FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
DIE HEAD RETAINER MECHANISM
EMERSON ELECTRIC COMPANY
a US Company
of 8000 WEST FLORISSANT AVENUE
ST. LOUIS, MISSOURI 63136 USA
Inventors: 1. Patil Prasad Chatursingh
2. Dakare Sachin Shashikant
3. Kundracik Richard M.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORME

FIELD OF INVENTION
The present invention relates to thread cutting mechanisms. In particular, it relates to a mechanism for locking a die head in a thread cutting machine, such as power drive, threading machine, screw machine and the like; more particularly, it relates to thread cutting operations where axial locking of the die head is required.
The present invention also relates to other fields, where the die head and such other locking mechanisms are used, e.g. in electric motors, compressors, valves, regulators, gearboxes and any other specific products or new models.
BACKGROUND OF INVENTION
Threads are used on a wide array of mechanical components, piping, and conduit for engaging components together and/or to provide a sealing connection between components. Numerous thread sizes and thread configurations are known, such as tapered threads and non-tapered or "straight" threads. Within each class, a variety of different thread forms have been developed and used depending upon the application, type of workpiece, customs of the locale, and preferences of the user.
Devices for forming threads on pipe ends are well known in the art. Such devices use one or more dies that form a helical thread extending from one region of the pipe to another region. The die is orbited about the axis of the pipe and/or the pipe is rotated while the die is engaged with a select region of the pipe to form the thread.

When assembling piping systems or when forming custom piping layouts, sections of pipe are typically out and threaded at a construction or assembly site. As a result, portable or semi-portable pipe threading devices have been developed which can be used at the job site to prepare threaded pipe ends.
Presently, hand held power drive units provide power to die heads during thread cutting operations on pipes. This power is provided by the power drive with angular velocity and torque dependent upon the type of thread, dies, and pipe. In such an operation, the die head needs to be retained in the axial direction to prevent disengagement with the power drive spindle. Particularly, force must be applied to the die head in the axial direction during the initial engagement of the die head with the pipe. In a present configuration of such power drives, a spring ring is used to lock the die head, which necessitates a higher effort for installing or removing the die head in the assembly. Moreover, for locking the axial movement of the die head in such spring ring of the available power drive, the spring ring is snap fitted in the groove on the face gear and subsequently provides locking of the die head. Thus, an excessively high force is required to fully engage the die head in the face gear with the spring ring resulting in a cumbersome and time consuming operation. However with continued use, this spring ring loses its stiffness (and locking force) so that replacement may be required.
Further other power drive units either use an internally threaded disc for axial locking of the die head or use a retaining ring to lock the die head resulting in greater time required for installing or removing the die head. The retaining ring is inserted behind the die head (after installation of the die head in the power drive) in an available groove. Therefore, an external device (e.g. a screw driver) is necessary for installing or removing the die head, in this case.

STATE OF THE ART
CN 101704141 discloses an electric pipe-cutting threading machine, aiming at overcoming the problems of narrow application range and low machining accuracy of common threading machines. The electric pipe-cutting threading machine comprises an automatic cutter-withdrawal device, a die-head, a scraper and a cutting knife, and is characterized in that the die-head comprises a baffle, a locking screw, a release lever, a transmission screw pressure spring, a transmission screw, a fastening card and a curve locking disk, which is arranged between a curve disk and a salver, and a locking hole which is cut on the curve disk. Further, a moon-groove is arranged on a die-disk, and the transmission screw pressure spring and the transmission screw are arranged in this moon-groove. A transmission hole is arranged on the curve locking disk, which is penetrated by the transmission screw. The baffle is shaped like an 'L' which is reversed vertically and articulated on the curve locking disk. The curve locking disk is provided with a blocking handle and a limiting lug. The release lever is articulated on the die-disk. The automatic cutter-withdrawal device comprises a sine block, a guiding rod, a left pressure spring and a right pressure spring, wherein the sine block is sheathed on the guiding rod and the left pressure spring and the right pressure spring are respectively fixed at two ends of the guiding rod.
CN 201644960 discloses a self-opening die head used in an electric tube-cut wire-sleeving machine, comprising a tray, a die with raised line grooves, a die tray with die grooves and a curve tray with arc raised lines and is characterized by also comprising a baffle, a locking screw, an unlocking handle, a transmission bolt pressure spring, a transmission bolt, a stopping tag and a curve locking disc with an arc adjusting groove, wherein the curve locking disc is mounted between the

tray and the curve tray which is internally provided with a locking hole, the locking screw penetrates through the locking hole and the arc adjusting groove,. The die tray is provided with moon grooves, the transmission bolt pressure spring and the transmission bolt are mounted in the moon grooves, the curve locking disc is provided with a transmission hole in which the transmission bolt penetrates, the baffle is articulated on the curve locking disc which is provided with a baffle handle and a stopping lug boss, and the unlocking handle is articulated with the periphery of the die tray.
US 2, 958, 877 discloses a self-opening die-head comprising a skeleton or frame having a hollow elongated shank, chasers mounted on said skeleton for reciprocal movement into and out of work-engaging position, and a chaser-operating member for moving said chasers into a work-engaging position, the combination comprising a ring-shaped latch-unit positioned around said shank and having a latching portion movable transversely outwardly with respect to the longitudinal axis of said shank into a latching position with said chaser-operating member in order to releasable hold said member in its chaser-closing position, spring means resiliently urging said latch-unit into said latching position, tripping means mounted within the shank of said skeleton for releasing said chaser-operating member, said tripping means having a trip member movable axially of said shank and located with one end in position for engagement with the work, said tripping means having camming means engaging the inner surface of said latch-unit at a point diametrically opposite said latching portion and operable upon axial movement of said trip member to cam said latch-unit against the urge of said spring means and thereby to move said latching portion out of said latching position wherein said latch-unit comprises a pair of complementary segments, a first of said segments comprising said latching portion, the second of said segments

being interlocked with the first so as to draw said first segment inwardly to unlatching position upon actuation of said trip member.
US 2, 739, 322 discloses a thread cutting die head, wherein a body member provided with a relatively fixed abutment; an axially shiftable chaser holder closing ring is mounted on said body member and resiliency biased toward said abutment in axial alignment therewith. Said closing ring has first and second annular radial surfaces offset axially and facing said abutment. A locking ring extends around the axis of the die head positioned between said closing ring and said abutment and having annular front and rear faces. Means are also disclosed to bodily displace said locking ring laterally of said die head between a first position to dispose the front face thereof in engagement with the first surface on said closing ring and a second position to dispose the front face thereof in engagement with said second surface of said closing ring, the rear face of said locking ring being engaged with said abutment in both positions whereby said locking ring is fixed against axial movement, the respective areas of engagement between said locking ring and said first and second surfaces and between said locking ring and said abutment being disposed at least in any three selected quadrants about the axis of said head.
OBJECTS OF THE INVENTION
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present invention to provide a die head retaining mechanism for easy positive installing or removing of the die head in the power drives.

It is another object of the invention to provide a die head retaining mechanism facilitating an application of force on the power drive for providing die head engagement with the pipe while commencing the threading operation.
It is yet another object of the invention to allow easy installation of the die head in the power drive.
It is a further object of the invention to provide a die head retaining mechanism in which much less effort/force is necessary for installing and removing the die head.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present invention.
SUMMARY OF THE INVENTION
In accordance with the present invention, a power drive is provided for thread cutting operation comprising:
- a housing;
- a face gear disposed in the housing with a plurality of slots and at least one groove;
- a die head retaining mechanism consisting of-

• a plurality of locking jaws;
• at least one compression spring;

• a drive ring having a plurality of cam profiles and means to compress said spring(s);
• a locking plate; and
• a plurality of clamping means;

- a die head disposed in the retaining mechanism;
- a retaining ring; and
- a bearing;
wherein the die head retaining mechanism is disposed between the face gear and the die head for installing or removing the die head in the power drive, each of the at least one locking jaw is disposed in a respective slot provided on the face gear and engaged with the cam profiles of the drive ring and at least one of the compression spring being disposed in a groove adapted to be compressed during rotation of the drive ring in order to allow the locking jaw to follow the cam profiles to move outward in a radial fashion to open or unlock the die head from the power drive.
Typically, the clamping means comprise a plurality of spring washers and screws for the assembly of the die head retaining mechanism on the face gear, and wherein the bearing is provided between the housing and the face gear and the bearing is retained by a retaining ring in a groove in the housing.
Typically, the face gear accommodates three equidistant locking jaws in three slots provided on its face oriented away from the housing, the face gear further including at least one circumferential groove for accommodating a preloaded compression spring, wherein during an anticlockwise rotation of the drive ring, the compression spring is compressed to allow the locking jaws to follow the cam

profiles of the drive ring and move outward in the radial direction to open or unlock the die head from the power drive.
Typically, the compression spring is preloaded by insertion into a groove in the face gear and during operation, the compression spring abuts one end of the groove and is constrained by the lug of the drive ring at the other end; the lug protruding from the drive ring into a corresponding recess or slot provided on the face gear, to allow the compression spring to be compressed, and the locking jaws moves outward in the radial direction to unlock the die head from the power drive.
BRIEF DESCRIPTION OF THE INVENTION
The die head retaining mechanism in accordance with the present invention will now be explained in more detail with reference to the non-limiting accompanying drawings in which:
Figure 1 shows a hand held portable power drive to provide input power to die head during threading operations.
Figure 2 shows a portion of the power drive with a section marked with arrows A-A for describing further details in following figures.
Figure 2a shows the sectional view through portion marked with arrows A-A indicated in Figure 2.
Figure 2b shows the spring ring, which is located between the face gear and the die head for locking thereof, as shown in Figure 2a.

Figure 3 shows various components of the power drive shown in Figure 1 with a die head retaining mechanism in accordance with the present invention.
Figure 4a shows a sectional assembled view of the face gear on the housing of the power drive in accordance with the present invention.
Figure 4b shows an enlarged sectional view of the face gear and the die head assembled by means of the die head retaining mechanism in accordance with the present invention.
Figure 5a shows one face of the drive ring in a perspective view.
Figure 5b shows another face of the drive ring in a perspective view.
Figure 6 shows a detailed sectional view of the face gear on the housing of the power drive showing the compression spring in sectional view.
Figure 7 shows a face gear shown in Fig, 5 in a perspective view.
Figure 8a shows a perspective view of the drive ring assembled with three retaining/locking jaws in accordance with the invention.
Figure 8b shows a perspective view of the face gear assembled with three retaining/locking jaws, and compression spring in accordance with the invention.

Figure 9a and Figure 9b show the working of the die head retaining mechanism in accordance with the invention.
DETAIL DESCRIPTION OF THE INVENTION
The die head retaining mechanism in accordance with the present invention will now be described with reference to the accompanying drawings which do not limit the scope and ambit of the disclosure. The description provided is purely by way of examples and illustrations.
Figure 1 shows a hand held portable power drive to provide input power to a die head during threading operations. It is configured for threading 1/8" through 2" die heads for threading pipes. The power drive provides an angular velocity and torque dependent upon the type of thread, dies, and pipe. In such an operation, the die head needs to be retained in the axial direction to prevent disengagement with the power drive spindle. Particularly, a force must be applied to the die head in the axial direction during the initial engagement of the die head with the pipe.
Figure 2 shows a portion of the power drive PD shown in Figure 1. Arrows A-A are marked therein, along which a cross-sectional view is shown and described further in the following Figures 2a and 2b.
Figure 2a shows the cross-sectional view of the spring ring 6 positioned in a groove on the face gear 2 for engaging the die head (DH) in the power drive.
Figure 2b shows the spring ring, which is snap fitted in the face gear and consequently causes the locking of the die head with respect to the face gear.

Figure 3 shows in a perspective exploded view, various components of the power drive incorporating a die head retaining mechanism in accordance with the present invention. The power drive includes a body or housing 1, a face gear 2, three retaining/locking jaw or inserts 3 disposed circumferentially equidistant on a face of the face gear 2, a bearing 4* compression spring 5, a retaining ring 6, a drive ring 7, a lock plate 8 and spring washers 9 and screws 10 for the complete assembly of the power drive with the aforementioned components.
Figure 4a is the sectional view of the power drive shown in Figure 3 assembled with locking jaws 3 in the face gear. The face gear 2 is housed in the housing 1. Three locking jaw 3 are disposed circumferentially and equidistantly. These locking jaws 3 are engaged with corresponding slots 7c in the face gear 2 and in the cam grooves 7a of the drive ring 7. A locking plate 8 is fitted to contain the die head retaining assembly by means of spring washers 9 and screws 10 (not shown in figure 4a but seen in fig 3) threaded into the face gear 2.
Figure 4b shows an enlarged sectional view of the die head retainer mechanism in accordance with the invention, for axial locking or unlocking the die head DH on the power drive for thread cutting operations. Here, the face gear 2 is mounted in the housing 1 (not shown in fig 4b but shown in fig 3) and three locking jaws 3 are placed circumferentially and equidistant from each other and in slots 7c provided in the face gear 2. The jaws 3 are engaged with the groove of the die head DH to retain the die head in the axial direction. The jaws 3 are also engaged with the cams 7a of the drive ring 7 to allow outward radial movement of the jaws 3 with anticlockwise rotation of the drive ring 7.

Figure 5a shows one face of the drive ring in a perspective view and Figure 5b shows another face of the drive ring in a perspective view, in which the protruding lugs (PL) can be clearly seen.
Figure 6 shows a detailed sectional view of the face gear 2 in the housing 1. In particular, it shows a compression spring 5 inserted in a groove or pocket 12 provided on the face gear 2. Here also, the housing 1 is shown fitted with the face gear 2, spring or locking ring 6, bearing 4, drive ring 7, and finally all components are assembled together in the housing by means of the locking plate 8 and spring washers 9 and screws 10.
Figure 7 shows a face gear 2 in a perspective view the face gear shown in Figure 3 clearly showing three slots 7c and the groove 12 for accommodating the compression spring 5 (not shown in Fig 7 but shown in Fig 3).
Figure 8a shows a perspective view of the drive ring 7 assembled with three retaining/locking jaws 3 in accordance with the invention, which are engaged in their respective cams 7a.
Figure 8b shows a perspective view of the face gear 2 assembled with three retaining/locking jaws 3 in accordance with the invention. In the normal position of the drive ring 7, locking jaws 3 are in a locked position. During an anticlockwise rotation of the drive ring 7, the lugs (PL) engage the spring 5 and compress it. Simultaneously, the locking jaws 3 follow the cam profile 7a provided on the drive ring 7, thus moving outward in the radial direction in order to disengage the jaws from the die head DH. One end of the compression spring 5 is engaged with the face gear groove 12 and the other end is engaged with the protruded portion or lug

(PL) of the drive gear 7. Without anticlockwise rotation of the drive ring, the compression spring 5 always urges or presses the drive ring lug (PL) into the face gear slot 13 to keep the locking jaws 3 in engagement with the die head DH. As already shown in Figure 3, after the assembly of the face gear 2 with the housing 1, compression spring 5, locking jaws 3 and drive ring 7 are assembled. Thereafter, the complete assembly is locked by the locking plate 8 by placing the spring washers 9 and then tightened by screws 10. In particular, the gripping area (GA) having pits and peaks of the drive ring 7 is configured in such a manner that in any orientation, the finger/hand can easily access and an easy grip can be made for rotation thereof.
Figure 9a and Figure 9b show that by an anticlockwise rotation of the drive ring 7, the locking jaws 3 are urged to follow the cam profile 7a provided on the drive ring 7, thus moving outward in the radial direction, the jaws are thereby disengaged from the die head.
The die head retaining mechanism in accordance with the present invention herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

The description herein after, of the specific embodiments of the die head retaining mechanism 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. 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.
TECHNICAL ADVANTAGES AND ECONOMIC SIGNIFICANCE
The technical advantages obtained with the die head retaining mechanism in accordance with the invention include the following:
- The effort and time required for the engagement and disengagement of the die head is less.
- A positive locking of the die head in the power drive is achieved.
- This mechanism facilitates application of force on the power drive for providing die head engagement with the pipe while commencing the threading operation.
- Ease of use for assembly of the die head.
- This mechanism can be used in all types of machines where axial locking of the die head is required.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression "at least" or "at least one" suggests the use of\] one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the invention as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

We Claim:
1. A power drive for thread cutting operation, said power drive comprising:
- a housing (1);
- a face gear (2) disposed in said housing with a plurality of slots (7c) and at least one groove (12);
- a die head retaining mechanism comprising-

• at least one locking jaw (3);
• at least one compression spring (5);
• a drive ring (7) having a plurality of cam profiles (7a) and means to compress said spring(s);
• a locking plate (8); and
• a plurality of clamping means;
• spring ring;

- a die head (DH) disposed in said retaining mechanism;
- a retaining ring (6); and
- a bearing (4);
wherein said die head retaining mechanism is disposed between said face gear (2) and said die head (DH) for installing or removing said die head in said power drive (PD), each of said at least one locking jaws (3) is disposed in a respective slot (7c) provided on said face gear and engaged with at least one said cam profile (7a) of said drive ring (7) and at least one said compression spring (5) is disposed in a groove (12) adapted to be compressed during rotation of said drive ring (7) to allow said locking jaws to follow said cam profiles (7a) to move outward in a radial fashion to open or unlock said die head from said power drive.

2. A power drive as claimed in claim 1, wherein said clamping means
comprise a plurality of spring washers (9) and screws (10) for the assembly of said die head retaining mechanism on said face gear (2), and wherein said bearing (4) is provided between said housing (1) and said face gear (2) and said bearing (4) is retained by a retaining ring (6) in a groove in said housing (1).
3. A power drive as claimed in claim 1, wherein said face gear (2)
accommodates three equidistant locking jaws (3) in three slots (7c) provide on its face oriented away from said housing (1), said face gear (2) further including at least one circumferential groove (12) for accommodating said preloaded compression spring (5), wherein during an anticlockwise rotation of said drive ring (7), said compression spring (5) is compressed to allow said locking jaws (3) to follow said cam profiles (7a) of said drive ring (7) and move outward in the radial direction to open or unlock said die head (DH) from said power drive.
4. A power drive as claimed in claim 1, wherein said compression spring (5) is
preloaded by insertion into said groove (12) in said face gear (2) and during operation, said compression spring abuts one end in said groove and is constrained by a lug (PL) of said drive ring (7) at the other end; said lug (PL) protrudes from said drive ring into a corresponding recess or slot (13) provided on said face gear, to allow said compression spring to be compressed, and said locking jaws (3) to move outward in the radial direction, and unlock said die head (DH) from said power drive (PD).

5. A power drive as claimed in claim 1, wherein a lug (PL) protrudes from said
drive ring (7) and engages one end of said compression spring (5) to compress it and other end of said compression spring is engaged in a groove (12) provided on said face gear (2), in order to move outward in the radial direction to disengage said locking jaws from said die head.
6. A power drive as claimed in claim 1 wherein the drive ring is provided with
a gripping area (GA) defined with circumferentially defined pits and peaks for gripping the drive ring in any orientation for rotation thereof.