DEVICE FOR MAKING HOLES IN SOFT POROUS MATERIAL

Abstract: Device for making holes in soft porous material, e.g. foamed silicone rubber in fire-sealing electric cable leads-through in walls and cealings. The device includes a rotatable shank (2) with an end cutter (1) arranged thereon and a centre pin (4) in the extention of the shank. Cutting bits in the shape of prismatic studs (6, 7) are arranged on the end cutter on its end plane, said bits being distributed so that uniform cutting is ensured. The centre pin (4) coacts with a non-rotating conical guide tip (5) which guides the device through the foamed material and prevents the holing direction unintentionally deviating from the one intended as a result of possible incorrect alignment of the shank.

Description: DEVICE FOR MAKING HOLES IN 5QFT POROUS MATERIAL TECHNICAL FIELD The present invention relates to a device for making holes, preferably in soft porous material, e.g. cellular rubber. One area in which there is a need of the inventive subject ' relates ti fire-sealing leads-through in walls and floors for electrical cables, pipes, ventilation ducts etc. (hereinafter referred to as "conduits) from one room to another. One such fire-sealing lead-through is described in the Swedish Patent Application No. 80Q2044-9. The lead-through described there includes a prefabricated body with a tubular shell arranged in a hole in a building component, in said shell there being arranged elastic fire- resistant foamed material, compressed transverse the longitudinal axis of the shell. One such foamed material of the silicone rubber type is commercially available under the designation "Dow Corning 3-6548 TRV". TECHNICAL BACKGROUND In laying conduits through a lead-through a partable sleeve with a removable concial tip has been forced through the foamed material, when dealing with slender or small-diameter conduits, the conduit then being taken through the sleeve, after which the latter has been removed. Since no foamed material has been removed but only compressed, the material springs back again when the sleeve is removed and engages sealingly against the conduit. With heavier conduits it is not possible to press a sleeve through the foamed material in this way. Compression of the material as well as the friction between sleeve and material will be too great, for which reason a hole with a somewhat smaller dimension than the conduit must be made first in the foamed material before a suitable sleeve can be forced through. Such holes are made with tools which best can be described as very rough round files, which work on the foamed material via axial movements executed manually. This work is troublesome and requires great proficiency for the hole to be truly cylindrical. Furthermore, it easily happens that the hole becomes too large, which means that there is no longer any sealing engagement of the foamed material against the conduit. In other words, the entire function of the fire seal is at hazard. DISCLOSURE OF INVENTION The present invention has the object of eliminating the above-mentioned drawbacks in making holes in firesealing leads-through of the type discussed here, by proposing a device which does not require proficiency or any great effort in handling, and with the aid of which a cylindrical hole can always be expected. The device in accordance with the invention includes a rotatable shank with a coupling means for retaining an end cutter at its one end portion. The characterizing features of the invention will be seen from the claims. A preferred embodiment of the invention will now be described in detail while referring to the appended drawings. DESCRIPTION OF FIGURES Figure 1 is an illustration of a holing device in position for making holes in a fire-sealing lead-through, the latter being shown in section. Figure 2 illustrates the same device as in Fig 1 while making a hole in the lead- through. Figure 3 is a section of the arrangement in Fig 2, taken through the foamed material of the lead-through in the same plane as the bottom of the hole being made, and with the device still in the hole. PREFERRED EMBODIMENT Figure 1 illustrates an embodiment of the holing device in position for making a hole in a fire-sealing lead-through, the lead-through portion being shown in section. The device includes a rotatable shank 2, at one end portion of which a coupling member 3 is adapted for retaining an end cutter 1 in one of a plurality of alternative positions, by a tooth running transverse the end plane of the coupling member being adapted for enmeshment with one of the grooves denoted on the drawing by numerals 45, 55 and 65. These numerals also denote the different hole diameters possible to achieve with the end cutter illustrated. A screw is adapted for engagement in a threaded central hole in the shank 2, the head of the screw being formed as a central pin 4 keeping the cutter pressed against the coupling member. The holing device also includes a guide tip 5, in which the pin 4 is rotatably mounted and which is urged through the foamed material by the pin during holing. The guide tip 5 guides the device through the material, independent of the attitude of the shank within a large angular range. This affords the advantage that drilling a hole on the skew is almost impossible, since the device follows the direction of the guide tip. If it is derired to increase the guiding effect, a long needle can be used to make a hole through the material, the tip then being* thrust into the hole, which it then follows during the holing process. Figure 2 illustrates a holing device as it is making a hole in a lead-through. The end cutter has a substantially flat surface in the cutting direction, there being a plurality of stud-like cutting bits 6 arranged such that when the cutter is rotated they move in substantially uniformly distributed paths, whereby an even cut is ensured. The bits 6, which suitably have a prismatic shape, grind the foamed material to powder when the device is caused to rotate. The device can be rotated by hand, e.g. with a brace or by machine, using an electric hand drilling machine. The form of the end cutter is such as to allow for passage backwards in the hole of the debris formed by making the hole. For holing in foamed silicone rubber, 2-3 mm wide bits have been found to be most suitable, and optium cutting is obtained when the bits project 3 mm from the surface of the cutter. Some of the bits, the edge bits 7, which are placed at the periphery of the cutter, are formed to dress the walls of the hole to the right diameter, a portion of them therefore lying outside the periphery of the cutter body, as will best be seen from Figure 3, which is a section of Figure 2, taken at a plane through the foamed material at a level with the bottom of the hole being made, and with the device still in the hole. It will further be seen from Figure 3 that the end cutter is provided with an elongate hole 8, enabling the previously-mentioned alternative positionings of the cutter in relation to the coupling member. When the device is set for making the smallest hole it is intended for, all the edge bits 7 will come into contact with the hole wall. Suitable extension of the edge bits 7 from the OMPI periphery of the cutter body has been found to be 1,5 mm for making holes in foamed silicone rubber, taking into account the holing result. The central pin 4 may, of course, be given the form of a guide tip, but, then, that unique property is lost that the holing takes place in the direction of the guide tip, even if the shank is inclined. Another disadvantage with this implementation is the generation of heat occuring if the guide tip rotates, and which must be taken into account when selecting material for the tip. With the proposed embodiment, both guide tip and end cutter can be made from plastics material. OMPI

Claims: C L A I S 1 Device for making holes, preferably in soft porous material, including a rotatable shank (2) with a coupling member (3) arranged at one end thereof for retaining an end cutter (1), characterized in that in the cutting direction the end cutter (1) has a substantially flat surface on which a plurality of stud-like cutting bits (6) are arranged, such that they move in substantially uniformly distributed paths when the cutter is rotated. 2 Device as claimed in claim 1, characterized in that the periphery of the end cutter (1) includes stud-like cutting .bits (7) for dressing the wall of the hole. 3 Device as claimed in claim 1 and 2, characterized in that the stud-like bits have a prismatic shape. 4 Device as claimed in claims 1-3, characterized in that the height of the bits above the flat surface is 1-5 mm. 5 Device as claimed in claims 1-3, characterized in that the height of the bits above the flat surface is 2-4 mm. 6 Device as claimed in claims 1-3, characterized in that the height of the bits above the flat surface is 3 mm. 7 Device as claimed in any of claims 1-6, characterized in that it includes a guide tip (5) arranged in the extension of the shank (2) in the cutting direction. 8 Device as claimed in claim 7, characterized in that the tip (5) has the shape of an elongate narrow cone. 9 Device as claimed in claimes 7-8, characterized in that the tip (5) is arranged for rotatation relative a guide pin (4) provided on the shank (2). 10 Device as claimed in claims 7-9, characterized in that the tip (5) is pivotable relative the shank (2). OMPI 11 Device as claimed in claims 1-10, characterized in that the end cutter (1) includes an elongate groove (8),. in which the coupling member (3) is arranged and which enables the cutter to be clamped both centrically and excentrically relative the shank (2). ϊυ E OMPI

Inventors: LEGERIUS BENGT EFRAIM, SIEBERT HANS WERNER
Applicants: ERICSSON TELEFON AB L M, LEGERIUS BENGT EFRAIM, SIEBERT HANS WERNER
Application year: 1982
Main classification: B29C17
IPC codes: B23B51