Improved crane for mounting on vehicles

Abstract

 The crane (1) comprises a main column (2) which is rotatable about a vertical axis and supports an operative arm (3) articulated thereto; the operative arm (3) is movable along axes arranged along vertical planes and is moved by at least one fluid-dynamic jack (7) interposed therebetween; the lower end of the jack (7) is articulated to the column (2) and the upper end of the jack (7) is connected to a hinge (6) for further articulation together with corresponding ends of at least one second jack (8), which is interposed between the first jack (7) and the operative arm (3), and of at least one connecting rod (5), the opposite end whereof is coaxially pivoted in the same point of rotation and articulation between the operative arm (3) and the main column (2); the first jack (7) and the second jack (8) provide lifting torques which have lever arms of presettable minimum and maximum extent.

Description

[0001] The present invention relates to an improved crane for mounting on vehicles.

[0002] The application of lifting devices, specifically cranes, to motor vehicles for industrial use has been known for a long time. This application has allowed to achieve a good individual operativity of each of such vehicles, typically trucks, which can perform operations which once required the distinct presence of a further vehicle assigned to the loading.

[0003] In these last years the art has been refined considerably, producing structures with increasingly compact dimensions or structures which can fold up in various manners, with the specific aim of not protruding from the transverse contour of the vehicle when the crane is in idle position and the vehicle travels on ordinary roads.

[0004] Research aimed at achieving increasingly high lifting forces has increased together with such compactness and articulation, and the most relevant disadvantages have been observed in this last field due to the constructive and structural limitations of current cranes.

[0005] In detail, it has been observed that when the angle defined between the axis of the main column and the axis of the lifting arm increases, the lever arm between said column and the lifting element (which is generally constituted by a hydraulic jack) decreases in value and consequently progressively reduces the lifting moment; all this leads to poor operative capability in a limited range of operation around the vehicle, but provides considerable force when the lifting arm is instead proximate to its horizontal position.

[0006] It is still therefore currently necessary to make a precise constructive choice: i.e., either provide the crane with a limited possibility of vertical angular rotation in order to avoid an excessive decrease of said lever arm and thus obtain a good compromise between operativity proximate to the vehicle or at a certain distance therefrom, or choose a crane which has good operativity exclusively at a considerable distance.

[0007] The technical aim of the present invention is to provide an improved crane for mounting on vehicles which can solve the above described problem with a single structure and furthermore provides a more fluid-like actuation than is currently available.

[0008] This aim is achieved by an improved crane for mounting on vehicles, of the kind comprising a main column which is rotatable about a substantially vertical axis and supports an operative arm which is articulated thereto, said arm being movable according to angles lying in vertical planes by at least one fluid-dynamic jack interposed therebetween, characterized in that a lower end of said jack is articulated to said column and an upper end of said jack is connected to a hinge for further pivoting together with corresponding ends of at least one second jack, interposed between said first jack and said operative arm, and at least one connecting rod, the opposite end of said connecting rod being pivoted coaxially in the same point of rotation and articulation between said operative arm and said main column, said first jack and said second jack providing lifting torques which have lever arms of presettable minimum and maximum extent.

[0009] Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of an improved crane for mounting on vehicles, illustrated only by way of non-limitative example in the accompanying drawings, wherein:

figure 1 is a side view of a possible embodiment of the invention in an operating position with the arm arranged horizontally;

figure 2 is a view thereof in a further operating position with the arm arranged substantially vertically;

figure 3 is a front view in a folded-up idle minimum-­bulk position;

figure 4, finally, is a Cartesian graph of the qualitative behavior of the force curves which can be applied respectively to a known crane manufactured to operate with a limited operating range, to a crane which constitutes the invention, and to a crane manufactured to operate with a long operating range.

[0010] With particular reference to the above described figures, the reference numeral 1 generally indicates an improved crane for mounting on vehicles which comprises a main column 2 which can rotate about a vertical axis A.

[0011] The main column 2 supports a protruding operative arm 3 which is articulated to the upper end of said column with at least one hinge 4 (or equivalent device); the corresponding end of a connecting rod 5 is connected to said hinge and rotates coaxially thereto, and the opposite end of said rod is coupled, by virtue of a further hinge 6, to the coinciding ends of a first jack 7 and a second jack 8 which are both fluid-dynamically actuated; the first jack 7 is located between said hinge 6 and the column 2, while the second jack 8 is located between said hinge 6 and the arm 3.

[0012] The Cartesian graph illustrated in figure 4 illustrates the qualitative behaviors of force curves: respectively, "α" is a curve related to a conventional crane suitable for operating with considerable ranges, "β" is a curve which indicates the same forces related to the invention, and "γ" is a curve illustrating the characteristic of the forces of a conventional crane adapted to operate with limited ranges.

[0013] The axis of the abscissas plots indicative load values in kgm; the ordinates plot the width of the lifting angle of the arm 3 with respect to a horizontal configuration.

[0014] The operation of the invention can be easily understood from the above description: the arm 3 moves from the folded idle configuration, as illustrated in figure 3, to its operative configuration: it can thus rise and/or fold conventionally according to the requirements.

[0015] However, the elevation angle with respect for example to a horizontal axis is divided into two half-angles with the concomitant action of the jacks 7 and 8 and of the rod 5, which acts as a spacer-like element between the axis A′ of the column 2 and the longitudinal axis B of the jack 7, thus maintaining therebetween a minimum lever arm, indicated by B′, even when said operative arm 3 is raised to the maximum possible height.

[0016] This division of the lifting angle determines a more fluid operation of the crane and, as can be qualitatively observed in the graph of figure 4 for the curve "β", after a progressive decrease of the available effort, a portion substantially comprised between 70° and 90 ° of elevation of the arm 3 in which said applicable effort remains substantially constant.

[0017] In practice, this allows the portion of arm 3 articulated directly to the column 2 to have a considerable lifting torque even if said lifting arm 3 operates while folded in the immediate vicinity of said column 2.

[0018] In practice it has been observed that the invention thus described achieves the intended aim.

[0019] The invention thus conceived is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept.

[0020] All the details may furthermore be replaced with other technically equivalent elements.

[0021] In practice, the materials employed, as well as the dimensions, may be any according to the requirements without thereby abandoning the scope of the protection of the following claims.

[0022] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting affect on the scope of each element identified by way of example by such reference signs.

Claims

1. Improved crane for mounting on vehicles, comprising a main column which is rotatable about a vertical axis and supports an operative arm which is articulated thereto, said arm being movable through angles lying in vertical planes, said arm being furthermore moved by at least one fluid-­dynamic jack interposed therebetween, characterized in that a lower end of said jack is articulated to said column and an upper end of said jack is connected to a hinge for further articulation together with corresponding ends of at least one second jack interposed between said first jack and said operating arm and of at least one connecting rod the opposite end whereof is hinged coaxially in the same point of rotation and articulation between said operative arm and said main column, said first jack and said second jack providing lifting torques with lever arms of presettable minimum and maximum extent.

2. Improved crane for mounting on vehicles according to claim 1, characterized in that the value of the lifting torque is substantially constant for operative arm lifting angles comprised between 65° and 90°.

Drawing