US2810571A

US2810571A - Door actuator

Info

Publication number: US2810571A
Application number: US325124A
Authority: US
Inventors: Paul R Ferguson; Harold W Ferguson
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-12-10
Filing date: 1952-12-10
Publication date: 1957-10-22
Anticipated expiration: 1974-10-22

Description

Oct. 22, 1957 P. R. FERGUSON ETAL 2,810,571

DOOR ACTUATOR 2 Sheets-Sheet 1 Filed Dec. 10; 1952 INVENTORS PAUL R. FERGUSON B HAROLD W FERGUSON I AT OPNEYS United States Patent DOOR ACTUATOR Paul R. Ferguson, Spotswood, N. J., and Harold W. Ferguson, New Britain, Conn.

Application December 10, 1952, Serial No. 325,124

21 Claims. (Cl. 26834) The present invention relates generally to automatically operated doors and, more particularly, to a door actuator of the type for use with a swinging door and which is of improved construction and performance characteristics.

The device of the present invention is of the type which will open a door by power means in response to an initiating action, such as the closing of a treadle or other type of switch and which will then close the door after the passage through the doorway has been completed. It is a general aim of the invention to provide a mechanism of this type which is of simple and compact construction and fool-proof in operation and which at the same time will have improved operating characteristics rendering the same adaptable for use in a wide variety of installations and furnishing a variety of performance characteristics, such as to meet the needs of widely varying installations.

A more particular aim of the invention is to provide a door actuator which can be precisely controlled and adjusted to give the particular type of door opening and closing movements desired in a given installation.

A further aim is to provide such a door actuator which Will have features of safety and of automatic operation such that the power operation of the door will not only proceed in a predetermined pattern suitable in ordinary situations, but which also will adapt its movements to changes in the situation and in response to several initiating media. Included in this aim is the providing of a door actuator which can be put in operation either by a momentary or sustained signal impulse, which will be prevented from again closing the door until passage through the door has been efiected, which will not be likely to injure or damage any person or thing in the path of movement of the door, and which will permit operation of the door in either direction without the need for the person to do anything except push the door, which may be the preferred mode of operation, particularly in case of panic.

Other objects will be in part obvious, and in part pointed out more in detail hereinafter.

The invention accordingly consists in the features of construction combination of elements and arrangement a of parts which will be exemplified in the construction hereafter set forth and the scope of the application of which will be indicated in the appended claims.

In the accompanying drawings:

Fig. l is a plan view of the door actuator with the top of the casing removed and with the control mechanisms deleted to show the operating parts, the associated elements, such as the door, being shown in phantom;

Fig. 2 is a central vertical cross-sectional view of the actuator as shown in Fig. l with the supplementary closing springs removed; and

Fig. 3 is a diagrammatic view showing the control system and a cross-sectional view of the cylinders.

Referring to the drawings and particularly Figs. 1 and 2, the door actuator of the present invention is adapted? ice to be mounted in a generally rectangular casing 10 having a removable top plate 11. The casing 10, if desired, may be disposed with its top plate at floor level and disposed at the door opening beneath the door which is to be actuated. As will be apparent, other locations of the actuator, including a mounting in the celling, would be equally feasible. As shown in phantom in Figs. 1 and 2, the door 12 normally closing the

openingbetween door jambs

13 and 14 is adapted to be fixed at its lower end on the spindle 20 which is journaled at the top and bottom in bearings provided by the generally U-shaped bracket 21 fixed to the bottom of the casing. The upper end of the bracket and spindle are accommodated in an opening 15 in the top plate 11. When the spindle 20 is attached to the door as indicated, the spindle becomes the lower pivot for the door and is in effect a door trunion. Therefore, by means of the spindle 20, the opening and closing movements of the door may be effected and controlled.

In accordance with the invention, rotary movement is imparted to the spindle 20 and the movement is controlled by a pair of

piston rods

22 and 23 which are connected together by a bracket 24 and adjustably secured to a coupling 25 connected by a pin 26 to the outer end of a crank arm 27. The crank arm 27 extends outwardly from a collar or hub 28 which is fixed to the spindle 20.

The piston rod 22 is connected to a piston 30 which is slidably received in an elongated cylinder 31 while the piston rod 23 is connected to a piston 32 received in a cylinder 33, the

cylinders

31 and 33 being disposed in close parallel relationship. The outer end walls of the

cylinders

31 and 33 are connected to a pivot shaft 34 which is journaled in its opposite ends in a bracket 35, the bracket 35 forming a lever arm which is pivotally mounted at 37 in a bracket 38 secured to the casing 10 and which is connected at its other end to a plunger 39 slidably received in a bracket 40 secured to the base I Except as described hereinafter, the bracket 35 may be considered as a stationary support for the ends of the

cylinders

31 and 33 which are arranged in parallel, one above the other. As will be apparent, the movements of the

pistons

30 and 32 within the

cylinders

31 and 33, respectively, are synchronized and will control the movement and position of the door 12.

In the illustration in the drawings, the door is pivoted at its left end as viewed in Figs. 1 and 2, and the door when opened is pivoted in a counterclockwise direction as viewed in Fig. 1. The apparatus is shown in the drawings in the position thereof when the door is closed. As will be apparent when the door is moved to open position by counterclockwise rotation as viewed in Fig. 1, the

crank arm 27 is pivoted in a counterclockwise direction approximately suflicient movement of the crank arm 27 being permitted by the extension 16 on the easing 10. As will be apparent from the description, the mechanism can be readily re-arranged to accommodate a door opening in the opposite direction.

In accordance with the invention, the movement of the piston 30 is made responsive to fluid pressure, preferably air, while the movement of the piston 32 is controlled by hydraulic pressure. Since the

pistons

30 and 32 are in effect coupled together in parallel, movements of the pistons, and, therefore, the door are controlled by two factors, namely the differential fluid pressure in cylinder 31 and the difierential hydraulic pressure in cylinder 33.

Referring to Fig. 3, the differential air pressure may be applied to the cylinder 31 from a source of air under pressure (not shownlwhich may be connected to the system at the shut-olf valve 50. In the embodiment shown, there is connected next adjacent the shut-off valve 50 a conventional filter 51 to insure that only clean and dry air will be employed in the system. Going from the filter 51 is a conduit 52 connected at its other end to a manually adjustable regulating valve 53. A conduit 54 extends from the valve 53 to the left-handcnd of the cylinder 31 as viewed in the drawings. Connected to the conduit 54 is a conventional pressure gauge 55. Connected in T with the conduit 52 is a second pressure regulating valve 56 which is connected by a conduit 57 to the solenoid control valve 58 which in turn is connected to the right-hand end of the cylinder 31. A pressure gauge 59 is connected to the valve 56. The solenoid operated valve 58 is of conventional construction and of atype available commercially and, therefore, is not shown in detail. The solenoid valve 52; is normally open, by which is meant that when de-energized, it vents the right-hand end of cylinder 31 to atmosphere. When the solenoid valve 58 is energized, however, it closes the vent to atmosphere and connects the cylinder 31 to the pressure line 57.

In accordance with the invention, the regulating valve 53 is adjusted to place a continuous air pressure on the left-hand end of cylinder 31 which normally is sufiicient to move the door to closing position. By way of example, such a pressure might be of the order of twenty pounds, as indicated on the gauge 55. It might be said here that it is preferred to include in the structure a pair of parallel springs 43 extending between the bracket 24 and the outer ends of the cylinders which springs not only assist in theclosing movement of the door, but will insure that the door will be closed in the event of power failure.

. The regulating valve 56 is adjusted to make available a' much higher pressure to the opposite end of the cylinder 31, say a pressure of the order of seventy pounds, as indicated on the gauge Consequently, when the solenoid valve 58 is de-energized, which is the normal situation, the right-hand end of cylinder 31 is vented to atmosphere while the left-hand end is under the continuous predetermined air pressure supplied through valve 53. Accordingly, the piston 31) is continuously subjected to pressure urging it into the position shown in Fig. 3, holding or moving the door into closed position. Accordingly, in

order to cause the door to close, all that is necessary is to relieve the pressure at the right-hand end of cylinder 31. As previously mentioned, the door is also biased into this. position by reasonof the springs 43. However,

when the solenoid valve 58 is energized, thereby closing the vent and subjecting the right-hand end of cylinder 31 to the higher predetermined air pressure, then the piston 30 will be urged in a left-hand direction as viewed in Fig. 3 to cause the door to open.

As previously mentioned, the movement of the piston 30, which may be referred to as the actuating piston,

is primarily responsive to air pressure, but is also controlled by the resistance to movement of the piston 32 which is coupled in parallel therewith and which may be referred to as thecontrol piston.

Movement of the control'piston 32 is controlled by hydraulic pressure created in the cylinder 33 which is filled with a noncompressible fluid, such as oil, and which is provided with meansfor metering the flow of the fluid between opposite ends of the cylinder 33.

As best seen in Fig. 3, the cylinder 33 is provided with baflle walls 66 adjacent the opposite ends of the cylinder which walls have a large central opening 61 and a small by-pass opening 62. The effective opening of the bypass openings 62 may be regulated by suitable adjustable valves 63. The piston 32 is provided with cylindrical bosses 64, which, at the end of the stroke, are adapted to engage snugly in the opening 61 of the adjacent bafiie wall. The result of this construction'is that during the 'main travel of the piston 32, the oil can freely pass rthrough the openings 61, but, at the end of the stroke .tric-eye, hand operated switch, etc.

when one of the protuberances 64 engages in an opening 61, the movement of the oil is restricted to the small by-pass opening 62, thus greatly increasing the resistance to the movement of the cylinder and creating a cushioning effect.

The opposite ends of the cylinder 33 are connected by

tubes

70 and 71 to opposite sides of an improved compound check valve 72 constructed in accordance with the invention. As best shown in Fig. 3 of the drawings, the check valve 72 comprises a casing 73 having a throughbore 74 and enlarged counterbores 75 and 76 at opposite ends thereof. The counterbores 75 and 76 in combination with the bore 74'form valve seats, indicated at 77 and 78 respectively. Disposed in the counterbores 75' and 76 for cooperation with the valve seats 77 and 73 are ball valves 79. The ball valves 79 are freely mounted within the counterbores 75 and 76 except in so far as outward movement is limited by the pins 80.

Aswill be apparent when the piston 30 and hence the piston 32 are moved in a left-hand direction during opening movement of the door, the oil will flow from the left-hand end of cylinder 33 through the tube 70 and check valve 72 and will return by means of tube 71 to the right-hand end of cylinder 33. During closing movement of the door, the direction of flow of the fluid will be in the reverse. During opening movement of the door, the direction of flow of the oil is such as to urge the left-hand ball 79 toward the seat '78, and the degree to which the ball is prevented from seating determines the metering orifice and hence the resistance of the piston 32 to opening movement of the door. The separation of the ball from the seat 78 is precisely controlled by the setting of a setscrew 81 having a tapered end which extends between the ball and the seat. As will be apparent, when the setscrew 81 is turned inwardly, a greater separation is provided and, conversely, when the setscrew 81. is turned outwardly, the ball is permitted reservoir tank 36 which is disposed above the level of the cylinder 33 and which is adapted to contain a supply of the fluid being utilized to control the movements of the piston 32. The reservoir 86 is open to atmosphere and is preferably made of transparent material so that the oil level can readily be determined by visual inspection. The

reservoir 86 acts as a compensator to take care of any variations in the capacity or rates of flow of oil to or from opposite ends of the cylinder 33. Also, it keeps the system filled at all times and failure of the mechanism through slow leakage of the fluid or entrainment of air bubbles is entirely avoided. Furthermore, the reservoir 36 permits the application of an electrical heating element 87 disposed adjacent the reservoir 86 which will maintain the oil at a desired temperature and hence fluidity. As shown in the wiring diagram of Fig. 3, the heater 87 is connected through a thermostat switch 88 to the power lines L1 and L2. The thermostat switch 88 is responsive ,to ambient temperature and connects in the heater 87 whenever the ambienttemperaturc drops to a point below that at which the desired fluidity of the oilis maintained.

The door actuator and control mechanism of the present invention is adapted to be connected to any desired initiating apparatus, such as, for example, a treadle, elec- For simplicity of presentation, the mechanism has been shown in the drawings connected to an electric mat switch of the type'shown in the Sheldon S. Roby. Patent No. 2,611,049, issued September 16, 1952. As fully disclosed in the aforesaid Roby patent, the electric mat switch comprises two sections 90 and 91 which are disposed in the door opening with the section 90 extending forwardly in the path of someone wishing to enter through the door and the section 91 being disposed rearwardly of the door and adapted to be walked on when the person has moved through the door opening. When a person is standing on the section 90, a circuit is closed through the

leads

92 and 93, and, when the person stands on the section 91, a circuit is closed through the

leads

93 and 94.

Referring to the wiring diagram of Fig. 3 in detail, it will be seen that the power line L2 is connected by line 101 to one side of the solenoid valve 58, while the other side of the solenoid valve 58 is connected by line 102 through solenoid switch 103 to the lead 92 of the mat section 90, the lead 93 of the mat switch being connected by line 104 to the power line L-1. Accordingly, when a person steps on the mat section 90, he closes the connection between leads 92 and 93, thus energizing the solenoid valve 58 and permitting air under high pressure to enter the right-hand side of the cylinder 31, thus causing movement of the

pistons

30 and 32 in a left-hand direction and thereby opening the door.

Immediately upon movement of the piston 32 in a left-hand direction, there is created fluid pressure on the left-hand end of cylinder 33 which will actuate and close a pressure actuated switch 110 which communicates with the left-hand end of the cylinder 33 by means of a coupling 111. One terminal of the pressure actuated switch 110 is connected by conductor 112 to the power line L1, while the other terminal of pressure actuated switch 110 is connected through a normally closed switch 113 and solenoid switch 103 to line 102 connected as previously mentioned to the solenoid valve 58. The switch 113 is normally closed and remains closed except when the door is in fully opened position. When the door is in fully opened position, the switch 113 is opened by a cam 115 which is fixed to the door spindle 20. It thus will be seen that when the door actuator is put into operation by a person stepping on the mat portion 90 or by any other initiating movement, the pressure created in the left-hand end of cylinder 33 which closes the pressure actuated switch 110 thereby creates an independent circuit to the solenod valve 58 which maintains the actuator in door opening condition irrespective of whether any further stimulus is provided, such as the person remaining standing on the mat portion 90. This feature is particularly important where it is desired to have a door open merely in response to the operator turning a handle or performing some other momentary manual operation.

Another advantage of the circuit just described is that it permits the door actuator to be put into a door opening cycle without requiring the operator to close any switches. All that the operator need do to initiate opening movement of the door, if he desires, is to push the door in an opening direction with suflicient velocity to create pressure in the left-hand end of cylinder 33 sufficient to close the pressure actuated switch 110. Also, if the door has begun to close while the person is still in the dorway, the person can quickly correct the situation by manually stopping the door and then starting the door in an opening direction, which is an added safety feature. The arrangement is not so sensitive, however, that slight or slow fluctuations of the door which might occur, such as the result of wind pressure, will be suflicient to place the mechanism in door opening condition.

A further advantage of the circuit so described is in the event that some person or object is standing in the way of the opening movement of the door. Assuming that the initial actuation of a switch, such as the mat section 90, has occurred momentarily so that this switch is no longer closed but that the door is continuing to open by reason of the closing of switch 110, the result of the obstruction to the movement of the door will be that the movement will be so slowed down'or checked momentarily sufficiently to relieve the pressure on the left-hand end of cylinder 33 whereby the switch will open and the mechanism will be put into the door closing cycle. By the same token, this same circuit may provide for automatic closing of the. door after the door has been opened to the desired full extent} In other words, when the door has been opened as far as it can be moved and the movement of the door ceases, the pressure in the left-hand'end of cylinder 33 will be dissipated and switch 110 will be permitted to open, thus de-energizing the solenoid valve 58 which causes the actuator to go into its door closing cycle. As a practical matter, however, it is deemed preferable to include and rely upon the switch 113 which rapidly and automatically de-energizes the solenoid valve 58 when the door has been opened to the full extent.

In the event a mat switch of the type shown inthe drawings is utilized, having a portion 91 on which a person moving through the doorway will normally step, the same may be connected to the coil of the solenoid switch 103. Accordingly, when the mat switch portion 91'is closed, the solenoid 103 is energized, thus breaking the connection between switch 113 and line 102 and at the same time connecting the switch 114 directly to the power line L1 without going through the pressure switch 110 and normally closed switch 113. The normally open switch 114 is open only when the door is in fully closed position, and it is moved to closed position by the cam 116 situated below the cam 115 whenever the door is in a position other than fully closed. As a result, if .a person has moved through the doorway a suflicient distance so that the switch portion 90 is no longer closed and has moved so slowly that the door has opened to a completely open position before the person has proceeded past the mat switch portion 91, the door actuator will be prevented from going into the door closing cycle until the person moves ed the mat portion 91, thus de-energizing the solenoid 1'03 and permitting the automatic closing arrangement to take over.

At the same time, if the door is closed and someone steps on the mat portion 91, the door will not be actuated by switch 91 because of the open switch 114, and will not be actuated by switch 90 because of the broken connection between switch 113 and line 102.

As previously mentioned, during normal operation of the door actuator, the bracket 35 is stationary and operates in exactly the same manner as though the bracket were immovably mounted on the casing 10. The reason that the bracket normally remains stationary is because the spring 41, operating on the plunger 39, is of such strength, taken in connection with the leverage or mechanical advantage afforded by the bracket 35, that it applies a pressure against the rear of the

cylinders

31 and 33 which greatly exceeds any pressures which can be developed by the air pressure applied to the cylinder 31. However, in the event that a suflicient force is applied to the door so as to pivot the door in a clockwise direction, movement of the door will be accommodated by the pivoting of bracket 35 and compression of the spring 41. As soon as the door has been moved sufficiently in a clockwise direction to move the pivot pin 26 beyond the line of centers between the spindle 20 and the pivot shaft 34, however, the spring 41 will expand and assist in the opening a movement of the door. In other words, the

piston rods

22 and 23 and the crank arm 27 form a toggle whichcan be moved past the center to urge the door in either direction. This feature is particularly important as a so-called panic release because it permits the door to be positioned for opening inwardly into a building while at the same time permitting persons within the building to pass outwardly through the doorway by applying sufiicient force to the door in an outward direction opposite to the normal opening movement of the door.

It thus will be seen that there has been provided in accordance with the invention a door actuator which is of simple :and compact construction and fool-proof in operation and yet which will provide many operational and safety features heretofore lacking in automatically operating door mechanisms. The device is extremely versatile, permitting its use in a wide variety and types of installations, and a degree of control is provided rendering the device convenient to use and insuring any of a variety of performance characteristics desired.

As many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the language used in the following claims is intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

We claim:

1. Door operating apparatus comprising power means for opening and closing the door, control means for regulating the rate of movement of the door comprising a hydraulic cylinder and a piston in said cylinder connected to the door for movement therewith, means for permitting passage of the fluid between opposite sides of the piston having an adjustable eiiective orifice, and means connected to the cylinder and responsive to the pressure therein during opening movement of the door for energizing the power means.

2. A door operating apparatus as recited in claim 1 wherein the last-named means includes a pressure actuated switch in fluid communication with one end of the cylinder.

3. Door operating apparatus comprising a pair of cylinders mounted in parallel arrangement, a piston in each cylinder, a piston rod connected to each piston, said rods being rigidly connected together and operatively connected to the door, means to apply fluid pressure connected to one of the cylinders to actuate the piston therein, and hydraulic control means connected to the other cylinder to regulate the rate of movement of the piston therein.

4. Door operating apparatus comprising a pair of cylinders disposed in parallel arrangement, a crank arm adapted to be connected to a door, a piston in each cylinder, a piston rod connected to each piston, said rods being rigidly connected together and secured to the outer end of the crank arm, means mounting the cylinders for limited movement in the direction of piston movement and for pivotal movement in the plane of crank movement, and means normally biasing the cylinders in the direction corresponding to door opening movement of the piston rods.

5. Door operating apparatus comprising a crank arm for attachment to the door, a piston and piston rod assembly pivotally attached to the end of the crank arm, a cylinder slidably receiving the piston and through one end of which said piston rod extends, fluid pressure means connected to the cylinder to actuate the piston in said cylinder, support means pivotally connected to the other end of the cylinder and mounted for movement in a direction away from the crank arm, and means biasing the support means toward the crank arm, said lastnamed means exerting a greater force on said cylinder than the fluid pressure means but being yieldable to per- V rnit operation of thedoor in a reverse direction.

6. Door operating apparatus in the form of a toggle comprising a lever forming one leg of the toggleattached to the door for pivoting movement therewith, a piston and piston rod assembly secured to the lever forming the I adapted to be connected to a door for opening and closing the door, hydraulic pressure means adapted to be operatively connected to a door to resist opening movement of the door, control means connected to the power means to momentarily energize the power means and initiate opening movement of the door, and second control means responsive to a change in hydraulic pressure in said hydraulic pressure means to independently ener gize the power means and continue the opening move.- ment of the door.

8. In a door operatiing apparatus, a control piston operatively connected to the door, a cylinder slidably re ceiving the piston, and means connected to the cylinder to form a fluid connection between opposite sides of the piston comprising a fluid passageway, a pair of oppositely directed and series connected one-way valves in said passageway, and means for adjusting the degree of seating of each of the valves.

9. The mechanism described in claim 8 wherein the one-way valves comprise valve seats facing in opposite directions with respect to the flow of liquid therethrough, closure members adapted to move alternately toward said valve seats in response to liquid flow therethrough, and means for adjustably limiting closing movement of the closure members to provide a metering orifice.

10. In a door operating apparatus, a control piston operatively connected to the door, a cylinder slidably receiving the piston, means connected to the cylinder to form a fluid passageway between opposite sides of the second leg of the toggle, a cylinder for said piston, fluid pressure means for operating the piston, and a support for the cylinder yiel-dable under greater pressure than that I exerted by said fluid presure means.

7. Door operating apparatus comprising power means.

piston, a pair of oppositely directed one-way valves in said passageway connected in series, and a liquid reservoir communicating with said passageway intermediate the valves.

11. In a door operating apparatus, a control piston operatively connected to the door, a cylinder slidably receiving the piston, means forming a fluid passageway between opposite ends of the cylinder, and a compound check valve in said passageway comprising a valve body having oppositely facing valve seats, a closure member for each seat movable toward its respective seat in response to liquid flow therethrough, and adjustable means for limiting movement of the closure members toward their respective seats.

12. The mechanism described in claim 11 wherein the closure member comprises a ball and the adjustable means comprises a set screw having a tapered end extending between the ball and its seat.

13. In a door-operating apparatus, a hydraulic cylinder, a piston therein, an axial forwardly extending extension of said piston, a restricted cylinder-portion for the reception of said extension, a by-pass from a point in said cylinder in front of said extension to a point to the rear of said piston, control means in said bypass, a controlled connection between a point in said cylinder forward of said piston but to the rear of said restriction and a point forward of the restriction.

14. Door operating apparatus comprising a hydraulic cylinder, a piston therein, an axial forwardly extending extension of said piston, a restricted cylinder-portion for the reception of said extension, a bypass from a point in said cylinder in front of said extension to a point to the rear of said piston, flow control means in said bypass, a pneumatic piston connected to said hydraulic piston, means for applying pneumatic pressure to the pneumatic piston for operating said pneumatic piston, a hydraulic pressure responsive switch connected to said hydraulic cylinder, means for operatively connecting the pistons to a door whereby said hydraulic piston will be 15'. Door operating apparatus comprising a pair of cylinders, a piston in each cylinder, a piston rod connected to each piston and to the door, means for applying fluid pressure to the end of one of said cylinders to open the door, a solenoid valve for controlling the last-named means, a hydraulic fluid in the second cylinder, means providing a metering orifice between opposite ends of the second cylinder, a pressure actuated switch in communication with the second cylinder, a first circuit for energizing the solenoid valve including a switch operable by a person wishing to open the door, and a second circuit including said pressure actuated switch for energizing the solenoid valve upon opening movement of the door.

16. Door operating apparatus comprising a first cylinder, a first piston slidably received in said cylinder and operatively connected to the door, means for applying fluid pressure to the cylinder to cause opening movement of the door, a solenoid valve for controlling the iastnamed means, a second cylinder containing hydraulic liquid, a second piston slidably received in the second cylinder and operatively connected to the door, means forming a passageway between opposite ends of the second cylinder and having a metering orifice, means for adjusting said metering orifice to regulate pressure produced in said hydraulic liquid during movement of said second piston as said door opens, a pressure responsive switch subjected to the hydraulic pressure in the second cylinder, a circuit for energizing the solenoid valve including said pressure responsive switch, and a switch in parallel with said pressure responsive switch whereby operation of the apparatus may be initiated.

17. Door actuating appartus comprising a first cylinder, a piston slidably received in said cylinder and operatively connected to the door, means for applying fluid pressure to the cylinder to cause opening movement of the door, a solenoid valve for controlling the last-named means, a second cylinder containing hydraulic liquid, a piston slid-. ably received in the second cylinder and operatively con nected to the door, means forming a passageway between opposite sides of the piston in said second cylinder and having an adjustable metering orifice, a pressure responsive switch communicating with the second cylinder at the end toward which the piston moves during opening movement of the door, a switch adapted to be closed by a person at one side of the door, a circuit for energizing the solenoid valve including said last-named switch and the pressure actuated switch in parallel, and switch means in said circuit responsive to position of the door for opening the circuit when the door is opened a predetermined amount.

18. Door operating apparatus comprising a pair of cylinders mounted in side by side parallel arrangement, a piston in each cylinder, a piston rod connected to each piston, said rods being rigidly connected together and operatively connected to the door, means for applying a difierential air pressure to opposite ends of one of said cylinders to actuate the piston therein, a solenoid valve for controlling the last-named means, means forming a passageway between opposite ends of the second cylinder, a liquid in the second cylinder, means forming a metering orifice in said passageway, a pressure responsive switch subjected to the liquid pressure in the second cylinder during opening movement of the door, means for energizing the solenoid valve including a switch adapted to be actuated by a person wishing to open the door,

means for energizing the solenoid valve responsive to the closing of said pressure responsive switch, and means for limiting opening movement of the door.

19. Door operating apparatus comprising a first cylinder, a first piston slidably received in said cylinder and operatively connected to the door, means for applying fluid pressure to the cylinder to cause opening movement of the door, a solenoid valve for controlling the lastnamed means, a second cylinder containing hydraulic liquid, a second piston slidably received in the second cylinder and operatively connected to the door, a by-pass passage between opposite ends of the second cylinder, a pair of oppositely directed one-way valves in said by-pass passage, means for adjusting the degree of seating of the valves to regulate pressure produced in said hydraulic liquid during movement of said second piston as said door opens, a pressure-responsive switch subjected to the hydraulic pressure in the second cylinder, a circuit for energizing the solenoid valve' including said pressureresponsive switch, and a switch in parallel with said pressure-responsive switch to initiate operation of the apparatus.

20. Door operating apparatus comprising a pair of cylinders, a piston in each cylinder, a piston rod connected to each piston, means to operatively connect each piston to a door, means to apply fluid pressure connected to one of the cylinders to actuate the piston therein, a liquid in the othey cylinder, hydraulic control means connected to said other cylinder to regulate the flow of liquid between opposite ends of the cylinder to control the rate of movement of the piston therein, fluid pressure responsive second control means to actuate said means to apply fluid pressure, and means forming a fluid connection between said control means and one end of said other cylinder.

21. Door operating apparatus comprising a hydraulic cylinder, a piston therein, an axial forward extension on said piston, a restricted portion adjacent one end of the hydraulic cylinder in which said forward extension is receivable, a fluid by-pass passage connected between a point on said cylinder in front of said extension to a point on said cylinder to the rear of said piston, fluid flow control means in said by-pass passage to regulate the rate of movement of said piston, a pneumatic cylinder, a piston therein operatively connected to the hydraulic piston for movement therewith in either direction, control means to actuate the pneumatic piston, and means to connect one of said pistons to a door for movement therewith.

References Cited in the file of this patent UNITED STATES PATENTS 1,018,268 Regan Feb. 20, 1912 1,201,761 Reed Oct. 17, 1916 1,429,528 Payne Sept. 19, 1922 1,494,135 Robison May 13, 1924 2,184,607 Swanson Dec. 26, 1939 2,202,303 Swanson May 28, 1940 2,283,577 Roby May 19, 1942 2,522,252 Billeter Sept. 12, 1950 2,536,489 Burke Jan. 2, 1951 2,606,022 Vander Veer et al Aug. 5, 1952