GB2083775A

GB2083775A - Trimming knife

Info

Publication number: GB2083775A
Application number: GB8119134A
Authority: GB
Original assignee: Precision Manufacturing Services Ltd
Current assignee: Precision Manufacturing Services Ltd
Priority date: 1980-09-17
Filing date: 1981-06-22
Publication date: 1982-03-31

Abstract

A retractable blade trimming knife comprises an elongate handle and a rack 15 and meshing wheel 11 or 11A for retracting a blade into the handle or for extending a blade from the handle. <IMAGE>

Description

SPECIFICATION Trimming knife This invention relates to a trimming knife of a kind comprising a handle housing a retractable,throw- away blade.

Conventionally, such knives comprise a hollow, elongate handle defined by a pair of scales, which may be metal or synthetic plastics, the scales being clamped together by a screw or other retaining means to define a hollow handle interior housing a spring loaded pawl and ratchet mechanism in metal or synthetic plastics - engageable in a selected position by a thumb-operated trigger to latch the blade either in a retracted position within the handle or in one of several exposed positions.

With such known knives, the extent of blade exposure from the handle in a selected exposed position depends on the number of stops provided in the ratchet. Thus three stops may be provided, while none of the three stops may expose the blade to an optimum extent for the particular trimming operation to be performed. In addition, the incorporation of some spring means in metal or synthetic plastics into the knife introduces the possibility of premature spring failure.

Furthermore, accidental pressure on the trigger during use of the knife may unintentionally cause retraction of the blade.

According to the present invention, a retractable blade trimming knife comprises an elongate handle and a rack and meshing wheel for retracting a blade into the handle or for extending a blade from the handle.

Thus, the knife in accordance with the invention has a blade that may be exposed to an infinitely variable extent between the fully retracted, storage position and a fully exposed position, for it can be readily ensured by appropriate selection of the wheel diameter and/or thread angle that rotation of the wheel by pressure on the blade is impossible.

Additionally, the avoidance of a spring means removes a component prone to failure, while finally the absence of a trigger to displace the blade ensures that during use the blade cannot be accidentally released.

Preferably, the wheel is rotatable about an axis parallel to the longitudinal axis of the handle and takes the form of a worm wheel although alternatively, the wheel may be rotatable about an axis normal to the longitudinal axis, taking the form of a gear wheel. It is also preferred for the handle to be formed from d pair of scales clamped together to define a hollow interior housing the rack and wheel with a portion of the wheel exposed for rotation by the user. Such exposed portion preferably comprises a knurled ring, which is preferably exposed at diametrically opposite portions through appropriate slots in each scale.Thus, each wheel may comprise a threaded portion, the knurled ring at one end thereof, with bearing locations at each end for location in semicircular recesses provided in each scale which when clamped together define two circular bearing housings. Preferably, the scales are metallic and produced by pressure die castings, although they could be of synthetic plastics produced by injection of compression moulding.

The rack and wheel mechanism may incorporate a blade carrier slidable longitudinally of the handle with a rack element attached to the blade carrier.

Such attachment may be by making the blade carrier and rack element a one piece member. Behind the blade carrier, the scale is preferably so shaped as to serve as a storage area for spare blades.

The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a first embodiment of knife in accordance with the invention with the blade shown in an extended position; Figure 2 corresponds to Figure 1 but shows one of the scales removed and the blade in a retracted position; Figure 3 is a section on the line Ill-Ill of Figure 2; Figure 4 is a section on the line IV-IV of Figure 2; Figure 5 is a side elevation of the blade carrier; Figure 6 is an end elevation of Figure 5; Figure 7 is a plan view of Figure 5; Figure 8 corresponds to Figure 2 but shows a second embodiment of knife in accordance with the invention; and Figure 9 details the rack and pinion mechanism of Figure 8.

In both embodiments like components have been accorded like reference numerals.

In the drawings, a retractable blade trimming knife 1 comprises an elongate handle 2 constituted by a pair of scales 3,4 e.g. of die cast zinc, clamped together by a screw 5 and defining a hollow interior 6.

Each scale 3,4 comprises inwardly directed pillars 7, 8 which are recessed to define circular bearing housing 9 to receive a pinlike bearing 10 provided at each end of a worm wheel 11 rotatable about the longitudinal axis of the handle 2 and provided adjacent one end with a knurled ring 12 which is exposed, at diametrically opposite portions 13 through slots 14 in each scale 3, 4. The worm wheel 11 is in mesh with a rack 15 formed integrally with carrier 16 slidable longitudinally of the handle so as to be capable of displacing a conventional blade 17 from a fully retracted position shown in Figure 2 to a fully exposed position shown in Figure 1, upon appropriate rotation of the knurled ring 12, the extent of exposure being infinitely variable between these limits, due to the employment of a rack and wheel. Although not illustrated, spare blades may be located in the area 18 (see Figure 3) behind the blade carrier 16.

In the embodiment of Figures 8 and 9 the knurled ring 12 is rotatable about an axis normal to the longitudinal axis of the handle 2 and is attached to a gearwheel 1 in mesh with the rack 15.

1. A retractable blade trimming knife comprising an elongate handle and a rack and meshing wheel for retracting a blade into the handle or for extending

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Trimming knife This invention relates to a trimming knife of a kind comprising a handle housing a retractable,throw- away blade. Conventionally, such knives comprise a hollow, elongate handle defined by a pair of scales, which may be metal or synthetic plastics, the scales being clamped together by a screw or other retaining means to define a hollow handle interior housing a spring loaded pawl and ratchet mechanism in metal or synthetic plastics - engageable in a selected position by a thumb-operated trigger to latch the blade either in a retracted position within the handle or in one of several exposed positions. With such known knives, the extent of blade exposure from the handle in a selected exposed position depends on the number of stops provided in the ratchet. Thus three stops may be provided, while none of the three stops may expose the blade to an optimum extent for the particular trimming operation to be performed. In addition, the incorporation of some spring means in metal or synthetic plastics into the knife introduces the possibility of premature spring failure. Furthermore, accidental pressure on the trigger during use of the knife may unintentionally cause retraction of the blade. According to the present invention, a retractable blade trimming knife comprises an elongate handle and a rack and meshing wheel for retracting a blade into the handle or for extending a blade from the handle. Thus, the knife in accordance with the invention has a blade that may be exposed to an infinitely variable extent between the fully retracted, storage position and a fully exposed position, for it can be readily ensured by appropriate selection of the wheel diameter and/or thread angle that rotation of the wheel by pressure on the blade is impossible. Additionally, the avoidance of a spring means removes a component prone to failure, while finally the absence of a trigger to displace the blade ensures that during use the blade cannot be accidentally released. Preferably, the wheel is rotatable about an axis parallel to the longitudinal axis of the handle and takes the form of a worm wheel although alternatively, the wheel may be rotatable about an axis normal to the longitudinal axis, taking the form of a gear wheel. It is also preferred for the handle to be formed from d pair of scales clamped together to define a hollow interior housing the rack and wheel with a portion of the wheel exposed for rotation by the user. Such exposed portion preferably comprises a knurled ring, which is preferably exposed at diametrically opposite portions through appropriate slots in each scale.Thus, each wheel may comprise a threaded portion, the knurled ring at one end thereof, with bearing locations at each end for location in semicircular recesses provided in each scale which when clamped together define two circular bearing housings. Preferably, the scales are metallic and produced by pressure die castings, although they could be of synthetic plastics produced by injection of compression moulding. The rack and wheel mechanism may incorporate a blade carrier slidable longitudinally of the handle with a rack element attached to the blade carrier. Such attachment may be by making the blade carrier and rack element a one piece member. Behind the blade carrier, the scale is preferably so shaped as to serve as a storage area for spare blades. The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a first embodiment of knife in accordance with the invention with the blade shown in an extended position; Figure 2 corresponds to Figure 1 but shows one of the scales removed and the blade in a retracted position; Figure 3 is a section on the line Ill-Ill of Figure 2; Figure 4 is a section on the line IV-IV of Figure 2; Figure 5 is a side elevation of the blade carrier; Figure 6 is an end elevation of Figure 5; Figure 7 is a plan view of Figure 5; Figure 8 corresponds to Figure 2 but shows a second embodiment of knife in accordance with the invention; and Figure 9 details the rack and pinion mechanism of Figure 8. In both embodiments like components have been accorded like reference numerals. In the drawings, a retractable blade trimming knife 1 comprises an elongate handle 2 constituted by a pair of scales 3,4 e.g. of die cast zinc, clamped together by a screw 5 and defining a hollow interior 6. Each scale 3,4 comprises inwardly directed pillars 7, 8 which are recessed to define circular bearing housing 9 to receive a pinlike bearing 10 provided at each end of a worm wheel 11 rotatable about the longitudinal axis of the handle 2 and provided adjacent one end with a knurled ring 12 which is exposed, at diametrically opposite portions 13 through slots 14 in each scale 3, 4. The worm wheel 11 is in mesh with a rack 15 formed integrally with carrier 16 slidable longitudinally of the handle so as to be capable of displacing a conventional blade 17 from a fully retracted position shown in Figure 2 to a fully exposed position shown in Figure 1, upon appropriate rotation of the knurled ring 12, the extent of exposure being infinitely variable between these limits, due to the employment of a rack and wheel.Although not illustrated, spare blades may be located in the area 18 (see Figure 3) behind the blade carrier 16. In the embodiment of Figures 8 and 9 the knurled ring 12 is rotatable about an axis normal to the longitudinal axis of the handle 2 and is attached to a gearwheel 1 in mesh with the rack 15. CLAIMS

1. A retractable blade trimming knife comprising an elongate handle and a rack and meshing wheel for retracting a blade into the handle or for extending a blade from the handle.

2. A knife as claimed in Claim 1, wherein the wheel is rotatable about an axis parallel to the longitudinal axis of the handle and takes the form a worm wheel.

3. A knife as claimed in Claim 1, wherein the pinion is rotatable about an axis normal to the longitudinal axis of the knife and takes the form of a gearwheel.

4. A knife as claimed in any preceding Claim, wherein the handle is formed from a pair of scales clamped together to define a hollow interior housing the rack and pinion mechanism with a portion of the pinion exposed for rotation by the user.

5. A knife as claimed in Claim 4, wherein the exposed portion comprises a knurled ring.

6. A knife as claimed in Claim 5, wherein the ring is exposed at diametrically opposite portions through appropriate slots in each scale.

7. A knife as claimed in Claim 5 or Claim 6, wherein the wheel comprises a threaded portion, the knurled ring at one end thereof, with bearing locations at each end for location in semicircular recesses provided in each scale which when clamped together define two circular bearing housings.

8. A knife as claimed in any preceding Claim, wherein the scales are metallic and produced by pressure die casting.

9. A knife as claimed in any one of Claims 1 to 7, wherein the scales are of synthetic plastics and produced by injection or compression moulding.

10. A knife as claimed in any preceding Claim, wherein the rack and meshing wheel incorporate a blade carrier slidable longitudinally of the rack mechanism attached to the blade carrier.

11. A knife as claimed in Claim 10, wherein the blade carrier and rack element are made as a one-piece member.

12. A knife as claimed in Claim 10 or Claim 11, wherein behind the blade carrier, the scale is so shaped as to serve as a storage for spare blades.

13. A retractable blade trimming knife substantially as hereinbefore described with reference to Figures 1 to 7 of the accompanying drawings.

14. A retractable blade trimming knifesubstantially as hereinbefore described with reference to Figures 8 and 9 of the accompanying drawings.