US 3012800 A
Description (OCR text may contain errors)
T. T. KOCH TRIP MECHANISM Dec. 12, 1961 2 Sheets$heet 1 Filed June 23, 1959 Inventor: Theodore T. Koch,
His Attorv Dec. 12, 1961 T. T. KOCH 3,012,800
TRIP MECHANISM Filed June 25, 1959 2 Sheets-Sheet 2 Inventor: Theodore T. Koch by M5. W gm His Attorneg.
United States Patent 3,012,800 TRIP MECHANISM Theodore T. Koch, Springfield, Pa., assignor to General Electric Company, a corporation of New York Filed June 23, 1959, Ser. No. 822,250 Claims. (Cl. 287--52.07)
This invention relates to trip mechanisms for electric circuit interrupters, and it relates more particularly to an improved trip shaft formed of mechanically joined metal parts.
In conventional electric circuit interrupters the mechanism which actuates circuit making and breaking contacts is latched in its closed circuit disposition by a tripping mechanism including a rotatable trip shaft. The trip shaft is provided with a latch member which, when in a normal position, props the mechanism in the closed circuit condition against strong forces of opening springs. Rotating the trip shaft to a tripped position unlatches or releases the operating mechanism of the interrupter for circuit opening movement in accordance with the opening forces.
In order to prevent malfunctioning of the circuit interrupter, particularly when subjected to sudden and severe mechanical shock as it is during a closing operation, it is very important that the trip shaft and its latch member be relatively stable, undistorted and properly aligned at all times. Yet the trip shaft must also be capable of sensitive and positive movement from its normal to its tripped position immediately when actuated by overcurrent responsive devices or other means.
It is a general object of the present invention to provide an improved trip mechanism which is rugged and reliable while being relatively simple and inexpensive in construction.
Another object of the invention is the provision of an improved trip mechanism capable of precision operation yet well suited for large-quantity production without corresponding precision in the manufacturing and assemblying of the component parts thereof.
In carrying out the invention in one form, I provide a circuit interrupter tripping mechanism comprising a hollow tube crimped tightly on an elongated shaft which is supported for rotary movement. A latch member is disposed on the tube and extends radially therefrom, the tube having protuberant portions raised at opposite sides of the latch member for retaining the latch member thereon. The latch member is provided at its distal end with a precision ground surface designed for releasably holding an abutting part of the interrupter mechanism in a latched position against the force of opening springs. A trip shaft assembly constructed in this manner is both rugged and reliable yet very simple and economical to manufacture.
The various parts of the trip shaft assembly may be mechanically joined by placing the hollow tube through an opening in the latch member and then swaging the tube to raise protuberances at opposite sides of. the latch member, thereby retaining the latch member on the tube, and by inserting the elongated shaft through the tube and then collapsing the tube against the shaft, thereby rigidly joining these two parts of the assembly. Having been assembled in this manner, the trip shaft assembly can be rotatably supported at the same points and in the same manner as it Will be supported in its mechanism environment in order to grind the surface of the distal end of the latch member to a desired shape. Thus my trip mechanism admits to being manufactured on a large quantity production basis with minimal human skill and effort, and small inaccuracies or relatively large manufacturing tolerances in the component parts of the trip shaft can betolerated without adversely affecting the perfection of the assembled mechanism and the precision with which it can perform its intended purpose.
My invention will be better understood and its various objects and advantages will be more fully appreciated from the following description taken in conjunction with the accompanying drawings in which:
FIG. 1 is an exploded perspective view of a circuit interrupter trip shaft constructed in accordance with my invention;
FIG. 2 is a partial side elevation of a trip mechanism employing the trip shaft of FIG. 1;
FIG. 3 is a section, partly broken away, taken along lines 3-3 of FIG. 2;
FIG. 4 is an exploded perspective view of the hollow tubular part and the latch assembly of the trip shaft; and
FIG. 5 is a side elevation of typical means for carrying out a precision grinding operation on the assembled trip shaft of my invention.
Referring now to FIGS. 1-3, I have shown a trip mechanism including a trip shaft 11 which comprises an elongated, solid shaft '12 of polygonal cross section, a hollow tubular member 13 on the shaft 12 and a dependent latch assembly 14 on the tube 13. The trip shaft is supported for rotary movement about a longitudinal axis by means of a pair of bearing members 15, shown in FIG. 1. The bearing members 15, which are in turn supported by a suitable frame structure 16 only partially shown in FIGS. 1 and 2, are disposed on the elongated shaft 12 immediately adjacent the opposite ends, respectively, of the tube 13, and the latch assembly 14 of the trip shaft is actuated by rotation of the shaft 12 in its bearings.
The latch assembly 14 of the trip shaft preferably comprises a latch member 17 and a paddle member 18 positioned in side-by-side relationship substantially midway between opposite ends of the tube 13. The latch and paddle members 17 and 18 have predetermined orientations or dispositions relative to each other, as is best seen in FIGS. 1 and 2, and their adjoining sides are disposed in engagement. Annular protuberances 19 are raised on the tube 13 at opposite sides of the proximal ends of members 17 and 18 for firmly retaining these dependent members on the tube. In other words, as is best seen in FIG. 3, raised portions 19 of the tube 13 press against opposite sides of the latch assembly 14 to establish a firm mechanical union therebetween. This result may be accomplished by swaging the tube 13 in a known manner.
Preferably the hollow tubular member 13 is in the form of a cylinder. Non-circular openings 20 are provided at the proximal ends of the dependent members 17 and 18 to accommodate the cylindrical tube 13. This construction as best seen in FIG. 4 where it can be observed that opening 20 in latch member 17 is irregularly expanded at four locations 21. Thus the perimeter 22 of the opening 20 is non-circular. In order to aifix the latch member 17 to the tube 13, as mentioned hereinbefore, protuberant portions 19 of the tube are respectively disposed at opposite sides of the latch member, and as can be seen in FIG. 3, a protuberant portion of the tube also presses against the perimeter 22 of the opening through the latch member. Since the opening is non-circular, the raising or bulging of the cylindrical tube 13 against the perimeter 22 provides a keying action between the tubular member and the latch member, whereby the mechanical joint between these two members is able to resist with great strength any tendency for one of the members to rotate relative to the other.
I In order rigidly to secure the tube 13 to the elongated actuating shaft 12 of the trip shaft, the end sections 13a of the tube are collapsed until they tightly adhere to the surface of the shaft 12. The shaft 12 preferably has at least one flat against which a collapsed portion of the tube 13 is pressed, and in the illustrated embodiment of my invention, as can be seen most clearly in FIG. 1, the shaft 12 actually has a square cross section and hence has four flats. By collapsing or crimping the tube 13 to conform it to the shape of the shaft 12 in the vicinity of the flats, a strong mechanical joint capable of withstanding high bending and tortional stresses is formed between these two parts of the trip shaft assembly.
The dependent latch member 17 protrudes radially from the tube 13, and its distal end is provided with a ground surface 23 which is conformed to a circumferential section of a right cylinder whose axis is the axis of rotation of the trip shaft 11. With the trip shaft in its normal position the ground surface 23 abuts a roller 24 carried at one end of an intermediate latch member 25, as is shown in FIG. 2. The other end of the intermediate latch member 25, which is pivotally mounted intermediate its ends on a rod 26 supported by the frame structure 16, is provided with means (not shown) disposed in self-releasing engagement with part of the operating mechanism of an electric circuit interrupter to maintain the operating mechanism in a latched closed disposition. The operating mechanism and related parts of a circuit interrupter with which my trip mechanism might be used is shown and described in Patent No. 2,96l,509 granted to L. L. Baird and R. J. Baskerville on November 22, 1960.
The resultant force for holding or restraining the circuit interrupter operating mechanism in its latched closed disposition against the force of opening springs is transmitted to the latch member 17 of the trip shaft 11 by the roller 24 which engages its surface 23. Because the surface 23 is ground to the circumferential shape mentioned above, the line of action of this resultant force is directed normal to the axis of rotation of the trip shaft and has no moment arm with respect thereto. This arrangement helps to eliminate accidental unlatching or release of the operating mechanism upon the occurrence of any relatively sudden and severe mechanical shock to the circuit interrupter. The latch member 17 is in compression and free of bending stresses, whereby any tendency to distort adversely the circumferential surface 23 is relieved.
The trip shaft 11 is biased in a clockwise direction to its normal position by a tension spring 27 interconnecting one end of the dependent member 18 and the intermediate latch member 25. Opening operation of the circuit interrupter is initiated by rotating the trip shaft 11 in a counterclockwise direction against its bias to a tripped position. As a result, the latch member 17 is removed from abutting relationship with the roller 24 thereby enabling the intermediate latch member 25 to move counterclockwise about rod 26. This releases the operating mechanism of the circuit interrupter for circuit opening movement in accordance with the opening springs.
Any suitable means may be used to rotate the trip shaft 11 from its normal to its tripped position in order to initiate an opening operation of the circuit interrupter. For example, in the illustrated embodiment of the trip mechanism an extension 28 is attached to member 18, and schematically illustrated element 29 is disposed to strike and tilt the extension 28. The element 29 may be actuated manually or by an overcurrent responsive device not shown. In actual practice it is conventional to attach still other torque applying means to the square actuating shaft 12 at various locations along its length for rotating the trip shaft 11.
In order to grind the distal end of the latch member 17, as mentioned hereinbefore, the trip shaft assembly can be conveniently supported for rotation about its longitudinal axis by bearings located on the shaft 12 immediately adjacent the opposite ends of the tube 13, in the same manner that the trip shaft is supported when assembled in the trip mechanism, of a circuit interrupter. The shaft can then be oscillated on the axis of rotation while the surface 23 is ground to a true circumferential section.
FIG. 5 of the drawings illustrates preferred means for performing this grinding operation. The illustrated means includes a trunnion 92 for supporting the trip shaft 11 in the manner described above and a grinding wheel 3. A lever 94 is attached to the shaft 12 for oscillating this shaft on the axis of rotation. The grinding wheel is rotatably mounted on a vertically movable support above the trunnion 92. The axis of the grinding wheel 93 is in the plane 86 of the axis of rotation of the trip shaft 11. The shaft is disposed so that the latch member 17 extends upwardly toward the grinding wheel, and the support 85 is lowered until the grinding wheel 93 makes contact with surface 23 of the latch member, as is ciearly indicated in FIG. 5. By moving the lever 94 to rotate the trip shaft back and forth and concurrently lowering the grinding wheel 93 in small increments, the surface 23 is ground to a true circumferential section with respect to the axis of rotation.
The grinding operation is completed when the radial distance between surface 23 of the latch member 17 and the axis of rotation of the trip shaft '11 has been reduced to a predetermined dimension. This predetermined dimension can be conveniently measured in the illustrated embodiment of the invention by means of the fixedly located bracket 87 provided with two pins 88 and 89 shown in FIG. 5. When the distal end of the latch member passes the pin 88 but does not pass the pin 89, so that the latch member can be moved to broken line position 17, the operator knows that the desired predetermined dimension has been realized.
Since the precision grinding operation is performed after all the components parts of the trip shaft 11 have been mechanically joined together, a highly precise and reliable construction is obtained. Yet it is unnecessary that each of the component parts be made with corresponding accuracy and precision. In other words, the shaft 12 may be slightly bent or the tube 13 may be cccentric 0n the shaft, or the latch member 17 may have certain inaccuracies, and still the assembled unit will not reflect any of these inaccuracies because the critical surface 23 of the latch member has been precisely formed with respect to the true axis of rotation of the trip shaft.
While I have shown and described a preferred form of my invention by way of illustration, many modifications will occur to those skilled in the art. I therefore contemplate by the claims which conclude this specification to cover all such modifications as fall within the true spirit and scope of my invention.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. A trip mechanism for an electric circuit interrupter comprising: an elongated shaft having at least one flat, a hollow tube on the shaft, and a dependent member on the tube, said tube having protuberant portions disposed at opposite sides of the dependent member for retaining the dependent member thereon and having at least one collapsed portion disposed tightly against the flat of the shaft thereby rigidly securing the tube to the shaft.
2. A trip mechanism for an electric circuit interrupter comprising: an elongated shaft having at least one flat, a hollow cylindrical tube on the shaft collapsed to conform to the shape of the shaft in the vicinity of said flat, and a dependent member on the tube having a non-circular opening, said tube extending through the opening of the dependent member and said dependent member being affixed to the tube by means of protuberant portions of the tube respectively disposed at opposite sides of the dependent member and against the perimeter of the open- 3. A trip mechanism for the operating mechanism of an electric circuit interrupter comprising: a rotatable shaft having at least one flat, a hollow cylindrical tube on the shaft collapsed to conform to the shape of the shaft in the vicinity of said fiat, and an assembly of at least two dependent members disposed in side-by-side relationship on the tube, said dependent members being provided respectively with noncircular openings through which said tube is extended and said assembly being affixed to the tube by means of protuberant portions raised on the tube adjacent opposite sides of the assembly and against the perimeter of the openings.
4. A trip mechanism for an electric circuit interrupter comprising: an elongated shaft supported for rotary movement about an axis, a hollow tube on the shaft, and a dependent member protruding radially from the tube, said tube having protuberant portions raised at opposite sides of the dependent member for retaining the dependent member thereon and having at least one collapsed portion disposed tightly against the shaft thereby rigidly securing the tube to the shaft.
5. In a trip mechanism of an electric circuit interrupter: an elongated shaft having at least one flat, a hollow tube on the shaft, a dependent assembly on the tube, first means for retaining the dependent assembly on the tube comprising protuberant portions of the tube raised at opposite sides of the dependent assembly in tight engagement therewith, and second means for rigidly securing the tube to the shaft comprising a portion of the tube tightly pressed against the flat of the shaft.
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