JPS60148730A - Cargo-handling device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to load handling equipment for handling heavy loads such as cargo containers, trailers and bulk cargo. More particularly, the invention is embodied in a load handling and conveyance vehicle having load handling equipment used to lift and convey heavy loads such as load containers, load trailers, and bulk loads. It is something.

The invention comprises a load handling device that can be used with support to move loads, such as cargo containers, from one location to another.

The apparatus has a generally longitudinally extending main lift beam. The beam has a forward end and a rearward end.

A first link means is pivotally connected to the aft end of the king lift beam and the support. Control beam means is located generally parallel to and below the live lift beam. Pivot means pivotally interconnects an intermediate portion of the control beam means to the first link means near an upper end of the second link means. A second link means is pivotally connected to the support and the aft end of the control beam means. A third link means is pivotally connected to the forward ends of the lift beam and control beam, and is also connected to the load carrying structure or gallows.

Garous is a releasable ramp structure that can be fixed to a cargo container. Support is busy and equipped,
Additionally, longitudinally extendable and retractable means pivotally connected to the intermediate portion of the lift beam move the lift beam from the retracted position to the extended position and back to the retracted position. It is used4. By doing this, the load holding structure will move along a straight path.

When the lift beam is in the retracted position, the lift beam is folded relative to the first link means and the control beam means, i.e. in a folded position, so that the load handling device has a generally low profile.

The extendable and retractable means are operable to pivot the first and second links about separate axes relative to the support to move the load carrying structure along a generally linear path. It consists of fluid actuated piston and cylinder means.

The load carrying structure does not deviate from a linear path during movement between the extended and retracted positions. The load-bearing structure is self-leveling during its vertical movement.

The second link means is provided with extendable and retractable means such as fluid actuated piston and cylinder means, the means being operable to change the length of the second link means. be. Reducing the length of the second link means moves the load carrying structure to a rearward tilted position. This places the load behind the normal linear path of motion of the load carrying structure and at a slightly upwardly inclined angle. Increasing the length of the second link means causes the load lifting structure to move into a forward inclined position 1σ towards the front of the linear movement path of the load lifting structure. The load carrying structure is positioned at a slightly downwardly inclined angle. In one form of the invention, the support is part of the frame of a vehicle that handles and transports loads. The vehicle has a forward drive wheel connected to the frame and a steerable wheel operatively mounted to the rear of the frame.

Load handling equipment operably mounted on the frame is used to lift and stack cargo containers and similar loads. The baggage handling device includes lift beam means located above the frame and extending longitudinally of the frame. The first link means is located below the lift beam means and is pivotally connected to the frame and the aft end of the lift beam means. A control beam means is located between the lift beam means and the g-link means. The aft end of the control beam means is connected to the second link means.

The forward ends of the control beam means and the main lift beam means are connected to third link means fixed to the load support structure. Since the center of gravity of the baggage handling device is behind the front drive wheels, the weight of the device will be distributed between both the front and rear wheels. The baggage handling device can be lowered into a folded position adjacent to the frame, so that the operator has a good view of the vehicle. The second link means includes
Extendable and retractable means, such as a hydraulic piston and cylinder assembly, may be included operable to change the length of the second linkage means to effect tilting of the load carrying structure.

It is an object of the invention to provide a vehicle with a movable load handling device that can be retracted into a folding position to give the vehicle a relatively low profile for handling objects such as cargo containers. That's true. Another object of the invention is to
cargo container with a relatively low profile,
Roll, on for unloading and unloading
and to provide a baggage handling machine that can be used as a roll, off vehicle. Still another object of the present invention is to provide a main lift beam, control beam and linkage means that are folded into a folded position relative to each other and have a relatively compact and low profile; Nevertheless, it is an object of the present invention to provide a baggage handling device in which the beam and linkage means can be extended to a relatively long extended position or reach. Yet another object of the invention is to connect a rotationally interconnected beam structure to a load carrier, which automatically levels the carrier and moves the carrier along a linear path from a retracted position. It is an object of the present invention to provide a baggage handling device operable to move to an extended position. A further object of the present invention is to provide a load handling vehicle with a lifting device operable to maintain a substantially constant and unchanging load on the wheels of the vehicle during a lifting operation. be. Yet another object of the invention is to enable rearward tilting of the load carrier during load handling movements of the device. It is an object of the present invention to provide a baggage handling device equipped with a control structure operable in this manner. These and other objects and advantages of the invention are set forth in the following description of one embodiment of a baggage handling device.

Referring to FIG. 1, there is shown a motor-driven vehicle, generally indicated at 10, having a generally horizontal longitudinal frame 11. As shown in FIG.

A pair of correction drive wheels [2] are attached to the front of the frame 11. A pair of rear steering wheels 13 are rotatably mounted at the rear of the frame 11. Wheel] 2 and 1: l? Therefore, the vehicle 10 is rotatably and drivably supported on the ground 14. In vehicle 10, internal combustion engine 16 is operatively coupled to drive wheels 12 by a power transmission and differential (not shown).

A cockpit 17 is mounted on the aft portion of the frame 11 adjacent to a steering control assembly 18 for the steering wheel 13.

A load handling device, generally designated 19, is operably mounted on frame 11 forward of cockpit 17. Device I
9 supports a load lifting structure or load carrier 21, known as a gullouse, which is used to handle load containers 22.

The lift structure 21 can be modified to handle 113 rope-supported loads that are not housed in a load trailer or container. Lifting structure 21 may be replaced by a fork or a load lifting mechanism as disclosed in US Pat. No. 4,016,992.

A vehicle IO is a baggage handling machine used in ports and terminals to lift and stack cargo containers. Load containers are removed from docks and docks by vehicle 10 and stacked at storage locations in a smooth and efficient manner. The vehicle 10 is equipped with baggage handling equipment 19 and has a relatively low profile so that it can be used as a roll-on and roll-off vehicle for loading and unloading cargo ships.

The vehicle frame 11 provides support for the load handling attachment 19. Vehicle 10 is an example of a mobile support that can be used for baggage handling device 19. The support is
It can also be a fixed foundation, a rotatable foundation, a movable platform, the frame of a railway vehicle, or a deck or frame structure of a ship or anchor. Baggage handling device 19
The can be used as a vertical lift or as a horizontal or lateral load transfer.

Referring to FIGS. 1 and 2, the baggage handling device 19 is
A longitudinally located main lift beam, generally designated 23, is located above and along the midplane of frame 11. The main lift beam 23 is a box beam structure having a generally flat bottom wall 24 and an upwardly converging top wall 26. The central cross section of the top wall 26 has a laterally extending apex. Lift beam 23 has a forward end 28 and a rearward end 29, with forward end 28 located above and slightly forward of the front of frame 11.

A longitudinally located main or first link, generally designated 31, is located below the main lift beam 23. As shown in FIG. 3, the i-end 32 of link 31 is integral with a cross member or crosshead 33. As shown in FIG. Part 3
3 has a horizontal hole that accommodates a large pivot pin 36. Both ends of the pivot pin 36 have sleeve bearings 37 mounted on the longitudinal side frame members 39 and 41.
and 38. Side frame members a9 and 4I are part of the vehicle frame 11,
Moreover, it generally extends in the vertical direction. The side frame members 39 and 41 are spaced laterally apart from each other and provide support for the baggage handling equipment 19.

The aft end 42 of the link 31 is located below the aft end of the main lift beam 23. A pair of upright side members or plates 43 and 44 of the rear end 42 are attached to the lift beam 23.
The rear end 290 is located adjacent to both sides. A transverse pivot pin 46 connects the beam 23 to the side members 43 and 4.
It is rotatably attached to the top of 4. The pin 46 connects the transverse sleeve 47 mounted within the end 29 and the side fronts 43 and 4.
4 and protrudes through sleeve bearings 48 and 49 mounted on the sleeve bearings 48 and 49, respectively.

A control beam or link, generally designated 51, is located longitudinally between the main lift beam 23 and the first link 3. As shown in FIGS. 1 and 4, beam 51 extends through a passageway or space 52 between side members 43 and 440 and below main lift beam 23. As shown in FIGS.

A transverse pivot pin 53 pivotally attaches the intermediate portion of control beam 51 to side members 43 and 44.

The pin 53 projects through a sleeve 54 attached to the control beam 51. A pair of sleeve bearings 56 and 57 mounted on the side members 43 and 44 respectively accommodate and rotatably accommodate both ends of the pivot pin 53. Pivot pin 53 provides a transverse pivot axis for control beam 51. The pivot axis for beam 51 is below and substantially parallel to the pivot axis of pin 46 for main beam 23.

As shown in FIGS. 2 and 5, the center portion 58 of the control beam 51 also extends upwardly from the pivot pin 53. As shown in FIGS. A transverse or cross member 59 is connected to the intermediate portion 58
It is fixed by welding or the like to the rear end of the A first pair of rearwardly facing arms 61 is secured to one end of cross member 59.

A second pair of rearwardly directed arms 62 are secured to the other end of cross member 59. Arms 61 and 62 are positioned laterally, ie, facing outward from both sides of engine 760.

A second link assembly, generally designated 63, includes arm 61.
and 62 and pivotally connected to the frame members 39 and 41. Link assembly 63 is used to control the rotational movement of control beam 51 and the forward and rearward tilting of load carrier 21.

Referring to FIG. 5, the link assembly 63 has first extendable and retractable means consisting of a rod 64 pivotally connected at its upper end to the rear end of the arm 61 by a pivot pin 66. are doing. The lower end of the rod 64 is attached to a piston and cylinder assembly 65 consisting of a cylinder having a chamber 68 containing a piston 69 .

A lower end of a downwardly directed rod 71 fixed to the piston 69 is rotatably mounted on a transverse stub shaft 72 .

The shaft 72 projects laterally from the plate 73. A nut and bolt assembly 74 secures the plate 73 to the side member 39Vc of the frame. The second link assembly 63 has second extendable and retractable means consisting of an upper long door 6 mounted with a transverse pivot pin 77 to the rear end of the arm 62. The lower end of the rod 76 is connected to a piston and cylinder assembly 78. The structure of piston and cylinder assembly 78 is identical to that of cylinder 67 and piston 69.

A rod 79 extending downwardly from the piston and cylinder assembly 78 is pivotally mounted to a transverse stub shaft 81 . Stub shaft 81 is attached to frame side member 41 by nut and bolt assembly 82.

Piston and cylinder assemblies 65 and 78 are actuated simultaneously to lengthen, retract, and shorten second link assembly 63. A hydraulic fluid system having a pump 83 operated by engine 16 supplies hydraulic fluid under pressure to control pulp 84 . A manual operating lever 86 or similar control of the control valve 84 is located in the cockpit 1.
7, the operator selectively controls the flow of hydraulic fluid toward and from the ends of the piston and cylinder assembly 65 to extend the piston and cylinder assembly 65. and degeneracy can be controlled.

One third link assembly 89 is shown in FIG.
It also consists of a pair of upright plates 91 and 92 fixed to the intermediate area of the load carrier 21. A transverse pivot pin 93 pivotally connects the forward end of main lift beam 23 to the upper ends of plates 91 and 92. Pivot pin 93 projects through a transverse sleeve 94 mounted within forward end 28 of main lift beam 23 . Both ends of pin 93 are rotatably mounted within sleeve bearings 96 and 97 mounted on the upper ends of plates 91 and 92. A downward facing ear or member 99 is connected to the plate 91.
and 92 are fixed to a transverse beam 103 mounted in the intermediate section. Ear 99 is located intermediate between plates 91 and 92.

The front end 101 of the control beam 51 is bifurcated and is located adjacent to both sides of the ears 990.

The restraining beam 51 is pivotally connected to the third link assembly 89 by a transverse pivot pin 02 projecting through an ear 99 and an aligned hole in the forward end 101. The transverse axis of pivot pin 02 is below and parallel to the transverse axis of pivot pin 93.

Returning to FIG. 1, the load carrier 21 consists of a U-shaped frame or beam 103 attached to plates 91 and 92. Frame 103 is supported in a generally horizontal position with the sides of the frame extending forward. A box structure 104 is located below the frame 103. A plurality of chains 106 connect the box structure 104 and suspend and support the box structure 104 from the frame 103. A hydraulic cylinder 107 is interposed between the plates 91 and 92 and the box structure 101 to move the box structure relative to the frame 103 and thereby move the lower container gripping unit 108 onto the cargo container 22. It can be manipulated to align with the top. The lower unit 108 includes a plurality of rotatable locking arms 109 that can fit into the corner units of the container 220 to attach the container 22 to the lower unit 108. A hydraulic cylinder (not shown) is operable to rotate locking arm 109 into locked and unlocked positions. Load carrier 21 is of a conventional load carrying structure used with load containers. This construction can be replaced by other constructions for handling load trailers, bulk cargo, and similar loads.

Main lift beam 23, main link 31 and control beam 51
is located longitudinally along the co-progressive vertical plane. All rotational movements of the main lift beam 23, main link 31, control beam 51 and linkage means 63 are about separate transverse axes perpendicular to this vertical plane. As shown in FIG. 1, when the king beam 23, the link 31, and the control beam 51 are in the folded position, that is, the folded position, the posture or profile of the mounting 19 is lowered. .

The baggage handling equipment [19 is constructed as shown in FIG. From the folded or folded position, it moves to the extended or raised position as shown in FIG. Extensible and retractable assembly 111 includes an elongated linear piston and cylinder assembly 113. As shown in FIG. 2, the lower end of piston and cylinder assembly 113 is pivotally connected to an inwardly directed pivot axis 114 fixed to frame member 39. As shown in FIG.

The upper end of the piston and cylinder assembly is rotatably mounted on a cylindrical pivot member 117.
have. The pivot member 117 is the raw lift beam 2
．． 3. The intermediate area of the holder is fixed and projects outwardly from the area.

Extendable and collapsible assembly 112 has a piston and cylinder assembly 118 connected at its lower end to a pivot axis 119 fixed to frame member 41. The upper end of the piston and cylinder assembly 118 is
It has a sleeve 121 rotatably mounted on a cylindrical pivot member 122.

Pivot member 122 is fixed to the side of main beam 230 and is axially aligned with pivot member 117.

Piston and cylinder assemblies 113 and 118 are actuated simultaneously to selectively raise or lower main beam 23. When the main beam 23 moves, the main link 31, the control beam 51 and the second link 3 articulate with respect to each other to provide support to the main beam 23. The relative movement of beams 23 and 51 and links 31 and 63 is such that the load carrier moves along a straight path as shown as vertical line 127 in FIG. The pressurized hydraulic fluid is transferred to the engine 16
is supplied from a pump 123 drivingly connected to. The pump 123 controls the pressurized hydraulic fluid to the pulp 12.
4, this control pulp 124 is connected to the lower end VC of piston and cylinder assemblies 113 and 118 by line 126. Since the pulp 124 is located in the cockpit 17, the operator of the vehicle can control the extension and folding of the main beam 23 and, as a result, the unloading sound of the cargo container 22. Other types of controls can be used to provide pressurized fluid to the piston and cylinder assembly. Piston and cylinder assembly 1
13 and 118 have relatively small folded lengths and large strokes, so they occupy very little space.

In the condition illustrated in FIG. 7, piston and cylinder assemblies 113 and 118 are in a fully extended position. Link assembly 89 moves in a generally vertical path along vertical plane 127. This plane of motion is maintained during operation of the device 19 from the retracted overlapping position illustrated in FIG. 1 to the fully extended position as illustrated in FIG. The king link 51 and the second link assembly 63 pivot about separate arcs so that the ball beam 23 and control beam 51 direct the carrier 21 into a generally horizontal position and its movement into a generally vertical plane. They will rotate and move relative to each other to maintain their position. The device 19 operates to lift the cargo container vertically. The vehicle 10 carries the lifted containers 21 to a stacking position. The device 19 then includes a piston and cylinder assembly 113
and 118 to position the container vertically in its storage location. The vehicle operator is not required to compensate for container arcing or rocking during side-by-side operations.

Referring to FIG. 8, the carrier 103 can be moved rearwardly, ie, to a rearward tilted position. This means that piston and cylinder assemblies 65 and 7
8, thereby reducing the overall length of the link assembly 63. As the length of the link assembly 63 increases, the forward tilting of the frame 103 in front of the vertical plane 127 results in K.

As illustrated in FIG. 1, the link 63 and the extendable and retractable means 11'l and 112 are pivotally connected to the frame adjacent on both sides of the drive wheel 12. . The center of gravity of the load handling device is behind the axis of the rumble wheel 12. Therefore, the weight of the baggage handling device 19 is distributed between the front wheels and the rear wheels. Main lift beam 23
, the control beam 51 and the links 52 and 63 are of a folded structure, and the connection point of the cargo handling device 19 is located on the frame 11, thereby achieving a longer length with less counterweight than in conventional cargo container lifting and transfer vehicles. A shorter vehicle frame can be used.

Having thus illustrated and described preferred embodiments of the baggage handling system and vehicle, those skilled in the art will appreciate that the structure, arrangement of structures, and extendable and retractable assemblies may depart from the invention. It will be understood that no changes may be made.

[Brief explanation of drawings]

FIG. 1 is a side view of a mobile container handling vehicle partially cut away to illustrate the baggage handling device, and FIG.
3 is an enlarged sectional view taken along line 3-3 in FIG. 1, and FIG. 4 is an enlarged sectional view taken along line 4-4 in FIG. It is a sectional view, and the fifth
6 is an enlarged sectional view taken along line 5--5 of FIG. 1 and a circuit diagram of the hydraulic control device for the second link means, and FIG. 6 is an enlarged sectional view taken along line 6--6 of FIG. 7 is a side view of the baggage handling device in an extended position, and FIG. 8 is similar to FIG. 7 showing the baggage handling device with the baggage carrier in a rearward tilted position This is a diagram. Code explanation 10...JIE decoy' 11...Vehicle frame 12.
...Front wheel drive wheel 13...Steering wheel outside eel 17...Cockpit 19...Luggage handling device 20...
Luggage lift structure 21... Luggage carrier 22... Loading container 23... Main lift beam 28... Front end 31... First link 51... Control beam 63
...Second link 5.78...Piston and cylinder assembly 84...Control valve 89...Third link assembly Applicant Reigo Incobo t/-
Ted says ゝ-Ii゛””:',,'.Layer' 1 Agent Patent attorney Takashi Hayashi Voice; 1,,J Continuation of page 1 @ Inventor Howard A. Suchi Kitat, Yuwart, United States of America 13748 0 Inventor Ropart J.L. Ngwerskiy, United States of America 07 S. Brace , olein 9f 23
Q, Portland, CRITZ MN 55369. Mabel Book Globe, 10295

Claims (1)

Claims: (1) a support; a live lift beam located above the support and extending generally longitudinally; further having a forward end and a rearward end; a first link means pivotally connected and having an upper end pivotally connected to an aft end of the lift beam; and a control beam means having forward and aft ends located generally parallel to said lift beam. , pivot means pivotally connecting the intermediate portion of the control beam means to the first link means proximate an upper end of the link means, and pivot means pivotally connected to the support and the aft end of the control beam means. a second link means mounted on the support and pivotably connected to both forward ends of the lift beam and the control beam means, and a third link means capable of being connected to the load lifting means; longitudinally extendable and retractable means pivotally connected to the intermediate portion of the lift beam, the lift beam being extended by extension of the extendable and retractable means; A load handling device in which the outer end is brought into an extended position and the outer end of the lift beam is moved from the extended position to a retracted position adjacent the support by retraction of the extendable and retractable means. (2) The upper end of the first link means has laterally spaced side members and means for pivotally connecting the side members to the rear end of the beam. The device according to item 1. 3. The apparatus of claim 2, wherein said control beam means extends between said side members of the beam. 4. The apparatus of claim 3, wherein said control beam means is located below said beam. (5) said control beam means is a linear rigid member between a first link means and a third link means, and a pair of arms are connected to said rigid member, said second link means being connected to said arms; 4. Device according to claim 3, characterized in that it is pivotally connected. (6) The device according to claim 5, wherein the second link means comprises a pair of link members rotatably connected to the arm and the support. (7) The link member includes extendable and retractable means for changing the length of the second link means and thereby moving the third link means to an inclined position. The device according to item 6. 8. The apparatus of claim 7, wherein said extendable and retractable means comprises a fluid actuated piston and cylinder assembly. (9) The support includes a longitudinal frame member located laterally relative to each other, a means for rotatably attaching the first link means to the frame member, and a means for rotatably attaching the second link means to the frame member. 4. An apparatus as claimed in claim 3, including means for attaching the frame member in a circular motion and means for dynamically attaching the extendable and retractable means to the frame member. a@ The device according to claim 1, characterized in that the length in the longitudinal direction of the second link means is shorter than the length in the longitudinal direction of the first link means. 0υ The second link means includes means for changing the length of the second link means.
Apparatus described in section. 02. Apparatus according to claim 11, characterized in that the means for varying the length of the second link means comprises fluid actuated piston and cylinder means. (131) The device according to claim 1, characterized in that the longitudinally extendable and retractable means comprises fluid-actuated piston and cylinder means. (14) Fluid-actuated The piston and cylinder means includes a pair of pistons and cylinders each having a first member fixed to the support and a movable second member extending generally in a transverse direction and pivotally connected to the intermediate portion of the beam. Claim 13 comprising a cylinder assembly, further characterized in that said piston and cylinder assembly are simultaneously operable to selectively move the beam to its extended and retracted positions. Apparatus as described. (151 supports are laterally positioned 1!-
a longitudinal frame member, means for rotationally attaching the first link means to the frame member, means for rotationally attaching the second link means to the frame member, and extendable and retractable; 2. The apparatus of claim 1, further comprising means for pivotally mounting said means on said frame member. 06) drive wheel means operably mounted on the forward end of the frame member, steerable wheel means operably mounted on the rearward end of the frame member, and power means for driving the drive wheel means; 16. A device according to claim 15, characterized in that it comprises: a η a frame having a forward end and an aft end; drive wheel means operably connected to the forward end of the frame;
a steerable wheel means operably mounted on the aft end of the frame; a lift beam means overlying the frame and extending longitudinally of the frame, the lift beam means having a forward end and an aft end; and adjacent to the frame; a first transverse pivot means pivotally connecting said lower end to the frame; said ti>- linking means having an upper end and said linking means having an upper end; a second transverse pivot means pivotally coupled to an aft end of the lift beam means; a control beam means having a forward end and an aft end located generally parallel to said lift beam means; a third transverse pivot means pivotally connected to the second link means near an upper end of the first link means; and a second link means pivotally connected to the frame and the aft end of the control beam means. , a fourth transverse pivot means pivotally connecting the second link means to the control beam means; a third link means located proximate the forward ends of the lift beam means and the control beam means; and the third link. fifth transverse pivot means for pivotally connecting means to forward ends of the lift beam means and the control beam means; said third link means being adapted to connect to a load lifting structure; and said third link means being adapted to connect to a load lifting structure; and a sixth transverse pivot means for pivotally connecting the vertically extendable and retractable means to an intermediate portion of the lift beam means. the outer end of the lift beam means moves to an extended position upon extension of the extendable and retractable means, and the outer end of the lift beam means extends when the extendable and retractable means is retracted. A load handling and transport vehicle moving from a position to a retracted position adjacent to said frame. The upper end of the first link means has laterally spaced side members, and the second pivot means connects the side members to the aft end of the lift beam means.
18. The device according to claim 17, characterized in that: (1!J) The apparatus of claim 18, wherein the control beam means extends between the side members of the lift beam means. 20. The installation of claim 19, wherein said lift beam means and said control beam means are located adjacent to each other when said lift beam means is in its retracted position. eυ The apparatus according to claim 18, wherein the control beam means is a rigid member. The apparatus according to claim 17. (c) The control beam means has a cross member, first and second arm members fixed to the cross member, and the second link means is rotatable to the frame. Claims 1, 2, and 3, comprising a pair of vertically connected members, wherein said fourth pivot member pivotally connects said pair of members to said first and second arm members. 18. The apparatus of claim 17. (to) the pair of members are extended to change the length of the second link means, thereby moving the third link means to a rearwardly inclined position about a generally horizontal transverse axis. 24. The device according to claim 23, characterized in that it comprises retractable and retractable means. (2) The device according to claim 24, characterized in that: (2) the second link means includes means for changing the length of the knee link means;
The device according to item 7. (271) Apparatus according to claim 26, characterized in that the means for changing the length of the second link means comprises at least one fluid-actuated piston and cylinder assembly. 18. The apparatus of claim 17, wherein the extendable and retractable means comprises a fluid actuated piston and cylinder assembly. a pair of piston and cylinder assemblies each having a first member fixed to the frame and a movable second member extending in a generally upright direction and pivotally connected to an intermediate portion of the lift beam means; 29. The piston and cylinder assembly is operable simultaneously to selectively move the lift beam means into its extended and retracted positions. Device.