US3091305A - Hydraulically operated portable scaffold - Google Patents

Description

May 28, 1963 E. C. PICKARD ETAL HYDRAULICALLY OPERATED PORTABLE SCAFFOLD 5 Shee ts-Sheet 1 Filed April 28. 1961 May 28, 1963 E. c. PICKARD ETAL 3,091,305

HYDRAULICALLY OPERATED PORTABLE SCAFFOLD 5 Sheets-Sheet 2 Filed April 28, 1961 May 28, 1963 E. c. PICKARD ETAL 3,091,305

HYDRAULICALLY OPERATED PORTABLE SCAFFOLD Filed April 28. 1961 5 Sheets-Shet 3 their 3 May 28, 1963 E. c. PICKARD ETAL 3,091,305

HYDRAULICALLY OPERATED PORTABLE SCAFFOLD 5 Sheets-Sheet 4 Filed April 28, 1961 May 28, 1963 E. c. PICKARD ETAL 3,091,305

HYDRAULICALLY OPERATED PORTABLE SCAFFOLD 5 Sheets-Sheet 5 Filed April 28, 1961 3,091,305 HYDRAULICALLY OPERATED PORTABLE SCAFFOLD Edgar C. Pickard, Glenshaw, Pa, and William R. .lacie son, Youngstown, and George A. Grappo, East Palestine, Ohio, assignors to Fordees Corporation, Leetonia,

Ohio, a corporation of Ohio Filed Apr. 28, I961, Ser. No. 106,310 Claims. (ill. 182-141) This invention relates to portable elevator apparatus and more particularly to a hydraulically elevatab le platform adapted to replace conventional scaffolding used in masonry work and other similar applications.

Although not limited thereto, the present invention is particularly adapted for use in applications where it is necessary to provide a scaffold for supporting men and materials above ground level. Such applications include, for example, the erection of building walls or replacing the brickwork in the slag pockets and uptakes of a steelmaking open hearth furnace.

In the past, scaffolding has usually been erected manually from lumber or fabricated steel sections which may be locked together one above the other. The erection and dismantling of such scaffolding, however, is costly, time consuming and sometimes dangerous. In addition, since scaffolding of this type must be built up in layers or tiers, it has the disadvantage of sometimes requiring the workman on the scaffold to stoop below or reach above a comfortable working level where he functions most efficiently.

As an overall object, the present invention seeks to provide a portable, hydraulically elevatable platform which may be used to replace conventional scaffolding or for elevating heavy articles and other similar applications.

More specifically, an object of the invention is to provide a hydraulically elevatable platform of the type described which provides for automatic, or at least semiautomatic, raising or lowering of workmen and materials to any desired height.

Still another object of the invention is to provide apparatus for expanding or collapsing a plurality of telescoping hydraulic cylinders or the like at the same rate so as to maintain a platform supported on those cylinders in a horizontal plane at all times.

In accordance with the invention, there is provided a base mounted on wheels or crawlers and which carries a plurality of telescoping, hydraulic cylinders or rams adapted to rise in a vertical direction. Supported by these rams is a horizontal platform, the arrangement being such that the platform may be raised or lowered as the hydraulic rams are raised or retracted, respectively.

In order to maintain the platform horizontal at all times and to prevent bending of the cylinders or rams due to unequal loadings, it is necessary to raise and retract all cylinders at the same rate. Accordingly, fluid metering devices are provided for delivering controlled amounts of fluid under pressure to all cylinders. In the embodiment of the invention shown herein, the fluid metering devices comprise hydraulic pump-motors which are geared together such that all pump-motors will operate in synchronism and deliver the proper amount of fluid under pressure to each cylinder.

3,091,305 Patented May 28, 1963 Although hydraulic pump-motors will meter the proper amount of fluid to the cylinders on the upward stroke of the platform, it has been found that when it is desired to lower the platform, its weight will not be sufficient to overcome the internal resistance of the pump-motors so as to force fluid out of the cylinders and collapse the same. Accordingly, in accordance with another aspect of the invention, means are provided for forcibly driving all pump-motors when it is desired to lower the platform whereby the pump-motors will expel fluid from each of the cylinders at controlled rates to maintain the platform level and prevent any binding of cylinders.

The above and other objects and features of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings which form a part of this specification, and in which:

FIGURE 1 is a side elevational view of the portable scaffold of the invention;

FIG. 2 is an end view of the scaffold shown in FIG. 1 and illustrating in dotted outline the expanded or elevated position of the platform;

FIG. 3 is a top view of the base and cylinder arrange ment of the invention taken substantially along line Ill--III of FIG. 1;

FIG. 4 is a cross-sectional view of the fluid metering motors of the invention taken substantially along line -lVIV of FIG. 3;

FIG. 5 is a cross-sectional view taken along line V--V of FIG. 4; and

FIG. 6 is a schematic diagram of the fluid control cir' cuit for the apparatus shown in FIGS. 14.

Referring now to the drawings, and particularly to FIGS. 1, 2 and 3, the portable scaffold shown includes a fabricated base 10 supported on a plurality of wheels 12, it being understood that the wheels may be replaced by crawlers or other ground-traversing means. Carried on the base 10 are six vertically expandable telescoping hydraulic cylinders 14a, 14b, 14c, 14d, 14c and 14 As shown, each of the cylinders 1411-14 is supported in an upright or vertical position by a plunality of gussets 16, these gussets being circumferentially spaced around each cylinder. Positioned on the tops of the cylinders 14a 14f is an elevatable platform 18 having a plurality slideable, retractable bars or arms 20 around its periphery on all four sides of the platform. These arms may be selectively extended to support planks 22 (FIG. 2) whereby the cross-sectional area of the platform 18 may be effectively increased.

Also supported on the base 10 is an electric motor 24 which drives a hydraulic pump, generally indicated at 26. At the right end of the base 10 as shown in FIGS. 1 and 3 is an operators console 28 having a plurality of valve control levers 3t thereon, the purpose of these levers being to operate valves which, in turn, control the various hydraulic operating instrumentalities of the scaffold in a manner hereinafter described.

Carried at the four corners of the base '10, adjacent the wheels 12, are four hydraulic jacks 32a, 32b, 32c and 32d. Each of the jacks 32a32d comprises a hydraulic cylinder having a pad 34 secured to the end of its piston rod and adapted to engage the ground surface when the hydraulic cylinder is pressurized to move its piston downwardly. The purpose of the jacks 32c-32d is to level the base and the platform 18 carried thereby. In this respect, levels 36 are provided at the four corners of the base 10. As will hereinafter be explained, each of the jacks 32a32d is provided with an associated one of the control levers 30, the arrangement being such that each lever may be actuated to either raise or lower one of the pressure pads 34. In this manner, each of the jacks 32a-32d will be pressurized to engage the pads 34 with the ground surface. Thereafter, the base 10 and platform 18 may be leveled by adjusting the various jacks while observing the levels 36 at the four corners of the base.

In using the scaffold of the invention, it will first be rolled into position on wheels 12 and the jacks 32a32d thereafter pressurized to fix the base 10 in position and level the same. Thereafter, the six telescoping cylinders 14a14f may be pressurized to elevate the platform 18 to any desired position, the fully extended position of the platform being shown in dotted outline in FIG. 2. In order to prevent binding of the cylinders 14a14f during the time that the platform 18 is elevated or lowered, and to maintain the platform level, it is necessary that all cylinders expand at the same rate. Since all cylinders are of the same size in the embodiment of the invention shown herein, this means that fluid under pressure must be delivered to, or expelled from, each one of the cylinders 14a-14f at the same rate.

In order to facilitate expansion or contraction of the cylinders 14a-14f at the same rate, means including fluid metering apparatus, generally indicated at 38, is provided. With reference to FIG. 3, it will be noted that the fluid metering apparatus 38 is mounted between a pair of plates 40 and 42 which extend upwardly from one side of the base 10. The fluid metering apparatus includes seven hydraulic pump-motors 44[l-44g circumferentially spaced around a common axis.

As shown in FIGS. 3 and 4, the fluid metering apparatus 38 is mounted on a circular plate 46 having a cup-shaped cover 48 secured to its outer periphery as by means of'bolts' 50. The cover 48, in turn, is secured by means of bolts or other suitable fastening means, not shown, to the plate 40. As shown, the hydraulic pumpmotors 44a44f are bolted or otherwise securely fastened to the circular plate 46 and are provided with shafts 52a52f which extend through associated openings in the circular plate 46. Connected to each of the shafts 52a52-f are pinion gears 54a54f which mesh with a large central idler gear 56 rotatable about an axis 58 which coincides with the axis about which the pump-motor 44a44f are circumferentially spaced. As Will be understood, the gear 56, together with the gears 54a-54f comprises a planetary gear arrangement wherein all of the gears 54tZ-54f must rotate in synchronism, thereby causing all of the pump-motors 44a44f to also operate in synchronism.

The pump-motors 44a44f may, for example, be of the type manufactured by the Dennison Engineering Company of Columbus, Ohio, and designated Model TMB l lF. A device of this type may be used as a hydraulic pump or as a hydraulic motor interchangeably without adjustment or alteration. Alternatively, the devices 44a44f may comprise hydraulic gear motors.

As shown in FIG. 5, each pump-motor unit consists of three major components: A housing 60 which provides a port connection 61 and a support for the bearings which carry the shafts 52a-5-2f; a pump cartridge,

not shown herein in detail, consisting of a rotor, vanes and cam rings; and a cap 64 with a port connection 66. Each pump-motor 44a44f will operate in either direction of rotation as a pump or motor. Changing the direction of shaft rotation reverses the direction of flow when used as a pump; while changing flow reverses direction of shaft rotation when used as a motor. Thus, either one of the ports 66 or 61 may be alternately used as an input port while the other is used as an output port. By introducing fluid pressure into one of the ports of any one of the pump-motors 4411-441, it will act as a motor to drive all other pump-motors in synchronism. Furthermore, even though pressure is delivered to a plurality of the pump-motors, they will operate in synchronism to deliver fluid at their output ports at the same rate by virtue of the fact that they are all mechanically interconnected through the gears 54a54f and gear 56.

The hydraulic control circuit for the scaffold of the invention is shown in FIG. 6. It comprises the motor 24 which drives pump 26 through mechanical linkage 68. The pump input port 70 is connected to a hydraulic reservoir 72 as shown, while the pump output port 74 is connected through conduit 76 to the input ports 78 and 79 of each of five control valves 80, 82, 84, 86 and 88. Each of the valves -88 may be of the self-centering type provided with a valve member 90 having springs 92 and 94 which serve to center the valve member into the positions shown in FIG. 6-. The valve member 90 of each valve is actuated by means of one of the levers 30a30e mounted on the operators console 28 shown in FIGS. 1 and 3. With reference to valve 80, when the operators lever 30a is depressed, the valve member 90 for this valve will move downwardly; whereas when the operators lever 30a i moved upwardly, the valve member 90 will also move upwardly. When, however, the lever 30a is released, the valve member 90 will always return to its central position shown in FIG. 6.

Each valve 80-88 is provided with five output ports 08, 100, 102, 104 and 106, these ports being identified with numerals only with respect to valves 80 and 88, it being understood that the other valves are identical. The input port 79 of valve 80 is connected through conduit 76 as shown to the output port 74 of pump 26. The input port 79, of each succeeding valve 30b30e, on the other hand, is connected to the output port 106 of the preceding valve in the system, the arrangement being such that with all valves in neutral position, fluid will flow from pump 26 through the input and output ports 79 and 106, respectively, of each valve 80-88 to the reservoir 72 through conduit 81. When, however, any one of the levers 30a-30'e is moved upwardly or downwardly, the serial path from the output of the pump to the reservoir 72 will be blocked. The output port of valve 80, for example, is connected to one side of the hydraulic jack 32a having a piston 33a therein; while the output port 102 of this same valve is connected to the other side of the hydraulic jack 32a. Interposed in parallel between output port 100 of each valve 80-86 and the top of each jack are a check valve 183 and metering valve 105. Similarly, a check valve 107 and metering valve 109 are connected in parallel between output port 102 of each valve 80-86 and the bottom of each jack. The check valves Will permit free flow of fluid into the top or bottom of their associated jacks, while the metering valves will throttle the discharge of fluid therefrom, thereby providing for slow, rather than rapid, actuation of the jacks. That is, when fluid under pressure is introduced into the bottom of jack 32a through its check valve 107, for example, the metering valve at the top of the jack will prevent too rapid movement of the piston 33a under the high pressure from pump 26. In a similar manner, the output ports 100 and 102 of each of the valves 82, 84 and 86 are connected through valves 103, 105 and 107, 109 to opposite sides, respectively, of the jacks 32b, 32c and 32d. The remaining output ports 98 and 104 of each of the valves 80-88 are connected through conduit 81 to the fluid reservoir 72.

When the actuating lever 30a, for example, is pushed downwardly, the connection between the input and output ports 79 and 104 of valve 80 will be blocked while input port 78 will be connected to output port 102 to deliver fluid under pressure to the bottom of the jack 32a through its associated check valve 107, thereby forcing piston 33a and the pad 34 associated with this jack upwardly, thus lowering the machine. At the same time, the output port 100 of valve 80 will be connected to output port 98 which communicates With the reservoir 72 so that the fluid from the upper end of the jack 32a will be expelled through its associated metering valve 105 to the reservoir. To raise the machine, the lever 38 is merely raised. Under these circumstances, the connection between ports 79 and 106 will again be blocked, but now input port 96 will be connected to output port 1%, thereby pressurizing the upper end of jack 32a while expelling liquid from the lower end of the jack which is now connected to reservoir 72 through ports 1112 and 1G4.

The operation of valves 8286 is identical to that described with respect to valve 81), and it will be understood that by proper manipulation of these valves, the base and platform 18 carried thereby may be leveled.

With reference to valve 88, its output port rat is connected through the parallel combination of check valve 112 and metering valve 113 and conduit 114 to the input ports of each of the hydraulic pump-motors 4411443. The output ports of these same pump-motors are each connected through an associated valve 116a-116f to one of the telescoping hydraulic cylinders 14a-14f. Thus, in order to expand the cylinders 141144)", the actuating lever 30:? on the operators console 28 will be pulled upwardly whereby input port 78 of valve 88 will be connected to output port 100. Under these circumstances, fluid under pressure is delivered through each one of the pump-motors 4411-44 to an associated one of the telescoping cylinders 14a14f. -By virtue of the fact that all of the pumpmotors Ma-44f are mechanically interconnected through gears 56 and 54a54g (schematically illustrated by the dotted line in FIG. 6), each one must operate in synchronism to deliver fluid to its associated telescoping cylinder at the same rate. Consequently, all cylinders will expand in synchronism to maintain the platform 18 level and prevent any binding in the cylinders.

When the actuating lever see was moved upwardly, it served also to connect output port 102 of valve 8 3 to the fluid reservoir 72 through output port 104. The port 102, it will be noted, is connected through conduit 118 and valve 120 .to one port of the seventh or last pumpmotor 44g. The other port of the pump-motor 44g is connected, as shown, to the reservoir 72. The valve 120 will be normally open; and, consequently, when the cylinders 14a-14f are being expanded, the pump-motor 44g will merely act as a pump to deliver fluid from the reservoir 72 through valve 124), conduit 118, valve 88 and conduit 81 back to the reservoir.

When, however, the actuating lever 30a is moved downwardly, the input port 7 8 will be connected to output port 1192, thereby delivering fluid under pressure through conduit 118 and valve 120 to the pump-motor 44g which, in turn, causes the gear 56 shown in FIG. 4 to rotate and drive all of the remaining pump-motors Ma-44f in synchronism, but in a direction opposite to that in which they are driven when the cylinders 14a14f are being expanded. Consequently, during this time, the pump-motors ida-44f serve to dispel liquid from each of the cylinders 14a-14f at the same time. The pump-motors 4401-44 are now connected through conduit 114 and valve 112 to output port 100 which, in turn, is now connected to output port 98 which leads to the reservoir 72. In order to lock the various cylinders 14a14f in their expanded positions, the normally open valves 116414161 may be closed. A metering valve 122 connects the conduit 118 leading to pumprnotor 44g to the reservoir 72, the purpose of this metering valve being to bleed off part of the fluid under pressure supplied to the pump-motor 44g and prevent too fast a collapse of the cylinders 14a14f. Relief valve 124 serves to prevent an excessive build up of pressure in the system and will open above a predetermined pressure to bypass fluid to reservoir 72 through conduit 81.

The valve 120 will be closed by a cam 121 on the platform 18, the arrangement being such that when the cylinders 14a-14f are completely collapsed and the platform is in its lowermost position, the cam 121 will engage valve to close the same, thereby stopping rotation of pump-motor 44g and the other pump-motors connected thereto. During this time fluid will not flow through the check valve 1'23 connected in parallel with valve 120, however, the valve 123 will open when the direction of fluid flow through the pump-motor 44g is reversed (i.e., when it is being driven by the other pumpmotors Mal-44f) to permit the platform 18 to be raised from its lowermost position when cam 121 closes valve 129.

It can thus be seen that the present invention provides metering devices (i.e., pump-motors 4412-44 for supplying fluid at the same rate to all of the cylinders 1411-14 to expand all cylinders in synchronism and maintain the platform 13 level While preventing any binding in the cylinders. At the same time, the pump-motor 44g serves to drive the remaining pump-motors to expel liquid from the cylinders 14a-14f and collapse the same at the same rate to maintain the platform level while preventing any binding of the cylinders. It has been found that in the absence of means such as pump-motor 44g for driving the remaining pump-motors, the weight of the platform 18 will not be suflicient to collapse the cylinders.

Although the invention has been shown in connection with a certain specific embodiment, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements Without departing from the spirit and scope of the invention.

We claim as our invention:

1. Apparatus for elevating a substantially horizontal platform comprising a plurality of vertically disposed expandable hydraulic cylinder devices positioned at spaced points beneath said platform, each of said hydraulic cylinder devices having the same volumetric capacity and all of said cylinder devices being adapted to expand in synchronism in response to like rates of fluid flow into the cylinders, hydraulic pumping means for supplying fluid under pressure to said hydraulic cylinder devices, a plurality of hydraulic motors each having an inlet port connected to said hydraulic pumping means and an outlet port connected to an associated one of said hydraulic cylinder devices, and idler means mechanically interconnecting all of said hydraulic motors to cause the same to operate in synchronism and deliver fluid under pressure to each of the hydraulic cylinder devices at the same rate.

2. Apparatus for elevating a substantially horizontal platform comprising a base, a plurality of verticallyexpandable hydraulic cylinder devices positioned between said base and said platform at spaced points, each of said hydraulic cylinder devices having the same volumetric capacity, a plurality of hydraulic pump-motors each having an inlet port connected to said hydraulic pumping means, an outlet port for each pump-motor connected to an associated one of said hydraulic cylinder devices, gear means operatively connected to each pump-rnotor and adapted to be rotated by a flow of fluid under pressure between said inlet and outlet ports, each of said hydraulic pump-motors being circumferentially spaced about a common axis, and idler gear means rotatable about said common axis and operatively connected to the gear means operatively connected to each of said hydraulic pumpmotors whereby all of the pump-motors will operate in synchronism to deliver fluid under pressure to each of said cylinder devices at the same rate.

3. Apparatus for elevating or lowering a substantially horizontal platform comprising a base, a plurality of vertically-expandable hydraulic cylinder devices interposed .at spaced points between the base and the platform, each of said hydraulic cylinder devices having the same volumetric capacity, hydraulic pumping means for supplying fluid under pressure to said hydraulic cylinder devices,

a plurality of hydraulic pump-motors each having an inlet port adapted to be connected to said hydraulic pumping means, an outlet port for each pump-motor connected to an associated one of said hydraulic cylinder devices, a separate hydraulic pump-motor having an inlet port adapted to be connected to said hydraulic pumping means, apparatus for mechanically interconnecting said plurality of pump-motors with the separate pump-motor whereby each motor will be driven in synchronism with the others, valve means for selectively connecting said hydraulic pumping means to either the inlet ports of said plurality of pump-motors or the inlet ports of said separate pumpmotor, the arrangement being such that when the valve means connects the pumping means to the inlet ports of the plurality of pump-motors fluid under pressure will be delivered to said cylinder devices at the same rate to expand the same in synchronism and elevate said platform, whereas when the valve means connects the pumping means to the inlet port of said separate pump-motor, the separate motor will cause the plurality of motors through said mechanical interconnecting apparatus to expel fluid from the cylinder devices at the same rate to collapse the cylinder devices in synchronism and lower said platform.

4. Apparatus for elevating or lowering a substantially horizontal platform comprising a base, a plurality of vertically-expandable hydraulic cylinder devices interposed iat spaced points between the base and the platform, hydraulic pumping means for supplying fluid under pressure to said hydraulic cylinder devices, a plurality of fluid metering devices each having an inlet port adapted to be connected to said hydraulic pumping means and an outlet port connected to an associated one of said hydraulic cylinder devices, means for controlling all of said metering devices whereby each metering device will supply fluid under pressure to its associated cylinder device at a rate to cause all of the cylinder devices to expand in synchronism and maintain said platform in a horizontal plane, said means for controlling said metering devices being adapted to cause fluid to be dispelled from the cylinder devices at rates such that the cylinder devices will collapse in synchronism to lower said platform while maintaining it in a horizontal plane.

5. Apparatus for elevating or lowering a substantially horizontal platform comprising a base, a plurality of vertically-exp andable hydraulic cylinder devices interposed at spaced points between the base and the platform, a fluid reservoir, hydraulic pumping means for supplying fluid under pressure from said hydraulic reservoir to said hydraulic cylinder devices, a plurality of hydraulic pumpmotors each having an inlet port adapted to be connected to said hydraulic pumping means, an outlet port for each pump-motor connected to an associated one of said hydraulic cylinder devices, a separate hydraulic pump-motor having an inlet port adapted to be connected to said hydraulic pumping means, apparatus for mechanically connecting said plurality of hydraulic motors with the separate hydraulic motor whereby each motor will be driven in synchronism with the others, and valve means for selectively connecting said hydraulic pumping means to the inlet ports of said plurality of pump-motors while simultaneously connecting the inlet port of said separate pumpmotor to said fluid reservoir, said valve means being adapted to selectively connect the inlet ports of said plurality of pump-motors to the fluid reservoir While con necting the inlet port of said separate pump-motor to said hydraulic pumping means, the arrangement being such that when the valve means connects the inlet ports of the plurality of pump-motors to the pumping means fluid under pressure will be delivered to each of said cylinder devices at the same rate to expand said cylinder devices in synchronism and elevate said platform, whereas when said valve mean-s connects the pumping means to the inlet port of said separate pump-motor, the said separate pump-motor will drive said plurality of motors to expel fluid from the cylinder devices at the same rate to lower said platform while maintaining the same in a horizontal plane.

6. Apparatus for elevating or lowering a substantially horizontal platform comprising a. base, a plurality of vertically-expandable hydraulic cylinder devices interposed at spaced points between the base and the platform, each of said hydraulic cylinder devices having the same volumetric capacity, hydraulic pumping means for supplying fluid under pressure to said hydraulic cylinder devices, a plurality of hydraulic pump-motors each having an inlet port adapted to be connected to said hydraulic pumping means, an outlet port for each pumpunotor connected to an associated one of said hydraulic cylinder devices, gear means operatively connected to each pump-motor and adapted to be rotated by a flow of fluid under pressure between said inlet and outlet Ports, a separate hydraulic pump-motor having an inlet port adapted to be connected to said hydraulic pumping means, an outlet port for the separate pump-motor, gear means operatively connected to said separate pump-motor and adapted to be rotated by a flow of fluid under pressure between the inlet and outlet ports, each of said plurality of hydraulic pump-motors and said separate hydraulic pumpmotor being circumferentially spaced about a common axis, gear means rotatable about said common axis and arranged to operatively engage the gear means of each of said pump-motors whereby all of the pump-motors will deliver fluid under pressure at the same rate, and the valve means for selectively connecting said hydraulic pumping means to the inlet ports of said plurality of pump-motors to cause each pump-motor to deliver fluid under pressure at the same rate to its associated hydraulic cylinder to expand all of the cylinders in synchronism, said valve means being adapted to selectively connect said hydraulic pumping means to the inlet port of said separate hydraulic pump-motor whereby the separate hydraulic pump-motor will drive the plurality of hydraulic motors to expel fluid from all of said cylinders at the same rate to retract the hydraulic cylinders in synchronism and lower said platform.

7. Apparatus for delivering fluid under pressure at the same rate to a plurality of hydraulic utilization devices comprising a plurality of hydraulic pump-motors each having an input port adapted for connection to a source of hydraulic pressure, an output port for each pump-motor connected to an associated one of said utilization devices, each of said hydraulic pump-motors being circumferentially spaced about a common axis, and gear idler means rotatable about said common axis and operatively connected to each of said hydraulic pump-motors to cause the pump-motors to operate in synchronism and deliver fluid at the same rate to said hydraulic utilization devices.

8. Apparatus for delivering or expelling fluid from a plurality of hydraulic utilization devices at the same rate comprising a source of fluid under pressure, a plurality of hydraulic pump-motors each having an inlet port adapted to be connected to said fluid pressure source, an outlet port for each pump-motor connected to an associated one of said hydraulic cylinder devices, gear means operatively connected to each pump-motor and adapted to be rotated by a flow of fluid under pressure between said inlet and outlet ports, a separate hydraulic pump-motor having an inlet port adapted to be connected to said fluid pressure source, each of said plurality of pump-motors and said separate pump-motor being circumferentially spaced around a common axis, gear means rotatable about said common axis and operatively connected to the gear means of said hydraulic pump-motors whereby the pump-motors will operate in synchronism to deliver fluid at the same rate, and valve means for selectively connecting said fluid pressure source to the inlet ports of said plurality of pump-motors whereby each pump-notor will deliver fluid under pressure to its associated hydraulic utilization device at the same rate, said valve means being adapted to selectively connect the hydraulic pumping means to the inlet port of said separate pump-motor whereby the separate pump-motor will drive the plurality of hydraulic pump-motors through said gear means to expel fluid from said hydraulic utilization devices at the same rate.

9. Apparatus for delivering fluid under pressure to a plurality of hydraulic utilization devices comprising a plurality of hydraulic pump-motors each having an input port adapted for connection to a source of hydraulic pressure and an output port connected to an associated one of said hydraulic utilization devices, and idler gear means mechanically interconnecting all of said hydraulic pump-motors to cause the same to operate in synchronism and deliver fluid to said utilization devices at controlled rates.

References Cited in the file of this patent UNITED STATES PATENTS 2,291,578 Johnson July 28, 1942 2,343,912 Lauck Mar. 14, 1944 10 2,481,047 Sloane Sept. 6, 1949 2,888,299 Balogh May 26, 1959 2,947,148 Young Aug. 2, 1960

Claims (1)

1. 6. APPARATUS FOR ELEVATING OR LOWERING A SUBSTANTIALLY HORIZONTAL PLATFORM COMPRISING A BASE, A PLURALITY OF VERTICALLY-EXPANDABLE HYDRAULIC CYLINDER DEVICES INTERPOSED AT SPACED POINTS BETWEEN THE BASE AND THE PLATFORM, EACH OF SAID HYDRAULIC CYLINDER DEVICES HAVING THE SAME VOLUMETRIC CAPACITY, HYDRAULIC PUMPING MEANS FOR SUPPLYING FLUID UNDER PRESSURE TO SAID HYDRAULIC CYLINDER DEVICES, A PLURALITY OF HYDRAULIC PUMP-MOTORS EACH HAVING AN INLET PORT ADAPTED TO BE CONNECTED TO SAID HYDRAULIC PUMPING MEANS, AN OUTLET PORT FOR EACH PUMP-MOTOR CONNECTED TO AN ASSOCIATED ONE OF SAID HYDRAULIC CYLINDER DEVICES, GEAR MEANS OPERATIVELY CONNECTED TO EACH PUMP-MOTOR AND ADAPTED TO BE ROTATED BY A FLOW OF FLUID UNDER PRESSURE BETWEEN SAID INLET AND OUTLET PORTS, A SEPARATE HYDRAULIC PUMP-MOTOR HAVING AN INLET PORT ADAPTED TO BE CONNECTED TO SAID HYDRAULIC PUMPING MEANS, AN OUTLET PORT FOR THE SEPARATE PUMP-MOTOR, GEAR MEANS OPERATIVELY CONNECTED TO SAID SEPARATE PUMP-MOTOR AND ADAPTED TO BE ROTATED BY A FLOW OF FLUID UNDER PRESSURE BETWEEN THE INLET AND OUTLET PORTS, EACH OF SAID PLURALITY OF HYDRAULIC PUMP-MOTORS AND SAID SEPARATE HYDRAULIC PUMPMOTOR BEING CIRCUMFERENTIALLY SPACED ABOUT A COMMON AXIS, GEAR MEANS ROTATABLE ABOUT SAID COMMON AXIS AND ARRANGED TO OPERATIVELY ENGAGE THE GEAR MEANS OF EACH OF SAID PUMP-MOTORS WHEREBY ALL OF THE PUMP-MOTORS WILL DELIVER FLUID UNDER PRESSURE AT THE SAME RATE, AND THE VALVE MEANS FOR SELECTIVELY CONNECTING SAID HYDRAULIC PUMPING MEANS TO THE INLET PORTS OF SAID PLURALITY OF PUMP-MOTORS TO CAUSE EACH PUMP-MOTOR TO DELIVER FLUID UNDER PRESSURE AT THE SAME RATE TO ITS ASSOCIATED HYDRAULIC CYLINDER TO EXPAND ALL OF THE CYLINDERS IN SYNCHRONISM, SAID VALVE MEANS BEING ADAPTED TO SELECTIVELY CONNECT SAID HYDRAULIC PUMPING MEANS TO THE INLET PORT OF SAID SEPARATE HYDRAULIC PUMP-MOTOR WHEREBY THE SEPARATE HYDRAULIC PUMP-MOTOR WILL DRIVE THE PLURALITY OF HYDRAULIC MOTORS TO EXPEL FLUID FROM ALL OF SAID CYLINDERS AT THE SAME RATE TO RETRACT THE HYDRAULIC CYLINDERS IN SYNCHRONISM AND LOWER SAID PLATFORM.

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