Tube, stopper and compression ring for blood sampling systems

An evacuated blood collection tube has a stopper made of deformable synthetic rubber, incorporating a skirt fitting over the outer wall of the tube neck, and integral with the skirt a plug that penetrates the neck of the tube. The sealing function is performed by two embodiments, the upper cylindrical sealing portion of the skirt and the plug. An annular recess surrounds the plug. A compression ring made of a more rigid material is set around the upper peripheral wall of the skirt that overlaps the cylindrical sealing portion. The compression ring cooperates with the rubber stopper and the tube to provide a clenching mechanism ensuring automated guidance of the tube in full sealing engagement over the plug. Furthermore it maintains a constant sealing pressure of the skirt over the tube optimizing vacuum preservation.

TECHNICAL FIELD 
The invention relates to tubes and in particular to evacuated tubes used 
for the collection of physiological fluids such as blood. 
BACKGROUND ART 
Conventional evacuated blood collection tubes are known to be made with a 
rubber stopper penetrating the inside of the tube 
intended to hold the vacuum and, at the same time prevent escape of the 
blood content. 
Most of the health hazards inherent to these tubes stem from this single 
sealing concept. The high radial pressure of the stopper against the tube 
inner wall needed to hold the vacuum results in strong bouncing effect 
when the stopper is removed. Blood deposits adhering to the sealing 
surface are dispersed as slashes and aerosols. 
Besides these blood dispersal phenomena, handling of these tubes expose the 
technicians to the risks of contact of the fingers with the large surface 
of the stopper smeared with blood. 
Arrangements have been proposed as an attempt to minimize these problems. 
One of them consists in plastic caps covering these conventional vacuum 
tubes rubber bungs. These caps are set over the stopper head and their 
rigid skirt extends below the head, concentrically to the tube. A free 
space is provided between the tube wall and the cap to permit handling. 
Although minimizing the risk of direct contact of fingers with the stopper 
walls, these caps did not resolve at all the blood dispersal phenomena, 
above described. It still is the same type of rubber bung that penetrates 
the tube to hold both the vacuum and blood so, the same effects of 
splashes and aerosols are produced which, the open end of the plastic cap 
totally fails to entrap. Systems cf this type have been described in 
literature. 
Another arrangement presents a stopper made with a rubber skirt fitting 
over the neck of the tube, and integral with the skirt a plug that 
penetrates the tube. The sealing function is performed by two separate 
means mostly, the plug for the blood content and the upper cylindrical 
sealing portion for vacuum. These two sealing means are separated by an 
annular recess surrounding the central plug. 
The stopper is movable outwardly on the tube from a sealing position to a 
venting position in which grooves or similar recesses having major axial 
components communicate the interior of the tube with the exterior (see 
FIGS. 1 and 2 of European patent No. 0022765). Although this system has 
improved handling of vacuum tubes, it still presents two major 
limitations. On the one hand, when the technician restoppers the tube, 
there is no mechanism which guarantees that the stopper plug is fully 
engaged inside the tube in the sealing position. The blind skirt fitting 
over the tube occults the position of the tube rim in relation to the 
central plug. As a consequence of this lack of visual control, it happens 
in routine use that the plug being partly engaged only or not engaged in 
the tube, blood spillage occurs unconspicuously within the system 
compromising the high standard of hygiene required today by laboratories. 
A clenching mechanism would be required to achieve systematic guidance to 
the complete sealing position. 
On the other hand, the pressure of the skirt wall around the tube neck 
outer wall tends to weaken over the time, due to the stretching condition 
of the stopper over the tube and to the deformability of the rubber 
material. As a consequence, vacuum may be lost. 
DISCLOSURE OF THE INVENTION 
The invention concerns the combination of a vial-type tube, and a stopper, 
the tube comprising a neck with an open end. The stopper comprises a 
hollow generally cylindrical body of deformable material having a head 
including a sealing membrane for fitting over and closing the open end of 
the tube and, an integral skirt extending from the head for sealibly 
fitting over the neck of the tube. An annular recess surrounds a 
protruding central plug of the sealing membrane and, a cylindrical sealing 
portion which extends from said annular recess beyond the plug is smooth 
and uninterrupted until it reaches the lower portion of the skirt such 
that, in the sealing position, the plug sealibly fits in the open end of 
the tube neck when, simultaneously the cylindrical sealing portion 
sealibly fits around the tube neck. 
An object of the invention is to provide such a combination with a 
clenching mechanism that achieves automated guidance of the tube to the 
fully engaged sealing position with the dual-sealing embodiment of the 
stopper. Furthermore, it is to improve the stability of vacuum inside the 
tube with the incorporation of a non-deformable element in the sealing 
system. 
The compression ring, usually made of plastic is set on the upper part of 
the rubber stopper and extends downwardly from the head around the upper 
part of the peripheral wall of the skirt that overlaps the inner 
cylindrical sealing portion. At least one annular segment of the inner 
wall ring fits against said peripheral wall, at a position intermediate 
between the annular groove and the lower cylindrical sealing portion. 
When the tube is introduced inside the stopper, as a result of the 
compression of the rubber wall between the tube and the outer ring, an 
annular serration forms on the inner surface of the cylindrical sealing 
portion, at the interface with the annular groove, against which the tube 
comes to a stop. 
The pressure needed to pass the rim of the tube over the resilient 
serration ensures that, under the impulse of the force released when the 
resistance yields, the tube enters the annular groove space and engages in 
complete sealing position over the central plug. 
When the stopper is removed from the tube, the same steps take place but in 
a reverse manner: once the stopper plug has been disengaged from the neck 
of the tube and the rim has passed below the annular groove to enter the 
cylindrical sealing portion, then the annular serration spontaneously 
forms back over the tube rim. The force thus released by decompression of 
the elastomer automatically lifts the stopper up to a position where its 
lower slanted section lies over the tube rim. This permits efficient, 
convenient one hand manipulation technique. 
The combination of the rubber stopper, the tube and the compression ring 
improves vacuum preservation in two ways. Firstly, the ring maintains the 
skirt outer diameter and therefore the sealing engagement over the tube 
wall at a constant level over the time. Secondly, as a result of the 
compression, the cylindrical sealing portion of the skirt is stretched 
into a longer segment over the tube neck, thus providing a larger barrier 
between the interior of the tube and the external environment.

BEST MODES FOR CARRYING OUT THE INVENTION 
FIG. 1 shows a tube, a stopper and a compression ring combination of which 
the tube neck (1') has a smooth cylindrical outer surface, and the stopper 
consists of a body of deformable material such as synthetic rubber, having 
a head (31) including a central dimple (34), and an integral skirt (33) 
extending flush from the generally cylindrical wall of the head. A 
self-sealing membrane (32) extends from the head as a central plug (38). 
This central plug is surrounded by an annular recess in the form of an 
inwardly facing annular groove (35) in the end of the skirt (33) adjacent 
the head (31). 
The inner wall of the skirt (33) is divided into two portions, an upper one 
(33'a), cylindrical and extending up to the groove (35), which is smooth 
and uninterrupted and seals around the tube neck (1'), and a lower one 
(33'b) extending to the edge of the skirt. 
An outer compression ring (40) made of plastic or similar resilence 
material is set at the periphery of the head (31) and extends downwardly 
around the skirt (33) at a level where it overlaps the upper cylindrical 
sealing portion (33'a), and fits against the peripheral wall (33) by the 
annular segment (41a). 
FIG. 2 shows a tube,a stopper and a compression ring combination in which 
the upper cylindrical sealing portion (33'a) is connected to the lower 
cylindrical portion (33'b) of slightly larger diameter by a slanted 
section (36). The diameter of this upper cylindrical sealing portion 
(33'a) is significantly smaller than the outer diameter of the tube neck 
(1'). 
FIG. 3 represents the entry of tube (1') inside the sealing portion (33'a) 
of the stopper of FIG. 2. The thickness of at least one annular segment of 
the skirt wall (33),overlapped by ring (40),is significantly larger than 
the breadth of space provided between the two concentric surfaces of the 
tube outer wall (1'b) and the ring inner wall (41a). 
On penetration of the tube, the ring inner wall (41a) prevents the inherent 
deformation of the skirt outwardly induced. As a result, the excess 
material is compressed upwardly and inwardly to form a resilient annular 
serration (39), at the interface of the annular groove (35) and of the 
sealing portion (33'a), against which the tube rim (1'c) comes to a stop, 
FIG. 4. 
The annular groove (35) extends beyond the plug (38) and provides a 
deformation space for the annular serration (39) pressed upwardly by the 
tube rim (1'c), before absorption between the tube wall (1b) and the ring 
(40). 
As shown in FIG. 5, the pressure needed to pass the tube rim over the 
resilient serration (39) is such that, once the resistance yields, under 
the impulse of the force released the tube enters into the annular recess 
space (35) and fully engages over the plug (38), achieving the automated 
clenching mechanism. 
For removing the stopper from the tube, the same steps take place, but in a 
reverse order as per FIGS. 5-4 and 3. Once the plug (38) has been 
disengaged and the tube rim (1'c) passed below the annular groove (35), 
then the annular serration (39) forms back over the tube rim. The force 
thus released by decompression of the compressed material, automatically 
lifts the stopper up to a stop position where the slanted section (36) 
lies above the tube rim (1'c). Since the lower portion of the skirt (33'b) 
is uncovered by the ring and freely deformable, the stopper fits in a 
stable position over the tube permitting a one-hand convenient and 
efficient manipulation. 
FIG. 6 shows a stopper of the same type as that of FIG. 2 in which the 
lower cylindrical portion (33'b) incorporates an axially directed groove 
(37),which extends from the skirt edge along this lower portion slightly 
into the upper portion (33'a) which otherwise is smooth and uninterrupted. 
The lower annular segment (41a) of the ring stops at distance above the 
outlet (37') of this axial groove. 
In the form of realisation of FIG. 6, the ring 40 differs from the previous 
representations by the abutments (42a) that extend as a cover, radially 
and inwardly from the peripheral wall of the ring to a central opening 
(44), acceeding to a chamber (44') defined in its top by said cover (42a), 
and in its bottom by the flat surface (31b) of the stopper head. 
The cover with the narrow central opening (44) leading into a chamber (44') 
protects the technician against contact with any trace of blood remaining 
on the head surface (31b) after the needle has been pulled out from the 
sealing membrane (32). 
In FIG. 7, the ring (40) incorporates vertical abutments (49) extending 
downwardly from the central opening (44) towards the head surface (31b). 
These abutments are able to transfer a pressure through the membrane (32) 
to the interior of the tube, when it is necessary to expell a drop of 
blood from the assembled sampling unit, for instance for making blood 
slides. In the form of realisation of FIG. 7, the lower edge of the 
peripheral wall of the ring is provided with at least one axial cut-out 
(41c). 
FIG. 8 shows a tube, a stopper and a compression ring combination in which 
the tube (2') incorporates an outwardly projecting annular bead (2"), 
forming a rim on the open end of the tube neck. The skirt (53) is provided 
with a second annular groove (56) adjacent to the cylindrical sealing 
portion (53'a) and an axially directed groove (57) extends from the edge 
of the skirt along this lower portion inner surface slightly into the 
upper portion (53'a). This axially directed groove (57) has a deeper 
section than the annular groove at the place they intersect. 
FIG. 9 shows a form of realisation in which the tube (3') has a rim (3") 
slightly protruding as an inward bead at the end of the neck. The stopper 
has an outwardly flaring groove (68') inset in the periphery of the plug 
(68) sealibly engaging with the rim (3"). The lower cylindrical portion 
(63'b) of the stopper is larger in diameter than the tube diameter (3'b), 
thus providing a venting recess communicating the interior of the tube 
with the outside, prior to complete removal of the stopper. 
Naturally, many variations may be made to the described embodiments and 
features of one embodiment may be combined with another embodiment, where 
appropriate. The term "axially directed groove" is intended to include 
grooves and similar recesses having major axial components to provide 
venting space between the tube outer wall and the skirt inner wall, in the 
lower portion of the skirt adjacent the cylindrical sealing portion.