Patent Publication Number: US-3876948-A

Title: Fuse alarm indicator

Description:
United States Patent 1 Blumenthal et al.  
 FUSE ALARM INDICATOR Inventors: Marianne Blumenthal; Joachim Choschzick; Gunter Glimm, all of Erlangen, Germany Siemens Aktiengesellschaft, Munich. Germ any Filed: Jan. 17, 1974 Appl. No.: 434,358  
 Assignee:  
 Foreign Application Priority Data Jan. 26, 1973 Germany 7302964 US. Cl. 337/409; 337/315 Int. Cl. H0lh 37/76 Field of Search 200/16, 149; 337/66, 238.  
 References Cited UNITED STATES PATENTS 8/1946 Wald 337/147 X [451 Apr. s, 1975 2.581.305 1/1952 Smith 337/186 X 3.274.358 9/1966 Hallerberg 337/148 3.593.247 7/1971 Collins et a1 337/148 X Primary Examiner-J. D. Miller Assistant Examiner-Fred E. Bell Attorney. Agent, or FirmKenyon &amp; Kenyon Reilly Carr &amp; Chapin A device for indicating the condition of an electric fuse in a main line. It comprises a carrier of insulating material which includes a cross piece having an opening which is coaxial with the firing pin of a priming cartridge and the plunger of a control-current switch which opening guides the axial movement of the firing pin to effect axial movement of the plunger to thereby cause a change in the condition of the switch and the control circuit in which it is connected.  
 ABSTRACT 4 Claims, 2 Drawing Figures FUSE ALARM, INDICATOR BACKGROUND OF THE INVENTION 1. Field of the Invention The invention concerns a fuse alarm indicator and particularly one in which a priming cartridge and a controlcurrent switch operated by the priming cartridge are mounted in a carrierseparate from the fuse to be mounted.  
 2. Description of the Prior Art For monitoring electrical installations&#39;it is usually required that the condition of an electric safety fuse in a main circuit be determined by an alarm indicator in a control circuit separate and apart from themain circuit.  
  It is known to use for this purpose. for instance. a socalled priming cartridge or actuator fuse which is connected in parallel with the fuse to be monitored and which has a lower current rating than the main fuse. It includes a spring-loaded firing pin embedded in a quenching medium. The pin is released when-the main fuse blows due to the diversion of current from the main line through the actuator fuse. A control-current switch (e.g., a microswitch) is positioned in suitable relationship to the actuator fuse so that the movement of the pin is utilized by the control switch for effecting suitable switching action thereof.  
  From the publication of the firm EFEN,&#39; entitled Heavy-Duty Signal Fuses for 500 to 1500 V, NS, the Feb. 1972 issue, it is known to combine the priming cartridge and the control current switch in an undetachable structural unit with the fuse to be monitored.  
  According to another design, the fuse&#39;alarm indicator is arranged separate from the fuse to be monitored on a carrier of insulating materiaL&#39;This is done so that several priming cartridges can act on a common control switch by means of a movable, insulating intermediate member. This construction has the advantage that it can be arranged physically separate from the fuses to be monitored. Further, it allows for monitoring of several fuses having different response characteristics.  
  A primary object of this invention is to provide a fuse alarm indicator which is separate from the main fuse to be monitored and which does not require an intermediate member between the priming cartridge and the control switch to effect the necessary cooperation between the two.  
  It is another object to provide a fuse alarm indicator which will also accommodate the electrically insulated wire in addition to provide a mounting location for the priming cartridge and control switch.  
 SUMMARY OF THE INVENTION over one end of the priming cartridge. This cross piece includes an opening which is coaxial with the center line of the firing pin of the priming cartridge. Further, the cross piece includes a pair of mounting tabs for securing a suitable control switch such that the switch actuating plunger is positioned in a way that its axis is coaxial with the centerline of the opening and the firing pin. The firing pin and actuating plunger are positioned in sufficient proximity that movement of the firing pin, in response to a blown main fuse causes movement of the actuating plunger effecting a changed condition in the switch and the contral circuit of which the latter forms a part.  
 DESCRIPTION OF THE PREFERRED EMBODIMENT Construction material and which comprises a carrier base 1 for securing the carrier to a mounting plate 20. The carrier base 1 includes a projection 15 and a screw mounting hole 14, each of which correspond positionally to a recess l6 and suitable screw hole 21, respectively, in mounting plate 20. This allows for secure mounting of the alarm indicator with the use of a single screw.  
  Additionally, carrier base 1 includes mounting pads 22 and 24. Secured to each of these in a known fashion is a suitable contact clip terminal lug unit l0-ll. The contact clip 10 and the terminal lu&#39;g 11 are electrically integral. The contact clips 10 are structured such that they provide suitableclearance between a priming cartridge 4 when placed in position in the contact clips 10 and a pair of electrical wires 12 which connect the alarm indicator of this invention to respective sides&#39;of the main fuse to be monitored. These electrical wires 12 are secured to the terminal lugs II by any suitable fashion, one of which is the screw-nut arrangement depicted in FIGS. 1 and 2.  
  The carrier further includes a U-shaped channel portion defined by side walls2 which are preferably perpendicular to the base section 1 and which extend out beyond the contact clip 10. This makes the priming cartridge 4 accessible only from the right or the alarm indicator as viewed in FIG. 2 and provides necessary protection to personnel who must service these indicators particularly where high voltages are involved.  
  Extending above the U-shaped cavity defined by side walls 2 and preferably molded to the carrier is a cross piece section 3 of the same insulating material compris ing the carrier base 1. The cross piece 3 includes an opening 6, therethrough, which is coaxially aligned with the longitudinal axis of the priming cartridge 4. The priming cartridge 4 is of a known variety and includes a spring loaded firing pin 7 extending from the end of the cartridge closest to opening 6.  
  Extending upward and away from the U-shaped channel are a pair of mounting tabs 26 and 28. Secured between these mounting tabs is a suitable current control switch mechanism 5, which preferably may be a microswitch, which includes an actuating plunger 8 for interrupting or changing the switch condition of mechanism 5. The control switch 5 is secured to the mounting tabs by rivets 9 and positioned between said mounting tabs 26 and 28 such that the actuating plunger 8 is axially aligned with the opening 6 of cross piece 3. In fact. the actuating plunger penetrates the opening 6 of cross piece 3 with the extreme end thereof lying in close proximity to the extreme end of firing pin 7. Protruding from the control current switch 5 are suitable terminals for connection to electrical wires 13. These latter wires are connected to a suitable control circuit which gives an indication of the main fuse condition in response to the switch position of the current control switch 5.  
  Operation in response to a blown main fuse, current otherwise flowing in the main line is directed to the alarm indicator of this invention by way of electrical lines 12. This current activates priming cartridge 4 to thereby release firing pin 7. The firing pin 7 extends itself, axially, further upward into the opening 6, engaging the actuating plunger 8. The actuating plunger 8 responsive to the movement of pin 7 has sufficient corresponding movement in the direction of the arrow to cause a change in the switch condition of control current switch 5. This changed condition as sensed by control lines 13 gives rise to a suitable alarm indicator at whatever location the alarm indicating apparatus might be&#39;positioned.  
 Advantages By providing that the contact clips 10 stand off from the carrier base 1, a space-saving is effected in that electrical lines 12 may be secured to the carrier from the same side as that from which the priming cartridge is removed and replaced.  
  Also. the use of an insulating cross piece 3 to electrically isolate the control current switch from the priming cartridge, eliminates the possibility of interaction between the higher potential of the lines 12 associated with the priming cartridge and the lower potential of the control circuit lines 13.  
  Further, the use of an intermediate member to convert movement of the firing pin to movement of a corresponding plunger in a contact switch, as is the case in prior art devices. has been eliminated through the direct operation of the control switch through movement of the firing pin.  
  By providing only one control switch 5 and priming cartridge 4 in but one carrier, wider latitude is allowed in .locating particular fuse alarm indicators. They may be grouped in any number side-by-side or alternately, where space limitations exist, they may be used singly.  
  Finally, as noted earlier, the use of the insulating walls 2, extending up from the carrier base. give necessary protection to personnel operating in the area by eliminating other than intended contact with the priming cartridge and particularly the voltages appearing on electrical lines 12.  
 7 It is to be appreciated that changes in the above embodiinent can be made without departing from the scope of the present invention. Variations of the specific construction disclosed can be made by those skilled in the art without departing from the invention as defined in the appending claims.  
  What is claimed is: 1. An alarm indicator for detecting the condition of 5 an electrical fuse which comprises:  
 a. carrier means made of electrical insulating material, said carrier means including i. a carrier base, including mounting pads positioned thereon,  
 ii. a crosspiece connected to said base, said crosspiece having a longitudinal opening therethrough,  
 iii. mechanical mounting means extending from said crosspiece;  
 b. electrical mounting means secured to said carrier base mounting pads including.  
 i. a pair of terminal lugs, to which are secured main electrical lines connecting said electrical fuse to said indicator;  
 ii. a pair of contact clips, each of which is electrically connected to a corresponding one of said terminal lugs;  
 - c. a priming cartridge including a firing pin, positioned in said contact clips such that the longitudinal axis of said cartridge and said firing pin is coaxial with the longitudinal axis of said longitudinal opening; and  
 d. control switch means, including an actuating plunger, secured to said carrier by said mechanical mounting means, said actuating plunger positioned in said longitudinal opening such that the plunger responds to axial movement of said firing pin to effect a change in the switch condition of said control switch means, said control switch means further including a pair of control electrical lines for detecting said switch condition.  
  2. The indicator of claim 1 wherein said carrier means further includes a pair of side walls extending from said carrier base outward beyond said priming 40 cartridge positioned in said contact clips, said pair of side walls thereby forming a U-shaped channel with said carrier base.  
  3. The indicator of claim 1 where said contact clips are positioned sufficiently outward from said carrier base such that said main electrical lines can pass between said cartridge and said carrier base.  
  4. The indicator of claim 1 where said main electrical lines are routed to one end of said indicator and where said control electrical lines are connected to said con- 50 trol switch means at the opposite end of said indicator.  
 I UNITED STATES PATENT QFFICE CERTIFICATE OF CECTEN r PATENT NO. 3, 48  
 DATED 1 April 8, 1975 INVENTOMS) 1 Marianne Blumenthal et a1 It is certified that error appears in theaboveidentified patent and that said Letters Patent are hereby corrected as shown below:  
 In Column 1, line 7, change &#34;controlcurrent&#34; to --control-current-- In Column 3, line 16, change &#34;indicator&#34; to --indication- Signed and sealed this 15th day of July 1975.  
  (SEAL) Attesh r Cw MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks UNITED STATES PATENT QFFKCE CETiFIfiAT F @UREQTEGN PATENT NO. 1 3,876,948 DATED 1 April 8, 1975 INVENTOR(5) I Marianne Blumenthal et al It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 In Column 1, line &#39;7, change &#34;controlcurrent&#34; to -control-current-- In Column 3, line 16, change &#34;indicator&#34; to --indication- Signed and sealed this 15th day of July 1975.  
  (SEAL) Attests&#34; Ci, MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks