Patent Description:
As a joint structure for piping members, as shown in Patent Literature <NUM>, there is a method of welding and joining a pair of piping members.

However, the joining of piping by welding has its own problem that post-treatment including various preparatory work, bead removal after welding, and pickling of pipes is needed, which leads to a long lead time and an increase in cost.

<CIT> discloses a pipe joint with screwable connectors.

The present invention has been made to solve the above-described problem, and main expected purpose thereof is to enable a pipe member and a pipe joint to be more firmly joined than before without using welding.

<FIG> is a schematic view illustrating the principle of the present invention, and relates to a joining structure between an outer peripheral surface of a pipe member P and a cylindrical member C mounted on the outer peripheral surface. Specifically, as illustrated in an upper drawing, annular protrusions t are formed on an inner peripheral surface of the cylindrical member C, and a pressing means Pr is provided that presses a predetermined axial width d on the outer peripheral surface of the cylindrical member C radially inward.

A lower part of <FIG> shows that the annular protrusions t gradually bite into the outer peripheral surface of the pipe member P by radially inward force while the pressing means Pr is moved to a right side as indicated by a broken line.

That is, the joining structure according to the present invention to which this principle is applied is a joining structure that airtightly or liquid-tightly joins an outer peripheral surface of a pipe member and an inner peripheral surface of a cylindrical member to be mounted on the pipe member, characterized in that an annular protrusion is formed on the inner peripheral surface of the cylindrical member, and the pipe member and the cylindrical member are inseparable.

As described above, since the annular protrusion is formed on the inner peripheral surface of the tubular member, the annular protrusion bites into the outer peripheral surface of the pipe member, so that a firmer joining structure than before can be obtained without using welding.

Furthermore, the pipe joint according to the present invention is joined to the pipe member, and is characterized by being included, together with the pipe member, in the above-described joining structure.

If such a pipe joint is used, it is possible to obtain the above-described joining structure, and the pipe joint can be firmly joined to the pipe member without using welding.

A specific embodiment of the pipe joint can be the pipe joint including a first member in which a housing space for housing the pipe member is formed, the cylindrical member interposed between the outer peripheral surface of the pipe member and an inner peripheral surface (hereinafter referred to as a housing surface) of the first member forming the housing space, and a pushing member that applies axial force to the cylindrical member.

In order to allow the annular protrusion formed on the inner peripheral surface of the cylindrical member to bite into the outer peripheral surface of the pipe member, it is preferable that the cylindrical member is configured to generate radially inward force by the axial force of the pushing member.

Here, a configuration of <FIG> illustrating main points of the pipe joint (a joint body as the first member, the cylindrical member, and a nut as the pushing member) will be examined.

When this pipe joint is used, first, with the cylindrical member mounted on the pipe member, these are inserted into the joint body, and the nut, which is the pushing member, is screwed to the joint body from a rear side of the cylindrical member. As a result, the cylindrical member can be pushed between the outer peripheral surface of the pipe member and the inner peripheral surface of the joint body.

Here, the inner peripheral surface of the joint body and the outer peripheral surface of the cylindrical member are inclined so as to gradually reduce the diameter toward an insertion direction of the pipe member, and a plurality of protrusions is provided on the inner peripheral surface of the cylindrical member. As a result, when the cylindrical member is pushed toward the joint body, the cylindrical member is crushed radially inward, and the protrusions bite into the pipe member.

However, if the inner peripheral surface of the joint body and the outer peripheral surface of the cylindrical member are inclined, as illustrated in <FIG>, the number of annular protrusions involved in the bite increases sharply when force for pushing the cylindrical member is increased, and thus force resisting the pushing force also increases sharply. In other words, the plurality of annular protrusions that bites into the pipe member acts as resistance at the same time, and thus the pushing force is larger. Therefore, tightening torque required to screw the nut to the joint body increases, and if the tightening torque is insufficient and the cylindrical member cannot be crushed until a sufficient crimping property is obtained, the pipe member comes off from the pipe joint.

The larger the diameter dimension of the pipe member, the larger the required tightening torque, and thus the above-described problem is more noticeable.

Therefore, in order to solve the above-described problem, the first member is formed with a force concentrating portion that concentrates the radially inward force on a part of the outer peripheral surface of the cylindrical member.

With such a configuration, the radially inward force generated by the axial force applied to the cylindrical member can be concentrated on a part of the outer peripheral surface of the cylindrical member. Thus, it is possible to reduce resistance when the cylindrical member is pushed, and as illustrated in the schematic view of <FIG>, the annular protrusions formed on the inner peripheral surface of the cylindrical member can bite into the outer peripheral surface of the pipe member one by one, for example.

As a result, force required to push the cylindrical member (for example, tightening torque when the nut is used) can be reduced, and thus the pipe joint according to the present invention can be applied to a large-diameter pipe member as well.

The force concentrating portion is a part of the housing surface and is a bulging surface that bulges radially inward.

Thus, force can be concentrated on the outer peripheral surface of the cylindrical member with a simple configuration.

It is preferable that, on a cross section parallel to an axial direction of the cylindrical member, a plurality of the annular protrusions is provided along the axial direction, and the plurality of annular protrusions is configured to bite into the outer peripheral surface of the pipe member one by one along the axial direction by the radially inward force generated in the cylindrical member.

With such a configuration, the force required to crush the cylindrical member is smaller than in a configuration in which the plurality of annular protrusions bites into the outer peripheral surface of the pipe member at once, and the force required to push the cylindrical member can be further reduced.

The plurality of annular protrusions can be the plurality of annular protrusions that forms a spiral shape formed continuously or annular shapes formed discontinuously.

With such annular protrusions, the crimping property and the sealability between the pipe member and the pipe joint can be improved.

An example of a specific configuration of the pushing member can be a configuration in which a nut screwed to the first member, and a cylindrical element that receives axial force from the nut and presses the cylindrical member toward the first member are included.

Furthermore, a method for forming a joining structure according to the present invention is a method for forming a joining structure that airtightly or liquid-tightly joins an outer peripheral surface of a pipe member and an inner peripheral surface of a cylindrical member to be mounted on the pipe member, the method being characterized by including a first step of mounting, on the pipe member, the cylindrical member having an annular protrusion on the inner peripheral surface, a second step of pressing a predetermined axial width of the cylindrical member radially inward, and a third step of causing the annular protrusion formed in the predetermined axial width of the cylindrical member to bite into the outer peripheral surface of the pipe member by the radially inward press.

When the joining structure is formed in this way, the annular protrusion formed on the inner peripheral surface of the cylindrical member bites into the outer peripheral surface of the pipe member, and thus it is possible to obtain a firmer joining structure than before without using welding.

It is preferable to further include a fourth step of shifting, along an axial direction, a region of the cylindrical member to be pressed radially inward in the second step.

In this case, the annular protrusion formed on the inner peripheral surface of the cylindrical member can gradually bite into the outer peripheral surface of the pipe member, and the force required to push the cylindrical member can be reduced.

According to the above-described present invention, it is possible to join a pipe member and a pipe joint more firmly than before without using welding, and reducing force required to push a cylindrical member makes it possible to use the pipe joint for connecting large-diameter pipe members.

A pipe member P is connected to a pipe joint <NUM> of the present embodiment, and specifically, as illustrated in <FIG>, the pipe joint <NUM> includes a joint body <NUM>, which is a first member formed with an insertion port H into which a part of the pipe member P (here, pipe end Pa) is inserted, a cylindrical member <NUM> mounted on the pipe end Pa, and a pushing member <NUM> that pushes the cylindrical member <NUM> toward the joint body <NUM>. The pipe joint <NUM> here connects a pair of pipe members P having their pipe ends Pa facing each other, and includes the cylindrical member <NUM> and the pushing member <NUM> used for each pipe member P.

Note that a configuration illustrated in <FIG> illustrates a state where one (left) pipe member P is already connected to the pipe joint <NUM> and another (right) pipe member P is not connected to the pipe joint <NUM>.

The pipe members P are connected to the joint body <NUM> while fluid is allowed to flow between the pipe members P, and the joint body <NUM> is formed with, as illustrated in <FIG>, housing spaces S for housing the pipe ends Pa inserted via the insertion ports H. The joint body <NUM> here connects the pair of pipe members P, and the pair of housing spaces S corresponding to the pipe ends Pa of the pipe members P and a communication passage L communicating these housing spaces S are formed.

More specifically, the joint body <NUM> forms a substantially rotating body shape, and the diameter dimension of a portion <NUM> of an inner peripheral surface that forms the housing space S (hereinafter, also referred to as a housing surface <NUM>) is larger than the diameter dimension of a portion that forms the communication passage L. A step portion is formed between the housing space S and the communication passage L, and the pipe member P inserted into the housing space can be locked by this step portion.

As illustrated in <FIG>, in a state where the pipe end Pa is housed in the above-described housing space S, the cylindrical member <NUM> is interposed between the housing surface <NUM> and an outer peripheral surface of the pipe end Pa, to ensure the adhesion and sealability between these surfaces. The cylindrical member <NUM> here is designed to be press-fitted into an annular space formed between the housing surface <NUM> and the outer peripheral surface of the pipe end Pa, and specifically, in a state before the press fitting, the outer diameter (diameter dimension of an outer peripheral surface <NUM>) is slightly larger than the diameter dimension of the housing surface <NUM>, and the inner diameter (diameter dimension of an inner peripheral surface <NUM>) is slightly larger than the diameter dimension of the pipe member P.

More specifically, the cylindrical member <NUM> has a substantially cylindrical shape, and includes a locking portion <NUM> that locks a tip end surface of the inserted pipe end Pa, and a pressed surface <NUM> that is pressed by the pushing member <NUM> described later. When the pressed surface <NUM> is pressed with an end surface of the pipe member P being in contact with the locking portion <NUM>, the cylindrical member <NUM> is configured to be inserted (press-fitted) into the housing space S together with the pipe member P. Note that the pressed surface <NUM> here is an inclined surface that is inclined with respect to an axial direction, but it is not always necessary to incline the pressed surface <NUM>.

Furthermore, the cylindrical member <NUM> is provided with a tapered portion <NUM> whose outer diameter gradually decreases toward a tip (side of the joint body <NUM>). The outer diameter on a tip side of the tapered portion <NUM> is made smaller than the diameter dimension of the housing surface <NUM> described above, a tip portion of the cylindrical member <NUM> can be easily inserted into the housing space S. On the other hand, the outer peripheral surface <NUM> of the cylindrical member <NUM> on a rear side of the tapered portion <NUM> extends along the axial direction without being inclined with respect to the axial direction.

Furthermore, as illustrated in <FIG>, the inner peripheral surface <NUM> of the cylindrical member <NUM> is provided with annular protrusions <NUM> that protrude radially inward. The annular protrusions <NUM> bite into the outer peripheral surface of the pipe end Pa when the cylindrical member <NUM> is press-fitted between the housing surface <NUM> and the outer peripheral surface of the pipe end Pa and is crushed in a radial direction. Here, a protruding direction of the annular protrusions <NUM> is a direction slightly inclined toward the tip side from the radial direction, but the protruding direction is not limited to this, and the annular protrusions may protrude in the radial direction, for example. In the present embodiment, the plurality of annular protrusions <NUM> is provided on a cross section along the axial direction, and these annular protrusions <NUM> are formed in a spiral shape as a whole. Note that the annular protrusions <NUM> may be in annular shapes formed discontinuously on the cross section along the axial direction. Furthermore, the annular protrusions <NUM> are provided on the inner peripheral surface <NUM> of the cylindrical member <NUM> on the rear side of the tapered portion <NUM>, and are not provided on the tapered portion <NUM>.

As illustrated in <FIG>, the pushing member <NUM> pushes the cylindrical member <NUM> toward the joint body <NUM>, and includes a pressing surface <NUM> that presses the pressed surface <NUM> of the cylindrical member <NUM>. The pushing member <NUM> of the present embodiment is a nut through which the pipe member P is inserted and that is screwed to a threaded portion formed on the outer peripheral surface of the joint body <NUM>. Note that the pressing surface <NUM> is an inclined surface that is inclined with respect to the axial direction in correspondence with the pressed surface <NUM>, but it is not always necessary to incline the pressing surface <NUM>.

As described above, a function of the pushing member <NUM> can be described, if the cylindrical member <NUM> is focused on, as pushing the cylindrical member <NUM> relative to the joint body <NUM>, but the function can be described, if the joint body <NUM> is focused on, as pulling the joint body <NUM> relative to the cylindrical member. That is, the pushing member <NUM> pulls the joint body <NUM> toward the cylindrical member <NUM> while shortening a distance from the joint body <NUM>, and at the same time, pushes the cylindrical member <NUM> into the joint body <NUM> while shortening the distance from the joint body <NUM>. "Pushing" in this specification is a concept including the both functions (pushing and pulling) described above.

Here, a method of connecting the pipe member P to the pipe joint <NUM> of the present embodiment will be described.

First, as illustrated in <FIG>, the pipe member P to be connected to the pipe joint <NUM> (pipe member P on a right side in <FIG>) is passed through the nut, which is the pushing member <NUM>, the pipe end Pa is pressed against the joint body <NUM> with the cylindrical member <NUM> mounted on (fitted onto) the pipe end Pa, and the tip portion (specifically, the tapered portion <NUM>) of the cylindrical member <NUM> is pressed against the insertion port H of the joint body <NUM>.

In this state, the nut, which is the pushing member <NUM>, is screwed to the joint body <NUM>. As a result, the pressing surface <NUM> of the pushing member <NUM> presses the pressed surface <NUM> of the cylindrical member <NUM>, axial force is applied from the pushing member <NUM> to the cylindrical member <NUM>, and the cylindrical member <NUM> is press-fitted into the housing space S together with the pipe end Pa while being crushed between the outer peripheral surface of the pipe end Pa and the housing surface <NUM>.

Therefore, as illustrated in <FIG>, <FIG>, and <FIG>, the pipe joint <NUM> of the present embodiment is configured so that the axial force applied to the cylindrical member <NUM> is converted into radially inward force, and the radially inward force is concentrated on a part of the outer peripheral surface <NUM> of the cylindrical member <NUM>.

More specifically, particularly as illustrated in <FIG>, the housing surface <NUM> of the joint body <NUM> is provided with a force concentrating portion X that converts the axial force applied to the cylindrical member <NUM> into the radially inward force and concentrates the radially inward force on a part of the outer peripheral surface <NUM> of the cylindrical member <NUM>. Note that, in <FIG>, it seems as if the housing surface <NUM> of the joint body <NUM> does not move and the cylindrical member <NUM> is pushed toward the housing surface <NUM>, but actually the joint body <NUM> is also pulled toward the cylindrical member <NUM>, as described above.

<FIG> and <FIG> illustrate results of FEM analysis of the force applied to the outer peripheral surface <NUM> of the cylindrical member <NUM> in this configuration. From the analysis results, it can be seen that the force is concentrated on a part of the outer peripheral surface <NUM> of the cylindrical member <NUM> by the force concentrating portion X. Note that the length of arrows in <FIG> and <FIG> indicate the magnitude of the force applied to the outer peripheral surface of the cylindrical member <NUM>. The longest arrow in the illustrated example corresponds to 700MPa.

The force concentrating portion X is, for example, a bulging surface that bulges radially inward from the housing surface <NUM>, and is a surface that receives the tip portion (tapered portion <NUM>) of the cylindrical member <NUM> in the state of <FIG>. Note that the force concentrating portion X here is provided in the vicinity of the insertion port H on the housing surface <NUM>, and a portion of the housing surface <NUM> where the force concentrating portion X is not provided extends along the axial direction without being inclined with respect to the axial direction.

When the axial force applied to the cylindrical member <NUM> is converted into the radially inward force by the force concentrating portion X and concentrated on a part of the outer peripheral surface <NUM> of the cylindrical member <NUM>, as illustrated in <FIG>, the cylindrical member <NUM> is crushed and deformed at the place where the force is concentrated, and the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> bite into the outer peripheral surface of the pipe member P.

As illustrated in <FIG>, <FIG>, and <FIG>, the force concentrating portion X of the present embodiment is configured so that, by concentrating the radially inward force on a part of the outer peripheral surface <NUM> of the cylindrical member <NUM>, the plurality of annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> gradually (for example, one by one) bites into the outer peripheral surface of the pipe member P along the axial direction.

As described above, the cylindrical member <NUM> is pushed toward the joint body <NUM> until the state illustrated in <FIG> while the nut, which is the pushing member <NUM>, is screwed to the joint body <NUM>, so that the cylindrical member <NUM> is press-fitted into the annular space formed between the housing surface <NUM> and the outer peripheral surface of the pipe end Pa, and the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> bite into the outer peripheral surface of the pipe end Pa, which firmly joins and connects the pipe member P and the pipe joint <NUM>. As a result, between the outer peripheral surface of the pipe end Pa and the inner peripheral surface <NUM> of the cylindrical member <NUM>, a joining structure is formed in which the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> is used and that has the sealability (airtightness or liquid-tightness) and is inseparable.

Since the pipe joint <NUM> configured in this way is provided with the force concentrating portion X so that the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> bite into the outer peripheral surface of the pipe member P one by one along the axial direction, force required to push the cylindrical member <NUM> (tightening torque of the nut, which is the pushing member <NUM>) can be reduced as compared with a configuration in which the plurality of annular protrusions <NUM> bites the outer peripheral surface of the pipe member P at once, and for example, the pipe joint <NUM> can be applied to a large-diameter pipe member P having an outer diameter of about <NUM>.

Furthermore, since the cylindrical member <NUM> is press-fitted into the annular space formed between the housing surface <NUM> and the outer peripheral surface of the pipe end Pa, and the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> bite into the outer peripheral surface of the pipe end Pa, it is possible to obtain excellent adhesion and sealability between the housing surface <NUM> and the outer peripheral surface of the pipe member P.

The photograph illustrated in <FIG> is the proof of this, and illustrates a result of keeping the pipe member P connected to the pipe joint <NUM> of the present embodiment in a sealed state and continuing to supply pressure oil. That is, in a case where the pipe member P is sealed and the pressure oil is continuously supplied, the pipe member P comes off from the pipe joint <NUM> if the adhesion between the housing surface <NUM> and the outer peripheral surface of the pipe member P is insufficient, and the pressure oil continues to leak if the sealability is insufficient, but actually, the pipe member P ruptured (a portion surrounded by a broken line in the photograph). This is proof that extremely high adhesion and sealability are obtained between the housing surface <NUM> and the outer peripheral surface of the pipe member P. Note that the pipe member P used here is made of carbon steel having an outer diameter of <NUM> and a thickness of <NUM>, and has a tensile strength of 500N/mm<NUM>. Note that the breaking pressure was <NUM> MPa.

Furthermore, as illustrated in <FIG>, a portion of the housing surface <NUM> other than the force concentrating portion X and the outer peripheral surface <NUM> of the cylindrical member <NUM> on the rear side of the tapered portion <NUM> extend along the axial direction without being inclined with respect to the axial direction. Thus, the radially inward force does not act on the cylindrical member <NUM> in a portion having passed through the force concentrating portion X of the cylindrical member <NUM>, and deformation of the cylindrical member <NUM> is suppressed, so that the pushing of the cylindrical member <NUM> is not hindered. As a result, the force required to push the cylindrical member <NUM> can be further reduced.

Furthermore, since the annular protrusions <NUM> formed on the inner peripheral surface <NUM> of the cylindrical member <NUM> have a spiral shape as a whole, the annular protrusions <NUM> bite into the outer peripheral surface of the pipe member P, so that the sealability can be further improved.

Note that the present invention is not limited to the above embodiment.

For example, as illustrated in <FIG>, a first member <NUM> into which a pipe end Pa is inserted may be a member different from a joint body <NUM>. Specifically, the first member <NUM> is configured so that a housing space S is formed in which the pipe end Pa is housed, as in the above embodiment, and a cylindrical member <NUM> is press-fitted between a housing surface <NUM> forming the housing space S and an outer peripheral surface of the pipe end Pa. Note that a communication passage L communicating with the housing space S is formed here over the first member <NUM> and the joint body <NUM>.

As illustrated in <FIG>, a pipe joint <NUM> here is configured so that an end surface <NUM> of the joint body <NUM> and an end surface <NUM> of the first member <NUM> face each other, and at the same time, and these end surfaces <NUM> and <NUM> are in close contact with each other via a sealing member Z such as an O-ring. Specifically, as in the above embodiment, a pushing member <NUM> pushes the cylindrical member <NUM> toward the first member <NUM>, so that the first member <NUM> is pushed toward the joint body <NUM>. As a result, the end surface <NUM> of the joint body <NUM> and the end surface <NUM> of the first member <NUM> come into close contact with each other via the sealing member Z such as an O-ring.

In such a configuration, since the first member <NUM> is a member different from the joint body <NUM>, the first member <NUM> can be separated from the joint body <NUM> when a nut, which is the pushing member <NUM>, is removed from the joint body <NUM>. In other words, the joint body <NUM> can be moved in a radial direction, the pipe joint <NUM> that is detachable from a pipe member P can be provided, and the workability in a narrow space or the like can be improved.

A pushing member <NUM> may be a pushing member illustrated in <FIG>.

Specifically, the pushing member <NUM> further includes, in addition to a nut 30a in the above embodiment, a cylindrical moving body 30b that receives axial force from the nut 30a and presses a cylindrical member <NUM> toward a joint body <NUM>.

The cylindrical moving body 30b has the inner diameter smaller than the outer diameter of the cylindrical member <NUM>, and a step portion <NUM> is formed on an inner peripheral surface of the cylindrical moving body 30b so as to protrude radially inward and receive an end portion of the cylindrical member <NUM>.

When this pipe joint <NUM> is used, as illustrated in <FIG>, a pipe member P is first passed through the nut 30a, and then the cylindrical moving body 30b is mounted. The cylindrical member <NUM> is then mounted on the pipe member P. In this state, the pipe member P is inserted into a housing space S. The cylindrical moving body 30b is then pushed toward the joint body <NUM> with the nut 30a, and thus the cylindrical moving body 30b is press-fitted between the cylindrical member <NUM> arranged on an outer peripheral surface of a pipe end Pa and a housing surface <NUM> of the joint body <NUM>.

With such a configuration, when the cylindrical moving body 30b is pushed by the pushing member <NUM>, an axial position of the pipe member P is not restricted. Furthermore, as illustrated in <FIG>, when the inner diameter of a left pipe member is larger than the outer diameter of a right pipe member, an axial mounting position of the right pipe member is not restricted at all, and thus a so-called double pipe structure is configured.

A pushing member <NUM> is not limited to the nut in the above embodiment, and may include, as illustrated in <FIG>, flange portions F provided at respective pipe ends Pa of a pair of pipe members P and connecting portions B such as screws for connecting the flange portions F.

Specifically, cylindrical members <NUM> are fitted onto the pair of pipe members P, and the respective pipe ends Pa are inserted into housing spaces S. In this state, when the connecting portions B such as screws are inserted into a plurality of screw holes formed in the flange portions F and are tightened, the cylindrical members <NUM> can be pushed while a separation distance between the flange portions F is reduced.

Note that, in a first member <NUM> in a configuration of <FIG>, the joint body in the above embodiment is divided into a first element 10a in which one housing space S is formed and a second element 10b in which another housing space S is formed, and facing surfaces of the first element 10a and the second element 10b are in close contact with each other via a sealing member Z such as an O-ring.

As illustrated in <FIG>, force concentrating portions X may be provided at a plurality of locations on a housing surface <NUM>.

Furthermore, as illustrated in <FIG>, a position of a force concentrating portion X is not limited to the vicinity of an insertion port H on a housing surface <NUM>, and the force concentrating portion X may be provided at a position away from the insertion port H on a side of a communication passage L.

Although the plurality of annular protrusions <NUM> is provided on the inner peripheral surface <NUM> of the cylindrical member <NUM> in the above embodiment, one annular protrusion <NUM> may be provided on an inner peripheral surface <NUM> of a cylindrical member <NUM>, as illustrated in <FIG>.

Although the pipe joint <NUM> in the above embodiment is for connecting the pair of pipe members P having their pipe ends Pa facing each other, a pair of pipe members P may be connected in a state where a connecting space forms an L shape and directions of pipe ends Pa are orthogonal to each other, for example, as illustrated in <FIG>.

Furthermore, although the pipe joint <NUM> in the above embodiment connects the pair of pipe members P, one side does not have to be a pipe member, and for example, a pipe joint <NUM> may be used to connect a port of a fluid device or the like and a pipe member P.

Furthermore, as illustrated in <FIG>, a pipe joint <NUM> is only required to be configured by use of at least a cylindrical member <NUM>, and the joint body <NUM> and the pushing member <NUM> in the above embodiment are not necessarily required.

Moreover, as illustrated in <FIG>, if an annular protrusion <NUM> formed on an inner peripheral surface <NUM> of a cylindrical member <NUM> bites into an outer peripheral surface of a pipe member P in advance, a pipe joint <NUM> does not have to be provided with a pushing member <NUM>.

More specifically, as illustrated in <FIG>, first, the pipe member P onto which the cylindrical member <NUM> is fitted is fixed to a stopper <NUM>. At this time, a pipe end Pa and the cylindrical member <NUM> are housed in a housing space S1 of a joint body corresponding member <NUM> corresponding to a joint body <NUM>. In this state, the pushing member <NUM> prepared separately from the pipe joint <NUM> is pushed into an annular space between an outer peripheral surface <NUM> of the cylindrical member <NUM> and a housing surface <NUM> forming the housing space S1 by, for example, a hydraulic cylinder <NUM>. Even in this case, axial force applied to the cylindrical member <NUM> by the hydraulic cylinder <NUM> is converted into radially inward force by a force concentrating portion X provided on an inner peripheral surface of the pushing member <NUM>, and is concentrated on the outer peripheral surface <NUM> of the cylindrical member <NUM>. As a result, the annular protrusion <NUM> bites into the outer peripheral surface of the pipe member P.

As described above, if the annular protrusion <NUM> bites into the outer peripheral surface of the pipe member P in advance, the pipe member P can be inserted deeply into a housing space S of the joint body <NUM>, and thus tightening torque required to screw a nut to the joint body <NUM> can be made very small.

The above example illustrated in <FIG> shows that the pushing member <NUM> is integrally fixed with the joint body corresponding member <NUM> by being pushed (press-fitted) to the depth of the housing space S1 in an axial direction and then separated from a tip portion of the cylinder <NUM>. Furthermore, a reference sign 60a indicates a threaded portion for joining. Note that, in this case, the joint body corresponding member <NUM> of the housing space S1 may not be provided. It is also possible to pull out the pushing member <NUM> while the pushing member <NUM> is fixed to the tip of the cylinder. When the pushing member <NUM> is pulled out, for example, the diameter of the pushing member <NUM> is increased in a radial direction by hydraulic pressure, so that pulling resistance can be reduced.

In addition, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made without departing from the claimed subject-matter.

Claim 1:
A pipe joint (<NUM>) that is joined to a pipe member (P), the pipe joint (<NUM>) comprising:
a first member (<NUM>) in which a housing space (S) for housing the pipe member (P) is formed;
a cylindrical member (<NUM>) that has an annular protrusion (<NUM>) formed on its inner peripheral surface (<NUM>) and that is interposed between the outer peripheral surface of the pipe member (P) and an inner peripheral surface of the first member (<NUM>) forming the housing space (S), the inner peripheral surface of the first member (<NUM>) constituting a housing surface (<NUM>); and
a pushing member (<NUM>) that is configured to apply an axial force to the cylindrical member (<NUM>); wherein
the pipe joint (<NUM>) is configured to generate radially inward force by the axial force applied to the cylindrical member (<NUM>) by the pushing member (<NUM>);
the first member (<NUM>) is formed with a force concentrating portion (X) that concentrates the radially inward force on a part of an outer peripheral surface (<NUM>) of the cylindrical member (<NUM>);
the annular protrusion (<NUM>) is configured to bite into the outer peripheral surface of the pipe member (P) due to the force which is made to be concentrated on the part of the outer peripheral surface (<NUM>) of the cylindrical member (<NUM>) by the force concentrating portion (X);
characterised in that the force concentrating portion (X) is a part of the housing surface (<NUM>) and is a bulging surface that bulges radially inward.