GB1605003A

GB1605003A - Adjustable-depth cutting apparatus

Info

Publication number: GB1605003A
Application number: GB3725180A
Authority: GB
Original assignee: OEC Europe Ltd
Current assignee: OEC Europe Ltd
Priority date: 1978-05-05
Filing date: 1978-05-05
Publication date: 1981-12-16

Description

(54) IMPROVEMENTS IN OR RELATING TO ADJUSTABLE-DEPTH CUTTING APPARATUS (71) We, OEC EUROPE LIMITED, formerly Zimmer Orthopaedic Limited, a British company, of 134 Brompton Road, London, SW3., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: According to the present invention, there is provided adjustable-depth cutting apparatus, comprising first and second parts turnable relatively to each other about a first axis, a reference, supporting surface provided on said first part for moving on a body to be cut, a third part extending in a direction transverse to said first axis for carrying a cutting blade, articulating means having an axis of articulation parallel to said first axis articulating said third part to one of the first and second parts, and a pin-and-slot connection connecting said third part to the other of the first and second parts, the pin having a longitudinal axis parallel to said first axis and said axis of articulation, and the slot extending in said direction, the arrangement being such that turning of said first and second parts relatively to each other displaces a cutting blade carried by said third part towards or away from said reference, supporting surface.

In order that the invention may be clearly understood and readily carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows a perspective view of a powered dermatome, Figure 2 shows a party sectional side elevation of the powered dermatome, Figure 3 shows an axial section through reciprocatory driving apparatus of the powered dermatome, Figure 4 shows a fragmentary perspective view of a detail of the reciprocatory driving apparatus, Figures 5A to 5D show in diagrammatic axial section respective stages during the operation of the driving apparatus.

Figures 6A and 6B show the powered dermatone in front elevation illustrating a dermatome blade and its mounting in respective differing positions, and Figure 7 shows a section taken on the line VII-VII of Figure 2.

Referring to the drawings, the powered dermatome includes a cylindrical casing 1 which contains a reciprocatory driving apparatus. This reciprocatory driving apparatus includes a compressed-air motor in the form of a double-acting piston-and-cylinder device 2, a valve device 3 arranged to control the supply of compressed air to one end and the other end, alternately, of the device 2, and a mechanical force-transmitting device 4 by way of which the device 2 operates the valve device 3. The device 2 comprises a piston 5 and a cylinder 6 co-axial with the casing 1. The piston 5 is fixed to a piston rod 7 which is co-axial with the casing 1 and which projects through a flanged bush 8 itself protruding coaxially from the forward end of the casing 1. Attached to the rear end of the piston rod 7 is a rigid hooked member 9 of the device 4. The device 4 also includes a toggle mechanism 10, which is most clearly seen from Figure 4. The toggle mechanism 10 comprises two rigid U-shaped members 11 and 12 mounted for turning about the outer ends of their arms, the arms of each U-shaped member 11 or 12 being directed towards the arms of the other U-shaped member 12 of 11. Fixed to the casing 1 are pins 13 which extend radially of the casing and coaxially with each other. At their inner ends, these pins 13 are formed as knife-edge bearings 14 for the outer ends of the arms of the U-shaped members 11 and 12. A helical tension spring 15 is attached to the respective bases of the respective U-shaped members 11 and 12 and thus tends to urge these bases towards each other. The member 9 is hooked under the base of the member 11, whilst another rigid hooked member 16 of the device 4 is hooked under the base of the member 12. The device 3 is in the form of a slide valve comprising a fixed valve member 17 encircling a reciprocatory valve member 18 attached to the member 16. The member 18 is formed with peripheral grooves 19 whereby the ports of the member 17 can appropriately communicate with each other. The ports of the member 17 include a compressed air inlet port 20. The port 20 is connected downstream of a bore-form inlet duct 21 extending axially through a flanged bush 22 co-axial with the casing 1 and closing the rear end thereof. The rear end of the bush 22 is internally threaded at 23 to be screwed to an end of a compressed air line (not shown). The rear end of the bush 22 is also externally screwthreaded to receive an internally threaded ring 24 which internally bounds an outlet duct for exhaust air. Intersecting the duct 21 is a diametral bore 25 in the bush 22, this bore being closed at one end and there receiving a helical compression spring 26 and open at its other end and there receiving an air flow regulating rod 27 which is linearly displaceable to project into the duct 21 to an adjustable extent. Co-axially encircling the bush 22 and the ring 24 is a control sleeve 28 which is rotatable about its own axis and is formed internally with a camming surface 29 bearing against the outer end of the rod 27. It will be appreciated that, on rotation of the sleeve 28 about its own axis, the camming surface 29 converts that rotary motion into linear motion of the rod 27 along the bore 25 and thus regulates the flow of compressed air along the duct 21. The rod 27 can in fact be displaced to a condition in which it completely blocks the duct 21 and thus reduces the rate of flow of compressed air along the duct 21 to zero.

The provision of the toggle mechanism 10 has the advantage that, in spite of the fact that the valve device 3 is operated by the device 2, the valve device 3 is not changed-over until very shortly before the piston 5 reaches each end of its stroke, so that the powered proportion of each stroke of the piston 5 is almost the whole of the stroke. The spring 15 is effectively used to delay the change-over by storing energy supplied by the piston 5 until substantially the last possible moment for the change-over. The manner of operation of the toggle mechanism will be most clearly understood from Figures 5A to SD Figure 5A shows the piston 5 approaching its right-hand end position. In this condition of the reciprocatory driving apparatus, the reciprocatory valve member 18 is in its left-hand end position in which the inlet port 20 communicates with the left-hand end of the cylinder 6 and the right-hand end of the cylinder 6 communicates with an exhaust port 30. The U-shaped member 12 is in its left-hand end position of swing, whilst the U-shaped member 11 is approaching its right-hand end position of swing. As the member 11 passes through the dead-centre condition of the mechanism 10, which occurs when the piston 5 is almost at its right-hand end position, the spring 15 almost instantaneously swings the member 12 into its right-hand end position of swing shown in Figure 5B. Thus, bia the member 16, the valve member 18 is displaced almost instananeously into its right-hand end position in which, as shown in Figure 5B, the inlet port 20 communicates with the right-hand end of the cylinder 6 whilst the left-hand end of the cylinder 6 communicates with an exhaust port 31. This causes the piston 5 to perform its leftward stroke. During this leftward stroke, the member 11 is swung leftwards by the member 9, Figure 5C showing the piston 2 and the member 11 approaching their left-hand end positions. Again, as the dead-centre condition of the toggle mechanism 10 is passed, the member 12 is almost instantaneously swung into its left-hand end position shown in Figure SD, the member 18 simultaneously being displaced into its left-hand end position. The piston 2 now performs its rightward stroke towards the position shown in Figure 5A, whereupon the cycle is repeated.

The piston rod 7 is capped at its outer end by a cylindrical bush 32 fixed co-axially thereto by a screw 33. The bushes 8 and 32 are closely encircled by an adjusting sleeve 34 which is so mounted on the bushes 8 and 32 as to be turnable about the axis thereof. Extending parallelly to this axis and force-fitted into a bore in the sleeve 34 is a pin 35 on which is pivotally mounted a lever 36. At its inner side the lever 36 has a cam surface 37 of varying radial spacing from the axis of the pin 35. The lever 36 also has two outer surfaces 38 and 39 which extend at right-angles to each other. On the user pressing on the surface 38 in one sense about the pin 35, the cam surface 37 is jammed against the bush 8 to retain the sleeve 34 in a desired position of turning about the bush 8, whilst, on pressing of the surface in the opposite sense about the pin 35, the surface 37 is unjammed from the bush 8. so that the sleeve 34 is turnable about the bush 8. A pin 40 having a head 41 extends parallel to the axis of the casing 1 and is force-fitted into a bore in the bush 8. The pin 40 passes with clearance through a bore 42 in the bush 32 and also through a key-hole slot 43 in an arm 44 of a mounting 45. The arm 44 extends perpendicularly to the axis of the casing 1, and the key-hole slot 43 extends along the arm 44. The head 41 is of a diameter which is too great to pass through the narrower portion of the key-hole slot 43 but which is small enough to pass with clearance through the wider portion of that slot. The mounting 45 is pivotally mounted on a pivot pin 46 which extends parallelly to the axis of the casing 1 and is force-fitted into a bore in the sleeve 34. The mounting 45 is a sliding fit on the pin 46. The mounting 45 has been moulded from thermoplastics and, during the moulding, has had a steel cutting blade 47 moulded therein so that the mounting and the blade form a unit. The blade 47 and its cutting edge extend along the mounting 45. Also force-fitted in a bore in the sleeve 34 is a pin 48 which extends parallelly to the axis of the casing 1 and carries co-axially rollers 49 which act as reference supports rolling over the surface of the skin and/or flesh to be sliced off by the reciprocatory blade 47. Relative turning of the sleeve 34, on the one hand, and the bushes 8 and 32, on the other hand, not only adjusts the depth of cut of the dermatome, which is determined by the spacing between the cutting edge of the blade 47 and the rollers 49, but can also bring the pin 40 to a condition in which it is aligned with the wider portion of the slot 43. Figures 6A and 6B illustrate such relative turning. In the relative position shown in Figure 6A, in which the pin head 41 is in the illustrated full-line position relative to the pin 48, the depth of cut is at a minimum. In this minimum depth setting, the dermatome is used particularly for removal of good skin for skin grafting. In the relative position of the pin head indicated by the dot-sash line 41' in Figures 6A and 6B, the depth of cut is at a maximum. In this maximum depth setting, the dermatome is used for removal of burnt flesh and skin. Continued relative turning of the pin 40 and the pin 48 brings the pin head into the position 41" shown in Figure 6B, affd in which the mounting 45 and the blade 47 can be slid along the pin 46 to remove them as a unit from the remainder of the dermatome. This arrangement has the advantage that the mounting and blade can be manufactured as a disposable unit to be thrown away after use and replaced by a new unit.

WHAT WE CLAIM IS: 1. Adjustable-depth cutting apparatus, comprising first and second parts turnable relatively to each other about a first axis, a reference, supporting surface provided on said first part for moving on a body to be cut, a third part extending in a direction transverse to said first axis for carrying a cutting blade, articulating means having an axis of articulation parallel to said first axis articulating said third part to one of the first and second parts, and a pin-and-slot connection connecting said third part to the other of the first and second parts, the pin having a longitudinal axis parallel to said first axis and said axis of articulation, and the slot extending in said direction, the arrangement being such that turning of said first and second parts relatively to each other displaces a cutting blade carried by said third part towards or away from said reference, supporting surface.

2. Apparatus as claimed in claim 1, wherein said first part is said one of said first and second parts.

3. Apparatus as claimed in claim 1 or 2, wherein said first part encircles and is arranged to turn about said second part.

4. Apparatus as claimed in any preceding claim, wherein said slot is a key-hole slot and said pin is formed with a shoulder which can be passed in a direction of said longitudinal axis through the wider portion of said key-hole slot but not through the narrower portion thereof, the arrangement being such that, in an end position of relative turning of the first and second parts, the pin extends through said wider portion and said third part can be displaced in a direction of said longitudinal axis to dismount said third part from said first and second parts.

5. Apparatus as claimed in any preceding claim, wherein said reference, supporting surface is a peripheral surface of a roller rotatably mounted on said first part and having its axis of rotation parallel to said first axis, said axis of articulation and said longitudinal axis.

6. Apparatus as claimed in any preceding claim, and further comprising releasable means arranged to hold said first and second parts in a desired relative position of turning.

7. Apparatus as claimed in claim 6 as appended to claim 3, wherein said releasable means comprises a cam turnably mounted on said first part and arranged to jam against a surface of said second part.

8. Apparatus as claimed in claim 1, 2, or 3, wherein said third part is readily removably connected to said first and second parts so that said third part and said blade can be readily removed therefrom as a unit.

9. Apparatus as claimed in claim 8, wherein said articulating means comprises a pivot pin which projects from said one of the first and second parts and on which said third part is pivotally borne, said third part being readily removable from said pivot pin by displacement along said pivot pin.

10. Apparatus as claimed in any preceding claim, and further comprising a fluidoperated piston-and-cylinder device arranged to reciprocate said third part and thus said blade longitudinally of said first axis, valve means arranged to control the supply of operating fluid to said device, and transmission means connecting said device to said valve means for operating said valve means to reverse the sense of operation of said device, said transmission means including delaying means for delaying operation of said valve means

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. on a pivot pin 46 which extends parallelly to the axis of the casing 1 and is force-fitted into a bore in the sleeve 34. The mounting 45 is a sliding fit on the pin 46. The mounting 45 has been moulded from thermoplastics and, during the moulding, has had a steel cutting blade 47 moulded therein so that the mounting and the blade form a unit. The blade 47 and its cutting edge extend along the mounting 45. Also force-fitted in a bore in the sleeve 34 is a pin 48 which extends parallelly to the axis of the casing 1 and carries co-axially rollers 49 which act as reference supports rolling over the surface of the skin and/or flesh to be sliced off by the reciprocatory blade 47. Relative turning of the sleeve 34, on the one hand, and the bushes 8 and 32, on the other hand, not only adjusts the depth of cut of the dermatome, which is determined by the spacing between the cutting edge of the blade 47 and the rollers 49, but can also bring the pin 40 to a condition in which it is aligned with the wider portion of the slot 43. Figures 6A and 6B illustrate such relative turning. In the relative position shown in Figure 6A, in which the pin head 41 is in the illustrated full-line position relative to the pin 48, the depth of cut is at a minimum. In this minimum depth setting, the dermatome is used particularly for removal of good skin for skin grafting. In the relative position of the pin head indicated by the dot-sash line 41' in Figures 6A and 6B, the depth of cut is at a maximum. In this maximum depth setting, the dermatome is used for removal of burnt flesh and skin. Continued relative turning of the pin 40 and the pin 48 brings the pin head into the position 41" shown in Figure 6B, affd in which the mounting 45 and the blade 47 can be slid along the pin 46 to remove them as a unit from the remainder of the dermatome. This arrangement has the advantage that the mounting and blade can be manufactured as a disposable unit to be thrown away after use and replaced by a new unit. WHAT WE CLAIM IS:

1. Adjustable-depth cutting apparatus, comprising first and second parts turnable relatively to each other about a first axis, a reference, supporting surface provided on said first part for moving on a body to be cut, a third part extending in a direction transverse to said first axis for carrying a cutting blade, articulating means having an axis of articulation parallel to said first axis articulating said third part to one of the first and second parts, and a pin-and-slot connection connecting said third part to the other of the first and second parts, the pin having a longitudinal axis parallel to said first axis and said axis of articulation, and the slot extending in said direction, the arrangement being such that turning of said first and second parts relatively to each other displaces a cutting blade carried by said third part towards or away from said reference, supporting surface.

until said device its in almost a stroke end condition.

11. Apparatus as claimed in claim 10, wherein said transmission means consists of mechanical force-transmitting means and said delaying means comprises mechanical energy-storing means.

12. Apparatus as claimed in claim 11, wherein said energy-storing means comprises a spring.

13. Apparatus as claimed in claim 12, wherein said delaying means comprises a toggle mechanism.

14. Apparatus as claimed in claim 13, wherein said transmission means comprises first and second relatively rigid U-shaped members of said mechanism mounted for turning about the outer ends of their arms, the arms of each U-shaped member being directed towards the arms of the other U-shaped member, a relatively rigid member by way of which said device is connected to the first U-shaped member for turning the same, and another relatively rigid member by way of which the second U-shaped member is connected to said valve means for operating the same, said spring being attached to the first and second U-shaped members at respective locations spaced from said outer ends.

15. Apparatus as claimed in claim 14, and further comprising knife-edge bearing means on which said outer ends bear.

16. Apparatus as claimed in anyone of claims 10 to 15, wherein said valve means comprises a slide valve.

17. Apparatus as claimed in any one of claims 10 to 16 and further comprising a regulating valve arranged to regulate the rate of flow of operating fluid to said valve means and thus to said device.

18. Apparatus as claimed in claim 17, wherein said regulating valve can reduce said rate of flow to zero.

19. Apparatus as claimed in claim 17 or 18, wherein said regulating valve comprises a fluid flow duct, a flow-regulating member extending transversely of said duct and linearly displaceable to project into said duct to an adjustable extent, a sleeve encircling said flow-regulating member and said duct and mounted for turning about its own axis, and an internal camming surface of said sleeve bearing against said flow-regulating member and arranged to convert turning motion of said sleeve to linear motion of said flow-regulating member.

20. Apparatus as claimed in any one of claims 10 to 19, wherein said piston-andcylinder device is double-acting and said valve means is arranged to control the supply of operating fluid to one end and the other end, alternately, of the cylinder.

21. A dermatome, substantially as hereinbefore described with reference to the accompanying drawings.