CRIMPER

Abstract: A crimp tool for deforming a crimp tube (10) around wires used in surgical procedures has a pair of relatively long handles (107, 108) pivotal about a rear pivot axis (106). Each handle extends forwardly of the rear pivot axis (106) to form a rear jaw member (101a, 101b). The handles have co-operating cam surfaces formed thereon so that when the handles are pivoted towards one another, the free ends of the rear jaw members move apart. The free ends of the rear jaw members (101a, 101b) each carry an intermediate pivot (103, 104). Forward jaw members (111, 112) are pivotable about the intermediate pivot (103, 104) and are pivotable about a common forward pivot axis (110). The forward jaw members (111, 112) extend forwardly of the forward pivot axis (110) so that the forward end portions thereof may engage the crimp tube to deform it. The length of the handles (107, 108) is substantially greater than the length of the rear jaw members (101a, 101b) and the length of the forward jaw members (111, 112) is substantially greater than the length of the forward end portions thereof. Consequently, the compressive force applied by the forward end portions of the foward jaw members is substantially greater than the compressive force applied by a user to the handles (107, 108). A latching ratchet system prevents interruption of the crimping operation before an adjustable completion state. Alternatively, a visual indicator gives information concerning the pressure exerted.

Description: CRIMPER The present invention relates to a crimp tool for crimping a hollow tube around a wire or cable to form a joint and, in particular, to a crimp tool for use in surgical procedures. A number of surgical techniques have evolved over recent years which involve the fastening of loops of wire or thin flexible cables around bony structures. One such procedure is described in our United Kingdom patent application no. 9202635.0. This procedure involves passing at least one wire loop around the site of a fracture to support and stabilize bone fragments. The ends of the wire or cable are passed through a generally cylindrical metal crimp tube from opposite ends thereof so that they extend substantially- parallel to one another but in opposite directions through the tube. The loop is then tightened to the required degree and the tube crimped to form a permanent joint to close the loop. The free ends of the wire or cable can then be snipped off where they protrude from the crimp tube. This particular form of crimped joint is particularly advantageous in surgical procedures because, once the loop is closed, the crimp tube lies flat against underlying structures and there are no projecting wire ends which might cause damage to surrounding tissues. The commonly used alternatives are to close the loop by twisting the ends of the wire together or to form a different kind of crimp joint by passing both wire ends through the crimp tube from the same end, leaving the crimp tube projecting from the closed loop. Both of these alternative methods leave projecting wire ends but, nevertheless, have the advantage that they permit the wire loop to be closed relatively easily. The wire loop can be tightened to the required degree by further twisting of the wire ends or by sliding the crimp tube towards the bone, as the case may be. The crimp can be formed relatively easily since the tube projects away from the bone into 'free space' . The method described in our co-pending application, no. 9202635.0 has the advantage that it leaves no projecting wire ends but has the disadvantage that it has hitherto been more difficult to form a reliable crimp joint with the crimp tube lying flat against the bone. It will be appreciated that the crimping operation must be sufficiently reliable to minimise the risk of the loop coming undone and the bone fragments becoming free to move at the site of a fracture. It is also important that the crimping operation should not be such that it causes the loop to loosen as the crimp is formed.. In accordance with a first aspect of the invention there is provided a crimp tool for deforming a crimp tube around at least one wire or cable; the tool having a pair of relatively long handles pivotable about a rear pivot axis toward and away from one another, each handle being extended forwardly of the rear pivot axis to form a rear jaw member, the handles having co-operating cam surfaces formed thereon such that pivoting of the handles towards one another causes the free ends of the rear jaw members to move apart; the free ends of the rear jaw members each carrying an intermediate pivot and the tool further comprising a pair of forward jaw members, the forward jaw members' being pivotable about the intermediate pivots carried by the free ends of the rear jaw members and being pivotable about a common forward pivot axis; the forward jaw members extending forwardly of the forward pivot axis so that the forward end portions thereof may engage the crimp tube to deform it; the length of the handles being substantially greater than the length of the rear jaw members and the length of the forward jaw members being substantially greater than the length of the forward end portions thereof so that the compressive force applied by the forward end portions of the forward jaw members is substantially greater than the compressive force applied by a user to the handles. In accordance with a second aspect of the invention there is provided a crimp tool for deforming a crimp tube around at least one wire or cable, the tool having a pair of handles pivotable toward and away from one another to bring a pair of opposed jaws into engagement with a crimp tube to crimp it, the tool including a first latching member carried by one handle and a second latching member carried by the other handle, the first and second latching members, in use, engaging one another when the jaws are in a partially-closed position and being so arranged that they cannot be disengaged from one another until the jaws have been moved together to a predetermined fully closed position. In accordance with a further aspect of the invention there is provided indicator means for providing a visual indication as to when the handles have been pivoted toward one another to the fully closed position. Crimp tools in accordance with the invention will now be described in detail, by way of example, with reference to the drawings, in which: Figure 1 shows a crimp tube and a part of a wire loop around a fracture site or the like; Figure 2 shows a first crimp tool in accordance with the invention; Figure 3a and 3b are a side view and end view respectively of the jaw ends of the tool of Figure 2; and Figure 4 shows a modified crimp tool in accordance with the invention; Figures 5a and 5b are fragmentary views of the indicator of figure 4; Figure 6 shows a further modified crimp tool in accordance with the invention; and Figure 7 is a fragmentary view of the ratchet of Figure 6. As mentioned above, it is desired to close a loop formed in a wire or flexible cable 10 by ςrimping a metal tube 12 around the wire or cable so that the crimp tube 12 grips the wire sufficiently firmly to prevent slipping. As shown in Figure 1, the two ends of the wire 10a and 10b are passed through the crimp tube 12 from opposite ends thereof so that they lie substantially parallel to one another within the tube 12. To render the closure of the loop permanent, the tube 12 is crimped to deform it around the wire 10. This is achieved using a crimp tool 100 of the kind shown in Figure 2. The crimp tool 100 has a pair of opposed jaws 101 and 102 which are hinged together at pivot 106. Each of the jaws 101 and 102 is itself hinged part-way along its length at pivots 103 and 104 respectively. The rear part 101a and 102a of each ja 101 and 102 is extended rearwardly to form a handle 107 or 108 and the handles 107 and 108 are formed with cam surfaces (not shown) so that, as the handles 107 and 108 are moved together about pivot 106 (as shown in dotted lines in Figure 2), the ends of the rear parts of the jaws 101a and 102a carrying pivots 103 and 104 move apart. At the forward end of the crimp tool 100, each of the jaws 101 and 102 is provided with a forward jaw member 111 and 112 connected to the rear parts of the jaws at the pivots 103 and 104 respectively. The forward jaw members 111 and 112 are themselves hinged together at pivot 110, close to their forward ends. . The forward ends of the two forward jaw members 111 and 112 are shaped to form co-operating die surfaces 113 and 114'. Thus, when a crimp tube 12 is disposed between the die surfaces 113 and 114 and the forward jaw members 111 and 112 are moved together, using the handles 107 and 108, the crimp tube 12 is deformed around the wire 10 to grip it tightly. It will be noted that the arrangement and spacing of the pivots 103, 104, 106 and 110 is such that a relatively large movement at the handles 107 and 108 is translated into a movement of very small magnitude at the forward jaw members 111 and 112. Consequently, since the torque applied by the surgeon through the handles 107 and 108 is transmitted through the tool 100 to the forward jaw members 111 and 112, the compressive force applied by the forward jaw members 111 and 112 to the crimp tube 12 is much greater than the force applied to the tool 100 by the surgeon. This assists the user -in forming a firm and reliable crimp. Since the magnitude of the movement of the forward jaw members toward and away from each other is very small, the movement can be regarded as linear despite the fact that the jaw members 111 and 112 are, in fact, pivoting about the pivot axis 110. This pseudo-linear movement in turn assists in reducing the chance of the crimp tube 12 being pushed out from between the jaw members 111 and 112. It is also to be noted that the forward end surfaces of the forward jaw members 111 and 112 are substantially flat and extend generally transversely of the crimp tool 100 and parallel to the line of movement of the jaw members 111 and 112, so that the crimp tube 12 can be crimped using the tool as close to the bone as possible. The ends of the forward jaw members 111 and 112 and, in particular, the die surfaces 113 and 114 are shown in greater detail in Figures 3a and 3b. From these figures, it will be seen that the crimping action produced by the jaws is such as to deform the crimp tube 12 about two different axes. The 'upper' jaw 111, as seen in the drawings, is provided with a protrusion 121 which co-operates with a recess 122 formed in the 'lower' jaw 112 so that the cylindrical crimp tube 12 is deformed to a tube of generally crescent-shaped crossrsection. At the same time, the protrusion 121 and recess 122 vary transversely of the jaws 11 and 112 with the protrusion 121 extending furthest at the centre of the jaws 111 and the recess 122 being deepest midway across the jaw 112. Consequently, the crimping action also deforms the crimp tube 12 along its longitudinal axis. This double crimping action helps to ensure that the crimped joint is very secure and reliable. Even though the construction of the tool 100 is designed to ensure that an adequate crimp force is applied to the crimp tube, there is, of course, a danger that the surgeon may not fully close the tool before releasing the crimp tube 12 from between the jaws. Figures 4 and 5 show a modified crimp tool 400 which is capable of providing the surgeon with a visible indication that the required pressure has been applied. The overall construction of the crimp tool 400 is broadly similar to that of the tool 100 shown in Figures 2 and 3 and so, for the sake of clarity, only those reference numerals necessary to identify the additional features shown in Figures 4 and 5 have been included in these drawings. Between the handles 407 and 408 of the tool 400, there are provided both an adjustable stop 430 and an indicator mechanism 440. The adjustable stop 430 projects from the surface of the handle 407 which faces handle 408 and engages, in use, a fixed stop 432 on handle 408 to limit movement of the handles 407 and 408 towards one another. The degree to which the adjustable stop 430 projects from handle 407 can be varied to change the extent to which the handles 407 and 408 can be moved together and, hence, to limit the compression of the crimp tube 12 by the jaws 411 and 412. This helps to avoid any chance of the crimp tube 12 being broken or split due to extreme pressure inadvertently being applied by the user. At the same time, however, it is, as mentioned above, important that sufficient pressure is applied to form a reliable crimp. With this in mind, the crimp tool 400 includes an indicator mechanism 440 consisting of two projecting tabs 442 and 444 extending from the handles 407 and 408. The tabs 442 and 440 are so positioned that, as the handles 407 and 408 are moved together, the tab 442 carried by handle 408 slidingly engages the tab 440 on handle 407 as shown in Figure 5a. The tab 440 has marked on.it an indicator scale 446 (for the sake of clarity, only one graduation on the scale is shown * ) and, in order to ensure that the required pressure has been exerted on the crimp tube 12, the handles 407 and 408 are simply moved together until the end of the tab 442 is brought into alignment with the appropriate marking on the scale 446. This ensures that the correct pressure is applied and that the same pressure can be applied at each crimping operation. A leaf spring assembly 448 is also mounted between the handles 407 and 408 so as to urge the handles apart. This arrangement ensures that positive action to close the jaws of the tool 400 around a crimp tube is required and that, if the surgeon relaxes his grip for any reason, the tool immediately releases the crimp tube. In a further modified version, shown in Figures 6 and 7, the tool 600, rather than merely providing an indication that the correct pressure has been applied, is so constructed that the grip on the crimp tube cannot be released until the necessary pressure has been exerted. Again, the tool 600 is broadly similar to the tool 100 shown in Figures 2 and 3 and, for ease of reference, only those parts which differ from those of the tool 100 have been allocated reference numerals in these drawings. The tool 600 shown in Figures 6 and 7 includes a ratchet mechanism 650 which prevents the handles 607 and 608 being moved apart until they have been closed to the degree necessary to apply the required pressure to the crimp tube. The ratchet mechanism 650 has a female part 652 carried by handle 608 and a co-operating male part 652 carried by handle 607. The female part 652 is a forked element having two tabs 656 extending parallel to one another and substantially parallel to the handle 607. Each tab 656 carried a single ratchet tooth 658 engageable with appropriately formed teeth on the male part 654 of the ratchet mechanism. The male part 654 consists of a single toothed plate 660 which has a plurality of ratchet teeth 662 formed on it. As the handles 607 and 608 are moved together the toothed plate 660 of the male part 654 moves between the tabs 656 of the female part and the ratchet teeth 658 and 662 engage one another. The tabs 656 are sufficiently resilient and the ratchet teeth 658 and 662 are so shaped that the teeth can move past one another as the handles 607 and 608 continue to move toward one another. However, the shaping of the teeth 658 and 662 is such that, once they are engaged, the toothed plate 660 cannot be withdrawn from between the tabs 656. Thus, movement of the handles 607 and 608 towards one another must continue until the toothed plate 660 is clear of the tabs 656 as shown in Figure 7. At this point, the toothed plate 660 can be deflected sufficiently to pass outside the tabs 656 as the handles 607 and 608 move apart again. It will be appreciated that by choosing the dimensions and locations of the male 654 and female parts 652 of the ratchet mechanism appropriately, it can be ensured that, once the mechanism is engaged, the handles 607 and 608 can only be moved apart once the necessary crimp pressure has been applied. Furthermore, if a leaf spring 648 is provided to urge the handles 607 and 608 apart, the tool 600 can be set at partial pressure (sufficient to grip the crimp tube but not sufficient to form the final crimp) with the ratchet teeth engaged, allowing final adjustments to the wire loop to be made with the tool 600 in place. The final crimp can then be made subsequently by closing the tool.

Claims: CLAIMS 1. A crimp tool for deforming a crimp tube around at least one wire or cable; the tool having a pair of relatively long handles pivotable about a rear pivot axis toward and away from one another, each handle being extended forwardly of the rear pivot axis to form a rear jaw member, the handles having co-operating cam surfaces formed thereon such that pivoting of the handles towards one another causes the free ends of the rear jaw members to move apart; the free ends of the rear jaw members each carrying an intermediate pivot and the tool further comprising a pair of forward jaw members, the forward jaw members being pivotable about the intermediate pivots carried by the free ends of the rear jaw members and being pivotable about a common forward pivot axis; the forward jaw members extending forwardly of the forward pivot axis so that the forward end portions thereof may engage the crimp tube to deform it; the length of the handles being substantially greater than the length of the rear jaw members and the length of the forward jaw members being substantially greater than the length of the forward end portions thereof so that the compressive force applied by the forward end portions of the forward jaw members is substantially greater than the compressive force applied by a user to the handles. 2. A crimp tool according to claim 1 including a latching mechanism disposed between the handles, the latching mechanism including a first latching member carried by one handle and a second latching member carried by the other handle, the first and second latching members, in use, engaging one another when the forward end portions of the forward jaw members are in a partially-closed position and being so arranged that they cannot be disengaged from one another until the forward end portions of the forward jaw members have been moved together to a predetermined fully closed position. 3. A crimp tool for deforming a crimp tube around at least one wire or cable, the tool having a pair of handles pivotable toward and away from one another to bring a pair of opposed jaws into engagement with a crimp tube to crimp it, the tool including a first latching member carried by one handle and a second latching member carried by the other handle, the first and second latching members, in use, engaging one another when the jaws are in a partially-closed position and being so arranged that they cannot be disengaged from one another until the jaws have been moved together to a predetermined fully closed position. 4. Apparatus according to claim 2 or 3 in which the first latching member includes a plate carrying at least one ratchet tooth and the second latching member includes a pair of opposed parallel tabs each bearing at least one co-operating ratchet tooth, pivoting movement of the handles toward one another being such as to bring the plate between the pair of opposed tabs at the partially-closed position so that the interengagement of the ratchet teeth prevents withdrawal of the plate from between the tabs, the plate being displaceable laterally of the tabs in the fully closed position so as to permit the handles to move apart again. 5. Apparatus according to any of claims 2 to 4 in which at least one of the first and second latching members is provided with a plurality of ratchet teeth so as to permit the handles to be retained by the interengagement of the teeth in a plurality of predetermined positioned. 6. Apparatus according to any preceding claim further including indicator means for providing a visual indication as to when the handles have been pivoted toward one another to the fully closed position. 7. A crimp tool for deforming a crimp tube around at least one wire or cable, the tool including indicator means for providing a visual indication as to when the handles have been pivoted toward one another to the fully closed position. 8. Apparatus according to claim 6 or 7 in which the indicator means includes a first indicator member mounted on one handle and projecting towards the other, and a second indicator member carried by the other handle and projecting towards the first handle, the first and second indicators and indicator members being so arranged that as the handles are pivoted towards one another, the first and second indicator members slide one over the other; at least one of the indicator members being provided with at least one indicator marking with which the end of the other indicator member is aligned in the fully closed position. 9. Apparatus according to any preceding claim in which the forward end portions of the forward jaw members engageable with the crimp tube are shaped to define " co-operating die surfaces which in use extend substantially parallel to the length of the crimp tube, the forward jaw members being so shaped that no part thereof extends forwardly of the die surfaces. 10. Apparatus according to any preceding claim in which the said co-operating die surfaces are shaped to form complementary concave and convex surfaces curved along a direction transverse to the crimp tube. 11. Apparatus according to any preceding claim in which the said co-operating die surfaces are shaped to form complementary concave and convex surfaces curved along a direction longitudinally to the crimp tube. 12. A crimp tool for deforming a crimp tube around at least one wire or cable, the crimp tube being substantially as hereinbefore described with reference to any of Figures 2 to 7.

Inventors: CROCKARD ALAN, LUGO BRENDA, MELLOUL RAPHAEL, CROCKARD, ALAN, LUGO, BRENDA, MELLOUL, RAPHAEL
Applicants: HILLWAY SURGICAL LTD, HILLWAY SURGICAL LIMITED
Application year: 1993
Main classification: A61B17
IPC codes: A61B17, B25B7, B25B27