Abstract:
An apparatus for mechanically locking the end positions of movable point sections, with two adjusting rods ( 12, 14  ), each of which is connected with one of the point sections and which are coupled mechanically with one another, with at least one locking tappet ( 28 ) for locking the adjusting rods in each case in one of their end positions and a force limiting device, which cancels the locking, when the force, exerted by the point sections on the adjusting rods, exceeds a certain value, and the force limiting device is formed by a coupling device ( 30, 32 ), which yields when stressed and is located between the adjusting rods ( 12, 14 ), and by a transfer mechanism ( 16, 38 ), which converts the movement of one of the adjusting rods into a movement for unlocking the locking tappet ( 28 ).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an apparatus for mechanically locking the end positions of movable point sections, with two adjusting rods, each of which is connected with one of the point sections and which are coupled mechanically with one another, with at least one locking tappet for locking the adjusting rods in each case in one of their end positions and a force limiting device, which cancels the locking, when the force, exerted by the point sections on the adjusting rods, exceeds a certain value. In particular, the invention relates to an apparatus for locking the points of streetcar rails. 
     In the case of point section devices, it is important that the movable point sections are held securely in their respective end position. When a vehicle runs over a facing point, that is, when the wheels of the rail-bounded vehicle first run on the free ends of the points, the one switch rail, the so-called closed switch rail, must lie tightly against the continuous rail, while the other switch rail, the so-called open switch rail, must be at a sufficient distance from the associated continuous rail, so that the wheels can safely pass through the shunt and the rail-bound vehicle is not damaged or derailed. On the other hand, when a certain force is exceeded, the points must be able to yield, so that the rails of the rail-bound vehicle can yield laterally, when the point is passed trailing and the rail is not in the correct position. In the case of points that can be forced, the points in such a case remain in the new position, in which they have been set, that is, the shunt is shifted by the wheels of the rail-bound vehicle. 
     Shunt-adjusting devices are known, for which the adjusting rods for adjusting the two points are uncoupled mechanically and actuated in each case directly by the driving mechanism of the adjusting device and locked by respective locking clamps (such as clamp point locks). The contacting switch rail is locked rigidly, for example, against a rigid rail, while the remote switch rail is held by the self-locking or fixable driving mechanism. This arrangement has the advantage that the contacting switch rail can be held in its end position with a force, which is significantly larger than that holding the remote switch rail. The relatively high cost of the construction is, however, a disadvantage. In addition, the driving mechanism cannot be changed over manually with an adjustment plate and, when the point is forced, the adjustment rods are separated from the driving mechanism, so that the driving mechanism must be actively tracked into the new shunt position, so that the points are ready to function once again. 
     From practical experience, an adjusting device of the type named above is known (Hanning &amp; Kahl HW 60 AW adjusting device), for which the two adjusting rods are coupled mechanically. The housing of the adjusting device preferably is disposed centrally between the two points, and the mutually coaxial adjusting rods enter the housing from opposite sides. Within the housing, the adjusting rods are rigidly connected with one another by a connecting piece. The locking tappet is disposed pivotably at the connecting piece and acts, on the one hand, with a locking plate, coupled with the driving mechanism of the adjusting device, and, on the other, with the force limiting device, disposed in the housing. Due to the force limiting device, both switch rails are held in the respective end position with the same force. If this force is exceeded when the points are forced, the force limiting device yields, the lock is unlocked and the shunt is shifted into the new position, in which the locking is brought about once again with the help of the locking tappet. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a device of the type named above, for which, in every end position, one of the two movable point sections (the closed switch rail) can be held with a larger force. 
     Pursuant to the invention, this objective is accomplished owing to the fact that the force limiting device is formed by a coupling device, which yields when stressed and is located between the adjusting rods, and by a transfer mechanism, which converts the movement of one of the adjusting rods into a movement for unlocking the locking tappet. 
     The force holding one of the movable point sections is limited by the force limiting device. In practice, this shunt part usually is the open switch rail. The adjusting rod for the closed switch rail, on the other hand, is locked at the housing with the help of the locking tappet with a theoretically unlimited force. When the point is forced, this locking is canceled only when the open switch rail was deflected somewhat and, as a result, the associated adjusting rod is moved. The holding force can also be larger than the force required to adjust the shunt. Without decreasing the holding force, the adjusting device can therefore be designed so it can easily be changed over manually or with the help of a driving mechanism, which need not be self-locking. 
     In a special embodiment, the locking tappet is held movably at a connecting piece, and the coupling device acts between the connecting piece and each of the adjusting rods and yields in each case only when the adjusting rod is stressed in one direction. 
     In the case of an adjusting device disposed between the points, the two adjusting rods preferably are disposed coaxially to one another and the connecting piece lies within the housing of the adjusting device between the free ends of the adjusting rods, so that it supports the adjusting rods rigidly. Coupling elements are then disposed so that they yield, when the associated adjusting rod is pulled out of the housing with a sufficiently large force. 
     The coupling elements may be formed, for example, by springs, force-limiting couplings, clamping elements and the like. 
     The transfer mechanism preferably is formed by a locking plate, which embraces catches fastened to the free ends of the adjusting rods and has a locking contour for the locking tappet held at the connecting piece. 
     For a different embodiment, preferably two locking tappets are held immovably in the direction of motion of the adjusting rods at a part of the apparatus, fastened to the housing, and movable in a direction perpendicularly thereto between a locking position, in which they lock the adjusting rods positively, and an unlocking position, which releases the adjusting rods. 
     This solution has the advantage that the locking of the adjusting rods, instead of taking place indirectly over a connecting piece, takes place directly at the housing of the apparatus and is based not on self-inhibiting effects, but on positive locking. By these means, a high functional reliability is achieved and the position, in which the adjusting rods are locked, can be defined precisely and, if necessary, adjusted. When two locking tappets are used, the two adjusting rods can also be adjusted independently. 
     Preferably, the locking tappets are constructed as ledges, which extend transversely to the adjusting rods and are supported sliding over inclined surfaces or by means of roll bodies on unlocking ledges, which extend parallel to the adjusting rods and can be moved in the longitudinal direction of the latter. The locking tappets then carry out strictly a translational movement during the locking and unlocking processes. This arrangement is particularly advantageous if the locking device is used in combination with a testing device, which scans the position of the switch rail with the help of test rods disposed parallel to the adjusting rods. The locking tappets of the locking device can then extend into the testing device and function there also for locking the test rods, so that additional safety is attained. The locking tappets then fall into the locking position only if the adjusting rods, as well as the test rods, are in the correct position. By scanning the position of the locking tappets, a signal can thus be obtained, which connects the locked status of the adjusting device by a logical AND with the status signal of the testing device. 
     The unlocking ledges, which interact with the closing tappets, preferably are fastened to a carriage, which is guided in the housing parallel to the adjusting rods and engages the carriage of the actuating drive. The function of this carriage thus is comparable to the function of the locking plate of the embodiment described first. 
     The locking plate or the carriage can be held in the housing by a tensioning mechanism, which has a dead center in the middle position of the locking plate and prestresses the locking plate elastically on either side of the dead center into the respective end position. Since the locking plate is coupled mechanically with the adjusting rods by means of the catch, the tensioning mechanism ensures that the adjusting rods, after overcoming the dead center, are transferred automatically into the respective end position. The shunt can therefore be changed over very simply with the help of an adjusting mechanism engaging the locking plate. The adjusting mechanism can be actuated, for example, manually, magnetically, by motor, hydraulically or pneumatically. 
     Due to the tensioning mechanism, the positively held contacting closed switch rail is additionally pressed elastically against the associated rail. The holding force for the open switch rail is composed additively of the force of the coupling element and the force of the tensioning mechanism. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred examples are described in greater detail in the following by means of the drawing, in which 
     FIG. 1 shows a partially sectional view of a first embodiment of the inventive device, 
     FIGS. 2 to  4  show views of the device of FIG. 1 in a middle position, an end position and in the initial phase while the point is being forced, 
     FIGS. 5 to  8  show diagrammatic sketches to explain the mode of functioning of the device of a second embodiment and 
     FIG. 9 shows a diagrammatic outline of the device of FIGS. 5 to  8 . 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows an open half shell of a housing  10  of a shunt adjusting apparatus, which is disposed centrally between two points, which are not shown. Two adjusting rods  12  and  14 , which are coaxial to one another, are connected with one of the points and enter the housing  10  from opposite sides. A catch  16  is fastened to the free end of each adjusting rod. 
     Between the two catches  16 , a connecting piece  18  is inserted which, at each end, has an end plate  20 , which is supported at the associated catch. The two end plates  20  are connected by upper and lower cross members  22  and  24 , through which an axle  26 , which is shown in section in the drawing, passes. A locking tappet  28 , which has approximately the shape of a double ax, is held between the upper and lower cross members  22 ,  24  rotatably on the axle  26 . 
     The adjusting rods  12  and  14  and the connecting piece  18  are held together by coupling devices  30 ,  32 , which are mounted on the outside of the catches  16 . The adjusting rods  12  and  14 , the connecting piece  18  with the locking tappet  28  and the coupling devices  30 ,  32  can thus be shifted as a unit along the common axis of the adjusting rods  12 ,  14 , as indicated by the double arrows in FIG.  1 . In this connection, the locking tappet  28  is guided on one side (at the top in FIG. 1) by a guiding ledge  34  that is attached to the housing. 
     On the opposite side (at the bottom in FIG.  1 ), the locking tappet  28  engages a locking contour  36  of a locking plate  38 , which in turn is guided on a guiding rod  40  attached to the housing. On each side, the locking plate  38  forms a stop  42  for the outer surface of the catch  16 . In FIG. 1, only the stop  42  on the right side can be recognized. 
     The coupling devices  30  and  32  are formed in each case by four springs  44 ,  46 , which are disposed symmetrically about the common axis of the adjusting rods  12 ,  14 . In the direction of viewing, the two springs  44  on the left side in FIG. 1 lie above the locking plate  38 , while on the right side in FIG. 1, the two springs  46 , of which one is shown in section and which lie below the locking plate, can be recognized. The springs  44 ,  46  are supported in each case with one end at the catch  16  and, with the other end, at a spring plate  48 , which is connected by a bolt  50  rigidly with the end plate  20  of the connecting piece  18 . The guiding ledge  34  is embraced in fork fashion by the end plates  20  and the parts of the catches  16  adjoining the end plates  20 . 
     The locking plate  38  is connected elastically by a tensioning mechanism  52  with the housing  10 . The tensioning mechanism is formed by two or, as in the example shown, by four springs  54  (compression springs), of which only two can be recognized in FIG.  1 . The springs  54  are in each case held with one end pivotally at a wall of the housing  10  and, at the other end, connected pivotally with the locking plate  38 . In the middle position of the symmetrically constructed shunt adjusting device shown in FIGS. 1 and 2, the springs  54  are compressed elastically in their dead center position. 
     In one opening  56  of the locking plate, a shaft  58  is disposed, which is connected rigidly with the locking plate and which can be engaged by an actuating drive, which is not shown and with which the locking plate  38  and, with that, also the adjusting rods  12 ,  14  can be shifted, in order to bring the points into their end positions. 
     If, for example, the locking plate  38  is moved with the help of the actuating drive out of the position shown in FIGS. 1 and 2 somewhat to the left, the compressed springs  54  are swiveled out of the dead center position and push the locking plate  38  along the guiding rod  40  further to the left as can be seen in FIG.  3 . In the initial phase of this movement (FIG.  2 ), the locking contour  36  of the locking plate engages the locking tappet  28 , so that the locking tappet and the connecting piece  18  also move to the left, until the locking tappet  28  falls into a recess  60  of the guiding ledge  34  (FIG.  3 ). The locking plate  38  alone then moves further and, with its locking contour  36 , locks the locking tappet  28  in the recess  60 . 
     The adjusting rod  12  is shifted to the left by the connecting piece  18 , so that the associated point is brought into contact with the rail. This point then is the closed switch rail. Since the connecting piece  18  is locked in the position shown in FIG. 3 by the locking tappet  28  and the locking contour  36  is locked at the guiding ledge  34 , which is connected with the housing, the closed switch rail also is locked rigidly in its position. 
     If the locking plate  38 , under the action of the springs  54  alone, moves further to the left, the stop  42  on the right side comes into contact with the catch  16  there. The force of the spring  54  then acts over the catch and the connecting piece  18  on the left adjusting rod  12 , so that the closed switch rail is additionally prestressed elastically in the closed position. By these means, any clearance between the closed switch rail and the rail is eliminated and, due to the rigid mechanical locking, the closed switch rail is secured in its position with a theoretically unlimited holding force. 
     The point, connected with the right adjusting rod  14 , is tightened by the above-described process initially by the force of the coupling device  32  and is then held in the end phase (FIG. 3) in the open position additionally by the force of the springs  54 . The holding force corresponds to the sum of the forces of the coupling device  32  and the springs  54 . Since the coupling device  32  is formed by a total of four springs  44 ,  46 , a high holding force is achieved even if one of these springs were to break. 
     However, if the shunt is changed over manually, it is only necessary to overcome the force of the springs  54  until these springs have passed over their dead center. By means of the appropriate movement of the locking plate  38 , the locking tappet  28  is unlocked, the connecting piece  18  is then carried along to the right in the drawing and finally the springs  54  bring about the further movement of the adjusting rods and the locking in the opposite end position. At the same time, the thickened right end of the locking tappet  28  falls into a recess of the guiding ledge  34 , which cannot be recognized in the drawing and corresponds to the recess  60 . 
     FIG. 4 illustrates the course of the movement in the event that the point is forced by the rail-bound vehicle. The closed switch rail, which is connected with the adjusting rod  12 , initially remains locked in the closed position. The open switch rail is deflected by the wheels of the rail-bound vehicle and pulls the adjusting rod  14  against the force of the coupling device  32  to the right, so that the catch  16 , which is connected with this adjusting rod  14 , is detached from the associated end plate of the connecting part  18 , as can be seen in FIG.  4 . Since this catch  16  is up against the stop  42 , the connecting plate  38  is carried along toward the right, so that the locking tappet  28  is released. The tension on the springs of the coupling device  32  can then be released, so that the connecting piece  18  is pulled along to the right. Due to the force of the left coupling device  30 , the adjusting rod  12  is carried along with this movement. As soon as the springs  54  have passed over their dead center, the shunt is changed over in the manner already described and locked once again. The actuating drive, coupled with the locking plate  38 , is carried along into the new position and is therefore ready to make adjustments once again immediately. 
     The holding force for the open switch rail can be adjusted, in that the pretension of the springs  44  and  46  is varied with the help of the bolt  50 , screwed into the spring plate  48 . 
     FIGS. 5 to  8  illustrate the principle of functioning of a device of a second example. 
     In FIG. 5, a closed switch rail  62  can be recognized, which is held at the free end of the adjusting rod  12  and lies against a rail  64 , as well as an open switch rail  66 , which is held at the free end of the adjusting rod  14  and lies at a distance from the associated rail  68 . 
     The adjusting rods  12 ,  14  are connected to one another by a coupling device  70 , which yields when stressed in tension. The coupling device  70  has a spring assembly or a spring  72 , which is supported with one end at the bottom of a cage  74  fastened to the adjusting rod  12  and, with the other end, at a spring plate  76 , fastened to the adjusting rod  14 . 
     Each of the adjusting rods  12 ,  14  is connected axially rigidly with an associated connecting fork  78  or  80 . The two connecting forks  78 ,  80  are embraced with some clearance by a carriage  82 , which can be moved in the longitudinal direction of the adjusting rods  12 ,  14  and is connected over a coupling  84  with the actuating drive, which is not shown. The carriage  82  carries unlocking ledges  86 , which interact over inclined surfaces  88  with corresponding inclined surfaces  90  of two locking tappets  92 ,  94 , which lie transversely to the locking ledges. The locking tappets  92 ,  94  can be moved vertically with the help of guides, which are not shown, in a housing or frame of the apparatus, which is not shown, and prestressed elastically with the help of springs  96  into a locked position, in which they secure the associated connecting fork  78  or  80  and, with that, the associated adjusting rod positively against an inwardly directed axial movement. 
     In FIG. 5, the locking tappet  92 , belonging to the adjusting rod  12 , is in the locked position, so that the closed switch rail  62  is locked positively in its position. The locking tappet  94 , on the other hand, is in the unlocked position, in which it lies on a flat section of the unlocking ledge  86 . The open switch rail  66  can therefore move against the force of the spring  72  in the direction of the rail  68  and is thus held in its position only by the holding force of this spring. 
     FIG. 6 illustrates the initial phase of a shunt adjustment process, for which the carriage  82  is moved with the help of the driving mechanism mentioned towards the right in the direction of the rail  68 . Since there is a certain clearance between the carriage  82  and the connecting forks  78 ,  80  and the connecting fork  78  is locked by the locking tappet  92 , the connecting forks initially do not participate in the movement of the carriage  82 . The unlocking ledges  86  therefore slide with their inclined surfaces on the corresponding inclined surfaces  90  of the locking tappet  92  and move this counter to the force of the spring  96  into the unlocked position. As soon as the carriage  82  comes up against the connecting fork  78 , the two adjusting rods  12 ,  14  move jointly with the carriage  82  further towards the right, as shown in FIG.  7 . 
     At the end of the adjusting process, if the switch rail  66  has become the closed switch rail and the switch rail  62  the open switch rail, the locking tappet  94  falls into the locking position, so that the switch rail  66  is locked. The state, then achieved, is the mirror image of the state in FIG.  5 . In a similar manner, the shunt can then be restored once again to the position shown in FIG.  5 . 
     FIG. 8 illustrates the initial phase of a forcing process, by means of which the point can be forced by a rail-bound vehicle. The open switch rail  66  is forced by the wheels of the rail-bound vehicle against the rail  68 . Because of the clearance between the carriage  82  and the connecting fork  80 , the adjusting rod  14  can move towards the right. At the same time, the spring  72  is compressed, since the cage  74  and the connecting fork  78  are locked at the locking tappet  92 . Because of the relative motion between the carriage  82  and the locking tappet  92 , this locking, however, is canceled, so that both adjusting rods  12 ,  14  can move jointly with the carriage  82  into the new position. At the end of the forcing process, the shunt, as in the case of a normal adjusting process, is locked with the help of the locking tappet  94 . 
     FIG. 9 illustrates a possible construction of the apparatus, which works according to the principle shown in FIGS. 5 to  8 . The state, shown in FIG. 9, corresponds to the state of FIG. 5, in which the switch rail, which is connected with the adjusting rod  12 , is the closed switch rail. 
     The whole of the apparatus is mounted between two frame plates  98  which, in relation to the rails  64 ,  68  are disposed rigidly in a housing not shown. The carriage  82  runs on guiding rods  100 , which extend between the frame plates  98 . The carriage  82  has two parts  102  here, which are the mirror image of one another and are connected together by transporting plates, which are not shown and, at the same time, form parts of the coupling for the actuating drive. The connecting forks  78  and  80  are also guided on the guiding rods  100 . Furthermore, it can be seen in FIG. 9 that the clearance of the connecting forks  78  and  80  relative to the carriage  82  is limited in both directions by stop surfaces  104  and  106 . 
     Each of the two parts  102  of the carriage  82  carries an unlocking ledge  86  which, on the upper side, has two oppositely inclined surfaces  88 . The two locking tappets  92  and  94  lie transversely over the locking ledge  86  and are guided, so that they cannot tilt, each on two vertical guiding bolts  108 . The two guiding bolts  108  for each locking tappet are fastened on a locking seat  110 , which is held adjustably on rods  112  extending parallel to the guiding rods  100 . The rods  112  are fastened in each case to one of the frame plates  98 . 
     In FIG. 9, the connecting tappet  92  is in the lowered locking position, in which it lies at cams  114  of the connecting fork  78 , locking them. The inclined surfaces  90  of the locking tappet  92  lie in a manner, which cannot be seen in FIG. 9, at the underside of the locking tappet and contact the inclined surfaces  88  of the unlocking ledge. 
     The locking tappet  94  lies on the ends of the unlocking ledges  86 , which are the lower ends in FIG. 9, and is held thereby in a raised unlocking position, so that the cams  114  of the connecting fork  80  can pass underneath the locking piece  94 . 
     During an adjusting process, the carriage  82  and the connecting ledge  86  in FIG. 9 move downward, so that the locking tappet  92  is raised by the inclined surfaces  88  into the unlocking position. If the locking is canceled, the locking fork  78  is carried along by the stop surfaces  104  and the connecting fork  80  is carried along by the stop surfaces  106  of the carriage. If the lower inclined surfaces  88  of the two locking ledges  86  reach the inclined surfaces  90  of the locking tappet  94 , the locking tappet  94  falls into the locking position behind (in FIG. 9 above) the cam  114  of the connecting fork  80 . 
     By adjusting the locking seats  110  on the rods  112 , the locked positions of the connecting forks and the adjusting rods  12 ,  14  can be adjusted independently of one another. 
     In FIG. 9, a test device  116  is indicated diagrammatically. It is disposed next to the locking device between the points and functions, in a known manner, for checking the positions of the points. The checking takes place with the help of test rods, which are not shown and are connected in an appropriate manner, like the adjusting rods  12 ,  14 , with the points. The locking tappets  92  and  94  are elongated to one side in such a manner, that they extend into the test device  116 . The advantageous possibility of locking the test rods in an appropriate manner, like the adjusting rods  12 ,  14 , with the help of the locking tappets  92  and  94 , arises out of this. The vertical positions of the locking tappets  92  and  94  can be scanned with the help of probes  118 . If, during a shunt adjusting process, as a result of the breakage of an adjusting rod, for example, the adjusting rods are moved into the new position, but the associated point is not, then the corresponding test rod remains in the original position and prevents the locking tappets  92  and  94  from falling into the locking position. Accordingly, the signals of the probes  118  indicate not only whether the adjusting rods were locked in the intended position, but also whether the shifting of the point is confirmed by an appropriate movement of the test rods. 
     For reasons of greater clarity, the coupling device  70 , acting between the connecting forks  78  and  80 , is not shown in FIG.  9 . 
     The driving mechanism for the carriage  82  can, as for the embodiment of FIGS. 1 to  4 , be equipped with a tensioning mechanism  52 . Alternatively, however, a different suitable type of driving mechanism can also be used.