referring to fig1 power assister device 10 is shown with syringe 12 engaging said device , butterfly needle 13 attached to said syringe by luer connector 50 and battery recharger 14 is ready to engage power assister device 10 by insertion of plug 44 into receptacle 42 . when assembled together , power assister device 10 and syringe 12 , along with handle 18 and trigger 20a - 20b , resemble a pistol . this configuration provides for firm hold control and convenient handleability . the power assister device 10 comprises a casing which serves as a housing and chassis for the components contained therein . referring to syringe 12 , as shown in fig1 , 3 and 9 , it comprises : a syringe barrel to receive an injectable agent therein , said syringe barrel having a luer connector 50 at one end thereof serving as means for attaching butterfly needle 13 thereto , and the other end of said tubular body having male coupling 46 to engage female coupling 38 . flange 52 of syringe 12 locates and fixes syringe within a complimentary slot ( not shown ) in front 16 of the power assister device 10 . loading of syringe 12 is exceptionally easy and practical , since the syringe is drop - loaded onto said slot without the need of any twisting or turning motion . positioned in said syringe barrel in a slideable relationship is piston 48 integral with male coupling 46 . as best seen in fig2 , 7 and 8 , the casing or housing of the power assister device 10 houses a d . c . motor 22 which produces angular rotation of gear 24 . gear 24 drives gear 26 which has internal thread 28 . linear movement of lead screw 30 is produced by preventing its rotation and by the angular rotation of internal thread 28 . a follower 32 , fixed to the back end of lead screw 30 , prevents rotation of the lead screw during linear movement by the engagement of peg 32a of the follower 32 rolling or sliding in slot 32b . d . c . motor 22 is powered by rechargeable batteries 40 , which are located in handle 18 of power assister device 10 . trigger switch 20a - 20b engageably coupled to batteries 40 and d . c . motor 22 has three positions : forward drive , reverse drive and off position . forward limit switch 36 is positioned so that lead screw follower 32 triggers the switch and stops the motor when piston 48 is in its extended position as shown in fig4 . likewise , the backwards limit switch 34 is positioned so that the lead screw follower 32 triggers the switch and stops the motor 22 when piston 48 is in its engagement position as shown in fig3 . the power assister device 10 is recharged by plugging recharger 14 in a standard electrical outlet and inserting plug 44 into receptacle 42 during periods in which the device is not in use . reference is now made to the operation of the hand - held power assister . the syringe 12 could be prefilled with an injectable liquid , such as contrast media , or the power assister device 10 could be used to fill the syringe . if not prefilled , the empty syringe 12 is loaded onto the front 16 of the device , having male coupling 46 engage female couple 38 , then placing the power assister device 10 in an upright position by placing it with is flat surface 9 on top of a flat object , such as a table . the syringe 12 is then filled with contrast media by first driving the piston 48 to its extended position within the syringe as shown in fig4 . a plastic tube ( not shown ) is attached to luer connector 50 and the contrast media is syphoned into the syringe 12 by placing the opposite end of the plastic tube in a container filled with contrast media and retracting piston 48 back into its engagement position . upon completion of the process the plastic tube is removed from the luer connector 50 and a butterfly needle 13 is attached thereto . after butterfly needle 13 is attached to luer connector 50 , the upright position of power assister device 10 is maintained until the air from syringe 12 and butterfly needle 13 is purged by driving piston 48 in the forward direction . to drive piston 48 forward or in reverse trigger switch 20a - 20b is provided . trigger switch 20a - 20b is positioned in handle 18 of the power assister device 10 to control both the forward and reverse motion of the piston : pressing 20b results in forward motion of piston 48 , while pressing 20a results in reverse motion thereof . when neither 20a nor 20b trigger switch is pressed , switch automatically reverts to neutral or off position and motor 22 becomes disengaged . in the case when the syringe 12 is prefilled with contrast media , the syringe is loaded in the same manner as above - described , then the power assister 10 is positioned in an upright position . syringe cap ( not shown ) is removed from luer connector 50 and butterfly needle 13 is attached to luer connector 50 . the air is then purged from the syringe as above - described . upon purging the air from syringe 12 , the power assister device 10 is held by the medical practitioner at handle 18 with index finger resting on trigger switch 20a - 20b which is in the off position . protective sheath ( not shown ) is removed from butterfly needle 13 and the same is inserted into the injection sight on the patient . the practitioner then activates motor 22 by pressing trigger switch 20b which electrically engages batteries 40 with motor 22 . motor 22 produces angular motion which is converted into linear motion through gears 24 and 26 acting on lead screw 30 . lead screw 30 drives piston 48 in the barrel of syringe 12 forcing contrast media through butterfly needle into the injection sight . piston 48 is driven by lead screw 30 at a steady rate , while the practitioner is able to visually observe the expulsion of the contrast media from syringe 12 . the medical practitioner is in complete control of the injection process . unlike with very expensive and complicated devices where electronics take complete control over the process with the exclusion of the medical practitioner , the instant power assister device accomplishes one result : responds to the desire of the practitioner by forcing the contrast media out of syringe 12 into the patient at a steady rate of delivery . the injection process may be interrupted any time upon releasing trigger switch into neutral position . when lead screw 30 is in its completely extended position , that is , piston 48 has completely discharged contrast media from syringe 12 , lead screw follower 32 triggers forward limit switch 36 to stop motor 22 . upon completing the injection process , butterfly needle 13 is disconnected from the patient and lead screw 30 is retracted to its initial engagement position . syringe 12 is disconnected from power assister device 10 by disengaging male coupling 46 from female coupling 38 and disengaging flange 52 from receiving slot on front portion 16 of the device 10 . as is apparent from the foregoing description , the power assister device of the present invention is extremely simple , compact , easy to hold and operate and is inexpensive . the lack of complicated electronic components virtually eliminates failures and breakdowns which plague complicated instruments . medical personnel have complete control during the use of the device which makes the practice of delivering contrast media to the patient a more tolerable and pleasant experience than that associated with bulky , complicated instrumentalities .
a hand - held power injection device is provided for injecting liquid , such as contrast media , into the vascular system of a mammal . the device comprises a pistol - shaped housing which encloses a battery - powdered d . c . motor for constant - rate delivery of liquid from a syringe .