Cap for a tube for extracting blood

A blood extraction cannula cap is provided with a skirt which can be inserted over a tube for receiving the blood, the upper portion of the skirt being closed and having a cannula bore for receiving a needle and a push button resiliently mounted on the end of the cap with the push button being connected to a closing member which closes a bore connecting the cannula to the interior of the cap.

BACKGROUND OF THE INVENTION 
The invention relates to a cap for a tube for extracting blood or the like, 
with a base, a cannula cone placed on the base and a skirt connected to 
the base having a locking mechanism for fixing the cap to the cylindrical 
body of the tube. 
It is already known to provide injection syringes with a removable cap, to 
make it possible to better clean a syringe, which is intended for use more 
than once. Moreover, a removable cap makes it possible to adapt cannulas 
of different diameters to the same injection syringe cylinder. The 
attachment and locking of the cap to the injection syringe cylinder is 
normally effected with a thread, where the cap skirt is provided with an 
internal thread and the lower end of the syringe cylinder with an external 
thread. However, it is also possible to use bayonet catches and spring 
catches as a locking element. 
If such an injection syringe is used for extracting blood, the doctor or 
nurse sticks the cannula with the plunger or piston rod initially 
completely depressed in the direction of the cap into the vein of a 
patient and then raises the piston rod connected to the syringe piston. As 
a result of this raising or pulling up action, the blood is sucked into 
the syringe cylinder. This requires two hands, because the syringe 
inserted in the vein must be held with one hand, whilst the other hand is 
used for raising the piston. 
SUMMARY OF THE INVENTION 
The problem of the invention is to provide an improved cap for a blood 
extraction tube, which permits one-handed operation during the removal of 
a liquid from a vessel, particularly when removing blood from a vein. 
According to the invention, this problem is solved by a cap of the 
aforementioned type, wherein a closing member is inserted in the cap skirt 
and in the inoperative position closes a cannula bore leading to the 
cannula cone by means of a closing surface, releasing the cannula bore by 
depressing an actuating element. The actuating element is preferably a 
pushbutton, a key, a lever or a similar element. 
Thus, the piston of a tube provided with a cap according to the invention 
and for example a tube in accordance with DE-OS No. 2,711,366 can be 
raised and locked in the raised position before sticking its cannula into 
the blood vessel of a patient, or into any vessel, e.g., a bottle, cup, 
etc. containing a treatment fluid. The closing member keeps the cannula 
bore closed, so that a vacuum is formed in the cylindrical body of the 
tube and this is vented on depressing the pushbutton acting on the closing 
member. If at the time of depressing the closing member, the cannula 
mounted on the cap is immersed in blood or some other liquid, the latter 
is sucked into the tube by the vacuum. This suction action can be done 
with one hand, because one finger of the hand holding the syringe is all 
that is required for depressing the pushbutton. 
Other advantageous developments of the invention can be gathered from the 
subclaims and the following specific description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Throughout the drawings, the same parts carry the same reference numerals. 
FIG. 1 is an exploded view of a cap 1, which is placed with an air tight 
fit on the end of a blood extraction tube or vessel 2 indicated by dot - 
dash lines in FIG. 2. According to FIG. 1, cap 1 has six components and 
specifically from top to bottom a pushbutton 26, a compression spring 24, 
a cap body 5, an O-ring 22, a closing member 38 and a separating member 
46. With the exception of compression spring 24 and O-ring 22, all the 
other components can easily be produced by injection molding. 
Separating member 46 shown in FIGS. 1 to 3 is a cylindrical solid body 
having guidance projections 52 on its lower edge. The external diameter of 
separating member 46 must be chosen in such a way that it is easily 
movable in the interior of a blood extracting tube 2 in which it is guided 
by guidance projections 52. In one construction, there are four 
longitudinal guidance projections 52 oriented in the axial direction of 
the separating member 46. At its upper end opposite to the guidance 
projections 52, separating member 46 has an upper edge 50 for receiving 
the closing member 38. Above upper edge 50, separating member 46 is 
terminated by a conical tip 48. Separating member 46 is not absolutely 
necessary for the operation of the cap according to the invention. The 
closing member has a smaller outer diameter than the corresponding 
interior diameter of the cap 5. 
Onto the conical cylindrical tip 48 of separating member 46 can be placed 
the closing member 38, which has a conical closing surface 40 and a 
cylindrical portion 42 connected to the base of the conical closing 
surface 40. The internal diameter of cylindrical portion roughly 
corresponds to the external diameter of the upper edge 50 extending in the 
form of a circumferential flange around separating member 46, so that 
cylindrical portion 42 snaps over the upper edge 50 for locking relative 
to separating member 46. The cone angle of closing surface 40 roughly 
corresponds to the cone angle of cylindrical tip 48, so that the closing 
member 38 snapped over the upper edge 50 is supported by the cylindrical 
conical tip 48. Onto the upper end of closing surface 40 is provided a tip 
44, which is shaped like a cylindrical rod. 
Cap body 5 has a base 6, which carries an eccentrically arranged cannula 
cone 4 and onto its side remote from cone 4 is connected a skirt 8, which 
is internally provided with an internal thread 14 for locking or fixing to 
the tube 2. Cannula cone 4 has a cannula bore 12, which extends through 
base 6 and consequently brings the interior of cap body 5 into flow 
connection with cannula cone 4. The cannula bore 12 issues into the 
vicinity of a shoulder 16 in base 6, in such a way that an O-ring 22 
placed on the inside of base 6 and supported by shoulder 16 is able to 
cover bore 12. 
An annular wall 18 surrounds the central bore 10 on the side of base 6 
facing cannula cone 4. The diameter of central bore 10 is slightly larger 
than the external diameter of tip 44 of closing member 38 and the oversize 
can be selected without difficulty by those skilled in this art. A few 
tenths of a millimeter are generally sufficient to allow a free 
displaceability of tip 44 in central bore 10. The height of wall 18, 
measured in the axial extension of cap 1, is chosen in such a way that it 
permits the guidance of pushbutton 26. 
Pushbutton 26 is a substantially cylindrical cap with a cover 30, which is 
closed with the exception of a cutout 34 and to which is connected a 
cylindrical side wall 32. Cutout 34 is provided at the location of the 
cannula cone 4, so that despite the eccentrically fitted cone 4, it makes 
it possible to depress pushbutton 26. A groove 28 (FIG. 3) running in the 
direction of a generatrix of side wall 32 diametrically faces cutout 34, 
so that groove 28 extends over the entire height of side wall 32. With 
pushbutton 26 fitted, an axial projection 29 provided on the inside of 
wall 32 engages in the groove 28 and prevents rotation of pushbutton 26, 
although permitting an axial displacement. A pin receiver 36 in the form 
of a hollow cylinder is shaped onto the bottom of cover 30 of pushbutton 
26 and its height is roughly the same as that of side wall 32. The 
internal diameter of pin receiver 36 is such that it can be force-fitted 
onto the tip 44 of closing member 38 so as to be securely held thereby and 
movable therewith. This leads to a force-locked connection between closing 
member 38 and pushbutton 26. 
Between cover 30 of pushbutton 26 and base 6 of cap body 5 is inserted a 
compression spring 24 surrounding pin receiver 36 and which normally 
presses the pushbutton 26 away from base 6 and consequently draws the 
closing member 38 against the bottom of base 6. Through an appropriate 
choice of the cone angle of closing surface 40, it is possible to seal 
O-ring 22 with closing surface 40 and press the same against base 6. Thus, 
O-ring 22 is forced onto the cannula bore 12, so that the interior cannula 
cone 4 is closed. There is also a sealing of central bore 10, because none 
of the air between O-ring 22 and closing surface 40 can pass into the 
space surrounded by skirt 8. Obviously, cannula bore 12 need not be at the 
support point of O-ring 22 and need merely be arranged within the radial 
width of the latter. By a corresponding construction of the contact 
surfaces for closing surface 40, it is also possible to bring about such a 
seal without the O-ring and as is the case with the construction according 
to FIGS. 3 or 4. 
According to the invention, cap 1 is fitted by initially pressing closing 
member 38 onto separating member 46. The O-ring 22 is then placed in the 
depression formed by shoulder 16 in base 6. Tip 44 is then passed through 
the central bore 10 of base 6, so that it projects out of base 6 within 
wall 18. The compression spring 24 is then placed over tip 44 and then the 
pushbutton 26 is forced onto tip 44 until depression of pushbutton 26 is 
still possible when closing surface 40 rests completely on O-ring 22. A 
sealing collar 19 (FIG. 3) seals the tip 44 relative to the central bore 
10. 
The thus fitted cap 1 can now be screwed, inserted or in some other way 
fitted to the blood extraction tube 2. For operation purposes, a per se 
known, not shown piston with its piston rod is placed in the cylinder end 
remote from cap 1 and is secured by a further, also known cap, which 
appropriately has a locking mechanism for holding the raised piston in the 
raised position. This is achieved in per se known manner in that the 
piston rod has thickened portions which, in the case of a powerful pulling 
action, can be moved through the cap and prevents any slipping back of the 
piston. If the pulling up and locking of the piston takes place with 
pushbutton 26 unactuated, a vacuum is formed in tube 2 which makes the 
cannula ready to operate. For sticking into a blood vessel or the like, a 
needle is placed on cannula cone 4 and the thus assembled syringe can be 
inserted in the vessel one-handed. The pushbutton 26 is then depressed 
with one finger, e.g., the index finger, so that the blood or liquid in 
the cannula and cannula cone 4 is rapidly sucked by the cannula bore 12 
into the tube 2 as a result of the vacuum in the latter. 
After removing the vacuum, O-ring 22 again closes the cannula bore 12 and 
prevents the escape of blood therefrom. By sealing pushbutton 26 it is 
possible to prevent the removal of blood. 
If the blood contained in the cylinder is to be centrifuged, separating 
member 46 can be held in locking engagement with the closing member 38 and 
consequently in the position according to FIG. 2 by means of its upper 
edge 50 and up to a predetermined g-number, whilst a preseparation of the 
blood constituents takes place. Only on exceeding the predetermined 
g-number is the separating member 46 released from the closing member 38, 
as is described e.g. in U.S. Pat. No. 4,154,690, the disclosure of which 
is incorporated herein by reference. 
FIG. 3 shows the second embodiment, in which the cannula bore 12 is closed 
by a valve seat 11 provided in a flat partition 7, instead of by an O-ring 
22. Partition 7 has formed thereon a number of ribs 15 on one side which 
faces the base 6 when mounted. Preferably there are six ribs which 
surround a middle bore 9 of the partition 7 and extend radially relative 
thereto. The ribs 15 are spaced advantageously with a distance between the 
periphery 17 of the partition 7 and the perimeter of the middle bore 9 to 
allow free distribution of the blood sucked into a flow channel 13 formed 
between the base 6 and the partition 7. The middle bore 9 has a diameter 
of a size so that the tip 44 of the closing member 38 can freely pass 
therethrough and that further there is an unobstructed blood flow path 
through an annular space formed between the tip 44 and the wall of the 
middle bore 9. Preferably the diameter of the middle bore 9 is 1.5 to two 
times larger than the external diameter of the tip 44. Middle bore 9 is 
aligned with the central bore 10 in base 6, so that the tip 44 of closing 
member 38 can simultaneously extend through middle bore 9 and central bore 
10 without tilting or jamming. Central bore 10 has a smaller diameter than 
middle bore 9 but a slightly larger diameter than tip 44, so that tip 44 
can actually slide within central bore 10 with slight friction. To seal 
the tip 44 a sealing collar 19 is provided on the outer side of base 6 
which faces the pushbutton 26, which sealing collar 19 prevents blood from 
leaking from the space between central bore 10 and tip 44. To effect the 
sealing action the upper rim of the sealing collar 19 engages the 
circumference of tip 44 which preferably has a cylindrical cross-section 
for this sealing purpose. 
The periphery 17 of flat partition 7 extends a little bit downwardly in the 
shown embodiment in the direction towards tube 2 to achieve better 
contacting of inner wall 3 of cap 1 and to prevent tilting and jamming of 
partition 7 when inserting into cap 1. Middle bore 9 is surrounded by the 
valve seat 11 which widens downwards and outwards and therefore faces the 
opposite direction of partition 7 than the ribs 15 face, so that its valve 
seat surface is part of a conical surface for a ring collar 21 which 
surrounds the base of tip 44 and thereby forms the end of closing surface 
40 adjacent to tip 44. In the embodiment of FIG. 3 opening or closing of 
the valve is therefore effected by ring collar 21 instead of closing 
surface 40, which ring collar is pressed against valve seat 11 by the 
action of the compression spring 24 acting on the ring collar 21 through 
pin receiver 36 and tip 44 frictionally secured thereto by a force fit as 
in the embodiment of FIGS. 1 and 2. Opening of the valve is effected by 
simply pressing pushbutton 26 which lifts ring collar 21 from valve seat 
11 and allows blood to flow from cannula bore 12 through flow channel 13 
and through middle bore 9 into tube 2. When pressure on pushbutton 26 is 
released, spring 24 moves the pushbutton upwardly to raise surface 40 and 
ring collar 21. 
FIG. 4 shows a third embodiment of the invention which is similar to the 
embodiment according to FIG. 3 to a large extent. Same parts are again 
provided with same reference numerals. The embodiment of FIG. 4 differs 
from the embodiment according to FIG. 3 in the shape of partition 27 which 
has the shape of a cone-like head instead of a flat plate. Partition 27 is 
again provided with radially extending ribs 15 on its top side which form 
a space between base 6 and partition 27 and thereby form a cone-like flow 
channel 23. The periphery 17 of partition 27 extends again downwards in 
axial direction to make it better conform to the inner wall of cap 1. In 
the center of partition 27 middle bore 9 is provided for receiving tip 44 
of closing member 38, said middle bore 9 again forming the annular space 
mentioned in connection with FIG. 3 for passing blood. Ring collar 21 
again seals flow channel 23 relative to the interior of tube 2, said ring 
collar in the embodiment of FIG. 4 directly contacting the lower side of 
partition 27. The lower side of partition 27 therefore forms a valve seat. 
The expert knows that an additional valve seat can be provided if 
necessary, e.g., if the angle of the lower side of partition 27 does not 
form a seat which reliably seals flow channel 23. With the exception of 
compression spring 24, all the components of cap 1 shown in FIGS. 1 
through 4 are appropriately injection molded from plastic. According to 
another construction, tip 44 is connected by means of a frangible section, 
having a predetermined breaking point, to closing member 38, whilst 
separating member 46 is integrally formed with the latter. This is 
indicated, by way of example, in dotted lines 46 in FIG. 3. Thus, during 
centrifuging after reaching a predetermined g-number the frangible section 
breaks and releases separating member 46. During centrifuging therefore a 
preseparation will be effected without separating element during the 
initial phase of centrifuging with the separating member 46 being 
separated from the closing member 38 only after increasing the speed to a 
predetermined value. 
The cap according to the invention has the advantage that it can be used in 
connection with normal cannulas which normally are provided with a "Luer" 
cone, which is a cone of a small angle of a few degrees. By eccentrically 
arranging the cannula cone 4 and due to pushbutton 26 the tube 2 can be 
handled with one hand only with the cap 1 and its tube 2 which is screwed 
into said cap or latched to it by some other means are held between thumb 
and middle finger to punctuate a blood vessel while the forefinger rests 
on the pushbutton 26. Whether a blood vessel has actually been punctuated 
can be determined by briefly pushing pushbutton 26 which was not possible 
in prior art devices. Further, the vacuum within the tube 2 and used for 
sucking blood can be shut off by closing the valve in cap 1 if a vein 
collapses. 
As is well understood, differently structured actuation elements can be 
used instead of the pushbutton for one-hand handling of the cap, such 
actuating elements being for e.g. keys, levers or other means which can be 
moved back to their initial position by plastic spring means or without 
any spring elements by actuating one or more levers. 
It will further be appreciated that the vacuum within the tube need not 
necessarily be generated by pulling the piston, instead it can be provided 
prior to use in that the tube is evacuated during manufacturing. This can 
be done in different ways, for e.g. by assembling within a vacuum chamber 
or by providing a check valve through which the tube can be evacuated or 
by any other means well known to the expert in this field.