US3484726A

US3484726A - Trip unit latch positioning means for constant latch bite

Info

Publication number: US3484726A
Application number: US690878A
Authority: US
Inventors: Albert Strobel
Original assignee: ITE Imperial Corp
Current assignee: Siemens Energy and Automation Inc; ITE Imperial Corp
Priority date: 1967-12-15
Filing date: 1967-12-15
Publication date: 1969-12-16
Anticipated expiration: 1986-12-16

Description

Dec. 16, 1969 A. STROBEL TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE Filed Dec. 15, 1967 5' Sheets-Sheet l y ,M w! a a 15 4 fl a ,M, M d i A. STROBEL Doc. 16, 1969 TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE Filed Dec. 15, 1967 5 Sheets-Sheet 2,

A. STROBEL Dec. 16, 1969 TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE 5 SheetsSheet 3 Filed Dec. 15, 1967 ART QSQQ a L M am A. STROBEL.

Dec. 16, 1969 TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE Filed D60. 15, 1967 5 Sheets-Sheet 4 /h in N m; q A% N? Ufl mm n JQ/l A- STROBEL Dec. 16, 1969 TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE 5 Sheets-Sheet 5 Filed Dec. 15, 1967 INVEN'I OR. A156??? 5776052;

United States Patent 3,484,726 TRIP UNIT LATCH POSITIONING MEANS FOR CONSTANT LATCH BITE Albert Strobe], Cherry Hill, N.J., assignor, by mesne assignments, to I-T-E Imperial Corporation, Philadelphia, Pa., a corporation of Delaware Filed Dec. 15, 1967, Ser. No. 690,878 Int. Cl. H01h 9/20 US. Cl. 335173 8 Claims ABSTRACT OF THE DISCLOSURE In a circuit breaker trip unit having a latch which operates a tripper of a circuit breaker for tripping the contacts of the breaker apart, a tripper bar having a latch plate thereon for preventing the latch from moving to trip the circuit breaker tripper; and a positioning means integral with the latch plate for positioning the latch with respect to the latch plate, whereby the latch bite, i.e., the amount the latch must slide to slide free of the latch plate, can be predetermined and remains constant.

This invention relates to a trip unit for a circuit breaker, and more particularly to a positioning means for positioning the latch of the trip unit.

Automatic circuit breakers are usually provided with a trip unit, which includes both a magnetic trip assembly, which is instantaneously responsive to a severe overload condition; and a thermal trip assembly, which is responsive to a moderate overload condition existing for a prolonged period. The actuation of either the instantaneous or the delayed trip assemblies actuates a mechanism which causes a tripper bar to be urged into rotational movement. The tripper bar has a latch plate thereto secured. A pivotally mounted latch is provided, which abuts the latch plate and the latch plate prevents the latch from rotating. The latch is connected with a tripping mechanism of a circuit breaker, which is to be operated by the trip unit. When the tripper bar in the trip unit rotates, it moves the latch plate away from its supporting position with respect to the latch, and the latch is thereby free to pivot under the influence of the tripper of the circuit breaker. As the latch pivots, it operates the circuit breaker tripper, thereby causing the contacts of the circuit breaker to separate.

The latch has a latch bite with respect to the latch plate on the tripper bar. The latch bite is defined as the length of the part of the latch in engagement with the latch plate that must be pivoted or slid free of the latch plate before the latch separates from the latch plate. The latch bite must be large enough to make the trip unit insensitive to normal shock and vibration that can be expected in the normal environment of the circuit breaker. The latch bite must be as small as possible so that the instantaneous magnetic trip assembly can cause tripping of the circuit breaker rapidly, with the latch having to move a minimum distance to slide free of the latch plate.

In a conventional trip unit, the tripper bar, with a latch plate attached, is pivotally mounted to a supporting member. The latch of the trip unit may either be mounted to the same support member as the tripper bar, or to a different support member. A stop determines the non-trip position of the tripper bar. There is an accumulation of manufacturing tolerances, including the positions of the bearings for the latch and the tripper bar and the length of the latch, which affect the relative positions of the latch and the latch plate and vary the latch bite among identical trip units. Frequently, a change of only a few thousandths of an inch may decide whether a circuit breaker trips consistently at particular current levels.

3,484,726 Patented Dec. 16, 1969 A separate adjustment feature for latch bite is an absolute necessity in prior art. Latch bite adjustment is obtained by use of an adjustable stop, which varies the position of the tripper bar. The adjustable stop, however, is out of contact with the latch. The adjustable stop usually comprises a finely threaded screw, requiring a tapped mating member in the tripper bar and a lock nut. Adjustments of the latch bite must be made during manufacture of the trip unit. This is time-consuming, and may require the manufacture and provision of readily accessible adjusting components, which may complicate the manufacture of a trip unit.

In the trip unit of the present invention, there is provided a positioning means, which operates on the latch itself, rather than on the tripper bar. The positioning means is connected with the tripper bar. The latch plate, which the latch also engages, is connected to the tripper bar. Therefore, the position of the latch with respect to the latch plate, and with respect to the tripper bar, is readily predetermined uniformly for all identically manufactured trip units, by the locating of the positioning means. No longer will the manufacturing tolerances which cause problems in prior art trip units have any effect on the latch bite. Only the positioning of the latch plate and of the positioning means itself will determne the latch bite.

In a preferred embodiment, the positioning means is adjacent the latch plate, whereby a manufacturer need not be concerned with the relative positions of the latch plate and the positioning means. In furtherance of the above, the latch plate and positioning means may be integrally formed.

The latch plate includes a first surface. As was noted, the latch is intended to rotate. The first surface of the latch plate engages the latch and prevents its rotation.

The latch is comprised of an arm mounted on a pivot. Depending on manufacturing tolerances in the positioning of the pivot for the latch, the spot on the latch which is mounted on the pivot, and the length of the element forming the latch, the radial length of the latch from its pivot is variable. The positioning means has a second surface, which engages the latch and is tilted to ensure that the latch bite, which is determined by the radial length of the portion of the latch that is in contact with the latch plate, remains constant. Therefore, with both the surface of the "latch plate and the surface of the positioning means, the

tioned is illustrated in US. Patent No. 3,319,195, issued to the inventor hereof and to John C. Brumfield on May 9, 1967, entitled Circuit Breaker Trip Unit Assembly and assigned to the assigne hereof. It is to be understood that the present invention may be used in conjunction with any trip unit having a latch requiring a predetermined latch bite.

Accordingly, it is the primary object of the present invention to provide identical latch bite in all identically designed circiut breaker trip units.

It is another object of the present invention to provide a means for providing such latch bite, which means operates directly on the latch.

It is a further object of the present invention to provide a means for providing constant predetermined latch bite in a circuit breaker trip unit without adjustments being necessary during manufacture.

These and other objects of the present invention will become apparent after the following description is read in conjunction with the accompanying drawings, in which:

FIGURE 1 is a cross-section through a trip unit in the untripped condition, showing a positioning means, designed in accordance with the principles of the invention, for a trip unit latch.

FIGURE 1a shows the trip unit of FIGURE 1 in the tripped condition.

FIGURE 1b is a fragmentary view of a trip unit, showing an alternate form of positioning means, in accordance with the invention.

FIGURE 2 shows a trip unit having a latch, which is positioned in accordance with the prior art.

FIGURE 3 is a cross-section through a circuit breaker containing a trip unit designed in accordance with the invention.

FIGURE 4 is a view in elevation, in partial crosssection, of a three-phase trip unit assembly containing the positioning means of the present invention.

FIGURE 5 is a plan view in the direction 55 of FIG- URE 1 of the trip unit, illustrated in FIGURE 1; and

FIGURE 6 is a view in elevation of a number of the components of the circuit breaker of FIGURE 3.

Referring to the figures, and particularly to FIGURE 1, the trip unit assembly 10 is connected with the bus bar 12, the bus bar being in the circuit being protected by the circuit breaker described below. The trip unit assembly 10 is illustrated as having both a magnetic trip assembly and a thermally actuated trip assembly. However, a trip unit assembly employing the positioning means of the present invention may have only one of these trip assemblies.

The magnetic trip assembly provides instantaneous tripping of the trip unit in the event of a very high overload condition in the circuit being protected.

Referring to FIGURES 1 and 4, the bus bar 12 passes between the arms of a U-shaped structure 21 comprised of magnetizable material which concentrates the magnetic flux generated around the bus bar 12 by the high overload current.

A movable shaft 20 passes through the later-described laminated plates 14 and the bus bar 12. Secured to shaft 20 is nut 23, which is threaded to mate with the threaded surface of shaft 20, whereby the position of nut 23 may be varied on shaft 20. Shaft 20 is biased upward, as viewed in FIGURE 1, by a biasing means or spring 22, which seats at one end on nut 23 and on the inside surface of the web of U-shaped magnet 21 at its other end.

A magnetizable armature 24, comprised of steel or other magnetically attractable material, is secured to shaft 20. When a high overload condition develops in the bus bar 12, the armature 24 is attracted toward the pole faces 21a of magnet 21 against the bias of biasing means 22. Therefore, biasing means 22 is provided to hold armature 24 away from the magnet, so that the shaft 20 will move downward, as viewed in FIGURE 1, to cause tripping, in a manner to be described.

A tripper bar engagement means 26 is mounted on shaft 20 for engaging the tripper bar. Shaft 20 has a screw-threaded exterior along which the threaded nut 26 may be moved, for adjusting the initial position thereof. In this manner, the distance armature 24 must move toward pole faces 21a of magnet 21 before tripper bar engaging means 26 engages the tripper bar may be adjusted. The nut 26 is adapted to extend into engagement with extension 28 on tripper bar 30.

The tripper bar 30 is pivotally secured at its pivot 32 to a fixed support 34. Movement of armature 24 toward pole faces 21a of magnet 21 causes nut 26 to press on extension 28, which pivots tripper bar 30 counterclockwise, in the direction of arrow 36. A biasing means 28, for example, a compression spring, is provided for biasing the tripper bar clockwise in the direction of arrow 40.

The structure that halts the rotation of tripper bar 30 in the direction of arrow is the trip unit latch 60, which will be described in further detail below.

If a thermally actuated trip assembly is provided, it is comprised of the bimetallic strip 42, which is conventionally formed of two face bonded strips of metal having different coeflicients of expansion, The bimetallic strip is thermally connected to the conductor 12, to be responsive to temperature increases therein, due to moderate overload conditions extending over a prolonged period. The bimetallic strip 42 is secured at 44 to the upward bent portion 46 of the laminated core elements 16. Heat in conductor 12 is thermally conducted through plate 18 and core elements 16 to strip 42. The end 48 of strip 42 is adapted to deflect to the left, in the direction of arrow 50, when the strip 42 is heated by bus bar 12.

Abutting element 52 is secured to tripper bar 30. In FIGURE 1, the abutting element is illustrated as a screw 52, which is engaged by end 48 of strip 42, when the strip 42 deflects in the direction of arrow 50. The screw 52 is threaded and is received in a threaded aperture in tripper bar 30, whereby rotation of screw 52 adjusts the extent to which it extends out of the tripper bar 30 toward the bimetallic strip 42. This determines the dis tance that end 48 of strip 42 must deflect in direction 50 before it engages the abutment portion 52 of tripper bar 30 to commence the counterclockwise rotation of tripper bar 30, which causes tripping.

Refer now to FIGURES 1, 4 and 5. Identical elements in all the figures are identically numbered. A latch is provided in the trip unit. Latch 60 has a latch tip 62 for engaging the latch plate and the positioning means of the invention, to be described below. The latch is mounted at its pivot 64 to fixed support 34, which is the support for the tripper bar, or to any other fixed support, such as the trip unit casing. The latch has a flange 66 on the other side of its pivot 64 from the latch tip 62, The flange 66 is dual purpose. Its upper edge 68 is adapted to be engaged by the extension 70 of circuit breaker cradle bracket:- 72, to be described in greater detail below. Suffice it to say now that the bracket 72 is biased to pivot counterclockwise around its pivot 74 in the direction of arrow 76, whereby the bracket extension 70 bears downward on upper surface 68 of tab 66, thereby to bias the latch 60 clockwise, in the direction of arrow 78 around the latch pivot 64.

A wound coil spring 84 is provided, having one end 86, in engagement with a fixed support on the trip unit casing and an end 88, which engages flange 66. The spring is normally biased to drive ends 86, 88 apart, thereby to normally bias the latch 60 counterclockwise in a direction opposite arrow 78. The latch 60 is prevented from rotating too far counter-clockwise by an abutment support element 90 (FIGURE 4), which is supported by support 34 or by the trip unit casing, to block movement of the latch 60.

The circuit breaker cradle bracket 72 is biased by the tripping mechanism of the circuit breaker, to be described below, in the direction of arrow 76, with a greater biasing force than that exerted by biasing means 84, whereby the latch is normally biased clockwise in the direction of arrow 78. Clockwise rotation of latch 60 is prevented by latch plate 94, which is engaged at its abutting surface 96 by latch tip 62 of latch 60. Latch plate 94 is secured to tripper bar 30 by rivets 98. The latch plate may be formed integrally with the tripper bar or may be a separate structure thereto secured, it being understood that the latch plate pivots with the tripper bar in the event of an overload to cause tripping of the circuit breaker.

As was noted above, in the event of an overload condition, the tripper bar 30 rotates counterclockwise. The rotation causes surface 96 of latch plate 94 to slide off and away from latch tip 62. The latch bite of the trip unit is defined as the length along the latch tip 62 that the surface 96 of the latch plate 94 must slide before the latch 60 is free of the latch plate 94. To ensure that trip units being used for identical applications will have identical latch bites to provide identical operation in the event of a predetermined fault condition, it is necessary to have the latch bite constant in all trip units. This is accomplished by providing the positioning means 100 of the invention, so that the latch 60 is in engagement therewith, when the latch tip 62 is in engagement with the latch plate 94. The positioning means is connected with the tripper bar, and is adapted to engage the latch 60 at a particular portion thereof. When the latch tip 62 is in engagement with the latch plate 94, the particular portion of the latch 60 has moved the positioning means, thereby moving the tripper bar to a predetermined position. If the latch 60 is moved to a different position, the portion of the latch in engagement with the positioning means correspondingly moves to a different position, which thereby moves the positioning means and the tripper bar to a corresponding extent. The positioning means is located so that when the portion of the latch in engagement with the positioning means is stationary, the latch bite is predetermined.

As shown in FIGURES 1 and 4, the positioning means comprises the plate 100, located adjacent the latch plate 94. The free end of the latch tip 62 engages the surface 102 of plate 100. Movement of the free end of latch tip 62, it is apparent, causes movement of plate 100 and of the tripper bar. When latch tip 62 is in engagement with surface 96 of latch plate 94, the free end of latch tip 62, in engagement with surface 102 of plate 100, will have rotated the tripper bar 30 to provide a predetermined latch bite. The positioning means 100 is preferably in direct contact with the latch plate 94, so that proper dimensioning of the latch plate 94 will ensure proper positioning of the latch tip 62.

If, as in the present invention, the positioning means is adjacent the latch plate, the latch bite is dependent only upon the precision with which the latch plate is formed and no separate latch bite adjusting means is required. As a practical matter, the latch plate may be formed with dimensional tolerances of i .003 inch, whereby there is no problem concerning the effect of dimensional tolerances on latch bite. On the other hand, with a prior art structure which is considered below, it will be seen that the latch bite in this structure is dependent upon a plurality of dimensional tolerances in element lengths and positions, which necessitates the provision of a separate adjusting means to adjust latch bite during manufacture and in the field.

While the positioning means 100 of the invention is shown as a separate structure secured to the latch plate 94, it is apparent that the latch plate and positioning means may be an integral unit formed with the requisite precision.

As was noted above, the positioning means may be located away from the latch plate 94, so long as it is in engagement with the latch 60. This increases somewhat the dimensional tolerance problem in that the relative positions of the latch plate and positioning means will require initial adjustment to obtain proper positioning. However, the object of the present invention will still be realized in that latch bite will no longer be dependent upon dimensional tolerances in bearing positions and latch lengths.

Latch 60 rotates and its movement at any time is perpendicular to its radius. On the pivoting latch, latch bite is measured radially along the latch. The positioning means compensates for the radial position, wi h respect to the latch. of the free end of the latch tip 62. Compensation for the radial position of the free end of latch 60 is obtained from surface 102 of positioning means 100. Prevention of rotation of latch 60 is obtained through surface 96 of latch plate 94. Since the

surfaces

96 and 102 each affect or cause movement in a different direction, the surfaces are tilted with respect to each other. In FIGURE 1, the

surfaces

96 and 102 form a pocket into which latch tip 62 fits.

Referring to FIGURE 1b, which is a fragmentary view of a trip unit showing an alternate form of the positioning means of the present invention, elements in FIGURE 1a having identical functions to those in FIGURE 1 are numbered the same as in FIGURE 1 with an a thereafter. Latch tip 62a engages latch plate 94a at the surface 96a thereof, which prevents latch 60a from rotating clockwise, in the direction of arrow 78a. The poSitioning means a is integral with the latch plate 94a and the latch tip 62a has a surface 104 which comes into engagement with surface 102a of positioning means 100a. Note that the surfaces 96a and 102a are tilted with respect to each other for the same reasons that were discussed in connection with

surfaces

96, 102 in FIGURE 1. The top of the indentation in latch 60a leading to latch tip 62a is beveled at 106 to provide a side along which the positioning means 100 might slide as the tripper bar 30a is being rotated due to the movement of the latch tip 62a toward the latch plate 94a. As was noted above, latch bite in the structure of FIGURE 1 is determined by proper machining of the latch plate 94 to the correct dimension. Therefore, latch bite may be readily determined at the outset and is not dependent upon the positions of bearings and the lengths of particular shafts and of the latch. Similarly, in the structure of FIGURE 1b, the extent of latch bite is determined by the length of the indented portion 108 of the latch tip 62a, which can be cut or machined with great precision.

Refer to FIGURES 1 and 1a which illustrate the operation of the trip unit 10. Assume that a high overload condition develops in the bus bar 12 in the circuit being protected. Magnetic flux is induced in the magnet 21 by the current in bus bar 12. The magnetic flux attracts armature 24 toward pole faces 21a of magnet 21, thereby drawing shaft 20 downward, as can be seen in FIGURE 1a. Nut 26 on shaft 20 is drawn into engagement with extension 28 on tripper bar 30 and this pivots the tripper bar 30 around its pivot 32 counterclockwise in the direction of arrow 36. It should be noted that the overload condition in the circuit 12 generates heat which is transmitted through the elements 16 of the core 14 to the bimetallic strip 42 whose end 48 begins to deflect in the direction of arrow 50. However, because the overload was sufficient to cause instantaneous tripping through the magnetic trip assembly, the thermal trip assembly never actively partook in the tripping of the trip unit. However, it did respond to the overload condition. Were the overload condition less severe, and if it extended over a protracted period, the instantaneous magnetic trip unit Would not operate but the bimetal 42 would be heated by the overload condition and deflect in the direction of arrow 50 to contact the abutment 52, which would rotate the tripper bar 30 counterclockwise in the direction of arrow 36 to trip the trip unit. Once the tripper bar 30 moves free of the latch tip 62 of latch 60, the latch pivots clockwise in the direction of arrow 78 around its pivot 64 because the force exerted on flange 66 of latch 60 by the extension 70 of circuit breaker cradle bracket 72 overcomes the biasing force of spring 84. The latch pivots clockwise in the direction of arrow 78 until it strikes a fixed abutment, such as surface 112 in the interior of the casing of the trip unit.

When the fault condition is corrected, the magnetic attraction of armature 24 ceases, the spring 22 moves the armature 24 upward, thereby moving upward the shaft 20 and the nut 26, and the magnetic trip assembly moves from its position of FIGURE 1a to its position of FIG- URE 1. Also, end 48 of bimetallic strip 42 deflects back to its original position. When the circuit breaker mechanism, to which the trip unit assembly is connected by bracket 72, is reset as will be described below, after the fault condition has been corrected the bracket 72 pivots out of the way of tab 66 of latch 60. This permits biasing spring 84 to pivot latch 60 counterclockwise, opposite the direction of arrow 78, until the latch tip 62 slides past latch plate 94. Compression spring 38 is biasing the tripper bar 30 clockwise, in the direction indicated by arrow 40, and when latch tip 62 moves beneath latch plate 94, spring 38 pivots tripper bar 30 clockwise so that the latch tip 62 is vagain in its position of FIGURE 1 with respect to the latch plate 94 and the positioning means 100.

Referring to FIGURE 2 which shows a trip unit designed in accordance with the prior art, identical elements to those in FIGURE 1 will be numbered identically to the corresponding element in FIGURE 1 with a prime after the number. The structure of FIGURE 2 can be identical to that of FIGURE 1 with the exception of the latch plate and positioning means. The latch plate 120 is secured in the manner of latch plate 94 to the tripper bar 30'. The latch plate has a surface 121 which is engaged by latch tip 62 for preventing rotation of the latch 60' in the direction indicated by arrow 78.

Unlike the structure of FIGURES 1 and 1a, there is no element equivalent to the positioning means 100 or 100a which affects the pivotal position of the tripper bar 30 as a result of the radial position of the latch tip 62' with respect to the pivot 64' of the latch 60'. The latch bite between latch tip 62 and surface 121 of latch plate 120 is determined by all of the following: the position of the pivot bearing 64, the length of latch 60', the position on latch 60' which receives pivot bearing 64', the position of pivot 32' of tripper bar 30', the position on tripper bar 30' which receives pivot 32 and the position of latch plate 120 on tripper bar 30.

Using the positioning means 100 or 100a of FIGURES 1 and la in conjunction with a latch, only one item, the surface 96 of latch plate 94 in engagement with latch tip 62 must be machined or formed to a precise dimension to obtain a predetermined latch bite. Any errors in the formation of this single element are insignificant. However, in the prior art structure of FIGURE 2, even if all the parts are formed and positioned with great precision, a small error in each of the items involved in the determina tion of latch bite may together cause a large error in the latch bite.

To compensate for the variations in prior art trip units resulting from these tolerances, prior art trip units require a separately adjustable tripper bar positioning means such as means 124, which is a threaded screw in a threaded aperture in bar 30', and which engages a fixed support, such as abutment surface 112. Adjustment of the position adjusting means 124 is accomplished by rotation of screw head 125. As the position adjusting means 24 is adjusted, the tripper bar is pivoted with respect to the latch tip 62 until the proper latch bite is obtained. Adjustment of position adjusting means 124 cannot be made until the tripper bar 30', latch plate 120 and latch 60' have been mounted in position since the position adjusting means 124 is moved to compensate for variations in the mounting and positioning of these various components among different trip units.

In addition, to operate the position adjusting means, an operator must have access to the latch tip 62 and the latch plate 120 to take measurements of the latch bite as position adjusting means 124 is adjusted, or elaborate fixturing to indicate the latch bite is required. -It is apparent that adjustment of prior art devices requires considerable time which need not be expended at all when a positioning means 100 of the present invention is employed.

The benefit of the present invention over the prior art arises from the connection of the latch bite determining means, or latch positioning means, with both the tripper bar and with the latch, rather than, as in the prior art, having the position adjusting means, which is connected with the tripper bar, engage a separate stop or abutment without contacting the latch.

One other distinction between the trip unit of the invention as shown in FIGURE 1 and the trip unit of the prior art, as shown in FIGURE 2, is the narrowness of the surface 96 of latch plate 94, as compared with the greater width of the surface 121 of the latch plate 120. Since the positioning means 100 in FIGURE 1 exactly positions the tripper bar 30 to provide proper latch bite, the latch plate 94 may be machined so that its surface 96 is the precise width for the desired latch bite. In prior are devices, however, since adjustment of the rotative position of the tripper bar 30' has to be made by the adjustment of the position adjusting means 124 after the latch 60' and tripper bar 30 are mounted in the trip unit, the surface 121 has greater width to accommodate the various latch bites which can develop prior to operation of means 124 due to the dimensional tolerances.

A trip unit designed in accordance with the present invention may be used in conjunction with ay circuit breaker making use of a trip unit. In FIGURE 3 hereof, for illustrative purposes, the trip unit is shown in a circuit breaker described in US. Patent No. 3,268,702, issued on Aug. 23, 1966 to Carl E. Gryctko, entitled Loosely Mounted Independent Coupling Means for Adjusting Contact Pressure and Contact Arm Position and assigned to the asignee hereof. Elements in FIGURE 3 herein corresponding to those in FIGURES l, 4 and 5 herein are identically numbered.

The circuit breaker shown in FIGURE 3 has a current path from the line terminal connector through terminal strap 152, stationary contacts 154, movable contacts 156, flexible braid 158, conductor 160, conductor 12, which passes through the trip unit 10, and load terminal connector 162. The movable contacts 156 are normally in engagement with the stationary contacts 154. When the circuit breaker trip unit is tripped, the circuit breaker is tripped open to the position shown in FIGURE 3 with the contacts 154, 156 separated.

Refer to both FIGURES 3 and 6. The movable contact carrying arm 164 is connected at pivotal connection 166 to toggle link 170 which meets the other toggle link 172 at a pivoting knee 174. A circuit breaker cradle 178 is pivotally mounted on pivot 180 which is mounted on a fixed support such as the frame or casing for the circuit breaker mechanism. The link 172 is pivotally connected at 184 to cradle 178. Thus, the pivotal movement of cradle 178 around its pivot 180 also causes movement of pivot 184 and hence of the

toggle comprising links

170, 172.

At the pivoting knee 174 is shaft 175 which moves into engagement with cradle 178 when the knee 174 is moved upward in FIGURE 3. Shaft 175 biases cradle 178 to pivot clockwise, as viewed in FIGURE 3, around the cradle pivot 180.

An operating handle is provided having a manually operable member 192 and guide tabs 194 which move in receiving slots provided in the casing of the circuit breaker. The handle is fixedly connected with the link 196 which is pivotally mounted on the handle pivot 198. The handle pivot 198 is secured to a fixed support such as the frame of the circuit breaker or the casing thereof.

Handle 190 has a tab 199 secured thereto for engaging a knob extending outward from pivot 184 to be thereby engaged. Pivot 184, as noted above, is affixed to cradle 178. When the handle 190 is pivoted counterclockwise, as viewed in FIGURE 3, the tab 199 engages the knob at pivot 184 and pivots the cradle counterclockwise around the cradle pivot 180.

Knee 174 has a triangular support member 202 thereon pivotally mounted to which are hooked two tension springs or other biasing means 204 for drawing the knee 174 toward the handle 190 and for biasing the handle link 196 securely into engagement with the fixed pivot 198. The springs 204 are hooked to the handle by hooks 206.

Fixedly secured to the cradle 178 is a transverse plate 210 adapted to be hooked by the overhanging extension 212 of the circuit breaker cradle bracket 72 described in connection with FIGURE 1. The bracket 72, as was there noted is pivotable around its pivot 74. A biasing means 214 has an end which bears on hooked extension 212 and an end which hooks the frame or casing of the circuit breaker. Biasing means 214 normally biases bracket 72 clockwise, as viewed in FIGURE 3.

The circuit breaker shown in FIGURE 3 protects a single phase. If the circuit being protected is multi-phase, a number of circuit breakers and trip units similar to those shown in FIGURE 3 are placed side by side. A tie bar 216 is provided, connected to each of the movable contact carrying arms 164. If any one of the arms 164 is pivoted to open the cooperating contacts in a particular phase, the tie bar ensures that all of the contact carrying arms simultaneously separate, thereby breaking the entire multi-phase circuit.

Operation of the trip unit of the present invention and of a circuit breaker used in conjunction therewith is illustrated in FIGURES 3 and 6. Start as in FIGURE 6, wherein the cooperating contacts are engaged, the handle 192, is over center to the right of knee 174 and the knee 174 is over center to the right of the

line joining pivots

180 and 184. In this condition, the stationary contacts 154 and movable contacts 156 are in engagement. The biasing springs 204 are pulling shaft 175 at knee 174 upward against cradle 178. The plate 210 is beneath the hooked extension 212 on cradle bracket 72 and the bias in the direction of arrow 226 of cradle 178 attempts to pivot bracket 72 counterclockwise in the direction of arrow 76. However, nose 70 of extension 72 is resting on surface 68 of latch 60, and latch 60 is prevented from pivoting under the force of springs 204 in the clockwise direction of arrow 78 by latch plate 94 secured to tripper bar 30.

When a fault condition develops in the circuit being protected the tripper bar 30 pivots counterclockwise in the direction of arrow 36, thereby freeing latch tip 62 of latch 60 from latch plate 94. Nothing prevent the rotation of latch 60 in the direction of arrow 36, and when this is permitted, cradle 178 pivots about pivot 180 in the direction of arrow 226, which pivots extension 72 in the direction of arrow 76 until plate 210 slips free of the extension 212. The upward bias of spring 204 on cradle 178, which causes plate 210 to move upward and pivots bracket 72 in the direction of arrow 76, also pivots latch 60 in the direction of arrow 78. Once plate 210 is free of extension 212, cradle 178 continues to pivot in the direction of arrow 226 without interference from extension 212.

Since bracket 72 is no longer affected through its extension 212 and through plate 210 biasing force of springs 204, the biasing means 214 pivots cradle bracket 72 in the direction opposite that of arrow 76. Bracket 72 pivots to its position of FIGURE 3 so that plate 210 can be moved beneath hooked extension 212 during relatch of the circuit breaker. When reclosing of the circuit breaker is completed, bracket 72 will again be biased in the direction of arrow 76 to bear upon surface 68 of flange 66 of latch 60.

Note the slot 215 in which the pivot 74 for cradle bracket 72 is positioned. During relatch, when plate 210 presses against extension 212 before it slides beneath the same, bracket 72 must be moved out of the way of plate 210. Slot 215 permits bracket 72 to be moved out of the way until plate 210 is hooked under the bracket.

Once bracket 72 has been biased into its position of FIGURE 3 by biasing means 214, latch 60 is no longer biased in the direction of arrow 78. Biasing means 84 attached to latch 60 causes the same to pivot in the direction opposite arrow 78 which moves latch 60 back to a position where it can engage latch plate 94 when tripper bar 30 returns to its normal position and the nose 70 of extension 72 is again pressed against surface 68 of latch 60'.

When cradle 178 pivots in the direction of arrow 226 about pivot 180, pivot 184 on the cradle also pivots, pulling toggle link 172 around until knee 174 is to the left of the line between pivots 184 and 166, whereupon the toggle collapses and the contacts 154, 156 are snapped apart.

When tripping of the circuit breaker occurs, handle 190 moves to an intermediate position shown in FIGURE 3. When it is desired to reclose the circuit breaker, handle 190 is pivoted in the direction of arrow 234 from its trip position shown in FIGURE 3. The tab 199 on the handle engages the knob at pivot 184 which thereby pivots cradle 178 counterclockwise, in the direction opposite that of arrow 226. Plate 210 is moved into engagement with extension 212 and then slides beneath the same Where it is engaged thereby.

Handle 190 is then pivoted to the position shown in FIGURE 6 in the direction opposite that of arrow 234. As handle 190 passes over and to the right of knee 174, the biasing springs 204 snap the knee 174 to the right in the direction of arrow 236. This causes an increase in the angle between the toggle links 170, 172, which forces the contact carrying arm 164 to pivot clockwise, as viewed in FIGURE 3, to move the movable contacts 156 into engagement with the stationary contacts 154.

The biasing force of spring 204 on shaft at knee 174 biases the cradle in the direction of arrow 226 around its pivot 180. This draws the plate 210 upwards, thereby pivoting cradle bracket 72 in the direction of arrow 76. The nose 70 of extension 72 presses on surface 68 of latch 60 and biases latch 60 in the direction of arrow 78, whereby latch tip 62 engages latch plate 94 to again ready the trip unit and the circuit breaker for another tripping operation.

While the trip unit of the present invention has been shown in conjunction with a particular embodiment of circuit breaker, it is to be understood that any circuit breaker may be used in conjunction with a trip unit designed in accordance with the invention.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. In a circuit breaker trip unit comprising, a trip assembly connected with and operative responsive to an overload condition in the circuit being protected; a tripper bar positioned to be engaged by and operated by said trip assembly in the event of an overload condition; cooperating means on said trip assembly and on said tripper bar for causing movement of said tripper bar in the event of an overload condition;

a latch connectible with a circuit breaker tripper for tripping apart the contacts of a circuit breaker; and

a latch plate connected with said tripper bar for engaging said latch and for holding same against such movement as would trip the circuit breaker contacts apart; said latch being movable with respect to said latch plate;

said tripper bar having a support and being movable with respect thereto to move said latch plate out of its holding position with respect to said latch; the improvement comprising, a latch positioning means connected to said tripper bar and having a first surface movable into engagement with said latch when said latch plate is in engagement with said latch;

said latch having a second portion movable into engagement with said first surface of said positioning means;

said first surface of said positioning means having a predetermined location with respect to said latch plate; said latch plate having a second surface against which said latch abuts for preventing movement of said latch to trip apart contacts of the circuit breaker;

said first and said second surfaces being tilted with respect to each other;

whereby the position of said latch with respect to said latch plate is determined by said positioning means, thereby determining the latch bite of said latch with respect to said latch plate.

2. In a circuit breaker trip unit comprising, a trip assembly connected with and operative responsive to an overload condition in the circuit being protected; a tripper bar positioned to be engaged by and operated by said trip assembly in the event of an overload condition; cooperating means on said trip assembly and on said tripper bar for causing movement of said tripper bar in the event of an overload condition;

a latch connectible with a circuit breaker tripper for tripping apart the contacts of a circuit breaker; and a latch plate connected with said tripper bar; said latch plate having a surface for engaging said latch and for holding same against such movement as would trip the circuit breaker contacts apart; said latch plate surface having a free end past which said latch moves to be free of said latch plate; said latch being movable with respect to said latch plate surface and being movable into engagement with said latch plate;

said tripper bar having a support and being movable with respect thereto to move said latch plate out of its holding position with respect to said latch; the improvement comprising, a latch positioning means connected to said tripper bar and having a first portion movable into engagement with said latch when said latch plate is in engagement with said latch;

said latch having a second portion movable into engagement with said first portion of said positioning means;

said first portion of said positioning means having a predetermined location with respect to said latch plate so as to engage said latch in a manner which causes said latch, when in engagement with said positioning means, to extend past a predetermined length of said latch plate surface inward from said free end of said latch plate surface;

whereby the position of said latch with respect to said latch plate is deter-mined by said positioning means, thereby determining the latch bite of said latch with respect to said latch plate. 3. In the circuit breaker trip unit of claim 2, the improvement further comprising,

said positioning means having a surface against which said latch abuts; said latch plate surface and said positioning means surface being tilted with respect to each other. 4. In the circuit breaker trip unit of claim 2, the improvement further comprising,

said positioning means being fixedly secured to said tripper bar; said latch engaging said positioning means in abutting fashion. 5. In the circuit breaker trip unit of provement further comprising,

claim 4, the imsaid positioning means being adjacent said latch plate.

'6. In the circuit breaker trip unit of claim 2, the improvement further comprising,

said positioning means being integral with said latch plate. 7. In the circuit breaker trip unit of claim 1, the improvement further comprising,

said first and said second surfaces forming a pocket into which said latch fits. 8. In the circuit breaker trip unit of claim 1, the improvement further comprising,

said positioning means being integral with said latch plate.

References Cited UNITED STATES PATENTS 2,354,162 7/1944 Weber 33535 2,574,093 11/1951 Edmunds 33535 2,673,264 3/1954 Cole 335--23 BERNARD A. GILHEANY, Primary Examiner H. BROOME, Assistant Examiner US. Cl. X.R. 335-23