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Title:
CONTROL CENTER FOR AN AERIAL DEVICE COMPRISING A ROTATABLE JOYSTICK
Document Type and Number:
WIPO Patent Application WO/2017/202880
Kind Code:
A1
Abstract:
Control center (30) for an aerial device (12), said aerial device (12) comprising a main boom part (14) mounted with a first end (20) on a turret (16), the main boom part (14) being inclinable around a horizontal axis in a first inclination movement (X1), rotatable around a vertical axis in a rotation movement (Y1), and extendable and retractable along its longitudinal extension direction in a first telescopic movement (L1), wherein the control center (30) comprises a first joystick (44) configured for controlling the first inclination movement (X1) by tilting the first joystick (44) around a first control axis, controlling the rotation movement (Y1) by tilting the first joystick (44) around a second control axis perpendicular to the first control axis, and for controlling the first telescopic movement (L1) by rotating the first joystick (44) around its stick axis (50).

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Inventors:
MAIER, Thomas (Institut Für Konstruktionstechnik und Technisches Design Forschungs- und Lehrgebiet Technisches Design Universität Stuttgart, Pfaffenwaldring 9, STUTTGART, 70569, DE)
SCHMID, Markus (Institut Für Konstruktionstechnik und Technisches Design Forschungs- und Lehrgebiet Technisches Design Universität Stuttgart, Pfaffenwaldring 9, STUTTGART, 70569, DE)
MANDEL, Roland (Institut Für Konstruktionstechnik und Technisches Design Forschungs- und Lehrgebiet Technisches Design Universität Stuttgart, Pfaffenwaldring 9, STUTTGART, 70569, DE)
KARLOVIC, Kristian (Institut Für Konstruktionstechnik und Technisches Design Forschungs- und Lehrgebiet Technisches Design Universität Stuttgart, Pfaffenwaldring 9, STUTTGART, 70569, DE)
POMIERSKY, Philipp (Institut Für Konstruktionstechnik und Technisches Design Forschungs- und Lehrgebiet Technisches Design Universität Stuttgart, Pfaffenwaldring 9, STUTTGART, 70569, DE)
KRAEMER, Jens (Frauenstraße 121, ULM/DONAU, 89073, DE)
Application Number:
EP2017/062480
Publication Date:
November 30, 2017
Filing Date:
May 23, 2017
Export Citation:
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Assignee:
IVECO MAGIRUS AG (Nicolaus Otto Str. 27, ULM, 89079, DE)
International Classes:
B66F11/04; E06C5/04; G05G9/047
Attorney, Agent or Firm:
FIUME, Orazio et al. (STUDIO TORTA S.p.A, Via Viotti 9, TORINO, 10121, IT)
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Claims:
CLAIMS

1. Control center (30) for an aerial device (12), said aerial device ( 12 ) comprising a main boom part ( 14 ) mounted with a first end (20) on a turret (16), the main boom part ( 14 ) being

inclinable around a hori zontal axis in a first inclination movement (XI ) ,

rotatable around a vertical axis in a rotation movement (Yl ) , and

extendable and rectractable along its longitudinal extension direction in a first telescopic movement (LI), wherein the control center (30) comprises a first j oystick (44) configured for

- controlling the first inclination movement (XI ) by tilting the first j oystick (44) around a first control axis ,

- controlling the rotation movement (Yl ) by tilting the first j oystick (44) around a second control axis perpendicular to the first control axis ,

- and for controlling the first telescopic movement (LI ) by rotating at least a section of the first j oystick (44) around its stick axis (50) .

2. Control center according to claim 1 , wherein the aerial device ( 12 ) further comprises an extension boom part (22 ) mounted to the second end of the main boom part ( 14 ) by a hinge mounting (24 ) and being inclinable around a hori zontal hinge axis with respect to the main boom part ( 14 ) in a second inclination movement (X2 ) , and the control center (30) comprises a second j oystick (46) configured for controlling the second inclination movement (X2 ) by tilting the second j oystick (46) around a tilting control axis of the second j oystick (46) .

3. Control center according to claim 2 , wherein the extension boom part (22 ) is extendable and retractable along its longitudinal extension direction in a second telescopic movement (L2 ) , and the second j oystick (46) is configured for controlling the second telescopic movement (L2 ) by rotating at least a section of the second j oystick (46) around its stick axis ( 53 ) .

4. Control center according to one of the preceding claims , wherein the first j oystick (44) comprises a lateral protrusion ( 52 ) protruding from the stick axis ( 50 ) in a radial direction .

5. Control center according to one of claims 2 to 4 , wherein the second j oystick (46) comprises a lateral protrusion ( 52 ) protruding from the stick axis in a radial direction .

6. Control center according to claim 4 or 5 , wherein the lateral protrusion ( 52 ) has a flag shape .

7. Control center according to one of the preceding claims , wherein at least one of the first j oystick (44) and the second j oystick (46) comprises at least one switch ( 60 , 62 ) disposed on its top end or on its circumferential surface .

8. Control center according to claim 7, wherein the at least one switch ( 60 , 62 ) is a movement restriction control switch for activating/deactivating a movement restriction of the aerial device ( 12 ) .

9. Control center according to claim 7 , wherein the at 1Θ cL St one switch ( 60 , 62 ) is a communication control switch for activating/deactivating a communication function of the aerial device ( 12 ) .

10. Control center according to one of the preceding claims , comprising at least one armrest (38) , with the first joystick (44) being disposed at a front end of the armrest (38) .

11. Control center according to claim 10 , wherein the first control axis of the first j oystick (44) is generally perpendicular to the extension direction of the armrest (38) .

12. Control center according to one of claims 2 to 11, comprising an operator ' s seat (32), with a backrest (36) and two left and right armrests (38,40) disposed laterally at two opposite sides of the backrest (36) , with the first j oystick (44) being disposed at one of the armrests (38) , and the second j oystick (46) being disposed at the other armrest (40).

13. Control center according to claim 12 , wherein the tilting control axis of the second j oystick (46) is generally perpendicular to the extension direction of the other armrest (40) .

14. Firefighting vehicle (10), comprising a turnable ladder as an aerial device ( 12 ) , and a control center (30) for controlling the turnable ladder according to one of the preceding claims .

Description:
"CONTROL CENTER FOR AN AERIAL DEVICE COMPRISING A ROTATABLE JOYSTICK"

TECHNICAL FIELD

The present invention relates to a control center for an aerial device .

BACKGROUND ART

One example for such an aerial device is a telescopic turnable ladder of a firefighting vehicle . It comprises at least one ladder set mounted on a turret with a first end, such that it can be inclined around a horizontal axis and rotated around a vertical turret axis . This ladder set shall be denoted as a main boom part in the following, while the inclination of this main boom part shall be denoted as a first inclination movement . Moreover, the main boom part can be telescopically extended and retracted along its longitudinal extension direction in a telescopic movement, which shall be denoted as first telescopic movement . In some embodiments , an extension boom part is mounted by a hinge mounting at the second end of the main boom part, such that the extension boom part can be inclined with respect to the main boom part in a second inclination movement . The extension boom part represents an extension of the ladder to increase its range in a radial direction from the turret, as well as the accessible height from the ground .

The different movements of the main boom part and, if present, the extension boom part are controllable by a human operator located at a control center which comprises different control means . A very common and approved control means is a j oystick, which is a control lever which can be tilted around two axes perpendicular to each other . Each axis corresponds to one degree of freedom to be controlled. In the present case, a joystick can be used for controlling the first inclination movement , i . e . the inclination of the main boom part, and the rotation movement of the main boom part around the turret .

The first telescopic movement of the main boom part represents an additional degree of freedom, which cannot be controlled by a j oystick according to the prior art . In a common solution, an additional control device is present at the control center, which is represented by a second j oystick for controlling the telescopic movement of the main boom part by a tilting movement of this second j oystick in a forward and rearward direction . This means that for controlling all degrees of freedom of the main boom part as discussed above, i . e . the first inclination movement, the rotation movement and the first telescopic movement, two different control devices are present which must be operated by the left and right end of the operator . That is , for controlling the main boom part, the movements of the left and right hands of the operator must be coordinated . It has turned out that this concept does not provide an intuitive and ergonomic way of controlling the different degrees of freedom even of simple ladders with only one main boom part . Moreover, this is even more true for more complex ladders which comprise an extension boom part at the free end of the main boom part, which is inclinable around a hori zontal hinge axis with respect to the main boom part, and which may also be extendable and retractable in a second telescopic movement .

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide a control center for an aerial device of the above kind which represents a control concept that allows an intuitive control of the inclination movement, the rotation movement and the telescopic movement of a main boom part as described above only by one j oystick .

This object is achieved by a control center comprising the features of claim 1.

According to the present invention, the control center comprises a first j oystick configured for controlling the first inclination movement of the main boom part by tilting the first j oystick around a first control axis , controlling the rotation movement of the main boom part around its vertical axis by tilting the first j oystick around a second control axis perpendicular to the first control axis , and for controlling the first telescopic movement by rotating at least a section of the first j oystick around the stick axis of the j oystick . The first and second control axis of the j oystick correspond to the usual j oystick axes, allowing an intuitive control of the inclination movement and the rotation movement, respectively . Extending and retracting the main boom part is performed by turning the j oystick around its stick axis . This concept allows the control of three different degrees of freedom of the main boom part by only one j oystick .

According to a preferred embodiment of the present invention, the aerial device further comprises an extension boom part mounted to the second end of the main boom part by a hinge mounting and being inclinable around a horizontal hinge axis with respect to the main boom part in a second inclination movement, and the control center comprises a second j oystick configured for controlling the second inclination movement by tilting the second j oystick around a tilting control axis of the second j oystick . Although two different joysticks are present in this embodiment, the degrees of freedom of moving the main boom part are controlled by the first j oystick only, while the movement of the tension boom part is controlled by a second j oystick separated from the first j oystick and being controllable in an independent way .

More preferably, the extension boom part is extendable and retractable along its longitudinal extension direction in a second telescopic movement, and the second j oystick is configured for controlling the second telescopic movement by rotating the second j oystick around its stick axis . In this way, the second telescopic movement is controlled in a way comparable to the control of the first telescopic movement by the first j oystick . This makes the way of controlling the first and second telescopic movement even more intuitive and ergonomic .

More preferably, the first j oystick comprises a lateral protrusion protruding from the stick axis in a radial direction . This lateral protrusion may be provided at an outer j acket portion of an end section of the first j oystick which is turnable around a fixed inner axis portion . It allows the user to get a better haptic feeling of the turning position of the j oystick around its stick axis , and it prevents slipping of the j oystick in this turning movement . This is important in particular for j oysticks which can be turned around their stick only against a restoring force, so that a certain torque must be applied to turn them. The application of such a turning torque is easier when the lateral protrusion is present . According to another preferred embodiment of the present invention, a second j oystick also comprises a lateral protrusion protruding from the stick axis in a radial direction .

Preferably the lateral protrusion has a flag shape.

More preferably, at least one of the first joystick and second j oystick comprises at least one switch disposed on its top end or on its circumferential surface . The term "switch" shall denote any switching device which is capable of being set into two different states , i . e . to be switched from one first state to a second state and back, including switching devices which remain in their present switching position after being switched, and also switching devices which are set back to their original switching state when no mechanical pressure by the operator is applied . Such switching devices can include switch buttons which keep a first state (corresponding to a first operation mode) when no pressure is applied, an which are switched into a second state (corresponding to a second operation mode ) when mechanical pressure is applied, which return to the first state when a pressure is released .

More preferably, the at least one switch is a movement restriction control switch for activating/deactivating a movement restriction of the aerial device .

Even more preferably, the at least one switch is a communication control switch for activating/deactivating a communication function of the aerial device .

According to another preferred embodiment of the present invention, the control center comprises at least one arm rest, with the first j oystick being disposed at the front end of the arm rest . In this embodiment, the human operator may lay her/his forearm on top of the arm rest, with her/his hand or finger operating the first j oystick . It is also possible that the second j oystick is disposed, in the same way, at the front end of another arm rest for taking the other forearm of the operator, to be operated by the other hand.

More preferably, the first control axis of the first j oystick is generally perpendicular to the extension direction of the arm rest .

According to another preferred embodiment of the present invention, the control center comprises an operator' s seat, with a back rest and two left and right arm rests , disposed laterally at two opposite sides of the back rest , with the first j oystick being disposed at one of the arm rest, at the second j oystick being disposed at the other arm rest . Preferably, the tilting control axis of the second j oystick is generally perpendicular to the extension direction of the other arm rest mentioned above .

The present invention is further related to a fire fighting vehicle , comprising a turnable ladder 3.S 3.ΓΊ aerial device, and a control center of the above kind .

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be elucidated more clearly with respect to preferred embodiments of the present invention, which will be described hereinafter by means of the following figures .

Fig . 1 is a schematic view of a firefighting vehicle according to a first embodiment of the present invention, demonstrating the different degrees of freedom of a turnable ladder as an aerial device mounted on top of the firefighting vehicle ;

Fig . 2 and 3 are different views of a control center of the turnable ladder of the firefighting vehicle shown in Fig . 1 ; and

Fig. 4 schematic view demonstrating the allocation of the different movements of the control devices of the control center shown in Fig . 2 and 3 to the different degrees of freedom shown in

Fig . 1.

BEST MODE FOR CARRYING OUT THE INVENTION

Fig . 1 shows a firefighting vehicle 10 comprising a turnable ladder 12 representing an aerial device which is mounted on top of a rear portion of the firefighting vehicle 10. The turnable ladder 12 comprises a main boom part 14 which is mounted with one end on a turret 16 to be rotatable around a vertical axis . A corresponding rotation movement shall be denoted as Yl in the following, as it is the case in Fig . 1. Moreover, the main boom part 14 can be inclined around a horizontal axis located at or near the turret 16 in a first inclination movement XI . By this inclination movement XI , the other end of the main boom part 14 can be lifted or lowered . The main boom part 14 represents a main ladder set of the turnable ladder 12 , which can be extended or retracted along its longitudinal extension direction in a first telescopic movement LI. In this first telescopic movement LI, the different elements of the ladder set (not shown in detail in Fig . 1 ) are shifted with regard to one another such that the free (second) end 18 of the main boom part moves away or approaches the first end 20 which is mounted on the turret

16.

At the second end 18 of the main boom part 14 , an extension boom part 22 is mounted by a hinge mounting 24 having a horizontal hinge axis . The extension boom part 22 is inclinable around the hinge axis 24 with respect to the main boom part 14 in a second inclination movement X2. In the present embodiment, the extension boom part 22 is also represented by a ladder set comprising different ladder elements that can be telescopically extended and retracted along the longitudinal extension direction of the extension boom part 22 in a second telescopic movement L2 to elongate or to shorten the length of the extension boom part 22. At the front top end of the extension boom part 22 , a rescue cage 42 is mounted .

The different movements XI , Yl , X2 , LI and L2 described above can be controlled from a control center 30 , which is shown in more detail in Fig . 2 and 3. The control center 30 comprises an operator' s seat 32 on which a human operator can sit . The operator' s seat 32 comprises a seating 34 , a backrest 36 disposed at the rear end of the seating 34 , and left and right armrests 38,40 disposed laterally at opposite sides of the backrest 36.

The armrests 38 , 40 are positioned such that a human operator sitting on the seating 34 , with her/his back resting on the backrest 36, may lay down her/his forearms in a comfortable position on top of the respective backrests 38 , 40. This allows a comfortable working position for the operator, with the top end, in particular the rescue cage 42 at the front top end of the extension boom part 22 in his field of view, to monitor all parts of the turnable ladder 12.

The control center 30 comprises two different control devices mounted on its left and right side in front of the respective armrests 38 , 40. A first control device of these two control devices is a first j oystick 44 , which is tiltable around two control axes perpendicular to each other, namely in the left/right direction, and in a front/back direction . The first j oystick 44 is mounted in a position that the operator can operate it with her/his left hand or finger ( s ) when her/his forearm rests on the left arm rest 38. It is noted here that the expressions "left", "right", "front" and "back" refer to the perspective of the sitting position of the operator .

The second control device, which is shown in Fig . 3 only, is a second j oystick 46 positioned at the front end of the right arm rest 40. In its configuration and disposition, the second j oystick 46 is provided similar to the first j oystick, so that the first j oystick 44 and the second j oystick 46 are arranged symmetrical with respect to an imaginary vertical mirror center plane through the apparatus seat 32. The second j oystick 46 is also tiltable around two control axes perpendicular to each other, namely in the left/right direction, and in a front/back direction . With respect to the configuration of each two perpendicular control axes , the first j oystick 44 and the second j oystick 46 correspond to common j oysticks for controlling two different degrees of freedom of a device to be controlled, as will be described later . Moreover, an upper end section of each of the first j oystick 44 and the second j oystick 46 is rotatable around the stick axis 50,53 of the respective j oystick . That is , additionally to the tilting movement of the stick axis 50,53 around the two perpendicular tilting control axes which are located at the bottom of the respective j oystick 44 , 46, the upper end section of the stick itself can be rotated in itself . This end section is formed by an outer j acket portion of the end section of the first j oystick which is turnable around a non-rotatable inner axis portion . This rotation is performed by applying a rotating force, i. e. a torque to the end section of the stick axis 50, 53 by the operator' s hand or fingers . It is noted that this rotation movement around the stick axis 50,53 can be performed independent from the tilting movement of the respective j oystick 44, 46 around a tilting control axis . The rotation of the j oystick 44, 46 around its stick axis 50,53 controls an additional degree of freedom of the device to be controlled, independent from the degrees of freedom which are controlled by tilting the respective j oystick 44, 46 around the first control axis and the second control axis , respectively .

For simplifying the application of a torque to the respective j oystick 44 , 46, each end section of the first j oystick 44 and second j oystick 46 is provided with a lateral protrusion 52 protruding from the stick axis 50,53 in a radial direction away from the stick axis 50,53. Each of these protrusions 52 is generally flag-shaped, i . e . it has the shape of a generally flat plate with a main plane crossing the stick axis 50,53. By this protrusion 52 , each j oystick 44, 46 has a cross section in a plane perpendicular to the stick axis 50, 53 which is shaped like a circle, corresponding to the cylindrical outer surface of the respective j oystick 44 , 46, but extending towards one radial direction to form the lateral protrusion 52. With other words , the upper end sections of the j oysticks 44, 46 are not round or cylindrical but non circular or at least irregular .

As can be taken from Fig . 3, the respective lateral flag- shaped protrusions 52 of the first j oystick 44 and the second j oystick 46 point towards each other . This position represents a neutral position of each j oystick 44 , 46, from which each of the first j oystick 44 and second j oystick 46 can be turned around its stick axis 50,53. According to the present embodiment, this turning movement is performed against a restoring torque, by which each of the j oystick 44 and the second j oystick 46 is set back to its neutral position shown in Fig . 3. That is , with no manual force applied to turn the respective j oystick 44 , 46, they return to their neutral position . The same stands for their tilting movements around their tilting control axes , which is performed against a restoring force to push each j oystick 44, 46 back into a neutral position, shown in Fig . 3.

As will be further explained in the following with respect to Fig . 4 , the first j oystick 44 and the second j oystick 46 are configured to control the different movements XI , X2 , Yl, LI and L2 of the turnable ladder 12 , as explained above with respect to Fig . 1.

The first j oystick 44 is configured to control the first inclination movement XI , i . e . the inclination of the main boom part 14 , by tilting the first j oystick 44 around its horizontal traverse tilting axis , which shall be denoted here as its first control axis , as demonstrated in the scheme in Fig . 4 on the left side, showing the first j oystick 44 schematically from the top, with its lateral protrusion 52 pointing to the right . Moreover, the left/right tilting movement of the first j oystick 44 around a second control axis perpendicular to the first control axis controls the rotation of the main boom part 14 around the turret 16, i . e . the rotation movement Yl in opposite directions . Pushing the first j oystick 44 to the left/right side corresponds to a swiveling movement of the main boom part 14 to the left/right side, respectively, while the first j oystick 44 in the front/rear direction corresponds to lifting or lowering the second end 18 of the main boom part 14.

Moreover, rotating the upper end section of first j oystick 44 around its stick axis 50 controls the first telescopic movement LI of the main boom part 14. In the present embodiment, rotating the end section of the first j oystick 44 in the counterclockwise direction corresponds to an extraction movement of the main boom part 14 , while rotating it in the opposite clockwise direction corresponds to a retraction of the main boom part 14.

In the neutral position of the first j oystick 44 , shown in Fig . 4 , the stick axis 50 of the first j oystick 44 , its first control axis and its second control axis (the latter extending in the front/rear direction, corresponding to the extension direction of the arm rest 38 in Fig . 2 and 3 ) all stand perpendicular to each other . In the tilting movements around the first control axis and the second control axis , respectively, the stick axis 50 is tilted with respect to at least one of the other of the first and second control axis .

As can be taken from the right portion of Fig . 4 , the second j oystick 46 has generally the same shape as the first j oystick 44. In more detail , the second j oystick 46 comprises a hori zontal traverse tilting control axis , around which the second j oystick 46 can be tilted in the forward/rearward direction for controlling the inclination movement of the extension boom part 22 with respect to the main boom part 14 , i . e . the second inclination movement X2. Together with the first j oystick 44 , both inclination movements , namely the first inclination movement XI of the main boom part 14 and the second inclination movement X2 of the extension boom part 22 are controlled, respectively, by tilting the respective first j oystick 44 and second j oystick 46 around a traverse control axis , which is the first control axis in case of the first j oystick 44 , and which is the traverse tilting control axis of the second j oystick 46. By this arrangement, the respective inclination movements XI and X2 can be controlled by separate j oysticks 44, 46 but control operations which are similar to each other, each including a forward/rearward tilting movement . This facilitates the control of the respective inclination movements XI and X2 by a human operator .

Moreover, an extension and retraction of the extension boom part 22 in a second telescopic movement L2 can be controlled by rotating the upper end portion of the second j oystick 46 around its stick axis 53. By applying a torque to this upper end portion of the second j oystick 46 at its lateral protrusion 52 in a circumferential direction, the extension boom part 22 is extended and elongated. By applying a torque to the lateral protrusion 52 of the second j oystick 46 in the opposite counterclockwise direction, the extension boom part 22 is retracted . Together with the first j oystick 44 , the respective first and second telescopic movements LI and L2 of the main boom part 14 and the extension boom part 22 are controlled by similar control operations to the respective first and second j oysticks 44 , 46, namely by turning the respective first j oystick 44 and second j oystick 46 around their respective stick axes 50,53. A respective extraction movement corresponds to a control operation of turning the respective first or second j oystick 44, 46 in a forward direction (which is the counterclockwise direction at the first j oystick 44 , and the clockwise direction at the second joystick 46, as demonstrated in Fig. 4), and a retraction movement corresponds to an operation of turning the respective j oystick 44, 46 in the opposite direction, i . e . turning the lateral protrusion 52 towards the operator . This way of operating the first j oystick 44 and second j oystick 46 is an intuitive way of controlling the first telescopic movement LI and second telescopic movement L2. It is noted that the different degrees of freedom of the movements of the main boom part 14 and the extension boom part 22 are controlled independently by two different control devices , represented by the first j oystick 44 , controlling the movements of the main boom part 14 , and the second j oystick 46, controlling the movements of the extension boom part 22. In an embodiment in which no extension boom part 22 is present at the second end of the main boom part 14 , the second j oystick 46 can be dispensed completely . In this case only the first j oystick 44 may be present as the only control device for controlling the main boom part 14 and all of its movements . Moreover, it is noted that like a common j oystick, the second j oystick 46 of the embodiment described above may have a horizontal tilting control axis perpendicular to the described tilting control axis for controlling the second inclination movement X2 , which is not used in the embodiment described in connection with Fig . 4. However, this additional tilting control axis can be used for other operation and controlling purposes , which shall not be described here . The positions and functions of the first j oystick 44 and the second j oystick 46 can be interchanged between each other . In particular, the first j oystick 44 can be provided on the right side of the apparatus seat 32 , while the second j oystick 46 may be provided on the left side of the apparatus seat 32.

As can be taken from Fig. 2 and 3, each of the first j oystick 44 and the second j oystick 46 comprises a switch disposed at the front of its top end, to be operated by one finger of the operator . In the present embodiment, each switch is configured as a push button 60,62 which is activated by applying a restoring force onto the respective push button 60 , 62. These push buttons 60, 62 may have different functions as desired . In the present embodiment, the push button 60 of the first j oystick 44 may be provided for activating a communication function of the aerial device, which is activated when the push button 60 is pushed . According to another embodiment of the present invention, this push button 60 is provided for activating/deactivating a movement restriction of the aerial device 12 , which may be, in the case of the present push button 60, a movement restriction of the main boom part 14. The other push button 62 of the second joystick 46 may be provided for activating or deactivating a movement restriction of the extension boom part 22. However, the operation function of the respective push buttons 60, 62 can be changed arbitrary. A third control device 64, independent from the first joystick 44 and the second j oystick 46, is disposed in front of the second j oystick 46 for controlling the operation of a display (not shown) in the viewing field of the operator, in front of the operator' s seat 32. This third control device 64 comprises a knob 66 which can be turned into opposite directions around a turning axis, and which can also be tilted around two perpendicular axes, like the first j oystick 44 or the second j oystick 46, to perform different control functions assigned to the display. These functions shall not be described further here . It is possible to provide the first joystick 44 and the second joystick 46 as proportional control devices, in which the respective tilting or rotation displacement is proportional to the movement speed. As already described above, the first j oystick 44 and the second joystick 46 can also be provided so as to return into a neutral position with no pressing or pulling force being applied to the respective first j oystick 44 or second joystick 46, and each joystick 44,46 can only be operated against a restoring force .

Although the joysticks 44 and 46 described herein have straight axes with the rotation axis of the upper end portion being a straight elongation of the fixed lower end portion, other embodiments are possible within the scope of the present invention in which the rotation axis of the upper end portion is inclined against the lower end portion, such that the respective j oystick 44, 46 comprises a bend or kink.