FIELD OF INVENTION

The present invention generally relates to pipes but more particularly to a method of producing a unitary pipe having a combination of square and circular cross sections, hereinafter referred to as combination pipe, for brevity.

BACKGROUND OF THE INVENTION The known means of producing or manufacturing pipe or elongated hollow forms by extrusion process normally yield a product with uniform cross section along its entire length. In certain applications or purposes for a pipe having varying cross sections, for example square and circular cross sections, for coupling or flow reduction uses, among others, a practical person or maker may combine a segment of a pipe having a square cross section and another segment of a pipe having a circular cross section, and heat-weld them at their adjoining ends. However, the aforesaid manner of joining the pipe segments could effect a weak connection considering that the welding procedure will be limited at the external or exposed surface area, thereby leaving a weak spot within the internal or hidden portion of the connection.

Consequently, the aforesaid manner or means of producing the combination pipe may result to a poor quality product that may not be able to withstand load-bearing and dynamic applications. Furthermore, the aforesaid means to produce the combination pipe normally requires a series of procedures consisting of cutting segments from pipes of different cross sections, holding in place the segments, heat-welding the adjoining ends of the segments, and grinding off the rough welded connection of the combination pipe, thus, making production limited and costly in terms of man-hours involved.

There is a need to create a unitary pipe having a combination of square and circular cross sections for brevity in both manufacturing process and installation.

SUMMARY OF INVENTION

Accordingly, it is a primary object of the present invention to provide a method of producing a combination pipe that can produce units or items which are materially unitary or monolithic, thereby insuring material strength, integrity and reliability for load-bearing and dynamic applications.

Another object of the present invention is to provide a method of producing a combination pipe that is easy to perform or practice, thereby facilitating mass production and insuring lower cost per piece or unit.

To fulfill the aforementioned objectives, a time and attendance recording method comprising providing a method of producing a unitary pipe having a combination of square and circular cross sections comprising the steps of securely clamping a workpiece or a pipe having a square cross section to a workpiece grip of a lathe machine; spinning the securely clamped workpiece according to a predetermined spinning speed by operating the lathe machine; heating up a predetermined portion of the workpiece with a heating torch; extinguishing the heating torch once the required maximum temperature is reached; pressing a roller having a flat rim against the heated portion of the workpiece to gradually transform its square cross section into a circular cross section; and pressing the transformed portion with a roller having a round rim when the workpiece is at a predetermined lower temperature to produce a rounded common spot of the square cross section and the transformed circular cross section.

A preferred embodiment of the present invention disclosed that the spinning speed of the workpiece ranges from 400 rpm to 600 rpm.

In another preferred embodiment of the present invention, the the required maximum temperature ranges from 750 °C to 850 °C.

In still another preferred embodiment of the present invention, the predetermined lower temperature ranges from 250 °C to 350 °C. Further embodiment of the present invention discloses a unitary pipe having a combination of square and circular cross sections produced according to the method in claim 1.

The present preferred embodiments of the invention consists of novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be effected by those skilled in the arts but without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the present invention will be more fully understood when considered with respect to the following detailed descriptions, appended claims and accompanying drawings wherein:

Figure 1 is a fragmentary perspective view of an assembly consisting of a clamped workpiece (10), for example a square sectioned pipe, a heating torch (12) or heating means and a pressure roller having a flat rim (13) in accordance to a preferred embodiment of the present invention; and

Figure 2 is a fragmentary perspective view of a similar assembly in Figure 1, where the workpiece (10) is transformed into a cylindrical shape.

Figure 3 is a fragmentary perspective view of the assembly having a pressure roller with a rounded rim (14) in accordance to another embodiment of the present invention.

Figure 4 is another fragmentary perspective view of the similar assembly in Figure 3, where sharp edges of the workpiece (10) is smoothen out.

Figure 5 is a side view of the workpiece (10) and roller with a flat rim (13) in accordance to a preferred embodiment of the present invention.

Figure 6 is a front view of the workpiece (10) with dotted lines showing shapes of workpiece (10) after each pass of the roller with the flat rim (13). Figure 7 is a side view of the workpiece (10) and the roller with a rounded rim (14) in accordance to another preferred embodiment of the present invention.

Figure 8 is a front view of the workpiece (10) with dotted lines showing shapes of inner surface of the workpiece (10) after each pass of the roller with the rounded rim (14).

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention shall be described according to the preferred embodiments of the present invention and by referring to the accompanying description and drawings. However, it is to be understood that limiting the description to the preferred embodiments of the invention and to the drawings is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim.

The present invention generally relates to pipes but more particularly to a method of producing a unitary pipe having a combination of square and circular cross sections, hereinafter referred to as combination pipe, for brevity.

Describing the present invention for the method of producing a combination pipe with reference to the accompanying drawings, it is shown that it starts with the step of securely clamping a workpiece or pipe having a square cross section (10) to a workpiece holder or grip (11) of a lathe machine. Once properly held or clamped, the lathe machine is operated to rotate or spin the workpiece (10) at a spinning speed of 400 revolutions per minute (rpm) to 600 rpm, preferably 500 rpm. While the workpiece (10) is spinned by the lathe machine, it is being heated up to a temperature ranging from 750 °C to 850 °C, preferably 800 °C, with a heating torch (12) or any similar heating means. The heating torch (12) can be an oxy-acetylene torch. A mandrel is preferred to be inserted into hollow of the workpiece (10) to constrain the workpiece (10) so that its axis does not move during the compression process. The mandrel can be removed from the workpiece (10) after the compression process. When the required temperature is reached or met, the heating torch (12) is withdrawn or extinguished. Thereafter, a roller having a flat rim (13) is pressed against the predetermined portion of the spinning workpiece (10) to gradually transform the heat- softened square-sectioned pipe into a cylindrical or circular-sectioned form. Upon being transformed into the desired cylindrical form, a roller having a round rim (14) is pressed against the transformed portion of the spinning workpiece (10) when it is still pliable and hot at a predetermined lower temperature ranging from 250 °C to 350 °C.

When corners of the workpiece (10) are compressed into arcs, the force acting on the workpiece (10) is intermittent. The workpiece (10) axis would change due to the intermittent force. As the use of the roller having a flat-surfaced rim (13) may leave circular grooves around the transformed portion of the workpiece (10), the roller having a round rim (14) will polish out the grooves to define a plain surface thereat. Furthermore, the roller with round rim (14) will cause the formation of a beveled or rounded common spot for the workpiece (10) and the transformed portion, thereby eliminating undesirable sharp edges or corners.

Apparently, with the pressing of rollers having the flat rim (13) or the rounded rom (14) against the heat-softened portion of the workpiece (10), the circular sectioned portion may have a reduced diameter but thicker material thickness, thereby providing a stronger coupling function.

Although this disclosure has described and illustrated certain preferred embodiments of the invention, it is to be understood that the invention is not restricted to those particular embodiments. Rather, the invention includes all embodiments, which are functional or mechanical equivalence of the specific embodiments and features that have been described and illustrated.