WO2016200273A1

WO2016200273A1 - Saw for forming a non-circular opening

Info

Publication number: WO2016200273A1
Application number: PCT/NO2016/050120
Authority: WO
Inventors: Tom-Arild BEKKEHEIEN
Original assignee: Tanjen Invent As
Priority date: 2015-06-11
Filing date: 2016-06-08
Publication date: 2016-12-15
Also published as: EP3307463A1; EP3307463A4; NO338990B1; NO20150761A1

Abstract

A saw (1) for forming a non-circular opening (34), the saw (1) including a roller chain (2) partially encircling a chain wheel (4) and a chain guide (6), the chain wheel (4) being supported in a holder body (8), and the chain wheel (4) being connectable to a driving device, and the roller chain (2) being provided with at least one first projecting knife (5; 22) on its side facing away from the holder body (8), and the at least one first knife (5; 22) being arranged at the outer periphery (24) of the roller chain (2).

Description

SAW FOR FORMING A NON-CIRCULAR OPENING

This invention relates to a saw for forming a non-circular opening. More particularly, it relates to a saw for forming a non-circular opening, the saw including a roller chain partly encircling a chain wheel and a chain guide. The chain wheel is supported in a holder body, and the chain wheel is provided with a coupling portion on one side. A driving device may be releasably connected to the coupling portion. The roller chain is provided with projecting knives on the side of the chain facing away from the coupling portion.

As the need for more contents in electrical junction boxes, for instance, has arisen, it has become usual to use junction boxes that require non-circular installation openings in plates or panels forming the panelling of a wall or ceiling. Installation openings of this kind are usually drilled at the installation site.

It is more laborious to cut out a non-circular installation opening than a circular installation opening which can be drilled in one operation with a circular holesaw. Such a non-circular opening is achieved by drilling two holes with a circular holesaw in such a way that the holes are offset relative to each other. It is also necessary to remove two triangle-like pieces that are formed between the two holes.

To remedy the problem, saws have been developed in which a chain, typically a roller chain, follows a track, and in which there are centred knives projecting from the chain. The knives are arranged to cut an opening in a wooden plate, for example, wherein the opening will have a shape like that of the track that the chain is following.

The patent publication US 5,853,269 discloses a holesaw for making a relatively rectangular opening. The chain is guided around in a track in a housing. To reduce wear, the track is provided with a wear post at each inside corner. Every other bolt in the chain has been replaced with a cylindrical saw tooth which is chisel-shaped at its free end portion. The chain may, with advantage, be a duplex chain to give the saw teeth better lateral support. To give even better lateral support to the saw teeth, the saw is provided with a guide plate, in against which the saw teeth are pressed when the chain is driven around. The chain is driven by a centred sprocket which is in engagement with the chain where the chain forms straight portions. The chain is thus carried tangentially onto the sprocket from two sides. The patent publication 6,565,294 shows an alternative holesaw which has many features in common with the holesaw shown in US 5,853,269 as far as providing a chain with saw teeth and driving the chain are concerned.

The patent publication US 3,833,311 shows a holesaw for making a relatively rectangular opening. At each corner, the holesaw is provided with a small sprocket over which a chain is carried. Every other bolt in the chain is replaced with a cylindrical saw tooth. Two of the sprockets are provided with a driving pin which may be connected to a hand-held tool, such as a drill.

The patent publication US 1,137,459 shows a holesaw in which a chain extends in a track in a guide plate. The guide plate is provided with a sprocket at either end. The chain is carried over the sprockets. One of the sprockets drives the chain. The outer links on one side of the chain are provided with cylinder-shaped saw teeth. The saw teeth are arranged in a centred manner on the outer links and the longitudinal axes of the saw teeth are parallel to the longitudinal axes of the bolts of the chain.

The patent publication US 2,517,901 shows a profile cutter which can cut out irregular shapes from materials in cloth form. The profile cutter includes a chain which is driven by a sprocket. The chain is guided around by guides so that a desired profile is formed. Cylinder-shaped knives are each attached to a respective tool holder. The tool holder is attached to the extended bolts of the chain so that each tool holder coincides with a respective outer link in the chain. Each knife is centred in the tool holder and the longitudinal axis of the knife is parallel to the longitudinal axes of the bolts of the chain.

Common to prior-art holesaws is that to achieve sufficient cutting depth, the saw teeth must project relatively far out from the chain. This is conditional on chain guides and the chain itself having relatively narrow clearances in order to provide a sufficiently accurate installation opening. A slight twisting of the link of the chain gives a relatively large lateral deviation at the point of the saw tooth, which may create an unclean cut. This is remedied by guide plates, against which the saw tooth is pressed because of the sharpening of the saw tooth, but this causes wear on the saw tooth. The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through the features which are specified in the description below and in the claims that follow.

In a first embodiment, the invention relates to providing a roller chain with knives along the outer periphery and the inner periphery of the roller chain on the sawing side of the roller chain. A number of the outer links of the roller chain are provided with saw teeth on their outer side, and a number of the outer links of the roller chain are provided with saw teeth on their inner side. Thereby material is removed from a groove that will have a width corresponding to the thickness of the roller chain. The roller chain may thereby be moved into the groove that is being formed. It is thus possible to turn the width of a duplex or triplex chain to account to achieve sufficient cutting depth, even with knives that project relatively insignificantly out from the roller chain. Thereby a plate or a panelling plank may be cut through and an installation opening is formed. The rigidity of the roller chain is thereby turned to account for sawing an installation opening with relatively great accuracy.

In a second embodiment, the invention relates to providing a roller chain with plate- shaped outer links which are bent so that a saw tooth standing perpendicularly on the outer link is formed. The saw tooth has a longitudinal direction that coincides with the longitudinal direction of the roller chain. The saw tooth projects from the roller chain at the outer side of the roller chain. Thereby, material is removed from a groove which will have a width corresponding to the thickness of the saw tooth. A narrow groove is thereby achieved, with a sufficient cutting depth for plates or panelling to be cut through without the roller chain being moved into the material or coming into contact with the material. This has the advantage of the sawing work creating little dust.

The invention is defined by the independent claim. The dependent claims define advantageous embodiments of the invention.

The invention relates, more specifically, to a saw for forming a non-circular opening, the saw including a roller chain partially encircling a chain wheel and a chain guide. The chain wheel is supported in a holder body. The chain wheel is provided with a coupling portion on one side. A driving device may be releasably connected to the coupling portion. The roller chain is provided with at least one first projecting knife on the side facing away from the coupling portion. The saw is characterized by the at least one knife being arranged at the outer periphery of the roller chain. In one embodiment, at least one second knife may be arranged at the inner periphery of the roller chain. During hole-making, a groove which is as wide as the thickness of the roller chain is thereby formed. The cutting depth is thereby not restricted by how far the knives project out from the roller chain in the cutting direction. Relatively robust chain-saw knives can be used and have turned out to be well suited for the purpose. The first knives and the second knives may be arranged alternatingly at the outer periphery and the inner periphery, respectively, of the roller chain to achieve a favourable material cutting.

It is advantageous that the holder body is provided with a one-hand handle for controlling the saw. A driving device, for example in the form of a drill connected to the chain wheel, may be held in the other hand.

A chain guide may be directly or indirectly connected to the holder body, and the chain guide may be adjustable in the radial direction of the chain wheel. Such a solution facilitates the tightening of the roller chain. In operation, the rollers of the roller chain rotate against the chain guide, which reduces the wear on the chain guide.

Depending on the desired cutting depth, the roller chain may be a simplex chain, a duplex chain or a triplex chain. Chains of further widths may be preferred in some cases.

A supporting plate may be connected to the chain guide and supported on the chain wheel on the opposite side of the chain wheel relative to the holder body. A solution like that supports the chain wheel and increases the accuracy of a drilled installation opening.

With the aim of keeping the saw steady against the object to be drilled, a drill bit that is arranged centrically in the chain wheel may project further out from the chain wheel than the knives. When drilling starts, the drill bit is first drilled somewhat into the object in which the installation opening is to be made, so that the saw will stay in the desired position against this as the knives engage with the object.

The saw according to the invention is well suited to be designed for making installation openings for most junction-box types. In a well-known embodiment for a junction box, the roller chain follows a path including two semicircles.

In a second embodiment, the knife may include a base, and the base may be attached to the chain on the bolts of the roller chain. The knife may comprise a knife blade which may project perpendicularly from the base, and the knife blade may be provided with a cutting edge in at least one of its two edge portions. Both edge portions may be provided with a respective cutting edge.

Because of its steady design with relatively short, outward-projecting knives, the saw has turned out to be efficient even by a considerable material thickness of the object in which the junction box is to be positioned.

A knife for a roller chain is described as well. The knife may include a base, and the base may be attached to the roller chain on the bolts of the roller chain. The knife may include a knife blade which may project perpendicularly from the base, and the knife blade may be provided with a cutting edge in at least one of its two edge portions. Both edge portions may be provided with a respective cutting edge.

The knife blade may taper towards its free end portion. The cutting edge may be formed by the knife being punched out from a larger plate. The cutting edge may be formed by honing the edge portion. The two edge portions may meet in a point.

In an alternative embodiment, the free end portion of the knife may be provided with at least one incision. The free end portion may be provided with two incisions. The incision may be provided with two edge portions. At least one edge portion of the incision may be provided with a cutting edge. The incision may be provided with two cutting edges.

The base may be rounded in its end portions. Each end portion may be provided with a hole. The base may have a size and a shape which make the base correspond to an outer link of a roller chain. A plate from which the knife is formed may have a thickness that corresponds to the thickness of the outer link of the roller chain. The base may be attached to a roller chain by the bolts of the roller chain being passed through the holes of the base. The base may constitute the outer link of the roller chain on one side of the roller chain. The base may be attached to a simplex chain, a duplex chain or a triplex chain.

In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings, in which :

Figure 1 shows a plan view of a saw according to the invention, seen from above; Figure 2 shows a view of the holesaw in a first embodiment, seen from below;

Figure 3 shows a section I-I of figure 1 of the first embodiment; Figure 4 shows the same as figure 3, but during the sawing of an object;

Figures 5A-D show an alternative design of a saw tooth, on a larger scale;

Figures 6A-B show a side view and a perspective view of a chain guide, on a different scale;

Figure 7 shows a holesaw in an alternative embodiment according to the invention, on the same scale as figure 2, with saw teeth as shown in figures 5A-D;

Figure 8 shows the same as figure 2, but in the alternative embodiment shown in figure 7; and

Figure 9 shows the same as figure 8, but during the sawing of an object.

In the drawings, the reference numeral 1 indicates a holesaw holdable by hand, including an endless roller chain 2 extending around a chain wheel 4 and a chain guide 6. The chain wheel 4 is supported in a holder body 8 by means of a first bearing 10. The chain guide 6 is attached to the holder body 8 by means of bolts not shown. The chain guide 6 is restrictedly adjustable in the radial direction of the chain wheel 4. A handle 12 is attached to the holder body 8.

On the opposite side of the chain wheel 4 and the chain guide 6, a supporting plate 14 is arranged. The supporting plate 14 is connected to the holder body 8 and the chain guide 6 as will be described later. A second bearing 16 forms a support between the chain wheel 4 and the supporting plate 14. The holder body 8, chain guide 6 and supporting plate 14, together with the bearings 10 and 16, form a steady support of the chain wheel 4.

The chain wheel 4 is provided with a centric driving pin 18 extending axially through it. The driving pin 18 includes a coupling portion 41 at one end portion for connection to a driving device not shown, typically in the form of a drill. At its opposite end portion, the driving pin 18 also includes an attachment for a drill bit 20 which is centric relative to the chain wheel 4.

On the side of the roller chain 2 facing away from the holder body 8, first knives 22 and second knives 22' are arranged. In a first embodiment as shown in figures 2-4, first knives 22 and second knives 22' are attached alternatingly at the outer periphery 24 and the inner periphery 26, respectively, of the roller chain 2. During sawing, the knives 22, 22' together form a groove 28 with a width 30 in an object as shown in figure 4. In this embodiment, the knives 22, 22' consist of so-called chain-saw knives, but other knife types may be practical in some cases.

An alternative type of knife is shown in figures 5A-D. The knife 5 is formed of a bent plate 51 so that a base 52 and a knife blade 53 is formed. The knife blade 53 projects perpendicularly from the base 52. The knife blade 53 is shown tapering towards its free end portion 59. In at least one of its two edge portions 54, 54', the knife blade 53 is provided with a cutting edge 51, 50'. Both edge portions 54, 54' may be provided with a respective cutting edge 50, 50'. The cutting edge 50, 50' may be formed by punching the plate 51 out from a larger plate. The cutting edge 50, 50' may alternatively be formed by honing the edge portion 54, 54' or by a combination of the two methods.

The two edge portions 54, 54' may meet in a point. In an alternative embodiment, the free end portion 59 is provided with at least one incision 55. In the embodiment that is shown in figures 5A-C, the free end portion 59 is provided with two incisions 55. The incision 55 is provided with two edge portions 56, 56'. At least one edge portion 56, 56' is provided with a cutting edge 57, 57'. In the figures 5A-C, the incision 55 is provided with two cutting edges 57, 57'.

The base 52 is rounded in its end portions and each end portion is provided with a hole 58, 58'. The base 52 has a size and a shape that make the base 52 correspond to an outer link in a roller chain 2. The plate 51 has a thickness corresponding to the thickness of the outer links of the roller chain 2. The base 52 is attached to a roller chain 2 of a kind known per se, by the bolts of the roller chain 2 being passed through the holes 58, 58' of the base 52. The base 52 is thereby attached to the roller chain 2 in the same way as an ordinary outer link and forms the outer link of the roller chain 2 on one side of the roller chain 2. The base 52 may be attached to a simplex chain, a duplex chain or a triplex chain.

The roller chain 2 is formed into an endless roller chain 2 in a known manner. The length is adjusted to the holesaw 1 so that the roller chain 2 is carried round the chain wheel 4 and the chain guide 6. The knife blade 53 projects from the roller chain 2 on the outer periphery 24 of the roller chain 4, as is shown in figures 7-9.

An embodiment in which both edge portions 54, 54' are provided with a cutting edge 50, 50' has the advantage of the holesaw 1 working in the same way whether the roller chain 2 is rotating clockwise or anticlockwise. The life of the knife 5 and thereby that of the roller chain 2 are extended. An embodiment in which both edge portions 56, 56' of the incision 55 are provided with cutting edges 57, 57' also have the advantage of the holesaw 1 working in the same way, whether the roller chain 2 is rotating clockwise or anticlockwise.

The chain guide 6 is shown in greater detail in figures 6A-B. The crescent chain guide 6 has a first side face 60 facing the holder body 8 in the position of application, and an opposite second side face 69 facing the supporting plate 14 in the position of application. Between the first side face 60 and the second side face 69, a circular, concave first side portion 61 is formed. The radius of the side portion 61 is somewhat larger than the radius of the chain wheel 4. In a position of application, the side portion 61 faces the chain wheel 4. The chain guide 6 further includes a second circular, convex side portion 63. The side portion 63 is stepped so that a sliding surface 65 is formed nearest to the second side face 69. The radius of the sliding surface 65 corresponds to the radius that the inner periphery 26 of the roller chain 2 follows around the chain wheel 4. The roller 21 of the roller chain 2 is carried along the sliding surface 65. The roller 21 will rotate around its axially through bolt so that there is little friction between the roller chain 2 and the sliding surface 65.

The chain guide 6 is provided with three holes 66, 66', 67 between the first side face 60 and the second side face 69. The holes 66, 66', 67 have an oval cross section.

The holder body 8, chain guide 6 and supporting plate 14 are fixed to each other with three screws (not shown). On its bottom side, the supporting plate 14 is provided with three countersunk holes, 76, 76' and 77, respectively. The holder body 8 is provided with three corresponding threaded holes on its bottom side. The middle one of these threaded holes 87 is shown in figures 3, 4, 8, 9. Two screws are passed through the holes 76, 76', the corresponding holes 66, 66' of the chain guide 6 and are secured to the holder body 8 in the corresponding threaded holes. A middle screw is passed through the hole 77, the corresponding hole 67 of the chain guide 6 and is secured to the holder body 8 in the corresponding threaded hole 87. The middle screw may, with advantage, be without threads in the portion that is inside the hole 67.

From the middle portion of the sliding surface 65, a threaded bore 68 extends in to the hole 67. A tightening screw (not shown) is positioned in the threaded bore 68. The tightening screw will abut against the middle screw in the hole 67. The tightening screw can be tightened and loosened by inserting a screwdriver or the like (not shown) to the tightening screw through an opening between two neighbouring rollers 21 in the roller chain 2. The roller chain 2 is tightened by the tightening of the screws being reduced somewhat. Then the tightening screw is turned in the bore 68 so that the chain guide 6 is brought closer to the edge portion of the supporting plate 14 in the radial direction of the chain wheel 4, so that the roller chain 2 will have just the right tightness. The chain guide 6 is movable relative to the screws as the holes 66, 66', 67 have oval cross sections. Then the screws in the holes 66, 66', 67 are tightened again. The roller chain 2 may be loosened from the chain wheel 4 and the chain guide 6 by the tightening of the screws being reduced somewhat and the tightening of the tightening screw being released. The roller chain 2 may then be put on by first tilting it off the sliding surface 65 of the chain guide 6 and then off the chain wheel 4. The roller chain 2 is fitted in the reverse order.

When an opening 34 is to be made in an object 32, the driving device, not shown, is started so that the sprocket 4 and the drill bit 20 rotates, whereby the roller chain 2 is driven as well. The drill bit 20, which projects further than the knives 22, 22', 5, is first brought somewhat into the object 32 so that the saw 1 will stay in position when the knives 22, 22', 5 come into engagement with the object 32.

In one embodiment of the saw 1, the knives 22, 22' cut a groove 28 into the object 32, the groove 28 having a sufficient width 30 for the roller chain 2 to be moved into the groove 28. Openings can thereby be drilled in materials that are thicker than the height 36 of the knives 22, 22'.

In the alternative embodiment of the saw 1, the knives 5 cut out a groove 28' in the object 32, the groove 28' being a narrower groove than the groove 28. The knife 5 has a height 36' which is larger than the thickness of the object 32. The saw 1 thereby cuts a hole in the object 32 without the base 52 of the knife 5 touching the object 32.

It should be noted that all the above-mentioned embodiments illustrate the invention, but do not limit it, and persons skilled in the art will be able to construct many alternative embodiments without departing from the scope of the attached claims. In the claims, reference numbers in parentheses are not to be regarded as restrictive. The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps that are not mentioned in the claims. The indefinite article "a" or "an" before an element does not exclude the presence of several such elements.

The fact that some features are indicated in mutually different dependent claims does not indicate that a combination of these features cannot be used with advantage.

Claims

C l a i m s

1. A saw (1) for forming a non-circular opening (34), the saw (i) comprising a roller chain (2) partially encircling a chain wheel (4) and a chain guide (6), the chain wheel (4) being supported in a holder body (8), and the chain wheel (4) being connectable to a driving device , and the roller chain (2) being provided with at least one first projecting knife (5; 22) on its side facing away from the holder body (8), c h a r a c t e r i z e d i n that the at least one first knife (5; 22) is arranged at the outer periphery (24) of the roller chain (2).

2. The saw (1) according to claim 1, wherein at least one second knife (22') is arranged at the inner periphery (24) of the roller chain (2).

3. The saw (1) according to claim 2, wherein the first knives (22) and the second knives (22') are arranged alternatingly at the outer periphery (24) and inner periphery (26), respectively, of the roller chain (2),

4. The saw (1) according to claim 1 or 2, wherein the holder body (8) is provided with a handle (12),

5. The saw (1) according to any one of the preceding claims, wherein the chain guide (6) is connected to the holder body (8).

6, The saw (1) according to any one of the preceding claims, wherein the chain guide (6) is adjustable in the radial direction of the chain wheel (4).

7. The saw (1) according to any one of the preceding claims, wherein the roller chain (2) is a duplex chain.

8, The saw (1) according to claims 1 to 6, wherein the roller chain (2) is a triplex chain,

9. The saw (1) according to any one of the preceding claims, wherein a supporting plate (14) is connected to the chain guide (6) and supported on the chain wheel (4) on the opposite side of the chain wheel (4) relative to the holder body (8).

10. The saw (1) according to any one of the preceding claims, wherein a dri!! bit (20) which is arranged centrically in the chain wheel (4) projects further out from the chain wheel (4) than the first knives (5; 22),

11. The saw (1) according to any one of the preceding claims, wherein the roller chain (2) follows a path which includes two serni-circles.

12. The saw (1) according to claim 1, wherein the knife (5) includes a base (52) and wherein the base (52) is attached to the roller chain (2) on the bolts of the roller chain (2).

13. The saw (1) according to claim 12, wherein the knife (5) includes a knife blade (53) projecting perpendicularly from the base (52), and the knife blade (52) is provided with a cutting edge (50, 50') in at least one of its two edge portions (54, 54').

14. The saw (1) according to claim 13, wherein both edge portions (54, 54') are each provided with a respective cutting edge (50, 50').