GB2547665A - Safety knife - Google Patents

Abstract

Safety knife comprising; a tubular knife body 12, blade carriage or carrier 16 that is at least part cylindrical in cross-section and located within the knife housing, a spring 40 applying biasing load to retract the knife, an actuator 36 secured to the carriage and projecting through a slot 34 formed in the body to allow the carriage to be driven against the biasing load. The slot comprises a first 34a and second 34b sections, in the intermediate section 34c between 34a and 34b the blade carriage undergoes angular movement relative to the body. The knife blade may be scalpel like with an actuator of rectangular cross-section. The actuator may be configured so that movement through intermediate section can only occur after adjusting the orientation of the actuator. The knife body may be metallic, textured or patterned.

Description

Safety Knife

This invention relates to a safety knife, and in particular to a knife of the type in which a blade thereof is stowed within a body of the knife when the knife is not in use, a biasing mechanism being provided to retract the blade into the body. More particularly, the invention relates to a knife of the type in which the blade thereof can be replaced. A number of designs of safety knife are known. Indeed, a number of designs are known in which a blade is retracted into a body of the knife when not in use, and in which a spring or other biasing means is provided to retract the blade into the knife body.

Knives are in widespread use in undertaking a range of craft activities and the like, the knives typically including a small, scalpel like blade mounted upon a handle. Often, the blade is non-movably mounted upon the handle. As a result, when not in use, the blade is still exposed and may present an accident or injury risk. With some designs, a cover is provided to allow the blade to be covered when not in use, but the covers often become lost and so there is still a risk of injury occurring when the knife is not in use and the blade is exposed. Furthermore, fitting the cover may itself present a risk of injury.

Where knives of the above described type are designed in such a manner that the blade can be replaced after use, the replacement process typically requires the user to pull or otherwise manipulate the blade to release it from the handle which may carry an injury risk.

It is an object of the invention to provide a knife in which at least some of the disadvantages associated with known knife designs are overcome or are of reduced effect.

According to the present invention there is provided a safety knife comprising a tubular knife body, a cylindrical or part cylindrical blade carriage located within the knife body, a spring applying a biasing load to the carriage urging the carriage in a retracting direction, and an actuator secured to the carriage and projecting through a slot formed in the body to allow the carriage to be driven against the biasing load to an extended position, wherein the slot comprises a first section, a second section offset from the first section, and an intermediate section between the first and second sections, wherein the carriage undergoes angular movement relative to the body as the actuator passes along the intermediate section. A blade mounted upon the carriage is normally located entirely within the body, the carriage being positioned such that the actuator is located at an end of the first section of the slot. When it is required to expose the blade for use, the actuator is moved along the first section of the slot. After use, the actuator is released and the blade retracted under the action of the spring. When it is desired to replace the blade, the actuator is moved completely along the first section, through the intermediate section, and along the second section to a position in which the blade can be detached from the carriage and replaced by a new blade. As the carriage has to be rotated or moved angularly relative to the body in order to undertake this movement, accidental movement of the carriage to this position is unlikely to occur.

Conveniently, the actuator is designed such that it has to be rotated in order to allow it to pass along the intermediate section. By way of example, the part of the actuator located within the slot may be of rectangular cross section and the width of the sections of the slot selected such that movement of the actuator along the intermediate section can only occur after adjusting the orientation of the actuator. Accordingly, accidental movement of the knife to a blade replacement position is resisted.

Alternatively, a detent or other mechanism may be provided to restrict the passage of the actuator along the intermediate section.

The slot may be designed such that the blade can be held in one or more exposed positions, if desired.

The body is conveniently of cylindrical shape.

The carriage is preferably of two part form, including a main part and a retainer attachable to the main part and arranged such that when the carriage is located within the knife body, the main part and the retainer cooperate with one another to retain a blade to the carriage.

The carriage is preferably provided with a threaded part to which the spring is secured. An opposite end of the spring is preferably secured to a threaded part of a plug that closes an end of the body.

The body may be provided with a surface texture, for example for aesthetic purposes or to aid gripping of the body in use. By way of example, a series of grooves or ridges may be provided. Alternatively, it may have a knurled finish.

It is envisaged that the body will be of metallic form, for example of steel or aluminium form. However, other materials may be used. By way of example, suitable plastics materials may be used. Indeed the body could be of a transparent plastics material if desired.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic view illustrating a knife in accordance with an embodiment of the invention; and

Figures 2 and 3 are views similar to Figure 1 illustrating the knife in other operating positions.

Referring to the accompanying drawings, a safety knife 10 is illustrated. The knife 10 comprises a knife body 12 of cylindrical tubular metallic construction. One end of the body 12 is closed by a plug 14. The other end is open. By way of example, the body 12 may be of steel or aluminium form. Although not shown, the body 12 may be provided with a surface pattern or texture. The pattern or texture may be intended to enhance the aesthetic appearance of the body 12. Additionally, or alternatively, it may be intended to assist a user in gripping the body 12. By way of example, the pattern or texture may take the form of a series of spaced grooves extending longitudinally of the body 12, a series of annular grooves, or helical grooves. Other options include providing the outer surface of the body 12 with a knurled finish or the like.

Whilst the knife body 12 shown is of metallic construction, it will be appreciated that the invention is not restricted in this regard and other materials may be used. By way of example, suitable plastics materials may be used. If desired, the material of the body 12 may be of transparent form, allowing the interior of the knife to be visible.

Within the knife body 12 is located a blade carriage 16 which carries a blade 18. The carriage 16 is of two part form, comprising a main part 20 and a retainer 22. The main part 20 is of generally cylindrical form, the diameter of which is substantially equal to the internal diameter of the body 12 such that the main part 20 is capable of sliding axially within body 12 and is capable of undergoing angular movement relative to the body 12. As shown, the main part 20 is shaped to include a flat 24, the flat 24 having lugs 26 projecting therefrom. A channel 28 is formed on the flat 24.

The retainer 22 is shaped to be received against the main part 20 adjacent the flat 24, a rib 30 of the retainer 22 being received within the channel 28.

In use, the blade 18, which is of scalpel like form in this embodiment, is located between the flat 24 and the retainer 22, the lugs 26 extending through openings formed in the blade 18. With the carriage 16 located within the body 12, the retainer 22 is held captive to the main part 20 by virtue of the engagement of the rib 30 within the channel 28, and the blade 18 is held captive to the carriage 16 by virtue of the lugs 26 extending through the openings formed in the blade 18.

The body 12 is formed with a slot 34. As shown in Figures 1 to 3, the slot 34 includes a first section 34a, a second section 34b offset from the first section 34a, and an intermediate section 34c interconnecting the first and second sections 34a, 34b. The slot 34 further includes a third section 34d substantially aligned with the intermediate section 34c.

An actuator 36 is rotatably mounted upon the carriage 16 and projects through the slot 34. The part 36a of the actuator 36 located within or riding along the slot 34 is of rectangular cross sectional shape, having a width substantially equal to the widths of the first, second and intermediate sections 34a, 34b, 34c, and a length greater than the widths of the first, second and intermediate sections 34a, 34b, 34c. At its end, the second section 34b includes an enlarged diameter part.

An end part of the carriage 16 remote from the blade 18 is formed with a screw threaded projection 38 onto which an end of a spring 40 is screwed, the opposite end of the spring 40 being screwed onto a threaded projection forming a part of the plug 14.

At rest, the spring 40 applies a biasing load to the carriage 16 urging the carriage 16 towards a retracted position in which the blade 18 is located entirely within the body 12 as shown in Figure 1. In this position, the actuator 36 is located at or adjacent an end of the slot 34.

From the rest position, when it is desired to use the knife, the actuator 36 is manipulated to drive the blade 18 to an exposed position. The manipulation of the actuator 36 involves driving the actuator towards the opposite end of the first section 34a of the slot 34. It will be appreciated that this movement of the carriage 16 is against the biasing load applied by the spring 40. If the actuator 36 is released, then the spring 40 will serve to return the knife to the condition shown in Figure 1, retracting the blade 18 into the knife body 12, and so minimising the risk of accident or injury.

If desired, as shown in Figure 2, once the blade 18 has been moved to the exposed position, the actuator 36 can be moved into the third section 34d of the slot 34 to hold the blade 18 in its exposed position. In order to allow this, the width of the third section 34d is greater than the widths of the other sections of the slot 34, being wide enough to accommodate the length of the part of the actuator 36 located within the slot 34.

Should it be desired to replace the blade 18, then with the knife in the condition in which the blade is exposed, the actuator 36 is moved through 90 degrees to align the width of the part 36a with the width of the intermediate section 34c, after which the actuator 36 can be driven along the intermediate section 34c, the carriage 16 rotating relative to the body 12 during this movement, to the second section 34b. After rotation of the actuator 36 through a further 90 degrees, the actuator 36 can be driven along the length of the second section 34b to partially expose the carriage 16 as shown in Figure 3. Rotation of the actuator 36 through a further 90 degrees can be used to latch the actuator 36 in this position at the enlarged end part of the second section 34b.

With the knife in the condition shown in Figure 3, the retainer 22 can be lifted away from the main part 20 of the carriage 16, allowing the blade 18 to be removed and replaced. The retainer 22 can then be refitted. Subsequent release of the actuator 36 allows the carriage 16 to be retracted back into the body 12, thereby ensuring that the blade 18 is held captive to the remainder of the knife. After appropriate manipulation of the actuator 36, the carriage 16 can be returned to the position shown in Figure 1.

It will be appreciated that the knife shown in the accompanying drawings is advantageous in that the blade 18 thereof can be automatically retracted into the body 12 when the knife is not in use, thereby reducing the risk of injury. When blade replacement is required, this can be achieved in a convenient manner with minimal risk to the operator. Accidental movement of the carriage to the blade replacement position is resisted through the need to manipulate the actuator in order to achieve this movement. As a result, the risk of user injury is reduced.

Whilst one embodiment of the invention is described herein, it will be appreciated that a wide range of modifications are possible without departing from the scope of the invention as defined by the appended claims. By way of example, additional slot sections may be provided to allow the blade to be latched in a range of different exposed and partially exposed positions. Where desired, an actuator with a square or round part riding within the slot could be provided, such an arrangement not requiring rotation of the actuator in order to move the carriage to the blade replacement position. A rotatable closure member may be provided at the open end of the body 12 to restrict access to the blade when retracted, the closure member including a slit through which the blade can project when in its extended, in use position, the closure member being telescopically fitted to accommodate movement of the carriage to the blade change position.

Although the knife described is intended for use as a craft knife with a scalpel like blade, the invention is not restricted to this manner of use, nor to knives with this style of blade.

Claims (13)

CLAIMS:

1. A safety knife comprising a tubular knife body, a cylindrical or part cylindrical blade carriage located within the knife body, a spring applying a biasing load to the carriage urging the carriage in a retracting direction, and an actuator secured to the carriage and projecting through a slot formed in the body to allow the carriage to be driven against the biasing load to an extended position, wherein the slot comprises a first section, a second section offset from the first section, and an intermediate section between the first and second sections, wherein the carriage undergoes angular movement relative to the body as the actuator passes along the intermediate section.

2. A knife according to Claim 1 wherein a blade is mounted upon the carriage.

3. A knife according to Claim 2, wherein the blade is of scalpel like form.

4. A knife according to any of the preceding claims, wherein the actuator has to be rotated in order to allow it to pass along the intermediate section.

5. A knife according to Claim 4, wherein the part of the actuator located within the slot is of rectangular cross section and the width of the sections of the slot are selected such that movement of the actuator along the intermediate section can only occur after adjusting the orientation of the actuator.

6. A knife according to any of Claims 1 to 3, wherein a detent or other mechanism is provided to restrict the passage of the actuator along the intermediate section.

7. A knife according to any of the preceding claims, wherein the slot is designed such that a blade can be held in one or more exposed positions.

8. A knife according to any of the preceding claims, wherein the body is of cylindrical shape.

9. A knife according to any of the preceding claims, wherein the carriage is of two part form, including a main part and a retainer attachable to the main part and arranged such that when the carriage is located within the knife body, the main part and the retainer cooperate with one another to retain a blade to the carriage.

10. A knife according to any of the preceding claims, wherein the carriage is provided with a threaded part to which the spring is secured.

11. A knife according to Claim 10, wherein an opposite end of the spring is secured to a threaded part of a plug that closes an end of the body.

12. A knife according to any of the preceding claims, wherein the body is provided with a surface texture or pattern.

13. A knife according to any of the preceding claims, wherein the body is of metallic form.