Tapered Bore Connector Background – Field of Invention This invention relates to an improved tapered bore connector. Objects and Advantages The primary object of the present invention is to provide a tapered bore connection that maintains connection to a mating connector. Specifically, the invention has the following advantages: 1. The connector maintains a secure connection with its mate even if plastic creep attempts to relieve the interference fit between mated tapered bore and tapered shaft. 2.
The connector provides the user with tactile feedback to indicate when sufficient force is applied to develop a secure interference fit between the mating connectors. These and other objects and advantages of this invention are achieved by employing the following design elements: Body The connector has a body element. In preferred embodiments, the body is generally cylindrical or conical in shape, but in other embodiments it could be almost any shape that could have a bore, a flange, a wing and a post attached to it. Bore.
A bore is located along a central axis of the body. In a preferred embodiment, the bore is tapered along a portion of its length and continues through to make a hole through the body. In other embodiments, the bore need not be tapered or full through. Flange(s) Near one end of the body is located one or more flanges. These flanges or lugs or ears protrude away from the body in a radial direction away from the body central axis. The protruding flange is cantilevered in the radial direction. That is, it hangs out in the radial direction.
Also, along with being cantilevered in the radial direction, the flange protrudes or cantilevers in the circumferential direction. That is, the flange is not continuously connected to the body in a direction along the circumference of the body. This double direction cantilevering, in both the radial and the circumferential directions, is a key component of the invention. Less Rigid Wing(s) Somewhere along the outside surface of the body are located one or more Less Rigid Wings. These Wings generally protrude away from the body in a radial direction.
More Rigid Wing Post(s) Directly adjacent to the Less Rigid Wings are More Rigid Posts. These elements are located in an offset plane relative to the Less Rigid Wings. The above mentioned advantages and design elements of this invention will become apparent from the following description taken in connection with the accompanying sketches, wherein is set forth by way of illustration and example, preferred embodiments of this invention. General Summary of Invention In a preferred embodiment, the invention could be defined as an improved female luer connector.
A luer connector is known for it luer taper. A luer taper is a standardized system of small-scale fluid fittings used for making leak-free connections between a male-taper fitting and its mating female part on medical and laboratory instruments, including hypodermic syringe tips and needles or stopcocks and needles. Named after the 19th century German medical instrument maker Hermann Wulfing Luer, it originated as a 6% taper fitting for glass bottle stoppers. Key features of Luer Taper connectors are defined in the ISO 594 standards (see Appendix B).
It is also defined in the DIN and EN standard 1707:1996 and 20594-1:1993. There are two varieties of Luer Taper connections: Luer-Slip and Luer-Lock. Luer-Slip fittings simply conform to Luer taper dimensions and are pressed together and held by friction (they have no threads). Luer-Lock fittings are securely joined by means of one or more flanges or tabbed hubs on the female fitting that screw into threads in a sleeve on the male fitting. The luer-Lock fitting was developed in the United States by Fairleigh S. Dickinson and is described in his patent (Appendix A).
Although intended to make a more secure fitting, I believe Dickinson’s design assumed metal connectors, otherwise he would not have selected such a steeply pitched thread to maintain the connection. He could not have anticipated the use of disposable plastic luer connectors and the inherent problems with maintaining a tight interference fit over extended time periods with plastic materials. It is well known in the art that plastic connectors exhibit creep over time that diminishes the taper to taper hoop stresses resulting in a loose connection.
The steeply pithed threads in the male collar do not significantly impede rotation and subsequent leakage. Unfortunately, the Luer/Dickinson design was so popular, and its interchangeability so critical to the medical device industry, that the design has never been significantly improved. In 1986, the ISO luer connector standard was established, a copy of which is attached in Exhibit B. This standard outlines the basic design parameters to ensure that the male and female connectors manufactured anywhere in the world can be mated.
The standard specifically calls out the design standards for a cantilevered lug or flange in the radial direction but does not specify a cantilevered lug in the circumferential direction. Almost all connectors are now made of plastic. In particular, many connectors are composed of polycarbonate, PVC, Acrylic, ABS or other plastic materials. Compared to metal connectors, all of these materials exhibit significant creep after being stressed for a long period of time. Due to plastic creep, the radial hoop stresses developed between male and female tapered surfaces can gradual reduce to essentially zero over time.
When this interference stress is diminished, the female luer flanges are free to rotate relative to the male luer threads. Free rotation combined with the steep thread pitch allows for easy disassembly causing fluid leakage or air inflow. A new female connector design is proposed that maintains a restraining friction fit between male threads and female luer flange even if substantial plastic creep occurs. The new invention meets the following conditions: 1. Complies with explicitly stated design parameters specified in ISO standard. 2.
Provides an improved interference fit between female connector flange and male connector threaded collar. 3. Provides the user with tactile feedback corresponding the applied torque. 4. Does not significantly increase the cost of the component. In particular, the improved design does not require an additional part. Like prior art, the new invention female connector has a body that has an internal tapered bore. The tapered bore could be of any dimension that mates with a corresponding male tapered shaft. In one embodiment, the bore taper is 6 degrees (included angle) as stated in the ISO standard.
At the larger diameter opening of the tapered bore, the body has at least one, or in a preferred embodiment, two flanges. The invention focuses on the relationship of this flange to the body. In prior art, the flange (or flanges) is cantilevered in the radially direction in accordance with ISO spec to allow the flange to engage with the internal threads of the collar of the mating male connector. When fully engaged bore to taper, the flange is in close contact with the threads. When overtightened, the flange and threads tend to bend or deform.
The bending or deformation in the flange is like a spring, urging the two tapered surfaces to stay in contact. As creep occurs in the stresses plastic components, the interference fit is relaxed, but the deformed flange acts like a spring to urge the two components together. Unfortunately, due to the short cantilever arm, the amount of spring travel is insignificant relative to the plastic relation due to creep. Over time, the interference fit is lost and the Luers can separate. In the new invention a flange with a longer cantilever arm is created in the circumferential direction.
This longer arm can accommodate more deflection when the flange is tightened against the thread surface. This deflection force is sufficient to keep the conical surfaces in close contact even as gradual creep occurs over time. A second related invention included in this application a new type of wing structure to help the user twist and rotate the female luer into the male luer. Two or more wings or panels located on the connector body is well known in the art. These wings allow the user to easily grab the body and apply a higher tightening torque with less force.
What these wings do not do, and what the new invention does is provide to the user a tactile indication of how much torque, or tightening is sufficient to ensure a tight fit without over tightening. Again, since these components could be plastic, over tightening can result in stress cracking. The invention relies on making the Wing as two elements, a less rigid Wing and a more rigid post. These two elements or panels are offset or spaced a certain distance apart. In the process of connecting, the user presses predominant against the less rigid Wing compared to the post (due to the offset or spacing).
As the connector is rotated and tightened, the restraining force of cantilevered flange against male connector thread is transmitted back to the user via the Wing and the Wing’s stiffness (a function of shape and material) is such that it bends toward the more rigid Post. When in close proximity to the Post, the user feels the rigid post and is signaled by the stiff post feeling to stop twisting. With a correct balance of wing and post material and design, the user will be signaled to continue twisting until a nominal interference torque is obtained. [pic] Figure 1 – Prior Art [pic] Figure 2 – Preferred embodiment.
[pic] Figure 3 – Preferred Embodiment [pic] Figure 4 – Theory of Operation [pic] Figure 5 – Preferred Embodiment [pic] Figure 6 – Theory of Operation [pic] Figure 7 – Preferred Embodiment [pic] Figure 8 – Supporting Design Theory Claims . Claim 1 . A connector comprising: . a) a body, said body has an internal conical bore surface forming an opening, said opening has an axis of symmetry; and . b) a flange, said flange is connected to said body and is cantilevered relative to said body in both an outward radial direction away from said axis of symmetry and in a circumferential direction around said axis of symmetry.
. . Claim 2 . A female connector having an internal tapered bore and a cantilevered flange and having a more flexible wing located in a non co-planar position relative to an adjacent less flexible post such that when a torque is applied to the flexible wing, the flexible wing deforms to advance to a more co-planar position relative to the less flexible post. Appendix A – Dickinson Patent [pic] Appendix B – ISO 594 Standard (selected pages) [pic] [pic] [pic].