US20140360002A1 - Method of forming pipe end structure - Google Patents
Method of forming pipe end structure Download PDFInfo
- Publication number
- US20140360002A1 US20140360002A1 US14/146,813 US201414146813A US2014360002A1 US 20140360002 A1 US20140360002 A1 US 20140360002A1 US 201414146813 A US201414146813 A US 201414146813A US 2014360002 A1 US2014360002 A1 US 2014360002A1
- Authority
- US
- United States
- Prior art keywords
- pipe blank
- pipe
- fitting
- blank
- edge
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D39/00—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders
- B21D39/04—Application of procedures in order to connect objects or parts, e.g. coating with sheet metal otherwise than by plating; Tube expanders of tubes with tubes; of tubes with rods
- B21D39/046—Connecting tubes to tube-like fittings
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
- B21K25/00—Uniting components to form integral members, e.g. turbine wheels and shafts, caulks with inserts, with or without shaping of the components
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T29/00—Metal working
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49826—Assembling or joining
- Y10T29/49908—Joining by deforming
Definitions
- the present disclosure relates to a method of forming a pipe end structure.
- a metal pipe is used as a hydraulic passage in a hydraulic drive system for driving a fork of a forklift, because the metal pipe has a sufficient rigidity to withstand high-pressure fluid (oil pressure).
- a metal connector joint
- a screw having a helical thread an external thread
- the connector and the metal pipe are connected at their end portions by known welding technologies such as an arc welding, a gas welding, and a brazing.
- U.S. Pat. No. 5,727,303 describes a metal pipe (tube) for an orifice.
- a tubular connector (a first fitting) having threads on its outer surface is fitted over an end portion of the metal pipe.
- a front end of the metal pipe which is on the front side of the connector, is expanded outwardly so as to be in close contact with a front opening edge of the connector.
- a conical extension on an anvil is inserted into an internal bore of the metal pipe to expand the front end portion of the metal pipe.
- the metal pipe is also expanded at a position adjacent to a rear end of the connector so as to be in close contact with a rear opening edge of the connector.
- the opening edge at the rear end has a recess extending around the metal pipe.
- a portion of the metal pipe is expanded into the recess.
- the metal pipe over which the connector is fitted at its end portion is vertically compressed (in a longitudinal direction of the metal pipe) to expand its end portion into the recess.
- a method of forming a pipe end structure includes providing a pipe assembly including a metal pipe blank, a ridge, and a tubular fitting, and pressing an inner surface of the pipe blank outwardly.
- the pipe blank has a through hole extending from one end to another end along an axial direction thereof.
- the ridge protrudes outward from an outer surface of the pipe blank.
- the fitting includes a threaded portion having a thread on an outer surface thereof.
- the fitting has a first edge and a second edge and is fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank.
- An inner surface of the pipe blank is pressed outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion being in contact with the second edge of the fitting.
- FIG. 1 is a side view of a tube end structure according to an embodiment.
- FIG. 2 is a front view of the tube end structure.
- FIG. 3 is a cross-sectional view of the tube end structure taken along a line A-A in FIG. 2 .
- FIG. 4 is a perspective view of a fitting.
- FIG. 5 is a side view of a pipe blank in which a front part thereof is illustrated in a cross section.
- FIG. 6 is a schematic view of a fixture, the pipe blank held by the fixture, and a pressing machine in a standby state.
- FIG. 7 is a schematic view illustrating a state in which a front end surface of a holder is in contact with a front end surface of the fixture.
- FIG. 8 is a schematic view illustrating a state in which a front end portion of the pipe blank is pressed and plastically deformed by the punch.
- FIG. 9 is a schematic view illustrating a state in which the front end portion of the pipe blank is further pressed and plastically deformed by the punch.
- FIG. 10 is a view illustrating a general configuration of a locking portion formation apparatus.
- FIG. 11 is a cross-sectional view of a part including the holder and a diameter expander of the locking portion formation apparatus.
- FIG. 12 is a top plan view of the diameter expander.
- FIG. 13 is a cross-sectional view illustrating a state in which the pipe blank, over which the fitting is fitted, is held by the holder.
- FIG. 14 is a cross-sectional view illustrating a locking portion formation step of a method of forming the pipe end structure according to an embodiment.
- FIG. 15 is a side view of a press-fit bar.
- FIG. 16 is a side view of a press-fit bar used in a method of forming a pipe end structure in an embodiment.
- FIG. 17 is a front view of the press fit bar illustrated in FIG. 16 .
- the end portion of the metal pipe and the connector having threads may be welded to be connected with each other.
- droplets of a welding material are likely to be attached to the threads during the welding.
- the droplets may lower the quality of a product that includes the metal pipe and the connector. This may lead a big problem. Specifically, this may deteriorate the quality of the threads, which may result in oil leakage.
- the welding between the end portion of the pipe and the connector is difficult for not only for an inexperienced worker, but also for a skilled worker. The welding lowers work efficiency.
- a technology for connecting the end portion of the pipe and the connector without welding is expected.
- the metal pipe over which the connector having a tubular shape is fitted may be compressed in a longitudinal direction of the metal pipe to expand the metal pipe as described in U.S. Pat. No. 5,727,303.
- the connector which may be referred to as a fitting, is easily separated from the metal pipe.
- the metal pipe may be buckled at a position where the connector is not attached when the metal pipe is compressed in the longitudinal direction to expand the end portion thereof. Such problems occur due to the compression of the metal pipe.
- An object of the technology described herein is to provide a method of forming a pipe end structure in which a fitting having a tubular shape is properly fixed to a predetermined position of a metal pipe blank without welding.
- the technology described herein provides a method of forming a pipe end structure that includes providing a pipe assembly including a metal pipe blank, a ridge, and a tubular fitting, and pressing an inner surface of the pipe blank.
- the metal pipe blank has a through hole extending from one end to another end along an axial direction thereof.
- the ridge protrudes outward from an outer surface of the pipe blank.
- the tubular fitting has a thread on an outer surface thereof.
- the fitting has a first edge and a second edge and is fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank.
- An inner surface of the pipe blank is pressed outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion that is in contact with the second edge of the fitting.
- the step of pressing the inner surface may include inserting a diameter expander configured to expand in a radial direction of the pipe blank into the through hole of the pipe blank and expanding the diameter expander inserted in the pipe blank in the radial direction of the pipe blank to press the inner surface of the pipe blank outwardly at the position adjacent to the second edge of the fitting.
- the diameter expander may include a plurality of elastic plates arranged in a tubular shape with a predetermined distance therebetween.
- Each of the elastic plates may be a fixed end at one end thereof and a free end at another end thereof, whereby the elastic plates are expandable in a radial direction of the pipe blank.
- the inner surface of the pipe blank may be pressed outwardly by the other ends of the elastic plates.
- the step of pressing the inner surface may include fixing the pipe blank of the pipe assembly to a fixture at a position adjacent to the rear edge of the fitting, and inserting a press fit bar into the though hole of the pipe blank from the one end toward the other end of the pipe blank.
- the press fit bar may have an elongated shape and include a press fit portion having an outer diameter larger than an inner diameter of the pipe blank, whereby the inner surface of the pipe blank is pressed outwardly such that the pipe blank has the locking portion.
- the press fit portion may have a cylindrical shape.
- the press fit portion may have a polygonal prism shape.
- the step of providing the pipe assembly may include compressing an end portion of the pipe blank in the axial direction of the pipe blank to increase a thickness of the end portion of the pipe blank in a radial direction, whereby the ridge protruding from the outer surface of the pipe blank is formed at the end portion of the pipe blank and fitting the fitting over the pipe blank so as to be in contact with the ridge at the first edge of the fitting.
- the step of providing the pipe assembly may include chamfering an one portion of the pipe blank to have an inclined surface that extends from the inner surface of the pipe blank outwardly at an angle.
- the step of expanding the diameter expander may include inserting an diameter adjuster having a cylindrical shape into a space defined by the elastic plates of the diameter expander and moving the diameter expander in the axial direction of the tube blank toward the one end of the tube blank.
- the diameter adjuster may have an outer diameter larger than that of the diameter expander.
- Each of the elastic plates may have a projection at the other end thereof.
- the projection may protrude radially outwardly from the outer surface of each elastic plate and may be configured to press the inner surface of the pipe blank when the diameter expander expands.
- the step of fixing the pipe assembly to the fixture may include positioning the pipe assembly to have a space between the second edge of the fitting and the fixture, whereby the part of the pipe blank protrudes at a position corresponding to the space to form the locking portion.
- the step of inserting the press fit bar into the though hole of the pipe blank may include moving the press fit bar inserted in the through hole of the pipe blank until a tip end of the press fit portion reaches a position corresponding to the second edge of the fitting.
- the fitting having a tubular shape is properly fixed to a predetermined position of the metal pipe blank without welding.
- FIGS. 1 to 13 A side view, a front view, and a cross-sectional view of a pipe end structure 1 according to a first embodiment are illustrated in FIG. 1 , FIG. 2 , and FIG. 3 , respectively.
- a right side and a left side in FIG. 1 correspond to a front side and a rear side of the pipe end structure 1 , respectively.
- the pipe end structure 1 includes a pipe 2 having an elongated shape and a fitting 3 having a threaded portion.
- the fitting 3 fits over a front end portion of the pipe 2 .
- the pipe end structure 1 is a component of a hydraulic passage for a fork of a forklift.
- the pipe end structure 1 is configured to be connected to another pipe end structure (not illustrated) via the fitting 3 .
- the pipe 2 has a tubular shape elongated in substantially one direction.
- the pipe 2 includes a circumferential wall 21 having an elongated tubular shape, a front ridge 22 located on a front end of the circumferential wall 21 , and a fluid passage 23 extending through the pipe 2 along its longitudinal direction.
- the circumferential wall 21 has a tubular shape extending in a front-to-rear direction (an axial direction) and is formed of a metal pipe blank, which will be described later.
- An inner surface 21 b of the circumferential wall 21 defines the fluid passage 23 . As illustrated in FIG.
- the front ridge 22 of the pipe 2 on the front side of the circumferential wall 21 protrudes radially outwardly from an outer surface of the circumferential wall 21 and extends around the circumferential wall 21 .
- the front ridge 22 has an outer diameter larger than that of the circumferential wall 21 located on a rear side thereof.
- the front ridge 22 has a surface that is machined to have a shape like a single thread, for example. As illustrated in FIG. 2 , a front surface 22 a of the front ridge 22 (i.e., a front surface of the pipe 2 ) has a circular ring shape.
- the fluid passage 23 defined by the inner surface of the circumferential wall 21 is a passage for an operating oil.
- the fitting 3 is fitted over the front end portion of the pipe 2 so as to be in contact with a rear edge of the front ridge 22 .
- the pipe 2 includes a locking portion 24 that protrudes radially outwardly from the outer surface of the circumferential wall 21 so as to be in contact with the rear edge of the fitting 3 .
- the pipe 2 is formed by processing the pipe blank by a plastic working and cutting. This step will be described later. An inner surface of the circumferential wall of the pipe blank (the circumferential wall 21 of the pipe 2 ) is pressed outwardly to plastically deform a part of the pipe blank. The plastically deformed part of the pipe blank becomes the locking portion 24 that has a larger diameter.
- FIG. 4 A perspective view of the fitting 3 is illustrated in FIG. 4 .
- the fitting 3 has a tubular shape elongated in substantially one direction.
- the fitting 3 having a tubular shape has a shorter length (a length along an axis L) than the pipe 2 having a tubular shape.
- the fitting 3 has an inner diameter that is larger than the outer diameter of the circumferential wall 21 of the pipe 2 .
- the fitting 3 includes a threaded portion 31 at its front portion.
- the threaded portion 31 includes helical threads 31 a on an outer surface 3 a of the fitting 3 .
- the fitting 3 includes a flange 32 at its rear portion. The flange 32 protrudes radially outwardly from the outer surface 3 a of the fitting 3 .
- the flange 32 protrudes more from the outer surface 3 a of the fitting 3 than the threaded portion 31 (the thread 31 a ).
- the flange 32 has a larger outer diameter than that of the threaded portion 31 .
- the outer surface 3 a of the fitting 3 includes a cylindrical surface portion 33 that has an outer diameter smaller than those of the threaded portion 31 and the flange 32 .
- the fitting 3 includes a through hole 34 extending through the fitting 3 in the front-to-rear direction.
- An inner surface 3 b of the fitting 3 defines the through hole 34 .
- the fitting 3 has a front edge (first edge) 35 and a rear edge (second edge) 36 .
- the front edge 35 has a front opening edge 35 a extending around a front edge of the thorough hole 34 .
- the rear edge 36 has a rear opening edge 36 a extending around a rear edge of the thorough hole 34 .
- a front portion of the circumferential wall 21 is inserted in the through hole 34 of the fitting 3 , and thus the fitting 3 is fixed to the pipe 2 . In this configuration, the fitting 3 fits over the circumferential wall 21 of the pipe 2 (a pipe blank, which will be described later).
- the inner surface 3 b of the fitting 3 which is fixed to the pipe 2 , is in close contact with the outer surface 21 a of the circumferential wall 21 .
- the front ridge 22 which is located in front of the fitting 3 , is in close contact with the front opening edge 35 a of the fitting 3 .
- the locking portion 24 which is located behind the fitting 3 , is in close contact with the rear opening edge 36 a of the fitting 3 .
- the fitting 3 is sandwiched between the front ridge 22 and the locking portion 24 in the front-to-rear direction.
- the above-described pipe end structure 1 is formed by a method described below.
- Step 1 a Step of Forming the Front Ridge
- a pipe blank 20 that will become the pipe 2 is pressed at its front end portion to have the front ridge 22 at the front portion thereof.
- FIG. 5 illustrates a front portion of the pipe blank 20 in the cross section.
- a metal pipe Carbon Steel Precision Tubes for Hydraulic Line Service
- the pipe blank 20 has a tubular shape extending straight.
- the pipe blank 20 has a front surface 20 a that is a flat circular ring surface.
- the pipe blank 20 has an inclined surface 20 b at its inner front end.
- the inner front end of the pipe blank 20 is chamfered to have the inclined surface 20 b that extends from the inner surface of the pipe blank 20 outwardly at an angle.
- the pipe blank 20 has an outer surface 20 c having a cylindrical surface.
- the pipe blank 20 includes a through hole 230 extending through the pipe blank 20 in the front-to-rear direction. The through hole 230 will be the fluid passage 23 of the pipe 2 .
- the pipe blank 20 has a circumferential wall 221 that will be the circumferential wall 21 of the pipe 2 .
- the fixture 4 is a device for holding the pipe blank 20 (i.e., a clamping device for pipe) and has a cuboidal shape.
- the fixture 4 includes a first fixing member 41 A and a second fixing member 41 B.
- the first fixing member 41 A is positioned above the second fixing member 41 B.
- the pipe blank 20 is sandwiched and held between the first fixing member 41 A and the second fixing member 41 B.
- the fixture 4 has a space 43 extending in the front-to-rear direction between the first fixing member 41 A and the second fixing member 41 B.
- the pipe blank 20 is fitted in the space 43 .
- the pipe blank 20 is held by the fixture 4 with a front end portion 20 d thereof sticking out of a front end surface 41 a of the fixture 4 .
- the end surface 41 a of the fixture 4 has an opening edge 41 b at a position corresponding to an end of the space 43 .
- the front end portion 20 d of the pipe blank 20 sticks out of the opening edge 41 b.
- the front end portion 20 d of the pipe blank 20 sticks out of the end surface 41 a of the fixture 43 by a predetermined length (a predetermined length M 1 ) that is required for the formation of the front ridge 22 .
- the pressing machine 5 is arranged in front of the pipe blank 20 held by the fixture 4 .
- the pressing machine 5 is reciprocatory movable in the front-to-rear direction along an axial line L by a known mechanism.
- the pressing machine 5 includes a punch 51 and a holder 55 .
- the punch 51 is configured to enter into the through hole 230 of the pipe blank 20 and press a front end of the pipe blank 20 .
- the holder 55 surrounds the punch 51 and has a surface to be in contact with the end surface 41 a of the fixture 4 .
- a front side and a rear side of the pressing machine 5 correspond to the left side and the right side in FIG. 6 , respectively.
- the punch 51 is provided on a front end of a slide shaft, which is not illustrated. As illustrated in FIG. 6 , the punch 51 includes an insertion portion 52 , a pressing portion 53 , and a body 54 .
- the insertion portion 52 has a shaft like shape with a rounded end.
- the pressing portion 53 extends from a rear edge (a base side) of the insertion portion 52 .
- the body 54 has a cylindrical shape and extends from a rear edge of the pressing portion 53 .
- the insertion portion 52 and the pressing member 53 are located on an extension line of a center line (an axial line) of the body 54 .
- the insertion portion 52 has a diameter slightly smaller than the inner diameter of the pipe blank 20 .
- the pressing portion 53 which extends from the rear edge (the base side) of the insertion portion 52 , has a concave shape opening toward the front side as a whole.
- the pressing portion 53 has a larger diameter than the insertion portion 52 .
- the pressing portion 53 is integrally formed with the insertion portion 52 . More specifically described, the pressing portion 53 includes a central pressing portion 53 a, a front-end pressing portion 53 b, and an outer pressing portion 53 c.
- the central pressing portion 53 a is configured to press the inner surface of the front end portion 20 d of the pipe blank 20 so as to expand the front end portion 20 d of the pipe blank 20 outwardly.
- the central pressing portion 53 a extends from a rear edge of the insertion portion 52 toward the rear side and has a shape like a truncated cone (a conical shape) with a sloped surface.
- the central pressing portion 53 a has an outer diameter gradually increasing from the front side toward the rear side.
- the front-end pressing portion 53 b is configured to press the front end surface 20 a of the pipe blank 20 from the front side toward the rear side of the pipe blank 20 , for example.
- the front-end pressing portion 53 b extends outwardly from an outer circumferential edge of a rear edge of the central pressing portion 53 a and has a circular ring surface surrounding the central pressing portion 53 a.
- the outer pressing portion 53 c is configured to press the outer surface of the front end portion 20 d of the pipe blank 20 inwardly.
- the outer pressing portion 53 c is located outward of the front-end pressing portion 53 b and has a slope surface that is a circular ring surface having an inner diameter gradually increasing from the rear side toward the front side.
- the holder 55 is moved along the axial line L together with the punch 51 until the holder 55 strikes the front end surface 41 a of the fixture 4 .
- the holder 55 has a tubular shape and surrounds the punch 51 .
- the holder 55 has a through hole extending therethrough in the front-to-rear direction (along the axial line L).
- the punch 51 is arranged in the through hole of the holder 55 .
- the punch 51 is configured to be moved forward along an inner surface 55 b of the holder 55 , which defines the through hole, beyond the holder 55 that is in contact with the fixture 4 .
- the holder 55 has a front end surface 55 a that is in contact with the front end surface 41 of the fixture 4 .
- the inner surface 55 b of the holder 55 and the outer surface of the punch 51 define a substantially tubular space 56 therebetween (see FIG. 7 ).
- the pressing machine 5 is coaxially arranged with the pipe blank 20 .
- the axial line of the punch 51 or the axial line of the holder 55 extends on the same line as the axial line L of the pipe blank 20 .
- the punch 51 is arranged in the holder 55 with the front end portion of the insertion portion 52 sticking out of the front end surface 55 a of the holder 55 .
- the space 56 of the holder 55 has a size that can house the front end portion 20 d of the pipe blank 20 .
- the punch 51 and the holder 55 are metal molded products that has high abrasion resistance.
- An operation of the pressing machine 5 in a standby state as illustrated in FIG. 7 is started when the slide shaft (not illustrated) starts moving.
- the punch 51 of the pressing machine 5 starts moving toward the pipe blank 20 along with the slide shaft.
- the holder 55 moves together with the punch 51 at the same speed with the moving speed of the punch 51 .
- the punch 51 continues to move toward the pipe blank 20 and the front end portion of the insertion portion 52 enters the through hole 230 of the pipe blank 20 .
- the front end surface 55 a of the holder 55 strikes the front end surface 41 a of the fixture 4 .
- the front end surface 55 a of the holder 55 that is in contact with the front end surface 41 a of the fixture 4 is schematically illustrated in FIG. 7 .
- the punch 51 does not press the front end portion 20 d of the pipe blank 20 at a moment when the front end surface 55 a of the holder 55 strikes the front end surface 41 a of the fixture 4 .
- the holder 55 remains stationary while the front end surface 55 a thereof is in contact with the front end surface 41 a of the fixture 4 .
- the punch 51 housed in the holder 55 moves further inside the pipe blank 20 as the slide shaft moves.
- the body 54 of the punch 51 moves forward along the inner surface 55 b of the holder 55 .
- the pressing part 53 of the punch 51 compresses the front end portion 20 d of the pipe blank 20 .
- the front end portion 20 d of the pipe blank 20 which is plastically deformed by the punch 51 is schematically illustrated in FIG. 8 .
- the insertion portion 52 and the pressing portion 53 of the punch 51 enter the pipe blank 20 by a predetermined distance that is properly determined depending on an intended shape of the pipe end portion.
- the moving distance of the punch 51 inside the pipe blank 20 can be properly controlled by setting a sliding distance (stroke) of the slide shaft that moves the punch 51 .
- the pressing machine 5 moves back along the axial line L and returns to the standby state as illustrated in FIG. 6 .
- the step of compressing the front end portion 20 d of the pipe blank 20 by the punch 51 is repeatedly performed multiple times.
- the moving (inserting) distance of the punch 51 inside the pipe blank 20 is controlled for each step. Specifically, the moving (inserting) distance of the pipe 51 inside the pipe blank 20 is set to be longer (deeper) with each step.
- the shapes of the insertion portion 52 and the pressing portion 53 of the punch 51 may be varied for each step. Specifically, the insertion portion 52 and the pressing portion 53 (the central pressing portion 53 a ) may have a larger diameter with each step.
- the front end portion 20 d of the pipe blank 20 which is plastically deformed by the punch 51 is schematically illustrated in FIG. 9 .
- the front end portion 20 d of the pipe blank 20 is kept pressed until the front end portion 20 d has a length M 2 that is half the predetermined length M 1 (the length along the axial line L).
- the front end portion 20 d of the pipe blank 20 is plastically deformed in a space defined by an outer surface of the punch 51 (the insertion portion 52 and the pressing portion 53 ), the inner surface 55 b of the holder 55 , and the front end surface 41 a of the fixture 4 .
- the front end portion 20 d of the pipe blank 20 is pressed to have a larger thickness by the pressing machine 5 , and thus the outer circumferential edge of the pipe blank 20 at the front end portion 20 d protrudes outwardly in a ring shape. As a result, the front end portion 20 d of the pipe blank 20 will become the front ridge 22 of the pipe 2 .
- the front end portion 20 d of the pipe blank 20 may be shaped by grinding as necessary.
- Step 2 a Step of Fitting the Fitting
- the fitting 3 is fitted over the pipe blank 20 that has the front ridge 22 .
- the fitting 3 is a separate member from the pipe blank 20 .
- the fitting 3 may be obtained by cutting a substantially hexagonal tubular member.
- the tubular member has a hole extending therethrough which will be the through hole 34 of the fitting 3 .
- a metal nut having an outer diameter (a maximum diameter) of 21.9 mm, an inner diameter of 9.9 mm, and a length of 20.0 mm is used as the tubular member.
- the rear end of the pipe blank 20 is inserted from an inner edge of a front opening edge 35 a of the fitting 3 into the through hole 34 of the fitting 3 to fit the fitting 3 over the pipe blank 20 .
- a position of the fitting 3 on the pipe blank 20 is adjusted so as to be in contact with the front ridge 22 located at the front end of the pipe blank 20 at its front edge 35 (the front opening edge 35 a ). In this way, the fitting 3 is fitted over the pipe blank 20 .
- the fitting 3 is movable on the pipe blank 20 .
- the fitting 3 is slidable on the pipe blank 20 in the front-to-rear direction and in a circumferential direction along the outer surface of the pipe blank 20 .
- Such an assembly of the pipe blank 20 and the fitting 3 may be referred to as a pipe assembly 100 .
- Step 3 a Step of Forming a Locking Portion Formation
- FIG. 10 A schematic configuration of a locking portion formation apparatus 6 is illustrated in FIG. 10 .
- the locking portion formation apparatus 6 is configured to form the locking portion 24 by expanding the pipe blank 20 of the pipe assembly 100 .
- the locking portion formation apparatus 6 includes a base 61 , supports 62 , a table 63 , a holder 64 , a diameter expander 65 , an adjuster 66 , a drive device 67 , a swing member 68 , and a link connector 69 .
- the base 61 is a base of the locking portion formation apparatus 6 , which is placed on a floor, for example.
- the base 61 is a metal flat plate, for example.
- the supports 62 are provided on the base 61 and support the table 63 above the base 61 . As illustrated in FIG. 10 , in this embodiment, two supports 62 are provided on the base 61 . One of the supports 62 is provided at one end of the base 61 which is on the left side in FIG. 10 . The other one of the supports 62 is provided at another end portion of the base 61 which is on the right side in FIG. 10 .
- the supports 62 each may be a metal flat plate.
- the supports 62 are provided on the base 61 so as to extend in an up-to-down direction (a vertical direction). A lower end and an upper end of each support 62 are fixed to the base 61 and the table 63 , respectively.
- the table 63 is supported by the supports 62 from below.
- the table 63 is a metal plate and extends between the supports 62 .
- the holder 64 is configured to hold a member to be processed by the locking portion formation apparatus 6 (the pipe blank 20 of the pipe assembly 100 ).
- the holder 64 is fixed on the table 63 .
- the holder 64 has a shape like a container that opens upward. At a middle of the holder 64 , the diameter expander 65 that is configured to be inserted into the through hole 230 of the pipe blank 20 is arranged.
- the holder 64 includes a mount 64 a, a wall 64 b, and a securing portion 64 c.
- a member to be processed is mounted on the mount 64 a.
- the wall 64 b extends upward from an outer end of the mount 64 a and surrounds the member to be processed on the mount 64 a.
- the securing portion 64 c is provided in the middle of the mount 64 c and the diameter expander 65 is secured thereto.
- the mount 64 a has a substantially cylindrical shape and is fitted in a concave attachment portion of the table 63 as illustrated in FIG. 11 .
- An upper surface of the mount 64 a is a flat surface on which the front end of the pipe blank 20 of the pipe assembly 100 is arranged.
- the wall 64 b is high enough to surround the threaded portion 31 of the fitting 3 of the pipe assembly 100 .
- the securing portion 64 c has a surface defining a through hole extending in the mount 64 a in an up-and-down direction (the vertical direction).
- a lower end portion of the diameter expander 65 having the elongated shape is fitted in the through hole defined by the securing portion 64 c so that the diameter expander 65 is secured by the securing portion 64 c.
- the diameter expander 65 is configured to press the inner surface of the pipe blank 20 of the pipe assembly 100 outwardly to form the locking portion 24 in the pipe blank 20 .
- the diameter expander 65 has an elongated cylindrical shape and is made of metal.
- the diameter expander 65 includes a base 65 a secured by the securing portion 64 c and a plurality of plates 65 b extending upward from the base 65 a.
- the base 65 a has a cylindrical shape and constitutes a lower end portion of the diameter expander 65 which is arranged in the vertical position.
- the diameter expander 65 is illustrated in the top plan view in FIG. 12 .
- the diameter expander 65 of this embodiment includes four plates 65 b.
- Each of the plates 65 b is an elastic plate (plate spring).
- the plates 65 b each have an elongated shape and have a circular arc cross section taken along perpendicular to the longitudinal direction thereof.
- the plates 65 b are arranged in a tubular shape (a ring shape) with a predetermined distance (a space S 1 ) therebetween.
- the plates 65 b adjacent to each other provide a slit therebetween.
- the slit corresponds to the space S 1 .
- the slit extends along a long side of the plate 65 b from one end thereof toward the other end thereof.
- the slit extends to a position near the base 65 a of the diameter expander 65 .
- Each plate 65 b has a projection 65 b 1 at a front end thereof.
- the projection 65 b 1 protrudes radially outwardly from the outer surface of the plate 65 b.
- four projections 65 b 1 are arranged in a circular shape with a space therebetween.
- the projections 65 b 1 are configured to press the inner surface of the circumferential wall 221 of the pipe blank 20 outwardly. Pressing the inner surface of the circumferential wall 221 by the projections 65 b 1 forms the locking portion 24 of the pipe blank 20 .
- the diameter expander 65 includes a through hole 65 c extending in the up-and-down direction (the vertical direction, the axial direction of the diameter expander 65 ).
- the diameter expander 65 has the outer diameter smaller than the inner diameter of the pipe blank 20 .
- Each of the plates 65 b of the diameter expander 65 is arranged in a vertical position as illustrated in FIG. 11 , for example.
- the table 63 includes a through hole 63 b extending through the table 63 in the up-and-down direction (the vertical direction) as illustrated in FIG. 11 .
- the through hole 63 b of the table 63 communicates with the through hole 65 c of the diameter expander 65 .
- the adjuster 66 that is configured to adjust the diameter of the diameter expander 65 is placed on the front end portion of the diameter expander 65 .
- the adjuster 66 has a cylindrical shape (a nut like shape) as a whole and an outer diameter larger than that of the diameter expander.
- the adjuster 66 includes a lower portion 66 a that has a conical shape with a diameter decreasing toward the lower side.
- the lower portion 66 a of the adjuster 66 is in contact with the front end portion of the diameter expander 65 .
- a link connector 69 having a bar-like shape is arranged to extend through the through hole 65 c.
- the link connector 69 is formed of an elongated metal bolt in this embodiment.
- the adjuster 66 is fixed to an upper end portion 69 a of the link connector 69 .
- the link connector 69 is arranged inside the diameter expander 65 (in the through hole 65 c ) so as to extend in the up-and-down direction.
- the link connector 69 includes a lower end portion 69 b that is attached to a swing member 68 configured to swing on a shaft 70 in the up-and-down direction.
- the swing member 68 has a shape elongated in the right-to-left direction (a horizontal direction).
- the swing member 68 is supported by the shaft 70 so as to be able to swing in the up-and-down direction.
- the swing member 68 is arranged between the base 61 and the table 63 .
- the locking portion formation apparatus 6 further includes a shaft bearing 71 that extends from a lower surface of the table 63 toward the base 61 .
- the shaft bearing 71 supports both ends of the shaft 70 .
- a first end portion 68 a of the swing member 68 which is located on the right side in FIG. 10 , is connected to the lower end portion 69 b of the link connector 69 .
- a second end portion 68 b of the swing member 68 which is located on the left side in FIG. 10 , is connected to a drive device 67 that is configured to move the swing member 68 in the up-and-down direction.
- the drive device 67 may be any known drive device such as a fluid pressure cylinder (for example, an air cylinder or an oil hydraulic cylinder).
- the drive device 67 is an oil hydraulic cylinder in this embodiment.
- the drive device 67 is arranged on the base 61 .
- the first end portion (the one end) 68 a of the swing member 68 moves down.
- This moves the link connector 69 which is attached to the first end portion 68 a of the swing member 68 , down.
- the lower end portion 69 b of the link connector 69 is gradually pulled down as the first end portion 68 a of the swing member 68 moves down.
- the link connector 69 connects between the first end portion 68 a of the swing member 68 and the adjuster 66 .
- the adjuster 66 moves down into the diameter expander 65 while pushing the plates 65 b of the diameter expander 65 outwardly as the link connector 69 is pulled down.
- the adjuster 66 moves down in the diameter expander 65 , the plates 65 b are pushed outwardly and the diameter expander 65 is forced to have a larger diameter at the front end portion thereof.
- the plates 65 b of the diameter expander 65 are each formed of a plate spring.
- the driving of the drive device 67 is controlled by a controller, which is not illustrated.
- the above-described locking portion formation apparatus 6 forms the locking portion 24 in the pipe blank 20 of the pipe assembly 100 .
- the step of forming the locking portion 24 in the pipe blank 20 will be described with reference to FIG. 13 .
- the pipe blank 20 of the pipe assembly 100 is held by the holder 64 .
- the diameter expander 65 to which the adjuster 66 is fitted, is inserted inside (the through hole 230 ) the pipe blank 20 from the front end thereof.
- the front end portion of the pipe blank 20 is placed on the mount 64 a such that the pipe blank 20 is arranged in a vertical position on the mount 64 a.
- the pipe blank 20 of the pipe assembly 100 is held by the holder 64 in this way.
- the projection 65 b 1 at the front end of the diameter expander 65 is positioned at a position corresponding to the rear edge 36 of the fitting 3 , which is fitted over the pipe blank 20 , or a position slightly above the rear edge 36 .
- the projection 65 b 1 is positioned slightly above the rear edge 36 of the fitting 3 .
- the rear opening edge 36 a at the rear edge 36 of the fitting 3 is inclined downward toward the inside of the fitting 3 , and thus the rear opening edge 36 a and the outer surface of the pipe blank 20 provide a recess.
- the drive device 67 of the locking portion formation apparatus 6 is driven to move down the adjuster 66 .
- the adjuster 66 pushes the inner surfaces of the plates 65 b of the diameter expander 65 , and thus the plates 65 b are pushed outwardly so that the diameter expander 65 expands in a radial direction toward the wall 221 of the pipe blanks 20 .
- the projections 65 b 1 at the front end of the diameter expander 65 press the inner surface of the wall 221 of the pipe blank 20 outwardly.
- the wall 221 of the pipe blank 20 is plastically deformed to have a larger diameter at the parts pressed by the projections 65 b 1 of the diameter expander 65 , and thus the locking portion 24 in contact with the rear edge 36 (the rear opening edge 36 a ) of the fitting 3 is formed.
- the formation of the locking portion 24 in the pipe blank 20 provides the pipe end structure 1 illustrated in FIG. 1 to FIG. 3 .
- the locking portion 24 protrudes from the outer surface of the pipe 20 (the pipe 2 ) and is in close contact with the rear edge 36 (particularly, the rear opening edge 36 a ) of the fitting 3 .
- the adjuster 66 is returned to the original position by the drive device 67 of the locking portion formation apparatus 6 .
- the diameter expander 65 contracts (the diameter of the diameter expander 65 decreases) to its original size, and thus the diameter expander 65 is allowed to be pulled out of the through hole 230 (the fluid passage 23 ).
- the diameter expander 65 is pulled out of the through hole 230 and the processed pipe blank having the locking portion 24 (the pipe end structure 1 ) is detached from the holder 64 .
- the locking portion 24 is formed at a predetermined position of the pipe blank 20 over which the fitting 3 is fitted.
- the pipe end structure 1 of this embodiment is produced. After the locking portion formation step, any step such as shaping may be performed on the pipe end structure 1 .
- the inner surface of the pipe blank 20 that will become the pipe 2 is pressed outwardly, and thus the circumferential wall 221 of the pipe blank 20 is radially expanded to form the locking portion 24 .
- the locking portion 24 is a protrusion evenly extending outwardly in a ring shape on the circumferential wall 21 of the pipe blank 20 .
- the method of forming the pipe end structure 1 of this embodiment provides the pipe end structure 1 in which the fitting 3 is hardly detached from the pipe blank 20 (the pipe 2 ).
- the fitting 3 is sandwiched between the locking portion 24 and the front ridge 22 on the pipe blank 20 (the pipe 2 ). In this configuration, the fitting 3 hardly moves in the longitudinal direction and the circumferential direction of the pipe blank 20 .
- the pipe blank 20 (the pipe 2 ) is hardly buckled.
- the fitting having a cylindrical shape is properly fixed to a predetermined position of the metal pipe blank without welding.
- the pipe 2 is a seamless pipe, and thus the fluid flowing in the pipe 2 does not leak out of the pipe 2 .
- a second embodiment will be described with reference to FIG. 14 and FIG. 15 .
- a method of forming a pipe end structure 1 A having a configuration illustrated in FIG. 14 will be described.
- the method according to this embodiment is the same as the method according to the first embodiment except for the locking portion formation step.
- a locking portion 24 A is formed in a pipe 2 A (a pipe blank 20 A) by a press fit bar 8 illustrated in FIG. 14 and FIG. 15 .
- the press fit bar 8 is pushed into a through hole 23 A of the pipe blank 20 A of the pipe assembly 100 from a front end of the pipe blank 20 A to form the locking portion 24 A.
- the press fit bar 8 is a component of a press fitting machine which is not illustrated.
- the press fitting machine further includes a member configured to move the press fit bar 8 in the front-to-rear direction.
- the press fit bar 8 includes an insertion portion 81 , a contact portion 82 extending from a rear edge of the insertion portion 81 , and a fixed shaft 83 extending from a rear edge of the contact portion 82 .
- the insertion portion 81 has a shaft like shape and is configured to be inserted into the through hole of the pipe blank 20 A.
- the contact portion 82 is configured to be in contact with a front end portion of the pipe blank 20 A when the insertion portion 81 is inserted into the through hole of the pipe blank 20 A.
- the fixed shaft 83 is fixed to another component of the press fitting machine.
- the insertion portion 81 has a cylindrical shape as a whole.
- the insertion portion 81 includes a press-fit portion 81 a at a front end side thereof.
- the press-fit portion 81 a has an outer diameter larger than remaining portions of the insertion portion 81 .
- the press-fit portion 81 a includes a front end portion 81 a 1 that has a diameter decreasing from the rear side toward the front thereof.
- the press-fit portion 81 a has an outer diameter that is larger than an inner diameter of the pipe blank 20 A without the locking portion 24 A.
- the press-fit portion 81 a is configured to press the inner surface of the circumferential wall 21 A of the pipe blank 20 A outwardly when the insertion portion 81 is inserted into the through hole of the pipe blank 20 A.
- the front end portion 81 a 1 of the press-fit portion 81 a is positioned near the rear edge 36 of the fitting 3 when the insertion portion 81 reaches the farthest point in the through hole of the pipe blank 20 A.
- the contact portion 82 has a larger diameter than the insertion portion 81 .
- the contact portion 82 has a front end surface 82 a having a circular ring shape. As described above, the front end portion 81 a 1 of the press-fit portion 81 a is positioned near the rear edge 36 of the fitting 3 when the insertion portion 81 is inserted into the through hole of the pipe blank 20 A and the front end portion of the pipe blank 20 A is in contact with the front end surface 82 a of the contact portion 82 .
- the pipe blank 20 A of the pipe assembly 100 is held by the fixture 4 (the fixture used in the front ridge formation step) at a position adjacent to the rear edge 36 of the fitting 3 .
- the pipe blank 20 A of the pipe assembly 100 is held by the fixture 4 with a small space between the front end surface 41 a of the fixture 4 and the rear edge (surface) of the fitting 3 , which is fitted over the pipe blank 20 A.
- the small space has a size required for the formation of the locking portion 24 A.
- the press-fit portion 81 a of the press fit bar 8 moves toward the rear side while pressing the inner surface of the circumferential wall 21 A of the pipe blank 20 outwardly.
- an outer surface 21 Aa of the circumferential wall 21 A is pressed against an inner wall 3 b of the fitting 3 so as to be in close contact with each other.
- the inner surface 21 Ab of the circumferential wall 21 A is plastically deformed as the press-fit portion 81 a moves in the pipe blank 20 . This forms the locking portion 24 A that is in contact with the rear edge 36 (the rear opening edge 36 a ) of the fitting 3 .
- the front end portion 81 a 1 of the press-fit portion 81 a moves in the through hole 23 A while scraping the inner surface 21 Ab of the circumferential wall 21 A.
- the scraped material of the circumferential wall 21 A of the pipe blank 20 A is gathered to a position behind the fitting 3 .
- the gathered material of the circumferential wall 21 A is in a protruded shape protruding from the outer surface 21 Aa of the pipe blank 20 A at a position between the front end surface 41 a of the fixture 4 and the rear edge (surface) 36 of the fitting 3 .
- the gathered material constitutes the locking portion 24 A.
- the insertion of the press fit bar 8 into the pipe blank 20 is performed until the locking portion 24 A is formed.
- the press fit bar 8 may be inserted once or twice or more into the pipe blank 20 to form the locking portion 24 A.
- the inner surface of the pipe blank 20 A which will become the pipe 2 A, is pressed outwardly such that the circumferential wall 21 A of the pipe blank 20 A is radially expanded to form the locking portion 24 A.
- the locking portion 24 A is a protrusion evenly extending outwardly in a ring shape on the circumferential wall 21 A of the pipe blank 20 A.
- the method of forming the pipe end structure 1 A of this embodiment provides the pipe end structure 1 A in which the fitting 3 is hardly detached from the pipe blank 20 A (the pipe 2 A). The fitting 3 is sandwiched between the locking portion 24 A and the front ridge 22 on the pipe blank 20 A (the pipe 2 A).
- the fitting 3 hardly moves in the longitudinal direction and the circumferential direction of the pipe blank 20 A.
- the pipe blank 20 A (the pipe 2 A) is hardly buckled.
- the fitting having a tubular shape is properly fixed to a predetermined position of the metal pipe blank without welding.
- the pipe 2 , 2 A included in the pipe end structure 1 , 1 A extends straight.
- the technology is not limited to this configuration.
- the pipe 2 may be bent in various curved shapes depending on the intended use of the pipe end structure (pipe routing).
- the front ridge 22 has the single thread shape.
- the technology is not limited to this configuration.
- the surface of the ridge may be a cylindrical surface.
- the shape of the front ridge 22 may be changed depending on an end structure of another pipe to which the pipe is connected.
- the rear opening edge 36 a at the rear edge 36 of the fitting 3 is inclined downward toward the inside of the fitting 3 , and thus a recess is provided between the rear opening edge 36 a and the outer surface of the pipe 20 , 20 A.
- the technology is not limited to this configuration.
- the rear opening edge 36 a of the fitting 3 may not have such an inclined part that provides a recess and may be flat.
- the pipe end structure 1 , 1 A is a component of the hydraulic passage for driving the fork of the fork lift.
- the technology is not limited to this configuration.
- the pipe end structure 1 , 1 A may be a component for any other products in some embodiments.
- the front ridge 22 has a ring-like front shape.
- the front ridge 22 may have a square tube shape, a triangular tube shape, a pentagonal tube shape, a hexagonal tube shape, or other tube shape (a ring shape) in some embodiments.
- the press fit bar 8 A has an insertion portion 81 A that has a different shape from the insertion portion 81 of the press fit bar 8 of the second embodiment.
- the press fit bar 8 of the second embodiment includes the press-fit portion 81 a that has a circular shape in a front view viewed along an axial direction of the press fit bar 8 .
- the press fit bar 8 A illustrated in FIG. 16 and FIG. 17 includes a press-fit bar 81 Aa that has a triangular shape (an example of polygonal shape) in a front view viewed along the axial direction.
- the front end portion 81 Aa 1 of the press-fit portion 81 Aa is positioned near the rear edge 36 of the fitting 3 when the insertion portion 81 is inserted in the pipe blank 20 A.
- the press fit bar 8 A having such a configuration has a smaller area that is in contact with the circumferential wall 21 A of the pipe blank 20 A than the press fit bar 8 of the second embodiment. With this configuration, the press fit bar 8 A can be easily inserted into the pipe blank 20 A of the press fit bar 8 .
- the locking portion formation step of forming the locking portion in the pipe blank 20 A may be performed by the insertion bar 8 A having the insertion portion 81 Aa that is in a polygonal shape such as a triangular shape.
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Abstract
A method of forming a pipe end structure includes providing a pipe assembly including a metal pipe blank, a ridge, and a tubular fitting, and pressing an inner surface of the pipe blank outwardly. The ridge protrudes outward from an outer surface of the pipe blank. The fitting includes a threaded portion having a thread on an outer surface thereof. The fitting has a first edge and a second edge and is fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank. An inner surface of the pipe blank is pressed outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion that is in contact with the second edge of the fitting.
Description
- This application claims priority from Japanese Patent Application No. 2013-120822 filed on Jun. 7, 2013. The entire contents of the priority application are incorporated herein by reference.
- The present disclosure relates to a method of forming a pipe end structure.
- As described in JP-A-2004-122151, a metal pipe is used as a hydraulic passage in a hydraulic drive system for driving a fork of a forklift, because the metal pipe has a sufficient rigidity to withstand high-pressure fluid (oil pressure). To connect the metal pipe to another pipe, a metal connector (joint) having a tubular shape is provided at an end of the metal pipe As described in JP-A-2004-122151, a screw having a helical thread (an external thread) is provided on an outer surface of the connector. The connector and the metal pipe are connected at their end portions by known welding technologies such as an arc welding, a gas welding, and a brazing.
- U.S. Pat. No. 5,727,303 describes a metal pipe (tube) for an orifice. A tubular connector (a first fitting) having threads on its outer surface is fitted over an end portion of the metal pipe. A front end of the metal pipe, which is on the front side of the connector, is expanded outwardly so as to be in close contact with a front opening edge of the connector. As described in U.S. Pat. No. 5,727,303, a conical extension on an anvil is inserted into an internal bore of the metal pipe to expand the front end portion of the metal pipe.
- The metal pipe is also expanded at a position adjacent to a rear end of the connector so as to be in close contact with a rear opening edge of the connector. The opening edge at the rear end has a recess extending around the metal pipe. A portion of the metal pipe is expanded into the recess. The metal pipe over which the connector is fitted at its end portion is vertically compressed (in a longitudinal direction of the metal pipe) to expand its end portion into the recess.
- A method of forming a pipe end structure includes providing a pipe assembly including a metal pipe blank, a ridge, and a tubular fitting, and pressing an inner surface of the pipe blank outwardly. The pipe blank has a through hole extending from one end to another end along an axial direction thereof. The ridge protrudes outward from an outer surface of the pipe blank. The fitting includes a threaded portion having a thread on an outer surface thereof. The fitting has a first edge and a second edge and is fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank. An inner surface of the pipe blank is pressed outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion being in contact with the second edge of the fitting.
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FIG. 1 is a side view of a tube end structure according to an embodiment. -
FIG. 2 is a front view of the tube end structure. -
FIG. 3 is a cross-sectional view of the tube end structure taken along a line A-A inFIG. 2 . -
FIG. 4 is a perspective view of a fitting. -
FIG. 5 is a side view of a pipe blank in which a front part thereof is illustrated in a cross section. -
FIG. 6 is a schematic view of a fixture, the pipe blank held by the fixture, and a pressing machine in a standby state. -
FIG. 7 is a schematic view illustrating a state in which a front end surface of a holder is in contact with a front end surface of the fixture. -
FIG. 8 is a schematic view illustrating a state in which a front end portion of the pipe blank is pressed and plastically deformed by the punch. -
FIG. 9 is a schematic view illustrating a state in which the front end portion of the pipe blank is further pressed and plastically deformed by the punch. -
FIG. 10 is a view illustrating a general configuration of a locking portion formation apparatus. -
FIG. 11 is a cross-sectional view of a part including the holder and a diameter expander of the locking portion formation apparatus. -
FIG. 12 is a top plan view of the diameter expander. -
FIG. 13 is a cross-sectional view illustrating a state in which the pipe blank, over which the fitting is fitted, is held by the holder. -
FIG. 14 is a cross-sectional view illustrating a locking portion formation step of a method of forming the pipe end structure according to an embodiment. -
FIG. 15 is a side view of a press-fit bar. -
FIG. 16 is a side view of a press-fit bar used in a method of forming a pipe end structure in an embodiment. -
FIG. 17 is a front view of the press fit bar illustrated inFIG. 16 . - The end portion of the metal pipe and the connector having threads may be welded to be connected with each other. In such a case, droplets of a welding material are likely to be attached to the threads during the welding. The droplets may lower the quality of a product that includes the metal pipe and the connector. This may lead a big problem. Specifically, this may deteriorate the quality of the threads, which may result in oil leakage. In addition, the welding between the end portion of the pipe and the connector is difficult for not only for an inexperienced worker, but also for a skilled worker. The welding lowers work efficiency. A technology for connecting the end portion of the pipe and the connector without welding is expected.
- The metal pipe over which the connector having a tubular shape is fitted may be compressed in a longitudinal direction of the metal pipe to expand the metal pipe as described in U.S. Pat. No. 5,727,303. However, it is difficult to evenly expand the metal pipe. If the metal pipe is not evenly expanded, the connector, which may be referred to as a fitting, is easily separated from the metal pipe. In addition, the metal pipe may be buckled at a position where the connector is not attached when the metal pipe is compressed in the longitudinal direction to expand the end portion thereof. Such problems occur due to the compression of the metal pipe.
- An object of the technology described herein is to provide a method of forming a pipe end structure in which a fitting having a tubular shape is properly fixed to a predetermined position of a metal pipe blank without welding.
- The technology described herein provides a method of forming a pipe end structure that includes providing a pipe assembly including a metal pipe blank, a ridge, and a tubular fitting, and pressing an inner surface of the pipe blank. The metal pipe blank has a through hole extending from one end to another end along an axial direction thereof. The ridge protrudes outward from an outer surface of the pipe blank. The tubular fitting has a thread on an outer surface thereof. The fitting has a first edge and a second edge and is fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank. An inner surface of the pipe blank is pressed outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion that is in contact with the second edge of the fitting.
- The step of pressing the inner surface may include inserting a diameter expander configured to expand in a radial direction of the pipe blank into the through hole of the pipe blank and expanding the diameter expander inserted in the pipe blank in the radial direction of the pipe blank to press the inner surface of the pipe blank outwardly at the position adjacent to the second edge of the fitting.
- The diameter expander may include a plurality of elastic plates arranged in a tubular shape with a predetermined distance therebetween. Each of the elastic plates may be a fixed end at one end thereof and a free end at another end thereof, whereby the elastic plates are expandable in a radial direction of the pipe blank. The inner surface of the pipe blank may be pressed outwardly by the other ends of the elastic plates.
- The step of pressing the inner surface may include fixing the pipe blank of the pipe assembly to a fixture at a position adjacent to the rear edge of the fitting, and inserting a press fit bar into the though hole of the pipe blank from the one end toward the other end of the pipe blank. The press fit bar may have an elongated shape and include a press fit portion having an outer diameter larger than an inner diameter of the pipe blank, whereby the inner surface of the pipe blank is pressed outwardly such that the pipe blank has the locking portion.
- The press fit portion may have a cylindrical shape.
- The press fit portion may have a polygonal prism shape.
- The step of providing the pipe assembly may include compressing an end portion of the pipe blank in the axial direction of the pipe blank to increase a thickness of the end portion of the pipe blank in a radial direction, whereby the ridge protruding from the outer surface of the pipe blank is formed at the end portion of the pipe blank and fitting the fitting over the pipe blank so as to be in contact with the ridge at the first edge of the fitting.
- The step of providing the pipe assembly may include chamfering an one portion of the pipe blank to have an inclined surface that extends from the inner surface of the pipe blank outwardly at an angle.
- The step of expanding the diameter expander may include inserting an diameter adjuster having a cylindrical shape into a space defined by the elastic plates of the diameter expander and moving the diameter expander in the axial direction of the tube blank toward the one end of the tube blank. The diameter adjuster may have an outer diameter larger than that of the diameter expander.
- Each of the elastic plates may have a projection at the other end thereof. The projection may protrude radially outwardly from the outer surface of each elastic plate and may be configured to press the inner surface of the pipe blank when the diameter expander expands.
- The step of fixing the pipe assembly to the fixture may include positioning the pipe assembly to have a space between the second edge of the fitting and the fixture, whereby the part of the pipe blank protrudes at a position corresponding to the space to form the locking portion.
- The step of inserting the press fit bar into the though hole of the pipe blank may include moving the press fit bar inserted in the through hole of the pipe blank until a tip end of the press fit portion reaches a position corresponding to the second edge of the fitting.
- According to the method of forming the pipe end structure described herein, the fitting having a tubular shape is properly fixed to a predetermined position of the metal pipe blank without welding.
- First embodiment will be described with reference to
FIGS. 1 to 13 . A side view, a front view, and a cross-sectional view of apipe end structure 1 according to a first embodiment are illustrated inFIG. 1 ,FIG. 2 , andFIG. 3 , respectively. A right side and a left side inFIG. 1 correspond to a front side and a rear side of thepipe end structure 1, respectively. - Pipe End Structure
- As illustrated in
FIG. 1 , thepipe end structure 1 includes apipe 2 having an elongated shape and a fitting 3 having a threaded portion. The fitting 3 fits over a front end portion of thepipe 2. Thepipe end structure 1 is a component of a hydraulic passage for a fork of a forklift. Thepipe end structure 1 is configured to be connected to another pipe end structure (not illustrated) via thefitting 3. - Pipe
- As illustrated in
FIG. 1 , thepipe 2 has a tubular shape elongated in substantially one direction. Thepipe 2 includes acircumferential wall 21 having an elongated tubular shape, afront ridge 22 located on a front end of thecircumferential wall 21, and afluid passage 23 extending through thepipe 2 along its longitudinal direction. Thecircumferential wall 21 has a tubular shape extending in a front-to-rear direction (an axial direction) and is formed of a metal pipe blank, which will be described later. Aninner surface 21 b of thecircumferential wall 21 defines thefluid passage 23. As illustrated inFIG. 3 , thefront ridge 22 of thepipe 2 on the front side of thecircumferential wall 21 protrudes radially outwardly from an outer surface of thecircumferential wall 21 and extends around thecircumferential wall 21. Thefront ridge 22 has an outer diameter larger than that of thecircumferential wall 21 located on a rear side thereof. Thefront ridge 22 has a surface that is machined to have a shape like a single thread, for example. As illustrated inFIG. 2 , afront surface 22 a of the front ridge 22 (i.e., a front surface of the pipe 2) has a circular ring shape. Thefluid passage 23 defined by the inner surface of thecircumferential wall 21 is a passage for an operating oil. - The
fitting 3 is fitted over the front end portion of thepipe 2 so as to be in contact with a rear edge of thefront ridge 22. Thepipe 2 includes a lockingportion 24 that protrudes radially outwardly from the outer surface of thecircumferential wall 21 so as to be in contact with the rear edge of thefitting 3. Thepipe 2 is formed by processing the pipe blank by a plastic working and cutting. This step will be described later. An inner surface of the circumferential wall of the pipe blank (thecircumferential wall 21 of the pipe 2) is pressed outwardly to plastically deform a part of the pipe blank. The plastically deformed part of the pipe blank becomes the lockingportion 24 that has a larger diameter. - Fitting
- A perspective view of the
fitting 3 is illustrated inFIG. 4 . Thefitting 3 has a tubular shape elongated in substantially one direction. The fitting 3 having a tubular shape has a shorter length (a length along an axis L) than thepipe 2 having a tubular shape. Thefitting 3 has an inner diameter that is larger than the outer diameter of thecircumferential wall 21 of thepipe 2. Thefitting 3 includes a threadedportion 31 at its front portion. The threadedportion 31 includeshelical threads 31 a on anouter surface 3 a of thefitting 3. Thefitting 3 includes aflange 32 at its rear portion. Theflange 32 protrudes radially outwardly from theouter surface 3 a of thefitting 3. In this embodiment, theflange 32 protrudes more from theouter surface 3 a of the fitting 3 than the threaded portion 31 (thethread 31 a). In other words, theflange 32 has a larger outer diameter than that of the threadedportion 31. Between the threadedportion 31 and theflange 32 of thefitting 3, theouter surface 3 a of thefitting 3 includes acylindrical surface portion 33 that has an outer diameter smaller than those of the threadedportion 31 and theflange 32. - The
fitting 3 includes a throughhole 34 extending through the fitting 3 in the front-to-rear direction. Aninner surface 3 b of thefitting 3 defines the throughhole 34. Thefitting 3 has a front edge (first edge) 35 and a rear edge (second edge) 36. Thefront edge 35 has afront opening edge 35 a extending around a front edge of thethorough hole 34. Therear edge 36 has arear opening edge 36 a extending around a rear edge of thethorough hole 34. A front portion of thecircumferential wall 21 is inserted in the throughhole 34 of thefitting 3, and thus thefitting 3 is fixed to thepipe 2. In this configuration, thefitting 3 fits over thecircumferential wall 21 of the pipe 2 (a pipe blank, which will be described later). Theinner surface 3 b of thefitting 3, which is fixed to thepipe 2, is in close contact with theouter surface 21 a of thecircumferential wall 21. - The
front ridge 22, which is located in front of thefitting 3, is in close contact with the front openingedge 35 a of thefitting 3. The lockingportion 24, which is located behind thefitting 3, is in close contact with therear opening edge 36 a of thefitting 3. In other words, thefitting 3 is sandwiched between thefront ridge 22 and the lockingportion 24 in the front-to-rear direction. - Method of Forming the Pipe End Structure
- Next, a method of forming the
pipe end structure 1 will be described with reference toFIGS. 5 to 13 . The above-describedpipe end structure 1 is formed by a method described below. - Step 1: a Step of Forming the Front Ridge
- In this step, a pipe blank 20 that will become the
pipe 2 is pressed at its front end portion to have thefront ridge 22 at the front portion thereof. - Specifically, the pipe blank 20, which will become the
pipe 2, is provided at first. A partial side cross-section of the pipe blank 20 is illustrated inFIG. 5 .FIG. 5 illustrates a front portion of the pipe blank 20 in the cross section. In this embodiment, a metal pipe (Carbon Steel Precision Tubes for Hydraulic Line Service) that has an outer diameter of 9.5 mm, an inner diameter of 6.5 mm, and a length of at least 150 mm is provided as thepipe blank 20. The pipe blank 20 has a tubular shape extending straight. The pipe blank 20 has afront surface 20 a that is a flat circular ring surface. The pipe blank 20 has aninclined surface 20 b at its inner front end. The inner front end of the pipe blank 20 is chamfered to have theinclined surface 20 b that extends from the inner surface of the pipe blank 20 outwardly at an angle. The pipe blank 20 has anouter surface 20 c having a cylindrical surface. The pipe blank 20 includes a throughhole 230 extending through the pipe blank 20 in the front-to-rear direction. The throughhole 230 will be thefluid passage 23 of thepipe 2. The pipe blank 20 has acircumferential wall 221 that will be thecircumferential wall 21 of thepipe 2. - Next, the pipe blank 20 is held by a
fixture 4 for a step of pressing the front end portion of thepipe blank 20. The pipe blank 20, which is held by thefixture 4, and apressing machine 5, which is in a standby state, are schematically illustrated inFIG. 6 . Thefixture 4 is a device for holding the pipe blank 20 (i.e., a clamping device for pipe) and has a cuboidal shape. Thefixture 4 includes a first fixingmember 41A and asecond fixing member 41B. Thefirst fixing member 41A is positioned above the second fixingmember 41B. The pipe blank 20 is sandwiched and held between the first fixingmember 41A and the second fixingmember 41B. Thefixture 4 has aspace 43 extending in the front-to-rear direction between the first fixingmember 41A and the second fixingmember 41B. The pipe blank 20 is fitted in thespace 43. The pipe blank 20 is held by thefixture 4 with afront end portion 20 d thereof sticking out of a front end surface 41 a of thefixture 4. The end surface 41 a of thefixture 4 has an openingedge 41 b at a position corresponding to an end of thespace 43. Thefront end portion 20 d of the pipe blank 20 sticks out of the openingedge 41 b. Thefront end portion 20 d of the pipe blank 20 sticks out of theend surface 41 a of thefixture 43 by a predetermined length (a predetermined length M1) that is required for the formation of thefront ridge 22. - After the pipe blank 20 is held by the
fixture 4, thefront end portion 20 d of the pipe blank 20 is compressed by thepressing machine 5. As illustrated inFIG. 6 , thepressing machine 5 is arranged in front of the pipe blank 20 held by thefixture 4. Thepressing machine 5 is reciprocatory movable in the front-to-rear direction along an axial line L by a known mechanism. Thepressing machine 5 includes apunch 51 and aholder 55. Thepunch 51 is configured to enter into the throughhole 230 of the pipe blank 20 and press a front end of thepipe blank 20. Theholder 55 surrounds thepunch 51 and has a surface to be in contact with theend surface 41 a of thefixture 4. A front side and a rear side of thepressing machine 5 correspond to the left side and the right side inFIG. 6 , respectively. Thepunch 51 is provided on a front end of a slide shaft, which is not illustrated. As illustrated inFIG. 6 , thepunch 51 includes aninsertion portion 52, apressing portion 53, and abody 54. Theinsertion portion 52 has a shaft like shape with a rounded end. Thepressing portion 53 extends from a rear edge (a base side) of theinsertion portion 52. Thebody 54 has a cylindrical shape and extends from a rear edge of thepressing portion 53. Theinsertion portion 52 and the pressingmember 53 are located on an extension line of a center line (an axial line) of thebody 54. - The
insertion portion 52 has a diameter slightly smaller than the inner diameter of thepipe blank 20. Thepressing portion 53, which extends from the rear edge (the base side) of theinsertion portion 52, has a concave shape opening toward the front side as a whole. Thepressing portion 53 has a larger diameter than theinsertion portion 52. Thepressing portion 53 is integrally formed with theinsertion portion 52. More specifically described, thepressing portion 53 includes a centralpressing portion 53 a, a front-end pressing portion 53 b, and an outerpressing portion 53 c. The centralpressing portion 53 a is configured to press the inner surface of thefront end portion 20 d of the pipe blank 20 so as to expand thefront end portion 20 d of the pipe blank 20 outwardly. The centralpressing portion 53 a extends from a rear edge of theinsertion portion 52 toward the rear side and has a shape like a truncated cone (a conical shape) with a sloped surface. The centralpressing portion 53 a has an outer diameter gradually increasing from the front side toward the rear side. The front-end pressing portion 53 b is configured to press the front end surface 20 a of the pipe blank 20 from the front side toward the rear side of the pipe blank 20, for example. The front-end pressing portion 53 b extends outwardly from an outer circumferential edge of a rear edge of the central pressingportion 53 a and has a circular ring surface surrounding the central pressingportion 53 a. The outerpressing portion 53 c is configured to press the outer surface of thefront end portion 20 d of the pipe blank 20 inwardly. The outerpressing portion 53 c is located outward of the front-end pressing portion 53 b and has a slope surface that is a circular ring surface having an inner diameter gradually increasing from the rear side toward the front side. - The
holder 55 is moved along the axial line L together with thepunch 51 until theholder 55 strikes the front end surface 41 a of thefixture 4. Theholder 55 has a tubular shape and surrounds thepunch 51. Theholder 55 has a through hole extending therethrough in the front-to-rear direction (along the axial line L). Thepunch 51 is arranged in the through hole of theholder 55. Thepunch 51 is configured to be moved forward along aninner surface 55 b of theholder 55, which defines the through hole, beyond theholder 55 that is in contact with thefixture 4. Theholder 55 has a front end surface 55 a that is in contact with the front end surface 41 of thefixture 4. Theinner surface 55 b of theholder 55 and the outer surface of thepunch 51 define a substantiallytubular space 56 therebetween (seeFIG. 7 ). Thepressing machine 5 is coaxially arranged with thepipe blank 20. In other words, the axial line of thepunch 51 or the axial line of theholder 55 extends on the same line as the axial line L of thepipe blank 20. As illustrated inFIG. 7 , thepunch 51 is arranged in theholder 55 with the front end portion of theinsertion portion 52 sticking out of the front end surface 55 a of theholder 55. Thespace 56 of theholder 55 has a size that can house thefront end portion 20 d of thepipe blank 20. In this embodiment, thepunch 51 and theholder 55 are metal molded products that has high abrasion resistance. - An operation of the
pressing machine 5 in a standby state as illustrated inFIG. 7 is started when the slide shaft (not illustrated) starts moving. Thepunch 51 of thepressing machine 5 starts moving toward the pipe blank 20 along with the slide shaft. Theholder 55 moves together with thepunch 51 at the same speed with the moving speed of thepunch 51. Thepunch 51 continues to move toward the pipe blank 20 and the front end portion of theinsertion portion 52 enters the throughhole 230 of thepipe blank 20. When theinsertion portion 52 enters the throughhole 230 by a predetermined distance, the front end surface 55 a of theholder 55 strikes the front end surface 41 a of thefixture 4. The front end surface 55 a of theholder 55 that is in contact with the front end surface 41 a of thefixture 4 is schematically illustrated inFIG. 7 . As illustrated inFIG. 7 , thepunch 51 does not press thefront end portion 20 d of the pipe blank 20 at a moment when the front end surface 55 a of theholder 55 strikes the front end surface 41 a of thefixture 4. - Then, the
holder 55 remains stationary while the front end surface 55 a thereof is in contact with the front end surface 41 a of thefixture 4. Contrary to this, thepunch 51 housed in theholder 55 moves further inside the pipe blank 20 as the slide shaft moves. Thebody 54 of thepunch 51 moves forward along theinner surface 55 b of theholder 55. Then, thepressing part 53 of thepunch 51 compresses thefront end portion 20 d of thepipe blank 20. This plastically deforms thefront end portion 20 d of the pipe blank 20 to have a larger diameter and a shorter length (dimension along the axial line L). Namely, the wall of the pipe blank 20 at thefront end portion 20 d becomes thicker. Thefront end portion 20 d of the pipe blank 20 which is plastically deformed by thepunch 51 is schematically illustrated inFIG. 8 . Theinsertion portion 52 and thepressing portion 53 of thepunch 51 enter the pipe blank 20 by a predetermined distance that is properly determined depending on an intended shape of the pipe end portion. The moving distance of thepunch 51 inside the pipe blank 20 can be properly controlled by setting a sliding distance (stroke) of the slide shaft that moves thepunch 51. After thepunch 51 compresses thefront end portion 20 d of the pipe blank 20, thepressing machine 5 moves back along the axial line L and returns to the standby state as illustrated inFIG. 6 . - In this embodiment, the step of compressing the
front end portion 20 d of the pipe blank 20 by thepunch 51, which is illustrated inFIG. 8 , is repeatedly performed multiple times. The moving (inserting) distance of thepunch 51 inside the pipe blank 20 (in the through hole 230) is controlled for each step. Specifically, the moving (inserting) distance of thepipe 51 inside the pipe blank 20 is set to be longer (deeper) with each step. The shapes of theinsertion portion 52 and thepressing portion 53 of thepunch 51 may be varied for each step. Specifically, theinsertion portion 52 and the pressing portion 53 (the central pressingportion 53 a) may have a larger diameter with each step. - The
front end portion 20 d of the pipe blank 20 which is plastically deformed by thepunch 51 is schematically illustrated inFIG. 9 . In this embodiment, as illustrated inFIG. 9 , thefront end portion 20 d of the pipe blank 20 is kept pressed until thefront end portion 20 d has a length M2 that is half the predetermined length M1 (the length along the axial line L). Thefront end portion 20 d of the pipe blank 20 is plastically deformed in a space defined by an outer surface of the punch 51 (theinsertion portion 52 and the pressing portion 53), theinner surface 55 b of theholder 55, and the front end surface 41 a of thefixture 4. - As described above, the
front end portion 20 d of the pipe blank 20 is pressed to have a larger thickness by thepressing machine 5, and thus the outer circumferential edge of the pipe blank 20 at thefront end portion 20 d protrudes outwardly in a ring shape. As a result, thefront end portion 20 d of the pipe blank 20 will become thefront ridge 22 of thepipe 2. Thefront end portion 20 d of the pipe blank 20 may be shaped by grinding as necessary. - Step 2: a Step of Fitting the Fitting
- In this step, the
fitting 3 is fitted over the pipe blank 20 that has thefront ridge 22. Thefitting 3 is a separate member from thepipe blank 20. Thefitting 3 may be obtained by cutting a substantially hexagonal tubular member. The tubular member has a hole extending therethrough which will be the throughhole 34 of thefitting 3. In this embodiment, a metal nut having an outer diameter (a maximum diameter) of 21.9 mm, an inner diameter of 9.9 mm, and a length of 20.0 mm is used as the tubular member. - The rear end of the pipe blank 20 is inserted from an inner edge of a
front opening edge 35 a of the fitting 3 into the throughhole 34 of the fitting 3 to fit the fitting 3 over thepipe blank 20. A position of the fitting 3 on the pipe blank 20 is adjusted so as to be in contact with thefront ridge 22 located at the front end of the pipe blank 20 at its front edge 35 (the front openingedge 35 a). In this way, thefitting 3 is fitted over thepipe blank 20. In this state in which thefitting 3 is fitted over the pipe blank 20, thefitting 3 is movable on thepipe blank 20. Specifically, thefitting 3 is slidable on the pipe blank 20 in the front-to-rear direction and in a circumferential direction along the outer surface of thepipe blank 20. Such an assembly of the pipe blank 20 and thefitting 3 may be referred to as apipe assembly 100. - Step 3: a Step of Forming a Locking Portion Formation
- In this step, an inner surface of the
pipe blank 20 of thepipe assembly 100 is pressed outwardly to expand the pipe blank 20 and form the lockingportion 24. A schematic configuration of a locking portion formation apparatus 6 is illustrated inFIG. 10 . The locking portion formation apparatus 6 is configured to form the lockingportion 24 by expanding thepipe blank 20 of thepipe assembly 100. As illustrated inFIG. 10 , the locking portion formation apparatus 6 includes abase 61, supports 62, a table 63, aholder 64, adiameter expander 65, anadjuster 66, adrive device 67, aswing member 68, and alink connector 69. - The
base 61 is a base of the locking portion formation apparatus 6, which is placed on a floor, for example. Thebase 61 is a metal flat plate, for example. The supports 62 are provided on thebase 61 and support the table 63 above thebase 61. As illustrated inFIG. 10 , in this embodiment, twosupports 62 are provided on thebase 61. One of thesupports 62 is provided at one end of the base 61 which is on the left side inFIG. 10 . The other one of thesupports 62 is provided at another end portion of the base 61 which is on the right side inFIG. 10 . The supports 62 each may be a metal flat plate. The supports 62 are provided on the base 61 so as to extend in an up-to-down direction (a vertical direction). A lower end and an upper end of eachsupport 62 are fixed to thebase 61 and the table 63, respectively. - The table 63 is supported by the
supports 62 from below. The table 63 is a metal plate and extends between thesupports 62. Theholder 64 is configured to hold a member to be processed by the locking portion formation apparatus 6 (thepipe blank 20 of the pipe assembly 100). Theholder 64 is fixed on the table 63. Theholder 64 has a shape like a container that opens upward. At a middle of theholder 64, thediameter expander 65 that is configured to be inserted into the throughhole 230 of the pipe blank 20 is arranged. - In
FIG. 11 , a portion around theholder 64 and thediameter expander 65 of the locking portion formation apparatus 6 is illustrated in a cross section. As illustrated inFIG. 11 , theholder 64 includes amount 64 a, awall 64 b, and a securingportion 64 c. On themount 64 a, a member to be processed is mounted. Thewall 64 b extends upward from an outer end of themount 64 a and surrounds the member to be processed on themount 64 a. The securingportion 64 c is provided in the middle of themount 64 c and thediameter expander 65 is secured thereto. - The
mount 64 a has a substantially cylindrical shape and is fitted in a concave attachment portion of the table 63 as illustrated inFIG. 11 . An upper surface of themount 64 a is a flat surface on which the front end of thepipe blank 20 of thepipe assembly 100 is arranged. Thewall 64 b is high enough to surround the threadedportion 31 of thefitting 3 of thepipe assembly 100. The securingportion 64 c has a surface defining a through hole extending in themount 64 a in an up-and-down direction (the vertical direction). A lower end portion of thediameter expander 65 having the elongated shape is fitted in the through hole defined by the securingportion 64 c so that thediameter expander 65 is secured by the securingportion 64 c. - The
diameter expander 65 is configured to press the inner surface of thepipe blank 20 of thepipe assembly 100 outwardly to form the lockingportion 24 in thepipe blank 20. Thediameter expander 65 has an elongated cylindrical shape and is made of metal. Thediameter expander 65 includes a base 65 a secured by the securingportion 64 c and a plurality ofplates 65 b extending upward from the base 65 a. The base 65 a has a cylindrical shape and constitutes a lower end portion of thediameter expander 65 which is arranged in the vertical position. - The
diameter expander 65 is illustrated in the top plan view inFIG. 12 . Thediameter expander 65 of this embodiment includes fourplates 65 b. Each of theplates 65 b is an elastic plate (plate spring). Theplates 65 b each have an elongated shape and have a circular arc cross section taken along perpendicular to the longitudinal direction thereof. Theplates 65 b are arranged in a tubular shape (a ring shape) with a predetermined distance (a space S1) therebetween. Theplates 65 b adjacent to each other provide a slit therebetween. The slit corresponds to the space S1. The slit extends along a long side of theplate 65 b from one end thereof toward the other end thereof. The slit extends to a position near the base 65 a of thediameter expander 65. - Each
plate 65 b has aprojection 65b 1 at a front end thereof. Theprojection 65b 1 protrudes radially outwardly from the outer surface of theplate 65 b. In this embodiment, fourprojections 65b 1 are arranged in a circular shape with a space therebetween. Theprojections 65b 1 are configured to press the inner surface of thecircumferential wall 221 of the pipe blank 20 outwardly. Pressing the inner surface of thecircumferential wall 221 by theprojections 65b 1 forms the lockingportion 24 of thepipe blank 20. - The
diameter expander 65 includes a throughhole 65 c extending in the up-and-down direction (the vertical direction, the axial direction of the diameter expander 65). Thediameter expander 65 has the outer diameter smaller than the inner diameter of thepipe blank 20. Each of theplates 65 b of thediameter expander 65 is arranged in a vertical position as illustrated inFIG. 11 , for example. The table 63 includes a throughhole 63 b extending through the table 63 in the up-and-down direction (the vertical direction) as illustrated inFIG. 11 . The throughhole 63 b of the table 63 communicates with the throughhole 65 c of thediameter expander 65. - The
adjuster 66 that is configured to adjust the diameter of thediameter expander 65 is placed on the front end portion of thediameter expander 65. Theadjuster 66 has a cylindrical shape (a nut like shape) as a whole and an outer diameter larger than that of the diameter expander. Theadjuster 66 includes alower portion 66 a that has a conical shape with a diameter decreasing toward the lower side. Thelower portion 66 a of theadjuster 66 is in contact with the front end portion of thediameter expander 65. Inside thediameter expander 65, alink connector 69 having a bar-like shape is arranged to extend through the throughhole 65 c. Thelink connector 69 is formed of an elongated metal bolt in this embodiment. Theadjuster 66 is fixed to anupper end portion 69 a of thelink connector 69. - The
link connector 69 is arranged inside the diameter expander 65 (in the throughhole 65 c) so as to extend in the up-and-down direction. As illustrated inFIG. 10 , thelink connector 69 includes alower end portion 69 b that is attached to aswing member 68 configured to swing on ashaft 70 in the up-and-down direction. As illustrated inFIG. 10 , theswing member 68 has a shape elongated in the right-to-left direction (a horizontal direction). Theswing member 68 is supported by theshaft 70 so as to be able to swing in the up-and-down direction. In the locking portion formation apparatus 6, theswing member 68 is arranged between the base 61 and the table 63. The locking portion formation apparatus 6 further includes a shaft bearing 71 that extends from a lower surface of the table 63 toward thebase 61. Theshaft bearing 71 supports both ends of theshaft 70. - As illustrated in
FIG. 10 , afirst end portion 68 a of theswing member 68, which is located on the right side inFIG. 10 , is connected to thelower end portion 69 b of thelink connector 69. As illustrated inFIG. 10 , asecond end portion 68 b of theswing member 68, which is located on the left side inFIG. 10 , is connected to adrive device 67 that is configured to move theswing member 68 in the up-and-down direction. Thedrive device 67 may be any known drive device such as a fluid pressure cylinder (for example, an air cylinder or an oil hydraulic cylinder). Thedrive device 67 is an oil hydraulic cylinder in this embodiment. Thedrive device 67 is arranged on thebase 61. - In the locking portion formation apparatus 6, when the second end portion (the other end) 68 b of the
swing member 68 is moved up by the drive of thedrive device 67, the first end portion (the one end) 68 a of theswing member 68 moves down. This moves thelink connector 69, which is attached to thefirst end portion 68 a of theswing member 68, down. In other words, thelower end portion 69 b of thelink connector 69 is gradually pulled down as thefirst end portion 68 a of theswing member 68 moves down. Thelink connector 69 connects between thefirst end portion 68 a of theswing member 68 and theadjuster 66. Theadjuster 66 moves down into thediameter expander 65 while pushing theplates 65 b of thediameter expander 65 outwardly as thelink connector 69 is pulled down. In this configuration, when theadjuster 66 moves down in thediameter expander 65, theplates 65 b are pushed outwardly and thediameter expander 65 is forced to have a larger diameter at the front end portion thereof. - Then, in the locking portion formation apparatus 6, when the second end portion (the other end) 68 b of the
swing member 68 is pulled down by the driving of thedrive device 67, the first end portion (the one end) 68 a of theswing member 68 moves up. This moves thelink connector 69, which is attached to thefirst end portion 68 a of theswing member 68, up. In other words, thelower end portion 69 b of thelink connector 69 is gradually pulled up as thefirst end 68 a of theswing member 68 moves upward. When thelink connector 69 is pulled up, theadjuster 66 that is in thediameter expander 65 moves upward to the original position at the front end portion of thediameter expander 65. Theplates 65 b of thediameter expander 65 are each formed of a plate spring. Theplates 65 b that are pushed outwardly return to its original vertical position and the diameter of thediameter expander 65 returns to its original diameter when theadjuster 66 returns to the original position at the front end portion of thediameter expander 65. The driving of thedrive device 67 is controlled by a controller, which is not illustrated. - In the locking portion formation step, the above-described locking portion formation apparatus 6 forms the locking
portion 24 in thepipe blank 20 of thepipe assembly 100. The step of forming the lockingportion 24 in the pipe blank 20 will be described with reference toFIG. 13 . InFIG. 13 , thepipe blank 20 of thepipe assembly 100 is held by theholder 64. Before thepipe blank 20 of thepipe assembly 100 is held by theholder 64, thediameter expander 65, to which theadjuster 66 is fitted, is inserted inside (the through hole 230) the pipe blank 20 from the front end thereof. Then, the front end portion of the pipe blank 20 is placed on themount 64 a such that the pipe blank 20 is arranged in a vertical position on themount 64 a. Thepipe blank 20 of thepipe assembly 100 is held by theholder 64 in this way. At this stage where thepipe blank 20 of thepipe assembly 100 is held by theholder 64, theprojection 65b 1 at the front end of thediameter expander 65 is positioned at a position corresponding to therear edge 36 of thefitting 3, which is fitted over the pipe blank 20, or a position slightly above therear edge 36. In this embodiment, theprojection 65b 1 is positioned slightly above therear edge 36 of thefitting 3. Therear opening edge 36 a at therear edge 36 of thefitting 3 is inclined downward toward the inside of thefitting 3, and thus therear opening edge 36 a and the outer surface of the pipe blank 20 provide a recess. - After the
pipe blank 20 of thepipe assembly 100 is held by theholder 64, thedrive device 67 of the locking portion formation apparatus 6 is driven to move down theadjuster 66. Theadjuster 66 pushes the inner surfaces of theplates 65 b of thediameter expander 65, and thus theplates 65 b are pushed outwardly so that thediameter expander 65 expands in a radial direction toward thewall 221 of thepipe blanks 20. When thediameter expander 65 expands in the radial direction, theprojections 65b 1 at the front end of thediameter expander 65 press the inner surface of thewall 221 of the pipe blank 20 outwardly. As a result, thewall 221 of the pipe blank 20 is plastically deformed to have a larger diameter at the parts pressed by theprojections 65b 1 of thediameter expander 65, and thus the lockingportion 24 in contact with the rear edge 36 (therear opening edge 36 a) of thefitting 3 is formed. The formation of the lockingportion 24 in the pipe blank 20 provides thepipe end structure 1 illustrated inFIG. 1 toFIG. 3 . As illustrated inFIG. 3 , the lockingportion 24 protrudes from the outer surface of the pipe 20 (the pipe 2) and is in close contact with the rear edge 36 (particularly, therear opening edge 36 a) of thefitting 3. - After the formation of the locking
portion 24, theadjuster 66 is returned to the original position by thedrive device 67 of the locking portion formation apparatus 6. As a result, thediameter expander 65 contracts (the diameter of thediameter expander 65 decreases) to its original size, and thus thediameter expander 65 is allowed to be pulled out of the through hole 230 (the fluid passage 23). Subsequently, thediameter expander 65 is pulled out of the throughhole 230 and the processed pipe blank having the locking portion 24 (the pipe end structure 1) is detached from theholder 64. According to the above described method, the lockingportion 24 is formed at a predetermined position of the pipe blank 20 over which thefitting 3 is fitted. - As described above, the
pipe end structure 1 of this embodiment is produced. After the locking portion formation step, any step such as shaping may be performed on thepipe end structure 1. - According to the method of forming the
pipe end structure 1 of this embodiment, the inner surface of the pipe blank 20 that will become thepipe 2 is pressed outwardly, and thus thecircumferential wall 221 of the pipe blank 20 is radially expanded to form the lockingportion 24. The lockingportion 24 is a protrusion evenly extending outwardly in a ring shape on thecircumferential wall 21 of thepipe blank 20. The method of forming thepipe end structure 1 of this embodiment provides thepipe end structure 1 in which thefitting 3 is hardly detached from the pipe blank 20 (the pipe 2). Thefitting 3 is sandwiched between the lockingportion 24 and thefront ridge 22 on the pipe blank 20 (the pipe 2). In this configuration, thefitting 3 hardly moves in the longitudinal direction and the circumferential direction of thepipe blank 20. According to the method of forming thepipe end structure 1 of this embodiment, the pipe blank 20 (the pipe 2) is hardly buckled. - According to the method of forming the
pipe end structure 1 of this embodiment, the fitting having a cylindrical shape is properly fixed to a predetermined position of the metal pipe blank without welding. In thepipe end structure 1, thepipe 2 is a seamless pipe, and thus the fluid flowing in thepipe 2 does not leak out of thepipe 2. - A second embodiment will be described with reference to
FIG. 14 andFIG. 15 . In this embodiment, a method of forming a pipe end structure 1A having a configuration illustrated inFIG. 14 will be described. The method according to this embodiment is the same as the method according to the first embodiment except for the locking portion formation step. Hereinafter, only the locking portion formation step will be described for the second embodiment. In the locking portion formation step of this embodiment, a lockingportion 24A is formed in apipe 2A (a pipe blank 20A) by a pressfit bar 8 illustrated inFIG. 14 andFIG. 15 . - The press
fit bar 8 is pushed into a throughhole 23A of the pipe blank 20A of thepipe assembly 100 from a front end of the pipe blank 20A to form the lockingportion 24A. The pressfit bar 8 is a component of a press fitting machine which is not illustrated. The press fitting machine further includes a member configured to move the pressfit bar 8 in the front-to-rear direction. The pressfit bar 8 includes aninsertion portion 81, acontact portion 82 extending from a rear edge of theinsertion portion 81, and a fixedshaft 83 extending from a rear edge of thecontact portion 82. Theinsertion portion 81 has a shaft like shape and is configured to be inserted into the through hole of the pipe blank 20A. Thecontact portion 82 is configured to be in contact with a front end portion of the pipe blank 20A when theinsertion portion 81 is inserted into the through hole of the pipe blank 20A. The fixedshaft 83 is fixed to another component of the press fitting machine. - The
insertion portion 81 has a cylindrical shape as a whole. Theinsertion portion 81 includes a press-fit portion 81 a at a front end side thereof. The press-fit portion 81 a has an outer diameter larger than remaining portions of theinsertion portion 81. The press-fit portion 81 a includes afront end portion 81 a 1 that has a diameter decreasing from the rear side toward the front thereof. The press-fit portion 81 a has an outer diameter that is larger than an inner diameter of the pipe blank 20A without the lockingportion 24A. - The press-
fit portion 81 a is configured to press the inner surface of thecircumferential wall 21A of the pipe blank 20A outwardly when theinsertion portion 81 is inserted into the through hole of the pipe blank 20A. Thefront end portion 81 a 1 of the press-fit portion 81 a is positioned near therear edge 36 of the fitting 3 when theinsertion portion 81 reaches the farthest point in the through hole of the pipe blank 20A. - The
contact portion 82 has a larger diameter than theinsertion portion 81. Thecontact portion 82 has a front end surface 82 a having a circular ring shape. As described above, thefront end portion 81 a 1 of the press-fit portion 81 a is positioned near therear edge 36 of the fitting 3 when theinsertion portion 81 is inserted into the through hole of the pipe blank 20A and the front end portion of the pipe blank 20A is in contact with the front end surface 82 a of thecontact portion 82. - As illustrated in
FIG. 14 , the pipe blank 20A of thepipe assembly 100 is held by the fixture 4 (the fixture used in the front ridge formation step) at a position adjacent to therear edge 36 of thefitting 3. The pipe blank 20A of thepipe assembly 100 is held by thefixture 4 with a small space between the front end surface 41 a of thefixture 4 and the rear edge (surface) of thefitting 3, which is fitted over the pipe blank 20A. The small space has a size required for the formation of the lockingportion 24A. - When the press
fit bar 8 is inserted in (into the throughhole 23A of) thepipe blank 20 of thepipe assembly 100, the press-fit portion 81 a of the pressfit bar 8 moves toward the rear side while pressing the inner surface of thecircumferential wall 21A of the pipe blank 20 outwardly. As a result, an outer surface 21Aa of thecircumferential wall 21A is pressed against aninner wall 3 b of the fitting 3 so as to be in close contact with each other. The inner surface 21Ab of thecircumferential wall 21A is plastically deformed as the press-fit portion 81 a moves in thepipe blank 20. This forms the lockingportion 24A that is in contact with the rear edge 36 (therear opening edge 36 a) of thefitting 3. Thefront end portion 81 a 1 of the press-fit portion 81 a moves in the throughhole 23A while scraping the inner surface 21Ab of thecircumferential wall 21A. As a result, the scraped material of thecircumferential wall 21A of the pipe blank 20A is gathered to a position behind thefitting 3. The gathered material of thecircumferential wall 21A is in a protruded shape protruding from the outer surface 21Aa of the pipe blank 20A at a position between the front end surface 41 a of thefixture 4 and the rear edge (surface) 36 of thefitting 3. The gathered material constitutes the lockingportion 24A. - The insertion of the press
fit bar 8 into the pipe blank 20 is performed until the lockingportion 24A is formed. The pressfit bar 8 may be inserted once or twice or more into the pipe blank 20 to form the lockingportion 24A. - As described above, according to the method of forming the pipe end structure 1A of this embodiment, the inner surface of the pipe blank 20A, which will become the
pipe 2A, is pressed outwardly such that thecircumferential wall 21A of the pipe blank 20A is radially expanded to form the lockingportion 24A. The lockingportion 24A is a protrusion evenly extending outwardly in a ring shape on thecircumferential wall 21A of the pipe blank 20A. The method of forming the pipe end structure 1A of this embodiment provides the pipe end structure 1A in which thefitting 3 is hardly detached from the pipe blank 20A (thepipe 2A). Thefitting 3 is sandwiched between the lockingportion 24A and thefront ridge 22 on the pipe blank 20A (thepipe 2A). In this configuration, thefitting 3 hardly moves in the longitudinal direction and the circumferential direction of the pipe blank 20A. In addition, according to the method of forming the pipe end structure 1A of this embodiment, the pipe blank 20A (thepipe 2A) is hardly buckled. - According to the method of forming the pipe end structure 1A of this embodiment, the fitting having a tubular shape is properly fixed to a predetermined position of the metal pipe blank without welding.
- The technology described herein is not limited to the above embodiments explained in the above description and the drawings. The technology described herein may include the following embodiments.
- (1) In the first and second embodiments, the
pipe pipe end structure 1, 1A extends straight. However, the technology is not limited to this configuration. In some embodiments, thepipe 2 may be bent in various curved shapes depending on the intended use of the pipe end structure (pipe routing). - (2) In the first and second embodiments, the
front ridge 22 has the single thread shape. However, the technology is not limited to this configuration. In some embodiments, the surface of the ridge may be a cylindrical surface. The shape of thefront ridge 22 may be changed depending on an end structure of another pipe to which the pipe is connected. - (3) In the first and second embodiments, the
rear opening edge 36 a at therear edge 36 of thefitting 3 is inclined downward toward the inside of thefitting 3, and thus a recess is provided between therear opening edge 36 a and the outer surface of thepipe 20, 20A. However, the technology is not limited to this configuration. In some embodiments, therear opening edge 36 a of the fitting 3 may not have such an inclined part that provides a recess and may be flat. - (4) In the first and second embodiments, the
pipe end structure 1, 1A is a component of the hydraulic passage for driving the fork of the fork lift. However, the technology is not limited to this configuration. Thepipe end structure 1, 1A may be a component for any other products in some embodiments. - (5) In the first and second embodiments, the
front ridge 22 has a ring-like front shape. However, the technology is not limited thereto. Thefront ridge 22 may have a square tube shape, a triangular tube shape, a pentagonal tube shape, a hexagonal tube shape, or other tube shape (a ring shape) in some embodiments. - (6) In the locking portion formation step according to the second embodiment, instead of the press
fit bar 8, another pressfit bar 8A as illustrated inFIG. 16 andFIG. 17 may be used. The pressfit bar 8A has aninsertion portion 81A that has a different shape from theinsertion portion 81 of the pressfit bar 8 of the second embodiment. The pressfit bar 8 of the second embodiment includes the press-fit portion 81 a that has a circular shape in a front view viewed along an axial direction of the pressfit bar 8. The pressfit bar 8A illustrated inFIG. 16 andFIG. 17 includes a press-fit bar 81Aa that has a triangular shape (an example of polygonal shape) in a front view viewed along the axial direction. Like the second embodiment, the front end portion 81Aa1 of the press-fit portion 81Aa is positioned near therear edge 36 of the fitting 3 when theinsertion portion 81 is inserted in the pipe blank 20A. The pressfit bar 8A having such a configuration has a smaller area that is in contact with thecircumferential wall 21A of the pipe blank 20A than the pressfit bar 8 of the second embodiment. With this configuration, the pressfit bar 8A can be easily inserted into the pipe blank 20A of the pressfit bar 8. The locking portion formation step of forming the locking portion in the pipe blank 20A may be performed by theinsertion bar 8A having the insertion portion 81Aa that is in a polygonal shape such as a triangular shape.
Claims (12)
1. A method of forming a pipe end structure, the method comprising;
providing a pipe assembly, the pipe assembly including:
a metal pipe blank having a through hole extending from one end to another end along an axial direction thereof;
a ridge protruding outward from an outer surface of the pipe blank; and
a tubular fitting includes a threaded portion having a thread on an outer surface thereof, the fitting having a first edge and a second edge and being fitted over the pipe blank with the first edge of the fitting being in contact with the ridge protruding from the pipe blank; and
pressing an inner surface of the pipe blank outwardly such that a part of the pipe blank protrudes from an outer surface of the pipe blank outwardly at a position adjacent to the second edge of the fitting, thereby forming a locking portion being in contact with the second edge of the fitting.
2. The method according to claim 1 , wherein the step of pressing of the inner surface includes:
inserting a diameter expander configured to expand in a radial direction of the pipe blank into the through hole of the pipe blank; and
expanding the diameter expander inserted in the pipe blank in the radial direction of the pipe blank to press the inner surface of the pipe blank outwardly at the position adjacent to the second edge of the fitting.
3. The method according to claim 2 , wherein
the diameter expander includes a plurality of elastic plates arranged in a tubular shape with a predetermined distance therebetween,
each of the elastic plates has a fixed end at one end thereof and a free end at another end thereof, whereby the elastic plates are expandable in a radial direction of the pipe blank, and
the inner surface of the pipe blank is pressed outwardly by the other ends of the elastic plates.
4. The method according to claim 1 , wherein
the step of pressing the inner surface includes:
fixing the pipe blank of the pipe assembly to a fixture at a position adjacent to the second edge of the fitting; and
inserting a press fit bar into the though hole of the pipe blank from the one end toward the other end of the pipe blank, the press fit bar having an elongated shape and including a press fit portion having an outer diameter larger than an inner diameter of the pipe blank, whereby the inner surface of the pipe blank is pressed outwardly such that the pipe blank has the locking portion.
5. The method according to claim 4 , wherein the press fit portion has a cylindrical shape.
6. The method according to claim 4 , wherein the press fit portion has a polygonal prism shape.
7. The method according to claim 1 , wherein the step of providing the pipe assembly includes:
compressing an end portion of the pipe blank in the axial direction of the pipe blank to increase a thickness of the end portion of the pipe blank in a radial direction, whereby the ridge protruding from the outer surface of the pipe blank is formed at the end portion of the pipe blank; and
fitting the fitting over the pipe blank so as to be in contact with the ridge at the first edge of the fitting.
8. The method according to claim 1 , wherein the step of providing the pipe assembly includes:
chamfering an one portion of the pipe blank to have an inclined surface that extends from the inner surface of the pipe blank outwardly at an angle.
9. The method according to claim 3 , wherein the step of expanding the diameter expander includes:
inserting an diameter adjuster having a cylindrical shape into a space defined by the elastic plates of the diameter expander, the diameter adjuster having an outer diameter larger than that of the diameter expander; and
moving the diameter expander in the axial direction of the tube blank toward the one end of the tube blank.
10. The method according to claim 3 , wherein each of the elastic plates has a projection at the other end thereof, the projection protrudes radially outwardly from the outer surface of each elastic plate and is configured to press the inner surface of the pipe blank when the diameter expander expands.
11. The method according to claim 4 , wherein the step of fixing the pipe assembly to the fixture includes positioning the pipe assembly to have a space between the second edge of the fitting and the fixture, whereby the part of the pipe blank protrudes at a position corresponding to the space to form the locking portion.
12. The method according to claim 4 , wherein the step of inserting the press fit bar into the though hole of the pipe blank includes moving the press fit bar inserted in the through hole of the pipe blank until a tip end of the press fit portion reaches a position corresponding to the second edge of the fitting.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2013-120822 | 2013-06-07 | ||
JP2013120822A JP5822872B2 (en) | 2013-06-07 | 2013-06-07 | Manufacturing method of piping terminal structure |
Publications (1)
Publication Number | Publication Date |
---|---|
US20140360002A1 true US20140360002A1 (en) | 2014-12-11 |
Family
ID=52004168
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US14/146,813 Abandoned US20140360002A1 (en) | 2013-06-07 | 2014-01-03 | Method of forming pipe end structure |
Country Status (2)
Country | Link |
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US (1) | US20140360002A1 (en) |
JP (1) | JP5822872B2 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP6446640B2 (en) * | 2016-05-24 | 2019-01-09 | 新郊パイプ工業株式会社 | Piping terminal structure and manufacturing method of piping terminal structure |
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Also Published As
Publication number | Publication date |
---|---|
JP5822872B2 (en) | 2015-11-25 |
JP2014237156A (en) | 2014-12-18 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: SHINKO PIPE KOGYO KABUSHIKI KAISHA, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:MORI, KENICHI;REEL/FRAME:031883/0265 Effective date: 20131129 |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |