US2838931A - Machine for testing hydraulic tappets - Google Patents

Description

June 17, 1958 M, VLALBAUGH 2,838,931

MACHINE FOR aypmuuc TAPPETS Fitefi'Nov. 4, 1954 s Sheets-Sheet 1 if I I I I ZZ M l in; .6? i

Z I I l n F! I 7% I 1 if 9/ 1 1a x /f 75 f? I f if v Attorney June 17, 1958 M. v. ALBAUGH 2,838,931

MAUHINEFOR TESTING HYDRAULIC TAPPETS Filed Nov. 4, 1954 Y s Sheets-Sheet 2 Inventor /d @Wg United States Patent 2,838,931 MACHINE FOR TESTING HYDRAULIC TAPPETS Merton V. Albaugh, Grand Rapids, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application November 4, 1954, Serial No. 466,782

2 Claims. (Cl. 73119) This invention relates generally to machines for testing hydraulic self-adjusting valve tappets under simulated operating conditions and, as hereinafter described and claimed, more specifically relates to improvements in certain respects in machines of the type disclosed in United States Patent 2,619,834, Kelley, patented December 2, 1952, and United States Patent 2,619,835, Albaugh, also patented December 2, 1952.

A common form of hydraulic tappet comprises a vertical cup-shaped cylinder closed at its upper end by a piston or plunger telescopically slidable and supported therein on a column of oil or other fluid confined in the bottom of the cylinder. The cylinder is slidably supported in the engine frame for longitudinally reciprocable movement in following one of the lobes on the camshaft, the piston moving therewith under the action of the oil column and effecting through suitable linkage a corresponding movement of the engine valve which is biased to closed position by a relatively stiff spring. The piston is provided with a passage extending longitudinally therethrough which is closable by a check-valve sensitive to pressure within the chamber below the piston but which opens upon removal of that pressure to permit a flow of oil into the chamber from a reservoir above the piston,' thereby tending to keep the pressure chamber filled at all times. A light spring is provided to bias the piston upwardly in the cylinder and thereby expand the tappet to take up the valve lash during the interval between lifting strokes when the engine valve spring is unstressed. It is such a tappet that is particularly adapted for testing in the improved machine forming the present invention.

'In order that hydraulic tappets of the general type described above may perform properly to maintain zero lash in an engine valve linkage, two functions are essential. The first of these is referred to as leak-down and is the rate at which the tappet collapses under load due to leakage of oil past the piston from the pressure chamber into the reservoir. A certain minimum leak-down is necessary to allow the tappet to collapse a suflicient amount to compensate for the thermal expansion of the other members of the valve linkage during engine warmup and a maximum limit of leak-down is necessary to insure that the amount of oil displaced from the pressure chamber during one engine valve lifting stroke is not more than can be returned through the check-valve to the pressure chamber during the interlude before the next stroke. The second necessary function is referred to as check-valve recovery, or ball recovery in tappets employing a ball-shaped check-valve, and is represented by the distance which the tappet will collapse upon a sudden application of load downwardly on the piston while the check-valve is closing from its fully open po sition. While this value must not exceed that which will insure sufficient engine valve opening and avoid excessive working of the tappet, it is also a measure of the capacity of the check-valve to pass oil from the reservoir to the pressure chamber and allow the tappet to expand when the load thereon is removed, and hence has a minimum as well as a maximum desirable limit.

In the prior machines disclosed in the patents referred to above, the leak-down tests were efiected by suitably loading the tappet and noting the time required for the tappet piston to move a predetermined distance relative to its cylinder. While this, without more, appeared to be satisfactory for testin the rate of leak-down of the tappets, it was found that because of minute imperfections or machining particles, etc., the tappet piston and cylinder sometimes tended to stick, resulting in unsatisfactory tests. Also, under actual operating conditions there is some tendency for the tappet cylinders and pistons to rotate relative to each other.

Hence it is the principal object of the present invention to provide means in a testing machine responsive to the rate of leak-down of hydraulic valve tappets which will rotate the tappet piston and cylinder relative to each other during the leak-down and check-valve recovery tests in order to more closely simulate actual operating conditions and to aid in overcoming any tendency on the part of the tappet elements to stick. i

For a fuller understanding of the principal object and certain additional objects of the instant invention reference may be had to the accompanying detailed description and drawings, in which:

Fig. 1 is a sectional view in elevation of the main portions of a hydraulic tappet testing machine having combined therewith means for rotating a tappet piston and cylinder relative to each other.

Fig. 2 is an outboard view in elevation of a portion of the testing machine of Fig. 1 with a tappet in place ready for testing.

Fig. 3 is a view taken on the line 3-3 of Fig. 2 illustrating how a tappet is received and retained in themachine ready for testing.

Fig. 4 is a typical example of a hydraulic valve tappet in section of the type particularly adapted for testing in the machine of the instant invention.

Fig. 5 is a view similar to a portion of Fig. l, but enlarged to more clearly illustrate certain details of the tappet receiving stations of the machine.

The machine as shown in thedrawings comprises a stationary supporting frame or pedestal 2 to the upper end of which are fixedly mounted upper and lower carupper and lower rollers 22 and 20 which are rotatably. mounted at circumferentially spaced points around the post 8 to the carriage supporting structures 6 and 4, respectively. A hood 24 attached to the upper structure 6 serves to partially enclose the upper portion of the machine, there being a suitably cut out section at the front of the machine to accommodate insertion and removal of tappets and observation of the test instruments. Circumferentially spaced around the carriage 16 are a plurality of tappet testing stations, designated generally by the numeral 25. Each test station includes a supporting means for the cylinder 26 of a tappet 28 comprising a platform member 30 disposed outwardly from the periphery of the lower supporting structure 4 and rigidly suspended from the carriage 16 by a member 32. Secured to the member 32 is aU-shaped block 36 for locating the tappet cylinder as it rotates around with the carriage 16 during the test. Fitted in the arms 3 ofthe block 36 is a set of limiting rollers 37 against which the tappet cylinder 26 is positioned when inserted in place on the platform 36 between the arms of the U-shaped block 36. Fitted in the arms of the block 36 are oppositely disposed spring-biased buttons 38 having rollers 39 which yieldingly engage the tappet cylinder 26 and retain it in position between the arms of block 36 and against the limiting rollers 37. Suspended above the carirage 16 and above the U-shaped block 36 is a weight 40 on an arbor 42. A downward extension 44 of the arbor 42 carries a nosepiece 46 at its lower end which is adapted to contact the upper end 48 of the tap pet piston 62 (see Fig. 4). Attached to the upper end of the arbor 42 is a follower roller 50. Fixed to the outer periphery of the upper supporting structure 6 is a cam member 54 which controls the vertical movements of each of the weights during the test cycle. Since the specific manner in which the weights are allowed to come into action in order to load the tappets during test does not form the subject matter of this invention, it appears necessary to state only that during the cycle the weights are first positively cammed downwardly after which they are left to rest freely so that they are supported through the column of the arbor 42, the downward extension including the nosepiece 46 thereby loading the top 48 of the tappet piston 62. If a fuller understanding of the cam member 54 including its mode of operation is desired, it is suggested that reference be made to the above-mentioned Albaugh patent.

lt will be observed that the movement of the rectangular arbor 42 is controlled by a plurality of oppositely disposed vertically acting roller assemblies 56 supported on carriage 16 which, while enabling the arbor to move freely up and down, tend to restrain any rotatable movement thereof about the arbor axis for a reason which will appear shortly.

Switching and timing means 57, 53, respectively, and deflection indicating means 66, which need be referred to only briefly, are provided in the machine to time the amount of leak-down and check-valve recovery, i. e., relative axial movement of the tappet piston with respect to the tappet cylinder during a given time interval. The means 57, 58 and 66 are, of course, for the purpose of making the machine responsive to the rate of leak-down and check-valve recovery of the tappets tested therein. Since these means, however, do not form the subject matter of the present invention and are essentially the same as in the above-mentioned Albaugh and Kelley patents, no further mention herein is deemed necessary with respect to them.

A hydraulic valve tappet of the type with which the present machine is particularly adapted to test is shown in Fig.4 and comprises an outer tappet cylinder, already indicated by the numeral 26. Adapted to both rotate and move axially in the cylinder is a tappet plunger or piston 62 having an upper closure end 48. The lower end of the tappet piston 62 is biased away from the lower end of the tappet cylinder 26 by means of a spring 64 interposed therebetween. The spring 64 also tends to hold a small cup 66 against the lower end of the piston 62, the cup 66 containing a ball check valve 68 adapted to open and close a .port 70 leading to the interior of the piston 62. For a more complete understanding of the type of'hydraulic tappet valve referred to herein it is suggested that reference be made to the United States Patent 2,667,149 to Purchas, in, et al., which describes in detail the structure, purpose and operation of such a valve. During the normal operation of a tappet such as the type referred to above there is some tendency on the part of the piston and cylinder to rotate relative to each other, which they can do because of the smooth cylindrical surfaces of both .parts, coupled with the fact that there is normally a thin film of oil between the walls of the parts. In spite of precise machining and careful polishing these Walls are occasionally subject to minute imperfections or particles thereon which sometimes tend to delay leak-down. If, however, the piston and cylinder are made to rotate relative to each other the delay in leak-down is overcome and actual operating conditions are more closely simulated. It is, therefore, proposed to cause these two members to rotate relative to each other by means of the structure next to be described.

Referring again to Fig. i it will be observed that directly below each of the platform members 30 is a small pinion 72 which is rigidly connected to a small shaft 74 having a turntable 76 formed on the top thereof. The turntable 76 rests on a ball bearing set '73 which is supported by the platform member 36 in a manner which enables the turntable 76 to rotate freely relative to the platform 36. Provided in the top of the turntable 76 is a small insert 8%) made of some frictional material and it is upon the insert 80 that the cylinder of the tappet piston actually sits. Secured to the stationary supporting frame or pedestal 2 immediately outboard of the lower part of the lower carriage supporting structure 4, as by studs 82, is a stationary gear 8 Which is in meshing engagement with the pinions '72 so that as the carriage 16 rotates about the bearings it; the pinion 72 and the turntable 76 are caused to rotate relative to the platform member 30 and the arbor 42. Since the nosepiece 46 during the test is in frictional engagement with the upper end of the tappet piston by reason of the weight 40 and the cylinder is in frictional engagement with the insert 80 in the top of the turntable 76 relative rotation will take place between the tappet piston and the tappet cylinder about the tappet axis. With this arrangement there would appear to be some tendency on the part of the arbor 42to also rotate through the frictional forces acting between inscrt and tappet cylinder and tappet piston and nosepiece 46. Any tendency on the part of the arbor to rotate, however, is resisted by the aforementioned rollers 56. In order to prevent injury to the testing machine operator a suitable shield 55 has been provided around the pinions 72 and gear 84 which is supported on and secured to the frame 2 by brackets 59 and studs 61 and 63.

One further feature of the testing machine which should be mentioned is an improved means for ejecting the tappets once the tests have been completed. Referring to Figs. 1, 2, 3 and, especially, 5 it will be observed that supported in the member 32 is a reciprocating member 86 which is normally biased to the position in which it is shown in Fig. 1 by means of a spring 88 acting between members 32 and 86. One end of the member 86 is provided with a pin 90 extending therethrough having a roller 92 thereon. The roller rotates along a cam 94 which at the proper place in the cycle for ejecting the tappet causes the roller to move outboard and the pin 90 to move to the left as viewed in Fig. l in slots 96. Movement to the left as viewed in the figure will cause the opposite end 9% of member 86 to engage the outer wall of the tappet cylinder 26 and push it past the spring-biased rollers 39 after which a new tappet may be inserted to be tested.

I claim:

1. In an hydraulic tappet testing machine including means responsive to the rate of leak-down of tappets of the type which include a cylinder and a piston reciprocable and rotatable in said cylinder, a stationary support, a carriage rotatably mounted on said support, two members arranged on said carriage to receive the tappet therebetween, one of said members engaging the tappet piston to axially load the tappet, the mutual contact area between said loading member and said tappet piston being larger than that of point contact, said member being movable relative to said carriage, the other of said members being adapted to engage the tappet cylinder, a gear train operatively connecting said other member to said stationary support and rotatably engaging said carriage, whereby rotation of the carriage effects rotation of said last named member relative to said carriage and consequent rotation of the tappet cylinder relative to the tappet piston and driving means for rotating said carriage.

2. In a machine for testing the rate of leak-down and check valve recovery of an hydraulic tappet including cylinder and piston reciprocable and rotatable in said cylinder, a stationary supporting member, a carriage rotatably mounted on said supporting member, a driven element rotatably mounted on said carriage for receiving and rotating the tappet cylinder about its axis on said carriage, a tappet loading member having guided vertical movement relative to the carriage engaging the tappet piston to axially load the tappet, the mutual contact area between said tappet loading member and said tappet piston being larger than that of. point contact, a gear train operatively connecting said driven element to said stationary supporting member including a pinion coaxially fixed to the element and a gear coaxial with said carriage, said gear being fixed to said supporting member and in meshing engagement with said pinion, and driving means for rotating said carriage whereby rotation of the tappet cylindeirelative to the tappet piston occurs during axial loading of the tappet between said driven element and loading member.

References Cited in the file of this patent UNITED STATES PATENTS

Images