Ihis invention relates to knives having removable protective covers for their cutting edges. The invention is particularly applicable to the design and manufacture of disposable surgical scalpels, but is also applicable to other knives, such as for model making or other domestic uses.

In accordance with a feature of the invention, a knife comprises a plastics moulded handle, to which a knife blade is secured, and a removable protective cover, for at least the cutting edge of the blade, formed integrally with the handle.

In a preferred form of the invention, both an end portion of the handle and the cover are each moulded in two generally co-planar halves connected together along a common fold line, and the halves of the cover are connected frangibly to the halves of the handle part, so that a blade can be located and secured in position by folding over the moulding and securing the respective halves together (as by welding). This preferred form of the invention will now be described by way of example, with reference to the accompanying drawings, in which:

Figs. 1 and 2 show a disposable scalpel with the cover in position to protect the blade, and having been removed, respectively; and

Figs. 3 and 4 are views of the unitary moulding for the handle and cover, as moulded, from opposite sides.

The scalpel shown in Figs. 1 and 2 comprises a handle 1 having a blade 2 set into one end of the handle, and a removable protective cover 3, which com¬ pletely envelops the blade as shown in Fig. 1, until removed for use of the scalpel (Fig.2).

As will be described in detail below, the cover 3 is formed integrally with the handle and is actually closed and formed in the same operation in which the blade is secured in position, thus assuring the integrity of the blade edge from that time on, until deliberately removed when the scalpel is to be used. The side walls of the cover are formed with matching notches 4 each having the form of an acute angle with a circular recess 5 at the apex, the recess having an arcuate extent in excess of l8θ°. The adjacent end portion 6 of the handle is shaped, on either side of the blade, to fit easily into the notch 4 and terminates in a part-circular tip 7 located in the recess 5« The cover 3 _. which is otherwise separate from the handle, is removed by pulling it longitudinally away from the handle, the resilience of the material enabling the tips 7 to snap out the corresponding recesses $ _*

Although the cover of a disposable surgical scalpel does not strictly need to be replaced, since the scalpel should be used for only one incision, the cover can be snap fitted back into position if desired, e.g. to shield the edge for disposal of the scalpel.

For knives intended for repeated use, the interconnec¬ ting portions can be dimensioned to be more durable to withstand repeated engagement and disengagement of the parts. Figs. 3 and 4 show the plastics parts of the

knife on a larger scale, in the form in which they are moulded.

The major part of the handle is solid, of a generally flattened rectangular cross-section, but the end portion of the handle is formed in two generally co-planar halves 5,9 connected together along a fold line 10. The cover is correspondingly formed in two halves 11,12 connected to each other along an exten¬ sion 13 of the fold line 10. The cover halves are connected to the handle halves only by frangible arcuate webs 15 around the tips 7, as seen in Fig. 3, which shows the eventual outer surfaces of the respective halves.

As seen in Fig. 4 _. the interior surfaces of the cover halves are completely smooth and planar, except for slightly raised boundary wall portions 11A, 12A extending along two sides. These portions have in turn a number of energy director pips 14 for eventual welding of the wall portions together by ultrasonic welding.

The inner surface of the handle half 8 is generally planar, except for raised rib 16 shaped to fit a standard, elongate hole in a scalpel blade. The rib also has two raised circular pips 17 and elongate energy directors lδ.

The inner surface of the other half 12 is planar except for two circular recesses 19 destined to receive the pips 17 when the halves are folded over against each other. At the transition between the solid portion of the handle and the adjacent edge of the half portion 8, there is a chamfered surface 20 having an energy director rib 20'. The corresponding rear edge 21 of the half 9 is also chamfered to mate with the surface 20.

In assembly, a finished blade is positioned over the rib 16, and the half portions 9 and 12 are folded over through lδθ° about the common fold line 10,13. and ultrasonically welded to their opposite halves at the locations of the energy directors 14 , 1S and 20.

During these operations, the frangible webs 15 are ruptured, so that the cover is retained to the handle by the engagement of the tips 7 in the recesses 5 _> any residue of the frangible web is readily ruptured by the act of deliberate removal of the cover. The scalpel is now ready for packaging and despatch to its eventual destination.

The main advantages of the scalpel are: that the handle and cover are formed from a single moulding; the act of securing the blade to the handle also completes the cover, iri situ over the blade; the blade edge is protected from the time the blade is secured to the handle; the cover is securely positioned against inadvertent removal; the blade is firmly secured in the handle and supported from both sides, by virtue of the sandwich construction.