Self-Tightening Soft Tubing Fitting and Method

1. Field of the Invention

The present invention relates to fittings which are used for securing and fastening soft tubing. More particularly, the present invention relates to an improved fitting that is self-tightening, so as to prevent slipping, inexpensive and has a simple two-piece construction that is simple to use.

2. Description of the Prior Art

Soft plastic tubing is a popular and versatile way of ducting fluids, and is used in a wide variety of both research and commercial applications. Such tubing is light and relatively easy to use, because of its flexibility. However, the higher grades of such tubing can be relatively expensive, which has led users to splice several shorter sections together for a new job rather than buying a new length of tubing. Fittings to effect such splicing and for securing and fastening soft tubing to other types of fluid ducting or storing structure are commercially available, but have many disadvantages. The most common prior art devices used for this purpose generally required a hose-type clamp or other fitting that was used to grip the inside and outside of the soft tubing, which reduced flow through the tubing by constricting the tubing. Such fittings commonly required a screwdriver or other device for locking and releasing the fitting onto the tubing, which required a substantial amount of labor time if multiple connections were to be made. In addition, due to the soft, elastic nature of the tubing, it was not unusual for the tubing to slip out of such fittings when relative tension existed between the tubing and the fitting. This was a serious problem, because the soft elastic nature of such tubing frequently causes it to unexpectedly shrink along its axis when internally pressurized, leading to unwanted tension between the tubing and fitting.

It is clear that there has existed a long and unfilled need in the prior art for an improved fitting for use with soft tubing that is simple and inexpensive to install, is effective against slipping when the tube is under tension, and that is less obstructive to fluid flow within the tubing while in use.

Accordingly, it is an object of the present invention to provide an improved fitting for use with soft tubing that is simple and inexpensive to install, wherein gripping force is increased proportionately to the tensile force which exists between fitting and tubing, and that does not unreasonably constrict the tubing during use.

According to one embodiment of the present invention, an improved two-piece fitting for use with soft tubing includes a body section defining an axially extending passage therein, a stem which is adapted for receiving a section of soft tubing over at least a portion thereof, the stem extending axially from the body section and having a passage defined therein which is in communication with the body section passage, a radially outwardly extending annular flange at an end of the stem that is distal from the body section and is adapted for sealing against an inner wall of the tubing, a sleeve element mounted for sliding movement on the stem and having an annular contact surface defined thereon which is adapted for sealing against an outer wall of the tubing, and structure for resisting movement of the sleeve element toward the body section, whereby a section of soft tubing may be tightly secured, in communication with the passages, between the sleeve element and the flange.

Preferably, the annular contact surface is formed on a lip portion of the sleeve element which extends radially inward toward the stem, so that the lip portion will catch on the secured tubing when tension is applied thereto, urging the annular contact surface toward the flange with greater force so as to ensure retention of the tubing in the connector.

In one embodiment, the structure resisting movement of the sleeve element includes structure for releasably locking the sleeve element with respect to the stem.

In yet another embodiment, the structure resisting movement of the sleeve includes radially inwardly projecting sleeve portions resiliently bearing against an outer conical contact surface of the stem obliquely facing away from the body section so as to bias the sleeve element toward the annular flange at the end of the stem element.

The present invention also includes a method of using the above-described connector for connecting and disconnecting a section of soft tubing to a desired tube or fitting, which includes connecting the fitting to the desired tube or fitting, slipping a section of soft tubing over the flange and pulling the sleeve toward the flange, so that the soft tubing is secured between the flange and the contact surface in communication with the axial passage, and is held in place by the releasable locking structure. To release the connector, the method of the present invention provides the additional steps of releasing the releasable locking structure, pushing the sleeve away from the flange and pulling the soft tubing off of the stem.

These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.

FIG. 1 is a perspective view of a connector constructed according to a first preferred embodiment of the present invention;

FIG. 2 is a sectional view of the connector illustrated in FIG. 1 depicting a piece of soft tubing being slipped thereover;

FIG. 3 is a cross-sectional view of the embodiment of FIG. 1 depicting the step of connecting the soft tubing to the connector;

FIG. 4 is a cross-sectional view of the embodiment of FIG. 1 depicting release of the soft tubing from the connector;

FIG. 5 is a view partially in cross-section of a connector constructed according to a second embodiment of the present invention, in which a piece of soft tubing is being secured to the connector;

FIG. 6 is a cross-sectional view of the second embodiment of the present invention taken along lines 6--6 in FIG. 5;

FIG. 7 is a view partially in cross-section of the embodiment illustrated in FIG. 5 depicting the connector when it is secured to a piece of plastic tubing;

FIG. 8 is a perspective view of a connector construed according to a third preferred embodiment of the present invention;

FIG. 9 is a sectional view of the connector illustrated in FIG. 8 depict a piece of soft tubing being slipped thereover;

FIG. 10 a cross-sectional view of the embodiment illustrated in FIG. 8 depicting the step of connecting the soft tubing to the connector; and

FIG. 11 is a cross-sectional view taken generally along line 11--11 in FIG. 10.

Referring to FIG. 1, a soft tubing fitting 10 according to a first embodiment of the invention is constructed as a standard male fitting including a body section 12 having a threaded portion 14 and a hexagonal section 16 which is adapted to receive a wrench or other fitting tool. Although a male fitting is shown in the illustrated embodiments, it is to be understood that a fitting connector according to the present invention may be used in other configurations, such as a dual connector fitting unit that has utility for splicing or a female unit, for example. As shown in FIG. 2, body section 12 has an axially extending bore 17 defined therein through which fluid may pass.

Referring to FIGS. 1-4, a stem 28 extends axially from body section 12 in a direction opposite the threaded portion 14. Stem 28 has an axial bore 29 defined therein which is in communication with the axial bore 17 in body section 12. As shown in FIGS. 1 and 2, stem 28 includes an inner core 18 and a pair of rail members 20 which are secured to inner core 18 at opposite sides thereof. Rail members 20, as clearly shown in FIG. 1, each have flat top surfaces 22 and a pair of curved side surfaces 24. As also shown in FIG. 1, a ratchet strip 26 is formed on each side of the inner core 18 between the rail members 20. Ratchet strip 26 includes a plurality of ratchet teeth 34, each tooth having a surface obliquely angled toward the body section 12.

Stem 28 is further provided with a flange portion 30 on which an annular surface 32 is formed, defining the maximum outer diameter of the flange. Flange 30 further has a conical contact surface 33 formed thereon which obliquely faces the body section 12, as is shown in FIG. 2.

In order to limit the extent that a soft plastic tube 36 may be slipped over the stem 28, the stem is further provided with an annular stop ring 38 midway between the ratchet strip 26 and flange 30. The stop ring 38 ensures that the tubing will not interfere with operation of the ratchet strip when the fitting connector is in use.

Referring again to FIGS. 1-4, a sleeve 40 is mounted on stem 28 for axial movement relative thereto. Sleeve 40 has a first grip surface provided on opposite sides of its circumference which are in the preferred embodiment constructed as raised platforms. Second grip surfaces 44 are spaced intermediate the first grip surfaces 42 and in the preferred embodiment are simply the smooth outside surface of the sleeve 40. As may be seen in FIGS. 1-4, sleeve 40 is substantially formed as a hollow cylinder, and has an inside surface 46 which is adapted to bear against the curved side surfaces 24 of the rail members 20. In this way, rail members 20 allow sleeve 40 and stem 28 to slide relative to each other, but constrain the two elements so that their axes remain coincident.

As best shown in FIGS. 2-4, sleeve 40 is provided with a pair of pawl-like projections 50 which extend radially inward from the inner surface 46 of sleeve 40 between rail members 20 so as to contact the teeth 34 of ratchet strip 26. In the preferred embodiment, the projections 50 have a width that is slightly less than the space which exists between the rails 20, which constrains sleeve 40 against rotation with respect to stem 28. As shown in FIG. 2, pawl-like projections 50 terminate an angled pawl surface 51 which is adapted to rest against the surfaces of teeth 34 which are obliquely angled toward the body section 12 as above described. In this way, sleeve 40 is constrained against movement away from the flange portion 30 of stem 28, such as when a tube is being clamped.

As shown in FIG. 3, sleeve 40 is provided with an inward radially extending lip portion 48 which defines the minimum inner diameter of the sleeve element. Annular lip portion 48 has a contact surface 49 defined thereon which faces the conical contact surface 33 of flange 30. The outer diameter of flange 30 and the inner diameter of lip 38 thus define an annular extrusion gap in which a tube may be clamped, which gap varies according to the relative displacement of stem 28 and sleeve 40.

All of the above-described connector elements are preferably constructed from a relatively rigid but flexible plastic material such as polypropylene or Delrin.sup..RTM., but other materials may be used within the scope of the invention. It is particularly important that sleeve 40 be fabricated from a material having a high degree of elasticity.

The operation of a fitting connector constructed according to the embodiment illustrated in FIGS. 1-4 may be explained as follows. As shown in FIG. 2, a length of tubing 36 may be slipped over flange portion 30 onto stem 28 until the tubing reaches the annual stop ring 38. Sleeve 40 is then gripped by the thumb and forefinger of a user at the second grip surfaces 44 to pull sleeve 40 toward flange 30, so that the tube 36 is securely gripped between contact surface 49 on the sleeve and conical contact surface 33 of the flange as is illustrated in FIG. 3. At this time, the pawl-like projections 50 will seat against one of the teeth on each side of ratchet section 26, thereby securing the sleeve against the tubing and flange.

Should axial tension develop between tube 36 and the fitting 10 during use, the tubing will pull against the downwardly extending, almost tooth-like annular lip portion 48, thereby urging the sleeve 40 and contact surface 49 proportionately tighter against the tube so as to prevent the tube from slipping out of the connector.

If it is desired to disconnect the tubing 36 from the connector, the user may place his or her thumb or forefinger on the first grip surfaces 42, as is depicted in FIG. 1. Because sleeve 40 is fabricated from an elastic, resilient material, sleeve 40 will deform under the force which is applied to first grip surfaces 42, causing the pawl-like projections 50 to deflect outwardly away from teeth 34, as is illustrated in FIG. 4. Sleeve 40 may then be pushed away from flange 30, allowing the soft tubing to be pulled off of stem 28.

A fitting 52 constructed according to a second embodiment of the present invention is illustrated in FIGS. 5-7. Fitting 52 is similar in construction to the above-described embodiment except for the below-described differences. In this embodiment, a stem 62 is provided with an inner core 54 which supports a pair of rail members 56, as is best shown in FIG. 6. As is also shown in FIG. 6, a pair of ratchet strips 58 having teeth 60 are provided on the inner core 54 of stem 62. Stem 62 is provided with a radially extending flange 64 at a distal end thereof and further includes an annular stop ring 66 formed between the flange 64 and ratchet strips 58 to limit the extent to which a tube 36 may be slipped thereover.

As shown in FIG. 6, a smooth surface 74 is formed on the inner core 54 next to each of the ratchet strips 58. Smooth surfaces 74 have substantially the same width about the periphery of inner core 54 as do ratchet strips 58.

Similarly to the first embodiment of the present invention that is above described, a sleeve 68 is provided with a pair of pawl projections 70 which are adapted to contact the teeth 64 of ratchet strip 58 and have a width that is substantially equal to the widths of ratchet strips 58 and smooth surfaces 74. Sleeve 68 includes an annular downwardly extending radial lip 72 which is analogous in form and function to lip portion 48 in the embodiment of FIGS. 1-4.

In operation, a tube 36 is slipped over stem 62 and flange 64 until in contacts the annular stop ring 66, to reach the position illustrated in FIGS. 5 and 7. Sleeve 68 is then pulled toward the flange 64 to reach the position illustrated in FIG. 7, so that the tube is secured by the ratchet mechanism between the relative contact surfaces of the sleeve 68 and flange 64. If tension is applied between the tube and the fitting in this state, the tube will catch on lip 72, thereby urging the contact surfaces of the sleeve and the flange together with proportionately more force.

When it is desired to release the tube 36 from a connector constructed according to the embodiment of FIGS. 6-8, sleeve 68 is rotated about its axis in the direction depicted by arrow 76 in FIG. 5, which causes pawl projections 70 to disengage from the teeth 60 of ratchet strip 58 and to be repositioned over the smooth surfaces 74 which are formed on the inner core 54. As a result, the sleeve may then be pushed away from the flange without interference by the ratchet mechanism, and the tube may then be pulled off of the stem 62.

Referring now to FIGS. 8-11 there is illustrated a soft tubing fitting 110 according to a third embodiment of the invention. The soft tubing fitting 110 is shown constructed as a standard male fitting including a body section 112 having a threaded portion 114 and a hexagonal section 116 which is adapted to receive a wrench or other fitting tool. In the preferred embodiment shown, the hexagonal section 116 has a diameter greater than the rest of the fitting to facilitate positioning of a wrench thereover. In FIGS. 8-10 the soft tubing fitting 110 is illustrated as being threadedly interconnected to a threaded bore 113 of a manifold structure 111. Although a male fitting is shown in the illustrated embodiments, it is to be understood that a fitting connector according to the present invention may be used in other configurations, such as a dual connector fitting unit that has utility for splicing or a female unit, for example. As shown in FIGS. 8-11, the body section 112 has an axially extending bore 117 defined therein through which fluid may pass.

Referring to FIGS. 8-11, a stem 128 extends axially from the body section 112 in a direction opposite the threaded portion 114. The stem 128 has an axial bore 129 defined therein which is in communication with the axial bore 117 in the body section 112. The stem 128 includes an inner core 118 and an outer core 119. The stem 128 is provided with a flange portion 130 proximate its end on which an annular cylindrical flange surface 132 is formed defining the maximum outer diameter of the flange portion 130. The flange portion 130 further has a conical contact surface 131 formed thereon which obliquely faces away from the body section 112 and a conical contact surface 133 formed thereon which obliquely faces the body section 112 as is generally illustrated in FIGS. 9 and 10. In order to limit the extent that a soft plastic tube 136 may be slipped over the stem 128, the stem 128 is further provided with an annular stop ring 138 midway between the inner and outer cores 118, 119. The stop ring 138 ensures that the tubing 136 will not interfere with operation of a sleeve 140.

The sleeve 140 is mounted on the stem 128 for axial movement relative thereto. The sleeve 140 has an annular grip surface 142 proximate an outer end thereof. The annular grip surface 142 includes two rows of radiused impressions 141, 143 disposed annularly about the sleeve 140 to aid in axially or rotatably moving the sleeve 140. As is illustrated, the sleeve 140 is substantially formed as a hollow cylinder and has an inside surface 146 including three elastic, axially projecting members 148 each having a radially inwardly projecting portion 149 adapted to resiliently bear against a surface of the inner core 118 which has a first conical contact surface 121 formed thereon which obliquely faces away from the flange portion 130 and a second conical contact surface 123 formed thereon which obliquely faces the flange portion 130.

As illustrated, the sleeve 140 is provided with the axially extending members 148 having the radially inwardly projecting end portions 149 which slide along the conical portions 121, 123 of the inner core 118 and bear against the contact surface 123 as generally illustrated in FIG. 10 when the sleeve 140 has been pulled over the end of the tubing 136 after having inserted the tubing 136 onto the outer core 119 of the stem 128. The radially inwardly projecting portions 149 include a cooperating shoulder portion 152 for cooperating with an annular shoulder portion 150 of the annular stop ring 138 to retain the sleeve 140 on the stem 128 when a tubing is not attached to the fitting 110. The sleeve 140 is freely movable along a cylindrical contact surface 115 of the stem, such that the end portions 149 do not resiliently bear against the cylindrical contact surface 115. As illustrated, in the preferred embodiment there are three axially extending resilient members 148 symmetrically disposed about the longitudinal axis of the fitting 110.

The sleeve 140 is provided with an inward radially extending lip portion 154 which defines the minimum inner diameter of the sleeve element 140. The annular lip portion 154 has a contact surface 156 defined thereon which faces the conical contact surface 133 of the outer core 119 of the stem 128. The outer diameter of the outer core 119 and the inner diameter of the lip portion 154 thus define an annular extrusion gap in which a tube may be clamped, which gap varies according to the relative displacement of the stem 128 and the sleeve 140. Moreover, the extrusion gap can be varied depending on the tubing being used.

As with the previous embodiments, the above described connector elements are preferably constructed from a relatively rigid but flexible plastic material such as polypropylene or Delrin (registered U.S. trademark) but other materials may be used within the scope of the invention. It is particularly important that the sleeve 140 be fabricated from material having a high degree of stiffness and resiliency.

The operation of a fitting connector constructed according to the embodiment illustrated in FIGS. 8-11 may be explained as follows. As shown in FIG. 9, a length of tubing 136 may be slipped over the outer core 119 of the stem 128 until the tubing 136 reaches the annular stop ring 138. The sleeve 140 is then manually gripped by the user such as by the thumb and forefinger of a user on the grip surface 142 to pull the sleeve 140 toward the outer core 119, so that the tubing 136 is securely gripped between the contact surface 156 on the sleeve 140 and the conical contact surface 133 of the flange 130. At this time, the radially inwardly projecting portions 149 of the resilient, axially extending members 148 will bear against the conical contact surface 123 so as to bias the sleeve 140 toward the flange portion 130 and resist movement of the sleeve 140 back toward the body section 112. It will be appreciated that the contact surface 123 might take on other configurations such as a ramped configuration, for example. The more pull extended on the tubing 136; e.g., as fluid pressure is applied, the smaller the extrusion gap between the flange portion 130 and the sleeve contact surface 156 will become so as to more firmly grip the tubing 136. This is due to the sleeve contact surface 156 gripping the tubing 136 and thus sliding with the tubing 136 toward the end of the stem 128 should the fluid pressure case the tubing 136 to move toward the end of the stem 128.

If it is desired to disconnect the tubing 136 from the fitting 110, the user may place his or her thumb or forefinger on the grip surface 142 and push the sleeve 140 away from the flange 130, allowing the tubing 136 to be pulled off the stem 128.

It will be appreciated that the conical surface 123 cooperates with the resilient axially extending members 148 to resist movement of the sleeve 140 away from the flange 130. In the embodiment shown in FIGS. 8-11, there are three such resilient axially extending members 148 symmetrically disposed about the longitudinal axis of the fitting 110. An annular should portion 160 also called an annular lip portion, intermediate of the conical contact surfaces 123, 121 provides an audible signal as the sleeve portions 149 slide thereover thus indicating when the sleeve 140 is biased toward the flange 130.

It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.