Field of Invention

This invention generally relates to permanent fasteners for fastening adjacent surfaces of a telecommunication network systems chassis.

Background of the Invention

Telecommunication circuit networks essentially consist of electronic devices arranged in a system. This system provides for a front panel consisting of a face plate, Printed circuit board (PCB), card cage and a latch mechanism on either side of the face plate to fasten the front panel with the chassis. The face plate area through the openings is the access point to the services offered by the PCB. The front panel with the PCB is guided by a card cage to attach the PCB with the back plane of the system. The card cage is a combination of two card guides fixed on either sides of a chassis which allows guiding of the PCB through its grooves. These card guides are permanently fastened to the chassis by a riveting mechanism where parts of the rivet projects outside the fastened assembly. The projection is to a minimum length of 4.5 mm. This projection of the rivet within the card guide frames occupies a significant space in the chassis thus reducing the real estate of the chassis. Further, whenever the front panel with PCB is jacked in to the card guide, the projection of the rivet interferes with the PCB and so, the card guides had to be fixed giving room for this projection which means that a minimum card guide height from its base should be 4.5 mm and above. This further reduces the real estate of the chassis. This formation of protuberances on both the surfaces of card guide as well as the chassis when joined by a riveting mechanism is not compatible with the requirement to be able to slide the various components into and out of the chassis. Further upon riveting, the bulkheads formed out of jointed metal sheets will also be incompatible with the proximity of various components within the chassis.

Another solution would be to use welding mechanism for fixing the card guide frames with the chassis. But inserting the welding machine in the particular location will be a difficult manufacturing process and it involves considerable time in making it. Another possible solution would be to use riveting mechanism where the rivet pins surface flush with the surfaces. But, using the above method increases the cost and manufacturing time thereby increasing the bill of material. Therefore a method to provide an effective permanent fastening of two parts using 'of the shelf parts is required to eliminate the above said disadvantages.

Summary of the Invention

According to one aspect of the invention, a method for permanently fastening a plurality of surfaces is accomplished by forming holes in the surfaces and placing the surfaces together so that the holes are arranged parallel to form a single hole therethrough; inserting a shank into the hole formed in the surfaces from the blind side thereof, the shank having a flanged portion at one end, which is head positioned to insert through the hole such that the flange portion abuts the surface at the blind side; and punching the shank; wherein the hole is circular at the outwardly facing surface of at least on the blind side, and the distal end of the shank is deformed during punching operation to form a permanent fastening joint such that the deformed part flushes with the surface, similar to the flanged part, in which, no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

Another aspect of the invention relates to providing a shank using 'off the shelf material', wherein the shank is procured from an existing blind rivet after removing the mandrel along with the mandrel head.

The above method has the advantage that access is only necessary to one side of the surfaces to be joined (the working side) and it is possible to form a permanent fastening joint that does not protrude on either side of the surfaces. Further the hole formed on the surfaces may be circular or frusto-conical at the blind side. Depending on the shape of the hole on the blind side, the flanged head of the shank engages the countersink hole, such that the end surface of the flange is preferably flat so that, after the punching operation is performed both the sides of the permanent fastening joint is substantially flush with the surfaces.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

Brief description of the drawings

The features, advantages and other aspects of the embodiments of the present invention will be obvious to any person skilled in the art to appreciate the invention when read with the following description taken in conjunction with the accompanying drawings.

Figure 1 depicts a protrusion of rivet fastening of a card guide with a chassis of a telecom equipment known in the prior art;

Figure 2 depicts an isometric top view of the rivet protrusion interfering with the card while jacking it in the chassis, that exists in the prior art;

Figure 3 depicts the shank, embodying the principles of the present invention.

Figure 4 depicts the manufacturing sequence employed in punching operation, embodying the principles of the present invention.

Figure 5 depicts the manufacturing sequence employed in punching operation, embodying the principles of another aspect of the present invention.

Figure 6 depicts the type of permanent fastening of a card guide with the chassis of telecom equipment embodying the principles of the present invention.

The figures are not drawn to scale and are illustrated for simplicity and clarity to help understand the various embodiments of the present invention. Throughout the drawings it should be noted that like reference numbers are used to depict the same or similar elements, features and structures.

Detail description of the Invention

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

Figs. 3 to 6, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way that would limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged telecommunication network systems. The terms used to describe various embodiments are exemplary. It should be understood that these are provided to merely aid the understanding of the description, and that their use and definitions in no way limit the scope of the invention.

By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Figure 1 and 2 shows the protrusion caused by conventional form of blind rivet fastening of a card guide with a chassis of telecom equipment. The card guide 2 is bound with the chassis 1 by providing a hole at the card guide platform 3 and the chassis such that both the holes are matched exactly to form one through hole. A rivet pin is passed through the hole and by the process of blind rivet mechanism both the surfaces are joined permanently. It is well known that some part of the mandrel head and the mandrel upon getting collapsed by rivet setting causes some protuberances 4 which may limit the available workspace on the blind side of the surface. This protuberance 4 may interfere with the placement of components while jacking in a card 6 through the rails 5 of the card guide as shown in figure 2.

FIG 3 to 6 depicts a novel method for permanent fastening of a plurality of surfaces, in which the fastening joint is flush with the outer surfaces of the joined workpieces embodying the principles of the present invention. It is to be noted that, for the sake of clarity in explaining the embodiments, words 'workpieces or workpiece' and 'surfaces or surface' are used interchangeably.

Figure 3 represents the shank 10 that is used in the method, has a flange 12 which forms the head portion at one end. The surface of the flange12 is flat at the facing surface 11 so as to flush with the surface of the workpiece. The shank 10 has a generally cylindrical part 14 following the head portion 12 and a radial recess 13 in between the flange 12 and cylindrical portion 14. The recessed portion 13 provides for cushioning of the shank material when the punching operation is in process so that part of the compressed shank material is housed within the recess. The distal end 16 of the shank has a generally flat hollow circular portion. The flange 12 may be shaped to form a part that tapers inwards towards the recess 13 in the form as frusto-conical, so that the hole that may be formed on the surfaces at the blind side may also be in the form as frusto-conical such that the frusto-conical shaped flange may engage the similar shaped hole at the blind side. The above described shank can be custom designed and also depending on the application requirements based on thickness of the workpiece, a shank portion can be immediately procured from the existing blind rivet by removing the mandrel along with the mandrel head. This has an increased advantage as the manufacturing process is minimized and bill of material is not increased as well.

Figure 4 depicts the manufacturing sequence employed in permanently fastening the surfaces, embodying the principles of the present invention.

In order to permanently fasten the surfaces a hole is formed in each workpiece 21 and 22 and the surfaces are placed together so that the holes are arranged parallel to form a single hole therethrough. The shank 10 is then inserted through the holes of both the surfaces 21 and 22 till the flange portion 12 abuts the blind side of the workpiece 22. A punching tool 30, punches the distal end 16 of the shank 10. The punching tool 30 applies force radially along the axis of the distal end 16 of the shank 10 to deform into the countersink hole at the working side, such that the deformed part flushes with the workpiece surface 21 similar to the flanged part at the blind side, in which no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

It is possible that instead of forming holes having a constant bore at the surfaces, the holes are countersunk so that each hole in the workpiece 21 and 22 can be frusto-conical in shape 23 and 24 respectively, expanding radially toward the outwardly oriented surface 21 and 22 of each workpiece. In this case, the flange portion 12 of the shank 10 has a frusto-conical shape matching the same dimensions of the countersink in the workpiece 22 so that the flanged head can be inserted into the hole formed in the blind side, and the frusto-conical part of the flange will seat itself in the countersink 24 with outwardly directed surface 25 flush with the surface 22 of the workpiece as shown in figure 5. The punching operation can then be set in the same manner as explained above so that the distal end 16 of the shank 10 is axially squashed by the punching tool and is deformed radially outwardly into the countersink 23 on the working side of the workpiece 21, such that the deformed part 26 flushes with the workpiece surface 21 similar to the flanged part at the blind side, in which no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

The size of the cylindrical part 14 (as shown in figure 3) of the shank is appropriately choosen so that the fastening joint formed has no part protruding above the outwardly oriented surfaces 26 and flushes with the surface of the surfaces 21 as shown in figure 5.

The method of punching operation embodying the principles of this invention can be done by a variety of methods including rivet setting. It is known that the distal end of the shank has such a configuration that it has no means of ensuring correct setting within the hole, and so this must be provided by the punching tool. In addition, the punching tool may have a jaw that bears on the shank and applies force on the distal end of the shank along the its axis radially to deform the distal end of the shank into the countersink, such that it flushes with the surface of the workpiece on its working side.

Figure 6 shows part of the chassis of telecom equipment with card guide in which the permanent fastening of two surfaces is formed in accordance with the present invention. The chassis 1 forms one workpiece on the working side and the card guide platform 3 forms another workpiece on the blind side. The fastening joint 7 has no protrusions on either side of the surfaces thus enabling placement of components and also not interfering while jacking in a card 6 through the rails 5 of the card guide 2 (as shown in figure 2).

The above method of permanent fastening of two surfaces, embodying the principles of this invention can be used to provide fastening joints for any permanent fastening application where real estate of the chassis pertaining to electronic equipments is a premium.

The embodiments of the shank pursuant to the principles of the invention can be made from any desired solid material preferably metal. Indeed, it can be made of steel, mild steel, plastic, fibre, moulded material making it weigh less and more portable. It could also be made of steel, mild steel, non-conducting alloys depending upon its applications.

It will thus be appreciated that those skilled in the art will be able to device numerous alternative arrangements that, while now shown or described herein, embody the principles of the invention and thus are within its spirit and scope.

The scope of the present disclosure includes any novel feature or combination of features disclosed therein either explicitly or implicitly or any generalisation thereof irrespective of whether or not it relates to the claimed invention or mitigates any or all of the problems addressed by the present invention. The applicant hereby reserves the right that new claims can be formulated to such features during the prosecution of this application or of any such further application derived there from.

We Claim:

1. A method for permanent fastening of a plurality of surfaces by steps
comprising of:

Forming holes in the surfaces and placing the surfaces together so that the holes are arranged parallel to form a single hole therethrough;

Inserting a shank into the hole formed in the surfaces from the blind side thereof, the shank having a flanged portion at one end, which is head positioned to insert through the hole such that the flange portion abuts the surface at the blind side; and
Punching the shank;

wherein the hole is circular at the outwardly facing surface of at least on the blind side, and the distal end of the shank is deformed during punching operation to form a permanent fastening joint such that the deformed part flushes with the surface similar to the flanged part, in which, no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

2. The method of claim 1, wherein, the shank from its flanged head is
substantially cylindrical and is deformed into the countersink on the working
side of the surface during punching operation thereof, such that the deformed
part flushes with the surface similar to the flanged part, in which no part of the
permanent fastening joint protrudes the outwardly facing surface of either
surfaces.

3. The method of claim 2, wherein, during punching operation, force is applied radially along the axis of the distal end of the shank to deform into the countersink, such that the deformed part flushes with the surface similar to the flanged part, in which no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

4. The method of claim 1, wherein, the distal end of the shank has a generally flat hollow circular portion which upon being punched by a punching tool along the axis radially, deforms into the countersink such that the deformed part flushes with the surface similar to the flanged part, in which no part of the permanent fastening joint protrudes the outwardly facing surface of either surfaces.

5. The method of claim 1, wherein forming hole includes forming a frusto-conical hole radially enlarged at the outwardly facing surface on both the sides of the surfaces.

6. The method of claim 1, wherein flanged portion includes flange having a frusto-conical part that engages the radial enlargement on the blind side of the hole when the shank is inserted in the hole.

7. The method of claim 6, wherein the frusto-conical part of the flange has a flat end surface that is substantially flush with the surface on the blind side thereof.