US2871720A

US2871720A - Rocker arm

Info

Publication number: US2871720A
Application number: US348345A
Authority: US
Inventors: Eldon K Ralston
Original assignee: Thompson Products Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1953-04-13
Filing date: 1953-04-13
Publication date: 1959-02-03
Anticipated expiration: 1976-02-03

Description

E. K. RALSTON Feb. 3, 1959 ROCKER ARM Filed April 15 1953 3 Sheets-Sheet 1 Feb. 3, 1959 E. K. RALSTON 71,

ROCKER ARM Filed April 13, 1953 v I s Sheets-Sheet 2 m? v, 2 u

' 5 H012 I Fa/szozz Feb. 3; 1959 E. RALSTON 2,871,720

I ROCKER ARM Filed April 13, 1953 I 5 Sheets-Sheet s United States Patent ROCKER ARM Eldon K. Ralston, Lyndhurst, Ohio, assignor to Thompiplilr Products, Inc., Cleveland, Ohio, a corporation of This invention relates to rocker arms for internal combustion engines and the like having maximum rigidity and strength together with minimum weight and polar moment of inertia. Specifically, this invention relates to rocker arms which are economical to manufacture and provide trusses between the push rod or tappet and the valve actuated thereby.

In accordance with this invention top and bottom metal straps disposed flatwise receive a tubular metal bushing therebetween and provide truss members substantially free from beam action to transmit loads while rocking about a shaft support for the bushing. A bearing sleeve liner is provided in the bushing. The bushing itself acts as a strut transferring load between the top and bottom straps and compares with a web member in a bridge suspension.

- The straps converge at a point as close as possible to the center line of load application at each end of the rocker arm for eliminating beam action between the load pointand the contactpoint. The lower strap wraps and supports the bushing over an area that carries substantially the entire bearing load. The valve contacting end of the straps is more distantly spaced from the bush-- ing than the push rod or tappet contacting end of the straps and a spacer is provided between the straps at tralizes the tendency of a beam deflection by acting as the push rod engaging end thereof. This spacer neua link forming the side of a quadralateral. Since the bending moment is negligible at the valve contacting end of the rocker arm the spacer or link is not necessary at the valve end. The straps converge rather abruptly from the bushing to the push rod contacting end and converge along a gentle slope from the bushing to the valve contacting end. This provides two triangular trusses forming'rigid frames no member of which can be deformed without deforming the other member. Beam bending action is thereby minimized.

It is then an object of this invention to provide a truss type rocker arm for internal combustion engines.

Another object of this invention is to provide a low inertia, light weight, strong and rigid rocker arm.

A further object of this invention is to provide rocker arms having flatwise disposed top and bottom straps embracing a tubular rock shaft receiving bushing and converging from both sides of the bushing to provide a short push rod contact end portion and a long valve contact end portion.

A further object of the invention is to provide a rocker arm composed of flatwise disposed top and bottom steel strips over the top and bottom of a tubular bushing and converging from the bushing to connected ends for coaction with a push rod and a valve tip respectively.

A specific object of the invention is to provide a fabricated truss type light weight and economical rocker arm with struts of uniform thickness but varying in width to uniformly distribute stresses encountered therein.

A further object of this invention is to provide a rocker arm composed of a bushing and strap members secured to the bushing and to each other so as to form twotriangular trusses for transmitting loads between a push rod and a valve.

' straps and spacer 15.

' screw-and the top strap 11.

Patented Feb. 3, 1959 ice Other and further objects of this invention will be apparent to those skilled in the art from the following detailed description of the annexed sheets of drawings, which, by way of preferred examples, illustrate several embodiments of the invention.

On the drawings:

Figure 1 is a side elevational view, with a part in vertical cross-section, illustrating a rocker arm according to this invention operatively mounted on a rock shaft and transmitting forces between a push rod and a valve.

Figure 2 is a top plan view of the rocker arm of Figure 1 illustrating the varying width of the truss struts.

Figure 3 is a longitudinal cross-sectional view along the line III-III of Figure 2.

Figure 3A is a fragmentary view similar to Figure 3 but showing another form of spacer.

Figure 4 is a side elevational view of a modified form of rocker arm according to this invention.

Figure 5 is a longitudinal cross-sectional view ofthe rocker arm of Figure 4.

Figure 6 is aside elevational view of still another modified form of rocker arm according to this invention.

Figure 7 is a longitudinal cross-sectional view of a further modified form of rocker arm according to this invention.

Figure 8 is a transverse cross-sectional view, with parts in elevation, taken along the line VIII-VIII of Figure 7. w

Figure 9 is a fragmentary longitudinal cross-sectional view of still anothermodified rocker arm according to this invention.

Figure 10 is a transverse cross-sectional view, with parts in elevation, taken along the line X--X of Figure 9.

Figure 11 is a fragmentary side elevational view of a portion of a modified rocker arm according to this invention carrying a roller for engaging the'tip end of a valve.

Figure 12 is an isometric view of the roller assembly of Figure 11.

Figure 13 is a fragmentary v1ew illustrating the man-- ner in which the strap members of the rocker arm are centered on the bushing.

Figure 14 is a side elevational view of a rockerarm according to this invention illustrating the manner in which forces are applied thereto in operation.

Figure 15 is a force diagram illustrating the force vectors applied to the rocker arm at the triangular truss formed on the push rod end portion of the arm.

Figure 16 is a view similar to Figure 15 but illustrating the force vectors at the valve tip end portionof the ing the manner in which the linkage controls deflection.-

As shown on the drawings:

The rocker arm 10 of'Figures 1'to'3 includes a top strap 11, a bottom strap 12, a tube 13, a bearing liner 14 in the tube 13, a spacer 15 between the

straps

11 and 12 at the push rod contact end of the rocker arm, and an internally threaded eylet 16 inserted through the This eyelet 16, as shown in Figure 1, receives an adjustment screw 17 therethrough. The adjustment screw has a rounded end 17a fitting in the recessed top end of a push rod 18. A locknut 19 on the adjusting screw is provided between the head 17b of the The top strap 11 is substantially straight being bowed at 11a to fit around a small arc of the top of the tube 13. I

This bowed portion 11a is bonded to the top of the tube by any suitable brazed bonds or welds 20. The strap slopes downwardly from the bend 11a to provide a long legllb and a short leg 110. The long leg 11b terminates in a substantially horizontal rounded end portion 11d while theshort leg 11c terminates in a flat eye He receiving the threaded eyelet 16 therethrough. This eye He is affixed to the eyelet by welded or brazed bonds2 1- and the eyelet also has an out-turned flange 16a spun over the top of the: eye 112.

The bottom strap 12 is bowed much more than the top strap 11 and has an arcuate portion 12a lapping about the lower third of the tube. 13 and bonded thereto by braze or weld. bonds 22. The strap 12 slopes upwardly from the bowed portion 12:: to provide a relatively long leg 12b and av relatively short leg 120. The long leg 12b terminates in a substantially horizontal end 12d with a somewhat rounded bottom. contour. A weld or braze bond 23 unites the

end portions

11d and 12d of the

straps

11 and 12. The end of the short leg 12c terminates in an eye 12e similar to. the eye He and receiving the eyelet 16 therethrough. Braze or weld bonds 24 unite the spacer 15 with the eye He and the eyelet 16 is spun over the bottom of the eye 12:: to provide a flange 16b underlying theeye.

The

straps

11 and 12 are of uniform thickness throughout their lengths. as shown in Figures 1 and 3.

The rounded end 12d of the strap 12 acts on the tip end of a valve stem 25 to compress the valve spring 25a thereby to open the valve when the push rod 18 raises the adjusting screw 17.

The tube 13 is most economically formed as a butted cylindrical stamping with the butted front 13a thereof at the top under the bowed portion 11a of the top strap 11. When the straps are brazed on the tube this joint is also brazed closed. Alternately the tube 13 can be economically formed of butt welded tubing with the welded seam 13a at the top of the rocker arm as shown. As will be hereinafter explained, the bearing forces on the tube 13 are applied to the bottom of the tube. As shown, the bearing liner 14 for the tube is rotatably mounted on a lubricant-fed hollow rock shaft 26 having a hole 26a in the bottom thereof to lubricate the bearing liner 14.

As shown in Figure 2, both

straps

11 and 12 have the same thickness but each strap varies in width along its length and lies flatwise on the tube 13 which extends on both sides beyond the edges of the straps. The wider portions of the straps are at the push rod end. This arrangement provides a long legged triangular truss and a short legged triangular truss with legs of uniform thickness but varying in width to uniformly distribute stresses. The long legged truss is composed of the strap legs 11b and 12b and one half of the tube 13. The short legged truss is composed of the

strap portions

11c and 120 and the other half of the tube. These triangular assemblies act as true truss suspension members in that no one member in the truss combination can be deformed without deforming another member. The only possible beam supports of the entire assembly occur at the extreme ends of the trusses and, as will be hereinafter explained, the spacer 15 together with the inserted eyelet 16 serve to provide a linkage which minimizes beam bending.

If desired as shown in Figure 3A the spacer can take the form of a curved stamped piece 15' overlying the highly curved leg 120 of the strap 12 and brazed thereto to increase the brazing contact area and to reinforce the leg 120.

In the modification a of Figures 4 and 5, parts identical with parts described in Figures 1 to 3, have been marked with the same reference numerals. In the modification 10a, the ends of the long legs 11b and 12b of the

straps

11 and 12 are not bowed or curved. These ends

portions

11d and 12d are flat and fully mate with each other. The weld bond 23 of the embodiment 19 is eliminated and instead of a round head rivet 27 has the shank 27a thereof snugly fitted in apertures of theflat ends 11d and 12d. A spun over outturned flange 27b on the shank 27a overlies the end 11d of the top strap 11 and a rounded head 27c underlies the portion 12d of the strap 12. The rounded head 27c acts on the tip end of the valve stem in the same manner as the rounded end 12d in the embodiment 10. However, the rivet head reinforces the long end of the assembly and decreases the beam effect.

In the modification 10b of Figure 6, parts identical with parts described in Figures 1 to 5 have been marked with the same reference numerals. In Figure 6 the long legs 11]; and 12b of the

straps

11 and 12 have spaced apart fiat ends 11d" and 12d" with a spacer 28 therebetween and welded thereto by weld bonds 29. The rounded head 270 of the rivet 27 underlies the portion 12d" while the spun over flange 27b of the rivet overlies the portion 11d".

portions

11d and 124" in the same manner as the spacer 15 between the eyes 11a and 122. This linkage effect further decreases any beam action at the valve contact end of the rocker arm.

In the embodiment shown in Figures 7 and 8, parts identical with parts described in Figures 1 to 6 have been marked with the same reference numerals. In the rocker arm lllc as shown in Figure 7, the end portions 112 and 12e of the straps 1-1 and 12 receive the spacer 1S therebetween and receive a plug 30 therethrough with spun over end flanges Slla and 30b securing the plug in position. This plug has a fragmental spherical recess 31 in its bottom face receiving the ball end 32 of a push rod 33. A passageway 30c connects the recess 31 with a side wall of the plug.

The top strap 11 receives thereover a hollow ribbed strap 34 having a central raised rib 34a providing a passageway 34b between the top face of the strap 11 and the bottom face of the strap 34. This strap 34 has a contour following the contour of the strap 11 and has flat eye end 340 overlying the eye end He and in turn, having flange 30a of the plug 30 spun thereover.

A hole 35 is formed through the top of the tube 13 and liner 14 in alignment with a hole 36 formed through the strap 11. The registering holes 35 and 36 feed lubricant supplied from the hollow rock shaft 26 to the passageway 34- which in turn, feeds the passageway 300 in the plug 30 to lubricate the socket 31 for the push rod.

The flat front ends 11d and 12d of the long legs 11b and 12b of the straps receive a rivet 27 therethrough in the same manner as described in connection with Figure 5 but this rivet 27 has a longer shank so that it can project through the end 34d of the top strap 34 and have an outtnrned flange 27b spun over this top strap.

The rocker arm 100 thus has a covered lubricant passage for lubricating the push rod with lubricant supplied from the bearing or rock shaft.

In the modification 10d of Figures 9 and 10, parts identical with those previously described have been marked with the same reference numerals. As shown, a top strap 11' has a central-corrugation therein providing an open bottomed passage 37 in the short leg thereof communicating with the bore 30c of the plug 30 to supply lubricant to the recess 31 of the plug. The tube 13' has a raised rib 38 along the top portion thereof providing a passageway receiving rock shaft supplied lubricant from the hole 35 in the liner 14 and discharging the lubricant through a hole 39 into the open bottomed passage 37 from which it will flow to the bore 300. In this embodiment, therefore, an open bottomed lubricant flow passage is provided in the upper strap and is fed from a channel provided in the tube.

In the embodiment 162 of Figure 11 the long legs 11b and 12b of the

straps

11 and 12 have their forward ends bowed as at 11d' and 1211" to provide a roller recess in the bottom face of the assembly. A groove 44) is pro- The spacer 28 provides alinkage between the vided in the raised end '11d' to receive a wire hanger 41 for a roller 42 which rides in the recess. As shown in Figure 12, this hanger 41 is a U-shaped member and has the bight portion 41a thereof for fitting in the groove 40 together with side legs 41b straddling the strap 11 and having rounded end portions 410 on the legs 41b merging with bottom legs 41e. These bottom legs have inturned ends 41d inserted in the ends of an aperture 42a of the roller 42. This roller 42 rides on the tip end of the valve and the hanger 41 suspends the roller so that it will bear against the rounded end 1251" of the bottom strap 12.

As shown in Figure 13, for ease in assembly of any of the embodiments of this invention, the top strap 11 and the bottom strap 12 can have apertures 43 and 44 respectively therethrough. The tube 13 has pierced outturned projections 45 fitting the apertures 43 and 44. These pierced portions and holes facilitate proper alignment of the straps on the tube and can be used as locators during assembly of the rocker arms of this invention.

Figure 14 indicates generally the manner in which the forces are applied to the rocker arms of this invention. The rocker arm embodiment a of Figures 4 and 5 has been selected as typical of the disclosures. As shown in Figure 14, Pp is the force applied by or acting on the push rod, Fv is the similar force of the valve stem and Fs is the resulting resisting force exerted by the rocker arm shaft on the bushing. It will be noted that these forces are always in the same general direction since their respective angles in relation to the rocker arm change only a small amount due to the small rotation of the rocker arm. The rocker arms of the present invention thus have the top and

bottom straps

11 and 12 forming substantially true trusses.

As diagrammatically illustrated in Figure 15 the push rod end of the rocker arm on which the force Fp is applied is translated to a force F'p in the top strap leg 11c and a force F"p in the bottom strap leg 120. These forces resist the push rod load Fp acting at the fulcrum of the straps. In Figure 16 the corresponding vector diagram and forces for the valve contact of the rocker are shown where the force Fv is translated into a force Fv' in the top strap leg 11b and a force F"v in the bottom strap leg 12b. Thus, the forces acting on the right and left hand parts of the top strap where they join the bushing are not equal and opposite. There is a resultant force transmitted through the bushing and the bushing thus acts as a strut member or as the third member of a triangular truss.

In the rocker arms of this invention all of the metal in the strap is stressed uniformly and the rocker arms of this invention can, therefore, be made with light weight material to decrease the polar inertia of the assembly.

While a beam stressed to the same surface stress as a truss may be more rigid than a truss, it has been found feasible to increase the section of the

straps

11 and 12 in the truss rocker arms of this invention to give the same or greater rigidity than that of a conventional beam unit and yet produce a lighter rocker arm with lower polar moment of inertia.

The following data illustrates the increased strength, and rigidity, and the decreased weight and polar inertia of the truss type rocker arms of this invention as compared with standard beam type stamped rocker arms:

In Figure 17 there is illustrated the manner in which fiat mated together ends 46 and 47 of the

straps

11 and 12 On the other hand, as shown in Figures 18 and 19, thespacer between the ends of the

straps

11 and 12 acts asa link 49 and as these ends are deflected upwardly as shown in Figure 19 the link 49 is swung inwardly at the bottom to arrest the rotation and rigidify the assembly. The resultant force F may actually be in an outward direction. The spacer and rivet assembly in the short legs 11b and 12b of the straps, therefore, offsets the bend of the ends of the straps by pulling the strap in from the bottom as shown in Figure 19 resisting furtherbending. A link arrangement for the long legs is not needed because the ends of these legs. are spaced a considerable distance from the rocker shaft support and bending deflection is negligible.

It will be noted in all of the rocker arms of this invention, the bottom strap laps a considerable are of the bottom of the tube 13., This strap, therefore, reinforces the tube over the area that carries substantially the entire load Fs as shown by the force diagram in Figure 14.

From the above descriptions it will thus be understood that this invention now provides economical, light weight, low inertia truss type rocker arms including substantially flat top straps and bowed bottom straps anchored to a bearing tube therebetween. The bearing tube is positioned closer to the push rod actuated end of the rocker arm than to the valve actuating end of the arm. The push rod actuated end has a spacer between the straps acting as a link to resist a beam bending action. The assemblies of straps, tubes, spacers, rivets and the like, can be secured in any conventional manner as by welding, riveting, brazing, or the like.

It will be understood that modifications and variations 7 may be effected without departing from the scope of the novel concepts of the present invention.

1 claim as my invention:

1. A rocker arm comprising a metal tube, a bearing liner in said tube, top and bottom straps extending transversely of said tube, weld bonds uniting said straps with the tube, said top strap having a substantially flat contour and enveloping only a small portion of the tube, said bottom strap lapping a substantial portion of the tube, said straps having short legs on one side of the tube and long legs on the other side of the tube, a spacer between the ends of the short legs of the straps, push rod means coacting with said ends, and the long legs of the straps being substantially longer than the short legs and converging to provide a valve contact end portion for therocker arm. v

2. A truss type rocker arm which comprises top and bottom truss members, an interposed bushing tube an- 1 chored thereto, said truss members converging at their ends to provide valve actuating and push rod actuated portions of the rocker arm, and said tube acting as a strut between the straps to coact therewith for forming a pair of triangular trusses.

3. A rocker arm comprising top and bottom straps, a bushing between said straps and secured thereto, said straps projecting beyond the bushings and converging to end portions, one end portion having relatively short legs and having opposed flat eyes, a spacer between said eyes, an eyelet extending through said eyes and said spacer, means securing said eyelet to said eyes, said long legs having mated together portions, and means at the ends of the long legs adapted to engage the tip end of a valve.

4. A truss type rocker arm which comprises a pair of substantially flat top straps, the uppermost top strap having a corrugated rib portion therein providing a passageway between the straps, a .U-shaped bottom strap, a rock shaft bushing between the top and bottom straps and secured thereto providing longitudinally spaced trusses, said, bushing having a lubricant aperture therethrough communicating with said passageway, said straps converging to flat eye end portions at one end thereof, a push rod receiving plug cooperable with another end of said straps, and a passageway connecting the push rod receiving portion of said plug with said oil passage between the straps.

5. A rocker arm comprising a tubular bearing bushing, superimposed first and second struts straddling the bushing and extending laterally thereof, a push rod engaging portion on one end of said struts, a valve tip engaging portion on the other end of said struts, and said struts being connected only at the ends and through the bushing to provide rigid triangular trusses with opposite side portions of the bushing.

6. A rocker arm which comprises a rock shaft bushing, a slightly bowed top strap secured flatwise on said bushing and extending laterally thereof, a U-shaped bottom strap engaging the bottom portion of the bushing and secured flatwise thereon to underlie the top strap, said straps being spaced and converging on each side of the bushing to form a valve contact end and a push rod contact end, said top strap having a hollow open bottom hollow rib extending longitudinally from the bushing to the push rod contact end, said bushing having a hollow rib seating in the rib of said top strap arranged to re ceive lubricant from a rock shaft in the bushing, and said bushing rib having an aperture for directing lubricant into the open bottom of the strap rib to flow along the strap rib to the push rod contact end.

. 7. A rocker arm which comprises a tubular rock shaft bushing, straps straddling said bushing and converging on opposite sides thereof to provide trusses therewith, a rivet secured in one convergent end of the straps having a valve tip contact head, a spacer between the other convergent ends of the straps, and a push rod engaging member carried by said other end.

References Cited in the file of this patent UNITED. STATES PATENTS 547,136 Barr Oct. 1, 1895 1,164,405 Schaeffer Dec. 14, 1915 1,306,119 Pharo June 10, 1919 1,467,964 Postol-Vinay Sept. 1, 1923 1,644,750 Short Oct. 11, 1927 1,699,657 Pagan Jan. 22, 1929 1,866,293 Chandler July 5, 1932 1,964,770 Runge July 3, 1934 2,176,083 Leake Oct. 17, 1939 2,199,914 Haberstump May 7, 1940 2,272,166 Leake Feb. 3, 1942 2,469,564 Leake May 10, 1949 2,572,968 Bachle Oct. 30, 1951 OTHER REFERENCES Publication: Smith, Welded Construction, Product Engineering, pp. 388-389 July 1942.