DESC:FIELD OF INVENTION

The present invention relates to a fixture for tappet clearance setting in internal combustion engines (ICE). In particular, the present invention relates to an electro-mechanical system for adjusting the tappet clearance in ICE. More particularly, the present invention relates to a fixture for rotating crankshafts to obtain correct tappets and cam lobe seat to felicitate proper tappet clearance setting.

BACKGROUND OF THE INVENTION

The tappet or cam follower or lifter is the part which runs on the camshaft and is vertically moved by the action of the rotating cam lobe. It is fitted low down in the engine block to drive a long thin pushrod up to the top of the engine, above the cylinder head. The rockers arranged on a rocker shaft under the rocker cover reverse the direction of the valve movement for pressing the valves downwards to open the same.

The tappet clearance is the gap provided between the valve stem and rocker arm for allowing a mechanical expansion and elongation of the valve stem and push rods on heating of the ICE. So, the tappet clearance is provided between the push rod and the adjustment screw. It is necessary to provide clearance for each of the overhead intake and exhaust valves for allowing the valve to be fully closed when the rocker arm returns to the original position.

If the tappet clearance is too small, the clearance may possibly be eliminated due to thermal expansion at high temperatures and push rods may bend. If the tappet clearance is too large, the push rod and the adjustment screw produce huge rattling noise when they contact each other.

In the current practice, the tappet clearance is ensured by providing a clearance on the other side of rocker arm, i.e. between the rocker arm pedestal and the valve stem. The tappet clearance is adjusted when rocker arm is at its original position with both inlet and exhaust valves in their closed condition. In this condition, the tappets are resting on the heel of cam lobe with the piston positioned at the compression top dead center (CTDC). The overlapping and closed condition of valves at CTDC occur during the power stroke cycle.

Since the firing order for four-cylinder engines is 1-3-4-2, the operator manually rotates the crankshaft 4 times by 180° each to perform tappet setting for individual cylinder in the same order as the firing order.

For tappet clearance setting, a feeler gauge is inserted between rocker arm pedestal and valve stem and the lock nut and adjusting screw are suitably adjusted.

PRIOR ART

WO 2015145282 A1 discloses an automated valve clearance adjustment system comprising a plurality of valve clearance adjustment units, movably attached to a spindle holder unit, through at least one rotary linear actuator. Each of valve clearance adjustment units is provided with a plurality of spindles, and each of the plurality of spindles is provisioned with a rotary actuator. Each of the plurality of spindles is coupled with at least one of nut runner and a screw driver for valve clearance adjustments. A plurality of sensors is provided in each of the plurality of valve clearance adjustment units to determine clearance. A control unit is interfaced with all the actuators and the plurality of sensors for adjusting the valve clearance.

US 6205850 B1 discloses a method for setting clearance between a tappet screw and a valve wherein the movement of the valve during opening and closing is monitored and used to calculate further linear movement of the tappet screw to provide a desired tappet clearance. In one embodiment, a predetermined imaginary zero point, which falls in a band of linear displacement during closing of the valve, is used to determine a distance the tappet screw must be further moved to provide the desired tappet clearance. In another embodiment, plural valve displacement measurements are taken, and the true zero point or valve closed position, and further movement of the tappet screw to provide the desired tappet clearance is determined based upon these plural measurements. In a further embodiment, movement of the valve head is directly monitored and used to set the tappet clearance.

US 7578276 B2 discloses an automatic tappet clearance adjusting device, comprising an adjusting unit adjusting the projected amount of a rocker arm by advancing and retreating an adjust screw to and from the tip of the rocker arm, a pressure setting part electrically controlling the pressure of an air supply source part based on the measurement signals of a primary side pressure sensor measuring the pressure of the air supply source part so that the pressure becomes a specified one, a supply pipeline allowing the air supply source part to communicate with a combustion chamber through a variable orifice, and a control mechanism part controlling the adjusting unit based on measurement signals of a secondary side pressure sensor measuring the pressure of the supply pipeline. The pressure is set to 1.5 kPa by the pressure setting part and the variable orifice.

US 6675115 B2 discloses a method for automatically setting valve clearances in internal combustion engines (also known as "tappet setting" or "valve lash setting") comprises a series of steps in which a rocker arm is set to a zero position that is recorded as a reference datum and an adjustment screw is then operated to set the rocker arm to a first reference position. The adjustment screw is then rotated through a predetermined angle so that the rocker arm is moved to a second reference position. The difference between the first and second reference positions and the predetermined angle are used to determine a coefficient relating the angular movement of the adjustment screw to linear movement of the rocker arm. The coefficient is then used to calculate the angular rotation of the adjustment screw required to set a predetermined valve clearance relative to the zero position. The initial adjustment of the rocker arm position serves to neutralize backlash in the valve drive train prior to setting the valve clearance. The method and associated apparatus may also be used to set the clearance between a rocker arm and other rocker arm actuated engine components.

DISADVANTAGES WITH THE PRIOR ART

The disadvantages with the existing tappet clearance setting system and operation are briefly discussed below:

The problem with the conventional tappet clearance setting operation is that a very high skill is required for carrying out this operation. Because, the up and down movements of the inlet and exhaust rocker arms need acknowledgement of the valve overlapping condition.

The tappet clearance setting is done depending on the operator’s experience and by feeling the gap with the help of the feeler gauge. In doing this, usually three related errors may occur:

• Inaccurate Cam lobe position.

• Inaccurate judgment of valve overlaps condition.

• Inaccurate Clearance Setting.

OBJECTS OF THE INVENTION

Some of the objects of the present invention - satisfied by at least one embodiment of the present invention - are as follows:

An object of the present invention is to provide a tappet clearance setting mechanism for Internal Combustion engines (ICEs).

Another object of the present invention is to provide a tappet clearance setting mechanism for Internal Combustion engine with the overhead valves operated by rocker arms.

Still another object of the present invention is to eliminate the operational failures of the valve train occurring due to improperly adjusted tappets on the cam lobe.

Yet another object of the present invention is to reduce the manual intervention in tappet setting operation for relieving the operator fatigue by minimizing manual setting.

A further object of the present invention is to reduce the manual intervention during the tappet setting operation and thereby reducing any chances of errors due to the operator’s fatigue inherent in the existing methods.

These and other objects and advantages of the present invention will become more apparent from the following description, when read with the accompanying figures of drawing, which are however not intended to limit the scope of the present invention in any way.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a semi-automatic tappet setting fixture for rotating the crankshaft of internal combustion engines (ICEs) to facilitate the correct setting of the tappet clearance for obtaining an optimal rocker arm positioning, the assembly comprising:

• a metallic base plate for mounting accessories thereon, the base plate having an extended middle plate and a metallic rib plate, a handle fitted on the base plate,

• a respective pneumatic cylinder mounted on either side of the base plate,

• the pneumatic cylinders forming a cam-based clamp for clamping the base plate with the crankcase,

• a servo motor mounted on a metallic square-section bracket attached to the base plate, a servo motor shaft fitted to a key-slotted transmission shaft for transmitting rotary motion of the servo motor,

• a cylindrical cover loading the bearing journal of the service motor shaft therein by means of brass bush supports,

• a plurality of hardened dolly press-fitted inside bushes for locating the crankcase on the fixture,

• a pinion gear having a square slot and bolted to the rear end of the transmission shaft for rotating a flywheel, and

wherein the fixture is mounted on a suspended spring balancer to be accurately aligned by manually engaging the dolly inside the crankshaft locating holes and by meshing the flywheel teeth with the pinion gear for actuating the cylinders for clamping the fixture with the crankcase to clamp the engine block between the cylinders for supporting the flywheel side flange of the crankcase and for rotating the flywheel.

Typically, a plurality of hardened dolly is press-fitted inside bushes for locating the crankcase on the fixture,

Typically, the plurality of hardened locating pins or dolly is manually engaged inside the locating hole of the crankshaft.

Typically, each dolly is fitted with Teflon on its rear for providing a cushioning effect during clamping of the base plate.

Typically, a tappet dancing tool is adjusted over one of the cylinders of the engine block.

Typically, a tappet dancing tool is clamped by screws adjusted over one of the cylinders of the engine block.

Typically, a pair of limit switches are positioned above a respective pair of rocker arms.

Typically, the tappet dancing tool is clamped by special screws.

Typically, a pair of limit switches of the tappet dancing tool is used for measuring an accurate position of the rocker arm at the compression top dead center (CTDC) position of the piston.

Typically, a control switch is pressed after fixture is properly clamped and tappet dancing tool is accurately positioned above the rocker arms of the cylinder.

In accordance with the present invention, there is also provided a method for setting the tappet clearance by using the semi-automatic tappet setting fixture as claimed in anyone of the claims 1 to 10, wherein the method comprises the steps of:

a. adjusting the fixture on the suspended spring balancer by the handle for meshing the pinion gear with the flywheel teeth,

b. positioning the tappet dancing tool over the cylinders by means of limit switches over two rocker arms, i.e. the inlet and exhaust respectively,

c. pressing the control switch for facilitating the servo motor to rotate the crankshaft until limit switches communicate to the PLC about achieving an optimal rocker arm positioning the respective cylinder,

d. removing the tappet dancing tool from top of the crankcase,

e. performing the tappet clearance setting for cylinder no. 1 with the servo motor rotating the crankshaft to obtain correct tappet positioning on the cam lobe for eliminating any manual rotation of the same, and

f. repeating the same operation of steps (a) to (e) for all four cylinders to simplify the tappet setting sequence in order of the cylinder numbers 1-2-3-4 against the conventional tappet setting sequence similar to the firing order of the cylinder numbers 1-3-4-2.

In an embodiment of the present invention, the tappet clearance setting process sequence is split in the following two steps:
(A) Step 1 comprising sub-steps of:

• Aligning the fixture for perfect meshing of flywheel teeth with pinion gear and positioning of locating pins on crankcase dowel holes;

• Actuating the pneumatic cylinder for clamping the crankcase;

• Positioning the tappet dancing tool above rocker arm of cylinder 4;
• Pressing the control switch and angular positioning of the crankshaft for obtaining the optimal rocker arm positioning to be saved in the PLC; and

(B) Step 2 comprising sub-steps of:

• Obtaining the tappet clearance for each cylinder while rotating the crankshaft by the servo motor according to the data prerecorded in the PLC for respective cylinders;

• Stopping the servo motor immediately on obtaining the optimal positioning of rocker arm for the respective cylinder by the servo motor;

• Insertion of the feeler gauge by the Operator between the rocker arm pedestal and the valve stem and tightening the lock nuts over the adjustment screw for each of the valve; and thereby eliminating the manual rotation of crankshaft.

DESCRIPTION OF THE INVENTION

A servo motor 4 drives a pinion gear which is meshed with the flywheel and a limit switch (i.e. the tappet dancing tool) is provided. Tappet dancing tool is used to gauge the exact position of rocker arms for a particular cylinder and the information is relayed to the motor to rotate the crankshaft until the compression top dead center (CTDC) of that cylinder is achieved. Thus, the initial position for tappet clearance settings of cylinder 1 is identified by a sensor, wherein the tappets are seated at the heal of cam lobes. The crank position of this cylinder is taken as datum. The motor rotates the crankshaft consecutively for each cylinder to obtain CTDC of the piston thereof. The information regarding the degrees of rotation of the crankshaft with respect to the first cylinder, for obtaining the CTDC of each cylinder has been stored in the PLC in advance.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings.

Figure 1a shows the perspective view of the fixture assembly configured in accordance with the present invention, for rotating the crankshaft to felicitate the correct setting of the tappet clearance.

Figure 1b shows another perspective view of the fixture assembly of Fig. 1a, as seen by turning the same by 900 in the clockwise direction.

Figure 1c shows a perspective view of the fixture assembly of Fig. 1a as seen from rear.

Figure 1d shows a perspective view of the fixture assembly of Fig. 1c by turning the same by 900 in the clockwise direction.

Figure 2a shows a front view of the fixture assembly of Fig.1b.

Figure 2b shows a side view of the fixture assembly of Fig.1b.

Figure 2c shows a top view of the fixture assembly of Fig.1b.

Figure 3a shows a front view of fixture assembly of Fig.1a deployed on a semi-assembled IC engine.

Figure 3b shows a perspective view from above of the fixture assembly of Fig.1d deployed on a semi-assembled IC engine.

Figure 3c shows a side view of the fixture assembly of Fig.3b deployed on a semi-assembled IC engine.

Figure 3d shows a top view of the fixture assembly of Fig.2c deployed on a semi-assembled IC engine.

Figure 4 is a line-diagram of the manner of internal communication of the system.

Figure 5 is a flow chart of the process for setting a tappet clearance by means of the tappet clearance setting fixture configured in accordance with the first embodiment of the present invention.

Figure 6 is a diagram indicating the correct position of the tappet with respect to the cam lobe for setting the tappet clearance.

Figure 7a is a diagram indicating the correct position of tappet with respect to cam lobe for setting the tappet clearance.

Figure 7b is a diagram indicating another incorrect position of tappet with respect to cam lobe for setting the tappet clearance.

DETALED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1a shows the perspective view of the fixture assembly 60 configured in accordance with the present invention, for rotating the crankshaft to felicitate the correct setting of the tappet clearance. The fixture 60 ensures an accurate alignment and meshing of the flywheel teeth (not shown) with the pinion gear through locating pins. Accordingly, the pinion gear 20 is aligned before pneumatic clamping thereof and subsequently, the fixture 60 is clamped with the help of a compact pneumatic cylinder 1 attached thereto. The pneumatic compact cylinders 1, 18 are used for applying force, when the flywheel teeth and pinion gear 20 are aligned. The pneumatic cylinders 1, 18 are mounted on the mild steel plate 2 (having a respective extended middle plate 3 either side thereof as support) and metallic rib plate 8. A corresponding hardened dolly 10,11,12,13 is fitted by press-fitting inside the bushes 14,15,16,17 respectively. For a proper self-alignment of the fixture 60, each hardened dolly 10,11,12,13 is manually engaged inside the locating hole of the crankshaft. A servo motor 4 is mounted on the rear support bracket 5 by means of bolts. The rear support bracket 5 is attached to the mild steel plate 2. The bearing journal 19 of the servo motor shaft 6 is loaded inside the cylindrical cover 9 by means of the brass bush supports (not shown) for providing alignment with the servo motor shaft 6. A transmission shaft 7 is fixed to the slotted servo motor shaft 6 by means of a key fitted therein. The pinion gear 20 with a square slot is fixed to the transmission shaft 7 by tightening an Allen bolt thereon.

Figure 1b shows another perspective view of the fixture assembly 60 of Figure 1a, as seen by turning the same by 900 in the clockwise direction.

Figure 1c shows a perspective view of the fixture assembly 60 of Figure 1a as seen from rear.

Figure 1d shows a perspective view of the fixture assembly 60 of Figure 1c by turning the same by 900 in the clockwise direction.

Figure 2a shows a front view of the fixture assembly 60 of Figure1b.

Figure 2b shows a side view of the fixture assembly 60 of Figure 1b.

Figure 2c shows a top view of the fixture assembly 30 of Figure 1b.

Figure 3a shows a front view of fixture assembly 60 of Figure 1a deployed on a semi-assembled IC engine for rotating the crankshaft and the tappet dancing tool. In step 1 of the tappet setting process, in which the optimal positioning of the rocker arms is determined for cylinder 4 and the crankshaft angular positioning is stored in PLC 35. Here, the fixture 60 is in its home position for clamping the semi assembled engine block 21 and for rotating the flywheel. The fixture 60 having compact pneumatic cylinder 1 is mounted on a mild steel plate 2 and a servo motor 4 is mounted on the support bracket 5 (see Fig.1a). A flywheel side dowel hole of the cylinder (not shown here) is properly located between the locating pins 10 and 11. The semi assembled engine block 21 is clamped between the pneumatic clamps 1 and 18 for providing support to the flywheel side flange of the crankcase (not shown here). Tappet dancing tool 22 is adjusted over cylinder no. 4 of the engine block 21. Two limit switches 23 and 24 are positioned above the rocker arms 26 and 25. The tappet dancing tool is clamped by special screws 27 and 28. The control switch 32 is pressed after the fixture 60 is properly clamped and tappet dancing tool 22 is properly positioned above the rocker arms 25, 26 of cylinder no. 4. The servo motor 4 rotates the flywheel, whereby the crankshaft also rotates; the limit switches 23 and 24 relay the information to PLC 35 to stop the servo motor 4 when the optimal position for the rocker arms 25, 26 is achieved.

Figure 3b shows a perspective view from above of the fixture assembly of Fig.2a deployed on a semi-assembled IC engine.

Figure 3c shows a side view of the fixture assembly of Fig.2a deployed on a semi-assembled IC engine.

Figure 3d shows a top view of the fixture assembly of Fig.2a deployed on a semi-assembled IC engine.

Figure 4 is a line-diagram of the manner of internal communication of the system, which occurs between PLC 35 and the control board 31 based on the information exchange of PLC 35 with the servo motor 29, limit switch 30, control switch 32 and actuator 33.

Figure 5 is a flow chart of the process for setting the tappet clearance by means of the tappet clearance setting fixture 60 configured in accordance with the first embodiment of the present invention.

The process includes the following steps:

110 - Detecting the IC Engine, looking up for the engine information,

120 - Loading PLC program, moving the fixture 60 and actuating limit switches 21, 22,

130 - Engaging the locating pins and pneumatic clamps of the fixture 60 with the cylinder block of the IC engine,

140 - Placing the limit switches on the rocker arm pedestal of the 4th cylinder and pressing the control switch 32,

150 - Removing the limit switches 21, 22 after reading is recorded,

160 - Pressing the control switch 32 to accurately adjust the tappet clearance for 1, 2, 3, 4 cylinders respectively, and

170 - Transferring the IC engine after accurate tappet clearance setting.

Figure 6 is a diagram indicating the correct position of the tappet 46 with respect to the cam lobe 48 for setting the tappet clearance. It shows wrench 42, push rod 44, tappet 46, cam lobe 48, adjustment screw 50, lock nut 52, rocker arm 54, feeler gauge 56 and valve 58.

Figure 7a is a diagram indicating the correct position of tappet 46 with respect to cam lobe 48 for setting the tappet clearance.

Figure 7b is a diagram indicating another incorrect position of tappet 46 with respect to cam lobe 48 for setting the tappet clearance.

In accordance with the present invention, there is provided a fixture 60 for meshing pinion gear with flywheel for rotating the crankshaft of automotive internal combustion engines, the fixture comprises:

• a servo motor 4 of 10 HP;

• a metallic square-section bracket 5 for supporting the servo motor 4;

• a metallic fixture base plate 2 for mounting the accessories;

• a key-slotted shaft 6 for transmitting rotary motion of the servo motor 4;

• a pinion gear 20 bolted to the rear of the shaft for rotating a flywheel;

• locating pins or dolly 10, 11 for locating the crankcase on the fixture 60;

• locating pins or dolly 12, 13 with Teflon fitted on its rear for cushioning effect while clamping the base plate 2;

• pneumatic cylinders 1, 18 mounted on either side of the base plate 2;

• a cam-based clamp operated by the pneumatic cylinders 1, 18 for clamping the base plate 2 with the crankcase;

• a handle fitted on the base plate 2; and

• locating pins or dolly 10, 11 for proper alignment of the base plate 2;

wherein the fixture is mounted on a pneumatic balancer and the fixture is adjusted on the rear side of the crankcase by means of the handle provided thereon and the fixture is accurately self-aligned by manually engaging the locating pins 10, 11 inside the locating holes of the crankcase.

Servo motor 4 is mounted on a bracket 5 and has a pinion gear 20 at the end of the shaft 6 thereof. The whole assembly is joined to the base plate 2 having other clamping mechanism also attached thereto. Then, the pneumatic cylinders 1, 18 are actuated in a forward movement to press the clamp on the crankcase. The pneumatically operated clamps are used for clamping the fixture to the engine block 21. It is ensured that the pinion gear 20 properly meshes with the flywheel teeth.

The tappet dancing tool 22 is brought down by pressing the pneumatic limit switch 23, 24. It is positioned on the inlet and exhaust valves of the first cylinder and the operation cycle is initiated.

A method for setting tappet clearance by means of a fixture for rotating the crankshaft for automotive IC engines, the method comprising the steps of:
a. adjusting the fixture on the suspended spring balancer by the handle provided on the crankshaft for adjusting a self-alignment of the fixture;

b. manually engaging locating pins inside the locating holes of the crankcase;

c. aligning the pinion gear teeth with the flywheel teeth before pneumatically clamping the crankcase with the fixture;

d. loading the tappet dancing tool over the cylinder head and locating it over fourth cylinder and tightening the bolts, the bushes provide support to avoid any metal to metal contact of the locating parts and cylinder head;

e. pressing the servo switch and relay button for crankshaft positional assertion for valve overlap and CTDC condition for fourth cylinder over input received from tappet dancing tool; untightening and release of the tappet dancing tool over zero balancer;

f. pressing the bearing by means of the hydraulic cylinder attached to the fixture; the pressing step comprises the sub-steps of:

g. Applying the required force by means of the hydraulic compact cylinder after aligning the crankshaft and pilot bearing inside the dolly;

h. Guiding the bearing concentric with respect to the center of the crankshaft bearing counter for pressing the crankshaft bearing in place.

TAPPET CLEARANCE SETTING PROCESS:

In accordance with the present invention, the tappet clearance setting process sequence split in two steps is shown in Fig 6, which is as follows:

Step 1

• Fixture is aligned for perfect meshing of flywheel teeth with pinion gear 20 and positioning of locating pins 23, 24 on crankcase dowel holes.

• Once the fixture is aligned, the pneumatic cylinder 1 and 18 is actuated to clamp the crankcase 21.

• Tappet dancing tool 22 is positioned above the rocker arms 25, 26 of cylinder 4.

• Control switch is pressed and crankshaft angular positioning over which the optimal rocker arm 25, 26 positioning achieved is saved to PLC 35.

Step 2

• Tappet clearance is performed for each cylinder where crankshaft is rotated by the servo motor 4 in accordance with the prerecorded data of PLC 35 for respective cylinders.

• Once the optimal positioning of rocker arms 25, 26 for that cylinder is achieved by the servo motor 4, it stops immediately.

• Operator then inserts feeler gauge 56 between the pedestal of the rocker arm 25, 26 and valve stem of the valve 58 and tightens lock nuts over adjustment screw 50 for each of the valve 58.

• Thus, the manual rotation of the crankshaft is eliminated.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The electro-mechanical system for tappet clearance setting configured in accordance with the present invention has the following advantages:

• Saves substantial reworking costs.

• Provides a rotation mechanism for crankshaft thus preventing operator fatigue and creating ergonomically green stage.

• Avoids/eliminates any incorrect tappet positioning over cam lobe.

• Light Weight fixture supported over zero spring balancer for user friendly operation.
• Modular design for multimodal application.

• Compact and robust design.

• Deskilling of tappet setting stage.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

The description provided herein is purely by way of example and illustration. The various features and advantageous details are explained with reference to this non-limiting embodiment in the above description in accordance with the present invention. The descriptions of well-known components and manufacturing and processing techniques are consciously omitted in this specification, so as not to unnecessarily obscure the specification.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, the skilled person will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments described herein and can easily make innumerable changes, variations, modifications, alterations and/or integrations in terms of materials and method used to configure, manufacture and assemble various constituents, components, subassemblies, assemblies and in terms of the size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

It is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.
The numerical values given of various physical parameters, dimensions and quantities are only approximate values and it is envisaged that the values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the disclosure unless there is a statement in the specification to the contrary.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, shall be understood to implies including a described element, integer or method step, or group of elements, integers or method steps, however, does not imply excluding any other element, integer or step, or group of elements, integers or method steps.

The use of the expression “a”, “at least” or “at least one” shall imply using one or more elements or ingredients or quantities, as used in the embodiment of the disclosure in order to achieve one or more of the intended objects or results of the present invention. ,CLAIMS:We claim:

1. A semi-automatic tappet setting fixture 60 for rotating the crankshaft of internal combustion engines (ICEs) to facilitate the correct setting of the tappet clearance for obtaining an optimal rocker arm positioning, said assembly 60 comprising:

• a metallic base plate 2 for mounting accessories thereon, said base plate 2 having an extended middle plate 3 and a metallic rib plate 8, a handle fitted on said base plate 2,

• a respective pneumatic cylinder 1, 18 mounted on either side of said base plate 2,

• said pneumatic cylinders 1, 18 forming a cam-based clamp for clamping said base plate 2 with the crankcase,

• a servo motor 4 mounted on a metallic square-section bracket 5 attached to said base plate 2, a servo motor shaft 6 fitted to a key-slotted transmission shaft 7 for transmitting rotary motion of said servo motor 4,

• a cylindrical cover 9 loading the bearing journal 19 of the service motor shaft 6 therein by means of brass bush supports,

• a plurality of hardened dolly 10, 11, 13, 14 press-fitted inside bushes 14, 15, 16, 17 for locating the crankcase on said fixture 60,

• a pinion gear 20 having a square slot and bolted to the rear end of said transmission shaft 7 for rotating a flywheel, and

wherein said fixture 60 is mounted on a suspended spring balancer to be accurately aligned by manually engaging said dolly 10, 11, 13, 14 inside the crankshaft locating holes and by meshing the flywheel teeth with said pinion gear 20 for actuating said cylinders 1,18 for clamping the fixture 60 with the crankcase to clamp said engine block 21 between said cylinders 1, 18 for supporting the flywheel side flange of the crankcase and for rotating the flywheel.
2. Fixture as claimed in claim 1, wherein a plurality of hardened dolly 10, 11, 13, 14 are press-fitted inside bushes 14, 15, 16, 17 for locating the crankcase on said fixture 60,

3. Fixture as claimed in claim 2, wherein said plurality of hardened locating pins or dolly 10, 11, 13, 14 is manually engaged inside the locating hole of the crankshaft.

4. Fixture as claimed in claim 3, wherein each dolly 10, 11, 13, 14 is fitted with Teflon on its rear for providing a cushioning effect during clamping of the base plate 2.

5. Fixture as claimed in claim 1, wherein a tappet dancing tool is adjusted over one of the cylinders of the engine block 21.

6. Fixture as claimed in claim 1, wherein a tappet dancing tool 22 is clamped by screws adjusted over one of the cylinders of the engine block 21.

7. Fixture assembly as claimed in claim 1, wherein a pair of limit switches 23, 24 are positioned above a respective pair of rocker arms 25, 26.

8. Fixture as claimed in claim 1, wherein said tappet dancing tool 22 is clamped by special screws 27, 28.

9. Fixture as claimed in claim 1, wherein a pair of limit switches 23, 24 of the tappet dancing tool 22 is used for measuring an accurate position of the rocker arm at the compression top dead center (CTDC) position of the piston.

10. Fixture as claimed in claim 3, wherein a control switch 32 is pressed after fixture 60 is properly clamped and tappet dancing tool 22 is accurately positioned above the rocker arms 25, 26 of said cylinder.

11. A method for setting the tappet clearance by using the semi-automatic tappet setting fixture as claimed in anyone of the claims 1 to 10, wherein the method comprises the steps of:

(a) adjusting the fixture on the suspended spring balancer by the handle for meshing the pinion gear with the flywheel teeth;

(b) positioning the tappet dancing tool over the cylinders by means of limit switches over two rocker arms, i.e. the inlet and exhaust respectively;

(c) pressing the control switch for facilitating the servo motor to rotate the crankshaft until limit switches communicate to the PLC about achieving an optimal rocker arm positioning the respective cylinder;

(d) removing the tappet dancing tool from top of the crankcase;

(e) performing the tappet clearance setting for cylinder no. 1 with the servo motor rotating the crankshaft to obtain correct tappet positioning on the cam lobe for eliminating any manual rotation of the same; and

(f) repeating the same operation of steps (a) to (e) for all four cylinders to simplify the tappet setting sequence in order of the cylinder numbers 1-2-3-4 against the conventional tappet setting sequence similar to the firing order of the cylinder numbers 1-3-4-2.

12. Method as claimed in claim 11, wherein the tappet clearance setting process sequence is split in the following two steps:

(A) Step 1 comprising sub-steps of:

• Aligning the fixture for perfect meshing of flywheel teeth with pinion gear and positioning of locating pins on crankcase dowel holes;

• Actuating the pneumatic cylinder for clamping the crankcase;

• Positioning the tappet dancing tool above rocker arm of cylinder 4;
• Pressing the control switch and angular positioning of the crankshaft for obtaining the optimal rocker arm positioning to be saved in the PLC; and

(B) Step 2 comprising sub-steps of:

• Obtaining the tappet clearance for each cylinder while rotating the crankshaft by the servo motor according to the data prerecorded in the PLC for respective cylinders;

• Stopping the servo motor immediately on obtaining the optimal positioning of rocker arm for the respective cylinder by the servo motor;

• Insertion of the feeler gauge by the Operator between the rocker arm pedestal and the valve stem and tightening the lock nuts over the adjustment screw for each of the valve; and thereby eliminating the manual rotation of crankshaft.

Dated: this 30th day of May 2017. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT