US2770297A

US2770297A - Hydraulically actuated articulated members

Info

Publication number: US2770297A
Application number: US404896A
Authority: US
Inventors: Mercier Jean; Jacques H Mercier
Original assignee: G M E CORP
Current assignee: G M E Corp
Priority date: 1954-01-19
Filing date: 1954-01-19
Publication date: 1956-11-13
Anticipated expiration: 1973-11-13
Also published as: DE1008139B

Description

NOV 13,1956 J. MERCIER ETAL 2,770,297

HYDRAULICALLY ACTUATED ARTICULATED MEMBERS Filed Jan. 19. 1954 2 Sheets-Sheet l ATTORNEYS Nov. 13, 1956 J. MERCIER Erm. 2,770,297

HYDRAULICALLY ACTUATED ARTICULATED MEMBERS Filed Jan. 19. 1954 2 Sheets-Sheet 2 .TL s l -f A? I FEV ATTO R N EYS United States Patent O HYDRAULICALLY ACTUATED ARTICULATED MEMBERS Application January 19, 1954, Serial No. 404,896 23 Claims. (Cl. 1GO-18S) This invention relates to the art of hydraulically actuated articulated members and more particularly to hydraulically actuated hatch covers.

As conducive to an understanding of the invention, it is noted that mar-ine hatch covers generally comprise a plurality of extremely heavy rectangular panels which lie in a horizontal plane. The use of a derrick or hoist to lift the individual panels out of the hatchway and to stack them in position away from the hatch so that it is open to receive cargo, is a burdensome and time-consuming chore that requires many personnel and delays the loading and unloading of a ship.

Where a plurality of hingedly connected pairs of hatch covers are used to cover the hatchway, and hydraulic means are used to open the hatchway, if one of the pairs of hatch covers folds to substantially vertical position before movement of the other pair or pairs of hatch covers, the folded pair may tilt about its hinge causing considerable stress and strain on such hinge and disengagement of the rollers of the hatch doors from the guide rails of the hatch opening along which they normally ride.

It is Iaccordingly among the objects of the invention to provide a hatch cover which with but a simple manipulation by a crew member without undue effort on his part, may readily be moved from closed to open position and vice-versa without the need of a derrick or hoist.

Another object of the invention is to provide a hydraulic system for actuating a plurality of pairs of hatch covers, which will insure that all of the pairs of hatch covers will open substantially half way before any one pair is moved to vertical position thereby preventing undue strain and stress on hinges, rollers and the like.

Another object of the invention is to provide a hydraulic system that is simple, compact, having but few moving parts that are not likely to become out of order, that is eicient in operation, requiring but a minimum quantity of fluid under pressure for opening and closing of the hatchway with resultant low power consumption.

According to one aspect of the invention, a pair of hydraulic units, one of which is double acting and the other single acting, are mounted in opposed relation rcspectively in each of a pair of hingedly connected members and the plungers of such hydraulic units react against opposed sides of a reaction member idly mounted between such hingedly connected member on a pivot rigid with one of said members, in such manner that the hinged members may be moved from one extreme position to another extreme position. Desirably the effective area of the plunger of the single acting unit is greater than that of the double acting unit so that it will first operate to move the hingedly connected member.

According to another aspect of the invention, a pair of hydraulic units are mounted in opposed relation respectively in each of a pair of hingedly connected members and the plungers of such units react against opposed sides of a reaction member idly mounted between the hingedly connected members on a pivot rigid with one ice of said members, in such manner that the hinged members may be moved from one extreme position to another. The equipment is designed so that the perpendicular distances to the hinge connection, from lines representing the initial `direction of the forces applied by the plungers to points on opposed sides of the reaction member will differ.

In the accompanying drawings in which are shown one or more of various possible embodiments of the several features of the invention,

Fig. l is a fragmentary perspective view of the deck of a ship showing a hatchway with the hatch doors in open position,

Fig. 2 is :a transverse sectional view of a pair of hatch door panels with the associated hydraulic vactuating system,

Fig. 3 is a perspective View of a hinge,

Fig. 4 is a plan view of a reaction member,

Fig. 5 is a diagrammatic view of a plurality of pairs of hatch covers,

Figs. 5a and 5b are diagrammatic views of the plurality of pairs of hatch covers in various posit-ions,

Figs. 6 and 7 are charts illustrating the operation of the equipment.

Referring now to Fig. l of the drawings, in the illustrative embodiment shown, the deck 11 of a ship has a conventional hatch opening l2 having a supporting rail 13 along each side. A plurality of substantially rectangular hatch covers 14 are provided of length such that the ends of each cover may rest on the rails 13 when in hatch :closing position as shown in Fig. 2.

As illustratively shown, two pairs of hatch covers 14 are provided, although it is to be understood that but a single pair or more than two pairs could be used. The two pairs of hatch covers, designated A and B, each has two panels A-1, A-Z; B-l, B-2 respectively with the panel A-l being pivotally connected to the adjacent end 15 of the opening 12 by means of hinge members 16. The adjacent lower edges 17 of the paneis of each pair of covers are connected 'as by means of hinges 18 and the adjacent upper edges of the panels A-2 and B-l are also connected as by hinges 19. The panels A-2 and B-1 at each corner of their commonly connected edges and each [corner of the free edge of panel B-2, desi-rably mount rollers 16 which ride along the beams 13 to facilitate opening and closing of said panels.

As the mechanism to actuate each of the pairs of covers is identical, only that associated with the cover A will be described in detail. The hinge 18 connecting the adjacent lower edges 17 of the panels A-l and A-2 has two hinge plates 20 (Fig. 3) which are affixed to beams 21 extending the length of each of the panels adjacent the edges 17 as is clearly shown in Fig. 2. Although but a single hinge 13 could connect the two panels A-l and B-l, in the illustrative embodiment shown, two hinges 18 are provided, one near each of the ends of the panels.

The hinges may be of the type having two spaced fingers 22 on the hinge plate affixed to one of the panels i. e., panel A1 straddled by two spaced fingers 23 on the hinge plate affixed to the other panel,I with a pintle or pin 2li extending through such fingers in conventional manner. The central finger which is generally provided to fit between the two spaced fingers 22 of the first hinge plate is desirably eliminated in the present construction and in its place a reaction member, preferably a plate 25 is provided.

The plate 25 (Fig. 4) may be substantially triangular in shape and has an

opening

26, 27 and 23 at each of its corners. The plate 25 is desirably positioned in a vertical plane with one of its corners between the two spaced 3 lingers 22 of the rst hinge plate so that the pin 24 extends freely through the opening 26 as is shown in Fig. 2.

Means are provided coacting with the reaction plate 25 to move the panels A-1 and A-2 from the closed position shown in Fig. 2 in which they lie in side by side relationship in -a horizontal plane, to open position as shown in Fig. l, in which they extend substantially parallel to each other in a vertical plane.

To this end, a pair of opposed actuating means are provided illustratively

hydraulic units

31 and 32 mounted respectively in panels A-1 and A-2. Although the opposed units 31, 32 m-ay be mounted in any suitable manner, the rear end of each of the units is desirably pivotally mounted as at 33 to a beam 34 extending longitudinally of the associated panel approximately midway between its side edges. The outer ends of the

reciprocable plungers

35, 36 of

units

31 and 32 respectively are pivotally connected to the reaction plate 25 by means of

pins

33, 39 extending through the outer end of the plungers and the openings 27 and 2S respectively. The hydraulic unit 31 is of the single acting type and has a cylinder 41 with but a single control port 42, preferably at one end. The hydraulic unit 32 is of the double acting type having a piston 43 affixed to its plunger 36 and slidably mounted in the bore of the cylinder 44 of such unit. The cylinder 44 has a pair of control ports 45 `and 46 positioned on each side of the piston 43.

ln the illustrative embodiment shown, as both hydraulic units are connected to the same source of iiuid under pressure, to insure that only one of the units will operate at a time, the effective areas of the reciprocating members of each of the units differ. Thus, for example, the effective area of the plunger 35 of the single lacting hydraulic unit 31 is greater than the effective area of the piston 43 of the double acting unit 32. Desirably, a stop 51 is aixed to the end of the plunger of the single acting unit 31 and a stop 52 is aixed to the end of cylinder 44 of double acting unit 32 to limit the outward movement of the plungers from their associated cylinders.

Although the hydraulic units may be supplied with fluid under pressure in any suitable manner, in the illustrative embodiment herein shown, the fluid pressure system comprises a reservoir 55 connected by line 56 to a pump 57 driven by motor M. The outlet of pump 57 leads through a one-way check valve S and is connected by line 59 to a pressure accumulator 61, such as for example, the Olaer accumulator manufactured by Greer Hydraulics, Inc. of Brooklyn, New York. rlfhe line 59 also leads to the inlet port 63 of a selector valve 64. The valve 64 in addition to port 63 has a discharge port 65 connected to the reservoir 55 by line 66 and two control ports 67 and 68 connected respectively by line 69 to control ports 42 and 46 of the hydraulic units and by line 71 to control port 45 of unit 32. The selector valve is of the conventional three-way type having an off position and two operating positions. In one of the operating positions, the inlet port 63 and control port 67 are connected so that uid under pressure may llow into the control ports 42 and 46 of the hydraulic units and the discharge portv 65 and control port 68 are connected so that the fluid will flow from hydraulic unit 32 to the reservoir. In the other operating position the inlet port 63 and the control port 68 are connected so that fluid under pressure may flow into the control port 45 of hydraulic unit 32 and the discharge port 65 is connected to control port 67 so that iluid will flow from the control ports 42 and 46 of the two hydraulic units back to the reservoir 55.

Operation To illustrate the operation of the equipment it will first be described with respect to a system having but a single pair of hatch covers such as A-l, A-2 shown in Fig. 1. To ready the system for operation, with valve 64 in off position, the accumulator 61 is rst charged by energizing motor M. When the pressure in the accumul-ator has reached a desired value, the motor M will be de-energized by conventional pre-set pressure control means (not shown) associated therewith.

To operate the hatchway, the selector valve 64 is actuated so that the inlet port 63 is connected to control port 67 and discharge port 65 is connected to control port 68. As a result, lluid under pressure will flow from the accumulator 61 through

ports

63, 67, line 69 into the ports 42 and 46 of the

hydraulic units

31 and 32. As the effective area of the plunger 35 is greater than that of the piston 43, and also due to the friction in the portion of line 69 between

units

31 and 32, the plunger 35 will first move to the right from the position shown in Fig. 2. As a result, the reaction plate 25 will be pivoted in a clockwise direction about the hinge pin 24 and a resultant force directed upwardly will be provided with the result that the two panels A-l, A-2 will move upwardly from their normal horizontal position. As the force exerted by the plunger 35 of unit 31 is greater than that exerted by the plunger 36 of the hydraulic unit 32, the latter unit will not function at this time. Consequently, it is only the force exerted by the plunger 35 that serves to lift the panels. During the movement of the plunger 35 of hydraulic unit 31, the plunger 36 of the hydraulic unit 32 will not move and will be in the position shown in Fig. 2. When the plunger 35 has reached the limit of its stroke, i. e., when stop 51 abuts against the end of the cylinder 41, the panels will have been pivoted each to a 45 degree angle, i. e., the angle between the panel at the pivot point 24 will be approximately 90 degrees.

At this time, since the plunger of the hydraulic unit 31 is incapable of further movement, as its stop 51 is against the end of cylinder 4l, the tluid under pressure in line 69 will then cause the plunger 36 of hydraulic unit 32 to move to the left As no movement will be imparted to the plunger of hydraulic unit 31 due to the greater area thereof against which the force of the uid under pressure is exerted, the movement of the plunger of hydraulic unit 32 reaching against plate 25 will further pivot the panels, until the piston 43 of the hydraulic unit 32 abuts against the stop 52 of the cylinder 44 at which time the doors will be in substantially vertical position.

In Fig. 7, the curve T which follows a sinusoidal law, represents the torque required to lift the panels from horizontal to vertical position.

As the hydraulic unit 32 does not function to lift the panels until they are at a degree angle with respect to each other, i. e., are half Way open, at which time considerably less torque is required to lift the panels than when they were in the original horizontal position, the dimensions of the hydraulic unit 32 may be considerably smaller than that of the hydraulic unit 31. As a result, the quantity of fluid under pressure required to be forced into the hydraulic unit 32 for full stroke is much less than that required for unit 31. Since less fluid is used than would be required if both hydraulic units were the same size, less power is required to recharge the accumulator which of course, entails considerable saving.

With the panels in vertical position, to move the panels to closed position it is merely necessary to set the selector valve so that the inlet port 63 is connected with control port 68 and the discharge port 65 is connected with control port 67. As a result fluid under pressure will flow from the pressure accumulator through line 71 into portV 45 of the hydraulic unit 32.

With the panels in vertical position, but little force is required to move them slightly away from vertical and thereafter the panels, due to their weight, require little or no force to move them to closed position. Consequently, the relatively small hydraulic unit 32 is adequate to start the closing action of the panels and to insure that they will move to closed horizontal position.

It is noted that during the first movement of the panels to their half-way position in which only the hydraulicV unit 3l is functioning, due to the fact that no fluid is owing through the line 7l there will be no back pressure and hence the liquid in the pressure accumulator need not be under as great a pressure as would be necessary if there was back pressure in the system which had to be overcome during initial movement of the panels. Although there is back pressure `when the second hydraulic unit 32 is operating, due to the ilow of uid through port d5 and the associated line 7l, as the pressure on the liquid reacting against the piston i3 need not be as great as that required to initially move the panels, the maximum pressure required in the accumulator to move the doors from half-way position to fully open position still is below that to which it is normally charged.

In addition to providing a great saving in power to open the panels, the provision of the single acting hydraulic unit in conjunction with a double acting unit insures that in a system in which there are a plurality of pairs or" panels of the above type connected to each other, all of the pairs will first assume half-way open position before any one pair attains a vertical position. Consequently, no one pair of panels will have to travel a considerable distance before the entire set of panels is fully open, with the harmful eiect that the vertical pair of panels traveling a considerable distance may tilt in one direction or the other causing undue strain on the hinge connection between such pair of panels and the adjacent pair and also causing the rollers associated with the vertical pair of panels to move off their tracks and possibly Jam.

Referring to Fig. 5 of the drawings, with two pairs of panels illustrated, when fluid under pressure is applied to line 69, for example, as the single acting units 31 are of greater size than the double acting units 32, one o1' the other of the units 3i would rst operate to raise its associated pair of panels, Once one or the other of the units 3l operated, as the pair of panels associated therewith require less and less torque to open as they are moved from horizontal position, the pair of panels trst moving away from horizontal position would otter less resistance to the tiow of uid in line 69 and hence such pair of panels would continue their upward movement and substantially no fluid would tlow `into the other hydraulic units. As the hydraulic unit 31 associated with panel A-l in addition to the load of the panels A-i and A-Z would also have to drag the panels B-l and B-2 toward the hinge ld before the panels A-l and A-Z could move upwardly, the hydraulic unit 3l of panel B-l would in all probability first operate.

As previously described with respect to the panels shown in Fig. 2, the hydraulic unit 3l of panel B-l would move to the limit of its stroke causing the panels B-l and B-2 to move upwardly until an angle of approximately 90 degrees was provided between such two panels as diagrammatically shown in Fig. Sa.

At this time, due to the fact that the area of `the hydraulic unit 3l. of panel A-l is greater than that of the hydraulic units 32, the hydraulic unit 31 would then function and the panels A-l and A-2 would then move to assume an angle of 90 degrees therebetween drawing the panels B-ll and B-2 toward the hinge 16.

At this time, the doors would be in the position shown in Fig. 5b. Since the hydraulic units 31 had reached the limit of their strokes, one or the other of the hydraulic units 32 would next be actuated. In view of the available pressure in the system, both of the hydraulic units 32 would operate, but as the hydraulic unit 32 of panel A-2 must also pull the panels B-l and 13 2, the hydraulic unit 32 of panel B-2 would operate at a much greater rate and would cause the panels B-l and B-2 to move into vertical position.

As the hydraulic unit 32 of panel A-2 has also been operating at this time, when the panels B-ll and B-Z reach vertical position, the panels A-1 and A-2 would have approached such position and consequently the Cil 6 panels B-l and B-2 would have but little distance to travel in vertical position before the panels A-l and`A-2 also had reached this position and all panels were fully open in vertical position.

As a result, tilting of any of the pairs of panels is substantially precluded and hence there is no likelihood of injury to the hinge connection or dislodgement of the rollers from the guide rails.

For most eicient operation of the hatch doors, it is desired that the hydraulic actuating system utilize as little fluid under as low a pressure as possible.

The curve of the torque T (Fig. 7) required to lift a pair of hatch covers may be represented by the following formula:

F=Pressure eiective area of plunger D=R sine a R=distance from pivotal connection of reaction plate to point of application of force thereto a=the angle between the extension of a line from the pivotal connection of the reaction plate through the point of application of force thereto and a line representing the direction of application of said force to the reaction plate Thus D=the perpendicular distance of the pivotal connection of the reaction plate from a line representing the initial direction of the force applied to a point on one side or" the reaction plate and D can be varied by changing either R or a Hence, the eicient operation afforded by the use of a single acting hydraulic unit may be enhanced by proper selection of the angles a (X and Y in Fig. 6) and the distance R1 and R2 shown in Fig. 6.

ln the curve of Fig. 7 the torque T necessary to lift the panels is maximum when the pair of panels is in horizontal position and minimum when they are in vertical position, i. e., when the two panels have moved a total of 180 degrees.

With a given force F1, it is apparent from Fig. 6 that the greater the angle X up to degrees, the greater the distance D1 and hence the greater the torque T1 which will be available to move the hatch covers.

With the maximum possible D1 provided. by the largest angle X that will still permit full movement of the panels to vertical position, due to their physical dimensions, the effective area A1 of the plunger of hydraulic unit 31 and the pressure P1 are selected so that the product of the three parameters D1, P1 and A1 will initially provide the desired torque T1 to lift the panels from horizontal position, i. e., a torque greater than T maximum in Fig. 7, yet which` will still be suicient to move the panels to their half-way position indicated at M in Fig. 7.

The curve T1, representing the torque F1D1 is shown in Fig. 7.

When the pair of panels has attained approximately half-way position, only the hydraulic unit 32 will then operate.

From the chart shown in Fig. 7, it is apparent that less torque is now required to move the panels to vertical position. l

As P1 is predetermined, based upon the pressure required to actuate hydraulic unit 31, the values of A2 of the piston of hydraulic unit 32 land D2 are selected so that a minimum of fluid under pressure is required to provide the necessary torque T2 to move the panels to Vertical position. Thus, angle Y is made as large as possible, (but less than 90 degrees) and A2 as small as possible.

A typical curve T2 representing the torque FzDz provided by hydraulic unit 32 is shown in Fig. 7.

By the selection of the appropriate angles X and Y, each of which is less than 90 degrees, and distances Ri and R2, the pressure in the system and the quantity of fluid required to be forced from the accumulator can be kept to a minimum. As a result, a minimum of power is required to charge the accumulator with attendant saving in cost. Where the system uses no accumulator but a pump only to supply the fluid under pressure, the power required to actuate the pump motor will be kept to a minimum.

With the equipment above described, dependable actuation of a pair of hatch covers is provided with low power consumption and where a plurality of pairs of covers are used, injury to the hinge connection is substantially precluded.

As many changes could be made in the above equipment, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, 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.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent of the United States is:

l. A system of the character described comprising a pair of pivotally connected members, a hydraulic unit in each of said members mounted in opposed relation, each of said units having a reciprocable plunger, a reaction member, a pivotal mount for said reaction member, one end of each of said plungers being connected to the reaction member on opposed sides thereof respectively, whereby upon movement of said plungers toward each other, said connected members will be rotated about their pivotal mount, the effective area of one of the plungers against which fiuid under pressure will react to move said plunger toward the other plunger being greater than the effective area of said other plunger against which fluid under pressure will react.

2. A system of the character described comprising a pair of pivotally connected members, a hydraulic unit in each of said members mounted in opposed relation, each of said units having a reciprocable plunger, a reaction member, a pivotal mount for said reaction member, one end of each of said plungers being connected to the reaction member on opposed sides thereof respectively, whereby upon movement of said plungers toward each other, said connected members will be rotated about their pivotal mount, one of said hydraulic units being of the single acting type and the other of the double acting type, the effective area of the single acting unit against which fluid under pressure will react being greater than the effective area of the double acting unit.

3. A system of the character described comprising a pair of pivotally connected members, a hydraulic unit in each of said members, mounted in opposed relation, each of said units having a reciprocable plunger, a reaction member, a pivotal mount for said reaction member extending parallel to the pivotal mount of said pair of members, one end of each of said plungers being connected to the reaction member on opposed sides thereof respectively, whereby upon movement of said plungers toward each other said connected members will be rotated about their pivotal mount, the eective area of one of said hydraulic units against which fiuid under pressure will react being greater than the effective area of the other hydraulic unit.

4. A system of the character described comprising a pair of pivotally connected members, a reaction member, a pivotal mount for said reaction member, means carried by each of said members operatively connected to said reaction member on opposed sides thereof respectively,

to exert force against said reaction member to rotate said connected members about their pivotal mount, the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of force thereto by one of said means differing from the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of force thereto by the other of said means.

5. A system of the character described comprising a pair of pivotally connected members, a reaction member, a pivotal mount for said reaction member extending parallel to the pivotal mount of said pair of members, a hydraulic unit carried by each of said pair of members, mounted in opposed relation, each of said units having a reciprocable plunger operatively connected at one end to said reaction member on opposed sides thereof respectively to exert force against said reaction member to rotate said connected members about their pivotal mount, the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of force thereto by the plunger of one of said hydraulic units being greater than the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of force thereto by the plunger of the other hydraulic unit.

6. The combination set forth in claim 5 in which the effective area of the hydraulic unit against which fluid under pressure will react to effect movement of one of said plungers is greater than the effective area of the other hydraulic unit against which uid under pressure will react to effect movement of the other of said plungers.

7. The combination set forth in claim 5 in which the effective area against which fluid under pressure will react to effect movement of the plunger of the first of said hydraulic units is greater than the effective area against which fluid under pressure will react to effect movement of the plunger of the other hydraulic unit.

8. The combination set forth in claim 5 in which one of said hydraulic units is of the single acting type and the other of the double acting type.

9. The combination set forth in claim 5 in which said first hydraulic unit is of the double acting type and the other hydraulic unit is of the single acting type.

10. The combination set forth in claim 5 in which said first hydraulic unit is of the double acting type and the other hydraulic unit is of the single acting type and the effective area against which fluid under pressure will react to effect movement of the plunger of the single acting unit is Igreater than the effective area against which fluid under pressure will react to effect movement of the plunger of the double acting unit.

ll. A system of the character described for controlling access to a hatchway comprising a plurality of pairs of pivotally connected panels adapted to extend over said hatchway to close the latter, adjacent panels of each pair being pivotally connected to each other, each of the pairs of said pairs of panels having a hydraulic unit mounted therein in opposed relation, each of said units having a reciprocable plunger, a reaction member for each of the pairs of panels, a pivotal mount for each of said reaction members, one end of each of the plungers being connected to opposed sides respectively of the associated reaction member, whereby upon movement of said plungers toward each other, the panels of each pairv will be rotated about their respective pivotal mounts, the effective area of one of the plungers against which fiuid under pressure will react to move said plunger toward the other plunger being greater than the effective area of said other plunger against which fluid under pressure will react.

l2. A system of the character described for controlling access to a hatchway, comprising a plurality of pairs of .pivotally connected panels adapted to extend over a hatchway to close the latter, adjacent panels of each pair being pivotally connected to each other, a reaction member for each ot the pairs of panels, a pivotal mount for each of said reaction members, means carried by cach of said panels operatively connected to the associated reaction member on opposed sides thereof respectively, to exert force against said reaction member to rotate the pairs of panels about their pivotal mounts, the perpendicular distance to the pivotal mount ot each reaction member from a line representing the direction of applica tion of torce thereto by one of the associated means differing from the perpendicular distance to the pivotal mount of said reaction member from a line representing the direction of application of force thereto by the other associated means.

13. A system of the character described tor controlling access to a substantially rectangular hatchway, comprising a plurality of pairs of pivotally connected substantially rectangular panels adapted to extend over said hatchway to close the latter, adjacent panels ot each pair f being pivotally connected to each other, the panel of one of said pairs adjacent one end of the hatchway being hinged to the latter, each of the panels of said pairs of panels having a hydraulic unit mounted therein in opposed relation, each of said units having a reciprocable plunger, a reaction member for each of the pairs ot panels, a pivotal mount for each of said reaction members, one end of each of the plungers being connected to opposed sides respectively of the associated reaction member, whereby upon movement of said plungers toward each other, the panels of each pair will be rotated about their respective pivotal mounts, the eiective area of one of the hydraulic units associated with each pair of panels, against which fluid under pressure will react being greater than the effective area of the other associated hydraulic unit.

14. The combination recited in claim 13 in which the perpendicular distance to the pivotal mount of each reaction member from a line representing the direction ot force thereto by the plunger of one of the associated hydraulic units is greater than the perpendicular distance to said pivotal mount from a line representing the direction of application of force to the reaction member from the plunger of the other associated hydraulic unit.

l5. A system of the character described for controlling access to a substantially rectangular hatchway comprising a pair of substantially rectangular pivotally connected panels adapted to extend over the hatchway to close the latter, means hingedly connecting one of the panels to one end ot the hatchway, a hydraulic unit in each of said panels, mounted in opposed relation, each of said units having a reciprocable plunger, a reaction member, a piv otal mount for said reaction member, one end ot each of said plungers being connected to the reaction member on opposed sides thereof respectively, whereby upon movement of said plungers toward each other, said panels Will be rotated about their pivotal mount and the hinge connection, the effective area of one of the plungers against which iiuid under pressure will react to move said plunger toward the other plunger being greater than the etective area of said other plunger against which tluid under pressure will react.

16. The combination set forth in claim 15 in which the pivotal connection for said panels and the pivotal mount for the reaction member are identical.

17. The combination set forth in claim 15 in which the pivotal connection for said panels and the pivotal mount for the reaction member are identical and the reaction member comprises a substantially triangular plate pivoted 4at one corner on its pivotal mount and pivotally connected at its two other corners to the ends of the associated plungers.

18. The combination recited in claim 15 in which one end of each of the hydraulic units is pivotally connected to the associated panel between its side edges.

19. A system of the character described comprising a pair of pivotally connected members, a reaction member, a pivotal mount for said reaction member, means carried by each of said members operatively connected to said reaction member on opposed sides thereof respectively, to exert force against said reaction member to rotate said connected members about their pivotal mount, the angle defined between a line representing the direction of original application of force by one of said means and the extension or" a line from the pivotal mount of said reaction member through the point of application of such force ditlering from the .angle deiined between a line representing the direction of original application of force by the other of said means and the extension of a line from the pivotal mount of said reaction member through the point of application of such last named force.

2i). The combination recited in claim. 19 in which said means comprises two units, one capable of exerting greater force than the other.

21. The combination recited in claim 20 in which the unit capable of exerting greater force is associated with the smaller angle.

22. A system of the character described comprising a pair of pivotally connected members, `a reaction member, a pivotal mount for said reaction member, means carried by each of said members operatively connected to said reaction member on opposed sides thereof respectively, to exert force against said reaction member to rotate said connected'members about their pivotal mount, the product of the force originally exerted by one of said means and the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of such force thereto by the associated means being greater than the product of the force originally exerted by the other of said means and the perpendicular distance to the pivotal mount of the reaction member from a line representing the direction of application of such second force thereto.

23. The combination recited in claim 22 in which the angle eiined between a line representing the direction of original application of force by said rst means and the extension of a line from the pivotal mount of said reaction member through the point of application of such force is less than the angle defined between a line representing the direction of original application of the second force by the other of said means and the extension of a line from the pivotal mount of said reaction member through the point of application of such second force,

References Cited in the iile of this patent UNITED STATES PATENTS 2,491,261 Greer etal Dec. 13, 1949