US 3270301 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Aug. 30, 1966 a. s. BENGTSSON PLUG'J TYPE MINIATURE RELAY WITH TRANSPARENT COVER Fila'd June 13, 1963 6 Sheets-Sheet 1 FlG.l
i mm 2.0
8 8 7 7 m m I w FIG.4
INVENTOR. Bertil S.Benqtsson "Moses. Mc.Glek & Toren.
ATTORN E YS fl- 1966 B. s. BENGTSSON 3,270,301
PLUG-13! TYPE MINIATURE RELAY WITH TRANSPARENT COVER Filed June 13, 1963 6 Sheets-Sheet 2 I I I05 2l8 4 zoo INVENTOR. 5 Bartel S. Benqtsson FIG.8 45
Moses, Mc Glew 6 Toren ATTORNEYS 8- 1966 a s. BENGTSSON 3,270,301
' PLUG-IN TYPE IINI AS'URE RELAY WITH TRANSPARENT COVER Filed June 13, 1963 I 6 Sheets-Sheet 3 INVENTOR. Berti! S. Benqtsson 1 g MosesMaGlew G'Toren ATTORNEYS.
PLUG-IN TYPE MINIATURE RELAY WITH TRANSPARENT COVER File d June 1:. 1963 B. S. BENGTSSON 6 Sheets-Sheet m 0 u m. m v a n r on. Q 6.. a o o E m Q wm m a M M 92 W w 0 1 m w m. m w n a A $2 m @m. m m 9 H mm. m m 09 NH m M 8 Mm w o N2 \.|1l...\. m. NO 7N9 I! .QQ H v Q Ne m Q or. N. GE 1 om. v 22 N2 H \m- 3 8. v 31 M 5 NE N9 r Om 1 '07 e vs, w.
8. N. NE vh m OE E N! b! 1% Aug. 30, 1966 a. s. BENGTSSON 3,
PLUG-IN TYPE MINIATURE RELAY WITH TRANSPARENT COVER 6 SheetsSheet 6 Filed June 13, 1963 a /////A\ :;a/////. 0 INVENTOR BERT. s, BENGTssoN m BY 234 "3 "I mi 3.270.301 ILUF-IN 'lYlI". MINIA'I'LRE RELAY WITH TRANSPARENT COVER IIcrtii licngtsson. Scituatc, Mass., assignor t Sigma Instrumcttts Inc., a corporation of Massachusetts Filed June 13, 1963, Ser. No. 287,675 l3 Claims. (Cl. 335-129) This invention relates to electric relays and is directed to features of c nstruction of relays having the principal object. of providing a relay of the greatest possible reliability in action and long life.
It is an object of the invention to provide a relay construction which can be easily assembled. adjusted and, if necessary, repaired. With these objects in view, a feature of thc invention consists in a construction in which the various switch contacts as well as the means for mounting the armature for its pivotal movement are all located in the front part of the relay so that these elements which require adjustmcnt and testinga'nd may show wear with long use'arc all accessible without necessitating the dismounting of the relay from its support or disconnection of the relay from the conductors connected to the relay terminals.
Other objects of the invention are to provide an armature mounting which is strong and durable and to provide connections between the armature and the movable switch contacts which are easily assembled and which operate with a minimum of friction.
For simplicity of manufacture, it is another object of the invention to provide a motor assembly which may be mounted on the base of the relay and a switch assembly which may be mounted on the motor assembly and connected therewith by contact finger lifters which transmit motion directly from the armature to the contact fingers without actual attachment to either the armature or the contact lingers. The contact fingers are preferably mounted in a pileor piles parallel with the actuating coil of the relay and so arranged that all space within the'relay casing is utilized most economically. thereby permitting the relays to be made of minimum overall dimensions.
A novel mode of assembly is. preferably used for the contact lingers in which they are held in accurately spaced relationship. which is not dependent upon the intcrleav'ingof the contact members and insulation layers. Accuracy of spacing is secured and is maintained throughout the life of the relay. Where insulating spacers are used to separate the lingers. changes in dimensions of the pileup may occur due to atmospheric conditions which cause swelling or shrinking of the insulating layers. Where spacing is dependent on interleaved layers, exact thickness of the layers must be secured and errors due to inaccuracy of thickness are cumulative.
Another feature of the contact fingers and means for mounting the samepcrmits the flexible part of the fingers to be made much longer than in prior art constructions without increasing the overall sire of the relay. The use of the long lingers enables them to be made of thicker stock than it short fingers were utilized and still permit the lingers to have the necessary flexibility. The life' of the contact lingers is thereby prolonged. The use of thicker stock als provides lingers of greater conductivity which reduces the internal resistance of the relay. The thickness of thc lingers also p r o'vides better contact alignment and enables the lingcrsiito resist distortion due to shock. i
lhe improvenwnts in mounting and dcsign'of the contact fingers described form the subject matter of an applicatiun for United States Patent filed on June It, I963,
United States Patent 0 Serial No. 287.03 now Patent No. 3,236,987 and there- I tore are not specifically covered herein. However, in-
3,270,301 Patented August 30, 1966 sofar as these features are specifically applicable to and embodied in the relay construction itself, claims to the relay including some of these details are made in the present application.
A further feature of the invention relates to an improved mounting of the armature.
mcnt'of the invention shown in the accompanying drawings. which form a part of this specification.
In the drawings:
FIG. 1 is a front view. FIG. 2 a side view, FIG. 3 a rear view and FIG. 4 atop view of therelay. In FIGS. 1, 2 and 4 the casing is shown in section;
FIG. 5 is a view on a larger scale showing the front of the relay casing with the casing retaining spring removed; 1
FIG. 6 is a perspective view of the front parts of the casing being broken away;
FIG. 7 is a vertical sectional view of the front of the casing and means for securing it;
FIG. 8 is a horizontal section of the parts shown in FIG. 7;
FIG. 9 is an exploded parts of the relay.
FIG. 10 is a side elevation of the coil, armature and certain'of the contact fingers, parts being broken away;
FIG. 11 is an elevation of the stationary contact fingers of the pile-up;
FIG. 12 is a side elevation of the pile-up shown in FIG. 11;
FIG. 13 is a view similar to FIG. 11 showing a part of the movable contact pile-up assembled with the fixed contact pile-up;
FIG. 14 is a front elevation showing the complete assembly of the fixed and movable contact fingers;
FIG. 15 is a fragmentary elevation on an enlarged of the relay,
perspective view showing various FIG. 16 is a fragmentary section showing the engage ment of one of the bracket plates with the comb;
FIG. 17 is a top view of the movable contact pile-up showing the movable contact fingers and one of their supporting combs;
FIG. 18 is an elevation of onc of the movable contact pile-ups showing the right hand set of fingers only;
FIG. 19 is a side elevation of the movable contact pile up shown in FIG. 18;
FIGS. 20 to 26 show a socket construction which may be used in connection with, the relay; FIG. 20 being a front view of the socket; FIG. 21 being a section on line 2I-2l of FIG. 20; FIG. 22 a rear view; FIG. 23 a perspective of a relay holding frame carried by the socket; FIG. 24 a section on line 24-24 of FIG. 20; FIG. 25 an enlarged sectional perspective showing the inside of one of the recesses in the socket; and FIG. 26 is an enlarged perspective of one of the spring contact clips.
In the drawings, some of the figures are on a larger scale than other figures. It will be understood, of course, that the actual dimensions of the relay will depend upon the use for which the relay is designed. The construction. however. can be embodied in very small relays and, in the case of the particular construction chosen for illustration, an idea of the actual size of the relay may be bin 32 and having a ferrous core 34. The bobbin is of rigid material such as a phenolic plastic and has a conventional head 36 at its front end and a head 38 at its rear end which carries a terminal block 40 having holes 42 in which are mounted the terminals 44 to which the ends (not? shown) of the coil windings are attached. The coil is mounted in a- U-shaped frame 48 ofmagnetic material. Shield plates 49 and 50 of a hard plastic, secured to the frame 48 by screws 51, serve the two-fold purpose of switch support and dust cover.
The front end of the core projects through the pivot plate 60 and has an enlarged head 62 resting on and supporting the plate. The pivot plate is preferably made of the form shown with an angular section 64 having knifeedgcs 66 upon which the armature 68 pivots. The pivot plate is made of non-magnetic material such as Phosphor bronze. The making of the pivot plate of non-magnetic material is important as it greatly increases the wear resistance because of lower pressure on the pivot edge, as
the magnetic field will not traverse the pivot plate, and also due to the same cause magnetic particles which would increase wear will not be attracted to this area. There is no fiux concentration at the knife-edge'as would occur if the pivot plate were of magnetic material. The armature 68 comprises a major portion 69 which passes across the head 62 of the corc a rearwardly bent section 70 which pivots on the knife-edges 66, and two spaced operating arm portions 72 which engage the contact spring lifters 74 which form the operative connection between the motor and the movable contact springs to be described.
in the armature. The pivot plate is provided with side lugs 86 which enter slots 88 in the sides of the frame 48 so as to locate' the pivot plate properly and help in sup porting the coil in position. The rear end of the core 34 projects through the bobbin 32 and fits tightly in a hole 90 in the rear end of the frame 48. The rear end of the core preferably makcs a driving fit with the hole 90 so that when driven through the hole, the bobbin and pivot plate 60 are locked firmly between the back of the frame and thehcad 62 of the core. The frame 48 is also provided with lugs 91 which form stops for locating the contact pile-ups, as will-he described below.
The armature 68 is held in position by means of a return spring 92 which has a portion 94 terminating in two lugs 96 which engage the T-hcad 84 of the pivot plate. The spring also has a return bend portion 98 which terminates in a bent edge flange 100 which tits in the wide portion 77 of the slot 76 in the armature and bears on the lugs 78. The spring 92 positions the armature by holding the rearwardly bent portions 70 in contact with the knife'edgcs 66 of the pivot plate. The springalso applies a biasing force to the armature which holds the lower edge of the armature portion 69 against the back stop tabs 80 of the plate 60. When the coil is energized, the armature part 69 is drawn towards the head 62 of the core until it is parallel therewith. This causes the arms 72 of the armature to push upv the spring lifters 74. The spring 92 provides the necessary biasing force to hold the armature part 69 away from the cadet the core when the coil is not energized.
When the relay is mounted against a perpendicular panel, as in the instance described, the coil is horizontal and the armature is on the frontend of the coil so that if the casing or housing of the relay is removed, the armature is exposed to view and its pivotal mounting on the knifecdges may be inspected and any defects corrected. Furthermore, the return spring 92 is also at the front end of the coil where it may be inspected and ad justed. The force applied by the spring may be adjusted by bending the tongue 82 of the pivot plate to which the end of the spring is attached.
The frame member bottom is provided with threaded holes 102. At the outer ends of the side arms of the frame, extensions 104 are provided which project through slots in the relay cover and which have slots 105 therein to receive the, retaining tongues of the cover retaining plate to be described below.
The switch assembly comprises a group of bracket plates carrying contact fingers and held together by comb members in a mani ncr which will be described in detail below. On the sides of the. pile-up assembly 106 are mounted spacer plates 107. This pile-up assembly is mounted adjacentto and carried by the frame 48, one of the spacerplates 107 resting on the side members of the frame-48 and bear- I ing againstthelugs 91. The pile-up assembly is directly secured in this position by means of a spring clip 108 having arms extending on each'side of the pile-up assembly and having an inwardly curved end 111 which holds the pile-up assembly against the frame. The ends of the arms of the spring clip 108 are bent over at 109 and snap over the lugs 110 on the frame, the curved end 111 being partly straightened out during this process so as to hold the pile-up in position under constant spring tension. The curved end 111 is provided with holes 112 in which parts of the pile-up mounting means are received. Inside of the spring clip a U-shaped layer of insulation 113 the holes 114 matching the holes 112. v
1n the construction here shown and as disclosed in said patent application Serial No. 287,039, the contact fingers are not piled one on. top of the other separated by insulating separators. Instead, the contact fingers are held in spaced relationship by means of notched combs which are passed through holes in the brackets carrying the contact fingers and forced into engagement with the edges of the holes by means of expansion elements, such as wedges.
Referring to FIGS. 11 and 12, these show the stationary contact pile-ups, each member comprising a bracket or plate having a long slot 122 therein and a shorter slot 124. Two of these stationary pile-ups are used in the illustrated construction as shown in FIGS. 1, 4 and 14. A series of the plates or brackets 120 is set up in a nest or fixture (not shown) which holds the plates or brackets in position properly spaced apart. The combs 125 and 126 are then inserted in the slots 122 and the wedges 128 are driven between the backs of the combs so as to force the notches 130 in the combs into engagement with the ends of the slots 122. The ends of the slots are wedge-shaped as indicated at 132 so that these wedgeis preferably mounted, this layer of insulation having shaped edges will bite into the combs at the bottom ot' the notches 130 and lock the bracket plates firmly in accurately spaced position. The combs 126, in addition to the notches 130, also have notches 134 between the .156 the spring contact fingers 160.
bracket-engaging notches, the notches 134 being for engagement with projections [36 formed on the bracket plates 150 on which are mounted the armaturemovable contact fingers to be described. The bracket plates 120 are provided with tabs 138 which, when the spring pileups are mounted in the relay, project through holes in the shield plates so that they may be plugged into suitable sockets or may be soldered to connecting wires or otherwise connected in circuit. The holes in the shield plates are preferably arranged in dilleriug but registering series as shown in FIG. 3. In one of the plates, for instance plate 49, are six holes 139 arranged in three rows of two each, two tabs 138 passing through each hole. In -plate there are three holes in each row, two narrow holes 139a each receiving one tab, and a wider central hole 13%, through which pass the two adjacent central tabs of each row. This arrangement of the holes and tabs provides a completely enclosed base, permits easy assembly and gives better support and alignment to the tabs.
The bracket plates preferably do not form the actual contact fingers or carry the contact buttons as in most spring-pilc-ups. Instead, the contact buttons 140 are carried on the ends of spring contact fingers 142 which have slots 144 therein wide enough to pass freely over the combs 125 and 126 and wedges 128, without contact therewith, the lower ends of the contact fingers being welded or otherwise secured to the bracket plates 120 below the slots 122 as indicated at points 146. In this way, a very substantial increase in length of the contact fingers is secured without any increase in the overall length of the spring pile up. This is because the contact fingers bend from points 146 which are at the further end of the means by which the contacts-are mounted, as represented in this case by the rear combs 126. On the contrary, in the ordinary spring pile-up, the only flexible part of the spring is that from the forward ends of the spacers between the contact fingers (which in this '-The movable contacts 164 mounted on the contact fingers 160 are moved by the lifters 74 which have rounded instance would be represented by the forward combs I 125) to the buttons of the contact springs. With the present construction, the length of the flexible contact fingers is practically at least double the tllexible length which could be secured by the old construction. This decreases the sharpness of the bend, reduces metal fatigue and enhances durability. It also has the important advantage of permitting a heavier stock to be used in the contact fingers, thereby securing a greater rigidity in a lateral direct-ion and .better alignment of the contacts. The greater weight of stock also provides a greater current capacity thereby reducing the resistance of the contact fingers of the relay. By properly shaping the contour of the contact fingers, the desired spring pressure of the fingers may be secured. In other words, the spring contact fingers are so shaped initially that they will press with a given force against the outer ends of the bracket plates and will present the proper resistance when engaged by the movable contacts.
A somewhat similar pile-up is used for the armature moved contacts. These contacts, as shown particularly in FIGS. 17, I8 and 19, comprise flanged bracket plates 150 which are held together by means of combs 152 separated by wedges 154 similar to the combs and wedges shown in connection with the stationary spring pile-ups. Brackets 150 have flanges 136 to which are welded at The brackets and fingers are formed as rights and lcfts arranged alternately and intermeshing respectively with the two series or stationary cont-act pile-ups described. The contact fingers have slots 162 therein through which pass the lifters 74 aforementioned. At the outer ends of the contact fingers 160 are the movable contact buttons 164. The assembled spring pile-ups are completed by having spacer plates and 172 placed on the sides thereof, these plates having holes 174 formed therein which snap over the ends of the combs.
bearing ends which rest on the armature portions 72.
.The lifters are provided with notches 192 which engage the movable contact fingers 160. The lifters pass through the slots 124 in the plates 120 and through the slots 147 I in the contact fingers 142. This means of connecting the motor to the switch elements is of the simplest character and embodies no connecting means other than the mere pressure of the curved portions 190 against the armature. There is an absolute minimum of friction. The lifters are preferably made of a very light material such as a hard plastic and the inertia of the movable system is reduced to a minimum. The armature itself has no switch parts permanently affixed thereto.
T he relay housing In many if not most instances, it is desirable to enclose the relay in a tight housing. 'It is also desirable to.
make the housing of a transparent material as this permits the operation of the relayto be inspected without nemoval of the housing. In many prior relays, plastic housings have been used which were secured to the relay by having parts of the plastic snapping into engagement with the relay base. However, where it was desired to use a transparent housing, ditficutly was ex perienced because the transparent material most available for housings is not resilient enough to form a part of the housing mounting means by snapping with projecttions or otherwise so as to hold it in place. In ac cordance with the present invention, a housing is utilized which is held in place by means of a metal retainer so that the resiliency of the housing is not iself relied upon for this purpose.
In the construction shown, the plastic housing or cover is indicated at 200 and has fixed to its outer surface a retainer 202 which comprises a spring metal plate preferably of cruciform shape having long arms 204 fitting in grooves 206 in the top of the cover and having outwardly bent ears 208. The retainer has cross arms 210 which lie in grooves 212 in the outer face of the cover. The central part of the cruciform retainer plate is depressed at 214 to fit into a recess 216 in the cover in which it is held by a rivet 218. The recess 216 is wider than the depression 214 and the hole 219 in the cover is also wider than the rivet 218, so that the retainer 202 may be moved slightly sideways to facilitate engagement and disengagement of the cross arms with the ears 104 of the frame 48. In the arms 210 there are cut-outs 220 near their ends and the portions inside of the cut-outs are bent out of the plane of the arms so as to form stops 222. When the cover is to be attached to the relay, it is pressed thereove'r and the ends of arms 210. are caused to snap between the perforated ears 104 of the frame 48. When it is desired to remove the cover, the ends of the arms are disengaged from the ears 104 and the cover is free to be lifted off.
The relay may be mounted upon the supporting panel in any suitable manner and the terminals may be connected to the conductors by soldering or in any other suitable way. However, it is often preferable to provide a supporting panel with a socket having socket contact members into which the terminal tabs on the relay may be pressed, thus supporting the relay mechanically as well as establishing electrical connections. FIGS. 20-26 show a suitable construction of socket. This is a hard plastic molding 228 having mounted spring terminals 232. The socket member 228 has two bosses 234 and 236 on its bottom which are separated by a portion of reduced thickness 238. In the latter are holes 240 and 242 which open into sunken depressions 244 and 246. In the hole 240 is a screw 248 which holds the socket member to the panel board or recesses 230 therein in which are are forced into their recesses.
wall 249, the screw being grounded in any suitable manner. The hole 242 receives a stud 250 on the relay base. A grounding spring 252 is mounted on the screw 248 and is engaged by the stud 250 so as to ground the magnetic circuit of the relay. The socket member is shown as provided with a relay retaining clip 260 haying a base frame 262 and two spring uprights 264 which extend up at each end of the relay and have hooked ends 266 which are engaged by the ends 208 of long arms 204 of the cover retaining plates 202, thus holding the relay to the panel board.
The spring clips 232 as shown particularly in F168. 21 and 26, are formed of two thicknesses of spring material of good conductivity such as Phosphor bronze, the lower parts of which form ilat stems 270 which are offset at 272 so as to form pairs of inwardly curved contact spring portions 274 which press against the tabs 138 projecting from the relay. The two thicknesses of material may, if desired, be formed from a single blank doubled upon itself. The clips 232 are retained in the recesses 230 by lances or short tongues 276 cut out of the stems 270 and bent so as to normally spring apart when the clips The recesses are formed with projecting ribs 278 (FIG. 25), located in the cutouts 280 between the pairs of contact spring portions 274. The lanccs 276 are pressed in as they slide over the ribs 278 and then spring out so that their tops 282 snap under the shoulders 284 at the bottoms of the ribs 278, thereby positivclylocking the clips 232 in their recesses.
In the lower parts of the recesses 230 are stop ribs 286 which .engage the offsets 272 of the clips 232-and properly locate the clips in the recesses.
While specific embodiments of the invention have been shown and described in detail to illustrate the application of'thc principles of the invention, it will be understood contact fingers extending parallel to the axis of the coil, the ends of the fingers being adjacent to the end of the coil where the armature is pivoted, said armature having an end extending outwardly from said bearing and operative on said contact fingers to actuate the latter upon pivoting of said armature, and means for supporting the contact pile-up near the opposite end of the coil, said pivot plate having fingers spaced from its said one end and bent therefrom andcxtending over the free end of said armature, and said fingers being bendable to pre-set one limit of pivotal movement of said armature.
2. A relay havinga motor assembly including a frame, a coil mounted in the frame having a core, the rear end of which is fixed to the frame, the outer end of the core having a head thereon, a pivot plate of non-magnetic material having a hole therein through whichthe coil core passes, the head of the core engaging the pivot plate and holding it to the coil, and an armature pivotally mounted on the pivot plate, the pivot plate having a transverse edge thereon, the armature bearing against said edge, the pivot plate having a neck projecting beyond said edge and an armature return spring, one end of which engages the armature and the other end of which engages said pivot plate, neck.
3. A relay having a motor assembly including a frame, a coil mounted in the frame having a core, the rear end of which is fixed to the frame, the outer end of the core having a head thereon, a pivot plate of non-magnetic material having a hole therein through which the coil core fluenced by said end of the core, a contact pile-up having passes, the head of the core engaging the pivot plate and holding it to the coil. and an armature pivot-ally mounted onthc pivot plate, the pivot plate carrying a bendabletab forming an adjustable back stop for the armature.
4. In an electric relay, a frame having parallel spaced legs, a coil mounted between said legs, and an armature carried by the frame, a con-tact pile-up comprising a plurality ofspaced bracket plates having registering slots therein, means for-securing said bracket plates together comprising toothed combs passed through the slots in said plates and means for holding said combs spread apart so that the teeth of the combs engage said bracket plates and hold them in proper spaced relationship, flexiblc contact fingers carried by said bracket plates extend ing parallel with the axis of said coil, a spacer plate mounted on a side of said contact pile-up, said spacer plate being mounted on the sides of the frame legs and bearing against locating stops formed on said legs, a spring clip passing over the contact pileup and spacer plate and holding said pile-up in fixed position on said.
frame and operating means connected tov said contact fingers and engaged with said armature for operation of said contact pile-up by said armature.
5. A construction as claimed in claim'4, in which the contact fingers'are secured at their rear ends to the rear ends of said bracket plates and are thereby free to bend practically throughout the entire length of the fingers.
6. An'electric relay comprising a motor assembly having a U-shaped frame, the transverse portion of said frame :having a hole therethrough, a magnetic core mounted in said frame having an end passing through said hole and forming a driving fit therewith, a plastic bobbin mounted on the core, a coil on the bobbin, a nonmagnetic armature pivot plate having a hole therein through which the magnetic core passes, the outer end of the core having a head bearing against the pivot plate I and holding the pivot plate and bobbin in position when the inner end of the core is driven through the hole in the frame.
- 7. An electric relay comprising a motor assembly having a U-shaped frame, said frame having a hole through the end of the U, a magnetic core mountedin said frame having an end passing through said hole and forming a driving fit therewith, a plastic bobbin mounted on the core, a coil on the bobbin, an armature pivot plate of non-magnetic material having a hole therein through which the core passes, the outer end of the core having a head bearing against the pivot plate and holdingthe pivot plate and bobbin in position when the inner end of the core is driven through the hole in the frame, 'said pivot plate having a transverse edge thereon, a magnetic armature pivoted on said edge, said pivot plate also having a neck projecting beyond said edge, a. spring engaging said armature and said neck and biased to hold the armature in position and to apply a biasing force thereto, and
acontact'pile-up secured to the frame.
8. An electric relay comprising a motor assembly and a contact finger assembly and a plastic casing enclosing said assemblies, and having fixed to its outer wall a spring plate for holding said casing in position, the motor assem.-
9. A construction as claimed in claim 8, in which the spring casing holding plate is shiftably mounted on the front of thecasing so as to facilitate the engagement and disengagement of the plate with said end formations.
10. A construction as claimed in claim 9, in'which the spring plate is of cruciform shape and has transverse arms which engage said end. formations, the plate and easing having interengaging formations preventing substantial angular displacement of the plate on the casing but permitting lateral displacement of the plate in the direction of said transverse arms.
11. A construction as claimed in claim 10, in which a socket member is provided for attachment to a support, said socket member having sockets therein for receiving and holding the contact pins of the relay, and a frame carried by the socket member having spring arms projecting therefrom, said arms having end formations engaging the ends of the longitudinal arms of the cruciform casing holding plate.
12. In a relay having a frame, a motor assembly and a contact pile-up assembly mounted thereon, said contact pile-up assembly including a plurality of contact elements having extensions projecting rearwardly therefrom, the frame carrying two superimposed plates of insulatingmaterial each of which has an opening large enough to permit two adjacent contact extensions to project therethrough, the opening in one plate permitting the passage of one pair of contact extensions, and the opening in the other plate permitting the passage of one of said contact extensions and of a third contact extension, said plates each having a solid portion overlying and closing the part of the opening in the other plate between the adjacent contact extensions extending through said plate.
13. A construction as claimed in claim 12, in which the relay is provided with a cover, the openings in the plates being staggered so that each plate covers all open portions in the other plate except those through which the contact extensions actually pass.
References Cited by the Examiner BERNARD A. GILHEANY, Primary Examiner.
ROBERT K. SCHAEFER, Examiner.
T. D. MACBLAlN, Assistant Examiner.