Safety syringe

A safety syringe 10 is disclosed and claimed. The syringe 10 comprises a tube 12 on which a hollow needle 16 is mountable for communicating with the inside of the tube. A plunger 28 is mounted in tube 12 for telescopic movement relative thereof. An outer sleeve 30 is mounted on the tube 12 and is moveable from a first needle - exposing position to a second needle covering position. Clips 40 are provided between tube 12 and sleeve 30 releasably to lock the sleeve in the said first position and permanently to lock the sleeve in the said second position. A formation 40.8 is provided on each clip on which pressure is exerted to release the clip when the sleeve is in its first position, without deformation of the sleeve.

INTRODUCTION AND BACKGROUND 
This invention relates to syringes and more particularly to safety syringes 
of the kind comprising a telescopically moveable outer sleeve for covering 
a needle of the syringe, after use. 
Various safety syringes of the kind referred to hereabove are known to the 
applicant. For example, in the specification of U.S. Pat. No. 4,655,751 to 
Harbaugh, there is disclosed such a safety syringe. The circular 
cylindrical sleeve of this syringe comprises a pair of integral, 
diametrically opposed and inwardly extending ears towards a rear end 
thereof. These ears, in use, co-operate with two pairs of opposed pockets 
defined respectively towards the rear and forward ends of a tube or barrel 
of the syringe. To release the ears from the rearward pockets, it is 
necessary to exert a force in a radially inwardly direction on the sleeve 
thereby to deform, more particularly, to oval the shape of the sleeve. 
This force must be exerted in opposed regions of the sleeve, spaced 
substantially ninety degrees from the ears. Finger grips are also provided 
on the sleeve in these regions. 
The disadvantages of this syringe are that it is as easy to deform the 
sleeve and to release the ears from the pair of forward pockets and 
thereby to remove the sleeve from the tube, as it is to release the ears 
from the aforementioned rearward pockets. Thus, the sleeve is releasably 
locked in both its first and second positions. Furthermore, the ears and 
finger grips which are disposed at ninety degree intervals on the sleeve 
obscure the visibility of graduation marks on the tube of the syringe. 
Still furthermore, the pockets and channels defined in the outer surface 
of the tube require too drastic a departure from the know and conventional 
design of tubes or barrels for syringes. 
OBJECT OF THE INVENTION 
It is an object of the present invention to provide a syringe with which 
the applicant believes the aforementioned disadvantages will at least be 
alleviated. 
SUMMARY OF THE INVENTION 
According to the invention there is provided a syringe comprising: 
a tube having a nozzle in a front end wall thereof and defining an opening 
at rear end thereof, a hollow needle being mountable on the tube to 
communicate with the nozzle; 
a plunger mounted in the tube to extend through the opening and for 
telescopic movement relative to the tube; 
the tube including a finger flange comprising two opposed finger grips 
positioned towards said rear end; 
an outer sleeve having a rear end and a front end mounted coaxially with 
the tube to be moveable relative to the tube in telescopic manner from a 
first needle-exposing position to a second needle covering position; 
locking means for releasably locking the sleeve in the first position and 
for permanently locking the sleeve in the second position; 
means extending beyond the sleeve for releasing the locking means when the 
sleeve is in the first position; and 
the means for releasing the locking means being actuable by applying 
pressure in a radially inwardly direction thereon, thereby to release the 
locking means without deformation of the sleeve. 
In this specification the term "permanently locked" is used to indicate 
that two parts are locked such that they cannot be disengaged without 
damage to the syringe as opposed to "releasably locked" which indicates 
that the parts may be disengaged from one another should the user so want, 
without any damage to the syringe. 
The syringe preferably comprises at least one clip which is separate from 
both the tube and the sleeve and which is located between the tube and 
sleeve, the clip embodying at least part of the locking means and the 
means for releasing the locking means. 
The clip may comprise a body, and the locking means may comprise a hook 
formation secured to the body to extend towards the rear end of the tube, 
releasably to co-operate with a finger flange at the rear end of the tube. 
The finger flange includes two diametrically opposed finger grips. Each of 
the finger grips is axially in line with a corresponding locking means on 
the tube. 
The clip preferably comprises a first radially outwardly extending 
formation on the body thereof for, in use, co-operating with a transverse 
hole defined in the sleeve thereby permanently to engage the sleeve. 
Further according to the invention the clip may comprise two resiliently 
flexible curved arms extending in opposite directions away from the body 
of the clip to embrace partially and to abut against the tube thereby to 
define a clearance between the body of the clip and the tube to urge the 
said first radially outwardly extending formation into the transverse hole 
in the sleeve, thereby to engage the sleeve. 
The means for releasing the locking means may comprise a second radially 
outwardly extending formation on the body of the clip. The said second 
radially outwardly extending formation being located beyond the rear end 
of the tube and also extending radially beyond the sleeve. 
At least one hole may be defined in the finger flange through which the 
said hook formation, in use, extends to co-operate with the flange, when 
the sleeve is in its first position. 
Further according to the invention the syringe may comprise guide means for 
preventing any rotational movement of the sleeve relative to the tube. The 
guide means preferably comprises an outwardly extending arrangement 
located towards the front end wall of the tube co-operating with at least 
one linear channel defined in an inside wall of the sleeve. The outwardly 
extending arrangement preferably comprises two pairs of spaced, radially 
outwardly extending lugs located in diametrically opposed regions on the 
tube co-operating with two linear channels defined in diametrically 
opposed regions in the sleeve. 
Each of the pairs of outwardly extending lugs may define a channel between 
them. The locking means may further comprise an inwardly extending hook 
formation on the at least one clip for locking the sleeve in the second 
position; the inwardly extending hook formation being secured to the body 
of the at least one clip and having an elongate limb extending towards the 
front wall of the tube and a rearwardly and inwardly extending limb; the 
said inwardly extending hook formation locking the sleeve in its second 
position with the said elongate limb extending through the channel and the 
rearwardly and inwardly extending limb engaging the front end wall of the 
tube on one side of the pair of lugs. At the same time shoulder formations 
on the clip abutt against an opposite side of the pair of lugs to prevent 
the sleeve from being removed from the tube. 
In the preferred embodiment, the syringe comprises two clips located 
between the sleeve and tube, in diametrically opposed regions thereof. 
Also according to the present invention there is provided a safety syringe 
comprising: 
a transparent tube of circular cross section having a nozzle in a front end 
wall thereof and defining an opening at a rear end thereof, a hollow 
needle being mountable on the tube to communicate with the nozzle, the 
tube having graduation marks in a linear elongate region on an outer 
surface thereof; 
a plunger mounted in the tube to extend through the opening and for 
telescopic movement relative to the tube; 
an outer transparent sleeve of substantially circular cross section having 
a rear end and a front end mounted co-axially with the tube to be moveable 
relative to the tube in telescopic manner from a first needle - exposing 
position to a second needle - covering position; 
guide means for preventing any rotational movement of the sleeve relative 
to the tube located in two diametrically opposed elongate regions of the 
syringe, substantially ninety degrees offset from the elongate region 
wherein the graduation marks are located; 
locking means for releasably locking the sleeve in the first position and 
for permanently locking the sleeve in the second position, the locking 
means also being located in the said two diametrically opposed elongate 
regions so that the said linear elongate region wherein the graduation 
marks are provided, is not obscured by the guide means and the locking 
means. 
Also included within the scope of the present invention is a medical 
instrument comprising: 
a tube having a nozzle in a front end wall thereof and defining an opening 
at a rear end thereof, a hollow needle being mounted at the nozzle so that 
a first half thereof extends forwardly beyond the tube and a second half 
rearwardly and into the tube; 
an evacuated cannister having a needle pierceable wall and which cannister 
is removably receivable in the tube; 
an outer sleeve having a rear end and a front end mounted coaxially with 
the tube to be moveable relative to the tube in telescopic manner from a 
first position wherein the said first half of the needle is exposed to a 
second position wherein the said first half of the needle is covered; 
locking means for releasably locking the sleeve in the first position and 
for permanently locking the sleeve in the second position; and 
means extending beyond the sleeve for releasing the locking means when the 
sleeve is in the first position; 
the means for releasing the locking means being actuable by applying 
pressure in a radially inwardly direction thereon, thereby to release the 
locking means without deformation of the sleeve.

DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
A syringe according to the invention is generally designated by the 
reference numeral 10 in FIGS. 1, 2 and 3a-3d. 
The syringe 10 comprises a transparent tube 12 of substantially circular 
transverse cross section. At one end of tube 12 there is provided an end 
wall 12.1 on which there is provided a nozzle 14. A hollow needle 16 is 
mountable on the nozzle to communicate with the inside of the tube. Also 
at the said one end of tube 12 there are provided two pairs of spaced 
outwardly projecting lugs 18 in diametrically opposed elongate and 
longitudinally extending regions on tube 12. Each pair of lugs 18 defines 
a channel 20 therebetween. At the other or rear end of tube 12 there is 
defined a mouth 22. An integral finger flange 21 including diametrically 
opposed finger grips 24.1 and 24.2 extends transversely to tube 12 at the 
said other end thereof. As is best shown in FIGS. 2, 3a, 3b, 4 and 5 
opposed holes 26 are defined in flange 24 finger grips 24.1 and 24.2 
immediately adjacent and radially outwardly from the aforementioned 
elongate regions on tube 12. Graduation marks 12.2 are provided on the 
tube 12. As best shown in FIGS. 3a, 3b and 3c, the graduation marks 12.2 
are located in a linear elongate region offset by ninety degrees from the 
said elongate regions wherein the pairs of lugs 18 are located. 
A plunger 28 is mounted in tube 12 and is moveable in telescopic fashion 
relative to tube 12--upon rearward movement to draw a fluid via needle 16 
into the tube and upon forward movement to expel the fluid from the tube 
via nozzle 14 and needle 16. As is best shown in FIG. 3d, the plunger 28 
comprises a piston 28.1 of a resiliently flexible material, a plunger stem 
28.2 and a transverse flange 28.3. 
The syringe further comprises a transparent sleeve 30 coaxially mounted on 
the tube 12 to move in telescopic fashion from a first, needle - exposing 
position (shown in FIG. 1) to a second, needle - covering position (shown 
in FIG. 2). Sleeve 30 comprises two internal channel defining formations 
32 in diametrically opposed longitudinally extending elongate regions 
thereof. At one end of sleeve 30 there is provided a tubular neck 34 
through which the needle extends, when the sleeve is in the first 
position. At the other end of sleeve 30 there is defined a mouth 36 
through which the tube 12 extends. Also towards the other or rear end of 
the sleeve and in the channel defining formations 32, there are defined 
opposed transverse holes 38. 
Between the tube 12 and sleeve 30 and partially in the channels defined by 
the formations 32, there is provided locking means in the form of two 
clips 40. As is best shown in FIGS. 3a, 3b and 3c, each clip comprises a 
body 40.1 and two transversely extending, curved arms 40.2. 
Each clip 40, at one end of body 40.1, comprises an inwardly extending hook 
formation comprising an elongate member 40.3 and a radially inwardly 
extending limb 40.4. At the other end of the body 40.1 there is provided a 
radially outwardly extending hook formation 40.5. On the outer surface of 
each clip body 40.1 there is provided a first radially outwardly extending 
formation 40.6 for engaging sleeve 30 as will be described in more detail 
hereinafter. Elongate member 40.3 and body 40.1 provide two opposed 
shoulder formations 40.7, one on each side of the elongate member 40.3. 
Between the said first radially outwardly extending formation 40.6 and 
outwardly extending hook formation 40.5, there is provided means for 
releasing the locking means comprising a second radially outwardly 
extending formation 40.8. 
As is best shown in FIGS. 1, 2, 3d, 4 and 5, clips 40 extend through the 
mouth 36 of sleeve 30 rearwardly towards the flange 24 on tube 12. 
In FIGS. 3a to 3d the assembly of the syringe 10 according to the invention 
is illustrated. The first step is to mount clips 10 in diametrically 
opposed regions on tube 12 with the arms 40.2 partially embracing the tube 
12 and so that elongate members 40.3 are located in the said 
longitudinally extending elongate regions on tube 12 and so that they may 
pass through channels 20. The clips are moved rearwardly towards flange 24 
so that hook formations 40.5 extend through holes 26 and engage flange 24 
on the other side thereof as tube 12, as shown in FIG. 4. 
As shown in FIG. 3c, sleeve 30 is fitted onto tube 12 with lugs 18 received 
in the channels defined by formations 32. Sleeve 30 is moved towards 
flange 24 until formation 40.6 slip into transverse holes 38. 
As shown in FIG. 4, with arms 40.2 (not shown in FIG. 4), abutting against 
the outer surface of tube 12, a clearance 42 is defined between the body 
40.1 of clips 40 and the outer surface of the tube 12. The inwardly 
extending hook formations which are trapped in the channels defined by 
formations 32 are deformed so that the inwardly extending limbs 40.4 are 
urged towards elongate members 40.3. Arms 40.2 urge formations 40.6 into 
transverse holes 38 defined in formations 32, thereby permanently to 
engage the sleeve 30. 
With hook formations 40.5 extending through holes 26 and engaging flange 
24, finger grips 24.1 and 24.2 the sleeve 30 is releasably locked in its 
needle-exposing position. 
After the syringe has been used, pressure is applied in a radially inwardly 
direction, on formations 40.8, thereby causing bodies 40.1 of the clips to 
move closer towards tube 12, so that hook formations 40.5 disengage flange 
24. 
Sleeve 30 with clips 40 are then moved towards the second position of the 
sleeve. The aforementioned opposed pairs of lugs 18, which fit in the 
channels defined by formations 32, act as guides to prevent any rotational 
movement of the sleeve 30 relative to tube 12. 
Elongate elements 40.3 and inwardly extending limbs 40.4 pass through the 
channels 20 defined by the pairs of lugs 18 and when the inwardly 
extending limbs reach the end wall 12.1 of the tube 12, they move, under 
the influence of their own resilience, to a position away from elongate 
member 40.3, thus abutting against the end wall 12.1 of the tube, as shown 
in FIG. 5. At the same time shoulder formations 40.7 abut against the ends 
of lugs 18 facing flange 24, so that they prevent the sleeve 30 from being 
removed from the tube 12. 
The sleeve 30 is then permanently locked in its second and needle covering 
position. 
After use, the complete syringe 10 is preferably disposed of. 
It will be appreciated that one of the advantages of the syringe 10 
according to the invention is that the sleeve 30 may be moved from its 
first needle-exposition position to its second position without any change 
of grip by the user of the syringe. More particularly, after the tube 12 
has been filled with the liquid to be expelled from the syringe, the 
syringe is held with the middle and forefingers of one hand resting on 
formations 40.8 and the thumb of that hand on the flange 28.3 of plunger 
28. The other hand supports the syringe by holding sleeve 30 in an 
intermediate region thereof. The liquid is expelled by urging the plunger 
28 towards needle 16 by means of the aforementioned thumb. 
After the fluid has been expelled, the sleeve 30 is released merely by 
urging the clips 40 inwardly by exerting pressure in a radially inward 
direction on formations 40.8, by means of the aforementioned middle and 
forefingers. The sleeve 30 is then moved towards its second position by 
the other hand still holding the sleeve as hereinbefore described. Thus, 
it is not necessary to remove the needle from the body injected with the 
liquid or to change grips, before the sleeve 30 is released. 
Another important advantage of the syringe according to the invention is 
that the clips 40 and channel defining formations 32 are located in 
diametrically opposed regions of the syringe leaving the regions between 
these two opposed regions blank, so that the graduation marks 12.2 on the 
tube 12 are clearly visible through sleeve 30. 
Yet another advantage is that the configuration of tube 12, apart from lugs 
18, is substantially the same as that of many conventional syringe 
barrels. Thus, the tube may be made using current multi-cavity injection 
moulding techniques. In some cases, existing moulds may simply be reworked 
to accommodate the aforementioned difference. 
A medical instrument according to the invention for withdrawing a fluid, 
such as blood, from a body is generally designated by the reference 
numeral 100 in FIG. 6. 
The instrument comprises a tube 12 and sleeve 30 similar to that of the 
syringe described hereinbefore. The sleeve 30 is also moveable from a 
first needle exposing position on tube 12 to be permanently locked in a 
second needle covering position by clips 40. 
However, the instrument comprises a double needle 116 mounted in the nozzle 
14 of the tube so that one half 116.1 thereof extends forwardly away from 
the tube and the other half 116.2 rearwardly into the tube. 
Also forming part of the instrument 100 is an evacuated cannister 102 
comprising a rigid tube 104 defining a blind bore. A needle pierceable 
membrane 106 covers an open end of the tube. 
In use, needle half 116.1 of the instrument is inserted into the body from 
which the fluid is to be withdrawn. The cannister 102 is next inserted 
into tube 12 so that needle half 116.2 pierces the membrane 106. The 
vacuum inside the tube causes the fluid to flow from the body into 
cannister 102. 
After the fluid sample has been withdrawn, the sleeve 30 is released and 
caused to move towards its second, needle covering position as 
hereinbefore described with reference to syringe 10. The cannister 102 
with the fluid is then removed from the tube 12. 
It will be appreciated that there are many variations in detail on the 
syringe according to the invention without departing from the scope and 
spirit of the appended claims.