Abstract:
A tube to be connected to a pipe is formed of a base portion, a wide portion and a narrow portion integrally molded together. The wide portion has an inner end extending to the base portion, and an opening formed at a side opposite to the inner end. An inner diameter of the wide portion is greater than that of the base portion. When the pipe is inserted, the base portion receives an insertion portion of the pipe, while the wide portion receives a projecting portion of the pipe therein. The narrow portion deformably projects inwardly from an inner circumference of the wide portion at a position away from the inner end. The narrower portion allows the projecting portion to pass therethrough in a pipe inserting direction by deformation thereof, and prevents the projecting portion from passing therethrough in a pipe removing direction opposite to the pipe inserting direction.

Description:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT 
     The invention relates to a tube to be connected to a pipe having a projecting portion at an insertion end portion, more particularly, an improvement of a connecting structure of the tube to be connected to the pipe. 
     Heretofore, a connector for connecting a pipe made of a, relatively hard material, such as steel, and a tube made of a relatively soft material, such as synthetic resin, has been, disclosed in, for example, Japanese Patent Publication (KOKAI) No. 5-196184. 
     The conventional connector, as shown in FIGS.  5 ( a ) and  5 ( b ), connects a tube T having a uniform outer diameter, to a pipe P having an insertion end portion P 1  with a uniform outer diameter and a flange portion F on a circumference of the insertion end portion P 1 . The connector includes a connector main portion C and a retainer R. 
     The connector C is formed of a mounting portion C 1 , a base portion C 2  and an attaching portion C 3 , which are integrally molded. The mounting portion C 1  has a cylindrical shape with a small diameter and a plurality of annular projections K of a hook shape on its outer circumferential surface. The base portion C 2  has a cylindrical shape of a sufficiently larger diameter than the insertion end portion P 1  of the pipe P, and houses therein a pair of O-rings  01 ,  02 , and a spacer S. The attaching portion C 3  has a cylindrical shape of a diameter larger than that of the base portion C 2 , and is provided with a pair of windows W at mutually facing portions. The connector main portion C is attached to the tube T by inserting the mounting portion C 1  into an opening end portion of the tube T. 
     The retainer R has a pair of openable elastic tongues A, and is attached to the attaching portion C 3  such that the tongues A are fitted in the respective windows W. The elastic tongues A are gradually inclined inwardly toward the base portion C 2  of the connector main portion C to thereby form a space smaller than an outer diameter of the flange portion F between the forward ends thereof. 
     In the conventional technique, when the pipe P is inserted into the connector main portion C, the elastic tongues A are pressed in a direction radially outwardly by the flange portion F, so that the elastic tongues A are suitably widened to thereby allow the flange portion F to pass therethrough. Thereafter, when the flange portion F has passed through the elastic tongues A, the respective tongues A return to the normal states by their respective restoring forces, and the respective forward ends of the elastic tongues A are pressed against the circumferential surface of the pipe P on the base end side of the flange portion F. 
     As a result, the pipe P is prevented from being disengaged from the connector through the flange portion F to thereby hold a connecting state between the pipe P and the tube T. 
     In case the conventional connector is used, as described above, since the pipe P and the tube T can be mutually connected by the insertion operation of the pipe P, the connecting operation can be easily carried out. 
     Also, in the insertion operation, the insertion force is suddenly changed after the forward ends of the elastic tongues A pass the flange portion F to thereby give an operator a moderate feeling, so that the operator can acknowledge the connecting state between the pipe P and the tube T through the moderate feeling. 
     However, in the above-described connector, it is necessary that the mounting portion C 1  of the connector main portion C is inserted into an opening end portion of the tube T. The insertion operation of the mounting portion C 1  requires a great force and is extremely troublesome since the mounting portion C 1  is pushed while gradually widening an inner diameter of the tube T. 
     Moreover, in case the above-described connector is used, it is necessary that not only the connector main portion C and the retainer but also the O-rings  01 ,  02  and  03  are interposed over the tube T and the pipe P. As a result, the number of parts for connecting the pipe P and the tube T becomes extremely large, which results in a high cost. 
     In view of the above defects, the present invention has been made, and an object of the invention is to provide a tube which can be connected to a pipe with an easy operation. 
     Another object of the present invention is to provide a tube as stated above, wherein a production cost can be greatly reduced. 
     Further objects and advantages of the invention will be apparent from the following description of the invention. 
     SUMMARY OF THE INVENTION 
     In order to attain the above objects, according to one aspect of the invention, there is provided a tube to be connected to a pipe including an insertion portion extending from an end surface with an approximately uniform horizontal sectional, and a, projecting portion extending radially outwardly from a circumference thereof and disposed at a position away from the end surface by a predetermined distance. 
     The tube is integrally formed of a base portion for allowing the insertion portion of the pipe to be inserted therein through an opening at an end surface; a wide portion formed at an open end portion of the base portion to allow the projecting portion of the pipe to be inserted; and a narrow portion projecting inward from an inner surface of the wide portion. The narrow portion is located at a portion closer to an opening side than the projecting portion of the pipe in case the insertion portion of the pipe is inserted into the base portion. In an ordinary state, the narrower portion prevents the projecting portion of the pipe from passing therethrough, and in case the narrower portion is elastically widened, the narrower portion allows the flange portion to pass therethrough. 
     According to a second aspect of the invention, the narrower portion in the first aspect is formed of a plurality of projections disposed side by side in a circumferential direction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG.  1 ( a ) is a sectional view of an essential part of an embodiment of a tube according to the present invention for showing a state before a pipe is inserted into the tube; 
     FIG.  1 ( b ) is a sectional view of the essential part of the embodiment of the tube according to the present invention for showing a state after the pipe is connected to the tube; 
     FIG.  2 ( a ) is a half sectional view of the whole tube as shown in FIG.  1 ( a ); 
     FIG.  2 ( b ) is an enlarged side view from a direction of an arrow  2 ( b ) in FIG.  2 ( a ); 
     FIG.  3 ( a ) is an explanatory view showing molds and an extruder for molding the tube as shown in FIGS.  1 ( a ) and  1 ( b ); 
     FIG.  3 ( b ) is an explanatory view for showing plural pairs of the molds shown in FIG.  3 ( a ) and disposed side by side; 
     FIG. 4 is an explanatory exploded perspective view for showing an example where the tube as shown in FIGS.  1 ( a ) and  1 ( b ) is applied; 
     FIG.  5 ( a ) is a sectional view of an essential part of a conventional connector for connecting a tube and a pipe, in a state before the tube is connected to the pipe; and 
     FIG.  5 ( b ) is a sectional view of an essential part of the conventional connector for connecting the tube and the pipe, in a state after the tube is connected to the pipe. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereunder, the present invention is explained based on the drawings showing embodiments thereof. 
     FIGS.  2 ( a ) and  2 ( b ) show an embodiment of a tube according to the present invention, i.e. a tube  20  to be connected to a fuel return pipe  10  of a pump chamber unit in a vehicle fuel supply system provided to a fuel tank  1 , as shown in FIG.  4 . 
     As shown in FIGS.  1 ( a ) and  1 ( b ), the fuel return pipe  10  to be connected has an insertion end portion  11  to be connected to the tube  20 . The insertion end portion  11  has almost the same outer diameter, and is formed of a cylindrical steel member. The insertion end portion  11  has also an annular flange portion  12 , i.e. projecting portion, around the whole circumference at a position spaced for a predetermine distance from a forward end surface  11   a.  As apparent from the drawing, the flange portion  12  has different outer shapes on a base end side and on a forward end side. More specifically, a part of the flange portion  12  positioned on the base end side (hereunder, simply referred to as “flange base end surface  12   a ”) of the fuel return pipe  10  projects perpendicular to an outer circumferential surface of the pipe. On the other hand, a part of the flange portion  12  positioned on the forward end side (hereunder, simply referred to as “flange forward end surface  12   b ”) of the fuel return pipe  10  gradually inclines outwardly from an outer circumferential surface to the base end side of the pipe  10 . 
     Incidentally, in the present embodiment, in case an outer diameter of the fuel return pipe  10  is 8 mm, the flange portion  12  has an outer diameter of 11 mm. Also, the fuel return pipe  10  has a length of 25 mm from the forward end surface  11   a  to the flange base end surface  12   a.    
     The tube  20  is integrally molded with a synthetic resin, such as 11-nylon (polyundecaneamide) and so on, and includes a first straight tube portion  21 , a corrugate portion  22 , a second straight tube portion  23  and a connector portion  24 . The first straight tube portion  21  is a cylindrical portion having a uniform inner diameter, i.e. of 7 mm, slightly smaller than an outer diameter of the fuel return pipe  10 . The corrugate portion  22  has a shape of bellows and a diameter lager than that of the first straight tube portion  21 , and can be easily bent. The second straight tube portion  23  has a cylindrical shape of the same inner diameter as that of the first straight tube portion  21 . The connector portion  24  is longer than a distance from the forward end surface  11   a  to the flange base end surface  12   a  of the fuel return pipe  10 , and includes a base portion  24   a , a wide portion  24 b and a narrow portion  24   c.    
     The base portion  24   a  has a cylindrical shape having an inner diameter same as the outer diameter of the fuel return pipe  10 , i.e. inner diameter of 8 mm. The base portion  24   a  is slightly shorter than a length from the forward end surface  11   a  to the flange forward end surface  12   b  of the fuel return pipe  10 . 
     The wide portion  24   b  constitutes an insertion port for the fuel return pipe  10 , and has an inner diameter larger than the outer diameter of the flange portion  12 , concretely 11.8 mm. 
     The narrow portion  24   c  is formed of four projections  24   d  provided on the inner circumferential surface of the wider portion  24   b  located at the same circular circumference. The projections  24   d  are disposed with an equal interval therebetween and project inwardly. Also, the projections  24   d  have spaces between mutually facing portions, i.e. 9.6 mm, larger than the outer diameter of the fuel return pipe  10  and smaller than the outer diameter of the flange portion  12 . The narrower portion  24   c  is formed such that in, case the fuel return pipe  10  is inserted into the deepest portion of the base portion  24   a  (refer to FIG.  1 ( b )), it is located at art opening side, relative to the side of the flange base end surface  12   a , at the inner circumferential surface of the wide portion  24   b . Also, when the respective projections  24   d  for constituting the narrow portion  24   c  are pressed radially outwardly, they can be elastically bent in that direction easily. 
     The tube  20  can be molded by various molding methods, such as an extrusion molding method and a blow molding method. For example, in the present embodiment, as shown in FIG.  3 ( a ), the tube  20  is molded by using a continuous extruder  30  for extruding a hollow portion. 
     The continuous extruder  30  includes plural pairs of single molds  31   a ,  31   b , . . . ,  31   n , and a pair of transferring mechanisms  32 R,  32 L for transferring the pairs of the single molds  31   a ,  31   b ,  31   n . As shown in FIG.  3 ( b ), in case the plural pairs of the single molds  31   a ,  31   b , . . . ,  31   n  are sequentially disposed side by side, there is constituted a series of cavities  33  corresponding to the first straight tube portion  21 , corrugate portion  22 , second straight tube portion  23  and connector portion  24  of the tube  20 . The respective pairs of the single molds  31   a ,  31   b , . . . ,  31   n  can be divided into two parts to cut the series of the cavities  33  in half. The transferring mechanisms  32 R,  32 L independently circulate the respective single molds  31   a ,  31   b , . . . ,  31   n  in the state divided on the upper side and the lower side by a suitable transferring device, such as a chain and belt, as shown in FIG.  3 ( a ), and the respective series of the single molds  31   a ,  31   b , . . . ,  31   n  are held in a contact state at a predetermined molding portion  34 . 
     In the continuous extruder  30 , a molten resin is sequentially supplied from an extruder  35  between the respective series of the single molds  31   a ,  31   b , . . . ,  31   n  mutually joined at the molding portion  34  to be adsorbed along the inner circumferential surfaces of the respective single molds  31   a ,  31   b , . . . ,  31   n , so that the tubes  20  of different shapes can be continuously molded in an axial direction. 
     In case the fuel return pipe  10  is connected to the tube  20  thus structured, first, as shown in FIG.  1 ( a ), an O-ring  40 , as a sealing member, having a smaller inner diameter than the outer diameter of the fuel return pipe  10  is disposed in the wide portion  24   b  of the connector portion  24  of the tube  20 . In this case, it is necessary to use the O-ring  40  having an outer diameter slightly larger than the inner diameter of the wider portion  24   b . Since the O-ring  40  can be easily deformed, in case the O-ring  40  is disposed in the wide portion  24   b , especially, to pass through the narrow portion  24   c , no troublesome operation is required. Incidentally, in the present embodiment, the O-ring  40  made of a material having a sufficient resistance with respect to a fuel like gasoline, for example, a fluoro-rubber is used. 
     Then, the fuel return pipe  10  is inserted from the forward end side thereof through the opening of the wide portion  24   b.    
     When the fuel return pipe  10  is inserted into the tube  20  and the flange portion  12  reaches the narrow portion  24   c , the respective projections  24   d  for constituting the narrow portion  24   c  are sequentially pressed radially outwardly by the inclination of the flange forward end surface  12   b  to thereby elastically deform, respectively. As a result, the spaces formed among the respective projections  24   d  at the narrow portion  24   c  are enlarged to allow the flange portion  12  of the fuel return pipe  10  to pass therethrough. 
     When the flange portion  12  of the fuel return pipe  10  has passed through the narrow portion  24   c  of the tube  20 , as shown in FIG.  1 ( b ), the plural projections  24   d  for constituting the narrow portion  24   c  return to the ordinary state, respectively, to again form the spaces, among the respective projections  24   d , which are larger than the outer diameter of the fuel return pipe  10  and smaller than the outer diameter of the flange portion  12 . 
     Thus, a movement in a disengaging direction of the fuel return pipe  10  with respect to the tube  20  is prevented by the flange base end surface  12   a  of the fuel return pipe  10  abutting against the projections  24   d , so that the tube  20  and the fuel return pipe  10  are held in a connected state. In this state, since the O-ring  40  disposed at the wide portion  24   b  is tightly pressed between an outer circumferential surface of the fuel return pipe  10  and an inner circumferential surface of the wide portion  24   b  to obtain a sufficient sealing ability therebetween, there is no risk of leaking of a fuel. 
     As described above, since the tube  20  can be attached by only inserting the fuel return pipe  10  thereinto, an attaching operation of the tube  20  can be extremely easily carried out. 
     Furthermore, the respective elements, i.e. the base portion  24   a , wide portion  24   b  and narrow portion  24   c , for constituting the connector portion  24  acting as a connector with respect to the fuel return pipe  10  are integrally molded, and at the same time, the connector portion  24  is also integrally molded with the first straight tube portion  21 , the corrugate portion  22  and the second straight tube portion  23 . Thus, the tube of the invention does not require any preparation in advance as in the conventional tube to thereby easily carry out the whole connecting operation, reduce the number of parts required for connecting the fuel return pipe  10 , and lower the cost. 
     Also, an insertion operation force is suddenly changed after the flange portion  12  passes through the respective projections  24   d  at the narrow portion  24   c  to give an operator a moderate feeling so that the operator can recognize its connecting state between the fuel return pipe  10  and the tube  20 . 
     Incidentally, in the above embodiment, although the tube  20  to be connected to the fuel return pipe  10  of the pump chamber unit in the vehicle fuel supply system is exemplified, the tube of the invention can also be applied to any tube to be connected to a pipe having a projecting portion on an outer surface of an insertion end portion. In this case, the tube does not necessarily have the corrugate portion. Also, the pipe to be connected does not necessarily have a circular cylinder, and for example, a pipe having a square pillar shape may be connected to the tube. 
     Also, in the above embodiment, although the narrow portion  24   c  is constituted by four projections  24   d , a plurality of the projections other than four projections may constitute the narrow portion, or only one annular projection may constitute the narrow portion. Incidentally, in case the annular projection constitutes the narrow portion, the projecting portion of the pipe to be connected does not necessarily have an annular shape. 
     As explained above, according to the present invention, the wide portion and the narrow portion are integrally molded to an opening end portion of the base portion of the tube to provide a connector function with respect to the pipe. Therefore, it is not required to attach the connector in advance to thereby simplify the connecting work of the pipe and, at the same time, to extremely reduce the number of parts, which results in reducing the cost. Also, since the projecting portions of the pipe provide the moderate feeling to the operator when the projecting portions pass through the narrow portions of the tube, the operator can recognize the connecting state with the pipe. 
     While the invention has been explained with reference to the specific embodiments of the invention, the explanation is illustrative and the invention is limited only by the appended claims.