referring now to the drawings the disposable surgical cutting instrument 100 of the present invention has a drive housing 12 of generally cylindrical form designed to be easily held in the surgeons hand . it should be noted at the outset that all parts of the invention which could possibly come in contact with the patient during an operation are sterilized and pyrogen free . a protective latex sheath 14 is adapted to be placed over the drive housing to protect the drive housing from contamination when the operation is performed . a disposable cutting head 16 is mounted on the drive housing 12 in engagement with the sheath 14 . the disposable cutting head is driven by a drive shaft of a micro motor mounted in the drive housing so that only the cutting head 16 and sheath 14 comes into contact with blood , vitreous and other materials during the operation . the drive housing 12 as shown in fig6 - 9 , 11 and 12 is constructed of two components comprising a power source section 18 and a motor section 20 . the power source section 18 has one end provided with an outer threaded surface 19 which is adapted to be screwed into a threaded inner surface 22 of the motor section to form the complete drive housing 12 . a free seated coiled spring 24 is seated in one end of the power source section 18 and abuts against a battery 26 which is slidably mounted in the housing for easy replacement to urge the battery toward a standoff sleeve 28 . the battery does not engage the standoff sleeve . the sleeve merely prevents electrical contact in case the battery is inadvertently installed backward . the standoff sleeve 28 is secured to a bulkhead 30 by cement means or press fit on the conductor . one end of the battery is engaged with a modified rivet contact 32 that is riveted in place . the bulkhead 30 is positioned within the motor housing section by a retaining ring 31 which is mounted in a channel cut in the housing . the set screw 34 contacts a motor support 36 mounted to the housing and holds the motor in place . a stripped wire 38 is bent and squeezed between the micromotor 40 and motor support 36 to form a connection . the micromotor 40 is mounted in the motor housing and is electrically connected to the contact 32 by wire 42 so that when switch 44 is depressed an electrical contact is made between the battery and the micromotor energizing the micromotor 40 to drive a hexagonal shaped drive shaft 46 of the micromotor . it should be noted that while the preferred embodiment discloses a hexagonal drive shaft 46 , the drive shaft could be square , flat or shaped in any other manner . the drive shaft end of the motor section forms a seat or channel 48 depending upon its construction and has two locking pins 50 protruding inwardly from the collar to fit bayonet slots 51 formed in the disposable cutting head 16 . the drive housing is covered by using a sheath assembly 52 comprising a sleeve 54 having a tapered end 56 upon which the latex sheath 14 is stretched and mounted . the other end 58 of sleeve 54 is open and flanged outward so that the drive housing can be easily inserted into the mounted sheath . the flexible latex sheath 14 has an open end 62 formed with a lip 64 which fits into the seat 48 defined in the motor section of the drive housing . the other end 66 of sheath 14 is closed . after the drive housing 12 has been deposited into the protective covering of the latex sheath the sleeve 54 is removed and lip 64 is inserted into the seat 48 formed in the end of the housing . the cutter head 16 is constructed with a body 70 having a varying diameter axial bore 71 cut therethrough . the bore 71 is cut in a series of steps so that the diameter narrows after each step . the steps form shoulders 69 , 72 , 73 and 74 which are adapted to respectively receive retainer ring 99 , retainer ring 92 , &# 34 ; o &# 34 ; ring 90 and flange 89 . the cutter body 70 is provided with a second bore 75 and a tubular extension 76 axially aligned with the bore allowing a suction or irrigation device to communicate with bore 71 . thus a syringe can be connected to the tubular extension 76 by a hose to provide suction to a chamber portion 71 a and the interior of tube 86 so that material severed by blade 84 travels through the tube into chamber portion 71 a past bore 75 into a suitable disposal means such as the syringe . alternatively a saline solution or other suitable fluid can travel the same path through the tube 86 to the eye . the body 70 has a generally tapered exterior surface and is cut at one end in an annular manner to receive a skirt 77 which is cemented to the annularly cut end of the body . the outer surface of the annularly cut end or tip 78 is provided with two bayonet slots 51 . when the tip 78 is inserted into the motor section , the tip 78 fits around the hexagonal drive shaft 46 of the micromotor with the skirt 77 projecting over the outer surface of the motor section and the latex sheath 14 . a clear plastic coupling member 80 is mounted in the cutter body bore 71 . the coupling member 80 has an axial bore 81 with a circular configuration at one end suitable to hold a coupling member drive shaft 82 and a suitably shaped configuration at the other end to slidably receive and hold the drive shaft 46 . in the preferred embodiment a coiled spring member 91 is seated in the hexagonal portion of the bore 81 and abuts against shoulder 93 which forms the end of the hexagonal portion of bore 81 . when the hexagonal drive shaft 46 is inserted into the hexagonal portion of the bore 81 the coupling member 80 is urged forward by spring member 91 to place blade 84 against the end of the tube housing 86 . the drive shaft 82 is notched at 83 to freely hold the blade 84 . in this preferred embodiment the blade 84 is freely mounted in notch 83 and is not secured to the drive shaft 82 . an external fixed thin walled tube 86 projects from the end of the body 70 with the distal end 87 being formed into a hemisphere closing it off . the proximal end 88 is opened and flanged outwardly so that it is seated on a first shoulder 74 in the interior of body 70 . the flanged end 88 is press fit to the shoulder or stop but it can be cemented if desired . a small cutting hole 89 is located in the distal end of the tube preferably positioned 180 ° from the hose nozzle or projection 76 . the blade 84 is preferably twisted into at least two revolutions with one end being flat so that it can be seated in the notch 83 cut in the end of drive shaft 82 with its distal end 85 being rounded so that it can easily rotate in the hemispherical shaped end 87 of the tube 86 . if desired a flat blade can be substituted for the twisted blade . in the twisted construction the blade is continuously urged forward against end 87 by spring means 91 . the blade is smaller in width than the inner diameter of tube 86 so as to just fit inside tube 86 and still be free to rotate . the rotation of the blade helps drive the severed material back through the tube 86 . a clear plastic seal retainer ring 92 and o ring 90 are mounted around the coupling member drive shaft 82 to keep fluids from entering into the cavity housing the coupling means , thus preventing any leakage of vitreous material , fluid , blood or other materials past the shaft . the o ring seal also prevents air from being drawn into the syringe via motor shaft leakage . the shaft 82 and o ring 90 effectively seal off bore 71 to form a fluid receiving chamber 71 a . a syringe 94 is connected to the hose nozzle 76 by flexible tubing 98 which is inserted over the hose nozzle or projection 76 on one end and onto a female luer - lok 96 in the syringe . thus suction or fluid can be transmitted to tube 86 . in the operation and before the actual cutting of the vitreous is to take place , the surgeon takes the drive housing 12 , drops it into the sleeve 54 made of a suitable material into an associated sheath 14 . the sheath lip 64 is inserted into the seat 48 of the drive housing and the disposable plastic cutter head 16 is mounted on to the housing so that bayonet slots 51 cut into the cutter head are mounted over the pins 50 of the motor section with the cutter head then being depressed and turned so that it is locked into place on pins 50 . simultaneously its outer skirt 77 extends down over the drive housing which is covered by flexible sheath 14 . the lip 64 in combination with the drive housing and cutter head forms a fluid tight seal so that any fluid that might enter under skirt 77 is prevented from contacting the motor housing by sheath 14 . the syringe 94 is then connected to the cutter hose nozzle 76 so that suction can be applied . a check valve 97 is mounted in the flexible tubing 98 to prevent the introduction of fluid into the eye . when the opening is made in the anterior aqueous chamber the cutter tube 86 is inserted in the chamber . the surgeon depresses the switch 44 of the micro motor 40 through the protective sheath 14 activating the motor and thereby rotating the blade 84 within the tube 86 . the blade 84 is constantly urged forward by the coupling member 80 through spring means 91 in the coupling member so that the blade edge 85 is pressed against the front of the tube and rotates over hole 89 cut in the end of the tube . as suction is applied to the instrument vitreous material is drawn into the hole . the rapidly rotating spring loaded blade 84 which fits flush against the hole 89 severs the vitreous carrying it into the tube with the construction of the blade 84 being such that it is carried into chamber 71 a of the cutter head and from there into a syringe or other suitable material disposal means . the cutter of the present invention , although specifically designed for eye surgery could also be used to remove any other body tissue in the same manner . because of the sealed nature of the internal structure of the tip , foreign materials cannot proceed past the blade drive shaft or chamber 71a so that no foreign materials contact the hexagonal drive shaft or interior of the drive housing . after the operation has been completed the surgeon rotates the cutter head releasing it from its bayonet connection and removes the head from the drive housing . the head is then thrown away or sterilized for future reuse and the latex protective sheath 14 is removed from the drive housing so that the drive housing is ready for the next operation . when the next operation is ready to begin a new disposable cutter head and a new disposable sheath are placed on the instrument as previously indicated so that no problem of sterilizing the instrument is incurred with the instrument being maintained in a sterile condition . in the foregoing description the invention has been described with reference to a particular preferred embodiment although it is to be understood that the specific details shown are merely illustrative and that the invention may be carried out in other ways without the departing from the true spirit and scope of the following appended claims .
a surgical instrument comprising a housing with a motor and source of power contained in the housing . a removable sheath is placed over the housing and a cutter assembly is removably mounted to the housing so that the housing is protected from external materials and contamination . the cutter assembly has a body , a tube projecting from the body , a blade positioned in the tube and a drive transfer mechanism mounted in the cutter body , connecting the blade to the motor . the tube defines an aperture and the blade in combination with the walls defining the aperture shears tissue entering the hole . a second passage is formed in the cutter body communicating with the tube to allow pressure differentials to be exerted to the tube .