Slewing ring brake

A slewing ring brake for use in heavy machinery including earthworking machinery. The slewing ring brake includes a slewing ring with a tooth system and a support member which is mounted in a manner to allow rotary movement of the support member relative to the slewing ring. The slewing ring brake also includes a brake block displaceably mounted on the support member, the brake block being displaceable between a braking position and a freewheeling position. In the braking position, the brake block engages with the tooth system thereby preventing rotary movement of the support member relative to the slewing ring. In the freewheeling position, the brake block disengages the tooth system thereby allowing rotary movement of the support member relative to the slewing ring

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to a slewing ring brake for use in heavy
 machinery including earthworking machinery. More particularly, the present
 invention relates to a brake for a slewing ring.
 2. Description of Related Art
 The use of a slewing ring in heavy machinery such as earthworking machinery
 is well known. In an excavator, for example, there is generally provided a
 fixed lower chassis and a rotatable upper chassis mounted in a rotary
 manner to the lower chassis. A circular track or a slewing ring having a
 tooth system on its outer circumference is generally fixedly attached to
 the lower chassis. The upper chassis generally includes gears which may be
 engaged with the tooth system and be rotationally actuated in order to
 allow rotation of the upper chassis with respect to the fixed lower
 chassis. This rotation may be actuated by a drive such as hydraulic
 motors. Thus, in order to rotate the upper chassis with respect to the
 lower chassis, it is only necessary for the drive to overcome the
 frictional torque and the moment of inertia of the mass. Therefore, it is
 relatively easy to rotate the upper chassis in this manner.
 However, this relatively easily attained rotation of the upper chassis can
 cause serious problems in use of these heavy machineries such as
 earthworking machinery. For instance, if the upper chassis includes a
 fixed rotary drill for making a hole in the ground, a relatively high
 torque can act on the upper chassis during the drilling process. This high
 torque caused by drilling can cause an undesired rotation of the upper
 chassis with respect to the lower chassis. Of course, this can cause
 serious problems in safety and can significantly impair the accuracy of
 the drilled hole.
 SUMMARY OF THE INVENTION
 Therefore, the primary object of the present invention is to provide a
 slewing ring brake that will prevent undesired rotational movement between
 a slewing ring which may be mounted on a lower chassis and a support
 member which may be mounted on an upper chassis.
 In accordance with one embodiment of the present invention, this object is
 achieved by a slewing ring brake having a slewing ring with a tooth system
 and a support member which is mounted in a manner to allow rotary movement
 of the support member relative to the slewing ring. In this embodiment,
 the slewing ring brake also includes a brake block displaceably mounted on
 the support member, the brake block being displaceable between a braking
 position and a freewheeling position. In the braking position, the brake
 block engages with the tooth system thereby preventing rotary movement of
 the support member relative to the slewing ring. In the freewheeling
 position, the brake block disengages the tooth system thereby allowing
 rotary movement of the support member relative to the slewing ring.
 In the various embodiments of the present invention specifically
 illustrated, the brake block engages the tooth system of the slewing ring.
 As a result of this wedging action, rotary movement between the support
 member and the slewing ring is prevented. The brake block can be engaged
 with the tooth system on the slewing ring by radially displacement or even
 by axial displacement. In addition, whereas the described tooth system is
 normally an external tooth system, an internal tooth system is also
 possible on the circular slewing ring.
 To prevent high stressing of a single tooth on the slewing ring and to
 ensure a durable slewing ring brake, the brake block in accordance with
 the present invention may be provided with several teeth constructed to
 mesh with the tooth system. The brake block is formed by a toothed
 section, which is shaped in correspondence to the tooth system on the
 slewing ring. For further relieving stresses in the individual teeth,
 there can also be several brake blocks which simultaneously engage the
 slewing ring.
 It is fundamentally possible to operate the brake block manually, e.g. by
 means of a screw spindle. However, in accordance with a preferred
 embodiment of the present invention, a power operated driving unit is
 provided for displacing the brake block between the braking position and
 the freewheeling position. For instance, a linear displacement of the
 brake block can be attained by using an electric motor with a screw
 spindle or a recirculating ball screw. In accordance with the present
 illustrated embodiments, a simple driving unit can be comprised of a
 pressure cylinder with a displaceable piston rod connected to the brake
 block which displaces the brake block between the brake position and the
 freewheeling position.
 In accordance with another embodiment of the present invention, the power
 operated driving unit includes at least one pressure cylinder and a
 transmission device for displacing the brake block in a radial direction
 substantially radial to the slewing ring. The transmission device converts
 a tangential displacement motion generated by the pressure cylinder which
 is substantially tangential to the slewing ring into a radial displacement
 motion substantially radial to the slewing ring. By having the
 displacement direction of the brake block at an angle of approximately
 90.degree. to the displacement motion of the pressure cylinder, a very
 robust construction of the slewing ring brake is attained through which a
 reliable braking is ensured, even in application of high torques.
 In accordance with one embodiment of the present invention, the
 transmission device for the displacement of the brake block includes a
 toggle lever mechanism.
 In an alternative embodiment, the transmission device includes a sliding
 wedge mechanism. In this embodiment, especially high forces can be applied
 to the slewing ring brake since there are no pivot pins or pivot bearings.
 According to another embodiment of the present invention, a measuring
 device for sending rotary movement between the slewing ring and the
 support member may also be provided. The measuring device may be connected
 to a control unit through which the displacement of the brake block into
 the braking position may be prevented when rotary movement is sensed. This
 ensures that the brake is not operated during rotary movement between the
 slewing ring and the support member which could damage the tooth system of
 the slewing ring and the teeth of the brake block. Of course, the
 measuring device for monitoring rotary movement, particularly monitoring
 upper chassis rotation, can be located at any appropriate point including
 the illustrated position or alternatively, on the drive motor, on the
 transmission or on transmission shafts.
 In accordance with the preferred embodiment of the present invention, the
 measuring device includes a rotatable measuring gear which meshes with the
 tooth system of the slewing ring and also includes a sensor for sensing
 rotation of the measuring gear. The sensor may be housed at a protected
 position at a distance from the slewing ring and may be an incremental
 encoder or transducer which can emit a pulse indicative of rotary motion
 on passing of the individual teeth of the measuring gear or a separate
 measuring disk. This particular embodiment provides a compact arrangement
 which is relatively simple to implement.
 The slewing ring brake in accordance with the present invention is
 particularly useful in earthworking machinery applications. The slewing
 ring brake may be located on one of either a first chassis or a second
 chassis which are mounted in a manner to allow rotary movement between the
 two chassis. The slewing ring would be provided on the other chassis. For
 instance, the slewing ring brake may be provided on the upper chassis
 which houses a drill and be operated to prevent undesired rotation of the
 upper chassis with respect to the lower chassis during drilling.
 These and other objects, features and advantages of the present invention
 will become more apparent form the following detailed description of the
 invention when viewed in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 FIG. 1 shows a slewing ring brake 10a in accordance with the present
 invention which will prevent undesired rotational movement of an upper
 chassis relative to a lower chassis such as in earthworking machinery. As
 can be easily appreciated, only a small portion of the slewing ring 11
 with a tooth system 12 is illustrated in detail in FIG. 1 since the
 slewing ring 11 may be relatively large in comparison to the slewing ring
 brake 10a. In addition, whereas the illustrated slewing ring 11 includes a
 tooth system 12 provided on the outer circumference of the slewing ring
 11, the present invention, in all the various embodiments, may be just as
 easily be applied to a slewing ring having a tooth system provided on the
 inner circumference of the slewing ring.
 The slewing ring brake 10a illustrated in FIG. 1 includes a brake block 14
 with correspondingly constructed teeth 18 which mesh with the tooth system
 12 of the slewing ring 11 and prevent relative rotation between the
 slewing ring 11 and the brake block 14. More than one tooth is provided on
 teeth 18 to reduce the stresses exerted on a particular tooth of the tooth
 system 12 as well as the teeth 18 thereby ensuring a durable slewing ring
 brake 10a. In this regard, the brake block 14 is displaceably arranged on
 a support member 13, only part of which is shown in FIG. 1. The support
 member 13 is fixedly attached to a rotatable structure such as an upper
 chassis which is rotatably mounted to a lower chassis with a fixedly
 mounted slewing ring 11. Consequently, the support member 13 is rotatable
 with respect to the slewing ring 11. Of course, in other applications, the
 mounting of the support member 13 and the slewing ring 11 may be reversed
 such that the slewing ring 11 may be attached to the upper chassis to
 rotates relative to the support member. However, in earthworking
 machinery, the slewing ring 11 is typically attached to the lower chassis
 which can be considered a first chassis whereas the upper chassis, which
 can be considered a second chassis, is usually rotatably mounted to the
 first chassis. A linear guide 17 formed by plates fixed to the support
 member 13 may also be provided to ensure linear movement. In the present
 illustrated embodiment, a power-operated driving unit such as a pressure
 cylinder 15 may be provided for controllably displacing the brake block
 14. The pressure cylinder 15 may be mounted to the support member 13 on
 one end and mounted to the brake block 14 on the other end by means of a
 piston rod 16. The pressure cylinder 15 can be hydraulically or
 pneumatically operated. Of course, it can be easily appreciated that in
 this embodiment as well as the other embodiments which will be discussed
 below, the power-operated driving unit may also be other devices such as
 electrical motors with a screw spindle or a recirculating ball screw,
 cams, solenoids, piezoelectric devices and the like.
 When the piston rod 16 is extended, the brake block 14 is moved into a
 braking position as clearly illustrated in FIG. 1. In this braking
 position, the teeth 18 of the brake block 14 engages (i.e. meshes) with
 the tooth system 12 of the slewing ring 11 thereby preventing the
 rotational movement of the slewing ring brake 10a and the corresponding
 support member 13 relative to the slewing ring 11. When the piston rod 16
 is retracted, the brake block 14 is linearly and radially moved back along
 the linear guide 17 such that the teeth 18 of the brake block 14
 disengages the tooth system 12 and there is a distance between the teeth
 18 and the tooth system 12. In this freewheeling position, the slewing
 ring brake 10a and the corresponding support member 13 can be freely
 rotated relative to the slewing ring 11.
 A measuring device 20 is provided on the support member 13 for measuring
 the relative rotational movement between the support member 13 and slewing
 ring 11. The measuring device 20 may be comprised of a measuring gear 21
 mounted in rotary manner on a holder 22, which is in turn, fixedly
 attached to the support member 13. The rotational movement of the
 measuring gear 21 can be detected by a sensor 23 which may be connected to
 a control unit 24. This control unit can prevent the extension of the
 piston rod 16 of the pressure cylinder 15 if relative movement between the
 slewing ring 11 and support member 13 is detected by the sensor, i.e.
 rotation of the measuring gear 21 is sensed. This ensures that the slewing
 ring brake 10a is not operated during rotary movement between the slewing
 ring 11 and the support member 13 which could damage the tooth system 12
 and the teeth 18. Of course, the measuring device 20 for monitoring rotary
 movement can be located at any appropriate point including the illustrated
 position or alternatively, on the drive motor, on the transmission or on
 transmission shafts (all not shown). The sensor (not shown) may be housed
 at a protected position at a distance from the stewing ring and may be an
 incremental encoder or transducer which can emit a pulse indicative of
 rotary motion on passing of the individual teeth of the measuring gear 21
 or a separate measuring disk (not shown). This particular embodiment
 provides a compact arrangement which is relatively simple to implement.
 It should also be recognized that the above described embodiment, as well
 as the embodiments described hereinbelow, may be further modified in
 accordance with the present invention. For instance, the various
 embodiments of the slewing ring brake may be modified such that the brake
 block is brought into engagement with the ring system of the slewing ring
 by being displaced in an axial direction or a combination of axial and
 radial directions. Moreover, more than one brake block may be provided to
 prevent rotary movement between the slewing ring and the support member to
 further increase the durability of the slewing ring and the slewing ring
 brake.
 FIG. 2 shows another slewing ring brake 10b in accordance with another
 embodiment of the present which is constructed in a corresponding manner
 to the slewing ring brake 10a illustrated in FIG. 1. The various
 components having corresponding similar functions are given the same
 reference numerals in this, and in the following embodiments, and thus,
 need not be explained further. As a modification of the previously
 described slewing ring brake 10a illustrated in FIG. 1, the slewing ring
 brake 10b includes a transmission device which displaces a brake block 14
 in a radial direction substantially radial to the slewing ring 11 by
 converting a tangential displacement motion substantially tangential to
 the slewing ring 11 into a radial displacement motion substantially radial
 to the slewing ring 11. In this regard, the slewing ring brake 10b
 includes sliding wedge mechanism 30 interposed between the brake block 14
 and a poweroperated driving unit such as a pressure cylinder 15 which
 provides the tangential displacement motion in the present embodiment. The
 sliding wedge mechanism 30 is provided on a piston rod 16 of the pressure
 cylinder 15 and includes a first wedge 31 with a first wedge surface 32
 having an angle of approximately 60.degree. to a longitudinal axis of the
 pressure cylinder 15. The first wedge surface 32 slidingly engages a
 second wedge surface 34 of a second wedge 33, which is formed on the brake
 block 14. The second wedge surface 34 may be at an angle of approximately
 30.degree. to the displacement direction of the brake block 14.
 As previously noted, in this embodiment of the present invention, the
 movement of the piston rod 16 of the pressure cylinder 15 is in a
 direction tangential to the circular slewing ring 11 (toward the right in
 the illustrated orientation of FIG. 2). Upon extending the piston rod 16
 out of the pressure cylinder 15, the brake block 14 is moved radially
 against the slewing ring 11 into a braking position due to the wedge
 surfaces 32, 34. More specifically, when the piston rod 16 is extended,
 the first wedge 31 is also displaced in the tangential direction (toward
 the right in the illustrated orientation of Figure. 2). The first wedge
 surface 32 contacts the second wedge surface 34 and radially displaces the
 second wedge 33 toward the slewing ring 11 (toward the bottom in the
 illustrated orientation of FIG. 2). In this manner, the brake block 14 is
 displaced until its teeth 18 engages the tooth system 12 of the slewing
 ring 11 thereby placing the slewing ring brake 10b in a braking position
 and preventing the rotational movement of the slewing ring brake 10b and
 the corresponding support member 13 relative to the slewing ring 11. By
 having the displacement direction of the brake block 14 being at an angle
 of approximately 90.degree. to the displacement motion of the pressure
 cylinder 15, a very robust construction of the slewing ring brake 10b is
 attained through which a reliable braking is ensured, even during
 application of high torques. Moreover, especially high forces can be
 applied to the slewing ring brake 10b in this embodiment since there are
 no pivot pins or pivot bearings.
 Through a corresponding retraction of the piston rod 16, the brake block 14
 can be moved radially away from the slewing ring 11 so that the teeth 18
 of the brake block 14 disengages the tooth system 12 of the slewing ring
 11 thereby placing the slewing ring brake 10b in a freewheeling position
 and allowing freewheeling rotation of the slewing ring brake 10b and the
 corresponding support member 13 relative to the slewing ring 11. This
 retraction of the piston rod 16 may be assisted by additional action of a
 return spring (not shown). To ensure linear movement of the first wedge 31
 and the second wedge 33, corresponding guide surfaces 35 formed by plates
 on the support member 13 are also provided in the illustrated example.
 Moreover, the slewing ring brake 10b may also be provided with a measuring
 device 20 for measuring the relative rotational movement between the
 support member 13 and slewing ring 11 in the same manner as the previously
 discussed embodiment of the slewing ring brake 10a of FIG. 1. In addition,
 as in the previously discussed embodiment, this measuring device 20 may be
 used with a control unit (not shown) to prevent the actuation of the
 slewing ring brake 10b if relative movement between the slewing ring 11
 and support member 13 is detected.
 A slewing ring brake 10c in accordance with yet another embodiment of the
 present invention is illustrated in FIG. 3. In place of the previously
 described sliding wedge mechanism, a transmission device having a toggle
 lever mechanism 40 is provided for displacing a brake block 14 in a radial
 direction substantially radial to the slewing ring 11 by converting a
 tangential displacement motion substantially tangential to the slewing
 ring 11, into a radial displacement motion substantially radial to the
 slewing ring 11. In this regard, a control bolt 41 (mounted
 perpendicularly to the plane of the drawing) is attached to a piston rod
 16 of a power-operated driving unit such as a pressure cylinder 15 which
 provides the tangential displacement motion in the present embodiment.
 Pivotably mounted on the control bolt 41 are a first toggle lever 42 and a
 second toggle lever 43 that extend in a substantially opposite directions
 from one another. The first toggle lever 42 extends roughly
 perpendicularly to the displacement direction of the piston rod 16 and in
 a radial direction toward the slewing ring 11. In addition, the first
 toggle lever 42 is pivotably connected to the brake block 14. The other
 end of the second toggle lever 43 is mounted on a bolt 44, which in turn,
 is rigidly connected to the support member 13.
 The toggle lever mechanism 40 is constructed in such a way that when the
 piston rod 16 is retracted, the brake block 14 is forced radially into the
 braking position, as shown in FIG. 3. More specifically, when the piston
 rod 16 is retracted into the pressure cylinder 15, the first toggle lever
 42 and the second toggle lever 43 are brought into an upright position as
 shown in FIG. 3 (i.e. substantially normal to a tangent of the slewing
 ring) from an angular position (not shown). It can be easily recognized
 that as the first toggle lever 42 and the second toggle lever 43 are moved
 from an angular position (not shown) into the upright position, the brake
 block 14 is radially displaced toward the 0slewing ring 11 (toward the
 bottom in the illustrated orientation of FIG. 3) until the teeth 18 of the
 brake block 14 engages the tooth system 12 of the slewing ring 11. Again,
 this engagement of the teeth 18 with the tooth system 12 places the
 slewing ring brake 10c in a braking position and prevents the rotational
 movement of the slewing ring brake 10c and the corresponding support
 member 13 relative to the slewing ring 11.
 Upon extending the piston rod 16, the first toggle lever 42 and the second
 toggle lever 43 are brought into an angular position (not shown) such that
 the brake block 14 is radially displaced away from the slewing ring 11
 (toward the top in the illustrated orientation of FIG. 3). This causes the
 disengagement of the teeth 14 on the brake block 14 with the tooth system
 12 of the slewing ring 11 thereby placing the slewing ring brake 10c in a
 freewheeling position and allowing the freewheeling rotation of the
 slewing ring brake 10c and the corresponding support member 13 relative to
 the slewing ring 11.
 Again, in the same manner as the previously discussed embodiments, the
 slewing ring brake 10c may also be provided with a measuring device 20 for
 measuring the relative rotational movement between the support member 13
 and slewing ring 11. The measuring device 20 can be used to prevent the
 extension of the piston rod 16 of the pressure cylinder 15 if relative
 movement between the slewing ring 11 and support member 13 is sensed.
 A slewing ring brake 10d with a modified toggle lever mechanism 40d is
 shown in FIG. 4. As can be seen, the slewing ring brake 10d is somewhat
 similar to the embodiment of the slewing ring brake 10c discussed
 previously. However, the toggle lever mechanism 40d with its first toggle
 lever 42d and its second toggle lever 43d is constructed in such a way
 that the slewing ring brake 10d is placed in a braking position when the
 piston rod 16 is extended from a power-operated driving unit such as a
 pressure cylinder 15. Thus, the first toggle lever 42d and the second
 toggle lever 43d are brought into an upright position as shown in FIG. 3
 (i.e. substantially normal to a tangent of the slewing ring) from an
 angular position (not shown) by extending the piston rod 16 from the
 pressure cylinder 15. As the first toggle lever 42d and the second toggle
 lever 43d are brought into an upright position, the brake block 14 is
 radially displaced toward the slewing ring 11 until the teeth 18 of the
 brake block 14 engages the tooth system 12 of the slewing ring 11 thereby
 placing the slewing ring brake 10d in a braking position and preventing
 the rotational movement of the slewing ring brake 10d and the
 corresponding support member 13 relative to the slewing ring 11.
 By retracting the piston rod 16 into the pressure cylinder 15, the first
 toggle lever 42d and the second toggle lever 43d are brought into an
 angular position (not shown) such that the brake block 14 is radially
 displaced away from the slewing ring 11 causing the disengagement of the
 teeth 18 on the brake block 14 with the tooth system 12 of the slewing
 ring 11 thereby allowing the freewheeling rotation of the slewing ring
 brake 10d and the corresponding support member 13 relative to the slewing
 ring 11.
 The toggle lever mechanism 40d of the slewing ring brake 10d is also
 provided with a return lever 45, which at one end, is connected to a
 control bolt 41d and on the other end, is connected to a spring mechanism
 46. In this particular embodiment of the slewing ring brake 10d, the
 spring mechanism 46 is tensioned through the extension of the piston rod
 16. Thus, upon disconnecting the pressure within the pressure cylinder 15,
 the spring mechanism 46 acts upon the return lever 45 to return the piston
 rod 16 back into the pressure cylinder 15. Of course, as can be easily
 recognized, the brake block 14 is simultaneously pulled back in a radial
 direction away from the slewing ring 11. In this manner, the toggle lever
 mechanism 40d with the spring mechanism 46 ensures full retraction of the
 piston rod and full disengagement of the teeth 18 with the tooth system
 12. Of course, like in the previously discussed embodiments, the slewing
 ring brake 10d may also be provided with a measuring device 20 for
 measuring the relative rotational movement which can be used to prevent
 the extension of the piston rod 16 of the pressure cylinder 15 if relative
 movement between the slewing ring 11 and support member 13 is detected.
 While various embodiments in accordance with the present invention have
 been shown and described, it is to be understood that the invention is not
 limited thereto. These embodiments may be changed, modified and further
 applied by those skilled in the art. For instance, as noted previously,
 the various embodiments of the slewing ring brake may be modified such
 that the brake block is brought into engagement with the ring system of
 the slewing ring by being displaced in an axial direction or a combination
 of axial and radial directions. In addition, more than one brake block may
 be provided to prevent rotary movement between the slewing ring and the
 support member to further increase the durability of the slewing ring and
 the slewing ring brake.
 Furthermore, the slewing ring brake in accordance with the present
 invention as described in the various embodiments above are particularly
 useful in earthworking machinery applications. The slewing ring brake may
 be located on either a first chassis or a second chassis which are mounted
 in a manner to allow rotary movement between them. The slewing ring would
 then be provided on the other chassis. For instance, the slewing ring
 brake may be provided on the upper chassis which houses a drill and be
 operated to prevent undesired rotation of the upper chassis with respect
 to the lower chassis during drilling. Of course, the slewing ring brake in
 accordance with the present invention may also be used in may other
 applications as well. Therefore, this invention is not limited to the
 details shown and described previously, but also includes all such changes
 and modifications which are encompassed by the appended claims.