US2746251A

US2746251A - Self-contained power actuator

Info

Publication number: US2746251A
Application number: US239800A
Authority: US
Inventors: Benjamin N Ashton
Original assignee: Electrol Inc
Current assignee: Electrol Inc
Priority date: 1951-08-01
Filing date: 1951-08-01
Publication date: 1956-05-22
Anticipated expiration: 1973-05-22

Description

May 22, 1956 B. N. ASHTON SELF-CONTAINED POWER ACTUATOR 2 Sheets-Sheet 1 Filed Aug. 1. 1951 INVENTOR. BENJAMIN N. ASHTON ATTORNEYS United States Patent SELF-CONTAINED rowan ACTUATOR Benjamin N. Ashton, Kingston, N. Y., assignor to Elec'troi Incorporated, Kingston, N. Y., a corporation of Delaware Application August 1, 1951, Serial No. 239,860

2 Claims. (Cl. 66-52) This invention relates to hydraulic actuators and more particularly to self-contained actuator assemblies adapted to be operated by means of simplified external control circuits.

Hydraulic actuators are well known for their low cost, high 'eflic'iency, rapid response characteristics and light weight, and for this reason are widely used wherever power actuators are needed. One limiting factor, however, in the use of hydraulic actuators as opposed to other types of power actuators, such as electro mechanical devices, is the control system. The control of hydraulic actuators is commonly effected by means of a valve assembly and pressure source located externally and remotely of the power converting unit itself. Hydraulic systems for use in aircraft, for example, may utilize a central valve control system for governing the flow of fluid to several actuators located throughout the plane. This necessitates the close maintenance of the various fluid conduits and presupposes the continuing operability of the central system and, in many cases, of each of the remote actuators.

It has been found, however, that improved operating characteristics including safety, reliability and efiiciency may be achieved by eliminating the central pressure source and control valve assembly, as well as the numerous pressure and discharge conduits which must necessarily radiate therefrom.

It is accordingly one object of this invention to provide an hydraulic actuator unit embodying within one compact housing all of the basic components of 'an hydraulic system.

It is another object of the invention to provide an eflicient hydraulic unit adapted to be externally controlled by means of simplified electrical control circuits.

It is a further object of the invention to provide an hydraulic power actuator assembly which is self-contained as a single unit and which may be Wholly controlled by means of electrical circuits or which may, alternatively, embody a control system utilizing both electrical and hydraulic control components.

In accordance with the invention an hydraulic unit may be provided which comprises a single housing 'having an hydraulic cylinder, an electric motor, and a pump mounted therein as a compact assembly to be controlled externally by means of an electric control circuit 'to the motor. The cylinder may be fitted with limit switches whereby the system is automatically shut oii at the completion of each stroke of a piston within the cylinder, and reversing of the piston within the cylinder may be accomplished effectively by reversing the motor and pump.

The invention further contemplates the use of accumulator means in the pressure lines for storing energy during one operation for use in a later operation, thereby to insure quick starting and lower power requirements at the outset of the second operation. If desired a valve system may be provided within the housing which is also electrically controlled and which facilitates 2,746,251 Patented May 22, 1956 the reversing of the movement of the piston -within 'the cylinder. In this embodiment the electrical control circuit for the motor is simplified in that the latter may be unidirectional.

The above and other features and objects of the .in-

ice

vention may be better understood with reference to the accompanying drawings in which:

Fig. 1 is a schematic diagram of an hydraulic system formed according to the invention;

Fig. 2 is a wiring diagram of the control circuit .for the hydraulic system shown in the schematic diagram of Fig. 1; i

Fig. 3 is a top view of a self-contained hydraulic power actuator embodying the electrical and hydraulic systems disclosed in Figs. 1 and 2;

Fig. 4 is a view in side elevation partly in section on the line 4-4 of Fig. 3 looking in the direction of the arrows; and

Fig. 5 is a View in transverse section taken 'on the line 55 of Fig. 4 looking in the direction of the arrows.

Referring to the drawings and to Figs. 1-5 in particnlar, the invention is shown as embodied in a self-contained, hydraulic actuator 10 assembled as a unit in housing or .frame 11. Generally the unit, as shown in Figs. 35,- includes an electric motor '12 connected to drive an hydraulic or gear pump 13, a check valve '14, an accumulator or storage device 15, a solenoid operated selector valve assembly 16, a fluid reservoir 17, and an hydraulic jack assembly 18 including a cylinder 18a formed in the 'frame 11 and having a piston 18b mounted therein for 'reciprocatory sliding movement.

Referring to the schematic diagram of Fig. 1, it will be seen that the system is connected so that the pump :13 draws fluid from the reservoir 17 through a conduit or duct 19 and discharges fluid under pressure into the conduit 20 in which the check valve 14 is located. The conduit 20 discharges into the selector valve assembly 16, which is connected to opposite ends of the hydraulic cylinder 13a by means of conduits 21 and 22. The "conduits 21 and 22 are alternately used as pressure and return lines by the action of the selector valve assembly 16 as described in detail below, and in this fashion the piston 18b may be caused to move to and train the cylinder. The discharge from the selector valve assembly 16 is fed by a return conduit 23 to the reservoir 17. The acclunulator 15 is connected to the pressure line "20 and a pressure relief valve 24 is connected between the pressure and

return conduits

22 and 23 respectively.

The electrical control circuit for the system as diagrammed in Fig. 2 includes a source of electrical energy such as a battery 24, for example, the negative terminal of which is connected by a conductor 25 to one terminal of the electric motor 12. The positive terminal of the battery 24 is connected by a conductor 26 to a double pole, double-throw switch 27 "having a first pair of stationary contacts 27a and 27b, and a second pair of stationary contacts 27c and 270?. The contact 27a is connected by a conductor 28 to one contact 29:: of a limit switch 29 (see also Fig. 4) which is mounted near the hydraulic jack 18 to be actuated by the piston 1812 at the completion of each stroke. The contact .271) is connected to a contact 2% of the limit switch 29 by a conductor 39. The contact 270 is connected by a conductor 34 to a coil 31 of the selector valve assembly 16. The coil 31 is connected to the negative terminal of the battery 24 by the conductor 25. The contact 27d of the switch 27 is connected by a conductor 35 to a coil 36 which is also connected to the negative terminal of the battery 24 by the conductor 25. The limit switch 29 is connected to the second terminal of the motor 12 by means of a conductor 33 to complete the electrical control circuit.

.ment of the piston.

Referring now to Fig. 4, it will be seen that the motor 12 is bolted to the frame 11 by bolts 34. The reservoir 17 is formed adjacent the motor mounting and the pump 13 is mounted in the reservoir chamber by means of bolts 35. The pump is coupled to the motor 12 by a shaft 36'. The pump draws fluid from the reservoir through an inlet 37 (Fig. and discharges the fluid through a duct or conduit 33 to a duct 39 (Fig. 5) which feeds the selector valve 16. It will be recalled that the selector valve controls the flow of fluid from the pump selectively into either end of the cylinder 18a.

The discharge conduit of the pump is fitted with the check valve 14 which is received in a recess 44 formed in a passage plate :41 which bounds one end of the reservoir. The check valve 14 comprises a ball 42'urged by coil spring 43 against the discharge end of the conduit 38. The conduit 38 also communicates by means of a bore 44 with the accumulator which comprises a domeshaped cover-plate 45 bolted to the passage plate 41 and housing a resilient, imperforate diaphragm 46 which forms a chamber to maintain the fluid pressure substantially uniform and to store pressure for subsequent strokes of the piston.

The selector valve 16 as best seen in Fig. 5, comprises a valve stem 47 received in an elongated sleeve 48 received in a through bore 48 formed in the passage plate 41. The valve stem 47 is formed with a series of three axially spaced cylindrical portions or slides 42, 5t and 51, which engage the inner walls of the sleeve 48. The sleeve 48 is formed on its outer surface with a series of five circumferential ducts 52 i 56 communicating with the inner surfaces by means of radial ducts 52 56', respectively. The duct 54 communicates with the pump through ducts 39-38 (corresponding to conduit 20 in Fig. 1). The duct 53 communicates with a horizontal duct 57 which leads to an external conduit 58 which leads through duct 58' (Fig. 4) to one end of the cylinder 18a. The duct 55 joins an inclined duct 59 which leads to the other end of the cylinder 18a. The ducts 52 and 56 both communicate with the'reservoir 17. These ducts correspond to conduit 23 in Fig. 1.

By moving the valve stem 47 up and down, the ducts 57, 58 and 59 can be made'to be pressure or return conduits for the cylinder, and the piston thereby is driven in one direction or the other according. to Wellknown principles.

To control the selector valve, the stem 47 is elon" gated and on the respective outer ends thereof,

solenoid cores

60 and 61 are mounted to be received in the

coil parts

31 and 36, described above. A fluid seal around the selector valve is effected by the sealing rings 62'and 63, and a neutral position for the valves is effected by means of the compression spring 64 which reacts in both directions against movement of the valve stem.

In operation, the hydraulic jack is operated by closing the switch 27 for achieving the desired direction of move This completes a circuit through the normally closed limit switch 29 to the motor 12 which starts the pump 13 operating to supply fluid under pressure through the conduit 20 to the selector valve assembly 16. The closing of the switch 27 for a desired direction of movement of the piston energizes one of the solenoid coils 31 or 36 of the selector valve assembly. If, for example, the piston is at the right hand end of the cylinder as viewed in Fig. 4, the selector valve stem 47 will be moved upwardly so that the fluid under pressure from the pump enters the selector valve by means of conduit 39 (Fig. 5) and discharges into the conduit 59, which communicates with the right hand end of the cylinder. The left hand end of the cylinder is at the same time connected by means of the conduit 58 and the ducts 57, 53 and 53 to the selector valve stem. The valve stem directs the flow through ducts 52 and 52 into the reservoir 17. Thus, fluid under pressure is furnished at the right hand side of the piS'FOll 18b and 4 a discharge circuit for the fluid is established at the left hand side of the piston.

The piston will move to the left until either the switch 27 is opened or the limit switch 29 is actuated by the arm 65' on the piston rod to deenergize the motor and stop the pump at the completion of the stroke of the piston. The piston may then be reversed and driven in the other direction by reversing the switch 27. This will energize the motor and drive the pump in the same hand of rotation as in the preceding stroke, but will also energize the solenoid coil 31, causing the valve stem 47 of the selector valve assembly 16 to move downwardly to establish a pressure circuit from the pump through the ducts 33, 39, 54 and 54, through the selector valve to ducts 53 and 53', and to the left hand side of the cylinder through the duct 57, the conduit 58 and duct 58'. At the same time a discharge circuit for the fluid back to the reservoir 17 is established through the duct 59, the ducts 55 and 55 of the selector valve, ducts 56' and 56, and back to the reservoir 17. This stroke will continue until such time as the switch 27 is opened or the limit switch 29 is actuated by means of a spring biased plunger 65 slidably received in the cylinder head and passing through a packing gland 66. Thus, it will be understood that a highly effective combination of electrical and hydraulic control is provided for operating the hydraulic jack 18 from a remote point without the use of interconnecting hydraulic pressure lines from the control point. The self-contained hydraulic actuator operates independently of any external pressure source, and provides a large degree of safety and reliability for a system employing several hydraulic actuators. Failure of one actuator unit, for example, will not result in any loss of fluid which might affect another actuator unit.

Thus it will be seen that a highly simplified and effective assembly design may be provided according to the invention for combining a pump, a motor, accumulators and an hydraulic jack into an integrated unit susceptible of remote control solely through electrical wiring. Although a preferred embodiment of the invention has been described above with reference to the drawings, it is to be understood that numerous modifications may be made in the design without departing from the scope of the invention, which should not, therefore, be limited except as set forth in the following claims.

I claim:

1. In an hydraulic system, a housing, a uni-directional electric motor carried by the housing, a chamber in said housing forming a fluid reservoir, a pump mounted in said chamber and connected to be driven by the motor, a cylinder formed in the housing, a piston mounted in said cylinder for reciprocatory movement therein, a doublethrow control switch having a movable contact adapted to be connected to a source of electrical energy and a pair of stationary contacts connected to the motor, a pair of limit switches connected respectively to the stationary contacts of the control switch and in series with the motor, said limit switches being normally closed and adapted to be opened by movement of the piston to its respective extreme positions, a selector valve mounted in the housing and for controlling the flow of fluid to the cylinder, electromagnetic mean for operating the selector valve and circuit means including switch means actuated with the said control switch connecting the electromagnetic means to the said source of electrical energy.

2. Hydraulic apparatus comprising a hydraulic jack including reciprocatable piston means, a pump, an electric motor for driving the pump, selector valve means for directing the output of the pump selectively to opposite sides of the piston, first and second electromagnetic means for operating the selector valve means, a control switch including a double-pole, double-throw switch having a pair of movable contacts connected to a source of electrical energy and two pairs of stationary contacts adapted to be selectively engaged by the movable contacts, limit switch means responsive to movement of the piston including a pair of normally closed switches each having a contact connected in series with the motor and each having a contact connected to a corresponding stationary contact of the control switch, means connecting the first and second electromagnetic means respectively to the other pair of stationary contacts of the control switch, and means completing an electrical circuit from the electromagnetic means and the motor to the source of electrical energy, whereby the selector valve may be operated by the control switch to cause the piston to be reciprocated while the motor and pump are operated in one direction only and whereby the motor will be deenergized by the limit switch means at the end of each stroke of the piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,948,951 Walker Feb. 27, 1934 6 Hill Dec. 2, 1941 Dean July 6, 1943 Piron Sept. 28, 1943 Fitch July 31, 1945 Shendrick Nov. 6, 1945 Huiferd Sept. 14, 1948 Hartman Dec. 28, 1948 Patterson May 22, 1951 Livers et al. May 29, 1951 Lee July 3, 1951 Ackerrnan Sept. 23, 1952 McLeod June 2, 1953 FOREIGN PATENTS Great Britain Jan. 26, 1943