Abstract:
A syringe holder has a barrel ( 1 ) with a needle shroud ( 4 ) telescopic into its leading end and urged forwardly by a spring ( 5 ). The shroud is rotatable into several set positions, being located by snap action of a nib ( 18 ) into longitudinal grooves within a forward extension ( 3 ) of the barrel ( 1 ). An abutment ( 21,20 ) on the shroud is thereby aligned with a selected one of several abutments ( 12,9,14 ) within the barrel, these all being at different axial positions. One setting prevents needle exposure; the others permit different amounts of needle exposure as the barrel ( 1 ) is urged forwardly during an injection.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates to needle protection devices. 
   A medical syringe is often placed in a pen-like firing device or a holder of barrel form. The more sophisticated devices have a trigger which, when actuated, causes the dose to be administered automatically. The barrel-like holders make handling the syringe easier. 
   But whatever the syringe may be mounted in, its needle has to project from the forward end, at least at the time of administering the dose. At other times, it is advisable for the syringe either to be retracted within its holder or for a shroud to be placed over the needle. 
   It is not always desirable to have the needle project to the same extent each time an injection is made. Sometimes, the injection should be deep into the flesh, and at other times it should be shallow. 
   It is the aim of this invention to provide a needle shroud arrangement which will protect the needle before and after use, but which can be adjusted to set the required depth of penetration. 
   SUMMARY OF THE INVENTION 
   According to the present invention there is provided a needle shroud assembly for a syringe holder, the assembly comprising a barrel and a tubular needle shroud captively telescoped into the forward end of the barrel, there being mutually facing abutments on the barrel and the shroud to limit the rearward telescopic movement of the shroud by different amounts according to its rotational position in relation to the barrel. 
   Preferably, the barrel and shroud have mutually interengageable detents to register the shroud in particular rotational positions, each interengagement allowing relative axial movement of the barrel and shroud so that abutments associated with the rotational position selected can engage. Conveniently, the detents are axially parallel grooves in either the barrel or shroud and a projection on the shroud or barrel that can snap into and out of the grooves. Advantageously the projection is on a thin element integrally moulded with the shroud, the grooves being in the barrel. 
   Preferably, the barrel has a set of forward facing internal abutments at different circumferential and axial positions, the shroud having a rearward facing abutment. 
   The barrel may have a main body with a reduced leading end and an extension that retentively telescopes over this leading end and which is adapted to keep the shroud captive. The set of forward facing abutments can then be provided by the reduced leading end. 
   The extension can be circumferentially located by longitudinal ribs on the reduced leading end engaging complementary grooves in the extension, and these may extend beyond the main body of the barrel to provide the detents for the projection on the shroud. The shroud will generally have a forward spring bias to a limiting position where the needle of a syringe within the barrel is concealed within the shroud. There will then be automatic protection of the needle before and after injection, and the shroud will retract by the amount allowed as the syringe is applied. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the invention, one embodiment will now be described, by way of example, with reference to the accompanying drawing, in which: 
       FIG. 1  is a perspective exploded view of a syringe holder with a needle shroud, 
       FIG. 2  is an end view of the shroud, and 
       FIG. 3  is a cross-section of an outer casing of the holder, and 
       FIG. 4  is a detail, in longitudinal section, of the forward part of the holder. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The syringe holder has a barrel with a main body  1  having a reduced forward end portion  2  and, an extension  3  which fits over that portion  2 . An adjustable tubular needle shroud  4  captive to the forward end of the barrel by the extension  3 , and a spring  5  urges the shroud  4  forwards. The manner of location of the syringe within the barrel is not material to this invention; suffice it to say that it is housed co-axially with its needle projecting forwardly from the barrel. 
   The portion  2  has external longitudinal ribs  6  which engage in corresponding internal grooves  7  in the extension  3 . Their numbers and circumferential spacing relate to the geometry of the stepped forward end of the portion  2  and the rear end configuration of the shroud  4  for reasons to be described below, and the grooves  7  are longer than their complementary ribs  6 . The portion  2  also has annular ribs  8 , less prominent than the ribs  6 , around its forward end, the foremost one being interrupted by two diametrically opposed recesses  9  in the end of the portion  2 . The extension  3  has complementary annular grooves  10  and the plastics material of which the main body  1 , 2  of the barrel and the extension  3  are made allows the latter to be snap fitted over the end portion  2  so that it abuts the shoulder  11  where the portion  2  begins, thus providing a smooth continuation of the barrel. 
   On one circumferential side of each recess  9  the portion  2  extends into a finger  12 , bevelled at its tip, and along one of these fingers runs one of the ribs  6 . On the other circumferential side of each recess  9  its mouth widens at a bevel  13  and then there is an arcuate, intermediate section  14  round to the opposite finger  12 . The other ribs  6  terminate at points along one of these sections. 
   The shroud  4  projects from the extension  3  and is axially grooved at  15  at its forward end to afford a good grip. Its rear end has a complex flange in two arcuate sections  16  and  17  to co-operate with the forward end portion  2  of the body  1 . The section  16  steps out from the shroud  4  to an extent such that its outer cylindrical envelope corresponds generally to the interior surface or the extension  3  and the exterior surface of the portion  2 . 
   But it has an outwardly projecting nib  18  at the centre of a thin bridge  19  standing away from the main body of the shroud over about half the arcuate length of the section  16 . This bridge  19  is reduced enough to form a spring (the shroud being an integral moulding of plastics material) and the nib  18  can thereby have snap action in and out of the grooves  7  in the extension  3 . The remaining portion of the section  16 , from one end of the bridge  19 , first doubles in thickness, in the rearward axial direction, to provide a step  20  and then extends further rearwardly in a projection  21 . 
   The other similar section  17  lacks the bridge  19  and nib  18 , that portion being solid, but it could exactly duplicate the section  16 . 
   The shroud  4  is normally urged forwards by the spring  5  so that the flange sections  16 ,  17  abut an inturned flange  22  at the mouth of the extension  3 . The shroud  4  is circumferentially located by the nib  18  engaging in one of the grooves  7  whose forward ends are exposed beyond the portion  2 . The grooves  7  and nib  18  are denoted herein as mutually interchangeable detents. 
   If it is the groove  7  engaged by the rib  6  nearest the bevel  13 , then the projections  21  align with the ends of the fingers  12 . This prevents or severely limits the rearward movement of the shroud, which then gives full protection to the needle of a syringe housed in the barrel. 
   By turning the shroud  4  left handed (as seen in  FIG. 1 ) the nib  18  snaps out of one groove  7  into the next, which aligns the projections  21  with the recesses  9 . The shroud can then be pushed rearwardly against the spring  5  until the projections  21  seat in those recesses, while the fingers  12  pass through the gaps between flange sections  16  and  17  to lie between the shroud  4  and the extension  3 . This is the maximum retracted position of the shroud and gives the greatest needle exposure. 
   For less needle exposure, the shroud is released and turned, again left handed, until the nib  18  engages in the third groove  7 . The projections  21  are then opposite the ends of the intermediate sections  14  adjacent the bevels  13 . This further rotation is not impeded by the fingers  12 : the gaps between the ends of the flange sections  16  and  17  are sufficiently large. 
   For even less needle exposure, the shroud  4  is released and rotated until the nib  18  engages the groove  7  with which the ribbed finger  12  co-operates. Then the ends of the fingers  12  will be opposite the bridge  19  and the corresponding portion of the section  17 , whether that be solid or another bridge. 
   The recesses  9 , fingers  12 , intermediate sections  14 , and projections  21  are denoted herein as mutually facing abutments. Prior to use, the shroud  4  is turned to align the abutments which will meet to give the desired needle exposure, and as the syringe is offered up the forward end of the shroud  4  meets the skin surrounding the intended puncture point. While the spring/barrel assembly is pushed forwards to make the needle penetrate, the shroud remains static and stops the barrel with the needle at the intended depth within the patients&#39; flesh. On withdrawal, the spring  5  pushes the shroud  4  forwards relative to the barrel, and thereby keeps the needle protected. 
   There can be marks on the extension  3  and exposed part of the shroud  4  to help the user make the correct adjustment. 
   It may in some circumstances be preferred to have the spring bias in the opposite direction, urging the shroud rearwardly. It would then normally be set at the position shown in  FIG. 1 , where the needle would not be exposed, and before injection the user would rotate the shroud to the required setting and let it go. The spring (acting between the flange  22  and the composite flange  16 ,  17 ) would then push the shroud back so that the needle was exposed by the desired amount. 
   It would also be possible to reverse the abutment and rib and groove arrangements. The set of abutments could be at different axial positions on the shroud rather than on the barrel and the equivalent of the finger  12  would then be on the barrel. And there could be grooves instead of ribs  6  and ribs instead of grooves  7 , with depressions in the shroud  4  into which those ribs could snap.