motor, a pump comprising a rotary impeller for supplying liquid under pressure for driving said motor, an electric motor driving said impeller in one direction, and means for reversing the flow of liquid to said hydraulic motor while the electric motor is running, so that the direction of action of said hydraulic motor may be reversed and its reverse movement begun under the full driving force of the electric motor, said means for reversing the flow of said liquid comprising a motor-device and a valve operated thereby, said motor-device comprising a pair o f solenoids, cores movable in said solenoids, and connections between said cores and said valve, and means for selectively energizing and de-energizing said solenoids, said cores and the valve being movableindependently of said solenoids when the latter are de-energized.

\ FRANK H. SMI'IH.v

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