US2120384A

US2120384A - Yieldable clutching means

Info

Publication number: US2120384A
Application number: US727136A
Authority: US
Inventors: Wohlfeld Jacob
Original assignee: GEORGE LOVEQUEST
Current assignee: GEORGE LOVEQUEST
Priority date: 1934-05-23
Filing date: 1934-05-23
Publication date: 1938-06-14
Anticipated expiration: 1955-06-14

Description

June 14, 1938; J, WOHLFELD 2,120,384

YIELDABLE CLUTCHING MEANS Filed May 23, 1954 I [WEN mg gbg s- 4TTORNE Y Patented June 14, 1938 YIELDABLE CLUTCHING MEANS Jacob Wohlfeld, Detroit, Mich, assignor to George Lovequest, Detroit, Mich.

Application May 23, 1934, Serial No. 727,136

'20 Claims.

The invention relates to yieldable clutching means for valve operating mechanism and other motion transmitting systems.

An object of the invention is to provide yield.-

5 able clutching means of durable, compact, and

inexpensive construction suitable for use in various motion transmitting systems, as in the valve operating mechanism of an internal'combustion engine to minimize noise and play and to auto- -matically compensate for variations in the length of the valve caused by temperature changes and wear, the clutching means being capable of mounting in a self-contained tappet permitting replacement'of a tappet of conventional type.

- Another object of the invention is to provide a yieldable clutching device having spring-urged friction means through which the operating pressure is transmitted, and a more specific object is to form the friction means by a confined plug of plastic or deformable material.

The invention .further consists in the several features hereinafter described and claimed.

In the accompanying drawing,

Fig. l is a sectional elevation of a valve operating mechanism equipped with a slack adjuster having yieldable clutching means embodying the invention, and

Fig. 2 is a detail view of some of the slack adjuster parts.

In the drawing, l designates the cylinder block of an internal combustion engine provided with the usual poppet valve ll engageable with a valve seat 12 and having its stem l3 slidably mounted in the block and urged to valve-closing position by the usual surrounding valve spring M bearing on a valve washer, l5 held on the stem by a. retainer 16. A tappet member I1 is slidably mounted in the cylinder block below and in axial allgnment'with the valve stem and has the usual enlarged lower end l8 periodically lifted by a cam IS on a cam shaft 20 to thereby actuate the valve.

It will be obvious that for the type of valve operated through a rocker arm, the valve stem 13 is replaced by the usual valve rod or push rod which may also be regarded as a valve stem.

The tappet member ll, instead of having the usual adjusting screw means, is provided with the. yieldable clutching means of the invention. The tappet -member forms a cylinder into the upper end of which is forced a tubular plunger body 2| having an annular flange 22 at its upper and engaging the upper face of the tappet member. A coiled spring 23 is housed within the tap- '55 pet member below the plunger body and bears at its upper end on a disk-like spring seat member I 24 limited in its upward movement by the lower end of the plunger body. A relief opening 25 is drilled into the lower portion of the tappet member.

The plunger body 2| has formed therein aligned upper and

lower bores

26 and 21, respectively, communicating with an intermediate upwardly diverging conical bore 28, the upper bore 26 being of larger diameter than the lower bore 7 21. An-upper plunger 29 is slidably mounted in the bore 26 and projects upward from the plunger body to engage the lower end of the valve stem l3. A lower plunger 30 is slidably mounted in the bore 21 and has a projecting conical lower end engageable with the upper face of the spring seat member 24, a recess 3! being formed in this face to receive the conical end. Between the

plungers

29 and 30 isinterposed a compact, substantially voidless plug or briquet 32 .of soft, plastic or deformable coherent material, such as graphite, although in some instances lead, a plastic amalgam, or rubber can be used.

. Fine powders, such as of carbon or metals, for instance, aluminum, are also usable. If desired, graphite may be mixed with the powders. The plug of solid but flowable material is confined by the plungers in the conical bore 28 which it. frictionally engages, and under pressure fills the entire space between the adjacent end faces of the plungers, the flowablematerial and the plug or mass formed thereby being substantially incompressible. The space within the conical bore forms what may be termed an extrusion chamber for the deformable plug. While the bores 26 and -35 21 and the plungers therein are here shown to .be of circular cross-section, it will be obvious that other cross-sections may be used.

Before the tappet assembly is installed in the engine, the free overall length of the assembly is slightly greater, say 0.015 inch, than the normal distance between the cam and lower endof thevalve stem, and the spring 23 forces the spring seat member 24 into abutment with the lower end of the plunger body 2|. When the tappet assembly is installed, the plunger 29 engaging the lower end of the valve stem gradually movesdownward under urge of the valve spring until the valve engages its seat and a small clearance, say 0.030 inch, exists between the. spring seat member and the bottom face of the plunger member, it being noted that the smaller plunger 30 movesfarther than the larger plunger 29. During this movement of the plungers, the interposed plug 32 lengthens and changes its shape,

unchanged. The deformable material presents a smooth surface which is in substantially continuoils or unbroken slidable contactwith thewalls of the chamber..

In operation, the valve is periodically actuated by the rotating cam shaft, the tappet member forming a motion-transmitting compression member. In the interval during which the valve is closed, the pressure of the tappet spring 23 acting upward through the valve seat member 24, the lower plunger 30, the plastic or flowable material 32, and the upper plunger 29, tends to increase the length of the tappet. This pressure is opposed by the somewhat greater valve spring pressure with the result that the tappet completely fills the space between the cam and the lower end of the valve stem, but does not lift the valve off its seat.

When the cam l9 lifts the tappet member H, the upper plunger 29 lifts the valve from its seat. During this movement, the force acting downward through the valve stem 13 is transmitted through the upper plunger 29 which in turn transmits it to the plastic or flowable material forming the plug 32. Some of this force. is used in overcoming the friction caused by moving the plastic material downward in the conical bore 28 of the plunger body 2| and in changing the shape of the plug, the balance of the force being transmitted to the smaller lower plunger 30 which in turn transmits it to the spring seat member 24,

then to the spring 23 and to the bottom portion of the tappet member l'l. During the interval from valve opening to maximum valve velocity upward, the valve spring pressure plus the force due to the inertia of the valve, valve spring, washer, retainer and upper plunger tend to shorten the tappet, while the tappet spring and friction of the flowable material oppose this total force. During the interval from maximum valve velocity upward to maximum valve velocity downward, the valve spring pressure minus the force due to the inertia of the valve, valve spring, washer, retainer and upper plunger and plus the force due to the inertia of the tappet assembly (lessupper plunger) tend to shorten the tappet, and the tappet spring and friction of the flowable material oppose this total force. During the interval from maximum valve velocity downward to valve closing, the forces acting are the same as those in the interval from valve opening to maximum valve velocity upward. The forces due to the inertia of the tappet spring seat member 24, lower plunger 30 and flowable material, although small, are added to the tappet spring pressure for the interval from maximum valve velocity upward to maximum valve velocity downward, and are subtracted from tappet spring pressure for the interval from valve opening to maximum valve velocity upward, and for the interval from maximum valve velocity downward to valve closing. By varying the tappet spring pressure, the relative areas of the upper and lower plungers, the friction or fiowability of the plastic material, and the shapeof the space through which the plastic material moves, to suit any particular valve meehanisir'i'i'it is possible to maintain a tappet assembly length that will fill the space between the cam and the lower end of the valve stem, with a positive seating of the valve and full valve lift, except for a very slight shortening during the valve-open period, say considerably less than 0.001 inch.

If the valve stem lengthens incident to an in- I Letters Patent is.

crease in temperature and the valve tends to ride, the upper plunger 29 gradually moves downward until the valve fully seats and a clearance of, say, 0.038 inch exists between the spring seat member 24 and the lower end of the plunger body 2|.

The pressure or force acting on the upper plunger 29 is transmitted to the lower plunger 30 through the plastic or flowable material which functions like a plastic metal, has a comparatively slow action, and can be confined under the operating pressures without appreciable loss. The plastic or. flowable material thus exerts a damping efiect. When the plunger 29 moves downward, the flowable material is extruded from the largerplunger bore. 26 to the small plunger bore 2| and the smaller plunger 30 moves downward a greater distance than the upper plunger. When the lower plunger moves upward, the flowable material is lifted relatively freely as a briquet away from the tapered walls of its chamber, and the upper plunger moves with the flowable material until the upper plunger abuts against the valve stem and stops. The lower plunger continues to move until the flowable material changing form entirely fills the con-I fining space. Obviously, the force applied to the smaller plunger necessary to move the larger plunger is less than that applied to the larger plunger in order to move the smaller plunger, considering the plunger body assembly as a unit consisting of the parts 2|, 29, 30, and 32.

In general, the tappet assembly herein described will automatically, when in action, increase or decrease in overall length to suit the variations in distance between the cam. and the end of the valve stem, so that the valve will seat vention is here shown to be embodied in a slack adjuster for a valve-operating mechanism, it is also applicable to other motion-transmitting systems wherein it is desired to minimize lost I motion, to compensate for variations incident to temperature changes and other causes, and to permit motion in one direction more freely than in the opposite direction. Among such systems are brake systems, shock absorbers, door checks,

remote control mechanisms, jacks ..too1 fixture locks, and the like.

What I claim new and desiregio secure by 1. The'combination of a body having bores and a chamber between and communicating with said bores, plungers in said bores, a compact, substantially voidless mass of soft, solid but flowable material confined in said chamber by said amass-i plungers in said bores, a mass of flowable material of high internal friction confined in said chamber by said plungers and engaging the walls of said chamber, and yielding means for applying pressure to said material through the smaller plunger.

3.- The combination of a motion-transmitting member having a pair of bores extending in the direction of motion, there being a chamber between and communicating with said b0res,,

plungers in said bores, a compact, substantially voidless mass of soft, solid but flowable material in said chambenfrictionally engaging the walls of said chamber, and spring means in said member for applying pressure to said material through one of said plungers.

4. The combination of a tubular member having a pair of axially spaced bores adjacent one end extending longitudinally of said member, theouter bore being of larger diameter than the inner bore and there being a communicating chamber between said bores, plungers slidable in said bores, a mass of solid but flowable material confined in said chamber by said plungers and frictionally engaging the walls of said chamber, spring means in said tubularmember for applying pressure to said material through the, smaller plunger, and stop means for limiting the movement of said spring means.-

6. A slack adjusting tappet comprising a movable tubular member, a plunger body secured in one end of said member and having bores at opposite ends extending longitudinally of said "member, there being a chamber between and communicating with said bores, plungers slidable in said bores, a mass of solid but fiowable material confined in said chamber by said plungers and frictionally engaging the walls of said chamber, and spring means in said tubular member for applying pressure to said material through the plunger at the inner end of said plunger body. 7. Yieldable clutching means comprising a pair of relatively movable members, friction means for resisting relative movement of said members in'cluding a compressed but flowable mass of graphite, and yielding means for applying pressure to said friction means and tending to move one member with respect to the other.

8. Yieldable clutching means comprising a pair of relatively movable members, friction means for resisting relative movement of said members ineluding a compressed but fiowable mass of powdered material, and yielding means for applying pressure to said friction means and tending to move one member with respect to the other.

9. Yieldable clutching means com'prisinga pair of relatively movable members, friction means for resisting relative movement of said members including a compressed but fiowable mass of powdered metal, and yielding means for applying pressure to said friction means and tending to move one member with respect to the other.

10. Yieldable clutching means comprising a pair of relatively movable members, friction means for resistingrelative movement of said members including a compressed but flowable mass of plastic metal, and yielding means for applying pressure to said friction means and tending to move one member with respect to the other.

11.Yieldable clutching means comprising a pair of relatively movable members, friction means for resisting relative movement of said members including a compressed but i'lowable mass of powdered carbon, 'and yielding means for applying pressure to said friction means and tending to move one member with respect to the other. I

12. Yieldable clutching means comprising a pair of relatively movable members, friction 'means for resisting relative movement of said members including a compressed but fiowable mass of graphite bearing material, and yielding means for applying pressure to said friction means and tending to move one member with respect to the other.

13. The combination of a body having a cham-' ber with walls, members movable in said body and communicating with said chamber, and a compact, substantially voidless mass of soft, solid but flowable friction material in said chamber for transmitting pressure between said members. and deformable by movement along said walls to retard relative movement.

14. The combination of a body having a chamber with converging walls, plungers movable in said body and communicating with said chamber, and a mass of solid but flowable material in said chamber for transmitting pressure between said plungers and deformable by movement along said converging walls to retard relative movement.

15. The combination of a body having a chamber with converging walls, a member relatively movable in said body and ,communicating with said chamber, and a mass of solid but. flowable friction material in said chamber engageable with said m mber and deformable by movement along said converging walls to retard relative movement of said body and member.

16. The combination of a pair of relatively movable members, and friction clutching means for resisting relative movement of said members and comprising a compact, substantially voidless mass of soft, solid but flowable friction material. said material being substantially incompressible and having a smooth deformable surface in substantially continuous frictional contact with the surfaces of said members.

17. The combination of a body having a pair of guide'openings of different cross-sectional area and a chamber at-the inner ends of said openings, members slidably fitting in said guide openings and forming the opposite'ends of said chamber, and'a dense mass of soft, solid but iiowable material confined in said chamber by said members and having a clutching engagement with the walls of said chamber, said chamber being larger at the end defined by the larger guide opening to permit relatively easier movement of said material toward said end than toward the smaller end, and means acting through the smaller member to applypressure to said material in a direction tending to effect the free movement of said material.

18. Yieldable clutching means comprising a pair of relatively movable members, friction means for resisting relative movement of said prising a confined mass of compact, soft, solid but 10 flowable graphite.-

20. The combination of relatively movable interfitting members forming a chamber, and friction clutching means for resisting relative movement of said members comprising a dense, substantially incompressible, briquet-like' mass of soft, solid but iiowable coherent material con-' fined in and filling said chamber and having a friction clutching engagement with walls of said chamber.

JACOB womr'mln. 10