US2339238A

US2339238A - Valve tappet

Info

Publication number: US2339238A
Application number: US482815A
Authority: US
Inventors: Buckley Arthur Burton
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-03-09
Filing date: 1943-04-12
Publication date: 1944-01-18
Anticipated expiration: 1961-01-18

Description

JanQlS, 1944. A. a; BUCKLEY VALVE TAPPET Filed April 12, 1943 5 Sheets-Sheet 1 I zvrzw Tog Jan. 18, 1944. A. B.- BUCKLEY 2,339,238

' VALVE TAPPET Filed April 12, 1943 3 Sheets-Sheet 2 16:9 .3. 166 j v w I f) "v Jan. 18, 1944-. BBUCKLEY 2,339,238

VALVE TAPPET Filed April 12, 1943 3 Sheets-Sheet 5 Patented Jan. 18, 1944 VALVE TAPPET Arthur Burton Buckley, Carshalton, England Application April 12, 1943, Serial No. 482,815 In Great Britain March 9, 1942 9 Claims. (Cl. 123-90) This invention relates to tappets of the type (hereinafter referred to as the type described) comprising male and female telescopic members that define an internal chamber of variable size adapted to contain a liquid and are movable one in relation to the other for determining the length of the tappet, provision being made for permitting a restricted escape of liquid from the internal chamber along a leakage path.

In tappets of the type described proposed heretofore, the restricted escape of liquid from the internal chamber has been so small as to be negligible in so far as interference with the operation of the tappets was concerned. In one such construction that comprised a tappet body in which a piston was slidable, and that contained a reservoir for liquid and a valve device controlling communication between it and a pressure chamber in the tappet body, the restricted flow of liquid set up (when the device was in operation) a small constant circulation of the liquid in a closed circuit from the pressure chamber at one side of the piston to a space, constituting a reservoir for oil in the body, at the other side of the piston. In this proposed earlier construction the arrangement was such that communication between an external source of supply under pressure was established with the interior of the tappet only at the moment of closure of the engine valve controlled by the tappet for the purpose of replenishing oil that had leaked away.

It is an object of the present invention to control the operation of a tappet of the type described in an improved manner.

Another object is to provide an improved construction of tappet of the type described which shall be self-priming.

A further object is to provide a non-atmospheric tappet of the type described for ensuring that air shall not collect in the tappet, and be readily expelled should this happen.

According to a feature of the invention there is provided a tappet of the type described wherein the telescopic members define a pressure chamber of variable size adapted to contain a liquid, a restricted escape of liquid from the pressure chamber being permitted, which tappet is characterised in that provision i made for controlling and adjusting the restricted-leakage from the pressure chamber independently of the fit of the piston in the body, and thereby controlling the operation of the tappet.

When a tappet as set forth above is combined witha fixed tappet guide member, and liquidsupply means arranged to supply liquid from an external source of supply under pressure by way of the guide member to the pressure chamber for elongating the tappet, the leakage-control means may be associated with the liquid-supply means.

The leakage-control means may comprise a valve device that is associated with means for supplying liquid under pressure to the pressure.

chamber.

When the tappet guide member has an inlet port for supplying liquid under pressure to the pressure chamber for elongating the tappet, according to another feature of the invention packing means is situated at opposite sides of said port for preventing liquid from escaping to atmosphere at the ends of the tappet by way of the joint between the tappet and the guide member. Such a tappet has the advantage of being.

self-priming.

Preferably the packing means is disposed so as to permit the escape into the atmosphere of air from within the tappet by way of said joint,

and at'the same time to cause the return of a substantial proportion of the tappet leakage to a liquid-supply conduit, which arrangement has the advantage that-the liquid consumption is reduced to a minimum with the corresponding 'ad-- ing in the liquid-supply means that quantity of liquid which is displaced from the tappet due to its contraction, and for regulating any excessive fluid pressure which may tend to be set up in the liquid-supply means due to that accommodation.

A preferably pneumatic pressure-absorbing device may be provided for relieving any excessive fluid pressure that is set up or tends to be set up in the liquid-supply conduit due to the injection of liquid from a tappet due to itscon-.

traction.

This pressure-absorbing ,device may be situated externally of the tappet in connection with a conduit for the l supply of liquid under pressure to.

the tappet.

Limiting means, preferably of the pin-andslot type, may be arranged in the tappet for automatically limiting the endwise movement of itstelescopic members one in-relation to the other. Other features of the invention relate to various constructions and arrangements of leakagecontrol means for permitting a restricted leakage pet, partly in longitudinal section, also having an internal valve device;

Figure 3 is a vertical section showing another modified construction of tappet according to the invention having an external valve-device,

Figure 4 is a detail view of the valve member removed from the tappet, and

Figure 5 is a diagram illustrating an oil-supply system for supplying a plurality of tappets as shown in Figure 3;

Figures 6 and are-longitudinal sections showing constructions of tappets according to the invention having external valve devices, and

Figure 8 is a transverse section taken on the line 8 -8 in'Figure '7, and V Figure 9 is a detail view of the valve member removed from the tappet shown in Figure 6.

Like reference characters designate like parts throughout the several views.

Referring first to the tappet assembly shown in Figure 1, a tappet, designated generally is movable endwise in a fixed tappet guide 22, and comprises two hollow, cylindrical, telescopic, male and

female members

24, 26, that enclose between them a main chamber, described hereinafter, of variable volumetric capacity for containing liquid, hereinafter referred to as oil. The telescopic member 24 is a female member that constitutes the tappet body, hereinafter referred to as; the body, and is formed as a'cylinder 28 at one end, with a stem 30 at its opposite end, whichstem has a foot 32 for bearing against a cam 34' on a cam shaft 35 for operating the valve gear of an engine with which the tappet is associated. The telescopic member'26 is a male member and constitutes a two-

diameter piston

36, 38" having an inner part 36 movable axially in the cylinder? 23, and an outer part 38 movable axially in the tappet guide 22, which outer part 38 has at its outer end a suitably-shaped external face 40 to bear against the tip of a stem 42 of an engine valve, or against some other member of the valve gean Obviously, if desired, the male member 25-may co-act with the cam 34, and the female member 24 with the valve stem 42 or other part of the valve gear.

Thefemale member has an axial bore comprising an internal chamber 44 that has an annularconical valve seat 46 at one end, and has its other end in open communication with the adjacent inner end of a cylindrical space 48 in the cylinder 28 by way of peripheral holes 50 in a plate or washer 52 that is also perforated centrally, .and maybe held inany convenient manner in the female member 24 at the inner end of the cylinder '28. As shown, this plate 52 is a pressfit in the female member, and lies against a shoulder 54 formed therein. The end portion of the said bore remote from the cylinder 28 forms a relatively small cylindrical space 54 that opens at, one end into the inner end of the chamber 44, and at its other end into the inner end of a radial oil=inlet hole 58.

The main chamber aforesaid in the tappet comprises the chamber 44, space 48 and hole 50, which together constitute a pressure chamber of variable volumetric capacity, and the space 56 and hole 58, which together form an ante-chamber situated at the inner end of the said pressure chamber 44, 48, 50.

An internal valve device comprises a springloaded valve member in the form of a ball 60 which pressed against its seat 46 by one end of a valvespring 62, whereof the other end bears against the plate 54. This valve member 60 is situated at the junction of the pressure chamber and ante-chamber, and permits a one-way flow "of oil from the ante-chamber 56, 58 to the pressure chamber 44, 50, 48. When this valve device is closed, and. the fluid pressure in the pressure chamber is greater than that in the ante-chamber, restricted leakage of oil can take place from the pressure chamber along a leakage path, the amount of which leakage can be controlled and regulated as described hereinafter.

The tappet guide 22 has a lateral port 64 for the'admission of 'oil into the tappet 20 from an external oil-supply system described hereinafter. The inner end of the female member 24 has an external annular groove 66, hereinafter referred to as an oil belt, which in all positions of. the tappet is in open communication with the oilsupply port 84, and has one end in open communication with'the radial hole 58 forming part of the said ante-chamber. The other end of the oil belt 65 is connected by a longitudinal groove 68, formed in the outside of the cylinder 28, with an annular space 10. This space is bounded within the tappet-guide 22 at one end by a shoulder 12 formed at the junction of the two parts 36,. 38 of the piston, and at the other end by an end.

face 14 of the cylinder 28. This end portion of the cylinder may be internally chamfered, as. The said leakage path from the after, that is independent of the fit 0f the piston in the body of the tappet, is provided for Varying the amount of restricted leakage along said path.

Connecting means for connecting the antechamber 56', 58 with an external oil-supply pipe l8,hereinafter referred to as an oil gallery, comprises the said port 54, and the said oil belt 65, thus ensuring a constant supply of oil under pressure to the ante-chamber 55, 58.

' Packing means is provided for rendering oiltight the joint between the tappet 20 and its guide 22, at opposite sides of the oil-supply connecting means,'which packing means, while preventing escape of oil, does permit the escape of any air that may tend to collect in the tappet and its oil-belt. As shown, this packing means comprises two

packingrings

80, 82, each in the form of apiston ring provided, respectively, in a groove 84 in the female member 24, and in a groove 86 in the part 38 of larger diameter of the male member 26. These

grooves

84, 86 and their

packing rings

80, 82 lie in spaced relation away from the opposite ends of the oil belt 66 and the annular space 10 connected therewith. By this means oil can be delivered to the tappet without substantial loss while permitting the tappet to function under the action of the oil pressure and the influence of the cam 34.

Limiting means may be provided for mechaniin pressure in the latter that tend to beset up cally limiting the elongation of the tappet. This limiting means may comprise a radial pin which enters a radial slot that is formed in the male member in the portion'iwhere it engages the female member, each Tend of said pin also en gaging corresponding holes in the female memher, the elongation of the tappet being governed by the length of said slot in the male Imember.

chamber 44 through a very narrow annular space at the joint 'ITbetWe'ent-he inner periphery of the cylinder 28 and the adjacentcylindrical face of the piston 36, owing to the absence of an hermetic oil seal betweenthese two parts.

This piston leakage flows into the oil belt 66 which is' in connection with the oil gallery of the engine with which the tappet is working, so that the oil in the oil belt 65 is at gallery pressure. Also a certain amount of oil leakage, hereinafter referred to as packing leakage, will take place from the oil system which supplies the tappets with oil in spite of the packing arrangements provided to minimise it, and the volume thus ejected in combination with the'aforesaid packing leakage, provides the'total restricted leakage aimed at, referred to herein as tappet leakage. The oil ejected from the pressure chamber flows into the oil gallery against gallery pressure. Since oil at normal pressures and temperatures is incompressible, this tappet leakage must be accommodated in some appropriate space, or be otherwise disposed-of, and it may profitably be used to supply cheer the other tappets of the same engine, whose demand for oil synchronises therewith. Partof a second tappet that is associated with the same engine and is connected to-the oil gallery 18, is diagrammatically shown at 220. This synchronism exists to a very marked degree in many engines, in which these tappets are conveniently employed, but to ensure the best-conditions of operation a pressure-absorbing device-designated generally 96, may be incorporated in the: oilv supply system comprising the oil gallery 78. i

As shown, this pressure-absorbing device 96 1S situated externally of the tappet guide 22', in open communication with the-oil gallery 18 for the supply of oil under pressure to the tappet .20 and other tappets associated with. the 'same engine. It comprises a cylindrical vertical vessel 53B, whereof the upper portion is hermetically closed and filled with air, and its lower portion is connected by a branch pipe N with the'oil gallery '18 that opens by way of the'port fie into each tappet guide 22. This lower portion of the vessel 98 is filled with oil from the oil galleryiB, to which an oil pump-not shown, can be connected at a tubular connection I 92 by way of a check valve its comprising a non-return valve member H36 constituted by a ball that controls communication between the: branch pipe I02 and a short tubular branch I38 connected to the oil gallery. Since the oil'in this vessel 98' is in direct communication with the oil gallery, any variations due to excess or deficit of oil arising from'the variations of the tappet demand, are equalised by the resilience of the air compressed above the oil in the vessel 98, whereby violent changes in gallery pressure are avoided." Control and regulating means for controllin the restricted tappet leakage comprises a springcontrolled relief valve I I!) arranged in direct communication with the oil gallery 18. Thisrelief valve has a duct! 12 that opens at one end into the tubular branch I08, and has its other end' controlled by a valve member in thei'r'orm of a ball H4 that is loaded by a coil spring H6, and

controls communication of the duct H2 with a tubular branch H8 that opens to atmosphere, andr'may deliver any escaping oil to the engine sump when thespring I it permits of-such escape. A set-screw H9 is provided foriaccurately adjust ing the pressure of the spring I IE on the ball I l4, and thereby regulating the tappet leakage. In

this connection it may be pointed out that the leakage from the pressure chamber Within the tappet is opposed by the fluid pressure of the oil outside the tappet, i. e., the oil-gallery fluid pressure, and this in turn is governed by the'packing means constituted by the piston rings 80, 82; 1

In the interval during which. the above-mentioned operations have been taking placefthe cam 3-i has continued to revolve, the engine valve associatedwith the tappet 20 has closed, and at that instant the tappet 20-finds itself shorter than it was by an amount determined by the cubic contents'of the tappet leakage before-it left the pressure chamber. The tappet being now no longer under the action of the pressure of the engine valve-spring, iszfree to elongate and it does so under the gallery pressure of the oil, which, by way of the connecting means 64, .66 and the ante-chamber 53, 58, gives access to the pressure chamber 44, thereby driving the male member 25, in the direction away from the female member24, which elongation of the-tappet will be arrested by the outer face 4% of the'male member abutting against the valve spindle '42 of the valve gear, or as otherwise provided by the limiting means 88, 9B: 1 4111 the foregoing description it has been assumed that during the interval when the tappet 29 has been functioning in the manner described, no alteration has taken place in any'of the componentparts of the valve mechanism, except inthe tappet itself. Assuming, for example, that during that interval one of the-components, e.-gi,- the engine valve stem, has lengthened under the heat of the engine, then thearnount of expansion of the tappet will be reduced by a corresponding amount. For example, asuming that the tappet leakage has shortened the tappet by six thousandths of an inch, and that the valve-stern has lengthened by one thousandth (a very exaggeratedfigure) then the tappet will elongate by five thousandths so as to maintain its correct length. If, on the other hand, the valve'stem has shortened by 'a corresponding or other amount within the range ofthe tappet, then the tappet will elon-' gate by an amount equal to the hypothetical six thousandths of an inch plus the amount by which the engine valve stem has shortened. The exceptionto this routine is when the engine valve. getshung upin its guides; in that case the elongation of the tappet is limited to therange permitted by the limiting

means

88, 90.

7 It frequently happens that when the above conditions occur, the vibrations of the engine free the held-up valve which, after liberation, con-' tinues to function as before. In the event of this happening in an engine equipped with tappets 20 as described above, the pressure of the engine valve spring induces a leakage of oil from the pressure chamber 44 until the tappet has assumed its correct length. The amount of this leakage is, however, out of all proportion to the demand ,of any of the adjacent tappets, so that the relief valve I I comes into operation and discharges the surplus to the engine sump or as may otherwise have been arranged.

To assist the starting of the engine an airprising a valve member I24 in the form of a ball which permits flow of oil into the tank, but prevents flow in the opposite direction into the oil gallery 18, to which the inlet valve I22 is connected by a branch pipe I26. When the engine is in operation, air above the oil in this tank I is necessarily kept at the maximumpressure reached by the gallery pressure, owing to the provision of its non-return valve I22, so that a reserve of compressed'air is always available for engine starting, if actuating means are provided for making this reserve available if required.

These actuating means may comprise an outlet cock designated generally I28 having an operating lever I30, which may be hand-operated, to release oil under air pressure when the engine is started. Alternatively, as shown, the cock may be in mechanical connection, as by a spring I32, with the electric started knob or push button of the engine to come into operation simultaneously with the starter motor and to be cut out with it. In either case, when the lever I30 is moved from its normal rest position, shown in full lines, to its starting position, shown in broken lines, a spigotelike member I34 of the cock having a flat face I36, on which rests a pusher member I38, lifts the ball I24, and permits the compressed air in the tank I20 to force oil out of the tank by way of an annular space, surrounding the member I34, into the oil'- supply system and towards the tappet. Any oil which has then been ejected from the pressure tank I20 during the engine-starting operation will subsequently be forced back into the same tank by the rising gallery pressure, and will be available to be drawn upon as occasion arises. Since the pressure tank I20 is hermetically sealed, and the non-return valve device I 22 and cock I28 are of simple construction and not liable to leak, the tank I20 will remain under pressure for an indefinite time and be always available 'to fulfil the purpose for which is has been installed.

It will be appreciated from the above that elongation of the tappet is effectedby the pressure of an external supply of oil used for enlarging the cubic contents of the main chamber of the tappet, without depending on any spring for moving the piston and body of the tappet relatively one to the other. Provision is made for accommodating in the oil-supply system any oil displaced from the main chamber due to its contraction, and also for relieving excessive oil pressure that is set up, or tends to be set up, in the tappet due to its contraction. It will also be appreciated that the valve-gear comprising one or more valve-gear units including a springloaded engine-valve and a self-adjusting, nonatmospheric tappet operating to be self-adjusting as to its length and to dissipate power thereby, is provided with means for storing said dissipated power pending its restoration to the tappet during its period of idleness, as by means of the air vessel I20 connected with the oil system supplying the tappet. The term non-atmospheric tappet refers to one in which the pressure chamber and ante-chamber in the tappet are shut ofi from the atmosphere during the operation of the tappet.

Referring now to Figure 2 showing a modified construction of tappet designated generally I40, movable in a fixed tappet guide I42, this tappet also comprises two hollow, cylindrical, telescopic, male and female members I44, I46 that enclose between them a main chamber of variable vclumetric capacity for containing oil. The telescopic member I46 is a female member that constitutes the tappet body, and is formed as a cylinder I48 at one end, and with a stem I50 at its opposite end, which stem bears against the tip of a stem 42 of an engine valve, or against some other member ofthe valve-gear. The male telescopic member I44 is a two-diameter piston I52, I54, whereof the inner part is movable axially in the cylinder I48, and the outer part I52, is movable axially in the tappet guide I42, which outer part I52 has a foot I56 for bearing against a cam 34 for operating the valve-gear comprising a valve having the stem 42. If desired, the female member I46 may co-act with the cam 34, and the male member I44 with the valve stem 42 or other part of the valve gear. A chamber in the hollow part I54 of the piston I44 contains a spring I60 and has at its inner end a radial port I62 leading to the joint where the male and female members loosely mate. The spring I60 bears at its outer end against an abutment in the form of a plate I64 that is seated on the inner end of the cylinder I48 and has apertures I66 which place the chamber I58 in the cylinder I54. in open communication with a three-diameter chamber I68, I69, I10 in the stem I50 of the female member I46. A valve member I12 in the form of a ball has a seat I14 at the junction of the two chambers I69 and I10, which ball is under the action of gravity and, when permitted by the fluid pressure in the tappet to do so, can rest on the plate I64 and place the chamber I 10 in open communication with the chamber I58 in the cylinder I54. This chamber I10 is connected by a radial inlet hole I16 to the outside face of the female member at the inner peripheral face I18 of the tappet guide. The chamber I58 in the cylinder and the chambers I68, I69 in its stem together with the holes I66 in the plate I64 constitute a pressure chamber corresponding to the pressure chamber 44, 50, 48 described above with reference to Figure 1, while the chamber I10 and radial hole I16 constitute an ante-chamber corresponding to the antechamber 56, 58 described above with reference to Figure l The tappet guide I42 has a lateral port I for the admission of oil into the tappet I40 from an external oil-supply system similar to that described above, and the female member I46 has an external annular groove. I82, hereinafter referred to as an oil belt, which corresponds to the oil belt 66 also described above with reference to Figure 1, and in all positions of the tappet is in open communication with the oil-supply port I80. This oil belt I82 has one end in open communication with the inlet hole I16 forming part of the ante-chamber. The other end of the oil belt is connected by a longitudinal groove I84 formed in the outside of the cylinder I48, with an annular space I86. This space I86 corresponds to the annular space I described above Leakage control means that is independent of the fit of the piston in the body of the tappet, is provided in the oil-supply system, as described 7 above with reference to Figure 1, for varying the amount of restricted leakage along said path.

Also, packing means in the form of two packing rings 80, 82, similar to those described above with reference to Figure 1, are provided respectively in the female member I46 and the male member I44. In addition, limiting

means

88, 90, similar to those described above with reference to Figure 1 are associated with the part I54 of the piston of smaller diameter.

This tappet is intended to operate in a substantially horizontal position, for example with its longitudinal axis, indicated at I92, lying at an angle to the horizontal plane, indicated at I94, so as to place the male member at a higher level than the female member.

The operation of this tappet I40 and the oils'upply system to which it is connected is similar to that of the tappet and its oil-supply system described above with reference to Figure 1, but

'difiers therefrom in that the spring I 60'assists the fluid-pressure in the pressure chamber in elongating the tappet, so that elongation of the tappet is not dependent solely on the gallery pressure. In addition, the ball valve 80 which closes under the action of gravity, is not seated under the action of a valve spring, but under the action of fluid-pressure in the pressure chamber when the fluid-pressure in that chamber is greater than the fluid-pressure in' the antec'hamber during the contraction of the tappet.

Referring now to Figures 3 to 5, a plurality of modified constructions of tappets, designated generally 200, are connected to an oil-supply system comprising an oil gallery 18, check valve I 0 3, relief valve H0, and pressure-absorbing device 96 as described above with reference to Figure 1. As clearly shown in Figure 3, each tappet 260 comprises two hollow, cylindrical,

telescopic members

202, 204 that enclose between them a pressure chamber 206 of variable volumetric capacity. One member 202 is a female member constituting the tappet body, and comprises a, cylinder 208 and a stem 2I0. The other telescopic member 204 is a male member constituting a two-diameter piston, whereof a part 2I2 of smaller diameter is slidable endwise in the cylinder 208 and carries a short piston-rod 216, and apart 2| 4 of larger diameter is slidable in a fixed tappet guide 2I8 that is integral with the cylinder block of the engine with which the tappet is associated. The piston-rod 2I6,'that bears against the valve stem 42 which is under the action of a valve'spring 2I9, is provided with limiting means 88, 90as described above with reference to Figure 1 for mechanically limiting the elongation of the tappet.

The female member 202 has an external annular groove 222 that surrounds thecylinder 208 and constitutes an oil belt which-is connected at one end by way of one ormore radial holes 224 with the pressure chamber 206; This pressure chamber is connected by a longitudinal groove 226, formed in the part 2I2 of'the piston, with an annular space I86, similar to that described above with reference to Figure 2, situated between the inner end face I90 of the cylinder and a shoulder [88 of the piston. Packing means in the form of

piston rings

84 and 86, similar to those described above with reference to Figure 1, are provided respectively in the female member 202 and the male member 204 at opposite ends of the oil belt 222. The tappet guide 2! has at 228 an annular groove constituting an inlet that opens at its inner periphery through the internal the pressure chamber.

cylindrical face 230, against which the tappet is movable, and at its outer periphery into the inner end of an oil duct 232, constituting a filling inlet hole, which is in open communication between its ends with the gallery 18 and is normally closed at its outer end by a grub screw 233. As described so far this tappet is similar to that described above with reference to Figure 1, but differs therefrom in that no valve device is provided within it.

An oil inlet-valve member 229 in the form of a detachable arcuate leaf spring is accommodated in the groove 228 and controls the supply ofoil to This valve member 229 has near one end a stop pin 23I which lies in a recess 233 formed in the tappet guide to receive it at a situation diametrically opposite to the inlet duct 232. The width of'the groove 228 is greater than the diameter of the duct 232,- and the width of the valve member 229 is less than that of the groove 228, so that-when the valve member 229 is unseated at the duct 232 oil can flow round it to the oil belt 222. I

In order to relieve any excessive fluid-pressure that may be set up in the pressure chamber 206, th ports 224 and longitudinal groove 226 of the oil belt 222, and th annular space I connected with the groove 222 together constituting a main chamber in the tappet, leakage means compris inga non-return relief or safety valve is provided outside the tappet for permitting a restricted escape of oil from the pressure chamber. This relief valve, designated generally 234, comprises a nut-equipped casing 236 that is secured in a cylindrical hole 238 in the tappet guide 2 I8 that opens at its inner end by way of a port 240 through the cylindrical face 280 ofa bore hole contain ing the tappet. The inner end of the hol 238 provides at 242 a conical seat fora valve member 244 in the form of a ball, opposite a second conical seat 243 formed on the inner end of the casing 236. A spring 246 bears at one end against this ball, and tends to seat it on the seat 242; the spring bearsat its other-end against an abutment 248 in the form of 'a setscrew that is adjustable in the valve casing 236 and can be secured in its adjusted position by a lock-nut 250, whereby the pressure of the spring on the ball 244 can beadjusted. The valve casing 236 has a lateral port 252 in open communication withthe oil inlet hole 232 by way of the liquid-supply conduit constituted by the oil gallery I8 situated in the tappet guide 2 I8.

The fluid pressure in the oil gallery always; tends to open the resilientvalve member .229 a 'nd, togetherwith the spring 246, tends to seat the ball 244on its seat'242; Th lift of the cam 34 isso which seat is situated re t as t plac t e ort 4!! in open relation with the annular space 186 in the tappet once each r volution of the cam. The oil in this annular space is always at the same pressure as that of the oil in the pressure chamber 206, so that if this pressure is excessive a restricted escape of leakage oil from the pressure chamber can take place when the cam 34 is at or near the top of its stroke, whIch leakage can be controlled and adiusted .bymeans of the sc w 8- he leaka e o l tha f o s a t ba l 4 d is e ec d from th aforesaid relief or safety valve 234 when the hall moves from the seat 242 to the seat 243, flows into the oil galler 18 against gallery fluid P 3I It will be appreciated from the above that in the construction of tappet shown in Figure 3, the leakage which occurs through the relief valve 234 depends principally on the oil pressure and ti heth o he e i a v s i g 46 and is t e efore independent of the fit of the piston 204 in he tappet body 202; it is also independent of the tempe ture of the o l xce t n o a a he 116 of oil through the relatively large passages through w fch it passes is affected by the terntre i t m l e en t t e f ec P d ce on' the operation of the tappet by temperature variations is much less than in th constructions described above with reference to Figures iand 2.. On the other hand, in the construction oi tappet shown in Figure 3, should any leakage occur past the packing rings 84, 86 it will influence the operation of the tappet, but its effect will be analogous to that produced by the piston leakage the constructions shown Figure 1 and 2, but there is this difference, namely that the leakage past the

packing ring

84, 86 is susceptible of being prevented by the resilient nature of the packing means, whilst when the leakage path comprises the joint between the adjacent faces of the male and female members no such compensating effect is possible. 'Moreover, in the construction shown Figure 3, the rate of tappet leakage, which plays a very important part in he operation of the tappet is adjustable at any time by means of the relief; valve 234, whilst in the constructions shown in Figures and the P s ea e s iiXed o efo all when the parts are manufactured, although. it, is susceptible of adjustment by the means described above. Further, in the construction shown in Figure Sleakage over and abov any packing;- ri lea ha a a lac oc urs on at the top of the tappet stroke, whereas the const i s Shown in Figures 1 an t conti ues forthe whole of the stroke, Referring now to Figure 6, a tappet designated generally 260, is provided with a combined I ta pet inlet-valve and tappet relief-valve, as; de-

scribed hereinafter, that has a valve mernber common to themboth, and is provided with means or dj ti g t hit to ula e e a pet; l ak ees p e 5 le; i a fixed. tapnet guide 262 comprises two hollow cylindrical, telescopic members, 264, 266 that enclose between them a pressure chamber; 268 of variable voll -r mertio capacity. The member 264 is a female member constituting the tappet body, and corn prises, a cylinder 210 and a stem 212. The qther telescopic member 266 is a male member con stituting a two-diameter pistonk whereof a part 214 of smaller diameter is slidable endwise the cylinder 210, and a part 216 of larger diameter is slidable in the internal c ndrical face 218;); the bore hole. inthe. tappet guide. 2.62: which. is

integral with the cylinder block .of the engine with which the tappet isassociated. The piston 1.114, 16 bears against the valve stem 42 controlled bya v lve spring 2. l 9,,and is. provided with limit 6 :in means 8, 9. as described above with reic eate to Fi ure l. prmechanically limitin th elong tion of the tappet.

The i male m m er 26. has an exter a annular groove 280 that surrounds the cylinder 210 10 an ons itute an oil; b t which is connect at the inner end of the y nderby way of one or mo e radial holes 282 with the pressure chamher 268, Additional radial holes 284 connectin the pressure chamber 268 with the oil belt are provided in the. cylinder wall at a situation beween its ends A compression coil sprin 288 that tends t9 elongate th t pp t is accommo dated in the cylinder 210 and bears against the inner end of the cylinder and the inner end of v the part 214 of the piston. The length of the pa t5 o he piston s pre r bly onsiderably shor er han the cylinder 210 and is m e hollow .12 29 192 1 1? where i intersects radial holes 281 connec n it with n a n ar pace I86 at the 2;; end or the cylinder. A short part of a circulaor-r le ka pat s provi ed at the joi t 88 bet een th se t o p rt 0 214 o t appet, which short part connects the pressure chamber 268 by way of the radial holes 281 and the annular space I86 with the annular groove 280.

Grooves

290, 292 for preventing oil from escaping at t e Oppos t end of t e t ppe in, the guide member 262 are provided respectively in the stem 212 of the female member 264, and in the larger part 216 of the mston. These grooves, which arepreferably of semi-circular crosssecti0n, even if not provided with piston rings or the like, constitute packing means for reducing the leakage of; oil between the tappet and its guide at the ends. of the tappet. Connecting means for connecting the pressure chamber 268 with an external liquid-supply cond-uit, shown asan oil gallery 18 in the tappet guide 262, comprises a filling hole or port 294 that places the gallery 18 in open connection with the oil belt 280 in all positions of, adjustment of the-tappet. A combined tappet inlet-valve and tappet relief-valve, designated generally 298 having a valve member 298 in the form of a ball, controls the flow oi oil through the inlet hole 294. This valve device 296. is constructed simi-. larly tothe valve device 234 shown in Figure. 3.. but d ffers her from in that, only one valve seat .3 pr v ded... aeamst Which the ball can be seatedpy fluid; pressure in the pressure chamber. Whenthe fluid pressure in the gallery 18 com-Q bined: with he pres ure of t e Spring 6. is i exce s; o the iu d pressure n the pressure ohamher; and the; ball 29 8 is lifted from its seat 243, 60 outwardmovement. of the ball is arrested owing o, i s o ta n wi h the. pe ip ery of the, cylinden 2 he i e t. s t at, oil can flow into the pressure chamber; Should the pressure. in the press nie chamber become excessive, how:- ever, the ball 29.8 will be, returned to its seat: 242, dur ng. which movement a restricted small 11 10 212 O leaka e; an. take, place from; the. pres chamber to the oil-supply system by way or he valv device. 2.9.6, a d the oil gallery 8;. In this construction the amount of thisleakage, is ad ustab e. according to. the, setting of the. screw; 248- which an-var the. time taken for. the; bait 2,9 81to;mov.e from one of its end positions. to the other...

1g; Referring now to Figures 7.; 8Land 9;. atappet',

designated generally 300. is movable endwise in a two-diameter fixed

tappet guide member

302, 304 which is distinct from a cylinder block 306 of the engine with which the tappet is associated. This tappet 300 comprises two hollow, cylindrical, telescopic male and female members 308, 3I0 that enclose between them a main chamber of variable volumetric capacity for containing oil. The telescopic member 308 is a female member that constitutes the tappet body, and is formed as a cylinder 3| 2 at one end, and with a stem 3I4 at its opposite end, which stem bears against the stem 42 of an engine valve, or against some other member of the valve gear. The male telescopic member 3I0 is a two-diameter piston 3I6, 3I8, whereof the inner part 3I8 of smaller diameter is movable axially in the cylinder 3I2, and the outer part 3I6 of larger diameter has a foot 320 for bearing against the cam 34 for operating the valve gear. If desired, the arrangement may be reversed, and the female member may cooperate with the cam 34, and the male member with the valve stem 42. This tappet 300 comprises a pressure chamber 268, a coil spring 286 therein, a radial port 282, an oil belt 280, and an annular space I86, similar to the corresponding parts described above with reference to Figure 6. A reduction in the diameter of the part 3I8 of the piston forms an annular space 322 which is in open relation with the pressure chamber 268 by way of a radial port 324 at the inner end of the pressure chamber 268.

Connecting means for connecting the pressure chamber 268 with an external oil-supply system of the kind described above with reference to Figure 1, comprises two radial inlet holes 326 formed in the guide member 302 in such a position as always to be in register with the oil belt 280 in all positions of adjustment of the tappet. Externally the guide member 302 has an annular groove 328, into which the outer ends of these holes 326 open, which groove 328 is always in open communication with a liquid-supply conduit 330 constituting or connected to an oil gallery.

A combined tappet inlet-valve and tappet relief-valve in the form of a detachable arcuate leaf spring 332, shown detached in Figure 9, is accommodated in the oil belt, which spring normally masks the filling inlets 326 and thereby closes them. This spring is formed or provided with two nipples 334 which lie diametrically opposite one another and enter into the inlet holes 326, and thereby hold the valve member against angular movement around the longitudinal axis of the tappet, and keep the valve member in position in the guide member 302. The stem 3 of the female member 308 is provided with flats 336 at opposite sides of it,-as shown most clearly in Figure 8. These flats enable the end portions of the spring 332 to be flexed inwards until the nipples 334 slide to such a position in the tappet guide 302 that they register with the filling inlets 326 and can snap into them. The resilient valve member 332 can be Withdrawn by a reverse operation, when the wedging action between the nipples and the filling inlets flex the spring inwards whilst the tappet is being withdrawn from its guide.

This valve member 332 performs the same functions as the valve member 298 described above with reference to Figure 6, but instead of being controlled by a spring 246 it is itself resilient, and tends to seat itself and close the inlet holes 326. When the fluid pressure in the oil gallery 330 exceeds that in the pressure chamber 263, the valve member 332 will be unseated and admit oil from the oil gallery by way of the said connecting means 326, 280, 282 to the pressure chamber 268. After being unseated, and during the return movement of the valve member 332 onto its seats at the inlet holes 326, opportunity is afforded for a short space of time for oil to leak from the pressure chamber back to the oil gallery. The amount of such leakage will be determined by the resiliency of the spring 332 constituting the valve member. By removing one such spring and replacing it by another spring having one or more different characteristics, such as a different degree of resilience, the leakage permitted from the tappet to the liquid-supply system can be controlled. Instead of two inlet 110165.326, only one or more than two may in some cases be provided.

The part 304 of the guide member is of larger diameter than the part 302, and is seated on a shoulder at 338 formed in the cylinder block 308. This arrangement facilitates the assembly of the tappet 300 and its guide member in the cylinder block, and the removal of the tappet when it is desired to substitute one valve member 332 for another.

In each of the tappet assemblies described above, provision is made for restricted leakage from the pressure chamber in the tappet by means which are independent of the fit ofthe male telescopic member in th female member, and in each construction that restricted leakage is adjustable. Moreover, owing to each of these telescopic members being provided withleakagepreventing annular grooves situated at or towards the opposite ends of the tappet, with or without piston rings or like packing means in the grooves, the main chamber in each tappet is shut off from the atmosphere, and the term non-atmospheric" applied to the tappets described above refers to this feature, which distinguishes them from tappets of the type described proposed heretofore, in which the flow of oil issuing from the tappets was unrestricted towards the atmosphere at one or both ends of the tappet guide. Such a nonatmospheric tappet is self-priming, and should any air collect, or tend to collect in any part of the internal main chamber within the tappet, such air will be automatically expelled when the tappet is operating in any position, except the constructions shown in Figures 1 and 2, whose use is particularly applicable to engines in which the longitudinal axis of the tappets lies in a horizontal plane, or at any other angular position provided th male member of the tappet operates at a higher level than the female member.

Various modifications may be made in the details of construction described above without departing from the invention. For example, when a tappet, such as the tappet I40 shown in Figure 2, tappet 260 shown in Figure 6, or tappet 300 shown in Figure 7, comprises an internal spring tending to elongate the tappet by forcing its telescopic members apart, which spring supplements the oil pressure in the oil gallery, the self-starting pressure tank I20 and the check valve I04 may be dispensed with, when the oil pressure inv the oil gallery is not adequate to operate the tappets. Moreover the invention is not limited to oil-operated tappets, provided that the component parts, particularly the diameters of the telescopic members, are correctly proportioned to cope with the loads against which they have to operate and to suit the viscosity and other char,

acterlstics of other liquids which are suitable to satisfy specific requirements.

I claim:

1. A tappet assembly comprising a tappet of the character described having two telescopic members that define a pressure chamber of variable size adapted to contain a liquid, and are movable one in relation to the other for determining the length of the tappet, one of which members constitutes the body of the tappet, and the other of which members constitutes a piston movable axially in relation thereto, restricted leakage of liquid from the pressure chamber being permitted, in combination with a fixed tappet guide member that has an inlet port for supplying liquid under pressure to the pressure chamber for elongating the tappet, leakage-control means for controlling the restricted leakage from the pressure chamber independently of th fit of the piston in the body, and thereby controlling the operation of the tappet, and means situated at opposite sides of said inlet port for preventing liquid from escaping to atmosphere at the ends of the tappet by way of the joint between the'tappet and the guide member, whereby the tappet is non-atmospheric and self-priming in any working position.

2. A tappet assembly as set forth in claim 1, wherein the said means is constructed and ar-- ranged so as to permit the escape into the atmosphere of air from within the tappet byway of said joint.

3. A tappet assembly comprising a tappet of the character described having two telescopic members that define a pressure chamber of variable size adapted to contain a liquid, and are movable one in relation to the other for determining the length of the tappet, one of which members constitutes the body of the tappet, and

the other of which members constitutes a piston movable axially in relation thereto, restricted leakage of liquid from the pressure chamber being permitted, in combination with a fixed tappet guide member, liquid-supply means arranged to supply liquid from an external source of supply under pressure by way of an inlet port in the guide member to the pressure chamber for elongating the tappet, and leakage-control means for controlling and adjusting the restricted leakage from the pressure chamber independently of the fit of the piston in the body, and thereby controlling the operation of the tappet, which leakage-control means comprises a non-return valve device that is associated with said liquid-supply means, and is situated externally of the tappet in'said guide member.

4. A tappet assembly comprising a tappet of the character described having two telescopic members that define a pressure chamber of variable size adapted to contain a liquid, and are movable one in relation to the other for determining the length of the tappet, one of which members constitutes the body of the tappet, and the other of which members constitutes a piston movable axially in relation thereto, a restricted escape of liquid from the pressure chamber being permitted, in combination with a fixed tappet guide member, liquid-supply means comprising a conduit that is arranged to supply liquid from an external source of supply under pressure by way of an inlet port in the guide member to the pressure chamber for elongating the tappet, and leakage-control means for controlling and adjusting the restricted leakage from the pressure chamber independently of the fit of the piston in thebody, and thereby controlling the operation of the'tappet, which leakage-control means is arranged to return escaped liquid to said conduit.

5. A tappet assembly as set forth in claim 4, wherein the liquid-supply conduit is provided with a non-return valve device that is carried by the guide member at the inlet port and controls the flow of liquid through thesame.

6. A tappet assembly as set forth in claim 4, wherein the leakage-control means comprises a valve device arranged to return the escaped liquid to said conduit, and the liquid-supply conduit is provided with a non-return valve device that is carried by the guide member at the inlet port, which valve devices are combined to form an unitary structure.

7. A tappet assembly comprising a tappet oi the character described having two telescopic members that define a pressure chamber of variable size adapted to contain a liquid, and are movable one in relation to the other for determining the length of the tappet, one of which members constitutes the body of the tappet, and the other of which members constitutes a piston movable axially in relation thereto, restricted leakage of liquid from the pressure chamber being permitted, in combination with a fixed tappet guide member, liquid-supply means arranged to supply liquid from an external source of supply under pressure by way of an inlet port in the guide member to the pressure chamber for elongating the tap said port and permits the escape of liquid through it when the valve member is moving in a direction away from the tappet.

8. A tappet assembly as set forth in claim 4,,

wherein the liquid supply conduit is provided with a non-return valve device that is carried by the guide member at the inlet port and controls the flow of liquid through the same, which valve device comprises two seats and has a valve member movable with play between the seats.

9. A tappet assembly as set forth in claim 4, wherein the liquid-supply conduit is provided with a non-return valve device that is carried by the guide member at the inlet port and controls the flow of liquid through the same, which leakage control valve device is constituted by a resilient valve member in the form of a leaf spring arranged to be readily removed, and to be replaced by one having different characteristics.

ARTHUR BURTON BUCKLEY.