US20030005741A1 - Method for bending a rigid pipe - Google Patents

Abstract

A method for bending a rigid pipe to accomplish a centerline radius less than or equal to the outside diameter of the pipe. Moreover, the method accomplishes such a bend whereby the wall thickness of the pipe on the outermost portion of the wall of the pipe is substantially maintained, as is the inside diameter throughout the bend of the pipe. The pipe bend is accomplished by first determining the desired angle of bend and the desired centerline radius. The arc length of the outermost portion of the pipe is then determined. The height and width of each corrugation is then selected in order to determine the length of the outer surface of each corrugation. The arc length is then divided by the corrugation length to determine the number of corrugations required to accomplish the desired bend. The pipe is then deformed to define the required number of corrugations having the determined height and width. After forming the corrugations, the pipe is bent through the selected degree of the bend.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• Not Applicable. [0001]
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
• Not Applicable. [0002]
BACKGROUND OF THE INVENTION
• 1. Field of Invention [0003]
• This invention relates to a method for bending a rigid pipe. More specifically, this invention relates to a method for bending a rigid pipe to define a centerline radius to outside diameter ratio of 1 or less without restricting the inside diameter of the pipe and without reducing the wall thickness of the pipe. [0004]
• 2. Description of the Related Art [0005]
• It is well known to bend rigid pipes for various reasons. One particular purpose for which pipes are bent is in the trucking industry. Pipes are used for fluid communication in typically low pressure environments. However, due to size and space constraints, it is required that the pipes be bent. [0006]
• The conventional manner in which rigid pipes are bent is illustrated in FIG. 1. Illustrated is an approximate ninety degree (90°) bend. The centerline radius r[0007] _CL′ is greater than the outside diameter d_o′ of the pipe 10′. As a result of the bend, the outermost portion of the wall 12 _o′ is thinned from the beginning portion of the bend to the central portion thereof. In the illustrated embodiment, the centerline radius r_CL′ is 3.0 inches and the outside diameter d_o′ is 2.5 inches. The pipe defines an initial wall thickness t₀′ of 0.065 inches. After deforming through a ninety degree bend, the various wall thicknesses at the locations illustrated have been measured as follows:

  		wall thickness
  	location	(inches)

  	t0' (nominal)	0.065
  	t1'	0.047
  	t2'	0.042
  	t3'	0.045
  	t4'	0.046
  	t5'	0.053

• Also created by this type of bending is a collapse of the outermost portion of the [0008] wall 12 _o′ with relation to the innermost portion of the wall 12 _i′, thereby reducing the inside diameter d_i′ of the pipe 10′.
• As a result of the reduced inside diameter d[0009] _i′ and the reduced wall thicknesses, it is well known that bending a pipe 10′ in this fashion compromises to an extent the integrity of the pipe 10′. Further, because the centerline radius r_CL′ is greater than the outside diameter d_o′, and specifically because there is a required centerline radius r_CL′ that is relatively large, there remain difficulties with installing the pipe due to other objects in the vicinity of the installation. For a larger centerline radius r_CL′, a larger volume of space is required.
BRIEF SUMMARY OF THE INVENTION
• Other objects and advantages will be accomplished by the present invention which serves to bend a rigid pipe to a centerline radius less than or equal to the outside diameter of the pipe. Moreover, the method is designed to accomplish such a bend whereby the wall thickness of the pipe on the outermost portion of the wall of the pipe is substantially maintained, as is the inside diameter throughout the bend of the pipe. [0010]
• The pipe bend is accomplished by first determining the desired angle of bend and the desired centerline radius. The outside diameter and nominal wall thickness of the pipe are also determined. Using this data, the arc length of the outermost portion of the pipe is determined. The height and width of each corrugation is then selected in order to determine the length of the outer surface of each corrugation. The arc length is then divided by the corrugation length to determine the number of corrugations required to accomplish the desired bend. [0011]
• The pipe is then deformed to define the required number of corrugations having the determined height and width. After forming the corrugations, the pipe is bent through the selected degree of the bend. As a result of the formation of the corrugations and the bending of the pipe, the centerline radius to outside diameter ratio is 1:1 or less. Further, the outermost wall defines a substantially smooth surface. The thickness of the wall remains substantially unchanged. Further, the inside diameter of the pipe remains substantially unreduced throughout the bend.[0012]
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
• The above mentioned features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which: [0013]
• FIG. 1 is a cross-sectional view of a pipe section bent at a ninety-degree (90°) angle using a prior art method; [0014]
• FIG. 2 is a perspective illustration of a pipe bent using the method for bending a rigid pipe of the present invention; [0015]
• FIG. 3 is a cross-sectional view of the pipe of FIG. 2 after initiation and before completion of the method of the present invention; [0016]
• FIG. 4 illustrates, in cross-section, the pipe of FIG. 2 bent using the method of the present invention; and [0017]
• FIG. 5 is a plan view of the pipe of FIG. 2 showing, in phantom, a flexible hose being mounted thereon. [0018]
DETAILED DESCRIPTION OF THE INVENTION
• A pipe bent using the method for bending a rigid pipe incorporating various features of the present invention is illustrated generally at [0019] 10 in the figures. The method of the present invention is designed for bending a rigid pipe to a centerline radius r_CL less than or equal to the outside diameter d_o of the pipe 10, to define a centerline radius to outside diameter ratio r_Cl:d_o of 1:1 or less. Moreover, in the preferred embodiment the method is designed to accomplish such a bend whereby the wall thickness of the pipe on the outermost portion 12 _o of the wall of the pipe 10 is substantially maintained, as is the inside diameter d_i throughout the bend of the pipe 10.
• FIG. 2 illustrates a perspective view of a pipe bent using the method of the present invention. After the [0020] pipe 10 has been bent, the outermost portion 12 _o of the wall of the pipe 10 defines an arc length l_o. The outermost portion 12 _o of the wall also defines a substantially smooth surface.
• As better illustrated in FIG. 3, the bend is accomplished by defining a number of corrugations. Each corrugation defines a height, h, and a width, w. The height h, width w, the arc length l[0021] _o, and the degree of the bend Θ_bend are determining factors for the number of corrugations required to accomplish the bend, while maintaining the integrity of the wall thickness t and inside diameter d_i of the pipe 10. Specifically, for a greater degree of bend Θ_bend, with all other factors remaining constant, a greater number of corrugations are required. On the other hand, with an increased height h or width w, the number of corrugations is reduced.
• After the corrugations are formed, the two ends of the [0022] pipe 10 are biased toward each other until the desired degree of bend Θ_bend has been accomplished. As illustrated in FIG. 4, once the bend has been accomplished, the outermost portion 12 _o of the wall defines a substantially constant thickness t showing a relatively small reduction as compared to the nominal thickness t_o. In one test performed on a pipe 10 bent using the method of the present invention, the values for the wall thickness t_0-5 were measured as follows:

  		wall thickness
  	location	(inches)

  	t0 (nominal)	0.065
  	t1	0.065
  	t2	0.057
  	t3	0.053
  	t4	0.052
  	t5	0.063

• In this embodiment, the bend of the [0023] pipe 10 defines a centerline radius r_CL of 1.75 inches for an outside pipe diameter d_o of 2.5 inches. The r_CL:d_o ratio is thus 1.75:2.5, or 0.7:1.
• As illustrated in FIG. 5, one embodiment of the [0024] pipe 10 bent using the method of the present invention defines a raised portion, or stop 14, at either end of the bend in order to define a stop 14 for a flexible hose 16 mounted thereon. In a conventional manner, the end of the pipe 10 is inserted into the end of the flexible hose 16 until the end of the hose 16 5 reaches the stop 14. A band clamp 18 is mounted over the hose 16 to accomplish securement of the hose 16 on the pipe 10. For pipes 10 defining the bend at a location away from the end thereof, the stop 14 may be omitted if desired.
• The pipe bend as described is accomplished by first determining the desired degree of bend Θ[0025] _bemd and the desired centerline radius r_CL. The outside diameter d_o and nominal wall thickness t₀ of the pipe 10 are also determined. Using this data, the arc length l_o of the outermost portion 12 _o of the pipe 10 is determined. Specifically, the arc length l_o is defined as: $I_o=2\Pi \left[r_{\mathrm{CL}}+\left(\frac{d_o}{2}\right)\right]·\frac{{\Theta }_{\mathrm{bend}}}{360}$

  
• where Θ[0026] _bend is the degree of the bend of the pipe 10. The height h and width w of each corrugation is then selected in order to determine the length l_c of the outer surface of each corrugation. The arc length l_o is then divided by the corrugation length l_c to determine the number of corrugations required to accomplish the desired bend.
• The [0027] pipe 10 is then deformed to define the required number of corrugations having the determined height h and width w, as illustrated in FIG. 3. After forming the corrugations, the pipe 10 is bent through the selected degree of the bend Θ_bend, as illustrated in FIG. 4. As a result of the formation of the corrugations and the bending of the pipe 10, the r_CL:d_o ratio is 1:1 or less. Further, the outermost wall 12 _o defines a substantially smooth surface. The thickness t of the wall remains substantially unchanged as shown above. Further, the inside diameter d_i of the pipe 10 remains substantially unreduced throughout the bend.
• It will be understood that the method steps may be altered to accomplish substantially the same results. For example, the number of corrugations may be selected, with the height h and width w of each corrugation being determined from this number based on the arc length l[0028] _o and the degree of bend Θ_bend. Other variations of the preferred method are equally effective.
• From the foregoing description, it will be recognized by those skilled in the art that a method for bending a rigid pipe offering advantages over the prior art has been provided. Specifically, the method is designed for bending a rigid pipe to a centerline radius less than or equal to the outside diameter of the pipe, to define a centerline radius to outside diameter ratio of 1:1 or less. Moreover, the method is designed to accomplish such a bend whereby the wall thickness of the pipe on the outermost portion of the wall of the pipe is substantially maintained, as is the inside diameter throughout the bend of the pipe. [0029]
• While a preferred embodiment has been shown and described, it will be understood that it is not intended to limit the disclosure, but rather it is intended to cover all modifications and alternate methods falling within the spirit and the scope of the invention as defined in the appended claims. [0030]

Claims (4)

Having thus described the aforementioned invention, I claim:

1. A method for bending a rigid pipe, said method comprising the steps of:

a) determining a degree of bend;

b) determining a centerline radius;

c) determining an arc length of an outermost portion of said pipe;

d) selecting a corrugation height and width;

e) determining a length of said corrugation;

f) determining a required number of corrugations;

g) deforming said pipe to define said required number of corrugations having said height and width;

h) bending said pipe through said degree of bend, whereby a ratio f said centerline radius and an outside diameter of said pipe is no greater than 1:1, whereby a thickness of the wall of said pipe remains substantially unreduced, and whereby an inside diameter of said pipe remains substantially unreduced.

2. The method of claim 1 wherein said arc length is determined as:

$I_o=2\Pi \left[r_{\mathrm{CL}}+\left(\frac{d_o}{2}\right)\right]·\frac{{\Theta }_{\mathrm{bend}}}{360},$

where l_o is said arc length, r_CL is said centerline radius, and wherein Θ_bend is said degree of bend.

3. A method for bending a rigid pipe, said method comprising the steps of:

a) determining a degree of bend;

b) determining a centerline radius;

c) determining an arc length of an outermost portion of said pipe;

d) selecting a number of corrugations to be formed in said pipe;

e) determining a length of said corrugation;

f) determining a corrugation height and width;

g) deforming said pipe to define said required number of corrugations having said height and width;

h) bending said pipe through said degree of bend, whereby a ratio f said centerline radius and an outside diameter of said pipe is no greater than 1:1, whereby a thickness of the wall of said pipe remains substantially unreduced, and whereby an inside diameter of said pipe remains substantially unreduced.

4. The method of claim 3 wherein said arc length is determined as:

$I_o=2\Pi \left[r_{\mathrm{CL}}+\left(\frac{d_o}{2}\right)\right]·\frac{{\Theta }_{\mathrm{bend}}}{360},$

where l_o is said arc length, r_CL is said centerline radius, and wherein Θ_bend is said degree of bend.

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