US2952757A - Pushbutton-operated overload switch - Google Patents

Description

P 13, 1960 J. ELLENBERGER 2,952,757

PUSHBUTTON-OPERATEID OVERLOAD SWITCH Filed Feb. 24, 1959 5 Sheets-Sheet l wvf/x/ro/e:

JA KOB ELLENBERGER PATENT AGENT Sept. 13, 1960 J. ELLENBERGER PUSHBUTTON-OPERATED OVERLOAD SWITCH 5 sheets-s heetwz Filed Feb. 24, 1959 /NVENTOR' JAKOB ELLENBERGER B, ZQM

PATENT AGENT p 13, 1960 J. ELLENBERGER 7 2,952,757

PUSHBUTTON-OPERATED OVERLOAD SWITCH Filed Feb. 24, 1959 5 SheetsSheet 3 IN VE N TOR I JAKOB ELLENBERGER B, Zyfl PA TENT AGENT Sept. 13, 1960 J. ELLENBERGER 2,952,757

PUSHBUTTON-OPERATED OVERLOAD swmcn Filed Feb. 24, 1959 5 Sheets-Sheet 4 JA KOB ELLENBERGER PA TENT AGENT #vvavroe:

Sept. 13, 1960 J. ELLENBERGER 2,952,757

PUSHBUTTON-OPERATED OVERLOAD SWITCH Filed Feb. 24, 1959 5 Sheets-Sheet 5 MEMO/2: JAKOB ELLENBERGER By /4 Q M PATENT AGENT United States Patent PUSHBU'ITON-OPERATED OVERLOAD SWITCH Jakob Ellenberger, Altdorf, near Nurnberg, Germany, as-

signor to Ellenberger & Poensgen G.m.b.H., Altdorf, near Nurnberg, Germany Filed Feb. 24, 1959, 'Ser. No. 795,006

Claims priority, application Germany Feb. 27, 1958 14 Claims. (Cl. 200-116) The present invention relates to a pushbutton operated overload switch with an automatic release mechanism which may be thermally and/or electromagnetically controlled, and more particularly to improvements in such a switch as described in my copending application, Serial No. 699,952, filed on December 12, 1957, now U.S. Patent No. 2,895,028.

This prior application described an overload switch of the type as mentioned above which is provided with a contact bridge in the shape of an angular lever which is freely pivotable on a control bridge which, in turn, is rigidly connected by a control rod to the spring-loaded pushbutton, and wherein the control bridge is also movable along the control rod in the axial direction thereof. When the switch is in the disconnecting or oif position, the control bridge presses the contact bridge against a stationary inclined surface whereby the contact bridge is pivoted so as to place a projection thereon into the path of movement of the control bridge. When the pushbutton is then depressed to place the switch into the connecting or on position, the control bridge will engage with and take along the contact bridge and pivot it so that its free end will interlock with a detent on a bimetallic holding spring.

It has now been found that this prior overload switch h'asthe disadvantage of being of a rather complicated construction in that particularly the control bridge there of has to be assembled of several parts, for example, of a separate carrier member for taking along the contact bridge and of projecting pivot members on which the contact bridge is suspended,

It is an object of the present invention to provide an overload switch of the type as described in the mentioned previous application, but which is of a considerably more simplified construction, consists of fewer parts, is more easily assembled, and may therefore be manufactured at less expense than the switch according to the previous application.

According to the present invention, the control bridge is made of a U-shaped cross section with the side wall portions thereof being of a substantially triangular shape as seen in a side view of the U-shaped body. The apices of these triangular side wall portions form the pivot points on which the contact bridge is pivotally suspended and movable when being shifted from its released or disconnecting position to its connecting position or vice versa. A compression spring is interposed between the control and contact bridges and acts upon the latter to effect a trip-freerelease of the switch independent of the release of the control rod and the control bridge thereon. Because of the U-shaped structure of the control bridge, this spring may be mounted within the control bridge, that is, between the triangular side walls thereof. Another advantageous feature of the invention resides in the fact that the control bridge and the control rod 'for operating the same may be combined to form one integral element so that the number of individual parts required to assemble the switch will thus be reduced.

Furthermore, While the control bridge of the previous switch construction required a separate carrier member for taking along the contact bridge when the push-button was depressed to the on position, the control bridge according to the present invention merely requires an undercut recess therein forming a detent which is adapted to engage with a projection on the contact bridge when the control bridge is being moved downwardly.

It constitutes another feature of the switch according to the present invention that at the side of the control bridge facing toward the detent on the bimetallic holding spring, the control bridge is provided with a flat surface which prevents the holding spring from bending toward the control rod when the contact bridge is in the released position. Thus, the control bridge is shaped so as always to insure a proper engagement of the switch.

In order to improve the facility and accuracy of the operation of the switch and to extend the life of its parts, the invention further provides the contact bridge at the side facing toward the bimetallic holding spring with an inclined surface which is adapted to engage with and slide along the detent on the holding spring so as to bend away the entire spring when the switch is being engaged. This has the advantage that there is no undue wear on the engaging surfaces and that the bimetallic spring is not subjected to any undue pressure but that it may yield over its entire effective length when the switch is being engaged.

In a very simple embodiment of the invention which is very easily and inexpensively produced, both the control bridge and the contact bridge are provided at least at one side with a riblike projection which extends parallel to the axis of the control rod and is slidably guided in a corresponding groove in the Wall of the switch housing. Thus, the control and contact bridges are both safely guided without requiring any separate guiding elements.

The simplified design of the control bridge has the further advantage that the control rod with the movable control elements thereon may be combined to form a single unit which may be easily inserted as a whole into a suitable recess in the switch housing. The individual parts are therefore first assembled to form the unit which is then inserted into the switch housing. The same applies to the bimetallic holding spring which together with its adjusting parts and connecting members also forms one structural unit which may be inserted at one time into the switch housing in which both units may then be secured by screws and rivets. The bimetallic spring then extends through a suitable aperture in the wall of the housing toward the outside and it is only secured to the housing near this aperture. Consequently, the bimetallic spring can bend freely along a much greater length than this was previously possible, which results in a greater sensitivity and accuracy of operation of the switch.

The terminal carrying the contact point which is in engagement with the contact bridge when the switch 'is in the operative position is also made of an elongated striplike shape so that it may likewise be easily inserted into a suitable recess in the switch housing and be automatically secured therein when the housing is being closed.

These and further objects, features, and advantages of the present invention will be more clearly apparent from the following detailed description thereof, particularly when read with reference to the accompanying drawings, in which- Figure 1 shows a longitudinal section of the overload switch according to the invention in the released or disconnecting position;

Figure 2 shows a cross section taken along line H-II ofFigurel;

Figure 3 shows a sectional view of the overload switch Patented Sept. 13, 1960 according to Figure 1, but in the engaged or connecting position;

Figure 4 shows a perspective view of the lower half of the switch housing;

Figure shows a perspective view of the control bridge unit;

Figure 6 shows a perspective view of the unit containing the bimetallic spring;

Figure 7 shows a front view of the control bridge;

Figure 8 shows a front view of the contact strip which is associated with the contact bridge;

Figure 9 shows a partial cross section of an overload switch according to a modification of the invention taken along line IX-IX of Figure Figure 10 shows a plan view of the switch according to Figure 9; while Figure 11 shows a cross section taken along XIXI of Figure 9.

Referring to the drawings, and first particularly to Figures 1 to 8, the switch housing consists of the two parts 1 and 2. Housing part 1 is provided with a recess 3 into which the control bridge unit 4 as shown in Figure 5 may be inserted. This unit consists of a control bridge 5 of a substantially U-shaped cross section, as shown particularly in Figure 7, with side wall portions of a substantially triangular shape, as clearly shown in Figures 1, 3, and 5. These side wall portions have outwardly projecting ribs 6 thereon which are adapted to slide in corresponding grooves 7 in both housing parts 1 and 2. The apexes 8 of the triangular walls including ribs 6 form the points on which a slightly inclined arm 9 of a contact bridge 10 rests when the switch is in the disconnecting or off position, as illustrated in Figure .1. Contact bridge 10 forms a substantially rectangular lever, the downwardly depending arm 11 of which carries a contact point 12 at its lower end facing toward the outside of the angular lever, while at a point intermediate its ends arm 11 is provided with an inwardly projecting detent 13. When the switch is in the released position, arm 9 will engage against an inclined surface 14 of housing part 1, as shown most clearly in Figures 3 and 4, so that arm 9 will then assume the inclined position, as shown in Figure 1. Control bridge 5 is rigidly and preferably integrally connected to a control rod 17, the lower end of which also supports spring 16. A coil spring 16 serving as a trip-free release is interposed between the bottom of control bridge 5 and arm 9 of contact bridge 10 to press the arm upwardly independently of the upward movement of control rod 17 when the switch is being released.

Control rod 17 carries on its upper end a pushbutton 18 and is slidably mounted within a tubular sleeve 19 under the action of a coil spring 20, the upper end of which engages upon a spring ring 21, while its lower end engages upon a washer 22 so as to urge the control rod upwardly toward the released position. All of these parts may be combined to form one unit, in which case washer 22 will be rigidly secured to sleeve 19, as shown in Figure 5, and may then be easily inserted intoaperture 3 in housing part 1. Sleeve 19 which is provided with screw threads 19 in the outside is locked against rotation and has for this purpose a longitudinal groove .19" into which a projection 1' engages which is provided at the upper end of housing part 1, as shown in Figure 4.

Control bridge 5 further has an undercut recess at the side facing toward arm 11 of the contact bridge. This recess forms an inclined surface 23 which terminates in a detent 24 and is operatively associated with detent 13 ion arm 11. Because of the inclined position of contact bridge 10 in the released position of the switch as shown in Figure 1, detent 13 will then engage from underneath with detent 24 so that, when pushbutton 18 is then depressed, contact bridge 10 will be taken along until the end portion 25 of its arm. 9 engages underneath the detent 26 which is secured to the bimetallic spring 27. During the downward movement of contact bridge 10, an inclined surface 28 on its end portion 25 engages with a corresponding inclined surface 29 on detent 26 to bend the bimetallic spring 27 backwardly until the contact bridge has been depressed sufficiently so that detent 26 can slide over the upper surface of end portion 25 and the bimetallic spring can again assume its straight position.

At the side facing toward the bimetallic spring 27, control bridge 5 also has a flat end surface 15' against which the detent 26 may engage in the released position of the switch and which serves to prevent spring 27 from bending beyond its straight position toward the control rod 17.

The bimetallic spring 27 carries a heating coil 30 and is according to the invention combined by means of a threaded sleeve 31 with terminal strips 32 and 33 so as to form a single unit, as shown particularly in Figure 6.

Sleeve 31 also contains a setscrew 34 with a conical tip 35 at its upper end which engages with a laterally projecting lug 36 on spring 27 to permit the tension of the latter to be adjusted.

Spring 27 is further provided near its lower end with a cutout 37 which is formed by stamping out lug 36 and gives the spring the proper elasticity.

According to a further feature of the invention, the complete bimetallic spring unit as shown in Figure 6 may be inserted into a receiving bracket 38 which forms an integral part of housing part 1, as shown in Figure 4. Bracket 38 is spaced a little distance from the side wall of housing part 1, the intervening gap 39 forming an aperture in the housing for the insertion of spring 27 so that the lower angular part 40 thereof will engage with the lower surface of bracket 38. By this construction it has been made possible to enlarge the effective length of the bimetallic spring, that is, the length be tween the holding detent 26 and the bending point 41 and thus to increase the sensitivity and accuracy of operation of the switch without increasing the length of the switch housing.

When pushbutton 18 is depressed and the switch is in the engaged position, the contact point 12 on contact bridge 10 engages with a contact point 42 on the upper end of a terminal strip 43- of a simple shape as shown in Figure 8, which is very easily produced. This terminal strip 43 may also be easily inserted into a recess 44 in each housing part 1 and 2, as shown in Figure 4.

The overload switch according to the invention is further provided with a manual release mechanism 45 consisting of an angular member secured to a pushbutton 48 and forming a detent 46 with an inclined surface 47. A coil spring 49 tends to maintain pushbutton 48 in its released position. When the latter is depressed against the action of spring 49, the inclined surface 47 on detent 46 engages with the upper end of the bimetallic spring 27 and thereby bends the same outwardly until the detent 29 thereon disengages from the end portion 25 of contact bridge 10, so that spring 20 can then return the control rod 17 with the control bridge 5 thereon to the upper released position and thereby pivot contact bridge 10* by its engagement with the inclined housing surface 14 about its pivot points 8 on control bridge 5 to the position shown in Figure 1 in which the detent 13 on contact bridge 10 passes underneath the detent 24 on control bridge 5 for the subsequent engagement of these detents when the pushbutton 18 is again depressed.

The modification of the overload switch according to the invention as shown in Figures 9 to 11 is substantially similar to the embodiment previously described and differs therefrom only in minor respects. At its right and left sides, the switch housing is provided with flanges 50 'for mounting the switch in a different manner from the switch according to Figures 1 to 4.' Furthermore, the pushbutton 18 is made of a different construction in that it has a recess 51 in its lower end into which a coil spring 52 is inserted which has the same function as spring 20 in Figures 1 and 3. The bimetallic spring 27 may be manually released to disengage the switch by a pushbutton 53 which in this case is mounted in the side wall of one housing part.

The operation of the new overload switch according to either embodiment is as follows:

If the switch is in the disconnecting position as shown in Figure 1 and is to be shifted to its operative position, pushbutton 18 is depressed into the switch housing. During this downward movement, the detent 24 on control bridge 5 engages with the detent 13 on contact bridge and takes the latter along until the end portion 25 of contact bridge passes underneath the detent 26 on the bimetallic spring 27. Prior to this time, the inclined surface 28 on contact bridge 10 engages with and slides along the inclined surface 29 on detent 26 and thereby bends the spring strip 27 in a clockwise direction until detent 26 passes over the upper edge of end portion 25 of the contact bridge, thereby permitting the spring strip to bend back to its straight position, as shown in Figure 3. In this position, the switch is engaged with the electric circuit then extending from terminal strip 43 through contact points 42 and 12, contact bridge 10, holding detent 26, and bimetallic spring 27 to terminal strip 33. The heating coil 30 is then likewise supplied with current through the terminal strip 32.

If an overload occurs, heating coil 30 will heat up the bimetallic spring 27 to such an extent that it will bend in a clockwise direction and its holding detent 26 will disengage from contact bridge 10 so that control rod 17 with control brdige 5 and contact bridge 10 thereon will be propelled upwardly by spring 20 or 52, respectively, until contact bridge 10* will engage with the inclined housing surface 14 and thereby be pivoted about the points 8 on control bridge 5 to the position illustrated in Figure 1. In this released position, contacts 12 and 42 as well as contacts 25 and 26 are separated from each other.

As previously indicated, the overload switch may also be released manually by an operation of pushbutton 48 or 53, respectively. When this pushbutton is depressed, its inclined surface 47 presses against the upper end of the bimetallic spring 27 and bends the same in a clockwise direction in the same manner as happens automatically at the occurrence of an excess current so that the holding detent 26 will disengage from contact bridge 10 allowing the latter together with control bridge 5 and control rod 17 to return to the disconnecting position.

A particular advantage of the overload switch according to the invention consists in the fact that it permits a trip-free release independent of an operation of control rod 17. This is effected by the compression spring 16 which tends to lift the contact bridge 10 from the control bridge 5. If the switch is, for example, in the connecting position as shown in Figure 3, and pushbutton 18 should for any reason remain stuck in its depressed position, this will not prevent the switch from releasing. As soon as detent 26 releases the contact bridge 10, the latter will then not be brought back to its disconnecting position by the action of spring 20 or 52 but by the action of spring 16, which then pushes the contact bridge 10 along the control rod 17 until the arm 9 of bridge 10 engages with the inclined housing surface 14.

Although my invention has been illustrated and described with reference to the preferred embodiments thereof, I wish to have it understood that it is in no way limited to the details of such embodiments, but is capable of numerous modifications within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1s:

1. In an overload switch having a housing with an inclined surface therein near its upper end, switch elements within said housing including a contact bridge forming a lever having a first upper arm and a second arm depending downwardly from said first arm, a control rod slidable in the axial direction within said housing, a pushbutton at one end of said control rod for moving the switch to the on position, a control bridge rigidly secured to the other end of said control rod, said control bridge having a substantially triangular shape, the apex of the upper corner of said triangular control bridge forming a pivot, said contact bridge being freely suspended at said upper arm of said lever on said pivot for pivotal movement relative to said control bridge, said contact bridge being also slidable above said pivot along said control rod and in the axial direction thereof, a holding spring, spring means tending to move said control rod and pushbutton and said control bridge with said contact bridge thereon to the off position and for thereby pressing said first arm of said contact bridge into engagement with said inclined housing surface, a projection on said second arm of said contact bridge, one of the lower corners of said triangular control bridge being superimposed to said projection on said second arm when said first arm is in engagement with said inclined housing surface, said lower corner forming a detent adapted to engage with said projection and to take along said contact bridge when said pushbutton is depressed to move said control bridge downwardly and the free end of said first arm of said contact bridge into locking engagement with said holding spring, at least one automatic overload-actuated releasing means connected to said holding spring for varying the position thereof so as to disengage said holding spring from said contact bridge and thereby to move said switch to the off position, and a compression spring forming a tripfree release interposed between said control bridge and said contact bridge for moving said contact bridge to the off position into engagement with said inclined housing surface independently of said control bridge if said control bridge fails to return to said off position.

2. An overload switch as defined in claim 1, wherein said triangular control bridge has a substantially U- shaped cross section with a bottom portion and substantially triangular side walls on said bottom portion forming the side arms of said U-shape, said compression spring being mounted on said bottom portion between said side walls.

3. An overload switch as defined in claim 1, wherein said control bridge and said control rod are integral with each other.

4. An overload switch as defined in claim 1, wherein said control bridge, said control rod, and said pushbutton are integral with each other.

5. An overload switch as defined in claim 1, wherein said lower corner of said control bridge has an undercut recess forming a detent adapted to engage with and to take along said contact bridge when said control bridge is moved downwardly.

6. An overload switch as defined in claim 1, wherein said control bridge is provided with a fiat surface at the other lower corner portion for preventing said holding spring from bending toward said control rod when said switch is in the off position.

7. An overload switch as defined in claim 1, wherein said free end of said first arm of said contact bridge is provided with an inclined surface adapted to engage with and to slide along a detent on said holding spring so as to bend said spring away from said contact bridge.

8. An overload switch as defined in claim 1, wherein said control bridge and said contact bridge have each at least at one side thereof a guiding rib extending parallel to the axis of said control rod, said switch housing having a corresponding groove in a wall thereof, said guiding ribs being slidably disposed within said groove.

9. An overload switch as defined inclaini 1, wherein said control rod with said control bridge, said compression spring, and said contact bridge thereon form a single unit adapted to be inserted as suchinto corresponding recesses in said switch housing.

10. An overeload switch as defined in claim 1, further comprising means for guiding said control rod, said spring means forming a compression springon said control rod and disposed within said guiding means, said control rod with said control bridge, said compression springs, said guiding means, and said contact bridge forming a single unit adapted to be inserted as such into corresponding recesses in said switch housing.

11. An overload switch as defined in claim 1, wherein said holding spring is a bimetallic strip, further comprising means for adjusting said spring, and terminals connected to said spring, said spring, said adjusting means, and said terminals being combined to form a unit adapted to be inserted as such into said switch housing, and means for securing said unit to said housing.

12. An overload switch as defined in claim 11, wherein said holding spring is mounted so as to extend laterally of said securing means, said spring extending into said housing through an aperture in the wall thereof allowing said spring to bend freely along its entire elfective length.

13. An overload switch as defined in claim 1, further comprising a terminal strip having a contact point thereon, said switch housing having a recess therein corresponding to the shape of said terminal strip and adapted to receive and hold the same, said depending arm of said contact bridge also having a contact point thereon adapted to engage with said contact point on said termi-" nal strip when said contact bridge is pivoted by its locking engagement with said holding spring in the on position of said switch.

14. An overload switch as defined in claim 1, fur-' ther comprising means for manually releasing said- References Cited in the file of this patent UNITED STATES PATENTS 2,476,648 Zeller July 19, 1949 2,741,681 Allard Apr. 10, 1956 2,768,262 Allard Oct. 23, 1956 2,816,192 Ingswergen Dec. 10, 1957 2,863,022

Powell Dec. 2, 1958

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