US2372206A - Mechanical compensator - Google Patents

Description

Marcvh 27, 1945. w. c, HOWARD, JR l 2,372,206

I MECHANIGAIJA coMPENsAToR Filed Mayu'zs, 1943 Patented Mar. 27, 1945 UNITED STATES PATENT oFFlcE mncnamc'zransn'ron William C. Howard, Jr., Richmond ,'Va assignor of twenty-two percent to T. Edward Kennedy, twenty-.two per cent to Karl B, Lutaeleven. per centr `toThimias C. Utter-back,` and eleven per cent to C. Archer Smith Application May Z6, 1943, Serial No. 488,619

16 Claims.

This invention relates to a mechanical compensator usable to providev for relative adjustment between two main parts and for transmitting a load between the main parts. The partsA are lso constructed that when a load is applied which tends to force the two main parts toward each other, the compensator automatically locks'andv carries the load, but when the load is removed, the compensator unlocks, and if the two'main parts are then moved relative to each other, the compensator automatically adjusts itself to the new positions of the main parts. If the load is now reapplied, the compensator again locks and assumes the load in its new position.

A particular object of the invention is' to provide a simple and reliable device capableof maintaining a clearance-free fit between mechanical parts regardless of wear or of changes in size of the parts due to temperature variations.

My Patent No. 2,326,780, `flied June 25, 1941, discloses a mechanical compensator which incorporates certain new principles of construction and operation. The present invention utilizes those same principles, but in a manner which attains the same results with a smaller number cf parts vand in a narrower space.

A typical installation involves thewuse of the device as an automatic tappet to provide at all times a clearance-free drive for the valves ofA internalcombustion engine. In such use the der' vice is installed in place of the usualtappet and is capable vof automatic lengthening to compensate for any wear or shortening of the parts;'of automatic locking on each lift of the valve cam so as to positively open the valve.; and ofautomatic unlocking on each stroke to permit shortening of the device to accommodate lengthening of the parts due to heat expansion. These results are achieved with a. minimum number of simple,

reliable parts located within a tappet bodysothat the automatic tappet has substantially the'same external appearance as a solid tappet'. u

These and other objects and advantages'of the invention will become apparent as .the description proceeds.

While preferred forms are disclosed herein for purposes of illustration, it should be understood that various changes in the construction and farrangement of parts may be made without departing from the spirit ofthe inventitm.

In the drawing: l

Figure 1 is a longitudinal section through apreferred form `of the invention showing related parts,the adjustment device being in its extended position.

`Figure 21s a view similar-to Figure l, but showingfthe parts in an intermediate, or starting position. i i

Figure 3 is a view similary to Figure 1, but showing the adjustment device in fully retracted position.

Figure 4 is an exploded view showing isometrically the operating parts of Figure 1.

Figure 5 is a cross section taken on line 5 5 of Figure 2.

Figure 6 is a cross section taken on line 6--6 of Figure 2.

Figure 7 is a longitudinal section similar to Figure 2 but showing a modication.

Figure 8 is a cross section similar but showing a further modication.

In a presently preferred form of the invention, shown in Figures 1 to 6, the tappet housing l0 is cylindrical on the exterior and is formed withy a cylindrical bore Il. Within the bore and resting on the bottom wall thereof is a lower pressure body l2, the main portion of which is approximately in the form of part of a cylinder with a nat inner face I3 and a iiat bottom `face I4. The. upper end has an upwardly facing at camiace-l5lwhich slopes inwardly yand downto Figure 6 -wardly to join the inner face I3.

The plunger I6, which forms .the compensating member, has a main body which is semi-circular in cross section,` with an outer curved wall l1 and an inner flat'face I8. At its lower end plunger I6 carries an inward projection' I9k formed with an inwardly and downwardly sloping i'lat cam face 20 which faces upwardly. At a point about intermediate its ends plunger I6 carries annward projection 2l rformed with an inwardly and downwardly sloping cam face 22 which faces upwardly and with an inwardly and upwardly sloping cam face 23 which faces downwardly.

The floating separator 24, which is located opposite plunger I6 and between the lower projection [9 and the intermediate projection 26, is partly cylindrical in form, having a flat face 25 which engagesinnerflat face i8 of plunger I6, and `alsohaving flat top and bottom faces 2B and 2l.

The intermediate pressure boda'7 28, which is located opposite intermediate projection 2| of plunger I6, is also partly cylindrical in form and has an .inwardly and downwardly sloping cam face 29 which faces upwardly, and an inwardly and Vupwardly sloping cam face 30 which faces downwardly.

The top pressure body 3l includes a. partly 5 cylindrical portion 32 which 'has a flat bottom face 33 and a reduced upward extension 34. The cylindrical portion 32 and the reduced extension 34 both carry a fiat face 35 which engages inner flat face I8 of plunger 16.

Suitable pressure transmitting devices are arranged to cooperate with the several cam faces described above. One form of device which is capable of transmittingv considerable pressure with minimum friction is the roller, which is used in the preferred form of compensator. three rollers are used, the roller 36 cooperating with the lower at face 21 of floating separator cam face 22 formed on the intermediate projection 2| forces roller 38 to Iroll toward the rightl (as viewed in Figure 2l) land outwardly on cam face 29.

During this upward movement of plunger I3 the intermediate pressure body 28 remains stationary. This vis because lower pressure body l2 remains seated on the bottom of bore Il; cam face 20 causes roller 36 to move toward the right and upwardly on cam face l; but cam face 23 moves upward the same distance as cam 2d and with camfaces l5 and 20, the'roller 31@ cooperating with the upper at face 26 of floating separator 24 and with cam faces 23 and 30, andv the roller 38 cooperating with lower flat face 33 of top pressure body 3|, and with cam faces 22 and 29.

The plunger I6 is biased upwardly by a take-upv In Figures 1, 2 and 3 the valve-operating camis indicated at 42, the valve stem at 43, and the valve spring at 44.

Installation Figure 1 illustrates the position of the partsof the tappet when the unit is in fully extended position ready for installation. y

In making the installation the valve stem 43 is lifted or removed, in the usual manner, and the automatic tappet is so dimensioned that when the valve spring 44 is released the valve stem 48 engages the end of extension 34 with the full force of the valve spring. This force immediately locks the automatic tappet inthe position of Figure 1 in a manner that will be explained subsequently.

It will be noted that in the position of Figure l the extension 45of the plunger I6 projects above the top of housing lll.'l This projecting end 45 serves as a trigger for tripping the locking mechanism. Tripping is done by merely applying a relatively light downward pressure to the end of projection 45, whereupon the tappet ceases toresist the downward pressure of valve spring 44 and the parts readjust themselves to the. normal starting position illustrated in Figure 2'. In this position the lower end of the tappet housingl l0 is resting. on the heel of cam 42; the valve is pressed against its seat by the full force of the valve spring minus the light counter-pressure of the take-up spring 39; the spring 39 is resiliently expanding the tappet to maintain it in direct contact with both cam 42 and valve stem 43; and there is no free clearance permitted anywhere between cam and valve stem.

It is believed that the present improved automatic tappet operates in the manner explained in my prior co-pending Patent No. 2,326,780 referred to above, but in order to make the correspondence of parts perfectly clear the explanation will be repeated with particular reference to the parts as disclosed herein.

Action in taking np clearance ber I6 upwardly, and the upward movement of Leo face 29 and permits ro-ller 3l to move to the left and upwardly along cam face 30. Tnus while upward movement of roller 36 causes upward movement of floating separator 24, which in turn pushes roller 31 upward, movement of roller 31 toward the left along cam face 3i) prevents this-roller from moving pressure body 28 upwardly.

Since intermediate pressure body 23 remains stationary, the upward movement of compensating member I6 causes roller 33 to move toward the right and upwardly on cam face 29, thus causing upward movement of the top pressure body 3|. f This movement continues until all clearance has .been taken up, i. e., all points of contact from cam 42 to valve stem 43 are snugly engaged under pressure derived from the takeup spring 39. f

Because the roller 38 is moved upwardly by co-action of cam faces 22 and 29 to cause-compensating movement of top pressure body 3l, these cam faces may be called compensating cam faces.

During this action of taking up clearance the parts move from their positions in Figure 2 toward their positions in Figure l, the latter view illustrating thepositions of the parts after the tappet has reached its extreme limit of outward extension. Since the projecting upper end 45 of plunger I6 also moves up, it may serve as a visual indicator of the fact that the tappet has reached its outer limit of extension. Thus, a shoulder 45 may be so formed as to come flush with the top of body l0 when the parts are in the position of Figure l.

Locking action in assuming load l As soon as the cam 42 begins to apply pressure to the lower end of the tappet housing Ill, the parts of the tappet are subjected to external pressure which causes the tappet to `lock automatically in substantially the position illustrated in Figure 2.

' Experiments have proved that the upper roller 38 is not involved in this locking action, and it is believed the locking action can most readily be explained by considering what occurs when thelower pressure body l2 and the intermediate pressure body 28 are forced toward each other. When this happens the cam surface I5 on the lower pressure body and the cam surface 3U on the intermediate pressure body form opposite walls of a constrictable wedge groove which,

while being constricted, forces the lower' roller The `wedglng force just described is sufllcient to resist any downward movement of plunger |6 under load applied to the plunger through the upper roller 38. This is apparently due to the fact that the-upper roller 38 divides its downwardpressure equally between the intermediate f pressure body 28 and the plunger lli (the angles of cam faces 22 and 29 being equal), hence the force applied to maintain the wedging kaction just described is equal to the force tending to move plunger I6 downwardly.

f But when additional force is applied directly to plunger I6 by pressing down on the lextension 45 in the manner previously described, the balance of forces is destroyed and the wedge lock is broken, permitting the `.plunger to move down. However, barring such external interference with the wedge lock, the locking force is proportionate to the load applied to the tappet, and hence the device can positively transmit any load within the mechanical strength of the material of the parts. Compensating for lengthening of value parts load, as recited in the previous section, therst part of the pressure is taken up by elastic deformation of the parts, which,-in a typical case, permits the tappet to yield to the extent of approximately 0.001 inch up to the time the full load is assumed. `This downward movement of 0.001 inch of the top pressure body 3| is transmitted downwardly through the top roller -38 and since this roller is supported equally on intermediate pressure body 28 and intermediate projection 2| of plunger It, a downward movement of approximately 0.001 inch is transmitted to intermediate pressure body 28 and t0 plunger I6. .At this point, that is, after all parts have been deformed to the full extent required by the load applied, the wedge lock previously explained becomes effective and there is no further yield of the tappet as it transmits the force of the cam to the valve.

When the load on the tappet is removed, the

wedge lock is released, and it has been found that this unlocking takes place before the tappet has resiliently expanded to rits original over-all 'Apparently the reason for this occurrence is that during the time the last part of the loadis being removed (the part that on application of the load caused an elastic deformation of 0.001 inch) the elastic return (release of elastic deformation) .causes the intermediate pressure body 28 to move upward slightly relative to plunger I0, thus causing roller. 38,to roll over against cam face 22. At this instant the top pressure body 3| is still being biased downwardly by a last part of the external load that is stronger than spring 39 andy hence this outward movement of roller 38 follows the line of least resistance and moves plunger I 6 downward, releasing the wedge lock.

The slight upward movement of intermediate pressure body 28 just mentioned is believed to re,- sult 'from the fact that when the tappet is under load, the load compresses a column which can be visualized in Figure 2 as including the lower pres, sure body I2, lower roller 36, Boating separator .2.4, intermediate feller 31 intermediate :pressure body 28, and upper roller 38. Elastic return acts mainly to permit a. lengthening of this column, moving the intermediate pressure body 28 upwardly with the unlocking result previously explained.

As for the elastic return of the parts that react between the lower projection I9 and intermediate projection 2| of plunger I6, the upward reaction of middle roller 31 on projection 2| appears to be exactlybalanced by the downward reaction of the lower roller 36 on the lower projection I0, hence these forces cancel each other. t

It has been found that 'one-half of the upward movement of intermediate pressure body 28 is utilized to move plunger I6 downward and theA in position of the lower end of the valve stem has taken place there would be a tendency for a clearance of 0.0005 inchl to appear'between the valve stem and the tappet. But this slight amount of potential clearance is kept from developing into actual clearance by take-up spring 39 pressing plunger IB upwardly to operate the parts in the manner previously explained under the heading "Action in taking up clearance.

If instead, the lower end of the valve stem has assumed a new position nearer to cam 42, such as might result from thermal expansion of the valve stem, the unlocking action just explained permits the top pressure body to be held down to a new position somewhat lower than its original position, within the 0.0005 inch potential clear# ance.

It can be seen therefore, that at the end of each load stroke the unit unlocks at La length 0.0005 inch shorter than it was on the previous stroke and that the tappet can accommodate itself on each stroke to an increase 0f 0.0005 inch in the length of the related parts. This back-off ofthe tappet is due to the action of elastic return in unlocking the parts, so it may appropriately be called elastic back-off.

The tappet can continue to shoten in this manner until it reaches the fully retracted position of Figure 3, in which the stem 40 is touching the bottom of the bore in housing l0. In this position the upper end of extension l5 of plunger I6 is flush with the top of housing I0, thus giving a signal that the tappet has reached its limit of accommodation in this direction.

It should be clear from the above explanation that the parts operatefto lengthen the tappet if necessary to take up clearance; that its locking parts provide a positive drive when external pressure is applied; and that the elastic back-off permits the tappet to shorten if the end of the valve stem moves closer to the cam. Because al1 of these actions take place within the tappet in response to external conditions, the unit is entirely self-contained and self-operating and is truly automatic, requiring no additional parts such as oil supply systems, inertia members, or operating rods. It therefore can be installed as easily as a conventional solid tappet.

`Inthe above description the improved tappet has been set forth as used in a conventional L-head internal combustion engine, but it is of course equally adapted for the operation of overhead or any other type of valves, and for all other types of mechanical linkage where it isdesired to eliminate clearance. And while the unit has been illustrated in a vertical positionl it can be used in any desired position.

Modifications can be made in various parts of the unit. Thus some variation can be made in the angle of the cam faces, which are illustrated at 45 to the vertical axis of the unit, although all cam faces should be at the same angle.

In comparing the details of the compensator disclosed herein with those disclosed in my copending Patent No. 2,326,780, it will be noted that the forms of the present application have fewer parts, since only three pressure-transmitting members are used, and that the compensator can be made with a smaller over-all diameter. This is because each of the parts, except for the rollers, is partly cylindrical, i. e., it extends only partly across the cylindrical bore and is complemented by another part to fill the cylindrical bore. The parts can therefore be giveny adequate size and strength with a smaller diameter than where certain of the parts must extend entirely around the periphery of a ciicular or other shaped bore.

Reference has already been made to the fact that in the preferred form rollers are used because they can transmit pressure with a minimum of frictional resistance. But in cases where more contact area is desired and a slight additional amount of frictional resistance can be tolerated the rollers may be replaced by sliding blocks such as illustrated at 36a, 31a and 38a in Figure 7. Each of these sliding blocks has a face at right angles to the vertical axis of the unit and two faces at the same angle as the cam faces on which they ride, being therefore generally triangular in form. The rollers, sliding blocks, or other equivalent devices are comprehended in the term 1 pressure transmitting devices as used in the appended claims.

Another possible modification is in the shape of the bore in the housing and of the cooperating surfaces of the operating parts. In the forms above described the bore is cylindrical and the surfaces of the operating parts in contact with the bore have the contour of part of a cylinder. While this cylindrical form appears to be most economical to manufacture at the present time, it is quite possible to use some other shape, such as the square form illustrated in Figure 8. In

this case the bore of the housing is square in cross section and the outside of the working parts have a corresponding contour with one at face parallel to the axes of the pressure-transmitting devices.

The housing is important only as supplying a wall to guide the operating parts and to hold them assembled during installation of the unit, and hence it may be dispensed with if the unit is to be installed in a ,bore in some other part.

I claim:

1. In a mechanical compensator of the type having a part formed with a bore of uniform diameter, a lower pressure body, an intermediate pressure body, a top pressure body, a compensating member, means biasing the compensating member toward the top pressure body, and means for transmitting pressure and movement between said parts, the improvement comprising: each of said lower, intermediate and top pressure bodies and the compensating member having a smooth wall in direct sliding engagement with the wall of the said bore.

2. A compensator as specied in claim l but in which the bore is square in cross section and the said pressure bodies and compensating member have their outer walls conforming to the square section.

3. In a mechanical compensator of the type having a part formed with a bore, a lower pressure body, an intermediate pressure body, a top pressure body, a compensating member, means biasing the compensating member toward the top pressure body, and means for transmitting pressure and movement between said parts, the improvement comprising: each of sagd lower and intermediate pressure bodies having an over-al1 lateral extent less than the diameter of said bore and being complemented by a portion of the compensating member to substantially ll the cross section of the bore.

4. In a mechanical compensator of the type having a part formed with a cylindrical bore, a lower pressure body, an intermediate pressure body, a top pressure body, a compensating member, means biasing the compensating member toward the top pressure body, and pressure-transmitting devices for transmitting pressure and movement between said parts, all of the parts being within said bore, the improvement which comprises: each of said lower and intermediate pressure bodies and said compensating member having a curved outer wall in contact with the wall of said cylindrical bore, and a straight part extending on a chord of sa;d cylindrical bore.

5. In a mechanical compensator of the type having a part formed with a cylindrical bore, a lower pressure body, an intermediate pressure body, a top pressure body, a compensating member, means biasing the compensating member toward the top pressure body, and pressure-trans mitting devices for transmitting pressure and movement between said parts, .a iioating separator located between some of the pressure-transmitting devices, the improvement which comprises: the compensating memberhaving a curved outer wall in contact with said cylindrical wall and having flat inner faces; each of said lower pressure body and the floating separator having a curved outer wall in contact with said cylindrical bore and having a at inner face cooperating with a nat face of the compensating member.

6. In a mechanical compensator of the type having a housing formed with a bore, a lower` pressure body, an intermediate pressure body, a top pressure body, a compensating member, means biasing the compensating member toward the top pressure body, and means for transmitting pressure and movement between said parts, the improvement comprising: an extension on the compensating member, said extension projecting to the end. of the housing and being accessible and visible from the exterior of the housing.

7. In a mechanical compensator of the type having a housing formed with a bore; a top pressure body; a compensating member; means biasing the compensating member toward the top pressure body and tending to increase the distance between the top and lower pressure bodies; means operable to lock the compensating member against movement when the top and lower pressure bodies are pressed together by external load, the locking means being unlockable by an external force moving the compensating member downward; the improvement comprising: an upfasvaace ward extension on the compensating member, said extension projecting to the, endof thev housing and bein-g accessible from the. exterior ofthe housing for application of unlocking. force to. the compensatingy member..

8. In a mechanical compensator of the type having a top pressure body', a compensating mem.- ber, means biasing the compensating member toward the top pressure body to cause compensating movement of. the top pressure body, and meansto lock the compensating member against movement, the improvement comprising: a single roller serving to transmit: compensating movement. to the top pressure body.

9. In a locking device for locking v.two parts movable relative to each other, of the type having v oppositel'y inclined cam surfaces on one of said movable parts forming sides of a fixed wedgeA groove, oppositely inclined cam surfaces carried by the other of said movable parts forming sides of a constrictable wedge groove, a floating separator intersecting the fixed and constrictable wedge grooves, pressure-transmitting means contacting the upper and lower sides of the floating separator, the improvement comprising: a single roller serving as the pressure-transmitting means in contact with the upper side of the floating separator, and a single roller serving as the pressure-transmitting means in contact with the lower side of the floating separator.

10. In a mechanical compensator of the type having a top pressure body, a compensating member, means biasing the compensating member toward the `topl pressure body to cause compensating movement of the top pressure body. and means to lock the compensating member against movement, the improvement comprising: a single pressure-transmitting device of generally triangular form serving to transmit compensating movement to the top pressure body.

11. In a locking device for locking two parts movable relative to each other, of the type having oppositely inclined cam surfaces on one of said movable parts forming sides of a fixed wedge groove, onpositely inclined cam surfaces carried by the other of sai-d movable parts forming sides of a constrictable wedge groove, a floating separator intersecting the fixed and constrictable wedge grooves. pressure-transmitting means contacting the upper and lower sides of the floating separator. the improvement comprising: each of said pressure-transmitting.` means being in the form of a generally triangular block.

12. In a mechanical compensator of the type having a housing formed with a bore; a top pressure body; a compensating member; means biasing the compensating member toward the top pressure body; means translating upward movement of the compensating member into upward movement of the top pressure body; means operable to lock the compensating member against downward movement when the too and lower pressure bodies are pressed together by external load, the locking means being unlockable by an external force moving the compensating member downward; the improvement comprising: an upward extension on the compensating member, said extension projecting to the end of the housinar and being accessblerfrom outside the housing for application of unlocking force to the comoensating member, said extension also being visible from outside the housing to indicate the position of the compensating member.

13; A mechanical compensator comprising: a part formed with a bore; a compensating memvrespectively havev oppositely sloping cam faces forniing sides of a constrictable wedge groove; a floating separatorintersecting the fixed and constrictable wedge groove, said separator having iiaty top and bottom faces; first and second pressuretransmitting. members in contact with the flat faces of the floating separator respectively and contacting the cam faces forming the fixed and restrictable wedge grooves; the intermediate pressurebody carrying a compensating cam face; a top.` pressure bodyI having a flat face on its lower side.; athird pressure-transmitting member contacting said flat. tace of the'top` pressure body, the compensating cam face of the compensating member, and the compensating cam face of the intermediate pressure body; and means biasing the compensating member toward the top pressure body; the compensating member, the lower pressure body, the floating separator,` the intermediate pressure body and the top pressure body y each having a smooth wall in sliding engagement with the wall of said bore.

14. A compensator as specified in claim 13 but in which the said bore is square in cross section and the parts contacting the wall of the bore are shaped to conform to said square shape.

15. A mechanical compensator comprising: a part formed with a bore; a compensating member having two oppositely sloping flat cam faces forming sides of a fixed wedge groove and carrying a flat compensating cam face; a lower pressure body and an intermediate pressure body which respectively have oppositely sloping flat cam faces forming sides of a constrictable wedge groove; a floating separator intersecting the fixed and constrictable wedge grooves, said separator having at top and bottom faces; `first and second pressure-transmitting members in contact with the flat faces of the floating separatorrespectively, and contacting the cam faces forming the fixed and restrictable wedge grooves; the intermediate pressure body carrying a flat compensating cam face; a top pressure body having a at face on its under side; a third pressure-transmitting member contacting said fiat face of the top pressure body, the compensating cam face of the compensating member, and the compensating cam face of the intermediate pressure body; and means biasing the compensating member toward the top pressure body; the compensating member having an outer wall conforming to and in contact with the wall of said bore, and having flat inner faces; each of said lower and upper pressure bodies and the floating separator having outer walls conforming to and in contact with the wall of said bore, and having a flat inner face cooperating with a flat face of the compensating member.

16. A mechanical compensator comprising a housing formed with a cylindrical bore; a compensating member having a lower projection with an upwardly facing at cam face, an intermediate projection with a downwardly facing flat cam face and an upwardly facing flat cam face, and an upward extension; a lower pressure body resting on the bottom wall of the bore and having an upwardly facing flat cam face; a floating separator located above the lower pressure body and having nat top and bottom faces disposed at angles to the vertical axis of the compensator; an intermediate pressure body located above the right Iioating separatorand having' a downwardly fao; ing flat cam face and an upwardly. facing atzcam face; a top pressure'body located-above the intermediate pressure body and having a reduced upper extension and having a flat face on its under side; means biasing the compensating member toward the top pressure body; a rst pressure-transmitting member contacting the cam face of the lower pressure body, the cam face of the lower projection of the compensating member, and the at bottom face of the floating separator; a second pressure-transmitting member contacting the Iiat top face of the floating separator, the downwardlyv facing cam face of the intermediate pressure body, and the downwardly 5 facing cam face of, the compensating member; a third pressure-transmitting member contacting the upwardly facing cam face-of theintermedi ate pressure body, the compensating cam face of the `compensating member, and the fiat lower face of the top pressure body; and means biasing the compensating member toward the top pressure body; the compensating member having an outer curved Wall conforming to and in contact with the wall of said bore, and having at inner faces; each of said lower, intermediate, and upper pressure bodies and the floating separator having outer curved walls conforming to and in contact with the wall of said bore; each of said lower and upper pressure bodies and the oating separator having a, at inner face cooperating with the fiat face of the compensating member.

WILLIAM C. HOWARD, JR.

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