US3315054A

US3315054A - Overload relay with snap-acting condition responsive switch

Info

Publication number: US3315054A
Application number: US467492A
Authority: US
Inventors: Langley Howard Dale
Original assignee: Federal Pacific Electric Co
Current assignee: Federal Pacific Electric Co
Priority date: 1965-06-28
Filing date: 1965-06-28
Publication date: 1967-04-18
Anticipated expiration: 1984-04-18
Also published as: GB1091440A

Description

April 18, 1967 H. D. LANGLEY 3,315,054 OVERLOAD RELAY WITH SNAP-ACTING CONDITION RESPONSIVE SWITCH 'Filed June 28, 1965 6 Sheets-Sheet 1 INVENTOR. DALE (AM/6L5) BY ML.

April 18, 1967 H. D. LANGLEY 3,315,054

OVERLOAD RELAY WITH SNAP-ACTING CONDITION RESPONSIVE SWITCH Filed June 28, 1965 6 Sheets-Shet 2 INVENTOR. H. @445 AAA/64 Er Apnl 18, 1967 H, D. LANGLEY 3,315,054

OVERLOAD RELAY WITH SNAP-ACTING CONDITION RESPONSIVE SWITCH Filed June 28, 1965 6 Sheets-Sheet 4 W FIG. 6

INVENTOR. f1. 0416 LANGLEY April 18, 1967 H. D. LANGLEY 3,335,054

OVERLOAD RELAY WITH SNAP-ACTING CONDITION RESPONSIVE SWITCH Filed June 28, 1965 6 Sheets-Sheet 6 F! 6, l3 0 INVENTOR.

,. A. DALE AAA/6.445;

ZATCHED" United States Fatent Ofihce 3,315,054 OVERLOAD RELAY WITH SNAP-ACTING CON- DITION RESPONSIVE SWITCH Howard Dale Langley, Cranford, N.J., assignor to Federal Pacific Electric Company, a corporation of Delaware Filed June 28, 1965, Ser. No. 467,492 16 Claims. (Cl. 200-116) This invention relates to overload relays and more particularly to overload relays incorporating trip-free switches.

Overload relays capable of protecting electrical apparatus against overload or unbalance are well known in the art. In one class of overload relays there are employed a plurality of current-responsive members, a switch, and an operative connection between the currentresponsive members and the switch for operating the switch to disconnect the protected apparatus. The disconnecting operation is provided by excessive uniform movement of the members in the event of overload and by non-uniform movement of the members in the event of an unbalance.

Bimetal elements, either directly or indirectly heated, may be used as current responsive devices and their current-responsive motion may be utilized to operate a switch or indicator. Where the bimetals are called upon to develop a considerable amount of force for operating or releasing a switch, problems occur, i.e., the greater the force the bimetals are called upon to supply, the stiffer the bimetal must be in order to avoid deflection due to the force required to trip the device being operated by the bimetal. As the loading of the bimetal is increased the bimetal must be made stiffer. A corollary reduction in sensitivity accompanies any increase in stiffness. Therefore, it is an object of this invention to provide an improved overload relay of the type described wherein the loading of the bimetal elements is minimized so as to avoid the aforementioned difficulties.

A further object of the invention is to provide an overload relay wherein the switch is responsive to the bimetal position with minimum loading of the bimetal.

Yet another object of this invention is to provide an overload relay including current-responsive bimetals and a switch having an adjustable operating point and ambient temperature compensation wherein changing the operating point does not affect the ambient temperature compensation.

Overload relays, and particularly the switches incorporated therein, are subject to vibration and shock which is produced either by sources external to the relay or by the operation of the relay itself. It is yet another object of this invention to provide an overload relay having minimized shock and vibration sensitivity.

It is a further object of this invention to provide an improved snap-operating switch having both a low opcrating force and a short operating stroke.

It is still another object of this invention to provide a trip-free snap operating switch having improved operating parameters.

It is yet another object of this invention to provide a trip-free snap-operating switch which utilizes a minimum number of parts and which is readily adaptable to massproduction assembly techniques without degradation of the desired operating characteristics.

The above and other objects and advantages and novel features of the invention will become apparent from the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is an exploded perspective view of the novel overload relay including the trip-free automatic switch and the current sensing means;

FIG. 2 is an exploded perspective view of an alternative V 3,315,054 Patented Apr. 18, 1967 70m] of current sensing means usable in the relay of FIG. 3 is a front elevational view, on an enlarged scale, of the overload relay of FIG. 1 with the cover removed, to reveal portions of the internal mechanism;

FIG. 4 is a plan view in cross section of the relay of FIG. 3 as viewed from the plane 44 of FIG. 3;

FIG. 5 is an explode-d perspective view of the trip-free automatic switch;

FIG. 6 is an exploded perspective view of operative portions of the trip-free switch of FIG. 5;

FIG. 7 is a side elevational view of the trip-free switch of FIG. 5 in the closed circuit condition with some parts in section and with other portions broken away or omitted in the interest of clarity;

FIG. 8 is an end elevational View in section of the tripfree switch of FIG. 7 as viewed from the plane 88 of FIG. 7;

FIG. 9 is an end elevational view of the switch of FIG. 7 as viewed from the plane 9-9 of FIG. 8;

FIG. 10 is a fragmentary side elevational view of the trip-free switch on an enlarged scale showing the switch mechanism in an intermediate position in the transition from the closed circuit condition to the open circuit condition;

FIG. 11 is a fragmentary side elevational view of the trip-free switch showing the switch mechanism in the open circuit condition;

FIG. 12 is a fragmentary end elevational view of the switch;

FIG. 13 is a greatly enlarged view of a portion of the bridging contact carriage shown in the latched condition;

FIG. 13a is a diagrammatic representation of the carriage path;

FIG. 14 is a fragmentary end view corresponding to FIG. 13 taken along the line 1414 of FIG. 13; and

FIG. 15 is a schematic circuit diagram of the overload relay incorporated in a motor starter.

The overload relay 20 includes a three-part enclosure formed of insulating material, including a base 22, switch enclosure 24 and cover 26. Three pairs of

external terminals

28, 30 project from the top of the enclosure and a fourth pair of

terminals

32, 34 which are part of the switch 36 project from the enclosure 24. To these terminals various electrical connections are made as will be explained in detail below.

Terminals

28, 32, 34 are formed for wire connections and terminal 30 is in the form of a contact stud for cooperation with a moving contact member (schematically shown in FIG. 15) as when the overload relay 20 is incorporated in a motor starter.

Three bimetals are shown, each Within a separate chamber in the enclosure (FIG. 3). Each of the bimetals 38 in FIGS. 1 and 3 is substantially U-shaped and has a long leg 38a and a short leg 38b connected by a bight portion 380. A heater 40, in the form of a loop of higher resistance metal than the bimetal, is positioned within the U-shaped portion of the heater. One leg of the loop is electrically and mechanically connected to leg 38b of the bimetal and the other leg of the loop is connected to a base mounted connector 42 by braid 44. Braid 46 is welded to leg 38a of the bimetal at one end and to a connector 48 that is joined to one external terminal 28. The connector 48 is rigidly secured to the base by screws. Bimetal 38 is mounted in the base 22 by a screw 50. A sleeve 52 and washer 54 are interposed between the screw 50 and the bimetal 38. The bimetal is free to pivot about the screw 50 but is restrained by a retainer 56 which traps leg 38b between the retainer and the adjacent wall of the chamber (FIG. 3). The retainer has a force fit with an appropriate recess in the enclosure. A circuit extends from external terminal 28, via connector 48, braid 46, bimetal 38, heater 40, braid 44, and connector 42 .3 to the opposite terminal 30 which is threadedly received in aperture 58.

Referring to FIG. 2 the form 'of bimetal and heater shown therein is particularly suited for low current levels. A heater 60 of resistance wire is wound about each bimetal 62 and is suitably protected by electrical and thermal insulation. Current will flow through the heater from one terminal 60a to the opposite terminal 60b to heat the bimetal so as to cause deflection. Bimetal 62 is supported on and connected to a connector 48' that is joined to one external terminal 28', The heater terminal 60b connects the heater to the bimetal 62. The other end of the heater is connected via a connector 42 t the second terminal 30. A circuit extends from one'external terminal 28, via connector 48, bimetal 62, heater terminal 60b, heater 60, heater terminal 60a and connector 42 to the opposite terminal 30. It will be noted that

connectors

42 and 48 and connectors 42' and 48' are respectively the same in both embodiments allowing either embodiment of overcurrent element to be employed depending upon the range of current to be monitored.

Where a three phase load as for example a motor 64 (FIG. is to be protected, a heater 40 or 60 is interposed as a series connector to the three phase supply L1, L2, L3, a separate heater element being available for each of the three phases.

The left-hand side of the

bimetals

38, 62 is the high expansion side, so that during the proper operation all three bimetals will deflect moderately to the right in FIGS. 1 to 4. In the event of overload all three bimetals will deflect to the right through a prominent distance so as to cause overload tripping as will be described. Typi cally, in the event of phase failure one of the bimetals will, upon cooling, shift to the left and in this condition will also cause tripping of the contacts, as will be seen. Similarly, phase unbalance will cause tripping of the contacts.

The

mechanism enabling bimetals

38 or 62 to operate the trip free switch 36 will now be described with particular' reference to FIGS. 1, 3 and 4. A pair of

strips

66, 68 of insulationare slidable in passages 70 formed in the walls separating the bimetal chambers from each other and in the wall 72 that separates the bimetals from the enclosure 24 at the left containing the switch 36. Bell crank 74 has a pivot 76 to slide 66 and another pivot 78 to slide 68. The end 74a of the arm of the 'bell crank 74 engages a portion 80 of the switch 36 to effect operation thereof. The lower, free end of each bimetal 38, 62 normally bears flatwise against the right-hand side 66a of a respective notch in slide 66, and against the left-hand side 68a of a respective notchin slide 68. It is apparent that shifting of the free ends of bimetals due to moderate heating of normal loads in all phases will simply cause portion 74a of bell crank 74 to slide along the surface of switch portion 80 without moving that portion. However, if slide 68 were arrested while bimetals 38 or 62 or any of them continued to deflect farther to theright, slide-66 would shift to the right and swing the bell crank 74 to deflect the portion 80 of switch 36. A stop 82 is mounted on the slide 68 for engagement with a portion of the calibrating means 84 of the switch- 36, to be described in detail later, for predetermining the. amount of shift of the slides that will be allowed and thereby determining the current value through the bimetals at which operation of the switch 36 will occur. Also, if all of the bimetals are shifted to the right of their positions shown in the drawings by normal-load heating, and if one of the bimetals should fail to receive heating current, the unheated bimetal would then shift to the left relative to the other bimetals. Slide 66 would be held in position by the normally heated bimetals, whereas the cool bimetal in shifting to the left would shift slide 68 and pivot 78 to the left, so as to swing bell crank 74 in the direction to operate the switch 36. Both overload operation and phase failure operation of the switch 36 is thus accomplished by the same mechanism. The force required to operate switch 36 is supplied by the bimetals acting through the

slides

66, 68 and the bell crank 74. Bell crank 74 has lever arm ratio which multiplies the bimetal force by a factor of 1.4. Since the switch 36 requires an extremely small force applied through a small distance, as described below, the bimetals 38 are very lightly loaded and therefore respond quickly to changes in the circuits they monitor.

Referring to FIGS. 1 and 5 the switch enclosure 24 has a top wall 86, bottom wall 88, front and back walls and 92 respectively, and one side wall 94; the opposite side wall is omitted, the enclosure 24 being closed at that side by wall 72 of the'base 22. -The switch 36 is secured to the base 22 by screws 96 that engage nuts 98 that are captive in the wall 72. Wall 90 and a keying projection 100 thereon are grooved at 102 to provide support and guidance for slide 68. A plurality of ventilation holes 104 and a contact sight or viewing hole v106 are provided in the side wall 94 and communicate to the interior of the switch enclosure 24.

A pair of stationary contacts 108, are mounted on

terminals

32, 34 respectively (FIG. 5). Terminal 32 is recessed in the enclosure wall 90 with contact 108 exposed to the interior of the enclosure. Similarly terminal 34 is recessed in a spacer block 112 with contact 110 exposed. The

terminals

32, 34 are provided with projections that closely fit appropriate recesses in the spacer block 11 2 and enclosure wall 90 to accurately and firmly position the

contacts

108, 110. The interior surface of the wall 90 and the surface of block 112 adjacent the

stationary contacts

108, 110 form smooth guide surfaces for the bridging contact 114 as shown in FIG. 11. Switch 36 is provided with a moving contact in the form of a bridge contact element 114 that simultaneously engages both of the coplanar

stationary contacts

108, 110 and is adapted to be moved relative thereto. Bridge con tact 114 has two active contact portions 114a,.114b of cylindrical configuration connected by an intermediate portion 114a of lesser diameter. The

stationary contacts

108, 110 and the bridging contact 114 are of high electrical conductivity metal such as silver. The cylindrical shape of the contact portions provides rolling engagement between the movable contact and the stationary contact during the resetting movement of the bridging contact to present a different portion of the bridging contact surface for engagement with the stationary contacts. Contac't portions 114a, 1141) are of different lengths, contact portion 114a being the longer of the two. Bridge contact 114 is mounted on a contact carriage 116, of insulation, formovement relative to the

stationary contacts

108, 110, and is capable of assuming a plurality of positions relative to the companion contacts as will be described in detail below. Contact carriage 116 has a complex unitary body portionthat is provided with a plurality of operative surfaces. Knob 118 and spacer 119 are formed on one side of the carriage. The knob 118 serves two separate functions; the knob functions as a latch member and as a cam follower. Reset cam 120 and helper cam 122 are formed on the other side of the carriage for cooperation withother portions of the switch 36 to be described. Contact carriage 116 is recessed at 124 and 126 at the top and bottom, respectively, for slidable retention on an end mounted support lever or guide member 128, of metal. Lever 128 is, in the embodiment of the drawings, approximately 1% inches long. The recesses at the top and bottom of carriage are of different lateral width for engagement with the upper and lower portions of the lever which are of corresponding width. The lower portion of lever 128 also provides a stop 130 for the carriage. An aperture 132 is formed in lever 128 to reduce the vibration sensitivity of the switch by reducing the mass of the lever and thereby reduce its inertia. Since the overload relay may be subjected to vibration, the reduction in vibration sensitivity of the moving parts of the switch 36 v is extremely advantageous.

Lever 128 is affixed at one end, as by staking, to a flat mounting spring 134 of unique configuration. A push-off compression spring 136 reacts between mounting spring 134 and carriage 116 to bias the carriage away from the lever mounting. Spacer 138 is interposed between the push-off spring 136 and the carriage 116 to provide a bearing surface for the spring. Lever 128 is formed at its free end to provide the cup-shaped portion 80 which has considerable width transverse the longitudinally extending body A") of the lever. The cup has a flat bottom surface 140 for engagement with bell crank arm 74a.

The front section of contact carriage 116, as viewed in FIG. 6, is U-shaped and has a pair of legs 140 and a bight portion 142 that project perpendicularly to the plane of its support lever 128. Contact 114 is positioned between the legs 140 and is resiliently urged into the bight portion 142 by the contact pressure coil spring 144. In the latched-contact condition a contact pressure spring 144 applies a contact pressure of approximately one ounce to the engaged contacts. Spring 144 is positioned in a passageway 146 in the body of the carriage and reacts between the lever 128 and the intermediate portion 1140 of the contact. The coil diameter of spring 144 is slightly less than the space between the legs and it is also slightly smaller than the length of the cont-act intermediate portion 114a. The spring and the contact are thereby interengaged and retained in the contact carriage but are movable relative thereto for purposes to be described below. The bridging contact may pivot in the plane of the legs but is prevented thereby from pivoting in any transverse plane. When the

contacts

114, 108, 110 are engaged the bridging contact 114 is displaced from the bight portion 142 thereby'compressing spring 144 to provide contact pressure.

A substantially square flat mounting spring 134 supports lever 128 and is formed of relatively thin spring material such as phosphor bronze or berrylium copper. Edge portions 134a, 1341), 1340, 134d of the spring are bent downward (FIG. 5) to stiffen the spring and for mounting the spring in the enclosure. It will be noted that opposed edges 134b and 1340 are tapered in width from edge 134a to edge portion 134d. Appropriately sized but parallel-sided recesses 148, 150 are provided in the front wall 90 and in a molded post 152 that extends from side wall 94, respectively, for receiving the tapered edges portions 134b, 1340 in a force fit. Recesses 148, 150 are displaced from one another vertically to incline the plane of the face 1342 of the spring relative to the front wall 90 thereby biasing the contact carriage 114 toward the front wall 90. The bias of lever 128 is approximately 1% ounces measured at the end 80 of the 1%." long lever 128. When the reaction of contact pressure spring 144 (one ounce) at the mid point of the lever GA" from the mounting spring) is deducted then the bias is ap roxi mately one ounce. The remaining bias plus a small amount due to the friction at the latch is the force that must be supplied by bell crank 74 to cause unlatching of the contact carriage. This low operating force is further reduced by the 1.4/1 mechanical advantage of the bell crank and allows the bimetals 38 to operate primarily as positioning devices with negligible loading. Therefore sensitive bimetals may be used. Arecess 154 in the side wall 94 interconnects recesses 148, 150 and receives spring edge 134a. Spring edge 134d is received in recess 156 formed in the spacer block 112 and firmly engages the bottom of the recess.

The face portion 134e of the mounting spring is provided with a pair of oppositely directed

concentric slots

158, 160. While the slots of the presently preferred embodiment are shown as arcuate or crescent shaped, it is conceivable that other configurations may be successfully employed. The end of lever 128 is secured to the center segment of the spring face 1342 with the longitudinal axis A-A of the lever concentric with the

slots

158, 160 and with the broad faces of the lever facing the bight of the arcs. The slots each extend in a cross-over relation beyond a plane BB which is, for purposes of definition,

identified as the central plane of the lever parallel to the broad faces of the lever. Lever 128 is thus connected to the outer or edge portions of the spring by a pair of diametrically opposed strips or

hands

162, 164 of spring material that remain between the overlapped portions of the slots. The C-C plane, a third plane of reference, is perpendicular to both the B-B plane and the axis A-A of the lever 128. The longitudinal axis A-A of the lever is initially angularly inclined in the BB and C-C planes before assembly to the enclosure to provide initial bias of the lever for purposes to be described below. When force is applied to the cup at a point that is not on the axis A-A twisting of the lever might occur. However, due to illustrated construction the lever is restrained against rotation or twisting about the axis AA by the

strips

162, 164 that act as end loaded Columns. This feature prevents twisting movement of the lever when the bell crank 74 operatively engages the cup 80 along surface on either side of the lever axis A-A.

Lever 128 may be pivoted about its mounting spring end in either the BB plane or the CC plane.' In pivoting the lever in the BB plane the stri s 162, 164 are twisted and act as torsion springs. In pivoting the lever in the C-C plane the

strips

162, 164 act as cantilevered leaf springs. The spring force required to deflect the strips when they act as either torsion springs or leaf springs is considerably different; much greater force being required to twist the strips. The strips, due to their column action, effectively prevent rotation of the lever about its axis A-A and provide differing bias forces resisting movement of the lever in either the BB or CC plane; the bias being greatest in the BB plane wherein the strips act as torsion springs. The foregoing structure provides a unique mode for mounting lever 128 in that friction at the pivot of the lever is avoided and at the same time the mounting provides different degrees of freedom of movement having different biasing forces associated therewith.

Referring to the drawings and particularly to FIGS. 13, 13a and 14, the contact carriage 116 and bridging contact 114 carried thereby, is capable of assuming a number of positions, in sequence, relative to the

stationary contacts

108, 110. In the latched position of the carriage the

contacts

108, 110, 114 are engaged and the carriage is releasably held against the sliding movement along the lever 128 by the engagement of the knob 118 and

latch surfaces

166a, 166/). Latch surfaces 166a, 1661] are formed on the interior face of the enclosure wall 94 and are contiguous and mutually perpendicular. The relaf tionship between latch surfaces 166a and latchsurface 166i) is shown in FIGS. 13 and 14 of the drawings. The under surface 118a of the knob is urged against latch surface 166a by the spring 136. The nose portion 118b of the knob is urged against lat-ch surface 166!) by the torsional aspect of the mounting spring 134 acting through the lever 128. The latch surfaces 1660, 16611 terminate ata position remote from the

stationary contacts

108, 110 at a common latch edge 168. With respect to latch surface 16601 the latch edge 168 marks the beginning of a contoured guide surface 170 which cooperates with the knob 1180 as will be described below. With respect to latch surface 16612, the latch edge 168 marks the short steep edge of a drop to a relatively flat receptor surface 162. When the knob portion 118b engages this surface, the carriage is said to be in its unlatched condition. The guide surface 170 is between and perpendicular to both a ramp 174, which has one end at the receptor surface 172, and a reset cam surface 176 which has one end at the latch surface 166a. Both the ramp 174 and the reset cam surface 176 have their other end at a second fiat surface 178. When the knob portion 118-b engages the fiat surface 178 vertically beneath its latched position on the latch surface 166a as illustrated in FIG. 13, the carriage is said to be in its resettable position. When the knob portion 118!) is in engagement with the fiat surface 178 but is displaced laterally from its resettable position, the carriage is said to be in its released remote position. Referring to FIG. 14, the flat surface 178 is intermediate the highest portion of the return cam surface 176 and the lowest portion of the ramp 174 but higher than the level of the latch surface 166]; and the level of the receptor surface 168.

- Switch 36 is provided with a resetter 182 which has two functions. The resetter is operable to effect resetting or relatching of the contact carriage; and it is also operable as a stop button for interrupting the circuit through the latched contacts. Resetter 182 is slidably captive between the switch enclosure 24 and the end wall 72 of the base 22 for reciprocating movement in a direction substantially parallel to the longitudinal axis of lever 128 when the carriage 116 is in the resettable and latched position. An end portion 184 of the resetter extends to the exterior of the switch enclosure 24 where it is accessible for operation of the reset member. The resetter is normally biased to the position shown in solid lines in FIG. 7 by a torsion spring 186 which reacts between the front wall 90 of the enclosure and notch 188. Beveled cam 190 is adapted to engage the reset cam 120 of carriage 114 in the resettable position thereof for restoring the carriage to its latched position. Resetter cam 190 has an angled face 190a that engages an angled face 120a of the reset came to deflect the carriage 116 and a fiat face 19% that engages a flat face 120!) of the reset cam for lifting the carriage. The reset cam 120 is normally out of the plane of the reciprocating movement of the resetter cam 190. Only when the carriage 116 is tilted in the BB plane toward the path of the resetter is the cam 120 in position for engagement with the resetter cam 190. The functions of the resetter will be more fully described during the discussion of the operation of the device. Resetter 182 has a tapered finger 192 which engages the bridging contact 114 during the reset operation to prevent contact closing until the carriage 114 is fully reset to the latched position. When the resetter is operated as a stop button with the contacts latched, the resetter interposes tapered finger 192 between the bridging portion contact 1140 and its companion stationary contact 110 (FIG. 7) thereby pivoting the bridging contact 114 away from the stationary contact. The reset and stop strokes of resetter 182 are identical and are shown in phantom lines in FIG. 7. Protuberance 194 is provided on the resetter opposite the cam 190 to minimize friction between the resetter and the base wall 72.

Referring to FIGS. 5, 8 and 12 the spacer block 112 is provided with a beveled surface 196 which is adapted to engage the helper cam 122 of the contact carriage in order to insure the separation of the reset cam 120 of the contact carriage from the resetter 182 at the end of the reset operation.

Referring to FIGS. 4, 5, ll and 12, calibration means 84 for setting the trip point of switch 36 includes lever 200 which is pivoted on a projection 202 in the switch housing 24. One end of the lever is formed to provide an indicator finger 204 that is visible through a slot 206 in the switch enclosure wall 86. Calibration lever 200 is maintained in a bearing groove formed in the projection 202 by spring 208 which reacts between the lever and the wall 72. Spring 208 is retained in position by lances 210. The position of lever 200 is changed by movement of an adjustment screw 212 supported at one end by wall 94 and at the other end by a bearing member 214. Bearing 214 engages an unthreaded portion at the end of the screw. Adjustment screw 212 threadedly engages a slide nut 218 which is held captive on the calibration lever by ears 220. Nut 218 slides along the lever as the relative position of the lever and screw are changed by the rotation of the screw. Manually graspable knob 216 is affixed to the end of the screw 212 which projects outside the enclosure to afford means for pivoting the lever and changing the trip point of switch 36.

Ambient temperature compensation for the overload relay is incorporated in the calibration means by a pair of

bimetals

222, 224 affixed to the end of the lever 200. The high expansion side of the compensating bimetals is in the same relative position with respect to the

slides

66, 68 as that of the bimetals 38 so that their position changes correspondingly with changes in ambient temperature. The compensating bimetals are joined together where they are secured to the lever but they are spaced from one another at their free end by a projection 226 formed on the bimetal 222. This construction allows relative movement between the bimetals without constraint which might possibly occur if they are joined together at both ends. Two bimetals are used to provide necessary stiffness while providing sensitivity. Bimetal 224 is longer than bimetal 222 and has its free end formed to provide a detent 228 for the stop 82 on the slide 68.

Reference will now be made to a typical mode of operation of the present overload relay, to facilitate a more thorough understanding of the invention. In the following description the trip-free switch 36 is initially in its latched condition with the bridging contact 114 in engagement with its companion

stationary contacts

108, 110. Referring to FIG. 15, when the start switch 232 is closed, the solenoid 230 is connected, through the latched contacts of the switch 36, across the power lines L1, L2. Energization of the solenoid causes the starter bridging contacts 236 and the holding switch 234 to close their respective circuits thereby energizing the motor 64 and maintaining the solenoid energized although the start switch 232 is released.

Upon the occurrence of an overload or a phase failure the

slides

66, 68 are operated (as described in detail above) to pivot the bell crank 74. In the illustrated embodiment of the invention the bell crank is urged against the end of the lever 128 with an extremely low force of the order of one to one and a quarter (1 to 1%) ounces which is sufficient to overcome the bias due to the mounting spring 134 and the slight friction at the latch. Under the urging of the bell crank 74 the switch lever 128 is caused to pivot to the right as viewed in FIG. 7. Movement of the lever end 80 a distance of approximately & of an inch is suflicient to unlatch the contact carriage 114. The pivotal movement of lever 128, under the urging of bell crank 74 causes the knob 118 of carriage 116 to slide along the latch surfaces 166a, 166b the knob being maintained in contact with the latch surfaces by the pushoff spring 136 and the mounting spring 134. As the carriage moves the bridging contact is nonetheless kept in engagement with its companion contacts with negligible change in contact pressure by the contact pressure spring 144. If the cause of the pivoting movement of hell crank 74 is removed and the bell crank withdraws before the knob 118 is driven off the latch edge 168 then the carriage 116 and lever 128 return to their initial position. The initial position is determined by the balancing of the force of the contact pressure spring against the force produced by the mounting spring 134.

The contact carriage 116 remains latched and the switch contacts engaged until the knob 118 is driven off latch edge 168 at which time the contacts part with a rapid snap action. As the knob 118 drops off the latch edge 168 it moves in two directions: Nose portion 118b bounces on the receptor surface 172 and slides therealong to the ramp \174 while the side 1180 of the knob engages and slides along guide surface 176. These movements are produced by the combined bias of pushoff spring 136 and mounting spring 134. The push-off spring supplies sufficient force to overcome friction and causes the carriage to slide down along the lever 128 and the knob nose portion 118b to slide along the ramp 174. The movement along the ramp 174 deflects the lever 128 in the BB plane (FIG. 6) further stressing the mounting spring 134 by putting the

strips

162, 164 further in torsion. The movement of the carriage in the BB plane tilts the carriage and places the reset cam in the plane of the resetter cam 190. The bounce of the knob toward the receptor surface 172 appears to reduce the amount of friction between the knob and the various cam surfaces. As the knob portion 118b slides along the ramp 174, knob portion 1180 slides along the adjacent guide surface 176 which surface deflects the contact carriage further away from the stationary contacts (FIG. 10). The further rearward movement of lever 128 in plane CC (FIG. 6) is caused by push-off spring 136. The rearward movement further stresses the

strips

162, 164 which act as leaf springs when the lever 1'28 is deflected in C-C plane. This movement in the C-C plane insures that the reset cam 120 of the carriage will be clear of the reciprocating path of the beveled cam 190 of the resetter in any position of the resetter during the movement of the carriage from its latched to its remote released position although the reset cam is displaced into the plane of the path of cam 190 thus insuring trip-free operation of the switch 36. The rearward movement of the lever also moves the cup-shaped end 80 thereof slightly away from the bell crank 74 which initiated the movement of the carriage along the latch surfaces 166a, 1661).

When the carriage 116 has followed guide surface 170 and ramp 174 to their respective ends at the surface 178 and has reached the stop 130 on lever .128 the carriage 116 is free to snap forward toward the wall 90 to the released remote position of FIG. 13a under the bias of mounting spring 134 with knob portion 118b sliding along surface 178. The position of the bell crank 74 controls the movement of carriage from the released remote position to the resettable position. In turn, the position of the bell crank is dependent up on the condition of the controlling bimetals. If the bimetals are not in condition for the resetting operation then the lever 128 and carriage 116 are kept from the resettable position until such time as the bell crank is withdrawn. The short stroke of the bell crank in the tripping direction is mirrored in the short retracting movement thereof required before the carriage 1 16 is in position to be reset. This is advantageous since it reduces the waiting time needed before the switch 36 can be reset. The released remote position of the lever 128 is illustrated in phantom in FIG. 11. The resettable position of the lever and carriage is shown in solid lines in FIG. 11.

When the switch 36 has been tripped and the carriage is in either its resettable or released remote position the bridging contact portion 114b is visible through the sight hole 106 (FIG. 1) thus providing visual indication of the unlatched position of the contact 114.

The resetting operation occurs as follows once the bell crank 74 has withdrawn and the lever 128 and carriage 116 have reached the resettable position. When knob 118 reaches the fiat surface 178 the carriage 116 has been tilted so that carriage cam 120 is in the plane of the path of resetter cam 190. To reset the switch, resetter 182 is depressed and rides downwardly within the casing against torsion spring 186. Cam face 190a on the resetter engages inclined face 120a -of the carriage reset cam and deflects the carriage rearward (to the right as viewed in FIG. 11). The rearward movement of the carriage is continued until cam 120 snaps forward over cam 190 (FIG. 11) under the bias of the mounting spring 134. However, this forward snap movement of lever 128 is terminated by its engagement with the bell crank 74. The kinetic energy of the moving parts is transferred to the bell crank and causes the bell crank to pivot thereby bringing the

slides

66, 68 against the bimetals 38."

under the impetus of Resetter 182 is allowed to rise torsion spring 186 and the flat face 19% of cam 190 engages the corresponding flat face 12011 of the carriage cam (FIGS. 11 and 12) and lifts the carriage I116 and the knob 118 rides up cam surface 176 which still further deflects the carriage in the BB plane at the same time push-off spring 136 is being compressed. The increased deflection increases the torsional forces stored in the mounting spring 134 and becomes effective to insure separation of the cam 120 from the resetter 182 as soon as the knob 118 passes over the edge of latch surface 166a. Toward the end of the resetting movement one end 1141) of the movable contact engages the stationary contact 108; however, the other end 114a of the contact is pivoted away from its companion contact by the finger 192 of the resetter. When the resetter has lifted the carriage 116 to the point where knob 118 snaps into the latched position the contact end 114a drops off the finger i192 onto stationary contact 110 with substantially snap action. The carriage 116 is, in its latched position, out of the plane of the path of movement of resetter 182. Finger 192 is also used to interrupt the circuit, that is, when the contacts are in the latched position if the reset member 182 is depressed, finger 192 is interposed between the stationary 110 contact and the contact end 114a thereby interrupting the circuit.

If the carriage 116 fails to leave the resetter 182 when knob 118 reaches the latch position, continued rise of the resetter brings helper cam 122 on the carriage into con tact with the inclined surface 196 on filler block 112. This contact develops a lateral force on the carriage 116 which causes it to drop from the reset member into the latched position.

Referring to FIG. 9, the calibration mechanism 84 previously described makes it possible to adjust the tripping point of the overload relay for a desired current value, within a given range, 'without the necessity of changing either the heating elements or the bimetals. By adjusting the position of the de-tent 228 relative to the normal-load position of the stop 82 carried by

slides

66, 68 it is possible to fix the amount of travel of the slide which is allowable, in response to uniform overloads, before the switch 36 is operated. The adjustment screw 212 provides rapid and precise means for pivoting the calibration lever 200 to set the overload relay, the setting current valve being indicated by the end 204 of the lever together with the index scale on the enclosure exterior. The ambient compensating

bimetals

222, 224, of which detent 228 is a part, provides compensation which corresponds to and corrects for the efiects of the ambient temperature on the bimetals 38.

The overload relay and trip free switch described above are compact, sturdy, and relatively vibration resistant. By providing means for adjusting the current at which tripping of the switch will occur it is possible to utilize any given overload relay for a variety of applications thereby reducing the number of relays which must be kept in stock.

Although one embodiment of the invention has been shown and described it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A switch including an enclosure, an elongated guide member mounted in said enclosure and movable from a first position to a second position, a carriage slidably mounted on said guide member and movable therewith between said first and second positions, a movable contact on said carriage, companion contact means mounted in said enclosure and engageable by said movable contact for closing the switch, biasing means in said enclosure resiliently urging said carriage along said guide member from a normal position wherein said contacts are in engagement toward a position remote from said normal position, restraining means in said enclosure in engagement with said carriage when said guide member is in said first position for releasably holding said carriage in said normal position, and deflecting means adjacent said guide member and movable into engagement therewith for moving said guide member from said first position toward said second position to release said carriage from said restraining means thereby to free said carriage for move 1 i ment toward said remote position and to open said contacts.

2. A switch including a casing of insulation having first and second walls that adjoin one another, a pair of companion contacts mounted on said first wall, said second wall being formed to provide a latch surface thereon, a lever, means in said casing mounting said lever at one end thereof for pivotal movement in a pair of mutually perpendicular planes, said planes being each perpendicular to a respective one of said walls, a contact carriage slidably mounted on said lever for movement between latched and released remote positions, biasing means resiliently urging said carriage toward said released remote position, a bridging contact carried by said contact carriage for engagement with said companion contacts in said latched position of said carriage, said contact carriage having a portion thereof in engagement with said latch surface to releasably retain said contact carriage in said latched position, and means for pivoting said lever to effect relative movement between said carriage carried thereby and said latch surface for unlatching said carriage whereby said contact carriage is free to move to said released remote position.

3. A switch including a casing of insulation, an elongated guide member pivotally mounted in said casing at one end thereof and movable in a given plane, a carriage slidably mounted on said guide member and movable therewith, a movable contact carried by said carriage, companion contact means mounted in said enclosure, said companion contact means being engaged by said movable contact in the closed condition of the switch, biasing means resiliently urging said carriage along said guide member from a normal position wherein said contacts are in engagement toward a position remote from said normal position, restraining means in said enclosure releasably engaging said carriage in said normal position, means for releasing said carriage for movement to said remote position and thereby to cause opening of said contacts, a reset member operable in a reset path parallel to said given plane and spaced therefrom, and deflecting means in said enclosure cooperating with said carriage tor deflecting said carriage in a direction transverse said given plane during its travel from said normal position to said remote position to bring said carriage into cooperative relation with said reset member.

4. A switch including a casing, elongated guide means mounted in said casing, a carriage slidably mounted on said guide means for movement therewith and therealong, a movable contact on said carriage, companion contact means mounted in said casing, said companion contact means being engaged by said movable contact in the normal closed condition of the switch, means resiliently urging said carriage along said guide means from a normal position wherein said contacts are closed toward a position remote from said normal position, contact pres sure means reacting between said movable contact and said carriage for resiliently urging said movable contact toward a projected position for engagement with said companion contact means, means for releasably restraining said carriage in said normal position against the bias of said first-mentioned biasing means, means for releasing the restraining means so that said carriage is moved by said carriage biasing means to said remote position, a reset member mounted in said casing and operable in a forward stroke and in a return stroke, said reset member including a first portion engageable with said carriage when said carriage is in said remote position for interlocking engagement therewith so that when said reset member is operated in said return stroke said carriage is operated into its normal position, said reset member additionally having a second portion engaging said movable contact for retracting said movable contact relative to said carriage during the return stroke of said reset member and until completion thereof, said second portion of said reset member being effective to retract said movable contact and thereby open said contacts when said reset member is operated in said forward stroke while said carriage is in its normal position.

5. A switch including a casing, an elongated guide member mounted in said casing, said guide member being movable from a given position in each of a first and second direction, a carriage slidably mounted on said guide member and movable therewith in both said directions, a movable contact on said carriage, companion contact means mounted in said casing, said contact means being engaged by said movable contact in a normal position of said contact carriage, resilient means engaging said carriage for biasing said carriage along said uide means from said normal position toward a position remote from said normal position, restraining means in said casing cooperating with said carriage when said guide member is in said given position for releasably holding said carriage in said normal position, means in said casing adjacent said guide member and movable into engagement therewith for deflecting said guide member in said first direction to release said carriage from said restraining means, further means in said casing cooperating with said carriage during movement thereof from said normal position to said remote position upon release of said restraining means for deflecting said guide member in said second direction, and a reset member mounted in said casing, said reset member being movable along a given path for engagement with said carriage to effect reset thereof upon deflection of said carriage in said second direction.

6. A switch including a casing, an elongated guide member mounted in said casing and being movable from a given position in each of a first direction and a second direction substantially perpendicular to each other, a carriage slidably mounted on said guide member and movable therewith in both said directions, a movable contact mounted on said carriage and companion contact means mounted in said casing, said contact means being engaged by said movable contact in a normal position of said contact carriage, means biasing said carriage along said guide member from said normal position toward a position remote from said normal position, restraining means in said casing cooperating with said carriage when said guide member is in said given position for releasably holding said carriage in said normal position, means adjacent said guide member and movable into engagement therewith for deflecting said'guide member in said first direction to release said carriage from said restraining means, means in said casing cooperating with said carriage during movement thereof from said normal position to said remote position after release of said restraining means for deflecting said guide member in said second direction, cam means in said casing engageable by said carriage for increasing the deflection of said guide means in said first direction during the travel of said carriage from said normal position to said remote position, spring means in said casing biasing said guide member toward said given position so that, upon completion of the travel of said carriage along said cam means, said carriage and said guide member are released for snapping return motion toward said releasing means, and a reset member movably mounted in said casing for movement along a given path substantially parallel to said guide member in its given position, said reset member being engageable with said carriage to eflect reset thereof upon deflection of said carriage in said second direction.

7. A switch including a casing of insulation having adjoining substantially planar first and second walls, a pair of companion contacts mounted on said first wall, latch means forming a part of said second wall, said latch including a projecting latch surface, a lever-like guide member mounted in said casing for pivotal movement in a pair of planes substantially perpendicular to the planes of each of said walls, respectively, a contact carriage slidably mounted on said lever for movement I in said enclosure for engaging said therewith and therealong whereby said contact carriage assumes latched, unlatched, remote released and resettable positions, in the sequence nammi, a bridging contact mounted on said contact carriage for'circuit closing engagement with said companion contacts, biasing means resiliently urging said contact carriage along said lever, said contact carriage including a latch portion for cooperation with said latch surface for releasably retaining said contact carriage in said latched position wherein said bridging contact engages said companion contacts, operating means operable in forward and reverse strokes for pivoting said lever in said forward stroke and thereby moving said contact carriage from said latched position to said unlatched position wherein said contacts are disengaged and said biasing means is free to shift said contact carriage to said released remote position, said operating means in said reverse stroke shifting said contact carriage from said released remote position to said resettable position, a resetter mounted in said casing for reciprocating movement in a given plane spaced from said plane of said second wall, said contact carriage being out of said resetter plane when said carriage is in said latched and unlatched positions, a cam surface on said second wall projecting above said plane of said wall, a cam follower on said contact carriage for engagement with said cam surface as said carriage moves from said unlatched position to said released remote position, said cam surface causing said cont-act carriage to be shifted into said resetter plane, said contact carriage being in said resetter plane in said released remote and said resettable positions, said resetter and said contact carriage having portions which mutually engage in said resettable position of said contact carriage for returningsaid contact carriage to said latched position.

8. An overcurrent responsive relay including an enclosure, a pair of stationary contacts mounted in said enclosure, a lever-like guide member, means mounting said lever in said enclosure, a contact carriage slidably mounted on said lever for movement therewith and therealong, a relatively movable bridging contact mounted on said contact carriage for engaging said stationary'contacts in a closed circuit position, bias means urging said contact carriage and said bridging contact carried thereby towardan open circuit position adjacent one end of said lever, latch means in saidenclosure for engaging said carriage to releasably restrain said bridging contact'in said closed circuit position, overcurrent responsive means for operating said latch means to release said contact carriage, and reset means for said carriage movably mounted in said enclosure, said reset means beingioperable to engage said contact carriage for returning said carriage to said latched closed circuit position thereof.

9. An overcurrent responsive relay including an enclosure, a pair of coplanar stationary contacts mounted in said enclosure, a lever-like guide member, means mounting said lever in said enclosure, a contact carriage slidably mounted on said lever for movement therewith and therealong, a relatively movable bridging contact for engaging said pair of stationary contacts in a closed circuit position, bias means urging said contact carriage and said bridging contact carried thereby toward an open circuit position adjacent one end of said lever, latch means carriage to releasably restrain said bridging contact in said closed circuit position, overcurrent responsive means in said enclosure for operating said latch means to release said contact carriage, and reset means mounted in said enclosure, said reset means being operable to engage said contact carriage for returning said contact carriage from said open circuit position to said latched closed circuit position thereof, said reset means including a portion interposable between said bridging contact and at least one of said stationary contacts in said latched position of said carriage to thereby interrupt the circuit to said contact without releasing said carriage.

10. An overcurrent responsive relay including an enclosure, a pair of stationary contacts mounted in said enclosure, a lever-like guide member, means mounting said lever in said enclosure, a contact carriage slidably mounted on said lever for movement therewith and therealong, a relatively movable bridging contact for engaging said pair of contacts in a closed circuit position, bias means urging said contact carriage and said bridging contact carried thereby toward an open circuit position adjacent one end of said lever, latch means in said enclosure for engaging said carriage to releasably restrain said bridging contact in said closed circuit position, said latch means including a stationary latch surface, said latch surface terminating in a latch edge, a cooperating latch member forming a part of said contact carriage, spring means movable with said contact carriage for providing contact pres sure between said bridging contact and said stationary contacts, said carriage being movable along said latch surface toward said latch edge and away from said stationary contacts, said spring means maintaining said contact pressure during said movement until said latch member passes said latch edge, overcurrent responsive means for moving said contact carriage and said latch member along said latch surface and beyond said latch edge to thereby release said contact carriage for movement to said open circuit position, and reset means mounted in said enclosure for engagement with said contact carriage for returning said carriage to said latched closed circuit position thereof.

11. A circuit protective device including an enclosure, a pair of contacts mounted in said enclosure, a lever-like guide member, means mounting said lever in said enclosure for movement in a pair of transverse planes, a relatively movable bridging contact, means mounting said bridging contact on said lever for reciprocating movement along a longitudinal axis thereof between a closed circuit position in engagement with said pair of contacts and a remote open circuit position, biasing means in said enclosure resiliently urging said bridging contact mounting means to said remote position, latching means in said enclosure for latching said bridging contact and said pair of contacts in engagement, circuit condition responsive means in said inclosure for moving said lever in one of said planes to release said latching means whereby said bridging contact means is free to move to said open circuit position, means in said enclosure for moving said lever and said bridging contact mounting means in said second plane to a reset position upon release of said latching means, and reset means movably mounted in said enclosure for returning said bridging contact mounting means to said closed circuit position.

12. A load-responsive device including an enclosure, a controlled element mounted in said enclosure, said controlled element including a longitudinally extending T-shaped lever having a relatively narrow body portion and a broad faced end, pivotal mounting means in said enclosure for said lever, said lever being attached to said mounting means at the end opposite said broadfaced end, said mounting means including bias means predisposing said lever to a given position and means preventing twisting of said member about the longitudinal axis thereof, a pair of stationary contacts mounted in said enclosure, a contact carriage slidably mounted on said lever for movement therealong and therewith, a bridging contact carried by said contact carriage, said contact carriage being movable along said lever between a closed circuit position with said bridging contact in engagement with said stationary contacts and a remote open circuit position, spring means urging said contact carriage to said remote position, latch means in said enclosure for releasably restraining said contact carriage in said closed circuit position, said latch means being operable in response to pivotal movement of said lever to release said carriage, load-responsive means capable of engaging said lever at various locations along said broad face thereof for pivotally moving said lever to a carriage releasing position against the force of said bias means, and relatching means in said enclosure including means adapted to engage said contact carriage and for returning said carriage to said latched position thereof.

13. An electrical switch including a casing of insulation, a movable contact and a companion contact in said casing, said companion contact being engageable by said movable contact in a closed condition of said switch, and operating mechanism for said movable contact, said operating mechanism including a lever, mounting means in said casing mounting said lever for pivotal movement, a carriage member for said movable contact slidably mounted on said lever for movement therealong in a first path between a latched position wherein said switch is closed and a remote position wherein said switch is open, means in said casing resiliently biasing said carriage member to said remote position, latch means in said casing for releasably restraining said carriage member in said latched position against movement in said first path, said latch means being released upon movement of said carriage in a second path away from said stationary contact, said second path being transverse said first path, means resiliently resisting movement of said carriage and said movable contact in said second path, and means for pivoting said lever for moving said carriage in said second path to release said carriage.

14. An electrical switch including a casing of insulation, a movable contact and a companion contact engageable by said movable contact in a closed condition of said switch, and operating mechanism for said movable contact, said operating mechanism including a lever, mounting means in said casing mounting said lever for pivotal movement, a carriage member for said movable contact slidably mounted on said lever for movement therealong and therewith, said carriage member being slidable along said lever in a first path between a latched position wherein said switch is closed and a remote position wherein said switch is open, means resiliently biasing said carriage member to said remote position, latch means in said casing for releasably restraining said carriage member in said latched position against movement in said first path, said latch means being operated to release said carriage by movement of said carriage in a second path away from said stationary contact, said second path being transverse said first path, means in said casing resiliently resisting movement of said carriage member and said movable contact in said second path, means for pivoting said lever for moving said carriage in said second path to release said carriage, reset means in said casing for restoring said carriage member in said latched position, said reset means including a reciprocable member having a portion that selectively engages said carriage, said carriage being out of the plane of the path of movement of said reciprocable member in said latched position, cam means in said casing for guiding said carriage in a third path of movement transverse said first and second path of movement from said latched position wherein said carriage member is out of the path of said reciprocable member to its remote position wherein said carriage member is engageable by said reciprocable member for return thereby to said latched position upon operation of said. reciprocable member.

15. A switch according to claim 2 wherein said means for mounting said lever in said casing includes a relatively fiat member of spring material having an outer mounting segment and an inner segment, said inner segment being connected to said outer segment by oppositely disposed strips of said spring material, said lever member being secured by one end to said inner segment with the longitudinal axis of said lever normal to the fiat member, said strips functioning as cantilevered leaf springs in a first path of movement of said lever about the secured end thereof to bias said lever to a given position, said strips functioning substantially as torsion springs in a second path of movement of said lever about the secured end thereof to bias said lever to said given position, said strips acting as end loaded columns for resisting twist of said lever about the longitudinal axis thereof.

16. A switch according to claim 15 wherein said strips of spring material are defined by a pair of oppositely disposed slots in said spring material whose end portions overlap the longitudinal axis of said lever, said strips being those portions of the spring material remaining between the overlapped slot ends, which strips connect said inner and outer segments of said spring.

References Cited by the Examiner UNITED STATES PATENTS 2,199,477 5/1940 Besag 200-122 2,217,488 10/1940 Mahnke 200-116 2,411,351 11/1946 Armstrong ZOO-116 2,749,407 6/1956 Walton et al. 200-116 2,766,352 10/1956 Enderli 200-116 2,824,932 2/ 1958 Ellenberger 200-116 2,833,887 6/1958 Schrack 200-116 2,872,548 2/1959 Christensen 200-116 3,022,403 2/1962 Pukk et al 200-122 3,185,793 5/1965 Ellenberger 200-116 3,265,831 8/ 1966 Ramsay et a1 200-116 FOREIGN PATENTS 488,020 6/ 1938 Great Britain. 994,436 6/ 1965 Great Britain.

BERNARD A. GILHEANY, Primary Examiner.

H. B. GILSON, Assistant Examiner.

Claims

1. A SWITCH INCLUDING AN ENCLOSURE, AN ELONGATED GUIDE MEMBER MOUNTED IN SAID ENCLOSURE AND MOVABLE FROM A FIRST POSITION TO A SECOND POSITION, A CARRIAGE SLIDABLY MOUNTED ON SAID GUIDE MEMBER AND MOVABLE THEREWITH BETWEEN SAID FIRST AND SECOND POSITIONS, A MOVABLE CONTACT ON SAID CARRIAGE, COMPANION CONTACT MEANS MOUNTED IN SAID ENCLOSURE AND ENGAGEABLE BY SAID MOVABLE CONTACT FOR CLOSING THE SWITCH, BIASING MEANS IN SAID ENCLOSURE RESILIENTLY URGING SAID CARRIAGE ALONG SAID GUIDE MEMBER FROM A NORMAL POSITION WHEREIN SAID CONTACTS ARE IN ENGAGEMENT TOWARD A POSITION REMOTE FROM SAID NORMAL POSITION, RESTRAINING MEANS IN SAID ENCLOSURE IN ENGAGEMENT WITH SAID CARRIAGE WHEN SAID GUIDE MEMBER IS IN SAID FIRST POSITION FOR RELEASABLY HOLDING SAID CARRIAGE IN SAID NORMAL POSITION, AND DEFLECTING MEANS ADJACENT SAID GUIDE MEMBER AND MOVABLE INTO ENGAGEMENT THEREWITH FOR MOVING SAID GUIDE MEMBER FROM SAID FIRST POSITION TOWARD SAID SECOND POSITION TO RELEASE SAID CARRIAGE FROM SAID RESTRAINING MEANS THEREBY TO FREE SAID CARRIAGE FOR MOVEMENT TOWARD SAID REMOTE POSITION AND TO OPEN SAID CONTACTS.