Pipe joints or couplings – With assembly means or feature – Guide and support
Patent
1997-06-23
1999-05-25
Arola, Dave W.
Pipe joints or couplings
With assembly means or feature
Guide and support
285390, 285423, F16L 3500
Patent
active
059063980
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a joint for joining two tubular plastic parts together by a threaded joint.
By constructing apparatus comprising plastic parts, joints are often provided by screwing tubular plastic parts together. By manufacturing medical equipment so as pen shaped injection syringes such a syringe may be provided by accommodating a cylinder ampoule in a housing comprising two tubular members which are screwed together, one member having an outer thread engaging an inner thread in the other member. The outer thread is provided on a cylindric part of the fist member, which cylindric part has a smaller diameter than the main diameter of the tubular member. Thereby the thread appears with a free end and an end adjacent to the first tubular member leaving, due to the different diameters of the threaded cylindric part and the tubular part, a shoulder against which the end surface at an open end of the second member may abut when the first member is screwed with its cylindric externally threaded part into an open end of the second member having an internal thread at this open end.
When plastic parts are screwed together in this way, two problems must be realized. One problem is that if the joint is tightened to provide a safe and locking abutment between the said end surface of the second element and the shoulder on the first element, stress impacts due to varying temperature may cause the plastic parts forming the joint to crack. Consequently care must be taken that the joint is only tightened to a degree allowing possible thermal movements of the plastic parts. Another problem is that it is often wanted that the two joined parts have a certain rotational position relative to each other, e.g. when marks on one of the part must be aligned with marks on the other part when the two part are screwed together. The treads must then be so adapted that the marks are aligned when the joint is appropriately tightened, but it will often be possible to tighten the joint a bit more. This will bring the marks out of alignment and may be damaging to the plastic parts as mentioned above.
Consequently it is necessary to provide a stop which locks the relative rotation of the parts to the rotational position in which the marks are aligned and the tightening of the joint is loose enough to not damage the plastic parts.
According to the invention this is obtained by a joint for joining a first and a second part so that this first and second part maintain a predefined rotational position in relation to each other, the joint comprising an internal thread in the first part the internal thread of which has an inner end and an outer free end receiving an outer free end of a corresponding external thread on the second part the external thread of which has an inner end adjacent to the second part, characterized in that a free end of the ridge and the inner end of the groove forming the threads are bounded by surfaces lying in a plane through the axis of the threads, and that the length of the threads are so adapted that a plane end surface of the ridge of one thread engage the plane end surface of the groove of the other thread when the two parts are screwed together and occupy the predefined mutual rotational position.
Appropriately the free ends of the ridges of both threads and the inner ends of both grooves may be bounded by surfaces lying in a plane through the axis of the threads.
When by each thread the outer end of the ridge is 180.degree. displaced from the inner end of the groove a good distribution of the abutment forces are obtained.
The thread may be a multiple thread to obtain a good joint with a minimum of screwing.
In the following the invention will be described with references to the drawings, wherein
FIG. 1 shows a joint according to the known art,
FIG. 2 shows the male part of a joint according to the invention,
FIG. 3 shows the female part of a joint according to the invention, and
FIG. 4 shows the male part of FIG. 2 in another rotational position.
The joint according to the known art as shown i FIG. 1 comp
REFERENCES:
patent: 873659 (1907-12-01), Blood
patent: 1465484 (1923-08-01), Richter
patent: 1645032 (1927-10-01), Wilson
patent: 2029798 (1936-02-01), Schellin
patent: 2179193 (1939-04-01), Parrish
patent: 4050721 (1977-09-01), Streit
patent: 5015014 (1991-05-01), Sweeney
patent: 5507538 (1996-04-01), Phillips
Larsen Andre
Mikkelsen S.o slashed.ren
Arola Dave W.
Lambiris, Esq. Elias J.
Novo Nordisk A S
Zelson Esq. Steve T.
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