Patent Description:
According to the present invention, it is provided a syringe having the features defined in claim <NUM>. In the following, there are described some arrangements, however, the scope of protection is defined by the claims. Some of the arrangements described in the following are helpful for understanding the present invention. One arrangement also includes a needle retraction mechanism and a laterally offset needle retraction cavity that is substantially coextensive with the length of the fluid chamber of the barrel. The needle is selectively retracted following an injection by sliding the barrel and needle retraction cavity transversely relative to the needle, thereby moving the needle retraction cavity laterally into coaxial alignment with the needle. The substantially full-length, laterally offset needle retraction cavity facilitates the optional use of longer retractable needles than are usable with conventional safety syringes having retractable needles and broadens the range of uses and procedures that are performable with the device without increasing the overall length of the syringe. Depending upon needle length, such uses and procedures can include, for example, performing spinal taps, administering epidural anesthesia, aspirating cysts, and the like, as well as for administering intradermal, subcutaneous or intramuscular injections.

Another aspect relates to a syringe having a barrel comprising a substantially cylindrical fluid chamber, a needle retraction cavity disposed in parallel and laterally spaced-apart relation to the fluid chamber, and at least one substantially flat, outwardly facing display surface to which indicia such as dosage scales can be applied using a conventional pad printing process. Still another aspect relates to a syringe having a barrel with two oppositely facing, substantially flat surfaces on which the same or different indicia can be pad printed without having to rotate the barrel, even when printing on <NUM>, <NUM> or smaller syringes. The substantially flat display surfaces also facilitate the application of indicia to a syringe by other processes such as embossing, injection molding, and the like.

Another aspect relates to a medical syringe comprising a barrel and plunger as disclosed above in combination with a frontal attachment having a forwardly projecting, rearwardly biased needle. The frontal attachment and barrel are desirably cooperatively configured so that the frontal attachment slidably engages a front portion of the barrel along an axis that is transverse to the longitudinal axis through the needle.

Another arrangement as described in relation to paragraph [<NUM>] above embodies a needle safety device having a needle tip shield that extends circumferentially around and is desirably coaxially aligned with the needle. The needle tip shield is desirably connected to or unitarily molded together with an elongate activation handle that is also part of the needle safety device and slidably engages the barrel. The needle safety device of this arrangement eliminates the need for having a needle retraction mechanism and a needle retraction cavity, and does not require transverse sliding movement of the barrel relative to the needle to protect users from accidental needle sticks. Following use of this arrangement of the syringe, the needle tip shield is selectively advanced to protect the user from the forwardly projecting needle tip by applying manual pressure to a touch surface of the activation handle that is located rearwardly of the needle and needle tip shield. The activation handle slidably engages the syringe barrel and is forwardly slidable relative to the barrel from a first position, in which the needle tip is uncovered, to a second position in which the needle tip is surrounded and protected against inadvertent needle sticks by the needle tip shield. Because the forwardly slidable needle safety device of this arrangement embodies a stop surface that prevents subsequent rearward movement of the device relative to the barrel of the syringe, the user is protected against subsequent accidental exposure of the needle tip and associated needle stick injuries. This arrangement combines the advantages of flat, printable surfaces having more easily readable dosage indicia with the cost advantages of a simpler but still effective and easy-to-use needle safety device to provide a safe and more affordable solution, particularly for persons needing frequent injections to treat various chronic health conditions. Furthermore, because the dosage markings and indicia are more easily readable by the user, there is less risk of administering an incorrect dosage of a medicinal fluid to a patient and thereby less risk of causing other unintended consequences.

Syringes intended for medical use typically have barrels comprising substantially cylindrical inside and outside walls, meaning that volumetric dosage indicia or other markings are applied to an arcuate outer surface during manufacture. This can be difficult, and especially so when the diameter of the barrel and radius of curvature of the outside wall are small (as with <NUM>, <NUM> and smaller syringes) and where the available outside surface area is extremely limited, or on syringes where different dosing scales or other indicia are applied to opposite sides of the barrel. In such instances it is often necessary to spin or rotate the barrel while printing, and it is also often difficult to read indicia such as dose measuring lines and the related numeric values or other markings because they wrap so far around the circumference of the barrel and because indicia or markings on one side are often viewable through the syringe and can confuse the user, sometimes leading to the commission of medical errors. For at least these reasons, syringes having substantially flat surfaces for use in applying dosage markings and other indicia are needed.

Medical syringes having rearwardly biased needles that retract into coaxially aligned retraction cavities disposed inside the plunger are known, having previously been disclosed, for example, in <CIT>; <CIT>; <CIT> and <CIT>. More recently, medical syringes having frontal attachments containing rearwardly biased needles that retract into needle retraction cavities that are part of the frontal attachment have been disclosed, for example, in <CIT>.

Even more recently, medical syringes with frontal attachments have been disclosed that slidably engage barrels having needle retraction cavities unitarily molded together with the barrel and disposed parallel to the fluid chamber. In <CIT> (FIGS. <NUM>-<NUM>), for example, the length of the needle retraction cavity is substantially shorter than the length of the fluid chamber inside the barrel and the needle retraction cavity does not cooperate with an outer wall of the barrel to form substantially flat outside surfaces that are adjacent to and substantially coextensive with the fluid chamber.

Other references disclosing devices arguably bearing some degree of similarity to various aspects or arrangements include the following: <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>.

In particular, it is provided a syringe having the features defined in claim <NUM>. According to one embodiment of the disclosure a syringe for medical use is disclosed that comprises a one-piece barrel having a fluid chamber and a laterally offset needle retraction cavity that are substantially parallel and separated by a common wall. The needle retraction cavity can have a non-circular cross-section and is desirably substantially coextensive in length with the fluid chamber, thereby facilitating the use of longer needles without increasing the overall length of the barrel in order to accommodate retraction of the longer needles as is the case with safety syringes that retract the needle into the barrel following use. The barrel further comprises an outer wall having at least one substantially flat, outwardly facing display surface upon which indicia such as a volumetric dosage scale, for example, can be applied using conventional pad printing technology or another similarly effective alternative means. The at least one substantially flat display surface is desirably disposed proximally to the fluid chamber and also desirably comprises a measurement scale that is longitudinally aligned with at least that portion of the fluid chamber that is useful for injecting or aspirating a fluid. According to one preferred arrangement two oppositely facing, longitudinally coextensive, substantially flat surfaces are provided, with each surface spanning at least a portion of an external wall of the fluid chamber and at least a portion of the external wall of the needle retraction cavity.

The subject syringe is particularly useful with syringes having usable volumes of <NUM> or less, which syringes typically have smaller barrel diameters that cause the volumetric dosage indicia applied to the outside surface to wrap around a greater portion of the circumference of the barrel. According to another preferred arrangement, pad printing technology (sometimes referred to as "tampography") is used to apply volumetric dosage indicia or other markings to the substantially flat display surface of the syringe. The needle retraction cavity can be made (preferably molded from a suitable polymeric material) with a non-circular cross-section and is offset laterally from the barrel to facilitate creation of a wider, outwardly facing, substantially flat display surface during manufacture. The substantially flat display surface desirably comprises at least one side that is proximal to the fluid chamber of the barrel and thereby provides an opportunity, if desired, for molding volumetric dosage markings or other indicia onto the otherwise flat display surface or embossing the indicia on or into the display surface.

Another arrangement of the subject syringe comprises a barrel and plunger as disclosed above in combination with a frontal attachment having a forwardly projecting, rearwardly biased needle. The frontal attachment and barrel are desirably cooperatively configured so that the frontal attachment slidably engages a front portion of the barrel along an axis that is transverse to the longitudinal axis through the needle. When the syringe is disposed in the use position, the needle is aligned with a first opening in the front of the barrel that is communicates with a substantially cylindrical fluid chamber inside the barrel to establish a coaxially aligned fluid flow path between the fluid chamber and the needle. A fluid seal is desirably seated around the first opening to resist fluid leakage between the frontal attachment and the barrel. The needle retraction cavity extends rearwardly from a second opening in the front of the barrel. in parallel and spaced-apart relation to the fluid chamber in the barrel, and desirably shares a common wall with at least a portion of fluid chamber. Following use of the syringe, relative transverse movement between the barrel and the frontal attachment repositions the rearwardly biased needle into alignment with the needle retraction cavity, thereby releasing the needle to be forced by the biasing means, typically a compressed spring, into a retracted position wherein the needle no longer projects forwardly from the syringe.

Another arrangement of the subject syringe embodies wider, substantially flat display surfaces disposed on a medical syringe having a unitary barrel and needle retraction cavity that cooperate with substantially flat edge portions of the surrounding flange to help prevent the syringe from rolling off a tray or other flat surface. The substantially flat surfaces also allow the flange around the barrel to be proportionally narrower as compared to the flanges of conventional syringes having tubular barrels and still provide larger surface areas that are more easily graspable by a user. The oppositely facing, substantially flat surfaces also improve stability and the degree of control that can be exercised over the syringe by a user during an injection or other procedure. Because the subject syringe has a barrel with a laterally offset needle retraction cavity that can be molded integrally with the fluid chamber, at least one, and preferably two (oppositely facing), substantially flat, outwardly facing surface areas are provided that are useful for the placement of an array comprising a volumetric scale or other indicia that are easily readable by the user and thereby reduce the likelihood of dosing errors during aspiration or injection.

Another arrangement comprises the subject syringe in combination with a selectively releasable needle cover that can also comprise a locking member configured to engage a portion of the barrel and resist sliding lateral movement of the barrel relative to the frontal attachment to prevent accidental retraction of the needle prior to using the syringe. Retraction of the needle following use of the syringe reduces the likelihood of reusing the syringe or of accidental needle sticks and the inadvertent transmission of blood-borne pathogens.

Another arrangement comprises the subject syringe in combination with a plunger cap that is releasably attached to the rear portion of the syringe, typically behind the finger flange, and is selectively removable prior to fluid aspiration or use. When both the needle cover and the plunger cap are in place, the needle and the internal, fluid-contacting portions of the syringe are enclosed and protected from contamination whether or not the syringe is also enclosed inside another package. Because of this, the syringes can be assembled and shipped in bulk prior to packaging and sterilization.

Although the subject syringe is especially useful in administering relatively small doses of a medicinal fluid such as insulin or a vaccine to a user by injection or infusion, the structure and operation of the apparatus is not limited to particular sizes, doses or procedures. For example, syringes configured as disclosed here can also be configured for use in aspirating fluid samples from patients during clinical procedures such as knee or spinal taps. Because the overall syringe length is reduced through use of the disclosed frontal attachment in combination with the novel barrel, longer needles can be used and still be retracted into the syringe following use. As used in this disclosure, "retracted" or "retraction" refer to the process by which a needle is moved from a forwardly projecting use position to a post-use position in which the needle point no longer projects forwardly from the frontal attachment, no matter whether the force acting upon the needle is pushing or pulling the needle tip rearwardly from the forwardly projecting position.

Another arrangement of a syringe for medical use is disclosed having a barrel with a longitudinally extending tubular fluid chamber and at least one longitudinally extending, outwardly facing, substantially flat indicia display surface disposed proximally to the fluid chamber, a plunger slidably inserted into the fluid chamber, a needle projecting forwardly from the barrel in fluid communication with the fluid chamber; and a needle safety device of fixed, predetermined length. The needle safety device desirably includes an activation handle slidably engaging the barrel and a forwardly projecting needle tip shield encircling the needle. In a first stop position, the needle tip shield is disposed around a nose portion of the barrel. In a second stop position, the activation handle is moved forwardly under manual pressure following use of the syringe, causing the needle tip shield to move forwardly to circumferentially surround and cover a tip end of the needle.

Another arrangement is disclosed that desirably embodies one and preferably two oppositely facing, substantially flat indicia display surfaces and also embodies a needle safety device having a needle tip shield that extends circumferentially around the needle and is desirably coaxially aligned with the needle. The needle tip shield is attached or connected to, or unitarily molded together with, an activation handle that slidably engages the barrel. Suitable rails, ramps, stop shoulders and detents or other similarly effective means are desirably provided as part of the needle safety device and the barrel so that the activation handle can be advanced smoothly and without substantial interference when desired, and will not accidentally retract afterward to expose the needle tip. The needle safety device of this arrangement eliminates the need for having a needle retraction mechanism, a needle retraction cavity or any transverse sliding movement of the barrel relative to the needle to protect users from accidental needle sticks. Following use of the syringe, the needle tip shield is selectively advanced to protect the user from the forwardly projecting needle tip by applying manual pressure to a touch surface of the activation handle that is located rearwardly of the needle and needle tip shield. The activation handle slidably engages the syringe barrel and is forwardly slidable relative to the barrel from a first position, in which the needle tip is uncovered, to a second position in which the needle tip is surrounded and protected against inadvertent needle sticks by the needle tip shield. The needle tip is desirably disposed sufficiently inside the needle tip shield once the needle safety device is fully extended relative to the barrel that someone handling the used syringe will not inadvertently be subjected to a needle stick injury by simply placing a fingertip over the end of the syringe.

In another arrangement, the activation handle further comprises a manually engageable touch surface.

In another arrangement, the barrel and the activation handle comprise cooperatively engageable elements that enable manually actuated and controllable, longitudinally slidable movement of the activation handle relative to the barrel between two predetermined stop positions. The first stop position is a fully retracted use position in which the needle tip shield substantially surrounds the nose. The second stop position is a fully extended post-use position in which the needle tip shield circumferentially surrounds a tip end of the forwardly projecting needle.

In one preferred arrangement, the forwardly projecting needle is disposed in fixed relation to the nose of the barrel but it will be appreciated upon reading this disclosure that a similarly configured syringe can be made with needles configured to be selectively attachable to the barrel.

These and other features of the present invention will be better understood from a consideration of the following detailed description of various arrangements and appended claims in conjunction with the accompanying drawings.

The syringe is further described and explained in relation to the following drawings wherein:.

It should be noted that the drawings are not necessarily to scale.

Referring to <FIG>, syringe <NUM> comprises barrel <NUM> further comprising substantially flat display surface <NUM>, frontal attachment <NUM>, outside wall <NUM> of fluid chamber <NUM> (visible in <FIG>), selectively removable needle cover <NUM>, an array of volumetric measuring indicia <NUM>, finger flange <NUM>, removable plunger cap <NUM> and locking member <NUM>. As shown in <FIG>, the principal volumetric measuring indicia <NUM> are applied to display surface <NUM>, including for example at least the Arabic numerals identifying the number of fluid units and the associated principal measurement indicia. It should be appreciated, however, that the accompanying figures of the drawings are for illustrative purposes and are not drawn to scale and that placement of some features such as the secondary unit markings <NUM> relative to substantially flat display surface <NUM> can vary from the positions shown. At least a portion of each secondary (individual) unit indicia or markings desirably commences on display surface <NUM> or proximal to the edge of display surface <NUM>, and optionally continues for a short distanced onto the curved outer wall of fluid chamber <NUM>. Such placement is understood to be within the operational capabilities of conventional pad printing technology that is now readily available to those of ordinary skill in the art.

As depicted in <FIG>, syringe <NUM> has frontal attachment <NUM> shown in the "pre-use" configuration with needle cover <NUM> and locking member <NUM> in place to prevent frontal attachment <NUM> from shifting laterally relative to barrel <NUM> prior to use because of pressure inadvertently applied to textured touch pad <NUM> or to the opposite side of barrel <NUM>. Removable plunger cap <NUM> is also installed behind finger flange <NUM> to prevent the plunger (not visible) from being accidentally withdrawn from barrel <NUM> and to prevent inadvertent contamination inside the rear opening of barrel <NUM> or around the rearwardly extending handle portion of the plunger, as seen in <FIG>, which is discussed below.

Referring to <FIG>, <FIG> and <FIG>, barrel <NUM> and frontal attachment <NUM> of syringe <NUM> are shown in the same position as in <FIG> except that needle cover <NUM> (with locking member <NUM>) is removed. The front opening into needle retraction cavity <NUM> is more clearly visible, and needle <NUM> is also visible, projecting forwardly from needle support member <NUM> of frontal attachment <NUM>. Circumferentially spaced, axially tapered ribs <NUM> are disposed around needle support member <NUM> and provide surfaces for frictional engagement with the inside surface of needle cover <NUM> prior to removal. In <FIG>, needle <NUM> is desirably coaxially aligned with the longitudinal axis through fluid chamber <NUM> (<FIG>).

Referring to <FIG>, needle cap <NUM> of syringe <NUM> further comprises a forwardly facing, inwardly tapered, substantially cylindrical sidewall having front end <NUM>, rearwardly facing annular collar <NUM>, and locking member <NUM> projecting rearwardly past annular collar <NUM>. Frontal attachment <NUM> further comprises forwardly projecting, substantially tubular needle support member <NUM> with front opening <NUM>, upper guide member <NUM>, lower guide member <NUM> (visible in <FIG>), and laterally projecting textured touch pad <NUM>.

Syringe <NUM> desirably includes needle <NUM> with forwardly facing beveled needle tip <NUM>, and a needle retraction mechanism further comprising coiled compression spring <NUM> and needle holder <NUM>. Needle holder <NUM> further comprises an elongated shaft <NUM> with tubular bore <NUM> that is insertable into the rear of spring <NUM>. The diameter of head <NUM> of needle holder <NUM> is sufficiently greater than the inside diameter of spring <NUM> that spring <NUM> can be held in compression by head <NUM> when frontal attachment <NUM> is slidably engaged with front portion <NUM> of barrel <NUM> as discussed in relation to <FIG> below. The rear end of needle <NUM> is insertable into tubular bore <NUM> of needle holder <NUM> and attachable in fixed relation to the inside of elongated shaft <NUM> by any suitable, commercially available means such as an adhesive. Although a needle retraction mechanism as disclosed here is satisfactory for use in syringe <NUM>, it will be appreciated that other similarly effective elements and mechanisms useful for rearwardly biasing needle <NUM> inside syringe <NUM> can also be used in making the invention.

Still referring to <FIG>, annular polymeric fluid seal <NUM> with tubular bore <NUM> is desirably insertable into recess <NUM> in front portion <NUM> of barrel <NUM> so that the forwardly facing end of seal <NUM> is disposed in abutting contact with rearwardly facing head <NUM> of needle holder <NUM> when the needle retraction mechanism is installed inside frontal attachment <NUM> and frontal attachment <NUM> is attached in slidable engagement with front portion <NUM> of barrel <NUM>. When frontal attachment <NUM> of syringe <NUM> is assembled to front portion <NUM> of barrel <NUM> during manufacture, a continuous, substantially linear, fluid flow path is established through needle <NUM>, needle holder <NUM> and annular fluid seal <NUM> into tubular, longitudinally extending fluid chamber <NUM> (visible in <FIG>).

In addition to front portion <NUM>, barrel <NUM> further comprises substantially flat display surface <NUM>, curved outside wall surface <NUM>, finger flange <NUM> and rearwardly projecting annular collar <NUM>. During assembly of syringe <NUM>, elastomeric plunger seal <NUM> is desirably installed on forwardly projecting boss <NUM> on the front end of plunger handle <NUM> opposite rearwardly facing plunger thumb pad <NUM>, and plunger handle <NUM> is then inserted into a rearwardly facing opening defined by annular collar <NUM>. Assembly of syringe <NUM> is then completed by installing substantially cylindrical plunger cap <NUM> on the rearwardly facing end of barrel <NUM>. Plunger cap <NUM> further comprises open front end <NUM>, cylindrical bore <NUM> and closed rear end <NUM>. Plunger cap <NUM> is installed around plunger thumb pad <NUM> and in frictional engagement with the outside wall of annular collar <NUM>. Volumetric measuring indicia <NUM> applied as discussed in relation to <FIG> also appear on the outwardly facing portions of substantially flat display surface <NUM> and curved outside wall surface <NUM>.

<FIG>, <FIG> and <FIG> further disclose the forwardly facing opening into needle retraction cavity <NUM> in relation to front portion <NUM> of barrel <NUM>. Needle retraction cavity <NUM> has a closed rear end that is adjacent to finger flange <NUM>, and is bounded by side walls <NUM>, <NUM>, bottom wall <NUM>, and a top wall that also includes upwardly facing, substantially flat display surface <NUM> of barrel <NUM>.

The assembly of frontal attachment <NUM> to front portion <NUM> of barrel <NUM> of syringe <NUM> is further described and explained in relation to <FIG>. Referring to <FIG>, annular fluid seal <NUM> (visible in <FIG>) is first inserted into recess <NUM> of front portion <NUM> of barrel <NUM>. Front portion <NUM> further comprises laterally extending top rail <NUM> and bottom rail <NUM> that are disposed in transverse relation to the longitudinal axis through fluid chamber <NUM> (<FIG>) of barrel <NUM>. Rounded attachment guides <NUM>, <NUM> are disposed forwardly of top and bottom rails <NUM>, <NUM>, respectively, and are configured to facilitate the assembly of frontal attachment <NUM> to front portion <NUM> of barrel <NUM> by passing above and below the arm connecting textured touch pad <NUM> to the back side of frontal attachment <NUM>.

Referring to <FIG>, annular opening <NUM> is provided in the back side of frontal attachment <NUM> to facilitate insertion of spring <NUM> and needle holder <NUM>, discussed above in relation to <FIG>, and spring <NUM> is desirably compressed between an annular shoulder inside front opening <NUM> (visible in <FIG>) and is held in compression behind head <NUM> of needle holder <NUM> while frontal attachment <NUM> is moved into sliding engagement with front portion <NUM> of barrel <NUM>. Frontal attachment <NUM> further comprises upper guide <NUM> having a downwardly facing, laterally extending recess <NUM> and lower guide <NUM> having an upwardly facing, laterally extending recess <NUM>. Upper ramp and lower ramp <NUM>, <NUM>, respectively, of frontal attachment <NUM> are configured to slide over two laterally spaced-apart sets of opposed ramps with blocking shoulders <NUM>, <NUM> (the lower set not being visible in <FIG>). Laterally extending top rail <NUM> and bottom rail <NUM> of front portion <NUM> of barrel <NUM> are desirably cooperatively engaged with upper and lower recesses <NUM>, <NUM>, respectively, by sliding frontal attachment <NUM> onto front portion <NUM> of barrel <NUM> when frontal attachment <NUM> and front portion <NUM> are positioned as shown in <FIG>. As pressure is applied to textured touch surface <NUM>, frontal attachment <NUM> moves along rails <NUM>, <NUM> until top and bottom blocking shoulders <NUM> of upper guide <NUM> pass over and then drops into facing relation to upper and lower blocking shoulders <NUM>. At this time, needle support member <NUM> and needle holder <NUM> (not shown in <FIG>) are desirably coaxially aligned with the longitudinal axis of fluid chamber <NUM> (visible in <FIG>). Any attempt to move frontal attachment <NUM> back to a disconnected position as shown in <FIG> will be resisted by facing and abutting contact between upper and lower blocking shoulders <NUM> of front portion <NUM> and top and bottom blocking shoulders <NUM>, <NUM>, respectively, of frontal attachment <NUM>.

<FIG> depict syringe <NUM> of <FIG> with the needle cover removed and with plunger cap <NUM> still in place and with textured touch surface <NUM> in the initial position relative to barrel <NUM> as described above. Needle <NUM> is installed inside bore <NUM> of needle holder <NUM>, which is seated inside needle support member <NUM> of frontal attachment <NUM>, with spring <NUM> compressed between head <NUM> (<FIG>) of needle holder <NUM>. Spring <NUM> applies a rearwardly directed biasing force to needle holder <NUM> and needle <NUM>, and is pressed by spring <NUM> into facing and abutting contact with the front surface of annular fluid seal <NUM>, thereby establishing a coaxially aligned fluid path through needle <NUM>, needle holder <NUM> and fluid seal <NUM> into fluid chamber <NUM> (visible in <FIG>) of barrel <NUM>. As shown in <FIG>, plunger seal <NUM> is pushed fully forward into substantially cylindrical fluid chamber <NUM> of barrel <NUM>.

Referring to <FIG>, syringe <NUM> is configured so that fluid can be aspirated into the syringe, with textured touch pad <NUM> again in the same initial position as previously described. Plunger cap <NUM> (as seen in <FIG>, <FIG>) is removed and plunger handle <NUM> is withdrawn as it would be while aspirating fluid into fluid chamber <NUM>. In <FIG> it is seen that needle retraction cavity <NUM> is substantially coextensive in length with fluid chamber <NUM>, thereby facilitating the placement of volumetric measuring indicia <NUM> on substantially flat surface <NUM> (visible in <FIG>) that facilitates full utilization of the volume of fluid chamber <NUM> and also facilitating the retraction of needles such as biopsy needles that are often substantially longer than needle <NUM> (visible inside needle retraction cavity <NUM> in <FIG> below). Once fluid is aspirated into fluid chamber <NUM>, fluid can also be injected into a patient or expelled from fluid chamber <NUM> by pressing forwardly on plunger thumb pad <NUM> while applying finger pressure against the forwardly facing side of flange <NUM>.

Referring to <FIG> and <FIG>, plunger handle <NUM> and plunger seal <NUM> have been pushed forwardly to empty fluid chamber <NUM>. To initiate needle retraction, pressure is applied to textured touch pad <NUM>, which moves frontal attachment to a position where needle support member <NUM> is aligned with needle retraction cavity <NUM>. Because needle retraction chamber <NUM> has a front opening that is larger than head <NUM> of repositioned needle holder <NUM>, the biasing force of compressed spring <NUM> pushes needle holder <NUM> rearwardly and causes needle holder <NUM> and needle <NUM> to be propelled into the distal end of needle retraction cavity <NUM>.

Referring again to <FIG>, the further application of force to textured touch surface <NUM> of frontal attachment <NUM> relative to barrel <NUM> as described above in relation to <FIG> produces sliding relative movement between frontal attachment <NUM> and front portion <NUM> of barrel <NUM>. This movement causes upper ramp <NUM> and lower ramp <NUM> to slide over the second set of opposed ramps and blocking shoulders <NUM> so that top and bottom blocking shoulders <NUM>, <NUM> are placed in facing and abutting contact with upper and lower blocking shoulders <NUM>, thereby preventing frontal attachment <NUM> from being returned to the use position relative to barrel <NUM>.

Referring to <FIG> generally, and specifically to <FIG>, another arrangement is disclosed comprising syringe <NUM> further comprising barrel <NUM>, needle safety device <NUM>, needle cap <NUM> and plunger cap <NUM>. Barrel <NUM> desirably comprises at least one longitudinally extending, substantially flat indicia display surface <NUM> marked with an easily readable volumetric scale. In one preferred arrangement, barrel <NUM> comprises two oppositely facing, substantially flat indicia display surfaces <NUM>, <NUM> (<FIG>). Following removal of needle cap <NUM> and plunger cap <NUM> (<FIG>) from the device, forwardly projecting needle <NUM> and rearwardly projecting plunger <NUM> (<FIG>) become visible. Needle <NUM> is coaxially aligned with plunger <NUM> and is held in fixed relation to a narrow bore <NUM> inside nose <NUM> (<FIG>, <FIG>, <FIG>) at the front end of barrel <NUM>. (Alternatively, it will be appreciated that needle <NUM> and nose <NUM> can be cooperatively configured so that needle <NUM> is releasably attachable to nose <NUM> if desired to permit the use of differently sized needles with barrel <NUM>.

Bore <NUM> places needle <NUM> in fluid communication with a fluid reservoir disposed inside tubular barrel <NUM> between nose <NUM> and plunger seal <NUM> on the front end of plunger handle <NUM>. When plunger handle <NUM> is pushed fully forward against the rear of nose <NUM> of barrel <NUM> prior to an injection (<FIG>) or following an injection (<FIG>) the fluid chamber is not visible. When syringe <NUM> is prepared for an injection, as discussed below, the fluid reservoir is the space (not visible in these views) inside tubular section <NUM> that is between the rear of nose <NUM> and the front of plunger seal <NUM> as fluid is drawn into syringe <NUM>.

Referring to <FIG>, needle safety device <NUM> also comprises activation handle <NUM> and needle tip shield <NUM>. Activation handle <NUM> further comprises rear end <NUM>, touch pad <NUM> and a pair of longitudinally extending channels <NUM> disposed on opposite sides of activation handle <NUM>. The function of channels <NUM> is discussed below in relation to sliding engagement with barrel <NUM>. Needle tip shield <NUM> further comprises inside bore <NUM> that is coaxially aligned with needle <NUM> and with nose <NUM> of barrel <NUM>. Needle tip shield <NUM> desirably has an inside diameter that will allow needle tip shield <NUM> to slide over and surround coaxially aligned nose <NUM> when in the position shown in <FIG>, <FIG> and needle tip shield <NUM> is sufficiently long to safely cover the tip end of needle <NUM> when moved forwardly as in <FIG>, <FIG>. Slight frictional engagement can be provided between the inside wall of needle tip shield <NUM> and nose <NUM> to help hold needle safety device <NUM> in a stable axial position relative to barrel <NUM> during use of syringe <NUM>. Needle safety device <NUM> is desirably unitarily molded from a polymeric material and is cooperatively sized and configured to slidably engage barrel <NUM>, also taking into consideration the range of needle lengths intended for use with syringe <NUM>.

Referring again to <FIG>, barrel <NUM> further comprises coaxially aligned nose <NUM> with internal bore <NUM> and tubular section <NUM> extending rearwardly from nose <NUM> to fingertip flange <NUM>. The rear end of tubular section <NUM> is open and communicates with the inside of cylindrical, rearwardly extending collar <NUM> to which plunger cap <NUM> is releasably attachable. Opposed indicia display surfaces <NUM>, <NUM> (<FIG>) are desirably parallel, longitudinally extending, substantially flat, printable surfaces each having an oppositely facing volumetric scale comprising appropriate indicia located adjacent to tubular section <NUM> to facilitate easy reading of a liquid level inside tubular section <NUM> by a user. A longitudinally extending rail <NUM> with an inwardly projecting retainer edge <NUM> is desirably provided on the inwardly facing walls of each of the outwardly facing indicia display surfaces <NUM>, <NUM>. Longitudinally extending rails <NUM> are cooperatively sized and configured to engage and provide a smooth, slidable interface along each of aligned channels <NUM> of needle safety device <NUM>. Barrel <NUM> is desirably molded from a medical grade polymeric material and is sufficiently transparent to permit the liquid level drawn into tubular section <NUM> of syringe <NUM> to be plainly viewed by a user. Still referring to <FIG>, plunger <NUM> further comprises thumb cap <NUM>, plunger handle <NUM>, plunger seal retainer body <NUM> and annular recess <NUM>.

The cooperatively configured structural elements and operation of needle safety device <NUM> relative to barrel <NUM> of syringe <NUM> are further described and explained in relation to <FIG>, <FIG>, <FIG>. During assembly of syringe <NUM>, activation handle <NUM> of needle safety device <NUM> is aligned with and inserted over tubular section <NUM> of barrel <NUM> with rails <NUM> engaging channels <NUM>. Needle safety device <NUM> is moved rearwardly relative to barrel <NUM> until needle tip shield <NUM> surrounds nose <NUM> of barrel <NUM> and rear end <NUM> of needle safety device <NUM> frictionally engages oppositely disposed rear stops <NUM>. Slide stops <NUM> each having a ramp <NUM> and stop shoulder <NUM> are provided rearwardly of rails <NUM> and forwardly of rear stops <NUM>. Opposed and facing ramps <NUM> allow activation handle <NUM> to slide forwardly relative to barrel <NUM> to a point where needle tip shield <NUM> covers and protects the tip end of needle <NUM> following use of syringe <NUM>. After the tip end of needle <NUM> is covered, opposed and facing stop shoulders <NUM> prevent activation handle <NUM> from being moved rearwardly relative to barrel <NUM> to again expose the needle tip.

When needle safety device <NUM> and needle tip shield <NUM> are disposed in the position shown in <FIG>, <FIG> (referred to as the "first stop position") relative to barrel <NUM> and needle <NUM>, needle tip shield <NUM> surrounds nose <NUM> of barrel and a portion of needle <NUM>. When needle safety device <NUM> of syringe <NUM> is in the first stop position, the front tip of needle <NUM> can be inserted through the stopper of a medicine vial (e.g., an insulin bottle) and medicine can be drawn into a fluid reservoir disposed inside tubular section <NUM> (<FIG>, <FIG>) of barrel <NUM> by pulling rearwardly on plunger <NUM> that slidably engages the inside wall of tubular section <NUM>.

Claim 1:
A syringe (<NUM>) for medical use, comprising:
a barrel (<NUM>) comprising:
a fluid chamber (<NUM>) comprising a tubular sidewall extending longitudinally,
a nose (<NUM>) disposed forwardly of the fluid chamber,
a rearwardly facing opening, and
two oppositely facing, substantially flat, parallel indicia display surfaces (<NUM>, <NUM>) extending longitudinally along the tubular sidewall and disposed in fixed relation to the fluid chamber (<NUM>),
each of the indicia display surfaces (<NUM>, <NUM>) comprising a longitudinally extending rail (<NUM>) projecting inwardly from an inwardly facing wall and volumetric dosage scale indicia disposed on an outwardly facing wall to facilitate reading of a liquid level inside the fluid chamber (<NUM>) through at least a portion of the tubular sidewall;
a plunger (<NUM>) slidably inserted into the fluid chamber (<NUM>) through the rearwardly facing opening;
a needle (<NUM>) projecting forwardly from the nose (<NUM>) in fluid communication with the fluid chamber (<NUM>); and
a needle safety device (<NUM>) comprising a needle tip shield (<NUM>), an activation handle (<NUM>) disposed rearwardly of the needle tip shield (<NUM>), and a longitudinally extending channel (<NUM>) disposed on each side of the activation handle (<NUM>);
wherein the longitudinally extending channels (<NUM>) are cooperatively sized and configured to engage and provide a slidable interface with the longitudinally extending rails (<NUM>) of the indicia display surfaces (<NUM>, <NUM>) to allow the needle safety device (<NUM>) to slide between a first stop position and a second stop position relative to the barrel (<NUM>);
wherein the needle tip shield (<NUM>) circumferentially surrounds the nose (<NUM>) of the barrel (<NUM>) when the needle safety device (<NUM>) is disposed in the first stop position; and
wherein the needle tip shield (<NUM>) circumferentially surrounds a front tip of the needle (<NUM>) when the needle safety device (<NUM>) is moved forwardly from the first stop position to the second stop position.