Self-contained mobile extendable tower

Claim 2

Apparatus for moving a load between different levels comprising in combination: a horizontal load platform, a main frame underlying said platform, a plurality of multistage mast assemblies arranged in parallel and interconnecting said main frame and the opposite ends of said platform and including an elongated horizontal axis pivot connection extending transversely of and interconnecting one end of said platform and one of said mast assemblies, separate hydraulic pumps of identical displacement connected in circuit with a respective one of said mast assemblies to supply pressurized fluid thereto and operable in either direction by common prime mover means to extend and retract said mast assemblies in unison, normally closed electrically actuated bleed valve means for bleeding fluid from the higher one of said ram assemblies as necessary to maintain said platform level despite the non-uniform loading of said mast assemblies during both extension and retraction of said platform, and non-level sensor means connected to said platform and responsive to pivotal movement of said platform about the axis of said pivotal connection to operate a selected one of said bleed valve means to bleed fluid from any higher one of said mast assemblies as necessary to maintain said platform level.

Claim 3

Apparatus as defined in claim 1 characterized in that said non-level sensor means is closely adjacent the upper end of one of said mast assemblies.

Claim 4

Apparatus as defined in claim 1 characterized in that said non-level sensor means is mounted on the upper end portion of one of said mast assemblies.

Claim 5

Apparatus as defined in claim 1 characterized in that said sensor means includes an electric switch connected in circuit with electrical operating means for said bleed valve means and normally so positioned that said bleed valve means is closed to block the escape of fluid from all of said mast assemblies so long as said platform is level and operable to open the bleed valve means of the highest one of said mast assemblies when said platform is not substantially level.

Claim 6

Apparatus as defined in claim 1 characterized in that said main frame is rigidly secured to a chassis having steerable front wheels and hydraulically power driven rear wheels, and control means for said power driven rear wheels and including accumulator means for cushioning initiation and cutoff of pressurized fluid to said power drive thereby to assure smooth starting and stopping of said chassis.

Claim 7

Apparatus as defined in claim 1 characterized in that said prime mover means comprises a reversible electric motor.

Claim 8

Apparatus as defined in claim 6 characterized in that said prime mover means comprises a reversible direct current motor energized from batteries carried by said main frame.

Claim 9

Apparatus as defined in claim 1 characterized in the provision of hydraulically powered chassis means supporting said main frame, and means for selectively operating at any time either said mast assemblies to change the level thereof or said hydraulically powered chassis means.

Claim 10

Apparatus as defined in claim 8 characterized in that said hydraulically powered chassis means includes accumulator means in circuit with the pressurized hydraulic fluid powering said chassis means effective to provide smooth starting and stopping thereof.

Claim 11

Apparatus as defined in claim 1 characterized in the provision of folding protective means hingedly interconnecting said platform and said main frame and protectively enclosing portions of the controls for said prime mover and said pumps.

Claim 12

Apparatus as defined in claim 10 characterized in that said folding protective means comprises a plurality of elongated rigid members hingedly connected together in end to end relation with one end movably supported at said platform and the other end movably supported at said main Frame, and flexible control means protected and supported by said rigid members and interconnecting control means for said apparatus located on said platform and other portions of said apparatus located on said main frame.

Claim 13

Apparatus as defined in claim 1 characterized in that said prime mover means comprises unidirectional power generating means coupled to said separate hydraulic pumps by reversible power transmission means.

Claim 14

Apparatus as defined in claim 12 characterized in that said main frame comprises a hydraulically powered steerable chassis, and fluid pump means having a driving connection with said unidirectional power generating means in advance of the drive connection of the latter to said reversible power transmission means.

Claim 15

Apparatus as defined in claim 12 characterized in the provision of control means on said platform operable to stop and start said power generating means at will from an operating control station on said platform irrespective of the elevation thereof above ground level.

Claim 16

Apparatus as defined in claim 1 characterized in that said prime mover means comprises an internal combustion engine coupled to said separate hydraulic pumps by reversible power transmission means.

Claim 17

Apparatus as defined in claim 15 characterized in the provision of control means for shifting said power transmission means between a neutral position, forward drive position and reverse drive position from a control station located on said platform.

Claim 18

Apparatus as defined in claim 16 characterized in that said control means includes hydraulic motor means located in part on said platform and in part on said main frame.

Claim 19

Apparatus as defined in claim 1 characterized in that said main frame is mounted on steerable front wheels and hydraulically driven rear wheels.

Claim 20

Apparatus as defined in claim 18 characterized in the provision of hydraulically powered means for steering said front wheels from a control station on said platform.

Claim 21

A tower assembly as defined in claim 19 characterized in the provision of means for deactivating the operation of said mast assemblies so long as power is being supplied to propel and/or to steer said chassis.

Claim 22

A tower assembly as defined in claim 19 characterized in the provision of means for automatically rendering the drive means for the pumps connected in circuit with said mast assemblies ineffective to drive said pumps while said hydraulically powered means for said front and rear wheels is activated.

Claim 23

A mobile chassis-supported extendable tower assembly for moving a load between different levels, said tower assembly comprising a main chassis frame closely spaced above the ground, a load platform overlying said main frame including a plurality of inverted upright yoke means overlying said platform and having the lower ends thereof fixed to said platform near the opposite ends thereof, multistage mast assemblies having their lower ends rigidly secured to said main frame and their upper ends secured to the upper end of a respective one of said yoke means, said mast assemblies having a retracted height corresponding generally to the height of said yoke means, power-driven pressurized fluid means for extending and retracting said masts in synchronism by pressurized fluid supplied to each of said mast assemblies, said last mentioned means including electrical level sensor means mounted on said platform effective to sense tilting of said platform away from the normal horizontal plane thereof and electrically connected to normally closed fluid bleed valves for each of said mast assemblies supported independently of said platform and automatically operable to bleed fluid from the higher one of said mast assemblies when and as necessary to restore said platform to the level condition thereof during both extension and retraction of said platform, said assembly being fully self-contained and operable from a source of power carried by said chassis.

Claim 24

A mobile chassis-supported extendable tower assembly for moving a load between different levels, said tower assembly comprising a main chassis frame closely spaced above the ground, a load platform overlying said main frame including a plurality of inverted upright yoke means overlying said platform and having the lower ends thereof fixed to said platform near the opposite ends thereof, multistage mast assemblies having their lower ends rigidly secured to said main frame and their upper ends secured to the upper end of a respective one of said yoke means, said mast assemblies having a retracted height corresponding generally to the height of said yoke means, power-driven pressurized fluid means for extending and retracting said masts in synchronism by pressurized fluid supplied to each of said mast assemblies, said last mentioned means including electrical level sensor means mounted on said platform effective to sense tilting of said platform away from the normal horizontal plane thereof and electrically connected to normally closed fluid bleed valves for each of said mast assemblies supported independently of said platform and automatically operable to bleed fluid from the higher one of said mast assemblies when and as necessary to restore said platform to the level condition thereof during both extension and retraction of said platform, said assembly being fully self-contained and operable from a source of power carried by said chassis.

Claim 25

A tower assembly aS defined in claim 22 characterized in that said electrical sensor means comprises a pair of electrical switches spaced from one another in a plane parallel to a plane common to the axes of said mast assemblies and respectively responsive to a clockwise and counterclockwise tilting of said platform away from the normal horizontal position thereof to open one or the other of an associated one of said fluid bleed valves until said platform has been restored to the level condition thereof.

Claim 26

A tower assembly as defined in claim 22 characterized in the provision of check valve means located in the fluid supply to said mast assemblies and effective to hold said platform locked in any elevated position thereof despite a failure in the operating condition of said power driven means, and manually actuated means operable to bleed fluid from each of said mast assemblies to lower the same in synchronism.

Claim 27

A tower assembly as defined in claim 22 characterized in that said power driven means includes similar reversible positive displacement pumps for each of said mast assemblies coupled to a common prime mover for operation in unison, check valve means between a source of hydraulic fluid and the inlet to said pump means to prevent reverse flow of fluid to the fluid source upon the unintended failure of said prime mover, and manually actuated fluid venting means between said check valve means and said pump means operable to lower said platform as the fluid in said mast assemblies escapes therefrom via said pump means and thence through said fluid venting means.

Claim 28

A tower assembly as defined in claim 22 characterized in the provision of manually controlled hydraulic motor means for driving an axially aligned pair of said chassis wheels and including accumulator means for cushioning acceleration and deceleration of said chassis.

Claim 29

A tower assembly as defined in claim 22 characterized in the provision of separate reversible hydraulic motors driving a respective one of the chassis wheels to propel said mobile tower assembly forwardly and rearwardly at the operator''s option.

Claim 30

A tower assembly as defined in claim 27 characterized in the provision of reversible hydraulic means for steering said tower assembly to the right and to the left from a control station on said platform.

Claim 31

A mobile extendable tower assembly comprising a heavy duty chassis having an elongated rigid main frame, an elongated load supporting platform overlying said main frame, similar upright tubular housings having their lower ends fixed to the opposite ends of said platform, a pair of multi-stage mast assemblies having their smaller ends secured to the interior upper ends of said housings and extending downwardly therethrough to fixed anchorages at the opposite ends of said chassis main frame, a prime mover coupled to separate reversible pump means operable to supply pressurized fluid to a respective one of said mast assemblies to raise and lower the same in unison, normally closed bleeder valve means supported independently of said platform for venting fluid from any higher one of said mast assemblies if said platform tilts away from a horizontal plane lengthwise thereof thereby to restore the level condition of said platform, and high sensitivity non-level sensor means including two pairs of electric contactors connected in circuit with a source of electrical energy and said bleeder valve means and operable to bleed fluid from any higher one of said mast assemblies during both extension and retraction of said platform as necessary to restore said platform to a level condition upon sensing a non-level condition of said platform.

Claim 32

A mobile extendable tower assembly comprising a heavy duty chassis having an elongated rigid main frame, an elongated load supporting platform overlying said main frame, similar upright tubular housings having their lower ends fixed to the opposite ends of said platform, a pair of multi-stage mast assemblies having their smaller ends secured to the interior upper ends of said housings and extending downwardly therethrough to fixed anchorages at the opposite ends of said chassis main frame, a prime mover coupled to separate reversible pump means operable to supply pressurized fluid to a respective one of said mast assemblies to raise and lower the same in unison, normally closed bleeder valve means supported independently of said platform for venting fluid from any higher one of said mast assemblies if said platform tilts away from a horizontal plane lengthwise thereof thereby to restore the level condition of said platform, and high sensitivity non-level sensor means including two pairs of electric contactors connected in circuit with a source of electrical energy and said bleeder valve means and operable to bleed fluid from any higher one of said mast assemblies during both extension and retraction of said platform as necessary to restore said platform to a level condition upon sensing a non-level condition of said platform.

Claim 33

A tower assembly as defined in claim 29 characterized in that said prime mover is coupled to said reversible pump means by reversible transmission means.

Claim 34

A tower assembly as defined in claim 29 characterized in the provision of means for lowering said platform independently of the operation of said prime mover and under the control of said non-Level sensor means.

Claim 35

A tower assembly as defined in claim 29 characterized in that said pairs of contactors are mounted at the upper end of one of said tubular housings.

Claim 36

A tower assembly as defined in claim 32 characterized in that said prime mover means comprises an internal combustion engine.

Claim 37

A tower assembly as defined in claim 33 characterized in the provision of manually operable control means on said platform for starting and stopping said engine.