Abstract:
Switch box for railway, tramway, points or similar, of the so called english type i.e. having four or more blades comprising a drive unit (M,  3, 4, 5, 5′, 5″, 5′″, 6 ) of the transfer motion of the blades (A 1 , A 1 ′, A 2 , A 2 ′) of the switch, and at least one group ( 12, 18, 120, 21, 24 ) of linear transmission of the drive motion to the blades, movable means ( 24, 124 ) to lock the blades in their respective position of closure. According to the invention, the said groups are housed in a box ( 1 ) which has substantially the dimensions and the shape of a sleeper and that is fitted in the track in place of and with the function of a sleeper.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a switch box for railway, tramway points, or similar particularly of the so called english type, i.e. with four or more blades and in which the blades connect in pairs with the rails of a track, according the preamble of claim 1. 
     From WO 94/27853 a switch box which is used in combination with a simple switch with only two blades. In this switchbox only the operating groups, the groups of linear transmission of the operating motion and the groups locking the blades in the closed positions are located inside the box. At a central slide, housed in the box branch out drive rods to operate the blades which are external to the same. The group locking the blades in the closed position acts on the very slide and not on the blades, while no means are provided allowing kicking of the blades, that is, the disengagement of the same from the locking means, under the action of a preset force which operates on the blades in direction of displacement of the same. 
     A further switch box of the type described at the beginning but used in combination of ta simple switch with only two blades is known from the U.S. Pat. No. 4,093,163. In this case, also the link rods to the blades are housed in the box in shape of a sleeper, while neither means of lockswitching, nor means of kicking are provided. 
     SUMMARY OF THE INVENTION 
     The invention has the purpose to realize a switch box for railway, tramway points, or similar, particularly for the so called english type switch, and according to the preamble of claim 1, in such a way, whereby means are provided in the same suitable to guarantee one or more or all of the functions of locking, lockswitching and/or kicking of the usual switch boxes all the elements being mobile, with the exception of the blades integrated inside the box shaped like a sleeper, and the same being realized with an extremely simple construction, of reduced dimensions and such to ensure the housing in the defined available volume, as well as of safe and sure operation. 
     In particular, the invention aims at the realization of a switch box in which movable means of locking the blades in the corresponding position of closure are provided both by the linear transmission unit of the operating motion, as well as directly by the actual blades, all to reach the maximum operational surety and safety of the switch box. 
     The invention attains the above mentioned aims with a switch box.of the type according to the preamble of claim 1 and showing in combination the features of the characterising part of claim 1. 
     The switch box shows means for locking the blades in their closed position and which are automatically disengaged at the closed position of the opposite blade at the moment the switch box is activated to operate the blade. 
     The switch box, has means of linear transmission, formed by a saddle, slide or similar which are moved transversally to the track, particularly orthogonally to the same, in the two directions between the two extreme end of stroke positions by a group translating the rotary motion into a linear motion and to which are linked a transmission rod for each of the two blades, while each blade is connected to a lever coupling it to the respective transmission rod thanks to corresponding movable means locking the blade in the closed position. 
     In particular, the coupling levers of the blades corresponding to the transmission rods form said movable locking means of the blades. 
     According to an advantageus feature of the invention, the means of locking the blades in position of closure, are only associated with the outermost blades of the four blades provided, while each of the two internal blades is locked in position of closure thanks to a rigid mechanical connection with the external blade which assumes the closed position of the same together with the internal blades. 
     This arrangement allows to lock the inner blades of the switch, by mantaining all the units inside the box having the form of a sleeper. 
     The invention presents further features and perfectionings which are the subject of the claims below. 
     The features of the invention and the advantages derived from the same are better prooven by the following description of an executive example illustrated as non-limiting claim in the enclosed drawings, in where: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIG. 1 shows a plan view of a so-called english type point with a switch box according to the invention. 
     The FIG. 2 shows a cross-section according to a vertical plane transversal to the track of a switch box according to the FIG.  1 . 
     The FIG. 3 shows an enlarged detail of the cross-section according to the vertical plane of FIG. 1, in the area of one point and one rail. 
     The FIGS. 4 and 5 show a detail relating to the drive slide and to the movable locking means of the same, in the locked and unlocked position respectively before the start of the translation. 
     The FIGS. 6 and 7 show two transversal cross-sections of the saddle and of the movable locking means according to FIG. 4, according to the line VI—VI and VII—VII respectively. 
     The FIG. 8 shows an enlarged plan view on the transmission rod-carrying slide in the closed position of translation with the guide integral with the drive slide. 
     The FIG. 9 shows an enlarged lateral cross-section in elevation of the rod-carrying saddle and of the drive slide. 
     The FIG. 10 shows a lateral cross-section of the rod carrying saddle and of the drive slide. 
     The FIG. 11 shows an enlarged partial view of the switch according to FIG. 1 in which only the area of the two external blades and the locking means relative to the same can be seen. 
     The FIGS. 12 to  14  show some phases of disengagment of the drive slide and the rod-carrying saddle in kicking condition and/or of impediment of the blade upon reaching the correct position of closure. 
     The FIGS. 15 and 16 show the locking means of the rails to the switch box. 
     The FIGS. 17 to  20  show different views and different cross-sections of the box for the blade position sensors, of the rod-carrying saddle and of the drive slide and the means for transforming the switch box from kicker to non-kicker. 
    
    
     DETAILED DESCRIPTION 
     In the FIGS. 1 and 2 a so-called english switch is shown, of the type foreseen in correspondence to crossings and with four blades. In the english type switch two tracks are provided with the rails B 1 , B 1 ′ and B 2 , B 2 ′ which co-operate with the blades A 1 ,A 1 ′ and A 2 , A 2 ′ respectively. In a box  1  with shape and dimensions corresponding substantially to those of a sleeper, are housed the means for shifting the blades A 1 , A 1 ′ and A 2 , A 2 ′. The switch box  1  in the shape of a sleeper has laterally widening fins  101  (FIGS. 15 and 16) which engage with the rail clips  2  of the rails B 1 , B 1 ′, B 2 , B 2 ′. These have a head  102  to overlap the rail foot of the rails B 1 , B 1 ′, B 2 , B 2 ′, while the remaining part consists of a tail which is clamped by means of bolts to the fins  101 . According to an advantageous perfectioning, one or both surfaces of contact facing each other of the rail clip  2  and of the fins  101 , can have teeth, or better a knurling parallel to the longitudinal axis of the track. This allows to obtain both a better registration of the relative position of the two parts, as well as a better clamping with regards to a relative translation between fin and rail clip  2 . 
     The switch box  21  in the shape of a sleeper extends itself for a certain length also outside the track substantially in a dimension corresponding to the sleepers and in one of said external extentions of the extremities is housed a drive motor generally of the electrical type indicated with M. The motor M activates by rotation by means of a bevel gear  5 ,  5 ′ transmission a threaded rod  3  which is connected to the output shaft  5 ″ of the transmission by means of a coupling  4  which can be of any type also of the type that disengage under condition of stress greater than a preset torque or clutch type. 
     Advantageously as evidenced in greater detail in FIG. 3, in combination with the drive motor M it is possible to provide means for manual activation which can consist of a crank  6  with a shaft  106  at the end of which a bevel gear  206  is provided that engages with a bevel gear  5 ′″ it also revolving together with the output shaft  5 ″ of the transmission which is coaxial the bevel gear  5 ′ connected to the motor. The two bevel gears  5 ′  5 ′″ are coaxial and have different diameters to ensure the appropriate transmission ratios suitable for driving with the motor M and for manual drive with the crank  6 . The crank  6  can be inserted into position of engagement with the bevel gear  5 ′″ of the transmission through an opening  7  in shape of a revolving support sleeve of the box  1  equipped with a lid  107 . 
     A Nut screw  8  is inserted on the threaded rod  3  which is housed in a manner to move freely axially between two opposite end of stroke stops  9  which are provided at the extremity on a first drive slide  12 . The drive slide  12  can slide in the two directions in the longitudinal sense of the threaded rod  3  on the bottom of the box  1  thanks to the wheels  13 . The nut screw  8  is connected in a reciprocally non revolving manner and translatable together thanks to a radial key  10  to a slide  11  which is therefore movable relative to the drive slide  12  between the two end of stroke stop walls  9  (FIGS. 7,  8 ). 
     The free travel of the nut screw  8  between the two end of stroke stops  9  is inferior to the global travel necessary to shift the blades between the two positions of closure of the blades A 1 , A 2  and A 1 ′ and A 2 ′ respectively to the corresponding rail. Therefore at the start of each phase of activation of the switch, the nut screw  8  and the slide  11  carry out a certain idle travel. This travel is used to activate in sense of disengagement the locking means of a first drive slide  12 . 
     The drive slide  12  is provided with wheels  13  and has in the middle area o bottom recess  112  provided with two notches  212  engaging a locking tooth  14 . The locking tooth is supported by spring loaded means  15  which push it firmly in position of engagement in the notches  212  and protrudes out of at least one lateral side of the slide  12  at least in the area of the notches  212 , preferably of both sides of the drive slide  12 . The slide  11  has in a position protruding from the lateral sides of the same respectively one roller  111  of a pair of coaxial rollers. The rollers  111  engage with cam tracks  116  realized by appropriate profiling of an longitudinal end edge in the example the lower one of the two levers  16  oscillating between themselves perfectly aligned, coincident and symmetric and which are fulcrated on the same shaft  316  which is supported by two stationary elements  616  placed on the two sides of the drive slide  12  and between which the said slide can freely pass during its travel. The two oscillating levers  16  extend themselves beyond the fulcrum shaft  316  towards the middle area of the drive slide  12 . The two oscillating levers  16  extend themselves along the two sides of the slide  12  up to the area of the slide  11  and the nut screw  8 . On the side opposite to the nut screw  8 , the oscillating levers terminate with a pressure head  416  which engages with the section of the locking tooth  14  of the drive slide  12  protruding out of the sides of the same. 
     The whole is realized in such a manner, whereby in position of end of stroke of the driving slide  12 , the rollers  111  of the slide  11  connected to the nut screw  8 , come to engage with the recessed area of the profiled edge of the lower end of the levers  16 , whereby the opposite extremity of pressure of the tooth is lifted from the locking tooth and this can under spring load penetrate into the notch  212  of the drive slide  12 . Upon movement in the opposite direction of the drive slide  12 , the nut screw  8  and with it the slide  11  performs a certain idle travel that is with regards to the same slide  12 , and the rollers of the slide  11  come to engage with the protruding area of the profiled lower front edge of the oscillating levers. In this condition, the pressure ends of the oscillating levers  16  engage with the tooth pushing it out of the notch  212  against the action of the spring. In this manner the drive slide  12  is released with regards to its translation before the nut screw  8  and the slide  11  come to stop against the end of stroke wall  9 , that is before the slide  12  starts to be driven or pushed. The leaf spring associated with the tooth, not only retains the tooth in position of engagement in the notches  212 , but also presses under spring load the levers  16  against the rollers  111 . 
     The FIGS. 4 and 5 show the starting phase of the travel unlocking the drive slide  12  by the nut screw  8  and the slide  11 . In FIG. 4, the slide has reached the end of stroke position corresponding to a motion to the left in direction of the arrow F 1 . The reversal of the direction of displacement of the slide indicated with F 2 , causes a first idle travel of the nut screw  8  and of the slide  11  until they come to a stop against the wall  9 . During this travel the rollers  111  have come into contact with the protruding area of the profiled lower leading edge  216  of the levers  16 , whereby the extensions  416  acting on the tooth  14  pushed it out of the notch  212  and the slide  12  is free to slide when the nut screw  8  and the slide  11  have come to a stop against the end of stroke wall  9 . Therefore further displacement of the nut screw  8  along the threaded rod  3  causes the drive slide  12  to move in direction of the arrow F 2 . 
     The end of stroke positions of the drive slide  12  are defined by a stationary stop  60  integral with the bottom of the box and through which passes an axial extension  412  of the slide  12  which has an enlarged striker  512  on the extension at its free extremity. In the two end of stroke positions one of the two faces of the end of stroke stop  6  comes into contact with the enlarged striker  512  on the extension  412  and the front end of the slide  12  respectively on which said extension is fitted. 
     On the drive slide  12  in a superimposed position is an integral guide  19  for a rod carrying saddle  18  which is integral with the translation of the drive slide  12 , thanks to a vertical pin or other fixed joint  618  and slides along the longitudinal side walls of the guide  19  in the box  1  thanks to the rollers  218 . The rod-carrying saddle  18  is of tubular construction, and the side walls of the same have a plan form in shape of isosceles trapezoids, forming at the opposite ends of each side wall  318  of the rod-carrying saddle  18  inclined surfaces  518  in a direction simmetrically opposed to each other and converging towards the central area of the very slide  18 . In the central area the rod carrying saddle  18 , has on the bottom and on the top side, a double slide guide respectively, that is on both sides or one side  418  for instance longitudinal central grooves, or half of the same, in which the extremities of a central rod  120  are housed. The central rod  120  is connected to the rod-carrying saddle  18  thanks to a pair of carriage springs  220 . Each of the two carriage springs is connected with the extrados side and in a simmetrical position with regards to the other carriage spring to the central rod  120 , whereby the plan seen from above has substantially the shape of an “X”, cut vertically in half by the rod  120 . Each of the free extremities of the carriage springs  220  has a roller  320 . The carriage springs  220  are dimensioned in such a manner, that each roller  320  engages with an inclined surface  518  of the rod-carrying saddle  18 . In particular, the rollers  320  at the extremities of each carriage spring  220  engage for each carriage spring respectively with the inclined surfaces  518  on the end sides of the very side of the rod-carrying saddle  18  towards which the carriage spring is faced. 
     The central rod  120  is fixed to the carriage springs  220 , substantially at one single blade, in particular in correspondence of the blade or more precisely of the tangential band of the carriage springs  220  to said rod  120  by means of a locking clamp  420 . 
     The central rod  120  connects at both its extremities thanks to the joints  22  with the transmission rods  21  which extend themselves up to the area underneath the corresponding rail B 1 , B 1 ′, B 2 , B 2 ′. The extremity  121  of the transmission rods is in shape of a plate, in the horizontal example and slides between two lateral guide walls  23 . In the extremities  121  of the transmission rods  21  a first elongated slot  221  is made in the top face which has a certain preset length and is foreseen closer to the coupling  22  to the central rod  120  of the rod-carrying saddle  18  and at a preset distance from this first groove  221 , in the end area a second angular elongated slot  321 . The first slot  221  is rectilinear and the axis of the same is parallel and coincident with the central longitudinal axis of the corresponding transmission rod  21 . The second slot  321  forms an obtuse angle and has a branch parallel to the central, longitudinal axis of the corresponding transmission rod  21 , but laterally offset relative to the latter, substantially in a measure corresponding to the length of the tooth  124  of an oscillating lever  24 , and a transversal, inclined branch which substantially terminates in correspondence to the central area of the transmission rod  21 . The length of projection of the second slot  321  on the longitudinal axis of the corresponding transmission rod  21  is substantially identical to the total length of the first slot  221 . 
     On the extremity  121  of each transmission rod  21  rests an oscillating lever  24  which is angled at its extremity in correspondence to the free extremity of the transmission rod  21 in order to form a coupling tooth  124 . From the lower rest surface of the oscillating lever  24  depart in a position coinciding with the slots  221  and  321  two transversal pins  224  and  324  which engage in the corresponding slots  221  and  321  of the extremities  121  of the transmission rods  21 . A pin  224  is provided in correspondence of the extremity of the oscillating levers  24  facing the rod-carrying slide  18 , while the other pin  324  is provided in an aligned position with the first  224 , with reference to the longitudinal axis of the longer branch of the oscillating levers  24  and in the area of the angle of the same. The distance between the two pins  224  and  324  is substantially corresponding to the distance of the projections on the longitudinal axis of transmission rods  21  of the extremities, on the same side, of the slots  221  and  321 , in such a way, that when the pin  224  stops against one of the extremities of the slot  221 , the pin  324  stops against the end on the same side of the angled slot  321  which in this case has the function of a guide track of the pin  324  and determines an angular displacement in the horizontal plane of the oscillating lever  24 , whose travel is sufficient to bring the lever alternately into position of engagement of the tooth  124  on the front end of the facing wall of the lateral guide  23  and in the position of disengagement of the same thanks to a relative displacement between transfer rod and oscillating lever  24 . 
     In coaxial position to the locking pin  224  in the rectilinear slot  221  of the transmission rod  21 , from the top side of each oscillating lever departs a tansversal extension connected to the blade which is formed by a bolt  424  with a head  524  in form of a spherical joint seat for a ball joint type appendix  25  integral with the blade A 1 , A 1 ′, A 2 , A 2 ′, in such a way, that the oscillating lever  24  is coupled with the corresponding blade A 1 , A 1 ′, A 2 , A 2 , in a revolving manner at least around the common axis with the pin  224  of the very lever  24 . The spherical appendix  25  departs from a small arm  125  fixed on the blade A 1 , A 1 ′, A 2 , A 2 ′, in particular to the longitudinal lateral surface of the same. 
     With reference to the FIGS. 1 to  14  the construction as per above, allows to obtain the following operation: 
     Operation under normal conditions. 
     Activating the threaded rod  3  whether by means of the motor M or the help of the crank, in order to obtain the displacment of the blades from one initial position of closure of one of said blades to the corresponding rail in the closed position of the blade opposite to the associated rail, at the start of the travel of the nut screw  8  and of the slide  11  associated with the same, relative with regards to the drive slide  12 , (FIGS. 4 and 5) the rollers  11  activate the locking levers  16  so as to release the drive slide  12  from the locking tooth  14 . Upon reaching the end of stroke stop  9  on the side facing in direction of travel of the drive slide  12 , this starts its travel and drags with it the rod-carrying slide  18  above it together with the rod  120  and therefore together with the transmission rods  21 . In the initial start-up position, the pins  224  and  324  of the oscillating levers  24  coupling with the blades initially closed stop against the extremity of the associated slots  221 ,  321  on the side of the same in front with regards to the direction of translation of the transmission rods  21 . Therefore, in an initial phase of the travel of translation of the transmission rods  21 , the transmission rod  21  associated with the closed blade in the start-up position carries out a relative motion with regards to the very blade and to the coupling oscillating lever  24 . The relative motion is such as to bring the lever  24  associated with the blade in position of closure in the start-up condition, into position of disengagement from the edge of the lateral guide wall  3 , while on the opposite side, the guide rod has executed a relative motion such, that the oscillating lever  24  associated with one or more blades which have to be brought into position of closure assumes a slightly inclined position and substantially of rest against the internal surface of the side wall of the guide  23  associated with it. Upon reaching this position, the pins  324  of all oscillating levers  24  connected to the corresponding blades A 1 , A 1 ′, have reached substantially an intermediate position between the extremity of the inclined branch and the extremity of the same in the angle area of the corresponding slots  321 . The oscillating levers  24  are retained in this position by effect of the lateral guides  23  against which they slide in their further travel during which , the arms  24  and with them the blades are driven together with the transmission rods  21 . The blade reaches the position of closure and at the same time the tooth  124  of the coupling oscillating lever  24  passes beyond the rear edge of the facing side wall of the guide  23 , with reference to the direction of translation of the transmission rods  21 , whereby the further translation of the transmission rods  21  determins the subsequent oscillation, especially of the oscillating lever  24  associated with the blade that has been brought into position of closure, into the position of engagement behind the facing front edge of the lateral guide walls. The oscillating lever of the blade that passed into the position of moving away from the associated rail is subsequently brought into a central position with regards to the lateral guides  23 . 
     In this way, the blade in position of closure is locked in position. 
     Upon reaching the position of closure opposite to the one at the start, the rollers  111  of the slide  1  associated with the nut screw  8  reach a new recessed part of the control cam  216  obtained thanks to the profiling of the oscillating levers  16  which are supported stationary on a lateral support  616  through which passes the drive slide  12 , so that the locking tooth  14  of the drive slide  12  penetrates into the corresponding notch  212  of the same, locking it in the position of closure it just reached. 
     With reference to the english type switch shown in the Figures, in which two pairs of blades A 1 , A 1 ′ and A 2 , A 2 ′ are provided, as the blades of the two pairs must assume the positions of closure constrained to each other for each pair, one single drive slide  12  is sufficient, with one single rod-carrying saddle  20  for all four of the blades. Besides the fact that four blades are provided, the english style switch differs from the normal one in that for the blades A 2  and A 1 ′ in the central area of the switch it is not possible to provide specific means for locking in position. Therefore, in these conditions, having the blade A 1  of a pair to assume the position of closure together with the blade A 2  of the other pair, the same are rigidly constrained together by a rod  26 , while the locking means, that is the coupling oscillating lever  24 , is provided only outside the track and in correspondence of the blade A 1 . The same identical construction is also foreseen for the blades A 1 ′ and A 2 ′ which assume together the position of closure to the respective rail. 
     With particular reference to the FIGS. 12 and 14, the particular construction of the rod-carrying saddle  18  makes the switch a kicker type. This means, that the switch can be activated by a train suddenly arriving from an opposite direction to the arrow T in FIG.  1  and from the incorrect track, will act with the wheel on the unlocked blade. 
     In these conditions, the wheel of the train exerts a force of displacement in direction of closure of the blade not locked to its associated rail and if the blade of the switch should not yield this would entail braking the same or in any case a derailment. 
     Thanks to the coupling carriage springs  20  and the rod-carrying saddle  18 , when on the unlocked blade a force of displacement of the same is exercised in direction of closure to the corresponding rail, and when this force is greater than the spring loaded one of the carriage springs  220 , the rollers of the rear branches of the two opposed carriage springs  220  slide against the inclined planes  518 , overcoming them and compressing the two associated branches of the carriage springs  220  one against the other, so that the central rod  120  and the associated transmission rods  21  are free from the drive slide  12  and can translate in the direction of the force exercised by the blade. The mechanism of the coupling oscillating lever which is perfectly independent from the one of the drive slide works in an analogous manner to the one decribed previously. 
     According to an advantageous feature, the inclined planes have a length such, that the sliding of the rollers from one extremity to the other of the same corresponds substantially to the length of the section of the angled slots  321  of the transmission rods that is rectilinear and parallel to the longitudinal axis of the transmission rods so that as evidenced in FIG. 13, as long as the rollers remain on the inclined planes  518  and do not reach the intermediate zone of the lateral walls of the rod-carrying saddle  18 , the oscillating levers  24  with the locked blades do not pass into a position of disengagement. This allows the mechanism of transmission to absorb slight mechanical stresses exercised on the blades, without causing the abandonment of the switch position. 
     The rod-carrying saddle  18  integral with the drive slide  12  allows to avoid stresses on the drive motor in case mechanical obstacles come between the blade and the corresponding rail during the closing phase. As a matter of fact if for example a stone or other prevents the rail to assume the final locking position , the drive slide can in any case be brought into the position of end of stroke, with a disengagement of the central rod  120  of the rod-carrying saddle  18  analogous to the one described in the phase of kicking. 
     With reference to the FIGS. 1,  3  and  17  and  19 , the switch box has sensors for the position of the blades, of the central rod  120  and the drive slide  12 . 
     For the external blades of the english type switch illustrated, the position sensors consist of limit switches  30  housed in small boxes  31  which adhere to outside the of the rail. The switches  30  are activated by a small rod  32  that passes transversly through the rails, protruding on the inside of the same against which acts the side of the blade facing it. 
     In the english type switch the end of stroke sensors of the central rod  120  and of the drive slide  12  are housed in a small box  35  on top of the switch box in the central section of the track or tracks B 1 . B 1 ′, B 2 , B 2 ′. 
     The FIGS. 17 and 19 show hybrid forms of execution of a small box  35  in that in combination with each other all the functionalities are provided whether for the english type switch or for the normal switch. In reality, as evidenced in FIG. 1, as the english type switch can be equipped with two small boxes  35 , the means illustrated with reference to the FIGS. 17 and 19 can be distributed on said two small boxes. 
     Through a slot  36  in the bottom of the small box  35 , at the inside of the same protrudes a slider  37  that is carried by the rod-carrying saddle, tubular  18  and integral with the drive slide  12 . The slot  36  has a length corresponding substantially to the travel of the drive slide and is oriented in direction of translation of the same. The slider  37  co-operates with two limit switches  38  and  38 ′ which are located at the end sections of the slot  36  at a distance and in a position corresponding to the stroke of the drive slide  12  and to the end of stroke positions of the same. The slider  37  acts thanks to inclined lead-in surfaces  137  on the trip buttons  138  of the switches. 
     The position sensors of the central rod  120  are made in a similar manner. A slot  36  oriented in direction of translation of the transmission rods  21  and of a length corresponding to the stroke of the same is provided in the bottom of the small box  35  coincident with the central rods  120 . Through the slot  36  protrudes in the interior of the small box a small segment of the rack  39  which engages with toothed rollers  140  associated with each of the two limit switches  40  arranged at appropriate distances and in appropraite positions analogous to what described for the drive slide  12  in the section of the extremities of the slot  36 . The toothed rollers have an axial tooth  240  on the side facing the switches  40  this tooth extending itself over a certain angular amplitude and connects with inclined sides  340  with the remaining section of the front edge of the roller  140 . The axial tooth  240  trips the pushbutton of the switch  40  and according to the position of the roller determined by the rack, the pushbutton  440  will be depressed or not. The passage of the rack over the toothed rollers determines therefore the signal of position of the central rod  120 . 
     Furthermore, in the central small box  35  of the english type switch position sensors are provided for the internal blades A 2 , A 1 ′. In this case, with particular reference to the FIGS. 9,  17  and  19 , a small activating rod  41  is foreseen analogous to the one for the outside rail A 1 , A 2 ′ and which passes from side to side through the associated rail B 1 ′, B 2 . The protruding extremity at the side of the opposite rail acts thanks to a pressure plate  141  on a further small rod  42  which is supported sliding in the wall of the small box  35  and which protrudes on the inside of the same, where it acts against an intermediate point of a transversal oscillating lever  43 , the free extremity of which acts in a manner of compression on the pushbutton tripping the limit switch  50 . 
     The small box  35  foreseen in the english type switch can only house the position sensor of the second internal blade A 1 ′, which is realized analogous to what described in the preceding paragraph, or rather it also can house position sensors for the drive slide  12  and the central slide  120  realized analogous to the one previously described, where in this case the slider  37  and the rack  38  are associated with other parts integral with the drive slide  12  and the central rod  120 . 
     With reference to the FIGS. 8,  17 ,  20  according to a further feature, it is possible to provide means with which to constrain firmly and in a movable manner the rod-carrying saddle  18  and therefore the drive slide  12  to the central rod  120 , thus enabling and disenabling the function of kicking of the switch. In particular this can be obtained thanks to a transversal, vertical pin  50  which engages in coincident holes or seatings in the central rod  120 . The pin  50  can be inserted manually thus impeding the heeling of the switch if not thanks to a manual intervention of modification or can be controlled in the two positions in an automatic manner, for example thanks to an electromagnet  51  whose activation or deactivation bring the pin  50  in position of engagement or disengagement of the central rod  120 . The whole can also be made in a different manner and with other actuating means. 
     According to an advantageous feature, the pin  50  engages with slots  52  in the central rod  120 , whose length is such to allow within preset limits a certain relative motion between the central rod  120  and the rod-carrying saddle  18 . This in particular to allow the rod-carrying saddle  18  and the drive slide  12  to always reach the end of stroke position where the motor M is deactivated also in the case when obstacles are found between the blade and the closure rail of the same which prevent the blade from locking in the end of stroke position against the rail. 
     The slots  52  have such a length, that the relative travel between the central rod and the saddle which in the case indicated above takes place against the action of the carriage springs  220  keep the rollers of the carriage springs always within the range of the inclined planes  518  of the rod-carrying saddle  18 . Therefore, the central rod can carry out small relative motions with regards to the rod-carrying saddle  18  and to the drive slide  12 , but can never be disengaged as in the case of the FIG. 14 when the switch is of the kicker type. 
     The pin  50  can simply be engaged or alternatively engaged and disengagned on comand thanks to the electromagnet  51 . 
     To allow for the activation of the switch, also in the case the pin is not automatically controllable in the active and inactive position, meccanical means are provided which bring the pin  50  automatically in the inactive position upon activation of the switch. In the present example for this purpose lifting means are provided associated with the rod-carrying saddle  18  and said means consist of inclined planes  154  of a cam track  54  that co-operate with a roller  53  supported in a revolving manner around an axis transversal to the direction of sliding of the central rod  120  and laterally offset in an aligned position with said inclined planes  154  at the free extremity of the pin  50 . 
     Activating the rod-carrying saddle  18 , before the pin  50  reaches the corresponding extremity of the associated slot  52  in the central rod  120 , the roller  53  on the pin  50  engages the inclinded plane of the cam  54  carried by the rod-carrying saddle  18  and therefore raises in position of disengagement from the corresponding slot  51  of the central rod  120 , leaving the latter free to move together with the rod-carrying saddle  18 . Upon reaching the end of stroke position of switching, an opposed inclined plane or an interruption of the cam track returns the pin  50  into the angaged position of the other slot  51  in the central rod  120  re-establishing the kicker condition.