EP3532424B1

EP3532424B1 - Foldable crane

Info

Publication number: EP3532424B1
Application number: EP17829057.3A
Authority: EP
Inventors: Branko Gril; Boris JERMAN
Original assignee: Tajfun LIV Proizvodnja In Razvoj doo
Current assignee: Tajfun LIV Proizvodnja In Razvoj doo
Priority date: 2016-10-25
Filing date: 2017-09-25
Publication date: 2021-12-15
Anticipated expiration: 2037-09-25
Also published as: ES2905851T3; RS63016B1; WO2018080403A1; PL3532424T3; SI25285A; SI25285B; EP3532424A1; PT3532424T; HRP20220306T1

Description

The object of the invention is a foldable crane, preferably a truck mounted crane including a crane base, i. e. a rotatable column, on which a lift arm is pivotally mounted, and a lift and articulated arms that are connected to each other through a rotatable coupling to move on the same plane. The articulated arm can be in the form of a tube, in which a telescopic articulated arm can be arranged. A hydraulic system is used for driving the articulated arm with respect to the lift arm. The hydraulic system operated between the lift arm and the articulated arm which contains at least one piston hydraulic cylinder attached laterally with respect to the lift and articulated arms. The crane preferably contains two piston hydraulic cylinders which are attached symmetrically with respect to the longitudinal axis of symmetry and laterally with respect to the lift and articulated arms. The piston hydraulic cylinder is mounted on one side to a lever system and on the other side directly to the lift arm. The rotatable column, the lift arm and the articulated arm are arranged in a Z-shape in the folded state of the crane; the articulated arm is folded above the lift arm.
The characteristics of the crane, i. e. its maximum working range and preservation of sufficient torque and force for lifting a load when the lift and articulated arms are in an extended position, are defined by its dimensions. Given the existing dimensions of the crane base, the lift and articulated arms, the horizontal reach of the crane should desirably extend to a maximum, while the crane should preserve sufficient torque and force for lifting a load. It is further desirable that the articulated arm is folded above the lift arm when the crane is in a folded state.
Foldable cranes are known from prior art, in which a lift and articulated arms are pivotally connected between each other and wherein a hydraulic cylinder is attached with one of its ends directly to the lift arm and with another of its ends directly to the articulated arm. All these cranes have limitations as to their maximum horizontal reach and limitations relating to providing sufficient force and torque for lifting a load when the crane is in the most loaded position, i. e. when the lift arm is in the horizontal position and the articulated arm approaches a dead centre or is in the dead centre. The dead centre is a position, in which the longitudinal axis of the hydraulic cylinder overlaps with the connecting point between the lift arm and the articulated arm. This is simultaneously the most extended position of the articulated arm with respect to the lift arm. In the most loaded position, the reach of the lift and articulated arms comes closest to its maximum value. A piston rod of the hydraulic cylinder comes closer to the attachment axis of the lift and articulated arms, which results in the fact that the crane in its extended position lacks sufficient power for lifting a load. For the crane to have a sufficient force for lifting a load a certain distance needs to be available between the longitudinal axis of the piston hydraulic cylinder or its piston rod and the attachment axis of the lift and articulated arms. The length of this distance defines the torque and force of the crane and indirectly also the maximum horizontal reach of the crane. If we want that sufficient force for lifting a load is preserved, the crane in its operating position should not reach the dead centre, i. e. the lift and articulated arms should not extend to their maximum and this means a shorter reach of the crane.
EP patent No. 1770050 describes a foldable crane, in which a hydraulic cylinder is attached with one of its ends to a lift arm and with another of its ends directly to an articulated arm. To simply reach an increase of a maximum horizontal outreach of the crane a solution is proposed that includes an articulated arm configured as a tube, in which a telescopic arm is mounted in a displaceable manner, wherein the working area of the articulated arm for moving the telescopic arm extends to the articulated connection of the articulated arm with the lift arm. Here, an increased outreach of the crane is reached by extending the space in the articulated arm, such that the length of the telescopic arm which is arranged within the articulated arm can be longer.
EP patent No. 2683645 discloses a foldable crane, in which an articulated arm includes a telescopic arm for reaching a longer reach of the working area of the crane. An additional hydraulic cylinder 6 is used for extending and retracting the telescopic arm, wherein one end of the hydraulic cylinder 6 is attached to the telescopic arm in a way that heavier loads may be lifted with the telescopic arm being extended in order to avoid deformation. Figure 1 shows a set of levers between the lift and articulated arms, wherein a hydraulic piston cylinder 10 is centrally attached with one end in the lift arm and the articulated arm cannot be folded above the lift arm.
EP patent No. 066567 described a foldable crane that discloses a set of levers between the lift and articulated arms, wherein the set of levers allows folding the articulated arm below the lift arm and the lift arm is positioned transversely with respect to the crane frame. The hydraulic piston cylinder is attached with one of its ends to the articulated arm and with another of its ends to the lift arm through a set of levers, which means that the entire mass of the hydraulic piston cylinder is on the articulated arm. The articulated arm can be only folded below the lift arm.
Foldable cranes are also disclosed in WO 92/04270 A1 , WO 98/17576 A1 , EP 2 683 645 A1 and EP 2 789 566 A1 . EP 2 248 753 A1 discloses a foldable crane according to the preamble of claim 1.
The above-mentioned disadvantages are solved by the crane of the invention, as defined in claim 1.
The foldable crane of the invention includes an additional set of levers belonging to each piston hydraulic cylinder. The set of levers consists of two lever elements whose first ends are pivotally connected with the piston hydraulic cylinder and to each other; one lever element is simultaneously pivotally connected with the lift arm with its second end, while the second lever element is pivotally connected with the articulated arm with its second end. The hydraulic piston cylinder is pivotally attached with one of its ends to the lift arm, while it is attached to the articulated arm through a set of levers. The crane contains two piston hydraulic cylinders, which are positioned symmetrically with respect to the axis of symmetry of the arms and laterally with respect to the lift and articulated arms at each side of the crane. The two sets of levers are connected with each other through a linking element via rotatable mounting that connects both lever elements with the piston hydraulic cylinder. A stiffer set of levers is herewith achieved.
Such attachment of the hydraulic cylinder to the lift and articulated arms still preserves a sufficient distance d between the longitudinal axis of the piston hydraulic cylinder or its piston rod and the attachment axis of the lift and articulated arms. As a result, the crane still has sufficient torque and lifting force of the crane in a position, in which the working outreach of the lift and articulated arm assembly is maximum. In fact, the crane of the invention never reaches the dead centre in its working position. Since the lever elements are attached at the lateral side of the articulated arm, the inner space of the articulated arm for receiving a telescopic arm is not additionally restricted and the telescopic arm can extend along the entire internal length of the articulated arm; in other words, the length of the telescopic arm is only limited by the position of the attachment of the lift and articulated arms. Moreover, such attachment of the piston hydraulic cylinder to the lift and articulated arms allows the articulated arm to fold above the lift arm and the crane has a Z-shape when folded.
The foldable crane of the invention has a considerably improved functionality as the torque and power of the crane are increased at the maximum working outreach of the crane. This allows lifting of heavier loads and lifting loads higher; at a given load capacity the maximum working outreach of the crane is increased. A further advantage lies in the fact that the articulated arm is more easily lifted by a heavier gripper in order to bring the crane from or into a working position. The dead centre of the crane, when the articulated arm is folded above the lift arm, can be overcome by gravity, i. e. by the weight of the articulated arm.
The invention will be described hereinbelow and illustrated on the figures which show:

Figure 1 - a crane in a folded position
Figure 2 - a lift and articulated arm assembly in a partly extended position in a preferred variant, side view
Figure 2a - a lift and articulated arm assembly in a partly extended position in a preferred variant - top view
Figure 3 - a lift and articulated arm assembly in a maximum extended position, i. e. in a maximum working outreach of the crane, in a preferred variant, side view
Figure 4 - a lift and articulated arm assembly in a folded position, side view.

The foldable crane shown in the figures includes a rotatable column 12, to which a lift arm 1 is pivotally mounted through an attachment point 13, an articulated arm 2, in which a telescopic arm 11 can be arranged, wherein the lift arm 1 and the articulated arm 2 are pivotally connected with each other in known ways via attachment point 3, a piston hydraulic cylinder 4 that operates between the lift arm 1 and the articulated arm 2, and a set of levers consisting of a first lever element 5 that has two ends 5a, 5b and a second lever element 6 that has two ends 6a, 6b. The first lever element 5 and the second lever element 6 are pivotally connected to each other through their first ends 5a and 6a in known ways via attachment point 9. The articulated arm 2 is centrally mounted to the lift arm 1.
The piston hydraulic cylinder 4 is connected to the attachment point 9 with its end 4b, while it is pivotally connected with its end 4a in known ways with the lift arm 1 via attachment point 7. The first lever element 5 is connected with its end 5b in known ways with the lift arm 1 via attachment point 8. The second lever element 6 is connected with its end 6b in known ways with the articulated arm 2 via attachment point 10.
According to the invention, the foldable crane contains two piston hydraulic cylinders 4 which are positioned symmetrically with respect to the longitudinal axis of symmetry and laterally with respect to the lift 1 and articulated arm 2 at each side of the crane, wherein each piston hydraulic cylinder 4 includes a belonging set of levers. The sets of levers are pivotally connected with each other by a linking element 14 via attachment point 9 which connects both lever elements with the piston hydraulic cylinder 4.
The first lever element 5 is longer than the second lever element 6. A ratio of the lengths of the first lever element 5 and the second lever element 6 impacts the lifting power of the crane and the crane's kinematics, i. e. the minimum angle α which can be reached between the lift arm 1 and the articulated arm 2 when the crane is in the bottommost point in the working position, the maximum working reach of the crane, and the torque of the crane, i. e. the length of the distance d. To reach optimum kinematics of the crane, the length of the first lever element 5 is at least twice the length of the second lever element 6, the length of the first lever element 5 is preferably at least three times longer than the length of the second lever element 6.
The ratios between the length of the piston cylinder 4 and the first 5 and second lever elements 6 are also defined by the distances x, y and z. The distance x between the attachment point 3 of the lift arm 1 with the articulated arm 2 and the attachment point 7 of the end 4a of the hydraulic piston cylinder 4 with the lift arm 1 must exceed the distance y between the attachment point 3 of the lift arm 1 with the articulated arm 2 and the attachment point 10 of the end 6b of the second lever element 6 with the articulated arm 2, wherein the distance z between the attachment point 3 of the lift arm 1 with the articulated arm 2 and the attachment point 8 of the end 5b of the first lever element 5 with the lift arm 1 must be smaller than the distance x and smaller than the distance y, the distance z is preferably as small as possible.
The attachment point 8 of the end 5b of the first lever element 5 with the lift arm 1 and the attachment point 3 of the lift arm 1 with the articulated arm 2 are positioned along the lift arm 1, wherein the attachment point 8 is positioned with respect to the attachment point 3 closer to the rotatable column 12. The attachment point 10 of the end 6b of the second lever element 6 with the articulated arm 2 is positioned on the articulated arm 2 and distant from the attachment point 3 in a direction towards the load attachment.
As the hydraulic piston cylinder 4 is directly attached to the lift arm 1, the entire mass of the cylinder is distributed on the lift arm 1, wherewith the carrying capacity of the crane is additionally increased and heavier loads can be lifted.
With the crane in the working position, the attachment point 9 which connects both lever elements with the piston hydraulic cylinder 4 is always located below the attachment point 10 of the end 6b of the second lever element 6 with the articulated arm 2. The maximum working outreach of the crane is yet further increased, the crane has higher carrying capacity at the maximum working outreach since the crane does not reach the dead centre at its maximum working outreach. With the crane in the folded position, the attachment point 9 is always located above the attachment point 10. Hence, the articulated arm 2 can fold on the lift arm 1 and the crane has a Z-shape when folded.

Claims

A foldable crane, preferably a truck crane, that includes a rotatable column (12), to which a lift arm (1) is pivotally mounted through an attachment point (13), and a lift (1) arm and an articulated arm (2) that are pivotally connected with each other via attachment point (3), and a hydraulic system that operates between the lift arm (1) and the articulated arm (2), and that contains two cylinders (4), which are positioned symmetrically with respect to the longitudinal axis of symmetry of the lift arm (1) and articulated arm (2) and attached laterally with respect to the lift arm (1) and articulated arm (2) at each side of the crane, characterised in that
each piston hydraulic cylinder (4) includes a belonging set of levers, and the two sets of levers are connected with each other by a linking element (14) via pivotal attachment (9) which connects both lever elements with the piston hydraulic cylinder (4),

and wherein each of said sets of levers consists of a first lever element (5) that has two ends (5a, 5b) and a second lever element (6) that has two ends (6a, 6b), and the first lever element (5) and the second lever element (6) are pivotally connected with each other through the first ends (5a) and (6a) via attachment point (9) and the first lever element (5) is pivotally connected with its end (5b) with the lift arm (1) via attachment point (8) and the second lever element (6) is pivotally connected with its end (6b) with the articulated arm (2) via attachment point (10), and the piston hydraulic cylinder (4) is pivotally connected with one end in the attachment point (9) with the ends (5a, 6a) of the first (5) and second lever element (6), while the belonging piston cylinder (4) is pivotally connected with its second end with the lift arm (1) via attachment point (7) and the articulated arm (2) is centrally attached to the lift arm (1),

and wherein the length of the first lever element (5) is longer than the length of the second lever element (6), and the attachment point (9) which connects both lever elements (5, 6) with the piston hydraulic cylinder (4) is located below the attachment point (10) of the end (6b) of the second lever element (6) with the articulated arm (2), while the crane is in the operating position, and the attachment point (9) is located above the attachment point (10) while the crane is in the folded position,

and wherein the distance (x) between the attachment point (3) of the lift arm (1) with the articulated arm (2) and the attachment point (7) of the end (4a) of the hydraulic piston cylinder (4) with the lift arm (1) exceeds the distance (y) between the attachment point (3) of the lift arm (1) with the articulated arm (2) and the attachment point (10) of the end (6b) of the second lever element (6) with the articulated arm (2), and the distance (z) between the attachment point (3) of the lift arm (1) with the articulated arm (2) and the attachment point (8) of the end (5b) of the first lever element (5) with the lift arm (1) is smaller than the distance (x) and smaller than the distance (y).
Crane according to Claim 1, characterized in that the length of the first lever element (5) is twice the length of the second lever element (6).
Crane according to Claim 1, characterized in that the length of the first lever element (5) is at least three times the length of the second lever element (6).
Crane according to anyone of Claims 1 to 3, characterized in that the articulated arm (2) is folded above the lift arm (1) and the crane has a Z-shape when folded.