Abstract: A vehicle crane system includes a vehicle crane with an attachment part, in particular a bracing device, which can be mounted on and removed from the telescopic jib of the vehicle crane, and to an attachment part transporting unit for transporting an attachment part of a telescopic jib of the vehicle crane. A mobile transporting device is provided for transporting the attachment part and has at least one loading arm, the free supporting end of which can be coupled to the attachment part carried or to be carried on the transporting device. The loading arm is arranged movably on the transporting device such that the attachment part can be moved between the transporting device and the telescopic jib. Furthermore, the transporting device has a tilting device which is designed for raising and lowering one side of the attachment part carried or to be carried on the transporting device.

Abstract: Lift assemblies and methods of operating same. A lift assembly for a vehicle includes at least one support member having a longitudinal axis lying on a plane and which is configured for attachment to the vehicle. A mast having a proximal end, a distal end, and a mast axis is pivotably coupled with the at least one support member at the mast proximal end. At least one gear arrangement is coupled between the at least one support member and the mast proximal end. The mast is pivotable relative to the at least one support member about an axis parallel with the plane through an angular displacement greater than 90 degrees. A boom is pivotably coupled with the mast proximate the mast distal end, and a first lift line is coupled with the boom.

Abstract: A track maintenance wagon (1) for picking up and/or laying a track panel (10), comprising a wagon frame (2) supported on on-track undercarriages (4), wherein two longitudinal beams (7) of the wagon frame (2) delimit a free opening and are transversely displaceable relative to one another, so that the free opening is changeable as to its width and, in a working position, has greater opening dimensions as a horizontal projection of the track panel (19), and wherein crane rails (8) are arranged on the longitudinal beams (7) for a gantry crane (11) mobile in the longitudinal direction (3) of the wagon. In this, buffers (13) are arranged at two free ends (12) of the longitudinal beams (7).

Abstract: Systems and methods for a mobile crane are provided. In particular, systems and methods are provided for a mobile crane that is designed to enable easy transportation on a railcar to and from a job site. The mobile crane facilitates quick changing between a transport configuration and a work configuration to enable increased productivity. The mobile crane is configured to be modular and thereby be configured to include various lifting and object manipulating features, as required by a specific application.

Abstract: A tracked vehicle includes a pilot control module which enables the pilot to steer the tracked vehicle using an existing joystick of the tracked vehicle. The tracked vehicle also includes a dual track drive pedal which drives the tracks of the vehicle simultaneously. The joystick is used to make steering corrections when utilizing the dual track drive pedal.

Abstract: An intravenous (IV) pole docking system for supporting medical equipment having a mast engaged to a base, the base having legs to support the mast and a lifting mechanism engaged to the base and the mast for moving the base along the mast in combination with an extension arm meant to reduce the IV pole footprint. The boom/IV pole system can reduce excess obstacles in and around hospital bed, surgical rooms and the like.

Abstract: A davit comprising a column which is mountable for rotation about a generally upright axis and a jib, the jib being attached to the column, characterised in that the column is provided, on a first side thereof, with ribs defining a first channel.

Abstract: A crane, in particular a tower crane, with a boom rotatable about an upright slewing gear axis and an out-of-service brake which permits and slows down the rotary movements of the boom in the out-of-service condition. The out-of-service brake is formed to operate in a rotational-speed-dependent manner such that with a greater rotational speed of the crane the applied braking torque is greater than with a smaller rotational speed of the crane.

Abstract: An enhanced stability crane (100) is described. Embodiments include a telescoping main support mast (114) upon which a crane base (106) resides. A boom (140) projects upwardly from the crane base and a jib (148) typically projects upwardly from the boom. A clamping assembly (108) resides on the main support mast and is configured to attach to an existing structure adjacent to the crane, in order to enhance stability. Multiple clamping assemblies can be distributed along the telescoping main support mast when it is extended. The existing structure is generally a tower structure (180) that is columnar and vertical in shape and orientation, and frequently has an elliptical horizontal cross-section. Tower structures are typically, but not necessarily, wind turbine towers. In some embodiments, the crane is mobile capable of lifting objects weighing about 110 tons to a height of about 400 feet. The crane typically adjusts to a collapsed configuration, enabling facile transport.

Abstract: A vehicle (1) for transporting ballast weights (4) which are intended for weighting a crane (2). The vehicle according to the invention is characterised in that the vehicle (1) has a ballast lifting device (5), by which the ballast weights (4) can be moved between a transport position located on the vehicle (1) and a usage position provided for on the crane (2).

Abstract: An access system for facilitating access to an elevated deck of a mobile crane includes a staircase having a support post defining an axis of inclination. A plurality of ascending steps is connected to the at least one support post, and a mounting bracket is pivotally coupled to an upper end of the at least one support post. The staircase is pivotable about a longitudinal axis such that a lower end of the at least one support post is induced to move in a lateral direction in response to pivotal motion of the at least one support post. A caster is coupled to the lower end of the support post for supporting the staircase on a ground surface. The caster supports the staircase on the ground surface throughout longitudinal movements of the staircase and lateral movements of the staircase induced by vertical movements of the mobile crane.

Abstract: Systems and methods for rig assembly and for erecting a mast of a rig and such systems with roller apparatus to facilitate movement of a mast section from a mover. In a first embodiment, the method includes erecting a rig mast section on a substructure, the substructure including a first substructure box spaced-apart from a second substructure box, the first substructure box comprising a first upper box above a first lower box and the second substructure box comprising a second upper box above a second lower box.

Abstract: A foldable gantry (10) comprising a beam (12) and a first leg assembly (14), the first leg assembly (14) being pivotally mounted at a first end (16) of the beam (12) such that the first leg assembly (14) can move between a first, stowed, position and a second, deployed, position.

Abstract: The present invention is a self-locking folding crane apparatus that can be installed onto any pivot shaft and held in place by small positioning devices such as clamps, slip-rings, bolts, shaft collars, pins, and other mechanical means; a substantial base is not needed to support the hoist as long as the pivot shaft is able to do so. The resulting hoist can be recoverably installed and optionally left on a vehicle or cart while it is in either an operative or stowed state. Unlike all other portable cranes that were found in prior art either singly or in combination, the present invention requires no assembly or disassembly between uses.

Abstract: A method of assembling a mobile lift crane that includes, during operation, i) a rotating bed having attached thereto a luffing jib hoist drum and line, and a rigging winch drum and line, ii) a boom pivotally mounted on the rotating bed, iii) a luffing jib pivotally mounted to the end of the boom, iv) a first strut also pivotally connected to the end of the boom, and v) a second strut connected to the boom below the connection point of the first strut, the method including: a) pivotally connecting the first strut to the end of the boom; b) pivotally connecting a first section of the second strut near the top of the boom; c) connecting the rigging winch line to the top of the first section; d) pivotally attaching a second section of the second strut to the first section such that the second section lies folded onto the first section, forming a folded second strut; and e) lifting the second section while retracting the rigging winch line to thereby bring the first and second sections into alignment with each ot

Abstract: A crane for mounting on a truck includes a base. The base includes a cargo bed welded or fastened to a frame and the frame for fastening to a chassis of a truck. The crane further includes a boom rotatable relative to the base between a vertical position and a horizontal position; a boom hoist operable to raise and lower the boom between the positions; and a load hoist operable to hoist cargo located proximate to a rear end of the truck when the boom is in the vertical position and operable to carry the cargo toward a cab of the truck as the boom is lowered to the horizontal position, thereby loading the cargo onto the cargo bed.

Abstract: A vertically-adjustable gantry assembly installation adapted for removal or placement of a train bridge-span of the type which spans and is supported by two piers, comprises a gantry assembly positioned on load-bearing first ground-support locations, the gantry assembly comprising a gantry and a ground-engaging vertical support and lift system, the vertical support and lift system adapted for supporting a combined weight of the gantry and a bridge span in at least one operational vertical position above respective bridge span support-surfaces of the piers including a position corresponding to a disembarking plane in which the leg portions are extended from a stowed position to an extent at least sufficient for the gantry assembly to self-liftoff the pre-installation conveyance system onto the first ground-support locations to effect the gantry assembly installation.

Abstract: A construction machinery body includes: a main frame; a gantry that is derrickably linked to the main frame, and includes a front leg member and a rear leg member that is linked to the front leg member at a front end side; a connecting member that is disposed between one end portion and another end portion of the front leg member in the gantry, and includes a connecting portion and a rope attaching portion; and a coupling member that links the connecting portion of the front leg member to the main frame in a state where the gantry is retracted.

Abstract: An upright support assembly for a gantry includes a base with primary ground engaging means, such as wheels and a stabilizing member which is pivotally connected to the support assembly so as to be moveable between a stowed position folded against the support assembly and a deployed position in which it engages the ground to hold the support assembly upright. The stabilizing member includes a ground engaging fitting at its outer end which is adapted to engage the ground in the deployed position to stabilize the support assembly in the upright position, and to engage and roll over the ground in the stowed position when the support assembly is lowered to the ground so that the base and primary ground engaging means can be lifted off the ground and the support assembly moved on the ground engaging fitting.

Abstract: A crane vessel including a revolving hoist crane and a method of using such a vessel are provided. The hoist crane includes a jib, main hoisting means and auxiliary hoisting means for raising and lowering a load. The main hoisting means include a main hoisting tackle with a main hoist upper block connected to the jib and a main hoist lower block. The main hoist lower block is assembled from a sheave block including the sheaves of the main hoist lower block and a load attachment assembly having the lowering weight and the main load attachment device. The crane vessel is provided with a load attachment assembly storage device for storage of the disassembled load attachment assembly and displacement means capable of engaging with and displacing the load attachment assembly while it is assembled to the sheave block and when the jib is supported by a jib rest.

Abstract: A first cutoff valve is disposed in a main duct ranging between a control valve and a bottom chamber of a hydraulic cylinder. A sequence valve in the first cutoff valve is disposed along such a direction as to control outflow of a hydraulic fluid from the bottom chamber and the hydraulic pressure in a rod chamber is applied to the sequence valve as an external pilot pressure. A second cutoff valve is disposed in a main duct ranging between the control valve and the rod chamber of the hydraulic cylinder. A sequence valve in the second cutoff valve, disposed along such a direction as to control outflow of the hydraulic fluid from the rod chamber, and the hydraulic pressure in the rod chamber is applied to the sequence valve as an internal pilot pressure.

Abstract: A combination transport and load handling vehicle that includes a truck having a chassis with a cab mounted to a forward portion of the chassis and a hitch plate mounted toward the rear of the chassis and a forklift assembly pivotally mounted to the chassis intermediate the cab and the hitch plate so that arms of the forklift are movable from a stowed position above the cab to a deployed position extending rearwardly of the chassis when no trailer is connected to the hitch plate. The forklift assembly has a lift frame including a boom pivotally mounted to the chassis and which supports a forklift tower along which the arms of the forklift device are movable adjustable.

Abstract: A crane, in particular a vehicle crane, includes a first crane arm and at least one second crane arm which are connected together by a joint. The crane arms are pivotable relative to each other by a drive having a piston-cylinder unit, in each case starting from one of the two end positions in which the crane arms are in substantially mutually parallel relationship until reaching a dead point when the longitudinal axis of the piston-cylinder unit is substantially on a line with the joint. There is provided at least one second drive by which it is possible to go beyond the dead point position of the piston-cylinder unit relative to the joint.

Abstract: A working machine (1) includes a frame (3), a body section (2) mounted to the frame (3) for pivotal movement about a vertical axis, a boom unit (7) having a plurality of booms, including a basal boom (7a), telescopically extendable from and retractable to one another. A support arm (14) is mounted to the body section (2) for pivotal movement about a horizontal axis. An end of the support arm (14) is coupled with the basal boom (7a). The basal boom (7a) is pivotable relative to the support arm (14) about a horizontal axis. A first hydraulically operable device extends from the body section (2) to the basal boom (7a) for pivoting the basal boom (7a) relative to the support arm (14) about the horizontal axis.

Abstract: A method of performing landscaping or construction work which utilizes portions of a known lift, crane or hoist unit in a novel way. Angled knuckle portions of the lift are modified to include reinforced eyelets or equivalent structures. A platform is hingedly mounted to the rear of a truck bed and also includes reinforced eyelet structures. Cables are provided between the lift eyelets and the platform eyelets to enable raising and lowering of the platform to conduct loading and unloading operations. A dump box for transporting soil or other products may be utilized in the system and is mounted between upper drive elements of the lift, crane or hoist.

Abstract: The present invention relates to a method of moving a large mobile crane having a luffable boom system. In accordance with the invention, the boom system is luffed down into a largely horizontal position for moving and is supported on a support block of a construction machine or of a small mobile crane so that the large mobile crane can be moved together with the construction machine or the small mobile crane. The invention further relates to a system for carrying out the aforesaid method.

Abstract: A crane for mounting on a truck includes a base. The base includes a cargo bed welded or fastened to a frame and the frame for fastening to a chassis of a truck. The crane further includes a boom rotatable relative to the base between a vertical position and a horizontal position; a boom hoist operable to raise and lower the boom between the positions; and a load hoist operable to hoist cargo located proximate to a rear end of the truck when the boom is in the vertical position and operable to carry the cargo toward a cab of the truck as the boom is lowered to the horizontal position, thereby loading the cargo onto the cargo bed.

Abstract: The present invention provides an integrated boom/underlift assembly in which an underlift is integrated to a first section of a boom. In order to achieve multifunction of the assembly, the underlift/vertical arm assembly is installed with a hydraulic cylinder, an auxiliary winch, a guide pulley, etc. so that the underlift can be operated independently and work closely with the boom to increase both stability and balance during the lifting operation. Additionally, the invented underlift can extend a much longer distance at a higher position than those currently in the art to catch a wrecked object and then works together with the boom.

Abstract: An upright support assembly for a gantry includes a base with primary ground engaging means, such as wheels and a stabilizing member which is pivotally connected to the support assembly so as to be moveable between a stowed position folded against the support assembly and a deployed position in which it engages the ground to hold the support assembly upright. The stabilizing member includes a ground engaging fitting at its outer end which is adapted to engage the ground in the deployed position to stabilize the support assembly in the upright position, and to engage and roll over the ground in the stowed position when the support assembly is lowered to the ground so that the base and primary ground engaging means can be lifted off the ground and the support assembly moved on the ground engaging fitting.

Abstract: The gantry pallet and allweather cover described includes, in its preferred embodiment, many improvements over the currently applied methods of storing, transporting and shipping the U.S. Navy's steam tube Gantry Cranes and accompanying appurtenances. Further included are lifting plates for safely lifting and/or handling and/or safely transporting the gantry pallet and allweather cover by a variety of methods. Another improvement is a provision for ridged, moisture barrier, non-corrosive cover that attaches to and seals against the gantry pallet frame. Another improvement involves a provision for on and off loading that allows substantial improvement in the speed of set-up and the safety in which, but not limited to, the U.S. Navy steam tube Gantry Cranes and accompanying appurtenances is applied to an aircraft carrier's catapult steam tubes.

Abstract: Apparatus and method for loading articles, such as wild game or the like, into an all terrain vehicle (ATV). The device provides a tripod-type support on the front upper part of the ATV having a pulley at its apex whereby the cable from a winch on the front of the ATV is passed over the pulley and then extends over the ATV to the rear of the ATV where a sled is placed on the rear of the ATV so that an article placed at the base of the sled can be pulled up the sled and loaded into the ATV.

Abstract: This invention relates to a crane vessel (1, 100) comprising a revolving hoist crane (20, 120) and a method of using such a vessel. The hoist crane comprises a jib (24, 124), main hoisting means and auxiliary hoisting means for raising and lowering a load. The main hoisting means comprise a main hoisting tackle (3, 130) with a main hoist upper block (38, 138) connected to the jib of the hoist crane and a main hoist lower block (39, 139). The vessel comprises a jib rest (10, 110) for supporting the jib when the crane is not in operation. According to the invention the main hoist lower block is assembled from a sheave block (163) comprising the sheaves (132) of the main hoist lower block and a load attachment assembly (133) comprising the lowering weight (137) and the main load attachment device (34, 134).

Abstract: A method of assembling a mobile lift crane that includes, during operation, i) a rotating bed having attached thereto a luffing jib hoist drum and line, and a rigging winch drum and line, ii) a boom pivotally mounted on the rotating bed, iii) a luffing jib pivotally mounted to the end of the boom, iv) a first strut also pivotally connected to the end of the boom, and v) a second strut connected to the boom below the connection point of the first strut, the method including: a) pivotally connecting the first strut to the end of the boom; b) pivotally connecting a first section of the second strut near the top of the boom; c) connecting the rigging winch line to the top of the first section; d) pivotally attaching a second section of the second strut to the first section such that the second section lies folded onto the first section, forming a folded second strut; and e) lifting the second section while retracting the rigging winch line to thereby bring the first and second sections into alignment with each ot

Abstract: A rotating superstructure includes: a front block on which a power unit that includes a prime mover; and a rear block on which a unit for raising and lowering a boom that includes a winch, a, and an arm. And the rotating superstructure is configured to be split into the front block and the rear block.

Abstract: The pipelayer crane apparatus comprises a lower, the lower comprising a lower frame, a pedestal, a lower bearing portion, a telescoping axle, a track roller, and a track shoe, an upper, the upper comprising a frame, a body, a cab, a pedestal, a upper bearing portion, and a counterweight, a lifting assembly, the lifting assembly comprising an adjacent portion, a remote portion, a joint, and a cylinder and a weldment, the weldment comprising a body, an extension, a winch, and securing members.

Abstract: Embodiments of the present invention generally relate to a pipelayer and a method for of loading a pipelayer or excavator for transportation. One embodiment includes a method for transporting a pipelayer or excavator from a first work site to a second worksite via a public road. The method includes acts of: raising the pipelayer or excavator off of track shoes of the pipelayer or excavator; removing a first track assembly from the pipelayer or excavator using a boom of the pipelayer or a boom assembly of the excavator; loading the first track assembly onto a first trailer of a first tractor-trailer using the boom of the remaining pipelayer or the boom assembly of the remaining excavator; removing the second track assembly from the pipelayer using the boom of the remaining pipelayer or the boom assembly of the remaining excavator; and loading the second track assembly onto the first trailer using the boom of the remaining pipelayer or the boom assembly of the remaining excavator.

Abstract: The within invention concerns a vehicle crane with a telescopic boom that can move on a horizontal axle and rotate on an upright axle with a pivot section, telescoping sections that can telescope out of the pivot section, and also with two anchor supports flexibly housed on one of the sections so that they can pivot out of transportation position, in which they are folded essentially parallel to each other against the section, and can be spread apart into an erect, particularly V-shaped, operation position. The invention also concerns a process for assembling or dissembling said anchor supports of the telescoping boom of the vehicle crane. According to the invention, when the boom is lying in essentially horizontal position, the anchor supports can be disassembled, are positioned on brackets provided next to the boom, and after the boom is raised are raised from the brackets and loaded by the boom itself.

Abstract: A mobile lift crane includes a carbody having moveable ground engaging members; a rotating bed rotatably connected to the carbody such that the rotating bed can swing with respect to the ground engaging members; a boom pivotally mounted on the rotating bed; a first hoist drum mounted in a first frame connected to the rotating bed; a second hoist drum mounted in a second frame connected to the rotating bed; and a third hoist drum mounted in a third frame indirectly connected to the rotating bed by being connected to at least one of the first and second hoist drum frames. Preferably load hoist drum frames are connected to the rotating bed by removable pins, the hoist drum and frame thus being detachable from the rotating bed as a combined unit.

Abstract: Each arm of the scissors comprises a handle with a rigid outer ring and an inner ring made of a flexible and elastically deformable material. The flexible inner ring includes a part resembling a length of tube and receiving one or more of a user's fingers, and a thin membrane-like part which connects the preceding part to the rigid outer ring of the handle. This configuration is both comfortable and firm.

Abstract: A portable crane and trailer system is disclosed. In a particular embodiment, the system includes a trailer, a crane post, and a crane. A first pair of outriggers is secured to a rear portion of the trailer and a second pair of outriggers is configured to be swung out rearward from the trailer to further increase the stability of the trailer, where the second pair of outriggers is deployed at approximately a 45 degree angle relative to the trailer. In addition, the system includes a removable A-frame removably connected between the rear portion of the trailer and the boom, where a first end of the A-frame is mounted to the rear portion of the trailer forming a base of the A-frame and a second end of the A-frame is connected at approximately the same location on the boom forming an apex of the A-frame.

Abstract: A transportable machine includes a frame that may be part of a motorized carriage and a machine for transport. The frame has, for example, one or more gaps defining an interface specially designed for engaging the machine. The machine includes elements adapted to fit within or otherwise engage the gaps of the frame. Fasteners join the machine and the frame, thus creating a transportable machine.

Abstract: A portable patient lift has spreadable support legs with a feature that enables the legs of the lift to operate in a first range of motion during operation, and a second range of motion for compact folding.

Abstract: The invention relates to a covering body for masts of construction cranes, electricity lines, or the like with an outer covering which is designed to partially or totally encase a mast in the direction of extension and/or peripheral direction and which furthermore has at least one rigid inner support, with which the outer covering can be arranged to be spaced at least partially at a distance from the mast. Finally, a fastening device for fastening the inner support to the mast is provided. Such a covering body according to the invention is further developed in that the inner support, by means of the fastening device, can be connected to the mast rotatably adjustable in the peripheral direction and/or adjustable in the direction of extension and that a device for active and/or passive variation of position and/or geometry of the outer covering is provided.

Abstract: The invention relates to an industrial truck comprising a gantry-type, high-rise wheeled chassis and at least one lifting device (15) for loads that can be picked up and transported between the wheels (5, 6). Said chassis consists of at least one first front travelling frame (1) and at least one second rear travelling frame (2). Each travelling frame (1, 2) is configured as a gantry consisting of vertical stanchions with articulated wheels at their base and a cross brace (7, 8) that interconnects the heads of the stanchions (3, 4). Each travelling frame has a connection assembly (9, 10), which projects towards the respective opposite travelling frame, the free end (11, 12) of each connection assembly being connected to the respective opposite travelling frame by means of articulations (13). Each connection assembly (9, 10) resembles a triangular boom or jib with a horizontal brace (31) and a diagonal brace (32).

Abstract: The game hanger apparatus is attachable to a tow hitch of a pickup truck. The folded game hanger can be taken to the site in the bed of the truck and speedily installed in the tow hitch for hanging, cleaning and butchering large game, such as deer and small bears. The apparatus comprises a mast and fixed boom of square cross-section, and having a winch, pulleys and a gambrel with a pair of end hooks and a pair of pins which engage a jib at the end of the boom to prevent the game from twisting. The horizontal bottom and top bars are locked in place by removable pins for operation, and unlocked by removing the pins for folding the unit for storage. The bottom bar is inserted into a tow hitch and locked in place with the hitch pin.

Abstract: A self-erecting tower crane for use on a construction site is supported at a top end of a tower that includes tower sections assembled in an end-to-end relationship relative to one another along a tower axis. The tower crane includes a boom assembly for selectively raising tower sections above ground. A boom support structure has an upper portion that rotatably supports the boom assembly relative to the tower axis, and a lower portion that is configured and sized for mounting on and releasably securing to the tower top end. A self-raising sleeve mounts on the tower for axial movement therealong, and selectively and releasably supports the boom support structure on the tower. The sleeve and the boom support structure include a side opening that is configured and sized for allowing a tower section to be assembled to the tower top end for the self-erection of the tower crane.

Abstract: A portable hoist system and method of use in combination with the rear bed and ball hitch of a pick-up truck. All of the system components may be contained in a portable bag about four feet long. The system components include plural boom sections, plural cables or support lines and a chain element. Two of the boom sections contain eyelets for support and lift purposes. The top side walls of the pick-up truck bed include eyelets for upward support of the boom sections.

Abstract: The present invention is for a portable hoist assembly that includes a base member, an upright support member and a boom. A winch and line are attached to the hoist assembly with an engagement member for lifting objects. The base member attaches to a receiving member. The receiving member may be a trailer hitch on a vehicle. The boom and base member pivot with respect to the support member to a collapsed storage position. The boom and base member extend substantially parallel to the support member, and an end of the boom attaches to the base member. The engagement member is inserted within the base member for storage.

Abstract: A portable lifting frame comprises an elongate track provided with a bogie movable there along. The bogie is adapted to accept a lifting device. An elongate support is provided for the track wherein the track and support are made up of two or more cojoining portions 2a and 2b. The co-joining portions 2a and 2b are hinged together end to end at pivotal hinges 3. The co-joining portions 2a and 2b have an open position where they lie in the same place and a closed position where they lie parallel to each other. The support is provided with two or more legs 4, 5, 6, 7 pivotally attached to one end of the support where only each leg is extendable. The other end of the support is provided with a support element.

Abstract: While a crawler body 110 is traveling, infrared sensors 144 and an elevational difference calculator 132 incorporated in a controller 130 detects the magnitude of a step present ahead of the crawler body 110. A safety speed calculator 134 calculates a safety speed based on the magnitude of the step detected and on the position of the platform 116 relative to the crawler body 110, which position is detected by various detectors 141˜143 and by a position calculator 133. A comparator 135 compares this safety speed with the traveling speed of the crawler body 110, and if the current speed of the crawler body 110 is greater than the safety speed, then the comparator 135 outputs a warning signal. Upon receiving this signal, a restrictor 136 controls a valve controller 131 to reduce the speed of the crawler body 110 such that the crawler body 110 can travel over the step safely.