TUBE FITTING

A fitting connects a first tube with a second tube. At least one of the tubes is twistable. The fitting includes a tubular body and a sleeve. A first axial end portion of the body includes a connector for the first tube. A second axial end portion of the body includes an annular groove and an internal thread. A first axial end portion of the sleeve includes an aunular protrusion to be press-fitted into the annular groove and an external thread to be engaged with the internal thread. A second axial end portion of the sleeve includes a connector for the second tube. A rotation angle between the internal and external threads necessary for connection therebetween is designed to fall within a range. At any angle within the range, the first tube connected with the body or the second tube connected with the sleeve can be twisted with one hand.

TECHNICAL FIELD

The invention relates to tube fittings, in particular, those using threads for connection of tubes.

BACKGROUND ART

Manufacture of semiconductors, medical supplies, medicines, foods or the like uses various chemical solutions or ultrapure water. It is desirable that piping equipment for use of such chemical solutions or the like should be easy to assemble due to necessity of frequent maintenance such as washing. The same is true for piping equipment installed in vehicles to carry gasoline, coolant water, exhaust gas or the like. Accordingly, for such pipe equipment, tube fittings capable of facilitating connection of tubes are useful.

As such a tube fitting, one disclosed in JP 2016-070387 A is known, for example, which includes a tubular body, a sleeve, and a union nut. The fitting body has a first axial end portion including a connector for a tube and a second axial end portion including an annular groove and an external thread. The sleeve has a first axial end portion including an annular protrusion and a second axial end portion including a connector for another tube. The union nut has an internal thread to be engaged with the external thread of the fitting body. The union nut, when being screwed into the external thread with the sleeve coaxially installed thereinside, pushes the sleeve against the fitting body, and thus, the annular protrusion of the sleeve is press-fitted into the annular groove of the fitting body. Then, surfaces of the annular protrusion tightly contact surfaces of the annular groove to seal gaps between the sleeve and the fitting body. Screwing the union nut into the external thread enables the press-fit of the annular protrusion into the annular groove more easily and reliably than pushing the sleeve against the fitting body directly with bare hands, and therefore, the tube fitting is easy to connect tubes with each other.

CITATION LIST

Patent Literature 1: JP 2016-070387 A

SUMMARY OF INVENTION

The tube fitting disclosed in JP 2016-070387 A has the union nut that is separable from both the fitting body and the sleeve. This eliminates the need to rotate both the fitting body and the sleeve when the union nut is screwed into the external thread of the fitting body, and thus, neither a tube connected with the fitting body nor another tube connected with the sleeve has to be twisted. Accordingly, screwing the union nut into the external thread of the fitting body is not subject to any restriction by torsional stiffness of tubes. However, the union nut has to be manufactured separately from both the fitting body and the sleeve, and thus, reduction in manufacturing cost of the tube fitting is difficult.

An object of the invention is to solve the above-mentioned problems, in particular, to provide a tube fitting that enables reduction in manufacturing cost while keeping sufficiently high operability for connection of tubes.

A tube fitting according to one aspect of the invention is used for connecting a first tube with a second tube. At least one of the first and second tubes is twistable. The tube fitting has a fitting body and a sleeve. The fitting body has a tubular shape whose first axial end portion includes a connector for the first tube, and whose second axial end portion includes an annular groove and an internal thread. The sleeve has a first axial end portion including au annular protrusion to be press-fitted into the annular groove and an external thread to be engaged with the internal thread. The sleeve further has a second axial end portion including a connector for the second tube. A rotation angle between the internal and external threads necessary for connection therebetween is designed to fall within a range. At any angle within the range, one of the first tube connected with the fitting body and the second tube connected with the sleeve can be twisted with one hand.

This tube fitting may allow the rotation angle between the internal and external threads necessary for connection therebetween to be 180 degrees or less. The fitting body may include a first engaging portion, and the sleeve may include a second engaging portion. The first engaging portion may protrude radially outward from a circumferential section of an outer periphery of the fitting body. The second engaging portion may protrude radially outward from a circumferential section of an outer periphery of the sleeve. The first engaging portion may be snap-fitted with the second engaging portion when a rotation angle between the internal and external threads reaches an engagement finish position.

A tube fitting according to another aspect of the invention is used for connecting a first tube with a second tube. At least one of the first and second tubes is twistable. The tube fitting has a fitting body and a sleeve. The fitting body has a tubular shape whose first axial end portion includes a connector for the first tube, and whose second axial end portion includes an annular groove and an external thread. The sleeve has a first axial end portion including an annular protrusion to be press-fitted into the annular groove and an internal thread to be engaged with the external thread. The sleeve further has a second axial end portion including a connector for the second tube. A rotation angle between the external and internal threads necessary for connection therebetween is designed to fall within a range. At any angle within the range, one of the first tube connected with the fitting body and the second tube connected with the sleeve can be twisted with one hand.

This tube fitting may allow the rotation angle between the external and internal threads necessary for connection therebetween to be 180 degrees or less. The fitting body may include a first engaging portion, and the sleeve may include a second engaging portion. The first engaging portion may protrude radially outward from a circumferential section of an outer periphery of the fitting body. The second engaging portion may protrude radially outward from a circumferential section of an outer periphery of the sleeve. The first engaging portion may be snap-fitted with the second engaging portion when a rotation angle between the external and internal threads reaches an engagement finish position. In an axial direction of the sleeve, the tip of the annular protrusion may be located within a range of the internal thread.

In the above-described tube fitting according to the invention, one of the fitting body and the sleeve includes the external thread, and the other includes the internal thread. Thus, this tube fitting does not require any union nut, in contrast to conventional tube fittings. On the other hand, this tube fitting needs twisting either the first tube connected with the fitting body or the second tube connected with the sleeve when the external thread is engaged with the internal thread. However, a rotation angle between the external and internal threads necessary for connection therebetween falls within a range, and at any angle within the range, either the first or second tube can be twisted with one hand. This can facilitate the twisting of the first or second tube as desired. As a result, this tube fitting enables reduction in manufacturing cost while keeping sufficiently high operability for connection of tubes.

When a conventional tube fitting is separated from connected tubes, there is a need to pull its sleeve and extract an annular protrusion of the sleeve from an annular groove of its fitting body. In contrast, the above-described tube fitting enables the annular protrusion to be extracted from the annular groove by a force disengaging the external thread from the internal thread. In addition, an angle at which the tube connected with the fitting body or the sleeve has to be twisted at that time falls within the range, at any angle within which the tube can be twisted with one hand. Therefore, this tube fitting has a higher operability for disconnection of tubes than the conventional tube fitting.

When the fitting body includes the first engaging portion and the sleeve includes the second engaging portion, a worker can put his/her fingers on the engaging portions to relatively rotate the fitting body and the sleeve around a common axis, and thus, the worker can easily exert circumferential force onto the fitting body and the sleeve. In addition, the tip of the first engaging portion is farther apart from the axis of the fitting body than other portions thereof, and the tip of the second engaging portion is farther apart from the axis of the sleeve than other portions thereof. Accordingly, by exerting circumferential force onto the tips of the engaging portions, the worker can apply larger torque to the fitting body and the sleeve than by exerting the same force onto other portions of the fitting body and the sleeve. Furthermore, the first and second engaging portions are snap-fitted when a rotation angle between the external and internal threads reaches an engagement finish position. By visually identifying appearance of the snap-fit of the first and second engaging portions and aurally identifying sound created by the snap-fit, the worker can easily confirm if the external and internal threads reach the engagement finish position.

When the first axial end portion of the sleeve includes the internal thread, in the axial direction of the sleeve, a tip of the annular protrusion may fall within a range of the internal thread. This facilitates reduction in axial thickness of both the first axial end portion of the sleeve and the second axial end of the fitting body connected with each other in contrast to when the first axial end portion of the sleeve includes the external thread. Such reduction in axal thickness leads to reduction in amount of material of the fitting body and the sleeve, and thus, it is advantageous to reduction in manufacturing cost of the tube fitting. In addition, the internal thread surrounds the tip of the annular protrusion, and thus, it also serves as a barrier for the tip to prevent the tip from potential deformation and damage due to unconsidered contact with an external object such as the fitting body.

DESCRIPTION OF EMBODIMENTS

The following will describe embodiments of the invention with reference to attached figures.

FIG.1is a perspective view showing an appearance of a tube fitting100according to embodiment 1 of the invention.FIG.2is a cross-section view along a line II-II inFIG.1. The tube fitting100is used for, for example, connecting a first hose510with a second hose520in cooling lines for a battery pack of an electric vehicle (EV), as shown inFIG.2. These hoses510and520are made of, for example, resin such as high-density polyethylene (HDPE) and used as lines allowing coolant water (LLC) to flow therethrough.

The tube fitting100consists of a fitting body200and a sleeve300, both of which are tubular members made of resin such as polyamide (PA) or glass-reinforced polyamide (PA-GF). As shown inFIG.2, the fitting body200is connected with the first hose510and the sleeve300is connected with the second hose520. An inner cavity201of the fitting body200and an inner cavity301of the sleeve300have circular cross-sections perpendicular to their respective axial directions, which have the same diameters. As shown inFIGS.1and2, when the fitting body200and the sleeve300are coaxially connected with each other, their inner cavities201and301allow the inside of the first hose510to communicate with the inside of the second hose520therethrough. In other words, the inner cavities201and301serve as a channel connecting the two hoses510and520and allowing LLC to flow therethrough. [Structure of Fitting Body]

One axial end portion210(which is hereinafter referred to as “first axial end portion”) of the fitting body200is a connector for the first hose510, which is coaxially placed within the first hose510, as shown inFIG.2. Since the outer diameter of the first axial end portion210is larger than the inner diameter of the first hose510, the first axial end portion210pushes the opening end of the first hose510radially outward when the first axial end portion210is press-fitted into the first hose510. Then, a restoring force of the opening end squeezes the first axial end portion210radially inward, and thus, the first hose510is fixed to the first axial end portion210and seals a gap between its inner periphery and an outer periphery of the first axial end portion210.

The other axial end portion220(which is hereinafter referred to as “second axial end portion”) of the fitting body200is a junction with the sleeve300, which includes an inner cylinder221, an annular groove230, a flange240, an internal thread250, and a first engaging portion260.

The inner cylinder221is a circular-cylindrical portion defining the inner cavity201of the fitting body200. The annular groove230is a circular-ring-shaped groove coaxially surrounding the inner cylinder221. A radially inward surface of the annular groove230is formed by an outer periphery of the inner cylinder221.

The flange240is a substantially circular-cylindrical portion coaxially surrounding the annular groove230, whose outer diameter is larger than the outer diameter of the first axial end portion210. A portion of an inner periphery of the flange240forms a radially outward surface of the annular groove230. In the vicinity of the boundary between the first axial end portion210and second axial end portion220of the fitting body200, the flange240is connected and integrated with the inner cylinder221as a single piece and forms a bottom231of the annular groove230. In the vicinity of an opening portion222of the inner cylinder221, the flange240extends toward the axial direction of the fitting body200(rightward inFIG.2), and a portion of the flange240reaches beyond the axial position of the opening portion222of the inner cylinder221. An inner periphery of the portion of the flange240is provided with an internal thread250, which is a double start thread, for example. Two thread ridges251and252spiral along the inner periphery of the flange240.

The first engaging portion260is a projection that protrudes radially outward (upward inFIGS.1and2) from a circumferential section of the outer periphery241of the flange240(the top section thereof inFIGS.1and2). A surface of the first engaging portion260whose position in the axial direction of the fitting body200is close to the opening portion222of the inner cylinder221(on the right side inFIG.2) has an engaging hole261.

One axial end portion310(which is hereinafter referred to as “first axial end portion”) of the sleeve300is a junction with the fitting body200, which includes an inner cylinder311, an annular protrusion320, an external thread330, a flange340, and a second engaging portion350.

The inner cylinder311is a circular-cylindrical portion defining the inner cavity301of the sleeve300. The annular protrusion320is a circular-ring-shaped protrusion coaxially surrounding an opening portion312of the inner cylinder311and extending toward the axial direction of the sleeve300(leftward inFIG.2) from the rim of the opening portion312. The external thread330is provided at an outer periphery of the inner cylinder311and engageable with the internal thread250of the fitting body200. In particular, the external thread330is a multi-start thread having the same number of thread ridges as those of the internal thread250, for example, a double start thread. Two thread ridges331and332spiral along an outer periphery of the inner cylinder311.

The flange340is a substantially circular-cylindrical portion coaxially surrounding the inner cylinder311and the annular protrusion320, whose outer diameter is larger than the outer diameter of the other axial end portion360(which is hereinafter referred to as “second axial end portion”) of the sleeve300. In the vicinity of the boundary between the first axial end portion310and second axial end portion360of the sleeve300, the flange340is connected and integrated with the first axial end portion310as a single piece. In the vicinity of a tip321of the annular protrusion320, the flange340extends toward the axial direction of the sleeve300(leftward inFIG.2) and reaches beyond the axial position of the tip321of the annular protrusion320.

The second engaging portion350is a projection that protrudes radially outward (upward inFIGS.1and2) from a circumferential section of an outer periphery341of the flange340(the top section thereof inFIGS.1and2). As shown inFIG.1, when the sleeve300is properly connected with the fitting body200, the second engaging portion350is located at the same position as the first engaging portion260of the fitting body200in a common circumferential direction shared by the fitting body200and the sleeve300.

The second engaging portion350includes a thin-plate part351and a thick-plate part352, which are plate-like parts perpendicular to the axial direction of the sleeve300(the left-right direction inFIG.2.) The thin-plate part351has an axial thickness smaller than that of the thick-plate part352. The thin-plate part351is located at substantially the same axial position as the tip342of the flange340. The thick-plate part352is located within substantially the same axial range as that of the inner cylinder311. There is an axial gap353between the thin-plate part351and the thick-plate part352. From a surface354of the thin-plate part351facing the first engaging portion260of the fitting body200when the sleeve300is connected with the fitting body200as shown inFIG.2(the left-side surface of the thin-plate part351inFIG.2), an engaging projection355protrudes toward the axial direction of the sleeve300(leftward inFIG.2). An axial length of the engaging projection355, shapes and sizes of cross-sections thereof perpendicular to the axial direction, and a radial position thereof are designed such that the engaging projection355is placed within the engaging hole261when the sleeve300is connected with the fitting body200as shown inFIG.2.

The second axial end portion360of the sleeve300is a connector for the second hose520, which is coaxially placed within the second hose520, as shown inFIG.2. Since the outer diameter of the second axial end portion360is larger than the inner diameter of the second hose520, the second axial end portion360pushes an opening end of the second hose520radially outward when the second axial end portion360is press-fitted into the second hose520. Then, a restoring force of the opening end squeezes the second axial end portion360radially inward, and thus, the second hose520is fixed to the second axial end portion360and seals a gap between its inner periphery and an outer periphery of the second axial end portion360. [Work of Connecting Hoses through Tube Fitting]

A work of connecting the first hose510with the second hose520through the tube fitting100is performed according to the following steps. At first, the first axial end portion210of the fitting body200is press-fitted into the opening end of the first hose510, and the second axial end portion360of the sleeve300is press-fitted into the opening end of the second hose520. Next, the external thread330is screwed into the internal thread250of the fitting body200.

Since the fitting body200is integrated with the internal thread250, one of the fitting body200and the sleeve300has to be rotated relative to the other around a common axis to screw the external thread330into the internal thread250. Already, the first hose510has been fixed to the fitting body200and the second hose520has been fixed to the sleeve300, and accordingly, the relative rotation of the fitting body200and the sleeve300twists at least one of the first hose510and the second hose520. Preferably, either the first hose510or the second hose520is twisted before the external thread330is screwed into the internal thread250. The twist is formed such that its angle is the same as that of relative rotation of the internal thread250and the external thread330necessary for connection therebetween, but its direction is opposite to that of the rotation. As a result, both the first hose510and the second hose520can be untwisted when the external thread330has been completely screwed into the internal thread250.

Hereinafter, a rotation angle between the internal thread250and the external thread330when thread ridges of one of them start to enter spaces between thread ridges of the other is referred to as “engagement start position.” Another rotation angle between the threads250and330when an axial length of a portion of the external thread330placed radially inside the internal thread250reaches a desired value is referred to as “engagement finish position.” The rotation angle from an engagement start position to an engagement finish position is a rotation angle between the threads250and330necessary for connection therebetween.

In particular, the rotation angle between the internal thread250and the external thread330necessary for connection therebetween is designed to fall within a range. At any angle within the range, a worker can twist with one hand either the first hose510connected with the fitting body200or the second hose520connected with the sleeve300. More specifically, the range may be, for example, 180 or less, or preferably, 90 or less. This design is attainable, for example, by adjusting the numbers of thread ridges or pitches of the threads250and330. This design enables the worker to twist either thread250or330at a desired angle only by twisting one hand, which holds one of the fitting body200and the sleeve300, relative to the opposite hand, which holds the other thereof.

[Seal between Fitting Body and Sleeve]

The annular groove230of the fitting body200and the annular protrusion320of the sleeve300are designed such that the annular protrusion320can be press-fitted into the annular groove230when the fitting body200is connected with the sleeve300as shown inFIG.2. Especially in the configuration where the fitting body200is separated from the sleeve300, the inner diameter of the annular protrusion320is slightly smaller than the diameter of the radially inward surface of the annular groove230, and/or the outer diameter of the annular protrusion320is slightly larger than the diameter of the radially outward surface of the annular groove230. Accordingly, when the fitting body200is connected with the sleeve300as shown inFIG.2, the radially inward surface of the annular groove230and the inner periphery of the annular protrusion320, and/or the radially outward surface of the annular groove230and the outer periphery of the annular protrusion320firmly press against each other to tightly contact each other. Thus, gaps between the fitting body200and the sleeve300are sealed.

Force that press-fits the annular protrusion320of the sleeve300into the annular groove230of the fitting body200is an axial force that the annular protrusion320receives when the external thread330of the sleeve300is screwed into the internal thread250of the fitting body200. Unevenness of this axial force in the circumferential direction of the annular protrusion320is smaller than that of axial force that the annular protrusion320receives when the fitting body200and the sleeve300are axially pushed against each other directly with bare hands. In addition, increase in tightening torque of the external thread330against the internal thread250can more easily increase the force that press-fits the annular protrusion320into the annular groove230than direct increase in the axial force that pushes the fitting body200and the sleeve300against each other.

In the work of connecting the internal thread250of the fitting body200with the external thread330of the sleeve300, a worker can put his/her fingers on the engaging portions260and350to relatively rotate the fitting body200and the sleeve300around a common axis, and thus, the worker can easily exert circumferential force onto the fitting body200and the sleeve300. In addition, the tip of the first engaging portion260is farther apart from the axis of the fitting body200than other portions of the fitting body200, and the tip of the second engaging portion350is farther apart from the axis of the sleeve300than other portions of the sleeve300. Accordingly, exerting circumferential force onto the tips of the engaging portions260and350can apply larger torque to the fitting body200and the sleeve300than exerting the same force onto other portions of the fitting body200and the sleeve300.

When the internal thread250of the fitting body200is connected with the external thread330of the sleeve300, change in rotation angle between the internal thread250and the external thread330is followed by displacement of the first engaging portion260of the fitting body200and the second engaging portion350of the sleeve300in a common circumferential direction of the fitting body200and the sleeve300. When a rotation angle between the threads250and330reaches an engagement finish position, the engaging portions260and350are located at the same circumferential positions, as shown inFIG.1. Accordingly, by seeing the engaging portions260and350located at the same circumferential positions, the worker can visually identify engagement of the threads250and330has been completed.

When a rotation angle between the internal thread250and the external thread330reaches an engagement finish position, the engaging projection355of the second engaging portion350is snap-fitted into the engaging hole261of the first engaging portion260as follows. Immediately before a rotation angle between the threads250and330reaches the engagement finish position, the engaging projection355hits a side surface262of the first engaging portion260. Then, the thin-plate part351of the second engaging portion350bows toward the thick-plate part352, and thus, the engaging projection355moves over the side surface262. When the threads250and330reaches the engagement finish position, the engaging projection355enters the engaging hole261and the bowing thin-plate part351returns to the original straight shape. In this manner, elasticity of the thin-plate part351is used to fit the engaging projection355into the engaging hole261, and thus, the second engaging portion350is engaged with the first engaging portion260to fix the sleeve300to the fitting body200.

The thin-plate part351, when returning from the bowing shape to the straight one, slaps the side surface262of the first engaging portion260. Then, sound of the slapping reverberates through the gap353between the thin-plate part351and the thick-plate part352. By hearing the reverberating sound, a worker can confirm by ear if a rotation angle between the threads250and330reaches the engagement finish position.

Merits of Embodiment 1

In the tube fitting100according to embodiment 1 of the invention, the fitting body200includes the internal thread250and the sleeve300includes the external thread330. Thus, the tube fitting100does not need any union nut in contrast to conventional tube fittings. On the other hand, the tube fitting100needs a twist of at least one of the fitting body200connected with the first hose510and the sleeve300connected with the second hose520when the external thread330is screwed into the internal thread250. However, the rotation angle between the thread250and330necessary for connection therebetween is designed to fall within a range. At any angle within the range, a worker can twist either the first hose510or the second hose520with one hand. This can facilitate the twisting of the first tube510or the second tube520as desired. As a result, the tube fitting100enables reduction in manufacturing cost while keeping sufficiently high operability for connection of tubes510and520.

Since the fitting body200is integrated with the internal thread250, the tube fitting100enables, when the sleeve300is removed from the fitting body200in the configuration shown inFIG.2, the annular protrusion320to be extracted from the annular groove230by a force disengaging the external thread330from the internal thread250. In addition, an angle at which either the first tube510or the second hose520has to be twisted at that time falls within the range, at any angle within which the tube510or520can be twisted with one hand. Therefore, the tube fitting100has a higher operability for disconnection of the tubes510and520.

FIG.3is a perspective view showing an appearance of a tube fitting110according to embodiment 2 of the invention.FIG.4is a cross-section view along a line IV-IV inFIG.3. In contrast to the tube fitting100according to embodiment 1, the tube fitting110has an external thread provided to the fitting body200and an internal thread provided to the sleeve300. Other components are similar in structure to those of the tube fitting100according to embodiment 1. InFIGS.3and4, components similar in structure to those shown inFIGS.1and2are marked by the same numbers as those shown inFIGS.1and2. In addition, the following explains portions of the tube fitting110different in structure from those of the tube fitting100according to embodiment 1, and explanation about other portions can be found in description of embodiment 1.

As shown inFIG.4, the second axial end portion220of the fitting body200includes a flange270and an external thread280, as well as the inner cylinder221, the annular groove230, and the first engaging portion260. The flange270is different from the flange240according to embodiment 1 as follows. The tip271of the flange270in the axial direction of the fitting body200(left-right direction inFIG.4) is located at the same position as the opening portion222of the inner cylinder221. In addition, in the vicinity of the tip271, the external thread280is provided with an outer periphery of the flange270, which is a double start thread, for example. Two thread ridges281and282spiral along the outer periphery of the flange270.

As shown inFIG.4, the first axial end portion310of the sleeve300includes a flange370and an internal thread380, as well as the inner cylinder311, the annular protrusion320, and the second engaging portion350. The flange370is different from the flange340according to embodiment 1 as follows. The internal thread380is provided with an inner periphery of the flange370, which can be engaged with the external thread280of the fitting body200, and in particular, which is a multi-start thread with the same number of thread ridges as those of the external thread280, for example, a double start thread. Two thread ridges381and382spiral along the inner periphery of the flange370.

In the tube fitting110, the fitting body200includes the external thread280and the sleeve300includes the internal thread380. Thus, the tube fitting110does not need any union nut, like the tube fitting100according to embodiment 1. In addition, like the tube fitting100, the tube fitting110is designed such that the rotation angle between the external thread280and the internal thread380necessary for connection therebetween falls within a range, at any angle within which either the first hose510or the second hose520can be twisted with one hand. This can facilitate the twisting of the first tube510or the second tube520as desired. As a result, like the tube fitting100, the tube fitting110enables reduction in manufacturing cost while keeping sufficiently high operability for connection of tubes510and520.

As shown inFIG.2, in the sleeve300according to embodiment 1, the entirety of the annular protrusion320is located outside the range of the external thread330in the axial direction (the left-right direction inFIG.2). Otherwise, not only the first axial end portion310of the sleeve300but also the second axial end portion220of the fitting body200would have been complex in structure and enlarged radially. In contrast, the sleeve300according to embodiment 2 allows the tip321of the annular protrusion320to be located inside the range of the internal thread380in the axial direction (the left-right direction inFIG.4). The fitting body200according to embodiment 2 allows the external thread280to be located inside the range of the annular groove230in the axial direction (the left-right direction inFIG.4). The second axial end portion220of the fitting body200and the first axial end portion310of the sleeve300shown inFIG.4is as complex in structure as those220and310shown inFIG.2. In addition, the range of the annular protrusion320overlaps that of the internal thread380in the axial direction of the sleeve300, and thus, it is easy to reduce the axial thickness of the first axial end portion310of the sleeve300. Similarly, the range of the annular groove230overlaps that of the external thread280in the axial direction of the fitting body200, and thus, it is easy to reduce the axial thickness of the second axial end portion220of the fitting body200. Such reduction in thickness of the sleeve300and the fitting body200decreases amounts of material thereof, thus being advantageous to reduction in manufacturing cost of the tube fitting110.

In the sleeve300according to embodiment 1, the flange340surrounds the tip321of the annular protrusion320, as shown inFIG.2. In the sleeve300according to embodiment 2, the flange370surrounds the tip321of the annular protrusion320, as shown inFIG.4. Since both the flanges340and370serve as a barrier for the tip321of the annular protrusion320, the tip321is prevented from potential deformation and damage due to unconsidered contact with an external object such as the fitting body200. In addition, the thread ridges381and382of the internal thread380protrude from the inner periphery of the flange370according to embodiment 2, and thus, space around the annular protrusion320is narrower than that according to embodiment 1. Accordingly, for the function of the barrier protecting the tip321, the flange370according to embodiment 2 is more superb than the flange340according to embodiment 1.

Modifications

Both the flange240of the fitting body200according to embodiment 1 and the flange270of the fitting body200according to embodiment 2 have a substantially circular-cylindrical shape, and from a circumferential section thereof, the first engaging portion260protrudes. Both the flange340of the sleeve300according to embodiment 1 and the flange370of the sleeve300according to embodiment 2 have a substantially circular-cylindrical shape, and from a circumferential section thereof, the second engaging portion350protrudes. However, the flanges are not limited to such shapes, but they may have other axially asymmetric shapes. For example, their cross sections perpendicular to their respective axial directions may have polygonal profiles.

FIG.5is a perspective view showing an appearance of a modification120of the tube fitting according to embodiment 1 of the invention.FIG.6is a cross-section view along a line VI-VI inFIG.5. In contrast to the tube fitting100according to embodiment 1, the tube fitting120has flanges of different shapes. Other components are similar in structure to those of the tube fitting100according to embodiment 1. InFIGS.5and6, components similar in structure to those shown inFIGS.1and2are marked by the same numbers as those shown inFIGS.1and2. In addition, the following explains portions of the tube fitting120different in structure from those of the tube fitting100according to embodiment 1, and explanation about other portions can be found in description of embodiment 1.

The second axial end portion220of the fitting body200includes a flange290, which is a tubular portion coaxially surrounding the annular groove230and whose cross-section perpendicular to its axial direction has a substantially hexagonal profile. A distance between two opposite edges of the hexagonal profile is larger than the outer diameter of the first axial end portion210. A portion of the inner periphery of the flange290forms a radially outward surface of the annular groove230. In the axial direction of the fitting body200(the left-right direction inFIG.6), the flange290extends beyond the position of the opening portion222of the inner cylinder221(to the right side thereof inFIG.6). The portion of the flange290beyond the position of the opening portion222is provided with an infernal thread250, which is a double start thread, for example. Two thread ridges253and254spiral along an inner periphery of the flange290.

The first axial end portion310of the sleeve300includes a flange390, which is a ring-shaped portion of the inner cylinder311extending radially outward from a portion313thereof located on the side opposite to the opening portion312thereof in the axial direction of the sleeve300(on the right side thereof inFIG.6). Cross sections of the flange390perpendicular to the axial direction have a substantially hexagonal profile. A distance between two opposite edges of the hexagonal profile is larger than the outer diameter of the second axial end portion360.

FIG.7is a perspective view showing an appearance of a modification of the tube fitting130according to embodiment 2 of the invention.FIG.8is a cross-section view along a line IIX-IIX inFIG.7. In contrast to the tube fitting110according to embodiment 2, the tube fitting130has flanges of different shapes. Other components are similar in structure to those of the tube fitting110according to embodiment 2. InFIGS.7and8, components similar in structure to those shown inFIGS.3and4are marked by the same numbers as those shown inFIGS.3and4. In addition, the following explains portions of the tube fitting130different in structure from those of the tube fitting110according to embodiment 2, and explanation about other portions can be found in description of embodiment 2.

The second axial end portion220of the fitting body200includes a flange295, which is a ring-shaped portion of the inner cylinder221extending radially outward from a portion223thereof located on the side opposite to the opening portion222thereof in the axial direction of the fitting body200(on the left side thereof inFIG.8). Cross sections of the flange295perpendicular to the axial direction have a substantially hexagonal profile. A distance between two opposite edges of the hexagonal profile is larger than the outer diameter of the first axial end portion210. From the flange295, an outer cylinder296protrudes toward the axial direction of the fitting body200(rightward inFIG.8), whose cross sections perpendicular to the axial direction are of substantially circular-ring shape, and whose axial tip297is located at the same position as the opening portion222of the inner cylinder221. An inner periphery of the outer cylinder296forms a radially outward surface of the annular groove230. On the other hand, an outer periphery of the outer cylinder296is provided with an external thread280.

The first axial end portion310of the sleeve300includes a flange395, which is a tubular portion coaxially surrounding the inner cylinder311and the annular protrusion320, and whose cross sections perpendicular to its axial direction have a substantially hexagonal profile. A distance between two opposite edges of the hexagonal profile is larger than the outer diameter of the second axial end portion360. In the axial direction of the sleeve300(the left-right direction inFIG.8), the flange395extends beyond the position of the tip321of the annular protrusion320(to the left side thereof inFIG.8). The inner periphery of the flange395is provided with an internal thread380surrounding the annular protrusion320.

Outer peripheries of the flanges290and390of the modified tube fitting120according to embodiment 1 and the flanges295and395of the modified tube fitting130according to embodiment 2 each have six corners291and391. In the work of connecting the fitting body200with the sleeve300, a worker can put his/her fingers on the corners291and391of the flanges290and390, or the corners291and391of the flanges295and395to relatively rotate the fitting body200and the sleeve300around a common axis, and thus, the worker can easily exert circumferential force onto the fitting body200and the sleeve300. In addition, change in rotation angle between the fitting body200and the sleeve300displaces the corners291and391of either the flanges290and390or the flanges295and395in a common circumferential direction. When a rotation angle between the external and internal threads reaches an engagement finish position, the corners291and391are located at the same circumferential positions, as shown inFIGS.5and7. Accordingly, by seeing the corners291and391located at the same circumferential positions, the worker can visually identify engagement of the external and internal threads has been completed.