FIELD OF THE INVENTION

The present invention relates to a cutter, and in particular, but not exclusively, to a cutter for use in removing a cast used to immobilize an injured body part from a limb or otherwise of a patient.

BACKGROUND TO THE INVENTION

Typical "plaster" casts for use in immobilising limbs or other parts of the body are composed of a padded fibre layer surrounded by a more rigid layer, such as a plaster or fibreglass tape layer. Conventional cast-cutters remove such casts by cutting through the rigid layer, with the padded layer subsequently being cut using scissors, or other like instruments. This is normally repeated at opposing sides of the cast to enable the cast to be removed in two sections.

Conventional cast-cutters typically comprise an oscillating blade or disc which abrades or saws the plaster or fibreglass. As a result, large quantities of dust may be produced and dispersed within the air. In order to minimise the release of dust particles, a dust extraction device may be required, which may be cumbersome and adds additional expense to the cutting device.

Furthermore, conventional cutters are generally noisy in operation due to the action of the blade cutting the cast material, in combination with a high-speed motor, and also due to the presence of the extraction device. The noise produced can be distressing, particularly to young patients, which may result in patients becoming agitated, making removal of the cast without causing injury more difficult. Additionally, the noise produced by conventional cast-cutters can present significant health and safety issues in that an operator should not be exposed to elevated noise levels for prolonged periods of times. Accordingly, in many jurisdictions, the length of time which an operator may use a conventional cast-cutter is restricted.

Additionally, in use, the blades of conventional cutters may become heated due to friction between the blade and the cast, which introduces the risk of burning the skin of the patient. Further, convention cast cutters which utilise a sawing action to remove a cast are known to produce significant levels of vibration which can be transmitted to the user, and indeed the patient, which is preferably to be avoided.

Due to the above problems, cast cutters which involve cutting the cast by a sawing action, even when operated by a skilled operator, may result in distress and injury to the patient, and give rise to health and safety considerations for the operator.

A cast cutter which seeks to solve the above noted problems is disclosed in the Inventor's/ Applicant's patent application publication numbers WO 2004/026207 and WO 2005/092267, the disclosure of which are incorporated herein by reference.

This background serves only to set a scene to allow a skilled reader to better appreciate the following description. Therefore, none of the above discussion should necessarily be taken as an acknowledgement that that discussion is part of the state of the art or is common general knowledge. One or more aspects/embodiments of the invention may or may not address one or more of the background issues.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided a cast- cutter for use in removing a cast from a patient.

The cast-cutter may comprise a body and a cutting assembly. The cutting assembly may be mountable on the body.

The cutting assembly may comprise first and second relatively moveable cutting members. The/each cutting member may define a cutting edge. The first and second cutting members may be configured to permit cooperation between the respective cutting edges to cut by a shearing action. The first and second cutting members may be configured to permit cooperation between the respective cutting edges to cut through a cast material by a shearing action.

At least one of the cutting members may comprise a preliminary portion. The preliminary portion may be configured to weaken or prepare a cast material prior to cutting through of the cast material by a shearing portion of the cutting edge.

The cast-cutter may be configured to weaken a first section or length of cast and also cut a second section or length of cast simultaneously. The second section or length of cast may have been previously weakened by the preliminary portion. The preliminary portion may comprise a non-severing portion. The preliminary portion may comprise a non-shearing portion.

The preliminary portion may be configured to deform or weaken the cast material at least primarily by a non-shearing action.

The preliminary portion may be configured to deform or weaken the cast material at least primarily by a non-cutting action.

The preliminary portion may be configured to perforate and/or puncture and/or soften and/or weaken and/or deform at least a portion of a layer, such as an outer or upper surface of a layer, of cast material. The preliminary portion may be configured to define an initial line of cut in the cast material for subsequent severing by the shearing portion.

The preliminary portion may be configured to at least primarily compressively deform or weaken the cast material prior to cutting through the cast material with the shearing portion. The cutting member may be configured or mounted to progressively shear the cast material as the cast material passes from a receiving or toe end of the cutting member to a discharging or heel end of the cutting member. The cutting member may be configured or mounted to increasingly shear the cast material as the cast material passes from the receiving end to the discharging end. The cutting member may be configured or mounted to increasingly shear the cast material as the cast material passes along the cutting member, from the preliminary portion to the shearing portion.

The preliminary portion may be configured to progressively weaken the cast material as the cast material passes along or adjacent the preliminary portion. The preliminary portion may be configured to progressively weaken the cast material to an increasing depth as the cast material passes along or adjacent the preliminary portion.

The preliminary portion may be configured to progressively weaken the cast material as it passes towards the shearing portion.

The preliminary portion may comprise a different property to the shearing portion. The different property may comprise a different form of cutting edge. The different form of cutting edge may comprise a different cutting geometry. The different property may comprise a different tip angle and/or a tip radius, such as when viewed in cross-section perpendicular to the direction of cut. The shearing portion may comprise a substantially continuous cutting edge. The preliminary portion may comprise a substantially discontinuous cutting edge, such as a plurality of cutting edges.

The shearing portion may be configured to engage the cutting edge of the other cutting member, such as to directly engage the cutting edge of the other cutting member at at least a point or line of contact during cutting. The preliminary portion may be mounted so as not to engage, such as not to directly engage, the cutting edge of the other cutting member during cutting.

The preliminary portion may be configured to grip the cast material. The preliminary portion may be configured to prevent or resist movement of the cast material relative to the cast-cutter, such as longitudinal movement in the line of cut away from the shearing portion or in a direction opposite to the direction of cut. The preliminary portion may be configured to grip the rigid layer of the cast.

The preliminary portion may be more distal to a pivot or support point of the cutting member relative to the shearing portion. The preliminary portion may exert a proportionally greater torque on the pivot or support point than the shearing portion, such resulting from a similar resistive force from the cast material in the preliminary or shearing portions (e.g. due to a greater moment or lever arm). The preliminary portion may be configured to reduce torque transmitted to the pivot or support point. The preliminary portion may be configured to create a plurality of stress concentrations in the cast material, such as simultaneously during a single stroke or cycle of the cast-cutter. Creating a plurality of stress concentrations may reduce a resistive force or torque. The plurality of stress concentrations may enable the cutting member to deform or penetrate deeper into the cast that may otherwise be possible.

The preliminary portion may comprise a toothed portion. The toothed portion may comprise a plurality of teeth.

The plurality of teeth may enable the cutting member to deform or penetrate deeper into the cast that may otherwise be possible, such as with a continuous cutting edge.

The cutting member may be configured and/or mounted such that the teeth move substantially in the direction of each tooth, such as towards/away from the points of the teeth. The cutting member may be configured and/or mounted such that the teeth move substantially in a non-sawing action. The cutting member may be configured and/or mounted such that the teeth move substantially perpendicular to the arrangement of teeth.

The teeth may comprise generally similar tooth properties to each other, such as pitch, width, height, cutting angles and the like. Alternatively the teeth may comprise at least one dissimilar tooth property.

The/each tooth may comprise a taper, tapering towards a point in the direction of the other cutting member or the cutting plane (e.g. for contacting or initially contacting the cast material with the point).

The teeth may comprise a pitch or pitches (e.g. a wavelength) in the range from about 0,2mm to about 3,0mm. The teeth may comprise a pitch or pitches in the range from about 0,5mm to about 2,0mm. The teeth may comprise a pitch or pitches in the range from about 0,2mm to about 3,0mm. The teeth may comprise a pitch or pitches of about 1.7mm.

The teeth may be evenly spaced or arranged.

Alternatively, the teeth may be unevenly spaced or arranged. The teeth may be arranged progressively closer together, such as progressively closer together in the direction of cut.

The teeth may comprise a maximum opening or separation, such as between adjacent teeth points, in the range of about 0,2mm to about 2,5mm. The teeth may comprise a maximum opening or separation, such as between adjacent teeth points, in the range of about 0,5mm to about 2,0mm. The teeth may comprise a maximum opening or separation, such as between adjacent teeth points, of about 1,2mm.

At least one tooth may be truncated. All of the teeth may be truncated. The point of the/each tooth may be truncated.

The/each tooth may comprise a truncated point such that the/each tooth has a length in the direction of cut at the point.

The shearing portion may comprise a non-toothed portion.

The preliminary portion may comprise a serrated cutting edge.

The shearing portion may comprise a non-serrated cutting edge.

Advantageously, in use, the cast-cutter of the present invention may be manipulated to position a cast material to be removed from a patient between the first and second cutting members, and subsequently activated to cause relative movement of the first and second cutting members to cause the cast material to be cut by cooperation of the cutting edges.

Preferably, the first and second cutting members of the cutting assembly are arranged such that during a cutting operation the cutting edges are aligned with a projected cutting plane, such that the cutting edges are adapted to engage and cooperate to produce a shearing strain in the cast material in order to cut the cast material along the projected cutting plane.

The cast material may be substantially arranged in a cast plane, the cast plane being substantially perpendicular to the cutting plane, intersecting the cutting plane to define a line of cut in a direction of cut.

The preliminary portion may be mounted or configured such that a preliminary clearance is provided between at least a section or length of the preliminary portion and the cutting edge of the other cutting member during cutting. The preliminary portion may be mounted or configured such that the preliminary clearance is always provided between the at least a section or length of the preliminary portion and the cutting edge of the other cutting member at all times during cutting. The preliminary portion may be mounted or configured such that the preliminary clearance is provided between substantially the entire preliminary portion and the cutting edge of the other cutting member during cutting. The preliminary portion may be mounted or configured such that the preliminary clearance is provided between all but one tooth of the preliminary portion and the cutting edge of the other cutting member during cutting. The preliminary clearance may be substantially in plane with or at least parallel to the cutting plane. The preliminary clearance may be substantially perpendicular to the cast plane.

Providing a preliminary clearance between the preliminary portion and the other cutting member may enable the preliminary portion to weaken or deform the cast material at least primarily by a non-shearing action. Providing a preliminary clearance between the preliminary portion and the other cutting member may allow contacting engagement of the cutting members or at least the cutting edges only in the severing or shearing portion. Providing a preliminary clearance between the preliminary portion and the other cutting member may reduce wear and/or prevent damage to one or both of the cutting members.

The preliminary portion may be aligned with the shearing portion. The preliminary portion may be substantially collinear with the shearing portion.

At least one of the cutting members may comprise an angled cross-section perpendicular to the line of cut. The angled cross-section may comprise a wedge. The wedge may comprise a face substantially parallel to the cutting plane. The wedge may comprise a plurality of slopes. The wedge may comprise a main or primary angle relative to the cutting plane or the face substantially parallel to the cutting plane. The primary angle may be defined between a first slope and the cutting plane or the face substantially parallel to the cutting plane. The primary angle may define a general shape of the wedge. The wedge may comprise a secondary angle relative to the cutting plane or the face substantially parallel to the cutting plane. The secondary angle may be defined between a second slope and the cutting plane or the face substantially parallel to the cutting plane. The secondary angle may define a cutting angle at or towards the tip or cutting edge of the cutting member. The second slope may intersect the face substantially parallel to the cutting plane.

The primary and secondary angles may be substantially different. The secondary angle may substantially greater than the primary angle. The secondary angle may be configured to provide an increased stiffness and/or strength, such as relative to the primary angle. The secondary angle may be configured to reduce or prevent damage to the tip or cutting edge of the cutting member.

The primary and/or secondary angle/s may be configured to reduce a force required to deform, cut or penetrate the cast material.

The primary angle may be in the range of about 5° to about 45°. The primary angle may be in the range of about 10° to about 30°. The primary angle may be in the range of about 12° to about 25°. The primary angle may be in the range of about 15° to about 23°. The primary angle may be about 20°.

The secondary angle may be in the range of about 20° to about 90°. The secondary angle may be in the range of about 45° to about 90°. The secondary angle may be about 60° to about 90°. The secondary angle may be in the range of about 80° to about 90°. The secondary angle may be about 87°. The wedge may comprise a radius/es and/or additional slopes, such as between the primary and secondary slopes.

The angled cross-section may be substantially constant along at least sections or lengths of the cutting member. For example, the angled cross-section may be substantially constant along the length of the preliminary portion. The angled cross- section may be substantially the same for each of the teeth of the toothed portion.

The angled cross-section may vary along at least sections or lengths of the cutting member. The angled cross-section may vary between the preliminary portion and the shearing portion and/or along the respective preliminary and/or shearing portion/s.

The primary and/or secondary angle/s may be substantially constant along at least sections or lengths of the cutting member. For example, the primary and/or secondary angle/s may be substantially constant along the length of the preliminary portion. The primary and/or secondary angle/s may be substantially the same for each of the teeth of the toothed portion.

The primary and/or secondary angle/s may vary along at least sections or lengths of the cutting member. The primary and/or secondary angle/s may vary between the preliminary portion and the shearing portion and/or along the respective preliminary and/or shearing portion/s.

The primary and/or secondary angle/s may increase in the direction of cut. The primary and/or secondary angle/s may increase in the direction of cut so as to assist in splaying the cast material or directing the cast material away from the cast and/or cutting plane/s as and/or after the cast is cut or cut through. The primary and/or secondary angle/s may increase progressively in the shearing portion.

The thickness of the tip of the cutting member may be substantially constant along at least a section or length of the cutting member. The thickness of the tip of the cutting member may be substantially constant along the preliminary portion. The thickness of the tip of at least two teeth may be substantially the same.

The thickness of the tip of the cutting member may vary along at least a section or length of the cutting member. The thickness of the tip of the shearing portion may be substantially greater than the thickness of the tip of at least a section or length of the preliminary portion. The thickness of the tip of the cutting member may vary along the shearing portion. The thickness of the tip of the cutting member may progressively increase along the length of the shearing portion in the direction of cut.

Increasing the thickness of the tip may increase the resistance of the cutting member to flexing and/or damage and/or wear, such as under loading or repeated loading. Providing an increased tip thickness in the shearing portion may provide for an increased rigidity, such that a contacting engagement between the cutting members is ensured in the shearing portion.

Providing a decreased thickness and/or teeth in the preliminary portion may enable an increased stress concentration, such as due to a reduced contact surface area between the preliminary portion and the cast material.

The tip thickness may be at least partially defined by the length of the second slope.

The cutting members may be arranged to define an opening therebetween in or parallel to the cutting plane. The opening may comprise a V-shape pointing in the direction of cut, with the opening generally greater to receive the cast initially, such as in the preliminary portion. The cutting members may define a shearing angle therebetween. The shearing angle may be defined at or adjacent a point of contact, overlap or crossover of the cutting members; and/or distal to the point of contact, overlap or crossover of the cutting members.

The shearing angle may be substantially constant along at least sections of the cutting assembly.

The shearing angle may vary between and/or along at least one or more sections of the cutting assembly.

The shearing angle may remain substantially constant as the cutting members move relatively.

The shearing angle may vary as the cutting members move relatively.

The shearing angle may be greater than about 4°; optionally greater than about 8°; optionally greater than about 10°; optionally greater than about 15°; optionally greater than about 20°; optionally greater than about 25°. The shearing angle may be less than about 30°; optionally less than about 25°; optionally less than about 20°; optionally less than about 15°; optionally less than about 12°; optionally less than about 8°.

The preliminary portion may be configured to enable a greater shearing angle. The preliminary portion may be configured to grip the cast such that the cast is prevented or at least restricted in longitudinal movement out of the opening, opposite to the direction of cut, such as due to a longitudinal component or vector of force resulting from the shearing angle between the cutting members.

The preliminary portion may be configured to enable a greater shearing angle of the at least a section/s of the preliminary and/or shearing portion/s (e.g. than would otherwise be enabled, without undue movement of the cast out of the opening.

An increased shearing angle may enable a reduced overall length of cutting assembly and/or a reduction in resistive or cutting force or torque, such as instantaneous and/or total resistive or cutting force or torque.

At least one of the cutting members may comprise a protrusion to guide the cast into the opening between the cutting members. The protrusion may be positioned or located on or extend to an opposite side of the cutting plane to the cutting edge of the related cutting member. The protrusion may be positioned or located on or extend to an opposite side of the cast plane to the cutting edge of the related cutting member.

The protrusion may be configured to at least resist movement of the cast longitudinally and/or laterally out of the opening, such as against the direction of cut (e.g. due to a longitudinal component or vector of force resulting from the shearing angle between the cutting members).

The protrusion may be configured to define a portion or section of reduced shearing angle between the cutting members. The portion or section of reduced shearing angle may comprise a negative shearing angle. The protrusion may be configured to force cast into the opening as a result of the relative movement of the cutting members towards each other.

The protrusion may be positioned or located so as to provide a direct counterforce to the other cutting member, such as to resist relative splaying of the cutting members. The protrusion may act as an anvil to a corresponding portion of the other cutting member. The protrusion may never come into contact with the other cutting member.

The cutting assembly may be configured not to overlap or crossover the cutting members (e.g. when viewed perpendicular to the cutting plane) at the protrusion.

Discrete portions of the cutting edges may be aligned with the projected cutting plane at any one time. Thus, as the first and second cutting members are moved relative to each other to effect cutting, the discrete point at which the cutting edges are aligned with the projected cutting plane will move along the length of the cutting members, in the direction of cut.

Alternatively, the entire length of the cutting edges or at least the shearing portion, or a substantial portion thereof, may be aligned with the projected cutting plane at the same time.

Each of the cutting members may comprise a preliminary portion. The preliminary portions may be configured to cooperate.

The first and second cutting members may be configured to permit cooperation between the respective cutting edges to cut by a shearing action while maintaining the inner faces in non-engaging relationship to provide an inner clearance therebetween.

The inner clearance provided between the respective inner faces may impede or prevent the cast material from binding between the cutting members during a cutting operation, which may otherwise cause unnecessary wear and ultimately damage the cutting members and possibly the cutting assembly, and may also cause the cutting members to be splayed apart while increasing the frictional load on the cutting assembly.

An inner face of at least one of the cutting members may be inclined outwardly from the projected cutting plane in order to provide clearance between the inner faces when the cutting assembly is operated. The inner face of both cutting members may be outwardly inclined from the projected cutting plane in order to provide clearance between said faces when the cutting assembly is operated.

Accordingly contact, such as a line or point contact, between the cutting edges may be ensured, such as at all times during cutting. Thereby, the inner clearance between the cutting edges at a point of cutting or shearing of the cast material may be at least reduced or substantially eliminated (e.g. such as to reduce splaying).

The shearing action of the cast-cutter may allow the cutting assembly to cut through the entire thickness of the cast, through both rigid and padded fibre or bandage layers, for example, eliminating the requirement for scissors or the like to cut through soft material once the rigid material has been cut using conventional methods.

The cutting assembly may cut through the rigid layer only, with the padded fibre layer or bandage layers being subsequently cut using conventional scissors or the like.

Cutting a cast material by a shearing action substantially reduces the noise, dust and other problems normally associated with rotating or oscillating blades, which thus reduces patient discomfort and anxiety, and also increases user safety.

Preferably, the cutting assembly of the cast-cutter is adapted to cut various types of casts, including plaster casts and synthetic, glass fibre casts which may comprise glass fibre tape or other similar rigid casting material.

The cutting assembly may be adapted to cut a cast in two directions.

Preferably, one of the first and second cutting members is fixed relative to the body, and the other cutting member is moveable, such that in order to effect cutting of a section of a cast the moveable member is moved towards the stationary member when the cast is positioned therebetween. The cast-cutter may comprise an end-stop to limit movement of the moveable cutting member. The cast-cutter may comprise an end stop to limit movement of the moveable member towards the other cutting member and/or the cast-cutter may comprise an end stop to limit movement of the moveable member towards the other cutting member. Where the cast-cutter comprises two or more end stops, the end stops may be unitary or integrally formed (e.g. one stop may function to limit movement in two directions).

One of the cutting members may be pivotally mounted relative to the other cutting member. In one embodiment, one member may include a lug which is accommodated in a suitable recess or land area on the other member. The pivotal member may be mounted to oscillate along an arcuate path about a pivot axis.

One of the cutting members may be mounted to be reciprocally moveable along a linear path relative to the other cutting member. One of the first and second cutting members may be rotatably mounted relative to the other cutting member and may be suitably formed and arranged to shear a cast material upon rotation.

The first and second cutting members may be moveable such that cutting is achieved by movement of the first and second members towards each other.

Preferably, the cutting assembly comprises a support member adapted to support the first and second cutting members. Preferably, the support member is adapted to fixedly support one of the first and second cutting members and to moveably support the other cutting member so that relative movement between the first and second cutting members may be achieved.

One cutting member may be integrally formed with the support member, or alternatively may be separately formed and rigidly secured thereto, for example by welding, bolting, riveting, clamping or the like. The support member may comprise an end stop to assist in locating or positioning the cutting member and/or limiting movement of the cutting member relative to the support member.

In a preferred embodiment of the present invention, the other of the first and second cutting members is moveably supported on the support member by being pivotally coupled thereto. Advantageously, the pivotally mounted cutting member may be coupled to the support member by means of a pivot pin arrangement. The pivot pin arrangement may be provided by, for example, a bolt, cantilever pin, press- fit pin, or the like.

In an alternative embodiment of the present invention, both the first and second cutting members may be non-rigidly connected to the support member of the cutting assembly.

Preferably, the cutting assembly is adapted to be releasably mountable on the body of the cast-cutter. This arrangement advantageously permits the cutting assembly to be readily removed from the cast-cutter for inspection, repair, re- sharpening or to be entirely replaced, for example. The ability to readily replace the entire cutting assembly also offers significant advantages in that the possibility of transmitting infection from patient to patient may be minimised.

The cutting assembly may be adapted to be secured to the body in alternate directions such that the cast-cutter may be used to cut a cast in at least two directions. The support member of the cutting assembly may be adapted to be mountable on the body of the cast cutter in order to secure the cutting assembly thereto. The support member may be adapted to be mountable on the body by way of a suitable bracket or flange arrangement or the like, and may be secured to the body by use of, for example, bolts, screws, a quick-release mechanism or the like. Alternatively, the support member may be mountable on the body by way of a suitable threaded connection, for example.

The cutting assembly may comprise a biasing means for biasing at least the cutting edges of the first and second cutting members laterally together. Advantageously, the biasing means provides a positive pressure between the first and second cutting members of the cutting assembly to assist in preventing lateral separation or splaying of the cutting members and to ensure an efficient cutting action is achieved and maintained.

The biasing means may comprise a spring biasing means, such as a sprung washer or a disc type spring or the like. Alternatively, or additionally, the biasing means may be provided by one or both of the first and second cutting members, for example by providing one or both members with a longitudinal curvature or profile. The curvature or profile, in use, may be adapted to cause an interference engagement between the cutting edges of the first and second cutting members causing one or both members to elastically deform, wherein the force of elastic recovery within one or both members acts to bias the cutting edges into contact engagement with each other.

The/each cutting edge/s of the first and/or second member/s may be provided as or on separate inserts or components from the respective cutting member which are secured to the first and/or second members respectively. The inserts may be releasably secured to the respective first and/or second member/s such that if a cutting edge becomes damaged or inefficient, it may be readily replaced without the need to replace the entire member upon which the cutting edge is located. Additionally, the provision of cutting edges on separate inserts allows the first and second members of the cutting assembly to be manufactured from a first material which does not have to exhibit the required mechanical properties to directly cut a cast material, which would generally be more expensive. The inserts may be manufactured from any suitable material such as polymeric, ceramic or metal or the like. Preferably, in use, one of the first and second cutting members is adapted to be positioned underneath a cast, between the cast material and the skin of a patient. Preferably, the cutting member to be positioned between the cast material and the skin of a patient may advantageously be utilised as a protecting member to protect the patient from injury while the cast-cutter is in use. The stationary member may be configured to be positioned or located more proximal to a patient's skin than the moveable member. The stationary member may be configured to be positioned or located at least partially between the cast (cut and/or uncut) and a patient's skin. The moveable member may be configured to be located or positioned distal to a patient's skin.

Preferably, the cutting assembly is adapted to be coupled to a drive means via a drive mechanism, wherein the drive mechanism transmits motion from the drive means to the cutting assembly for causing relative movement between the cutting members to effect cutting.

In a preferred embodiment of the present invention, the drive mechanism is adapted to reciprocate. In this preferred embodiment the drive mechanism may comprise a reciprocating drive pin coupled to the drive means by a suitable transmission arrangement, and also coupled to one of the cutting members.

In an alternative arrangement, the drive mechanism may be adapted to rotate or oscillate or the like.

The drive pin may be coupled to one of the cutting members via a connector. The connector may comprise an engagement portion for transferring drive between the drive pin and the cutting member. The engagement portion may be configured to eliminate play between the connector and the cutting member or the drive pin. The connector may be substantially rigidly connected to the other of the drive pin or the cutting member that is not engaged by the engagement portion. The connector may be integrally formed with the other of the drive pin or the cutting member that is not engaged by the engagement portion. The engagement portion may comprise an interference fit between the connector and the cutting member or the drive pin.

The drive mechanism may be configured to terminate the connection between the drive means and the cutting assembly upon reaching a predefined force exerted by the cutting assembly, and specifically between the cutting members. This arrangement advantageously minimises the possibility of causing damage to the cutting assembly by attempting to cut a material which may be beyond the safe capability of the particular cutting assembly. In one embodiment of the present invention the drive mechanism may comprises a slip pin or shear pin coupling arrangement adapted to be activated or sheared when the predefined force is reached.

Preferably, the cutting assembly is operated by electric drive means. Preferably, the electric drive means comprises an electric motor. Advantageously, control circuitry may be provided and adapted to permit the required control of the electric motor to be achieved. The control circuitry may incorporate safety features such as thermal and current tripping circuits. For example a self-resetting current tripping circuit may be provided which is adapted to prevent or cease operation of the cast-cutter upon reaching a predetermined current load.

Preferably, the electric motor comprises braking means adapted to prevent movement of the cutting means when the cast-cutter is deactivated. In a preferred embodiment of the present invention, the braking means is provided by permitting the electric motor to be short-circuited to generate a transitory back e.m.f. to rapidly stop rotation of the motor. Advantageously, the cast-cutter may comprise one or more electrical resistors through which the electric motor may be short-circuited in order to accommodate a brief surge in the current when the cast-cutter is deactivated, and to thus protect the components and electrical connections of any control circuitry.

Alternatively, the cutting assembly may be operated by hydraulic drive means. Alternatively further, the cutting assembly may be operated by pneumatic drive means.

Advantageously, the cast cutter may be powered by an electrical power supply, such as a mains supply either alone or in combination with a transformer and/or a rectifier, or alternatively, or indeed additionally, by a local power supply such as a battery pack.

Advantageously, the cast-cutter may include visual signal means which are activated when power is supplied thereto. Such visual signal means may comprise one or more LEDs or the like.

Conveniently, the cast-cutter may be activated by depressing or otherwise closing a normally open main switch, and deactivated by releasing said switch. Preferably, the cast-cutter comprises at least one safety switch which must be depressed or released before the cast-cutter can be operated by the main switch. This prevents the cast-cutter from being inadvertently activated by accidentally depressing the main switch. Advantageously, visual signal means may be provided and activated when the at least one safety switch is operated.

In a preferred embodiment of the present invention, the cast-cutter comprises two safety switches, wherein at least one of the two safety switches must be depressed or otherwise activated before the cast-cutter may be operated by the main switch. Advantageously, one of the two safety switches is positioned on the cast-cutter to permit ease of use by a right-handed operator, and the other of the two safety switches is positioned to permit ease of use by a left-handed operator.

Preferably, the cast-cutter further comprises a safety guard disposed around the cutting assembly to prevent accidental injury by trapping a finger, for example, while the cutter is in use. The guard may be fixed in place or alternatively may be retractable to allow access to the cutting assembly for cleaning or maintenance, for example. Where the safety guard is retractable, the guard may include a safety switch such that the cast-cutter may only be operated when the safety guard is positioned correctly in place.

In a preferred embodiment of the present invention, the cast-cutter comprises a safety guard having a fixed portion and a retractable portion moveably mounted on the fixed portion. In this embodiment, the retractable portion is adapted to be retracted to permit access to the cutting assembly, for example to engage a cast material during a cast removal operation. Preferably, the retractable portion is pivotally mounted on the fixed portion.

The retractable portion may be mounted so as to prevent removal of the retractable portion. The retractable portion may be mounted on or within the fixed portion such that the retractable portion is non-removable from the fixed portion, at least in normal use. The retractable portion may be substantially permanently mounted to the fixed portion, such as by the mounting of the pivot to allow the retractable portion to pivot. The retractable and/or fixed portion/s of the safety guard may be transparent such that the cutting assembly may be safely viewed by a user to ensure correct operation and that a correct line of cut is being achieved.

Advantageously, the various components of the cast-cutter may be coated with a material to prolong service life or to allow ease of cleaning or the like. For example, a Teflon®, Diamond Like Carbon, ceramic or like coating may be utilised.

Advantageously also, various portions of the cast-cutter may be hardened to ensure longevity. For example, the cutting edges of the cutting members may be hardened, for example using mechanical or chemical hardening techniques.

At least the cutting edges of the respective cutting members may comprise different properties. For example, the cutting edge of the first cutting member may comprise a different hardness from the cutting edge of the second cutting member.

According to a second aspect of the present invention, there is provided a method of removing a cast from a patient, said method comprising the steps of:

providing a cast cutter according the first aspect;

manipulating the cast-cutter to position a cast material to be removed from a patient between the first and second cutting members; and

activating the cast-cutter to cause relative movement of the first and second cutting members to cause the cast material to be cut by cooperation of the cutting edges.

According to a third aspect of the invention there is provided a cutting assembly for a cast-cutter according to the first aspect.

According to a fourth aspect of the invention there is provided a cutting member for a cutting assembly according to the third aspect.

The invention includes one or more corresponding aspects, embodiments or features in isolation or in various combinations whether or not specifically stated (including claimed) in that combination or in isolation. For example, it will readily be appreciated that features recited as optional with respect to the first aspect may be additionally applicable with respect to the other aspects without the need to explicitly and unnecessarily list those various combinations and permutations here. Optional features as recited in respect of a method may be additionally applicable to an apparatus; and vice versa. For example, the apparatus may be configured to perform any of the acts or steps of a method.

In addition, corresponding means for performing one or more of the discussed functions are also within the present disclosure.

It will be appreciated that one or more embodiments/aspects may be useful in cutting casts.

The above summary is intended to be merely exemplary and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a cast-cutter in accordance with an embodiment of the present invention;

Figure 2 is a side view of the cast-cutter of Figure 1;

Figure 3 is an alternative side view of the cast-cutter of Figure 1 with a safety guard removed;

Figure 4 shows a side view of cutting members for use in the cast-cutter of Figure 1 in an open position;

Figure 5 shows a side view of the cutting members of Figure 4 in a closed position;

Figure 6 shows a perspective view of a portion of the cutting members of Figure 4;

Figure 7 shows an alternative perspective view of a portion of the cutting members of Figure 4;

Figure 8 shows a further alternative perspective view of the cutting members of Figure 4;

Figure 9 shows a detail perspective view of a portion of a preliminary portion of one of the cutting members of Figure 4;

Figure 10 shows a cross-sectional view of a portion of the cutting members of Figure 4 taken along line A-A shown in Figure 4;

Figure 11 shows a detail of the cross-section of Figure 10; Figure 12 shows a cross-sectional view of a portion of the cutting members of Figure 4 taken along line B-B shown in Figure 4;

Figure 13 shows a detail of the cross-section of Figure 10;

Figure 14 shows a front view of the cutting members of Figure 4;

Figure 15 shows a perspective front view of the cutting members of Figure 4;

Figure 16 shows a top perspective view of an alternative guard for use in the cast-cutter of Figure 1;

Figure 17 shows a bottom perspective view of the guard of Figure 16;

Figure 18 shows a rear perspective view of the drive connector for use in the cast-cutter of Figure 1;

Figure 19 shows a front perspective view of the drive connector of Figure 18.

DETAILED DESCRIPTION OF THE DRAWINGS

Reference is first made to Figures 1 and 2 of the drawings in which there is shown alternative views of a cast-cutter 10 in accordance with an embodiment of the present invention. The cast-cutter 10 comprises a body 12 incorporating a handle portion 14 and a head portion 16, upon which head portion is mounted a cutting assembly 18 (Figure 2). A safety guard 20 is secured to the head portion 16 to surround the cutting assembly 18. The safety guard 20 comprises a fixed portion 22 and a retractable portion 24 (Figure 1) pivotally mounted on the fixed portion 22 via pivot 26. The retractable portion 24 incorporates a lever 28 so that a user may retract portion 24, for example to align the cutting assembly 18 with a cast to be removed from a patient. The retractable portion 24 is shown in an extended position in Figure 1, and in a retracted position in Figure 2.

The cast-cutter 10 further comprises a main switch 30 and two safety switches

32, 34, all located on the handle 14, said switches 30, 32, 34 for activating the cutting assembly 18. Operation of the cutting assembly 18 is achieved by simultaneously activating the main switch 30 and one of the two safety switches 32, 34. The switching arrangement is such that a right handed operator may grip the handle 14 with their right hand and operate the main switch 30 with their trigger finger and safety switch 34 with their thumb, thus providing a comfortable operating position. Similarly, a left handed operator may grip the handle 14 with their left hand while operating the main switch with their trigger finger and safety switch 32 with their thumb, again providing a comfortable operating position.

In the embodiment shown, the cast-cutter 10 is operated by an electric D.C. motor (not shown) positioned within the body 12 and provided with electrical energy via electrical cable 36. As shown, the handle 14 is aligned with the intended direction of cut which provides a user with improved control when using the cast-cutter 10.

A visual light display 35 is provided which incorporates three LEDs 35a, 35b, 35c which are adapted to visually convey the operational status of the cast-cutter. In the embodiment shown, LED 35a indicates if power is being supplied to the cast- cutter 10, LED 35b indicates if one of the safety switched 32, 34 is depressed, and

LED 35c indicates if the main switch 30 has been depressed. Thus, when all LEDs are illuminated the cast-cutter is in operation.

Reference is now made to Figure 3 in which a portion of the cast-cutter 10 of Figures 1 and 2 is shown with the safety guard 20 removed to expose the cutting assembly 18. The cutting assembly 18 comprises a support member 38, a pivoting cutting member 40 pivotally mounted on the support member 38 via pivot 42, and a stationary cutting member 44 rigidly secured to the support member 38. The cutting members 40, 44 incorporate respective cutting edges 46, 48 which in use cooperate to cut a cast material by a shearing action.

The support member 38 is releasably mounted on the body 12 of the cast- cutter 10 via a bracket and bolting arrangement 50 (bolts not shown). Accordingly, the entire cutting assembly 18 may be removed from the cast cutter 10 for inspection, repair, resharpening or replacement or the like.

The pivoting cutting member 40 is releasably coupled to a reciprocating drive rod 52 via a fixing 54, such that the reciprocating rod 52 causes the pivoting member

40 to move relative to the fixed member 44 to effect cutting. The fixing 54 is advantageously a removeable component which assists to transmit reciprocal motion of the rod 52 to pivoting motion of the member 40. The reciprocating rod 52 is coupled to the electric motor (not shown) via a suitable transmission arrangement (also not shown).

In use, the retractable portion 24 (Figure 1) of the guard 20 may be retracted to position the edge of a cast to be removed between the cutting edges 46, 48 of the cutting members 40, 44. The cast-cutter 10 may then be activated by the switching arrangement 30, 32, 34 to move the pivoting cutting member 40 relative to the stationary cutting member to thus effect cutting of the cast material. The cast-cutter 10 may then be moved along the length of the cast to remove said cast from the patient, wherein the stationary cutting member slides between the cast and the patient's skin, thus acting to protect the patient from injury.

Figure 3 illustrates the cutting plane 80, which is substantially vertical, almost parallel with the plane of the paper in Figure 3. Perpendicular to the cutting plane 80, is the cast plane 82 for the cast (not shown), which is substantially horizontal in Figure 3. The cutting and cast planes 80, 82 intersect at the line of cut or projected line of cut 84, with an arrow 90 indicating the direction of cut.

Advantageously, in use, the cast-cutter 10 is manipulated to position a cast material to be removed from a patient between the first and second cutting members 40, 44, and subsequently activated to cause relative movement of the first and second cutting members 40, 44 to cause the cast material to be cut by cooperation of the cutting edges 46, 48.

The first and second cutting members 40, 44 of the cutting assembly 18 are arranged such that during a cutting operation the cutting edges 46, 48 are aligned with the projected cutting plane 80, such that the cutting edges 46, 48 are configured to engage and cooperate to produce a shearing strain in the cast material in order to cut the cast material along the projected cutting plane 80.

Referring now to Figure 4, there is shown a side view of cutting members 40, 44 for use in the cast-cutter 10 of Figure 1 in an open position.

The pivoting cutting member 40 comprises a preliminary portion 110. The preliminary portion 110 is configured to weaken or prepare a cast material prior to cutting through of the cast material by a shearing portion 112 of the cutting edge 46. The cast-cutter 10 is configured to weaken a first section or length of cast and also cut a second section or length of cast simultaneously. The second section or length of cast may have been previously weakened by the preliminary portion 110.

The preliminary portion 110 comprises a non-severing portion. The preliminary portion 110 is configured to deform or weaken the cast material at least primarily by a non-shearing action. The preliminary portion 110 is configured to perforate or puncture or soften and weaken or deform at least a portion of a layer, such as an outer or upper surface of a layer, of cast material. The preliminary portion 110 is configured to define an initial line of cut in the cast material for subsequent severing by the shearing portion 112.

The preliminary portion 110 is configured to at least primarily compressively deform or weaken the cast material prior to cutting through the cast material with the shearing portion 112. The cutting member 40 is configured or mounted to progressively shear the cast material as the cast material passes from a receiving or toe end of the cutting member 40 to a discharging or heel end of the cutting member 40. The cutting member 40 is configured or mounted to increasingly shear the cast material as the cast material passes from the receiving end to the discharging end. The cutting member 40 is configured or mounted to increasingly shear the cast material as the cast material passes along the cutting member 40, from the preliminary portion 110 to the shearing portion 112.

The preliminary portion 110 is configured to progressively weaken the cast material as the cast material passes along or adjacent the preliminary portion 110. The preliminary portion 110 is configured to progressively deform the cast material to an increasing depth as the cast material passes along or adjacent the preliminary portion 110. The preliminary portion 110 is configured to progressively weaken the cast material as it passes towards the shearing portion 112.

The preliminary portion 110 comprises a different property to the shearing portion 112. The different property comprises a different form of cutting edge. The different form of cutting edge comprises a different cutting geometry. The shearing portion 112 comprises a substantially continuous cutting edge. The preliminary portion 110 comprises a substantially discontinuous cutting edge.

The shearing portion 112 is configured to engage the cutting edge 48 of the stationary cutting member 44, such as to directly engage the cutting edge of the stationary cutting member 44 at at least a point or line of contact during cutting. The preliminary portion 110 is mounted so as not to engage, such as not to directly engage, the cutting edge 48 of the stationary cutting member 44 during cutting.

The preliminary portion 110 is configured to grip the cast material. The preliminary portion 110 is configured to prevent or resist movement of the cast material relative to the cast-cutter 10, such as longitudinal movement in the line of cut away from the shearing portion 112 or in a direction opposite to the direction of cut 90. The preliminary portion 110 is configured to grip the rigid layer of the cast.

The preliminary portion 110 is more distal to the pivot and support point 42 of the cutting member 40 relative to the shearing portion 112. The preliminary portion

110 exerts a proportionally greater torque on the pivot or support point 42 than the shearing portion 112, such as resulting from a similar resistive force from the cast material in the preliminary or shearing portions 110, 112 (e.g. due to a greater moment or lever arm). The preliminary portion 110 is configured to reduce torque transmitted to the pivot or support point 42. The preliminary portion 110 is configured to create a plurality of stress concentrations in the cast material, such as simultaneously during a single stroke or cycle of the cast-cutter 10. Creating a plurality of stress concentrations may reduce a resistive force or torque. The plurality of stress concentrations may enable the cutting member 40 to deform or penetrate deeper into the cast that may otherwise be possible.

The preliminary portion 110 comprises a toothed portion. The toothed portion comprises a plurality of teeth 114.

The plurality of teeth 114 may enable the cutting member 40 to deform or penetrate deeper into the cast that may otherwise be possible, such as with a continuous cutting edge.

The cutting member 40 is configured and mounted such that the teeth 114 move substantially in the direction of each tooth 114, such as towards and away from the points 116 of the teeth 1 14. The cutting member 40 is configured and/or mounted such that the teeth 114 move substantially in a non-sawing action. The cutting member 40 is configured and mounted such that the teeth 114 move substantially perpendicular to the arrangement of teeth 114.

The teeth 114 comprise generally similar tooth properties to each other, such as pitch, width, height, cutting angles and the like. Each tooth 114 comprises a taper, tapering towards a point 116 in the direction of the stationary cutting member 40 or the cutting plane 82 (e.g. for contacting or initially contacting the cast material with the point 116). The teeth 1 14 comprise a pitch (e.g. a wavelength) of about 1.7mm. The teeth 114 are evenly spaced or arranged.

The teeth 114 comprise a maximum opening or separation, such as between adjacent teeth 114 points, of about 1,2mm.

As can be seen in all of Figures 6 to 9, all of the teeth 114 are truncated. The point 116 of each tooth 114 is truncated. Each tooth comprises a truncated point such that each tooth has a length in the direction of cut at the point (e.g. the point of the tooth is a line or face, rather than a point).

The shearing portion 112 comprises a non-toothed portion. The shearing portion 112 comprises a non-serrated cutting edge.

As can be seen in the closed configuration of Figure 5, the preliminary portion 110 is mounted and configured such that a preliminary clearance is always provided between at least a section or length of the preliminary portion 110 and the cutting edge of the other cutting member 40 during cutting. The preliminary clearance is substantially in plane with or at least parallel to the cutting plane 80. The preliminary clearance is substantially perpendicular to the cast plane 82.

Providing a preliminary clearance between the preliminary portion 110 and the stationary cutting member 44 may enable the preliminary portion 110 to weaken or deform the cast material at least primarily by a non-shearing action. Providing a preliminary clearance between the preliminary portion 110 and the stationary cutting member 44 allows contacting engagement of the cutting members 40, 44 only in the severing or shearing portion 112. Providing a preliminary clearance between the preliminary portion 110 and the stationary cutting member 44 may reduce wear and/or prevent damage to one or both of the cutting members 40, 44.

The preliminary portion 110 is aligned with the shearing portion 112. The preliminary portion 110 is substantially collinear with the shearing portion 112.

As can be seen in Figures 10 to 13, the pivoting cutting member 40 comprises an angled cross-section perpendicular to the line of cut 90. The angled cross-section comprises a wedge. The wedge comprises a face 118 substantially parallel to the cutting plane 80. The wedge comprises a plurality of slopes. The wedge comprises a main or primary angle 120 relative to the cutting plane 80 or the face 118 substantially parallel to the cutting plane 80. The primary angle 120 is defined between a first slope 122 and the cutting plane 80 or the face 118 substantially parallel to the cutting plane 80. The primary angle 120 defines a general shape of the wedge. The wedge comprises a secondary angle 124 relative to the cutting plane 80 or the face 118 substantially parallel to the cutting plane 80. The secondary angle 124 is defined between a second slope 126 and the cutting plane 80 or the face 118 substantially parallel to the cutting plane 80. The secondary angle 124 defines a cutting angle at or towards the tip 116 or cutting edge 46 of the cutting member 44. The second slope 126 intersects the face 118 that is substantially parallel to the cutting plane 80.

The primary and secondary angles 120, 124 are substantially different. The secondary angle 124 is substantially greater than the primary angle. The secondary angle 124 is configured to provide an increased stiffness and strength, such as relative to the primary angle 120. The secondary angle 124 is configured to reduce or prevent damage to the tip 116 or cutting edge 46 of the cutting member 44.

The primary 120 angle is configured to reduce a force required to deform, cut or penetrate the cast material. The primary angle is about 20°. The secondary angle is about 87°.

The angled cross-section is substantially constant along at least sections or lengths of the cutting member 44. The angled cross-section is substantially constant along the length of the preliminary portion 110. The angled cross-section is substantially the same for each of the teeth 114 of the toothed preliminary portion 110.

The angled cross-section varies along at least sections or lengths of the cutting member 44. The angled cross-section varies between the preliminary portion 110 and the shearing portion 112 and along the shearing portion 112.

The primary and secondary angles 120, 124 are substantially constant along at least sections or lengths of the cutting member 44. The primary and secondary angles 120, 124 are substantially constant along the length of the preliminary portion 110. The primary and secondary angles 120, 124 are substantially the same for each of the teeth 114 of the toothed preliminary portion 110.

The primary and secondary angles 120, 124 are substantially the same between the preliminary portion 110 and the shearing portion 112. However, the primary angle 120 increases in the direction of cut 90 so as to assist in splaying the cast material or directing the cast material away from the cast or cutting planes 80, 82 as and after the cast is cut or cut through. The primary angle 120 increases progressively only in the shearing portion 112.

The thickness of the tip 130 of the cutting member 44 is substantially constant along at least a section or length of the cutting member 44. The thickness of the tip 130 of the cutting member 44 is substantially constant along the preliminary portion 110. The thickness of the tip 130 of all of the teeth 114 is substantially the same.

The thickness of the tip 130 of the cutting member 44 varies along at least a section or length of the cutting member 44. The thickness of the tip 130 of the shearing portion 112 is substantially greater than the thickness of the tip 130 of the preliminary portion 110.

The thickness of the tip 130 of the cutting member 44 varies along the shearing portion 112. The thickness of the tip 130 of the cutting member 44 progressively increases along the length of the shearing portion 112 in the direction of cut 90.

Increasing the thickness of the tip 130 increases the resistance of the cutting member 44 to flexing or damage or wear, such as under loading or repeated loading. Providing an increased tip thickness in the shearing portion 112 provides for an increased rigidity, such that a contacting engagement between the cutting members

40, 44 is ensured in the shearing portion 112.

Providing a decreased thickness and teeth 114 in the preliminary portion 110 enables an increased stress concentration, such as due to a reduced contact surface area between the preliminary portion 110 and the cast material.

The tip thickness 130 is at least partially defined by the length of the second slope 126.

The cutting members 40, 44 are arranged to define an opening 140 therebetween in or parallel to the cutting plane. The opening 140 comprises a V-shape pointing in the direction of cut 90, with the opening 140 generally greater to receive the cast initially, such as in the preliminary portion 110. The cutting members 40, 44 define a shearing angle 150 therebetween. The shearing angle 150 is defined at or adjacent a point of contact, overlap or crossover 160 of the cutting members 40. The shearing angle 150 is substantially constant along at least sections of the cutting assembly. The shearing angle 150 varies as the cutting members 40, 44 move relatively, as can be seen comparing Figures 4 and 5. The shearing angle 150 varies between about 10° and about 15.

The preliminary portion 110 is configured to enable a greater shearing angle

150. The preliminary portion 110 is configured to grip the cast such that the cast is prevented or at least restricted in longitudinal movement out of the opening 140, opposite to the direction of cut 90, such as due to a longitudinal component or vector of force resulting from the shearing angle 150 between the cutting members 40, 44.

The preliminary portion 110 is configured to enable a greater shearing angle

150 of at least a section of the shearing portion 112 (e.g. than would otherwise be enabled, without undue movement of the cast out of the opening 140).

An increased shearing angle 150 enables a reduced overall length of cutting assembly 18 or a reduction in resistive or cutting force or torque, such as instantaneous and/or total resistive or cutting force or torque.

Referring now primarily to Figures 14 and 15, the stationary cutting member 44 comprises a protrusion 166 to guide the cast into the opening 140 between the cutting members 40, 44. The protrusion 166 is positioned or located on or extends to an opposite side of the cutting plane 80 to the cutting edge 48 of the stationary cutting member 44. The protrusion 166 is positioned or located on or extend to an opposite side of the cast plane 82 to the cutting edge 48 of the stationary cutting member 44.

The protrusion 166 is configured to at least resist movement of the cast longitudinally and/or laterally out of the opening 140, such as against the direction of cut 90 (e.g. due to a longitudinal component or vector of force resulting from the shearing angle between the cutting members).

The protrusion 166 is configured to define a portion or section of reduced shearing angle 150 between the cutting members 40, 44. In the embodiment shown, the portion or section of reduced shearing angle 150 comprises a negative shearing angle 168, as can be seen in Figure 4 and 5. The protrusion 166 is configured to force cast into the opening 140 as a result of the relative movement of the cutting members

40, 44 towards each other 44, 40. The protrusion 166 is positioned or located so as to provide a direct counterforce to the other cutting member 40, which is the pivoting cutting member 40 in the embodiment shown, such as to resist relative splaying of the cutting members 40, 44. The protrusion 166 acts as an anvil to a corresponding portion of the pivoting cutting member 40. The protrusion 166 never comes into contact with the pivoting cutting member 40. The cutting assembly 18 is configured not to overlap or crossover the cutting members 40, 44 (e.g. when viewed perpendicular to the cutting plane 80) at the protrusion 166.

Figures 16 and 17 show perspective views of an alternative guard 220 for use in the cast-cutter 10 of Figure 1. The guard 220 is generally similar to that shown in

Figure 1, with similar features indicated by similar reference numerals incremented by 200. Accordingly, the safety guard 220 has a fixed portion 222 and a retractable portion 224 moveably mounted on the fixed portion. In this embodiment, the retractable portion 224 is adapted to be retracted to permit access to the cutting assembly 18, for example to engage a cast material during a cast removal operation.

Here, the retractable portion 224 is pivotally mounted on the fixed portion 222.

The retractable portion 224 is mounted so as to prevent removal of the retractable portion 224. The retractable portion 224 is mounted on or within the fixed portion such that the retractable portion 224 is non-removable from the fixed portion 222, at least in normal use. The retractable portion 224 is substantially permanently mounted to the fixed portion 222, such as by the mounting of the pivot 226 to allow the retractable portion 224 to pivot.

Referring now primarily to Figures 18 and 19, which show perspective views of the drive connector 54 for use in the cast-cutter 10 of Figure 1. The drive pin 52 is coupled to the stationary cutting member 40 via the connector 54. The connector 54 comprises an engagement portion 400 for transferring drive between the drive pin 52 and the cutting member 40. The engagement portion 400 is configured to eliminate play between the connector 54 and the cutting member 40. The connector 54 is substantially rigidly connected to the drive pin 52 via snap-fit 300. The engagement portion 400 comprises an interference fit between the connector 54 and the cutting member 40. A number of embodiments have been described above in accordance with aspects of the present invention. It should be appreciated that these various embodiments may be used in various combinations and are not limited for use as specifically shown and described.

It will be appreciated that any of the aforementioned apparatus may have other functions in addition to the mentioned functions, and that these functions may be performed by the same apparatus.

The applicant hereby discloses in isolation each individual feature described herein and any combination of two or more such features, to the extent that such features or combinations are capable of being carried out based on the present specification as a whole in the light of the common general knowledge of a person skilled in the art, irrespective of whether such features or combinations of features solve any problems disclosed herein, and without limitation to the scope of the claims. The applicant indicates that aspects of the present invention may consist of any such individual feature or combination of features. It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the invention.