Patent Application
20080314701
The present invention relates to an industrial truck in accordance with the preamble of claim 1. Such an industrial truck is known, for example, from EP 1 759 950 A1.
Industrial trucks of the type mentioned at the outset are also in widespread use, however. In order to meet the conventional safety requirements for industrial trucks, they need to have both a service brake and a parking brake. In the mentioned document, an electrically actuated service brake can also be used as parking brake. Furthermore, if necessary a mechanical or hydraulic emergency brake system or emergency actuation system can be integrated in the brake system.
As regards further prior art, reference is made to the documents DE 102 59 878 A1, DE 101 50 803 B4, DE 10 2005 043 608 A1, DE 10 2005 005 669 A1, DE 198 31 541 A1, DE 198 10 593 A1 and DE 102 25 038 A1.
For safety reasons it is preferred to actuate different brake systems, such as the service brake system and the parking brake system, on the basis of different physical action principles in order to be able to make further use of at least the respective other system in the event of failure of one system. In this case, this is particularly advantageous if the parking brake is actuatable electrically since this considerably reduces the complexity involved on the industrial truck for installation and maintenance of the parking brake.
It is therefore the object of the present invention to provide an industrial truck of the type mentioned at the outset which has a high degree of safety in terms of braking operation with at the same time a simple construction.
This object is achieved according to the invention by an industrial truck of the generic type, in which the parking brake is actuatable electrically. Therefore, the service brake can be provided as usual by a mechanical and/or pneumatic and/or hydraulic braking circuit with a high degree of operational reliability, with at the same time it being possible for the parking brake to be actuated electrically. This ability to actuate the parking brake electrically can be realized by piezoelectric actuators, at least one electric motor and the like. Particularly preferably, the ability to actuate the parking brake electrically is however realized by at least one electrically switchable electromagnet, since this can safely provide very high actuating forces whilst taking up a very small amount of physical space. In addition, it is also easily possible to realize comparatively large actuation paths of several millimeters using an electromagnet in contrast to, for example, piezoelectric actuators.
In accordance with the present invention, the design is such that the industrial truck comprises a first armature disc, which is associated with the parking brake, has ferromagnetic material and is movable between an active position, in which it activates the braking force generation and braking force transmission apparatus for generating and transmitting a braking force to the at least one wheel, and an inactive position, in which it does not activate the braking force generation and braking force transmission apparatus. The first armature disk can have only locally ferromagnetic material, preferably has predominantly ferromagnetic material and is particularly preferably manufactured substantially completely from ferromagnetic material.
A further advantage of the industrial truck according to the invention is the fact that the above-described braking function can be implemented in a single braking unit, which can be in the form of a dry-running braking unit. A braking unit equipped in this way can advantageously be flange-connected directly to the motor, for example in such a way that the motor is installed between two bearing plates, with a transmission being flange-connected to one bearing plate of the motor and the braking unit being flange-connected to the opposite bearing plate of the motor. Such dry-running brakes cause fewer losses, in particular do not cause any churning losses, with the result that they can be operated with a higher degree of efficiency. At the same time, the replacement of the oil, which is otherwise regularly necessary, can be dispensed with, with the result that the intervals for regular maintenance can be extended in comparison with wet-running brakes.
The “braking force generation and braking force transmission apparatus” can be any apparatus which is suitable for generating a braking force and transmitting it to a wheel. This may be a magnet arrangement of an eddy current brake, which, however, does not allow braking to a speed of zero, and is preferably at least one brake disc, which runs between friction linings and is connected in torque-transmitting fashion to the wheel. Likewise, a brake lamella stack known per se with fixed and rotatable brake lamellas which are arranged alternately in the axial direction can be used as the “braking force generation and braking force transmission apparatus”.
A particularly space-saving and installation-friendly design of the braking unit provided in the industrial truck can be obtained by virtue of the fact that one and the same braking force generation and braking force transmission apparatus is associated with both the service brake and the parking brake in such a way that both an actuation of the service brake and an actuation of the parking brake activates the braking force generation and braking force transmission apparatus for generating and transmitting a braking force to the at least one wheel. As has already been explained above, it is preferable for reasons of operational reliability if the braking force generation and braking force transmission apparatus generates the braking force which is transmittable to a wheel in a force-fitting, in particular frictional manner. Such braking force generation and braking force transmission apparatuses have proven successful in a large number of applications and allow complete and rapid braking of the industrial truck to a standstill as well as the immobilizing of the industrial truck when it is at a standstill.
In order to ensure that the industrial truck is safely immobilized in the event of failure of the power supply, the invention can provide that the industrial truck comprises an immobilizing prestressing device, which exerts an immobilizing prestressing force on the first armature disk so as to prestress it towards the active position. In this case, an electrically actuatable actuator, in particular an energized electromagnet, can hold the first armature disk in the inactive position. When the energizing of the electrically actuatable actuator comes an end, the force effect thereof also comes to an end, with the result that the immobilizing prestressing force is no longer compensated for by the force of the actuator and thus can move the first armature disk into the active position.
The immobilizing prestressing device can comprise, in a case which is particularly simple in design terms and is therefore preferred, at least one compression spring, which exerts the abovementioned immobilizing prestressing force. In order to increase the immobilizing prestressing force, it is preferable to provide a plurality of compression springs. Force can be introduced in a particularly targeted manner using helical compression springs.
In order to be able to introduce the immobilizing prestressing force into the first armature disk as uniformly and symmetrically as possible and therefore to prevent the first armature disk from becoming stuck in an undesirable manner, it is furthermore preferred to arrange the plurality of compression springs equidistantly, in particular along a circumferential direction of the armature disc. In order to prevent the service brake function from being influenced by the preferred electromagnet mentioned previously, the invention can provide, in order to achieve a braking effect of the service brake, that it comprises a non-ferromagnetic second armature disc, which is associated with the service brake and which is displaceable between an engagement position, in which it activates the braking force generation and braking force transmission apparatus for generating and transmitting a braking force to the at least one wheel, and a disengagement position, in which it does not activate the braking force generation and braking force transmission apparatus. As a result of its non-ferromagnetic properties, the second armature disk can be displaced without a force originating from the electromagnet which is associated with the parking brake needing to be overcome during this displacement. As a result, a small actuating device which provides a comparatively low actuating force is sufficient for displacing the second armature disc.
The braking unit provided in the industrial truck manages with very little physical space when the first and the second armature disk are movable or displaceable along a common trajectory, are preferably arranged coaxially and are movable or displaceable along the common axis.
Since the service brake is generally actuated substantially more often than the parking brake, it is expedient to design and arrange elements of the service brake in such a way that the service brake is actuatable independently of the parking brake and in particular independently of movements of component parts associated with the parking brake. This can be achieved, for example, by virtue of the fact that the second armature disc, when viewed in the direction of the common movement trajectory, is arranged between the braking force generation and braking force transmission apparatus and the first armature disc. In addition, with such an arrangement the first armature disk can be arranged very close, that is without the second armature disk being interposed, to the electromagnet, which interacts with the first armature disc.
In contrast, the parking brake is generally actuated when the industrial truck is in any case at a standstill, with the result that co-actuation of individual component parts associated with the service brake does not interfere during actuation of the parking brake. An arrangement can therefore be provided in which the first armature disc, during its movement from the inactive position into the active position, displaces the second armature disk from the disengagement position towards the engagement position, preferably into the engagement position. As a result, in addition always the same brake component part (in this case the second armature disc) can interact with the braking force generation and braking force transmission apparatus, with the result that the braking unit advantageously comprises a small number of component parts which are subject to wear. In this case, during braking undesirable play and undesirable dead movements can be prevented by the second armature disk bearing against the first armature disk when the second armature disk is located in its disengagement position.
In order to ensure that no residual braking force acts on the industrial truck during normal traveling operation without any actuation of the brake, it can be provided that the industrial truck comprises a service prestressing device, which exerts a service prestressing force on the second armature disk which prestresses it towards the disengagement position. In the preferred case described above in which the first and second armature disks are movable along a common trajectory, the service prestressing device can be supported on the first armature disc. In this case, the service prestressing force acting on the second armature disk acts on the first armature disk as a supporting force in the direction towards its active position. As a result of this arrangement, when the parking brake is released, i.e. when the first armature disk is moved from the active position into the inactive position, the second armature disk can be displaced from the engagement position into the disengagement position in a very simple manner without an additional actuator. In a particularly simple and space-saving manner, the service prestressing device can comprise an undular washer.
It may furthermore be desirable to be able to disengage the braking unit manually in the case of its failure by intervention from the outside. For this purpose, the industrial truck may comprise an emergency lifting apparatus, with which at least the parking brake can be disengaged manually.
In a manner which is particularly reliable and simple in design terms, the emergency lifting apparatus can be in form-fitting engagement with the first armature disc. For example, the emergency lifting apparatus can comprise an actuator, which passes through and engages behind the first armature disk and by means of which the first armature disk is movable at least from the active position into the inactive position. The actuator can be actuatable by hand or by means of a tool. In general, the braking unit with the service brake and the parking brake, or at least a multitude of component parts associated therewith, is accommodated in a brake housing. In this case, it is particularly advantageous for reducing the complexity involved with actuation if the actuator is actuatable from outside the brake housing, in which at least the first armature disk is accommodated.
As has already been described above, the braking force generation and braking force transmission apparatus can comprise a brake backplate, which is fixed in position in relation to a brake housing accommodating the service brake and the parking brake, and at least one brake lamella which is movable relative thereto, preferably with a brake lining provided on the brake backplate and/or on the at least one brake lamella. In this case, a braking force of the service brake can be provided in a very simple manner by virtue of the fact that the second armature disk in its engagement position presses the at least one brake lamella against the fixed brake backplate.
In accordance with an advantageous development of the present invention, the braking effect which is or can be generated by the brake backplate, brake lamella and second armature disk can be further increased by virtue of the fact that, on its side pointing towards the brake lamella, the second armature disk is provided with a brake lining. The brake lining can be designed to have one or more parts. In accordance with a first possible embodiment of the present invention, the brake backplate can be provided on the brake housing. For this purpose, the brake backplate can either be formed integrally on a brake housing part or can be fixedly connected to a brake housing section as a separate component part. In accordance with a further alternative embodiment, the brake backplate can also be provided on a drive motor of the industrial truck. It is also true in this case that the brake backplate can be formed integrally on the drive motor, for example the motor housing or a motor housing section, or can be fixedly connected to the drive motor as a separate component part. When the drive motor has a steel housing, the brake backplate is particularly preferably formed integrally as a section of the drive motor, for example as a so-called bearing plate (non-drive-end bearing plate or B-bearing plate (“B-Lagerschild”)).
In order to prevent damage from occurring in the braking device as a result of particularly vigorous actuation of the service brake, it can be provided that at least the braking torque which is applicable by the service brake is limited in terms of absolute value by means of overload protection means in order to prevent excessively high braking torques from being exerted.
The applicant reserves the right to claim quite generally separate protection for an Industrial truck with at least one driven wheel, which is adapted to being braked during traveling operation by means of a service brake and which is adapted to being immobilized by a parking brake, the industrial truck comprising a braking force generation and braking force transmission apparatus, which is adapted to generating a braking force and to transmitting it to at least one wheel, preferably a driven wheel, the service brake being actuatable mechanically and/or pneumatically and/or hydraulically, and the parking brake being actuatable electrically, in particular electromagnetically, characterized in that at least the braking torque which is applicable by the service brake is limited in terms of absolute value by means of overload protection means in order to prevent excessively high braking torques.
In this case, the industrial truck can have an actuating element for actuating the service brake, which actuating element is to be actuated by an industrial truck driver and by means of which an actuator element, which is coupled in force-transmitting fashion to the second armature disc, is adjustable from a non-actuating position towards an actuating position. In this case, particularly simple design measures can be used to achieve the overload protection of the service brake by virtue of the overload protection means comprising a spring, which is arranged in force-transmitting fashion between the actuator element and the second armature disc. In addition, it can be provided that the actuating element has a limited actuation range and/or the actuator element has a limited adjustment range, with the result that the maximum braking force which is achievable using the overload protection means can also be safely predetermined. The actuation range is in this case not just limited by the braking elements, such as the above-described brake lamella and the second armature disc, bearing against one another, but is predetermined and limited independently of the state of any wear parts which may be provided in the brake.
The present invention will be explained in more detail below with reference to an exemplary embodiment. In the drawing:
In
The actuating lever 38, as a common central actuating lever, actuates both the braking unit 10 and the braking unit (not illustrated) of the wheel 82.
In
Accommodated in the brake housing 12 is an electromagnet 18, which in the energized state attracts a first ferromagnetic armature disk 20, against the effect of immobilizing prestressing springs 22, towards a circumferential projection 24 of the housing body 14.
In
The immobilizing prestressing springs 22 are helical compression springs, which are arranged at the same angular distance from one another around the central axis 26 of the braking device 10. As a result, a symmetrical prestressing force can be exerted on the first armature disk 20, which prestresses the first armature disk 20 towards the pressure plate 16.
A second non-ferromagnetic armature disk 28 bears against that end side of the first armature disk 20 which points towards the pressure plate 16. While the first armature disk 20 is associated with the parking brake or a parking brake function, the second armature disk 28 is associated with the service brake or a service brake function.
The first and the second armature disk 20 and 28, respectively, are both movable along the central axis 26 of the braking unit 10.
Arranged in the axial direction between the pressure plate 16 and the second armature disk 28 is a brake disk 32, which is connected to a hub 30 for common rotation purposes but is movable axially relative thereto and which bears circumferential brake linings 34 and 36 on its two end faces, which point in opposite directions. The hub 30 is connected in torque-transmitting fashion to a driven wheel (not illustrated) of the industrial truck, possibly with a transmission interposed.
An actuating lever 38 is accommodated in the housing body 14 in such a way that it is rotatable about the central axis 26 but is axially immovable. The actuating lever 38 has a cylindrical engagement section with a serrated end-face contour 40 at its end 39 which protrudes into the brake housing 12. In more precise terms, the development of the contour 40 in one plane is a zigzag line with three peaks and three troughs. The peaks and the troughs each have a distance of approximately 120 from one another. A peak is removed from the closest trough in the circumferential direction by approximately 60. When viewed in developed form, directly adjacent peaks and troughs in the example shown in
The end 39 of the actuating lever 38 interacts with a first actuator part 42, which is accommodated in the housing body 14 in such a way that it is axially displaceable, but fixed against rotation. The first actuator part 42 has an opposing contour 44 which is complementary to the contour 40 of the end 39. On rotation of the actuating lever 38 about the axis 26, a relative movement of the contours 40 and 44 against one another arises, as a result of which, starting from the position shown in
As a result, an initially untensioned overload spring 46, which is supported at one end on the first actuator part 42 and at the other end on a second actuator part 48, is compressed, with the result that the overload spring 46, with increasing axial displacement of the first actuator part 42, exerts an increasing axial compressive force on the second actuator part 48.
The second actuator part 48 is fixedly connected to the second armature disk 28 for the common axial movement. An undular washer 50 is provided between an annular collar 48a and a radially inner section of the first armature disk 20, which undular washer 50 prestresses the annular collar 48a away from the first armature disk 20 and therefore prestresses the second armature disk 28 towards the first armature disk 20. When the compressive force exerted by the overload spring 46 on the second actuator part 48 as a result of the displacement of the first actuator part 42 exceeds the prestressing force exerted in the opposite direction by the undular washer on the second actuator part 48, the second actuator part 48, which is accommodated in the brake housing 12 in such a way that it is fixed against rotation, but axially movable, begins to move gradually in the direction of the compressive force, i.e. towards the brake disk 32. As a result, the second armature disk 28 comes to bear against the brake lining 36 and displaces the brake disk 32 in the axial direction until the brake lining 34 bears against the pressure plate 16. The brake disk 32 with its brake linings 34 and 36 is therefore clamped in between the pressure plate 16 and the second armature disk 28 depending on the extent of the actuation of the actuating lever 38, it being possible for the frictional force (braking force) occurring at the brake linings 34 and 36 to be metered by the actuation of the actuating lever 38.
The overload spring 46 and the engagement contours 40 and 44 in this case ensure that the maximum achievable braking force is limited. This is determined by the maximum axial displaceability of the first actuator part 42 which can be achieved as a result of the contours 40 and 44 and by the spring stiffness of the overload spring 46.
If a complete immobilization of the industrial truck is desired, the energizing of the electromagnet 18 is switched off by a corresponding actuation by the industrial truck driver, with the result that its force effect on the first armature disk 20 comes to an end. As a result, the force compensating for the prestressing force of the immobilizing prestressing springs 22 is dispensed with, with the result that the immobilizing prestressing springs 22 move the first armature disk 20 and with it the second armature disk 28 towards the left in
The parking brake or parking brake function is released by renewed energizing of the electromagnet 18, whose attraction force on the first armature disk 20 is greater than the force exerted by the immobilizing prestressing springs 22. As a result of the arrangement of the undular washer 50 between the second actuator part 48 and the first armature disk 20, the attraction of the first armature disk 20 by the electromagnet 18 towards the circumferential projection 24 also results in a movement of the second armature disk 28 away from the brake disk 32 and towards the electromagnet 18, with the result that the action of the parking brake can be completely cancelled.
The process of releasing the service brake takes place simply by ending the actuation of the actuating lever 38. The undular washer 50, which is compressed during actuation of the service brake, resets the second armature disk 28 via the second actuator part 48 into the disengagement position shown in
It is readily comprehensible to a person skilled in the art that the immobilizing prestressing springs 22 need to be designed in terms of their spring stiffness so as to match the desired immobilizing force and the immobilizing movement path provided. Then, the electromagnet 18 needs to be dimensioned based on the spring stiffness of the immobilizing prestressing springs 22 and their number.
In addition, the spring stiffnesses of the overload spring 46, on the one hand, and the undular washer 50, on the other hand, need to be matched to one another taking into consideration the deformation in each case associated with these springs. In the example shown in
At its longitudinal end 63 which is positioned away from the screw head, a securing plate 64 is held by a retaining screw 66 on the longitudinal end 63 of the screw 62. The retaining screw 66 and the screw 62 are arranged coaxially, i.e. the retaining screw 66 is screwed coaxially into the shaft of the screw 62.
As a result of the countersunk head provided on the retaining screw 66, the securing plate 64 is connected to the longitudinal end 63 of the screw 62 without any play. The dimension of the securing plate 64 in the radial direction in relation to the central axis 26 of the braking unit 10 is selected in such a way that the opening 68 of the first armature disk 20, through which the screw 62 passes, has the screw 62, which is provided with the securing plate 64, engaging behind it, i.e. the radial dimension of the securing plate 64 is greater than the diameter of the opening 68.
Provision can moreover be made for the emergency lifting apparatus 60 to be prestressed into the position shown in
As a result of the movement of the screw 62 in the direction of the arrow 70, a first armature disk 20, which is located in an undesirable manner in the active position, can be moved into the inactive position from outside the brake housing 12. Such a movement of the screw 62 advantageously takes place using a tool, for example a forked wedge, which is driven between the screw head of the screw 62 and the outer face of the housing body 14, which acts as the bearing face therefor. The parking brake function of the braking unit 10 can therefore be cancelled in the event of an undesirable power failure.
As an alternative to the illustrated embodiment of the emergency lifting apparatus, the latter can also be designed as follows: if the available physical space permits it, the first armature disk 20 can be designed in such a way that it protrudes radially beyond the second armature disk 28 in at least one circumferential section, preferably in a plurality of circumferential sections, possibly along its entire circumference. An eccentric lever, which is pivotable about an eccentric axis of rotation, which is preferably orthogonal with respect to the central axis 26 and is parallel to the plane of extent of the first armature disk 20, can be arranged in the axial direction on that end side of the first armature disk 20 which points away from the electromagnet 18. The eccentric lever can be rotatably actuated from the outside by an eccentric shaft. As a result of the rotary actuation, the eccentric lever finally comes to bear against that side of the first armature disk 20 which points away from the electromagnet, with the result that, as the torque acting on the eccentric shaft increases, an axial force acting on the first armature disk 20 is applicable, which force acts against the prestressing force of the immobilizing prestressing springs 22, with the result that the first armature disk 20 can be moved into its inactive position or at least out of its active position by means of the eccentric lever being rotated.
In order to prevent the first armature disk 20 from becoming stuck during emergency disengagement, advantageously a plurality of eccentric levers can be arranged distributed around the circumference of the first armature disk 20, preferably axially (in relation to the central axis 26) opposite one another in pairs. If an uneven number of eccentric levers is provided, these should be arranged distributed at the same angular distance from one another along the circumference of the first armature disk 20 so as to prevent the first armature disk 20 from becoming stuck during the emergency disengagement.
Preferably, the at least one eccentric lever is fixable, so that, when the first armature disk 20 has been moved out of its active position by the at least one eccentric lever, said first armature disk 20 can be held in the position reached by the described emergency disengagement actuation as a result of the at least one eccentric lever being fixed and the eccentric levers can be released.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102007028688.2 | Jun 2007 | DE | national |
