turning to fig1 a -- 1c and 2a and 2b , details of the hollow inner tube needle adapter 210 are seen . the hollow inner tube has an outer surface 242 having a front shoulder 246 of relatively large diameter . the front shoulder 246 is defined by a front face 247 and a rear abutment face 248 . extending forwardly from front face 247 is a nose 401 which has axial protrusions 403 which are used to retain a needle guard ( not shown ). the needle guard is removed before the winged infusion needle device is used . directly behind the front shoulder 246 is a first groove 238 which is defined on one side by the abutment face 248 and on its other side by the termination ( rear abutment face ) 250 of a ramped surface 252 . the ramped surface 252 starts with a diameter smaller than that of the front shoulder 246 and ramps downward away from the first groove 238 . ramp 252 terminates in a long valley defined by outer surface 242 of needle adapter 210 . the valley has a relatively constant diameter which is preferably substantially equal to the diameter of the first groove 238 . the valley ends in a ramp 254 which increases in diameter as it extends away from the front end of the needle adapter 210 . ramp 254 is followed by ramp 256 which ramps down to a second groove 236 . the second groove 236 contains a plurality of ratchet teeth 400 ( best seen in fig1 c ) which are preferably ramped to increase in outer diameter ( see fig1 a ) as they extend toward the rear end of the inner tube . as will be described hereinafter , the ramped teeth serve the function of preventing unintended rotation between the inner tube and the outer shield , but permit forced rotation . by having the teeth spaced at twelve degree intervals , forced rotations of twelve degrees , or multiples thereof , is permitted to help prevent collapse of a fistula . of course , if desired , other spacings could be utilized . the root diameter of the ratcheted groove 236 is preferably of a diameter equal to , or slightly larger than the diameter of the valley 242 . the ratcheted groove 236 terminates in a rear abutment surface 259 which is interrupted by the ramped teeth 400 . the surface 259 is also the terminating surface of a rear ramp 262 . the rear ramp 262 preferably includes a marker or indicator 405 which may take the form of marks , a notch , a raised indicator , etc . the marker 405 is provided to indicate how the inner tube 210 and the needle 300 which is fixed therein are rotated relative to the outer shield . as shown in fig1 a , the marker 405 includes an arrow and the letter &# 34 ; b &# 34 ; which signifies the bevel 408 of the needle 300 . as shown in fig1 a , the letter b is located on a plateau 409 which terminates rear ramp 262 . the plateau 409 sits between the rear ramp 262 and the ribbed connecting end 264 of the needle adapter 210 . the connecting end 264 has outwardly extending ribs 219 as indicated for coupling with standard tubing ( not shown ). the connecting end 264 preferably also includes a conically shaped inner surface 410 which increases in diameter as it extends from the end of needle 300 outward to the end 420 of the inner tube . as previously indicated , the inner tube 210 is hollow . in the preferred embodiment , the inner tube 210 is formed around a needle 300 such as seen in fig1 b , by insert molding techniques . with such a manufacturing process , the inner surface 211 of the inner tube 210 bonds to the needle 300 to prevent relative movement therebetween . however , if desired , and as shown in the parent application hereto , u . s . application ser . no . 07 / 416 , 927 , the inner surface can be modified so that a short needle can be inserted and glued into place . turning to fig3 a - 3d , details of the outer sleeve 212 are shown . outer sleeve 212 includes flexible wings 273 which are used as means for attachment of the winged needle device to a patient . the flexible wings 273 are attached to the outer surface 270 of the outer sleeve 212 . projecting from the top outer surface 270 of the outer sleeve 212 are thumb grips or ribs 291 which provide the practitioner with a friction surface when utilizing the winged needle device . as indicated in fig3 b , the outer sleeve 212 has a flat but tapered bottom surface 295 with the thickness of the bottom increasing according to a two and one half degree slope as it extends away from the front end of the outer sleeve . as a result , when the inner tube 210 and needle 300 are located in the outer sleeve , the needle assumes a downward angle preferably of about two and one half degrees , and is more easily inserted into the fistula . outer sleeve 212 is hollow and has an inner surface 271 of a diameter slightly larger than the outer diameter of shoulder 246 of the inner tube 210 . however , towards its rear end , the inner surface of outer sleeve 212 is arranged with two ramps 285 and 292 , although , if desired , ramp 285 may be replaced with a non - ramped ramped protrusion . ramp 285 provides outer sleeve 212 with a decreasing inner diameter as it extends toward the rear end of the outer sleeve . ramp 285 terminates in an abutment face 289 which is followed by a flat surface 287 having an inner diameter approximately equal to the outer diameter of shoulder 246 of inner tube 210 . flat surface 287 ends with ramp 292 which has also has a decreasing inner diameter as it extends toward the rear end of the outer sleeve . the inner diameter at the end of ramp 292 , however , is of significantly smaller diameter than that of ramp 285 and of significantly smaller diameter than the diameter of shoulder 246 . the inner surface of the outer sleeve 212 terminates in a ratcheted ramped protrusion 234 which is arranged to cooperate with the ratchet teeth 400 of the inner tube . thus , the ratchet 450 of ramped protrusion 234 is an inward ratchet ( i e . is notched ) to accommodate the teeth 400 of the inner tube , with the notches increasing in root diameter as they extend rearward and away from the front of the outer sleeve 212 . in assembling the winged needle device , the outer shield 212 and the inner tube 210 are coaxially aligned with the rear portion of the inner tube 210 at the front of the front portion of the outer sleeve 212 . relative movement between the inner tube 210 and outer sleeve 212 causes inner tube 210 to slide through outer sleeve 212 until the ratcheted ramped protrusion 234 of the outer sleeve 212 engages the ratcheted ramped groove 236 ( as seen in fig2 b ) of the inner tube , with abutment face 259 of inner tube 210 abutting the rear surface 299 of outer shield 212 , with ramp 256 of inner tube 210 engaging ramp 292 of outer sleeve 212 , and with ratchet teeth 400 of the inner tube engaged in notches 450 of the outer shield 212 . in the assembled position , the ramp 256 of the inner tube 210 in conjunction with protrusion 234 of the outer shield 212 serves to hold the outer shield in its retracted position ( i . e . prevents inadvertent forward movement of the shield ) during use of the winged needle assembly . on the other hand , the abutment face 259 of the inner tube 210 in conjunction with protrusion 234 , serves to keep the inner tube from sliding backward and out of assembly . at the same time , the seating of the ratchet teeth 400 of the ratcheted ramped groove 236 of the inner tube into the ratchet notches 450 of the ratcheted ramped protrusion 234 of the outer shield serves to prevent inadvertent or undesired rotation of the inner tube 210 relative to the outer shield 212 . in use , the winged needle assembly including an intravenous needle 300 is held by the practitioner with the wings 273 being squeezed upwards against the outer surface 270 of the outer sleeve 212 . the practitioner then inserts the needle 300 into a fistula . after insertion , the needled device is rested on the arm or body of the patient , and the flexible wings 273 may be used as a taping surface such that the needled device may be taped to the patient . should the fistula into which the needle 300 is inserted collapse , or be in danger of collapsing , the practitioner at any time may rotate the needle in the fistula by holding the outer shield 212 in place and by grasping and outer shield 212 in place . depending on the angular arrangement of the ratchet teeth 400 and notches 450 , the needle 300 may be rotated by desired amounts . with the ratchet teeth and notches of the preferred embodiment , rotation may be effected in twelve degree increments . each respective forcing of the teeth over the notches preferably provides an audible click , while marker 405 provides a visual indication of the rotation of the needle relative to the outer shield 212 . thus , if it is desired to rotate the needle by approximately ninety degrees , either seven or eight clicks ( 84 or 96 degrees ) should occur . regardless , the same rotation procedure may be used over and over again with varying degrees of rotation if desired . when treatment is completed and it is desired to remove the contaminated needle from the fistula , either of two procedures may be utilized to shield the needle . in one procedure , the tape is removed from the arm of the patient and the winged needle device removed . holding the outer sleeve 212 in one hand such as with thumb on grips 291 and forefinger on bottom surface 295 , and gripping the tube ( not shown ) extending from the ribbed end 264 of the inner tube 210 in the other hand , the inner tube 210 is pulled back relative to the outer shield 212 until positive locking is obtained as shown in fig2 a . in a second procedure , before the tape is removed , a finger of the practitioner is placed preferably on the top outer surface of the outer sleeve 212 , while the ribbed end 264 of the inner tube 210 ( with attached tube -- not shown ) are gripped with other fingers of the same or a different hand . the inner tube is then pulled back relative to the outer shield until positive locking is obtained , thereby withdrawing the needle from the vein and immediately shielding it in the safety device . regardless of the procedure used , in pulling the inner tube back relative to the outer sleeve , some minor initial force is required to overcome resistance of protrusion 234 sliding over ramp 256 . however , once the protrusion slides over ramp 256 , little force is needed to continue sliding the outer shield over the valley of the inner tube . extremely minor resistance is encountered when ramp 252 of the inner tube encounters ramp 285 of the outer sleeve . more resistance , however , is encountered when ramp ( or protrusion ) 285 encounters shoulder 246 . with the application of differential force , and due to the ramped nature of ramp 285 and the rounding of the edge of shoulder 246 , ramp 285 is slid over shoulder 246 until it snaps over the shoulder 246 with abutment face 289 of the outer shield 212 in contact with abutment surface 247 of the inner tube shoulder . at the same time , protrusion 234 sits in first groove 238 with the rear surface 299 of the outer sleeve abutting abutment surface 250 of the inner tube , and shoulder 246 contacts surface 287 . in this locked position , the needle is shielded entirely and securely by the outer shield 212 . two locking interactions are established ( surface 289 against shoulder 246 , and end surface 299 against surface 250 ) as seen in fig2 a to prevent the movement of the inner tube forward and the reexposing of the needle , while the relative sizes of the protrusion 234 and the shoulder 246 prevent any possibility of the outer shield 212 being pulled forward off of the inner tube 210 . in order for the winged needle assembly to function such that locking in the shielded position is irreversible but such that the inner tube can be assembled into an unshielded position which is not inadvertently upset , certain relative diameters and lengths between grooves , ramps , etc . of the inner tube and outer shield are desirable . preferred dimensions are set forth in the parent application hereto u . s . patent application ser . no . 07 / 416 , 927 . also , in order for the ramped ratchet teeth 400 of the inner tube to properly engage and function with the ramped ratcheted protrusion of the outer shield , certain relative diameters and angles are desired . for example , the root diameter of ratchet teeth 400 is preferably 0 . 146 inches , while the ratchet teeth 400 at their largest ( i . e . at stop face 259 ), have a diameter of 0 . 168 inches . the slope of the ratchet teeth ramp is preferably approximately ten and one - half degrees . similarly , the inner diameter of the ramped ratcheted protrusion 234 at its narrowest is 0 . 148 inches , while the diameter of the notches at their widest is 0 . 169 inches . the slope at which the notches expand is preferably the same as the slope of the ratchet teeth ramp . also , while only fourteen ratchet teeth 400 are shown in fig1 c so as to reduce the amount of force required to rotate the inner tube in the outer shield , it will be appreciated that fewer or more teeth could be provided . with the preferred dimensions , and using an inner tube made of a polyurethane / polycarbonate blend ( sold under the trademark &# 34 ; texin &# 34 ; 4210m by mobay , inc .) and an outer shield made of a combination of polypropylene ( 70 % by weight ) and kraton ( 30 % by weight ), rotation of the inner tube and needle relative to the outer shield is possible with the exertion of a little force , although inadvertent rotation will not occur . also , with the preferred dimensions and materials , once the shield is locked in the shielding position , it is virtually impossible to force relative movement between the inner tube and outer shield which would reexpose the contaminated needle . there has been described and illustrated herein safety winged needle devices for use as part of a fistula set in blood collection and hemodialysis . while particular embodiments of the invention have been described , it is , not intended that the invention be limited thereby , as it is intended that the invention be as broad in scope as the art will allow . thus , while exact dimensions of several aspects of the inner tube and the winged outer shield of the invention were provided to show a preferred embodiment , it will be recognized that other dimensions could be utilized . similarly while particular materials and weight percentages were described , other materials and / or percentages could be utilized . also , while the locations along the inner tube and winged shield of particular elements of the invention were described , it will be appreciated that those locations are not necessarily fixed . for example , while the ratchet mechanism for preventing accidental rotation , but permitting desired rotation of the inner tube relative to the outer shield was described as being located at the rear ends of the inner tube and outer shield , it will be appreciated that a similar mechanism could be located at the front ends of the components ; although such an arrangement is not preferred because of possible resulting torque problems . similarly , the thumb grips , while shown at towards the front end of the outer shield , could be located more centrally or towards the rear if desired . therefore , it will be apparent to those skilled in the art that yet other changes and modifications may be made to the invention as described without departing from the scope of the invention as so claimed .
shielded winged needled medical devices for use as part of fistula sets and which minimize accidental needlesticks of the skin by an exposed contaminated needle are provided . the medical devices include a hollow inner tube body , and a sliding hollow outer winged shield . the inner tube has a foward groove and a ratcheted rear groove on the outside surface thereof , a shoulder of relatively large diameter forwardly adjacent the front groove , and a ramp of diameter smaller than the shoulder rearwardly adjacent the front groove . the outer shield has an inner surface with first and second ramps and a ratcheted protrusion which terminates the second ramp . the ratcheted protrusion sits in the ratcheted rear groove of the inner tube while the winged needle device is being used and eliminates inadvertent rotation while permitting forced rotation at any time between the inner tube and outer shield . after use , the outer shield may be slid forward relative to the inner tube , overcoming resistance given by the engagement of the protrusion and a ramp forward the rear groove , until the protrusion slides up the ramp rearwardly adjacent the front groove and locks in the forward groove . in this forward position , the now - contaminated needle is shielded , with the ramps , grooves , and shoulder of the inner tube and outer shield providing an absolute lock which may not be overcome by manual force .