Abstract:
The invention relates to a spring brake cylinder with an emergency release device, comprising the following: a housing in which a spring-loaded piston can be moved axially with a piston rod, at least one spring-loaded spring, wherein the emergency release device comprises an actuation device, an emergency release mechanism to interrupt the power transmission between the spring-loaded piston and the piston rod and a holding device for holding the emergency release device in a transmission condition. The invention further includes a blocking device to prevent the holding device from holding of the emergency release mechanism in a transmission position when the spring-loaded piston only partly released

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     The invention relates to a pneumatically, hydraulically or electromechanically operated spring brake cylinder with an emergency release device. The brake cylinder includes a housing, in which a spring-loaded piston is axially displaceable by a piston rod, at least one spring-loaded spring, and, in the case of pneumatic or hydraulic operation, a pressure connection for admitting pressure fluid to the spring-loaded piston. The emergency release device includes an operating device and an emergency release mechanism for interrupting the transmission of force between the spring-loaded piston and the piston rod with a holding device for holding the emergency release device in a transmission condition. 
     From German Patent Documents DE PS 26 08 502, corresponding to U.S. Pat. No. 4,063,491, and DE PS 27 48 540, corresponding to U.S. Pat. No. 4,226,168, brake cylinders are known with emergency release devices for the interruption and the automatic return of the braking function of a spring-loaded cylinder, in which case, the emergency release lever for the emergency release must be operated or held until the accumulated spring force is completely reduced. 
     Although these solutions have been successful per se, when the operating or emergency release lever is not operated or held sufficiently long, at extremely low temperatures, conditions of the spring accumulator are conceivable which result only in a partial force reduction. Because of the viscosity of the lubricants, which increases with the falling temperature, the time period until the force is completely reduced is lengthened in comparison to higher temperatures. During this time period, the emergency release lever would therefore have to remain operated or held in order to completely reduce the accumulated spring force. 
     Here, the invention uses a different approach. The invention starts with the recognition of the present problems and, in view of these problems, has the object of further developing the spring brake cylinder of the above-mentioned type such that situations are reliably avoided in which only a partial reduction or build-up of force takes place. 
     The invention solves this task. The holding device for holding the emergency release device at different holding positions is supplemented by a blocking device for preventing the holding of the holding device when the spring-loaded piston is only partially released. This prevents a holding, particularly an engaging of the emergency release operation when the spring accumulator is only partially released. Thus, for the emergency release of the spring accumulator, a one-time brief operation of the emergency release lever will be sufficient because the premature engaging of the blocking mechanism is reliably prevented by the blocking device. 
     According to one embodiment of the invention, the blocking device comprises a locking bar which locks the emergency release mechanism of the spring accumulator in the released position until the spring accumulator is completely released or is operative again. 
     In a cost-effective constructively simple further development, the holding device has a detent pawl acting upon a gear wheel. However, it is also conceivable that the holding device is designed to be rotating and/or linear and/or locking and/or clamping and permits several holding positions. A spring in the transmission of force of the operation of the emergency release device in a simple manner prevents intermediate conditions of the detent pawl. 
     According to various embodiments of the invention, particularly the following locking bar arrangements are useful: 
     between the spring-loaded housing and the spring-loaded piston, or 
     between the piston rod and the spring-loaded piston, or 
     between the piston rod and the spring-loaded housing. 
     Additional advantageous further developments of the invention are contained herein. 
     In the following, essentially two different basic embodiments of the invention and the blocking devices implemented within the scope of the invention will be described in detail with reference to the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a brake cylinder, according to the present invention, taken along lines AA of FIG.  2 . 
     FIG. 2 a  is a cross-sectional view of a brake cylinder, according to the present invention, taken along lines BB of FIG.  1 . 
     FIG. 2 b  is a side view of a detent pawl of FIG. 2 a.    
     FIG. 2 c  is a cross-sectional view of the detent pawl taken along lines CC of FIG. 2 b.    
     FIGS. 3 a  and  3   b  show the spring-loaded cylinder released by pressure. 
     FIGS. 4 a  and  4   b  show the spring actuator in the braking position and start of the emergency release operation. 
     FIGS. 5 a  and  5   b  show emergency release operation and detent pawl locked. 
     FIGS. 6 a  and  6   b  show the spring actuator emergency-released and the emergency release operation withdrawn. 
     FIG. 7 shows a second embodiment of a brake cylinder with an emergency release device, according to the present invention, similar to that of FIG.  1 . 
     FIG. 8 a  shows a cross-sectional view of a third embodiment of a brake cylinder with emergency release device incorporating the principles of the present invention. 
     FIG. 8 b  shows an enlarged portion of FIG. 8 a.    
     FIG. 9 is an end view of the embodiment of FIG.  8 . 
     FIGS. 10 a  and  10   b  are perspective views of the third embodiment of the emergency release device. 
     FIG. 11 shows another embodiment similar to that of FIG. 8 with a modified lock and bar arrangement. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First, by means of an example of embodiment one with reference to FIGS. 1 and 2, the function of the spring accumulator of the first embodiment of the invention will be described. 
     FIGS. 1 and 2 show two different views of a spring-loaded cylinder  2  having a housing  4  in which a spring-loaded piston  6  is arranged in an axially displaceable manner and on whose outer circumference sealing devices and sliding bands  8   a - 8   c  are distributed. The spring-loaded springs  14 ,  16  are arranged between the spring-loaded piston  6  and an axial housing cover  10  which is fastened on the inner circumference of the housing  4  by a snap ring  12 . 
     Between the spring-loaded piston  6  and the housing  4 , a pressure space  18  is constructed which can be acted upon by pressure by an air connection  20  in the circumference of the housing  4 . The spring brake can be released and applied by the venting and bleeding by way of the air connection  20 . When the spring accumulator  4  is not in the emergency released operating condition, the force of the spring-loaded springs  14 ,  16  is supported by way of the spring-loaded piston  6  and either the pressure in the pressure space or volume  18  or a piston rod  24  on the spring loaded piston  6  on the braking device which is otherwise not shown here. 
     For releasing the engaged spring brake also without compressed air, the spring-loaded cylinder  6  has an emergency release device  26  which permits an interruption of the transmission of force between the spring-loaded piston  6  and the piston rod  24 . 
     In the illustrated example, the emergency release device  26  or the emergency release mechanism portion of  26  is essentially based on the function of a spindle arrangement  28  with a detent pawl  30  which is swivellably disposed between two mutually axially offset sections  10   a  and  10   b  of the housing cover  10 . A threaded spindle  32  of the spindle arrangement transmits force between the spring-loaded piston  6  and the piston rod  24 . The resulting torque of the spindle arrangement is transmitted in the blocked or transmission condition by a displaceable guide  34  having an adjusting spring  36  to a gear wheel  38 , which can be blocked or released by the detent pawl  30  (see particularly also FIGS.  2  and  5 ). For this purpose, one end of the detent pawl  30  engages in the gear wheel  38  in one of the operating positions of the emergency release device. In contrast, the other end of the detent pawl  30  can be lifted out of the toothing of the gear wheel  38  by an emergency operating unit with a Bowden cable  42  and a restoring spring  44  constructed at the Bowden cable and a pressure spring  46 . The rotation of the gear wheel  38  is released in this position of the detent pawl  30 . As a result, the transmission of force between the spring-loaded piston  6  and the piston rod  24  can be interrupted. The detent pawl  30  can be swivelled about an axis  31 . A catch spring  33  presses one end of the detent pawl  30  in the direction of the toothing of the gear wheel  38 . 
     When the emergency release device is operated when a braking or spring force is applied to the piston rod  24 , a rotation of the threaded spindle  32  will be caused when the braking force is reduced so that the spring-loaded piston  6  impacts on the housing  4 . In order to prevent another locking of the detent pawl  30  during the release operation, a locking bar  48  is arranged on the interior surface of section  10   b  of the spring accumulator cover or housing cover  10 , which locking bar  48  holds back the lifted-out detent pawl  30 . 
     The locking bar  48  essentially has a bolt-type shape and, on its end facing the housing cover section  10   b , is equipped with a locking head  51 . Between the two-part housing cover  10   a ,  10   b  (which has an indentation in this area) and the locking head  51  (with an axial recess), a locking spring  49  is arranged which presses the locking bar  48  in the direction of the detent pawl  30 . In one of the operating positions, the locking head  51  engages in a lateral stepped recess  35  of the detent pawl  30  for receiving the locking bolt  48  and locks the detent pawl  30  in its release position (see FIG. 5 b ). The section of the locking bar  48  facing away from the locking head  51  has a bolt-type construction penetrating the interior housing cover section  10   a . When the spring-loaded piston  6  is displaced in the direction of the housing cover  10 , it compresses the locking bar spring  49  and presses the locking head  51  of locking bar  48  out of its engaged position in the dent pawl  30  (FIGS.  1  and  2 ). Thus, only when the spring-loaded piston  6 , after a release operation, is again in the operative position, will the locking bar  48  release the detent pawl again for an engagement. 
     The optional display device  54  illustrated in FIG. 2 shows the “emergency-released” condition of the spring-loaded cylinder  2 , in which the display device  54  is contacted by the detent pawl  30 , as shown in FIGS. 5 and 6 a.    
     Essentially, the following different positions of the spring accumulator are obtained before and after an emergency release operation: (Sequence: Operative—emergency releasing—operative) 
     1. Spring-Loaded Cylinder  2  Released by Pressure (FIG.  3 ): 
     The spring-loaded cylinder  2  is released by the pressure in the pressure volume  18 , and the spring-loaded piston is displaced in the direction of the housing cover  10 . No braking force is applied to the piston rod  24 , and the detent pawl  30  and the gear wheel  38  are in the locked condition. 
     2. Spring-Accumulator in the Braking Position, Start of the Emergence Release Operation (FIG.  4 ): 
     The spring-loaded cylinder  2  is in its braking position. The pressure volume or the pressure space  18  is without pressure. The force of the spring-loaded springs  14 ,  16  is applied to the piston rod  24 . 
     The emergency release operation is initiated by a pulling on the emergency release operation device. By way of the pressure spring  46  and the driving device  40 , the detent pawl  30  is lifted out of the toothing of the gear wheel  38 . 
     3. Emergency Release Operation, Detent Pawl  30  Locked (FIG.  5 ): 
     The spring-loaded springs  14 ,  16  are supported by the spring-loaded piston  6  on the spring-loaded housing cover  10 . The piston rod  24  is free of force, and it was moved into its starting position by the back pressure spring  50 . 
     By means of the engaged locking head  51  of locking bar  48 , the detent pawl  30  is held in its release position, and the display device  54  is active. 
     4. Spring Accumulator Emergency-Released, Emergency Release Operation Withdrawn (FIG.  6 ): 
     The spring-loaded cylinder is in the “emergency-released” condition, and the detent pawl  30  is locked. The emergency release operation device or driver  40  was moved into the starting position by the restoring spring  44 . 
     5. Spring Accumulator Which Is Operative Again (FIG.  3 ): 
     The applying of pressure into the pressure volume  18  leads to the restoration of the readiness condition of the spring accumulator  2 . The locking bar  48  holds the detent pawl  30  in the released condition until the spring-loaded springs  14 ,  16  again have their prestress and the spring-loaded piston  6  takes up its right end position, as illustrated in FIG.  3 . The piston  6  moves the locking bar  48  to the right and the locking head  51  out of engagement with the detent pawl  30 . After the engagement of the detent pawl  30  and gear wheel  38 , the tensional connection between the spring-loaded piston  6  and the piston rod  24  is restored. 
     In order to ensure the engaging of the locking bar  31  in the detent pawl  30  during an operation of the emergency release device, the pressure spring  46  is provided in the transmission of force between the emergency release device and the driving device  40 . The prestressing of the pressure spring  46  ensures the swivelling movement of the pawl  30  from the initial travel of unlocking of the gear wheel  38  to the further travel to the locking by the locking bar  48 . 
     FIG. 7 shows a modification of the embodiment of FIGS. 1 to  6 . In this embodiment, a free running device of the gear wheel  38 , here, a cone clutch  52 , is constructed in the transmission of force between the spring-loaded piston  6  and the piston rod  24 . The cone clutch  52  permits a reduction of the shock occurring during the emergency release operation because it ensures an unhindered continued running of the gear wheel  38  and of the threaded spindle  32  after the emergency release operation. 
     In the first embodiment of FIGS. 1 to  6  and the modification of this embodiment according to FIG. 7, the detent pawl  30  and its locking device  48  are situated in the springloaded or housing cover  10  which is fixedly connected with the spring-loaded housing  4 . The locking bar  48  is operated by the spring-loaded piston. The pawl  30  itself is arranged between two sections  10   a  and  10   b  of the housing cover  10  which can be assembled. 
     The embodiment of FIGS. 8,  9  and  10  basically differs from the embodiment of FIG. 1 as a result of the arrangement of the detent pawl  30  and of the locking bar  48 . The detent pawl  30  and the pertaining locking bar  48  are arranged on the piston rod  24 . The locking bar  48  is moved by the threaded spindle  58  which is rotatable relative to the springloaded piston  24 . 
     The second embodiment of FIGS. 8,  9  and  10  therefore shows another possibility of the locking bar arrangement. In this embodiment, the detent pawl  30  is rotatably arranged on the piston rod  34  by a bolt (in this regard, see the bore  30 ′ in the pawl  30 ; see FIGS. 10 a ,  10   b ) and is operated by the spring-loaded piston  6 . In this embodiment, the spring-loaded piston  6  and the spring-loaded spring  14  are arranged such that the pressure space  18  is situated on the right-hand side of the spring-loaded piston  6  in the drawing. The spring-loaded piston  6  is disposed on the threaded spindle  58  which, at one of its ends, if fixedly screwed to the spring-loaded piston  6 . In its area facing away from the piston  6 , the spindle  58  is provided with a type of trapezoidal thread. In the area of the trapezoidal thread, the threaded spindle  58  is screwed into a sleeve  62  provided with a corresponding internal thread. The sleeve  62  is provided with an external toothing at its end facing away from the springloaded piston  6 , so that the gear wheel  38 ′ is constructed in this area of the sleeve  62 . In one of its operating positions, the detent pawl  30 , which is arranged on an end area of the axially and radially displaceable holding plate  56 , engages in the gear wheel  38 ′ and blocks it. An operation of the emergency release device displaces the plate  56  radially and releases the pawl  30  from the gear wheel  38 ′ and thereby interrupts the transmission of force between the spring-loaded piston  6  and the piston rod  24 . In this case, the locking bar  48 —pushed forward by the locking bar spring  49 ′—engages in an opening of the holding plate  56  and locks it radially. The locking bar  48  is moved and released by the spindle  58  fixedly connected with the spring-loaded piston  6 . 
     In this embodiment of the invention, the locking bar  48  is therefore arranged between the piston rod  24  and the spring-loaded piston  6 . The locking bar spring  49 ′ is disposed between the piston rod  24  and the spring-loaded piston  6 . The holding plate  56  is radially displaceable in an interior cylindrical attachment  63  of the brake cylinder housing and moves axially with the piston rod  24  and the spring-loaded piston  6 . The radial displacement of the plate  56  takes place by a coil spring  64  which is supported on a bolt  65  in the holding plate  56  and on a holding part  66  which, in an immobile manner, is screwed to the piston rod  24  by a bolt  68 . 
     As an alternative, a locking bar operation is conceivable between the piston rod  24  and the spring-loaded housing  4 . Such an embodiment is illustrated in FIG.  11 . The basic construction of this embodiment is similar to the embodiment of FIGS. 8 to  10  with respect to the coupling of the spring-loaded piston  6 . However, the locking bar  48  is constructed such that it impacts during the moving of the piston rod  24  from the spring-loaded housing  4  and, during a continued movement, is rotated about an axis  47 . This rotating movement and a reverse rotating movement by the spring  49  between the piston rod  6  and the locking bar  48  move the locking bar  48  into its two operating positions and, in this manner, move it into and out of the recess  64  of the holding plate  56 . 
     Although the present invention has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The spirit and scope of the present invention are to be limited only by the terms of the appended claims.