Pipe joint

Abstract: A pipe joint is provided in which the sealing performance produced by an elastic sealing member 3 housed in a joint body 1 is improved. At one end of a fluid passage 4 that extends through the joint body 1, there is disposed an enlarged diameter recess 8 having, at an inner side thereof, a housing 5 for the sealing member 3 and, at the mouth side thereof, a housing 7 having an engaging groove 6 for a tube holding mechanism 2. The joint body 1 is a cold-forged component of a metal material. A guide member 13 made of a springy metal material is disposed on the outer circumferential side of the tube holding mechanism 2 and has an engaging section 13b elastically engaged in a slip-resistant state with the engaging groove 6 of the housing 7 for the tube holding mechanism 2.

Description: The present invention relates to a quick-type pipe joint used for connection of various kinds of fluid pressure apparatus and a tube primarily in an air pressure circuit. A conventional quick-type pipe joint for use in an air pressure circuit has a cylindrical joint body for housing a tube holding mechanism which is made of a metal material. This joint body typically has a fluid passage extending therethrough. A housing for housing a sealing member and an enlarged diameter recess for housing the aforesaid tube holding mechanism are disposed at one end of the fluid passage and are made by cutting a metal material such as brass or the like. However, in the known joint body the surface roughness of the inner surface of the housing for sealing member does not necessarily reach a value suitable for sealing and, in some cases, air may possibly leak out, though only slightly, between the sealing member and the aforesaid inner surface of the housing of the joint body. Also, in the known joint body cutting dusts produced during processing may remain adhered to the inner surface of the housing for the sealing member, whereby a defective product with incomplete sealing may be produced even though the processing is carried out appropriately. Further, in the aforesaid conventional pipe joint, it is usually the case that a guide member is made of synthetic resin and is snap-fit onto the inside of the joint body made of the metal material. In this case, the strength of the pipe joint is largely dominated by the temperature characteristics of the synthetic resin guide member. There has been a strong desire for improvements in strength, thermal characteristics, and durability in various application fields. An example of a conventional quick-type pipe joint is disclosed in FR 2772458. The document teaches a device for coupling a tube to a rigid element having a bore. The bore has a wider diameter part in which an insert having a tubular body portion and a nose portion are located. A groove is formed between the body portion and the nose portion in which a washer is fitted. A tubular declutching slide is provided inside the body portion of the insert and is slidable within respect thereto. A tube may be connected to the rigid member by inserting the tube into the declutching slide, and therefore into the bore of the rigid member. The washer is provided with teeth which grip and retain the tube in the bore. Removal of the tube from the bore is achieved by sliding a declutching slide towards the washer so that the end of the declutching slide pushes against and raises the teeth of the washer away from the tube. However, the document also teaches the provision of a closed removable intermediate ring which prevents unintentional sliding of the declutching slide towards the washer. Accordingly, a tube may only be removed from the coupling device if the intermediate ring has been removed. The present invention is intended to solve one or more of these problems, and an object thereof is to provide a pipe joint in which the sealing performance of an elastic sealing member housed in a joint body is improved. Another object of the present invention is to provide a pipe joint with improved assembly of the elastic sealing member and improved air-tightness by using a joint body formed with an inner surface having better surface roughness so as to be more suitable as a sealing surface. Another object of the present invention is to provide a pipe joint with improved strength, thermal characteristics, and durability. A pipe joint of the present invention comprising a cylindrical joint is described in the appended claim. The pipe joint having the aforesaid construction can be used in the same manner as a conventional pipe joint. However, since the joint body in which the inner rear side of the enlarged diameter recess disposed at one end of the fluid passage is made into a housing for the elastic sealing member is constructed as a cold-forged component of a metal material, it is possible easily to obtain a joint body having an improved surface roughness as compared with the case in which the joint body is made by a cutting process or the like. In particular, the surface roughness of the aforesaid housing for the elastic sealing member is improved, and its variation is stabilised, so that the sealing between the elastic sealing member and the inner surface of the housing can be made stable and more certain, and the sealing performance produced by the elastic sealing member can be improved. Furthermore, there is no generation of contaminants at the time of forming the joint body, such as generation of cutting dusts which accompanies cutting or the like. Therefore, the possibility of air-tightness being hindered by adhesion of such contaminants to the inner surface of the housing for the elastic sealing member is avoided, and the cause of poor air-tightness is removed, whereby the assemblage will be easy and the quality of the product can be heightened. By providing a guide member of a springy metal material disposed on the outer circumferential side of the tube holding mechanism and pressed into the aforesaid joint body, and elastically engaging the sharp edge at the tip of the engaging section which is formed by folding the inner side turnup section of the guide member, in a slip-resistant state with the engaging groove of the joint body, then a pipe joint with improved strength, thermal characteristics, and durability can be obtained because both the guide member and joint body are made of metal and, therefore, the influence of temperature on their joining strength is small. Further, by forming the aforesaid guide section of the guide member for guiding the release bush, the aforesaid projection, and the aforesaid engaging section on the inner end side of the guide member by pressing a plate of metal material and by disposing the guide member with the projection in contact with the inner circumference of the enlarged diameter recess of the joint body, the tube holding mechanism can be positioned stably in the enlarged diameter recess, the rigidity of the product itself increases, and the resistance to the rocking of the guide member is improved, so that air-tightness and durability against rocking of the tube and vibration of the joint body are improved. Moreover, this guide member can be made as a simple and multifunctional component, and a stable mounting thereof on the joint body can be ensured. The invention will now be further described by way of example with reference to the accompanying drawings in which: Fig. 1 is a cross-sectional view illustrating an embodiment of a pipe joint according to the present invention. Fig. 2 is a cross-sectional view of a joint body in the aforesaid embodiment. Fig. 3 is a cross-sectional view of a guide member in the aforesaid embodiment. Fig. 1 illustrates an embodiment of a pipe joint according to the present invention. The pipe joint for a tube according to this embodiment includes a cylindrical joint body 1, a tube holding mechanism 2 incorporated in said joint body 1 for holding an end of the tube, and an elastic sealing member 3 housed in the joint body 1. The aforesaid joint body 1 is made by cold-forging an iron-based metal material and, as will be understood from Fig. 2, a fluid passage 4 for passing fluid through the tube to a fluid pressure apparatus is disposed inside of the joint body 1 so as to penetrate through said joint body 1 in an axial direction. An enlarged diameter recess 8 is disposed at one end of this fluid passage 4, and this enlarged diameter recess 8 is composed of a housing 5 located on the inner rear side of the fluid passage 4 for housing a sealing member 3 and a housing 7 located on the mouth side of the fluid passage 4 for housing the tube holding mechanism 2. Said housing 7 includes an engaging groove 6 that engages with the tube holding mechanism 2. Further, a screw-type attachment 9 for attaching to the fluid pressure apparatus is disposed on the outer circumference at the other end of this joint body 1. The aforesaid tube holding mechanism 2 includes a chuck 10 made of metal and having a plurality of engaging pawls 10a that engage with an outer surface of the inserted tube, a collet 11 located outside of said chuck 10 for holding the chuck 10, a release bush 12 held with its tip end inserted in said chuck 10 for opening the aforesaid engaging pawls 10a to release them from the tube by pressing, and a guide member 13 for housing these members stably in the housing section 7 in the joint body 1. A portion of this guide member 13 is elastically engaged in a slip-resistant state with the engaging groove 6 in said housing 7. In the aforesaid chuck 10, the aforesaid plurality of engaging pawls 10a with inwardly bent tip ends are formed by disposing a plurality of slits 10b in a cylindrical member made of metal, and elasticity in the radial direction is imparted to these engaging pawls 10a by the aforesaid slits 10b. The engaging pawls 10a bite the outer circumferential surface of the tube to hold the tube. The aforesaid collet 11 is formed of synthetic resin in a cylindrical shape capable of holding the chuck 10 from the outside, and includes an inwardly-extending flange 11a at an end located on the mouth side of the enlarged diameter recess 8 of the joint body 1, i.e. at an outer end. This flange 11a engages with an end portion of the aforesaid chuck 10 located at the end opposite to the engaging pawls 10a to restrain the chuck 10 from escaping when a force in the direction of drawing the tube out is applied. Elasticity in the radial direction is imparted to an end portion of the collet 11 located on the inner rear side of the enlarged diameter recess 8 of the joint body 1, i.e. to an inner end portion, by disposing slits (not illustrated) similar to those of the aforesaid chuck 10. The aforesaid release bush 12 is held in a state with its tip end inserted into the chuck 10, and includes a head portion 12a that protrudes to the outside of the joint body 1 for pressing and a leg portion 12c having elasticity imparted in the radial direction by the slits 12b formed in the axial direction for opening. The inside of the aforesaid release bush 12 is made into an insertion hole 12d for the tube 3. This release bush 12 is prevented from escaping from said collet 11 by confronting the tip end of the aforesaid leg portion 12c with the inside of the engaging pawls 10a in the aforesaid chuck 10 and engaging a peripheral step portion 12e with the inwardly-extending flange 11a of the collet 11. By pressing the head portion 12a to press the leg portion 12c in the tip end direction of the engaging pawls 10a of the chuck 10, the engaging pawls 10a are press-opened to release the engagement between the engaging pawls 10a and the tube. To the outer circumferential portion of the aforesaid tube holding mechanism 2, a guide member 13 is fitted for elastically engaging the tube holding mechanism 2 itself in a slip-resistant state in the housing 7 of the joint body 1. Referring to Fig. 3, this guide member 13 is formed of a springy metal material in a cylindrical shape and, by outwardly folding the metal material, a turnup section 13a is formed over the entire circumference of the inner end portion of the guide member 13 inserted into the inner rear side of the enlarged diameter recess 8 of the joint body 1. An engaging section 13b having a sharp edge is formed at the tip end of this turnup section 13a. The aforesaid turnup section 13a expands and contracts elastically in the radial direction of the guide member 13 by the springiness of the metal material used as a raw material. By pressing the guide member 13 into the housing 7 in mounting the tube holding mechanism 2 into the housing 7, the turnup section 13a is pressed into the housing 7 while expanding or contracting in accordance with the uneven shape of the inner circumference of the housing 7. By enlarging the diameter in the engaging groove 6 of the housing 7, the edge of the engaging section 13b at the tip end engages elastically with the groove wall of the engaging groove 6 to be brought into a slip-resistant state. This allows the tube holding mechanism 2 to be housed stably in the housing 7. On the other hand, by inwardly folding the raw material, a guide section 13c for guiding the release bush 12 is formed over the entire circumference of the outer end portion of the aforesaid guide member 13, i.e. the end portion located on the mouth side of the enlarged diameter recess 8 of the joint body 1. Further, a projection 13d which is in contact with the inner circumference of the enlarged diameter recess 8 of the joint body 1 is formed on the outer circumferential portion of the guide member 13 by bending said outer circumferential portion to protrude outward. The aforesaid guide section 13c serves to guide the release bush 12 in the axial direction of the enlarged diameter recess 8 so that the operations of pushing, pressing, and returning the release bush 12 can be performed stably within the joint body 1. The aforesaid guide section 13c abuts the outer circumferential surface on the inner side of the head portion 12a of the release bush 12 at the mouth portion of the enlarged diameter recess 8 to an extent that does not hinder the operations of the release bush 12. Further, the projection 13d serves to stabilize the guide member 13 to prevent movement of the guide member 13 in the enlarged diameter recess 8 so that the tube holding mechanism 2 will not move in a radial direction within the enlarged diameter recess 8. The guide section 13c for guiding the release bush, the projection 13d, the turnup section 13a, and the engaging section 13b in this guide member 13 are integrally formed by pressing a metal plate member. This allows the tube holding mechanism 2 to be positioned stably in the enlarged diameter recess 8, whereby the rigidity of the product itself increases and, at the same time, the resistance against rocking of the guide member 13 is improved. Therefore, air-tightness and durability can be improved against rocking of the tube and vibration of the joint body itself. Moreover, this guide member 13 can be made into a simple and multifunctional component, and a stable state of being mounted on the joint body 1 can be ensured. Further, since the aforesaid guide member 13 is formed of metal in the same manner as the aforesaid joint body 1, the influence of temperature on their joining strength will be small, so that the pipe joint as a whole will be extremely superior in strength, thermal characteristics, and durability. The aforesaid elastic sealing member 3 is housed in the housing for sealing member 5 of the enlarged diameter recess 8 of the joint body 1, and is in a state of being interposed between the aforesaid tube holding mechanism 2 and the step portion 8a of the enlarged diameter recess 8. This elastic sealing member 3 serves to seal the outer circumference of the tube inserted in the fluid passage 4, and this tube is inserted up to a position of hitting a stopper section 4a having a smaller diameter than the diameter of the housing for sealing member 5 in an inner rear side deeper than the enlarged diameter recess 8 in the fluid passage 4 of the joint body 1 through an insertion hole 12d in the aforesaid release bush 12. The joint body 1 having the above-described construction is formed as a cold-forged product of an iron-based metal material. This improves the dimension precision thereof and allows the finish after processing to be smooth with superior surface roughness as compared with the case in which the joint body 1 is subjected to a cutting process. Measurements have revealed that the surface roughness (Rmax) of the joint body 1 molded by cold-forging is 1.00 to 2.00, whereas the surface roughness (Rmax) of a conventional joint body formed by cutting is 4.00 to 7.00. This means that the joint body 1 has a surface roughness which is improved to the extent of making it suitable as a sealing surface to be brought into contact with the elastic sealing member 3 for sealing and the variation thereof is stabilised, whereby the air-tightness of the elastic sealing member 3 can be improved. In order to bring the surface roughness of a joint body formed by cutting to the level of a cold-forged product, a secondary process is required. For example, a rolling process or a fine cutting process such as lapping, buffing or forming by burnishing must be carried out, thereby requiring additional labour. Moreover, if cutting dust is produced by cutting, it is necessary to remove the cutting dust so that it will not be an obstacle against sealing. For this reason, some cost increase is inevitable for improvement of the quality of products produced by cutting. However, with cold-forging the cost can be reduced and, in addition, there is no generation of cutting dust or the like that will be an obstacle against sealing, as is the case when using a cutting process. The pipe joint having the aforesaid construction can be used in the same manner as a conventional pipe joint. However, since the joint body 1 in which the inner rear side of the enlarged diameter recess 8 disposed at one end of the fluid passage 4 is made into a housing 5 for the elastic sealing member is constructed as a cold-forged component of a metal material, it is possible easily to obtain a joint body 1 having improved surface roughness as compared with the case in which the joint body is made by a cutting process or the like. In particular, according to the aforesaid joint body 1, the surface roughness of the housing 5 for the elastic sealing member is improved, its variation is stabilised, and also it is possible to avoid the case in which the air-tightness is hindered by adhesion of contaminants generated at the time of molding to the inner surface of the housing the elastic sealing member 3. Therefore, the sealing between the elastic sealing member 3 and the inner surface of the housing 5 can be made stable and certain, the sealing performance produced by the elastic sealing member 3 can be improved, and the quality of the product can be heightened. In the above-described embodiment, the tube holding mechanism 2 is elastically engaged in a slip-resistant state with the housing 7 in the joint body 1 by means of the turnup section 13a of the guide member 13 in the tube holding mechanism 2. However, it is not limited to this alone, and instead of this, a portion of the tube holding mechanism 2 may be engaged with the housing 7. According to the pipe joint of the present invention described above in detail, since the joint body in which the inner rear side of the enlarged diameter recess is made into a housing for the elastic sealing member is constructed as a cold-forged component of a metal material, it is possible to improve the surface roughness more with ease as compared with a case in which the joint body is made by a cutting process or the like case. In particular, the surface roughness of the aforesaid housing for the elastic sealing member is improved, and its variation is stabilized, so that the sealing between the elastic sealing member and the inner surface of the housing can be made stable and certain, and the sealing performance produced by the elastic sealing member can be improved. Furthermore, there is no generation of contaminants at the time of molding the joint body, such as the generation of cutting dusts accompanying the cutting or the like. Therefore, it is possible to avoid the case in which the air-tightness is hindered by adhesion of such contaminants to the inner surface of the housing for the elastic sealing member, and the cause of poor air-tightness is removed, whereby the assemblage will be easy and the quality of the product can be heightened.

Claims: A pipe joint comprising a cylindrical joint body (1), a tube holding mechanism (2) for holding an end of a tube in a freely engageable and disengageable manner, and an elastic sealing member (3) for sealing around the tube, the joint body (1) having a fluid passage (4) extending therethrough in the axial direction thereof with an enlarged diameter recess (8) formed in a portion of the fluid passage (4) towards an end thereof, the enlarged diameter recess (8) including a housing (7) for the tube holding mechanism (2) on the passage entrance side and a housing (5) for the sealing member (3) on the side inward of the passage (4), wherein an engaging groove (6) is disposed on an inner circumferential surface of the housing (7) for the tube holding mechanism (2) and an attachment (9) for attaching to a fluid pressure apparatus is disposed on the other end of the joint body (1), wherein the elastic sealing member (3) is housed in the sealing member housing (5) for sealing between the inner surface of the housing (5) for the sealing member (3) and the outer surface of a tube inserted through the tube holding mechanism (2), wherein the tube holding mechanism (2) is housed in a slip-resistant state in the housing (7) for the tube holding mechanism (2) by elastically engaging a portion thereof with the engaging groove (6), wherein the tube holding mechanism (2) includes a plurality of engaging pawls (10a) for elastically engaging with an outer circumference of the inserted tube and a cylindrical release bush (12) that allows withdrawal of the tube by releasing the engaging pawls (10a) by a pushing operation, and wherein a cylindrical guide member (13) is fitted onto an outer circumference of the tube holding mechanism (2), characterised in that the guide member (13) is made of a springy metal material and has a turnup section (13a) formed at an end portion of the cylinder and an engaging section (13b) with a sharp edge formed at the tip of the turnup section (13a) by outward folding, the tube holding mechanism (2) being housed in the slip-resistant state in the housing (7) by elastically engaging the engaging section (13b) with the engaging groove (6), in that the guide member (13) includes a guide section (13c) formed by inwardly folding an other end portion of the cylinder and a projection (13d) formed by folding a portion of the cylinder to protrude outwardly, the guide section (13) guiding operation of the release bush (12) by sliding contact with an outer circumferential surface of the release bush (12) and the projection (13d) holding the tube holding mechanism (2) stably in the enlarged diameter recess (8) by abutting an inner circumferential surface of the enlarged diameter recess (8), in that the guide section (13c), the projection (13d), and the turnup section (13a) of the guide member (13) are integrally formed by pressing of a plate of metal material, and in that the joint body (1) comprises a cold-forged component of a metal material.

Inventors: MORI SHIZUO, NAKAZUMI MASAHIRO, MORI, SHIZUO, NAKAZUMI, MASAHIRO, Mori, Shizuo, c/o SMC Corporation Tsukuba, Nakazumi, Masahiro, c/o SMC Corporation Tsukuba
Applicants: SMC CORP, SMC CORPORATION
Application year: 2000
Main classification: F16L37
IPC codes: F16L37