in one aspect , the invention features a surgical tool for operating within a body cavity through a discrete opening while being manipulated from outside of the body . the tool has the advantage that the headpiece can be manipulated or steered from outside of the body to move through a plane and at an angle to the tool &# 39 ; s entry path . a tool 10 constructed in accordance with the teachings of the invention is shown in fig1 which is a generally schematic view . the tool 10 is a generic endoscopic instrument meaning that it is suitable for use in conjunction with any form of endoscopic surgery wherein access to a patient &# 39 ; s internal organs is provided through a discrete opening which is either surgically created or naturally occurring . the tool is intended to be utilized by being introduced to the interior of a patient through an endoscope or other form of relatively small diameter sheath . it has been found that the invention is particularly well suited for use in laparoscopic surgery . broadly , the instrument 10 includes three main sections , a head 12 , a control member 14 , and an elongated rigid member 16 extending therebetween . as will be described in greater detail herein below , the rigid member 16 is hollow . during endoscopy , laparoscopic or otherwise , the head 12 is disposed internally of the patient while the control member 14 is located outside of the patient for manipulation by a surgeon . to introduce the head 12 into the interior of the patient , an endoscope ( not shown ) is utilized in a known fashion to provide a discrete opening . so , for example , in laparoscopic surgery , an endoscope is passed through a patient &# 39 ; s abdominal wall to provide access to the patient &# 39 ; s peritoneal cavity . the tool 10 is then passed through the endoscope to position the head 12 internally of the patient . for purposes of illustration , forceps 11 are shown mounted on the head 12 . as previously mentioned , however , various surgical instruments , actuable and non - actuable , can be utilized . for embodiments of the invention utilizing surgical instruments requiring an energy supply , such as laser knives , electric or laser cauterizing apparatus , and fiber optics , connection 19 is provided . depending on the type of instrument mounted on the head 12 , the connection 19 can be located either perpendicularly to the longitudinal axis l , as shown in the figure , or parallel thereto . for example , when the instrument is a laser powered device , to simplify the coupling of laser energy from the connection 19 to the head 12 , the connection will typically be oriented parallelly to the longitudinal axis l . as shown in the figure , the control member 14 has at least one degree of manipulability as indicated by arrows 15 . that is , the control member 14 can be manipulated so as to be angularly offset from the rigid member &# 39 ; s longitudinal axis l . similarly , the head 12 can be angularly offset from the longitudinal axis l as indicated by arrows 13 . in the illustrated embodiment of the invention , when the control member 14 is manipulated to be angularly offset from the longitudinal axis l , the head 12 is oppositely but correspondingly angularly offset . that is , for example , a 45 ° offset of the control member 14 causes a 45 ° offset of the head 12 . as discussed in greater detail below , however , the tool 10 can be constructed so that the angular offsets of the control member 14 and the head 12 , while corresponding , are not equal . also , in the illustrated embodiments the control member 14 and the head 12 travel in the same plane . again , however , the tool 10 can be constructed , so that they travel in different planes . fig2 is a partial section view of one embodiment of the invention wherein a rigid coupling member 18 couples the control member 14 to the head 12 . the coupling member 18 is pivotably connected to the control member 14 at a coupling pivot 22 and to the head 12 at a coupling pivot 26 . the control member itself is rotatable about an axis 20 and the head is rotatable about an axis 24 . it is significant that the coupling pivots 22 and 26 are displaced from the control member rotational axis 20 and the head rotational axis 24 respectively . as a result , it can be seen that manipulating the control member 14 so that it becomes angularly offset from the longitudinal axis l causes longitudinal displacement of the rigid coupling member 18 . this longitudinal displacement is translated by the coupling pivot 26 to rotational displacement of the head 12 about the head rotational axis 24 . accordingly , angular displacement of the control member 14 results in corresponding angular displacement of the head 12 . if the distance which the coupling pivot 22 is offset from the rotational axis 20 is equal to the distance which the coupling pivot 26 is offset from the rotational axis 24 , the angular displacement of the control member 14 and the head 12 will be equal . if however , the coupling pivots 22 and 26 are offset different distances from their respective rotational axes 20 and 24 , the angular displacements of the control member 14 and head 12 will not be equal . depending on the requirements of specific applications , therefore , the geometry of the coupling pivots 22 and 26 and rotational axes 20 and 24 can be selected accordingly . for example , if the distance from coupling pivot 22 to rotational axis 20 is greater than the distance from coupling pivot 26 to the rotational axis 24 , a specified degree of angular offset of the control member 14 will result in a greater degree of angular offset of the head 12 . of course , the opposite is true as well . as a result , the invention provides a surgical tool that can specifically be constructed to suit a given surgical application as well as a surgeon &# 39 ; s personal preference . additionally , while the illustrated embodiment of the invention shows a tool wherein angular manipulation of the control member 14 causes opposed angular movement of the head 12 , the tool 12 can be constructed so that the control member 14 and the head 12 move in the same direction . this can be achieved , for example , in the following manner . as illustrated , when the member 14 and head 12 are aligned with longitudinal axis l , coupling pivots 22 and 26 are located at three o &# 39 ; clock in relation to rotational axes 20 and 24 respectively . if , however , the tool 10 were constructed so that , when the head 12 and control member 14 are axially aligned , the coupling pivot 22 is , at three o &# 39 ; clock and the coupling pivot 26 is at nine o &# 39 ; clock , rotational manipulation of the control member 14 would cause articulation of the head 12 in the same direction . as shown in fig2 and 3 , another coupling mechanism 28 runs generally parallel to the coupling member 18 within the rigid member 16 . this coupling mechanism 28 is for embodiments of the invention wherein the control member 14 has a second degree of manipulability for actuating an actuable operating device such as forceps 11 , mounted on the head 12 . in embodiments of the invention , as illustrated in fig4 a through 4c , wherein the head 12 carries an instrument that does not require actuation , such as , for example , a hook tip 50 , fiber optic lasers 52 , a curved spatula electrode 54 for either coagulation or cauterization , and the like , the control member 14 need only have one degree of manipulability . in any event , the illustrated coupling mechanism 28 is more clearly visible in fig3 wherein it is shown that the coupling mechanism 28 includes a rigid tube 30 from the front of which runs a group of small diameter cables 32 . a spring 34 is also fixed to the front of the tube 30 and a connecting element 36 is fixed to the end of the spring 34 . in this manner , longitudinal movement of the spring 34 and cables 32 is transmitted via the connecting element 36 to the actuating member on the head 12 . to actuate the actuating member , the control member 14 is manipulated as indicated by arrows 17 . this causes longitudinal displacement of the coupling member 28 either toward or away from the head 12 . in the case of the coupling element being moved toward the head 12 , the spring becomes compressed thereby exerting a pushing force on the connecting element 36 . in the case of the coupling element 28 being moved away from the head 12 , the cables 32 exert a pulling force on the connecting element 36 . accordingly , manipulation of the control member 14 results in actuation in a known fashion of an actuating member located on the head 12 . it is a significant feature of the invention that the coupling element 28 includes the illustrated group of cables 32 and that the cables 32 are exposed at that portion of the coupling element 28 located adjacent the rotational axis 24 . there is also a flexible connection ( not shown ) between the tube 30 and the control member 14 adjacent the rotational axis 20 . as a result , when the control member 14 is manipulated to be angularly offset from the longitudinal axis l , thereby causing a corresponding angular articulation of the head 12 , the cables 32 and the connection will flex . this enables articulation of the control member 14 and the head 12 and prevents inadvertent actuation of the actuable operating device . were the coupling element 28 entirely rigid , on the other hand , articulation of the head 12 and control member 14 would be inhibited and inadvertent actuation would occur . another embodiment of the invention is shown in fig5 and 6 wherein rather than by the rigid coupling element 18 , angular displacement of the control member is transmitted to the head 12 via a cable 38 and a pulley 40 . the cable 38 is fixed to the pulley 40 such as by , for example , spot welding , so that movement of the cable 38 causes rotational movement of the pulley 40 . the pulley 40 , in turn , is fixed to the head 12 by a screw 42 and the cable 38 is secured to the control member 14 by screws 44 . so , as illustrated , displacement of the control member 14 , as indicated by arrows 43 , results in the cable 38 causing rotational movement of the pulley 40 which is transmitted to the head 12 by the screw 42 . as shown in phantom , the cable 38 is guided around a hub 46 before being secured by the screws 44 . the provides proper spacing of the cable 38 as it passes through the rigid member 16 . also , the screws 44 can be turned to selectively position the control member 14 with respect to the head 12 and to adjust the tension along the cable 38 . while in the illustrated embodiment the cable 38 travels through the rigid member 16 generally parallel to the longitudinal axis l , the cable 38 could be arranged in a crossing pattern . in such a case , the head 12 would articulate in the same direction as the control member 14 . similarly to the embodiment depicted in fig2 and 3 , the embodiment of the invention shown in fig5 and 6 includes another coupling element 48 for actuating an actuating member located on the head 12 . the coupling element 48 includes a group of cables 50 passing through a fixed guide tube 52 . again , the cables are exposed adjacent the pivot axes of the control member 14 and the head 12 to both afford articulability to these elements and to prevent inadvertent actuation during steering . the cables are &# 34 ; semi - rigid &# 34 ; in that while necessarily being flexible enough to bend during angular manipulation , the cables 50 must be rigid enough so that when they are longitudinally displaced toward the head 12 they exert a pushing force to effect actuation of an actuable operating device such as the tongs 44 shown . it has been found that a bundle made of four strands of spring steel each of diameter 0 . 5 mm and spot welded together at one or both ends is suitable for this purpose . in still another embodiment of the invention , as shown in fig7 the head 12 and control member 14 are mounted to the rigid member 16 so that they can pivot about a point p . this provides this embodiment of the invention with the ability to manipulate the control member 14 , and thereby the head 12 , in multiple planes . a hemisphere 60 fits in a socket 62 defined by the elongated rigid member 16 . the hemisphere 60 includes a hole 64 to allow a coupling element , like coupling elements 28 and 48 discussed above , to pass from the control member 19 to the head 12 in order to couple the head 12 and control member 14 together . in this embodiment of the invention like hemispheres 60 are located at opposite ends of the rigid member 16 . steering rods 66 transmit displacement of the hemisphere 60 at the control member end of the rigid member 16 to the hemisphere 60 located at the opposite end of the rigid member 16 . the arrangement of the steering rods 64 is shown in fig7 a which is a view taken along line a -- a of fig7 . as stated , the advantage of this embodiment of the invention is that by mounting each of the control member 14 and the head 12 to the rigid member 16 via this ball and socket arrangement , non - planar movement can be transmitted from the control member 14 to the head 12 . while various features and embodiments of the invention have been described in detail , it should be understood that other alterations will be apparent to those skilled in the art and are intended to be embraced within the spirit and scope of the invention . the invention is to be defined , therefore , not by the preceding description but by the claims that follow .
a surgical tool for operating within a body cavity through a small diameter opening includes a substantially rigid member which is elongated along a first axis and which has a cross - sectional dimension to fit within the opening . a head is mounted on one end of the rigid member for movement in at least one plane through an angle with respect to the first axis . an operable control member is mounted on an opposite end of the rigid member for having at least one degree of manipulability . the control member is coupled to the head member through the rigid member such that manipulation of the control member through an angle with respect to the first axis causes movement of the head member through a corresponding angle . accordingly , the head member can be steered within a body cavity by control external to the body cavity . in some embodiments , the control member is manipulable to a second degree for actuating an actuating member mounted on the head .