US2654356A

US2654356A - Hydraulic tappet

Info

Publication number: US2654356A
Application number: US106413A
Authority: US
Inventors: Oldberg Sidney
Original assignee: Eaton Manufacturing Co
Current assignee: Eaton Corp
Priority date: 1949-07-23
Filing date: 1949-07-23
Publication date: 1953-10-06
Anticipated expiration: 1970-10-06

Description

Oct. 6, 1953 s. OLDBERG :2,654,356

HYDRAULIC TAPPET Filed July 23,-1949 34 I6 fr! Iii ' lW///////////// .A

INVHVTOR. SIDNEY OLDBERG 3 tive axial holding means between the sleeve and plunger in the relative movement thereof to the body in which the plunger is reciprocable.

The ilexible sleeve in so being secured at its end extremities upon the plunger and body provides for the hermetic sealing of a hydraulic fluid completely lling the spaces provided between the plunger and body such that a reservoir or low pressure chamber is provided near one end of the plunger having valve controlled communication with a high pressure or compression chamber formed at the other end of the plunger between the plunger and body. In one form of sleeve made of rubber or similar resilient material the annular wall thereof extending between the secured ends thereof is of such strength and resiliency as to bear on the hydraulic uid in the low compression chamber or reservoir with substantially atmospheric pressure when the plunger is extended a maximum amount relative to the body in which it is reciprocable and is capable of being distendable an amount radially outwardly sufficient to maintain a substantially constant volumetric space for the hydraulic fluid. This is essentially necessary for the proper function of the tappet in the displacement of fluid from one chamber to the other chamber in the operational extension and contraction of the tappet. The tappet, as shown by Fig. l, is at its normal operating length and as such the plunger is relatively movable axially in both directions therefrom relative to the tappet body. A modified form of sleeve is made of fabric or similar substantially non-distendable material and as such is assembled on the plunger and body with the plunger bottomed thereby establishing its maximum volumetric holding capacity whereby upon the extension of the plunger it merely collapses inward radially with atmospheric pressure impressed on the uid contained therein.

For the purpose of reducing servicing costs and making a self-contained self-compensating device that is adaptable to a plurality of different engines the device is embodied in a unit adaptable to insertion in a tappet body per se. As a service replacement unit it need thus be only necessary to lift the valve from off its seat to allow ample space to remove the faulty unit and replace same with a new one thereby alleviating the otherwise .required tearing down or dismantling of the complete valve gear system.

Referring to the drawings for more specific details of the invention, I represents generally an automatic length compensating mechanism in the specific form of a tappet for use in a valve gear system of internal combustion engines effective to take up clearance therein automatically as same results to quiet the operation thereof. The tappet comprises a cylindrical tappet body I2 open at one end and closed at its other end providing a cavity I4 therein adapted to receive an automatic length compensating self-contained unit I6 therein.

The unit IB comprises a cylindrical body I8 closed at one end and open at its other end providing a cavity 20 therein in which a plunger menttherein and has welded or otherwise suitably secured at its closed end a mushroom-shaped head 26 adapted to be engaged by an engine cam member or the like, not shown.

The plunger member 22 includes an annular reduced portion 28 of lesser diameter than head portion 38 and body portion 32, axially spaced therebetween, the purpose of which will hereinafter appear and provides fluid passage 34 therethrough extending centrally through the body portion 32 into connection with the reduced annular portion 28. The passage 34 is adapted to communicate with a high pressure or compression chamber 36 formed between the end extremity of body portion 32 of the plunger and closed inner end of body I8 controlled as by a disc valve 38 adapted to be positioned on valve seat 48 provided at the terminus of passage 34 in chamber 36. The valve seat and valve 38 are so cooperably shaped as to provide for solely annular line sealing contact therebetween thereby assuring an effective seal and valve 38 is limited in its radial and axial movements respectively by an annular enclosure 4I forming a part of body portion 32 of plunger 22 having a plurality of radial slots therein for free passage of fluid therethrough and a coil spring 42 the end coil of which bears in overlapping relation on enclosure 40 so as to limit the movement of the valve axially therefrom. The spring 42 which is interposed in compression chamber 38 between the inner closed end of body I8 and the enclosure 4I serves to normally bias the plunger outwardly of the body I8 and by providing for slight clamping or holding of the end coils respectively on the plunger and body the spring acts as a rotation prevention means between the plunger and body so as to prevent the possible distortion or twisting of rubber which might tend to injure or destroy its function.

The head portion 38 of plunger 22 is coupled to the open end of body I8 by a resilient rubber or like material sleeve 44 secured therebetween one end of which is held in pressed sealing relation upon the exterior surface of body I8 near its open end by an annular clip member 46 secured upon one end extremity of the sleeve. The clip 46 provides a lip portion 48 inwardly radially e'xtended and turned back axially on itself having a portion of the end of the sleeve annularly clamped therein such that it can not be extended axially therefrom and an axial annular portion 58 bearing annularly externally of the sleeve near its one extremity effective to cause a radial bearing in sealing engagement of the inner wall of the sleeve on the external surface of the body I8. The clip 48 for the purpose of stiffening or reinforcing same is provided with a rib or annular turned end 52 at its annular end disposed away from lip 48. The curved section of lip portion 48 of clip 46 in its clamping position on the one end extremity of sleeve 44 and with the clip and sleeve assembled on the external surface of the body I8 abuts the upper axial shoulder of annular rib 24, thus positively inhibiting the axial movement of the Sleeve and clip in one direction on the body I8.

A clip 54 similar to clip 48 but of a size to conform with the size of sleeve 44 at end 56 thereof and head portion 30 upon which end 58 of sleeve 44 is to be secured is clamped upon end 56 of sleeve 44 and is provided with

portions

58, 68 and 62 corresponding in structure and purpose to the

portions

48, 50 and 52 o-f clip 48. The llip 58 of clip 54 serves at its extremity to positively inhibit the axial movement of end 56 of the sleeve from movement relative to head 30 of the plunger during the reciprocation thereof by its receipt in an annular groove 64 formed on the external surface of head 30.

The external vsurfaces'of the respective plunger 22 and body |8 upon which the respective ends of the sleeve 44 are pressed for sealing and holding engagement are provided with a plurality of parallel grooves 66 into which portions of the sleeve are pressed to insure an effective sealing and holding thereon. F The fsl'eeve 44 'in Vextending between the head 30 of the plunger and external surface of the b'ody |8 provides in conjunction with the annular reduced portion of plunger member v2'2 a low pressure chamber or reservoir 68 having vcomi munication by way of passage 34 with compression chamber 36.

y The body portion of plunger 22 is of a diameter slightly smaller than the diameter oi cavity permitting of a predetermined hydraulic fluid leakage or leakdown along the corresponding walls thereof between the low and high pressure chambers, '6B and 3'6 respectively.

It has been generally determined for the best operation of the tappet under all conditions to which it is to be subjected that a lluid should be employed permitting rof a wide range of temperature use without much effect therein as to viscosity 'and the like and one permitting of a reasonable degree o'f machining tolerances of the parts thereof so as to provide for a structure that may be economically manufactured.

l Fig. @illustrates a 'modified form of tube or sleeve |00 yfrom that employed in the structure of Fig. 1 adaptable for use similarly to sleeve 44 between plunger 22 and cylindrical body |6.

"'Sleeve'l' terminates in opposite extremities '|02 and |04 respectively upon which are clamped clip 'members |06 and |5078 respectively, said clip members adapted to serve a like purpose as the clips 46 and A54 clamped to sleeve 44. The sleeve |00 is vpreferably made of a vfabric material of substantially non-resilient character folded over at'point ||'0 such that end extremity |02 thereof extends in the sam-e direction as extremity |04 with said end |02 disposed radially inwardly oi the main body portion ||2 of the sleeve.

The sleeve '|00 as shown Iby Fig. 5 is in its maxi- 'mum contracted length as it would appearat the 'time "of b'ot'toming of plunger V22Y relative to body 'I6 whereby upon elongation of the tappe't per se and movement of the plunger from the body with the sleeve disposed between the plunger and body the lsleeve would become elongated. It will be 'observed that because of the assembled size of 'the 'sleeve '|00 at its minimum length it would be at its maximum 'volumertic holding capacity thereby establishing a condition Whereinlno appreciable pressure other than atmospheric is impressed upon the fluid contained in the reservoir of the tappet by the sleeve.

ns. the 'tappet telong'ates and the sleeve is lengthened axially the main body portion of the sleeve collapses or moves radially inwardly induced by atmospheric pressure externally there'- 'of as compared 'to the slight vacuum created internally of the sleeve brought about through the -movement of the lluld from the reservoir Ato the 4Ahigh compression chamber of the tappet as the 'tappet isfelongated through the biasing vapart of lthe plunger from the body by spring 42. Inv-this manner 'the sleeve operates to maintain the lvol- 'un'e internally of the tappet constant Without imposing a resilient load of varying degree to the;

iluid.

The sleeve 44 differs 'from the sleeve |00 in the fact that because of its resilient nature it can be assembled to the plunger and body at normal operating length of the tappet in a lslightly outwardly radial distention as the plunger `is bottamed and approaching normal static axial length and zero distention when the tappet is elongated to its maximum height.

Aside from the hereinbefor'e recited comparison of actuation of the sleeves 44 and '|00 the 'tappet per se l0 would be operable comparably through the use of either sleeve and that is, upon requirement for an elongation thereof or relative move ment ofthe plunger l22 outwardly from .the body I6 to compensate for clearance in a valve gear or like system in which it is employed fluid :flows from chamber 68 through the passages 34 .in the plunger and past valve '36 into'chamber '36. This nuid now action is caused by the creation of a slight vacuum in chamber 3'6 through the outward movement of the end of the plunger therein causing an enlargement of the volume of chamber 'A 36 which in turn necessitates. the requirement for more fluid to lill same. Simultaneously as chamber 36 increases in volume vchamber 68 decreases in volume 'through the atmospheric pressure imposed upon the sleeve externally 'thereof andthe normal resiliency of say sleeve '44 tending to move the iluid .from chamber 68 or ythe atmospheric pressure solely acting externally in the case -of use of sleeve |00. l

In the 'case of -either sleeve r44 or sleeve |00 it is of vital importance that the clips secured thereon at the end extremities thereof elect a positive hermetic seal upon the ,plunger and body inhibiting the leakage of fluid from the tappet or seepage of air into the tappet.

With the 4provision of a predetermined clearance between 'the outer periphery of the plunger and Wall of cavity .|20 in body llli .a predetermined rate of leakage between chambers 36 vand 63 lis provided permitting 'of the contraction of the tappet, that is inward axial movement of the plunger toward the bottom of cavity 20 in cylinder IB against the resistance of spring 42 Vand rate yof 'flow of :duid'from chamber 36 to chamber 68 along the Wall clearance space.

As the fluid nows from chamber 36 into chami ber 68 the volumes of the chambers vary, charmh ber 68 yincreasing in volume vas 'chamber 36 decreases such that in the case of sleeve 44 and because of its inherent resiliency :it is dist'ended slightly radially outward to compensate for the increase in volume of chamber 68 during this phase of operation of the tappet. The `sleeve |00 because of lits substantially non-resil ient 'structure and mode 'of application te the tappet -upon the contraction thereof substan- 'tially 'resumes Yits .maximum Avolumetric carrying capacity such as shown by Fig. 5 'wherein the fluid `'capacity of thesle'eve .1in JKassociation with the plunger and body is .increased Aside lfrom the difference l.in resiliency of the 4materials Ifrom which sleeves Mfand V00 aremade accounting for the slight variation in operating characteristics 'to one another the basic function of the sleeves is 'identical to that of providing an effective sealing of the lluid Within the internal confines of the 'sleeve -and cylinder body and'or .providing volume variation compensating means lin the chamber disposed intermediate the .plunger and sleeve whereby vsubstantially lonly atmos pheric pressure is imposed at all times on the uid of said chamber.

' While this invention has been described in connection with certain specific embodiments, the principle involved is susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention, therefore, is limited only as indicated by the scope of the appended claims.

What I claim is:

. 1. In a lash take-up device for valve gear and the like, a hollow cylinder closed at one end, a plunger slidable in said cylinder and projecting outwardly of the open end thereof, a passageway through said plunger communicating at one end thereof with the chamber defined by the inner end of said plunger and the closed end of said cylinder, said plunger having an axial recess at its inner end, the bottom of said recess defining an annular valve seat around the inner end of said passageway, a one-way valve on the valve seat in the recess of said plunger, a counterbore in said recess defining an annular axially facing shoulder, a spring in said chamber, having one end seated against said shoulder, urging said plunger outwardly of said cylinder, the axial distance from said seat to said shoulder being greater than the thickness of said valve, the inside diameter of said one end of said compression spring being less than the diameter of said valve whereby said spring retains said valve in said recess in proximity to said valve seat, a iiexible tubular sleeve surrounding and clamped at one end to the outer surface of said cylinder adjacent the open end thereof and clamped at its other end to the projecting portion of said plunger, said plunger, cylinder end, and sleeve defining a reservoir therebetween, said passageway communicating at its other endrwith said reservoir, the means for clamping said sleeve to said cylinder and plunger comprising, annular metallic clips each having an inner and outer annular portion between which the ends of the sleeve are clamped, the said inner annular portions snugly embracing the said cylinder and plunger, respectively, each of said outer annular portions extending axially inwardly of the ends of said sleeve beyond the corresponding ends of said inner annular portions and being resiliently biased at their inner ends to press said sleeve radially inwardly, and circumferential grooves around said cylinder and plunger, respectively, radially inwardly of the said inner ends of said outer annular portions whereby said resilient outer annular portions press said flexible sleeve into said grooves to effect a liquid-tight seal between said sleeve and said cylinder and plunger.

2. In a lash take-up device for valve gear and the like, a hollow cylinder closed at one end, a plunger slidable in said cylinder, a passageway through said plunger communicating at one end thereof with a chamber defined by the inner end of said plunger and the closed end of said cylinder, said plunger having an axial recess at its inner end, the bottom of said recess defining an annular valve seat around the inner end of said passageway, a disc valve element in said recess and engageable with said valve seat, a counterbore in said recess defining an annular axially facing shoulder, a compression spring seated at one endy against said shoulder and bearing at its other end against the closed end of said cylinder, the axial distance from said valve seat to said shoulder being greater than the thickness of said valve disc, the inside diameter of said one end of said compression spring being less than the diameter of said valve disc whereby said spring retains said disc in said recess in proximity to said valve seat. l

3. A device as defined in claim 2 wherein the peripheral wall of said recess is provided with radial slots extending axially inwardly beyond said shoulder to provide passageways for fluid.

4. In -a lash take-up device for valve gear and the like, a hollow cylinder closed at one end, a plunger slidable in said cylinder, a passageway through said plunger communicating at one end thereof with a chamber defined by the inner ends of said cylinder and plunger, said plunger having a centrally located axial recess at its inner end, with the bottom of said recess defining an annular valve seat around the inner end of said passageway, a flat valve element received in and movable in said recess and engageab-le with said valve seat, said recess beingl of an axial length greater than the thickness of the valve, a compression spring in said chamber urging the plunger outwardly of the cylinder, having one axial end bearing against the inner closed end of the cylinder and its other end bearing against the inner end of the plunger adjacent to the recess, with a portion of said one end of the spring inward radially overhanging the recess, the inside diameter of said one end of the spring being less than the maximum Width of the valve element whereby said spring retains said valve element in said recess in proximity to said valve seat.

5. In a lash take-up device for valve gear and the like, a hollow cylinder closed at one end, a plunger slidable in said cylinder and projecting outwardly of the open end thereof, a passageway through said plunger communicating at one end thereof with the chamber defined by the innery end of said plunger and the closed end of said cylinder, said plunger having an axial recess at its inner end, the bottom of said recess defining an annular valve seat around the inner end of said passageway, a one-way valve on the valve seat in the recess of said plunger, a counterbore in said recess defining an annular axially facing shoulder, a spring in said chamber, having one end seated against said shoulder, urging said plunger outwardly of said cylinder, the axial distance from said seat to said shoulder being greater than the thickness of said valve, the inside diameter of said one end of said compression spring being less than the diameter of said valve whereby said spring retains said valve in said recess in proximity to said valve seat, a flexible tubular sleeve surrounding and clamped at one end to the outer surface of said cylinder adjacent the open end thereof and clamped at its other end to the projecting portion of said plunger, said plunger, cylinder end, and sleeve dening a reservoir therebetween, and said passageway communicating at its other end with Said reservo SIDNEY OLDBERG.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,062,580 Bollee May 27, 1913 1,916,191 Burkhardt July 4, 1933 2,098,115 Voorhies Nov. 2, 1937 2,187,008 Baxter Jan. 16, 1940 2,211,817 Huierd et al. Aug. 20, 1940 2,278,963 Arola Apr. 7, 1942 2,378,046 Stergis June 12, 1945 2,386,317 Jenny et a1. Oct. 9, 1945 2,492,030 Beekley Dec. 20, 1949 2,547,798 Truxell, Jr. Apr. 3, 1951