DESC:FIELD OF INVENTION

The present invention relates to a device for the manufacture of gears. In particular, the present invention relates to the manufacture of better quality components, like crown wheels. More particularly, the present invention relates to manufacture of high-quality press-quenched crown wheels. The present invention also relates to a method for manufacturing high-quality crown wheels by press-quenching process.

BACKGROUND OF THE INVENTION

By definition, Crown wheels are thin disc-shaped components forming a part of the driveline of any automobile. Conventionally, thin-walled structures are distorted by rapid quenching thereof. The thermal shocks caused due to this rapid quenching leads to uncontrolled distortion in such quenched thin-walled structures, if not checked appropriately.

Press quenching is a method of controlled quenching of these thin-walled crown wheels, which eliminates any distortion thereof. This is performed by holding down the component with great force while it is being quenched. The press-quenching process is a challenging activity, requiring utmost control on the parameters controlling the quenching process and thereby which affects the gear quality parameters of the crown wheels.

The quality parameters being monitored here are flatness of the back face and ovalness of the principal internal diameter. Conventionally, these parameters are controlled by press-quenching crown wheels under pressure dies provided with expanders or taper mandrels, ground base plates, pressure rings kept in a quenching medium like oil, polymer or water.

The solution in accordance with the present invention aims at improving abovementioned two parameters, i.e. the ovalness and flatness, in order to improve the overall gear quality.

Quenching is the process of controlled cooling of components (such as crown wheels) to induce a favorable phase transformation. Since crown wheels are highly susceptible to distortion by rapid cooling, these are quenched in press-quenches. Crown wheels are thin disc-walled structures, which are easily distorted on undergoing thermal shocks.

Therefore, in order to maintain their original form, Crown wheels are required to be subjected to controlled press-quenching, i.e. by holding down crown wheels while these undergo any thermal shock.

CONVENTIONAL PRESS QUENCHING METHODS AND DISADVANTAGES

The conventional press quenching set-up is based on three individual dies for pressing down the component, e.g. crown wheels to be quenched. The first two dies are configured as the outer and inner pressure rings to hold down on the component from the top. The third die is an expander radially opening up due to a central taper. As the central ram comes down and applies a force on the crown wheel, this force balances the collapsing force of the internal diameter of the crown wheel. All this proceeds in a continuously flowing quenching medium, such as oil, polymer or water to perform press quenching of the crown wheel.

Press quenched components have their buy-off on two main quality parameters, ovalness of the internal diameter and back-face flatness. Internal diameters are measured by conventional variable bore dial-gauges, whereas the back-face flatness is measured by feeler gauges.

US2914311A discloses the entire quenching process and the expandable segmented dies meant for maintaining roundness on the internal bore of crown wheels are not in one-piece, but have multiple independent segmented petals. These expanding members (petals) comprise mutually independent segments. Thus, these petals do not maintain their form but only adopt the form superimposed by the ram. Moreover, the outer cylindrical contact area grips the bore at specific points rather than the entire internal bore.
Further, the document discloses as to how the segmented dies grip the internal bore when expanded by the rams, but this contact that happens is theoretically a line contact and the number of line contacts are equal to the number of segments.

Therefore, the contact pattern breaks, wherever these independent segments end in their expanded condition. In addition, the document mentions expandable segmented independent dies actuated by a single frusto-conical ram, which conventionally offers very little control on the outer form of the expandable segmented independent dies, since it in itself is not generated on the segments. This is because by design conceptualization, it cannot maintain/ generate/superimpose its form on the internal bore.

US2914311A discloses the entire quenching process for crown wheels with their specific equipment that looks at the entire process holistically. The segmented dies in this patent being coarse in nature and being actuated by the frusto-conical ram offering little control on the internal bore of the component being quenched. Here, changes in applied pressure may not give consistent control on the cylindrical shape or roundness of the internal bore.

US8034285B2 discloses quenching equipment and dies predominantly meant for bearing races. It also discloses concept of quenching which locates and clamps the part on two conical surfaces that only generates a line contact on the top and bottom sides. It does not involve any apparatus to maintain cylindrical shape or roundness by any expanding mechanism.

United States Patent US 8034285 B2 discloses the entire quenching process for bearing races and rings with their specific equipment that looks at the entire process holistically. The concept disclosed in this patent has no possibility of controlling the pressure being applied on the internal bore in the radial direction, since the component just rests on the edges of the inner bores which may lead to concavity or convexity on the internal bore of the component thus not being able to achieve the parameters for maintaining cylindrical shape or roundness.

DISADVANTAGES WITH THE PRIOR ART

However, the disadvantages of the conventional press-quenched components, such as steel rings or crown gears are briefly discussed below:

• Low gear quality because of non-uniform gaps present between gear teeth, which are critical while gears are intermeshing.

• Due to exposure to thermal shocks, there is distortion of gears and the tooth spacing between adjacent teeth varies, so poor-quality gears are manufactured.

• No control in gear teeth spacing, which leads to the critical ovalness of the internal diameter and non-flat back-face of the gear.

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 device for distortion-free press-quenching of the components like a crown wheel.

Another object of the present invention is to provide a device for manufacturing high-quality press-quenched components, e.g. crown wheels.

Still another object of the present invention is to provide a device, which ensures ovalness of the internal diameter and back-face flatness of crown wheels.

A further object of the present invention is to provide a device, which maintains a constant gap between gear teeth of crown wheels.

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.
STATEMENT OF THE INVENTION

In accordance with the present invention, there is provided a device for manufacturing high-quality press-quenched components, wherein the device comprises:

• a supporting surface at the bottom face thereof;

• a tool holder disposed at the top face thereof and to function as a cap for supporting the component to be press-quenched;

• a collet configured with predefined profiles for imparting the desired rigidity and stiffness of the device;

• one taper cone each disposed above and below the collet; and

• a plurality of guide studs and a respective fastener therefor;

wherein the supporting surface, tool holder, collet and taper cones each are configured with a respective concentric internal bore for placing a central ram to apply a force on the component to be quenched, and the outer periphery of the collet is configured to impart a maximum surface contact of the collet with the inner diameter of the component mounted above the collet.

Typically, the supporting surface has the largest outer diameter for fully supporting the components disposed thereupon and the internal diameter equal to the internal diameter of the collet and taper cones.

Typically, the tool holder has an internal diameter less than the internal diameters of the collet and taper cones and a countersunk step on the upper face of the tool holder for holding the component to be press-quenched.

Typically, the taper cones comprise a respective taper outer surface contacting the internal taper surfaces of the collet disposed between the taper cones.

Typically, the collet is configured as a single-piece expanding type collet for achieving the maximum surface contact.
Typically, the profiles configured on collet are formed as a plurality of radially disposed slits and/or grooves equally spaced on the outer periphery of the collet to facilitate a uniform radial expansion or contraction of the outer periphery of the collet through the wedging action of the taper cones disposed above and below the collet for maintaining the true circular form thereof in order to achieve a maximum surface contact and to enable a uniform flow of the quenching medium, preferably oil flowing through the plurality of slits and/or grooves.

Typically, the outer diameter of collet is made dominant on the internal diameter of the component to be quenched for accurately controlling the form thereof by controlling the resultant ramming force on collet.

Typically, the collet expands and contracts and withstands the forces applied by the central ram and maintains the dominating outer diameter thereof by the collapsing the internal diameter of the component to be quenched.

Typically, the device comprises three guide studs inserted from the supporting surface side and a respective fastener is tightened thereon after placing the component to be press-quenched and held thereon, the guide studs being inserted through holes successively made at 1200 through the faces of the device.

Typically, the thickness of the collet at the dominating outer diameter thereof is configured more than the internal diameter of the component to be quenched to be supported thereon and inner annular diameter of the collet is more than the outer diameter of the studs, the thickness of the inner annular diameter of the collet being less than outer diameter of the studs.

Typically, the edges of the outer and inner diameter of the supporting surface 1, tool holder 2, collet 3 and taper cones 4 as well as the and bores of the holes provided therein are suitably chamfered.

In accordance with the present invention, there is also provided a method manufacturing high-quality press-quenched components by means of the aforesaid device, wherein the method involves the steps of:
(a) Assembling the crown wheel to be press-quenched by placing it on the supporting surface of the device and by tightening the crown wheel using studs and fasteners;

(b) Applying a downward force on the countersunk portion of the tool holder 2 by means of a central ram to guide the same on guide studs 5;

(a) Transmitting the same downward force to move the upper taper cone 4 downward;

(b) Wedging the tool holder 2 supported on the upper taper cone 4 above the collet 3;

(c) Expanding the upper part of the collet 3 uniformly by exerting a downward force by pressing the upper taper cone 4 in order to wedge on the taper surface of the lower taper cone 4 disposed under the collet 3;

(d) Uniformly opening the collet 3 and keeping it firmly on the upper and bottom faces thereof and gripping the internal diameter of the component to be press-quenched, preferably a crown wheel; and

(e) Uniformly expanding or contracting the outer periphery of the collet 3 for maintaining its true circular form on applying an external force thereon form by achieving the maximum surface contact with the component to be press-quenched, preferably a crown wheel.

DESCRIPTION OF THE INVENTION

Accordingly, the present invention is related to the press-quenched gears and more particularly to the development of a quenching method to give a better gear quality, e.g. press quenched crown wheels.

The present invention very rigidly controls the shape of crown wheel inner diameter having a direct impact on its quality.

The idea underlying the present invention make a device which does not allow the collapse of internal diameter in an uncontrolled manner and which avoids development of undesired stresses on removing the crown wheel therefrom after press-quenching operation.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

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

Figure 1 shows an isometric view of a crown wheel assembled on the device configured in accordance with the present invention for performing distortion-free press-quenching of the crown wheel.

Figure 2 shows the device configured in accordance with the present invention for performing distortion-free press-quenching of the crown wheel.

Figure 3 shows the isometric sectioned view of the crown wheel assembled on the device marked with different components thereof.

Figure 4 shows an isometric sectioned view of the device of Figure 1 marked with different components thereof.

Figure 5 shows the exploded view of the crown wheel to be assembled on the device marked with different components thereof for performing distortion-free press-quenching thereof.

Figure 6 shows the top view of the crown wheel assembled on the device of Figure 1 configured in accordance with the present invention and marked with a section line A-A’ for showing further thereof in Figure 7.

Figure 7 shows the sectional front view cut-out across section A-A’ of the device assembled with the crown wheel as shown in Figure 6. It is to be noted that the concept of a dominant collet expander as shown in Figures 1 to 6 is used here.

DETALED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Figure 1 shows an isometric view of a crown wheel 10 assembled on the device 20 configured in accordance with the present invention for performing distortion-free press-quenching of the crown wheel.

Figure 2 shows the device 20 configured in accordance with the present invention for performing distortion-free press-quenching of crown wheel 10. The device 20 is marked with different components including a supporting surface 1 functioning as ground base for accommodating three counter bore guide studs 5 thereon. The tool holder 2 functions as a cap for holding the collet 3 and upper and lower taper cones 4 in place. The tool holder 2 also acts as top guide for three guide studs 5. Three nuts 6 are provided for assembling and clamping or locking the entire tool assembly 20 in place by tightening over the guide nuts 5.

Figure 3 shows an isometric sectioned view of the crown wheel 10 assembled on the device 20 of Figure 2 by means of three nuts 6 tightened on a respective guide stud 5 passed through the tool holder 2.

Figure 4 shows the isometric sectioned view of the device 20 of Figure 1, marked with different components thereof.

Figure 5 shows the exploded view of the crown wheel 10 to be assembled on the device 10 and marked with different components 1 to 6 thereof for performing a distortion-free press-quenching thereof.

Figure 6 shows the top view of the crown wheel 10 assembled on the device 20 configured in accordance with the present invention. The section plane A-A’ is also marked for further description with reference to Figure 7.

Figure 7 shows the sectional front view cut-out across section A-A’ of the device assembled with the crown wheel as shown in Figure 6. It is to be noted that the concept of dominant collet expander used here as shown in Figs. 1-6.

WORKING OF THE INVENTION

The working of the device configured in accordance with the present invention for distortion-free press-quenching of the crown wheel is as follows:

- Assembling the crown wheel to be press-quenched by placing it on the supporting surface of the device and by tightening the crown wheel using studs and fasteners;

- Applying a force on the conical portion of the tool holder 2 to exert a downward force while guiding it on three guide studs 5.

- Transmitting the same downward force on the upper taper cone 4 to move it downward.

- Simultaneously, wedging the tool holder 2 and riding it on the upper taper cone 4 present on the top side of the collet 3.

- Expanding the upper part of the collet 3 uniformly and exerting a downward force by the single-piece upper taper cone 4 to cause the lower taper cone 4 disposed on the lower side of the collet 3 to get wedged on the conical surface on the lower taper cone 4.

- Uniformly opening the collet 3 and keeping it rigid on both sides and gripping the internal diameter of the component, e.g. crown wheel.

- Uniformly expanding or contracting the collet 3 about its cylindrical form or diameter, thereby maintaining the true circular form thereof even on applying an external force.

The collet 3 expands axially due to the pattern configured thereon, as seen in the cross-sectional view of Figure 7. Thus, the collet 3 expands radially due to the patterns configured thereon as seen in Figure 5. The features are designed by considering the rigidity and stiffness required for the device 20 and the materials used and also based on the dynamic flow of the quenching medium.

The outer form of the collet 3 also has a specific form to achieve a maximum surface contact, when the collet 3 is expanded and it actually grips the component and then act as a guide or wall against the collapsing internal diameter of the crown wheel to achieve a good run-out or roundness on the internal diameter (unlike conventional expander which offers little control on the run-out or roundness).

Moreover, with the ram force in control, it is possible to modulate and control the collapse of the internal diameter, so that excessive stresses are not generated (unlike in a taper mandrel which needs to be pulled out).

In addition, by controlling the resultant force on the collet 3, the outer diameter of the collet 3 is made dominant on the internal diameter of the crown wheel 10, thereby accurately controlling its form.

The design of the collet 3 plays a major role in the elegance of this design, so that even though it expands (i.e. its stiffness is lower than that of a similar disc-shaped component) and contracts, it is able to withstand forces exerted by central ram and by the collapsing internal diameter of the crown wheel 10 as it maintains its own dominating outer circular form.

All the slits aid in uniform circular expansion and flow of oil, while the unique cross-section helps in uniform expansion of the outer circular form through taper action to accurately control the form on the internal diameter of the crown wheel 10 to give good repeatability and reproducibility. This helps in getting good quality gear class in crown wheels 10 being manufactured.

The device configured according to the present invention offers a superior quenching tool over the existing conventional quenching process. It presents an innovative quenching tool that controls the ovalness on the internal bores of steel rings to be quenched.

The device configured according to the present invention fundamentally comprises of single-piece expanding collet that achieves maximum continuous surface contact with the internal bore in terms of cylindrical shape and roundness, including grooves strategically formed for quenching medium flow.
The device configured according to the invention has an expanding single-piece collet which is rigid as well as flexible enough to be actuated by two conical surfaces by a wedging action that expands the collet uniformly at top and bottom through the application of force via a ram.

The method devised according to the invention offers an improved process by using a superior quenching tool which has several advantages over the existing conventional quenching process.

The method devised according to the invention controls the form on the outer diameter of the collet very accurately, which is achieved by designing the collet considering overall rigidity and stiffness parameters to achieve maximum surface contact under process application. Also, this form is consistently controlled by small modulations in ram pressure by this novel design concept.

TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE

The device configured in accordance with the present invention for distortion-free press-quenching of the crown wheel has the following technical and economic advantages:

• Provides high-quality press-quenched components, e.g. crown wheels.

• Eliminates distortion due to thermal shocks during press-quenching.

• Ensures ovalness of the internal diameter and back-face flatness.

• Maintains a constant gap between gear teeth.

The exemplary embodiments described in this specification are intended merely to provide an understanding of various manners in which this embodiment may be used and to further enable the skilled person in the relevant art to practice this invention. The description provided herein is purely by way of example and illustration.

Although, the embodiments presented in this disclosure have been described in terms of its preferred embodiments, the skilled person in the art would readily recognize that these embodiments can be applied with modifications possible within the spirit and scope of the present invention as described in this specification by making 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 & spirit of 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.

These and other changes in the preferred embodiment of the invention will be apparent to those skilled in the art from the disclosure herein, whereby 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.

Many of the fastening, connection, processes and other means and components utilized in this invention are widely known and used in the field of the invention described, and their exact nature or type is not necessary for an understanding and use of the invention by a person skilled in the art and they will not therefore be discussed in significant detail.

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.

Also, any reference herein to the terms ‘left’ or ‘right, ‘up’ or ‘down, or ‘top’ or ‘bottom’ are used as a matter of mere convenience, and are determined by standing at the rear of the machine facing in its normal direction of travel.

Furthermore, the various components shown or described herein for any specific application of this invention can be widely known or used in the art by persons skilled in the art and each will likewise not therefore be discussed in significant detail. When referring to the figures, like parts are numbered the same in all of the figures. ,CLAIMS:We claim:

1. A device for manufacturing high-quality press-quenched components, wherein the device comprises:

• a supporting surface 1 at the bottom face thereof;

• a tool holder 2 disposed at the top face thereof and to function as a cap for supporting the component to be press-quenched;

• a collet 3 configured with predefined profiles for imparting the desired rigidity and stiffness of the device;

• one taper cone 4 each disposed above and below the collet 3; and

• a plurality of guide studs 5 and a respective fastener 6 therefor;

wherein the supporting surface 1, tool holder 2, collet 3 and taper cones 4 each are configured with a respective concentric internal bore for placing a central ram to apply a force on the component to be quenched, and the outer periphery of the collet 3 is configured to impart a maximum surface contact of the collet with the inner diameter of said component mounted above the collet 3.

2. Device as claimed in claim 1, wherein the supporting surface 1 has the largest outer diameter for fully supporting the components disposed thereupon and the internal diameter equal to the internal diameter of the collet 3 and taper cones 4.

3. Device as claimed in claim 1, wherein the tool holder 2 has an internal diameter less than the internal diameters of the collet 3 and taper cones 4 and a countersunk step on the upper face of the tool holder 2 for holding the component to be press-quenched.

4. Device as claimed in claim 1, wherein the taper cones 4 comprise a respective taper outer surface contacting the internal taper surfaces of the collet disposed between the taper cones 4.

5. Device as claimed in claim 1, wherein the collet 3 is configured as a single-piece expanding type collet for achieving the maximum surface contact.

6. Device as claimed in claim 5, wherein the profiles configured on collet 3 are formed as a plurality of radially disposed slits and/or grooves equally spaced on the outer periphery of the collet 3 to facilitate a uniform radial expansion or contraction of the outer periphery of the collet 3 through the wedging action of the taper cones 4 disposed above and below the collet 3 for maintaining the true circular form thereof in order to achieve a maximum surface contact and to enable a uniform flow of the quenching medium, preferably oil flowing through said plurality of slits and/or grooves.

7. Device as claimed in claim 6, wherein the outer diameter of collet 3 is made dominant on the internal diameter of the component to be quenched for accurately controlling the form thereof by controlling the resultant ramming force on collet 3.

8. Device as claimed in claim 7, wherein the collet 3 expands and contracts and withstands the forces applied by the central ram and maintains the dominating outer diameter thereof by the collapsing the internal diameter of the component to be quenched.

9. Device as claimed in anyone of the claims 1 to 8, wherein the device comprises three guide studs 5 inserted from the supporting surface 1 side and a respective fastener 6 is tightened thereon after placing the component to be press-quenched and held thereon, the guide studs 5 being inserted through holes successively made at 1200 through the faces of the device.

10. Device as claimed in claim 8, wherein the thickness of the collet at the dominating outer diameter thereof is configured more than the internal diameter of the component to be quenched to be supported thereon and inner annular diameter of the collet is more than the outer diameter of the studs 5, the thickness of the inner annular diameter of the collet 3 being less than outer diameter of the studs 5.
11. Device as claimed in anyone of the claims 1 to 10, wherein the edges of the outer and inner diameter of the supporting surface 1, tool holder 2, collet 3 and taper cones 4 as well as the and bores of the holes provided therein are suitably chamfered.

12. A method of manufacturing high-quality press-quenched components, preferably distortion-free press-quenched crown wheels by means of the device claimed in anyone of the claims 1 to 11, wherein the method involves the steps of:
(a) Assembling the crown wheel to be press-quenched by placing it on the supporting surface of the device and by tightening the crown wheel using studs and fasteners;

(b) Applying a downward force on the countersunk portion of the tool holder 2 by means of a central ram to guide the same on guide studs 5;

(c) Transmitting the same downward force to move the upper taper cone 4 downward;

(d) Wedging the tool holder 2 supported on the upper taper cone 4 above the collet 3;

(e) Expanding the upper part of the collet 3 uniformly by exerting a downward force by pressing the upper taper cone 4 in order to wedge on the taper surface of the lower taper cone 4 disposed under the collet 3;

(f) Uniformly opening the collet 3 and keeping it firmly on the upper and bottom faces thereof and gripping the internal diameter of the component to be press-quenched, preferably a crown wheel; and

(g) Uniformly expanding or contracting the outer periphery of the collet 3 for maintaining its true circular form on applying an external force thereon form by achieving the maximum surface contact with the component to be press-quenched, preferably a crown wheel.

Dated: this day of 30th September 2016. SANJAY KESHARWANI
APPLICANT’S PATENT AGENT