US1655965A - Impulse starter for magnetos - Google Patents

Description

' Jan. 10, 1928.

S. D. LIVINGSTON IMPULSE STARTER FOR MAGNETOS Filed April 1, 192

2 Sheets-Shaev l INVENTOR 577mm,:- y D. l/wlvss a/v ATTORNEY Jan. 10, 1928. 1,655,965

5. D. LIVINGSTON IMPULSE STARTER FOR MAGNETOS Filed April 1? 1 926 2 Sheets-Sheet 2 33 /3&

5 llll INVENTOR 57/44/15) A l/w/vajro/v ATTORNEY Patented Jan. 10, 1928.

UNITED STATES PATENT OFFICE.

STANLEY D. LIVINGSTON, OF FREEPORT, NEW YORK, ASSIGNOR T EISEMANN MAG- NETO CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

IMPULSE STARTER FOR MAGNETOB.

Application filed April 1, 1926. Serial No. 99,049.

My invention relates to impulse starters for ignition magnetos, and its .objeot is to provide certain novel features by which the operation of such devices is considerably improved.

In prior impulse starters utilizing centrifugal pawls for holding and releasing the driven member, there has always existed the inherent objection of changes in the cut-out speed with continued service. Let me ex plain more fully what I mean. It is well known that in impulse starters as hereto= fore constructed, there is a fixed catch-plate engaged by a centrifugal pawl on the driven 5 member for holding the latter stationary while the driving member is rotated to wind up the spring. In those previous devices, the engagement between the catch-plate and pawl has always been along two sharp lines or edges formed by straight shoulders provided on those two parts. When the speed of the engine is sufficiently high, the pawl flies out of locking engagement with the catch-plate and the impulse starter operates like a coupling. However, with those sharp engaging edges on the catch-plate and pawl, the latter would continue to engage the catch-plate even when the contact point was only a few thousandths of an inch, and the unit would function as an impulse starter. At a slightly higher speed, no engagement would occur and the unit would cut out, as the engineers say, and act simply as a coupling. But if the unit should continue to 6 operate at this critical speed, a new hours service would wear off the sharp point of engagement and this would change the cutout speed. By the critical speed I mean the speed at which the pawl just engages the catch-plate and alternately catches and misses. I found, for instance, by actual tests that when a unit of the type referred to was operated as an impulse starter for about 100 hours, the wear which always took place on the pawls and catch-plate invariably changed the point of cut-out. Further, I observed that, if the impulse starter was operated at a certain critical speed, the wear at the engaging points on pawl and catchplate would be excessive and in a few hours the unit was completely destroyed so far as service was concerned.

The present invention is for the purpose of completely removing the foregoing objection and disadvantage in prior impulse starters, and to that end I provide a construction in which the engaging surfaces on the pawl and catch-plate are rounded or beveled in such a way as to eliminate any hair-trigger adjustment. The pawls either engage the catch-plate or they slide off. There is no wear at the critical point of engagement, and therefore the point of cutout is not varied by use. I have demonstrated this by severe tests.

The practical advantages of my invention will be fully understood from a detailed description of the impulse starter shown in the accompanying drawings, in which .Fig. 1 is a side elevation of an impulse starter constructed in acordance with my invention, the cover surrounding the parts being shown in section;

Fig. 2 is a face view of Fig. 1;

Fig. 3 is a longitudinal sectlon on line 33 of Fig. 2;

Fig. 4 is a section on line 4.-4: of Fig. 1, showing the construction and mounting of the pawls, one of which is in engagementwith a fixed catch-plate;

Fig. 5 is a transverse section on line 5-5 of Fig. 1, showing the interior of the cupshaped driving member;

Fig. 6 is a fragmentary plan view in section on line 6-6 of Fig. 5, showing how the cover is held in position;

Fig. 7 is an enlarged view showing the locking pawl in engagement with the catchplate; and

Fig. 8 is a View similar to Fig. 7, showing the pawl in position to slide off the catchplate at the cutout speed.

' The impulse starter shown in the drawings comprises a driving member 1 and a driven member 2. -The driving member 1 is in the form of a cylindrical casing or cup, and the driven member 2 consists of a disk carrying a pair of weighted pawls 3 and 4 pivoted on studs 5. As seen in Fig. 3, the studs 5 project rearwardly, and the pawls 3 and 4 are mounted outside the housing 6 formed by the members 1 and 2. The driven disk 2 is rigidly fixed on a hub 7, which is keyed on the projecting end 8 of the magneto shaft. The magneto structure need not be described, since the magneto forms no part of my invention, and I have therefore shown only a portion of the magneto frame M. The hub 7 is held against axial movement on the magneto shaft by a cup-shaped washer 9 and a screw 10. The washer 9 has an annular flange or shoulder 11 which retains the driving cup 1 on the cylindrical extension 7 of hub 7. The member 1, which is rotatably mounted onhub 7, is provided with radial coupling lu s 12 for engaging a suitable driving membei (such as a coupling disk) operated at the proper speed from the engine shaft. It will be-seen from the foregoing that the drivingv member 1 is rotatably mounted on the magneto shaft, and that the driven member 2 is always rigidly con- .nected with the magneto shaft.

In thie chamber 6 formed by the members 1 and 2 is mounted a' strong coil spring 13 for releasably connecting the members 1 and- 2, as will presentlj be explained in detail.

The outer end 13 of spring 13 is hookedover the lug- 14 on casing 1, and the inner end 13? of-the spring is inserted in a slot in the hub 7. The lug 14 maybe formed integral with member 1 by upsetting the metal, as indicated in Fig. 5. f In assembling theparts 1, 2 and 13, the spring is placed under initial tension.

1 Each pawl 3 and 4 has a weighted trailing end 15 and a tip 16. The trailing end 15 of each pawl has a locking shoulder 17 arranged to engage a fixed stop 18, usually. called a catch-plate. The pawls are -preferably made of heavy flat metal free from .lateral bends, so as to have increased strength and durability.

By means made flat, t e pawls can be punched from a thick piece of hardened steel. Attention is called to the fact that the stop shoulder 17 of each pawl is formed with a rounded edge 17.

- The catch-plate 18 is provided at one or both I ment. The locking shoulder 19 has a bev-.

5 hard steel rigidly secured to a plate 20, as: by welding or'otherwise. Plate 20 is at ends with a locking shoulder 19 adapted to be engaged by the shoulder 17 of the pawl to hold the driven member 2 against moveelled or rounded edge 19' over whichthe rounded point 17' of the pawl is adapted to slide at the cut-out speed of the unit, as will be more fully explained later on.

The fixed stop or catch 18 is a piece of tached to the magneto frame by screws 21 or other fastening means. An opening 22 in plate 20 allows the magneto shaft to pro ect therethrough.

of peripheral or arcuate projections 23 which. extend axially over pawls 3 and 4 into radial alignment therewith. Which.

ever pawl engages the catchplate'18, its tip 16 projects into the path of the projections 23, as may be seen from Fig. 4. Therefore,

' when either projection 23 moves over the tip of the locking pawl, it forces the same inwardly and thereby. rocks the pawl out of locking contact with stop 18. One or both ends 23' of projections 23 are preferably bev The driving cup 1.is provided with a pair elled 'to..facilitate engagement with the tip projections 23 engage the trailing ends I) of projections 24. The projections 24 on the driven member 2 also act as stops against the inward movement of the driving cup 1 on hub 7, as may be observed in Fig. 1. .In

other words, the driving cup is rotatably held on hub 7 between the flange 11 of washer 9 and the projections 24 of disk 2. I

The driving cup 1 is surrounded by a cylindrical cover 25 removably secured to v the back-plate 20, which is provided with an annular flange or shoulder 20' for seating the rear edge of the cover. This is' best shown in Figs. 1 and 3. The front edge 26 of the coveris shaped as an annular hollow bead in which is held a ring 27 of felt or other soft dust-excluding material. As seen from Figs. 1 and 3, the ring 27 projects beyond the metal of the cover into contact with the driving cup 1, whereby a practically dust-proof casing is formed around the impulse starter. This is of particular advantage on vehicles operating .dusty regions,

such as tractors, where abrasive dust quickly accumulates on exposed parts, and not only interfers with their proper operation, but shortens their life as well. .The felt rin 27 is securely'fastened in position by slig tly dishing the outer rim or flange 28 of the cover, as clearly indicated in Figs. 1 and 3.

To permit quick and easy positioning and removal of cover 25, I use a pair of spring clamps 29 pivoted at 30 to lugs or cars 31 on plate 20. Looking hooks 32 formed on clamps 29 areadapted to snap over'the recessed rim of flange 26 for holding the cover firmly in position. Finger extensions 33 al low easy manipulation of the clamps.-

The operation of the impulse starter above described is as follows:

When the driving member 1. is rotated in. the direction indicated by the arrow a in' Figs. 1 and 4, the spring'13 is wound up, because the pawl 3 engages the catch-plate 18. This windlng up of the spring continues un- -il one of the rojections 23 on the driving cup 1 strikes t e tip 1670f the locking pawl,- whereupon the shoulder 17 is moved out of contact with 'ca'tch plate 18, and the tensioned spring suddenly impels the driven member2 in the direction of arrow'y (Fig. 4). Since member 2 is fixed on the magneto shaft, the latter receives a sudden rapid movement Suf- .ficient to generate the required s arking current. If the engine does not fire on the first impulse of member 2, the operation described is repeated until the magneto generates the starting spark. When the engine attains a certain speed, the weighted ends of projections 23 on the riving cup. Now, be-

tween the lower speed at which the pawl is locked to the. catch-plate and the cut-out speed at which the pawl clears the catchplate, thereis a critical speed when the pawl Inst engages the catch-plate. I might sa that at this speed the pawl flutters into an out of contact with the catch-plate, alternately missing and catching. In prior 1mpulse starters, where the pawl and catch-' plate engage along straight edges with sharp ends, the cut-out speed depends upon a hairtrigger engagement that changes with the wear of the sharp engaging edges on pawl and catch-plate. Hence, in. those previous devices, a uniform cut-out speed is im ossible under continued service. This objectionable featureis entirely overcome by the novel construction of locking shoulders on catch;

' engages the shoulder 19 of the catch-plate,

plate and pawl. Referring to the enlarged views of Figs. 7 and 8, the shoulder 17 of the.

pawl at-lower speedeither fully or partially as shown in Fig. 7. In either case, the pawl is positively locked tothe catch-plate. As the speed increases, the amount of enga ement between the surfaces 17 and 19 ecreases to a point where only the bevelled or rounded ed es 17 and 19 meet, whereupon Y 'the pawl slides off the catch-plate and a unit ceases to function as an im ulse sta; er. This position of the parts is i ustrated in Fig. 8 on an exaggerated scale. I might explain that Figs. and 8 (in-the drawings as originally filed) show thepawl and catchplate about twice the actual size, while the other H ures show the impulse starter in 'full size. omparing Figs. 7 and 8,it will be .clear that the pawl either 'positivel engages thev catch-plates or it slides off. ereis .no wear at the critical point of e agement and remains unchanged by continued use. I have operated impulse starters of this new construction at speeds that were reviously; considered Gl'ltlv cal (i. e., where 't e pawl alternately catches and misses), and this severe test showed a uniform cut-out. In the particular a driving member arrang ment illustrated in the drawings and which I have actually used in practice under working conditions, the rounded e e 17 on the pawl is; formed on a radius 0 about 0.047 inch. I mention this by way of example and not as a. limitation. By adjusting the weight of the pawl, it is possible to obtain a cut-out at some redetermined s eed. There is no wear on t e rounded sur aces 17 and .19 when they engage, (see Fig. 8 because there is no load on the pawl for t e reason that the latter slides off the'catch-plate instead-of up-the spring.

What I claim as my invention is:

1'. In an impulse starter for magnetos, the combination of a driving member, a driven member connected to the magneto shaft, a spring connected between said members, a centrifugal pawl pivoted on said driven member and provided with a shoulder, a fixed stop also provided with a shoulder, each of said shoulders consisting of straight locking surface and a rounded out outzedge, said shoulders be' so arranged that normally and at lowspee the locking surfaces engage to hold the driven member temporarily ag'ainstrotation while the driving member is operated to fplace said spring driven member, said rounded edges of the' locking1 shoulders causin -,sa1d Pawl automatica y to slide out o engagement said stop at predetermined cut-out speed.

2. In an impulse starter for magnetos, the

combination of a driving member, a driven member connected to the magneto shaft, a spring connected to said members a pawl pivoted on said driven member, said pawl consisting of a flat piece of metal having a weighted trailing end provided with a shoulder, a fixed stop also provided with a shoulder, each of said shoulders consisting of a straight lockingsurface and a rounde cut-out edge, said shoulders being so arranged that normally and at low the locking surfaces'engage to hold the driven .member temporarily against rotation while the drivin member is operated'tp place said spring un er tension, a rojectionon sa d to engage the tip of said pawl and rock the same to release said interlocking surfaces, so that the tensioned spring imparts a rapid rotation to the driven member, saitLrounded edges of the locking shoulders causing said'pawl automatically to slide out of engagement with said stop at predetermined cut-out speed.

STANLEY n'mvmesron.

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