Patent Publication Number: US-3878491-A

Title: Electrical switching apparatus having the armature and contact bridge carrier flexibly coupled together

Description:
United States Patent Rauter et al.  
 [75] Inventors: Giinther Rauter; Glinther Bohlke.  
 both of Amberg; Giinther Weissberger, Riedenburg, all of Germany [73] Assignee: Siemens Aktiengesellsehalt, Munich,  
 Germany [22] Filed: Aug. 24, 1972 [21] Appl. No.: 283,426  
 [30] Foreign Application Priority Data Aug. 25, 1971 Germany 2142464 [52] U.S. Cl. 335/270; 335/277; 335/193 [51] Int. Cl. H0&#34; 7/08 [58] Field of Search 335/104, 105, 193, 194, 335/270, 271, 274, 277  
 [56] References Cited UNITED STATES PATENTS 1,936,098 11/1933 Pengilly et al. 335/270 llf [451 Apr. 15, 1975 2,434,096 1/1948 Hycrs et al 335/277 3,060,355 10/1962 Kruzic.............. 335/277 3,453,571 7/1969 Koertge l 335/277 X 3,663,908 5/1972 Kane et a1 335/277 X FOREIGN PATENTS OR APPLICATIONS 1,143,904 2/1963 Germany 335/270 Primary Examiner-G. Harris Attorney, Agent, or Firm-l(eny0n &amp; Kenyon Reilly Carr &amp; Chapin [57] ABSTRACT Switch gear having an armature and contact bridge carrier flexibly coupled together, with means to prevent relative flexing of the two unless the force on the contact bridge carrier exceeds a certain minimum. The coupling is by means of a pin inserted with play through a bore in the armature and connected to the carrier at its ends. Springs between armature and carrier tend to force them apart to bear on a flat protuberance located in the armature bore. This forces the armature and carrier to a static position as the flat protuberance is disposed on the interior surface of the bore, until the force of the armature overcomes the spring, at which point the linkage can flex.  
 12 Claims, 10 Drawing Figures PATENTEDAPR 1 5.915  
 SHEET 2 p z Fig.6  
 Fig.7  
 Fig.8  
 Fig.9  
 Fig.10  
 ELECTRICAL SWITCHING APPARATUS HAVING THE ARMATURE AND CONTACT BRIDGE CARRTER FLEXIBLY COUPLED TOGETHER BACKGROUND OF THE INVENTION 1. Field of the Invention The invention of this application relates to electrical switch gearv in particular, the invention pertains to structure for coupling the armature to the contact bridge carrier. This structure holds the two elements rigid when armature force is below a minimum and allows flexibility at the coupling only when the minimum force is exceeded.  
 2. Description of the Prior Art The present invention relates to electrical switch gear such as is used to open and close electrical circuits carrying high power. Such circuits typically include a movable armature with a power means, such as an electromagnet, for moving the armature, and a contact bridge carrier coupled to the armature. The contact bridge carrier bears thereon a conductive member which, when the carrier is moved by the armature, closes a circuit between two electrical contacts. Both the armature and carrier are often mounted slidably in guides.  
  Such an apparatus is shown, for example in German published patent application No. 1,143,904. It is known in such apparatus to couple the contact bridge carrier to the armature in a rigid fashion. Such an arrangement is, however, not completely satisfactory. When the armature and contact bridge carrier are rigidly coupled, this lack of compliance between the carrier and armature results in objectionable chatter of both the contact bridge carrier and armature against their respective guides. Furthermore, the absence of flexibility between the two elements causes the contact bridge to strike the contacts at an angle which may be somewhat oblique to the plane of the two contcts to be connected. This, of course, results in excessive wear on the contacts, and on the contact bridge, as well as impairment of the quality of the contact made. Additionally, the chatter of armature and contact bridge carrier against their respective guides or bearing results in accelerated wear, and inhibits the speed and smoothness of the operation of the device.  
  One attempted solution to this problem is shown in the German published patent application designated hereinabove. In that example, the contact bridge carrier and armature are flexibly coupled. The armature is joined to the contact bridge carrier by means of a round pin protruding through a bore in the armature and extending into a portion of the contact bridge carrier A leaf spring is interposed in a recess in the contact bridge carrier between the top central portion of the armature and the contact bridge carrier. The bore through the armature is sufficiently large that the pin extending through it has substantial *play.  
  This structure dictates that the armature, at least in the plane perpendicular to the axis of the round pin, is free to rotate without lirriit over a large arc. This freedom of motion is present at all times.  
  The operation of such an apparatus reduces some of the problems of chatter, but introduces other problems. Due to the unlimited flexibility; of the coupling be tween armature and contact bridge carrier, the armature is allowed to assume inclined positions in its bearings or guides. Since the armature motion is provided by means of an electromagnetic circuit, the armature inclination dictates that the portions of the magnetic circuit attached thereto will also assume the inclination. This means that the air gaps in the magnetic circuit powering the armature will become irregular when the armature becomes inclined, the magnet being less efficient. This in turn introduces the necessity for the use of greater electric current to power the magnet than would be the case if the armature were not inclined and the air gaps were symmetrical. The consequence of this is that, in order to effect sufficient power to enable the armature force to close tha contact bridge completely, it may become necessary to overheat the electromagnet.  
  Keeping in mind these disadvantages of the prior art, it is a primary purpose of this invention to provide electrical switch gear which overcomes simultaneously the disadvantages of rigidly coupling the armature to the contact bridge carrier and those of coupling these two elements with unlimited capacity for flexing over a wide are.  
  It is a more particular object of this invention to provide an electrical switch gear apparatus which solves these problems by maintaining a rigid coupling between armature and contact bridge carrier throughout most of the increment of motion of the apparatus. but which is capable of allowing flexing between the two elements when the armature force on the contact bridge carrier exceeds a certain predetermined value.  
  It is still another object of this invention to provide electrical switch gear apparatus in which the maximum degree of flexing between armature and contact bridge carrier is limited.  
 SUMMARY OF THE INVENTION The present invention overcomes the disadvantages of the prior art mechanisms discussed hereinabove by the provision of a unique apparatus for coupling the armature of the switch gear to the contact bridge carrier in such a way that the benefits of both rigid coupling and a flexible coupling are obtained. The armature is coupled to the contact bridge carrier by means of a pin inserted through a bore in the armature and into slideably mounted bushings which are connected to the contact bridge carrier. The armature bore is sufficiently larger than the cross sectional area of the pin to allow for substantial play of the pin. interposed between the side of the pin facing the contact bridge car rier and the interior of the armature bore is a flat protuberance having a flat contact surface thereon. Inter posed between the top of the armature facing the contact bridge carrier and the contact bridge carrier itself are strong compression springs. These springs tend to press apart the contact bridge carrier and armature. Under these conditions, the interior of the armature bore adjacent the flat protuberance is forced against the flat protuberance. This maintains the armature and contact bridge carrier in a statically rigid position relative to one another as long as the armature force pressing the armature toward the contact bridge carrier is not great enough to overcome the springs. When that minimum is exceeded, however, as for example when the contact bridge of the carrier is pressed against the stationary contacts across which the circuit is to be closed, the armature continues to press until the spring force is overcome. Under these conditions, the play in the armature bore allows the armature bore interior and the contact surface of the flat protuberance minute &#39;ipoinrv Cl llLll Whit-h isnt&#39;ii tron tltieti omit [Ulltitlit ll en iLLiH It. ime  
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 Elt J is a side tie [.liaetl in scetn n showing the enti odinent of i -l t i r Ell is 2 vznpizi reptesi l t lt iii the i-emliitp n the .irtitatnre and contact hr nge tnrriei at tr ptotted against the ii switch em inven ecu: Appiirattr tn accord-J! out may the it housing dc tllltll 1 ititabit titted ippendiees iii plastic ttaeited to the hushings llit&#39;initilcllirii ieeairiei 51s upr-e witness or bushings li. t ontue&#39;i bridge carrier the upper regi ns thcreot ontitct hridgr; r&#39;ri ext nds no 5 ts :ti&#39;il p hill; shown tiring oinliied twin the snitch gear a .4 i; a front Lleittlllrlt rien til the switch gear ot E and has provision tor carrying a contact bridge (not shown it The contact hridge is made of conductive material and is positioned with respect to a pair of contacts (also not shown) such that, when the contact i bridge carrier 5 moves up and down vertically on the sliding bushings the circuit between the contacts may he opened and closed in response thereto by the selectire placement or&#34; the contact bridge between the contacts.  
  The contact bridge carrier 5 is moved by means of a movable armature 4 which extends downwardly into a magnet An electrical :oil 3 is disposed about magnet ,2 such than when cur; ent is passed through coil 3, magnet 2 prm ides energy to apply force to armature 4. Armature it fitted in sliding fashion into magnet 2.  
  Armature 4 is coupled to contact bridge carrier 5 in accordance with a unique structure The armature is rmided with a bore 8 extending therethrough. Bushings l2 are also provided with bores corresponding to armature bore 8 such that, when a pin, such as is shown at ii, is inserted through the armature bore, it may also be correspondingly inserted into the bores in bushings :2. l he erosssee ons of both armature bore 8 and pin ii are preterahly rectangular in shape. the dimensions of the cross-scctional area of bore 8 being considerably larger than those otpin 6, in order to allow for substantial play between pin 6 and armature 4.  
  Biasing means 9. in this case shown as compression springs are fastened to and interposed between contact bridge carrier 5 and the top of armature 4. It can be seen that springs 9 tend to separate the armature and contact bridge carrier. but are prevented from completely doing so by the connection of pin 6 between armature 4 to bushings 12 which are connected to contact bridge carrier 5.  
  iccording to the present invention there is provided hetween the upper surface of pin 6 and the upper interior wall of armature bore 8 a Hat protuberance ll) havplanar fashion the top of armature bore 8 when springs 9 press the armature down and simultaneously tend to lift The tontact bridge carrier against the downward push on armature 4.  
  Such an apparatus as is illustrated in FIG i (and also in FIGS. LZ4) is capable ofopcratively coupling the armature and contact hridgc carrier in a unique fashion it is evident that. as long as no upward force is applied to armature 4 h magnet 2. the compressive force of the springs &#39;9 tending to separate the armature and contact hridge carrier maintains th two elements in a lttilt&#34; and stable position. This is true because the top surface bore it rests tirmly on and is pressed against the tin contact surlaee 7 of protuberance 19. This maintains the two elements static and stable during m st conditions oi operation this relation continues even when upward force applied to armature 4 by the magnet so tong as the upward force applied is less than sufficient to t-rereonn; the compressive force of springs in On the other hand when the armature force is suffiient o lli lllt&#39;f compress springs 9, the top of the interior oi armature hurt; 8 lifts off planar surface 7 (the pin; hettaeen armature bore 8 and pin 6 permits this} and the armature and contact bridge carrier are permitted to lies. re &#39;liently The magnitude of such flexing is, of course, limited by the degree of play between bore it and pin it ing a flat contact surface &#34;7 suitable for engaging in a When the switch gear apparatus of this invention is actuated. the armature exerts force in an upward direc tion, carrying the contact bridge carrier along with it by way of the connection via springs 9. During this phase of operation, as long as the armature force is not suffi- .&#39;ient to compress further the spring 9, the two elements are held in a stable nonflexible coupled equilibrium. This means that. during the early portions of movement of the switch gear, when the armature force required to move theh contact bridge carrier is generally small, armature and carrier are maintained in a stable aligned relationship. thus providing that armature 4 slides within magnet 2 in a smooth stroke, such that the air gaps of the magnetomotive system are remained substantially uniform. This means that the magnet and coil operate at or near their greatest efficiency. and minimizes the amount of current which is necessary to actuate the device. This, of course, reduces the likelihood of any overheating of the coil.  
  When the contact bridge begins to engage the cntacts, it becomes necessry that some flexing take place between armature and contact bridge carrier. This is in order to provide that the contact bridge will align itself properly on the contacts which necessitates some compliance from the contact bridge carrier.  
  The coupling of this apparatus is thus capable of providing this additional compliance when it is needed, without the necessity, as in the prior art, for tolerating flexibility of these two elements during the entire stroke of the apparatus.  
  A number of variations of the apparatus and method ofthis invention are also possible. An example is shown in FIG. 5. In that figure the flat protuberance, rather than being located on pin 6. is located on the interior upper surface of bore 8, as indicated at 20.  
  Still other means of providing for the protuberance discussed above are shown in FIGS. 6-9. In FIG, 6 the protuberance is shown as being formed by a steel pad which is attached to pin 6. The steel pad need not have a perfectly flat upper surface, but may alternately have an undulating surface having coplanar peaks, such as is shown in FIG. 7 at 16.  
  Still another variation relates to the method of securing a steel pad to pin 6. In FIGS. 8 and 9 there is shown a steel pad having a generally U-shaped cross-section and having legs 17 which are disposed to wrap around at least three sides of pin 6. This latter embodiment provides a steel pad member which, while removable from pin 6, is also easily securable thereto in a firm fashion. Making the protuberance front a separate steel pad affords the flexibility of imparting physical properties to the protuberance which differ from those of the pin.  
  lo the prior art discussed hereinabove, the spring providing biasing of the armature against the contact bridge carrier applies its force to the central point of the armature. This location of the force application point tends to exaggerate, rather than limit the tendency of the armature and contact bridge carrier to bend relatively at their coupling. In this invention, the springs are placed in such a fashion that the position of stable equilibrium tends to be that position at which the armature and contact bridge carrier are linearly aligned. In this case, the springs 9 are four in number, and are disposed in a rectangular pattern. The points of application of the force of springs 9 are transversely displaced from the center ofthe planar contact surface of protuberance 10 in such a way that the force points and the center of surface 7 define the corners of con gruent triangles which are symmetrically disposed about the center of surface 7.  
  FIG. 10 shows a static force diagram which plots the torques generated by the armature force and the opposing spring forces as a function of inclination or bending between the armature and contact bridge car rier. The linear characterisitic designated as 18 represents the torque generated by the armature force, which increases as a function of the inclination of the elements. The torque generated by the spring, which opposes this armature torque is designated as 19. As can be seen in FIG. 10, the torque generated by the springs is, due to the fact that the springs are under constant compression, of a uniform value as long as the armature force remains below a certain level. Of course, when the armature force exceeds the force generated by the springs, and the springs, are thereby com pressed further, the springs also generate more force as indicated on the characteristic 19 of FIG. [0.  
  it can be seen from the discussion hereinabovc that applicants have invented a particular form of switch gear apparatus having a coupling between armature and contact bridge carrier which overcomes the disadvantages of both rigid and exclusively flexible coupling therebetween, while simultaneously achieving the benefits of both.  
  The disclosure herein is intended to be illustrative, and it is realized that persons ofordinary skill in the art could modify or change the disclosures and embodiments herein described without departing from the spirit of this invention.  
 What is claimed is:  
  1. In a switch gear apparatus having an armature, means to apply force to move the armature in one direction, a contact bridge carrier mounted for motion in the one direction in a guide means, and being flexibly connected to the armature, the improvement comprising:  
 means to selectively prevent relative flexing between the armature and carrier when the force of the armature thereon is below a predetermined value and to permit such flexing when said force exceeds said predetermined value, said armature having a bore therethrough, and said means for preventing flexing comprising an elongated pin having a crosssection of smaller dimensions than that of said bore, and having length greater than said bore, said pin being thereby insertable with play through said bore, a protuberance disposable in the region of the interior side of said bore nearest said carrier, said protuberance having a plurality of coplanar points at its extremities, means for connecting the ends of said pin to said carrier when said pin is inserted into said bore with its ends protruding therefrom, and bias means interposed between said carrier and said armature to resiliently apply force to said armature and carrier to force said armature and carrier apart, whereby, when said pin is inserted through said bore and its ends connected to said carrier, said armature and carrier are prevented from flexing when armature force is insufficient to overcome said bias means, by means of said armature bore and pin bearing on said protuberance, and said armature and carrier are permit ted to flex relatively only when the force of said armature on said carrier is sufficient to overcome the force of said bias means. and release the pressure on said protuberance 2. The apparatus of claim 1. further comprising means for limiting the maximum degree of flexion between the armature and the carrier.  
  3. The apparatus of claim 1 in which said bias means applies force at points which are displaced transversely to the direction of movement of said armature and are located outside the region defined by said protuberance.  
  4. The apparatus of claim 3, in which said points of application are four in number. and define, with the center of said protuberance. two congruent symmetrically disposed triangles.  
  5. The apparatus of claim 1, in which said protuberance has a planar surface and is located on one side of said pin.  
  6. The apparatus of claim I, in which said protuberance has a planar surface perpendicular to the direction of motion of said armature.  
  7. The apparatus of claim 1. in which said protuberance is located on the inside surface of said bore nearest said carrier, and has a planar surface which is perpendicular to the direction of motion of said armature.  
  8. The apparatus of claim I, in which said pin and said bore are of rectangular cross section.  
  9. The apparatus of claim 1, in which said protuberance comprises a steel pad mounted on said pin.  
  10. The apparatus of claim 9, in which said steel pad is of a substantially U-shaped cross section extending around said pin.  
  11. The apparatus of claim 1, in which said connection between the ends of said pin and said carrier comprises plastie bushings.  
  12. The apparatus of claim 11, in which said guide means comprises:  
 a. a slide appendage on each of said bushings, and  
 b7 21 set of parallel ways fixedly disposed to engage said appendages for sliding motion therein.