~ ~77~7 This invention relates to cranes or lifting arms and particularly a crane suitahle for mounting on the back of a truck.
Various sorts of cranes for lifting objects, building materials or machinery are known in the art. These cranes can be p~ovided with a base adapted for mounting on the back of a truck. Often such cranes are mounted just behind the cab portion of the truck. With such cranes the driver of the truck can either load or unload the truck -10 without the need for separate loading machinery such as a travelling crane or fork lift truck. Truck-mounted cranes are particularly useful for the loading or unloading of - materials at locations where separate loading equipment is not readily available or cannot ba provided.
' 15 It is known to provide a truck-mounted crane having a generally upright rotatable column mounted on a supporting base, a first boom extending from the top of the column and a second boom connected to the first boom. Hydraulic piston-cylinder mechanisms are used to pivot the two booms relative to each other and relative to the upright column.
The second boom ca~ be made extensible by providing telescoping inner and outer arms. `
One requirement for a truck-mounted crane is that it must be capable of being stored in a relatively small space when not in use and when the truck is in motion.
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~ 177~7 Otherwise the truck cannot be loaded as much as it otherwise could be. Also the crane cannot extend beyond ~he sides of the truck if it is not to pose a danger to traffic passing by the truck on the road. The height of the crane when ~tored of course cannot be too great because the truck must be able to pass under bridges, electrical cables, etc.
Because of the constraints on the amount of room that the crane can take up when stored on the truck, the size of the booms is necessarily limited~
However, if the booms are made quite small, the reach of the crane is limited and the crane may become unsuitable for some job applications. In order to overcome the difficulty of storing a truck-mounted crane in a small space, some cranes have been constructed with their second boom mounted alongside the end of the first boom to which it is connected. This permits the second boom to be brought to a position where it crosses the column. In other words, the centre portion of the second boom can be manoeuvred so that it lies adjacent the bottom end of the upright column. Such cranes are sold under the trade mark HIAB and include HIAB
models 345 and 650. One difficulty encountered with a side-mounted second boom is that the joint between the second boom and the first boom is weak having regard to the twisting force to which it is subjected under maximum loads.
Accordingly, the joint between the second boom and the first boom must be reinforced or strengthened and this requires additional manufacturing time and expense.
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Accordingly, the present invention seeks to provide a crane which only takes up a relatively small amount of space when it is rnanoeuvred into a storage or transport position. At the same time the second boom, which can be made extensible, can be quite long as compared to prior art cranes requiring the same amount of space.
Acco,rding to the invention, a crane for lifting objects or materials comprises a supporting base and a rotatable upright column having a bottom end mounted on the base and an opening in the side thereof. The crane includes a first boom having an inner end and an outer end and pivotally mounted at the inner end to the top end of the columnO First pivot means can be used to pivot the first ` boom relative to the column. A second boom is pivotally mounted at one end to the outer end of the first boom and a second pivot means can be used to pivot the second boom relative,to the first boom., The second boom can be manoeuvred to a position where the second boom extends through the opening in the column for storage or transport of the crane.
Preferably the second boom is extensible and includes telescoping inner and outer members. The inner arm is brought to a retracted position and is substantially within the outer arm w,hen the second boom is in the position where it extends through the opening.
In the preferred embodiment a hydraulically operated rack and pinion mechanism is provided for rotating the upright column about a vertical axis relative to the supporting base.
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77~7 Further advantages and features will become ; apparent from the following detailed description of a preferred embodiment wherein reference is made to the accompanying drawings.
In the drawings, Figure 1 is a perspective view showing how a crane constructed in accordance with the invention can be mounted in the back of a pick-up truck;
Figure 2 is a rear elevation of the crane with some parts not illustrated for sake of clarity and part of the column broken away; and Figure 3, which appears on the same sheet as Figure 1, is a detailed view along the line 3-3 of Figure 2 showing the hydraulically operated mechanism for rotating the column.
The illustrated crane 10 is provided with a supporting base 12 and a rotatable upright column 14 having a bottom end mounted on the base. The supporting base includes an upright cylinder 16 and a channel-shaped, elongate member 18 rigidly connected to the cylinder. The ~ member 18 has a flat, rectangular top 20 and two short legs ; 22 extending downwardly from the longitudinal edges of the top 20. Extending outwardly from the bottom of each leg 22 is a flange 24. When the crane 10 is mounted in the back of !, 25 a truck such as the truck 26 illustrated in broken linesl the flanges 24 are bolted to the frame of the truck. In the illustrated embodiment, two bolts 28 extend through each `:.
' ~ 177~47 ~ 6 --flange. If desired, the supporting base 12 can be strengthened in the region of the bolts by means o~
triangular ribs 30.
Preferably means are provided for rotating the column 14 about a vertical axis relative to the base 12. In the illustrated embodiment the rotating means includes a hydraulically operated rack 32 and ~ cooperating pinion gear 34 connected to the column 14. ~s shown in Figure 3, the rack is mounted in the side of a cylindrical, elongate piston member 36 which in turn is mounted in the cylinder 1 and two further cylinders 38 and 40. The cylinders 38 and 40 are constructed in a similar manner and each is bolted by means of a flange 42 to an annular flange 44 formed on the cylinder 16. A hori~ontally-extending passageway 46 is formed adjacent one side of the cylinder 16 to accommodate the piston 3~. The movement of the piston 36 depends upon whether hydraulic fluid is fed under pressure t`hrough the hose 48 into the left hand end of cylinder 38 or is fed under pressure through the hose 50 into the right hand end of the cylinder 40. The pinion gear 34 is mounted on a shaft 52 which is connected to a circular plate 54 from which the column 14 extends upwardly. In the illustrated embodiment, movement of the piston 36 to the le~t will cau~e the column 14 to rotate counter-clockwise while movement to the right will cause the column to rotate clockwise.
Preferably means are provided for limiting the amount of rotation of the column 14 to about 180 degrees. This is 7~7 desirable in order that the crane when mounted in the position shown in Figure 1 cannot inadvertently be rotated to a position where it damages the cab 56 of the truck. The degree o~ movement can be limited by reason of the fact that the amount of movement of the piston 36 in cylinders 16, 38, and 40 is itself limited. The crane as illustrated in Figures 1 and 2 is in one extreme position for rotation.
In order to rotate to the other extreme position, the column 14 would be rotated counter-clockwise 180 degrees so that the booms of the crane extend to the right as viewed from the rear of the truck.
The column 14 comprises an end plate 58 and two spaced-apart side plates 60 all of which extend su,bstantially the length of the column. The end plate connects the side plates 60 together and it has an op~ning 62 formed therein. The purpose of the opening will be explained in detail hereinafter but it will be noted from Figure 2 that the length of the opening is approximately one half the height of the column 14.
Connnected to the top end of the column 14 is a first boom 64 having an inner end 66 and an outer end 68.
The first boom 64 is substantially U-shaped in cross-section with the top of the boom being closed. As shown in Figure 1, hydraulic hoses 66 can be connected to the top of~the boom if desired. The first boom 64 is pivotally mounted by ; means of a pin 70 which extends into the side plates 60 of the column. The side plates can be reinforced by means of .
~ ~ 77~47 annular bearing plates 72 mounted on the outside of the plates 60. Means are provided for pivoting the first boom 64 relative to the column and in the illustrated embodiment the pivoting means comprise two hydraulic cylinders 74 and their associated pistons 76 which are mounted on opposite -sides o~ and outside the column 14. In particular the bottom end of each cylinder 74 is pivotally mounted by means of a pin 78~to the lower end of the column. The outer end of the piston 76 is pivotably connected by means of a pin 80 to an inner end portion of the first boom. As can be seen from Figure 1, the means for pivoting the first boom relative to the column leaves the interior of ~he column 14 empty and it therefore can be used when the crane is manoeuvred to its storage position as hereinafter explained.
The second boom 82 is preferabl~ an extensible boom and therefore includes telescoping inner and outer arms 84 and 86. The outer arm 86 is pivotally connected at one end to the outer end 68 of the boom 64. A pivot pin 88 extends through the end of the outer arm 86 and into the side plates of the boom 64. Means are provided for pivoting the second boom relative to the first boom 64, In particular a hydraulic cylinder 89 and its a~sociated piston 91 are pivotall~ connected to ~he two booms. The closed end of the cylinder 89 is positioned inside the ~irst boom 6~
where a pivot pin 93 connects the end of the cylinder to the sides of the boom 64. The outer end of the piston is ~ ~77~7 g located inside the outer arm 86 and is fastened thereto by means of a pivot pin at 95.
Mounted along the top of the second boom 82 is a hydraulic cylinder 90 and an associated piston 92 and this piston-c~linder com~ination is used to extend or retract the inner arm 84 as desired. The outer end of the piston 92 is connected to a short connec~ing plate 94 that extends from the top of the inner arm 84 (as shown in Figure 1). A
further connecting plate 96 is used to attach the crane hook 98 to the end of the inner arm 84. The manner in which the inner arm 84 is slidably mounted in the outer arm 86 is well ~ known in the art and does not form part of the present invention. Accordingly a detailed description of the manner inner arm 84 is slidably mounted in the outer arm 84 is well known in the art and does not form part of the present invention. Accordingly a detailed description of tha manner in which the inner arm 84 is slidably mounted is deemed unnecessary.
As shown in Figure 2, the second boom 82 can be manoeuvred to a position where the second boom extends throught the opening 62 for storage or transport of the crane. In this way the crane can be stored using a minimum of spacç. At the same time the second boom 82 is relatively long and this provides the crane with excellent reach capability, particularly in view of the fact that the second boom can be an extensible boom~
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' ~ ~ !77~7 ` 10 -In order to bring the second boom to the position - shown in ~igure 2, the first boom 64 is raised sufficiently to enable the second boom 82 to be pivoted to a position - inside the back of the pick-up truck. The second boom 82 is then pivoted further in the counter-clocXwise (as seen in Figure 1) until the second boom has been pivoted as far as possible towards the column 14. The first boom 64 can then be lowered to the position shown in Figure 2 or even lower if desired. It will be particularly noted that because the second boom 82 is in an elevated position in the storage position, a minimum o~ room in the back of the truck is required for the crane.
The preferred truck-mounted crane shown comes equipped with a source of pressurized hydraulic fluid mounted on the supporting base 12. This source comprises a hydraulic pump, a hydraulic fluid reservior 98 connected to the pump and a motor for driving the pump. The motor 100 is mounted on top of the fluid reservior while the hydraulic pump 102 is mounted on the siae of the reservior. The pump can be a 2,000 pound working pressure gear pump with a release valve set at 1,450 P.S.I. The fluid reservior is mounted at one end of the supporting base 12. Bolts 104 extend through flanges 106 formed on opposite sides of the reservior. The bolts either extend through holes in the top 20 of the base or through hole~ formed in short angle ` members 108 rigidly fastened to the outside of a leg 22. By means of this source of pressurized hydraulic fluid, all of .
~ ~77~47 the above described piston-cylinder combinations are operated as is the rack and pinion mechanism for rotating the column 1~. For sake of clarity, only portions of the re~uired hydraulic hoses are shown in the drawings. The - control valves for operating the various piston-cylinder combinations are mounted at 110 on top of a post 114 fastened to the base 12. These valves are operated by the manual controls 112. In Figure 1 there are four controls shown. One of these will rotate the column about its vertical axis and a second will pivot the first boom relative to the column. A third lever pivots the second boom relative to the first boom and the fourth lever extends or retrac~s the inner arm of the second boom.
- It is a relatively simple and straightforward operation to mount the crane of the invention in the back of a standard pick-up truck. All that is required i~s the drilling of four holes through the bed of the truck and through the frame beneath. The position of these holes will correspond to the position of the holes formed in the flanges 24 of the base of the crane. As can be seen from the above description, no further steps need be taken to make the crane operational.
Furthermore the use of an opening 62 in the column avoids the need to mount the second boom 82 on the side of the end portion 68 of the first boom. The second boom is in fact mounted in a conventional manner to the first boom.
vertical plane defined by a longitudinally extending centre line of the second boom ex~ends along a longitudinally extending centre line of the first boom.
It will be appreciated that various modifications can be made to the crane described above and illustrated in the drawings without departing from the spirit and scope of the invention. For example, other devices could be used to rotate the column about its vertical axis. The supporting base could also have quite a different configuration than that shown and in fact the configuration will depend to a large extent on where the crane is to b~ mounted.
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