Mitre cutter device for cable ditches

A mitre cutter arrangement is provided for making mitred cuts in cable ditches. The arrangement comprise a mitre table with a base and a number of guide members extending from the base of the table in spaced relationship so as to accommodate standardized sizes of the cable ditches; clamps for clamping the cable ditch to the mitre table, and a mitre ruler provided with at least one flange extending along the side edge thereof and a groove extending in the longitudinal direction of the ruler. The groove receives a saw blade, and clamps are provided which secure the mitre ruler to the cable ditch. A saw device, guided by mitre ruler, carriers the saw blade as well as guide wheels running along the mitre ruler.

FIELD OF THE INVENTION 
The present invention relates to mitre cutter devices for making mitred 
cuts in metal channel members. 
BACKGROUND OF THE INVENTION 
It often happens that in buildings, especially factory or store buildings 
but also in other localities, that the existing electric conduits are 
applied in elongated, three-sided channels made from metal, plastic or the 
like, These channels, also called cable ditches, are usually mounted with 
their open side turned upwards hanging on hooks at the ceilings of the 
buildings but it also happens that they are provided close to the walls or 
beneath shelves provided along the walls of the spacing. Sometimes, the 
cable ditches are covered by means of a lid forming material but rather 
often they are left open without such lid forming material. 
Dependent upon the room planning, it is usually impossible to provide the 
cable ditches fully linearly straight but they have, practically in all 
cases, to be mounted in bends or angles, which means that one will have to 
cut the cable ditches in some mitre relation between their ends. It is of 
utmost importance that these mitre joints are tight and that the ends of 
the two cable ditch sections attach each other closely so that the joint 
is not visible or at least so that the joint will be as little visible as 
possible. 
A mitre cut is easily provided in a satisfactory way when the material is 
wood, such as is the case in making a picture frame, but as the cable 
ditches are practically exclusively made from plastic or metal which 
cannot be sawed as nicely as wood, extremely good tools are required for 
the mitre cutting of these materials. As a rule, the mitre cutting has to 
be made at the building place, and the mitre cutter apparatus hiterto 
known, which could be used for mitre cutting of cable ditches, have been 
stationary and were so big and heavy that they were not suitable for 
transportation to and from the building place and, still less, for 
transportation within the building place. 
SUMMARY OF THE INVENTION 
The present invention regards a mitre cutter apparatus giving an 
exceedingly good mitre cut result without visible joints or with only 
scarcely visible joints, and which is, furthermore, adjustable for 
deliberate angles and is light and convenient so that it may be 
transported not only from a store to the building place but also from one 
place to another one within the building. 
The mitre cutter apparatus according to the invention comprises the 
following parts, separable from each other but cooperating: a mitre cutter 
table with borders provided to adapt to different widths of the cable 
ditches, clamps or similar attachment means for attaching the cable ditch 
to the cable ditch mitre cutter table, a mitre cutter ruler to be placed 
over the cable ditch, to be adjusted into the correct angle and to be 
locked by means of clamps or similar means, and a mitre cutter saw which 
is preferably of the type that is driven by an electric motor and provided 
with a rotating saw blade. 
The invention will be further described below in connection with the 
embodiments shown in the drawings, but it is understood that the invention 
shall not be limited to these embodiments but that all different types of 
modifications may exist within the frame work of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The cable ditch shown in FIG. 9 comprises three sides, one of which 30 
being turned downwardly in the mounted state of the ditch and the two 
sides 31 and 32 being connected to the first mentioned one. At their free 
sides, the last mentioned ones, usually, are provided with a rolled hem 33 
and 34, respectively. These rolled hems have for their purpose to make 
possible the hanging up or mounting of the cable ditch at a ceiling with 
the open side turned upwardly, thereby enclosing the cables. When 
providing a joint between the sections of the cable ditch, one section is 
placed at right angle over the other one end, by drawing or engraving, 
lines are marked on the angular places of each of the two cross sides 31 
and 32 of each of the two cable ditches. Guided by these markings one may, 
thereafter, provide the corresponding angular marking on the upper side 30 
which will, when the cable ditch is mounted in its final place, be its 
bottom side. Thereafter, the cable ditch is placed on the mitre cutter 
table, one cross side or longitudinal flange 31 being placed tight to, 
i.e., in engagement with the outer side 35 of one of the parallel borders 
36-39 and so on of the mitre cutter table. These borders are adapted to 
standardized dimensions of the cable ditches, so that the outer cross side 
32 or longitudinal flange of the cable ditch 30 will tightly engage the 
side of another one of the said borders 37, 38 and so on, located further 
away from, i.e., spaced a predetermined standardized distance from flange 
36. Thereafter, the cable ditch is clamped to the mitre cutter table, for 
instance by means of a clamp of the type shown in FIG. 8, which is applied 
with one arm 40 over the side 30 of the cable ditch and the other arm 41 
under the mitre cutter table, said clamp thereafter being tightened by 
means of the screw 42. 
Hereafter, the mitre ruler, shown in FIGS. 1 and 2, is placed over the 
cable ditch clamped to the mitre cutter table. A pair of the mitre ruler 
comprises a bottom 10, and, along each of the longitudinal sides, 
perpendicularly outwardly extending flanges 11' and 11" as well as, close 
to one of said flanges 11', and a groove 12, extending along the major 
part of the length of the ruler through its bottom 10, with a bridge 13 
remaining at each end for stabilization of the construction of the ruler 
during the mitre cutting procedure. The ruler, thereafter, is placed in 
correct position over the cable ditch according to the engraving made and 
on the cable ditch referred to above is clamped by clamping means of 
suitable type, for instance clamps of same type as shown in FIG. 8. The 
system, thereafter, is prepared for making the mitre cut. This cutting 
takes place my means of a saw device, which is shown in FIGS. 3-6. 
The saw device comprises a motor casing 14, see FIGS. 3 and 4, in 
connection with a gear box 15 of a type that the rotational movement of 
the vertical motor shaft will be transferred into a rotational movement of 
a horizontal shaft 16. This out put shaft 16 carries the saw blade 17. 
Two guide wheel hangers or support brackets 18 and 19, respectively, are 
attached to to the motor casing 14 or the gear box 15. For clarification 
of the description, the guide wheel hanger 18 has been shown separated 
from its place of attachment. In this embodiment as illustrated in FIG. 3, 
the two wheels 20, carried by hanger 18 would, in the drawing figure, have 
been concealed by the saw blade 17, making the drawing difficult to 
understand. 
The wheels 20 are intended to run in the groove 12 of the mitre ruler when 
the apparatus is used for a mitre cutting procedure. The wheel hanger 19 
also carries or supports two guide wheels 21 running or riding on the 
flange 11", when the apparatus is used, flange 11" being shown in FIGS. 1 
and 2. 
One of the guide wheels 20 is shown in enlarged scale in FIG. 5. The shaft 
22 of a said wheel 20 is rotatably mounted on a downwardly turned portion 
24 of the wheel hanger 18, and shaft 22 carries the wheel 20, which has a 
profile including a central annular portion 26 of a shape, which is 
preferably rectangular, so that this annular portion 26 will have a width 
accurately adapted for free movement in the groove 12 at the same time as 
the major portions of the periphery of said wheel 20 on the opposite sides 
of central portion 26 ride or run on the edges of the ruler bottom 10 at 
each side of the groove 12. One of the wheels 20 is located in front of 
and will run before the saw blade and the other one is located behind and 
will run after said saw blade. 
One of the guide wheels 21 is shown in section in FIG. 6. This guide wheel 
21 is provided with a peripheral groove 25 in the otherwise smooth, 
cylindrical surface 27. The groove 25, as to its shape and dimension, is 
adapted to the upper edge of the flange 11". The shaft of the guide wheel 
shown in FIG. 6 is indicated by 25. The hanger 18 as well as the hanger 
19, each carry preferably two, but in any case at least, two such guide 
wheels. 
When making a mitre cut, the saw apparatus illustrated in FIGS. 3-6 is 
placed over the mitre ruler such that the wheels 20 will run in the groove 
12 and the wheels 21 will run on the flange 11", the saw motor thereafter 
being started and the cut executed. 
By this arrangement, comprising a number of parts separable from each 
other, the apparatus is easy transportable. The parts may easily be 
mounted together at the working place, and one will, by means of the 
system described get an exceedingly nice cut through the cable ditch with 
edges so smooth, that they are scarcely or not at all visible, once the 
ditch has been mounted in its place. 
Referring to FIGS. 10 to 13, in this embodiment, a mitre table 50 is formed 
by a number of transverse channels or beams 51-55. Beams 51-55 support a 
plurality of borders or guides 56-60, which are preferably in the shape of 
angle beams with their flanges attached to the bases of the underlying 
beams 51-55. 
The relative positioning of the mitre table 50 and the mitre ruler 1 of 
FIG. 13 takes place, in this embodiment, by means of bolts or pins which 
cooperate with corresponding holes or one or more channels. Thus, in the 
specific embodiment illustrated, a bolt 67 is attached to the channel beam 
51, and a hole 68 is provided in the bottom 61 of the mitre ruler. Futher 
bolts or pins 69, 70, 71, 72 are attached to each of the channel beams 51, 
52, 53 and 54, respectively. These bolts or pins 69, 70, 71 and 72 
correspond to a groove 73 in the bottom of the mitre ruler 2. The groove 
73 is shaped in such a way that the bolts 69-72 may be inserted thereon. 
In order that the mitre ruler shall assume a position perpendicular to the 
longitudinal direction of the mitre table when the bolt 67 is inserted 
into the hole 68, the bolt 69 should be inserted into the groove 73. This 
will give a mitre angle of 90.degree.. 
In a corresponding way, the bolts 70, 71 and 72, when introduced into the 
groove 73, provide mitre angles of 60.degree., 45.degree. and 30.degree., 
as indicated by the dashed lines 75, 77, 78 and 79 in FIG. 12. 
When mounting a cable ditch for the purpose of cutting it at a given mitre 
angle, the cable ditch is first placed over the mitre table shown in FIGS. 
10-12, with its flange 31 engaging the edge of the border 56 at left in 
FIG. 10, and the other flange 32 of the cable ditch engaging the right 
side of any one of the borders 57, 58, 59 or 60, dependent upon the size 
of the cable ditch. Thereafter, the mitre ruler 2 is placed over the cable 
ditch, with the bolt 67 being inserted into the hole 68, a selected bolt 
of the bolts 69-72 being inserted into the groove 73. The system is then 
ready for a cutting operating using the saw device described above and 
shown in FIGS. 3 and 4.