DESC:FIELD OF INVENTION

The present invention relates to a system for controlling tapping depth for producing threaded holes. In particular, the invention relates to an ultrasonic sensor system for controlling the depth of tapping in pre-drilled holes in automotive components. More particularly, the invention relates to an ultrasonic sensor system for controlling the tapping depth of threaded to be obtained in pre-drilled holes of automotive components, in a contactless manner.

BACKGROUND OF THE INVENTION

Generally, threaded holes for bolt fasteners and the like are made by tapping operation, e.g. on a Flexiarm tapping machine-1285. The tapping operation is to be done only up to a certain depth according to the requirement. An arrangement of a mechanical spring loaded rod and at least one proximity switch is used for controlling the tapping depth up to which the tapping tool should reach to obtain the desired tapping depth measured with respect to a reference position provided on such Flexiarm tapping machine. The spindle of this machine is brought in proximity of the component to be tapped for fastening a respective bolt therein. For example, in automotive cylinder heads loaded on the trunnion fixture of such Flexiarm tapping machines, the spindle of the tapping machine holding the tap is brought just at the level of the cylinder head face and the tapping operation is started thereafter.

DISADVANTAGES WITH THE PRIOR ART

It is often observed that in a conventional arrangement of the mechanical spring loaded rod and proximity switch, the spindle rotation starts even before the tap is introduced in the drilled hole to be tapped. Such idle spindle rotations are also counted by the machine as actual tapping rotations, whereby the spindle holding the tap prematurely reverses its movement, i.e. even before reaching the desired depth of tapping in the drilled hole. This results in incompletely tapped holes.
Further, such mechanical systems provided with proximity switches cannot measure the actual tapping depth inside the drilled holes to provide an accurate feedback through PLC program in such Flexiarm tapping machines. Moreover, the complexity of the problem increases further due to different heights of the components to be tapped by the same Flexiarm tapping machine. For example, four different types of cylinder heads, e.g. of 2, 3 and 4-cylinder type of cylinder heads (see Figures 4-5) are required to be tapped on the same Flexiarm tapping machine.

Since such incompletely tapped holes can only be detected during subsequent checking of the tapped hole dimensions, normally there is a need for reworking such incompletely tapped holes to make confirm the same according to the designed requirements of the components. This additional reworking operation substantially increases the cost of tapping operation and thereby of the overall production costs of the components, e.g. cylinder heads.

DESCRIPTION OF THE PRESENT INVENTION

Accordingly, the present inventors have proposed to eliminate such incompletely tapped holes and thereby obviated any need for reworking operation earlier needed due to incomplete tapping of the threaded holes on tapped components, e.g. automotive cylinder heads.

This is achieved by introducing an ultrasonic sensor system for controlling the tapping depth for threaded holes for bolts fastening, for example in automotive cylinder heads.

This tapping operation control is performed in a contactless manner, which is described in details in the following with reference to the accompanying figures.

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 system for controlling the tapping depth in a contactless manner on the automotive components.

Another object of the present invention is to provide an ultrasound-based tapping depth control system for automotive components like cylinder heads.

Still another object of the present invention is to provide a tapping depth control system, which completely eliminates rejections of tapped components because of incomplete tapping depth.

Yet further object of the present invention is to provide an ultrasonic tapping depth control system, which can perform tapping operation accurately on the cylinder heads of different heights.

A further object of the present invention is to provide an ultrasonic tapping depth control system, which is economical.

A still further object of the present invention is to provide an ultrasonic tapping depth control system is to eliminate time lost in reworking of the incompletely tapped holes.

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 an ultrasonic sensor system fitted on tapping machines having at least one spindle actuation mechanism for actuating the tap fitted on the spindle to a respective tapping depth, the system is configured for controlling tapping depths in threaded holes in automotive components in a contactless manner, the ultrasonic sensor system comprising:

• at least one reference plate;

• at least one ultrasonic sensor disposed facing a respective reference plate;

• a controller for storing the reference values of respective tap depths and for comparing the actual tap depths obtained in the pre-drilled holes to be tapped in automotive components;

wherein the controller is electronically connected to the ultrasonic sensor emitting sound pulses towards the reference plate and for capturing the echo signals reflected back from the reference plate and also for storing reference values for different automotive component having a particular height.

Typically, the controller uses the standard reference value as the value ‘0’ corresponding to the top surface of the pre-drilled component to be tapped to obtain threaded holes of corresponding size therein.

Typically, the controller actuates the spindle actuation mechanism of the tapping machine for starting the tapping operation as soon as the controller determines the tap-depth to be higher than value ‘0’.

Typically, the controller continuously measures the distances of the tapping tool from the top face and stops the tapping operation as soon as the tap depth reaches the predefined tap depth for the respective component being tapped stored in the controller.

Typically, the controller initiates retraction of the spindle carrying the tapping tool immediately after the tapping operation is stopped.

Typically, the controller completely stops the spindle rotation as soon as the tap depth value again reaches ‘0’ standard reference value or the tip of the tap retracts back to the level of top face of the component being machined.

Typically, the component to be tapped is an automotive cylinder head.

In accordance with the present invention, there is also provided a method for controlling tapping depths in threaded holes in automotive components in a contactless manner using the ultrasonic sensor, the method comprises the steps of:

- Storing the predefined tap depths for different components to be tapped using the ultrasonic sensor system;

- Initiating a sound pulse towards the reference plate fixed on the trunnion fixture of the tapping machine;

- Receiving the echo signal reflected back from the reference plate;

- Measuring the time elapsed from the initiation of the sound pulse to the receipt back of the echo signal by the ultrasonic sensor;

- Calculating the half value of the measured time;

- Obtaining the height of the ultrasonic sensor from the reference plate to be used as standard reference value as ‘0’ value of tap depth corresponding to the top surface of the component pre-drilled with a hole of corresponding size and to be tapped to a predefined depth;

- Standard reference value calculated by measuring the distances of the top face and the bottom face of the cylinder head as well as by capturing the actual position of the tap in the drilled hole to be tapped;

- Lowering the spindle carrying the tapping tool on the drilled hole to be tapped on the component and actuating the rotation of the spindle as soon as the tap depth captured by the controller rises above ‘0’ or the tap comes in contact with the front face of the component to be tapped;

- Stopping the downward movement of the spindle as soon as the controller captures the tap depth as equal to the predefined tap depth for the respective component being tapped;

- Retracting the spindle carrying the tapping tool upwards from the tapped hole;

- Stopping the spindle rotation immediately as soon as the controller captures the tap depth equals ‘0’ standard reference value again;
- Shifting the spindle carrying tapping toll to the next drilled hole in the component to be tapped;

- Continuing the method steps above for each drilled hole of the component to be tapped to the predefined depth stored in the controller.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The present invention will be briefly described with reference to the accompanying drawings, which include:

Figure 1 shows a conventional Flexiarm tapping machine-1285 provided with a trunnion fixture for loading the automotive cylinder head for conducting multiple tapping operations.

Figure 2 shows a conventional arrangement of mechanical spring loaded rod and proximity switches provided on the tapping machine shown in Figure 1.

Figure 3 shows a perspective view of the cylinder head loaded on the trunnion fixture of the tapping machine shown in Figure 1.

Figure 4 shows the various types of cylinder heads having different heights.

Figure 5 shows the various types of cylinder heads having different heights of front face for facing after loading them in the trunnion fixture of the tapping machine shown in Figure 1. It also shows the common rear face for tapping after 1800 indexing on the trunnion fixture.

Figure 6 shows the principle of the ultrasonic depth measurement system used in the ultrasonic sensor system in accordance with the present invention for controlling the tapping depth in threaded holes in a contactless manner.

Figure 7 shows a graphical representation of the comparison of rejection and reworking of the tapping operations on various automotive cylinder heads before and after implementation of the ultrasonic sensor system in accordance with the present invention.

Figure 8 shows the ultrasonic sensor system in accordance with the present invention for measuring and controlling tapping depth in a contactless manner. It includes a reference plate and an ultrasonic sensor for accurate control of the tapping depth in drilled hole of the automotive cylinder head of different heights.

Figure 9 shows the ultrasonic sensor system in accordance with the present invention for measuring and controlling tapping depth in a contactless manner.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

In the following, different embodiments of the present invention will be described in more details with reference to the accompanying drawings without limiting the scope and ambit of the present invention in any way.

Figure 1 shows a conventional Flexi-arm tapping machine 10 provided with a trunnion fixture 12 for loading the automotive cylinder head 26 for conducting multiple tapping operations. In this system, the spindle rotation may start even before actual entry of the tap in the drilled hole to be tapped. This means that the idle rotations of the spindle are also counted as actual tapping rotations, leading to incorrect measurements of the actual status of the tapping operations. Further, the mechanical system of this Flexi-arm tapping machine 10 also requires a plurality of proximity switches for sensing the different heights of the tapping surfaces on various types of cylinder heads required to be tapped in multiple drilled holes.

Figure 2 shows a conventional arrangement 14 of the mechanical spring loaded rod and a plurality of proximity switches provided on Flexiarm 24 of the tapping machine 10 shown in Figure 1. A reference plate 16 is also provided below the arrangement 14 for relatively measuring the tapping depth in the hole drilled on the face of the automotive cylinder head. The tap 20 is securely locked on the spindle under the Flexi-arm 24, which is axially moveable in a vertical direction for making the threaded hole in the cylinder head to the desired depths at different locations 18 on the cylinder head 26.

Figure 3 shows a perspective view of the cylinder head 26 loaded on the common trunnion fixture 12 of the Flexi-arm tapping machine 10 shown in Figure 1.

Figure 4 shows the various types of cylinder heads having different heights. It can be seen that a cylinder head for a 4-cylinder unit is substantially higher than a cylinder head for a 3-cylinder unit. Similarly, a cylinder head for a 3-cylinder unit is substantially higher than a cylinder head for a 2-cylinder unit. This poses a serious problem during tapping operation on the conventional Flexi-arm tapping machine-1285 shown by reference numeral 10 in Figure 1. This is because the difference in the height of cylinder heads of various types cannot be accurately measured by the conventional arrangement 14 of the mechanical spring-loaded rod and proximity switches (see Figure 1) due to limitation in the depth sensing system thereof.

Figure 5 shows the various types of cylinder heads (4-cylinder, 3-cylinder and 2-cylinder) also having different heights of front face after loading them in the trunnion fixture 12 of the Flexiarm tapping machine 10 shown in Figure 1. The common rear face for tapping after 1800 indexing on the trunnion fixture 12 is also shown. There are four steps T1, T2, T3 and T4 involved during tapping of these cylinder heads. These cylinder heads are accommodated in the common trunnion fixture 12 for tapping at different heights as shown in this figure. Initially, the height of the front face (P2) of a cylinder head out of the 4-cylinder or 3-cylinder or 2-cylinder cylinder head batch to be tapped is measured with respect to the reference plate 16.

Subsequently, the common rear-face (T1) of the cylinder head is also measured by turning or indexing the common trunnion fixture by 1800 for tapping. In this way, there are four (4) different heights (at T1, T2, T3 and T4) to be sensed and recorded with respect to the upper or entry face (P2) of the respective cylinder head, by using the ultrasonic depth sensor system, i.e. common rear face and 3 different heights of the 3 types of cylinder heads (with 4-cylinders, 3-cylinders and 2-cylinders).

Figure 6 shows the principle of the ultrasonic distance measurement. The ultrasonic sensors emit short, high-frequency sound pulses at regular intervals, which are propagated in air at the velocity of sound. When they strike an object, they are reflected back as echo signals to the same sensor, which computes the distance to the object/target based on the time elapsed between emitting the sound signals and receiving the echo signals. The above principle is used in the ultrasonic sensor system 100 (see Figure 8) for accurately measuring the tapping depth achieved in the drilled holes of the cylinder head. At step I, the ultrasonic sensor emits a sound pulse, which travels towards the target (e.g. end of tapping in the respective drilled hole on the cylinder head), the distance of which is to be measured. At step 2, the sensor senses the instant of reflection of this sound pulse from the surface of the target. In the third and final step III, the sensor receives the reflected sound pulse and records the time of reception thereof. The time required for travelling the distance existing between the sensor and the target is measured and calculated as half the time taken from the instant of emitting the sound pulse (I) to receipt of the reflected sound pulse (III) by the sensor.

Figure 7 shows a graphical representation of the comparison of rejection and reworking of the tapping operations on various automotive cylinder heads depicted in defects part per million (PPM) before and after implementation of the ultrasonic sensor system 100 (see Figure 8) in accordance with the present invention. The number of defects recorded during the first half and second half of the financial year 2013-2014 was found to be 112 and 123 respectively. The ultrasonic depth measurement system in accordance with the present invention was implemented from start of the first quarter of the financial year 2014-2015. Since implementation of this ultrasonic sensor system on the conventional Flexiarm tapping machine 1285 being used for tapping different types of the cylinder heads at the automotive parts manufacturing facilities of the applicant, the occurrence of the incorrectly tapped cylinder heads was totally eliminated and therefore the reworking costs were completely avoided. This also boosted the morale of the machine operators and substantially reduced the overall tapping time/unit as well.
Moreover, the conventional mechanical arrangement provided with proximity switches by the machine manufacturer is prone to contamination by dust and debris as well as sensitive to vibrations prevalent on a typical shop floor; whereas the ultrasonic depth sensor system in accordance with the present invention is not at all susceptible to any such harmful effects.

Figure 8 shows the ultrasonic sensor system 100 in accordance with the present invention for measuring and controlling tapping depth in a contactless manner. It includes a reference plate 105 and an ultrasonic sensor 110 for accurate control of the tapping depth in the drilled hole of automotive cylinder heads of different heights. In this improved ultrasonic depth measurement system 100, the spindle rotation starts only up to a predefined distance. Unlike the mechanical arrangement 14 for tap depth measurement provided by the manufacturer of Flexiarm tapping machine 10, there are no idle rotations of spindle, because the spindle rotations start only on actual entry of the tap into the drilled hole. The most important advantage of this improved ultrasonic sensor system 100 is that up to 100 different heights can be programmed on a single ultrasonic sensor, which facilitates the tapping operations in a large variety of cylinder heights using a single ultrasonic depth sensing system 100 fitted in the same Flexiarm tapping machine 10.

Figure 9 shows a Flexiarm tapping machine retrofitted with an ultrasonic depth measurement system 100 in accordance with the present invention for controlling the tapping depth of threaded holes in a contactless manner. The ultrasonic depth measurement system 100 includes a reference plate 105, an ultrasonic sensor 110 emitting sound pulses 112, which are reflected back as echo signals 114 towards a controller 116. The controller 116 stores the reference values of the distance measured in terms of the time elapsed for travelling the sound pulses from the sensor 110 to the reference plate. This standard reference value is used for measuring the distances of the front face and rear face of the cylinder head 120 as well as the actual position of the tap 122 in the drilled hole already made therein. The controller also stores the respective tap depth D preset for a particular type of cylinder head 120.
This preset depth D can be varied according to different models of the cylinder head to be tapped. It is also provided in the ultrasonic depth measurement sensor system 100 that the spindle 118 cannot rotate in air (position P1). The spindle 118 can start rotating only when it comes in contact with the front face of the cylinder head 120 (position P2). As soon as the preset depth D is reached by the tap 122, a signal is generated and communicated to the controller 116 to immediately stop tapping operation and the spindle 118 is retracted upwards and out of the cylinder head 120, which brings the spindle 118 in contact with air, thereby stopping its rotation. Subsequently, the spindle 118 is moved to the next drilled hole on the cylinder head 120 for to starting another tapping operation.

WORKING OF THE INVENTION

Flexiarm tapping machine 10 is retrofitted with an ultrasonic depth measurement system 100 (Figure 9) in accordance with the present invention for controlling the tapping depth in threaded holes in a contactless manner. The system 100 includes a reference plate 105, an ultrasonic sensor 110 emitting sound pulses 112, which are reflected back as echo signals 114 towards a controller 116. The controller 116 stores the reference values of the distance measured in terms of the time elapsed for travelling the sound pulses from the sensor 110 to the reference plate. This standard reference value is used for measuring the distances of the front face and rear face of the cylinder head 120 as well as the actual position of the tap 122 in the drilled hole already made therein. The controller also stores the respective tap depth D preset for a particular type of cylinder head 120. This preset depth D can be varied according to different models of the cylinder head to be tapped. It is also provided in the ultrasonic depth measurement sensor system 100 that the spindle 118 cannot rotate in air (position P1). The spindle 118 can start rotating only when it comes in contact with the front face of the cylinder head 120 (position P2, also see Figure 5). As soon as the preset depth D is reached by the tap 122, a signal is generated and communicated to the controller 116 to immediately stop tapping operation and the spindle 118 is retracted upwards and out of the cylinder head 120, which brings the spindle 118 in contact with air, thereby stopping its rotation completely and bring it again in an idle position. Subsequently, the spindle 118 is moved to the next drilled hole on the cylinder head 120 for to starting another tapping operation.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The improved ultrasonic depth measurement system configured in accordance with the present invention has the following technical and economic advantages:

• Spindle rotation starts only at predefined reference distance.

• No idle rotations of spindle.

• Up to 100 different heights can be programmed on a single ultrasonic sensor system.

• Large variety of cylinder heights can be tapped by a single ultrasonic depth sensing system.

• Ultrasonic depth sensor system is not at all susceptible to any harmful effects such as contamination by dust and debris as well as the vibrations prevalent on a typical shop floor.

• Cost of poor quality to be sustained due to the rework or rejection of cylinder heads is totally eliminated by preventing the occurrence of the incorrectly tapped cylinder heads.

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.

It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. 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.

Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Although the embodiments presented in this disclosure have been described in terms of its preferred embodiments, a person skilled in the art may 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 and assemblies, in terms of their size, shapes, orientations and interrelationships without departing from the scope and spirit of the present invention.

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.

While considerable emphasis has been placed on the specific features of the preferred embodiment described here, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiments without departing from the principles of the invention. ,CLAIMS:We claim:

1. An ultrasonic sensor system fitted on tapping machines having at least one spindle actuation mechanism for actuating the tap fitted on the spindle to a respective tapping depth, the system is configured for controlling tapping depths in threaded holes in automotive components in a contactless manner, the ultrasonic sensor system comprising:

• at least one reference plate;

• at least one ultrasonic sensor disposed facing a respective reference plate;

• a controller for storing the reference values of respective tap depths and for comparing the actual tap depths obtained in the pre-drilled holes to be tapped in an automotive component;

wherein the controller is electronically connected to the ultrasonic sensor emitting sound pulses towards the reference plate and for capturing the echo signals reflected back from the reference plate and also for storing reference values for different automotive component of a particular height.

2. Ultrasonic sensor system as claimed in claim 1, wherein the controller uses the standard reference value as the value ‘0’ corresponding to the top surface of the pre-drilled component to be tapped to obtain threaded holes of corresponding size therein.

3. Ultrasonic sensor system as claimed in claim 2, wherein the controller actuates the spindle actuation mechanism of the tapping machine for starting the tapping operation as soon as the controller determines the tap-depth to be higher than value ‘0’.

4. Ultrasonic sensor system as claimed in claim 2, wherein the controller continuously measures the distances of the tapping tool from the top face and stops the tapping operation as soon as the tap depth reaches the predefined tap depth for the respective component being tapped stored in the controller.

5. Ultrasonic sensor system as claimed in claim 2, wherein the controller initiates retraction of the spindle through reverse rotation carrying the tapping tool immediately after the tapping operation is stopped.

6. Ultrasonic sensor system as claimed in claim 2, wherein the controller completely stops the spindle rotation as soon as the tap depth value again reaches ‘0’ standard reference value or the tip of the tap retracts back to the level of top face of the component being machined.

7. Ultrasonic sensor system as claimed in anyone of the claim 1 to 6, wherein the component to be tapped is an automotive cylinder head.

8. A method for controlling tapping depths in threaded holes in automotive components in a contactless manner using the ultrasonic sensor as claimed in anyone of claims 1 to 7, the method comprises the steps of:

- Storing the predefined tap depths for different components with top surfaces at different heights to be tapped using the ultrasonic sensor system;

- Initiating a sound pulse towards the reference plate fixed on the trunnion fixture of the tapping machine;

- Receiving the echo signal reflected back from the reference plate;

- Measuring the time elapsed from the initiation of the sound pulse to the receipt back of the echo signal by the ultrasonic sensor;

- Calculating the half value of the measured time;

- Obtaining the height of the ultrasonic sensor from the reference plate to be used as standard reference value as ‘0’ value of tap depth corresponding to the top surface of the component pre-drilled with a hole of corresponding size and to be tapped to a predefined depth;

- Standard reference value calculated by measuring the distances of the top face and the bottom face of the cylinder head as well as by capturing the actual position of the tap in the drilled hole to be tapped;

- Lowering the spindle carrying the tapping tool on the drilled hole to be tapped on the component and actuating the rotation of the spindle as soon as the tap depth captured by the controller rises above ‘0’ or the tap comes in contact with the front face of the component to be tapped;

- Stopping the downward movement of the spindle as soon as the controller captures the tap depth as equal to the predefined tap depth for the respective component being tapped;

- Retracting the spindle carrying the tapping tool upwards from the tapped hole through reverse rotation;

- Stopping the spindle rotation immediately as soon as the controller captures the tap depth equals ‘0’ standard reference value again;

- Shifting the spindle carrying tapping toll to the next drilled hole in the component to be tapped;

- Continuing the method steps above for each drilled hole of the component to be tapped to the predefined depth stored in the controller.
DIGITSLLY SIGNED

Dated: this day of 02nd July, SANJAY KESHARWANI
APPLICANT’S PATENT AGENT