GB2071487A

GB2071487A - Brush trimmer

Info

Publication number: GB2071487A
Application number: GB8102321A
Authority: GB
Original assignee: Ebser Maschf
Current assignee: Ebser Maschf
Priority date: 1980-02-02
Filing date: 1981-01-26
Publication date: 1981-09-23
Also published as: IT8147670A0; DE3003772C2; IT1142263B; DE3003772A1; BE887318A

Abstract

An apparatus for trimming brushes and brooms comprising two displaceable cutter members 1 & 4 retained in grooves formed in a cutter body which is rotatable about its longitudinal axis and a fixed cutter member 2, the cutting edges of the displaceable cutters, in use, co-operating with the cutting edge of the fixed cutter to produce a shearing effect, the displaceable cutter members and the fixed cutter member being disposed obliquely to one another to define a shearing angle therebetween wherein each displaceable cutter comprises a plurality of cutter portions, 1x, 1y, 1z, eg straight ground, the cutter portions being fixedly mounted in a groove formed in the cutter body, which groove extending from end to end of the cutter body at the predetermined shearing angle relative to the axis of the cutter body, the groove being longitudinally divided into sections, the length of each section corresponding to the length of the cutter portion mounted therein, each section of the groove having the same cutting breast or front rake angle at one of its ends so that each cutter portion, at the beginning of its cutting operation, subtends the predetermined shearing angle relative to the cutting edge of the fixed cutter which extends parallel to the axis of the cutter body. <IMAGE>

Description

SPECIFICATION Brush or broom shearing device The present invention relates to an apparatus for trimming brushes and brooms having two or more displaceable cutters retained in a cutter member which is rotatable about its longitudinal axis, the cutting edges of the cutters being located in opposition to the cutting edge of a fixed cutter so as to cooperate therewith. When the displaceable cutters and the fixed cutter are in their cutting positions, a shearing angle is defined therebetween. In other words, when cutting is being effected the displaceable cutters and the fixed cutter do not extend parai- lel to one another.

When manufacturing brushes, brooms or the like, the bristles or hair is inserted into the brush or broom head after the latter has had suitable bores formed therein. The apparatuses used for producing brushes and brooms therefore usually comprise boring and bristle or hair filling machines. The inserted bristles or hair are usually of irregular length and have to be trimmed to the required length by means of a shearing device. Such shearing ortrimming devices may form an integral part of the boring and filling device so that all three devices may be provided in a single apparatus. On the other hand, the cutting device may be a separate apparatus. For the purpose of the present invention however, this is of no consequence; and only a shearing or trimming device will be described.

A known shearing device for trimming the filling material usually comprises a cylindrical cutter body which is rotatable about its longitudinal axis and on which two or more displaceable cutters are fixedly mounted so as to rotate with the body. To retain the cutters, grooves are milled into the cylindrical surface of the cutter body into which the displaceable cutters are inserted and secured. The displaceable cutters are usually in opposition to the cutting edge of a fixed cutter. In the cutting position, the cutting edges of the displaceable cutters contact or pass very close to the cutting edge of the fixed cutter. To achieve a shear-like cut, the fixed cutter is so arranged as to extend obliquely to the axis of the cutter body. The angle thus formed between the cutting edge of the fixed cutter and the cutting edges of the rotary cutters is referred to as the shearing angle.

Two types of known cutter will now be described in greater detail with reference to the accompanying drawings, in which: Fig. 1A shows a plan view of the cutters of a first known device; Fig. 1 B shows a vertical section through the cutters shown in Fig. 1A, and Figs. 2A and 2B show views similar to Figs. 1A and 1 B respectively of a second known device.

In Figs. 1A and 1 B, the rotary cutter is designated 1 and the fixed cutter 2. The fixed cutter subtends an angle 3 with the axis of the cutter body or with the cutting edges of the displaceable cutters. The inciination of the fixed cutter is evident by comparing the different positions of its two end points 3' and 3". In Fig. 1 B, a second displaceable cutter 4 disposed opposed the first displaceable cutter is shown.

The more obliquely the cutting edge of the fixed cutter extends with respect to the displaceable cutters, the smoother the cut produced and the lower the power required to drive the rotary cutter. The inclination of the cutters does, however, raise a problem. To achieve cutting over the entire width of the cutting edge, the rotary cutter must be arcuate. The radius of curvature of th is arc increases as the angle of inclination is increased. If the cutting edge of the rotary cutter is straight-ground, cutting only occurs at the two ends of the blade. Between the ends, a gap is formed which is at a maximum in the central region of the blade, and hence the material located between it and the fixed cutter is crushed and torn rather than cut.

It is also known that the rotary cutter must have a definite curvature, the size of which depends upon the shearing angle at which the cutters operate. With a large shearing angle, the curature must also be large and with a shearing angle of zero, the cutter may be straight-ground. In the latter case, however, the filling material is chopped over the whole width virtually simultaneously. This, however, requires a considerable expenditure of power and the noise produced is somewhat loud. Moreover, there is also the danger that the cutters may be deflected and be caused to strike against one another. If th is happens, the cutters may be damaged.

It is, of course, also possible to locate the cutting edge of the fixed cutter in a position in which it extends parallel to the axis of the rotary cutter body.

In such a case, the rotary cutters are obliquely set in the cutter body. Such an arrangement is shown in Figs. 2A and 2B, in which components identical to those shown in Fig. 1 are provided with the same reference numerals. The two known devices are substantially identicai; the chief difference being that, in the Fig. 2 arrangement, the rotary cutters 1 and 4 are bevelled instead of the fixed cutter. The shearing angle in turn is again denoted by 3, and the bevel is evident from viewing the ends 3' and 3" of the rotary cutter 1. As is to be expected, such an arrangement does not overcome the problems which have been discussed hereinbefore in connection with the embodiment shown in Fig. 1. In the Fig.

2 embodiment, it is still necessary for the cutting edge to be arcuate if the cutters are located obliquely.

It is, of course, possible to grind cutting edges to provide them with concave or convex surfaces. Such grinding is, however, relatively difficult to achieve and necessitates the use of complex and expensive grinding device. Such grinding devices may, in fact, prove costlier than the shearing device. Because of these high costs, brush or broom manufacturers utilising the shearing devices do not regrind the cutters themselves. On the other hand, having the cutters reground by the manufacturer of the shearing device means that the shearing device is unusable for a long period of time, which is uneconomic.

From the above description, it will be apparent that it is desirable, despite the oblique location of the cutting edges of the cutters, that is to say, utilising a shearing angle which is greater than zero, to use cutters which are straight-ground. The present invention therefore seeks to provide an apparatus in which this can be achieved.

In accordance with the present invention there is provided an apparatus for trimming brushes and brooms comprising two displaceable cutter members retained in grooves formed in a cutter body which is rotatable about its longitudinal axis and a feed cutter member, the cutting edges of the displaceable cutters, in use, co-operating with the cutting edge of the fixed cutter to produce a shearing effect, the displaceable cutter members and the fixed cutter member being disposed obliquely to one another to define a shearing angle therebetween wherein each displaceable cutter comprises a plurality of cutter portions, the cutter portions being fixedly mounted in a groove formed in the cutter body, which groove extending from end to end of the cutter body at the predetermined shearing angle relative to the axis of the cutter body, the groove being longitudinally divided into sections, the length of each section corresponding to the length of the cutter portion mounted therein, each section of the groove having the same cutting breast or front rake angle at one of its ends and the cutter portions, at the beginning of the cutting operation, subtend the predetermined shearing angle relative to the cutting edge of the fixed cutter which extends parallel to the axis of t;le cutter body.

Preferably, the rotatable cutter bodies each have cutter members located in pairs opposite each other, the butt positions of opposite sets of cutters being in register with one another.

One embodiment of the present invention will now be described, by way of example, with referpence to Figs. 3A and 3B. In the drawings, Fig. 3A is a plan view of a cutter body forming part of the apparatus of the present invention and Fig. 3B shows three sectional views taken along the lines a-b, c-d and e-f respectively of Fig. 3A.

In Fig. 3A, there is shown a displaceable cutter member 1 and a fixed cutter member 2. These cutter members define a shearing angle 3 and the oblique positioning of the cutters can be easily seen at the ends 3' and 3". A second roatary set of cutters 4 is shown in Fig.3B.Agroove6 is milled in a cutter body 8 for the displaceable cutter members. Bores are formed in the groove 6, the reason which will be described hereinafter, Fig. 3B shows three different cross-sections through the cutter body shown in Fig.

3A. In Fig. 3B, however, the fixed cutter 2 is only shown in the section on the line C-cl for the sake of clarity. This Figure should substantially show the position of the displaceable cutters.

To obtain the necessary shearing angle 3, the groove 6 is formed in the cutter body at an oblique angle to the axis 7 of the cutter body 8. In the embod iment shown, the shearing angle 3 is about 3 . Other shearing angles can, however, be employed. The size of the shearing angle is dependent upon the intended use of the shearing device. The cutting edge of the fixed cutter 2 is aligned so as to extend parallel to the axis 7 of the cutter body. The displaceable cutters 1 and 4, which are secured in the groove 6, have their cutting edges disposed at the shearing angle with respect to the cutting edge of the fixed cutter due to the oblique disposition relative to the axis 7 of the cutter body.

Each displaceable cutter is sub-divided into a plur5 ality of cutter portions. Each individual cutter portion is, ideally about 50 mm long. The individual cutters are denoted, in Figs. 3A and 3B by 1X, 1Y and 1Z. The individual cutter portions are straight-ground, that is to say, they have a straight cutting edge. This is achieved by milling the groove 6 in a specific man ner to be described in further detail hereinafter. By so doing, it is possible to provide an arrangement in which no gaps are present between cutting edge of the displaceable cutter portions and the cutting edge of the fixed cutter during the cutting operation. The groove 6 is milled in a number of individual sections corresponding to the number of individual cutter portions, each groove section having a length compatible with the cutter portion associated therewith.

This is necessary because the cutting or breast angle for each section have to be accordingly adapted. By term "cutting, or breast angle", there is to be understood the angle formed by the line drawn from the mounting or securing point of the displaceable cutters in the groove to the cutting edge thereof and the radius drawn from the axis of the cutter body. This cutting or breast angle for the cutting edge of the rotary cutters is correct only at one point, this being at the point at which the rotary cutting edge contacts the fixed cutting edge for the first time. Thus, if a single continuous groove was produced by milling, the cutting angle would be completely incorrect at the other end of the groove. This is why the groove is milled in separate sections; the breast angle being corrected at the end of milling each section by rotating the cutter body.The cutting angle is therefore again correct at the commencement of the milling of the next section. The correct cutting or breast angle is ascertained by empirical means. The bores 5 serve to allow the milling cutter to run out after each 50 mm section has been milled.

It has been found that a section of 50 mm is the maximum length in which the deviation of the cutting, breast or front rake angle from the correct valve over the length of the section does not impair the efficiency of the cutting operation. Utilising such a length of division means that, despite a rectilinear grinding ofthe cutter a satisfactory shearing-like cut of the filling material by the cutter blades is ensured, even though the overall length to be cut may be greater, in some cases substantially greater, than 50 mm. Shearing devices made in this manner cut smoothly and the cutters may be ground on a simple grinding block. Since each cutter body has at least two opposed sets of cutters, it is highly desirable to ensure in the interests of a smooth running, that the butt positions of the cutters on one side overlap the butt positions of the cutter on the other side.

Claims

1. An apparatus for trimming brushes and brooms comprising two displaceable cutter members retained in grooves fornied in a cutter body which is rotatable about its longitudinal axis and a fixed cutter member, the cutting edges of the displaceable cutters, in use, co-operating with the cutting edge of the fixed cutter two produce a shearing effect, the displaceable cutter members and the fixed cutter member being disposed obliquely to one another to define a shearing angle therebetween wherein each displaceable cutter comprises a plurality of cutter portions, the cutter portions being fixedly mounted in a groove formed in the cutter body, which groove extending from end to end of the cutter body at the predetermined shearing angle relative to the axis of the cutter body, the groove being longitudinally divided into sections, the length of each section corresponding to the length of the cutter portion mounted therein, each section of the groove having the same cutting breast or front rake angle at one of its ends and the cutter portions, at the beginning of the cutting operation, subtend the predetermined shearing angle relative to the cutting edge of the fixed cutter which extends parallel to the axis of the cutter body.

2. An apparatus as claimed in claim 1, characterised by the feature that the rotatable cutter bodies each have cutter member located in pairs opposite each other, the butt positions of opposite sets of cutters being in registerwith one another.

3. An apparatus as claimed in claim 1 constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in Figs. 3A and 3B of the accompanying drawings.