US1717162A - Internal-combustion engine - Google Patents

Description

June 11, 1929. H. E. McCRAYv INTERNAL coMBUsTIoN ENGINE Original Filed Feb. 15, 1925 2 Sheets-Shee't w'en or nung.

June11,1929. HfEMCCRAY 1,117,162

INTERNAL COMBUSTION ENGINE Original Filed Feb. l5, 19225 2 Sheets-Shaml 2 lilik@ (7M zi LM,

Patented June 1l, 1929.

UNITED: STATES PATENT oFFlcE.

HAROLD E. MCCRAY, OF WATERLOO, AIOlA, A'SSIGNOR TO JOHN DEERE TRACTOR COMPANY, OF WATERLOO, IOWA, A CORPORATION OF OWA.

IN-TJ'JRNAL-COMBUSTION ENGINE.

Original application filed February 15, 1923, Serial N'o. 619,081.

April 27, 1925.

has Jfor its object to provide ignition devices of improved design which may be used `with either magneto or battery ignition, and which, when the current is furnished by a magnetouvill operate pcrcussively to separate the contact points very abruptly, thereby giving a most effective spark; also to provide a construction by which the accumulation of carbon in the bearings of the movable electrode will be in large measure, if not entirely, prevented, and to improve ignition devices of this character in other respects, as willbe hereinafter pointed out.

In theaccompanying drawings, in which I have illustrated my improved ignition devices as applied to an internal combustion engine oi the type'shown and described in my pending application, Serial No. 619,081, filed Feb-v ruary 15, 1923, of which application this is a F 1 is a sideelevation of the complete engine, with one iiy-wheel removed, and the crank shaft bearings at one side of the engine shown in section;

l41 2 is apartial end view showing my improved ignition devices; n f

Fig. 3 is a partial horizontal section 011 line 3--3 of Fig. Q;

Fig. l is a partial longitudinal vertical section on line -llof F1g. 3; and

Fie'. is a partial plan view illustrating the ignition devices.

Referring to the drawings,-6 indicates the base of the engine, which in the illustrated construction is vin the form of a casting adapted to be bolted or otherwise suitably secured to a supporting plate 7, of wood or other suitable material, andto contain within it a tank for hydrocarbon,liquid fuel which is supplied to the engine cylinder through a pipe 8 shown in Fig. 1. Mounted on the `base 6 isa crank case 9, upon the side portions of which is mountedl a crank shaft 10 in suitable upper and lower bearings 11', 12. The crank shaft 10 preferably carries two ily-wheels 13, one at each side of the engine, and it operates a pitman 14- by which it is connected to a piston lo. indicated by dotted lines in Fig. 1. Cast integral with thecrank case 9 is a cylinder Divided and this application ziled Serial No. 26,156.

bleek 16, which is also'a' water hopper, the construction of the cylinder block being best shown in Fig. 3, in which 17 indicates the en gine cylinder and` 18 a water receptacle that extends around the cylinder 17, the outer wall of the cylinderblock being spaced from said cylinder to form said receptacle. A removable cover 19 is provided for the crank case i 9, sol that access may readily be had to the interior thereof, and a magneto 20 is mounted on the crank caseat one side 0f the engine and is driven by the crank shaft through suitable intermediate gearing, not shown, to furnish I current for ignition purposes.

As shown in Figi 3, the cylinder block 1s provided with a removable head 21, which is secured in place by bolts 22, shown in Fig. Q. Said head is provided with an ignitionchamber 23 and an exhaust chamber 24, the latter beingarranged to 4discharge through a muiller 25. Also mounted in the head 21 are an intake valve 2G and an exhaust valve 27,1which are respectively held normally on their seats by springs 28, 29 mounted on the stems 30, 31 of said valves. A suitable combustible mixture is supplied te the cylinder 17 through a mixer body in the form of a nozzle or pipe 32 which connects with the engine cylinder through the port that is normally closed by the intake valveQG. Said mixer body extends downward from said' port and is open at Vits lower end, where it is provided with a tity ofliquid fuel admitted lto said nozzle Y may be nicely regulated. The intake valve 26 is opened by the suction of the piston, but mechanism `must be provided foropening the exhaust valve 27 to purge the cylinder 17 of consumed gases before the admission thereto of a fresh charge of fuel. This is accon'iplished by means of a rocking lever 36 mounted between its ends on a pivot 37 in such position `that one arm 37a thereof ex* tends over the exhaust valve stem 31. ,This arm carries a tappet 38 in the form of a bolt adjustably secured in said arm so that its normal distance from the outer en'd of the valve stem 31. may be adjusted. Obviously by rocking the lever 36 in the appropriate direction the tappet 38 will strike the valve stein 31 and move it inwardly, thereby open ing the. exhaust valve. lVhen the pressure applied through said tappet is removed, the spring 29 serves to restore the exhaust valve to its normal position in-th-c usual way. A spring 39, connected with the lever 36 and with a standard 40 which projects trom the head 21 and carries the pivot 37, serves to hold the lever 36 in the position shown in Fig. 3, which is its normal or inoperative position. The opposite arm 37b .of said lever is connected with an operating rod 41, by the reciprocation of which said lever is rocked to alternately open and close the exhaust valve as the engine operates. This reciprocation of the rod 41 is effected by means ot a cam 42 that is carried by a shaft 43 mounted in one ot the side walls of the crank case and arranged to be rotated by the crank shaft through suitable gearing. The cam 42 and shaft 43 are indicated by dotted lines in Fig. 1. The edge oi the cam 42A is in line with the axis of the rod 41, and between the operat in g tace of said cam and said rod is a follower lever 44 pivoted at its lower end on Varpivot 45, as shown by dotted lines in said figure. By this construction the direct thrust of the cam is t 1ansmitted to the rod 41 through said follower lever, so that there is no side thrust' on said rod. The follower lever 44 is provided with a laterally projecting lug 46 adjacent to the end of the rod 41, the purpose of which is to cooperate with other mechanism that need not be described, to hold the rod 41 in its extreme position to the left as viewed in Fig. 1, so that the exhaust valve will be held open and ignition prevented, as is ldesirable in some circumstances. This mechanism is fully described in my said parent application. For present purposes it will sufiice to say that when the rod 41 is moved to the left from the position `shown in Fig. 1

by the operation of the cam 42, the exhaust valve 27 is opened. The spring 39 returns the rod 41 to its normal position, shown in Fig. 1, when it is free to move in that direction.

The ignition devices which form the subject matter oit my present application are associated with the ignition chamber 23 and operate to form a spark therein at the proper times, under the control of a governor located in the crank case and driven by the crank shaft. The construction and arrangement of the governing devices by which the timing of the spark is controlled, are not illustrated in this application, as they constitute part of the subject matter oit the application hereinbefore referred to, out of which this applica` tion was divided, and a detailed description thereof is not necessary to an understandingr of my present invention. i

My improved ignition devices comprise a stationary electrode 47 which 'extends through a passage 48 in a bracket 49 that 1s secured to the head 21 adjacent to the ignition chamber 23, as shown in Fig. 3, the inner end of said electrode extending into said chamber where it. is provided with a contact device 50. Said electrode is held from electrical contact with the bracket 49, and the passage 48 is closed, by gaskets 51, 52, of any suitable non-conducting material, that iit into the ends of said passage. The ignition devices also comprise a. rotatable electrode 53, in the form of a rod or shatt,the inner end ot which extends into the ignition chamber 23 through a passage parallel with and adj acent to the passage 48, andcarries a laterally projecting arm 54 provided with a contact point 55 that is adapted to be moved into or out of engagement with the contact point 50 by rotation of the electrode 53. As shown in Fig. 3, the passage in the bracket 49 through which the electrode 53 extends is so shaped as to provide a comparatively narrow inner bearing 56 for the inner end portion of said electrode, and a recess or chamber 57 outside of and adjacent to said bearing provides a clear space around said electrode. The purposent this arrangement is to prevent the accumulation oit carbon and residue of unburned fuel oil in the short inner bearing 56 by maintaining the inner end portion of the electrode 53 and the bearing at a high temperature incident to the operation ot the engine, leaving the carbon to collect in the chamber or recess 57 where it will do no harm. By making the bearing short and by substantially surrounding the outer end ot the bearing with the restricted air space 57, the entire length of the bearing is maintained at a tcmperature above that of the condensing point of the products ot combustion leaking out around the igniter electrode. Hence these by-products of combustion will remain in liquid or gaseous state at the outer end of the inner bearing so that they can drop down or iiow out into the air space where they will be incapable of fouling the electrode or causing it to stick. The outer end of the electrode 53 is journaled in and projects through an outer bearing 53 provided in an arm 59 that forms a part ot the bracket 49. The outer bearing 58 is ot course axially alined with the inner bearing 56. It will be noted that the inner end of the electrode 53 is provided with a head 60, the neck of which is tapered and lits in a tapered seat at the inner end of the bearing` 56, and mounted upon the outer end portion of said electrode beyond the arm 59 is a coiled spring 61, one en-d of which is connected with said arm and the other end ot which is connected toa pin 62 carried by said electrode, as best shown in Fig. 3. This spring serves several purposes, one of which is to exert end thrust on the electrode 53 tending to hold the head on its seat and so llO prevent end pl-ay of the electrode. lVhere make and break ignition is used, as is the case in the arrangement illustrated, said spring also tends to hold the contact point 55 in engagement with the contact point by exerting torque on the electrode 53 tending to rotate it in a clockwise direction as Viewed in Fig. l. Said spring may, however, be adjusted so that it will operate to hold the contact point away from the contact point 50, as would be done if battery instead of magneto ignition weie used.

Fixedly secured to the electrode 53 at a point between the inner and outer bearings thereof, and preferably nearer the inner bearing 56, is a clutch member 63 that, as hereinafter described, is arranged to be percussively actuated by a clutch member 6l that is rotatably mounted on the electrode 53 and which clutch member 6l is integral with a hammer block 65 rotatably mounted upon said electrode between its outer bearing 5S and the clutch member 63, as best shown in F ig. 3. One of said clutch/members, in the present inn stance the clutch member 6i', is provided with a laterally projectinglug` 66 that projects toward the opposite clutch member and into a recess or notch 67 formed therein, asshown in Figs. 3 and As best shown in the latter figure, said recessv subtends a somewhat greaterarc than the lug 66, so that notwithstanding Vthe two clutch members aie interlocked by the projection of the lug 66 into the recess 67, considerable lost motion is permitted between said members. The normal positionof these parts is shown in Fig. 4t, from an inspection of which it will be seen that when the contact point 55 is in engagement with the contact point 50, the clutch member Gt may rock to a considerable extent independently of the clutch member 3 in a clockwise direction as viewed in said figure, the object of which is to permit the hammer block to swing through a limited arc in one direction without rotating the electi'ode 53. Rotation of the clutch member 64 in the opposite direction, however, will cause said electrode 53 to rotate with it, owing to the engagement of the lug 66 with that portion of the recess 67 against which it abuts. A spring 68 coiled upon the clutch member 6a and having one of its ends connected with said clutch member by a pin 69 carried by the. hammer block 65, and its other end connected with the clutch member 63 by a pin 70, tends to hold the two members of the clutch in the position shown in Figs. 3 and 4r. The described arrangement of these parts is for the purpose of percussively actuating the electrode to separate contact points and 50 for make and break ignition, and the manner in which this is accomplished will presently appear.

As shown in Fig. 1, the hammer block 65 normally extends diagonally downward from secured to the exhaust valve operating rod Lil. Adjacent Vto the pivot .is a spring 77, one end of which is connected with the bracket 76, while its other end engages the trip bar end of said bar upwardly, or, in other words,

`to rotate it in a clockwise direction as viewed in Fig. l. rlhe free end of said trip bar normally extends into the notch 73, and its upfper margin bears against a planev surface 7 6 on the hammer block adjacent to the plane surface 72,` as best shown in Fig. l.

Bearing in mind the foregoing description of these parts, it will be understood that when they are in the position shown in said ligure, at which time the Contact points will be in the position shown in F 4, and the. exhaust valve willbe in its closed position, if the rod tl be moved to the lett as viewed in Fig. l, the trip bar 74:, by reason of its engagement with the notch. 73, will act to swing` the ham-- mer block 65 in a clockwise direction about the electrode 53, thereby increasingthe tension of the spring 68. In this operation the lug 66 moves to the opposite end of the recess 67 in the clutch member 63, which remains stationary with contact point 55 in engagn ment with Contact point 50. As this movement of the hammer block continues, the plane surface 72 of said hammer block will swing into engagement with the upper surface of the 'tri p bar 74e, ii'ioving the free end of .Jaid bar downward against the action of the spring 7 7, so that the free end of said bar will clear the point of the notch 73, thereby permitting the iod 4l and trip bar 74 to continu-e to move in the saine direction without furH ther rotating the hammer block 65. Assoon, however, as the trip bar 7 4 is clear of the notch 7 3, the spring 68 will act to rotate the hammer block, together with its clutch member 64, quickly and forcibly in the opposite direction. This reverse rotation of the hammer block will cause the lug 66 of its clutch meinber to move back in the recess 67 and act percussively in a circular direction upon the clutch member 63 in. opposition to the tension of the spring 61, which it overcomes by its inertia, thereby rotating the electrode 53 in a counter-clockwise direction as seen in Fig. t, so that its Contact point 55 is moved Y again actuate them.

point in engagement with the contact point 50. By this construction the Contact points are effectively and very abruptly separated by the hammer-like blow delivered by the hammer block G5 through its clutch member 64 to the clutch member 63, which latter functions as a sort of anvil to take such blow and transmit it through the rotary electrode to the movable contact point carried thereby. As the hammer block is comparatively heavy, and the electrode 53 is relatively quite light, the electrode is rotated at high speed, thereby giving a very quick and positive break so that exact timing of the firing is obtained.

lVhile the .firing operation just described is occurring, vthe valve operating rod il continues to move to the lett as viewed in Fig. l, and as its movement actuates the exhaust valve operating lever 3G to rock it in a clockwise direction as viewed in Fig. 3, it will at the proper time act-nate the exhaust valve to move it oil' of its scat, thereby premitting the burned gases in the cylinder to be discharged therefrom. rllhese operations are of course properly timed so that the exhaust valve does not open until after the ignited charge has done its work. IVhen the valve operating rod 4d. Vreturns to its normal position, the free end of the trip bar Tl again moves into the notch 73, as illustrated in Fig. l. Obviously if the valve operating rod l1 be kept in position to hold the exhaust valve open to permit the engine to run for a greater or less length of time under the momentum of the [ly-wheels, as has been suggested, the ignition devicesI will knot be operated, as their operation depends upon the reciprocatory movement of the rod 41; that is to say, after once having actuated the ignition devices, it must return against to its initial position before it can So far as the ignition devices are concerned, however, it is immaterial how long a time intervenes before said bar is returned to its initial position, as after the hammer block G5 has been tripped in the manner described, the parts are ready to be j again actuated.

Electric current is supplied to the fixed electrode 52 by a cable 7 9, one end of which is connected with the magneto, while its other end is attached to a connector 8() secured to said electrode. The other terminal of the magneto is grounded in any convenient way to the frame of the engine.

What I claim as my invention and desire to secure by Letters Patent, is

1. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an ignition chamber and mea-ns for supplying fuel thereto, of a rotary electrode extending into said ignition chamber, supporting means for said electrode having a comparatively narrow bearing therefor adjacent to said ignition chamber, and an air space around said electrode outside of and adjacent to said bearing, an outer bearing for said electrode coaxial with said first-mentioned bearing, clutch mechanism mounted on said electrode between said bearings and arranged for actuating said rotary electrode and an electrode adapted to cooperate with said rotary electrode.

2. In an ignition apparatus for internal combustion engines, the combination with a cylinder having Van ignition chamber and means for supplying fuel thereto, of a rotary electrode extending into said ignition chamber, supporting means for said electrode having a comparatively narrow bearing therefor adjacent to said ignition chamber, and an air space around said electrode outside of and adjacent to said bearing, an outer bearing for said electrode coaxial with said first-mentioned bearing, a spring arranged to exert end thrust on said electrode and tending to hold said electrode in its normal position, clutch mechanism mounted on said electrode between said bearings and arranged for actuating said rotary electrode and an electrode adapted to cooperate with said rotary electrode.

3. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an ignition chamber, and means for supplying fuel thereto, of a rotary electrode extending into said ignition chamber, and supporting means for said electrode comprising a bracket having a comparatively narrow bearing therefor adjacent to said ignition chamber, an air space around said electrode outside of and adjacent to said bearing, an arm having a bearing for the outer end portion of said electrode arranged coaxially with said first-mentioned bearing, two cooperating clutch members mounted on said electrode between said bearings and arranged to actuate said electrode and a spring mounted on said electrode and connected therewith and with said arm, said spring tending to hold said electrode in its normal position and to exert end thrust thereon.

4. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an ignition chamber, and means for supplying fuel thereto, of a rotary electrode extending into said ignition chamber, and supporting means for said electrode con'iprising a bracket having a comparatively narrow bearing therefor adjacent to said ignition chamber, an air space around said electrode outside of and adjacent to said bearing, an arm extending from said bracket on one side of said electrode, said arm having a bearing for the outer end portion of said electrode arranged coaxially with said first-mentioned bearing, clutch mechanism mounted on said electrode between said bearings and arranged for actuating said rotary electrode, and a stationary electrode mounted in said bracket on the opposite side of said rotary Lie' electrode to said arm and adapted to cooperate with said rotary electrod 5. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an ignition chamber and means for supplying fuel thereto, oi a rotary electrode extending into said ignition chamber, supporting means for said electrode having a coii'iparatively narrow bearing therefor adjacent to said ignition chamber, and an air space around said electrode outside of and adjacent to said bearing, anouter bearing i'or said electrode coaxial with said lirstmentioned bearing, actuating devices for said electrode comprising a clutch member mounted thereon and secured thereto between said bearings, and a hammer block loosely mounted on said electrode between said bearings, said hammer block having a clutch member adapted to cooperate with said first-mentioned clutch member, and rotatable to a limited extent relatively thereto.

6. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an .ignition chamber, and means for supplying lfuel thereto, ot a rotary 4electrode extending into said yignition chamber, and supporting means for said electrode comprising a bracket having a;eoii'ipai'atively narrow bearing therefor adjacent. to said ignition chamber, an air spacearound said electrode outside of and adjacent to said bearing,

and an arm having a 'bearing for the outer end `portion of said electrode arranged coaxially with said first-mentioned bearing, a stationary electrode mounted in said bracket and adapted to cooperate with said rotary electrode, a coiled spring vmounted upon the outer end portion of said lrotary electrode,

one end of said spring being connected with said arm and the other end with said electrode, for normally holding said rotary electrode in contact with said stationary electrode, and clutch mechanism carried by said rotary electrode between said bearings for controlling the actuation thereof.

7. In an ignition apparatus for internal combustion engines, the combination with a Acylinder having an ignition chamber, -and means for supply fuel thereto, oi a rotary electrode extending into said ignition' chamber, and supporting -m'eans for'said electrode comprising a bracket having acomparatively narrow bearing therefor adjacent to said ignition chamber, an air space around said electrode outside of and adjacent to said bearing, and a-ii arm having a bearing -tor the outer end portion of said electrode arranged ycoaxially with said ltii'st-iiient'-ioned bearing, a stationary electrode mounted in said bracket'and adapted to cooperate with ysaid rotary electrode, a coiled spring mounted upon the outer `end portion of said rotary electrode, `one end of said spring being .connected withsaid Aarm and the 'other end with lsaid electrode, for

`normally holding said rotary electrode in `rotary electrode and having a clutch member adapted to cooperate with saidv first-mentioned clutch member, and being rotatable to v.a limited extent relatively thereto.

8. In an ignition apparatus for internal combustion engines, the combination with a cylinder having an ignition chamber, and means for supplying fuel thereto, of a. rotary electrode extending into said ignition chamber, and supporting means for said electrode comp rising a bracket having an inner. bearing adjacent to said ignition chamber and an outer bearing'spaced from said inner bearing and coaxial therewith, said rotary electrode being journaled in `both of said bearings, a spring coiled about the outer end of said rotary electrode beyond said outer bearing, said spring tending to hold said electrode in its normal yposition and to exert end thrust thereon, a first clutch member secured to said rotary electrode between said bearings, .a second clutch member rotatably mounted on said electrode between said bearings, means affording a lost motion connection between said clutch members, a spring connected to said second clutch. member forvnormally holding said clutch members in .predetermined relation, a Ihammer block extending from said second clutch member, and a trip member for oscillating` said hammer block.y

9. In an ignition apparatus for internal combustion engines, the combination with va cylinder having an ignition chamber, id. means lor supplying fuel thereto, of a rory electrode extending into said ignition chainber, and supporting means for said electrode comprising a bracket having an inner bearing adjacent to said ignition chamber and an out# cr bear ing spaced from said inner bearing and ycoaxial therewith, saidyrotary electrode comelectrode between said bearings, a second lclutch member rotatably mounted on said rotary electrode between said bearings, means affording a. lost motion connection between vsaid clutch members, lak spring. effective between said clutch members 'fer normally ber, an inner bearing adjacent to said igni- I tion chamber and an outer bearing spaced from said inner bearing and coaxial therewith, said rotary electrode being' ournaled in both ot' said bearings, a spring coiled about the outer end of said rotary electrode beyond said outer bearing,a tirst clutch member secured to said rotary electrode between said bearings, a second clutch memberrotatably mountedA on said rotary electrode between said bearings, a stud on one of said clutch members engaging in a recess in the other oiE said clutch members, a spring coiled about said clutch members for normally holding the latter in predetermined relation, a. hammer block portion extending from said second clutch member, a trip bar 'for oscillating said hammer block, said hammer block having a notch thc-rein 'for-receiving said trip bar, and a surface on said hammer block for ejecting said trip bar trom said notch after a predetermined oscillation of said hammer block- 11. In an ignition apparatus for internal combustion engines, the combination with a cylinder Vhaving an ignition chamber, and means for supplying fuel thereto, of a rotary electrode entendinginto said ignition chamber, an inner bearing adjacent to said ignition chamber and an outer bearing spaced from said inner bearing and coaxial therewith, said rotary electrode being journaled in both ot said bearings, a spring connected with said rotary electrode for holding said electrode in its normal position, a iirst clutch member secured to said rotary electrode between said bearings, a second clutch member rotatably mounted on said rotary electrode between said bearings, means affording a lost motion connection between said clutch members, a second'spring for normally holding said clutch members in predetermined relation, and means for oscillating said second clutch member.

12. In an ignition apparatus 'for internal combustion engines, the combination with a cylinder having an ignition chamber, and means tor supplying iinel thereto, of a rotary electrode extending into said ignition chamber and comprising a shoulder portion seating against a seating surface, an inner bearing adjacent to said ignition chamber and an outer bearing spaced Jfrom said inner bearing and coaxial therewith, said rotary electrode heilig 'journaled in both ot said bearings, clutch mechanism mounted on said rotary electrode between said bearings and arranged for actuating said electrode, and a spring eooperating with said electrode, said spring applyingtlirustingpressure to said electrode for maintaining said shoulder portion in engagement with said seating surface, and also acting torsionally on said electrode to maintain the latter in its normal position, said spring being arranged to have its tension reversed for holding said electrode in diii'erent normal positions for adapting said electrode either to battery or magneto ignition.

13. Internal' combustion engine ignition apparatus adaptable either to battery or magneto ignition, comprising a stationary electrode, a rotary electrode adapted to contact therewith, bearing means tor said rotary electrode, a spring operatively connected with said rotary electrode and mounted so as to permit the normal tension ot said spring to be reversed whereby said spring can be made effective either to normally hold said rotary electrode in contact Vwith said stationary electrode or out ot contact therewith, and percussion mechanism associated with said rotary electrode and operative to aetuate the same for magneto or battery ignition irrespective of the direction in which the tension et said spring acts on said rotary electrode.

14. Internal combustion engine ignition apparatus adaptable either to magneto or battery ignition, comprising a stationary electrode, a bracket having inner and outer spaced bearings, a rotary electrode journaled in said bearings and adapted to contact with said stationary electrode, a torsion spring operatively connected with said rotary elect-rode and mounted so as'to permit the normal tension of said spring to be reversed whereby said spring canbe made effec-tive either to normally hold said rotary electrode in contact with said stationary electrode `for magneto ignition or out ot contact therewith for battery ignition, actuating devices for said rotary electrode eon'lprising a clutch member mounted thereon and secured thereto between said bearings, a hammer block loosely mounted on said electrode between said bearings, said hammer block having a clutch member adapted to cooperate with said first Vmentioned clutch member and rotatable to a limited extent relatively thereto, a seeondary spring operatively connected between said iirst clutch member and said hammer block and normally tending to rotate the latter in one direction relatively to said first clutch member, and a trip member for actuating said hammer bloclr, said hammer block serving under the actuation of said trip member to transmit pressure through said secondary spring for causing said rotary electrode to contact with said stationary electrode in opposition to the action of said torsion spring when the latter is adjusted to normally hold the rotary electrode out of contact with the stationary electrode.

HAROLD E. MCCRAY.

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