Abstract:
A relay having a base on which is arranged an electromagnetic system that actuates at least one pair of closing contact springs and at least one pair of opening contact springs where actuation is effected by a slide having actuation lugs located at different heights relative to the fixing of the active spring contacts for actuating the active opening spring contacts at a height different from that of the active closing spring contacts so that the characteristic curve of the magnetic system can be better adjusted to that of the spring contacts.

Description:
BACKGROUND OF THE INVENTION 
   The present application is related to PCT application EP 99/07278 filed on Oct. 1, 1999 and claims the priority data thereof. 
   1. Field of the Invention 
   The invention relates to a relay, having: a base which defines a base plane; a magnet system arranged on the base and having a coil, a core and an armature; at least one pair of closing spring contacts and at least one pair of opening spring contacts, each pair of spring contacts including an active and a passive spring contact, and each spring contact being secured in the base, standing perpendicular to the base plane, and bearing at its end remote from the base a contact portion; and an actuating slide which is movable parallel to the base plane and which acts on each movable spring contact, in each case in the vicinity of the contact portion. 
   2. Summary of the Prior Art 
   A relay of this type with forcibly guided contacts is known from DE 195 40 739 A1. There, the individual contact springs are arranged insulated from one another, with special structural measures also being taken to prevent short circuits in the event that contact portions become detached from the spring contacts. In this known relay, the active spring contacts, below the contact portions, are guided and actuated in laterally open slots in a slide. Laterally open actuating portions alter the stability of the slide, however, with the result that such slides already have a tendency to warp even during manufacture and do not retain optimum dimensional stability in operation either. A further problem with relay constructions of this kind consists in the fact that the force for opening the opening springs has to be overcome at the beginning of the movement of attraction of the armature, while the force for closing the closing contacts occurs towards the end of the armature movement of attraction. Since the force of an electromagnet system is small at the beginning of the armature movement of attraction, however, and only rises steeply towards the end of the movement of attraction, when the operational air gap is almost closed, application of the opening force is a problem which is typically solved by making the magnet system large in size, with this over-sizing not being necessary to close the closing contacts. 
   SUMMARY OF THE INVENTION 
   The object of the present invention is to construct a relay of the type mentioned at the outset such that the characteristic curve of the spring can be better adapted to that of the magnet system. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     According to the invention, this object is achieved in that the slide acts on the active opening spring contacts at a different spacing as regards the way it is secured in the base from that at which it acts on the active closing spring contacts. 
     The formation of a slide, according to the invention, having different points of action on the opening spring contacts and the closing spring contacts as regards the way they are clamped in the base is achieved in that the opening contacts are opened with as small a force as possible and as long a distance as possible, while the closing contacts are closed with a short lever arm over a short distance. In this way, the force to be applied to open the opening contacts is therefore adapted to the force of the magnet system, smaller at the beginning of the movement of attraction, while the great magnetic force at the end of the movement of attraction of the armature is sufficient to actuate the closing contacts over a short distance, that is to say with a small lever arm. The result is an adaptation of the characteristic curve of the spring to that of the magnet system which is more precise overall, so that the magnet system itself is relatively small in size. 
     In a preferred-embodiment of the relay according to the invention, it may furthermore be provided that all the active spring contacts are of the same construction, so that neither the active opening spring contacts nor the active closing spring contacts are pre-tensioned in the direction of the associated passive spring contacts. The opening spring contacts are then actuated by an armature spring, while the closing spring contacts are actuated by the magnet system. 
     Further advantageous embodiments are specified in the subclaims. 
       FIG. 1  shows a relay formed according to the invention, in an exploded illustration; 
       FIG. 2  shows the relay from  FIG. 1  in the assembled condition, with the slide partially cut away and without a cover, in a perspective illustration; 
       FIG. 3  shows the relay from  FIG. 2  in a rotated perspective illustration; 
       FIG. 4  shows the relay from  FIGS. 1  to  3  in side view, partially in longitudinal section; 
       FIGS. 5 and 6  show the slide of the relay from  FIGS. 1  to  4  in two perspective views; and 
       FIG. 7  shows a graph to illustrate the fundamental form of the force/distance characteristic curves of the magnet system and the springs of the relay. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The relay illustrated in  FIGS. 1  to  6  has a base  1  made of insulating material, which is substantially flat in form and defines a base side  10 , and with a cover  2  forms a closed housing. The base  1  has a flat, trough-shaped recess  11  for receiving a magnet system, while the remaining part, having raised side walls  12 , a longitudinal intermediate wall  13  and transverse walls  14 , forms two rows of contact beam chambers  15 . These contact beam chambers  15  narrow downwardly in the manner of slots to form plug-type channels  16  (see FIG.  4 ), in order to receive fixed contact beams  21  or spring contact beams  22  which may be plugged in, in each case from above, perpendicularly to the base plane  10 . The fixed contact beams  21  each form at their free ends passive (or fixed) spring contacts  23  with fixed contact portions  24  secured thereto, while active (or movable) spring contacts  25  with movable contact portions  26  secured to their free ends are in each case secured to the spring contact beams  22 . 
   The magnet system serving to actuate the relay has a U-shaped core yoke  31  with a core limb  32  and a yoke limb  33 . A coil body  34  bears an excitation coil  35  and receives the core limb  32  in an axial through opening. Since this core limb has a smaller width than the yoke limb  33 , because of the limited width of the core, an additional flux guide part  36  is inserted into the interior of the coil, together with the core limb  32 . In this way, the cross-section of iron within the coil is enlarged, as are the pole surfaces  32   a  and  36   a , with which an armature  37  co-operates. This armature is mounted at the free end of the yoke limb  33  with the aid of an armature spring  38 , and forms an operational air gap in a conventional manner with the pole surfaces  32   a ,  36   a . Two restoring limbs  39  of the armature spring  38  provide the rest position for the contacts, in the non-excited condition of the magnet system. 
   Movement of the armature  37  is transmitted by way of an armature extension portion  37   a  to a slide  40  and by way of the latter to the active spring contacts  25 . Since the spring contacts are arranged on the side of the magnet system opposite the armature, the slide has a connection portion  41  which extends above the coil and is adjoined by an actuating portion  42  which is set back in a stepped manner, downwardly in the direction of the base plane. This actuating portion forms, together with a central longitudinal wall  43  and side walls  44  and transverse walls  45  and  46  respectively, frames for each individual spring contact, which screen these spring contacts, with the exception of the respectively first passive spring contacts  24 R and the respectively last passive spring contacts  23 R and  23 A 2 , which are in the end regions of the actuating portion  42  of the slide  40  and thus do not need any screening on one side with respect to an adjacent spring contact. By way of explanation, it should be noted here that the active and passive spring contacts  25  and  23  in  FIG. 4  are provided with additional designations to indicate the type of contact, in other words  23 A 1 ,  23 A 2  for passive operational spring contacts (closing spring contacts),  23 R for passive rest spring contacts (opening spring contacts),  25 A 1  and  25 A 2  for active operational spring contacts (closing spring contacts) and  25 R for active rest spring contacts (opening spring contacts). Within the frames of the slide  40 , formed by partition walls  43 ,  44 ,  45  and  46 , windows  47  are recessed for the active spring contacts and windows  48  are recessed for the passive spring contacts, respectively. The respective passive spring contacts  23  and active spring contacts  25  project through these windows so that the ends bearing contact portions  24  and  26  respectively are each located above the actuating portion  42  of the slide and substantially within the frames formed by partition walls  43 ,  44 ,  45  and  46 . 
   Those transverse walls or blocking walls  46 , which each separate co-operating active and passive spring contacts, each have an approximately semi-circular recess  49  to match the round contour of the contact portions. A movable contact portion  26  of the active spring contacts  25  is guided respectively in this recess  49 . This means that the active spring contact can itself bear snugly against the blocking wall  46  or a blocking rib  50  projecting from the blocking wall. Moreover, the slide forms actuating lugs  52  which project inwards in each case from the side walls  44  and actuate the active operational spring contacts or the active rest spring contacts respectively at different heights. The active spring contacts are in this case each arranged within the window  47  and are guided between the respective blocking rib  50  and the associated actuating lug  51  or  52  with a small amount of play. This means that if a contact welds, all the other active spring contacts are also blocked with respect to any further switching actuation. 
   When the relay is put together, first of all the assembled magnet system is inserted in the recess  11  in the base  1 , with the armature spring  38  being secured between the yoke limb  33  and the base. The slide  40  is placed with its connection portion  41  on the magnet system, with the restoring limbs  39  of the armature spring  38  suspended in the apertures  41   a  in the slide. The armature itself is at the same time mounted on the yoke limb  33  and suspended by means of its extension portion  37   a  in the aperture  41   b  in the slide  40 . 
   Once the slide  40 , which is seated with its longitudinal partition wall  43  on the longitudinal wall  13  and with the longitudinal walls  44  on the side walls  12  of the base  1 , has been mounted, the spring contacts are mounted. For this, all the spring contacts are inserted through the appropriate windows  47  and  48  in the slide, into the chambers  15  of the base, and secured in the plug-type slots  16 . All the fixed contact beams  21  with the passive spring contacts  23  are of the same construction and straight, so that they can be inserted into the base perpendicularly with respect to the base plane. Moreover, all the active spring contacts  25  with their spring contact beams  22  are of the same construction and straight, so that they can be inserted through the associated windows  47  in the slide, perpendicularly with respect to the base plane, regardless of their function as operational spring contacts  25 A 1 ,  25 A 2  or rest spring contacts  25 R. The slide  40  is for this purpose held in a central position in opposition to the pre-tension of the armature spring  38 . 
   With this construction, all the spring contacts must be inserted into the base from above through the already mounted slide  40 , because the end portions of the spring contacts, at least those of the active spring contacts  25  having the contact portions  26 , have a larger cross-section than the windows  47 , so that the slide cannot be pushed from above over the spring contacts afterwards. As a result of these relative sizes, on the one hand the slide is made stable because of the closed frames around the spring contacts, and on the other hand a broken-off contact portion cannot fall through a window  47  down into a spring chamber and there perhaps cause a short circuit. 
   In the non-excited condition of the magnet system, the slide is drawn into the rest position by the restoring force of the armature spring  38 , that is to say to the right in FIG.  4 . During this, the rest spring contacts  25 R, which are straight in the untensioned condition, are drawn to the right, into the position shown in  FIG. 4 , so that they make contact with the passive spring contact  23 R. 
   When the magnet system is excited, the slide is moved to the left in  FIG. 4 , and the active rest spring contact  25 R is raised away from the passive rest spring contact  23 R and moved into its opened operational position by the blocking rib  50 R. At the same time, the slide acts by means of the actuating lugs  51  laterally on the active operational spring contacts  25 A 1  and  25 A 2 , and moves the latter in the direction of the passive operational spring contacts  23 A 1  and  23 A 2  until the corresponding operational contacts have been made. When the excitation is switched off, the armature spring  38  restores the rest condition, with the slide  40  acting laterally by way of the actuating lugs  52  on the contact portions  26 R and making the rest contacts. If one of the contacts welds, then the narrow guideway of the active spring contacts  25  ensures that further movement of the slide  40  and thus further actuation of the other contacts is blocked. If, for example, a rest contact welds, hen the slide is blocked to prevent further movement, by way of the blocking rib  50 R, which acts directly next to the contact portion. The operational contacts cannot therefore close. If, by contrast, an operational contact welds, then similarly by way of the blocking rib  50 A acting on the associated spring contact next to the welded contact, the position of the slide is prevented from being restored and the rest contacts are prevented from being actuated. 
   Since, moreover, all the active spring contacts are constructed to be straight, they have the effect of opening by themselves. If for example an actuating lug  51  or  52  on the slide breaks, then the active spring contact (opening contact) concerned opens, or is not closed (in the case of a closing contact). If by contrast the armature spring  38  breaks, then all the rest contacts (opening contacts) open and all the closing contacts are not closed again. 
   As can be seen from the description and in particular from  FIGS. 4 ,  5  and  6 , the actuating lugs  52  for the active rest spring contacts  25 R are substantially higher up with respect to the base plane than the actuating lugs  51  for the active operational spring contacts  25 A 1  and  25 A 2 . As a result, the force/distance leverage is different for the operational contacts and the rest contacts. Since the magnet system is in each case strongest in the closed condition, that is to say when the armature is attracted or almost at the attracted position, while when the armature has fallen away the force increases only slowly as a result of the large air gap, normally the magnet system must be sized so as to ensure that the magnet system applies sufficient force even at the beginning of the armature movement of attraction, in order to actuate the rest contacts in the opening direction and hence to overcome the restoring force of the armature spring. As a result of the offset arrangement of the actuating points or the actuating lugs  51  and  52  with respect to the base plane, the effect is that the active opening spring contacts are actuated with less force and over a longer distance, while the active closing spring contacts are made to close over a short distance as a result of the shorter leverage. At this moment, the magnet system already has more force since the armature has already largely approached the pole surface. As a result of this measure, in particular with the construction of a safety relay in which no switch-over contacts are used, but rather separately actuable opening and closing contacts, the efficiency of the magnet system can be increased, with the result that it can be of smaller size than is otherwise conventionally the case. 
   In the graph of  FIG. 7 , the way the force/distance characteristic curves are adapted is shown. Here, f designates the characteristic curve of the totalled spring forces and m designates the characteristic curve of the magnet system. The forces F which act in each case in opposition to one another are applied over the distance s, which represents the movement of the armature and the movement of the slide  40  between the rest position (on the right in  FIG. 4 , with the armature opened) and the operational position (on the left in  FIG. 4 , with the armature closed). In the rest condition, the slide is for example at the point s 1  or to the right of it, depending on the contact erosion. When the armature is attracted, the slide moves to the left, with the force m of the magnet system first rising only slowly. In this range, as far as s 2 , however, the opening force to be overcome (at the active rest spring contact or the armature spring adapted thereto) is also still relatively small because of the large leverage. From s 2  to s 3 , the active operational spring contacts produce a more steeply rising spring force which is overcome by a magnetic force m, which also rises more steeply in this range. From s 3  to the point of abutment, both the spring force f and the magnetic force rise steeply. This is the range of the overtravel to the point s 4 .